Calculation of total electron excitation cross-sections and partial electron ionization cross-sections for the elements. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Green, T. J.

1973-01-01

Computer programs were used to calculate the total electron excitation cross-section for atoms and the partial ionization cross-section. The approximations to the scattering amplitude used are as follows: (1) Born, Bethe, and Modified Bethe for non-exchange excitation; (2) Ochkur for exchange excitation; and (3) Coulomb-Born of non-exchange ionization. The amplitudes are related to the differential cross-sections which are integrated to give the total excitation (or partial ionization) cross-section for the collision. The atomic wave functions used are Hartree-Fock-Slater functions for bound states and the coulomb wave function for the continuum. The programs are presented and the results are examined.

Hydrodynamic flow of ions and atoms in partially ionized plasmas.

PubMed

Nemirovsky, R A; Fredkin, D R; Ron, A

2002-12-01

We have derived the hydrodynamic equations of motion for a partially ionized plasma, when the ionized component and the neutral components have different flow velocities and kinetic temperatures. Starting from the kinetic equations for a gas of ions and a gas of atoms we have considered various processes of encounters between the two species: self-collisions, interspecies collisions, ionization, recombination, and charge exchange. Our results were obtained by developing a general approach for the hydrodynamics of a gas in a binary mixture, in particular when the components drift with respect to each other. This was applied to a partially ionized plasma, when the neutral-species gas and the charged-species gas have separate velocities. We have further suggested a generalized version of the relaxation time approximation and obtained the contributions of the interspecies encounters to the transport equations.

The CoRoT target HD 49933: a possible seismic signature of heavy elements ionization in the deep convective zone

NASA Astrophysics Data System (ADS)

Brito, Ana; Lopes, Ilídio

2017-04-01

We use a seismic diagnostic, based on the derivative of the phase shift of the acoustic waves reflected by the surface, to probe the outer layers of the star HD 49933. This diagnostic is particularly sensitive to partial ionization processes occurring above the base of the convective zone. The regions of partial ionization of light elements, hydrogen and helium, have well-known seismological signatures. In this work, we detect a different seismic signature in the acoustic frequencies, which we showed to correspond to the location where the partial ionization of heavy elements occurs. The location of the corresponding acoustic glitch lies between the region of the second ionization of helium and the base of the convective zone, approximately 5 per cent below the surface of the stars.

Collision effects on propagation characteristics of electromagnetic waves in a sub-wavelength plasma slab of partially ionized dense plasmas

NASA Astrophysics Data System (ADS)

Bowen, LI; Zhibin, WANG; Qiuyue, NIE; Xiaogang, WANG; Fanrong, KONG; Zhenyu, WANG

2018-01-01

Intensive collisions between electrons and neutral particles in partially ionized plasmas generated in atmospheric/sub-atmospheric pressure environments can sufficiently affect the propagation characteristics of electromagnetic waves, particularly in the sub-wavelength regime. To investigate the collisional effect in such plasmas, we introduce a simplified plasma slab model with a thickness on the order of the wavelength of the incident electromagnetic wave. The scattering matrix method (SMM) is applied to solve the wave equation in the plasma slab with significant nonuniformity. Results show that the collisions between the electrons and the neutral particles, as well as the incident angle and the plasma thickness, can disturb the transmission and reduce reflection significantly.

Effect of partially ionized impurities and radiation on the effective critical electric field for runaway generation

NASA Astrophysics Data System (ADS)

Hesslow, L.; Embréus, O.; Wilkie, G. J.; Papp, G.; Fülöp, T.

2018-07-01

We derive a formula for the effective critical electric field for runaway generation and decay that accounts for the presence of partially ionized impurities in combination with synchrotron and bremsstrahlung radiation losses. We show that the effective critical field is drastically larger than the classical Connor–Hastie field, and even exceeds the value obtained by replacing the free electron density by the total electron density (including both free and bound electrons). Using a kinetic equation solver with an inductive electric field, we show that the runaway current decay after an impurity injection is expected to be linear in time and proportional to the effective critical electric field in highly inductive tokamak devices. This is relevant for the efficacy of mitigation strategies for runaway electrons since it reduces the required amount of injected impurities to achieve a certain current decay rate.

Simulations of Hall reconnection in partially ionized plasmas

NASA Astrophysics Data System (ADS)

Innocenti, Maria Elena; Jiang, Wei; Lapenta, Giovanni

2017-04-01

Magnetic reconnection occurs in the Hall, partially ionized regime in environments as diverse as molecular clouds, protostellar disks and regions of the solar chromosphere. While much is known about Hall reconnection in fully ionized plasmas, Hall reconnection in partially ionized plasmas is, in comparison, still relatively unexplored. This notwithstanding the fact that partial ionization is expected to affect fundamental processes in reconnection such as the transition from the slow, fluid to the fast, kinetic regime, the value of the reconnection rate and the dimensions of the diffusion regions [Malyshkin and Zweibel 2011 , Zweibel et al. 2011]. We present here the first, to our knowledge, fully kinetic simulations of Hall reconnection in partially ionized plasmas. The interaction of electrons and ions with the neutral background is realistically modelled via a Monte Carlo plug-in coded into the semi-implicit, fully kinetic code iPic3D [Markidis 2010]. We simulate a plasma with parameters compatible with the MRX experiments illustrated in Zweibel et al. 2011 and Lawrence et al. 2013, to be able to compare our simulation results with actual experiments. The gas and ion temperature is T=3 eV, the ion to electron temperature ratio is Tr=0.44, ion and electron thermal velocities are calculated accordingly resorting to a reduced mass ratio and a reduced value of the speed of light to reduce the computational costs of the simulations. The initial density of the plasma is set at n= 1.1 1014 cm-3 and is then left free to change during the simulation as a result of gas-plasma interaction. A set of simulations with initial ionisation percentage IP= 0.01, 0.1, 0.2, 0.6 is presented and compared with a reference simulation where no background gas is present (full ionization). In this first set of simulations, we assume to be able to externally control the initial relative densities of gas and plasma. Within this parameter range, the ion but not the electron population is heavily affected by collisions with the neutrals. In line with experimental results, we observe reduction of the reconnection rate and no variation of the half-thickness of the ion diffusion region with decreasing IP (increasing gas density). Contrarily to the experiments, we can confidently state that these effects are not influenced by boundary constraints. We then provide an explanation for the behaviour observed.

Multi-fluid Modeling of Magnetosonic Wave Propagation in the Solar Chromosphere: Effects of Impact Ionization and Radiative Recombination

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

Maneva, Yana G.; Laguna, Alejandro Alvarez; Poedts, Stefaan

2017-02-20

In order to study chromospheric magnetosonic wave propagation including, for the first time, the effects of ion–neutral interactions in the partially ionized solar chromosphere, we have developed a new multi-fluid computational model accounting for ionization and recombination reactions in gravitationally stratified magnetized collisional media. The two-fluid model used in our 2D numerical simulations treats neutrals as a separate fluid and considers charged species (electrons and ions) within the resistive MHD approach with Coulomb collisions and anisotropic heat flux determined by Braginskiis transport coefficients. The electromagnetic fields are evolved according to the full Maxwell equations and the solenoidality of the magneticmore » field is enforced with a hyperbolic divergence-cleaning scheme. The initial density and temperature profiles are similar to VAL III chromospheric model in which dynamical, thermal, and chemical equilibrium are considered to ensure comparison to existing MHD models and avoid artificial numerical heating. In this initial setup we include simple homogeneous flux tube magnetic field configuration and an external photospheric velocity driver to simulate the propagation of MHD waves in the partially ionized reactive chromosphere. In particular, we investigate the loss of chemical equilibrium and the plasma heating related to the steepening of fast magnetosonic wave fronts in the gravitationally stratified medium.« less

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

Critical parameters, thermodynamic functions, and shock Hugoniot of aluminum fluid at high energy density

NASA Astrophysics Data System (ADS)

Zaghloul, Mofreh R.

2018-03-01

We present estimates of the critical properties, thermodynamic functions, and principal shock Hugoniot of hot dense aluminum fluid as predicted from a chemical model for the equation-of-state of hot dense, partially ionized and partially degenerate plasma. The essential features of strongly coupled plasma of metal vapors, such as multiple ionization, Coulomb interactions among charged particles, partial degeneracy, and intensive short range hard core repulsion are taken into consideration. Internal partition functions of neutral, excited, and multiply ionized species are carefully evaluated in a statistical-mechanically consistent way. Results predicted from the present model are presented, analyzed and compared with available experimental measurements and other theoretical predictions in the literature.

Communication: Electron ionization of DNA bases.

PubMed

Rahman, M A; Krishnakumar, E

2016-04-28

No reliable experimental data exist for the partial and total electron ionization cross sections for DNA bases, which are very crucial for modeling radiation damage in genetic material of living cell. We have measured a complete set of absolute partial electron ionization cross sections up to 500 eV for DNA bases for the first time by using the relative flow technique. These partial cross sections are summed to obtain total ion cross sections for all the four bases and are compared with the existing theoretical calculations and the only set of measured absolute cross sections. Our measurements clearly resolve the existing discrepancy between the theoretical and experimental results, thereby providing for the first time reliable numbers for partial and total ion cross sections for these molecules. The results on fragmentation analysis of adenine supports the theory of its formation in space.

Multi-fluid Approach to High-frequency Waves in Plasmas. III. Nonlinear Regime and Plasma Heating

NASA Astrophysics Data System (ADS)

Martínez-Gómez, David; Soler, Roberto; Terradas, Jaume

2018-03-01

The multi-fluid modeling of high-frequency waves in partially ionized plasmas has shown that the behavior of magnetohydrodynamic waves in the linear regime is heavily influenced by the collisional interaction between the different species that form the plasma. Here, we go beyond linear theory and study large-amplitude waves in partially ionized plasmas using a nonlinear multi-fluid code. It is known that in fully ionized plasmas, nonlinear Alfvén waves generate density and pressure perturbations. Those nonlinear effects are more pronounced for standing oscillations than for propagating waves. By means of numerical simulations and analytical approximations, we examine how the collisional interaction between ions and neutrals affects the nonlinear evolution. The friction due to collisions dissipates a fraction of the wave energy, which is transformed into heat and consequently raises the temperature of the plasma. As an application, we investigate frictional heating in a plasma with physical conditions akin to those in a quiescent solar prominence.

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.

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.

Communication: Electron ionization of DNA bases

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

Rahman, M. A.; Krishnakumar, E., E-mail: ekkumar@tifr.res.in

2016-04-28

No reliable experimental data exist for the partial and total electron ionization cross sections for DNA bases, which are very crucial for modeling radiation damage in genetic material of living cell. We have measured a complete set of absolute partial electron ionization cross sections up to 500 eV for DNA bases for the first time by using the relative flow technique. These partial cross sections are summed to obtain total ion cross sections for all the four bases and are compared with the existing theoretical calculations and the only set of measured absolute cross sections. Our measurements clearly resolve themore » existing discrepancy between the theoretical and experimental results, thereby providing for the first time reliable numbers for partial and total ion cross sections for these molecules. The results on fragmentation analysis of adenine supports the theory of its formation in space.« less

Partial Return Yoke for MICE Step IV and Final Step

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

Witte, Holger; Plate, Stephen; Berg, J.Scott

2015-06-01

This paper reports on the progress of the design and construction of a retro-fitted return yoke for the international Muon Ionization Cooling Experiment (MICE). MICE is a proof-of-principle experiment aiming to demonstrate ionization cooling experimentally. In earlier studies we outlined how a partial return yoke can be used to mitigate stray magnetic field in the experimental hall; we report on the progress of the construction of the partial return yoke for MICE Step IV. We also discuss an extension of the Partial Return Yoke for the final step of MICE; we show simulation results of the expected performance.

Partial return yoke for MICE step IV and final step

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

Witte, H.; Plate, S.; Berg, J. S.

2015-05-03

This paper reports on the progress of the design and construction of a retro-fitted return yoke for the international Muon Ionization Cooling Experiment (MICE). MICE is a proof-of-principle experiment aiming to demonstrate ionization cooling experimentally. In earlier studies we outlined how a partial return yoke can be used to mitigate stray magnetic field in the experimental hall; we report on the progress of the construction of the partial return yoke for MICE Step IV. We also discuss an extension of the Partial Return Yoke for the final step of MICE; we show simulation results of the expected performance.

Thermal diffusion in partially ionized gases - The case of unequal temperatures. [in solar chromosphere

NASA Technical Reports Server (NTRS)

Geiss, J.; Burgi, A.

1987-01-01

Previous calculations of thermal diffusion coefficients in partially ionized gases are extended to the case of unequal neutral and ion temperatures and/or temperature gradients. Formulas are derived for the general case of a major gas as well as for minor atoms and ions. Strong enhancements of minor-ion thermal diffusion coefficients over their values in the fully ionized gas are found when the degree of ionization in the main gas is relatively low. However, compared to the case of equal temperatures, the enhancements are less strong when the neutrals are cooler than the ions. The specific case of the H-H(+) mixture, which is important in the study of solar and stellar atmospheres, is discussed as an application.

Large-scale fluctuations in the cosmic ionizing background: the impact of beamed source emission

NASA Astrophysics Data System (ADS)

Suarez, Teresita; Pontzen, Andrew

2017-12-01

When modelling the ionization of gas in the intergalactic medium after reionization, it is standard practice to assume a uniform radiation background. This assumption is not always appropriate; models with radiative transfer show that large-scale ionization rate fluctuations can have an observable impact on statistics of the Lyman α forest. We extend such calculations to include beaming of sources, which has previously been neglected but which is expected to be important if quasars dominate the ionizing photon budget. Beaming has two effects: first, the physical number density of ionizing sources is enhanced relative to that directly observed; and secondly, the radiative transfer itself is altered. We calculate both effects in a hard-edged beaming model where each source has a random orientation, using an equilibrium Boltzmann hierarchy in terms of spherical harmonics. By studying the statistical properties of the resulting ionization rate and H I density fields at redshift z ∼ 2.3, we find that the two effects partially cancel each other; combined, they constitute a maximum 5 per cent correction to the power spectrum P_{H I}(k) at k = 0.04 h Mpc-1. On very large scales (k < 0.01 h Mpc-1) the source density renormalization dominates; it can reduce, by an order of magnitude, the contribution of ionizing shot noise to the intergalactic H I power spectrum. The effects of beaming should be considered when interpreting future observational data sets.

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.

Vacancies and holes in bulk and at 180° domain walls in lead titanate

NASA Astrophysics Data System (ADS)

Paillard, Charles; Geneste, Grégory; Bellaiche, Laurent; Dkhil, Brahim

2017-12-01

Domain walls (DWs) in ferroic materials exhibit a plethora of unexpected properties that are different from the adjacent ferroic domains. Still, the intrinsic/extrinsic origin of these properties remains an open question. Here, density functional theory calculations are used to investigate the interaction between vacancies and 180° DWs in the prototypical ferroelectric PbTiO3, with a special emphasis on cationic vacancies and released holes. All vacancies are more easily formed within the DW than in the domains. This is interpreted, using a phenomenological model, as the partial compensation of an extra-tensile stress when the defect is created inside the DW. Oxygen vacancies are found to be always fully ionized, independently of the thermodynamic conditions, while cationic vacancies can be either neutral or partially ionized (oxygen-rich conditions), or fully ionized (oxygen-poor conditions). Therefore, in oxidizing conditions, holes are induced by neutral and partially ionized Pb vacancies. In the bulk PbTiO3, these holes are more stable as delocalized rather than small polarons, but at DWs, the two forms are found to be possible.

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.

Coffee-ring effects in laser desorption/ionization mass spectrometry.

PubMed

Hu, Jie-Bi; Chen, Yu-Chie; Urban, Pawel L

2013-03-05

This report focuses on the heterogeneous distribution of small molecules (e.g. metabolites) within dry deposits of suspensions and solutions of inorganic and organic compounds with implications for chemical analysis of small molecules by laser desorption/ionization (LDI) mass spectrometry (MS). Taking advantage of the imaging capabilities of a modern mass spectrometer, we have investigated the occurrence of "coffee rings" in matrix-assisted laser desorption/ionization (MALDI) and surface-assisted laser desorption/ionization (SALDI) sample spots. It is seen that the "coffee-ring effect" in MALDI/SALDI samples can be both beneficial and disadvantageous. For example, formation of the coffee rings gives rise to heterogeneous distribution of analytes and matrices, thus compromising analytical performance and reproducibility of the mass spectrometric analysis. On the other hand, the coffee-ring effect can also be advantageous because it enables partial separation of analytes from some of the interfering molecules present in the sample. We report a "hidden coffee-ring effect" where under certain conditions the sample/matrix deposit appears relatively homogeneous when inspected by optical microscopy. Even in such cases, hidden coffee rings can still be found by implementing the MALDI-MS imaging technique. We have also found that to some extent, the coffee-ring effect can be suppressed during SALDI sample preparation. Copyright © 2013 Elsevier B.V. All rights reserved.

Two-center interference effects in (e, 2e) ionization of H2 and CO2 at large momentum transfer

NASA Astrophysics Data System (ADS)

Yamazaki, Masakazu; Nakajima, Isao; Satoh, Hironori; Watanabe, Noboru; Jones, Darryl; Takahashi, Masahiko

2015-09-01

In recent years, there has been considerable interest in understanding quantum mechanical interference effects in molecular ionization. Since this interference appears as a consequence of coherent electron emission from the different molecular centers, it should depend strongly on the nature of the ionized molecular orbital. Such molecular orbital patterns can be investigated by means of binary (e, 2e) spectroscopy, which is a kinematically-complete electron-impact ionization experiment performed under the high-energy Bethe ridge conditions. In this study, two-center interference effects in the (e, 2e) cross sections of H2 and CO2 at large momentum transfer are demonstrated with a high-statistics experiment, in order to elucidate the relationship between molecular orbital patterns and the interference structure. It is shown that the two-center interference is highly sensitive to the phase, spatial pattern, symmetry of constituent atomic orbital, and chemical bonding nature of the molecular orbital. This work was partially supported by Grant-in-Aids for Scientific Research (S) (No. 20225001) and for Young Scientists (B) (No. 21750005) from the Ministry of Education, Culture, Sports, Science and Technology.

Basic results on the equations of magnetohydrodynamics of partially ionized inviscid plasmas

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

Nunez, Manuel

2009-10-15

The equations of evolution of partially ionized plasmas have been far more studied in one of their many simplifications than in its original form. They present a relation between the velocity of each species, plus the magnetic and electric fields, which yield as an analog of Ohm's law a certain elliptic equation. Therefore, the equations represent a functional evolution system, not a classical one. Nonetheless, a priori estimates and theorems of existence may be obtained in appropriate Sobolev spaces.

The electromagnetic interchange mode in a partially ionized collisional plasma. [spread F region

NASA Technical Reports Server (NTRS)

Hudson, M. K.; Kennel, C. F.

1974-01-01

A collisional electromagnetic dispersion relation is derived from two-fluid theory for the interchange mode coupled to the Alfven, acoustic, drift and entropy modes in a partially ionized plasma. The fundamental electromagnetic nature of the interchange model is noted; coupling to the intermediate Alfven mode is strongly stabilizing for finite k sub z. Both ion viscous and ion-neutral stabilization are included, and it was found that collisions destroy the ion finite Larmor radius cutoff at short perpendicular wavelengths.

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.

Fundamental Processes in Partially Ionized Plasmas

DTIC Science & Technology

1988-08-01

thermal plasma chemistry , may significantly underestimate Lie importance of radiation losses. Also shown in Figure 4 are the earlier measurements of Emmons...in Thermal Plasma Chemistry ," 8th Int’l Symposium on Plasma Chemistry , Tokyo Japan, August 1987. 4. Kruger, Charles H., "Nonequilibrium Effects in...Annual Gaseous Electronics Conference, Minneapolis, MN, October 1988. 7. Kruger, C. H., "Nonequilibrium Effects in Thermal Plasma Chemistry ," Submitted

Role of ionization and electron drift velocity profile to Rayleigh instability in a Hall thruster plasma

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

Singh, Sukhmander; Malik, Hitendra K.

Role of ionization to Rayleigh instability is clarified in a Hall thruster plasma under the variety of profiles of electron drift velocity, namely, step-like profile (SLP) and two different super-Gaussian profiles (SGP1 and SGP2). For this, a relevant Rayleigh equation is derived and solved numerically using fourth-order Runge-Kutta method. Interestingly, an upper cutoff frequency of oscillations {omega}{sub max} is realized for the occurrence of the instability that shows dependence on the ionization rate {alpha}, electron drift velocity u{sub 0}, electron cyclotron frequency {Omega}, azimuthal wave number k{sub y}, plasma density n{sub 0}, density gradient {partial_derivative}n{sub 0}/{partial_derivative}x, ion (electron) thermal speedmore » V{sub thI}(V{sub thE}), and ion (electron) plasma frequency {omega}{sub pi}({omega}{sub pe}). The frequency {omega}{sub max} follows the trend {omega}{sub max} (for SGP2) >{omega}{sub max} (for SLP) >{omega}{sub max} (for SGP1) and shows a similar behaviour with ionization for all types of the velocity profiles. The instability is found to grow faster for the higher {alpha} and the ion temperature but it acquires lower rate under the effect of the higher electron temperature; the perturbed potential also varies in accordance with the growth rate. The electron temperature influences the growth rate and cutoff frequency less significantly in comparison with the ion temperature.« less

Transport equations for partially ionized reactive plasma in magnetic field

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

Zhdanov, V. M.; Stepanenko, A. A.

2016-06-08

Transport equations for partially ionized reactive plasma in magnetic field taking into account the internal degrees of freedom and electronic excitation of plasma particles are derived. As a starting point of analysis the kinetic equation with a binary collision operator written in the Wang-Chang and Uhlenbeck form and with a reactive collision integral allowing for arbitrary chemical reactions is used. The linearized variant of Grad’s moment method is applied to deduce the systems of moment equations for plasma and also full and reduced transport equations for plasma species nonequilibrium parameters.

Results from the Heavy Ions In Space (HIIS) experiment on the ionic charge state of solar energetic particles

NASA Technical Reports Server (NTRS)

Tylka, Allan J.; Boberg, Paul R.; Adams, James H., Jr.; Beahm, Lorraine P.; Kleis, Thomas

1995-01-01

It has long been known that low-energy solar energetic particles (SEP's) are partially-ionized. For example, in large, so-called 'gradual' solar energetic particle events, at approximately 1 MeV/nucleon the measured mean ionic charge state, Q, of Fe ions is 14.1 +/- 0.2, corresponding to a plasma temperature of approximately 2 MK in the coronal or solar-wind source material. Recent studies, which have greatly clarified the origin of solar energetic particles and their relation to solar flares, suggest that ions in these SEP events are accelerated not at a flare site, but by shocks propagating through relatively low-density regions in the interplanetary medium. As a result, the partially-ionized states observed at low energies are expected to continue to higher energies. However, up to now there have been no high-energy measurements of ionic charge states to confirm this notion. We report here HIIS observations of Fe-group ions at 50-600 MeV/nucleon, at energies and fluences which cannot be explained by fully-ionized galactic cosmic rays, even in the presence of severe geomagnetic cutoff suppression. Above approximately 200 MeV/nucleon, all features of our data -- fluence, energy spectrum, elemental composition, and arrival directions -- can be explained by the large SEP events of October 1989, provided that the mean ionic charge state at these high energies is comparable to the measured value at approximately 1 MeV/nucleon. By comparing the HIIS observations with measurements in interplanetary space in October 1989, we determine the mean ionic charge state of SEP Fe ions at approximately 200-600 MeV/nucleon to be Q = 13.4 plus or minus 1.0, in good agreement with the observed value at approximately 1 MeV/nucleon. The source of the ions below approximately 200 MeV/nucleon is not yet clear. Partially-ionized ions are less effectively deflected by the Earth's magnetic field than fully-ionized cosmic rays and therefore have greatly enhanced access to low-Earth orbit. Moreover, at the high energies observed in HIIS, these ions can penetrate typical amounts of shielding. We discuss the significance of the HIIS results for estimates of the radiation hazard posed by large SEP events to satellites in low-Earth orbit, including the proposed Space Station orbit. Finally, we comment on previous reports of low-energy below-cutoff Fe-group ions, which some authors have interpreted as evidence for partially-ionized galactic cosmic rays. The LDEF flux levels are much smaller than the corresponding fluxes in these previous reports, implying that the source of these ions has an unusual solar-cycle variation and/or strongly increases with decreasing altitude.

Interrelated structures of the transport shock and collisional relaxation layer in a multitemperature, multilevel ionized gas

NASA Technical Reports Server (NTRS)

Vinolo, A. R.; Clarke, J. H.

1973-01-01

The gas dynamic structures of the transport shock and the downstream collisional relaxation layer are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. In the microscopic model of the atom, three electronic levels are accounted for. By using an asymptotic technique, the shock morphology is found on a continuum flow basis. This procedure gives two distinct layers in which the nonequilibrium effects to be considered are different. A transport shock appears as the inner solution to an outer collisional relaxation layer. The results show four main interesting points: (1) on structuring the transport shock, ionization and excitation rates must be included in the formulation, since the flow is not frozen with respect to the population of the different electronic levels; (2) an electron temperature precursor appears at the beginning of the transport shock; (3) the collisional layer is rationally reduced to quadrature for special initial conditions, which (4) are obtained from new Rankine-Hugoniot relations for the inner shock.

Dynamical orientation effects in atomic ionization by impact of protons and positrons

NASA Astrophysics Data System (ADS)

Fregenal, Daniel; Barrachina, Raúl; Bernardi, Guillermo; Suárez, Sergio; Fiol, Juan

2011-10-01

Recent results in ionization collisions with positrons and protons showed that just above the two-body threshold, for electron velocities close to the final projectile's velocity, the electron-projectile continuum dipole is narrowly oriented along the direction of motion of its centre-of-mass, with the negative charge pointing towards the residual target. Although a forward-backward asymmetry in the vicinity of the two-body threshold has been studied many year ago in ion impact ionization collisions, that was by far a much milder effect that left no fingerprint on the cusp position. Our results show that the phenomena is present for ionization by impact of both protons and positrons. In this communication, through measurements on H+ + He and calculations we analyze in detail this effect that can be linked to a dynamical alignment of the two-body subsystem in the continuum. Recent results in ionization collisions with positrons and protons showed that just above the two-body threshold, for electron velocities close to the final projectile's velocity, the electron-projectile continuum dipole is narrowly oriented along the direction of motion of its centre-of-mass, with the negative charge pointing towards the residual target. Although a forward-backward asymmetry in the vicinity of the two-body threshold has been studied many year ago in ion impact ionization collisions, that was by far a much milder effect that left no fingerprint on the cusp position. Our results show that the phenomena is present for ionization by impact of both protons and positrons. In this communication, through measurements on H+ + He and calculations we analyze in detail this effect that can be linked to a dynamical alignment of the two-body subsystem in the continuum. This work was partially supported by the Consejo Nacional de Investigaciones Cientificas y Tecnicas, Universidad Nacional de Cuyo and Fundacion Balseiro.

Effects of ionizing energetic electrons and plasma transport in the ionosphere during the initial phase of the December 2006 magnetic storm

NASA Astrophysics Data System (ADS)

Suvorova, A. V.; Huang, C.-M.; Dmitriev, A. V.; Kunitsyn, V. E.; Andreeva, E. S.; Nesterov, I. A.; Klimenko, M. V.; Klimenko, V. V.; Tumanova, Yu. S.

2016-06-01

The initial phase of a major geomagnetic storm on 14 December 2006 was selected in order to investigate the ionizing effect of energetic electrons in the ionosphere. The global network of GPS receivers was used to analyze the total electron content (TEC). A strong positive ionospheric storm of ~20 TEC units (TECU) with ~6 h duration was observed on the dayside during the interval of northward interplanetary magnetic field. At the same time, the NOAA/POES satellites observed long-lasting intense fluxes of >30 keV electrons in the topside ionosphere at middle and low latitudes, including a near-equatorial forbidden zone outside of the South Atlantic Anomaly (SAA). We found that the TEC increases overlapped well with the enhancements of energetic electrons. Modeling of the ionospheric response by using a Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere, based on the standard mechanisms of plasma transport, could only partially explain the ionospheric response and was unable to predict the long-duration increase of TEC. For the energetic electrons, we estimated the ionizing effect of ~45 TECU and ~23 TECU in the topside ionosphere, respectively, inside and outside of SAA. The ionizing effect contributed from 50% to 100% of TEC increases and provided the long duration and wide latitudinal extension of the positive ionospheric storm. This finding is a very important argument in supporting significant ionizing effect of energetic electrons in the storm time ionosphere both at middle and low latitudes.

Aerobrake plasmadynamics - Macroscopic effects

NASA Technical Reports Server (NTRS)

Shebalin, John V.

1990-01-01

The flow around an aerobraking spacecraft (such as the Aeroassist Flight Experiment reentry vehicle) will contain a region of partially ionized gas, that is, a plasma. It is shown here by numerical simulation that macroscopic plasmadynamic effects (which are not included in standard aerothermodynamic simulations) will have a noticeable effect on the reentry flow field. In particular, there are thermoelectric phenomena which can have a major influence in flow dynamics at the front of an ionizing bowshock. These thermoelectric phenomena arise because of the presence of large density and temperature gradients at the front of a reentry bowshock, and they include strong local magnetic fields, electric currents, and ohmic heating. One important result is the dramatic increase in temperature (over the case where plasma effects are neglected) at a reentry shock front; the implication is that macroscopic plasmadynamic effects can no longer be neglected in simulations of hypersonic reentry flow fields.

On contribution of known atomic partial charges of protein backbone in electrostatic potential density maps.

PubMed

Wang, Jimin

2017-06-01

Partial charges of atoms in a molecule and electrostatic potential (ESP) density for that molecule are known to bear a strong correlation. In order to generate a set of point-field force field parameters for molecular dynamics, Kollman and coworkers have extracted atomic partial charges for each of all 20 amino acids using restrained partial charge-fitting procedures from theoretical ESP density obtained from condensed-state quantum mechanics. The magnitude of atomic partial charges for neutral peptide backbone they have obtained is similar to that of partial atomic charges for ionized carboxylate side chain atoms. In this study, the effect of these known atomic partial charges on ESP is examined using computer simulations and compared with the experimental ESP density recently obtained for proteins using electron microscopy. It is found that the observed ESP density maps are most consistent with the simulations that include atomic partial charges of protein backbone. Therefore, atomic partial charges are integral part of atomic properties in protein molecules and should be included in model refinement. © 2017 The Protein Society.

On contribution of known atomic partial charges of protein backbone in electrostatic potential density maps

PubMed Central

2017-01-01

Abstract Partial charges of atoms in a molecule and electrostatic potential (ESP) density for that molecule are known to bear a strong correlation. In order to generate a set of point‐field force field parameters for molecular dynamics, Kollman and coworkers have extracted atomic partial charges for each of all 20 amino acids using restrained partial charge‐fitting procedures from theoretical ESP density obtained from condensed‐state quantum mechanics. The magnitude of atomic partial charges for neutral peptide backbone they have obtained is similar to that of partial atomic charges for ionized carboxylate side chain atoms. In this study, the effect of these known atomic partial charges on ESP is examined using computer simulations and compared with the experimental ESP density recently obtained for proteins using electron microscopy. It is found that the observed ESP density maps are most consistent with the simulations that include atomic partial charges of protein backbone. Therefore, atomic partial charges are integral part of atomic properties in protein molecules and should be included in model refinement. PMID:28370507

Two-dimensional Radiative Magnetohydrodynamic Simulations of Partial Ionization in the Chromosphere. II. Dynamics and Energetics of the Low Solar Atmosphere

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

Martínez-Sykora, Juan; Pontieu, Bart De; Hansteen, Viggo H.

2017-09-20

We investigate the effects of interactions between ions and neutrals on the chromosphere and overlying corona using 2.5D radiative MHD simulations with the Bifrost code. We have extended the code capabilities implementing ion–neutral interaction effects using the generalized Ohm’s law, i.e., we include the Hall term and the ambipolar diffusion (Pedersen dissipation) in the induction equation. Our models span from the upper convection zone to the corona, with the photosphere, chromosphere, and transition region partially ionized. Our simulations reveal that the interactions between ionized particles and neutral particles have important consequences for the magnetothermodynamics of these modeled layers: (1) ambipolarmore » diffusion increases the temperature in the chromosphere; (2) sporadically the horizontal magnetic field in the photosphere is diffused into the chromosphere, due to the large ambipolar diffusion; (3) ambipolar diffusion concentrates electrical currents, leading to more violent jets and reconnection processes, resulting in (3a) the formation of longer and faster spicules, (3b) heating of plasma during the spicule evolution, and (3c) decoupling of the plasma and magnetic field in spicules. Our results indicate that ambipolar diffusion is a critical ingredient for understanding the magnetothermodynamic properties in the chromosphere and transition region. The numerical simulations have been made publicly available, similar to previous Bifrost simulations. This will allow the community to study realistic numerical simulations with a wider range of magnetic field configurations and physics modules than previously possible.« less

Two-dimensional Radiative Magnetohydrodynamic Simulations of Partial Ionization in the Chromosphere. II. Dynamics and Energetics of the Low Solar Atmosphere

NASA Astrophysics Data System (ADS)

Martínez-Sykora, Juan; De Pontieu, Bart; Carlsson, Mats; Hansteen, Viggo H.; Nóbrega-Siverio, Daniel; Gudiksen, Boris V.

2017-09-01

We investigate the effects of interactions between ions and neutrals on the chromosphere and overlying corona using 2.5D radiative MHD simulations with the Bifrost code. We have extended the code capabilities implementing ion-neutral interaction effects using the generalized Ohm’s law, I.e., we include the Hall term and the ambipolar diffusion (Pedersen dissipation) in the induction equation. Our models span from the upper convection zone to the corona, with the photosphere, chromosphere, and transition region partially ionized. Our simulations reveal that the interactions between ionized particles and neutral particles have important consequences for the magnetothermodynamics of these modeled layers: (1) ambipolar diffusion increases the temperature in the chromosphere; (2) sporadically the horizontal magnetic field in the photosphere is diffused into the chromosphere, due to the large ambipolar diffusion; (3) ambipolar diffusion concentrates electrical currents, leading to more violent jets and reconnection processes, resulting in (3a) the formation of longer and faster spicules, (3b) heating of plasma during the spicule evolution, and (3c) decoupling of the plasma and magnetic field in spicules. Our results indicate that ambipolar diffusion is a critical ingredient for understanding the magnetothermodynamic properties in the chromosphere and transition region. The numerical simulations have been made publicly available, similar to previous Bifrost simulations. This will allow the community to study realistic numerical simulations with a wider range of magnetic field configurations and physics modules than previously possible.

Absolute total and partial dissociative cross sections of pyrimidine at electron and proton intermediate impact velocities

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

Wolff, Wania, E-mail: wania@if.ufrj.br; Luna, Hugo; Sigaud, Lucas

Absolute total non-dissociative and partial dissociative cross sections of pyrimidine were measured for electron impact energies ranging from 70 to 400 eV and for proton impact energies from 125 up to 2500 keV. MOs ionization induced by coulomb interaction were studied by measuring both ionization and partial dissociative cross sections through time of flight mass spectrometry and by obtaining the branching ratios for fragment formation via a model calculation based on the Born approximation. The partial yields and the absolute cross sections measured as a function of the energy combined with the model calculation proved to be a useful toolmore » to determine the vacancy population of the valence MOs from which several sets of fragment ions are produced. It was also a key point to distinguish the dissociation regimes induced by both particles. A comparison with previous experimental results is also presented.« less

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 computed tomography dose index (CTDI), a concept normally used in diagnostic radiology. This involved experimental determination of the fan beam thickness using the ion chambers to acquire fan beam profiles and extrapolation to a 'zero-size' detector. In conclusion, improvements have been made in the accuracy of small field dosimetry measurements in stereotactic radiotherapy and helical tomotherapy. This was completed through introduction of an original technique involving micro-CT imaging for sensitive volume determination and potentially ion chamber calibration coefficients, the use of appropriate Monte Carlo derived correction factors for RDF measurement, and the exploitation of the partial volume effect for helical tomotherapy fan beam dosimetry. With improved dosimetry for a wide range of challenging small x-ray field situations, it is expected that the patient's radiation safety will be maintained, and that clinical trials will adopt calibration protocols specialized for modern radiotherapy with small fields or beamlets. Keywords. radiation therapy, ionization chambers, small field dosimetry, stereotactic radiotherapy, helical tomotherapy, micro-CT.

Effects of low-dose ionizing radiation and menadione, an inducer of oxidative stress, alone and in combination in a vertebrate embryo model.

PubMed

Bladen, Catherine L; Kozlowski, David J; Dynan, William S

2012-11-01

Prior work has established the zebrafish embryo as an in vivo model for studying the biological effects of exposure to low doses of ionizing radiation. One of the known effects of radiation is to elevate the levels of reactive oxygen species (ROS) in tissue. However, ROS are also produced as by-products of normal metabolism and, regardless of origin, ROS produce similar chemical damage to DNA. Here we use the zebrafish embryo model to investigate whether the effects of low-dose (0-1.5 Gy) radiation and endogenous ROS are mechanistically distinct. We increased levels of endogenous ROS by exposure to low concentrations of the quinone drug, menadione. Imaging studies in live embryos showed that exposure to 3 μM or higher concentrations of menadione dramatically increased ROS levels. This treatment was associated with a growth delay and morphologic abnormalities, which were partially or fully reversible. By contrast, exposure to low doses of ionizing radiation had no discernable effects on overall growth or morphology, although, there was an increase in TUNEL-positive apoptotic cells, consistent with the results of prior studies. Further studies showed that the combined effect of radiation and menadione exposure are greater than with either agent alone, and that attenuation of the expression of Ku80, a gene important for repair of radiation-induced DNA damage, had only a slight effect on menadione sensitivity. Together, results suggest that ionizing radiation and menadione affect the embryo by distinct mechanisms.

Formation of β-FeSi 2 thin films by partially ionized vapor deposition

NASA Astrophysics Data System (ADS)

Harada, Noriyuki; Takai, Hiroshi

2003-05-01

The partially ionized vapor deposition (PIVD) is proposed as a new method to realize low temperature formation of β-FeSi 2 thin films. In this method, Fe is evaporated by E-gun and a few percents of Fe atoms are ionized. We have investigated influences of the ion content and the accelerating voltage of Fe ions on the structural properties of β-FeSi 2 films deposited on Si substrates. It was confirmed that β-FeSi 2 can be formed on Si(1 0 0) substrate by PIVD even at substrate temperature as low as 350, while FeSi by the conventional vacuum deposition. It was concluded that the influence of Fe ions on preferential orientation of β-FeSi 2 depends strongly on the content and the acceleration energy of ions.

Advanced carbon-based material C{sub 60} modification using partially ionized cluster and energetic beams

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

Du Yuancheng; Ren Zhongmin; Ning Zhifeng

1997-06-20

Two processes have been undertaken using Partially ionized cluster deposition (PICBD) and energetic ion bombardment beams deposition (IBD) respectively. C{sub 60} films deposited by PICBD at V=0 and 65 V, which result in highly textured close-packed structure in orientation (110) and being more polycrystalline respectively, the resistance of C{sub 60} films to oxygen diffusion contamination will be improved. In the case of PICBD, the ionized C{sub 60} soccer-balls molecules in the evaporation beams will be fragmented in collision with the substrate under the elevated accelerating fields Va. As a new synthetic IBD processing, two low energy (400 and 1000 eV)more » nitrogen ion beams have been used to bombard C{sub 60} films to synthesize the carbon nitride films.« less

Radiation of partially ionized atomic hydrogen

NASA Technical Reports Server (NTRS)

Soon, W. H.; Kunc, J. A.

1990-01-01

A nonlinear collisional-radiative model for determination of production of electrons, positive and negative ions, excited atoms, and spectral and continuum line intensities in stationary partially ionized atomic hydrogen is presented. Transport of radiation is included by coupling the rate equations for production of the electrons, ions, and excited atoms with the radiation escape factors, which are not constant but depend on plasma conditions. It is found that the contribution of the negative ion emission to the total continuum emission can be important. Comparison of the calculated total continuum emission coefficient, including the negative ion emission, is in good agreement with experimental results.

Collisional-radiative nonequilibrium in partially ionized atomic nitrogen

NASA Technical Reports Server (NTRS)

Kunc, J. A.; Soon, W. H.

1989-01-01

A nonlinear collisional-radiative model for determination of nonequilibrium production of electrons, excited atoms, and bound-bound, dielectronic and continuum line intensities in stationary partially ionized atomic nitrogen is presented. Populations of 14 atomic levels and line intensities are calculated in plasma with T(e) = 8000-15,000 K and N(t) = 10 to the 12th - 10 to the 18th/cu cm. Transport of radiation is included by coupling the rate equations of production of the electrons and excited atoms with the radiation escape factors, which are not constant but depend on plasma conditions.

Elastic scattering of X-rays and gamma rays by 2S electrons in ions and neutral atoms

NASA Astrophysics Data System (ADS)

Costescu, A.; Spânulescu, S.; Stoica, C.

2012-08-01

The nonrelativistic limit of Rayleigh scattering amplitude on 2s electrons of neutral and partially ionized atoms is obtained by making use of the Green Function method. The result takes into consideration the retardation, relativistic kinematics and screening effects. The spurious singularities introduced by the retardation in a nonrelativistic approach are cancelled by the relativistic kinematics. For neutral and partially ionized atoms, a screening model is considered with an effective charge obtained by fitting the Hartree-Fock charge distribution with pure Coulombian wave functions corresponding to a central potential of a nucleus with Zeff as the atomic number. The total cross section of the photoeffect on the 2s electrons is also calculated from the imaginary part of the forward scattering amplitude by means of the optical theorem. The numerical results obtained are in a good agreement (10%) with the ones obtained by Kissell for the Rayleigh amplitude and by Scofield for the Photoeffect total cross section on the 2s electrons, for atoms with atomic number 18 ≤ Z ≤ 92 and photon energies ω≤αZm. (α=1/137,... is the fine structure constant, m is the electron mass).

Ionization potential for the 1s{sup 2}2s{sup 2} of berylliumlike systems

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

Chung, K.T.; Zhu, X.W.; Wang, Z.W.

1993-05-01

The 1s{sup 2}2s{sup 2}, ground state energies of beryllium- like systems are calculated with a full-core plus correlation method. A partial saturation of basis functions method is used to extrapolated a better nonrelativistic energy. The 1s{sup 2}2s{sup 2} ionization potentials are calculated by including the relativistic corrections, mass polarization and QED effects. These results are compared with the existing theoretical and experimental data in the literature. The predicted BeI, CIII, NIV, and OV ionization potentials are within the quoted experimental error. Our result for FVI, 1267606.7 cm{sup -1}, supports the recent experiment of Engstrom, 1267606(2) cm{sup -1}, over the datummore » in the existing data tables. The predicted specific mass polarization contribution to the ionization potential for BeI, 0.00688 a.u., agrees with the 0.00674(100) a.u. from the experiment of Wen. Using the calculated results of Z=4-10, 15, and 20, we extrapolated the results for other Z systems up to Z=25 for which the ionization potentials are not explicitly computed.« less

Star of Lima - Overview and optical diagnostics of a barium Alfven critical velocity experiment

NASA Technical Reports Server (NTRS)

Wescott, E. M.; Stenbaek-Nielsen, H. C.; Hallinan, T.; Foeppl, H.; Valenzuela, A.

1986-01-01

The Alfven critical velocity mechanism for ionization of a neutral gas streaming across the magnetic field has been demonstrated in laboratory experiments. In March 1983, two rocket-borne experiments with Ba and Sr tested the effect in the wall-less laboratory of space from Punto Lobos, Peru, near 430 km altitude. 'Star of Lima' used a conical Ba shaped charge aimed at an instrument payload about 2 km away. Because of rocket overperformance the detonation occurred in partial sunlight, so that less than 21.6 percent of the ionizing UV was present. Particle and field measurements indicate the production of hot electrons and waves in the energy and frequency range that are respectively predicted to produce a cascade of ionization by the Alfven mechanism. However, the ionization fluxes and wave energy density did not reach cascade levels, and optical observations indicate that only 2.5 to 5 x 10 to the 20th Ba ions were produced. A substantial portion and perhaps all of the ionization could have been produced by solar UV. The failure of the Alfven process in this experiment is not well understood.

Structure and evolution of fossil H II regions

NASA Technical Reports Server (NTRS)

Mccray, R.; Schwarz, J.

1971-01-01

The structure and evolution of a fossil H II region created by a burst of ionizing radiation from a supernova is considered. The cooling time scale for the shell is about 10 to the 6th power years. Superposition of million-year-old fossil H II regions may account for the temperature and ionization of the interstellar medium. Fossil H II regions are unstable to growth of thermal condensations. Highly ionized filamentary structures form and dissipate in about 10,000 years. Partially ionized clouds form and dissipate in about 10 to the 6th power years.

Dosimetry using silver salts

DOEpatents

Warner, Benjamin P.

2003-06-24

The present invention provides a method for detecting ionizing radiation. Exposure of silver salt AgX to ionizing radiation results in the partial reduction of the salt to a mixture of silver salt and silver metal. The mixture is further reduced by a reducing agent, which causes the production of acid (HX) and the oxidized form of the reducing agent (R). Detection of HX indicates that the silver salt has been exposed to ionizing radiation. The oxidized form of the reducing agent (R) may also be detected. The invention also includes dosimeters employing the above method for detecting ionizing radiation.

Demystifying Introductory Chemistry. Part 3: Ionization Energies, Electronegativity, Polar Bonds, and Partial Charges.

ERIC Educational Resources Information Center

Spencer, James; And Others

1996-01-01

Shows how ionization energies provide a convenient method for obtaining electronegativity values that is simpler than the conventional methods. Demonstrates how approximate atomic charges can be calculated for polar molecules and how this method of determining electronegativities may lead to deeper insights than are typically possible for the…

Partial photoionization cross sections of NH4 and H3O Rydberg radicals

NASA Astrophysics Data System (ADS)

Velasco, A. M.; Lavín, C.; Martín, I.; Melin, J.; Ortiz, J. V.

2009-07-01

Photoionization cross sections for various Rydberg series that correspond to ionization channels of ammonium and oxonium Rydberg radicals from the outermost, occupied orbitals of their respective ground states are reported. These properties are known to be relevant in photoelectron dynamics studies. For the present calculations, the molecular-adapted quantum defect orbital method has been employed. A Cooper minimum has been found in the 3sa1-kpt2 Rydberg channel of NH4 beyond the ionization threshold, which provides the main contribution to the photoionization of this radical. However, no net minimum is found in the partial cross section of H3O despite the presence of minima in the 3sa1-kpe and 3sa1-kpa1 Rydberg channels. The complete oscillator strength distributions spanning the discrete and continuous regions of both radicals exhibit the expected continuity across the ionization threshold.

Hugoniot measurements of double-shocked precompressed dense xenon plasmas

NASA Astrophysics Data System (ADS)

Zheng, J.; Chen, Q. F.; Gu, Y. J.; Chen, Z. Y.

2012-12-01

The current partially ionized plasmas models for xenon show substantial differences since the description of pressure and thermal ionization region becomes a formidable task, prompting the need for an improved understanding of dense xenon plasmas behavior at above 100 GPa. We performed double-shock compression experiments on dense xenon to determine accurately the Hugoniot up to 172 GPa using a time-resolved optical radiation method. The planar strong shock wave was produced using a flyer plate impactor accelerated up to ˜6 km/s with a two-stage light-gas gun. The time-resolved optical radiation histories were acquired by using a multiwavelength channel optical transience radiance pyrometer. Shock velocity was measured and mass velocity was determined by the impedance-matching methods. The experimental equation of state of dense xenon plasmas are compared with the self-consistent fluid variational calculations of dense xenon in the region of partial ionization over a wide range of pressures and temperatures.

Theoretical studies of photoexcitation and ionization in H2O

NASA Technical Reports Server (NTRS)

Diercksen, G. H. F.; Kraemer, W. P.; Rescigno, T. N.; Bender, C. F.; Mckoy, B. V.; Langhoff, S. R.; Langhoff, P. W.

1982-01-01

Theoretical studies using Franck-Condon and static-exchange approximations are reported for the complete dipole excitation and ionization spectrum in H2O, where (1) large Cartesian Gaussian basis sets are used to represent the required discrete and continuum electronic eigenfunctions at the ground state equilibrium geometry, and (2) previously devised moment-theory techniques are employed in constructing the continuum oscillator-strength densities from the calculated spectra. Comparisons are made of the calculated excitation and ionization profiles with recent experimental photoabsorption studies and corresponding spectral assignments, electron impact-excitation cross sections, and dipole and synchrotron-radiation studies of partial-channel photoionization cross sections. The calculated partial-channel cross sections are found to be atomic-like, and dominated by 2p-kd components. It is suggested that the latter transition couples with the underlying 1b(1)-kb(1) channel, accounting for a prominent feature in recent synchrotron-radiation measurements.

The collisional drift mode in a partially ionized plasma. [in the F region

NASA Technical Reports Server (NTRS)

Hudson, M. K.; Kennel, C. F.

1974-01-01

The structure of the drift instability was examined in several density regimes. Let sub e be the total electron mean free path, k sub z the wave-vector component along the magnetic field, and the ratio of perpendicular ion diffusion to parallel electron streaming rates. At low densities (k sub z lambda 1) the drift mode is isothermal and should be treated kineticly. In the finite heat conduction regime square root of m/M k sub z Lambda sub 1) the drift instability threshold is reduced at low densities and increased at high densities as compared to the isothermal threshold. Finally, in the energy transfer limit (k sub z kambda sub e square root of m/M) the drift instability behaves adiabatically in a fully ionized plasma and isothermally in a partially ionized plasma for an ion-neutral to Coulomb collision frequency ratio.

Transport properties of an asymmetric mixture in the dense plasma regime

DOE PAGES

Ticknor, Christopher; Kress, Joel David; Collins, Lee A.; ...

2016-06-23

Here, we study how concentration changes ionic transport properties along isobars-isotherms for a mixture of hydrogen and silver, representative of turbulent layers relevant to inertial confinement fusion and astrophysics. Hydrogen will typically be fully ionized while silver will be only partially ionized but can have a large effective charge. This will lead to very different physical conditions for the H and Ag. Large first principles orbital free molecular dynamics simulations are performed and the resulting transport properties are analyzed. Comparisons are made with transport theory in the kinetic regime and in the coupled regime. The addition of a small amountmore » of heavy element in a light material has a dramatic effect on viscosity and diffusion of the mixture. This effect is explained through kinetic theory as a manifestation of a crossover between classical diffusion and Lorentz diffusion.« less

Iodine Plasma Species Measurements in a Hall Effect Thruster Plume

DTIC Science & Technology

2013-04-01

direction f = species fraction 0g = gravitational constant at Earth’s surface, 9.81 m/s 2 I = current, subscripts b for beam, c for cathode, d for...Hall effect thruster uses crossed electric and magnetic fields to generate and accelerate ions. The gas in the discharge is partially ionized, although...early 1960s.10 Ions are weakly magnetized and most are accelerated directly out of the channel, forming the ion beam. The bulk of the cathode

Invariant criteria for bound states, degree of ionization, and plasma phase transition

NASA Technical Reports Server (NTRS)

Girardeau, M. D.

1990-01-01

Basis invariant characterizations of bound states and bound fraction of a partially ionized hydrogen plasma are given in terms of properties of the spectrum of eigenvalues and eigenfunctions of the equilibrium quantum statistical one-proton-one-electron reduced density matrix. It is suggested that these can be used to place theories of a proposed plasma-ionization phase transition on a firm foundation. This general approach may be relevant to cosmological questions such as the quark deconfinement-confinement transition.

Effects of Low-Dose Ionizing Radiation and Menadione, an Inducer of Oxidative Stress, Alone and in Combination in a Vertebrate Embryo Model

PubMed Central

Bladen, Catherine L.; Kozlowski, David J.; Dynan, William S.

2014-01-01

Prior work has established the zebrafish embryo as an in vivo model for studying the biological effects of exposure to low doses of ionizing radiation. One of the known effects of radiation is to elevate the levels of reactive oxygen species (ROS) in tissue. However, ROS are also produced as byproducts of normal metabolism and, regardless of origin, ROS produce similar chemical damage to DNA. Here we use the zebrafish embryo model to investigate whether the effects of low-dose (0–1.5 Gy) radiation and endogenous ROS are mechanistically distinct. We increased levels of endogenous ROS by exposure to low concentrations of the quinone drug, menadione. Imaging studies in live embryos showed that exposure to 3 μM or higher concentrations of menadione dramatically increased ROS levels. This treatment was associated with a growth delay and morphologic abnormalities, which were partially or fully reversible. By contrast, exposure to low doses of ionizing radiation had no discernable effects on overall growth or morphology, although, there was an increase in TUNEL-positive apoptotic cells, consistent with the results of prior studies. Further studies showed that the combined effect of radiation and menadione exposure are greater than with either agent alone, and that attenuation of the expression of Ku80, a gene important for repair of radiation-induced DNA damage, had only a slight effect on menadione sensitivity. Together, results suggest that ionizing radiation and menadione affect the embryo by distinct mechanisms. PMID:23092554

Interrelated structures of the transport shock and collisional relaxation layer in a multitemperature, multilevel ionized gas

NASA Technical Reports Server (NTRS)

Vinolo, A. R.; Clarke, J. H.

1972-01-01

The gas dynamic structures of the transport shock and the downstream collisional relaxation layer are evaluated for partially ionized monatomic gases. Elastic and inelastic collisional nonequilibrium effects are taken into consideration. Three electronic levels are accounted for in the microscopic model of the atom. Nonequilibrium processes with respect to population of levels and species plus temperature are considered. By using an asymptotic technique the shock morphology is found on a continuum flow basis. The asymptotic procedure gives two distinct layers in which the nonequilibrium effects to be considered are different. A transport shock appears as the inner solution to an outer collisional relaxation layer in which the gas reaches local equilibrium. A family of numerical examples is displayed for different flow regimes. Argon and helium models are used in these examples.

Modeling of shallow and inefficient convection in the outer layers of the Sun using realistic physics

NASA Technical Reports Server (NTRS)

Kim, Yong-Cheol; Fox, Peter A.; Sofia, Sabatino; Demarque, Pierre

1995-01-01

In an attempt to understand the properties of convective energy transport in the solar convective zone, a numerical model has been constructed for turbulent flows in a compressible, radiation-coupled, nonmagnetic, gravitationally stratified medium using a realistic equation of state and realistic opacities. The time-dependent, three-dimensional hydrodynamic equations are solved with minimal simplifications. The statistical information obtained from the present simulation provides an improved undserstanding of solar photospheric convection. The characteristics of solar convection in shallow regions is parameterized and compared with the results of Chan & Sofia's (1989) simulations of deep and efficient convection. We assess the importance of the zones of partial ionization in the simulation and confirm that the radiative energy transfer is negliglble throughout the region except in the uppermost scale heights of the convection zone, a region of very high superadiabaticity. When the effects of partial ionization are included, the dynamics of flows are altered significantly. However, we confirm the Chan & Sofia result that kinetic energy flux is nonnegligible and can have a negative value in the convection zone.

Correlation between octanol/water and liposome/water distribution coefficients and drug absorption of a set of pharmacologically active compounds.

PubMed

Esteves, Freddy; Moutinho, Carla; Matos, Carla

2013-06-01

Absorption and consequent therapeutic action are key issues in the development of new drugs by the pharmaceutical industry. In this sense, different models can be used to simulate biological membranes to predict the absorption of a drug. This work compared the octanol/water and the liposome/water models. The parameters used to relate the two models were the distribution coefficients between liposomes and water and octanol and water and the fraction of drug orally absorbed. For this study, 66 drugs were collected from literature sources and divided into four groups according to charge and ionization degree: neutral; positively charged; negatively charged; and partially ionized/zwitterionic. The results show a satisfactory linear correlation between the octanol and liposome systems for the neutral (R²= 0.9324) and partially ionized compounds (R²= 0.9367), contrary to the positive (R²= 0.4684) and negatively charged compounds (R²= 0.1487). In the case of neutral drugs, results were similar in both models because of the high fraction orally absorbed. However, for the charged drugs (positively, negatively, and partially ionized/zwitterionic), the liposomal model has a more-appropriate correlation with absorption than the octanol model. These results show that the neutral compounds only interact with membranes through hydrophobic bonds, whereas charged drugs favor electrostatic interactions established with the liposomes. With this work, we concluded that liposomes may be a more-appropriate biomembrane model than octanol for charged compounds.

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.

Evidence for unnatural-parity contributions to electron-impact ionization of laser-aligned atoms

DOE PAGES

Armstrong, Gregory S. J.; Colgan, James Patrick; Pindzola, M. S.; ...

2015-09-11

Recent measurements have examined the electron-impact ionization of excited-state laser-aligned Mg atoms. In this paper we show that the ionization cross section arising from the geometry where the aligned atom is perpendicular to the scattering plane directly probes the unnatural parity contributions to the ionization amplitude. The contributions from natural parity partial waves cancel exactly in this geometry. Our calculations resolve the discrepancy between the nonzero measured cross sections in this plane and the zero cross section predicted by distorted-wave approaches. Finally, we demonstrate that this is a general feature of ionization from p-state targets by additional studies of ionizationmore » from excited Ca and Na atoms.« less

The temporal behaviour of MHD waves in a partially ionized prominence-like plasma: Effect of heating and cooling

NASA Astrophysics Data System (ADS)

Ballester, J. L.; Carbonell, M.; Soler, R.; Terradas, J.

2018-01-01

Context. During heating or cooling processes in prominences, the plasma microscopic parameters are modified due to the change of temperature and ionization degree. Furthermore, if waves are excited on this non-stationary plasma, the changing physical conditions of the plasma also affect wave dynamics. Aims: Our aim is to study how temporal variation of temperature and microscopic plasma parameters modify the behaviour of magnetohydrodynamic (MHD) waves excited in a prominence-like hydrogen plasma. Methods: Assuming optically thin radiation, a constant external heating, the full expression of specific internal energy, and a suitable energy equation, we have derived the profiles for the temporal variation of the background temperature. We have computed the variation of the ionization degree using a Saha equation, and have linearized the single-fluid MHD equations to study the temporal behaviour of MHD waves. Results: For all the MHD waves considered, the period and damping time become time dependent. In the case of Alfvén waves, the cut-off wavenumbers also become time dependent and the attenuation rate is completely different in a cooling or heating process. In the case of slow waves, while it is difficult to distinguish the slow wave properties in a cooling partially ionized plasma from those in an almost fully ionized plasma, the period and damping time of these waves in both plasmas are completely different when the plasma is heated. The temporal behaviour of the Alfvén and fast wave is very similar in the cooling case, but in the heating case, an important difference appears that is related with the time damping. Conclusions: Our results point out important differences in the behaviour of MHD waves when the plasma is heated or cooled, and show that a correct interpretation of the observed prominence oscillations is very important in order to put accurate constraints on the physical situation of the prominence plasma under study, that is, to perform prominence seismology.

A multispectral view of the periodic events in η Carinae†‡§¶

NASA Astrophysics Data System (ADS)

Damineli, A.; Hillier, D. J.; Corcoran, M. F.; Stahl, O.; Groh, J. H.; Arias, J.; Teodoro, M.; Morrell, N.; Gamen, R.; Gonzalez, F.; Leister, N. V.; Levato, H.; Levenhagen, R. S.; Grosso, M.; Colombo, J. F. Albacete; Wallerstein, G.

2008-06-01

A full description of the 5.5-yr low excitation events in η Carinae is presented. We show that they are not as simple and brief as previously thought, but a combination of two components. The first, the slow variation component, is revealed by slow changes in the ionization level of circumstellar matter across the whole cycle and is caused by gradual changes in the wind-wind collision shock-cone orientation, angular opening and gaseous content. The second, the collapse component, is restricted to around the minimum, and is due to a temporary global collapse of the wind-wind collision shock. High-energy photons (E > 16 eV) from the companion star are strongly shielded, leaving the Weigelt objects at low-ionization state for more than six months. High-energy phenomena are sensitive only to the collapse, low energy only to the slow variation and intermediate energies to both components. Simple eclipses and mechanisms effective only near periastron (e.g. shell ejection or accretion on to the secondary star) cannot account for the whole 5.5-yr cycle. We find anti-correlated changes in the intensity and the radial velocity of P Cygni absorption profiles in FeII λ6455 and HeI λ7065 lines, indicating that the former is associated to the primary and the latter to the secondary star. We present a set of light curves representative of the whole spectrum, useful for monitoring the next event (2009 January 11). Based partially on data collected at the OPD-LNA/MCT. Based partially on data collected at ESO telescopes. ‡ Based partially on data collected at Casleo Observatory. § Based partially on data collected at Magellan Telescopes. ¶ Based partially on data collected at CTIO. ∥ E-mail: damineli@astro.iag.usp.br

Differential cross sections for ionizations of H and H2 by 75 keV proton impact

NASA Astrophysics Data System (ADS)

Igarashi, A.; Gulyás, L.

2018-02-01

We have calculated total, partial and fully differential cross sections (FDCSs) for ionizations of H and H2 by 75 keV proton impact within the framework of the continuum-distorted-wave-eikonal-initial-state (CDW-EIS) approximation. Applying the single active electron model, the interaction between the projectile and the target ion is taken into account in the impact parameter picture. Extension of the CDW-EIS model to the molecular target is performed using the two-effective center approximation. The obtained results are compared with those of experimental and other theoretical data when available. The agreements between the theories and the experimental data are generally reasonable except for some cases of the FDCSs.

Elastic scattering of low energy electrons in partially ionized dense semiclassical plasma

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

Dzhumagulova, K. N., E-mail: dzhumagulova.karlygash@gmail.com; Shalenov, E. O.; Ramazanov, T. S.

2015-08-15

Elastic scattering of electrons by hydrogen atoms in a dense semiclassical hydrogen plasma for low impact energies has been studied. Differential scattering cross sections were calculated within the effective model of electron-atom interaction taking into account the effect of screening as well as the quantum mechanical effect of diffraction. The calculations were carried out on the basis of the phase-function method. The influence of the diffraction effect on the Ramsauer–Townsend effect was studied on the basis of a comparison with results made within the effective polarization model of the Buckingham type.

Absolute partial photoionization cross sections of ethylene

NASA Astrophysics Data System (ADS)

Grimm, F. A.; Whitley, T. A.; Keller, P. R.; Taylor, J. W.

1991-07-01

Absolute partial photoionization cross sections for ionization out of the first four valence orbitals to the X 2B 3u, A 2B 3g, B 2A g and C 2B 2u states of the C 2H 4+ ion are presented as a function of photon energy over the energy range from 12 to 26 eV. The experimental results have been compared to previously published relative partial cross sections for the first two bands at 18, 21 and 24 eV. Comparison of the experimental data with continuum multiple scattering Xα calculations provides evidence for extensive autoionization to the X 2B 3u state and confirms the predicted shape resonances in ionization to the A 2B 3g and B 2A g states. Identification of possible transitions for the autoionizing resonances have been made using multiple scattering transition state calculations on Rydberg excited states.

Consistent transport coefficients in astrophysics

NASA Technical Reports Server (NTRS)

Fontenla, Juan M.; Rovira, M.; Ferrofontan, C.

1986-01-01

A consistent theory for dealing with transport phenomena in stellar atmospheres starting with the kinetic equations and introducing three cases (LTE, partial LTE, and non-LTE) was developed. The consistent hydrodynamical equations were presented for partial-LTE, the transport coefficients defined, and a method shown to calculate them. The method is based on the numerical solution of kinetic equations considering Landau, Boltzmann, and Focker-Planck collision terms. Finally a set of results for the transport coefficients derived for a partially ionized hydrogen gas with radiation was shown, considering ionization and recombination as well as elastic collisions. The results obtained imply major changes is some types of theoretical model calculations and can resolve some important current problems concerning energy and mass balance in the solar atmosphere. It is shown that energy balance in the lower solar transition region can be fully explained by means of radiation losses and conductive flux.

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

Lee, Gyeong Won; Shim, Jaewon; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr

The influence of renormalization plasma screening on the entanglement fidelity for the elastic electron-atom scattering is investigated in partially ionized dense hydrogen plasmas. The partial wave analysis and effective interaction potential are employed to obtain the scattering entanglement fidelity in dense hydrogen plasmas as functions of the collision energy, the Debye length, and the renormalization parameter. It is found that the renormalization plasma shielding enhances the scattering entanglement fidelity. Hence, we show that the transmission of the quantum information can be increased about 10% due to the renormalization shielding effect in dense hydrogen plasmas. It is also found that themore » renormalization shielding effect on the entanglement fidelity for the electron-atom collision increases with an increase of the collision energy. In addition, the renormalization shielding function increases with increasing collision energy and saturates to the unity with an increase of the Debye length.« less

The Suzaku Observation of NGC 3516: Complex Absorption and the Broad and Narrow Fe K Lines

NASA Technical Reports Server (NTRS)

Markowitz, Alex; Reeves, James N.; Miniutti, Giovanni; Serlemitsos, Peter; Kunieda, Hideyo; Taqoob, Tahir; Fabian, Andrew C.; Fukazawa, Yasushi; Mushotzky, Richard; Okajima, Takashi;

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.

Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen.

PubMed

Buchheit, R G; Schreiner, H R; Doebbler, G F

1966-02-01

Buchheit, R. G. (Union Carbide Corp., Tonawanda, N.Y.), H. R. Schreiner, and G. F. Doebbler. Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen. J. Bacteriol. 91:622-627. 1966.-Growth rate of the fungus Neurospora crassa depends in part on the nature of metabolically "inert gas" present in its environment. At high partial pressures, the noble gas elements (helium, neon, argon, krypton, and xenon) inhibit growth in the order: Xe > Kr> Ar > Ne > He. Nitrogen (N(2)) closely resembles He in inhibitory effectiveness. Partial pressures required for 50% inhibition of growth were: Xe (0.8 atm), Kr (1.6 atm), Ar (3.8 atm), Ne (35 atm), and He ( approximately 300 atm). With respect to inhibition of growth, the noble gases and N(2) differ qualitatively and quantitatively from the order of effectiveness found with other biological effects, i.e., narcosis, inhibition of insect development, depression of O(2)-dependent radiation sensitivity, and effects on tissue-slice glycolysis and respiration. Partial pressures giving 50% inhibition of N. crassa growth parallel various physical properties (i.e., solubilities, solubility ratios, etc.) of the noble gases. Linear correlation of 50% inhibition pressures to the polarizability and of the logarithm of pressure to the first and second ionization potentials suggests the involvement of weak intermolecular interactions or charge-transfer in the biological activity of the noble gases.

Mass separation of deuterium and helium with conventional quadrupole mass spectrometer by using varied ionization energy

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

Yu, Yaowei; Hu, Jiansheng, E-mail: hujs@ipp.ac.cn; Wan, Zhao

2016-03-15

Deuterium pressure in deuterium-helium mixture gas is successfully measured by a common quadrupole mass spectrometer (model: RGA200) with a resolution of ∼0.5 atomic mass unit (AMU), by using varied ionization energy together with new developed software and dedicated calibration for RGA200. The new software is developed by using MATLAB with the new functions: electron energy (EE) scanning, deuterium partial pressure measurement, and automatic data saving. RGA200 with new software is calibrated in pure deuterium and pure helium 1.0 × 10{sup −6}–5.0 × 10{sup −2} Pa, and the relation between pressure and ion current of AMU4 under EE = 25 eVmore » and EE = 70 eV is obtained. From the calibration result and RGA200 scanning with varied ionization energy in deuterium and helium mixture gas, both deuterium partial pressures (P{sub D{sub 2}}) and helium partial pressure (P{sub He}) could be obtained. The result shows that deuterium partial pressure could be measured if P{sub D{sub 2}} > 10{sup −6} Pa (limited by ultimate pressure of calibration vessel), and helium pressure could be measured only if P{sub He}/P{sub D{sub 2}} > 0.45, and the measurement error is evaluated as 15%. This method is successfully employed in EAST 2015 summer campaign to monitor deuterium outgassing/desorption during helium discharge cleaning.« less

SOLAR HARD X-RAY SOURCE SIZES IN A BEAM-HEATED AND IONIZED CHROMOSPHERE

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

O'Flannagain, Aidan M.; Gallagher, Peter T.; Brown, John C.

2015-02-01

Solar flare hard X-rays (HXRs) are produced as bremsstrahlung when an accelerated population of electrons interacts with the dense chromospheric plasma. HXR observations presented by Kontar et al. using the Ramaty High-Energy Solar Spectroscopic Imager have shown that HXR source sizes are three to six times more extended in height than those predicted by the standard collisional thick target model (CTTM). Several possible explanations have been put forward including the multi-threaded nature of flare loops, pitch-angle scattering, and magnetic mirroring. However, the nonuniform ionization (NUI) structure along the path of the electron beam has not been fully explored as amore » solution to this problem. Ionized plasma is known to be less effective at producing nonthermal bremsstrahlung HXRs when compared to neutral plasma. If the peak HXR emission was produced in a locally ionized region within the chromosphere, the intensity of emission will be preferentially reduced around this peak, resulting in a more extended source. Due to this effect, along with the associated density enhancement in the upper chromosphere, injection of a beam of electrons into a partially ionized plasma should result in an HXR source that is substantially more vertically extended relative to that for a neutral target. Here we present the results of a modification to the CTTM, which takes into account both a localized form of chromospheric NUI and an increased target density. We find 50 keV HXR source widths, with and without the inclusion of a locally ionized region, of ∼3 Mm and ∼0.7 Mm, respectively. This helps to provide a theoretical solution to the currently open question of overly extended HXR sources.« less

The operation of 0.35 μm partially depleted SOI CMOS technology in extreme environments

NASA Astrophysics Data System (ADS)

Li, Ying; Niu, Guofu; Cressler, John D.; Patel, Jagdish; Liu, S. T.; Reed, Robert A.; Mojarradi, Mohammad M.; Blalock, Benjamin J.

2003-06-01

We evaluate the usefulness of partially depleted SOI CMOS devices fabricated in a 0.35 μm technology on UNIBOND material for electronics applications requiring robust operation under extreme environment conditions consisting of low and/or high temperature, and under substantial radiation exposure. The threshold voltage, effective mobility, and the impact ionization parameters were determined across temperature for both the nFETs and the pFETs. The radiation response was characterized using threshold voltage shifts of both the front-gate and back-gate transistors. These results suggest that this 0.35 μm partially depleted SOI CMOS technology is suitable for operation across a wide range of extreme environment conditions consisting of: cryogenic temperatures down to 86 K, elevated temperatures up to 573 K, and under radiation exposure to 1.3 Mrad(Si) total dose.

Ionized-Cluster Beam/Partially Ionized Beam Deposition of Electro- Optical and Nonlinear Optical Organic Materials and Device Development

DTIC Science & Technology

1993-08-29

4’- CH3 O--\\\\4 4N -2 nitrostilbene NO 2J (MMONS) 4’-dimethylamfino OCH3 -N-4-stylbazolium j, o3 - 200 3125 1000 tosylate (DAST)or 0 3 (CH3)2N CH3 Styrylpyridinium PH cyanine dye 400 1490 470 ( SPCD ) SO4 (CH3 ½2N lh3 20

Dopant-induced ignition of helium nanoplasmas—a mechanistic study

NASA Astrophysics Data System (ADS)

Heidenreich, Andreas; Schomas, Dominik; Mudrich, Marcel

2017-12-01

Helium (He) nanodroplets irradiated by intense near-infrared laser pulses form a nanoplasma by avalanche-like electron impact ionizations (EIIs) even at lower laser intensities where He is not directly field ionized, provided that the droplets contain a few dopant atoms which provide seed electrons for the EII avalanche. In this theoretical paper on calcium and xenon doped He droplets we elucidate the mechanism which induces ionization avalanches, termed ignition. We find that the partial loss of seed electrons from the activated droplets starkly assists ignition, as the Coulomb barrier for ionization of helium is lowered by the electric field of the dopant cations, and this deshielding of the cation charges enhances their electric field. In addition, the dopant ions assist the acceleration of the seed electrons (slingshot effect) by the laser field, supporting EIIs of He and also causing electron loss by catapulting electrons away. The dopants’ ability to lower the Coulomb barriers at He as well as the slingshot effect decrease with the spatial expansion of the dopant, causing a dependence of the dopants’ ignition capability on the dopant mass. Here, we develop criteria (impact count functions) to assess the ignition capability of dopants, based on (i) the spatial overlap of the seed electron cloud with the He atoms and (ii) the overlap of their kinetic energy distribution with the distribution of Coulomb barrier heights at He. The relatively long time delays between the instants of dopant ionization and ignition (incubation times) for calcium doped droplets are determined to a large extent by the time it takes to deshield the dopant ions.

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.

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.

Bound and continuum energy distributions of nuclear fragments resulting from tunneling ionization of molecules

NASA Astrophysics Data System (ADS)

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

2018-03-01

We present the theory of tunneling ionization of molecules with both electronic and nuclear motion treated quantum mechanically. The theory provides partial rates for ionization into the different final states of the molecular ion, including both bound vibrational and dissociative channels. The exact results obtained for a one-dimensional model of H2 and D2 are compared with two approximate approaches, the weak-field asymptotic theory and the Born-Oppenheimer approximation. The validity ranges and compatibility of the approaches are identified formally and illustrated by the calculations. The results quantify that at typical field strengths considered in strong-field physics, it is several orders of magnitude more likely to ionize into bound vibrational ionic channels than into the dissociative channel.

Studies of Quasar Outflows

NASA Technical Reports Server (NTRS)

Arav, Nahum

2002-01-01

The main aim of this research program is to determine the ionization equilibrium and abundances in quasar outflows. Especially in the broad absorption line QSO PG 0946+301. We find that the outflow's metalicity is consistent with being solar, while the abundance ratio of phosphorus to other metals is at least ten times solar. These findings are based on diagnostics that are not sensitive to saturation and partial covering effects in the BALs (Broad Adsorption Lines), which considerably weakened previous claims for enhanced metalicity. Ample evidence for these effects is seen in the spectrum.

Growth Responses of Neurospora crassa to Increased Partial Pressures of the Noble Gases and Nitrogen

PubMed Central

Buchheit, R. G.; Schreiner, H. R.; Doebbler, G. F.

1966-01-01

Buchheit, R. G. (Union Carbide Corp., Tonawanda, N.Y.), H. R. Schreiner, and G. F. Doebbler. Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen. J. Bacteriol. 91:622–627. 1966.—Growth rate of the fungus Neurospora crassa depends in part on the nature of metabolically “inert gas” present in its environment. At high partial pressures, the noble gas elements (helium, neon, argon, krypton, and xenon) inhibit growth in the order: Xe > Kr> Ar ≫ Ne ≫ He. Nitrogen (N2) closely resembles He in inhibitory effectiveness. Partial pressures required for 50% inhibition of growth were: Xe (0.8 atm), Kr (1.6 atm), Ar (3.8 atm), Ne (35 atm), and He (∼ 300 atm). With respect to inhibition of growth, the noble gases and N2 differ qualitatively and quantitatively from the order of effectiveness found with other biological effects, i.e., narcosis, inhibition of insect development, depression of O2-dependent radiation sensitivity, and effects on tissue-slice glycolysis and respiration. Partial pressures giving 50% inhibition of N. crassa growth parallel various physical properties (i.e., solubilities, solubility ratios, etc.) of the noble gases. Linear correlation of 50% inhibition pressures to the polarizability and of the logarithm of pressure to the first and second ionization potentials suggests the involvement of weak intermolecular interactions or charge-transfer in the biological activity of the noble gases. PMID:5883104

Giant plasmon excitation in single and double ionization of C60 by fast highly charged Si and O ions

NASA Astrophysics Data System (ADS)

Kelkar, A. H.; Kadhane, U.; Misra, D.; Tribedi, L. C.

2007-09-01

Se have investigated single and double ionization of C60 molecule in collisions with 2.33 MeV/u Siq+ (q=6-14) and 3.125 MeV/u Oq+ (q=5-8) projectiles. The projectile charge state dependence of the single and double ionization yields of C60 are then compared to those for an ion-atom collision system using Ne gas as a target. A large difference between the gas and the cluster target behaviour was partially explained in terms of a model based on collective excitation namely the giant dipole plasmon resonance (GDPR). The qualitative agreement between the data and GDPR model prediction for single and double ionization signifies the importance of single and double plasmon excitations in the ionization process. A large deviation of the GDPR model for triple and quadruple ionization from the experimental data imply the importance of the other low impact parameter processes such as evaporation, fragmentation and a possible solid-like dynamical screening.

An equation of state for partially ionized plasmas: The Coulomb contribution to the free energy

NASA Astrophysics Data System (ADS)

Kilcrease, D. P.; Colgan, J.; Hakel, P.; Fontes, C. J.; Sherrill, M. E.

2015-09-01

We have previously developed an equation of state (EOS) model called ChemEOS (Hakel and Kilcrease, Atomic Processes in Plasmas, Eds., J. Cohen et al., AIP, 2004) for a plasma of interacting ions, atoms and electrons. It is based on a chemical picture of the plasma and is derived from an expression for the Helmholtz free energy of the interacting species. All other equilibrium thermodynamic quantities are then obtained by minimizing this free energy subject to constraints, thus leading to a thermodynamically consistent EOS. The contribution to this free energy from the Coulomb interactions among the particles is treated using the method of Chabrier and Potekhin (Phys. Rev. E 58, 4941 (1998)) which we have adapted for partially ionized plasmas. This treatment is further examined and is found to give rise to unphysical behavior for various elements at certain values of the density and temperature where the Coulomb coupling begins to become significant and the atoms are partially ionized. We examine the source of this unphysical behavior and suggest corrections that produce acceptable results. The sensitivity of the thermodynamic properties and frequency-dependent opacity of iron is examined with and without these corrections. The corrected EOS is used to determine the fractional ion populations and level populations for a new generation of OPLIB low-Z opacity tables currently being prepared at Los Alamos National Laboratory with the ATOMIC code.

Partial-reflection studies of D-region winter variability. [electron density measurements

NASA Technical Reports Server (NTRS)

Denny, B. W.; Bowhill, S. A.

1973-01-01

D-region electron densities were measured from December, 1972, to July, 1973, at Urbana, Illinois (latitude 40.2N) using the partial-reflection technique. During the winter, electron densities at altitudes of 72, 76.5, and 81 km show cyclical changes with a period of about 5 days that are highly correlated between these altitudes, suggesting that the mechanism responsible for the winter anomaly in D-region ionization applies throughout this height region. From January 13 to February 3, a pronounced wave-like variation occurred in the partial-reflection measurements, apparently associated with a major stratospheric warming that developed in that period. During the same time period, a traveling periodic variation is observed in the 10-mb height; it is highly correlated with the partial-reflection measurements. Electron density enhancements occur approximately at the same time as increases in the 10-mb height. Comparison of AL and A3 absorption measurements with electron density measurements below 82 km indicates that the winter anomaly in D-region ionization is divided into two types. Type 1, above about 82 km, extends horizontally for about 200 km while type 2, below about 82 km, extends for a horizontal scale of at least 1000 km.

Partially ionized gas flow and heat transfer in the separation, reattachment, and redevelopment regions downstream of an abrupt circular channel expansion.

NASA Technical Reports Server (NTRS)

Back, L. H.; Massier, P. F.; Roschke, E. J.

1972-01-01

Heat transfer and pressure measurements obtained in the separation, reattachment, and redevelopment regions along a tube and nozzle located downstream of an abrupt channel expansion are presented for a very high enthalpy flow of argon. The ionization energy fraction extended up to 0.6 at the tube inlet just downstream of the arc heater. Reattachment resulted from the growth of an instability in the vortex sheet-like shear layer between the central jet that discharged into the tube and the reverse flow along the wall at the lower Reynolds numbers, as indicated by water flow visualization studies which were found to dynamically model the high-temperature gas flow. A reasonably good prediction of the heat transfer in the reattachment region where the highest heat transfer occurred and in the redevelopment region downstream can be made by using existing laminar boundary layer theory for a partially ionized gas. In the experiments as much as 90 per cent of the inlet energy was lost by heat transfer to the tube and the nozzle wall.

Indirect contributions to electron-impact ionization of Li+ (1 s 2 s S31 ) ions: Role of intermediate double-K -vacancy states

NASA Astrophysics Data System (ADS)

Müller, A.; Borovik, A.; Huber, K.; Schippers, S.; Fursa, D. V.; Bray, I.

2018-02-01

Fine details of the cross section for electron-impact ionization of metastable two-electron Li+(1 s 2 s S31) ions are scrutinized by both experiment and theory. Beyond direct knockoff ionization, indirect ionization mechanisms proceeding via formation of intermediate double-K-vacancy (hollow) states either in a Li+ ion or in a neutral lithium atom and subsequent emission of one or two electrons, respectively, can contribute to the net production of Li2 + ions. The partial cross sections for such contributions are less than 4% of the total single-ionization cross section. The characteristic steps, resonances, and interference phenomena in the indirect ionization contribution are measured with an experimental energy spread of less than 0.9 eV and with a statistical relative uncertainty of the order of 1.7%, requiring a level of statistical uncertainty in the total single-ionization cross section of better than 0.05%. The measurements are accompanied by convergent-close-coupling calculations performed on a fine energy grid. Theory and experiment are in remarkable agreement concerning the fine details of the ionization cross section. Comparison with previous R-matrix results is less favorable.

Applicability of post-ionization theory to laser-assisted field evaporation of magnetite

DOE PAGES

Schreiber, Daniel K.; Chiaramonti, Ann N.; Gordon, Lyle M.; ...

2014-12-15

Analysis of the mean Fe ion charge state from laser-assisted field evaporation of magnetite (Fe3O4) reveals unexpected trends as a function of laser pulse energy that break from conventional post-ionization theory for metals. For Fe ions evaporated from magnetite, the effects of post-ionization are partially offset by the increased prevalence of direct evaporation into higher charge states with increasing laser pulse energy. Therefore the final charge state is related to both the field strength and the laser pulse energy, despite those variables themselves being intertwined when analyzing at a constant detection rate. Comparison of data collected at different base temperaturesmore » also show that the increased prevalence of Fe2+ at higher laser energies is possibly not a direct thermal effect. Conversely, the ratio of 16O+:16O2+ is well-correlated with field strength and unaffected by laser pulse energy on its own, making it a better overall indicator of the field evaporation conditions than the mean Fe charge state. Plotting the normalized field strength versus laser pulse energy also elucidates a non-linear dependence, in agreement with previous observations on semiconductors, that suggests a field-dependent laser absorption efficiency. Together these observations demonstrate that the field evaporation process for laser-pulsed oxides exhibits fundamental differences from metallic specimens that cannot be completely explained by post-ionization theory. Further theoretical studies, combined with detailed analytical observations, are required to understand fully the field evaporation process of non-metallic samples.« less

Determination of the microenvironment-pH and charge and size characteristics of amino acids through their electrophoretic mobilities determined by CZE.

PubMed

Piaggio, Maria V; Peirotti, Marta B; Deiber, Julio A

2007-10-01

Effective electrophoretic mobility data of 20 amino acids reported in the literature are analyzed and interpreted through simple physicochemical models, which are able to provide estimates of coupled quantities like hydrodynamic shape factor, equivalent hydrodynamic radius (size), net charge, actual pK values of ionizing groups, partial charges of ionizing groups, hydration number, and pH near molecule (microenvironment-pH of the BGE). It is concluded that the modeling of the electrophoretic mobility of these analytes requires a careful consideration of hydrodynamic shape coupled to hydration. In the low range of pH studied here, distinctive hydrodynamic behaviors of amino acids are found. For instance, amino acids with basic polar and ionizing side chain remain with prolate shape for pH values varying from 1.99 to 3.2. It is evident that as the pH increases from low values, amino acids get higher hydrations as a consequence each analyte total charge also increases. This result is consistent with the monotonic increase of the hydrodynamic radius, which accounts for both the analyte and the quite immobilized water molecules defining the electrophoretic kinematical unit. It is also found that the actual or effective pK value of the alpha-carboxylic ionizing group of amino acids increases when the pH is changed from 1.99 to 3.2. Several limitations concerning the simple modeling of the electrophoretic mobility of amino acids are presented for further research.

Effect of ionizing radiation on some quality attributes of nutraceutically valued lotus seeds.

PubMed

Bhat, Rajeev; Karim, A A

2009-01-01

Radiation processing has been employed successfully for value addition of food and agricultural products. Preliminary studies were undertaken to evaluate the changes induced by ionizing radiation (up to 30 kGy), in the form of gamma irradiation and electron beam irradiation, on some quality attributes and nutritive values of nutraceutically valued lotus seeds. Significant loss in seed firmness was recorded between control and irradiated seeds, irrespective of radiation source. Similarly, the specific viscosity of irradiated lotus seeds decreased significantly up to a dose of 7.5 kGy. Starch increased after exposure to gamma or electron beam irradiation, whereas the total phenolic contents were decreased. Gamma irradiation revealed an enhancement in protein, while the electron beam showed a decrease. Partial oxidation of the seeds during radiation treatments might have occurred as evidenced from the decomposition profiles (thermogravimetry) during heating. It is evident that ionizing radiation brought about significant and variable changes in the quality and nutritive values of lotus seed. Further exploration of this technology for safety and quality is warranted.

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

Oliver, R.; Soler, R.; Terradas, J.

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

Space colonization - Some physiological perspectives

NASA Technical Reports Server (NTRS)

Winkler, L. H.

1978-01-01

Physiological criteria determining the design of the habitat for a space colony with 10,000 people are discussed. Centrifugally generated earth-normal gravity, maximum ionizing radiation dose standards less than or equal to 0.5 rem/year (obtained with passive shielding), and an atmosphere with reduced nitrogen partial pressures were established as design requirements for the habitat. However, further research is needed to determine whether humans experience complete adaptation to weightlessness and whether there are long-term effects of breathing various atmospheric mixtures and pressures.

The X-ray and ultraviolet absorbing outflow in 3C 351

NASA Astrophysics Data System (ADS)

Mathur, Smita; Wilkes, Belinda; Elvis, Martin; Fiore, Fabrizio

1994-10-01

3C 351 (z = 0.371), and X-ray-'quiet' quasar, is one of the few quasars showing signs of a 'warm absorber' in its X-ray spectrum; i.e., partially ionized absorbing material in the line of sight whose opacity depends on its ionization structure. The main feature in the X-ray spectrum is a K-edge due to O VII or O VIII. 3C 351 also shows unusually strong, blueshifted, associated, absorption lines in the ultraviolet (Bahcall et al. 1993) including O VI (lambda lambda 1031, 1037). This high ionization state strongly suggests an identification with the X-ray absorber and a site within the active nucleus. In this paper we demonstrate that the X-ray and UV absorption is due to the same material. This is the first confirmed UV/X-ray absorber. Physical conditions of the absorber are determined through the combination of constraints derived from both the X-ray and UV analysis. This highly ionized, outflowing, low-density, high-column density absorber situated outside the broad emission line region (BELR) is a previously unknown component of nuclear material. We rule out the identification of the absorber with a BELR cloud as the physical conditions in the two regions are inconsistent with one another. The effect of the X-ray quietness and IR upturn in the 3C 351 continuum on the BELR is also investigated. The strengths of the high-ionization lines of C IV lambda-1549 and O VI lambda-1034 with respect to Lyman-alpha are systematically lower (up to a factor of 10) in the material ionized by the 3C 351 continuum as compared to those produced by the 'standard' quasar continuum, the strongest effect being on the strength of O VI lambda-1034. We find that for a 3C 351-like continuum, C III) lambda-1909 ceases to be a density indicator.

Dynamic correlation effects in fully differential cross sections for 75-keV proton-impact ionization of helium

NASA Astrophysics Data System (ADS)

Niu, Xiaojie; Sun, Shiyan; Wang, Fujun; Jia, Xiangfu

2017-08-01

The effect of final-state dynamic correlation is investigated for helium single ionization by 75-keV proton impact analyzing fully differential cross sections (FDCS). The final state is represented by a continuum correlated wave (CCW-PT) function which accounts for the interaction between the projectile and the residual target ion (PT interaction). This continuum correlated wave function partially includes the correlation of electron-projectile and electron-target relative motion as coupling terms of the wave equation. The transition matrix is evaluated using the CCW-PT function and the Born initial state. The analytical expression of the transition matrix has been obtained. We have shown that this series is strongly convergent and analyzed the contribution of their different terms to the FDCS within the perturbation method. Illustrative computations are performed in the scattering plane and in the perpendicular plane. Both the correlation effects and the PT interaction are checked by the preset calculations. Our results are compared with absolute experimental data as well as other theoretical models. We have shown that the dynamic correlation plays an important role in the single ionization of atoms by proton impact at intermediate projectile energies, especially at large transverse momentum transfer. While overall agreement between theory and the experimental data is encouraging, detailed agreement is lacking. The need for more theoretical and experimental work is emphasized.

Magnetic Reconnection in Strongly Magnetized Regions of the Low Solar Chromosphere

NASA Astrophysics Data System (ADS)

Ni, Lei; Lukin, Vyacheslav S.; Murphy, Nicholas A.; Lin, Jun

2018-01-01

Magnetic reconnection in strongly magnetized regions around the temperature minimum region of the low solar atmosphere is studied by employing MHD-based simulations of a partially ionized plasma within a reactive 2.5D multi-fluid model. It is shown that in the absence of magnetic nulls in a low β plasma, the ionized and neutral fluid flows are well-coupled throughout the reconnection region. However, non-equilibrium ionization–recombination dynamics play a critical role in determining the structure of the reconnection region, leading to much lower temperature increases and a faster magnetic reconnection rate as compared to simulations that assume plasma to be in ionization–recombination equilibrium. The rate of ionization of the neutral component of the plasma is always faster than recombination within the current sheet region even when the initial plasma β is as high as {β }0=1.46. When the reconnecting magnetic field is in excess of a kilogauss and the plasma β is lower than 0.0145, the initially weakly ionized plasmas can become fully ionized within the reconnection region and the current sheet can be strongly heated to above 2.5× {10}4 K, even as most of the collisionally dissipated magnetic energy is radiated away. The Hall effect increases the reconnection rate slightly, but in the absence of magnetic nulls it does not result in significant asymmetries or change the characteristics of the reconnection current sheet down to meter scales.

Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

NASA Astrophysics Data System (ADS)

Lichtenberg, Dennis L.

During this period some important breakthroughs were accomplished in understanding the relationships between molecular ionization energies and bond energies in transition metal complexes, in understanding the electronic factors of carbon-hydrogen bond activation by transition metals, in characterizing small molecule bonding interactions with transition metals, and in investigating intermolecular interactions in thin films of transition metal complexes. The formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies was developed into a single equation which unifies the treatment of covalent bonds, ionic bonds, and partially ionic bonds. The relationship was used to clarify the fundamental thermodynamic information relating to metal-hydrogen, metal-alkyl, and metal-metal bond energies. The ionization energies were also used to correlate the rates of carbonyl substitution reactions of (eta(sup 5)-C5H4X)Rh(CO)2 complexes, and to reveal the factors that control the stability of the transition state. The investigations of the fundamental interactions of C-H sigma and sigma* orbitals metals were continued with study of eta(sup 3)-1-methylallyl metal complexes. Direct observation and measurement of the stabilization energy provided by the agostic interaction of the C-H bond with the metal was obtained. The ability to observe the electronic effects of intermolecular interactions by comparing the ionizations of metal complexes in the gas phase with the ionizations of thin solid organometallic films prepared in ultra-high vacuum was established. Most significantly, the scanning tunneling microscope imaging of these thin films was accomplished.

Introduction to total- and partial-pressure measurements in vacuum systems

NASA Technical Reports Server (NTRS)

Outlaw, R. A.; Kern, F. A.

1989-01-01

An introduction to the fundamentals of total and partial pressure measurement in the vacuum regime (760 x 10 to the -16th power Torr) is presented. The instrument most often used in scientific fields requiring vacuum measurement are discussed with special emphasis on ionization type gauges and quadrupole mass spectrometers. Some attention is also given to potential errors in measurement as well as calibration techniques.

How to examine soil sorption of ionizable organic compounds and avoid varying pH?

NASA Astrophysics Data System (ADS)

Borisover, Mikhail

2017-04-01

Multiple natural and anthropogenic organic compounds including new and emerging pollutants undergo ionization in aqueous solutions, and their sorption by soils and sediments is contributed by presence of both molecular and ionized species. Better understanding of environmental fate of organic chemicals requires taking into account interactions of molecular and ionized species with environmental sorbents. A "standard" (and undoubtedly important) procedure for differentiating contributions of molecular and ionized species into the overall soil sorption of an organic compound involves varying pH of solution in batch sorption experiments. However, varying pH is (1) often not possible, without destroying a sorbent, e.g., due to the buffer capacity of soils containing carbonates, (2) difficult for further interpretation, since it changes not only the ionization status of a solute in a solution but also the sorbent structure, e.g., a conformation of organic matter, and/or ionization of surface functional groups, (3) making difficult (or even impossible) to explicitly evaluate the role of dissolved species-bulk water interactions, directly affecting the affinity of a sorbate to distribute between water and a sorbent. Indeed, both molecular and ionized species undergo interactions with the solvent bulk and, at least in the case of the ionized ones, there was no a simple way to quantify organic ion-water interactions and their role in organic ion distribution between soil and water phases. This paper presents a "counter-intuitive" approach to examine sorption interactions of an ionizable compound, without experimenting with varied pH. The approach is based on an idea of replacing an initial state in sorption transfer of an ionizable compound from the solvent bulk to a solvated (hydrated) sorbed state: a traditional coefficient describing distribution of a partially ionized compound between a hydrated sorbent and a co-equilibrated aqueous phase is converted to the coefficient describing the transfer of the sorbing compound from its initial molecular (non-ionized) state (in a solution or in the gas phase) to the final hydrated sorbed state equilibrated with the actual aqueous solution of this ionizable compound. In this way, any contributions from the bulk solvent-organic ion interactions into the sorption transfer may be excluded; in addition, further any solute-solvent interactions may be taken out of the consideration. Therefore, compound's sorption characteristics "cleared" of solute-solvent interactions may be obtained, and a better understanding of relations between interactions in a sorbed phase and a molecular structure of organic sorbates can be reached. The approach is illustrated by examining sorption of variously ionized organic compounds, i.e., those belonging to the pharmaceuticals and personal care products (triclosan, gemfibrozil, galaxolide), and aliphatic organic acids on natural and organic amendment-enriched soils. Specifically, it is demonstrated how the greater H-donating ability of trifluoroacetic acid, as compared with acetic acid, strengthens the acid interactions in the soil phase. In another series of examples, it is shown how hydrophobic and non-ionizing galaxolide interacts weakly with soils, as compared with partially ionized triclosan and almost fully ionized gemfibrozil, i.e., leading to the conclusions not reachable based only on the direct comparison of experimentally measured distribution coefficients.

Valence ionized states of iron pentacarbonyl and eta5-cyclopentadienyl cobalt dicarbonyl studied by symmetry-adapted cluster-configuration interaction calculation and collision-energy resolved Penning ionization electron spectroscopy.

PubMed

Fukuda, Ryoichi; Ehara, Masahiro; Nakatsuji, Hiroshi; Kishimoto, Naoki; Ohno, Koichi

2010-02-28

Valence ionized states of iron pentacarbonyl Fe(CO)(5) and eta(5)-cyclopentadienyl cobalt dicarbonyl Co(eta(5)-C(5)H(5))(CO)(2) have been studied by ultraviolet photoelectron spectroscopy, two-dimensional Penning ionization electron spectroscopy (2D-PIES), and symmetry-adapted cluster-configuration interaction calculations. Theory provided reliable assignments for the complex ionization spectra of these molecules, which have metal-carbonyl bonds. Theoretical ionization energies agreed well with experimental observations and the calculated wave functions could explain the relative intensities of PIES spectra. The collision-energy dependence of partial ionization cross sections (CEDPICS) was obtained by 2D-PIES. To interpret these CEDPICS, the interaction potentials between the molecules and a Li atom were examined in several coordinates by calculations. The relation between the slope of the CEDPICS and the electronic structure of the ionized states, such as molecular symmetry and the spatial distribution of ionizing orbitals, was analyzed. In Fe(CO)(5), an attractive interaction was obtained for the equatorial CO, while the interaction for the axial CO direction was repulsive. For Co(eta(5)-C(5)H(5))(CO)(2), the interaction potential in the direction of both Co-C-O and Co-Cp ring was attractive. These anisotropic interactions and ionizing orbital distributions consistently explain the relative slopes of the CEDPICS.

An equation of state for partially ionized plasmas: The Coulomb contribution to the free energy

DOE PAGES

Kilcrease, D. P.; Colgan, J.; Hakel, P.; ...

2015-06-20

We have previously developed an equation of state (EOS) model called ChemEOS (Hakel and Kilcrease, Atomic Processes in Plasmas, Eds., J. Cohen et al., AIP, 2004) for a plasma of interacting ions, atoms and electrons. It is based on a chemical picture of the plasma and is derived from an expression for the Helmholtz free energy of the interacting species. All other equilibrium thermodynamic quantities are then obtained by minimizing this free energy subject to constraints, thus leading to a thermodynamically consistent EOS. The contribution to this free energy from the Coulomb interactions among the particles is treated using themore » method of Chabrier and Potekhin (Phys. Rev. E 58, 4941 (1998)) which we have adapted for partially ionized plasmas. This treatment is further examined and is found to give rise to unphysical behavior for various elements at certain values of the density and temperature where the Coulomb coupling begins to become significant and the atoms are partially ionized. We examine the source of this unphysical behavior and suggest corrections that produce acceptable results. The sensitivity of the thermodynamic properties and frequency-dependent opacity of iron is examined with and without these corrections. Lastly, the corrected EOS is used to determine the fractional ion populations and level populations for a new generation of OPLIB low-Z opacity tables currently being prepared at Los Alamos National Laboratory with the ATOMIC code.« less

Partial discharge testing of bulk transformer oil

NASA Astrophysics Data System (ADS)

Rohwein, G. J.

The generation of partial discharges in bulk transformer oil was investigated experimentally to determine the dominant conditions which contribute to their formation and growth under repetitive impulse stresses. The motivation for conducting these experiments arose from a problem with partial discharges and breakdowns occurring in the insulating oil around the high voltage switch in a continuous running 1.5 MV repetitive pulser system. From the experiment it was found tht repetitive stressing caused low level field ionization around the electrodes which led to bubble formation and eventually partial discharges. There were also qualitative indications of charge accumulation in the oil. Photographic records of numerous shot sequences were used to study the phenomena.

Photoexcitation and ionization in carbon dioxide - Theoretical studies in the separated-channel static-exchange approximation

NASA Technical Reports Server (NTRS)

Padial, N.; Csanak, G.; Mckoy, B. V.; Langhoff, P. W.

1981-01-01

Vertical-electronic static-exchange photoexcitation and ionization cross sections are reported which provide a first approximation to the complete dipole spectrum of CO2. Separated-channel static-exchange calculations of vertical-electronic transition energies and oscillator strengths, and Stieltjes-Chebyshev moment methods were used in the development. Detailed comparisons were made of the static-exchange excitation and ionization spectra with photoabsorption, electron-impact excitation, and quantum-defect estimates of discrete transition energies and intensities, and with partial-channel photoionization cross sections obtained from fluorescence measurements and from tunable-source and (e, 2e) photoelectron spectroscopy. Results show that the separate-channel static-exchange approximation is generally satisfactory in CO2.

Photoionization Modeling

NASA Technical Reports Server (NTRS)

Kallman, T.

2010-01-01

Warm absorber spectra are characterized by the many lines from partially ionized intermediate-Z elements, and iron, detected with the grating instruments on Chandra and XMM-Newton. If these ions are formed in a gas which is in photoionization equilibrium, they correspond to a broad range of ionization parameters, although there is evidence for certain preferred values. A test for any dynamical model for these outflows is to reproduce these properties, at some level of detail. In this paper we present a statistical analysis of the ionization distribution which can be applied both the observed spectra and to theoretical models. As an example, we apply it to our dynamical models for warm absorber outflows, based on evaporation from the molecular torus.

Absolute photoionization cross sections of two cyclic ketones: cyclopentanone and cyclohexanone.

PubMed

Price, Chelsea; Fathi, Yasmin; Meloni, Giovanni

2017-05-01

Absolute photoionization cross sections for cyclopentanone and cyclohexanone, as well as partial ionization cross sections for the dissociative ionized fragments, are presented in this investigation. Experiments are performed via a multiplexed photoionization mass spectrometer utilizing vacuum ultraviolet (VUV) synchrotron radiation supplied by the Advanced Light Source of Lawrence Berkeley National Laboratory. These results allow the quantification of these species that is relevant to investigate the kinetics and combustion reactions of potential biofuels. The CBS-QB3 calculated values for the adiabatic ionization energies agree well with the experimental values, and the identification of possible dissociative fragments is discussed for both systems. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

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.

Single and double multiphoton ionization of Li and Be atoms by strong laser fields

NASA Astrophysics Data System (ADS)

Telnov, Dmitry; Heslar, John; Chu, Shih-I.

2011-05-01

The time-dependent density functional theory with self-interaction correction and proper asymptotic long-range potential is extended for nonperturbative treatment of multiphoton single and double ionization of Li and Be atoms by strong 800 nm laser fields. We make use of the time-dependent Krieger-Li-Iafrate (TDKLI) exchange-correlation potential with the integer discontinuity which improves the description of the double ionization process. However, we have found that the discontinuity of the TDKLI potential is not sufficient to reproduce the characteristic feature of double ionization. This may happen because the discontinuity of the TDKLI potential is related to the spin particle numbers only and not to the total particle number. Introducing a discontinuity with respect to the total particle number to the exchange-correlation potential, we were able to obtain the knee structure in the intensity dependence of the double ionization probability of Be. This work was partially supported by DOE and NSF and by NSC-Taiwan.

Mathematical physics approaches to lightning discharge problems

NASA Technical Reports Server (NTRS)

Kyrala, A.

1985-01-01

Mathematical physics arguments useful for lightning discharge and generation problems are pursued. A soliton Ansatz for the lightning stroke is treated including a charge generation term which is the ultimate source for the phenomena. Equations are established for a partially ionized plasma inding the effects of pressure, magnetic field, electric field, gravitation, viscosity, and temperature. From these equations is then derived the non-stationary generalized Ohm's Law essential for describing field/current density relationships in the horizon channel of the lightning stroke. The discharge initiation problem is discussed. It is argued that the ionization rate drives both the convective current and electric displacement current to increase exponentially. The statistical distributions of charge in the thundercloud preceding a lightning dischage are considered. The stability of the pre-lightning charge distributions and the use of Boltzmann relaxational equations to determine them are discussed along with a covered impedance path provided by the aircraft.

Laser-driven acceleration of electrons in a partially ionized plasma channel.

PubMed

Rowlands-Rees, T P; Kamperidis, C; Kneip, S; Gonsalves, A J; Mangles, S P D; Gallacher, J G; Brunetti, E; Ibbotson, T; Murphy, C D; Foster, P S; Streeter, M J V; Budde, F; Norreys, P A; Jaroszynski, D A; Krushelnick, K; Najmudin, Z; Hooker, S M

2008-03-14

The generation of quasimonoenergetic electron beams, with energies up to 200 MeV, by a laser-plasma accelerator driven in a hydrogen-filled capillary discharge waveguide is investigated. Injection and acceleration of electrons is found to depend sensitively on the delay between the onset of the discharge current and the arrival of the laser pulse. A comparison of spectroscopic and interferometric measurements suggests that injection is assisted by laser ionization of atoms or ions within the channel.

Design Features and Commissioning of the Versatile Experiment Spherical Torus (VEST) at Seoul National University

NASA Astrophysics Data System (ADS)

J. Chung, K.; H. An, Y.; K. Jung, B.; Y. Lee, H.; C., Sung; S. Na, Y.; S. Hahm, T.; S. Hwang, Y.

2013-03-01

A new spherical torus called VEST (Versatile Experiment Spherical Torus) is designed, constructed and successfully commissioned at Seoul National University. A unique design feature of the VEST is two partial solenoid coils installed at both vertical ends of a center stack, which can provide sufficient magnetic fluxes to initiate tokamak plasmas while keeping a low aspect ratio configuration in the central region. According to initial double null merging start-up scenario using the partial solenoid coils, appropriate power supplies for driving a toroidal field coil, outer poloidal field coils, and the partial solenoid coils are fabricated and successfully commissioned. For reliable start-up, a pre-ionization system with two cost-effective homemade magnetron power supplies is also prepared. In addition, magnetic and spectroscopic diagnostics with appropriate data acquisition and control systems are well prepared for initial operation of the device. The VEST is ready for tokamak plasma operation by completing and commissioning most of the designed components.

Partially ionized plasmas including the third symposium on uranium plasmas

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

Krishnan, M.

1976-09-01

Separate abstracts are included for 28 papers on electrically generated plasmas, fission generated plasmas, nuclear pumped lasers, gaseous fuel reactor research, and applications. Five papers have been previously abstracted and included in ERA.

Correction factors for ionization chamber measurements with the ‘Valencia’ and ‘large field Valencia’ brachytherapy applicators

NASA Astrophysics Data System (ADS)

Gimenez-Alventosa, V.; Gimenez, V.; Ballester, F.; Vijande, J.; Andreo, P.

2018-06-01

Treatment of small skin lesions using HDR brachytherapy applicators is a widely used technique. The shielded applicators currently available in clinical practice are based on a tungsten-alloy cup that collimates the source-emitted radiation into a small region, hence protecting nearby tissues. The goal of this manuscript is to evaluate the correction factors required for dose measurements with a plane-parallel ionization chamber typically used in clinical brachytherapy for the ‘Valencia’ and ‘large field Valencia’ shielded applicators. Monte Carlo simulations have been performed using the PENELOPE-2014 system to determine the absorbed dose deposited in a water phantom and in the chamber active volume with a Type A uncertainty of the order of 0.1%. The average energies of the photon spectra arriving at the surface of the water phantom differ by approximately 10%, being 384 keV for the ‘Valencia’ and 343 keV for the ‘large field Valencia’. The ionization chamber correction factors have been obtained for both applicators using three methods, their values depending on the applicator being considered. Using a depth-independent global chamber perturbation correction factor and no shift of the effective point of measurement yields depth-dose differences of up to 1% for the ‘Valencia’ applicator. Calculations using a depth-dependent global perturbation factor, or a shift of the effective point of measurement combined with a constant partial perturbation factor, result in differences of about 0.1% for both applicators. The results emphasize the relevance of carrying out detailed Monte Carlo studies for each shielded brachytherapy applicator and ionization chamber.

Progress report on the Heavy Ions in Space (HIIS) experiment

NASA Technical Reports Server (NTRS)

Adams, James H., Jr.; Beahm, Lorraine P.; Boberg, Paul R.; Tylka, Allan J.

1993-01-01

One of the objectives of the Heavy Ions In Space (HIIS) experiment is to investigate heavy ions which appear at Long Duration Exposure Facility (LDEF) below the geomagnetic cutoff for fully-ionized galactic cosmic rays. Possible sources of such 'below-cutoff' particles are partially-ionized solar energetic particles, the anomalous component of cosmic rays, and magnetospherically-trapped particles. In recent years, there have also been reports of below-cutoff ions which do not appear to be from any known source. Although most of these observations are based on only a handful of ions, they have led to speculation about 'partially-ionized galactic cosmic rays' and 'near-by cosmic ray sources'. The collecting power of HIIS is order of magnitude larger than that of the instruments which reported these results, so HIIS should be able to confirm these observations and perhaps discover the source of these particles. Preliminary results on below-cutoff heavy-ions are reported. Observations to possible known sources of such ions are compared. A second objective of the HIIS experiment is to measure the elemental composition of ultraheavy galactic cosmic rays, beginning in the tin-barium region of the periodic table. A report on the status of this analysis is presented.

ASYMMETRIC MAGNETIC RECONNECTION IN WEAKLY IONIZED CHROMOSPHERIC PLASMAS

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

Murphy, Nicholas A.; Lukin, Vyacheslav S., E-mail: namurphy@cfa.harvard.edu

2015-06-01

Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection,more » the current sheet thins to the scale of the neutral–ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak-field (high-density) upstream region into the strong-field upstream region results from a neutral pressure gradient. Consequently, neutrals dragged along with the outflow are more likely to originate from the weak-field region. The Hall effect leads to the development of a characteristic quadrupole magnetic field modified by asymmetry, but the X-point geometry expected during Hall reconnection does not occur. All simulations show the development of plasmoids after an initial laminar phase.« less

The accuracy of seminumerical reionization models in comparison with radiative transfer simulations

NASA Astrophysics Data System (ADS)

Hutter, Anne

2018-06-01

We have developed a modular seminumerical code that computes the time and spatially dependent ionization of neutral hydrogen (H I), neutral (He I), and single-ionized helium (He II) in the intergalactic medium (IGM). The model accounts for recombinations and provides different descriptions for the photoionization rate that are used to calculate the residual H I fraction in ionized regions. We compare different seminumerical reionization schemes to a radiative transfer (RT) simulation. We use the RT simulation as a benchmark, and find that the seminumerical approaches produce similar H II and He II morphologies and power spectra of the H I 21 cm signal throughout reionization. As we do not track partial ionization of He II, the extent of the double-ionized helium (He III) regions is consistently smaller. In contrast to previous comparison projects, the ionizing emissivity in our seminumerical scheme is not adjusted to reproduce the redshift evolution of the RT simulation, but directly derived from the RT simulation spectra. Among schemes that identify the ionized regions by the ratio of the number of ionization and absorption events on different spatial smoothing scales, we find those that mark the entire sphere as ionized when the ionization criterion is fulfilled to result in significantly accelerated reionization compared to the RT simulation. Conversely, those that flag only the central cell as ionized yield very similar but slightly delayed redshift evolution of reionization, with up to 20 per cent ionizing photons lost. Despite the overall agreement with the RT simulation, our results suggest that constraining ionizing emissivity-sensitive parameters from seminumerical galaxy formation-reionization models are subject to photon nonconservation.

The accuracy of semi-numerical reionization models in comparison with radiative transfer simulations

NASA Astrophysics Data System (ADS)

Hutter, Anne

2018-03-01

We have developed a modular semi-numerical code that computes the time and spatially dependent ionization of neutral hydrogen (H I), neutral (He I) and singly ionized helium (He II) in the intergalactic medium (IGM). The model accounts for recombinations and provides different descriptions for the photoionization rate that are used to calculate the residual H I fraction in ionized regions. We compare different semi-numerical reionization schemes to a radiative transfer (RT) simulation. We use the RT simulation as a benchmark, and find that the semi-numerical approaches produce similar H II and He II morphologies and power spectra of the H I 21cm signal throughout reionization. As we do not track partial ionization of He II, the extent of the double ionized helium (He III) regions is consistently smaller. In contrast to previous comparison projects, the ionizing emissivity in our semi-numerical scheme is not adjusted to reproduce the redshift evolution of the RT simulation, but directly derived from the RT simulation spectra. Among schemes that identify the ionized regions by the ratio of the number of ionization and absorption events on different spatial smoothing scales, we find those that mark the entire sphere as ionized when the ionization criterion is fulfilled to result in significantly accelerated reionization compared to the RT simulation. Conversely, those that flag only the central cell as ionized yield very similar but slightly delayed redshift evolution of reionization, with up to 20% ionizing photons lost. Despite the overall agreement with the RT simulation, our results suggests that constraining ionizing emissivity sensitive parameters from semi-numerical galaxy formation-reionization models are subject to photon nonconservation.

Metabolomics study on the hepatoprotective effect of scoparone using ultra-performance liquid chromatography/electrospray ionization quadruple time-of-flight mass spectrometry.

PubMed

Zhang, Aihua; Sun, Hui; Dou, Shengshan; Sun, Wenjun; Wu, Xiuhong; Wang, Ping; Wang, Xijun

2013-01-07

Scoparone is an important constituent of Yinchenhao (Artemisia annua L.), a famous medicinal plant, and displayed bright prospects in the prevention and therapy of liver injury. However, the precise molecular mechanism of hepatoprotective effects has not been comprehensively explored. Here, metabolomics techniques are the comprehensive assessment of endogenous metabolites in a biological system and may provide additional insight into the mechanisms. The present investigation was designed to assess the effects and possible mechanisms of scoparone against carbon tetrachloride-induced liver injury. Ultra-performance liquid chromatography/electrospray ionization quadruple time-of-flight mass spectrometry (UPLC/ESI-Q-TOF/MS) combined with pattern recognition approaches including principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were integrated to discover differentiating metabolites. Results indicate five ions in the positive mode as differentiating metabolites. Functional pathway analysis revealed that the alterations in these metabolites were associated with primary bile acid biosynthesis, pyrimidine metabolism. Of note, scoparone has a potential pharmacological effect through regulating multiple perturbed pathways to the normal state. Our findings also showed that the robust metabolomics techniques are promising for getting biomarkers and clarifying mechanisms of disease, highlighting insights into drug discovery.

Simulator training to minimize ionizing radiation exposure in the catheterization laboratory.

PubMed

Katz, Aric; Shtub, Avraham; Solomonica, Amir; Poliakov, Adva; Roguin, Ariel

2017-03-01

To learn about radiation and how to lower it. Patients and operators are routinely exposed to high doses of ionizing radiation during catheterization procedures. This increased exposure to ionizing radiation is partially due to a lack of awareness to the effects of ionizing radiation, and lack of knowledge on the distribution and behavior of scattered radiation. A simulator, which incorporates data on scattered ionizing radiation, was built based on multiple phantom measurements and used for teaching radiation safety. The validity of the simulator was confirmed in three catheterization laboratories and tested by 20 interventional cardiologists. All evaluators were tested by an objective knowledge examination before, immediately following, and 12 weeks after simulator-based learning and training. A subjective Likert questionnaire on satisfaction with simulation-based learning and training was also completed. The 20 evaluators learned and retained the knowledge that they gained from using the simulator: the average scores of the knowledge examination pre-simulator training was 54 ± 15% (mean ± standard deviation), and this score significantly increased after training to 94 ± 10% (p < 0.001). The evaluators also reported high levels of satisfaction following simulation-based learning and training according to the results of the subjective Likert questionnaire. Simulators can be used to train cardiology staff and fellows and to further educate experienced personnel on radiation safety. As a result of simulator training, the operator gains knowledge, which can then be applied in the catheterization laboratory in order to reduce radiation doses to the patient and to the operator, thereby improving the safety of the intervention.

The concerted impact of galaxies and QSOs on the ionization and thermal state of the intergalactic medium

NASA Astrophysics Data System (ADS)

Kakiichi, Koki; Graziani, Luca; Ciardi, Benedetta; Meiksin, Avery; Compostella, Michele; Eide, Marius B.; Zaroubi, Saleem

2017-07-01

We present a detailed analysis of the ionization and thermal structure of the intergalactic medium (IGM) around a high-redshift (z = 10) QSO, using a large suite of cosmological, multifrequency radiative transfer simulations, exploring the contribution from galaxies as well as the QSO, and the effect of X-rays and secondary ionization. We show that in high-z QSO environments both the central QSO and the surrounding galaxies concertedly control the reionization morphology of hydrogen and helium and have a non-linear impact on the thermal structure of the IGM. A QSO imprints a distinctive morphology on H II regions if its total ionizing photon budget exceeds that of the surrounding galaxies since the onset of hydrogen reionization; otherwise, the morphology shows little difference from that of H II regions produced only by galaxies. In addition, the spectral shape of the collective radiation field from galaxies and QSOs controls the thickness of the I-fronts. While a UV-obscured QSO can broaden the I-front, the contribution from other UV sources, either galaxies or unobscured QSOs, is sufficient to maintain a sharp I-front. X-ray photons from the QSO are responsible for a prominent extended tail of partial ionization ahead of the I-front. QSOs leave a unique imprint on the morphology of He II/He III regions. We suggest that, while the physical state of the IGM is modified by QSOs, the most direct test to understand the role of galaxies and QSOs during reionization is to perform galaxy surveys in a region of sky imaged by 21 cm tomography.

Observation of variable pre-eclipse dips and disk winds in the eclipsing LMXB XTE J1710-281

NASA Astrophysics Data System (ADS)

Raman, Gayathri; Maitra, Chandreyee; Paul, Biswajit

2018-04-01

We report the first detection of highly ionized Fe species in the X-ray spectrum of the eclipsing and dipping Low Mass X-ray Binary XTE J1710-281. Using archival Chandra and Suzaku observations, we have carried out a spectro-timing analysis of the source during three different epochs. We compare the average orbital profile and obtain differences in pre-eclipse dip morphologies between different observation epochs. We observe an orbit to orbit evolution of the dips for the first time in this source in both the Chandra observations, reflecting changes in the structure of the accretion disc in timescales of hours. We further perform intensity resolved spectroscopy for both the Chandra and the Suzaku data to characterize the changes in the spectral parameters from the persistent to the dipping intervals. We find that the absorbers responsible for the dips, can be best described using a partially ionized partial covering absorber, with an ionization parameter, log(ξ) of ˜2. The photon index of the source remained at ˜2 during both the Chandra and the Suzaku observations. In the 0.6-9 keV Suzaku spectra, we detect a broad 0.72 keV Fe L-alpha emission line complex and two narrow absorption lines at ˜6.60 keV and ˜7.01 keV. The highly ionized Fe line signatures, being an indicator of accretion disc-winds, has been observed for the first time in XTE J1710-281.

Partial cross sections of helium satellites at medium photon energies

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

Wehlitz, R.; Sellin, I.A.; Hemmers, O.

1997-04-01

Still of current interest is the important role of single ionization with excitation compared to single ionization alone. The coupling between the electrons and the incoming photon is a single-particle operator. Thus, an excitation in addition to an ionization, leading to a so-called satellite line in a photoelectron spectrum, is entirely due to electron-electron interaction and probes the electron correlation in the ground and final state. Therefore the authors have undertaken the study of the intensity of helium satellites He{sup +}nl (n = 2 - 6) relative to the main photoline (n = 1) as a function of photon energymore » at photon energies well above threshold up to 900 eV. From these results they could calculate the partial cross-sections of the helium satellites. In order to test the consistency of their satellite-to-1s ratios with published double-to-single photoionization ratios, the authors calculated the double-to-single photoionization ratio from their measured ratios using the theoretical energy-distribution curves of Chang and Poe and Le Rouzo and Dal Cappello which proved to be valid for photon energies below 120 eV. These calculated double-to-single ionization ratios agree fairly well with recent ion measurements. In the lower photon energy range the authors ratios agree better with the ratios of Doerner et al. while for higher photon energies the agreement is better with the values of Levin et al.« less

Ionospheres of the terrestrial planets

NASA Astrophysics Data System (ADS)

Schunk, R. W.; Nagy, A. F.

1980-11-01

The theory and observations relating to the ionospheres of the terrestrial planets Venus, the earth, and Mars are reviewed. Emphasis is placed on comparing the basic differences and similarities between the planetary ionospheres. The review covers the plasma and electric-magnetic field environments that surround the planets, the theory leading to the creation and transport of ionization in the ionospheres, the relevant observations, and the most recent model calculations. The theory section includes a discussion of ambipolar diffusion in a partially ionized plasma, diffusion in a fully ionized plasma, supersonic plasma flow, photochemistry, and heating and cooling processes. The sections on observations and model calculations cover the neutral atmosphere composition, the ion composition, the electron density, and the electron, ion, and neutral temperatures.

Absolute photoionization cross sections of furanic fuels: 2-ethylfuran, 2-acetylfuran and furfural.

PubMed

Smith, Audrey R; Meloni, Giovanni

2015-11-01

Absolute photoionization cross sections of the molecules 2-ethylfuran, 2-acetylfuran and furfural, including partial ionization cross sections for the dissociative ionized fragments, are measured for the first time. These measurements are important because they allow fuel quantification via photoionization mass spectrometry and the development of quantitative kinetic modeling for the complex combustion of potential fuels. The experiments are carried out using synchrotron photoionization mass spectrometry with an orthogonal time-of-flight spectrometer used for mass analysis at the Advanced Light Source of Lawrence Berkeley National Laboratory. The CBS-QB3 calculations of adiabatic ionization energies and appearance energies agree well with the experimental results. Several bond dissociation energies are also derived and presented. Copyright © 2015 John Wiley & Sons, Ltd.

Electrospray ionization and time-of-flight mass spectrometric method for simultaneous determination of spermidine and spermine.

PubMed

Samejima, Keijiro; Otani, Masahiro; Murakami, Yasuko; Oka, Takami; Kasai, Misao; Tsumoto, Hiroki; Kohda, Kohfuku

2007-10-01

A sensitive method for the determination of polyamines in mammalian cells was described using electrospray ionization and time-of-flight mass spectrometer. This method was 50-fold more sensitive than the previous method using ionspray ionization and quadrupole mass spectrometer. The method employed the partial purification and derivatization of polyamines, but allowed a measurement of multiple samples which contained picomol amounts of polyamines. Time required for data acquisition of one sample was approximately 2 min. The method was successfully applied for the determination of reduced spermidine and spermine contents in cultured cells under the inhibition of aminopropyltransferases. In addition, a new proper internal standard was proposed for the tracer experiment using (15)N-labeled polyamines.

Changes in interstellar atomic abundances from the galactic plane to the halo

NASA Technical Reports Server (NTRS)

Jenkins, E. B.

1982-01-01

A few, specially selected interstellar absorption lines were measured in the high resolution, far ultraviolet spectra of 200 O and B type stars observed by the International Ultraviolet Explorer (IUE). For lines of sight extending beyond about 500 pc from the galactic plane, the abundance of singly ionized iron atoms increases relative to singly ionized sulfur. However, the relative abundances of singly ionized sulfur, silicon and aluminum do not seem to change appreciably. An explanation for the apparent increase of iron is the partial sputtering of material off the surfaces of dust grains by interstellar shocks. Another possibility might be that the ejecta from type I supernovae enrich the low density medium in the halo with iron.

Performance Theory of Diagonal Conducting Wall MHD Accelerators

NASA Technical Reports Server (NTRS)

Litchford, R. J.

2003-01-01

The theoretical performance of diagonal conducting wall crossed field accelerators is examined on the basis of an infinite segmentation assumption using a cross-plane averaged generalized Ohm's law for a partially ionized gas, including ion slip. The desired accelerator performance relationships are derived from the cross-plane averaged Ohm's law by imposing appropriate configuration and loading constraints. A current dependent effective voltage drop model is also incorporated to account for cold-wall boundary layer effects including gasdynamic variations, discharge constriction, and electrode falls. Definition of dimensionless electric fields and current densities lead to the construction of graphical performance diagrams, which further illuminate the rudimentary behavior of crossed field accelerator operation.

Correlation-driven charge migration following double ionization and attosecond transient absorption spectroscopy

NASA Astrophysics Data System (ADS)

Hollstein, Maximilian; Santra, Robin; Pfannkuche, Daniela

2017-05-01

We theoretically investigate charge migration following prompt double ionization. Thereby, we extend the concept of correlation-driven charge migration, which was introduced by Cederbaum and coworkers for single ionization [Chem. Phys. Lett. 307, 205 (1999), 10.1016/S0009-2614(99)00508-4], to doubly ionized molecules. This allows us to demonstrate that compared to singly ionized molecules, in multiply ionized molecules, electron dynamics originating from electronic relaxation and correlation are particularly prominent. In addition, we also discuss how these correlation-driven electron dynamics might be evidenced and traced experimentally using attosecond transient absorption spectroscopy. For this purpose, we determine the time-resolved absorption cross section and find that the correlated electron dynamics discussed are reflected in it with exceptionally great detail. Strikingly, we find that features in the cross section can be traced back to electron hole populations and time-dependent partial charges and hence, can be interpreted with surprising ease. By taking advantage of element-specific core-to-valence transitions even atomic spatial resolution can be achieved. Thus, with the theoretical considerations presented, not only do we predict particularly diverse and correlated electron dynamics in molecules to follow prompt multiple ionization but we also identify a promising route towards their experimental investigation.

Partial discharges and breakdown in C3F8

NASA Astrophysics Data System (ADS)

Koch, M.; Franck, C. M.

2014-10-01

Traditional search processes of gases or gas mixtures for replacing SF6 involve time consuming measurements of partial discharges and breakdown behaviour for several voltage waveforms and different field configurations. Recently a model for prediction of this behaviour for SF6 was described in literature. The model only requires basic properties of the gas such as the critical field strength and the effective ionization coefficient, which can be obtained by swarm parameter measurements, and thermodynamic properties, which can be calculated. In this paper, we show for the well-known and electronegative gas octafluoropropane (C3F8) that it is possible to transfer the model developed for SF6 to this gas to describe the breakdown behaviour of C3F8. Thus the model can be beneficial in the screening process of new insulation gases.

Modeling photoionization of aqueous DNA and its components.

PubMed

Pluhařová, Eva; Slavíček, Petr; Jungwirth, Pavel

2015-05-19

Radiation damage to DNA is usually considered in terms of UVA and UVB radiation. These ultraviolet rays, which are part of the solar spectrum, can indeed cause chemical lesions in DNA, triggered by photoexcitation particularly in the UVB range. Damage can, however, be also caused by higher energy radiation, which can ionize directly the DNA or its immediate surroundings, leading to indirect damage. Thanks to absorption in the atmosphere, the intensity of such ionizing radiation is negligible in the solar spectrum at the surface of Earth. Nevertheless, such an ionizing scenario can become dangerously plausible for astronauts or flight personnel, as well as for persons present at nuclear power plant accidents. On the beneficial side, ionizing radiation is employed as means for destroying the DNA of cancer cells during radiation therapy. Quantitative information about ionization of DNA and its components is important not only for DNA radiation damage, but also for understanding redox properties of DNA in redox sensing or labeling, as well as charge migration along the double helix in nanoelectronics applications. Until recently, the vast majority of experimental and computational data on DNA ionization was pertinent to its components in the gas phase, which is far from its native aqueous environment. The situation has, however, changed for the better due to the advent of photoelectron spectroscopy in liquid microjets and its most recent application to photoionization of aqueous nucleosides, nucleotides, and larger DNA fragments. Here, we present a consistent and efficient computational methodology, which allows to accurately evaluate ionization energies and model photoelectron spectra of aqueous DNA and its individual components. After careful benchmarking, the method based on density functional theory and its time-dependent variant with properly chosen hybrid functionals and polarizable continuum solvent model provides ionization energies with accuracy of 0.2-0.3 eV, allowing for faithful modeling and interpretation of DNA photoionization. The key finding is that the aqueous medium is remarkably efficient in screening the interactions within DNA such that, unlike in the gas phase, ionization of a base, nucleoside, or nucleotide depends only very weakly on the particular DNA context. An exception is the electronic interaction between neighboring bases which can lead to sequence-specific effects, such as a partial delocalization of the cationic hole upon ionization enabled by presence of adjacent bases of the same type.

Identification and Relative Quantification of Bioactive Peptides Sequentially Released during Simulated Gastrointestinal Digestion of Commercial Kefir.

PubMed

Liu, Yufang; Pischetsrieder, Monika

2017-03-08

Health-promoting effects of kefir may be partially caused by bioactive peptides. To evaluate their formation or degradation during gastrointestinal digestion, we monitored changes of the peptide profile in a model of (1) oral, (2) gastric, and (3) small intestinal digestion of kefir. Matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy analyses revealed clearly different profiles between digests 2/3 and kefir/digest 1. Subsequent ultraperformance liquid chromatography-electrospray ionization-tandem mass spectrometry identified 92 peptides in total (25, 25, 43, and 30, partly overlapping in kefir and digests 1, 2, and 3, respectively), including 16 peptides with ascribed bioactivity. Relative quantification in scheduled multiple reaction monitoring mode showed that many bioactive peptides were released by simulated digestion. Most prominently, the concentration of angiotensin-converting enzyme inhibitor β-casein 203-209 increased approximately 10 000-fold after combined oral, gastric, and intestinal digestion. Thus, physiological digestive processes may promote bioactive peptide formation from proteins and oligopeptides in kefir. Furthermore, bioactive peptides present in certain compartments of the gastrointestinal tract may exert local physiological effects.

Thermoelectric power factor enhancement by ionized nanoparticle scattering

NASA Astrophysics Data System (ADS)

Bahk, Je-Hyeong; Bian, Zhixi; Zebarjadi, Mona; Santhanam, Parthiban; Ram, Rajeev; Shakouri, Ali

2011-08-01

We show theoretically that the thermoelectric power factor can be enhanced in degenerate semiconductors when embedded nanoparticles donate carriers to the matrix and replace conventional impurity dopants as scattering centers. Nanoparticle scattering rates calculated by the partial wave method indicate a mobility enhancement over materials with equivalent doping by isolated ionized impurities while the Seebeck coefficient remains nearly intact. We find that the thermoelectric power factor of In0.53Ga0.47As from 300 K to 800 K is enhanced by 15% - 30% by nanoparticles 3-4 nm in diameter.

Ion-atom charge-transfer reactions and a hot intercloud medium. [in interstellar space

NASA Technical Reports Server (NTRS)

Steigman, G.

1975-01-01

An investigation is conducted concerning the ionization equilibrium of carbon in a hot intercloud medium (ICM), taking into account various charge-transfer reactions. Attention is given to problems related to observations of carbon along the lines of sight to several unreddened stars. It is pointed out that the observed underabundance of C III and overabundance of C I can be consistent with the presence of a hot, partially ionized ICM, provided that two of the charge-transfer reactions considered are rapid at thermal energies.

Convection in Neptune's magnetosphere

NASA Technical Reports Server (NTRS)

Hill, T. W.; Dessler, A. J.

1990-01-01

It is assumed that nonthermal escape from Triton's atmosphere produces a co-orbiting torus of unionized gas (presumably nitrogen and hydrogen) that subsequently becomes ionized by electron impact to populate a partial Triton plasma torus analogous to the Io plasma torus in Jupiter's magnetosphere. Centrifugal and magnetic-mirror forces confine the ions to a plasma sheet located between the magnetic and centrifugal equators. The ionization rate, and hence the torus ion concentration, is strongly peaked at the two points (approximately 180 deg apart in longitude) at which Triton's orbit intersects the plasma equator. During the course of Neptune's rotation these intersection points trace out two arcs roughly 75 deg in longitudinal extent, which we take to be the configuration of the resulting (partial) plasma torus. The implied partial ring currents produce a quadrupolar (four-cell) convection system that provides rapid outward transport of plasma from the arcs. Ring-current shielding, however, prevents this convection system from penetrating very far inside the plasma-arc distance. It is suggested that this convection/shielding process accounts for the radial confinement of trapped particles (150 keV or greater) within L = 14.3 as observed by the Voyager LECP instrument.

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.

Suppression of diamagnetism by neutrals pressure in partially ionized, high-beta plasma

NASA Astrophysics Data System (ADS)

Shinohara, Shunjiro; Kuwahara, Daisuke; Yano, Kazuki; Fruchtman, Amnon

2016-12-01

Suppression of diamagnetism in a partially ionized plasma with high beta was experimentally investigated by the use of Langmuir and Hall sensor probes, focusing on a neutrals pressure effect. The plasma beta, which is the ratio of plasma to vacuum magnetic pressures, varied from ˜1% to >100% while the magnetic field varied from ˜120 G to ˜1 G. Here, a uniform magnetized argon plasma was operated mostly in an inductive mode, using a helicon plasma source of the Large Helicon Plasma Device [S. Shinohara et al., Phys. Plasmas 16, 057104 (2009)] with a diameter of 738 mm and an axial length of 4860 mm. Electron density varied from 5 × 1015 m-3 to <3 × 1018 m-3, while an argon fill pressure was varied from ˜0.02 Pa to 0.75 Pa as well as the magnetic field mentioned above, with the fixed radio frequency (rf) and power of 7 MHz and ˜3.5 kW, respectively. The observed magnetic field reduction rate, a decrease of the magnetic field divided by the vacuum one, was up to 18%. However, in a certain parameter regime, where the product of ion and electron Hall terms is a key parameter, the measured diamagnetic effect was smaller than that expected by the plasma beta. This suppressed diamagnetism is explained by the neutrals pressure replacing magnetic pressure in balancing plasma pressure. Diamagnetism is weakened if neutrals pressure is comparable to the plasma pressure and if the coupling of plasma and neutrals pressures by ion-neutral collisions is strong enough.

INJECTION TO RAPID DIFFUSIVE SHOCK ACCELERATION AT PERPENDICULAR SHOCKS IN PARTIALLY IONIZED PLASMAS

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

Ohira, Yutaka, E-mail: ohira@phys.aoyama.ac.jp

2016-08-10

We present a three-dimensional hybrid simulation of a collisionless perpendicular shock in a partially ionized plasma for the first time. In this simulation, the shock velocity and upstream ionization fraction are v {sub sh} ≈ 1333 km s{sup −1} and f {sub i} ∼ 0.5, which are typical values for isolated young supernova remnants (SNRs) in the interstellar medium. We confirm previous two-dimensional simulation results showing that downstream hydrogen atoms leak into the upstream region and are accelerated by the pickup process in the upstream region, and large magnetic field fluctuations are generated both in the upstream and downstream regions.more » In addition, we find that the magnetic field fluctuations have three-dimensional structures and the leaking hydrogen atoms are injected into the diffusive shock acceleration (DSA) at the perpendicular shock after the pickup process. The observed DSA can be interpreted as shock drift acceleration with scattering. In this simulation, particles are accelerated to v ∼ 100 v {sub sh} ∼ 0.3 c within ∼100 gyroperiods. The acceleration timescale is faster than that of DSA in parallel shocks. Our simulation results suggest that SNRs can accelerate cosmic rays to 10{sup 15.5} eV (the knee) during the Sedov phase.« less

Equation-of-State Scaling Factors

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

Scannapieco, Anthony J.

2016-06-28

Equation-of-State scaling factors are needed when using a tabular EOS in which the user de ned material isotopic fractions di er from the actual isotopic fractions used by the table. Additionally, if a material is dynamically changing its isotopic structure, then an EOS scaling will again be needed, and will vary in time and location. The procedure that allows use of a table to obtain information about a similar material with average atomic mass Ms and average atomic number Zs is described below. The procedure is exact for a fully ionized ideal gas. However, if the atomic number is replacemore » by the e ective ionization state the procedure can be applied to partially ionized material as well, which extends the applicability of the scaling approximation continuously from low to high temperatures.« less

Plasma diagnosis as a tool for the determination of the parameters of electron beam evaporation and sources of ionization

NASA Astrophysics Data System (ADS)

Mukherjee, Jaya; Dileep Kumar, V.; Yadav, S. P.; Barnwal, Tripti A.; Dikshit, Biswaranjan

2016-07-01

The atomic vapor generated by electron beam heating is partially ionized due to atom-atom collisions (Saha ionization) and electron impact ionization, which depend upon the source temperature and area of evaporation as compared to the area of electron beam bombardment on the target. When electron beam evaporation is carried out by inserting the target inside an insulating liner to reduce conductive heat loss, it is expected that the area of evaporation becomes significantly more than the area of electron beam bombardment on the target, resulting in reduced electron impact ionization. To assess this effect and to quantify the parameters of evaporation, such as temperature and area of evaporation, we have carried out experiments using zirconium, tin and aluminum as a target. By measuring the ion content using a Langmuir probe, in addition to measuring the atomic vapor flux at a specific height, and by combining the experimental data with theoretical expressions, we have established a method for simultaneously inferring the source temperature, evaporation area and ion fraction. This assumes significance because the temperature cannot be reliably measured by an optical pyrometer due to the wavelength dependent source emissivity and reflectivity of thin film mirrors. In addition, it also cannot be inferred from only the atomic flux data at a certain height as the area of evaporation is unknown (it can be much more than the area of electron bombardment, especially when the target is placed in a liner). Finally, the reason for the lower observed electron temperatures of the plasma for all the three cases is found to be the energy loss due to electron impact excitation of the atomic vapor during its expansion from the source.

Dustbuster: a New Generation Impact-ionization Time-of-flight Mass Spectrometer for in situ Analysis of Cosmic Dust

NASA Astrophysics Data System (ADS)

Austin, D. E.; Ahrens, T. J.; Beauchamp, J. L.

2000-10-01

We have developed and tested a small impact-ionization time-of-flight mass spectrometer for analysis of cosmic dust, suitable for use on deep space missions. This mass spectrometer, named Dustbuster, incorporates a large target area and a reflectron, simultaneously optimizing mass resolution, sensitivity, and collection efficiency. Dust particles hitting the 65-cm2 target plate are partially ionized. The resulting ions are accelerated through a modified reflectron that focuses the ions in space and time to produce high-resolution spectra. The instrument, shown below, measures 10 x 10 x 20 cm, has a mass of 500 g, and consumes little power. Laser desorption ionization of metal and mineral samples (embedded in the impact plate) simulates particle impacts for instrument performance tests. Mass resolution in these experiments is near 200, permitting resolution of isotopes. The mass spectrometer can be combined with other instrument components to determine dust particle trajectories and sizes. This project was funded by NASA's Planetary Instrument Definition and Development Program.

Process for analyzing CO.sub.2 in seawater

DOEpatents

Atwater, James E.; Akse, James R.; DeHart, Jeffrey

1997-01-01

The process of this invention comprises providing a membrane for separating CO.sub.2 into a first CO.sub.2 sample phase and a second CO.sub.2 analyte phase. CO.sub.2 is then transported through the membrane thereby separating the CO.sub.2 with the membrane into a first CO.sub.2 sample phase and a second CO.sub.2 analyte liquid phase including an ionized, conductive, dissociated CO.sub.2 species. Next, the concentration of the ionized, conductive, dissociated CO.sub.2 species in the second CO.sub.2 analyte liquid phase is chemically amplified using a water-soluble chemical reagent which reversibly reacts with undissociated CO.sub.2 to produce conductivity changes therein corresponding to fluctuations in the partial pressure of CO.sub.2 in the first CO.sub.2 sample phase. Finally, the chemically amplified, ionized, conductive, dissociated CO.sub.2 species is introduced to a conductivity measuring instrument. Conductivity changes in the chemically amplified, ionized, conductive, dissociated CO.sub.2 species are detected using the conductivity measuring instrument.

Observation of anisotropic interactions between metastable atoms and target molecules by two-dimensional collisional ionization electron spectroscopy

NASA Astrophysics Data System (ADS)

Kishimoto, Naoki; Ohno, Koichi

Excited metastable atoms colliding with target molecules can sensitively probe outer properties of molecules by chemi-ionization (Penning ionization) from molecular orbitals in the outer region, since metastable atoms cannot penetrate into the repulsive interaction wall around the molecules. By means of two-dimensional measurements using kinetic energy analysis of electrons combined with a velocity-resolved metastable beam, one can obtain information on the anisotropic interaction between the colliding particles without any control of orientation or alignment of target molecules. We have developed a classical trajectory method to calculate the collision energy dependence of partial ionization cross-sections (CEDPICS) on the anisotropic interaction potential energy surface, which has enabled us to study stereodynamics between metastable atoms and target molecules as well as the spatial distribution of molecular orbitals and electron ejection functions which have a relation with entrance and exit channels of the reaction. Based on the individual CEDPICS, the electronic structure of molecules can also be elucidated.

Partially Ionized Beam Deposition of Silicon-Dioxide and Aluminum Thin Films - Defects Generation.

NASA Astrophysics Data System (ADS)

Wong, Justin Wai-Chow

1987-09-01

Detect formation in SiO_2 and Al thin films and interfaces were studied using a partially ionized beam (PIB) deposition technique. The evaporated species (the deposition material) were partially ionized to give an ion/atom ratio of <=q0.1% and the substrate was biased at 0-5kV during the deposition. The results suggest that due to the ion bombardment, stoichiometric SiO_2 films can be deposited at a low substrate temperature (~300 ^circC) and low oxygen pressure (<=q10^{-4} Torr). Such deposition cannot be achieved using conventional evaporation-deposition techniques. However, traps and mobile ions were observed in the oxide and local melt-down was observed when a sufficiently high electric field was applied to the film. For the PIB Al deposition on the Si substrate, stable Al/Si Schottky contact was formed when the substrate bias was <=q1kV. For a substrate bias of 2.5kV, the capacitance of the Al/Si interface increased dramatically. A model of self-ion implantation with a p-n junction created by the Al^+ ion implantation was proposed and tested to explain the increase of the interface capacitance. Several deep level states at the Al/Si interface were observed using Deep Level Transient Spectroscopy (DLTS) technique when the film was deposited at a bias of 3kV. The PIB Al films deposited on the Si substrate showed unusually strong electromigration resistance under high current density operation. This phenomenon was explained by the highly oriented microstructure of the Al films created by the self-ion bombardment during deposition. These findings show that PIB has potential applications in a number of areas, including low temperature thin film deposition, and epitaxial growth of thin films in the microelectronics thin film industry.

Leaky Integrate and Fire Neuron by Charge-Discharge Dynamics in Floating-Body MOSFET.

PubMed

Dutta, Sangya; Kumar, Vinay; Shukla, Aditya; Mohapatra, Nihar R; Ganguly, Udayan

2017-08-15

Neuro-biology inspired Spiking Neural Network (SNN) enables efficient learning and recognition tasks. To achieve a large scale network akin to biology, a power and area efficient electronic neuron is essential. Earlier, we had demonstrated an LIF neuron by a novel 4-terminal impact ionization based n+/p/n+ with an extended gate (gated-INPN) device by physics simulation. Excellent improvement in area and power compared to conventional analog circuit implementations was observed. In this paper, we propose and experimentally demonstrate a compact conventional 3-terminal partially depleted (PD) SOI- MOSFET (100 nm gate length) to replace the 4-terminal gated-INPN device. Impact ionization (II) induced floating body effect in SOI-MOSFET is used to capture LIF neuron behavior to demonstrate spiking frequency dependence on input. MHz operation enables attractive hardware acceleration compared to biology. Overall, conventional PD-SOI-CMOS technology enables very-large-scale-integration (VLSI) which is essential for biology scale (~10 11 neuron based) large neural networks.

High-temperature electronic structure with the Korringa-Kohn-Rostoker Green's function method

NASA Astrophysics Data System (ADS)

Starrett, C. E.

2018-05-01

Modeling high-temperature (tens or hundreds of eV), dense plasmas is challenging due to the multitude of non-negligible physical effects including significant partial ionization and multisite effects. These effects cause the breakdown or intractability of common methods and approximations used at low temperatures, such as pseudopotentials or plane-wave basis sets. Here we explore the Korringa-Kohn-Rostoker Green's function method at these high-temperature conditions. The method is all electron, does not rely on pseudopotentials, and uses a spherical harmonic basis set, and so avoids the aforementioned limitations. It is found to be accurate for solid density aluminum and iron plasmas when compared to a plane-wave method at low temperature, while being able to access high temperatures.

Determination of Kicker Vacuum Requirements

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

Schulze, Martin E.

This note examines the effect of elevated vacuum pressures in the kicker region of the DARHT 2nd Axis which can lead to changes in the beam tune due to the long pulse length. The kicker uses Rexolite as an insulator supporting the electrodes. Rexolite is hygroscopic resulting is a large outgassing rate and prolonged pump down times after exposure to atmospheric conditions. LAMDA [1] is used to simulate the effect of ionization of the residual gas resulting in partial space charge neutralization and changes to the tune between the beginning and end of the pulse. The effect of the ion-hosemore » instability is also examined. The purpose of this note is to establish/validate the required pressure in the downstream transport.« less

Performance Theory of Diagonal Conducting Wall Magnetohydrodynamic Accelerators

NASA Technical Reports Server (NTRS)

Litchford, R. J.

2004-01-01

The theoretical performance of diagonal conducting wall crossed-field accelerators is examined on the basis of an infinite segmentation assumption using a cross-plane averaged generalized Ohm s law for a partially ionized gas, including ion slip. The desired accelerator performance relationships are derived from the cross-plane averaged Ohm s law by imposing appropriate configuration and loading constraints. A current-dependent effective voltage drop model is also incorporated to account for cold-wall boundary layer effects, including gasdynamic variations, discharge constriction, and electrode falls. Definition of dimensionless electric fields and current densities leads to the construction of graphical performance diagrams, which further illuminate the rudimentary behavior of crossed-field accelerator operation.

Evaluation of γ-cyclodextrin effect on permeation of lipophilic drugs: application of cellophane/fused octanol membrane.

PubMed

Muankaew, Chutimon; Jansook, Phatsawee; Loftsson, Thorsteinn

2017-06-01

According to the Biopharmaceutics Classification System, oral bioavailability of drugs is determined by their aqueous solubility and the ability of the dissolved drug molecules to permeate lipophilic biological membranes. Similarly topical bioavailability of ophthalmic drugs is determined by their solubility in the aqueous tear fluid and their ability to permeate the lipophilic cornea. Enabling pharmaceutical excipients such as cyclodextrins can have profound effect on the drug bioavailability. However, to fully appreciate such enabling excipients, the relationship between their effects and the physicochemical properties of the permeating drug needs to be known. In this study, the permeation enhancing effect of γ-cyclodextrin (γCD) on saturated drug solutions containing hydrocortisone (HC), irbesartan (IBS), or telmisartan (TEL) was evaluated using cellophane and fused cellulose-octanol membranes in a conventional Franz diffusion cell system. The flux (J), the flux ratio (J R ) and the apparent permeability coefficients (P app ) demonstrate that γCD increases drug permeability. However, its efficacy depends on the drug properties. Addition of γCD increased P app of HC (unionized) and IBS (partially ionized) through the dual membrane but decreased the P app of TEL (fully ionized) that displays low complexation efficacy. The dual cellophane-octanol membrane system was simple to use and gave reproducible results.

Theoretical and Observational Studies of the Central Engines of AGN

NASA Technical Reports Server (NTRS)

Sivron, Ran

1995-01-01

In Active Galactic Nuclei (AGN) the luminosity is so intense that the effect of radiation pressure on a particle may exceed the gravitational attraction. It was shown that when such luminosities are reached, relatively cold (not completely ionized) thermal matter clouds may form in the central engines of AGN, where most of the luminosity originates. We show that the spectrum of emission from cold clouds embedded in hot relativistic matter is similar to the observed spectrum. We also show that within the hot relativistic matter, cold matter moves faster than the speed of sound or the Alfven speed, and shocks form. The shocks provide a mechanism by which a localized perturbation can propagate throughout the central engine. The shocked matter can emit the observed luminosity, and can explain the flux and spectral variability. It may also provide an efficient mechanism for the outward transfer of angular momentum and provide the outward flow of winds. With observations from X-ray satellites, emission features from the cold and hot matter may be revealed. Our analysis of X-ray data from the Seyfert 1 galaxy MCG - 6-30-15 over five years using detectors on the Ginga and Rosat satellites, revealed some interesting variable features. A source with hot matter emits non-thermal radiation which is Compton reflected from cold matter and then absorbed by warm (partially ionized) absorbing matter in the first model, which can be fit to the data if both the cold and warm absorbers are near the central engine. An alternative model in which the emission from the hot matter is partially covered by very warm matter (in which all elements except Iron are mostly ionized) is also successful. In this model the cold and warm matter may be at distances of up to 100 times the size of the central engine, well within the region where broad optical lines are produced. The flux variability is more naturally explained by the second model. Our results support the existence of cold matter in, or near, the central engine of MCG -6-30-15. Cold matter in the central engine, and evidence of the effects of shocks, is probably forthcoming with future X-ray satellites.

Particle-In-Cell simulation concerning heat-flux mitigation using electromagnetic fields

NASA Astrophysics Data System (ADS)

Lüskow, Karl Felix; Duras, Julia; Kemnitz, Stefan; Kahnfeld, Daniel; Matthias, Paul; Bandelow, Gunnas; Schneider, Ralf; Konigorski, Detlev

2016-10-01

In space missions enormous amount of money is spent for the thermal protection system for re-entry. To avoid complex materials and save money one idea is to reduce the heat-flux towards the spacecraft. The partially-ionized gas can be controlled by electromagnetic fields. For first-principle tests partially ionized argon flow from an arc-jet was used to measure the heat-flux mitigation created by an external magnetic field. In the successful experiment a reduction of 85% was measured. In this work the Particle-in-Cell (PIC) method was used to simulate this experiment. PIC is able to reproduce the heat flux mitigation qualitatively. The main mechanism is identified as a changed electron transport and by this, modified electron density due to the reaction to the applied magnetic field. Ions follow due to quasi-neutrality and influence then strongly by charge exchange collisions the neutrals dynamics and heat deposition. This work was supported by the German Space Agency DLR through Project 50RS1508.

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

Zhang, Shuai; Driver, Kevin P.; Soubiran, Francois

As one of the simple alkali metals, sodium has been of fundamental interest for shock physics experiments, but knowledge of its equation of state (EOS) in hot, dense regimes is not well known. By combining path integral Monte Carlo (PIMC) results for partially ionized states at high temperatures and density functional theory molecular dynamics (DFT-MD) results at lower temperatures, we have constructed a coherent equation of state for sodium over a wide density-temperature range of 1.93-11.60 g/cm 3 and 10 3–1.29×10 8 K. We find that a localized, Hartree-Fock nodal structure in PIMC yields pressures and internal energies that aremore » consistent with DFT-MD at intermediate temperatures of 2×10 6 K. Since PIMC and DFT-MD provide a first-principles treatment of electron shell and excitation effects, we are able to identify two compression maxima in the shock Hugoniot curve corresponding to K-shell and L-shell ionization. Our Hugoniot curves provide a benchmark for widely used EOS models: SESAME, LEOS, and Purgatorio. Due to the low ambient density, sodium has an unusually high first compression maximum along the shock Hugoniot curve. At beyond 10 7 K, we show that the radiation effect leads to very high compression along the Hugoniot curve, surpassing relativistic corrections, and observe an increasing deviation of the shock and particle velocities from a linear relation. Here, we also compute the temperature-density dependence of thermal and pressure ionization processes.« less

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.

LLE review

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

Bradley, D.K.

1989-01-01

This volume of the LLE Review, covering the period October--December 1989, contains an article discussing saturation effects and power-balance considerations in the design of high-power lasers and an article describing numerical modeling of the effects of power imbalances on target behavior. The advanced technology section reports on the development of a liquid crystal laser-beam apodizer and an experiment to study the high-intensity ionization of noble gases. Finally, the activities of the National Laser Users Facility and the GDL and OMEGA laser facilities are summarized. The highlights of this issue are: The problem of achieving power balance in high-efficiency, multibeam lasersmore » has been studied in terms of gain-saturation effects and the nonlinear nature of harmonic frequency conversion. It is shown that power imbalance can be minimized by balancing the gains and losses in equivalent amplification stages in each beamline. The effects of target implosion behavior of various power-imbalance sources in the OMEGA laser system have been studied using the two-dimensional hydrodynamics code ORCHID. The simulations show good agreement with an experiment in which a deliberate power imbalance was applied to the target drive. Laser-beam apodizers with large clear apertures have been fabricated using cholesteric liquid crystals. A soft-edge profile has been achieved by filling a cell with two separate liquid crystals with different selective-reflection bands, and allowing them to partially mix at the interface. A study of the ionization of noble gases in the tunneling regime using high- intensity, 1-ps pulses from the tabletop terawatt laser (T{sup 3}) has been carried out. The measured ion production is well predicted by a Coulomb barrier suppression ionization theory.« less

Origin of the X-ray Spectral Variation and Seemingly Broad Iron Line Strucuture in the Seyfert Galaxies

NASA Astrophysics Data System (ADS)

Ebisawa, Ken; Naoki, Iso

2012-07-01

X-ray intensities and spectra of the Seyfert galaxies are known to be variable. Some of the sources have characteristic seemingly broad iron line structure, and their spectral variations are small in the iron line energy band. MCG-6-30-15 is such an archetypal source, and Miyakawa (2011) proposed a "Variable Partial Covering (VPC)" model to explain its continuum spectral variation, seemingly broad iron line structure, and small spectral variation in the iron energy band simultaneously, only due to variation of a single parameter. That single parameter is the "partial covering fraction" to describe the geometrical fraction of the X-ray emitting area covered by the ionized absorbers in the line of sight. The intrinsic X-ray luminosity is hardly variable in this model. We have applied the VPC model to the 27 Seyfert galaxies observed with Suzaku, and found that spectral variations of the 22 sources are successfully explained by this model only varying the partial covering fraction. Intrinsic X-ray luminosities of Seyfert galaxies are not variable, as opposed to what they apparently seem, and gravitationally red-shifted iron line is not necessary. Those ionized absorbing clouds are most likely to be Broad Line Region (BLR) clouds, and we will be able to constrain the BLR structure from X-ray observations.

In-Source Reduction of Disulfide-Bonded Peptides Monitored by Ion Mobility Mass Spectrometry

NASA Astrophysics Data System (ADS)

Stocks, Bradley B.; Melanson, Jeremy E.

2018-02-01

Many peptides with antimicrobial activity and/or therapeutic potential contain disulfide bonds as a means to enhance stability, and their quantitation is often performed using electrospray ionization mass spectrometry (ESI-MS). Disulfides can be reduced during ESI under commonly used instrument conditions, which has the potential to hinder accurate peptide quantitation. We demonstrate that this in-source reduction (ISR) is predominantly observed for peptides infused from acidic solutions and subjected to elevated ESI voltages (3-4 kV). ISR is readily apparent in the mass spectrum of oxytocin—a small, single disulfide-containing peptide. However, subtle m/z shifts due to partial ISR of highly charged (z ≥ 3) peptides with multiple disulfide linkages may proceed unnoticed. Ion mobility (IM)-MS separates ions on the basis of charge and shape in the gas phase, and using insulin as a model system, we show that IM-MS arrival time distributions (ATDs) are particularly sensitive to partial ISR of large peptides. Isotope modeling allows for the relative quantitation of disulfide-intact and partially reduced states of the mobility-separated peptide conformers. Interestingly, hepcidin peptides ionized from acidic solutions at elevated ESI voltages undergo gas-phase compaction, ostensibly due to partial disulfide ISR. Our IM-MS results lead us to propose that residual acid is the likely cause of disparate ATDs recently measured for hepcidin from different suppliers [Anal. Bioanal. Chem. 409, 2559-2567 (2017)]. Overall, our results demonstrate the utility of IM-MS to detect partial ISR of disulfide-bonded peptides and reinforce the notion that peptide/protein measurements should be carried out using minimally activating instrument conditions. [Figure not available: see fulltext.

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).

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).

An Analytic Formulation of the 21 cm Signal from the Early Phase of the Epoch of Reionization

NASA Astrophysics Data System (ADS)

Raste, Janakee; Sethi, Shiv

2018-06-01

We present an analytic formulation to model the fluctuating component of the H I signal from the epoch of reionization during the phase of partial heating. During this phase, we assume self-ionized regions, whose size distribution can be computed using excursion set formalism, to be surrounded by heated regions. We model the evolution of the heating profile around these regions (near zone) and their merger into the time-dependent background (far zone). We develop a formalism to compute the two-point correlation function for this topology, taking into account the heating autocorrelation and heating-ionization cross-correlation. We model the ionization and X-ray heating using four parameters: efficiency of ionization, ζ number of X-ray photons per stellar baryon, N heat; spectral index of X-ray photons, α and minimum frequency of X-ray photons, ν min. We compute the H I signal in the redshift range 10 < z < 20 for the ΛCDM model for a set of these parameters. We show that the H I signal for a range of scales 1–8 Mpc shows a peak strength of 100–1000 (mK)2 during the partially heated era. The redshift at which the signal makes a transition to a uniformly heated universe depends on the modeling parameters; e.g., if ν min is changed from 100 eV to 1 keV, this transition moves from z ≃ 15 to z ≃ 12. This result, along with the dependence of the H I signal on the modeling parameters, is in reasonable agreement with existing results from N-body simulations.

Matrix-assisted laser desorption/ionization time-of-flight vs. fast-atom bombardment and electrospray ionization mass spectrometry in the structural characterization of bacterial poly(3-hydroxyalkanoates).

PubMed

Impallomeni, Giuseppe; Ballistreri, Alberto; Carnemolla, Giovanni Marco; Franco, Domenico; Guglielmino, Salvatore P P

2015-05-15

Bacterial poly(3-hydroxyalkanoates) (PHAs) are an emergent class of plastic materials available from renewable resources. Their properties are strictly correlated with the comonomeric composition and sequence, which may be determined by various mass spectrometry approaches. In this paper we compare fast-atom bombardment (FAB) and electrospray ionization (ESI) to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) of partially pyrolyzed samples. We determined the compositions and sequences of the medium-chain-length PHAs (mcl-PHAs) prepared by bacterial fermentation of Pseudomonas aeruginosa ATCC 27853 cultured in media containing fatty acids with 8, 12, 14, 18, and 20 carbon atoms as carbon sources by means of MALDI-TOFMS of pyrolyzates, and compared the results with those obtained by FAB- and ESI-MS in previous studies. MALDI matrices used were 9-aminoacridine (9-AA) and indoleacrylic acid (IAA). MALDI-TOFMS was carried out in negative ion mode when using 9-AA as a matrix, giving a semi-quantitative estimation of the 3-hydroxyacids constituting the PHAs, and in positive mode when using IAA, allowing us, through statistical analysis of the relative intensity of the oligomers generated by pyrolysis, to establish that the polymers obtained are true random copolyesters and not a mixture of homopolymers or copolymers. MALDI-TOFMS in 9-AA and IAA of partial pyrolyzates of mcl-PHAs represents a powerful method for the structural analysis of these materials. In comparison with FAB and ESI, MALDI provided an extended mass range with better sensitivity at higher mass and a faster method of analysis. Copyright © 2015 John Wiley & Sons, Ltd.

DETECTION OF THE INTERMEDIATE-WIDTH EMISSION LINE REGION IN QUASAR OI 287 WITH THE BROAD EMISSION LINE REGION OBSCURED BY THE DUSTY TORUS

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

Li, Zhenzhen; Zhou, Hongyan; Wang, Huiyuan

2015-10-20

The existence of intermediate-width emission line regions (IELRs) in active galactic nuclei has been discussed for over two decades. A consensus, however, is yet to be arrived at due to the lack of convincing evidence for their detection. We present a detailed analysis of the broadband spectrophotometry of the partially obscured quasar OI 287. The ultraviolet intermediate-width emission lines (IELs) are very prominent, in high contrast to the corresponding broad emission lines (BELs) which are heavily suppressed by dust reddening. Assuming that the IELR is virialized, we estimated its distance to the central black hole to be ∼2.9 pc, similarmore » to the dust sublimation radius of ∼1.3 pc. Photo-ionization calculations suggest that the IELR has a hydrogen density of ∼10{sup 8.8}–10{sup 9.4} cm{sup −3}, within the range of values quoted for the dusty torus near the sublimation radius. Both its inferred location and physical conditions suggest that the IELR originates from the inner surface of the dusty torus. In the spectrum of this quasar, we identified only one narrow absorption-line system associated with the dusty material. With the aid of photo-ionization model calculations, we found that the obscuring material might originate from an outer region of the dusty torus. We speculate that the dusty torus, which is exposed to the central ionizing source, may produce IELs through photo-ionization processes, as well as obscure BELs as a natural “coronagraph.” Such a “coronagraph” could be found in a large number of partially obscured quasars and may be a useful tool to study IELRs.« less

Total Ionizing Dose Influence on the Single-Event Upset Sensitivity of 130-nm PD SOI SRAMs

NASA Astrophysics Data System (ADS)

Zheng, Qiwen; Cui, Jiangwei; Liu, Mengxin; Zhou, Hang; Liu, Mohan; Wei, Ying; Su, Dandan; Ma, Teng; Lu, Wu; Yu, Xuefeng; Guo, Qi; He, Chengfa

2017-07-01

Effect of total ionizing dose (TID) on single-event upset (SEU) hardness of 130 nm partially depleted (PD) silicon-on-insulator (SOI) static random access memories (SRAMs) is investigated in this paper. The measurable synergistic effect of TID on SEU sensitivity of 130-nm PD SOI SRAM was observed in our experiment, even though that is far less than micrometer and submicrometer devices. Moreover, SEU cross section after TID irradiation has no dependence on the data pattern that was applied during TID exposure: SEU cross sections are characterized by TID data pattern and its complement data pattern are decreased consistently rather than a preferred state and a nonpreferred state as micrometer and sub-micrometer SRAMs. The memory cell test structure allowing direct measurement of static noise margin (SNM) under standby operation was designed using identical memory cell layout of SRAM. Direct measurement of the memory cell SNM shows that both data sides' SNM is decreased by TID, indicating that SEU cross section of 130-nm PD SOI SRAM will be increased by TID. And, the decreased SNM is caused by threshold shift in memory cell transistors induced by “radiation-induced narrow channel effect”.

Effects of magnetic fields on photoionized pillars and globules

NASA Astrophysics Data System (ADS)

Mackey, Jonathan; Lim, Andrew J.

2011-04-01

The effects of initially uniform magnetic fields on the formation and evolution of dense pillars and cometary globules at the boundaries of H II regions are investigated using 3D radiation-magnetohydrodynamics simulations. It is shown, in agreement with previous work, that a strong initial magnetic field is required to significantly alter the non-magnetized dynamics because the energy input from photoionization is so large that it remains the dominant driver of the dynamics in most situations. Additionally, it is found that for weak and medium field strengths an initially perpendicular field is swept into alignment with the pillar during its dynamical evolution, matching magnetic field observations of the 'Pillars of Creation' in M16 and also some cometary globules. A strong perpendicular magnetic field remains in its initial configuration and also confines the photoevaporation flow into a bar-shaped dense ionized ribbon which partially shields the ionization front and would be readily observable in recombination lines. A simple analytic model is presented to explain the properties of this bright linear structure. These results show that magnetic field strengths in star-forming regions can in principle be significantly constrained by the morphology of structures which form at the borders of H II regions.

Total Ionizing Dose Response of Different Length Devices in 0.13 μm Partially Depleted Silicon-on-Insulator Technology

NASA Astrophysics Data System (ADS)

Zhang, Meng-Ying; Hu, Zhi-Yuan; Zhang, Zheng-Xuan; Fan, Shuang; Dai, Li-Hua; Liu, Xiao-Nian; Song, Lei

2017-08-01

Not Available Supported by the Weapon Equipment Pre-Research Foundation of China under Grant No 9140A11020114ZK34147, and the Shanghai Municipal Natural Science Foundation under Grant Nos 15ZR1447100 and 15ZR1447200.

Can surface-applied zeolite reduce ammonia losses from feedyard manure? A laboratory study

USDA-ARS?s Scientific Manuscript database

Ammonia emission from beef cattle feedyard manure results in losses of nitrogen (N), which may negatively affect environmental quality. The magnitude and rate of ammonia volatilization from feedyards partially depends on the amount of urinary urea excreted and ionization of ammonium into ammonia fol...

Photoionization using the xchem approach: Total and partial cross sections of Ne and resonance parameters above the 2 s22 p5 threshold

NASA Astrophysics Data System (ADS)

Marante, Carlos; Klinker, Markus; Kjellsson, Tor; Lindroth, Eva; González-Vázquez, Jesús; Argenti, Luca; Martín, Fernando

2017-08-01

The XCHEM approach interfaces well established quantum chemistry packages with scattering numerical methods in order to describe single-ionization processes in atoms and molecules. This should allow one to describe electron correlation in the continuum at the same level of accuracy as quantum chemistry methods do for bound states. Here we have applied this method to study multichannel photoionization of Ne in the vicinity of the autoionizing states lying between the 2 s22 p5 and 2 s 2 p6 ionization thresholds. The calculated total photoionization cross sections are in very good agreement with the absolute measurement of Samson et al. [J. Electron Spectrosc. Relat. Phenom. 123, 265 (2002), 10.1016/S0368-2048(02)00026-9], and with independent benchmark calculations performed at the same level of theory. From these cross sections, we have extracted resonance positions, total autoionization widths, Fano profile parameters, and correlation parameters for the lowest three autoionizing states. The values of these parameters are in good agreement with those reported in earlier theoretical and experimental work. We have also evaluated β asymmetry parameter and partial photoionization cross sections and, from the latter, partial autoionization widths and Starace parameters for the same resonances, not yet available in the literature. Resonant features in the calculated β parameter are in good agreement with the experimental observations. We have found that the three lowest resonances preferentially decay into the 2 p-1ɛ d continuum rather than into the 2 p-1ɛ s one [Phys. Rev. A 89, 043415 (2014), 10.1103/PhysRevA.89.043415], in agreement with previous expectations, and that in the vicinity of the resonances the partial 2 p-1ɛ s cross section can be larger than the 2 p-1ɛ d one, in contrast with the accepted idea that the latter should amply dominate in the whole energy range. These results show the potential of the XCHEM approach to describe highly correlated process in the ionization continuum of many-electron systems, in particular molecules, for which the XCHEM code has been specifically designed.

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 field with a strength of in excess of a megavolt per meter strong enough to ionize any gas molecules passing through the holes. An accelerator grid and an electrostatic deflector focus the ions from the field ionizer into the rotating-field cell of the RFMS. The potentials applied to the electrodes of the cell to generate the rotating electric field typically range from 1 to 13 V. The ions travel in well-defined helices within this cell, after which they are collected in a Faraday cup. The mass of most of the molecules reaching the Faraday cup decreases with increasing frequency of rotation of the electric field in the cell. Therefore, the frequency of rotation of the electric field is made to vary in order to scan through a desired range of ion masses: For example, lightweight gas molecules are scanned at frequencies in the megahertz range, while DNA and other large organic molecules are scanned at kilohertz frequencies.

An all-fiber partial discharge monitoring system based on both intrinsic fiber optic interferometry sensor and fluorescent fiber

NASA Astrophysics Data System (ADS)

Yin, Zelin; Zhang, Ruirui; Tong, Jie; Chen, Xi

2013-12-01

Partial discharges (PDs) are an electrical phenomenon that occurs within a transformer whenever the voltage stress is sufficient to produce ionization in voids or inclusions within a solid dielectric, at conductor/dielectric interfaces, or in bubbles within liquid dielectrics such as oil; high-frequency transient current discharges will then appear repeatedly and will progressively deteriorate the insulation, ultimately leading to breakdown. Fiber sensor has great potential on the partial discharge detection in high-voltage equipment for its immunity to electromagnetic interference and it can take direct measurement in the high voltage equipment. The energy released in PDs produces a number of effects, resulting in flash, chemical and structural changes and electromagnetic emissions and so on. Acoustic PD detection is based on the mechanical pressure wave emitted from the discharge and fluorescent fiber PD detection is based on the emitted light produced by ionization, excitation and recombination processes during the discharge. Both of the two methods have the shortage of weak anti-interference capacity in the physical environment, like thunder or other sound source. In order to avoid the false report, an all-fiber combined PD detection system of the two methods is developed in this paper. In the system the fluorescent fiber PD sensor is considered as a reference signal, three F-P based PD detection sensors are used to both monitor the PD intensity and calculate the exact position of the discharge source. Considering the wave band of the F-P cavity and the fluorescent probe are quite different, the reflection spectrum of the F-P cavity is in the infrared region, however the fluorescent probe is about 600nm to 700nm, thus the F-P sensor and fluorescent fiber probe can be connected in one fiber and the reflection light can be detected by two different detectors without mutual interference. The all-fiber partial discharge monitoring system not only can detect the PDs but also can ensure the position of the PD source and is of great anti-interference capacity in harsh environment.

Regularization of moving boundaries in a laplacian field by a mixed Dirichlet-Neumann boundary condition: exact results.

PubMed

Meulenbroek, Bernard; Ebert, Ute; Schäfer, Lothar

2005-11-04

The dynamics of ionization fronts that generate a conducting body are in the simplest approximation equivalent to viscous fingering without regularization. Going beyond this approximation, we suggest that ionization fronts can be modeled by a mixed Dirichlet-Neumann boundary condition. We derive exact uniformly propagating solutions of this problem in 2D and construct a single partial differential equation governing small perturbations of these solutions. For some parameter value, this equation can be solved analytically, which shows rigorously that the uniformly propagating solution is linearly convectively stable and that the asymptotic relaxation is universal and exponential in time.

Uncatalyzed, Regioselective Oxidation of Saturated Hydrocarbons in an Ambient Corona Discharge.

PubMed

Ayrton, Stephen T; Jones, Rhys; Douce, David S; Morris, Mike R; Cooks, R Graham

2018-01-15

Atmospheric pressure chemical ionization (APCI) in air or in nitrogen with just traces of oxygen is shown to yield regioselective oxidation, dehydrogenation, and fragmentation of alkanes. Ozone is produced from ambient oxygen in situ and is responsible for the observed ion chemistry, which includes partial oxidation to ketones and C-C cleavage to give aldehydes. The mechanism of oxidation is explored and relationships between ionic species produced from individual alkanes are established. Unusually, dehydrogenation occurs by water loss. Competitive incorporation into the hydrocarbon chain of nitrogen versus oxygen as a mode of ionization is also demonstrated. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometric analysis of degradation products after treatment of methylene blue aqueous solution with three-dimensionally integrated microsolution plasma

NASA Astrophysics Data System (ADS)

Shirafuji, Tatsuru; Nomura, Ayano; Hayashi, Yui; Tanaka, Kenji; Goto, Motonobu

2016-01-01

Methylene blue can be degraded in three-dimensionally integrated microsolution plasma. The degradation products have been analyzed by matrix-assisted laser desorption ionization time-of-flight (MALDI TOF) mass spectrometry to understand the degradation mechanisms. The results of MALDI TOF mass spectrometry have shown that sulfoxide is formed at the first stage of the oxidation. Then, partial oxidation proceeds on the methyl groups left on the sulfoxide. The sulfoxide is subsequently separated to two benzene derivatives. Finally, weak functional groups are removed from the benzene derivatives.

Correlated electron-hole mechanism for molecular doping in organic semiconductors

NASA Astrophysics Data System (ADS)

Li, Jing; D'Avino, Gabriele; Pershin, Anton; Jacquemin, Denis; Duchemin, Ivan; Beljonne, David; Blase, Xavier

2017-07-01

The electronic and optical properties of the paradigmatic F4TCNQ-doped pentacene in the low-doping limit are investigated by a combination of state-of-the-art many-body ab initio methods accounting for environmental screening effects, and a carefully parametrized model Hamiltonian. We demonstrate that while the acceptor level lies very deep in the gap, the inclusion of electron-hole interactions strongly stabilizes dopant-semiconductor charge transfer states and, together with spin statistics and structural relaxation effects, rationalize the possibility for room-temperature dopant ionization. Our findings reconcile available experimental data, shedding light on the partial vs. full charge transfer scenario discussed in the literature, and question the relevance of the standard classification in shallow or deep impurity levels prevailing for inorganic semiconductors.

Is the Ejecta of ETA Carinae Overabundant or Overexcited

NASA Technical Reports Server (NTRS)

Gull, Theodore; Davidson, Kris; Johansson, Sveneric; Damineli, Augusto; Ishibashi, Kaxunori; Corcoran, Michael; Hartman, Henrick; Viera, Gladys; Nielsen, Krister

2003-01-01

The ejecta of Eta Carinae, revealed by HST/STIS, are in a large range of physical conditions. As Eta Carinae undergoes a 5.52 period, changes occur in nebular emission and nebular absorption. "Warm" neutral regions, partially ionized regions, and fully ionized regions undergo significant changes. Over 2000 emission lines, most of Fe-like elements, have been indentified in the Weigelt blobs B and D. Over 500 emission lines have been indentified in the Strontium Filament. An ionized Little Homunculus is nestled within the neutral-shelled Homunculus. In line of sight, over 500 nebular absorption lines have been identified with up to twenty velocity components. STIS is following changes in many nebular emission and absorption lines as Eta Carinae approaches the minimum, predicted to be in June/July 2003, during the General Assembly. Coordinated observations with HST, CHANDRA, RXTE, FUSE, UVES/VLT, Gemini and other observatories are following this minimum.

Investigation on the absolute and relative photoionization cross sections of 3 potential propargylic fuels.

PubMed

Winfough, Matthew; Meloni, Giovanni

2017-12-01

Absolute photoionization cross sections for 2 potential propargylic fuels (propargylamine and dipropargyl ether) along with the partial ionization cross sections for their dissociative fragments are measured and presented for the first time via synchrotron photoionization mass spectrometry. The experimental setup consists of a multiplexed orthogonal time-of-flight mass spectrometer and is located at the Advanced Light Source facility of the Lawrence Berkeley National Laboratory in Berkeley, California. Data for a third propargylic compound (propargyl alcohol) were taken; however, because of its low signal, due to its weakly bound cation, only the dissociative ionization fragment from the H-loss channel is observed and presented. Suggested pathways leading to formation of dissociative photoionization fragments along with CBS-QB3 calculated adiabatic ionization energies and appearance energies for the dissociative fragments are also presented. Copyright © 2017 John Wiley & Sons, Ltd.

Discovery of a photoresponse amplification mechanism in compensated PN junctions

NASA Astrophysics Data System (ADS)

Zhou, Yuchun; Liu, Yu-Hsin; Rahman, Samia N.; Hall, David; Sham, L. J.; Lo, Yu-Hwa

2015-01-01

We report the experimental evidence of uncovering a photoresponse amplification mechanism in heavily doped, partially compensated silicon p-n junctions under very low bias voltage. We show that the observed photocurrent gain occurs at a bias that is more than an order of magnitude below the threshold voltage for conventional impact ionization. Moreover, contrary to the case of avalanche detectors and p-i-n diodes, the amplified photoresponse is enhanced rather than suppressed with increasing temperature. These distinctive characteristics lead us to hypothesize that the inelastic scattering between energetic electrons (holes) and the ionized impurities in the depletion and charge neutral regions of the p-n junction in a cyclic manner plays a significant role in the amplification process. Such an internal signal amplification mechanism, which occurs at much lower bias than impact ionization and favors room temperature over cryogenic temperature, makes it promising for practical device applications.

Discovery of a photoresponse amplification mechanism in compensated PN junctions

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

Zhou, Yuchun; Rahman, Samia N.; Hall, David

2015-01-19

We report the experimental evidence of uncovering a photoresponse amplification mechanism in heavily doped, partially compensated silicon p-n junctions under very low bias voltage. We show that the observed photocurrent gain occurs at a bias that is more than an order of magnitude below the threshold voltage for conventional impact ionization. Moreover, contrary to the case of avalanche detectors and p-i-n diodes, the amplified photoresponse is enhanced rather than suppressed with increasing temperature. These distinctive characteristics lead us to hypothesize that the inelastic scattering between energetic electrons (holes) and the ionized impurities in the depletion and charge neutral regions ofmore » the p-n junction in a cyclic manner plays a significant role in the amplification process. Such an internal signal amplification mechanism, which occurs at much lower bias than impact ionization and favors room temperature over cryogenic temperature, makes it promising for practical device applications.« less

PIG (partially ionized globule) anatomy - Density and temperature structure of the bright-rimmed globule IC 1396E

NASA Technical Reports Server (NTRS)

Serabyn, E.; Guesten, R.; Mundy, L.

1993-01-01

The density and temperature structure of the bright-rimmed cometary globule IC 1396E is estimated, and the possibility that recent internal star formation was triggered by the ionization front in its southern surface is assessed. On the basis of NH3 data, gas temperatures in the globule are found to increase outward from the center, from a minimum of 17 K in its tail to a maximum of 26 K on the surface most directly facing the stars ionizing IC 1396. On the basis of a microturbulent radiative transfer code to model the radial dependence of the CS line intensities, and also the intensities of the optically thin 2-1 and 5-4 lines toward the cloud center, a radial density dependence of r exp -1.55 to r exp -1.75 is found.

Process for analyzing CO[sub 2] in air and in water

DOEpatents

Atwater, J.E.; Akse, J.R.; DeHart, J.

1999-06-08

The process of this invention comprises providing a membrane for separating CO[sub 2] into a first CO[sub 2] sample phase and a second CO[sub 2] analyte phase. CO[sub 2] is then transported through the membrane thereby separating the CO[sub 2] with the membrane into a first CO[sub 2] sample phase and a second CO[sub 2] analyte liquid phase including an ionized, conductive, dissociated CO[sub 2] species. Next, the concentration of the ionized, conductive, dissociated CO[sub 2] species in the second CO[sub 2] analyte liquid phase is chemically amplified using a water-soluble chemical reagent which reversibly reacts with undissociated CO[sub 2] to produce conductivity changes therein corresponding to fluctuations in the partial pressure of CO[sub 2] in the first CO[sub 2] sample phase. Finally, the chemically amplified, ionized, conductive, dissociated CO[sub 2] species is introduced to a conductivity measuring instrument. Conductivity changes in the chemically amplified, ionized, conductive, dissociated CO[sub 2] species are detected using the conductivity measuring instrument. 43 figs.

Process for analyzing CO.sub.2 in air and in water

DOEpatents

Atwater, James E.; Akse, James R.; DeHart, Jeffrey

1999-01-01

The process of this invention comprises providing a membrane for separating CO.sub.2 into a first CO.sub.2 sample phase and a second CO.sub.2 analyte phase. CO.sub.2 is then transported through the membrane thereby separating the CO.sub.2 with the membrane into a first CO.sub.2 sample phase and a second CO.sub.2 analyte liquid phase including an ionized, conductive, dissociated CO.sub.2 species. Next, the concentration of the ionized, conductive, dissociated CO.sub.2 species in the second CO.sub.2 analyte liquid phase is chemically amplified using a water-soluble chemical reagent which reversibly reacts with undissociated CO.sub.2 to produce conductivity changes therein corresponding to fluctuations in the partial pressure of CO.sub.2 in the first CO.sub.2 sample phase. Finally, the chemically amplified, ionized, conductive, dissociated CO.sub.2 species is introduced to a conductivity measuring instrument. Conductivity changes in the chemically amplified, ionized, conductive, dissociated CO.sub.2 species are detected using the conductivity measuring instrument.

Process for analyzing CO{sub 2} in seawater

DOEpatents

Atwater, J.E.; Akse, J.R.; DeHart, J.

1997-07-01

The process of this invention comprises providing a membrane for separating CO{sub 2} into a first CO{sub 2} sample phase and a second CO{sub 2} analyte phase. CO{sub 2} is then transported through the membrane thereby separating the CO{sub 2} with the membrane into a first CO{sub 2} sample phase and a second CO{sub 2} analyte liquid phase including an ionized, conductive, dissociated CO{sub 2} species. Next, the concentration of the ionized, conductive, dissociated CO{sub 2} species in the second CO{sub 2} analyte liquid phase is chemically amplified using a water-soluble chemical reagent which reversibly reacts with undissociated CO{sub 2} to produce conductivity changes therein corresponding to fluctuations in the partial pressure of CO{sub 2} in the first CO{sub 2} sample phase. Finally, the chemically amplified, ionized, conductive, dissociated CO{sub 2} species is introduced to a conductivity measuring instrument. Conductivity changes in the chemically amplified, ionized, conductive, dissociated CO{sub 2} species are detected using the conductivity measuring instrument. 43 figs.

The Contribution of Ionizing Stars to the Far-Infrared and Radio Emission in the Galaxy

NASA Astrophysics Data System (ADS)

Terebey, S.; Fich, M.; Taylor, R.

1999-12-01

A summary of research activities carried out in this eighth and final progress report. The final report includes: this summary document, copies of three published research papers, plus a draft manuscript of a fourth research paper entitled "The Contribution of Ionizing Stars to the FarInfrared and Radio Emission in the Milky Way; Evidence for a Swept-up Shell and Diffuse Ionized Halo around the W4 Chimney/Supershell." The main activity during the final quarterly reporting period was research on W4, including analysis of the radio and far-infrared images, generation of shell models, a literature search, and preparation of a research manuscript. There will be additional consultation with co-authors prior to submission of the paper to the Astrophysical Journal. The results will be presented at the 4th Tetons Summer Conference on "Galactic Structure, Stars, and the ISM" in May 2000. In this fourth and last paper we show W4 has a swept-up partially ionized shell of gas and dust which is powered by the OCl 352 star cluster. Analysis shows there is dense interstellar material directly below the shell, evidence that that the lower W4 shell "ran into a brick wall" and stalled, whereas the upper W4 shell achieved "breakout" to form a Galactic chimney. An ionized halo is evidence of Lyman continuum leakage which ionizes the WIM (warm ionized medium). It has long been postulated that the strong winds and abundant ionizing photons from massive stars are responsible for much of the large scale structure in the interstellar medium (ISM), including the ISM in other galaxies. However standard HII region theory predicts few photons will escape the local HII region. The significance of W4 and this work is it provides a direct example of how stellar winds power a galactic chimney, which in turn leads to a low density cavity from which ionizing photons can escape to large distances to ionize the WIM.

The Contribution of Ionizing Stars to the Far-Infrared and Radio Emission in the Galaxy

NASA Technical Reports Server (NTRS)

Terebey, S.; Fich, M.; Taylor, R.

1999-01-01

A summary of research activities carried out in this eighth and final progress report. The final report includes: this summary document, copies of three published research papers, plus a draft manuscript of a fourth research paper entitled "The Contribution of Ionizing Stars to the FarInfrared and Radio Emission in the Milky Way; Evidence for a Swept-up Shell and Diffuse Ionized Halo around the W4 Chimney/Supershell." The main activity during the final quarterly reporting period was research on W4, including analysis of the radio and far-infrared images, generation of shell models, a literature search, and preparation of a research manuscript. There will be additional consultation with co-authors prior to submission of the paper to the Astrophysical Journal. The results will be presented at the 4th Tetons Summer Conference on "Galactic Structure, Stars, and the ISM" in May 2000. In this fourth and last paper we show W4 has a swept-up partially ionized shell of gas and dust which is powered by the OCl 352 star cluster. Analysis shows there is dense interstellar material directly below the shell, evidence that that the lower W4 shell "ran into a brick wall" and stalled, whereas the upper W4 shell achieved "breakout" to form a Galactic chimney. An ionized halo is evidence of Lyman continuum leakage which ionizes the WIM (warm ionized medium). It has long been postulated that the strong winds and abundant ionizing photons from massive stars are responsible for much of the large scale structure in the interstellar medium (ISM), including the ISM in other galaxies. However standard HII region theory predicts few photons will escape the local HII region. The significance of W4 and this work is it provides a direct example of how stellar winds power a galactic chimney, which in turn leads to a low density cavity from which ionizing photons can escape to large distances to ionize the WIM.

Mechanism of Action for Anti-Radiation Vaccine in Reducing the Biological Impact of High-Dose Irradiation

NASA Technical Reports Server (NTRS)

Maliev, Vladislav; Popov, Dmitri; Jones, Jeffrey A.; Casey, Rachael C.

2006-01-01

Ionizing radiation is a major health risk of long-term space travel, the biological consequences of which include genetic and oxidative damage. In this study, we propose an original mechanism by which high doses of ionizing radiation induce acute toxicity. We identified biological components that appear in the lymphatic vessels shortly after gamma irradiation. These radiation-induced toxins, which we have named specific radiation determinants (SRD), were generated in the irradiated tissues and then collected and circulated throughout the body via the lymph circulation and bloodstream. Depending on the type of SRD elicited, different syndromes of acute radiation sickness (ARS) were expressed. The SRDs were developed into a vaccine used to confer active immunity against acute radiation toxicity in immunologically naive animals. Animals that were pretreated with SRDs exhibited resistance to lethal doses of gamma radiation, as measured by increased survival times and survival rates. In comparison, untreated animals that were exposed to similar large doses of gamma radiation developed acute radiation sickness and died within days. This phenomenon was observed in a number of mammalian species. We partially analyzed the biochemical characteristics of the SRDs. The SRDs were large molecular weight (200-250 kDa) molecules that were comprised of a mixture of protein, lipid, carbohydrate, and mineral. Further analysis is required to further identify the SRD molecules and the biological mechanism by which the mediate the toxicity associated with acute radiation sickness. By doing so, we may develop an effective specific immunoprophylaxis as a countermeasure against the acute effects of ionizing radiation.

Equation of state and shock compression of warm dense sodium—A first-principles study

DOE PAGES

Zhang, Shuai; Driver, Kevin P.; Soubiran, Francois; ...

2017-02-21

As one of the simple alkali metals, sodium has been of fundamental interest for shock physics experiments, but knowledge of its equation of state (EOS) in hot, dense regimes is not well known. By combining path integral Monte Carlo (PIMC) results for partially ionized states at high temperatures and density functional theory molecular dynamics (DFT-MD) results at lower temperatures, we have constructed a coherent equation of state for sodium over a wide density-temperature range of 1.93-11.60 g/cm 3 and 10 3–1.29×10 8 K. We find that a localized, Hartree-Fock nodal structure in PIMC yields pressures and internal energies that aremore » consistent with DFT-MD at intermediate temperatures of 2×10 6 K. Since PIMC and DFT-MD provide a first-principles treatment of electron shell and excitation effects, we are able to identify two compression maxima in the shock Hugoniot curve corresponding to K-shell and L-shell ionization. Our Hugoniot curves provide a benchmark for widely used EOS models: SESAME, LEOS, and Purgatorio. Due to the low ambient density, sodium has an unusually high first compression maximum along the shock Hugoniot curve. At beyond 10 7 K, we show that the radiation effect leads to very high compression along the Hugoniot curve, surpassing relativistic corrections, and observe an increasing deviation of the shock and particle velocities from a linear relation. Here, we also compute the temperature-density dependence of thermal and pressure ionization processes.« less

Evidence for extended chromospheres surrounding red giant stars

NASA Technical Reports Server (NTRS)

Stencel, R. E.

1982-01-01

Observational evidence and theoretical arguments are summarized which indicate that regions of partially ionized hydrogen extending several stellar radii are an important feature of red giant and supergiant stars. The implications of the existence of extended chromospheres are examined in terms of the nature of the other atmospheres of, and mass loss from cool stars.

REVIEW OF DRAFT REVISED BLUE BOOK ON ESTIMATING CANCER RISKS FROM EXPOSURE TO IONIZING RADIATION

EPA Science Inventory

In 1994, EPA published a report, referred to as the “Blue Book,” which lays out EPA’s current methodology for quantitatively estimating radiogenic cancer risks. A follow-on report made minor adjustments to the previous estimates and presented a partial analysis of the uncertainti...

Texture analysis of CoGe2 alloy films grown heteroepitaxially on GaAs(100) using partially ionized beam deposition

NASA Astrophysics Data System (ADS)

Mello, K. E.; Murarka, S. P.; Lu, T.-M.; Lee, S. L.

1997-06-01

Reflection x-ray pole figure analysis techniques were used to study the heteroepitaxial relationships of the cobalt germanide CoGe2 to GaAs(100). The alloy films were grown using the partially ionized beam deposition technique, in which low energy Ge+ ions are employed to alter the heteroepitaxial orientation of the CoGe2 deposits. The CoGe2[001](100)∥GaAs[100](001) orientation, which has the smallest lattice mismatch, was found to occur for depositions performed at a substrate temperature around 280 °C and with ˜1200 eV Ge+ ions. Lowering the substrate temperature or reducing the Ge+ ion energy leads to CoGe2(100) orientation domination with CoGe2[100](010)∥GaAs[100](001) and CoGe2[100](001)∥GaAs[100](001). Substrate temperature alone was seen to produce only the CoGe2(100) orientation. For CoGe2(001) films, additional energy was required from Ge+ ions in the evaporant stream.

A global plasma model for reactive deposition of compound films by modulated pulsed power magnetron sputtering discharges

NASA Astrophysics Data System (ADS)

Zheng, B. C.; Wu, Z. L.; Wu, B.; Li, Y. G.; Lei, M. K.

2017-05-01

A spatially averaged, time-dependent global plasma model has been developed to describe the reactive deposition of a TiAlSiN thin film by modulated pulsed power magnetron sputtering (MPPMS) discharges in Ar/N2 mixture gas, based on the particle balance and the energy balance in the ionization region, and considering the formation and erosion of the compound at the target surface. The modeling results show that, with increasing the N2 partial pressure from 0% to 40% at a constant working pressure of 0.3 Pa, the electron temperature during the strongly ionized period increases from 4 to 7 eV and the effective power transfer coefficient, which represents the power fraction that effectively heats the electrons and maintains the discharge, increases from about 4% to 7%; with increasing the working pressure from 0.1 to 0.7 Pa at a constant N2 partial pressure of 25%, the electron temperature decreases from 10 to 4 eV and the effective power transfer coefficient decreases from 8% to 5%. Using the modeled plasma parameters to evaluate the kinetic energy of arriving ions, the ion-to-neutral flux ratio of deposited species, and the substrate heating, the variations of process parameters that increase these values lead to an enhanced adatom mobility at the target surface and an increased input energy to the substrate, corresponding to the experimental observation of surface roughness reduction, the microstructure transition from the columnar structure to the dense featureless structure, and the enhancement of phase separation. At higher N2 partial pressure or lower working pressure, the modeling results demonstrate an increase in electron temperature, which shifts the discharge balance of Ti species from Ti+ to Ti2+ and results in a higher return fraction of Ti species, corresponding to the higher Al/Ti ratio of deposited films at these conditions. The modeling results are well correlated with the experimental observation of the composition variation and the microstructure transition of deposited TiAlSiN compound films, demonstrating the applicability of this approach in understanding the characteristics of reactive MPPMS discharges as well as the composition and microstructure of deposited compound films. The model for reactive MPPMS discharges has no special limitations and is applicable to high power impulse magnetron sputtering discharges as well.

Defect chemistry and characterization of Hg(1-x)Cd(x)Te

NASA Technical Reports Server (NTRS)

Vydyanath, H. R.

1981-01-01

Undoped mercury cadmium telluride crystals were subjected to high temperature equilibration at temperatures ranging from 400 C to 655 C in various Hg atmospheres. Hall effect and mobility measurements were carried out on the crystals quenched to room temperature subsequent to the high temperature equilibration. The variation of the hole concentration in the cooled crystals at 77 K as a function of the partial pressure of Hg at the equlibration temperatures, together with a comparison of the hole mobility in the undoped samples with that in the copper and phosphorous doped samples yielded a defect model for the undoped crystals, according to which, the undoped crystals are essentially intrinsic at the equilibration temperatures and the native acceptor defects are doubly ionized. Native donor defects appear to be negligible in concentration, implying that the p to n conversion in these alloys is mainly due to residual foreign donor impurities. The thermodynamic constants for the intrinsic excitation process as well as for the incorporation of the doubly ionized native acceptor defects in the undoped crystals were obtained.

Weak soft X-ray excesses need not result from the high-frequency tail of the optical/ultraviolet bump in active galactic nuclei

NASA Technical Reports Server (NTRS)

Czerny, Bozena; Zycki, Piotr T.

1994-01-01

The broad-band ROSAT/EXOSAT X-ray spectra of six Seyfert 1 galaxies are fitted by a model consisting of a direct power law and a component due to reflection/reprocessing from a partially ionized, optically thick medium. The reflected spectrum contains emission features from various elements in the soft X-ray range. In all objects but one (Mrk 335), the fit is satisfactory, and no additional soft X-ray excess is required by the data. This means that in most sources there is no need for the thermal 'big blue bumps' to extend into soft X-rays, and the soft X-ray excesses reported previously can be explained by reflection/reprocessing. Satisfactory fits are obtained for a medium ionized by a source radiating at less than or approximately 15% of the Eddington rate. The fits require that the reflection is enhanced relative to an isotropically emitting source above a flat disk. The necessary high effectiveness of reflection in the soft X-ray band requires strong soft thermal flux dominating over hard X-rays.

Petroleomics by electrospray ionization FT-ICR mass spectrometry coupled to partial least squares with variable selection methods: prediction of the total acid number of crude oils.

PubMed

Terra, Luciana A; Filgueiras, Paulo R; Tose, Lílian V; Romão, Wanderson; de Souza, Douglas D; de Castro, Eustáquio V R; de Oliveira, Mirela S L; Dias, Júlio C M; Poppi, Ronei J

2014-10-07

Negative-ion mode electrospray ionization, ESI(-), with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was coupled to a Partial Least Squares (PLS) regression and variable selection methods to estimate the total acid number (TAN) of Brazilian crude oil samples. Generally, ESI(-)-FT-ICR mass spectra present a power of resolution of ca. 500,000 and a mass accuracy less than 1 ppm, producing a data matrix containing over 5700 variables per sample. These variables correspond to heteroatom-containing species detected as deprotonated molecules, [M - H](-) ions, which are identified primarily as naphthenic acids, phenols and carbazole analog species. The TAN values for all samples ranged from 0.06 to 3.61 mg of KOH g(-1). To facilitate the spectral interpretation, three methods of variable selection were studied: variable importance in the projection (VIP), interval partial least squares (iPLS) and elimination of uninformative variables (UVE). The UVE method seems to be more appropriate for selecting important variables, reducing the dimension of the variables to 183 and producing a root mean square error of prediction of 0.32 mg of KOH g(-1). By reducing the size of the data, it was possible to relate the selected variables with their corresponding molecular formulas, thus identifying the main chemical species responsible for the TAN values.

Ionization of pyridine: Interplay of orbital relaxation and electron correlation.

PubMed

Trofimov, A B; Holland, D M P; Powis, I; Menzies, R C; Potts, A W; Karlsson, L; Gromov, E V; Badsyuk, I L; Schirmer, J

2017-06-28

The valence shell ionization spectrum of pyridine was studied using the third-order algebraic-diagrammatic construction approximation scheme for the one-particle Green's function and the outer-valence Green's function method. The results were used to interpret angle resolved photoelectron spectra recorded with synchrotron radiation in the photon energy range of 17-120 eV. The lowest four states of the pyridine radical cation, namely, 2 A 2 (1a 2 -1 ), 2 A 1 (7a 1 -1 ), 2 B 1 (2b 1 -1 ), and 2 B 2 (5b 2 -1 ), were studied in detail using various high-level electronic structure calculation methods. The vertical ionization energies were established using the equation-of-motion coupled-cluster approach with single, double, and triple excitations (EOM-IP-CCSDT) and the complete basis set extrapolation technique. Further interpretation of the electronic structure results was accomplished using Dyson orbitals, electron density difference plots, and a second-order perturbation theory treatment for the relaxation energy. Strong orbital relaxation and electron correlation effects were shown to accompany ionization of the 7a 1 orbital, which formally represents the nonbonding σ-type nitrogen lone-pair (nσ) orbital. The theoretical work establishes the important roles of the π-system (π-π* excitations) in the screening of the nσ-hole and of the relaxation of the molecular orbitals in the formation of the 7a 1 (nσ) -1 state. Equilibrium geometric parameters were computed using the MP2 (second-order Møller-Plesset perturbation theory) and CCSD methods, and the harmonic vibrational frequencies were obtained at the MP2 level of theory for the lowest three cation states. The results were used to estimate the adiabatic 0-0 ionization energies, which were then compared to the available experimental and theoretical data. Photoelectron anisotropy parameters and photoionization partial cross sections, derived from the experimental spectra, were compared to predictions obtained with the continuum multiple scattering approach.

Microscale Solubility Measurements of Matrix-Assisted Laser Desorption-Ionization (MALDI) Matrices Using Attenuated Total Reflection (ATR) Fourier Transform Infrared Spectroscopy (FT-IR) Coupled with Partial Least Squares (PLS) Analysis.

PubMed

Gorre, Elsa; Owens, Kevin G

2016-11-01

In this work an attenuated total reflection Fourier transform infrared (FT-IR) absorption based method is used to measure the solubility of two matrix-assisted laser desorption-ionization (MALDI) matrices in a few pure solvents and mixtures of acetonitrile and water using low microliter amounts of solution. Results from a method that averages the values obtained from multiple calibration curves created by manual peak picking are compared to those predicted using a partial least squares (PLS) chemometrics approach. The PLS method provided solubility values that were in good agreement with the manual method with significantly greater ease of analysis. As a test, the solubility of adipic acid in acetone was measured using the two methods of analysis, and the values are in good agreement with solubility values reported in literature. The solubilities of the MALDI matrices α-cyano-4-hydroxy cinnamic acid (CHCA) and sinapinic acid (SA) were measured in a series of mixtures made from acetonitrile (ACN) and water; surprisingly, the results show a highly nonlinear trend. While both CHCA and SA show solubility values of less than 10 mg/mL in the pure solvents, the solubility value for SA increases to 56.3 mg/mL in a 75:25 v/v ACN:water mixture. This can have a significant effect on the matrix-to-analyte ratios in the MALDI experiment when sample protocols call for preparation of a saturated solution of the matrix in the chosen solvent system. © The Author(s) 2016.

Effects of the immobilization supports on the catalytic properties of immobilized mushroom tyrosinase: a comparative study using several substrates.

PubMed

Marín-Zamora, María Elisa; Rojas-Melgarejo, Francisco; García-Cánovas, Francisco; García-Ruiz, Pedro Antonio

2007-09-30

Mushroom tyrosinase was immobilized from an extract onto glass beads covered with one of the following compounds: the crosslinked totally cinnamoylated derivatives of glycerine, D-sorbitol, D-manitol, 1,2-O-isopropylidene-alpha-D-glucofuranose, D-glucuronic acid, D-gulonic acid, sucrose, D-glucosone, D-arabinose, D-fructose, D-glucose, ethyl-D-glucopyranoside, inuline, dextrine, dextrane or starch, or the partially cinnamoylated derivative 3,5,6-tricinnamoyl-D-glucofuranose which was obtained by the acid hydrolysis of 1,2-O-isopropylidene-alpha-d-glucofuranose. The enzyme was immobilized by direct adsorption onto the support and the quantity of tyrosinase immobilized was found to increase with the hydrophobicity of the supports. The kinetic constants of immobilized tyrosinase acting on the substrates, 4-tert-butylcatechol, dopamine and DL-dopa, were studied. When immobilized tyrosinase acted on 4-tert-butylcatechol, the values of K(m)(app) were lower than these obtained for tyrosinase in solution while, when dopamine and DL-dopa were used, the K(m)(app) were higher. The order of the substrates as regards their ionizable groups, DL-dopa (two ionizable groups)>dopamine (one ionizable group)>4-tert-butylcatechol (no ionizable group) coincided with the order of the K(m)(app) values shown by tyrosinase immobilized on the hydrophobic supports, and was the inverse of that observed for tyrosinase in solution. The K(m)(app) values of immobilized tyrosinase were in all cases higher than those of soluble tyrosinase and depended on the nature of the support and the hydrophobicity of the substrate, meaning that it is possible to design supports with different degrees of selectivity towards a mixture of enzyme substrates in the reaction medium.

A Combined Desorption Ionization by Charge Exchange (DICE) and Desorption Electrospray Ionization (DESI) Source for Mass Spectrometry

NASA Astrophysics Data System (ADS)

Chan, Chang-Ching; Bolgar, Mark S.; Miller, Scott A.; Attygalle, Athula B.

2011-01-01

A source that couples the desorption ionization by charge exchange (DICE) and desorption electrospray ionization (DESI) techniques together was demonstrated to broaden the range of compounds that can be analyzed in a single mass spectrometric experiment under ambient conditions. A tee union was used to mix the spray reagents into a partially immiscible blend before this mixture was passed through a conventional electrospray (ES) probe capillary. Using this technique, compounds that are ionized more efficiently by the DICE method and those that are ionized better with the DESI procedure could be analyzed simultaneously. For example, hydroquinone, which is not detected when subjected to DESI-MS in the positive-ion generation mode, or the sodium adduct of guaifenesin, which is not detected when examined by DICE-MS, could both be detected in one experiment when the two techniques were combined. The combined technique was able to generate the molecular ion, proton and metal adduct from the same compound. When coupled to a tandem mass spectrometer, the combined source enabled the generation of product ion spectra from the molecular ion and the [M + H]+ or [M + metal]+ ions of the same compound without the need to physically change the source from DICE to DESI. The ability to record CID spectra of both the molecular ion and adduct ions in a single mass spectrometric experiment adds a new dimension to the array of mass spectrometric methods available for structural studies.

A feasibility study of ion implantation techniques for mass spectrometer calibration

NASA Technical Reports Server (NTRS)

Koslin, M. E.; Krycuk, G. A.; Schatz, J. G., Jr.; White, F. A.; Wood, G. M.

1978-01-01

An experimental study was undertaken to examine the feasibility of using ion-implanted filaments doped with either an alkali metal or noble gas for in situ recalibration of onboard mass spectrometers during extended space missions. Implants of rubidium and krypton in rhenium ribbon filaments were subsequently tested in a bakeable 60 deg sector mass spectrometer operating in the static mode. Surface ionization and electron impact ion sources were both used, each yielding satisfactory results. The metallic implant with subsequent ionization provided a means of mass scale calibration and determination of system operating parameters, whereas the noble gas thermally desorbed into the system was more suited for partial pressure and sensitivity determinations.

Microwave continuum measurements and estimates of mass loss rates for cool giants and supergiants

NASA Technical Reports Server (NTRS)

Drake, S. A.; Linsky, J. L.

1986-01-01

Attention is given to the results of a sensitive, 6-cm radio continuum survey conducted with the NRAO VLA of 39 of the nearest single cool giants and supergiants of G0-M5 spectral types; the survey was conducted in order to obtain accurate measurements of the mass loss rates of ionized gas for a representative sample of such stars, in order to furnish constraints for, and a better understanding of, the total mass loss rates. The inferred angular diameters for the cool giant sources are noted to be twice as large as photospheric angular diameters, implying that these stars are surrounded by extended chromospheres containing warm partially ionized gas.

Cataract production in mice by heavy charged particles

NASA Technical Reports Server (NTRS)

Ainsworth, E. J.; Jose, U.; Yang, V. V.; Barker, M. E.

1981-01-01

The cataractogenic effects of heavy charged particles are evaluated in mice in relation to dose and ionization density. The relative biological effectiveness in relation to linear energy transfer for various particles is considered. Results indicated that low single doses (5 to 20 rad) of Fe 56 or Ar 40 particles are cataractogenic at 11 to 18 months after irradiation; onset and density of the opacification are dose related and cataract density (grade) at 9, 11, 13, and 16 months after irradiation shows partial linear energy transfer dependence. The severity of cataracts is reduced significantly when 417 rad of Co 60 gamma radiation is given in 24 weekly 17 rad fractions compared to giving this radiation as a single dose, but cataract severity is not reduced by fractionation of C12 doses over 24 weeks.

PDSOI and Radiation Effects: An Overview

NASA Technical Reports Server (NTRS)

Forgione, Joshua B.

2005-01-01

Bulk silicon substrates are a common characteristic of nearly all commercial, Complementary Metal-Oxide-Semiconductor (CMOS), integrated circuits. These devices operate well on Earth, but are not so well received in the space environment. An alternative to bulk CMOS is the Silicon-On-Insulator (SOI), in which a &electric isolates the device layer from the substrate. SO1 behavior in the space environment has certain inherent advantages over bulk, a primary factor in its long-time appeal to space-flight IC designers. The discussion will investigate the behavior of the Partially-Depleted SO1 (PDSOI) device with respect to some of the more common space radiation effects: Total Ionized Dose (TID), Single-Event Upsets (SEUs), and Single-Event Latchup (SEL). Test and simulation results from the literature, bulk and epitaxial comparisons facilitate reinforcement of PDSOI radiation characteristics.

Influence of Total Ionizing Dose Irradiation on Low-Frequency Noise Responses in Partially Depleted SOI nMOSFETs

NASA Astrophysics Data System (ADS)

Peng, Chao; En, Yun-Fei; Lei, Zhi-Feng; Chen, Yi-Qiang; Liu, Yuan; Li, Bin

2017-11-01

Not Available Supported by the National Postdoctoral Program for Innovative Talents under Grant No BX201600037, the Science and Technology Research Project of Guangdong Province under Grant Nos 2015B090901048 and 2015B090912002, and the Distinguished Young Scientist Program of Guangdong Province under Grant No 2015A030306002.

Modelling extended chromospheres

NASA Technical Reports Server (NTRS)

Linsky, J. L.

1986-01-01

Attention is given to the concept that the warm, partially ionized plasma (presently called chromosphere) associated with such stars as Alpha Boo and Rho Per extends outwards at least several photospheric radii. Calculations are presented for the Mg II K line in light of two input model atmospheres. Specific predictions are deduced from the results obtained by each of the two models.

Biological effects of Trichoderma harzianum peptaibols on mammalian cells.

PubMed

Peltola, Joanna; Ritieni, Alberto; Mikkola, Raimo; Grigoriev, Pavel A; Pócsfalvi, Gabriella; Andersson, Maria A; Salkinoja-Salonen, Mirja S

2004-08-01

Trichoderma species isolated from water-damaged buildings were screened for toxicity by using boar sperm cells as indicator cells. The crude methanolic cell extract from Trichoderma harzianum strain ES39 inhibited the boar sperm cell motility at a low exposure concentration (50% effective concentration, 1 to 5 microg [dry weight] ml of extended boar semen(-1)). The same exposure concentration depleted the boar sperm cells of NADH(2). Inspection of the exposed boar sperm cells by transmission electron microscopy revealed damage to the plasma membrane. By using the black lipid membrane technique, it was shown that the semipurified metabolites (eluted from a SepPak C(18) cartridge) of T. harzianum strain ES39 induced voltage-dependent conductivity. The high-performance liquid chromatography-purified metabolites of T. harzianum strain ES39 dissipated the mitochondrial membrane potential (Deltapsi(m)) of human lung epithelial carcinoma cells (cell line A549). The semipurified metabolites (eluted from a SepPak C(18) cartridge) of T. harzianum strain ES39 were analyzed by mass spectrometry (MS). Matrix-assisted laser desorption ionization and nanoflow electrospray ionization MS revealed five major peptaibols, each of which contained 18 residues and had a mass ranging from 1,719 to 1,775 Da. Their partial amino acid sequences were determined by collision-induced dissociation tandem MS.

Biological Effects of Trichoderma harzianum Peptaibols on Mammalian Cells

PubMed Central

Peltola, Joanna; Ritieni, Alberto; Mikkola, Raimo; Grigoriev, Pavel A.; Pócsfalvi, Gabriella; Andersson, Maria A.; Salkinoja-Salonen, Mirja S.

2004-01-01

Trichoderma species isolated from water-damaged buildings were screened for toxicity by using boar sperm cells as indicator cells. The crude methanolic cell extract from Trichoderma harzianum strain ES39 inhibited the boar sperm cell motility at a low exposure concentration (50% effective concentration, 1 to 5 μg [dry weight] ml of extended boar semen−1). The same exposure concentration depleted the boar sperm cells of NADH2. Inspection of the exposed boar sperm cells by transmission electron microscopy revealed damage to the plasma membrane. By using the black lipid membrane technique, it was shown that the semipurified metabolites (eluted from a SepPak C18 cartridge) of T. harzianum strain ES39 induced voltage-dependent conductivity. The high-performance liquid chromatography-purified metabolites of T. harzianum strain ES39 dissipated the mitochondrial membrane potential (Δψm) of human lung epithelial carcinoma cells (cell line A549). The semipurified metabolites (eluted from a SepPak C18 cartridge) of T. harzianum strain ES39 were analyzed by mass spectrometry (MS). Matrix-assisted laser desorption ionization and nanoflow electrospray ionization MS revealed five major peptaibols, each of which contained 18 residues and had a mass ranging from 1,719 to 1,775 Da. Their partial amino acid sequences were determined by collision-induced dissociation tandem MS. PMID:15294840

Proton transfer mediated by the vibronic coupling in oxygen core ionized states of glyoxalmonoxime studied by infrared-X-ray pump-probe spectroscopy.

PubMed

Felicíssimo, V C; Guimarães, F F; Cesar, A; Gel'mukhanov, F; Agren, H

2006-11-30

The theory of IR-X-ray pump-probe spectroscopy beyond the Born-Oppenheimer approximation is developed and applied to the study of the dynamics of intramolecular proton transfer in glyoxalmonoxime leading to the formation of the tautomer 2-nitrosoethenol. Due to the IR pump pulses the molecule gains sufficient energy to promote a proton to a weakly bound well. A femtosecond X-ray pulse snapshots the wave packet route and, hence, the dynamics of the proton transfer. The glyoxalmonoxime molecule contains two chemically nonequivalent oxygen atoms that possess distinct roles in the hydrogen bond, a hydrogen donor and an acceptor. Core ionizations of these form two intersecting core-ionized states, the vibronic coupling between which along the OH stretching mode partially delocalizes the core hole, resulting in a hopping of the core hole from one site to another. This, in turn, affects the dynamics of the proton transfer in the core-ionized state. The quantum dynamical simulations of X-ray photoelectron spectra of glyoxalmonoxime driven by strong IR pulses demonstrate the general applicability of the technique for studies of intramolecular proton transfer in systems with vibronic coupling.

The Fifth ISM Phase as Revealed by Faraday Rotation

NASA Astrophysics Data System (ADS)

Heiles, Carl E.

2011-01-01

In the diffuse ISM, phases are classically categorized as largely ionized or neutral. The neutral phases come in two flavors, the Cold and Warm Neutral Media (the CNM and WNM), which have typical temperatures 50 and 5000 K. The ionized phases also come in two flavors, again classified by temperature: the Warm and Hot Ionized Media (the WIM and the HIM), which have typical temperatures 8000 and 106 K. There lurks a fifth phase, the Warm Partially Ionized Medium (WPIM). This is not widely recognized, mainly because it's presence is hard to establish observationally. It is well represented by the Local Interstellar Cloud (LIC), whose properties are very well specified in a series of papers by Redfield and Linsky. This fifth phase has a relatively high electron column but low emission measure, so it is not easily seen in H alpha. However, if the region is permeated by a typical magnetic field ( 6 microGauss), then it can produce a recognizable signature in Faraday rotation. We show a few examples and discuss the potential for large-scale mapping of this fifth ISM phase. Support for this work was provided in part by NSF grant AST-0908572.

Metabolic and respiratory status of cold-stunned Kemp's ridley sea turtles (Lepidochelys kempii).

PubMed

Innis, Charles J; Tlusty, Michael; Merigo, Constance; Weber, E Scott

2007-08-01

"Cold-stunning" of sea turtles has been reported as a naturally occurring stressor for many years; however, the physiologic status of cold-stunned turtles has only been partially described. This study investigated initial and convalescent venous blood gas, acid-base, and critical plasma biochemical data for 26 naturally cold-stunned Kemp's ridley sea turtles (Lepidochelys kempii) from Cape Cod, MA, USA. Samples were analyzed for pH, pCO(2), pO(2), bicarbonate, plasma osmolality, sodium, potassium, chloride, ionized calcium, ionized magnesium, glucose, lactate, and blood urea nitrogen using a clinical point-of-care analyzer. Data were corrected for the patient's body temperature using both species-specific and more general correction methods. In general, venous blood gas, acid-base, and plasma biochemical data obtained for surviving cold-stunned Kemp's ridley sea turtles were consistent with previously documented data for sea turtles exposed to a wide range of temperatures and physiologic stressors. Data indicated that turtles were initially affected by metabolic and respiratory acidosis. Initial pH-corrected ionized calcium concentrations were lower than convalescent concentrations, and initial pH-corrected ionized magnesium concentrations were higher than convalescent concentrations.

In silico modelling of radiation effects towards personalised treatment in radiotherapy

NASA Astrophysics Data System (ADS)

Marcu, Loredana G.; Marcu, David

2017-12-01

In silico models applied in medical physics are valuable tools to assist in treatment optimization and personalization, which represent the ultimate goal of today's radiotherapy. Next to several biological and biophysical factors that influence tumour response to ionizing radiation, hypoxia and cancer stem cells are critical parameters that dictate the final outcome. The current work presents the results of an in silico model of tumour growth and response to radiation developed using Monte Carlo techniques. We are presenting the impact of partial oxygen tension and repopulation via cancer stem cells on tumour control after photon irradiation, highlighting some of the gaps that clinical research needs to fill for better customized treatment.

Validation of Multitemperature Nozzle Flow Code

NASA Technical Reports Server (NTRS)

Park, Chul; Lee, Seung -Ho.

1994-01-01

A computer code nozzle in n-temperatures (NOZNT), which calculates one-dimensional flows of partially dissociated and ionized air in an expanding nozzle, is tested against three existing sets of experimental data taken in arcjet wind tunnels. The code accounts for the differences among various temperatures, i.e., translational-rotational temperature, vibrational temperatures of individual molecular species, and electron-electronic temperature, and the effects of impurities. The experimental data considered are (1) the spectroscopic emission data; (2) electron beam data on vibrational temperature; and (3) mass-spectrometric species concentration data. It is shown that the impurities are inconsequential for the arcjet flows, and the NOZNT code is validated by numerically reproducing the experimental data.

Applications of PET CT in clinical practice: Present and future

NASA Astrophysics Data System (ADS)

Costa, Durval Campos

2007-02-01

Radionuclide imaging and specially positron emission tomography (PET) has already demonstrated its benefits in three major medical subjects, i.e. neurology, cardiology and particularly clinical oncology. More recently the combination of PET and X-ray computed tomography (CT) as PET-CT led to a significant increment of the already large number of clinical applications of this imaging modality. This "anatomy-metabolic fusion" also known as Metabolic Imaging has its future assured if we can: (1) improve resolution reducing partial volume effect, (2) achieve very fast whole body imaging, (3) obtain accurate quantification of specific functions with higher contrast resolution and, if possible, (4) reduce exposure rates due to the unavoidable use of ionizing radiation.

Does radiative feedback by the first stars promote or prevent second generation star formation?

NASA Astrophysics Data System (ADS)

Ahn, Kyungjin; Shapiro, Paul R.

2007-03-01

We study the effect of starlight from the first stars on the ability of other minihaloes in their neighbourhood to form additional stars. The first stars in the Λ cold dark matter (ΛCDM) universe are believed to have formed in minihaloes of total mass ~105-6 Msolar at redshifts z >~ 20, when molecular hydrogen (H2) formed and cooled the dense gas at their centres, leading to gravitational collapse. Simulations suggest that the Population III (Pop III) stars thus formed were massive (~100 Msolar) and luminous enough in ionizing radiation to cause an ionization front (I-front) to sweep outward, through their host minihalo and beyond, into the intergalactic medium. Our previous work suggested that this I-front was trapped when it encountered other, nearby minihaloes, and that it failed to penetrate the dense gas at their centres within the lifetime of the Pop III stars (<~3 Myr). The question of what the dynamical consequences were for these target minihaloes, of their exposure to the ionizing and dissociating starlight from the Pop III star requires further study, however. Towards this end, we have performed a series of detailed, one-dimensional (1D), radiation-hydrodynamical simulations to answer the question of whether star formation in these surrounding minihaloes was triggered or suppressed by radiation from the first stars. We have varied the distance to the source (and, hence, the flux) and the mass and evolutionary stage of the target haloes to quantify this effect. We find (1) trapping of the I-front and its transformation from R-type to D-type, preceded by a shock front; (2) photoevaporation of the ionized gas (i.e. all gas originally located outside the trapping radius); (3) formation of an H2 precursor shell which leads the I-front, stimulated by partial photoionization; and (4) the shock-induced formation of H2 in the minihalo neutral core when the shock speeds up and partially ionizes the gas. The fate of the neutral core is mostly determined by the response of the core to this shock front, which leads to molecular cooling and collapse that, when compared to the same halo without external radiation, is (a) expedited, or (b) delayed, or (c) unaltered, or (d) reversed or prevented, depending upon the flux (i.e. distance to the source) and the halo mass and evolutionary stage. When collapse is expedited, star formation in neighbouring minihaloes or in merging subhaloes within the host minihalo sometimes occurs within the lifetime of the first star. Roughly speaking, most haloes that were destined to cool, collapse and form stars in the absence of external radiation are found to do so even when exposed to the first Pop III star in their neighbourhood, while those that would not have done so are still not able to. A widely held view that the first Pop III stars must exert either positive or negative feedback on the formation of the stars in neighbouring minihaloes should, therefore, be revisited.

A RELATION BETWEEN THE WARM NEUTRAL AND IONIZED MEDIA OBSERVED IN THE CANADIAN GALACTIC PLANE SURVEY

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

Foster, T.; Kothes, R.; Brown, J. C., E-mail: Tyler.Foster@nrc-cnrc.gc.ca

2013-08-10

We report on a comparison between 21 cm rotation measure (RM) and the optically thin atomic hydrogen column density (N{sub H{sub I}}({tau} {yields} 0)) measured toward unresolved extragalactic sources in the Galactic plane of the northern sky. H I column densities integrated to the Galactic edge are measured immediately surrounding each of nearly 2000 sources in 1 arcmin 21 cm line data, and are compared to RMs observed from polarized emission of each source. RM data are binned in column density bins 4 Multiplication-Sign 10{sup 20} cm{sup -2} wide, and one observes a strong relationship between the number of hydrogenmore » atoms in a 1 cm{sup 2} column through the plane and the mean RM along the same line of sight and path length. The relationship is linear over one order of magnitude (from 0.8 to 14 Multiplication-Sign 10{sup 21} atoms cm{sup -2}) of column densities, with a constant RM/N{sub H{sub I}}{approx} -23.2 {+-} 2.3 rad m{sup -2}/10{sup 21} atoms cm{sup -2}, and a positive RM of 45.0 {+-} 13.8 rad m{sup -2} in the presence of no atomic hydrogen. This slope is used to calculate a mean volume-averaged magnetic field in the second quadrant of (B{sub Parallel-To }) {approx}1.0 {+-} 0.1 {mu}G directed away from the Sun, assuming an ionization fraction of 8% (consistent with the warm-neutral medium; WNM). The remarkable consistency between this field and (B) = 1.2 {mu}G found with the same RM sources and a Galactic model of dispersion measures (DMs) suggests that electrons in the partially ionized WNM are mainly responsible for pulsar DMs, and thus the partially ionized WNM is the dominant form of the magneto-ionic interstellar medium.« less

The p53-reactivating small molecule RITA induces senescence in head and neck cancer cells.

PubMed

Chuang, Hui-Ching; Yang, Liang Peng; Fitzgerald, Alison L; Osman, Abdullah; Woo, Sang Hyeok; Myers, Jeffrey N; Skinner, Heath D

2014-01-01

TP53 is the most commonly mutated gene in head and neck cancer (HNSCC), with mutations being associated with resistance to conventional therapy. Restoring normal p53 function has previously been investigated via the use of RITA (reactivation of p53 and induction of tumor cell apoptosis), a small molecule that induces a conformational change in p53, leading to activation of its downstream targets. In the current study we found that RITA indeed exerts significant effects in HNSCC cells. However, in this model, we found that a significant outcome of RITA treatment was accelerated senescence. RITA-induced senescence in a variety of p53 backgrounds, including p53 null cells. Also, inhibition of p53 expression did not appear to significantly inhibit RITA-induced senescence. Thus, this phenomenon appears to be partially p53-independent. Additionally, RITA-induced senescence appears to be partially mediated by activation of the DNA damage response and SIRT1 (Silent information regulator T1) inhibition, with a synergistic effect seen by combining either ionizing radiation or SIRT1 inhibition with RITA treatment. These data point toward a novel mechanism of RITA function as well as hint to its possible therapeutic benefit in HNSCC.

Modeling of laser-induced ionization of solid dielectrics for ablation simulations: role of effective mass

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly

2010-11-01

Modeling of laser-induced ionization and heating of conduction-band electrons by laser radiation frequently serves as a basis for simulations supporting experimental studies of laser-induced ablation and damage of solid dielectrics. Together with band gap and electron-particle collision rate, effective electron mass is one of material parameters employed for the ionization modeling. Exact value of the effective mass is not known for many materials frequently utilized in experiments, e.g., fused silica and glasses. Because of that reason, value of the effective mass is arbitrary varied around "reasonable values" for the ionization modeling. In fact, it is utilized as a fitting parameter to fit experimental data on dependence of ablation or damage threshold on laser parameters. In this connection, we study how strong is the influence of variations of the effective mass on the value of conduction-band electron density. We consider influence of the effective mass on the photo-ionization rate and rate of impact ionization. In particular, it is shown that the photo-ionization rate can vary by 2-4 orders of magnitude with variation of effective mass by 50%. Impact ionization shows a much weaker dependence on effective mass, but it significantly enhances the variations of seed-electron density produced by the photo-ionization. Utilizing those results, we demonstrate that variation of effective mass by 50% produces variations of conduction-band electron density by 6 orders of magnitude. In this connection, we discuss the general issues of the current models of laser-induced ionization.

Micrometeoroid ablation simulated in the laboratory

NASA Astrophysics Data System (ADS)

Sternovsky, Zoltan; Thomas, Evan W.; DeLuca, Michael; Horanyi, Mihaly; Janches, Diego; Munsat, Tobin L.; Plane, John M. C.

2016-04-01

A facility is developed to simulate the ablation of micrometeoroids in laboratory conditions, which also allows measuring the ionization probability of the ablated material. An electrostatic dust accelerator is used to generate iron and meteoric analog particles with velocities 10-50 km/s. The particles are then introduced into a cell filled with nitrogen, air or carbon dioxide gas with pressures adjustable in the 0.02 - 0.5 Torr range, where the partial or complete ablation of the particle occurs over a short distance. An array of biased electrodes is used to collect the ionized products with spatial resolution along the ablating particles' path, allowing thus the study of the temporal resolution of the process. A simple ablation model is used to match the observations. For completely ablated particles the total collected charge directly yields the ionization efficiency for. The measurements using iron particles in N2 and air are in relatively good agreement with earlier data. The measurements with CO2 and He gases, however, are significantly different from the expectations.

Fabrication of gas sensor based on field ionization from SWCNTs with tripolar microelectrode

NASA Astrophysics Data System (ADS)

Cai, Shengbing; Zhang, Yong; Duan, Zhemin

2012-12-01

We report the nanofabrication of a sulfur dioxide (SO2) sensor with a tripolar on-chip microelectrode utilizing a film of single-walled carbon nanotubes (SWCNTs) as the field ionization cathode, where the ion flow current and the partial discharge current generated by the field ionization process of gaseous molecules can be gauged to gas species and concentration. The variation of the sensitivity is less than 4% for all of the tested devices, and the sensor has selectivity against gases such as He, NO2, CO, H2, SO2 and O2. Further, the sensor response presents well-defined and reproducible linear behavior with regard to concentration in the range investigated and a detection limitation of <˜0.5 ppm for SO2. More importantly, a tripolar on-chip microelectrode with SWCNTs as a cathode exhibits an impressive performance with respect to stability and anti-oxidation behavior, which are significantly better than had been possible before in the traditional bipolar sensor under explicit circumstances at room temperature.

Acceleration of ions and neutrals by a traveling electrostatic wave

NASA Astrophysics Data System (ADS)

Lee, K. H.; Lee, L. C.; Wong, A. Y.

2018-02-01

We propose a new scheme for accelerating a weakly ionized gas by externally imposing a sinusoidal electrostatic (ES) potential in a tubular system. The weakly ionized gas consists of three fluid components: neutral hydrogen fluid ( H ), positively charged fluid ( H + ), and negatively charged fluids ( H - and/or e - ), as an example. The sinusoidal ES potential is imposed on a series of conductive meshes in the tubular system, and its phase varies with time and space to mimic a traveling ES wave. The charged fluids are trapped and accelerated by the sinusoidal ES potential, while the neutral fluid is accelerated through neutral-ion collisions. The neutral fluid can be accelerated to the wave phase velocity in a few neutral-ion collision times. The whole device remains charge-neutral, and there is no build-up of space charge. The acceleration scheme can be applied to, for example, the propulsion of glider in the air, partially ionized plasma in a chamber, spacecraft, and wind tunnel.

An equation for the prediction of human skin permeability of neutral molecules, ions and ionic species.

PubMed

Zhang, Keda; Abraham, Michael H; Liu, Xiangli

2017-04-15

Experimental values of permeability coefficients, as log K p , of chemical compounds across human skin were collected by carefully screening the literature, and adjusted to 37°C for the effect of temperature. The values of log K p for partially ionized acids and bases were separated into those for their neutral and ionic species, forming a total data set of 247 compounds and species (including 35 ionic species). The obtained log K p values have been regressed against Abraham solute descriptors to yield a correlation equation with R 2 =0.866 and SD=0.432 log units. The equation can provide valid predictions for log K p of neutral molecules, ions and ionic species, with predictive R 2 =0.858 and predictive SD=0.445 log units calculated by the leave-one-out statistics. The predicted log K p values for Na + and Et 4 N + are in good agreement with the observed values. We calculated the values of log K p of ketoprofen as a function of the pH of the donor solution, and found that log K p markedly varies only when ketoprofen is largely ionized. This explains why models that neglect ionization of permeants still yield reasonable statistical results. The effect of skin thickness on log K p was investigated by inclusion of two indicator variables, one for intermediate thickness skin and one for full thickness skin, into the above equation. The newly obtained equations were found to be statistically very close to the above equation. Therefore, the thickness of human skin used makes little difference to the experimental values of log K p . Copyright © 2017 Elsevier B.V. All rights reserved.

Matlab fractal techniques used to study the structural degradation caused by alpha radiation to laser mirrors

NASA Astrophysics Data System (ADS)

Ioan, M.-R.

2018-01-01

Almost all optical diagnostic systems associated with classical particle accelerators or with new state-of-the-art particle accelerators, such as those developed within the European Collaboration ELI-NP (Extreme Light Infrastructure-Nuclear Physics) (involving extreme power laser beams), contain in their infrastructure high quality laser mirrors, used for their reflectivity and/or their partial transmittance. These high quality mirrors facilitate the extraction and handling of optical signals. When optical mirrors are exposed to high energy ionizing radiation fields, their optical and structural properties will change over time and their functionality will be affected, meaning that they will provide imprecise information. In some experiments, being exposed to mixed laser and accelerated particle beams, the deterioration of laser mirrors is even more acute, since the destruction mechanisms of both types of beams are cumulated. The main task of the work described in this paper was to find a novel specific method to analyse and highlight such degradation processes. By using complex fractal techniques integrated in a MATLAB code, the effects induced by alpha radiation to laser mirrors were studied. The fractal analysis technique represents an alternative approach to the classical Euclidean one. It can be applied for the characterization of the defects occurred in mirrors structure due to their exposure to high energy alpha particle beams. The proposed method may be further integrated into mirrors manufacturing process, as a testing instrument, to obtain better quality mirrors (enhanced resistance to high energy ionizing beams) by using different types of reflective coating materials and different deposition techniques. Moreover, the effect of high energy alpha ionizing particles on the optical properties of the exposed laser mirrors was studied by using spectrophotometric techniques.

The production of CO(+) (B2Sigma +) from dissociative photoionization excitation of CO2

NASA Technical Reports Server (NTRS)

Wu, C. Y. R.; Judge, D. L.

1986-01-01

The dissociative photoionization excitation process in CO2 is studied. In contrast to previous studies, attention is focused on the vibrational and rotational levels produced in fragment ions, partial cross-section measurements for producing such fragment ions in a specific quantum state, and the mechanisms that govern the dissociative ionization excitation processes. The partial fluorescence cross section for the production of CO(+) (B2Sigma +) from CO2 over a wide wavelength range was measured. It is concluded that the production of the CO(+) (B2Sigma +) fragment near the threshold is through a direct dissociative photoionization process.

Saha equation, single and two particle states

NASA Technical Reports Server (NTRS)

Kraeft, W. D.; Girardeau, M. D.; Strege, B.

1990-01-01

Single- and two-particle properties in a dense plasma are discussed in connection with their role in the mass action law for a partially ionized plasma. The two-particle-bound states are nearly density independent, while the continuum is essentially shifted. The single-particle states are damped, and their energy has a negative shift and a parabolic behavior for small momenta.

The generation, destination, and astrophysical applications of magnetohydrodynamic turbulence

NASA Astrophysics Data System (ADS)

Xu, Siyao; Lazarian, Alex; Zhang, Bing

2017-01-01

The ubiquitous turbulence in the interstellar medium (ISM) participates in astrophysical processes over a huge dynamic range of scales. Understanding the turbulence properties in the multiphase, magnetized, partially ionized, and compressible ISM is the fundamental step prior to the studies of the ISM physics and other fields of astrophysics. I feel that a triad of analytical, numerical and observational efforts provides a winning combination to understand this complex system and solve long-standing puzzles. I have intensively studied the fundamental physics of magnetohydrodynamic (MHD) turbulence, and focused on two primary domains, dynamo and dissipation, which concern the origin of strong magnetic fields and the destination of turbulence, respectively. I further applied my theoretical studies in interpreting numerical results and observational data in various astrophysical contexts. The advanced analyses of MHD turbulence enable me to address a number of challenging astrophysical problems, e.g. the importance of magnetic fields for star formation in the early and present-day universe, new methods of measuring magnetic fields, the density distribution in the Galaxy and the host galaxy of a fast radio burst, the diffusion and acceleration of cosmic rays in partially ionized ISM phases.

PROM7: 1D modeler of solar filaments or prominences

NASA Astrophysics Data System (ADS)

Gouttebroze, P.

2018-05-01

PROM7 is an update of PROM4 (ascl:1306.004) and computes simple models of solar prominences and filaments using Partial Radiative Distribution (PRD). The models consist of plane-parallel slabs standing vertically above the solar surface. Each model is defined by 5 parameters: temperature, density, geometrical thickness, microturbulent velocity and height above the solar surface. It solves the equations of radiative transfer, statistical equilibrium, ionization and pressure equilibria, and computes electron and hydrogen level population and hydrogen line profiles. Moreover, the code treats calcium atom which is reduced to 3 ionization states (Ca I, Ca II, CA III). Ca II ion has 5 levels which are useful for computing 2 resonance lines (H and K) and infrared triplet (to 8500 A).

A low-energy metal-ion source for primary ion deposition and accelerated ion doping during molecular-beam epitaxy

NASA Astrophysics Data System (ADS)

Hasan, M.-A.; Knall, J.; Barnett, S. A.; Rockett, A.; Sundgren, J.-E.

1987-10-01

A single-grid electron-impact ultrahigh vacuum (UHV) compatible low-energy ion gun capable of operating with a low vapor pressure solid source material such as In is presented. The gun consists of a single chamber which integrates the functions of an effusion cell, a vapor transport tube, and a glow discharge ionizer. The initial results of experiments designed to study the role of ion/surface interactions during nucleation and the early stages of crystal growth in UHV revealed that, for deposition on amorphous substrates, the use of a partially ionized In(+) beam resulted in a progressive shift towards larger island sizes, a decreased rate of secondary nucleation, and a more uniform island size distribution.

Numerical Studies of Impurities in Fusion Plasmas

DOE R&D Accomplishments Database

Hulse, R. A.

1982-09-01

The coupled partial differential equations used to describe the behavior of impurity ions in magnetically confined controlled fusion plasmas require numerical solution for cases of practical interest. Computer codes developed for impurity modeling at the Princeton Plasma Physics Laboratory are used as examples of the types of codes employed for this purpose. These codes solve for the impurity ionization state densities and associated radiation rates using atomic physics appropriate for these low-density, high-temperature plasmas. The simpler codes solve local equations in zero spatial dimensions while more complex cases require codes which explicitly include transport of the impurity ions simultaneously with the atomic processes of ionization and recombination. Typical applications are discussed and computational results are presented for selected cases of interest.

Theory of space charge limited currents in films and nanowires with dopants

NASA Astrophysics Data System (ADS)

Zhang, Xiaoguang; Pantelides, Sokrates

2015-03-01

We show that proper description of the space charge limited currents (SCLC) in a homogeneous bulk material must account fully for the effect of the dopants and the interplay between dopants and traps. The sharp rise in the current at the trap-filled-limit (TFL) is partially mitigated by the dopant energy levels and the Frenkel effect, namely the lowering of the ionization energy by the electric field, which is screened by the free carriers. In nanowires, lack of effective screening causes the trap occupation at small biases to reach a high level comparable to the TFL in bulk. This explains the high current density in SCLCs observed in nanowires. This work is supported by the LDRD program at ORNL. Portion of this research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

Energy dependence of effective electron mass and laser-induced ionization of wide band-gap solids

NASA Astrophysics Data System (ADS)

Gruzdev, V. E.

2008-10-01

Most of the traditional theoretical models of laser-induced ionization were developed under the assumption of constant effective electron mass or weak dependence of the effective mass on electron energy. Those assumptions exclude from consideration all the effects resulting from significant increase of the effective mass with increasing of electron energy in real the conduction band. Promotion of electrons to the states with high effective mass can be done either via laserinduced electron oscillations or via electron-particle collisions. Increase of the effective mass during laser-material interactions can result in specific regimes of ionization. Performing a simple qualitative analysis by comparison of the constant-mass approximation vs realistic dependences of the effective mass on electron energy, we demonstrate that the traditional ionization models provide reliable estimation of the ionization rate in a very limited domain of laser intensity and wavelength. By taking into account increase of the effective mass with electron energy, we demonstrate that special regimes of high-intensity photo-ionization are possible depending on laser and material parameters. Qualitative analysis of the energy dependence of the effective mass also leads to conclusion that the avalanche ionization can be stopped by the effect of electron trapping in the states with large values of the effective mass.

High-resolution electron spectroscopy of lanthanide (Ce, Pr, and Nd) complexes of cyclooctatetraene: the role of 4f electrons.

PubMed

Kumari, Sudesh; Roudjane, Mourad; Hewage, Dilrukshi; Liu, Yang; Yang, Dong-Sheng

2013-04-28

Cerium, praseodymium, and neodymium complexes of 1,3,5,7-cyclooctatetraene (COT) complexes were produced in a laser-vaporization metal cluster source and studied by pulsed-field ionization zero electron kinetic energy spectroscopy and quantum chemical calculations. The computations included the second-order Møller-Plesset perturbation theory, the coupled cluster method with single, double, and perturbative triple excitations, and the state-average complete active space self-consistent field method. The spectrum of each complex exhibits multiple band systems and is assigned to ionization of several low-energy electronic states of the neutral complex. This observation is different from previous studies of M(COT) (M = Sc, Y, La, and Gd), for which a single band system was observed. The presence of the multiple low-energy electronic states is caused by the splitting of the partially filled lanthanide 4f orbitals in the ligand field, and the number of the low-energy states increases rapidly with increasing number of the metal 4f electrons. On the other hand, the 4f electrons have a small effect on the geometries and vibrational frequencies of these lanthanide complexes.

Analysis of staged Z-pinch implosion trajectories from experiments on Zebra

NASA Astrophysics Data System (ADS)

Ross, Mike P.; Conti, F.; Darling, T. W.; Ruskov, E.; Valenzuela, J.; Wessel, F. J.; Beg, F.; Narkis, J.; Rahman, H. U.

2017-10-01

The Staged Z-pinch plasma confinement concept relies on compressing an annular liner of high-Z plasma onto a target plasma column of deuterium fuel. The interface between the liner and target is stable against the Magneto-Rayleigh-Taylor Instability, which leads to effective fuel compression and makes the concept interesting as a potential fusion reactor. The liner initiates as a neutral gas puff, while the target plasma is a partially ionized (Zeff < 10 percent column ejected from a coaxial plasma gun. The Zebra pulsed power generator (1 MA peak current, 100 ns rise time) provides the discharge that ionizes the liner and drives the Z-pinch implosion. Diverse diagnostics observe the 100-300 km/s implosions including silicon diodes, photo-conducting detectors (PCDs), laser shadowgraphy, an XUV framing camera, and a visible streak camera. The imaging diagnostics track instabilities smaller than 0.1 mm, and Z-pinch diameters below 2.5 mm are seen at peak compression. This poster correlates the data from these diagnostics to elucidate implosion behavior dependencies on liner gas, liner pressure, target pressure, and applied, axial-magnetic field. Funded by the Advanced Research Projects Agency - Energy, DE-AR0000569.

Radiative effects during the assembly of direct collapse black holes

NASA Astrophysics Data System (ADS)

Smith, Aaron; Becerra, Fernando; Bromm, Volker; Hernquist, Lars

2017-11-01

We perform a post-processing radiative feedback analysis on a 3D ab initio cosmological simulation of an atomic cooling halo under the direct collapse black hole (DCBH) scenario. We maintain the spatial resolution of the simulation by incorporating native ray-tracing on unstructured mesh data, including Monte Carlo Lyman α (Ly α) radiative transfer. DCBHs are born in gas-rich, metal-poor environments with the possibility of Compton-thick conditions, NH ≳ 1024 cm-2. Therefore, the surrounding gas is capable of experiencing the full impact of the bottled-up radiation pressure. In particular, we find that multiple scattering of Ly α photons provides an important source of mechanical feedback after the gas in the sub-parsec region becomes partially ionized, avoiding the bottleneck of destruction via the two-photon emission mechanism. We provide detailed discussion of the simulation environment, expansion of the ionization front, emission and escape of Ly α radiation, and Compton scattering. A sink particle prescription allows us to extract approximate limits on the post-formation evolution of the radiative feedback. Fully coupled Ly α radiation hydrodynamics will be crucial to consider in future DCBH simulations.

A novel multiphysic model for simulation of swelling equilibrium of ionized thermal-stimulus responsive hydrogels

NASA Astrophysics Data System (ADS)

Li, Hua; Wang, Xiaogui; Yan, Guoping; Lam, K. Y.; Cheng, Sixue; Zou, Tao; Zhuo, Renxi

2005-03-01

In this paper, a novel multiphysic mathematical model is developed for simulation of swelling equilibrium of ionized temperature sensitive hydrogels with the volume phase transition, and it is termed the multi-effect-coupling thermal-stimulus (MECtherm) model. This model consists of the steady-state Nernst-Planck equation, Poisson equation and swelling equilibrium governing equation based on the Flory's mean field theory, in which two types of polymer-solvent interaction parameters, as the functions of temperature and polymer-network volume fraction, are specified with or without consideration of the hydrogen bond interaction. In order to examine the MECtherm model consisting of nonlinear partial differential equations, a meshless Hermite-Cloud method is used for numerical solution of one-dimensional swelling equilibrium of thermal-stimulus responsive hydrogels immersed in a bathing solution. The computed results are in very good agreements with experimental data for the variation of volume swelling ratio with temperature. The influences of the salt concentration and initial fixed-charge density are discussed in detail on the variations of volume swelling ratio of hydrogels, mobile ion concentrations and electric potential of both interior hydrogels and exterior bathing solution.

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.

Non-ideal magnetohydrodynamic simulations of the two-stage fragmentation model for cluster formation

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

Bailey, Nicole D.; Basu, Shantanu, E-mail: N.Bailey@leeds.ac.uk, E-mail: basu@uwo.ca

2014-01-01

We model molecular cloud fragmentation with thin-disk, non-ideal magnetohydrodynamic simulations that include ambipolar diffusion and partial ionization that transitions from primarily ultraviolet-dominated to cosmic-ray-dominated regimes. These simulations are used to determine the conditions required for star clusters to form through a two-stage fragmentation scenario. Recent linear analyses have shown that the fragmentation length scales and timescales can undergo a dramatic drop across the column density boundary that separates the ultraviolet- and cosmic-ray-dominated ionization regimes. As found in earlier studies, the absence of an ionization drop and regular perturbations leads to a single-stage fragmentation on pc scales in transcritical clouds, somore » that the nonlinear evolution yields the same fragment sizes as predicted by linear theory. However, we find that a combination of initial transcritical mass-to-flux ratio, evolution through a column density regime in which the ionization drop takes place, and regular small perturbations to the mass-to-flux ratio is sufficient to cause a second stage of fragmentation during the nonlinear evolution. Cores of size ∼0.1 pc are formed within an initial fragment of ∼pc size. Regular perturbations to the mass-to-flux ratio also accelerate the onset of runaway collapse.« less

Red shift of the SF6 vibration spectrum induced by the electron absorption: An ab initio study

NASA Astrophysics Data System (ADS)

Tang, Bin; Zhang, Long-Fei; Han, Fang-Yuan; Luo, Zong-Chang; Liang, Qin-Qin; Liu, Chen-Yao; Zhu, Li-Ping; Zhang, Jie-Ming

2018-01-01

As a widely used gas insulator, sulfur hexafluoride (SF6) has a large cross section for electron absorption, which may make the molecule ionized to the -1 charge state in the high-voltage environment. Using ab initio calculations, we show that the absorbed electron is located averagely on the six F atoms, occupying the antibonding level of the s-p σ bonds and increasing the S-F bond length. The ionized SF6- molecule decreases its decomposition energy to only 1.5 eV, much lower than that of the neutral molecule (4.8 eV), which can be understood according to the occupying of the antibonding orbital and thus weakening of the s-p σ bonds. The weakening of the bonds results in an obvious red shift in the vibrational modes of the ionized SF6- molecule by 120-270 cm-1, compared to those of the neutral molecule. The detailed origin of these vibrational modes is analyzed. Since the appearance of the ionized SF6- molecules is before the decomposition reaction of the SF6- molecule into low-fluoride sulfides, this method may improve the sensitivity of the defection of the partial discharge and save more time for the prevention of the insulation failure in advance.

A Theoretical Study of the Outer Layers of Eight Kepler F-stars: The Relevance of Ionization Processes

NASA Astrophysics Data System (ADS)

Brito, Ana; Lopes, Ilídio

2017-07-01

We have analyzed the theoretical model envelopes of eight Kepler F-stars by computing the phase shift of the acoustic waves, α (ω ), and its related function, β (ω ). The latter is shown to be a powerful probe of the external stellar layers since it is particularly sensitive to the partial ionization zones located in these upper layers. We found that these theoretical envelopes can be organized into two groups, each of which is characterized by a distinct β (ω ) shape that we show to reflect the differences related to the magnitudes of ionization processes. Since β (ω ) can also be determined from the experimental frequencies, we compared our theoretical results with the observable β (ω ). Using the function β (ω ), and with the purpose of quantifying the magnitude of the ionization processes occurring in the outer layers of these stars, we define two indexes, {{Δ }}{β }1 and {{Δ }}{β }2. These indexes allow us to connect the microphysics of the interior of the star with macroscopic observable characteristics. Motivated by the distinct magnetic activity behaviors of F-stars, we studied the relation between the star’s rotation period and these indexes. We found a trend, in the form of a power-law dependence, that favors the idea that ionization is acting as an underlying mechanism, which is crucial for understanding the relation between rotation and magnetism and even observational features such as the Kraft break.

Modeling of HT and HTO release from irradiated lithium metazirconate

NASA Astrophysics Data System (ADS)

Beloglazov, S.; Nishikawa, M.; Glugla, M.; Kinjyo, T.

2004-08-01

Modeling studies of tritium release from irradiated Li 2ZrO 3 (MAPI) pebbles have been carried out in order to evaluate the effect of purge gas composition on tritium release behavior. The release characteristics were obtained by temperature programmed desorption (TPD) technique in the series of post-irradiation experiments in JRR-4 research reactor of JAERI. Nitrogen with hydrogen at various partial pressures (100 and 1000 Pa) was used as a purge gas. Two sets of ionization chambers and its dedicated electrometers allowed the tritium concentration to be monitored in the chemical form of HT and overall tritium concentration in the mixture HT and HTO simultaneously during desorption runs. The tritium release curves were numerically fitted in order to evaluate the mass transfer coefficients.

Stability of Nonstationary Cooling of Pure Hydrogen Gas with Respect to the Number of Discrete Levels Taken into Account

NASA Astrophysics Data System (ADS)

Belova, O. M.; Bychkov, K. V.

2018-03-01

The effect of the number K of atomic hydrogen levels taken into account on the cooling of the gas behind a shock front is studied. The calculations are done for the conditions in the atmospheres of long-period Mira Ceti type variables. K ranges from 2 to 25. The electron temperature Te(t; K) and ionization state x(r,K) asymptotically approach limiting functions Te(t) and x(t) that are independent of K. After the maximum electron temperature is reached, a partial equilibrium phase sets in, during which the populations of the highly excited discrete levels with principal quantum numbers ≥ 8 obey the Saha equation for the instantaneous electron temperature and density.

Electrophoresis of small particles and fluid globules in weak electrolytes

NASA Technical Reports Server (NTRS)

Baygents, J. C.; Saville, D. A.

1991-01-01

An examination is conducted of the influence of partial ionization on the electrophoresis of small particles and fluid globules, with a view to the nature of conditions under which dissociation-association (D-A) alters electrokinetics. It is found that, since D-A processes are important in cases where double-layer polarization and relaxation would otherwise prevail, the predicted effect on electrophoretic mobility is greatest for the drops and bubbles whose surfaces are fluid and convection within the interface is significant. While the computation scheme used applies only to situations where forcing-field magnitude is small, the results obtained indicate that D-A processes involving ionogenic solutes may be significant in apolar liquids where electrokinetic phenomena are driven by strong forcing fields.

D-region differential-phase measurements and ionization variability studies

NASA Technical Reports Server (NTRS)

Weiland, R. M.; Bowhill, S. A.

1978-01-01

Measurements of electron densities in the D region are made by the partial-reflection differential-absorption and differential-phase techniques. The differential-phase data are obtained by a hard-wired phase-measuring system. Electron-sensity profiles obtained by the two techniques on six occasions are plotted and compared. Electron-density profiles obtained at the same time on 30 occasions during the years 1975 through 1977 are averaged to form a single profile for each technique. The effect of varying the assumed collision-frequency profile on these averaged profiles is studied. Time series of D-region electron-sensity data obtained by 3.4 minute intervals on six days during the summer of 1977 are examined for wave-like disturbances and tidal oscillations.

Evidence for extended chromospheres surrounding red giant stars

NASA Technical Reports Server (NTRS)

Stencel, R. E.

1981-01-01

There is now an increasing amount of both observational evidence and theoretical arguments that regions of partially ionized hydrogen extending several stellar radii are an important feature of red giant and supergiant stars. This evidence is discussed and the implications of the existence of extended chromospheres in terms of the nature of the outer atmospheres of, and mass loss from, cool stars are examined.

Vibrational and Electronic Energy Transfer and Dissociation of Diatomic Molecules by Electron Collisions

NASA Technical Reports Server (NTRS)

Huo, Winifred M.; Langhoff, Stephen R. (Technical Monitor)

1995-01-01

At high altitudes and velocities equal to or greater than the geosynchronous return velocity (10 kilometers per second), the shock layer of a hypersonic flight will be in thermochemical nonequilibrium and partially ionized. The amount of ionization is determined by the velocity. For a trans atmospheric flight of 10 kilometers per second and at an altitude of 80 kilometers, a maximum of 1% ionization is expected. At a velocity of 12 - 17 kilometer per second, such as a Mars return mission, up to 30% of the atoms and molecules in the flow field will be ionized. Under those circumstances, electrons play an important role in determining the internal states of atoms and molecules in the flow field and hence the amount of radiative heat load and the distance it takes for the flow field to re-establish equilibrium. Electron collisions provide an effective means of transferring energy even when the electron number density is as low as 1%. Because the mass of an electron is 12,760 times smaller than the reduced mass of N2, its average speed, and hence its average collision frequency, is more than 100 times larger. Even in the slightly ionized regime with only 1% electrons, the frequency of electron-molecule collisions is equal to or larger than that of molecule-molecule collisions, an important consideration in the low density part of the atmosphere. Three electron-molecule collision processes relevant to hypersonic flows will be considered: (1) vibrational excitation/de-excitation of a diatomic molecule by electron impact, (2) electronic excitation/de-excitation, and (3) dissociative recombination in electron-diatomic ion collisions. A review of available data, both theory and experiment, will be given. Particular attention will be paid to tailoring the molecular physics to the condition of hypersonic flows. For example, the high rotational temperatures in a hypersonic flow field means that most experimental data carried out under room temperatures are not applicable. Also, the average electron temperature is expected to be between 10,000 and 20,000 K. Thus only data for low energy electrons are relevant to the model.

Effects of retinoic acid-inducible gene-I-like receptors activations and ionizing radiation cotreatment on cytotoxicity against human non-small cell lung cancer in vitro.

PubMed

Yoshino, Hironori; Iwabuchi, Miyu; Kazama, Yuka; Furukawa, Maho; Kashiwakura, Ikuo

2018-04-01

Retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) are pattern-recognition receptors that recognize pathogen-associated molecular patterns and induce antiviral immune responses. Recent studies have demonstrated that RLR activation induces antitumor immunity and cytotoxicity against different types of cancer, including lung cancer. However a previous report has demonstrated that ionizing radiation exerts a limited effect on RLR in human monocytic cell-derived macrophages, suggesting that RLR agonists may be used as effective immunostimulants during radiation therapy. However, it is unclear whether ionizing radiation affects the cytotoxicity of RLR agonists against cancer cells. Therefore, in the present study the effects of cotreatment with ionizing radiation and RLR agonists on cytotoxicity against human non-small cell lung cancer cells A549 and H1299 was investigated. Treatment with RLR agonist poly(I:C)/LyoVec™ [poly(I:C)] exerted cytotoxic effects against human non-small cell lung cancer. The cytotoxic effects of poly(I:C) were enhanced by cotreatment with ionizing radiation, and poly(I:C) pretreatment resulted in the radiosensitization of non-small cell lung cancer. Furthermore, cotreatment of A549 and H1299 cells with poly(I:C) and ionizing radiation effectively induced apoptosis in a caspase-dependent manner compared with treatment with poly(I:C) or ionizing radiation alone. These results indicate that RLR agonists and ionizing radiation cotreatment effectively exert cytotoxic effects against human non-small cell lung cancer through caspase-mediated apoptosis.

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.

UV Lamp as a Facile Ozone Source for Structural Analysis of Unsaturated Lipids Via Electrospray Ionization-Mass Spectrometry

NASA Astrophysics Data System (ADS)

Stinson, Craig A.; Zhang, Wenpeng; Xia, Yu

2017-12-01

Ozonolysis of alkene functional groups is a type of highly specific and effective chemical reaction, which has found increasing applications in structural analysis of unsaturated lipids via coupling with mass spectrometry (MS). In this work, we utilized a low-pressure mercury lamp (6 W) to initiate ozonolysis inside electrospray ionization (ESI) sources. By placing the lamp near a nanoESI emitter that partially transmits 185 nm ultraviolet (UV) emission from the lamp, dissolved dioxygen in the spray solution was converted into ozone, which subsequently cleaved the double bonds within fatty acyls of lipids. Solvent conditions, such as presence of water and acid solution pH, were found to be critical in optimizing ozonolysis yields. Fast (on seconds time scale) and efficient (50%-100% yield) ozonolysis was achieved for model unsaturated phospholipids and fatty acids with UV lamp-induced ozonolysis incorporated on a static and an infusion nanoESI source. The method was able to differentiate double bond location isomers and identify the geometry of the double bond based on yield. The analytical utility of UV lamp-induced ozonolysis was further demonstrated by implementation on a liquid chromatography (LC)-MS platform. Ozonolysis was effected in a flow microreactor that was made from ozone permeable tubing, so that ambient ozone produced by the lamp irradiation could diffuse into the reactor and induce online ozonolysis post-LC separation and before ESI-MS.

Mitigation effect of an FGF-2 peptide on acute gastrointestinal syndrome after high-dose ionizing radiation.

PubMed

Zhang, Lurong; Sun, Weimin; Wang, Jianjun; Zhang, Mei; Yang, Shanmin; Tian, Yeping; Vidyasagar, Sadasivan; Peña, Louis A; Zhang, Kunzhong; Cao, Yongbing; Yin, Liangjie; Wang, Wei; Zhang, Lei; Schaefer, Katherine L; Saubermann, Lawrence J; Swarts, Steven G; Fenton, Bruce M; Keng, Peter C; Okunieff, Paul

2010-05-01

Acute gastrointestinal syndrome (AGS) resulting from ionizing radiation causes death within 7 days. Currently, no satisfactory agent exists for mitigation of AGS. A peptide derived from the receptor binding domain of fibroblast growth factor 2 (FGF-P) was synthesized and its mitigation effect on AGS was examined. A subtotal body irradiation (sub-TBI) model was created to induce gastrointestinal (GI) death while avoiding bone marrow death. After 10.5 to 16 Gy sub-TBI, mice received an intramuscular injection of FGF-P (10 mg/kg/day) or saline (0.2 ml/day) for 5 days; survival (frequency and duration) was measured. Crypt cells and their proliferation were assessed by hematoxylin, eosin, and BrdU staining. In addition, GI hemoccult score, stool formation, and plasma levels of endotoxin, insulin, amylase, interleukin (IL)-6, keratinocyte-derived chemokine (KC) monocyte chemoattractant protein 1 (MCP-1) and tumor necrosis factor (TNF)-alpha were evaluated. Treatment with FGF-P rescued a significant fraction of four strains of mice (33-50%) exposed to a lethal dose of sub-TBI. Use of FGF-P improved crypt survival and repopulation and partially preserved or restored GI function. Furthermore, whereas sub-TBI increased plasma endotoxin levels and several pro-inflammation cytokines (IL-6, KC, MCP-1, and TNF-alpha), FGF-P reduced these adverse responses. The study data support pursuing FGF-P as a mitigator for AGS.

Direct Analysis in Real Time Mass Spectrometry of Potential By-Products from Homemade Nitrate Ester Explosive Synthesis

PubMed Central

Sisco, Edward; Forbes, Thomas P.

2016-01-01

This work demonstrates the coupling of direct analysis in real time (DART) ionization with time-of-flight mass spectrometry (MS) in an off-axis configuration for the trace detection and analysis of potential partially nitrated and dimerized by-products of homemade nitrate ester explosive synthesis. Five compounds relating to the synthesis of nitroglycerin (NG) and pentaerythritol tetranitrate (PETN) were examined. Deprotonated ions and adducts with molecular oxygen, nitrite, and nitrate were observed in the mass spectral responses of these compounds. A global optimum temperature of 350 °C for the by-products investigated here, enabled single nanogram to sub nanogram trace detection. Matrix effects were examined through a series of mixtures containing one or more compounds (sugar alcohol precursors, by-products, and/or explosives) across a range of mass loadings. The explosives MS responses experienced competitive ionization in the presence of all by-products. The magnitude of this influence corresponded to both the degree of by-product nitration and the relative mass loading of the by-product to the explosive. This work provides a characterization of potential by-products from homemade nitrate ester synthesis, including matrix effects and potential challenges that might arise from the trace detection of homemade explosives (HMEs) containing impurities. Detection and understanding of HME impurities and complex mixtures may provide valuable information for the screening and sourcing of homemade nitrate ester explosives. PMID:26838397

Solving the Excitation and Chemical Abundances in Shocks: The Case of HH 1

NASA Astrophysics Data System (ADS)

Giannini, T.; Antoniucci, S.; Nisini, B.; Bacciotti, F.; Podio, L.

2015-11-01

We present deep spectroscopic (3600-24700 Å ) X-shooter observations of the bright Herbig-Haro object HH 1, one of the best laboratories to study the chemical and physical modifications caused by protostellar shocks on the natal cloud. We observe atomic fine structure lines, H i and He i recombination lines and H2 ro-vibrational lines (more than 500 detections in total). Line emission was analyzed by means of Non-local Thermal Equilibiurm codes to derive the electron temperature and density, and for the first time we are able to accurately probe different physical regimes behind a dissociative shock. We find a temperature stratification in the range 4000 K \\div 80,000 K, and a significant correlation between temperature and ionization energy. Two density regimes are identified for the ionized gas, a more tenuous, spatially broad component (density ˜103 cm-3), and a more compact component (density ≥slant 105 cm-3) likely associated with the hottest gas. A further neutral component is also evidenced, having a temperature ≲10,000 K and a density >104 cm-3. The gas fractional ionization was estimated by solving the ionization equilibrium equations of atoms detected in different ionization stages. We find that neutral and fully ionized regions co-exist inside the shock. Also, indications in favor of at least partially dissociative shock as the main mechanism for molecular excitation are derived. Chemical abundances are estimated for the majority of the detected species. On average, abundances of non-refractory/refractory elements are lower than solar of about 0.15/0.5 dex. This indicates the presence of dust inside the medium, with a depletion factor of iron of ˜40%. Based on observations collected at the European Southern Observatory, (92.C-0058).

Two-parameter partially correlated ground-state electron density of some light spherical atoms from Hartree-Fock theory with nonintegral nuclear charge

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

Cordero, Nicolas A.; March, Norman H.; Alonso, Julio A.

2007-05-15

Partially correlated ground-state electron densities for some spherical light atoms are calculated, into which nonrelativistic ionization potentials represent essential input data. The nuclear cusp condition of Kato is satisfied precisely. The basic theoretical starting point, however, is Hartree-Fock (HF) theory for the N electrons under consideration but with nonintegral nuclear charge Z{sup '} slightly different from the atomic number Z (=N). This HF density is scaled with a parameter {lambda}, near to unity, to preserve normalization. Finally, some tests are performed on the densities for the atoms Ne and Ar, as well as for Be and Mg.

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.

Physical processes associated with current collection by plasma contactors

NASA Technical Reports Server (NTRS)

Katz, Ira; Davis, Victoria A.

1990-01-01

Recent flight data confirms laboratory observations that the release of neutral gas increases plasma sheath currents. Plasma contactors are devices which release a partially ionized gas in order to enhance the current flow between a spacecraft and the space plasma. Ionization of the expellant gas and the formation of a double layer between the anode plasma and the space plasma are the dominant physical processes. A theory is presented of the interaction between the contactor plasma and the background plasma. The conditions for formation of a double layer between the two plasmas are derived. Double layer formation is shown to be a consequence of the nonlinear response of the plasmas to changes in potential. Numerical calculations based upon this model are compared with laboratory measurements of current collection by hollow cathode-based plasma contactors.

Metabolomic Analysis of Oxidative and Glycolytic Skeletal Muscles by Matrix-Assisted Laser Desorption/IonizationMass Spectrometric Imaging (MALDI MSI)

NASA Astrophysics Data System (ADS)

Tsai, Yu-Hsuan; Garrett, Timothy J.; Carter, Christy S.; Yost, Richard A.

2015-06-01

Skeletal muscles are composed of heterogeneous muscle fibers that have different physiological, morphological, biochemical, and histological characteristics. In this work, skeletal muscles extensor digitorum longus, soleus, and whole gastrocnemius were analyzed by matrix-assisted laser desorption/ionization mass spectrometry to characterize small molecule metabolites of oxidative and glycolytic muscle fiber types as well as to visualize biomarker localization. Multivariate data analysis such as principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were performed to extract significant features. Different metabolic fingerprints were observed from oxidative and glycolytic fibers. Higher abundances of biomolecules such as antioxidant anserine as well as acylcarnitines were observed in the glycolytic fibers, whereas taurine and some nucleotides were found to be localized in the oxidative fibers.

Miniature Ion-Mobility Spectrometer

NASA Technical Reports Server (NTRS)

Hartley, Frank T.

2006-01-01

The figure depicts a proposed miniature ion-mobility spectrometer that would be fabricated by micromachining. Unlike prior ion-mobility spectrometers, the proposed instrument would not be based on a time-of-flight principle and, consequently, would not have some of the disadvantageous characteristics of prior time-of-flight ion-mobility spectrometers. For example, one of these characteristics is the need for a bulky carrier-gas-feeding subsystem that includes a shutter gate to provide short pulses of gas in order to generate short pulses of ions. For another example, there is need for a complex device to generate pulses of ions from the pulses of gas and the device is capable of ionizing only a fraction of the incoming gas molecules; these characteristics preclude miniaturization. In contrast, the proposed instrument would not require a carrier-gas-feeding subsystem and would include a simple, highly compact device that would ionize all the molecules passing through it. The ionization device in the proposed instrument would be a 0.1-micron-thick dielectric membrane with metal electrodes on both sides. Small conical holes would be micromachined through the membrane and electrodes. An electric potential of the order of a volt applied between the membrane electrodes would give rise to an electric field of the order of several megavolts per meter in the submicron gap between the electrodes. An electric field of this magnitude would be sufficient to ionize all the molecules that enter the holes. Ionization (but not avalanche arcing) would occur because the distance between the ionizing electrodes would be less than the mean free path of gas molecules at the operating pressure of instrument. An accelerating grid would be located inside the instrument, downstream from the ionizing membrane. The electric potential applied to this grid would be negative relative to the potential on the inside electrode of the ionizing membrane and would be of a magnitude sufficient to generate a moderate electric field. Positive ions leaving the membrane holes would be accelerated in this electric field. The resulting flux of ions away from the ionization membrane would create a partial vacuum that would draw more of the gas medium through the membrane. The figure depicts a filter electrode and detector electrodes located along the sides of a drift tube downstream from the accelerator electrode. These electrodes would apply a transverse AC electric field superimposed on a ramped DC electric field. The AC field would effect differential transverse dispersal of ions. At a given instant of time, the trajectories of most of the ions would be bent toward the electrodes, causing most of the ions to collide with the electrodes and thereby become neutralized. The DC field would partly counteract the dispersive effect of the AC field, straightening the trajectories of a selected species of ions; the selection would vary with the magnitude of the applied DC field. The straightening of the trajectories of the selected ions would enable them to pass into the region between the detector electrodes. Depending on the polarity of the voltage applied to the detector electrodes, the electric field between the detector electrodes would draw the selected ions to one of these electrodes. Hence, the current collected by one of the detector electrodes would be a measure of the abundance of ions of the selected species. The ramping of the filter- electrode DC voltage would sweep the selection of ions through the spectrum of ionic species.

Observation of two-center interference effects for electron impact ionization of N2

NASA Astrophysics Data System (ADS)

Chaluvadi, Hari; Nur Ozer, Zehra; Dogan, Mevlut; Ning, Chuangang; Colgan, James; Madison, Don

2015-08-01

In 1966, Cohen and Fano (1966 Phys. Rev. 150 30) suggested that one should be able to observe the equivalent of Young’s double slit interference if the double slits were replaced by a diatomic molecule. This suggestion inspired many experimental and theoretical studies searching for double slit interference effects both for photon and particle ionization of diatomic molecules. These effects turned out to be so small for particle ionization that this work proceeded slowly and evidence for interference effects were only found by looking at cross section ratios. Most of the early particle work concentrated on double differential cross sections for heavy particle scattering and the first evidence for two-center interference for electron-impact triple differential cross section (TDCS) did not appear until 2006 for ionization of H2. Subsequent work has now firmly established that two-center interference effects can be seen in the TDCS for electron-impact ionization of H2. However, in spite of several experimental and theoretical studies, similar effects have not been found for electron-impact ionization of N2. Here we report the first evidence for two-center interference for electron-impact ionization of N2.

Electron-impact ionization of silicon tetrachloride (SiCl4).

PubMed

Basner, R; Gutkin, M; Mahoney, J; Tarnovsky, V; Deutsch, H; Becker, K

2005-08-01

We measured absolute partial cross sections for the formation of various singly charged and doubly charged positive ions produced by electron impact on silicon tetrachloride (SiCl4) using two different experimental techniques, a time-of-flight mass spectrometer (TOF-MS) and a fast-neutral-beam apparatus. The energy range covered was from the threshold to 900 eV in the TOF-MS and to 200 eV in the fast-neutral-beam apparatus. The results obtained by the two different experimental techniques were found to agree very well (better than their combined margins of error). The SiCl3(+) fragment ion has the largest partial ionization cross section with a maximum value of slightly above 6x10(-20) m2 at about 100 eV. The cross sections for the formation of SiCl4(+), SiCl+, and Cl+ have maximum values around 4x10(-20) m2. Some of the cross-section curves exhibit an unusual energy dependence with a pronounced low-energy maximum at an energy around 30 eV followed by a broad second maximum at around 100 eV. This is similar to what has been observed by us earlier for another Cl-containing molecule, TiCl4 [R. Basner, M. Schmidt, V. Tamovsky, H. Deutsch, and K. Becker, Thin Solid Films 374 291 (2000)]. The maximum cross-section values for the formation of the doubly charged ions, with the exception of SiCl3(++), are 0.05x10(-20) m2 or less. The experimentally determined total single ionization cross section of SiCl4 is compared with the results of semiempirical calculations.

Evidence for active galactic nucleus feedback in the broad absorption lines and reddening of MRK 231 {sup ,}

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

Leighly, Karen M.; Baron, Eddie; Lucy, Adrian B.

2014-06-20

We present the first J-band spectrum of Mrk 231, which reveals a large He I* λ10830 broad absorption line with a profile similar to that of the well-known Na I broad absorption line. Combining this spectrum with optical and UV spectra from the literature, we show that the unusual reddening noted by Veilleux et al. is explained by a reddening curve like those previously used to explain low values of total-to-selective extinction in Type Ia supernovae. The nuclear starburst may be the origin and location of the dust. Spatially resolved emission in the broad absorption line trough suggests nearly fullmore » coverage of the continuum emission region. The broad absorption lines reveal higher velocities in the He I* lines (produced in the quasar-photoionized H II region) compared with the Na I and Ca II lines (produced in the corresponding partially ionized zone). Cloudy simulations show that a density increase is required between the H II and partially ionized zones to produce ionic column densities consistent with the optical and IR absorption line measurements and limits, and that the absorber lies ∼100 pc from the central engine. These results suggest that the He I* lines are produced in an ordinary quasar BAL wind that impacts upon, compresses, and accelerates the nuclear starburst's dusty effluent (feedback in action), and the Ca II and Na I lines are produced in this dusty accelerated gas. This unusual circumstance explains the rarity of Na I absorption lines; without the compression along our line of sight, Mrk 231 would appear as an ordinary iron low-ionization, broad absorption line quasar.« less

Long-term biological effects induced by ionizing radiation--implications for dose mediated risk.

PubMed

Miron, S D; Astărăstoae, V

2014-01-01

Ionizing radiations are considered to be risk agents that are responsible for the effects on interaction with living matter. The occurring biological effects are due to various factors such as: dose, type of radiation, exposure time, type of biological tissue, health condition and the age of the person exposed. The mechanisms involved in the direct modifications of nuclear DNA and mitochondrial DNA are reviewed. Classical target theory of energy deposition in the nucleus that causes DNA damages, in particular DNA double-strand breaks and that explanation of the biological consequences of ionizing radiation exposure is a paradigm in radiobiology. Recent experimental evidences have demonstrated the existence of a molecular mechanism that explains the non-targeted effects of ionizing radiation exposure. Among these novel data, genomic instability and a variety of bystander effects are discussed here. Those bystander effects of ionizing radiation are fulfilled by cellular communication systems that give rise to non-targeted effects in the neighboring non irradiated cells. This paper provides also a commentary on the synergistic effects induced by the co-exposures to ionizing radiation and various physical agents such as electromagnetic fields and the co-exposures to ionizing radiation and chemical environmental contaminants such as metals. The biological effects of multiple stressors on genomic instability and bystander effects are also discussed. Moreover, a brief presentation of the methods used to characterize cyto- and genotoxic damages is offered.

THE EFFECT OF IONIZING RADIATION ON PREGNANCY AND FETAL DEVELOPMENT (in Russian)

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

Pobedinskii, N.M.

1961-01-01

A review is presented on the reactions of pregnant animais to radiation, the effect of ionizing radiation on the fetus and offspring of man and animal, the mechanism of the action of ionizing radiation on the fetus, and the protective action of agents such as mercamine and heroin. It is stressed that the effect of a dose of ionizing radiation varies with the stage of pregnancy at the time of irradiation (80 references). (TTT)

Study of inelastic processes in Li+-Ar, K+-Ar, and Na+-He collisions in the energy range 0.5-10 keV

NASA Astrophysics Data System (ADS)

Lomsadze, Ramaz A.; Gochitashvili, Malkhaz R.; Kezerashvili, Roman Ya; Schulz, Michael

2017-11-01

Absolute cross sections are measured for charge-exchange, ionization, and excitation processes within the same experimental setup for the Li{}+-Ar, K{}+-Ar, and Na{}+-He collisions in the ion energy range of 0.5-10 keV. The results of the measurements and schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The experimental results show that the charge-exchange processes occur with high probabilities and electrons are predominantly captured in ground states. The contributions of various partial inelastic channels to the total ionization cross section are estimated, and a primary mechanism for the process is identified. In addition, the energy-loss spectrum is applied in order to estimate the relative contribution of different inelastic channels, and to determine the mechanisms for the ionization and for some excitation processes of Ar resonance lines for the {{{K}}}+-Ar collision system. The excitation cross sections for the helium and for the sodium doublet lines for the Na{}+-He collision system both reveal some unexpected features. A mechanism to explain this observation is suggested.

Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

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

Lichtenberger, D.L.

1991-10-01

The formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies has been developed into a single equation which unifies the treatment of covalent bonds, ionic bonds, and partially ionic bonds. This relationship has been used to clarify the fundamental thermodynamic information relating to metal-hydrogen, metal-alkyl, and metal-metal bond energies. We have been able to obtain a direct observation and measurement of the stabilization energy provided by the agostic interaction of the C-H bond with the metal. The ionization energies have also been used to correlate the rates of carbonyl substitution reactions of ({eta}{sup 5}-C{sub 5}H{sub 4}X)Rh(CO){sub 2}more » complexes, and to reveal the electronic factors that control the stability of the transition state. The extent that the electronic features of these bonding interactions transfer to other chemical systems is being investigated in terms of the principle of additivity of ligand electronic effects. Specific examples under study include metal- phosphines, metal-halides, and metallocenes. Especially interesting has been the recent application of these techniques to the characterization of the soccer-ball shaped C{sub 60} molecule, buckminsterfullerene, and its interaction with a metal surface. The high-resolution valence ionizations in the gas phase reveal the high symmetry of the molecule, and studies of thin films of C{sub 60} reveal weak intermolecular interactions. Scanning tunneling and atomic force microscopy reveal the arrangement of spherical molecules on gold substrates, with significant delocalization of charge from the metal surface. 21 refs.« less

Standard partial molar volumes of some aqueous alkanolamines and alkoxyamines at temperatures up to 325 degrees C: functional group additivity in polar organic solutes under hydrothermal conditions.

PubMed

Bulemela, E; Tremaine, Peter R

2008-05-08

Apparent molar volumes of dilute aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), N,N-dimethylethanolamine (DMEA), ethylethanolamine (EAE), 2-diethylethanolamine (2-DEEA), and 3-methoxypropylamine (3-MPA) and their salts were measured at temperatures from 150 to 325 degrees C and pressures as high as 15 MPa. The results were corrected for the ionization and used to obtain the standard partial molar volumes, Vo2. A three-parameter equation of state was used to describe the temperature and pressure dependence of the standard partial molar volumes. The fitting parameters were successfully divided into functional group contributions at all temperatures to obtain the standard partial molar volume contributions. Including literature results for alcohols, carboxylic acids, and hydroxycarboxylic acids yielded the standard partial molar volume contributions of the functional groups >CH-, >CH2, -CH3, -OH, -COOH, -O-, -->N, >NH, -NH2, -COO-Na+, -NH3+Cl-, >NH2+Cl-, and -->NH+Cl- over the range (150 degrees C

Effects of retinoic acid-inducible gene-I-like receptors activations and ionizing radiation cotreatment on cytotoxicity against human non-small cell lung cancer in vitro

PubMed Central

Yoshino, Hironori; Iwabuchi, Miyu; Kazama, Yuka; Furukawa, Maho; Kashiwakura, Ikuo

2018-01-01

Retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) are pattern-recognition receptors that recognize pathogen-associated molecular patterns and induce antiviral immune responses. Recent studies have demonstrated that RLR activation induces antitumor immunity and cytotoxicity against different types of cancer, including lung cancer. However a previous report has demonstrated that ionizing radiation exerts a limited effect on RLR in human monocytic cell-derived macrophages, suggesting that RLR agonists may be used as effective immunostimulants during radiation therapy. However, it is unclear whether ionizing radiation affects the cytotoxicity of RLR agonists against cancer cells. Therefore, in the present study the effects of cotreatment with ionizing radiation and RLR agonists on cytotoxicity against human non-small cell lung cancer cells A549 and H1299 was investigated. Treatment with RLR agonist poly(I:C)/LyoVec™ [poly(I:C)] exerted cytotoxic effects against human non-small cell lung cancer. The cytotoxic effects of poly(I:C) were enhanced by cotreatment with ionizing radiation, and poly(I:C) pretreatment resulted in the radiosensitization of non-small cell lung cancer. Furthermore, cotreatment of A549 and H1299 cells with poly(I:C) and ionizing radiation effectively induced apoptosis in a caspase-dependent manner compared with treatment with poly(I:C) or ionizing radiation alone. These results indicate that RLR agonists and ionizing radiation cotreatment effectively exert cytotoxic effects against human non-small cell lung cancer through caspase-mediated apoptosis. PMID:29541243

Angular dependence of EWS time delay for photoionization of @Xe

NASA Astrophysics Data System (ADS)

Mandal, Ankur; Deshmukh, Pranawa; Kheifets, Anatoli; Dolmatov, Valeriy; Manson, Steven

2017-04-01

Interference between photoionization channels leads to angular dependence in photoionization time delay. Angular dependence is found to be a common effect for two-photon absorption experiments very recently. The effect of confinement on the time delay where each partial wave contributions to the ionization are studied. In this work we report angular dependence and confinement effects on Eisenbud-Wigner-Smith (EWS) time delay in atomic photoionization. Using and we computed the EWS time delay for free and confined Xe atom for photoionization from inner 4d3/2 and 4d5/2 and outer 5p1/2 and 5p3/2 subshells at various angles. The calculated EWS time delay is few tens to few hundreds of attoseconds (10-18 second). The photoionization time delay for @Xe follows that in the free Xe atom on which the confinement oscillations are built. The present work reveals the effect of confinement on the photoionization time delay at different angles between photoelectron ejection and the photon polarization.

The p53-Reactivating Small Molecule RITA Induces Senescence in Head and Neck Cancer Cells

PubMed Central

Chuang, Hui-Ching; Yang, Liang Peng; Fitzgerald, Alison L.; Osman, Abdullah; Woo, Sang Hyeok; Myers, Jeffrey N.; Skinner, Heath D.

2014-01-01

TP53 is the most commonly mutated gene in head and neck cancer (HNSCC), with mutations being associated with resistance to conventional therapy. Restoring normal p53 function has previously been investigated via the use of RITA (reactivation of p53 and induction of tumor cell apoptosis), a small molecule that induces a conformational change in p53, leading to activation of its downstream targets. In the current study we found that RITA indeed exerts significant effects in HNSCC cells. However, in this model, we found that a significant outcome of RITA treatment was accelerated senescence. RITA-induced senescence in a variety of p53 backgrounds, including p53 null cells. Also, inhibition of p53 expression did not appear to significantly inhibit RITA-induced senescence. Thus, this phenomenon appears to be partially p53-independent. Additionally, RITA-induced senescence appears to be partially mediated by activation of the DNA damage response and SIRT1 (Silent information regulator T1) inhibition, with a synergistic effect seen by combining either ionizing radiation or SIRT1 inhibition with RITA treatment. These data point toward a novel mechanism of RITA function as well as hint to its possible therapeutic benefit in HNSCC. PMID:25119136

Opacity from two-photon processes

DOE PAGES

More, Richard M.; Hansen, Stephanie B.; Nagayama, Taisuke

2017-07-22

Here, the recent iron opacity measurements performed at Sandia National Laboratory by Bailey and collaborators have raised questions about the completeness of the physical models normally used to understand partially ionized hot dense plasmas. We describe calculations of two-photon absorption, which is a candidate for the observed extra opacity. Our calculations do not yet match the experiments but show that the two-photon absorption process is strong enough to require careful consideration.

SPATIAL DAMPING OF PROPAGATING KINK WAVES IN PROMINENCE THREADS

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

Soler, R.; Oliver, R.; Ballester, J. L., E-mail: roberto.soler@wis.kuleuven.be

Transverse oscillations and propagating waves are frequently observed in threads of solar prominences/filaments and have been interpreted as kink magnetohydrodynamic (MHD) modes. We investigate the spatial damping of propagating kink MHD waves in transversely nonuniform and partially ionized prominence threads. Resonant absorption and ion-neutral collisions (Cowling's diffusion) are the damping mechanisms taken into account. The dispersion relation of resonant kink waves in a partially ionized magnetic flux tube is numerically solved by considering prominence conditions. Analytical expressions of the wavelength and damping length as functions of the kink mode frequency are obtained in the thin tube and thin boundary approximations.more » For typically reported periods of thread oscillations, resonant absorption is an efficient mechanism for the kink mode spatial damping, while ion-neutral collisions have a minor role. Cowling's diffusion dominates both the propagation and damping for periods much shorter than those observed. Resonant absorption may explain the observed spatial damping of kink waves in prominence threads. The transverse inhomogeneity length scale of the threads can be estimated by comparing the observed wavelengths and damping lengths with the theoretically predicted values. However, the ignorance of the form of the density profile in the transversely nonuniform layer introduces inaccuracies in the determination of the inhomogeneity length scale.« less

Methods of chemically converting first materials to second materials utilizing hybrid-plasma systems

DOEpatents

Kong, Peter C.; Grandy, Jon D.

2002-01-01

In one aspect, the invention encompasses a method of chemically converting a first material to a second material. A first plasma and a second plasma are formed, and the first plasma is in fluid communication with the second plasma. The second plasma comprises activated hydrogen and oxygen, and is formed from a water vapor. A first material is flowed into the first plasma to at least partially ionize at least a portion of the first material. The at least partially ionized first material is flowed into the second plasma to react at least some components of the first material with at least one of the activated hydrogen and activated oxygen. Such converts at least some of the first material to a second material. In another aspect, the invention encompasses a method of forming a synthetic gas by flowing a hydrocarbon-containing material into a hybrid-plasma system. In yet another aspect, the invention encompasses a method of degrading a hydrocarbon-containing material by flowing such material into a hybrid-plasma system. In yet another aspect, the invention encompasses a method of releasing an inorganic component of a complex comprising the inorganic component and an other component, wherein the complex is flowed through a hybrid-plasma system.

Improved classification of evidence for EMF health risks.

PubMed

Leitgeb, Norbert

2012-08-01

Classifying evidence of causality between a risk factor and its potential health effect is challenging, in particular in an already emotional situation. Even the assessment of health risks by designated bodies may still depend on their composition of individuals with their background, bias, and, in worst case, their interests. This may explain opposing conclusions from the same pool of data which, consequently, may undermine credibility if not communicated properly. To overcome existing weakness in classifying and communicating evidence of health risks such as from electromagnetic fields, a new rule-based approach is presented. Developed by the German Commission on Radiological Protection (SSK), it discloses step-by-step the criteria for weighing scientific data and pools partial evidences of different scientific approaches to conclude on the overall evidence of causality between risk factor and effects. The validity of the approach is demonstrated by analyzing evidence of carcinogenicity of ionizing radiation, mobile phone use, and nocturnal exposure to visible light.

Partial dust obscuration in active galactic nuclei as a cause of broad-line profile and lag variability, and apparent accretion disc inhomogeneities

NASA Astrophysics Data System (ADS)

Gaskell, C. Martin; Harrington, Peter Z.

2018-04-01

The profiles of the broad emission lines of active galactic nuclei (AGNs) and the time delays in their response to changes in the ionizing continuum ("lags") give information about the structure and kinematics of the inner regions of AGNs. Line profiles are also our main way of estimating the masses of the supermassive black holes (SMBHs). However, the profiles often show ill-understood, asymmetric structure and velocity-dependent lags vary with time. Here we show that partial obscuration of the broad-line region (BLR) by outflowing, compact, dusty clumps produces asymmetries and velocity-dependent lags similar to those observed. Our model explains previously inexplicable changes in the ratios of the hydrogen lines with time and velocity, the lack of correlation of changes in line profiles with variability of the central engine, the velocity dependence of lags, and the change of lags with time. We propose that changes on timescales longer than the light-crossing time do not come from dynamical changes in the BLR, but are a natural result of the effect of outflowing dusty clumps driven by radiation pressure acting on the dust. The motion of these clumps offers an explanation of long-term changes in polarization. The effects of the dust complicate the study of the structure and kinematics of the BLR and the search for sub-parsec SMBH binaries. Partial obscuration of the accretion disc can also provide the local fluctuations in luminosity that can explain sizes deduced from microlensing.

THE INFLUENCE OF IONIZING RADIATION ON IMMUNITY

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

Troitskii, V.L.

1958-01-01

The effects of radiation on the natural resistance of an organism to certain infectious diseases, largely as observed in laboratory experiments on animals, are discussed. Although the mechanism of this process is only partially understood, many particulars, such as a decrease in the number of leucocytes in the blood, or depression of the fagocyte activity in the reticulo-endothelial system, under the influencc of radiation, are known. Other effects of radiation reflected in changes in tissue perviousness, and disturbance of the barrier characteristics are discussed. The influence of total irradiation on the perviousness of the gastric-intestinal tract to toxins of dysenterymore » bacteria was studied. Such irradiation increases the perviousness of the intestine wall to dysentery toxins. The influence of radiation in lowering the bactericide characteristics of the skin, and in suppressing development of the Schwarzmann phenomenon are cited as factors which may have signiflcance in lowering the natural resistance of the organism. Radiation effects on the bactericide characteristics of rabbit serum are also discussed. Appearance of bacteria in the blood of irradiated animals, believed to originate in the digestive tract, is also discussed. Autointection is a very significant factor in radiation sickness, and it is concluded that even small doses of ionizing radiation can turn latent infection into clinically pronounced infection. The influence of ionizing radiation on the production of antibodies is also treated. Experiments showed that the introduction of antigens to rabbits following irradiation produces only minute quantities of agglutinins, while the ability to produce antibodies is re-established after 3-4 weeks. Reproduction of antitoxic immunity is also dealt with briefly. Experiments also showed that the first phase of antibody formation is radiation-sensitive, while the later phase is radiation- resistant, i.e., radiation applied shortly after immunization tends to slow the process of antibody formation. Thus, once this process is started, it is harmed little even by large doses of radiation. Repeated small doses of radiation, over a long period of time, tend to decrease the harmful effect of a large dose on the formation of antibodies, when immunization follows irradiation. (TCO)« less

Ionospheric modification using relativistic electron beams

NASA Technical Reports Server (NTRS)

Banks, Peter M.; Fraser-Smith, Anthony C.; Gilchrist, B. E.

1990-01-01

The recent development of comparatively small electron linear accelerators (linacs) now makes possible a new class of ionospheric modification experiments using beams of relativistic electrons. These experiments can potentially provide much new information about the interactions of natural relativistic electrons with other particles in the upper atmosphere, and it may also make possible new forms of ionization structures extending down from the lower ionosphere into the largely un-ionized upper atmosphere. The consequences of firing a pulsed 1 A, 5 Mev electron beam downwards into the upper atmosphere are investigated. If a small pitch angle with respect to the ambient geomagnetic field is selected, the beam produces a narrow column of substantial ionization extending down from the source altitude to altitudes of approximately 40 to 45 km. This column is immediately polarized by the natural middle atmosphere fair weather electric field and an increasingly large potential difference is established between the column and the surrounding atmosphere. In the regions between 40 to 60 km, this potential can amount to many tens of kilovolts and the associated electric field can be greater than the field required for breakdown and discharge. Under these conditions, it may be possible to initiate lightning discharges along the initial ionization channel. Filamentation may also occur at the lower end to drive further currents in the partially ionized gases of the stratosphere. Such discharges would derive their energy from the earth-ionosphere electrical system and would be sustained until plasma depletion and/or electric field reduction brought the discharge under control. It is likely that this artificially-triggered lightning would produce measurable low-frequency radiation.

The Impact of Diffuse Ionized Gas on Emission-line Ratios and Gas Metallicity Measurements

NASA Astrophysics Data System (ADS)

Zhang, Kai; Yan, Renbin; MaNGA Team

2016-01-01

Diffuse Ionized Gas (DIG) is prevalent in star-forming galaxies. Using a sample of galaxies observed by MaNGA, we demonstrate how DIG in star-forming galaxies impact the measurements of emission line ratios, hence the gas-phase metallicity measurements and the interpretation of diagnostic diagrams. We demonstrate that emission line surface brightness (SB) is a reasonably good proxy to separate HII regions from regions dominated by diffuse ionized gas. For spatially-adjacent regions or regions at the same radius, many line ratios change systematically with emission line surface brightness, reflecting a gradual increase of dominance by DIG towards low SB. DIG could significantly bias the measurement of gas metallicity and metallicity gradient. Because DIG tend to have a higher temperature than HII regions, at fixed metallicity DIG displays lower [NII]/[OII] ratios. DIG also show lower [OIII]/[OII] ratios than HII regions, due to extended partially-ionized regions that enhance all low-ionization lines ([NII], [SII], [OII], [OI]). The contamination by DIG is responsible for a substantial portion of the scatter in metallicity measurements. At different surface brightness, line ratios and line ratio gradients can differ systematically. As DIG fraction could change with radius, it can affect the metallicity gradient measurements in systematic ways. The three commonly used strong-line metallicity indicators, R23, [NII]/[OII], O3N2, are all affected in different ways. To make robust metallicity gradient measurements, one has to properly isolate HII regions and correct for DIG contamination. In line ratio diagnostic diagrams, contamination by DIG moves HII regions towards composite or LINER-like regions.

The collapse of a molecular cloud core to stellar densities using radiation non-ideal magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Wurster, James; Bate, Matthew R.; Price, Daniel J.

2018-04-01

We present results from radiation non-ideal magnetohydrodynamics (MHD) calculations that follow the collapse of rotating, magnetized, molecular cloud cores to stellar densities. These are the first such calculations to include all three non-ideal effects: ambipolar diffusion, Ohmic resistivity, and the Hall effect. We employ an ionization model in which cosmic ray ionization dominates at low temperatures and thermal ionization takes over at high temperatures. We explore the effects of varying the cosmic ray ionization rate from ζcr = 10-10 to 10-16 s-1. Models with ionization rates ≳10-12 s-1 produce results that are indistinguishable from ideal MHD. Decreasing the cosmic ray ionization rate extends the lifetime of the first hydrostatic core up to a factor of 2, but the lifetimes are still substantially shorter than those obtained without magnetic fields. Outflows from the first hydrostatic core phase are launched in all models, but the outflows become broader and slower as the ionization rate is reduced. The outflow morphology following stellar core formation is complex and strongly dependent on the cosmic ray ionization rate. Calculations with high ionization rates quickly produce a fast (≈14 km s-1) bipolar outflow that is distinct from the first core outflow, but with the lowest ionization rate, a slower (≈3-4 km s-1) conical outflow develops gradually and seamlessly merges into the first core outflow.

Air ions and mood outcomes: a review and meta-analysis

PubMed Central

2013-01-01

Background Psychological effects of air ions have been reported for more than 80 years in the media and scientific literature. This study summarizes a qualitative literature review and quantitative meta-analysis, where applicable, that examines the potential effects of exposure to negative and positive air ions on psychological measures of mood and emotional state. Methods A structured literature review was conducted to identify human experimental studies published through August, 2012. Thirty-three studies (1957–2012) evaluating the effects of air ionization on depression, anxiety, mood states, and subjective feelings of mental well-being in humans were included. Five studies on negative ionization and depression (measured using a structured interview guide) were evaluated by level of exposure intensity (high vs. low) using meta-analysis. Results Consistent ionization effects were not observed for anxiety, mood, relaxation/sleep, and personal comfort. In contrast, meta-analysis results showed that negative ionization, overall, was significantly associated with lower depression ratings, with a stronger association observed at high levels of negative ion exposure (mean summary effect and 95% confidence interval (CI) following high- and low-density exposure: 14.28 (95% CI: 12.93-15.62) and 7.23 (95% CI: 2.62-11.83), respectively). The response to high-density ionization was observed in patients with seasonal or chronic depression, but an effect of low-density ionization was observed only in patients with seasonal depression. However, no relationship between the duration or frequency of ionization treatment on depression ratings was evident. Conclusions No consistent influence of positive or negative air ionization on anxiety, mood, relaxation, sleep, and personal comfort measures was observed. Negative air ionization was associated with lower depression scores particularly at the highest exposure level. Future research is needed to evaluate the biological plausibility of this association. PMID:23320516

Comparison of two equation-of-state models for partially ionized aluminum: Zel'dovich and Raizer's model versus the activity expansion code

NASA Astrophysics Data System (ADS)

Harrach, Robert J.; Rogers, Forest J.

1981-09-01

Two equation-of-state (EOS) models for multipy ionized matter are evaluated for the case of an aluminum plasma in the temperature range from about one eV to several hundred eV, spanning conditions of weak to strong ionization. Specifically, the simple analytical mode of Zel'dovich and Raizer and the more comprehensive model comprised by Rogers' plasma physics avtivity expansion code (ACTEX) are used to calculate the specific internal energy ɛ and average degree of ionization Z¯*, as functons of temperature T and density ρ. In the absence of experimental data, these results are compared against each other, covering almost five orders-of-magnitude variation in ɛ and the full range of Z¯* We find generally good agreement between the two sets of results, especially for low densities and for temperatures near the upper end of the rage. Calculated values of ɛ(T) agree to within ±30% over nearly the full range in T for densities below about 1 g/cm3. Similarly, the two models predict values of Z¯*(T) which track each other fairly well; above 20 eV the discrepancy is less than ±20% fpr ρ≲1 g/cm3. Where the calculations disagree, we expect the ACTEX code to be more accurate than Zel'dovich and Raizer's model, by virtue of its more detailed physics content.

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

Hargreaves, L. R.; Colyer, C.; Stevenson, M. A.

A number of previous studies have suggested the possibility of two-center interference effects in the single ionization of diatomic molecules such as H{sub 2} and N{sub 2}. While interference effects have been successfully observed in the ionization of H{sub 2}, to date evidence for interference in N{sub 2} ionization has yet to be conclusively demonstrated. This study presents triply differential cross sections for electron impact ionization of N{sub 2}, measured using the (e,2e) technique. The data are probed for signatures of two-center interference effects. Evidence for interference manifesting in the cross sections is observed.

Potential of mean force for electrical conductivity of dense plasmas

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

Starrett, C. E.

The electrical conductivity in dense plasmas can be calculated with the relaxation-time approximation provided that the interaction potential between the scattering electron and the ion is known. To date there has been considerable uncertainty as to the best way to define this interaction potential so that it correctly includes the effects of ionic structure, screening by electrons and partial ionization. The current approximations lead to significantly different results with varying levels of agreement when compared to bench-mark calculations and experiments. Here, we present a new way to define this potential, drawing on ideas from classical fluid theory to define amore » potential of mean force. This new potential results in significantly improved agreement with experiments and bench-mark calculations, and includes all the aforementioned physics self-consistently.« less

Potential of mean force for electrical conductivity of dense plasmas

DOE PAGES

Starrett, C. E.

2017-09-28

The electrical conductivity in dense plasmas can be calculated with the relaxation-time approximation provided that the interaction potential between the scattering electron and the ion is known. To date there has been considerable uncertainty as to the best way to define this interaction potential so that it correctly includes the effects of ionic structure, screening by electrons and partial ionization. The current approximations lead to significantly different results with varying levels of agreement when compared to bench-mark calculations and experiments. Here, we present a new way to define this potential, drawing on ideas from classical fluid theory to define amore » potential of mean force. This new potential results in significantly improved agreement with experiments and bench-mark calculations, and includes all the aforementioned physics self-consistently.« less

Potential of mean force for electrical conductivity of dense plasmas

NASA Astrophysics Data System (ADS)

Starrett, C. E.

2017-12-01

The electrical conductivity in dense plasmas can be calculated with the relaxation-time approximation provided that the interaction potential between the scattering electron and the ion is known. To date there has been considerable uncertainty as to the best way to define this interaction potential so that it correctly includes the effects of ionic structure, screening by electrons and partial ionization. Current approximations lead to significantly different results with varying levels of agreement when compared to bench-mark calculations and experiments. We present a new way to define this potential, drawing on ideas from classical fluid theory to define a potential of mean force. This new potential results in significantly improved agreement with experiments and bench-mark calculations, and includes all the aforementioned physics self-consistently.

Detection of a noble gas molecular ion, 36ArH+, in the Crab Nebula.

PubMed

Barlow, M J; Swinyard, B M; Owen, P J; Cernicharo, J; Gomez, H L; Ivison, R J; Krause, O; Lim, T L; Matsuura, M; Miller, S; Olofsson, G; Polehampton, E T

2013-12-13

Noble gas molecules have not hitherto been detected in space. From spectra obtained with the Herschel Space Observatory, we report the detection of emission in the 617.5- and 1234.6-gigahertz J = 1-0 and 2-1 rotational lines of (36)ArH(+) at several positions in the Crab Nebula, a supernova remnant known to contain both molecular hydrogen and regions of enhanced ionized argon emission. Argon-36 is believed to have originated from explosive nucleosynthesis in massive stars during core-collapse supernova events. Its detection in the Crab Nebula, the product of such a supernova event, confirms this expectation. The likely excitation mechanism for the observed (36)ArH(+) emission lines is electron collisions in partially ionized regions with electron densities of a few hundred per centimeter cubed.

Collision energy-resolved study of the emission cross-section and the Penning ionization cross-section in the reaction of BrCN with He*(2 3S)

NASA Astrophysics Data System (ADS)

Kanda, Kazuhiro; Yamakita, Yoshihiro; Ohno, Koichi

2001-12-01

The dissociative excitation of BrCN producing CN(B 2Σ +) fragment by the collision of He *(2 3S) was investigated by the collision energy-resolved electron and emission spectroscopy using time-of-flight method with a high-intensity He * beam. The Penning electrons ejected from BrCN and the subsequent CN ( B2Σ +- X2Σ +) emission were measured as a function of collision energy in the range of 90-180 meV. The formation of CN ( B2Σ +) is concluded to proceed dominantly via the promotion of an electron from Π-character orbital, by comparison between the collision energy dependence of the partial Penning ionization cross-sections and the CN ( B2Σ +- X2Σ +) emission cross-section.

Separation and identification of neutral cereal lipids by normal phase high-performance liquid chromatography, using evaporative light-scattering and electrospray mass spectrometry for detection.

PubMed

Rocha, João M; Kalo, Paavo J; Ollilainen, Velimatti; Malcata, F Xavier

2010-04-30

A novel method was developed for the analysis of molecular species in neutral lipid classes, using separation by normal phase high-performance liquid chromatography, followed by detection by evaporative light-scattering and electrospray ionization tandem mass spectrometry. Monoacid standards, i.e. sterol esters, triacylglycerols, fatty acids, diacylglycerols, free sterols and monoacylglycerols, were separated to baseline on microbore 3 microm-silica gel columns. Complete or partial separation of molecular species in each lipid class permitted identification by automatic tandem mass spectrometry of ammonium adducts, produced via positive electrospray ionization. After optimization of the method, separation and identification of molecular species of various lipid classes was comprehensively tested by analysis of neutral lipids from the free lipid extract of maize flour. 2010 Elsevier B.V. All rights reserved.

Stefan-Maxwell Relations and Heat Flux with Anisotropic Transport Coefficients for Ionized Gases in a Magnetic Field with Application to the Problem of Ambipolar Diffusion

NASA Astrophysics Data System (ADS)

Kolesnichenko, A. V.; Marov, M. Ya.

2018-01-01

The defining relations for the thermodynamic diffusion and heat fluxes in a multicomponent, partially ionized gas mixture in an external electromagnetic field have been obtained by the methods of the kinetic theory. Generalized Stefan-Maxwell relations and algebraic equations for anisotropic transport coefficients (the multicomponent diffusion, thermal diffusion, electric and thermoelectric conductivity coefficients as well as the thermal diffusion ratios) associated with diffusion-thermal processes have been derived. The defining second-order equations are derived by the Chapman-Enskog procedure using Sonine polynomial expansions. The modified Stefan-Maxwell relations are used for the description of ambipolar diffusion in the Earth's ionospheric plasma (in the F region) composed of electrons, ions of many species, and neutral particles in a strong electromagnetic field.

Method and apparatus for preventing cyclotron breakdown in partially evacuated waveguide

DOEpatents

Moeller, Charles P.

1987-01-01

Cyclotron breakdown is prevented in a partially evacuated waveguide by providing a section of waveguide having an axial cut therein in order to apply a potential across the two halves of the waveguide. This section is positioned in the waveguide crossing the area of electron cyclotron resonance. The potential applied across the waveguide halves is used to deflect seed electrons into the wall of the waveguide in order to prevent ionization of gas molecules and creation of more electron ion pairs which would result in cyclotron breakdown. Support means is also disclosed for electrically isolating the waveguide halves and transition means is provided between the section of the waveguide with the axial cut and the solid waveguide at either end thereof.

Losartan sensitizes selectively prostate cancer cell to ionizing radiation.

PubMed

Yazdannejat, H; Hosseinimehr, S J; Ghasemi, A; Pourfallah, T A; Rafiei, A

2016-01-11

Losartan is an angiotensin II receptor (AT-II-R) blocker that is widely used by human for blood pressure regulation. Also, it has antitumor property. In this study, we investigated the radiosensitizing effect of losartan on cellular toxicity induced by ionizing radiation on prostate cancer and non-malignant fibroblast cells. Human prostate cancer (DU-145) and human non-malignant fibroblast cells (HFFF2) were treated with losartan at different concentrations (0.5, 1, 10, 50 and 100 µM) and then these cells were exposed to ionizing radiation. The cell proliferation was determined using MTT assay. Our results showed that losartan exhibited antitumor effect on prostate cancer cells; it was reduced cell survival to 66% at concentration 1 µM. Losartan showed an additive killing effect in combination with ionizing radiation on prostate cancer cell. The cell proliferation was reduced to 54% in the prostate cancer cells treated with losartan at concentration 1 µM in combination with ionizing radiation. Losartan did not exhibit any toxicity on HFFF2 cell. This result shows a promising effect of losartan on enhancement of therapeutic effect of ionizing radiation in patients during therapy.

High-throughput flow injection analysis mass spectroscopy with networked delivery of color-rendered results. 2. Three-dimensional spectral mapping of 96-well combinatorial chemistry racks.

PubMed

Görlach, E; Richmond, R; Lewis, I

1998-08-01

For the last two years, the mass spectroscopy section of the Novartis Pharma Research Core Technology group has analyzed tens of thousands of multiple parallel synthesis samples from the Novartis Pharma Combinatorial Chemistry program, using an in-house developed automated high-throughput flow injection analysis electrospray ionization mass spectroscopy system. The electrospray spectra of these samples reflect the many structures present after the cleavage step from the solid support. The overall success of the sequential synthesis is mirrored in the purity of the expected end product, but the partial success of individual synthesis steps is evident in the impurities in the mass spectrum. However this latter reaction information, which is of considerable utility to the combinatorial chemist, is effectively hidden from view by the very large number of analyzed samples. This information is now revealed at the workbench of the combinatorial chemist by a novel three-dimensional display of each rack's complete mass spectral ion current using the in-house RackViewer Visual Basic application. Colorization of "forbidden loss" and "forbidden gas-adduct" zones, normalization to expected monoisotopic molecular weight, colorization of ionization intensity, and sorting by row or column were used in combination to highlight systematic patterns in the mass spectroscopy data.

Dissecting the Molecular Mechanism of Ionizing Radiation-Induced Tissue Damage in the Feather Follicle

PubMed Central

Chen, Xi; Liao, Chunyan; Chu, Qiqi; Zhou, Guixuan; Lin, Xiang; Li, Xiaobo; Lu, Haijie; Xu, Benhua; Yue, Zhicao

2014-01-01

Ionizing radiation (IR) is a common therapeutic agent in cancer therapy. It damages normal tissue and causes side effects including dermatitis and mucositis. Here we use the feather follicle as a model to investigate the mechanism of IR-induced tissue damage, because any perturbation of feather growth will be clearly recorded in its regular yet complex morphology. We find that IR induces defects in feather formation in a dose-dependent manner. No abnormality was observed at 5 Gy. A transient, reversible perturbation of feather growth was induced at 10 Gy, leading to defects in the feather structure. This perturbation became irreversible at 20 Gy. Molecular and cellular analysis revealed P53 activation, DNA damage and repair, cell cycle arrest and apoptosis in the pathobiology. IR also induces patterning defects in feather formation, with disrupted branching morphogenesis. This perturbation is mediated by cytokine production and Stat1 activation, as manipulation of cytokine levels or ectopic Stat1 over-expression also led to irregular feather branching. Furthermore, AG-490, a chemical inhibitor of Stat1 signaling, can partially rescue IR-induced tissue damage. Our results suggest that the feather follicle could serve as a useful model to address the in vivo impact of the many mechanisms of IR-induced tissue damage. PMID:24586618

The application of ionizers in domestic refrigerators for reduction in airborne and surface bacteria.

PubMed

Kampmann, Y; Klingshirn, A; Kloft, K; Kreyenschmidt, J

2009-12-01

To investigate the antimicrobial effect of ionization on bacteria in household refrigerators. Ionizer prototypes were tested with respect to their technical requirements and their ability to reduce surface and airborne contamination in household refrigerators. Ion and ozone production of the tested prototypes were measured online by an ion meter and an ozone analyser. The produced negative air ion (NAI) and ozone amounts were between 1.2 and 3.7 x 10(6) NAI cm(-3) and 11 and 19 ppb O(3), respectively. To test the influence of ionization on surface contamination, different materials like plastic, glass and nutrient agar for simulation of food were inoculated with bacterial suspensions. The reduction rate was dependent on surface properties. The effect on airborne bacteria was tested by nebulization of Bacillus subtilis- suspension (containing spores) aerosols in refrigerators with and without an ionizer. A clear reduction in air contamination because of ionization was measured. The antimicrobial effect is dependent on several factors, such as surface construction and airflow patterns within the refrigerator. Ionization seems to be an effective method for reduction in surface and airborne bacteria. This study is an initiation for a new consumer tool to decontaminate domestic refrigerators.

A Radiation Chemistry Code Based on the Greens Functions of the Diffusion Equation

NASA Technical Reports Server (NTRS)

Plante, Ianik; Wu, Honglu

2014-01-01

Ionizing radiation produces several radiolytic species such as.OH, e-aq, and H. when interacting with biological matter. Following their creation, radiolytic species diffuse and chemically react with biological molecules such as DNA. Despite years of research, many questions on the DNA damage by ionizing radiation remains, notably on the indirect effect, i.e. the damage resulting from the reactions of the radiolytic species with DNA. To simulate DNA damage by ionizing radiation, we are developing a step-by-step radiation chemistry code that is based on the Green's functions of the diffusion equation (GFDE), which is able to follow the trajectories of all particles and their reactions with time. In the recent years, simulations based on the GFDE have been used extensively in biochemistry, notably to simulate biochemical networks in time and space and are often used as the "gold standard" to validate diffusion-reaction theories. The exact GFDE for partially diffusion-controlled reactions is difficult to use because of its complex form. Therefore, the radial Green's function, which is much simpler, is often used. Hence, much effort has been devoted to the sampling of the radial Green's functions, for which we have developed a sampling algorithm This algorithm only yields the inter-particle distance vector length after a time step; the sampling of the deviation angle of the inter-particle vector is not taken into consideration. In this work, we show that the radial distribution is predicted by the exact radial Green's function. We also use a technique developed by Clifford et al. to generate the inter-particle vector deviation angles, knowing the inter-particle vector length before and after a time step. The results are compared with those predicted by the exact GFDE and by the analytical angular functions for free diffusion. This first step in the creation of the radiation chemistry code should help the understanding of the contribution of the indirect effect in the formation of DNA damage and double-strand breaks.

The effects of focusing power on TEA CO2 laser-induced gas breakdown and the consequent pulse shaping effects

NASA Astrophysics Data System (ADS)

Beheshtipour, Saleheh; Safari, Ebrahim; Majdabadi, Abbas; Silakhori, Kaveh

2018-02-01

Transversely Excited Atmospheric (TEA) CO2 laser pulses were used in order to generate an optical breakdown in a variety of mono- and polyatomic molecules using different focusing powers. The dependence of the spark kernel geometry and the transmitted pulse shapes on the focusing power as well as the pressure, molecular weight, and ionization energy of the gases was investigated in detail. Partial removal of the transmitted pulse tail in the 0.05-2.6 μs range together with shortened spikes in the 10-60 ns range has been observed by applying a 2.5 cm focal length lens for all the gases. At higher focal lengths, this effect is only incompletely observed for He gas. Spatial-temporal analyses of the laser beams and the relevant plasma plumes indicate that this behavior is due to the drop in the plasma density below the critical level, before the laser pulse tail is completed.

Mechanisms of Radiation Induced Effects in Carbon Nanotubes

DTIC Science & Technology

2016-10-01

the defect types created for both ionizing and non-ionizing particles under exposure to high total ionization and displacement damage doses. Carbon...and displacement damage doses. Additionally, the radiation effects on CNT carrier transport parameters (mobility, lifetime, conductivity) have been...thermal oxidation. 2. Radiation Testing of SWCNTs 2.1 Displacement Damage Dose Effects as a Function of SWCNT Electronic-Type Displacement damage does

Taurine Protects Mouse Spermatocytes from Ionizing Radiation-Induced Damage Through Activation of Nrf2/HO-1 Signaling.

PubMed

Yang, Wenjun; Huang, Jinfeng; Xiao, Bang; Liu, Yan; Zhu, Yiqing; Wang, Fang; Sun, Shuhan

2017-01-01

The increasing prevalence of ionizing radiation exposure has inevitably raised public concern over the potential detrimental effects of ionizing radiation on male reproductive system function. The detection of drug candidates to prevent reproductive system from damage caused by ionizing radiation is urgent. We aimed to investigate the protective role of taurine on the injury of mouse spermatocyte-derived cells (GC-2) subjected to ionizing radiation. mouse spermatocytes (GC-2 cells) were exposed to ionizing radiation with or without treatment of Taurine. The effect of ionizing radiation and Taurine treatment on GC-2 cells were evaluated by cell viability assay (CCK8), cell cycle and apoptosis. The relative protein abundance change was determined by Western blotting. The siRNA was used to explore whether Nrf2 signaling was involved in the cytoprotection of Taurine. Taurine significantly inhibited the decrease of cell viability, percentage of apoptotic cells and cell cycle arrest induced by ionizing radiation. Western blot analysis showed that taurine significantly limited the ionizing radiation-induced down-regulation of CyclinB1 and CDK1, and suppressed activation of Fas/FasL system pathway. In addition, taurine treatment significantly increased the expression of Nrf2 and HO-1 in GC-2 cells exposed to ionizing radiation, two components in antioxidant pathway. The above cytoprotection of Taurine was blocked by siNrf2. Our results demonstrate that taurine has the potential to effectively protect GC-2 cells from ionizing radiation- triggered damage via upregulation of Nrf2/HO-1 signaling. © 2017 The Author(s). Published by S. Karger AG, Basel.

Caffeic acid phenethyl ester preferentially sensitizes CT26 colorectal adenocarcinoma to ionizing radiation without affecting bone marrow radioresponse

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

Chen, Y.-J.; Institute of Traditional Medicine, National Yang-Ming University, Taipei, Taiwan; Graduate Institute of Sport Coaching Science, Chinese Culture University, Taipei, Taiwan

2005-11-15

Purpose: Caffeic acid phenethyl ester (CAPE), a component of propolis, was reported capable of depleting glutathione (GSH). We subsequently examined the radiosensitizing effect of CAPE and its toxicity. Methods and Materials: The effects of CAPE on GSH level, GSH metabolism enzyme activities, NF-{kappa}B activity, and radiosensitivity in mouse CT26 colorectal adenocarcinoma cells were determined. BALB/c mouse with CT26 cells implantation was used as a syngeneic in vivo model for evaluation of treatment and toxicity end points. Results: CAPE entered CT26 cells rapidly and depleted intracellular GSH in CT26 cells, but not in bone marrow cells. Pretreatment with nontoxic doses ofmore » CAPE significantly enhanced cell killing by ionizing radiation (IR) with sensitizer enhancement ratios up to 2.2. Pretreatment of CT26 cells with N-acetyl-L-cysteine reversed the GSH depletion activity and partially blocked the radiosensitizing effect of CAPE. CAPE treatment in CT26 cells increased glutathione peroxidase, decreased glutathione reductase, and did not affect glutathione S-transferase or {gamma}-glutamyl transpeptidase activity. Radiation activated NF-{kappa}B was reversed by CAPE pretreatment. In vivo study revealed that pretreatment with CAPE before IR resulted in greater inhibition of tumor growth and prolongation of survival in comparison with IR alone. Pretreatment with CAPE neither affected body weights nor produced hepatic, renal, or hematopoietic toxicity. Conclusions: CAPE sensitizes CT26 colorectal adenocarcinoma to IR, which may be via depleting GSH and inhibiting NF-{kappa}B activity, without toxicity to bone marrow, liver, and kidney.« less

Advanced PIC-MCC simulation for the investigation of step-ionization effect in intermediate-pressure capacitively coupled plasmas

NASA Astrophysics Data System (ADS)

Kim, Jin Seok; Hur, Min Young; Kim, Chang Ho; Kim, Ho Jun; Lee, Hae June

2018-03-01

A two-dimensional parallelized particle-in-cell simulation has been developed to simulate a capacitively coupled plasma reactor. The parallelization using graphics processing units is applied to resolve the heavy computational load. It is found that the step-ionization plays an important role in the intermediate gas pressure of a few Torr. Without the step-ionization, the average electron density decreases while the effective electron temperature increases with the increase of gas pressure at a fixed power. With the step-ionization, however, the average electron density increases while the effective electron temperature decreases with the increase of gas pressure. The cases with the step-ionization agree well with the tendency of experimental measurement. The electron energy distribution functions show that the population of electrons having intermediate energy from 4.2 to 12 eV is relaxed by the step-ionization. Also, it was observed that the power consumption by the electrons is increasing with the increase of gas pressure by the step-ionization process, while the power consumption by the ions decreases with the increase of gas pressure.

UV Lamp as a Facile Ozone Source for Structural Analysis of Unsaturated Lipids Via Electrospray Ionization-Mass Spectrometry.

PubMed

Stinson, Craig A; Zhang, Wenpeng; Xia, Yu

2018-03-01

Ozonolysis of alkene functional groups is a type of highly specific and effective chemical reaction, which has found increasing applications in structural analysis of unsaturated lipids via coupling with mass spectrometry (MS). In this work, we utilized a low-pressure mercury lamp (6 W) to initiate ozonolysis inside electrospray ionization (ESI) sources. By placing the lamp near a nanoESI emitter that partially transmits 185 nm ultraviolet (UV) emission from the lamp, dissolved dioxygen in the spray solution was converted into ozone, which subsequently cleaved the double bonds within fatty acyls of lipids. Solvent conditions, such as presence of water and acid solution pH, were found to be critical in optimizing ozonolysis yields. Fast (on seconds time scale) and efficient (50%-100% yield) ozonolysis was achieved for model unsaturated phospholipids and fatty acids with UV lamp-induced ozonolysis incorporated on a static and an infusion nanoESI source. The method was able to differentiate double bond location isomers and identify the geometry of the double bond based on yield. The analytical utility of UV lamp-induced ozonolysis was further demonstrated by implementation on a liquid chromatography (LC)-MS platform. Ozonolysis was effected in a flow microreactor that was made from ozone permeable tubing, so that ambient ozone produced by the lamp irradiation could diffuse into the reactor and induce online ozonolysis post-LC separation and before ESI-MS. Graphical Abstract ᅟ.

UV Lamp as a Facile Ozone Source for Structural Analysis of Unsaturated Lipids Via Electrospray Ionization-Mass Spectrometry

NASA Astrophysics Data System (ADS)

Stinson, Craig A.; Zhang, Wenpeng; Xia, Yu

2018-03-01

Ozonolysis of alkene functional groups is a type of highly specific and effective chemical reaction, which has found increasing applications in structural analysis of unsaturated lipids via coupling with mass spectrometry (MS). In this work, we utilized a low-pressure mercury lamp (6 W) to initiate ozonolysis inside electrospray ionization (ESI) sources. By placing the lamp near a nanoESI emitter that partially transmits 185 nm ultraviolet (UV) emission from the lamp, dissolved dioxygen in the spray solution was converted into ozone, which subsequently cleaved the double bonds within fatty acyls of lipids. Solvent conditions, such as presence of water and acid solution pH, were found to be critical in optimizing ozonolysis yields. Fast (on seconds time scale) and efficient (50%-100% yield) ozonolysis was achieved for model unsaturated phospholipids and fatty acids with UV lamp-induced ozonolysis incorporated on a static and an infusion nanoESI source. The method was able to differentiate double bond location isomers and identify the geometry of the double bond based on yield. The analytical utility of UV lamp-induced ozonolysis was further demonstrated by implementation on a liquid chromatography (LC)-MS platform. Ozonolysis was effected in a flow microreactor that was made from ozone permeable tubing, so that ambient ozone produced by the lamp irradiation could diffuse into the reactor and induce online ozonolysis post-LC separation and before ESI-MS. [Figure not available: see fulltext.

Catalytic hydrodeoxygenation of methyl-substituted phenols: correlations of kinetic parameters with molecular properties.

PubMed

Massoth, F E; Politzer, P; Concha, M C; Murray, J S; Jakowski, J; Simons, Jack

2006-07-27

The hydrodeoxygenation of methyl-substituted phenols was carried out in a flow microreactor at 300 degrees C and 2.85 MPa hydrogen pressure over a sulfided CoMo/Al(2)O(3) catalyst. The primary reaction products were methyl-substituted benzene, cyclohexene, cyclohexane, and H(2)O. Analysis of the results suggests that two independent reaction paths are operative, one leading to aromatics and the other to partially or completely hydrogenated cyclohexanes. The reaction data were analyzed using Langmuir-Hinshelwood kinetics to extract the values of the reactant-to-catalyst adsorption constant and of the rate constants characterizing the two reaction paths. The adsorption constant was found to be the same for both reactions, suggesting that a single catalytic site center is operative in both reactions. Ab initio electronic structure calculations were used to evaluate the electrostatic potentials and valence orbital ionization potentials for all of the substituted phenol reactants. Correlations were observed between (a) the adsorption constant and the two reaction rate constants measured for various methyl-substitutions and (b) certain moments of the electrostatic potentials and certain orbitals' ionization potentials of the isolated phenol molecules. On the basis of these correlations to intrinsic reactant-molecule properties, a reaction mechanism is proposed for each pathway, and it is suggested that the dependencies of adsorption and reaction rates upon methyl-group substitution are a result of the substituents' effects on the electrostatic potential and orbitals rather than geometric (steric) effects.

Direct analysis in real time mass spectrometry of potential by-products from homemade nitrate ester explosive synthesis.

PubMed

Sisco, Edward; Forbes, Thomas P

2016-04-01

This work demonstrates the coupling of direct analysis in real time (DART) ionization with time-of-flight mass spectrometry (MS) in an off-axis configuration for the trace detection and analysis of potential partially nitrated and dimerized by-products of homemade nitrate ester explosive synthesis. Five compounds relating to the synthesis of nitroglycerin (NG) and pentaerythritol tetranitrate (PETN) were examined. Deprotonated ions and adducts with molecular oxygen, nitrite, and nitrate were observed in the mass spectral responses of these compounds. A global optimum temperature of 350 °C for the by-products investigated here enabled single nanogram to sub nanogram trace detection. Matrix effects were examined through a series of mixtures containing one or more compounds (sugar alcohol precursors, by-products, and/or explosives) across a range of mass loadings. The explosives MS responses experienced competitive ionization in the presence of all by-products. The magnitude of this influence corresponded to both the degree of by-product nitration and the relative mass loading of the by-product to the explosive. This work provides a characterization of potential by-products from homemade nitrate ester synthesis, including matrix effects and potential challenges that might arise from the trace detection of homemade explosives (HMEs) containing impurities. Detection and understanding of HME impurities and complex mixtures may provide valuable information for the screening and sourcing of homemade nitrate ester explosives. Published by Elsevier B.V.

Mitigation Effect of an FGF-2 Peptide on Acute Gastrointestinal Syndrome After High-Dose Ionizing Radiation

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

Zhang Lurong; Sun Weimin; Wang Jianjun

Purpose: Acute gastrointestinal syndrome (AGS) resulting from ionizing radiation causes death within 7 days. Currently, no satisfactory agent exists for mitigation of AGS. A peptide derived from the receptor binding domain of fibroblast growth factor 2 (FGF-P) was synthesized and its mitigation effect on AGS was examined. Methods and Materials: A subtotal body irradiation (sub-TBI) model was created to induce gastrointestinal (GI) death while avoiding bone marrow death. After 10.5 to 16 Gy sub-TBI, mice received an intramuscular injection of FGF-P (10 mg/kg/day) or saline (0.2 ml/day) for 5 days; survival (frequency and duration) was measured. Crypt cells and theirmore » proliferation were assessed by hematoxylin, eosin, and BrdU staining. In addition, GI hemoccult score, stool formation, and plasma levels of endotoxin, insulin, amylase, interleukin (IL)-6, keratinocyte-derived chemokine (KC) monocyte chemoattractant protein 1 (MCP-1) and tumor necrosis factor (TNF)-alpha were evaluated. Results: Treatment with FGF-P rescued a significant fraction of four strains of mice (33-50%) exposed to a lethal dose of sub-TBI. Use of FGF-P improved crypt survival and repopulation and partially preserved or restored GI function. Furthermore, whereas sub-TBI increased plasma endotoxin levels and several pro-inflammation cytokines (IL-6, KC, MCP-1, and TNF-alpha), FGF-P reduced these adverse responses. Conclusions: The study data support pursuing FGF-P as a mitigator for AGS.« less

OSIRIS Modeling of High Energy Electron Transport in Warm Dense Matter

NASA Astrophysics Data System (ADS)

May, J.; Yabuuchi, T.; McGuffey, C.; Wei, Ms; Beg, F.; Mori, Wb

2016-10-01

In experiments on the Omega EP laser, a high intensity laser beam (eA /me c > 1) is focused onto a gold foil, generating relativistic electrons. Behind the Au foil is a layer of plastic foam through which the electrons are allowed to transport, and on the far side of the CH from the gold is a copper foil; electron fluence is measured by recording the k- α from that foil. The foam layer is either pre-ionized via a shock launched from an ablator irradiated earlier with a beam perpendicular to the high intensity beam; or the foam is in the solid state when the high intensity beam is switched on. In the latter case the foam - which has an initial density of 200mg /cm3 - heats to a temperature of 40eV and rarifies to a density of 30mg /cm3 . Results show an order of magnitude decrease in k- α when the CH layer is pre-ionized compared to cold CH. OSIRIS simulations indicate that the primary explanation for the difference in transport seen in the experiment is the partial resistive collimation of the beam in the higher density material, caused by collisional resistivity. The effect seems to be mostly caused by the higher density itself, with temperature having minimal effect. The authors acknowledge the support of the Department of Energy under contract DE-NA 0001833 and the National Science Foundation under contract ACI 1339893.

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…

Computational tests of quantum chemical models for excited and ionized states of molecules with phosphorus and sulfur atoms.

PubMed

Hahn, David K; RaghuVeer, Krishans; Ortiz, J V

2014-05-15

Time-dependent density functional theory (TD-DFT) and electron propagator theory (EPT) are used to calculate the electronic transition energies and ionization energies, respectively, of species containing phosphorus or sulfur. The accuracy of TD-DFT and EPT, in conjunction with various basis sets, is assessed with data from gas-phase spectroscopy. TD-DFT is tested using 11 prominent exchange-correlation functionals on a set of 37 vertical and 19 adiabatic transitions. For vertical transitions, TD-CAM-B3LYP calculations performed with the MG3S basis set are lowest in overall error, having a mean absolute deviation from experiment of 0.22 eV, or 0.23 eV over valence transitions and 0.21 eV over Rydberg transitions. Using a larger basis set, aug-pc3, improves accuracy over the valence transitions via hybrid functionals, but improved accuracy over the Rydberg transitions is only obtained via the BMK functional. For adiabatic transitions, all hybrid functionals paired with the MG3S basis set perform well, and B98 is best, with a mean absolute deviation from experiment of 0.09 eV. The testing of EPT used the Outer Valence Green's Function (OVGF) approximation and the Partial Third Order (P3) approximation on 37 vertical first ionization energies. It is found that OVGF outperforms P3 when basis sets of at least triple-ζ quality in the polarization functions are used. The largest basis set used in this study, aug-pc3, obtained the best mean absolute error from both methods -0.08 eV for OVGF and 0.18 eV for P3. The OVGF/6-31+G(2df,p) level of theory is particularly cost-effective, yielding a mean absolute error of 0.11 eV.

Modeling Acute Health Effects of Astronauts from Exposure to Large Solar Particle Events

NASA Technical Reports Server (NTRS)

Hu, Shaowen; Kim, Myung-Hee Y.; Cucinotta, Francis A.

2011-01-01

In space exploration outside the Earth s geomagnetic field, radiation exposure from solar particle events (SPE) presents a health concern for astronauts, that could impair their performance and result in possible failure of the mission. Acute risks are of special concern during extra-vehicular activities because of the rapid onset of SPE. However, most SPEs will not lead to acute risks but can lead to mission disruption if accurate projection methods are not available. Acute Radiation Sickness (ARS) is a group of clinical syndromes developing acutely (within several seconds to 3 days) after high dose whole-body or significant partial-body ionizing radiation exposures. The manifestation of these syndromes reflects the disturbance of physiological processes of various cellular groups damaged by radiation. Hematopoietic cells, skin, epithelium, intestine, and vascular endothelium are among the most sensitive tissues of human body to ionizing radiation. Most ARS symptoms are directly related to these tissues and other systems (nervous, endocrine, and cardiovascular, etc.) with coupled regulations. Here we report the progress in bio-mathematical models to describe the dose and time-dependent early human responses to ionizing radiation. The responses include lymphocyte depression, granulocyte modulation, fatigue and weakness syndrome, and upper gastrointestinal distress. The modest dose and dose-rates of SPEs are predicted to lead to large sparing of ARS, however detailed experimental data on a range of proton dose-rates for organ doses from 0.5 to 2 Gy is needed to validate the models. We also report on the ARRBOD code that integrates the BRYNTRN and SUMDOSE codes, which are used to estimate the SPE organ doses for astronauts under various space travel scenarios, with our models of ARS. The more recent effort is to provide easy web access to space radiation risk assessment using the ARRBOD code.

Effects of the Carrier-Envelope Phase in the Multiphoton Ionization Regime

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

Nakajima, Takashi; Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581; Watanabe, Shuntaro

2006-06-02

We theoretically investigate the effects of the carrier-envelope phase of few-cycle laser pulses in the multiphoton ionization regime. For atoms with low ionization potential, total ionization yield barely exhibits phase dependence, as expected. However, population of some bound states clearly shows phase dependence. This implies that the measurement of the carrier-envelope phase would be possible through the photoemission between bound states without energy-and-angle-resolved photoelectron detection. The considered scheme could be particularly useful to measure the carrier-envelope phase for a light source without an amplifier, such as a laser oscillator, which cannot provide sufficient pulse energy to induce tunneling ionization.

Evaluation of the dosimetric properties of a diode detector for small field proton radiosurgery.

PubMed

McAuley, Grant A; Teran, Anthony V; Slater, Jerry D; Slater, James M; Wroe, Andrew J

2015-11-08

The small fields and sharp gradients typically encountered in proton radiosurgery require high spatial resolution dosimetric measurements, especially below 1-2 cm diameters. Radiochromic film provides high resolution, but requires postprocessing and special handling. Promising alternatives are diode detectors with small sensitive volumes (SV) that are capable of high resolution and real-time dose acquisition. In this study we evaluated the PTW PR60020 proton dosimetry diode using radiation fields and beam energies relevant to radiosurgery applications. Energies of 127 and 157 MeV (9.7 to 15 cm range) and initial diameters of 8, 10, 12, and 20mm were delivered using single-stage scattering and four modulations (0, 15, 30, and 60mm) to a water tank in our treatment room. Depth dose and beam profile data were compared with PTW Markus N23343 ionization chamber, EBT2 Gafchromic film, and Monte Carlo simulations. Transverse dose profiles were measured using the diode in "edge-on" orientation or EBT2 film. Diode response was linear with respect to dose, uniform with dose rate, and showed an orientation-dependent (i.e., beam parallel to, or perpendicular to, detector axis) response of less than 1%. Diodevs. Markus depth-dose profiles, as well as Markus relative dose ratio vs. simulated dose-weighted average lineal energy plots, suggest that any LET-dependent diode response is negligible from particle entrance up to the very distal portion of the SOBP for the energies tested. Finally, while not possible with the ionization chamber due to partial volume effects, accurate diode depth-dose measurements of 8, 10, and 12 mm diameter beams were obtained compared to Monte Carlo simulations. Because of the small SV that allows measurements without partial volume effects and the capability of submillimeter resolution (in edge-on orientation) that is crucial for small fields and high-dose gradients (e.g., penumbra, distal edge), as well as negligible LET dependence over nearly the full the SOBP, the PTW proton diode proved to be a useful high-resolution, real-time metrology device for small proton field radiation measurements such as would be encountered in radiosurgery applications.

THE EFFECT OF IONIZING RADIATIONS ON ONTOGENESIS IN BIRDS

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

Dinu, M.

1963-01-01

The effect of strong doses of ionizing radiations on the ontogenetic development of birds and formation of mutations was studied. The data obtained show that ionizing radiations have a different effect on the biological substratum, depending on their nature and relationship to physiological limits. Gamma radiations have a negative action on the biochemical process altering ths substratum and upsetting the entity of heredity. It was found that x rays produce a temporary stimulating effect on metabolic processes influencing the vitality, ontogenetic development, resistance, the appearance of sexual instinct, and the fertility. Ionizing radiations affect functioning of endocrinic glands and consequentlymore » the ratio of sexes in the offspring. From the results obtained it cand be stated that strong doses of ionizing radiations may be used to obtain variation of mutations, and that in general they are a factor in the evolution of the living organism. (OTS)« less

Absolute electron-impact total ionization cross sections of chlorofluoromethanes

NASA Astrophysics Data System (ADS)

Martínez, Roberto; Sierra, Borja; Redondo, Carolina; Rayo, María N. Sánchez; Castaño, Fernando

2004-12-01

An experimental study is reported on the electron-impact total ionization cross sections (TICSs) of CCl4, CCl3F, CCl2F2, and CClF3 molecules. The kinetic energy of the colliding electrons was in the 10-85 eV range. TICSs were obtained as the sum of the partial ionization cross sections of all fragment ions, measured and identified in a linear double focusing time-of-flight mass spectrometer. The resulting TICS profiles—as a function of the electron-impact energy—have been compared both with those computed by ab initio and (semi)empirical methods and with the available experimental data. The computational methods used include the binary-encounter-Bethe (BEB) modified to include atoms with principal quantum numbers n⩾3, the Deutsch and Märk (DM) formalism, and the modified additivity rule (MAR). It is concluded that both modified BEB and DM methods fit the experimental TICS for (CF4), CClF3, CCl2F2, CCl3F, and CCl4 to a high accuracy, in contrast with the poor accord of the MAR method. A discussion on the factors influencing the discrepancies of the fittings is presented.

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

Müller, Alfred; Bernhardt, Dietrich; Borovik, Alexander

Single, double, and triple photoionization of Ne + ions by single photons have been investigated at the synchrotron radiation source PETRA III in Hamburg, Germany. Absolute cross-sections were measured by employing the photon-ion merged-beams technique. Photon energies were between about 840 and 930 eV, covering the range from the lowest-energy resonances associated with the excitation of one single K-shell electron up to double excitations involving one K- and one L-shell electron, well beyond the K-shell ionization threshold. Also, photoionization of neutral Ne was investigated just below the K edge. The chosen photon energy bandwidths were between 32 and 500 meV,more » facilitating the determination of natural line widths. The uncertainty of the energy scale is estimated to be 0.2 eV. For comparison with existing theoretical calculations, astrophysically relevant photoabsorption cross-sections were inferred by summing the measured partial ionization channels. Discussion of the observed resonances in the different final ionization channels reveals the presence of complex Auger-decay mechanisms. The ejection of three electrons from the lowest K-shell-excited Ne + (1s2s 2p 6 2S 1/2) level, for example, requires cooperative interaction of at least four electrons.« less

Matrix effect in matrix-assisted laser desorption/ionization mass spectra of derivatized oligomeric polyols.

PubMed

Borisov, Roman S; Polovkov, Nikolai Yu; Zhilyaev, Dmitry I; Zaikin, Vladimir G

2013-01-30

Herein we describe a strong matrix effect observed in the matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectra of silylated glycerol alkoxylates and manifested in the loss of the silyl groups in the presence of carboxyl-containing matrices. Commercially available glycerol alkoxylates containing three end OH groups as well as three matrices - 2,5-dihydroxybenzoic acid (DHB), 3-indoleacrylic acid (IAA) and 1,8,9-anthracenetriol (dithranol) - were chosen for the investigation. N,O-Bis(trimethylsilyl)trifluoroacetamide containing 1% trimethylchlorosilane, acetic anhydride and a formylation mixture (formic acid/acetyl chloride) were used for derivatization. Initial oligomers and derivatized products were analyzed by MALDI-ToF-mass spectrometry (MS) on an Autoflex II instrument, equipped with a nitrogen laser (λ 337 nm), in positive ion reflectron mode. Only [M + Na](+) ions were observed for underivatized polymers and for completely derivatized polymers in the presence of DHB and dithranol, respectively. In the case of IAA the mass spectra revealed sets of peaks for underivatized, and for partially and completely derivatized oligomers. No similar 'matrix effect' was observed in the case of acylated glycerol alkoxylates (acyl = formyl, acetyl): only peaks for completely derivatized oligomers were obtained in all matrices: DHB, IAA and dithranol. Using 1,9-nonandiol, we showed that the 'matrix effect' was due to trans-silylation of carboxyl-containing matrices (DHB and IAA) during co-crystallization of silylated oligomers and matrices. The obtained results show that matrix molecules can participate as reactive species in MALDI-ToF-MS experiments. The matrix should be carefully chosen when a derivatization approach is applied because the analysis of spectra of the completely derivatized products is particularly desirable in the quantitative determination of functional end-groups. Copyright © 2012 John Wiley & Sons, Ltd.

Radiation sterilization of medical devices. Effects of ionizing radiation on ultra-high molecular-weight polyethylene

NASA Astrophysics Data System (ADS)

Buchalla, R.; Schüttler, C.; Bögl, K. W.

1995-02-01

Sterilization by ionizing radiation has become, next to ethylene oxide treament, the most important "cold" sterilization process for medical devices made from plastics. The effects of ionizing radiation on the most important polymer for medical devices, ultra-high molecular-weight polyethylene, are briefly described in this review.

The modulating impact of illumination and background radiation on 8 Hz-induced infrasound effect on physicochemical properties of physiolagical solution.

PubMed

Baghdasaryan, Naira; Mikayelyan, Yerazik; Barseghyan, Sedrak; Dadasyan, Erna; Ayrapetyan, Sinerik

2012-12-01

At present, when the level of background ionizing radiation is increasing in a number of world locations, the problem of the study of biological effect of high background radiation becomes one of the extremely important global problems in modern life sciences. The modern research in biophysics proved that water is a most essential target, through which the biological effects of ionizing and non-ionizing radiations are realized. Therefore, there is no doubt about the strong dependency of non-ionizing radiation-induced effect on the level of background radiation. Findings have shown that illumination and background radiation have a strong modulation effect on infrasound-induced impacts on water physicochemical properties, which could also have appropriate effect on living organisms.

Effect of Lipophilicity and Drug Ionization on Permeation Across Porcine Sublingual Mucosa.

PubMed

Goswami, Tarun; Li, Xiaoling; Jasti, Bhaskara R

2017-01-01

Sublingual route is one of the oldest alternative routes studied for the administration of drugs. However, the effect of physical-chemical properties on drug permeation via this route has not been systemically investigated. The objective of this study was to determine the effect of two key physicochemical properties, lipophilicity and ionization, on the transport of drugs across porcine sublingual mucosa. A series of β-blockers were used to study the effect of lipophilicity on drug permeation across the sublingual mucosa, while nimesulide (pKa 6.5) was used as a model drug to study the effect of degree of ionization on sublingual mucosa permeation of ionized and unionized species. Permeation of β-blockers increased linearly with an increase in the lipophilicity for the range of compounds studied. The permeability of nimesulide across sublingual mucosa decreased with an increase of pH. The flux of ionized and unionized forms of nimesulide was determined to delineate the contribution of ionized and unionized species to the total flux. At low pH, the apparent flux was primarily contributed by unionized species; however, when the pH is increased beyond its pKa, the primary contributor to the apparent flux, nimesulide, is ionized species. The contribution of each species to the apparent flux was shown to be determined by the thermodynamic activity of ionized or unionized species. This study identified the roles of lipophilicity and thermodynamic activity in drug permeation across the sublingual mucosa. The findings can help guide the design of sublingual drug delivery systems with optimal pH and solubility.

Photoevaporating stellar envelopes observed with Rayleigh beacon adaptive optics

NASA Technical Reports Server (NTRS)

Mccullough, P. R.; Fugate, R. Q.; Christou, J. C.; Ellerbroek, B. L.; Higgins, C. H.; Spinhirne, J. M.; Cleis, R. A.; Moroney, J. F.

1995-01-01

We present H-alpha and I-band images of a approximately 1 min diameter field centered on theta(sup 1) C Ori made with a unique adaptive optics system that uses either starlight or Rayleigh-backscattered laser light to correct for atmospheric wavefront distortion. Approximately one-half of the stars in this region are positionally associated with knots of ionized gas, which are interpreted as photoevaporating envelopes of low-mass stars. The acronyms 'partially ionized globule' (PIGs), external ionized (accretion) disks in the environs of radiation sources (EIDERs), or protoplanetary disks (ProPlyDs) all refer to these same knots. The H-alpha fluxes of the PIGs are proportional to their 2 cm radio continumm flux densities, and for nearly all the ionized knots, the 2 cm brightness temperatures are consistent with theta(sup 1) C Ori as the primary source of ionization. The comet-like morphology of the bright nebulosities is modeled as the result of an equilibrium between photoionization, recombination, and shadowing. The radii of the ionized 'head' of the cometary PIGs grow with distance from theta(sup 1) C Ori; the radii range from approximately less than or equal to 0.05 sec to approximately 0.25 sec. We interpret the size-distance relationship as evidence that the envelopes all have the same density profile and mass-loss rate within a factor of 2. Faint, arcuate wisps are observed 1 sec to 2 sec distance from some of the cometary nebulosities; these are modeled as bow shocks caused by the wind from theta(sup 1) C Ori. The positions of the stars associated with the PIGs in the observational H-R diagram indicate they are pre-main-sequence stars with masses less than approximately 3 solar mass, with approximately 1 solar mass being typical. Their medium I-K color is 2.9.

Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

NASA Astrophysics Data System (ADS)

Horn, R.; Ihmann, K.; Ihmann, J.; Jentoft, F. C.; Geske, M.; Taha, A.; Pelzer, K.; Schlögl, R.

2006-05-01

A newly developed apparatus combining a molecular beam mass spectrometer and a catalytic wall reactor is described. The setup has been developed for in situ studies of high temperature catalytic reactions (>1000°C), which involve besides surface reactions also gas phase reactions in their mechanism. The goal is to identify gas phase radicals by threshold ionization. A tubular reactor, made from the catalytic material, is positioned in a vacuum chamber. Expansion of the gas through a 100μm sampling orifice in the reactor wall into differentially pumped nozzle, skimmer, and collimator chambers leads to the formation of a molecular beam. A quadrupole mass spectrometer with electron impact ion source designed for molecular beam inlet and threshold ionization measurements is used as the analyzer. The sampling time from nozzle to detector is estimated to be less than 10ms. A detection time resolution of up to 20ms can be reached. The temperature of the reactor is measured by pyrometry. Besides a detailed description of the setup components and the physical background of the method, this article presents measurements showing the performance of the apparatus. After deriving the shape and width of the energy spread of the ionizing electrons from measurements on N2 and He we estimated the detection limit in threshold ionization measurements using binary mixtures of CO in N2 to be in the range of several hundreds of ppm. Mass spectra and threshold ionization measurements recorded during catalytic partial oxidation of methane at 1250°C on a Pt catalyst are presented. The detection of CH3• radicals is successfully demonstrated.

Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

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

Horn, R.; Ihmann, K.; Ihmann, J.

2006-05-15

A newly developed apparatus combining a molecular beam mass spectrometer and a catalytic wall reactor is described. The setup has been developed for in situ studies of high temperature catalytic reactions (>1000 deg. C), which involve besides surface reactions also gas phase reactions in their mechanism. The goal is to identify gas phase radicals by threshold ionization. A tubular reactor, made from the catalytic material, is positioned in a vacuum chamber. Expansion of the gas through a 100 {mu}m sampling orifice in the reactor wall into differentially pumped nozzle, skimmer, and collimator chambers leads to the formation of a molecularmore » beam. A quadrupole mass spectrometer with electron impact ion source designed for molecular beam inlet and threshold ionization measurements is used as the analyzer. The sampling time from nozzle to detector is estimated to be less than 10 ms. A detection time resolution of up to 20 ms can be reached. The temperature of the reactor is measured by pyrometry. Besides a detailed description of the setup components and the physical background of the method, this article presents measurements showing the performance of the apparatus. After deriving the shape and width of the energy spread of the ionizing electrons from measurements on N{sub 2} and He we estimated the detection limit in threshold ionization measurements using binary mixtures of CO in N{sub 2} to be in the range of several hundreds of ppm. Mass spectra and threshold ionization measurements recorded during catalytic partial oxidation of methane at 1250 deg. C on a Pt catalyst are presented. The detection of CH{sub 3}{center_dot} radicals is successfully demonstrated.« less

On the Effects of Bremsstrahlung Radiation During Energetic Electron Precipitation

NASA Astrophysics Data System (ADS)

Xu, Wei; Marshall, Robert A.; Fang, Xiaohua; Turunen, Esa; Kero, Antti

2018-01-01

Precipitation of energetic particles into the Earth's atmosphere can significantly change the properties, dynamics, as well as the chemical composition of the upper and middle atmosphere. In this paper, using Monte Carlo models, we simulate, from first principles, the interaction of monoenergetic beams of precipitating electrons with the atmosphere, with particular emphasis on the process of bremsstrahlung radiation and its resultant ionization production and atmospheric effects. The pitch angle dependence of the ionization rate profile has been quantified: the altitude of peak ionization rate depends on the pitch angle by a few kilometers. We also demonstrate that the transport of precipitating electron energy in the form of bremsstrahlung photons leads to ionization at altitudes significantly lower than the direct impact ionization, as low as ˜20 km for 1 MeV precipitating electrons. Moreover, chemical modeling results suggest that the chemical effects in the atmosphere due to bremsstrahlung-induced ionization production during energetic electron precipitation are likely insignificant.

Dissociative and double photoionization cross sections of NO from threshold to 120 A

NASA Technical Reports Server (NTRS)

Samson, J. A. R.; Masuoka, T.; Pareek, P. N.

1985-01-01

The partial photoionization cross sections for producing the NO(+) parent ion and the O(+), N(+), and NO(2+) fragmentations from neutral NO are presented from 120 to 614 A. The results indicate predissociation of the 3 pi (21.72 eV) and B-prime 1Sigma(+) (22.73 eV) electronic states of NO(+). The photoionization threshold for double ionization was found to be 39.4 + or - 0.12 eV.

Hybrid Parallelization of Adaptive MHD-Kinetic Module in Multi-Scale Fluid-Kinetic Simulation Suite

DOE PAGES

Borovikov, Sergey; Heerikhuisen, Jacob; Pogorelov, Nikolai

2013-04-01

The Multi-Scale Fluid-Kinetic Simulation Suite has a computational tool set for solving partially ionized flows. In this paper we focus on recent developments of the kinetic module which solves the Boltzmann equation using the Monte-Carlo method. The module has been recently redesigned to utilize intra-node hybrid parallelization. We describe in detail the redesign process, implementation issues, and modifications made to the code. Finally, we conduct a performance analysis.

Ghost peaks observed after AP-MALDI experiment may disclose new ionization mechanism of matrix assisted hypersonic velocity impact ionization

PubMed Central

Moskovets, Eugene

2015-01-01

RATIONALE Understanding the mechanisms of MALDI promises improvements in the sensitivity and specificity of many established applications in the field of mass spectrometry. This paper reports a serendipitous observation of a significant ion yield in a post-ionization experiment conducted after the sample has been removed from a standard atmospheric pressure (AP)-MALDI source. This post-ionization is interpreted in terms of collisions of microparticles moving with a hypersonic velocity into a solid surface. Calculations show that the thermal energy released during such collisions is close to that absorbed by the top matrix layer in traditional MALDI. The microparticles, containing both the matrix and analytes, could be detached from a film produced inside the inlet capillary during the sample ablation and accelerated by the flow rushing through the capillary. These observations contribute some new perspective to ion formation in both laser and laserless matrix-assisted ionization. METHODS An AP-MALDI ion source hyphenated with a three-stage high-pressure ion funnel system was utilized for peptide mass analysis. After the laser was turned off and MALDI sample was removed, ions were detected during a gradual reduction of the background pressure in the first funnel. The constant-rate pressure reduction led to the reproducible appearance of different singly- and doubly-charged peptide peaks in mass spectra taken a few seconds after the end of the MALDI analysis of a dried-droplet spot. RESULTS The ion yield as well as the mass range of ions observed with a significant delay after a completion of the primary MALDI analysis depended primarily on the background pressure inside the first funnel. The production of ions in this post-ionization step was exclusively observed during the pressure drop. A lower matrix background and significant increase in relative yield of double-protonated ions are reported. CONCLUSIONS The observations were partially consistent with a model of the supersonic jet from the inlet capillary accelerating detached particles to kinetic energies suitable for matrix-assisted hypersonic-velocity impact ionization. PMID:26212165

Global scale equatorial ionization anomaly (EIA) response to magnetospheric disturbances based on the May-June 1987 SUNDIAL-coordinated observations

NASA Astrophysics Data System (ADS)

Abdu, M. A.; Walker, G. O.; Reddy, B. M.; de Paula, E. R.; Sobral, J. H. A.; Fejer, B. G.

1993-07-01

Equatorial ionization anomaly (EIA) responses to magnetospheric disturbances have been investigated using ionosonde and geomagnetic data sets obtained for different longitude sectors during the 9-day (28 May-7 June) globally-coordinated SUNDIAL 87 campaign. Attention is focused on the EIA response features of the two magnetically most-disturbed days of the campaign window, 29 May and 6 June. Anomalous EIA inhibition and development were simultaneously observed at widely separated (American and Asian) longitude sectors, accompanied respectively by events of morning electrojet reversal and evening partial ring current development. A numerical model of the low-latitude ionosphere has been used to quantify the role that a disturbance electric field could play in the observed EIA response features. The implications of the results on the global low-latitude disturbance electric field pattern is discussed.

Interaction Between Cytochrome c and the Hapten 2,4-Dinitro-fluorobenzene by Electrospray Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Wu, Bo; Chu, Yan-qiu; Dai, Zhao-yun; Ding, Chuan-fan

2008-06-01

Allergic contact dermatitis is a delayed hypersensitivity reaction, which results from skin exposure to low molecular weight chemicals such as haptens. To clarify the pathogenic mechanism, electrospray ionization mass spectrometry (ESI-MS) and hydrogen/deuterium (H/D) exchange, as well as UV spectroscopy, were applied to determine the interaction between the model protein cytochrome c (cyt c) and the hapten 2,4-dinitro-fluorobenzene (DNFB). The ESI-MS results demonstrate that the conformation of cyt c can change from native folded state into partially unfolded state with the increase of DNFB. The equilibrium state H/D exchange followed by ESI-MS further confirms the above results. UV spectroscopy indicates that the strong-field coordination between iron of heme (prosthetic group) and His18 or Met80 of cyt c is not obviously affected by the hapten.

Direction sensitive neutron detector

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

Ahlen, Steven; Fisher, Peter; Dujmic, Denis

2017-01-31

A neutron detector includes a pressure vessel, an electrically conductive field cage assembly within the pressure vessel and an imaging subsystem. A pressurized gas mixture of CF.sub.4, .sup.3He and .sup.4He at respective partial pressures is used. The field cage establishes a relatively large drift region of low field strength, in which ionization electrons generated by neutron-He interactions are directed toward a substantially smaller amplification region of substantially higher field strength in which the ionization electrons undergo avalanche multiplication resulting in scintillation of the CF.sub.4 along scintillation tracks. The imaging system generates two-dimensional images of the scintillation patterns and employs track-findingmore » to identify tracks and deduce the rate and direction of incident neutrons. One or more photo-multiplier tubes record the time-profile of the scintillation tracks permitting the determination of the third coordinate.« less

Low-Energy Electron Interactions with CF_4

NASA Astrophysics Data System (ADS)

Christophorou, Loucas G.; Olthoff, James K.; Rao, M. V. V. S.

1996-10-01

Carbon tetrafluoride is one of the most widely used components of feed gas mixtures employed for a variety of plasma assisted materials processing applications. In this presentation, we synthesize and assess the available information on the cross sections and rate coefficients of collisional interations of CF4 with electrons.(L. G. Christophorou, J. K. Olthoff, and M.V. V. S. Rao, J. Phys. Chem. Ref. Data, submitted (May 1996)) A ``recommended'' data set is presented, based upon available data for: (i) cross sections for electron scattering (total, elastic, momentum, differential, inelastic), electron impact ionization (total and partial), electron impact dissociation, and electron attachment; and (ii) coefficients for electron transport, electron attachment, and electron impact ionization. -Research sponsored in part by the U.S. Air Force Wright Laboratory under contract F33615-96-C-2600 with the University of Tennessee. Also, Department of Physics, The University of Tennessee, Knoxville, TN.

Charge-Transfer Processes in Warm Dense Matter: Selective Spectral Filtering for Laser-Accelerated Ion Beams

NASA Astrophysics Data System (ADS)

Braenzel, J.; Barriga-Carrasco, M. D.; Morales, R.; Schnürer, M.

2018-05-01

We investigate, both experimentally and theoretically, how the spectral distribution of laser accelerated carbon ions can be filtered by charge exchange processes in a double foil target setup. Carbon ions at multiple charge states with an initially wide kinetic energy spectrum, from 0.1 to 18 MeV, were detected with a remarkably narrow spectral bandwidth after they had passed through an ultrathin and partially ionized foil. With our theoretical calculations, we demonstrate that this process is a consequence of the evolution of the carbon ion charge states in the second foil. We calculated the resulting spectral distribution separately for each ion species by solving the rate equations for electron loss and capture processes within a collisional radiative model. We determine how the efficiency of charge transfer processes can be manipulated by controlling the ionization degree of the transfer matter.

Fast high-throughput method for the determination of acidity constants by capillary electrophoresis: I. Monoprotic weak acids and bases.

PubMed

Fuguet, Elisabet; Ràfols, Clara; Bosch, Elisabeth; Rosés, Martí

2009-04-24

A new and fast method to determine acidity constants of monoprotic weak acids and bases by capillary zone electrophoresis based on the use of an internal standard (compound of similar nature and acidity constant as the analyte) has been developed. This method requires only two electrophoretic runs for the determination of an acidity constant: a first one at a pH where both analyte and internal standard are totally ionized, and a second one at another pH where both are partially ionized. Furthermore, the method is not pH dependent, so an accurate measure of the pH of the buffer solutions is not needed. The acidity constants of several phenols and amines have been measured using internal standards of known pK(a), obtaining a mean deviation of 0.05 pH units compared to the literature values.

Surfactant-enhanced alkaline flooding: Buffering at intermediate alkaline pH

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

Rudin, J.; Wasan, D.T.

1993-11-01

The alkaline flooding process involves injecting alkaline agents into the reservoir to produce more oil than is produced through conventional waterflooding. The interaction of the alkali in the flood water with the naturally occurring acids in the reservoir oil results in in-situ formation of soaps, which are partially responsible for lowering IFT and improving oil recovery. The extent to which IFT is lowered depends on the specific oil and injection water properties. Numerous investigators have attempted to clarify the relationship between system chemical composition and IFT. An experimental investigation of buffered alkaline flooding system chemistry was undertaken to determine themore » influence of various species present on interfacial tension (IFT) as a function of pH and ionic strength. IFT was found to go through an ultralow minimum in certain pH ranges. This synergism results from simultaneous adsorption of un-ionized and ionized acid species on the interface.« less

A review of reaction rates and thermodynamic and transport properties for an 11-species air model for chemical and thermal nonequilibrium calculations to 30000 K

NASA Technical Reports Server (NTRS)

Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.; Lee, Kam-Pui

1990-01-01

Reaction rate coefficients and thermodynamic and transport properties are reviewed and supplemented for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium up to temperatures of 3000 K. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Curve fits are given for the various species properties for their efficient computation in flowfield codes. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in a high energy environment. Limitations of the approximate mixing laws are discussed for a mixture of ionized species. An electron number-density correction for the transport properties of the charged species is obtained. This correction has been generally ignored in the literature.

Final states in Si and GaAs via RF μSR spectroscopy

NASA Astrophysics Data System (ADS)

Kreitzman, S. R.; Pfiz, T.; Sun-Mack, S.; Riseman, T. M.; Brewer, J. H.; Williams, D. Ll.; Estle, T. L.

1991-02-01

The ionization of muonium centers in Si and GaAs have been studied using radio frequency (RF) resonant techniques. In Si all three muonic centers are detectable by RF. No evidence was found for delayed Mu and Mu* states at any temperature. However, our results on the diamagnetic final state (μ{f/+}) show that it is composed of prompt fractions (as seen by conventional μSR) and delayed fractions arising from the ionization of Mu* and Mu. We observe a full μ{f/+} fraction at 317 K when the Mu relaxation rate is above 10 μs-1. GaAs differs from the situation in Si in that we observed only a partial conversion of Mu* and Mu to a μ+ final state up to 310 K in spite of the fact that the transverse field relaxation rates become very high at 150 and 250 K respectively.

Quantum Spin Ice under a [111] Magnetic Field: From Pyrochlore to Kagome

NASA Astrophysics Data System (ADS)

Bojesen, Troels Arnfred; Onoda, Shigeki

2017-12-01

Quantum spin ice, modeled for magnetic rare-earth pyrochlores, has attracted great interest for hosting a U(1) quantum spin liquid, which involves spin-ice monopoles as gapped deconfined spinons, as well as gapless excitations analogous to photons. However, the global phase diagram under a [111] magnetic field remains open. Here we uncover by means of unbiased quantum Monte Carlo simulations that a supersolid of monopoles, showing both a superfluidity and a partial ionization, intervenes the kagome spin ice and a fully ionized monopole insulator, in contrast to classical spin ice where a direct discontinuous phase transition takes place. We also show that on cooling, kagome spin ice evolves towards a valence-bond solid similar to what appears in the associated kagome lattice model [S. V. Isakov et al., Phys. Rev. Lett. 97, 147202 (2006), 10.1103/PhysRevLett.97.147202]. Possible relevance to experiments is discussed.

CCC calculated integrated cross sections of electron-H2 scattering

NASA Astrophysics Data System (ADS)

Zammit, Mark; Fursa, Dmitry; Savage, Jeremy; Bray, Igor

2016-09-01

Recently we applied the molecular convergent close-coupling (CCC) method to electron scattering from molecular hydrogen H2. Convergence of the major integrated cross sections has been explicitly demonstrated in the fixed-nuclei approximation by increasing the number of H2 target states in the close-coupling expansion from 9 to 491. The calculations have been performed using a projectile partial wave expansion with maximum orbital angular momentum Lmax = 8 and total orbital angular momentum projections | M | <= 8 . Coupling to the ionization continuum is modeled via a large pseudo state expansion, which we found is required to obtain reliable elastic and excitation cross sections. Here we present benchmark elastic, single-ionization, electronic excitation and total integrated cross sections over a broad energy range (0.1 to 300 eV) and compare with available experiment and previous calculations. Los Alamos National Laboratory and Curtin University.

Fundamentals of Radiation Physics

DTIC Science & Technology

2008-07-01

Sources of Ionizing Radiation Electrically generated • Charged particle accelerators • Van de Graaff generator , cyclotron linear accelerator ...Presented at the Armed Forces Radiobiology Research Institute Scientific Medical Effects of Ionizing Radiation Course July 28 through August 1, 2008...conducted once a year, focuses on the latest research about the medical effects of ionizing radiation to help clinicians, health physicists, and

Extending helium partial pressure measurement technology to JET DTE2 and ITER.

PubMed

Klepper, C C; Biewer, T M; Kruezi, U; Vartanian, S; Douai, D; Hillis, D L; Marcus, C

2016-11-01

The detection limit for helium (He) partial pressure monitoring via the Penning discharge optical emission diagnostic, mainly used for tokamak divertor effluent gas analysis, is shown here to be possible for He concentrations down to 0.1% in predominantly deuterium effluents. This result from a dedicated laboratory study means that the technique can now be extended to intrinsically (non-injected) He produced as fusion reaction ash in deuterium-tritium experiments. The paper also examines threshold ionization mass spectroscopy as a potential backup to the optical technique, but finds that further development is needed to attain with plasma pulse-relevant response times. Both these studies are presented in the context of continuing development of plasma pulse-resolving, residual gas analysis for the upcoming JET deuterium-tritium campaign (DTE2) and for ITER.

Dynamics of Hollow Atom Formation in Intense X-Ray Pulses Probed by Partial Covariance Mapping

NASA Astrophysics Data System (ADS)

Frasinski, L. J.; Zhaunerchyk, V.; Mucke, M.; Squibb, R. J.; Siano, M.; Eland, J. H. D.; Linusson, P.; v. d. Meulen, P.; Salén, P.; Thomas, R. D.; Larsson, M.; Foucar, L.; Ullrich, J.; Motomura, K.; Mondal, S.; Ueda, K.; Osipov, T.; Fang, L.; Murphy, B. F.; Berrah, N.; Bostedt, C.; Bozek, J. D.; Schorb, S.; Messerschmidt, M.; Glownia, J. M.; Cryan, J. P.; Coffee, R. N.; Takahashi, O.; Wada, S.; Piancastelli, M. N.; Richter, R.; Prince, K. C.; Feifel, R.

2013-08-01

When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called “partial covariance mapping” to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.

Ionized calcium concentrations in squid axons

PubMed Central

1976-01-01

Values for ionized [Ca] in squid axons were obtained by measuring the light emission from a 0.1-mul drop of aequorin confined to a plastic dialysis tube of 140-mum diameter located axially. Ionized Ca had a mean value of 20 x 10(-9) M as judged by the subsequent introduction of CaEGTA/EGTA buffer (ratio ca. 0.1) into the axoplasm, and light measurement on a second aequorin drop. Ionized Ca in axoplasma was also measured by introducing arsenazo dye into an axon by injection and measuring the Ca complex of such a dye by multichannel spectrophotometry. Values so obtained were ca. 50 x 10(-9) M as calibrated against CaEGTA/EGTA buffer mixtures. Wth a freshly isolated axon in 10 mM Ca seawater, the aequorin glow invariably increased with time; a seawater [Ca] of 2-3 mM allowed a steady state with respect to [Ca]. Replacement of Na+ in seawater with choline led to a large increase in light emission from aequorin. Li seawater partially reversed this change and the reintroduction of Na+ brought light levels back to their initial value. Stimulation at 60/s for 2-5 min produced an increase in aequorin glow about 0.1% of that represented by the known Ca influx, suggesting operationally the presence of substantial Ca buffering. Treatment of an axon with CN produced a very large increase in aequorin glow and in Ca arsenazo formation only if the external seawater contained Ca. PMID:818340

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.

Battery-Powered RF Pre-Ionization System for the Caltech Magnetohydrodynamically-Driven Jet Experiment: RF Discharge Properties and MHD-Driven Jet Dynamics

NASA Astrophysics Data System (ADS)

Chaplin, Vernon H.

This thesis describes investigations of two classes of laboratory plasmas with rather different properties: partially ionized low pressure radiofrequency (RF) discharges, and fully ionized high density magnetohydrodynamically (MHD)-driven jets. An RF pre-ionization system was developed to enable neutral gas breakdown at lower pressures and create hotter, faster jets in the Caltech MHD-Driven Jet Experiment. The RF plasma source used a custom pulsed 3 kW 13.56 MHz RF power amplifier that was powered by AA batteries, allowing it to safely float at 4-6 kV with the cathode of the jet experiment. The argon RF discharge equilibrium and transport properties were analyzed, and novel jet dynamics were observed. Although the RF plasma source was conceived as a wave-heated helicon source, scaling measurements and numerical modeling showed that inductive coupling was the dominant energy input mechanism. A one-dimensional time-dependent fluid model was developed to quantitatively explain the expansion of the pre-ionized plasma into the jet experiment chamber. The plasma transitioned from an ionizing phase with depressed neutral emission to a recombining phase with enhanced emission during the course of the experiment, causing fast camera images to be a poor indicator of the density distribution. Under certain conditions, the total visible and infrared brightness and the downstream ion density both increased after the RF power was turned off. The time-dependent emission patterns were used for an indirect measurement of the neutral gas pressure. The low-mass jets formed with the aid of the pre-ionization system were extremely narrow and collimated near the electrodes, with peak density exceeding that of jets created without pre-ionization. The initial neutral gas distribution prior to plasma breakdown was found to be critical in determining the ultimate jet structure. The visible radius of the dense central jet column was several times narrower than the axial current channel radius, suggesting that the outer portion of the jet must have been force free, with the current parallel to the magnetic field. The studies of non-equilibrium flows and plasma self-organization being carried out at Caltech are relevant to astrophysical jets and fusion energy research.

Outflowing OH+ in Markarian 231: The Ionization Rate of the Molecular Gas

NASA Astrophysics Data System (ADS)

González-Alfonso, E.; Fischer, J.; Bruderer, S.; Ashby, M. L. N.; Smith, H. A.; Veilleux, S.; Müller, H. S. P.; Stewart, K. P.; Sturm, E.

2018-04-01

The oxygen-bearing molecular ions OH+, H2O+, and H3O+ are key species that probe the ionization rate of (partially) molecular gas that is ionized by X-rays and cosmic-rays permeating the interstellar medium. We report Herschel far-infrared and submillimeter spectroscopic observations of OH+ in Mrk 231, showing both ground-state P-Cygni profiles, and excited line profiles with blueshifted absorption wings extending up to ≈1000 km s‑1. In addition, OH+ probes an excited component peaking at central velocities, likely arising from the torus probed by the OH centimeter-wave megamaser. Four lines of H2O+ are also detected at systemic velocities, but H3O+ is undetected. Based on our earlier OH studies, we estimate an abundance ratio of {OH}/{OH}}+∼ 5{--}10 for the outflowing components and ≈20 for the torus, and an OH+ abundance relative to H nuclei of ≳10‑7. We also find high OH+/H2O+ and OH+/H3O+ ratios; both are ≳4 in the torus and ≳10–20 in the outflowing gas components. Chemical models indicate that these high OH+ abundances relative to OH, H2O+, and H3O+ are characteristic of gas with a high ionization rate per unit density, \\zeta /{n}{{H}}∼ (1{--}5)× {10}-17 cm3 s‑1 and ∼(1–2) × 10‑16 cm3 s‑1 for the above components, respectively, an ionization rate of ζ ∼ (0.5–2) × 10‑12 s‑1, and a low molecular fraction, {f}{{{H}}2}∼ 0.25. X-rays appear to be unable to explain the inferred ionization rate, and thus we suggest that low-energy (10–400 MeV) cosmic-rays are primarily responsible for the ionization, with {\\dot{M}}CR}∼ 0.01 M ⊙ yr‑1 and {\\dot{E}}CR}∼ {10}44 erg s‑1 the latter corresponds to ∼1% of the luminosity of the active galactic nucleus and is similar to the energetics of the molecular outflow. We suggest that cosmic-rays accelerated in the forward shock associated with the molecular outflow are responsible for the ionization, as they diffuse through the outflowing molecular phase downstream.

Two-color above-threshold and two-photon sequential double ionization beyond the dipole approximation

NASA Astrophysics Data System (ADS)

Grum-Grzhimailo, A. N.; Gryzlova, E. V.; Kuzmina, E. I.; Chetverkina, A. S.; Strakhova, S. I.

2015-04-01

Two nonlinear atomic photoprocesses are theoretically considered with the emphasis on the photoelectron angular distributions and their modifications due to violation of the dipole approximation: sequential two-photon double ionization and two-color above threshold ionization. These reactions are now accessible with X-ray free electron lasers. Both processes are exemplified by the ionization of krypton: from the 4p shell in the sequential two-photon double ionization and from the 2s shell in the two-color above-threshold ionization, which are compared to the Ar(3p) and Ne(1s) ionization, respectively. Noticeable nondipole effects are predicted.

Ion energies in high power impulse magnetron sputtering with and without localized ionization zones

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

Yang, Yuchen; Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720; Tanaka, Koichi

2015-03-23

High speed imaging of high power impulse magnetron sputtering discharges has revealed that ionization is localized in moving ionization zones but localization disappears at high currents for high yield targets. This offers an opportunity to study the effect ionization zones have on ion energies. We measure that ions have generally higher energies when ionization zones are present, supporting the concept that these zones are associated with moving potential humps. We propose that the disappearance of ionization zones is caused by an increased supply of atoms from the target which cools electrons and reduces depletion of atoms to be ionized.

Systematic investigation of ion suppression and enhancement effects of fourteen stable-isotope-labeled internal standards by their native analogues using atmospheric-pressure chemical ionization and electrospray ionization and the relevance for multi-analyte liquid chromatographic/mass spectrometric procedures.

PubMed

Remane, Daniela; Wissenbach, Dirk K; Meyer, Markus R; Maurer, Hans H

2010-04-15

In clinical and forensic toxicology, multi-analyte procedures are very useful to quantify drugs and poisons of different classes in one run. For liquid chromatographic/tandem mass spectrometric (LC/MS/MS) multi-analyte procedures, often only a limited number of stable-isotope-labeled internal standards (SIL-ISs) are available. If an SIL-IS is used for quantification of other analytes, it must be excluded that the co-eluting native analyte influences its ionization. Therefore, the effect of ion suppression and enhancement of fourteen SIL-ISs caused by their native analogues has been studied. It could be shown that the native analyte concentration influenced the extent of ion suppression and enhancement effects leading to more suppression with increasing analyte concentration especially when electrospray ionization (ESI) was used. Using atmospheric-pressure chemical ionization (APCI), methanolic solution showed mainly enhancement effects, whereas no ion suppression and enhancement effect, with one exception, occurred when plasma extracts were used under these conditions. Such differences were not observed using ESI. With ESI, eleven SIL-ISs showed relevant suppression effects, but only one analyte showed suppression effects when APCI was used. The presented study showed that ion suppression and enhancement tests using matrix-based samples of different sources are essential for the selection of ISs, particularly if used for several analytes to avoid incorrect quantification. In conclusion, only SIL-ISs should be selected for which no suppression and enhancement effects can be observed. If not enough ISs are free of ionization interferences, a different ionization technique should be considered. 2010 John Wiley & Sons, Ltd.

Factors that affect molecular weight distribution of Suwannee river fulvic acid as determined by electrospray ionization/mass spectrometry

USGS Publications Warehouse

Rostad, Colleen E.; Leenheer, Jerry A.

2004-01-01

Effects of methylation, molar response, multiple charging, solvents, and positive and negative ionization on molecular weight distributions of aquatic fulvic acid were investigated by electrospray ionization/mass spectrometry. After preliminary analysis by positive and negative modes, samples and mixtures of standards were derivatized by methylation to minimize ionization sites and reanalyzed.Positive ionization was less effective and produced more complex spectra than negative ionization. Ionization in methanol/water produced greater response than in acetonitrile/water. Molar response varied widely for the selected free acid standards when analyzed individually and in a mixture, but after methylation this range decreased. After methylation, the number average molecular weight of the Suwannee River fulvic acid remained the same while the weight average molecular weight decreased. These differences are probably indicative of disaggregation of large aggregated ions during methylation. Since the weight average molecular weight decreased, it is likely that aggregate formation in the fulvic acid was present prior to derivatization, rather than multiple charging in the mass spectra.

Temperature relaxation in supernova remnants, revisited

NASA Technical Reports Server (NTRS)

Itoh, H.

1984-01-01

Some supernova remnants are expanding into a partially neutral medium. The neutral atoms which are engulfed by the fast blast shock are collisionally ionized to eject low-energy secondary electrons. Calculations are conducted of the temperature relaxation through Coulomb collisions among the secondary electrons, the shocked electrons, and the ions, assuming that the three species have Maxwellian velocity distributions. The results are applied to a self-similar blast wave. If the efficiency of collisionless electron heating at the shock front is high in young remnants such as Tycho, the secondary electrons may be much cooler than both the shocked electrons and the ions. In this case, the emergent X-ray continuum spectrum will have a two-temperature, or a power-law, appearance. This effect may have been observed in the bright rim of the remnant of SN 1006.

Development of a highly-sensitive Penning ionization electron spectrometer using the magnetic bottle effect

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

Ota, Masahiro; Ishiguro, Yuki; Nakajima, Yutaro

2016-02-01

This paper reports on a highly-sensitive retarding-type electron spectrometer for a continuous source of electrons, in which the electron collection efficiency is increased by utilizing the magnetic bottle effect. This study demonstrates an application to Penning ionization electron spectroscopy using collisional ionization with metastable He*(2{sup 3}S) atoms. Technical details and performances of the instrument are presented. This spectrometer can be used for studies of functional molecules and assemblies, and exterior electron densities are expected to be selectively observed by the Penning ionization.

Bilogical effects of ionizing radiation: epidemiological surveys and laboratory animal experiments. Implications for risk evaluation and decision processes

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

Fabrikant, J.I.

1981-04-01

General background is given for an understanding of the potential health effects in populations exposed to low-level ionizing radiations. The discussion is within the framework of the scientific deliberations and controversies that arose during preparation of the current report of the committee on the biological effects of ionizing radiation of the National Academy of Science - National Research Council (1980 Beir-III Report). (ACR)

Self Organization in Compensated Semiconductors

NASA Astrophysics Data System (ADS)

Berezin, Alexander A.

2004-03-01

In partially compensated semiconductor (PCS) Fermi level is pinned to donor sub-band. Due to positional randomness and almost isoenergetic hoppings, donor-spanned electronic subsystem in PCS forms fluid-like highly mobile collective state. This makes PCS playground for pattern formation, self-organization, complexity emergence, electronic neural networks, and perhaps even for origins of life, bioevolution and consciousness. Through effects of impact and/or Auger ionization of donor sites, whole PCS may collapse (spinodal decomposition) into microblocks potentially capable of replication and protobiological activity (DNA analogue). Electronic screening effects may act in RNA fashion by introducing additional length scale(s) to system. Spontaneous quantum computing on charged/neutral sites becomes potential generator of informationally loaded microstructures akin to "Carl Sagan Effect" (hidden messages in Pi in his "Contact") or informational self-organization of "Library of Babel" of J.L. Borges. Even general relativity effects at Planck scale (R.Penrose) may affect the dynamics through (e.g.) isotopic variations of atomic mass and local density (A.A.Berezin, 1992). Thus, PCS can serve as toy model (experimental and computational) at interface of physics and life sciences.

A detailed analysis of the high-resolution X-ray spectra of NGC 3516: variability of the ionized absorbers

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

Huerta, E. M.; Krongold, Y.; Jimenez-Bailon, E.

2014-09-20

The 1.5 Seyfert galaxy NGC 3516 presents a strong time variability in X-rays. We re-analyzed the nine observations performed in 2006 October by XMM-Newton and Chandra in the 0.3 to 10 keV energy band. An acceptable model was found for the XMM-Newton data fitting the EPIC-PN and RGS spectra simultaneously; later, this model was successfully applied to the contemporary Chandra high-resolution data. The model consists of a continuum emission component (power law + blackbody) absorbed by four ionized components (warm absorbers), and 10 narrow emission lines. Three absorbing components are warm, producing features only in the soft X-ray band. Themore » fourth ionization component produces Fe XXV and Fe XXVI in the hard-energy band. We study the time response of the absorbing components to the well-detected changes in the X-ray luminosity of this source and find that the two components with the lower ionization state show clear opacity changes consistent with gas close to photoionization equilibrium. These changes are supported by the models and by differences in the spectral features among the nine observations. On the other hand, the two components with higher ionization state do not seem to respond to continuum variations. The response time of the ionized absorbers allows us to constrain their electron density and location. We find that one component (with intermediate ionization) must be located within the obscuring torus at a distance 2.7 × 10{sup 17} cm from the central engine. This outflowing component likely originated in the accretion disk. The three remaining components are at distances larger than 10{sup 16}-10{sup 17} cm. Two of the absorbing components in the soft X-rays have similar outflow velocities and locations. These components may be in pressure equilibrium, forming a multi-phase medium, if the gas has metallicity larger than the solar one (≳ 5 Z {sub ☉}). We also search for variations in the covering factor of the ionized absorbers (although partial covering is not required in our models). We find no correlation between the change in covering factor and the flux of the source. This, in connection with the observed variability of the ionized absorbers, suggests that the changes in flux are not produced by this material. If the variations are indeed produced by obscuring clumps of gas, these must be located much closer in to the central source.« less

A Double-Blind Placebo-Controlled Crossover Trial of Intravenous Magnesium Sulfate for Foscarnet-Induced Ionized Hypocalcemia and Hypomagnesemia in Patients with AIDS and Cytomegalovirus Infection

PubMed Central

Huycke, Mark M.; Naguib, M. Tarek; Stroemmel, Mathias M.; Blick, Kenneth; Monti, Katherine; Martin-Munley, Sarah; Kaufman, Chris

2000-01-01

Foscarnet (trisodium phosphonoformate hexahydrate) is an antiviral agent used to treat cytomegalovirus disease in immunocompromised patients. One common side effect is acute ionized hypocalcemia and hypomagnesemia following intravenous administration. Foscarnet-induced ionized hypomagnesemia might contribute to ionized hypocalcemia by impairing excretion of preformed parathyroid hormone (PTH) or by producing target organ resistance. Prevention of ionized hypomagnesemia following foscarnet administration could blunt the development of ionized hypocalcemia. To determine whether intravenous magnesium ameliorates the decline in ionized calcium and/or magnesium following foscarnet infusions, MgSO4 at doses of 1, 2, and 3 g was administered in a double-blind, placebo-controlled, randomized, crossover trial to 12 patients with AIDS and cytomegalovirus disease. Overall, increasing doses of MgSO4 reduced or eliminated foscarnet-induced acute ionized hypomagnesemia. Supplementation, however, had no discernible effect on foscarnet-induced ionized hypocalcemia despite significant increases in serum PTH levels. No dose-related, clinically significant adverse events were found, suggesting that intravenous supplementation with up to 3 g of MgSO4 was safe in this chronically ill population. Since parenteral MgSO4 did not alter foscarnet-induced ionized hypocalcemia or symptoms associated with foscarnet, routine intravenous supplementation for patients with normal serum magnesium levels is not recommended during treatment with foscarnet. PMID:10898688

Free radical production by high energy shock waves--comparison with ionizing irradiation.

PubMed

Morgan, T R; Laudone, V P; Heston, W D; Zeitz, L; Fair, W R

1988-01-01

Fricke chemical dosimetry is used as an indirect measure of the free radical production of ionizing irradiation. We adapted the Fricke ferrous sulfate radiation dosimeter to examine the chemical effects of high energy shock waves. Significant free radical production was documented. The reaction was dose dependent, predictably increased by acoustic impedance, but curvilinear. A thousand shocks at 18 kilovolts induced the same free radical oxidation as 1100 rad cobalt-60 gamma ionizing irradiation, increasing to 2900 rad in the presence of an air-fluid zone of acoustic impedance. The biological effect of these free radicals was compared to that of cobalt-60 ionizing irradiation by measuring the affect on Chinese hamster cells by clonogenic assay. While cobalt-60 irradiation produced a marked decrease in clonogenic survivors, little effect was noted with high energy shock waves. This suggested that the chemical effects produced by shock waves were either absent or attenuated in the cells, or were inherently less toxic than those of ionizing irradiation.

Implementation of ionizing radiation environment requirements for Space Station

NASA Technical Reports Server (NTRS)

Boeder, Paul A.; Watts, John W.

1993-01-01

Proper functioning of Space Station hardware requires that the effects of high-energy ionizing particles from the natural environment and (possibly) from man-made sources be considered during design. At the Space Station orbit of 28.5-deg inclination and 330-440 km altitude, geomagnetically trapped protons and electrons contribute almost all of the dose, while galactic cosmic rays and anomalous cosmic rays may produce Single Event Upsets (SEUs), latchups, and burnouts of microelectronic devices. Implementing ionizing radiation environment requirements for Space Station has been a two part process, including the development of a description of the environment for imposing requirements on the design and the development of a control process for assessing how well the design addresses the effects of the ionizing radiation environment. We will review both the design requirements and the control process for addressing ionizing radiation effects on Space Station.

Influence of field ionization effect on the divergence of laser-driven fast electrons

NASA Astrophysics Data System (ADS)

Lang, Y.; Yang, X. H.; Xu, H.; Jin, Z.; Zhuo, H. B.

2018-07-01

The effect of field ionization on the divergence of fast electrons (E k ≥ 50 keV), driven by ultrashort-ultraintense laser pulse interaction with plasma, is studied by using 2D3V particle-in-cell simulations. It is found that, due to temperature anisotropy of the fast electrons in the ionizing target, strong fluctuant magnetic fields in the preplasma region is generated through Weibel instability. In turn, the field induces an enhancement of the hot electron divergence for the target with ionization process. Meanwhile, compared with the target without an ionization process, larger divergence of hot electrons can also be seen in the ionizing target with laser intensity varying from 5 × 1019 W/cm2 to 5 × 1020 W/cm2 and the divergence is weakly dependent on target materials for a fixed profile of preplasma. The results here are useful for the application of laser-driven fast electron beams.

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.

Coulomb-repulsion-assisted double ionization from doubly excited states of argon

NASA Astrophysics Data System (ADS)

Liao, Qing; Winney, Alexander H.; Lee, Suk Kyoung; Lin, Yun Fei; Adhikari, Pradip; Li, Wen

2017-08-01

We report a combined experimental and theoretical study to elucidate nonsequential double-ionization dynamics of argon atoms at laser intensities near and below the recollision-induced ionization threshold. Three-dimensional momentum measurements of two electrons arising from strong-field nonsequential double ionization are achieved with a custom-built electron-electron-ion coincidence apparatus, showing laser intensity-dependent Coulomb repulsion effect between the two outgoing electrons. Furthermore, a previously predicted feature of double ionization from doubly excited states is confirmed in the distributions of sum of two-electron momenta. A classical ensemble simulation suggests that Coulomb-repulsion-assisted double ionization from doubly excited states is at play at low laser intensity. This mechanism can explain the dependence of Coulomb repulsion effect on the laser intensity, as well as the transition from side-by-side to back-to-back dominant emission along the laser polarization direction.

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 length control mechanism of extreme ionization products.« less

Dissociative and double photoionization cross sections of NO from threshold to 120 A

NASA Technical Reports Server (NTRS)

Samson, J. A. R.; Masuoka, T.; Pareek, P. N.

1985-01-01

The partial photoionization cross sections for producing the NO(+) parent ion and the O(+), N(+), and NO2(+) fragment ions from neutral NO are presented from 120 to 614 A. The results indicate predissociation of the c(sup3) pi (21.72 eV) and B prime (sup 1) sigma (+) (22.73 eV) electronic states of NO(+). The photoionization threshold for double ionization was found to be 39.4 + or 0.12 eV.

A review of reaction rates and thermodynamic and transport properties for the 11-species air model for chemical and thermal nonequilibrium calculations to 30000 K

NASA Technical Reports Server (NTRS)

Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.

1989-01-01

Reaction rate coefficients and thermodynamic and transport properties are provided for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in such environments.

Synergistic effect of ozonation and ionizing radiation for PVA decomposition.

PubMed

Sun, Weihua; Chen, Lujun; Zhang, Yongming; Wang, Jianlong

2015-08-01

Ozonation and ionizing radiation are both advanced oxidation processes (AOPs) without chemical addition and secondary pollution. Also, the two processes' efficiency is determined by different pH conditions, which creates more possibilities for their combination. Importantly, the combined process of ozonation and ionizing radiation could be suitable for treating wastewaters with extreme pH values, i.e., textile wastewater. To find synergistic effects, the combined process of ozonation and ionizing radiation mineralization was investigated for degradation of polyvinyl alcohol (PVA) at different pH levels. A synergistic effect was found at initial pH in the range 3.0-9.4. When the initial pH was 3.0, the combined process of ozonation and ionizing radiation gave a PVA mineralization degree of 17%. This was 2.7 times the sum achieved by the two individual processes, and factors of 2.1 and 1.7 were achieved at initial pH of 7.0 and 9.4, respectively. The combined process of ozonation and ionizing radiation was demonstrated to be a feasible strategy for treatment of PVA-containing wastewater. Copyright © 2015. Published by Elsevier B.V.

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.

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.

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.

Immune responses of a wall lizard to whole-body exposure to radiofrequency electromagnetic radiation.

PubMed

Mina, Despoina; Sagonas, Kostas; Fragopoulou, Adamantia F; Pafilis, Panayiotis; Skouroliakou, Aikaterini; Margaritis, Lukas H; Tsitsilonis, Ourania E; Valakos, Efstratios D

2016-01-01

During the last three decades, the number of devices that emit non-ionizing electromagnetic radiation (EMR) at the wireless communication spectrum has rapidly increased and possible effects on living organisms have become a major concern. The purpose of this study was to investigate the effects of radiofrequency EMR emitted by a widely used wireless communication device, namely the Digital Enhanced Communication Telephony (DECT) base, on the immune responses of the Aegean wall lizard (Podarcis erhardii). Adult male lizards were exposed 24 h/day for 8 weeks to 1880-1900 MHz DECT base radiation at average electric field intensity of 3.2 V/m. Immune reactivity was assessed using the phytohemagglutinin (PHA) skin swelling and mixed lymphocyte reaction (MLR) tests. Our results revealed a noticeable suppression (approximately 45%) of inflammatory responses in EMR-exposed lizards compared to sham-exposed animals. T cell-mediated responses were marginally affected. Daily radiofrequency EMR exposure seems to affect, at least partially, the immunocompetence of the Aegean wall lizard.

Fast molecular shocks. I - Reformation of molecules behind a dissociative shock

NASA Technical Reports Server (NTRS)

Neufeld, David A.; Dalgarno, A.

1989-01-01

The physical and chemical processes that operate in the cooling gas behind a fast, dissociative, single-fluid shock propagating in a dense interstellar cloud are discussed. The treatment extends previous theoretical work on fast molecular shocks by including the effects of the conversion of Ly-alpha photons into radiation of the two-photon continuum and into H2 Lyman band emission lines, the effects of CO photodissociation following line absorption, and the formation and destruction of molecules containing the elements nitrogen, silicon, and sulphur, and of the complex hydrocarbons. Abundance profiles for the molecular species of interest are presented. After molecular hydrogen begins to reform, by means of gas phase and grain surface processes, the neutral species OH, H2O, O2, CO, CN, HCN, N2, NO, SO, and SiO reach substantial abundances. The molecular ions HeH(+), OH(+), SO(+), CH(+), H2(+), and H3(+), are produced while the gas is still hot and partially ionized. Emissions from them provide a possible diagnostic probe of fast molecular shocks.

Effect of polacrilin potassium as disintegrant on bioavailability of diclofenac potassium in tablets : a technical note.

PubMed

Bele, Mrudula H; Derle, Diliprao V

2012-09-01

Polacrilin potassium is an ion exchange resin used in oral pharmaceutical formulations as a tablet disintegrant. It is a weakly acidic cation exchange resin. Chemically, it is a partial potassium salt of a copolymer of methacrylic acid with divinyl benzene. It ionizes to an anionic polymer chain and potassium cations. It was hypothesized that polacrilin potassium may be able to improve the permeability of anionic drugs according to the Donnan membrane phenomenon. The effect of polacrilin potassium on the permeability of diclofenac potassium, used as a model anionic drug, was tested in vitro using diffusion cells and in vivo by monitoring serum levels in rats. The amount of drug permeated across a dialysis membrane in vitro was significantly more in the presence of polacrilin potassium. Significant improvement was found in the extent of drug absorption in vivo. It could be concluded that polacrilin potassium may be used as a high-functionality excipient for improving the bioavailability of anionic drugs having poor gastrointestinal permeability.

Kinematics of NGC 4826: A sleeping beauty galaxy, not an evil eye

NASA Technical Reports Server (NTRS)

Rubin, Vera C.

1994-01-01

A recent high resolution H I study of the Sab galaxy NGC 4826 (1992) reveals that the sense of rotation of the neutral gas reverses from the inner to the outer disk. The present paper reports on optical spectra at high velocity resolution in four position angles in NGC 4826, which cover the region of the gas reversal and which reveal a high degree of complexity. In the inner disk, which includes the prominent dusty lane, the stars and gas rotate in concert, and the spiral arms trail (for the adopted geometry). Arcs of ionized gas are observed partially encircling the nucleus; expansion velocities reach 400 km/s. At distances just beyond the prominent dust lane, the ionized gas exhibits a rapid, orderly velocity fall and within 500 parsecs it has reversed from 180 km/s prograde to 200 km/s retrograde; it also has a component radial toward the nucleus of over 100 km/s. The stars, however, continue their prograde rotation. Beyond this transition zone, the neutral gas continues its retrograde rotation, stellar velocities are prograde, but the sense of the almost circular arms is not established. Because of its kinematical complexity as well as its proximity, NGC 4826 is an excellent early-type galaxy in which to observe the long term effects of gas acquistion or a galaxy merger on a disk galaxy.

Dynamic properties of the energy loss of multi-MeV charged particles traveling in two-component warm dense plasmas.

PubMed

Fu, Zhen-Guo; Wang, Zhigang; Li, Meng-Lei; Li, Da-Fang; Kang, Wei; Zhang, Ping

2016-12-01

The energy loss of multi-MeV charged particles moving in two-component warm dense plasmas (WDPs) is studied theoretically beyond the random-phase approximation. The short-range correlations between particles are taken into account via dynamic local field corrections (DLFC) in a Mermin dielectric function for two-component plasmas. The mean ionization states are obtained by employing the detailed configuration accounting model. The Yukawa-type effective potential is used to derive the DLFC. Numerically, the DLFC are obtained via self-consistent iterative operations. We find that the DLFC are significant around the maximum of the stopping power. Furthermore, by using the two-component extended Mermin dielectric function model including the DLFC, the energy loss of a proton with an initial energy of ∼15 MeV passing through a WDP of beryllium with an electronic density around the solid value n_{e}≈3×10^{23}cm^{-3} and with temperature around ∼40 eV is estimated numerically. The numerical result is reasonably consistent with the experimental observations [A. B. Zylsta et al., Phys. Rev. Lett. 111, 215002 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.215002]. Our results show that the partial ionization and the dynamic properties should be of importance for the stopping of charged particles moving in the WDP.

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.

Factors that affect molecular weight distribution of Suwannee river fulvic acid as determined by electrospray ionization/mass spectrometry

USGS Publications Warehouse

Rostad, C.E.; Leenheer, J.A.

2004-01-01

Effects of methylation, molar response, multiple charging, solvents, and positive and negative ionization on molecular weight distributions of aquatic fulvic acid were investigated by electrospray ionization/mass spectrometry. After preliminary analysis by positive and negative modes, samples and mixtures of standards were derivatized by methylation to minimize ionization sites and reanalyzed.Positive ionization was less effective and produced more complex spectra than negative ionization. Ionization in methanol/water produced greater response than in acetonitrile/water. Molar response varied widely for the selected free acid standards when analyzed individually and in a mixture, but after methylation this range decreased. After methylation, the number average molecular weight of the Suwannee River fulvic acid remained the same while the weight average molecular weight decreased. These differences are probably indicative of disaggregation of large aggregated ions during methylation. Since the weight average molecular weight decreased, it is likely that aggregate formation in the fulvic acid was present prior to derivatization, rather than multiple charging in the mass spectra. ?? 2004 Elsevier B.V. All rights reserved.

Health Risk of Radon

MedlinePlus

... related lung cancer in women. Top of Page Biological Effects of Ionizing Radiation (BEIR) VI Report: "The ... of Sciences' (NAS) latest report on radon, the Biological Effects of Ionizing Radiation (BEIR) VI Report (1999). ...

κ -distributed protons in the solar wind and their charge-exchange coupling to energetic hydrogen

DOE PAGES

Heerikhuisen, J.; Zirnstein, Eric; Pogorelov, Nikolai

2015-03-16

The interaction between the solar wind and the interstellar medium represents a collision between two plasma flows, resulting in a heliosphere with an extended tail. While the solar wind is mostly ionized material from the corona, the interstellar medium is only partially ionized. The ion and neutral populations are coupled through charge-exchange collisions that operate on length scales of tens to hundreds of astronomical units. About half the interstellar hydrogen flows into the heliosphere where it may charge-exchange with solar wind protons. This process gives rise to a nonthermal proton, known as a pickup ion, which joins the plasma. Inmore » this paper we investigate the effects of approximating the total ion distribution of the subsonic solar wind as a generalized Lorentzian, or κ distribution, using an MHD neutral code. We illustrate the effect different values of the κ parameter have on both the structure of the heliosphere and the energetic neutral atom flux at 1 AU. We find that using a κ distribution in our simulations yields levels of energetic neutral atom flux that are within a factor of about 2 or 3 over the IBEX-Hi range of energies from 0.5 to 6 keV. In conclusion, while the presence of a suprathermal tail in the proton distribution leads to the production of high-energy neutrals, the sharp decline in the charge-exchange cross section around 10 keV mitigates the enhanced transfer of energy from the ions to the neutrals that might otherwise be expected.« less

Simulated Space Environment Effects on a Candidate Solar Sail Material

NASA Technical Reports Server (NTRS)

Kang, Jin Ho; Bryant, Robert G.; Wilkie, W. Keats; Wadsworth, Heather M.; Craven, Paul D.; Nehls, Mary K.; Vaughn, Jason A.

2017-01-01

For long duration missions of solar sails, the sail material needs to survive harsh space environments and the degradation of the sail material controls operational lifetime. Therefore, understanding the effects of the space environment on the sail membrane is essential for mission success. In this study, we investigated the effect of simulated space environment effects of ionizing radiation, thermal aging and simulated potential damage on mechanical, thermal and optical properties of a commercial off the shelf (COTS) polyester solar sail membrane to assess the degradation mechanisms on a feasible solar sail. The solar sail membrane was exposed to high energy electrons (about 70 keV and 10 nA/cm2), and the physical properties were characterized. After about 8.3 Grad dose, the tensile modulus, tensile strength and failure strain of the sail membrane decreased by about 20 95%. The aluminum reflective layer was damaged and partially delaminated but it did not show any significant change in solar absorbance or thermal emittance. The effect on mechanical properties of a pre-cracked sample, simulating potential impact damage of the sail membrane, as well as thermal aging effects on metallized PEN (polyethylene naphthalate) film will be discussed.

Ion-Exchange Chromatography: Basic Principles and Application.

PubMed

Cummins, Philip M; Rochfort, Keith D; O'Connor, Brendan F

2017-01-01

Ion-Exchange Chromatography (IEC) allows for the separation of ionizable molecules on the basis of differences in charge properties. Its large sample-handling capacity, broad applicability (particularly to proteins and enzymes), moderate cost, powerful resolving ability, and ease of scale-up and automation have led to it becoming one of the most versatile and widely used of all liquid chromatography (LC) techniques. In this chapter, we review the basic principles of IEC, as well as the broader criteria for selecting IEC conditions. By way of further illustration, we outline basic laboratory protocols to partially purify a soluble serine peptidase from bovine whole brain tissue, covering crude tissue extract preparation through to partial purification of the target enzyme using anion-exchange chromatography. Protocols for assaying total protein and enzyme activity in both pre- and post-IEC fractions are also described.

Discrimination of excess toxicity from baseline level for ionizable compounds: Effect of pH.

PubMed

Li, Jin J; Zhang, Xu J; Wang, Xiao H; Wang, Shuo; Yu, Yang; Qin, Wei C; Su, Li M; Zhao, Yuan H

2016-03-01

The toxic effect can be affected by pH in water through affecting the degree of ionization of ionizable compounds. Wrong classification of mode of action can be made from the apparent toxicities. In this paper, the toxicity data of 61 compounds to Daphnia magna determined at three pH values were used to investigate the effect of pH on the discrimination of excess toxicity. The results show that the apparent toxicities are significantly less than the baseline level. Analysis on the effect of pH on bioconcentration factor (BCF) shows that the log BCF values are significantly over-estimated for the strongly ionizable compounds, leading to the apparent toxicities greatly less than the baseline toxicities and the toxic ratios greatly less than zero. A theoretical equation between the apparent toxicities and pH has been developed basing on the critical body residue (CBR). The apparent toxicities are non-linearly related to pH, but linearly to fraction of unionized form. The determined apparent toxicities are well fitted with the toxicities predicted by the equation. The toxicities in the unionized form calculated from the equation are close to, or greater than the baseline level for almost all the strongly ionizable compounds, which are very different from the apparent toxicities. The studied ionizable compounds can be either classified as baseline, less inert or reactive compounds in D. magna toxicity. Some ionizable compounds do not exhibit excess toxicity at a certain pH, due not to their poor reactivity with target molecules, but because of the ionization in water. Copyright © 2015 Elsevier Ltd. All rights reserved.

The role of plasma/neutral source and loss processes in shaping the giant planet magnetospheres

NASA Astrophysics Data System (ADS)

Delamere, P. A.

2014-12-01

The giant planet magnetospheres are filled with neutral and ionized gases originating from satellites orbiting deep within the magnetosphere. The complex chemical and physical pathways for the flow of mass and energy in this partially ionized plasma environment is critical for understanding magnetospheric dynamics. The flow of mass at Jupiter and Saturn begins, primarily, with neutral gases emanating from Io (~1000 kg/s) and Enceladus (~200 kg/s). In addition to ionization losses, the neutral gases are absorbed by the planet, its rings, or escape at high speeds from the magnetosphere via charge exchange reactions. The net result is a centrifugally confined torus of plasma that is transported radially outward, distorting the magnetic field into a magnetodisc configuration. Ultimately the plasma is lost to the solar wind. A critical parameter for shaping the magnetodisc and determining its dynamics is the radial plasma mass transport rate (~500 kg/s and ~50 kg/s for Jupiter and Saturn respectively). Given the plasma transport rates, several simple properties of the giant magnetodiscs can be estimated including the physical scale of the magnetosphere, the magnetic flux transport, and the magnitude of azimuthal magnetic field bendback. We will discuss transport-related magnetic flux conservation and the mystery of plasma heating—two critical issues for shaping the giant planet magnetospheres.

New Experimental Results of Simulating Micrometeoroid Ablation in the Laboratory

NASA Astrophysics Data System (ADS)

Sternovsky, Zoltan; Thomas, Evan; DeLuca, Michael; Janches, Diego; Munsat, Tobin; Plane, John

2017-04-01

A facility is developed to simulate the ablation of micrometeoroids in laboratory conditions, which also allows measuring the ionization probability of the ablated material. An electrostatic dust accelerator is used to generate iron, aluminum and meteoric analog particles with velocities 10-50 km/s. The particles are then introduced into a cell filled with nitrogen, air or carbon dioxide gas with pressures adjustable in the 0.02 - 0.5 Torr range, where the partial or complete ablation of the particle occurs over a short distance. An array of biased electrodes is used to collect the ionized products with spatial resolution along the ablating particles' path, allowing thus the study of the temporal resolution of the process. A new optical observation setup using a 64 channel PMT system was added to the setup to allow the observation of the ablating particle and deceleration of the particle from the neutral drag. A simple ablation model is used to match the observations. For completely ablated particles the total collected charge directly yields the ionization efficiency. The measurements using iron particles in N2 and air are in relatively good agreement with earlier data. The new experimental data using aluminum particles suggest that the neutral drag acting of the particle is smaller than expected.

Reactively-sputtered zinc semiconductor films of high conductivity for heterojunction devices

NASA Technical Reports Server (NTRS)

Stirn, Richard J. (Inventor)

1986-01-01

A high conductivity, n-doped semiconductor film is produced from zinc, or Zn and Cd, and group VI elements selected from Se, S and Te in a reactive magnetron sputtering system having a chamber with one or two targets, a substrate holder, means for heating the substrate holder, and an electric field for ionizing gases in the chamber. Zinc or a compound of Zn and Cd is placed in the position of one of the two targets and doping material in the position of the other of the two targets. Zn and Cd may be placed in separate targets while a dopant is placed in the third target. Another possibility is to place an alloy of Zn and dopant, or Zn, Cd and dopant in one target, thus using only one target. A flow of the inert gas is ionized and directed toward said targets, while a flow of a reactant gas consisting of hydrides of the group VI elements is directed toward a substrate on the holder. The targets are biased to attract negatively ionized inert gas. The desired stochiometry for high conductivity is achieved by controlling the temperature of the substrate, and partial pressures of the gases, and the target power and total pressure of the gases in the chamber.

Photoionization of Ne Atoms and Ne + Ions Near the K Edge: PrecisionSpectroscopy and Absolute Cross-sections

DOE PAGES

Müller, Alfred; Bernhardt, Dietrich; Borovik, Alexander; ...

2017-02-17

Single, double, and triple photoionization of Ne + ions by single photons have been investigated at the synchrotron radiation source PETRA III in Hamburg, Germany. Absolute cross-sections were measured by employing the photon-ion merged-beams technique. Photon energies were between about 840 and 930 eV, covering the range from the lowest-energy resonances associated with the excitation of one single K-shell electron up to double excitations involving one K- and one L-shell electron, well beyond the K-shell ionization threshold. Also, photoionization of neutral Ne was investigated just below the K edge. The chosen photon energy bandwidths were between 32 and 500 meV,more » facilitating the determination of natural line widths. The uncertainty of the energy scale is estimated to be 0.2 eV. For comparison with existing theoretical calculations, astrophysically relevant photoabsorption cross-sections were inferred by summing the measured partial ionization channels. Discussion of the observed resonances in the different final ionization channels reveals the presence of complex Auger-decay mechanisms. The ejection of three electrons from the lowest K-shell-excited Ne + (1s2s 2p 6 2S 1/2) level, for example, requires cooperative interaction of at least four electrons.« less

Study of the effect of collisionality and cooling on the interactions of counter-streaming plasma flows as a function of wire material

NASA Astrophysics Data System (ADS)

Collins, Gilbert; Valenzuela, Julio; Aybar, Nicholas; Conti, Fabio; Beg, Farhat

2017-10-01

We report on the effects wire material on collisionality and radiative cooling on the interactions of counter-streaming plasma jets produced by conical wire arrays on the 200 kA GenASIS driver. In these interactions, mean free path (λmfp) scales with jet velocity (vjet4),atomic mass (A2), and ionization (Z*-4), while cooling scales with atomic mass. By changing the material of the jets one can create slowly cooling, weakly collisional regimes using C, Al, or Cu, or strongly cooled, effectively collisionless plasmas using Mo or W. The former produced smooth shocks soon after the jets collide (near the peak current of 150 ns) that grew in size over time. Interactions of the latter produced multiple structures of a different shape, at a later time ( 300 ns) that dissipated rapidly compared to the lower Z materials. We will report on the scaleability of these different materials to astrophysical phenomena. This work was partially supported by the Department of Energy Grant Number DE-SC0014493.

Jeans instability in collisional strongly coupled dusty plasma with radiative condensation and polarization force

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

Prajapati, R. P., E-mail: prajapati-iter@yahoo.co.in; Bhakta, S.; Chhajlani, R. K.

2016-05-15

The influence of dust-neutral collisions, polarization force, and electron radiative condensation is analysed on the Jeans (gravitational) instability of partially ionized strongly coupled dusty plasma (SCDP) using linear perturbation (normal mode) analysis. The Boltzmann distributed ions, dynamics of inertialess electrons, charged dust and neutral particles are considered. Using the plane wave solutions, a general dispersion relation is derived which is modified due to the presence of dust-neutral collisions, strong coupling effect, polarization force, electron radiative condensation, and Jeans dust/neutral frequencies. In the long wavelength perturbations, the Jeans instability criterion depends upon strong coupling effect, polarization interaction parameter, and thermal loss,more » but it is independent of dust-neutral collision frequency. The stability of the considered configuration is analysed using the Routh–Hurwitz criterion. The growth rates of Jeans instability are illustrated, and stabilizing influence of viscoelasticity and dust-neutral collision frequency while destabilizing effect of electron radiative condensation, polarization force, and Jeans dust-neutral frequency ratio is observed. This work is applied to understand the gravitational collapse of SCDP with dust-neutral collisions.« less

Chemometric of the retention mechanism on butyl column: effect and relation of pH and pKa.

PubMed

Kouskoura, Maria G; Mitan, Constantina V; Markopoulou, Catherine K

2015-12-01

Reversed phase chromatographic separations are optimized for analytes containing ionizable groups by adjustment of pH of mobile phases. As it seems the pK(a). values of compounds affect their retention because of the variety in their solvation. However, it is of stressful need to predict their behavior taking into account also a series of other parameters. This work focuses on the development of ten different models, using partial least squares regression, which will identify and quantify the impact of several factors in the chromatographic behavior of 104 analytes. The combined effect of their numerous characteristics is obvious since along with pH (at 2.3 and 6.2), factors such as lipophilicity, molecular volume, polar surface area and the presence of specific moieties in their structures are not diminished. On the contrary, they work increasing or counterbalancing several effects on the retention time. The models compiled can be applied to predict with reliability (R2 > 0.865 and Q2 > 0.777) the behavior of unknown drugs.

Photo-ionization cross-section of donor-related in (In,Ga)N/GaN core/shell under hydrostatic pressure and electric field effects

NASA Astrophysics Data System (ADS)

El Ghazi, Haddou; John Peter, A.

2017-04-01

Hydrogenic-like donor-impurity related self and induced polarizations, bending energy and photo-ionization cross section in spherical core/shell zinc blende (In,Ga)N/GaN are computed. Based on the variational approach and within effective-mass and one parabolic approximations, the calculations are made under finite potential barrier taking into account of the discontinuity of the effective-mass and the constant dielectric. The photo-ionization cross section is studied according to the photon incident energy considering the effects of hydrostatic pressure, applied electric field, structure's radius, impurity's position and indium composition in the core. It is obtained that the influences mentioned above lead to either blue shifts or redshifts of the resonant peak of the photo-ionization cross section spectrum. The unusual behavior related to the structure radius is discussed which is as a consequence of the finite potential confinement. We have shown that the photo-ionization cross section can be controlled with adjusting the internal and external factors. These properties can be useful for producing some device applications such as quantum dot infrared photodetectors.

Electrospray ionization mass spectrometry and partial least squares discriminant analysis applied to the quality control of olive oil.

PubMed

Alves, Junia O; Botelho, Bruno G; Sena, Marcelo M; Augusti, Rodinei

2013-10-01

Direct infusion electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS] is used to obtain fingerprints of aqueous-methanolic extracts of two types of olive oils, extra virgin (EV) and ordinary (OR), as well as of samples of EV olive oil adulterated by the addition of OR olive oil and other edible oils: corn (CO), sunflower (SF), soybean (SO) and canola (CA). The MS data is treated by the partial least squares discriminant analysis (PLS-DA) protocol aiming at discriminating the above-mentioned classes formed by the genuine olive oils, EV (1) and OR (2), as well as the EV adulterated samples, i.e. EV/SO (3), EV/CO (4), EV/SF (5), EV/CA (6) and EV/OR (7). The PLS-DA model employed is built with 190 and 70 samples for the training and test sets, respectively. For all classes (1-7), EV and OR olive oils as well as the adulterated samples (in a proportion varying from 0.5 to 20.0% w/w) are properly classified. The developed methodology required no ions identification and demonstrated to be fast, as each measurement lasted about 3 min including the extraction step and MS analysis, and reliable, because high sensitivities (rate of true positives) and specificities (rate of true negatives) were achieved. Finally, it can be envisaged that this approach has potential to be applied in quality control of EV olive oils. Copyright © 2013 John Wiley & Sons, Ltd.

The Physical Nature of the Sharp Spectral Feature at 7 keV Detected in 1H0707-495

NASA Technical Reports Server (NTRS)

Brandt, Niel

2005-01-01

XMM-Newton acquired data on the accepted target, 1H0707-495, on 2002 October 13 during revolution 0521. The observation was successful, with only about 5% data loss due to background flaring. We compared the data from this observation with earlier data taken on this Narrow-Line Seyfert 1 about two years before, performing interpretation studies in the context of the partial-covering model. Our second longer observation once again displays a sharp (< 200 eV) spectral drop above 7 keV. However, in comparison to the first observation, the edge depth and energy have changed significantly. In addition to changes in the edge parameters, the high-energy spectrum appears steeper. The changes in the high-energy spectrum can be adequately explained in terms of a partial-covering absorber out-flowing from the central region. The low-energy spectrum also shows significant long-term spectral variability, including (1) a substantial increase in the disk temperature, (2) detection of an approx. 0.9 keV emission feature, and (3) the presence of ionized absorption that was detected during the ASCA mission. The large increase in disk temperature, and the more modest rise in luminosity, can be understood if we consider a slim-disk model for 1H0707-495. In addition, the higher disk luminosity could be the driving force behind the outflow and the re-appearance of an ionized medium during the second XMM-Newton observation.

Single photon ionization of van der Waals clusters with a soft x-ray laser: (CO2)n and (CO2)n(H2O)m.

PubMed

Heinbuch, S; Dong, F; Rocca, J J; Bernstein, E R

2006-10-21

Pure neutral (CO2)n clusters and mixed (CO2)n(H2O)m clusters are investigated employing time of flight mass spectroscopy and single photon ionization at 26.5 eV. The distribution of pure (CO2)n clusters decreases roughly exponentially with increasing cluster size. During the ionization process, neutral clusters suffer little fragmentation because almost all excess cluster energy above the vertical ionization energy is taken away by the photoelectron and only a small part of the photon energy is deposited into the (CO2)n cluster. Metastable dissociation rate constants of (CO2)n+ are measured in the range of (0.2-1.5) x 10(4) s(-1) for cluster sizes of 5< or =n< or =16. Mixed CO2-H2O clusters are studied under different generation conditions (5% and 20% CO2 partial pressures and high and low expansion pressures). At high CO2 concentration, predominant signals in the mass spectrum are the (CO2)n+ cluster ions. The unprotonated cluster ion series (CO2)nH2O+ and (CO2)n(H2O)2+ are also observed under these conditions. At low CO2 concentration, protonated cluster ions (H2O)nH+ are the dominant signals, and the protonated CO2(H2O)nH+ and unprotonated (H2O)n+ and (CO2)(H2O)n+ cluster ion series are also observed. The mechanisms and dynamics of the formation of these neutral and ionic clusters are discussed.

ADVISORY ON UPDATED METHODOLOGY FOR ESTIMATING CANCER RISKS FROM EXPOSURE TO IONIZING RADIATION

EPA Science Inventory

The National Academy of Sciences (NAS) published the Biological Effects of Ionizing Radiation (BEIR) committee's report (BEIR VII) on risks from ionizing radiation exposures in 2006. The Committee analyzed the most recent epidemiology from the important exposed cohorts and factor...

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.

Density-Functional Theory with Optimized Effective Potential and Self-Interaction Correction for the Double Ionization of He and Be Atoms

NASA Astrophysics Data System (ADS)

Heslar, John; Telnov, Dmitry; Chu, Shih-I.

2012-06-01

We present a self-interaction-free (SIC) time-dependent density-functional theory (TDDFT) for the treatment of double ionization processes of many-electron systems. The method is based on the Krieger-Li-Iafrate (KLI) treatment of the optimized effective potential (OEP) theory and the incorporation of an explicit self-interaction correction (SIC) term. In the framework of the time-dependent density functional theory, we have performed 3D calculations of double ionization of He and Be atoms by strong near-infrared laser fields. We make use of the exchange-correlation potential with the integer discontinuity which improves the description of the double ionization process. We found that proper description of the double ionization requires the TDDFT exchange-correlation potential with the discontinuity with respect to the variation of the spin particle numbers (SPN) only. The results for the intensity-dependent probabilities of single and double ionization are presented and reproduce the famous ``knee'' structure.

The different origins of high- and low-ionization broad emission lines revealed by gravitational microlensing in the Einstein cross

NASA Astrophysics Data System (ADS)

Braibant, L.; Hutsemékers, D.; Sluse, D.; Anguita, T.

2016-07-01

We investigate the kinematics and ionization structure of the broad emission line region of the gravitationally lensed quasar QSO2237+0305 (the Einstein cross) using differential microlensing in the high- and low-ionization broad emission lines. We combine visible and near-infrared spectra of the four images of the lensed quasar and detect a large-amplitude microlensing effect distorting the high-ionization CIV and low-ionization Hα line profiles in image A. While microlensing only magnifies the red wing of the Balmer line, it symmetrically magnifies the wings of the CIV emission line. Given that the same microlensing pattern magnifies both the high- and low-ionization broad emission line regions, these dissimilar distortions of the line profiles suggest that the high- and low-ionization regions are governed by different kinematics. Since this quasar is likely viewed at intermediate inclination, we argue that the differential magnification of the blue and red wings of Hα favors a flattened, virialized, low-ionization region whereas the symmetric microlensing effect measured in CIV can be reproduced by an emission line formed in a polar wind, without the need of fine-tuned caustic configurations. Based on observations made with the ESO-VLT, Paranal, Chile; Proposals 076.B-0197 and 076.B-0607 (PI: Courbin).

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.

Effects of the magnetic field gradient on the wall power deposition of Hall thrusters

NASA Astrophysics Data System (ADS)

Ding, Yongjie; Li, Peng; Zhang, Xu; Wei, Liqiu; Sun, Hezhi; Peng, Wuji; Yu, Daren

2017-04-01

The effect of the magnetic field gradient in the discharge channel of a Hall thruster on the ionization of the neutral gas and power deposition on the wall is studied through adopting the 2D-3V particle-in-cell (PIC) and Monte Carlo collisions (MCC) model. The research shows that by gradually increasing the magnetic field gradient while keeping the maximum magnetic intensity at the channel exit and the anode position unchanged, the ionization region moves towards the channel exit and then a second ionization region appears near the anode region. Meanwhile, power deposition on the walls decreases initially and then increases. To avoid power deposition on the walls produced by electrons and ions which are ionized in the second ionization region, the anode position is moved towards the channel exit as the magnetic field gradient is increased; when the anode position remains at the zero magnetic field position, power deposition on the walls decreases, which can effectively reduce the temperature and thermal load of the discharge channel.

INVESTIGATION OF THE HUMIDITY EFFECT ON THE FAC-IR-300 IONIZATION CHAMBER RESPONSE.

PubMed

Mohammadi, Seyed Mostafa; Tavakoli-Anbaran, Hossein

2018-02-01

The free-air ionization chamber is communicating with the ambient air, therefore, the atmospheric parameters such as temperature, pressure and humidity effect on the ionization chamber performance. The free-air ionization chamber, entitled as FAC-IR-300, that design at the Atomic Energy Organization of Iran, AEOI, is required the atmospheric correction factors for correct the chamber reading. In this article, the effect of humidity on the ionization chamber response was investigated. For this reason, was introduced the humidity correction factor, kh. In this article, the Monte Carlo simulation was used to determine the kh factor. The simulation results show in relative humidities between 30% to 80%, the kh factor is equal 0.9970 at 20°C and 0.9975 at 22°C. From the simulation results, at low energy the energy dependence of the kh factor is significant and with increasing energy this dependence is negligible. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Formation of negative hydrogen ion: polarization electron capture and nonthermal shielding.

PubMed

Ki, Dae-Han; Jung, Young-Dae

2012-09-07

The influence of the nonthermal shielding on the formation of the negative hydrogen ion (H(-)) by the polarization electron capture are investigated in partially ionized generalized Lorentzian plasmas. The Bohr-Lindhard method has been applied to obtain the negative hydrogen formation radius and cross section as functions of the collision energy, de Broglie wave length, Debye length, impact parameter, and spectral index of the plasma. The result shows that the nonthermal character of the plasma enhances the formation radius of the negative hydrogen, especially, for small Debye radii. It is found that the nonthermal effect increases the formation cross section of the negative hydrogen. It is also found that the maximum position of the formation cross section approaches to the collision center with an increase of the spectral index. In addition, it is found that the formation cross section significantly decreases with an increase of the Debye length, especially, for small spectral indices.

Charge transfer to ground-state ions produces free electrons

PubMed Central

You, D.; Fukuzawa, H.; Sakakibara, Y.; Takanashi, T.; Ito, Y.; Maliyar, G. G.; Motomura, K.; Nagaya, K.; Nishiyama, T.; Asa, K.; Sato, Y.; Saito, N.; Oura, M.; Schöffler, M.; Kastirke, G.; Hergenhahn, U.; Stumpf, V.; Gokhberg, K.; Kuleff, A. I.; Cederbaum, L. S.; Ueda, K

2017-01-01

Inner-shell ionization of an isolated atom typically leads to Auger decay. In an environment, for example, a liquid or a van der Waals bonded system, this process will be modified, and becomes part of a complex cascade of relaxation steps. Understanding these steps is important, as they determine the production of slow electrons and singly charged radicals, the most abundant products in radiation chemistry. In this communication, we present experimental evidence for a so-far unobserved, but potentially very important step in such relaxation cascades: Multiply charged ionic states after Auger decay may partially be neutralized by electron transfer, simultaneously evoking the creation of a low-energy free electron (electron transfer-mediated decay). This process is effective even after Auger decay into the dicationic ground state. In our experiment, we observe the decay of Ne2+ produced after Ne 1s photoionization in Ne–Kr mixed clusters. PMID:28134238

On the modulation of X ray fluxes in thunderstorms

NASA Technical Reports Server (NTRS)

Mccarthy, Michael P.; Parks, George K.

1992-01-01

The production of X-ray fluxes in thunderstorms has been attributed to bremsstrahlung. Assuming this, another question arises. How can a thunderstorm modulate the number density of electrons which are sufficiently energetic to produce X-rays? As a partial answer to this question, the effects of typical thunderstorm electric fields on a background population of energetic electrons, such as produced by cosmic ray secondaries and their decays or the decay of airborne radionuclides, are considered. The observed variation of X-ray flux is shown to be accounted for by a simple model involving typical electric field strengths. A necessary background electron number density is found from the model and is determined to be more than 2 orders of magnitude higher than that available from radon decay and a factor of 8 higher than that available from cosmic ray secondaries. The ionization enhancement due to energetic electrons and X-rays is discussed.

Validation of multi-temperature nozzle flow code NOZNT

NASA Technical Reports Server (NTRS)

Park, Chul; Lee, Seung-Ho

1993-01-01

A computer code NOZNT (Nozzle in n-Temperatures), which calculates one-dimensional flows of partially dissociated and ionized air in an expanding nozzle, is tested against five existing sets of experimental data. The code accounts for: a) the differences among various temperatures, i.e., translational-rotational temperature, vibrational temperatures of individual molecular species, and electron-electronic temperature, b) radiative cooling, and c) the effects of impurities. The experimental data considered are: 1) the sodium line reversal and 2) the electron temperature and density data, both obtained in a shock tunnel, and 3) the spectroscopic emission data, 4) electron beam data on vibrational temperature, and 5) mass-spectrometric species concentration data, all obtained in arc-jet wind tunnels. It is shown that the impurities are most likely responsible for the observed phenomena in shock tunnels. For the arc-jet flows, impurities are inconsequential and the NOZNT code is validated by numerically reproducing the experimental data.

Kinetic description of electron beams in the solar chromosphere

NASA Technical Reports Server (NTRS)

Gomez, Daniel O.; Mauas, Pablo J.

1992-01-01

We formulate the relativistic Fokker-Plank equation for a beam of accelerated electrons interacting with a partially ionized plasma. In our derivation we conserved those terms contributing to velocity diffusion and found that this effect cannot be neglected a priori. We compute the terms accounting for elastic and inelastic collisions with neutral hydrogen and helium. Collisions with neutral hydrogen are found to be dominant throughout the chromosphere, except at the uppermost layers close to the transition region. As an application, we compute the loss of energy and momentum for a power-law beam impinging on the solar chromosphere, for a particular case in which the Fokker-Planck equation can be integrated analytically. We find that most of the beam energy is deposited in a relatively thin region of the chromosphere, a result which is largely insensitive to the theoretical method employed to compute the energy deposition rate.

The effects of surgery and anesthesia on blood magnesium and calcium concentrations in canine and feline patients.

PubMed

Brainard, Benjamin M; Campbell, Vicki L; Drobatz, Kenneth J; Perkowski, Sandra Z

2007-03-01

To demonstrate the effect of anesthesia and surgery on serum ionized magnesium and ionized calcium concentrations in clinical canine and feline patients. 37 client-owned dogs, ASA PS I-III and 10 client-owned cats, ASA PS I, all receiving anesthesia for elective or emergent surgery at a Veterinary Teaching Hospital. Plasma ionized and serum total magnesium, and plasma ionized calcium were measured prior to and after a group-standardized anesthetic protocol. Regardless of pre-operative medication (hydromorphone or butorphanol), anesthetic induction (thiopental or lidocaine/hydromorphone/diazepam (LHD) and propofol combination), or type of surgical procedure (peripheral surgery or laparotomy), post-operative plasma ionized calcium concentration decreased in all groups of dogs, while post-operative plasma ionized magnesium increased in all groups, although the changes were not always significant. The dogs who were induced with an LHD and propofol technique had a greater increase in ionized magnesium (0.36 +/- 0.07 to 0.42 +/- 0.07 mmol L(-1)) than the group in which anesthesia was induced with thiopental (0.41 +/- 0.07 to 0.42 +/- 0.07 mmol L(-1), p = 0.009). The cats showed similar changes in ionized magnesium and ionized calcium, and also had a significant increase in serum total magnesium (2.17 +/- 0.20 to 2.31 +/- 0.25 mg dL(-1), p = 0.009) CONCLUSIONS, CLINICAL RELEVANCE: A post-operative decrease in ionized calcium was demonstrated in healthy animals, as well as an increase in ionized or total magnesium after various anesthetic protocols and surgeries. These changes, while statistically significant, do not appear to be clinically significant, as values remained within reference ranges at all times.

Simulated Space Environment Effects on a Candidate Solar Sail Material

NASA Technical Reports Server (NTRS)

Kang, Jin Ho; Bryant, Robert G.; Wilkie, W. Keats; Wadsworth, Heather M.; Craven, Paul D.; Nehls, Mary K.; Vaughn, Jason A.

2017-01-01

For long duration missions of solar sail vehicles, the sail material needs to survive the harsh space environment as the degradation of the sail material determines its operational lifetime. Therefore, understanding the effects of the space environment on the sail membrane is essential for mission success. In this study, the effect of simulated space environments of ionizing radiation and thermal aging were investigated. In order to assess some of the potential damage effects on the mechanical, thermal and optical properties of a commercial off the shelf (COTS) polyester solar sail membrane. The solar sail membrane was exposed to high energy electrons [about 70 keV and 10 nA/cm(exp. 2)], and the physical properties were characterized. After about 8.3 Grad dose, the tensile modulus, tensile strength and failure strain of the sail membrane decreased by 20 to 95%. The aluminum reflective layer was damaged and partially delaminated but it did not show any significant change in solar absorbance or thermal emittance. The mechanical properties of a precracked sample, simulating potential impact damage of the sail membrane, as well as thermal aging effects on metallized PEN (polyethylene naphthalate) film, will be discussed.

ON-LINE ANALYSIS OF AQUEOUS AEROSOLS BY LASER DESORPTION IONIZATION. (R823980)

EPA Science Inventory

In this work the effects of water on the laser desorption ionization mass spectra of single aerosol particles are explored. Aqueous aerosols are produced by passing dry particles through a humid environment so that they undergo deliquescent growth. Laser desorption ionization is ...

CONSULTATION ON UPDATED METHODOLOGY FOR ESTIMATING CANCER RISKS FROM EXPOSURE TO IONIZING RADIATION

EPA Science Inventory

The National Academy of Sciences (NAS) expects to publish the Biological Effects of Ionizing Radiation (BEIR) committee's report (BEIR VII) on risks from ionizing radiation exposures in calendar year 2005. The committee is expected to have analyzed the most recent epidemiology f...

Kynurenic Acid Prevents Cytoskeletal Disorganization Induced by Quinolinic Acid in Mixed Cultures of Rat Striatum.

PubMed

Pierozan, Paula; Biasibetti-Brendler, Helena; Schmitz, Felipe; Ferreira, Fernanda; Pessoa-Pureur, Regina; Wyse, Angela T S

2018-06-01

Kynurenic acid (KYNA) is a neuroactive metabolite of tryptophan known to modulate a number of mechanisms involved in neural dysfunction. Although its activity in the brain has been widely studied, the effect of KYNA counteracting the actions of quinolinic acid (QUIN) remains unknown. The present study aims at describing the ability of 100 μM KYNA preventing cytoskeletal disruption provoked by QUIN in astrocyte/neuron/microglia mixed culture. KYNA totally preserved cytoskeletal organization, cell morphology, and redox imbalance in mixed cultures exposed to QUIN. However, KYNA partially prevented morphological alteration in isolated primary astrocytes and failed to protect the morphological alterations of neurons caused by QUIN exposure. Moreover, KYNA prevented QUIN-induced microglial activation and upregulation of ionized calcium-binding adapter molecule 1 (Iba-1) and partially preserved tumor necrosis factor-α (TNF-α) level in mixed cultures. TNF-α level was also partially preserved in astrocytes. In addition to the mechanisms dependent on redox imbalance and microglial activation, KYNA prevented downregulation of connexin-43 and the loss of functionality of gap junctions (GJs), preserving cell-cell contact, cytoskeletal organization, and cell morphology in QUIN-treated cells. Furthermore, the toxicity of QUIN targeting the cytoskeleton of mixed cultures was not prevented by the N-methyl-D-aspartate (NMDA) antagonist MK-801. We suggest that KYNA protects the integrity of the cytoskeleton of mixed cultures by complex mechanisms including modulating microglial activation preventing oxidative imbalance and misregulated GJs leading to disrupted cytoskeleton in QUIN-treated cells. This study contributed to elucidate the molecular basis of KYNA protection against QUIN toxicity.

Understanding the strong intervening O VI absorber at zabs ˜ 0.93 towards PG1206+459

NASA Astrophysics Data System (ADS)

Rosenwasser, B.; Muzahid, S.; Charlton, J. C.; Kacprzak, G. G.; Wakker, B. P.; Churchill, C. W.

2018-05-01

We have obtained new observations of the partial Lyman limit absorber at zabs=0.93 towards quasar PG 1206+459, and revisit its chemical and physical conditions. The absorber, with N({H I})˜ 10^{17.0} cm-2 and absorption lines spread over ≳1000 km s-1 in velocity, is one of the strongest known O VI absorbers at \\log N({{O VI}})= 15.54 ± 0.17. Our analysis makes use of the previously known low- (e.g. Mg II), intermediate- (e.g. Si IV), and high-ionization (e.g. C IV, N V, Ne VIII) metal lines along with new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph (COS) observations that cover O VI and an HST/ACS image of the quasar field. Consistent with previous studies, we find that the absorber has a multiphase structure. The low-ionization phase arises from gas with a density of \\log (n_H/cm^{-3})˜ -2.5 and a solar to supersolar metallicity. The high-ionization phase stems from gas with a significantly lower density, i.e. \\log (n_H/cm^{-3}) ˜ -3.8, and a near-solar to solar metallicity. The high-ionization phase accounts for all of the absorption seen in C IV, N V, and O VI. We find the the detected Ne VIII, reported by Tripp et al. (2011), is best explained as originating in a stand-alone collisionally ionized phase at T˜ 10^{5.85} K, except in one component in which both O VI and Ne VIII can be produced via photoionization. We demonstrate that such strong O VI absorption can easily arise from photoionization at z ≳ 1, but that, due to the decreasing extragalactic UV background radiation, only collisional ionization can produce large O VI features at z ˜ 0. The azimuthal angle of ˜88° of the disc of the nearest (68 kpc) luminous (1.3L*) galaxy at zgal = 0.9289, which shows signatures of recent merger, suggests that the bulk of the absorption arises from metal enriched outflows.

The X-ray spectrum and spectral energy distribution of FIRST J155633.8+351758: a LoBAL quasar with a probable polar outflow

NASA Astrophysics Data System (ADS)

Berrington, Robert C.; Brotherton, Michael S.; Gallagher, Sarah C.; Ganguly, Rajib; Shang, Zhaohui; DiPompeo, Michael; Chatterjee, Ritaban; Lacy, Mark; Gregg, Michael D.; Hall, Patrick B.; Laurent-Muehleisen, S. A.

2013-12-01

We report the results of a new 60 ks Chandra X-ray Observatory Advanced CCD Imaging Spectrometer S-array (ACIS-S) observation of the reddened, radio-selected, highly polarized `FeLoBAL' quasar FIRST J1556+3517. We investigated a number of models of varied sophistication to fit the 531-photon spectrum. These models ranged from simple power laws to power laws absorbed by hydrogen gas in differing ionization states and degrees of partial covering. Preferred fits indicate that the intrinsic X-ray flux is consistent with that expected for quasars of similarly high luminosity, i.e. an intrinsic, dereddened and unabsorbed optical to X-ray spectral index of -1.7. We cannot tightly constrain the intrinsic X-ray power-law slope, but find indications that it is flat (photon index Γ = 1.7 or flatter at a >99 per cent confidence for a neutral hydrogen absorber model). Absorption is present, with a column density a few times 1023 cm-2, with both partially ionized models and partially covering neutral hydrogen models providing good fits. We present several lines of argument that suggest the fraction of X-ray emissions associated with the radio jet is not large. We combine our Chandra data with observations from the literature to construct the spectral energy distribution of FIRST J1556+3517 from radio to X-ray energies. We make corrections for Doppler beaming for the pole-on radio jet, optical dust reddening and X-ray absorption, in order to recover a probable intrinsic spectrum. The quasar FIRST J1556+3517 seems to be an intrinsically normal radio-quiet quasar with a reddened optical/UV spectrum, a Doppler-boosted but intrinsically weak radio jet and an X-ray absorber not dissimilar from that of other broad absorption line quasars.

Effect of multiple plasmon excitation on single, double and multiple ionizations of C60 in collisions with fast highly charged Si ions

NASA Astrophysics Data System (ADS)

Kelkar, A. H.; Kadhane, U.; Misra, D.; Kumar, A.; Tribedi, L. C.

2007-06-01

We have investigated the single and multiple ionizations of the C60 molecule in collisions with fast Siq+ projectiles for various projectile charge states (q) between q = 6 and 14. The q-dependence of the ionization cross sections and their ratios is compared with the giant dipole plasmon resonance (GDPR) model. The excellent qualitative agreement with the model in case of single and double ionizations and also a reasonable agreement with the triple (and to some extent with quadruple) ionization (without evaporation) yields signify dominant contributions of the single-, double- and triple-plasmon excitations on the single- and multiple-ionization process.

TH-CD-BRA-07: MRI-Linac Dosimetry: Parameters That Change in a Magnetic Field

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

O’Brien, D. J.; Sawakuchi, G. O.

Purpose: In MRI-linac integrated systems, the presence of the magnetic (B-)field has a large impact of the dose-distribution and the dose-responses of detectors; yet established protocols and previous experience may lead to assumptions about the commissioning process that are no longer valid. This study quantifies parameters that change when performing dosimetry with an MRI-linac including beam quality specifiers and the effective-point-of-measurement (EPOM) of ionization chambers. Methods: We used the Geant4 Monte Carlo code for this work with physics parameters that pass the Fano cavity test to within 0.1% for the simulated conditions with and without a 1.5 T B-field. Amore » point source model with the energy distribution of an MRI-linac beam was used with and without the B-field to calculate the beam quality specifiers %dd(10)× and TPR{sup 20}{sub 10}, the variation of chamber response with orientation and the how the B-field affects the EPOM of ionization chambers by comparing depth-dose curves calculated in water to those generated by a model PTW30013 Farmer chamber. Results: The %dd(10)× changes by over 2% in the presence of the B-field while the TPR{sup 20}{sub 10} is unaffected. Ionization chamber dose-response is known to depend on the orientation w.r.t. the B-field, but two alternative perpendicular orientations (anti-parallel to each other) also differ in dose-response by over 1%. The B-field shifts the EPOM downstream (closer to the chamber center) but it is also shifted laterally by 0.27 times the chamber’s cavity radius. Conclusion: The EPOM is affected by the B-field and it even shifts laterally. The relationship between %dd(10)× and the Spencer-Attix stopping powers is also changed. Care must be taken when using chambers perpendicular to the field as the dose-response changes depending on which perpendicular orientation is used. All of these effects must be considered when performing dosimetry in B-fields and should be accounted for in future dosimetry protocols. This project was partially funded by Elekta Ltd.« less

THE URINE PROTEOME FOR RADIATION BIODOSIMETRY: EFFECT OF TOTAL BODY VERSUS LOCAL KIDNEY IRRADIATION

PubMed Central

Sharma, Mukut; Halligan, Brian D.; Wakim, Bassam T.; Savin, Virginia J.; Cohen, Eric P.; Moulder, John E.

2009-01-01

Victims of nuclear accidents or radiological terrorism are likely to receive varying doses of ionizing radiation inhomogeneously distributed over the body. Early biomarkers may be useful in determining organ-specific doses due to total body irradiation (TBI) or partial body irradiation. We used liquid chromatography and mass spectrometry to compare the effect of TBI and local kidney irradiation (LKI) on the rat urine proteome using a single 10 Gy dose of X-rays. Both TBI and LKI altered the urinary protein profile within 24 hours with noticeable differences in Gene Ontology categories. Some proteins including fetuin-B, tissue kallikrein, beta-glucuronidase, vitamin D-dependent calcium binding protein and chondroitin sulfate proteoglycan NG2 were detected only in the TBI group. Some other proteins including major urinary protein-1, RNA binding protein 19, neuron navigator, Dapper homolog 3, WD repeat and FYVE domain containing protein 3, sorting nexin-8, ankycorbin and aquaporin were detected only in the LKI group. Protease inhibitors and kidney proteins were more abundant (fraction of total scans) in the LKI group. Up/Uc ratio and urinary albumin abundance decreased in both TBI and LKI groups. Several markers of acute kidney injury were not detectable in either irradiated group. Present data indicate that abundance and number of proteins may follow opposite trends. These novel findings demonstrate intriguing differences between TBI and LKI, and suggest that urine proteome may be useful in determining organ-specific changes caused by partial body irradiation. PMID:20065682

The urine proteome for radiation biodosimetry: effect of total body vs. local kidney irradiation.

PubMed

Sharma, Mukut; Halligan, Brian D; Wakim, Bassam T; Savin, Virginia J; Cohen, Eric P; Moulder, John E

2010-02-01

Victims of nuclear accidents or radiological terrorism are likely to receive varying doses of ionizing radiation inhomogeneously distributed over the body. Early biomarkers may be useful in determining organ-specific doses due to total body irradiation (TBI) or partial body irradiation. The authors used liquid chromatography and mass spectrometry to compare the effect of TBI and local kidney irradiation (LKI) on the rat urine proteome using a single 10-Gy dose of x-rays. Both TBI and LKI altered the urinary protein profile within 24 h with noticeable differences in gene ontology categories. Some proteins, including fetuin-B, tissue kallikrein, beta-glucuronidase, vitamin D-dependent calcium binding protein and chondroitin sulfate proteoglycan NG2, were detected only in the TBI group. Some other proteins, including major urinary protein-1, RNA binding protein 19, neuron navigator, Dapper homolog 3, WD repeat and FYVE domain containing protein 3, sorting nexin-8, ankycorbin and aquaporin were detected only in the LKI group. Protease inhibitors and kidney proteins were more abundant (fraction of total scans) in the LKI group. Urine protein (Up) and creatinine (Uc) (Up/Uc) ratios and urinary albumin abundance decreased in both TBI and LKI groups. Several markers of acute kidney injury were not detectable in either irradiated group. Present data indicate that abundance and number of proteins may follow opposite trends. These novel findings demonstrate intriguing differences between TBI and LKI, and suggest that urine proteome may be useful in determining organ-specific changes caused by partial body irradiation.

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.

Effect of ionization, bedding, and feeding on air quality in a horse stable.

PubMed

Siegers, Esther Willemijn; Anthonisse, Milou; van Eerdenburg, Frank J C M; van den Broek, Jan; Wouters, Inge M; Westermann, Cornélie Martine

2018-05-01

Organic dust is associated with Equine asthma. Ionization should reduce airborne dust levels. To determine the effect of ionization of air, type of bedding, and feed on the levels of airborne dust, endotoxin, and fungal colonies in horse stables. 24 healthy University-owned horses occupied the stables. A randomized controlled cross-over study. Four units with 6 stables were equipped with an ionization installation (25 VA, 5000 Volt Direct Current). Horses were kept either on wood shavings and fed haylage (2 units), or on straw and fed dry hay (2 units). Measurements were performed with and without activated ionization, during daytime and nighttime, repeatedly over the course of a week and repeatedly during 4-6 weeks. Statistical analysis was performed using a mixed effect model with Akaike's Information Criterion for model reduction and 95% profile (log) likelihood confidence intervals (CI). Ionization did not alter concentrations of dust, endotoxin, or fungi, fewer. In the units with straw and hay, the concentration of dust, endotoxin, and fungi (difference in logarithmic mean 1.92 (95%CI 1.71-2.12); 2.86 (95%CI 2.59-3.14); 1.75 (95%CI 1.13-2.36)) were significantly higher compared to wood shavings and haylage. The installation of a negative air-ionizer in the horse stable did not reduce concentrations of dust, endotoxin, and viable fungal spores. The substantial effect of low dust bedding and feed is confirmed. Copyright © 2018 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

Ionizing radiation-induced mutagenesis: radiation studies in Neurospora predictive for results in mammalian cells

NASA Technical Reports Server (NTRS)

Evans, H. H.; DeMarini, D. M.

1999-01-01

Ionizing radiation was the first mutagen discovered and was used to develop the first mutagenicity assay. In the ensuing 70+ years, ionizing radiation became a fundamental tool in understanding mutagenesis and is still a subject of intensive research. Frederick de Serres et al. developed and used the Neurospora crassa ad-3 system initially to explore the mutagenic effects of ionizing radiation. Using this system, de Serres et al. demonstrated the dependence of the frequency and spectra of mutations induced by ionizing radiation on the dose, dose rate, radiation quality, repair capabilities of the cells, and the target gene employed. This work in Neurospora predicted the subsequent observations of the mutagenic effects of ionizing radiation in mammalian cells. Modeled originally on the mouse specific-locus system developed by William L. Russell, the N. crassa ad-3 system developed by de Serres has itself served as a model for interpreting the results in subsequent systems in mammalian cells. This review describes the primary findings on the nature of ionizing radiation-induced mutagenesis in the N. crassa ad-3 system and the parallel observations made years later in mammalian cells.

Ionizing Shocks in Argon. Part 2: Transient and Multi-Dimensional Effects (Preprint)

DTIC Science & Technology

2010-09-09

stability in ionizing monatomic gases. Part 1. Argon ,” J. Fluid Mech., 84, 55 (1978). 2M. P. F. Bristow and I. I. Glass, “ Polarizability of singly...Article 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Ionizing Shocks in Argon . Part 2: Transient...Physics. 14. ABSTRACT We extend the computations of ionizing shocks in argon to unsteady and multi-dimensional, using a collisional-radiative

Proteomic Screening of Antigenic Proteins from the Hard Tick, Haemaphysalis longicornis (Acari: Ixodidae)

PubMed Central

Kim, Young-Ha; slam, Mohammad Saiful; You, Myung-Jo

2015-01-01

Proteomic tools allow large-scale, high-throughput analyses for the detection, identification, and functional investigation of proteome. For detection of antigens from Haemaphysalis longicornis, 1-dimensional electrophoresis (1-DE) quantitative immunoblotting technique combined with 2-dimensional electrophoresis (2-DE) immunoblotting was used for whole body proteins from unfed and partially fed female ticks. Reactivity bands and 2-DE immunoblotting were performed following 2-DE electrophoresis to identify protein spots. The proteome of the partially fed female had a larger number of lower molecular weight proteins than that of the unfed female tick. The total number of detected spots was 818 for unfed and 670 for partially fed female ticks. The 2-DE immunoblotting identified 10 antigenic spots from unfed females and 8 antigenic spots from partially fed females. Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF) of relevant spots identified calreticulin, putative secreted WC salivary protein, and a conserved hypothetical protein from the National Center for Biotechnology Information and Swiss Prot protein sequence databases. These findings indicate that most of the whole body components of these ticks are non-immunogenic. The data reported here will provide guidance in the identification of antigenic proteins to prevent infestation and diseases transmitted by H. longicornis. PMID:25748713

The ionizing effect of low-energy cosmic rays from a class II object on its protoplanetary disc

NASA Astrophysics Data System (ADS)

Rodgers-Lee, D.; Taylor, A. M.; Ray, T. P.; Downes, T. P.

2017-11-01

We investigate the ionizing effect of low-energy cosmic rays (CRs) from a young star on its protoplanetary disc (PPD). We consider specifically the effect of ∼3 GeV protons injected at the inner edge of the PPD. An increase in the ionization fraction as a result of these CRs could allow the magnetorotational instability to operate in otherwise magnetically dead regions of the disc. For the typical values assumed we find an ionization rate of ζCR ∼ 10-17 s-1 at 1 au. The transport equation is solved by treating the propagation of the CRs as diffusive. We find for increasing diffusion coefficients the CRs penetrate further in the PPD, while varying the mass density profile of the disc is found to have little effect. We investigate the effect of an energy spectrum of CRs. The influence of a disc wind is examined by including an advective term. For advective wind speeds between 1 and 100 km s-1 diffusion dominates at all radii considered here (out to 10 au) for reasonable diffusion coefficients. Overall, we find that low-energy CRs can significantly ionize the mid-plane of PPDs out to ∼1 au. By increasing the luminosity or energy of the CRs, within plausible limits, their radial influence could increase to ∼2 au at the mid-plane but it remains challenging to significantly ionize the mid-plane further out.

High-resolution threshold photoionization of N sub 2 O

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

Wiedmann, R.T.; Grant, E.R.; Tonkyn, R.G.

1991-07-15

Pulsed field ionization (PFI) has been used in conjunction with a coherent vuv source to obtain high-resolution threshold photoelectron spectra for the (000), (010), (020), and (100) vibrational states of the N{sub 2}O{sup +} cation. Simulations for the rotational profiles of each vibronic level were obtained by fitting the Buckingham--Orr--Sichel equations (A. D. Buckingham, B. J. Orr, and J. M. Sichel, Philos. Trans. R. Soc. London, Ser. A {bold 268}, 147 (1970)) using accurate spectroscopic constants for the ground states of the neutral and the ion. The relative branch intensities are interpreted in terms of the partial waves of themore » outgoing photoelectron to which the ionic core is coupled and in terms of the angular momentum transferred to the core. The PFI technique also allows us to report an improved value for the ionization potential of N{sub 2}O of 103 963{plus minus}5 cm{sup {minus}1}.« less

On the possible source of the ionization in the nighttime Martian ionosphere. I - Phobos 2 HARP electron spectrometer measurements

NASA Technical Reports Server (NTRS)

Verigin, M. I.; Gringauz, K. I.; Shutte, N. M.; Haider, S. A.; Szego, K.; Kiraly, P.; Nagy, A. F.; Gombosi, T. I.

1991-01-01

The measurements of electron spectra in the Martian magnetosphere by the HARP instrument on board the Phobos 2 orbiter are presented. The energy of the electrons (a few tens of electron volts) is sufficient for the impact ionization of the planetary neutral gas, and the characteristic flux of electrons (about 10 exp 8/sq cm per sec) could produce the nightside ionospheric layer with a peak density of a few thousands of electrons per cubic centimeter, which corresponds to densities observed earlier during radio occultations of the Mars 4 and 5 and Viking 1 and 2 spacecraft. The possibility of magnetospheric electron precipitation into the nightside atmosphere of Mars is in agreement with the mainly induced nature of the magnetic field in the planetary magnetotail (as at Venus), while the variability of the Martian nightside ionosphere may be explained by the partial screening of the atmosphere by a weak intrinsic magnetic field of the planet.

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.

Conformational relaxation and water penetration coupled to ionization of internal groups in proteins.

PubMed

Damjanović, Ana; Brooks, Bernard R; García-Moreno, Bertrand

2011-04-28

Molecular dynamics simulations were used to examine the effects of ionization of internal groups on the structures of eighteen variants of staphylococcal nuclease (SNase) with internal Lys, Asp, or Glu. In most cases the RMSD values of internal ionizable side chains were larger when the ionizable moieties were charged than when they were neutral. Calculations of solvent-accessible surface area showed that the internal ionizable side chains were buried in the protein interior when they were neutral and moved toward crevices and toward the protein-water interface when they were charged. The only exceptions are Lys-36, Lys-62, and Lys-103, which remained buried even after charging. With the exception of Lys-38, the number of internal water molecules surrounding the ionizable group increased upon charging: the average number of water oxygen atoms within the first hydration shell increased by 1.7 for Lys residues, by 5.2 for Asp residues, and by 3.2 for Glu residues. The polarity of the microenvironment of the ionizable group also increased when the groups were charged: the average number of polar atoms of any kind within the first hydration shell increased by 2.7 for Lys residues, by 4.8 for Asp residues, and by 4.0 for Glu residues. An unexpected correlation was observed between the absolute value of the shifts in pK(a) values measured experimentally, and several parameters of structural relaxation: the net difference in the polarity of the microenvironment of the charged and neutral forms of the ionizable groups, the net difference in hydration of the charged and neutral forms of the ionizable groups, and the difference in RMSD values of the charged and neutral forms of the ionizable groups. The effects of ionization of internal groups on the conformation of the backbone were noticeable but mostly small and localized to the area immediately next to the internal ionizable moiety. Some variants did exhibit local unfolding.

Deconvolution of gas chromatographic data

NASA Technical Reports Server (NTRS)

Howard, S.; Rayborn, G. H.

1980-01-01

The use of deconvolution methods on gas chromatographic data to obtain an accurate determination of the relative amounts of each material present by mathematically separating the merged peaks is discussed. Data were obtained on a gas chromatograph with a flame ionization detector. Chromatograms of five xylenes with differing degrees of separation were generated by varying the column temperature at selected rates. The merged peaks were then successfully separated by deconvolution. The concept of function continuation in the frequency domain was introduced in striving to reach the theoretical limit of accuracy, but proved to be only partially successful.

Suppression of electron spin relaxation in Mn-doped GaAs.

PubMed

Astakhov, G V; Dzhioev, R I; Kavokin, K V; Korenev, V L; Lazarev, M V; Tkachuk, M N; Kusrayev, Yu G; Kiessling, T; Ossau, W; Molenkamp, L W

2008-08-15

We report a surprisingly long spin relaxation time of electrons in Mn-doped p-GaAs. The spin relaxation time scales with the optical pumping and increases from 12 ns in the dark to 160 ns upon saturation. This behavior is associated with the difference in spin relaxation rates of electrons precessing in the fluctuating fields of ionized or neutral Mn acceptors, respectively. For the latter, the antiferromagnetic exchange interaction between a Mn ion and a bound hole results in a partial compensation of these fluctuating fields, leading to the enhanced spin memory.

Suppression of Electron Spin Relaxation in Mn-Doped GaAs

NASA Astrophysics Data System (ADS)

Astakhov, G. V.; Dzhioev, R. I.; Kavokin, K. V.; Korenev, V. L.; Lazarev, M. V.; Tkachuk, M. N.; Kusrayev, Yu. G.; Kiessling, T.; Ossau, W.; Molenkamp, L. W.

2008-08-01

We report a surprisingly long spin relaxation time of electrons in Mn-doped p-GaAs. The spin relaxation time scales with the optical pumping and increases from 12 ns in the dark to 160 ns upon saturation. This behavior is associated with the difference in spin relaxation rates of electrons precessing in the fluctuating fields of ionized or neutral Mn acceptors, respectively. For the latter, the antiferromagnetic exchange interaction between a Mn ion and a bound hole results in a partial compensation of these fluctuating fields, leading to the enhanced spin memory.

Dissociative and double photoionization of CO from threshold to 90 A

NASA Technical Reports Server (NTRS)

Masuoka, T.; Samson, J. A. R.

1981-01-01

Partial cross sections for molecular photoionization (CO(+)), dissociative photoionization (C(+) and O(+)), and dissociative double photoionization (C(2+)) in CO have been measured from their thresholds to 90 A using techniques of mass spectrometry. The results are compared with data reported previously. Several peaks observed in the cross section curves for dissociated fragments are tentatively assigned by comparing with those in the photoelectron spectra reported for CO. It is concluded that the shoulder in the total absorption cross section curve between 400 and 90 A results solely from the dissociative ionization processes.

Characterization of Arcjet Flows Using Laser-Induced Fluorescence

NASA Technical Reports Server (NTRS)

Bamford, Douglas J.; O'Keefe, Anthony; Babikian, Dikran S.; Stewart, David A.; Strawa, Anthony W.

1995-01-01

A sensor based on laser-induced fluorescence has been installed at the 20-MW NASA Ames Aerodynamic Heating Facility. The sensor has provided new, quantitative, real-time information about properties of the arcjet flow in the highly dissociated, partially ionized, nonequilibrium regime. Number densities of atomic oxygen, flow velocities, heavy particle translational temperatures, and collisional quenching rates have been measured. These results have been used to test and refine computational models of the arcjet flow. The calculated number densities, translational temperatures, and flow velocities are in moderately good agreement with experiment

Influence of ionizing radiation on the immune response

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

Brocadeszaalberg, O.

1974-01-01

The effects of ionizing radiation on the immune response are reviewed. Following an introduction on the function of the immune apparatus, the effect of radiation in the different cell types of the immune system is described. The possible consequences of these effects on the prognosis of radiation victims are discussed. (GRA)

THE EFFECTS OF IONIZING RADIATIONS ON THE BIOCHEMISTRY OF MAMMALIAN TISSUES.

DTIC Science & Technology

Contents: The effects of Ionizing Radiations on the Biochemistry of Mammalian Tissues: (1) Studies on the Effect of X-irradiation on Coenzyme A ... Levels of the Livers of Mice; (2) Influence of X-irradiation on the Development of a Detoxification System for Phosphorothioates in the Livers of Rats

Evaluation of effective energy for QA and QC: measurement of half-value layer using radiochromic film density.

PubMed

Gotanda, T; Katsuda, T; Gotanda, R; Tabuchi, A; Yamamoto, K; Kuwano, T; Yatake, H; Takeda, Y

2009-03-01

The effective energy of diagnostic X-rays is important for quality assurance (QA) and quality control (QC). However, the half-value layer (HVL), which is necessary to evaluate the effective energy, is not ubiquitously monitored because ionization-chamber dosimetry is time-consuming and complicated. To verify the applicability of GAFCHROMIC XR type R (GAF-R) film for HVL measurement as an alternative to monitoring with an ionization chamber, a single-strip method for measuring the HVL has been evaluated. Calibration curves of absorbed dose versus film density were generated using this single-strip method with GAF-R film, and the coefficient of determination (r2) of the straight-line approximation was evaluated. The HVLs (effective energies) estimated using the GAF-R film and an ionization chamber were compared. The coefficient of determination (r2) of the straight-line approximation obtained with the GAF-R film was more than 0.99. The effective energies (HVLs) evaluated using the GAF-R film and the ionization chamber were 43.25 keV (5.10 mm) and 39.86 keV (4.45 mm), respectively. The difference in the effective energies determined by the two methods was thus 8.5%. These results suggest that GAF-R might be used to evaluate the effective energy from the film-density growth without the need for ionization-chamber measurements.

Photoelectron circular dichroism of bicyclic ketones from multiphoton ionization with femtosecond laser pulses.

PubMed

Lux, Christian; Wollenhaupt, Matthias; Sarpe, Cristian; Baumert, Thomas

2015-01-12

Photoelectron circular dichroism (PECD) is a CD effect up to the ten-percent regime and shows contributions from higher-order Legendre polynomials when multiphoton ionization is compared to single-photon ionization. We give a full account of our experimental methodology for measuring the multiphoton PECD and derive quantitative measures that we apply on camphor, fenchone and norcamphor. Different modulations and amplitudes of the contributing Legendre polynomials are observed despite the similarity in chemical structure. In addition, we study PECD for elliptically polarized light employing tomographic reconstruction methods. Intensity studies reveal dissociative ionization as the origin of the observed PECD effect, whereas ionization of the intermediate resonance is dominating the signal. As a perspective, we suggest to make use of our tomographic data as an experimental basis for a complete photoionization experiment and give a prospect of PECD as an analytic tool. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of the dosimetric properties of a diode detector for small field proton radiosurgery

PubMed Central

Teran, Anthony V.; Slater, Jerry D.; Slater, James M.; Wroe, Andrew J.

2015-01-01

The small fields and sharp gradients typically encountered in proton radiosurgery require high spatial resolution dosimetric measurements, especially below 1–2 cm diameters. Radiochromic film provides high resolution, but requires postprocessing and special handling. Promising alternatives are diode detectors with small sensitive volumes (SV) that are capable of high resolution and real‐time dose acquisition. In this study we evaluated the PTW PR60020 proton dosimetry diode using radiation fields and beam energies relevant to radiosurgery applications. Energies of 127 and 157 MeV (9.7 to 15 cm range) and initial diameters of 8, 10, 12, and 20 mm were delivered using single‐stage scattering and four modulations (0, 15, 30, and 60 mm) to a water tank in our treatment room. Depth dose and beam profile data were compared with PTW Markus N23343 ionization chamber, EBT2 Gafchromic film, and Monte Carlo simulations. Transverse dose profiles were measured using the diode in "edge‐on" orientation or EBT2 film. Diode response was linear with respect to dose, uniform with dose rate, and showed an orientation‐dependent (i.e., beam parallel to, or perpendicular to, detector axis) response of less than 1%. Diode vs. Markus depth‐dose profiles, as well as Markus relative dose ratio vs. simulated dose‐weighted average lineal energy plots, suggest that any LET‐dependent diode response is negligible from particle entrance up to the very distal portion of the SOBP for the energies tested. Finally, while not possible with the ionization chamber due to partial volume effects, accurate diode depth‐dose measurements of 8, 10, and 12 mm diameter beams were obtained compared to Monte Carlo simulations. Because of the small SV that allows measurements without partial volume effects and the capability of submillimeter resolution (in edge‐on orientation) that is crucial for small fields and high‐dose gradients (e.g., penumbra, distal edge), as well as negligible LET dependence over nearly the full the SOBP, the PTW proton diode proved to be a useful high‐resolution, real‐time metrology device for small proton field radiation measurements such as would be encountered in radiosurgery applications. PACS numbers: 87.56.‐v, 87.56.jf, 87.56.Fc PMID:26699554

A comparative study of disinfection efficiency and regrowth control of microorganism in secondary wastewater effluent using UV, ozone, and ionizing irradiation process.

PubMed

Lee, O-Mi; Kim, Hyun Young; Park, Wooshin; Kim, Tae-Hun; Yu, Seungho

2015-09-15

Ionizing radiation technology was suggested as an alternative method to disinfection processes, such as chlorine, UV, and ozone. Although many studies have demonstrated the effectiveness of irradiation technology for microbial disinfection, there has been a lack of information on comparison studies of disinfection techniques and a regrowth of each treatment. In the present study, an ionizing radiation was investigated to inactivate microorganisms and to determine the critical dose to prevent the regrowth. As a result, it was observed that the disinfection efficiency using ionizing radiation was not affected by the seasonal changes of wastewater characteristics, such as temperature and turbidity. In terms of bacterial regrowth after disinfection, the ionizing radiation showed a significant resistance of regrowth, whereas, on-site UV treatment is influenced by the suspended solid, temperature, or precipitation. The electric power consumption was also compared for the economic feasibility of each technique at a given value of disinfection efficiency of 90% (1-log), showing 0.12, 36.80, and 96.53 Wh/(L/day) for ionizing radiation, ozone, and UV, respectively. The ionizing radiation requires two or three orders of magnitude lower power consumption than UV and ozone. Consequently, ionizing radiation can be applied as an effective and economical alternative technique to other conventional disinfection processes. Copyright © 2015 Elsevier B.V. All rights reserved.

Lithium atoms on helium nanodroplets: Rydberg series and ionization dynamics

NASA Astrophysics Data System (ADS)

Lackner, Florian; Krois, Günter; Ernst, Wolfgang E.

2017-11-01

The electronic excitation spectrum of lithium atoms residing on the surface of helium nanodroplets is presented and analyzed employing a Rydberg-Ritz approach. Utilizing resonant two-photon ionization spectroscopy, two different Rydberg series have been identified: one assigned to the nS(Σ) series and the other with predominantly nP(Π) character. For high Rydberg states, which have been resolved up to n = 13, the surrounding helium effectively screens the valence electron from the Li ion core, as indicated by the apparent red-shift of Li transitions and lowered quantum defects on the droplet with respect to their free atom counterparts. For low n states, the screening effect is weakened and the prevailing repulsive interaction gives rise to strongly broadened and blue-shifted transitions. The red-shifts originate from the polarization of nearby He atoms by the positive Li ion core. As a consequence of this effect, the ionization threshold is lowered by 116 ± 10 cm-1 for Li on helium droplets with a radius of about 40 Å. Upon single-photon ionization, heavy complexes corresponding to Li ions attached to intact helium droplets are detected. We conclude that ionization close to the on-droplet ionization threshold triggers a dynamic process in which the Li ion core undergoes a transition from a surface site into the droplet.

Connecting the dots: a correlation between ionizing radiation and cloud mass-loss rate traced by optical integral field spectroscopy

NASA Astrophysics Data System (ADS)

McLeod, A. F.; Gritschneder, M.; Dale, J. E.; Ginsburg, A.; Klaassen, P. D.; Mottram, J. C.; Preibisch, T.; Ramsay, S.; Reiter, M.; Testi, L.

2016-11-01

We present an analysis of the effect of feedback from O- and B-type stars with data from the integral field spectrograph Multi Unit Spectroscopic Explorer (MUSE) mounted on the Very Large Telescope of pillar-like structures in the Carina Nebular Complex, one of the most massive star-forming regions in the Galaxy. For the observed pillars, we compute gas electron densities and temperatures maps, produce integrated line and velocity maps of the ionized gas, study the ionization fronts at the pillar tips, analyse the properties of the single regions, and detect two ionized jets originating from two distinct pillar tips. For each pillar tip, we determine the incident ionizing photon flux Q0, pil originating from the nearby massive O- and B-type stars and compute the mass-loss rate dot{M} of the pillar tips due to photoevaporation caused by the incident ionizing radiation. We combine the results of the Carina data set with archival MUSE data of a pillar in NGC 3603 and with previously published MUSE data of the Pillars of Creation in M16, and with a total of 10 analysed pillars, find tight correlations between the ionizing photon flux and the electron density, the electron density and the distance from the ionizing sources, and the ionizing photon flux and the mass-loss rate. The combined MUSE data sets of pillars in regions with different physical conditions and stellar content therefore yield an empirical quantification of the feedback effects of ionizing radiation. In agreement with models, we find that dot{M}∝ Q_0,pil^{1/2}.

Theory of ionizing neutrino-atom collisions: The role of atomic recoil

NASA Astrophysics Data System (ADS)

Kouzakov, Konstantin A.; Studenikin, Alexander I.

2016-04-01

We consider theoretically ionization of an atom by neutrino impact taking into account electromagnetic interactions predicted for massive neutrinos by theories beyond the Standard Model. The effects of atomic recoil in this process are estimated using the one-electron and semiclassical approximations and are found to be unimportant unless the energy transfer is very close to the ionization threshold. We show that the energy scale where these effects become important is insignificant for current experiments searching for magnetic moments of reactor antineutrinos.

CARCINOGENIC EFFECTS OF LOW DOSES OF IONIZING RADIATION

EPA Science Inventory

Carcinogenic Effects of Low Doses of Ionizing Radiation

R Julian Preston, Environmental Carcinogenesis Division, NHEERL, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

The form of the dose-response curve for radiation-induced cancers, particu...

Selective protection of poly(tetra-fluoroethylene) from effects of chemical etching

DOEpatents

Martinez, Robert J.; Rye, Robert R.

1991-01-01

A photolithographic method for treating an article formed of polymeric material comprises subjecting portions of a surface of the polymeric article to ionizing radiation; and then subjecting the surface to chemical etching. The ionizing radiation treatment according to the present invention minimizes the effect of the subseuent chemical etching treatment. Thus, selective protection from the effects of chemical etching can be easily provided. The present invention has particular applicability to articles formed of fluorocarbons, such as PTFE. The ionizing radiation employed in the method may comprise Mg(k.alpha.) X-rays or lower-energy electrons.

Atomic physics effects on tokamak edge drift-tearing modes

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

Hahm, T.S.

1993-03-01

The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold {Delta}{sup Th}, produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

Atomic physics effects on tokamak edge drift-tearing modes

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

Hahm, T.S.

1993-03-01

The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold [Delta][sup Th], produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

The effects of low doses of ionizing radiation - A question of ethics

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

Tschaeche, A.N.

1996-12-31

Three ethical questions are asked and answered about the current state of affairs concerning how those in power manipulate public understanding of the effects of low doses of ionizing radiation. The questions are as follows: (1) Is it ethical to frighten people when you do not know that there is anything to be frightened of? (2) Is it ethical to be so conservative that resources are spent to solve a problem that may not exist? (3) Is it ethical not to tell the whole truth about the effects of low levels of ionizing radiation?

Time-dependent density-functional theory with optimized effective potential and self-interaction correction and derivative discontinuity for the treatment of double ionization of He and Be atoms in intense laser fields

NASA Astrophysics Data System (ADS)

Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

2013-05-01

We present a self-interaction-free time-dependent density-functional theory (TDDFT) for the treatment of double-ionization processes of many-electron systems. The method is based on the extension of the Krieger-Li-Iafrate (KLI) treatment of the optimized effective potential (OEP) theory and the incorporation of an explicit self-interaction correction (SIC) term. In the framework of the time-dependent density functional theory, we have performed three-dimensional (3D) calculations of double ionization of He and Be atoms by intense near-infrared laser fields. We make use of the exchange-correlation potential with the integer discontinuity which improves the description of the double-ionization process. We found that a proper description of the double ionization requires the TDDFT exchange-correlation potential with the discontinuity with respect to the variation of the total particle number (TPN). The results for the intensity-dependent rates of double ionization of He and Be atoms are presented.

Effect of ion compensation of the beam space charge on gyrotron operation

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

Fokin, A. P.; Glyavin, M. Yu.; Nusinovich, G. S.

In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ionmore » compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations.« less

The Influence of the Photoionizing Radiation Spectrum on Metal-Line Ratios in Ly(alpha) Forest Clouds

NASA Technical Reports Server (NTRS)

Giroux, Mark L.; Shull, J. Michael

1997-01-01

Recent measurements of Si IV/C IV ratios in the high-redshift Ly(alpha) forest (Songaila & Cowie, AJ, 112, 335 (1996a); Savaglio et at., A&A (in press) (1997)) have opened a new window on chemical enrichment and the first generations of stars. However, the derivation of accurate Si/C abundances requires reliable ionization corrections, which are strongly dependent on the spectral shape of the metagalactic ionizing background and on the 'local effects' of hot stars in nearby galaxies. Recent models have assumed power-law quasar ionizing backgrounds plus a decrement at 4 Ryd to account for He II attenuation in intervening clouds. However, we show that realistic ionizing backgrounds based on cosmological radiative transfer models produce more complex ionizing spectra between 1-5 Ryd that are critical to interpreting ions of Si and C. We also make a preliminary investigation of the effects of He II ionization front nonoverlap. Because the attenuation and reemission by intervening clouds enhance Si IV relative to C the observed high Si IV/C IV ratios do not require an unrealistic Si overproduction (Si/C greater than or equal to 3 (Si/C)(solar mass)). If the ionizing spectrum is dominated by 'local effects' from massive stars, even larger Si IV/C IV ratios are possible. However, unless stellar radiation dominates quasars by more than a factor of 10, we confirm the evidence for some Si overproduction by massive stars; values Si/C approx. 2(Si/C)(solar mass) fit the measurements better than solar abundances. Ultimately, an adequate interpretation of the ratios of C IV, Si IV, and C II may require hot, collisionally ionized gas in a multiphase medium.

Effects of Ionizing Radiation on Cellular Structures, Induced Instability, and Carcinogenesis

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

Resat, Marianne S.; Arthurs, Benjamin J.; Estes, Brian J.

2006-03-01

According to the American Cancer Society, the United States can expect 1,368,030 new cases of cancer in 2004 [1]. Among the many carcinogens Americans are exposed to, ionizing radiation will contribute to this statistic. Humans live in a radiation environment. Ionizing radiation is in the air we breathe, the earth we live on, and the food we eat. Man-made radiation adds to this naturally occurring radiation level thereby increasing the chance for human exposure. For many decades the scientific community, governmental regulatory bodies, and concerned citizens have struggled to estimate health risks associated with radiation exposures, particularly at low doses.more » While cancer induction is the primary concern and the most important somatic effect of exposure to ionizing radiation, potential health risks do not involve neoplastic diseases exclusively but also include somatic mutations that might contribute to birth defects and ocular maladies, and heritable mutations that might impact on disease risks in future generations. Consequently it is important we understand the effect of ionizingradiation on cellular structures and the subsequent long-term health risks associated with exposure to ionizing radiation.« less

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

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

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

Germann, Matthias; Willitsch, Stefan, E-mail: stefan.willitsch@unibas.ch

2016-07-28

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

Propagation of electromagnetic waves in a weak collisional and fully ionized dusty plasma

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

Jia, Jieshu; Yuan, Chengxun, E-mail: yuancx@hit.edu.cn; Gao, Ruilin

2016-04-15

The propagation properties of electromagnetic (EM) waves in fully ionized dusty plasmas is the subject of this study. The dielectric relationships for EM waves propagating in a fully ionized dusty plasma was derived from the Boltzmann distribution law, taking into consideration the collision and charging effects of the dust grains. The propagation properties of the EM waves in a dusty plasma were numerically calculated and studied. The study results indicated that the dusty grains with an increased radius and charge were more likely to impede the penetration of EM waves. Dust grains with large radii and high charge cause themore » attenuation of the EM wave in the dusty plasma. The different density of the dust in the plasma appeared to have no obvious effect on the transmission of the EM waves. The propagation of the EM waves in a weakly ionized dusty plasma varies from that in a fully ionized dusty plasma. The results are helpful to analyze the effects of dust in dusty plasmas and also provide a theoretical basis for future studies.« less

A simple way to model nebulae with distributed ionizing stars

NASA Astrophysics Data System (ADS)

Jamet, L.; Morisset, C.

2008-04-01

Aims: This work is a follow-up of a recent article by Ercolano et al. that shows that, in some cases, the spatial dispersion of the ionizing stars in a given nebula may significantly affect its emission spectrum. The authors found that the dispersion of the ionizing stars is accompanied by a decrease in the ionization parameter, which at least partly explains the variations in the nebular spectrum. However, they did not research how other effects associated to the dispersion of the stars may contribute to those variations. Furthermore, they made use of a unique and simplified set of stellar populations. The scope of the present article is to assess whether the variation in the ionization parameter is the dominant effect in the dependence of the nebular spectrum on the distribution of its ionizing stars. We examined this possibility for various regimes of metallicity and age. We also investigated a way to model the distribution of the ionizing sources so as to bypass expensive calculations. Methods: We wrote a code able to generate random stellar populations and to compute the emission spectra of their associated nebulae through the widespread photoionization code cloudy. This code can process two kinds of spatial distributions of the stars: one where all the stars are concentrated at one point, and one where their separation is such that their Strömgren spheres do not overlap. Results: We found that, in most regimes of stellar population ages and gas metallicities, the dependence of the ionization parameter on the distribution of the stars is the dominant factor in the variation of the main nebular diagnostics with this distribution. We derived a method to mimic those effects with a single calculation that makes use of the common assumptions of a central source and a spherical nebula, in the case of constant density objects. This represents a computation time saving by a factor of at least several dozen in the case of H ii regions ionized by massive clusters.

Poster — Thur Eve — 10: Partial kV CBCT, complete kV CBCT and EPID in breast treatment: a dose comparison study for skin, breasts, heart and lungs

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

Roussin, E; Archambault, L K; Wierzbicki, W

The advantages of kilovoltage cone beam CT (kV CBCT) imaging over electronic portal imaging device (EPID) such as accurate 3D anatomy, soft tissue visualization, fast rigid registration and enhanced precision on patient positioning has lead to its increasing use in clinics. The benefits of this imaging technique are at the cost of increasing the dose to healthy surrounding organs. Our center has moved toward the use of daily partial rotation kV CBCT to restrict the dose to healthy tissues. This study aims to better quantify radiation doses from different image-guidance techniques such as tangential EPID, complete and partial kV CBCTmore » for breast treatments. Cross-calibrated ionization chambers and kV calibrated Gafchromic films were used to measure the dose to the heart, lungs, breasts and skin. It was found that performing partial kV CBCT decreases the heart dose by about 36%, the lungs dose by 31%, the contralateral breast dose by 41% and the ipsilateral breast dose by 43% when compared to a full rotation CBCT. The skin dose measured for a full rotation CBCT was about 0.8 cGy for the contralateral breast and about 0.3 cGy for the ipsilateral breast. The study is still ongoing and results on skin doses for partial rotation kV CBCT as well as for tangential EPID images are upcoming.« less

Debris- and radiation-induced damage effects on EUV nanolithography source collector mirror optics performance

NASA Astrophysics Data System (ADS)

Allain, J. P.; Nieto, M.; Hendricks, M.; Harilal, S. S.; Hassanein, A.

2007-05-01

Exposure of collector mirrors facing the hot, dense pinch plasma in plasma-based EUV light sources to debris (fast ions, neutrals, off-band radiation, droplets) remains one of the highest critical issues of source component lifetime and commercial feasibility of nanolithography at 13.5-nm. Typical radiators used at 13.5-nm include Xe and Sn. Fast particles emerging from the pinch region of the lamp are known to induce serious damage to nearby collector mirrors. Candidate collector configurations include either multi-layer mirrors (MLM) or single-layer mirrors (SLM) used at grazing incidence. Studies at Argonne have focused on understanding the underlying mechanisms that hinder collector mirror performance at 13.5-nm under fast Sn or Xe exposure. This is possible by a new state-of-the-art in-situ EUV reflectometry system that measures real time relative EUV reflectivity (15-degree incidence and 13.5-nm) variation during fast particle exposure. Intense EUV light and off-band radiation is also known to contribute to mirror damage. For example offband radiation can couple to the mirror and induce heating affecting the mirror's surface properties. In addition, intense EUV light can partially photo-ionize background gas (e.g., Ar or He) used for mitigation in the source device. This can lead to local weakly ionized plasma creating a sheath and accelerating charged gas particles to the mirror surface and inducing sputtering. In this paper we study several aspects of debris and radiation-induced damage to candidate EUVL source collector optics materials. The first study concerns the use of IMD simulations to study the effect of surface roughness on EUV reflectivity. The second studies the effect of fast particles on MLM reflectivity at 13.5-nm. And lastly the third studies the effect of multiple energetic sources with thermal Sn on 13.5-nm reflectivity. These studies focus on conditions that simulate the EUVL source environment in a controlled way.

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

Propagation characteristics of electromagnetic waves in dusty plasma with full ionization

NASA Astrophysics Data System (ADS)

Dan, Li; Guo, Li-Xin; Li, Jiang-Ting

2018-01-01

This study investigates the propagation characteristics of electromagnetic (EM) waves in fully ionized dusty plasmas. The propagation characteristics of fully ionized plasma with and without dust under the Fokker-Planck-Landau (FPL) and Bhatnagar-Gross-Krook (BGK) models are compared to those of weakly ionized plasmas by using the propagation matrix method. It is shown that the FPL model is suitable for the analysis of the propagation characteristics of weakly collisional and fully ionized dusty plasmas, as is the BGK model. The influence of varying the dust parameters on the propagation properties of EM waves in the fully ionized dusty plasma was analyzed using the FPL model. The simulation results indicated that the densities and average radii of dust grains influence the reflection and transmission coefficients of fully ionized dusty plasma slabs. These results may be utilized to analyze the effects of interaction between EM waves and dusty plasmas, such as those associated with hypersonic vehicles.

Radioresistance of GGG Sequences to Prompt Strand Break Formation from Direct-Type Radiation Damage

PubMed Central

Black, Paul J.; Miller, Adam S.; Hayes, Jeffrey J.

2016-01-01

Purpose As humans, we are constantly exposed to ionizing radiation from natural, man-made and cosmic sources which can damage DNA, leading to deleterious effects including cancer incidence. In this work we introduce a method to monitor strand breaks resulting from damage due to the direct effect of ionizing radiation and provide evidence for sequence-dependent effects leading to strand breaks. Materials and methods To analyze only DNA strand breaks caused by radiation damage due to the direct effect of ionizing radiation, we combined an established technique to generate dehydrated DNA samples with a technique to analyze single strand breaks on short oligonucleotide sequences via denaturing gel electrophoresis. Results We find that direct damage primarily results in a reduced number of strand breaks in guanine triplet regions (GGG) when compared to isolated guanine (G) bases with identical flanking base context. In addition, we observe strand break behavior possibly indicative of protection of guanine bases when flanked by pyrimidines, and sensitization of guanine to strand break when flanked by adenine (A) bases in both isolated G and GGG cases. Conclusions These observations provide insight into the strand break behavior in GGG regions damaged via the direct effect of ionizing radiation. In addition, this could be indicative of DNA sequences that are naturally more susceptible to strand break due to the direct effect of ionizing radiation. PMID:27349757

Ionization Study of Isomeric Molecules in Strong-field Laser Pulses

DOE PAGES

Zigo, Stefan; Le, Anh-Thu; Timilsina, Pratap; ...

2017-02-10

Through the use of the technique of time-of-flight mass spectroscopy, we obtain strong-field ionization yields for randomly oriented 1,2-dichloroethylene (1,2-DCE) (C 2H 2Cl 2) and 2-butene (C 4H 8). Here, we are interested in studying the effect of conformal structure in strong-field ionization and, in particular, the role of molecular polarity. That is, we can perform strong-field ionization studies in polar vs non-polar molecules that have the same chemical composition. Here, we report our findings through the ionization yields and the ratio (trans/cis) of each stereoisomer pair as a function of intensity.

Compendium of Single Event Effects, Total Ionizing Dose, and Displacement Damage for Candidate Spacecraft Electronics for NASA

NASA Technical Reports Server (NTRS)

LaBel, Kenneth A.; O'Bryan, Martha V.; Chen, Dakai; Campola, Michael J.; Casey, Megan C.; Pellish, Jonathan A.; Lauenstein, Jean-Marie; Wilcox, Edward P.; Topper, Alyson D.; Ladbury, Raymond L.;

Gold-Containing Indoles as Anti-Cancer Agents that Potentiate the Cytotoxic Effects of Ionizing Radiation

PubMed Central

Craig, Sandra; Gao, Lei; Lee, Irene; Gray, Thomas; Berdis, Anthony J.

2012-01-01

This report describes the design and application of several distinct gold-containing indoles as anti-cancer agents. When used individually, all gold-bearing compounds display cytostatic effects against leukemia and adherent cancer cell lines. However, two gold-bearing indoles show unique behavior by increasing the cytotoxic effects of clinically relevant levels of ionizing radiation. Quantifying the amount of DNA damage demonstrates that each gold-indole enhances apoptosis by inhibiting DNA repair. Both Au(I)-indoles were tested for inhibitory effects against various cellular targets including thioredoxin reductase, a known target of several gold compounds, and various ATP-dependent kinases. While neither compound significantly inhibits the activity of thioreoxin reductase, both showed inhibitory effects against several kinases associated with cancer initiation and progression. The inhibition of these kinases provides a possible mechanism for the ability of these Au(I)-indoles potentiate the cytotoxic effects of ionizing radiation. Clinical applications of combining Au(I)-indoles with ionizing radiation are discussed as a new strategy to achieve chemosensitization of cancer cells. PMID:22289037

The ionization parameter of star-forming galaxies evolves with the specific star formation rate

NASA Astrophysics Data System (ADS)

Kaasinen, Melanie; Kewley, Lisa; Bian, Fuyan; Groves, Brent; Kashino, Daichi; Silverman, John; Kartaltepe, Jeyhan

2018-07-01

We investigate the evolution of the ionization parameter of star-forming galaxies using a high-redshift (z˜ 1.5) sample from the FMOS-COSMOS (Fibre Multi-Object Spectrograph-COSMic evOlution Survey) and matched low-redshift samples from the Sloan Digital Sky Survey. By constructing samples of low-redshift galaxies for which the stellar mass (M*), star formation rate (SFR), and specific star formation rate (sSFR) are matched to the high-redshift sample, we remove the effects of an evolution in these properties. We also account for the effect of metallicity by jointly constraining the metallicity and ionization parameter of each sample. We find an evolution in the ionization parameter for main-sequence, star-forming galaxies and show that this evolution is driven by the evolution of sSFR. By analysing the matched samples as well as a larger sample of z< 0.3, star-forming galaxies we show that high ionization parameters are directly linked to high sSFRs and are not simply the by-product of an evolution in metallicity. Our results are physically consistent with the definition of the ionization parameter, a measure of the hydrogen ionizing photon flux relative to the number density of hydrogen atoms.

The effect of surface charge, negative and bipolar ionization on the deposition of airborne bacteria.

PubMed

Meschke, S; Smith, B D; Yost, M; Miksch, R R; Gefter, P; Gehlke, S; Halpin, H A

2009-04-01

A series of experiments were conducted to evaluate the effect of surface charge and air ionization on the deposition of airborne bacteria. The interaction between surface electrostatic potential and the deposition of airborne bacteria in an indoor environment was investigated using settle plates charged with electric potentials of 0, +/-2.5kV and +/-5kV. Results showed that bacterial deposition on the plates increased proportionally with increased potential to over twice the gravitational sedimentation rate at +5kV. Experiments were repeated under similar conditions in the presence of either negative or bipolar air ionization. Bipolar air ionization resulted in reduction of bacterial deposition onto the charged surfaces to levels nearly equal to gravitational sedimentation. In contrast, diffusion charging appears to have occurred during negative air ionization, resulting in an even greater deposition onto the oppositely charged surface than observed without ionization. Static charges on fomitic surfaces may attract bacteria resulting in deposition in excess of that expected by gravitational sedimentation or simple diffusion. Implementation of bipolar ionization may result in reduction of bacterial deposition. Fomitic surfaces are important vehicles for the transmission of infectious organisms. This study has demonstrated a simple strategy for minimizing charge related deposition of bacteria on surfaces.

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

FUV Detection of the Primary Star of eta Carinae

NASA Astrophysics Data System (ADS)

Davidson, K.; Smith, N.

2006-06-01

Using FUSE data, Iping et al (2005, ApJ 633, L37) report a direct detection of the elusive hot companion of eta Car. We argue, however, that much of the observed emission represents the primary star, with no proof that any of it comes from a secondary star. The hypothetical companion should dominate the ionizing radiation below 912 A, but this is not true for wavelengths around 1100 A observed with FUSE. Moreover, since a companion's UV would be partially reprocessed by the primary star's wind, any detection is likely to be ambiguous.The non-spherical primary wind allows production of strong UV radiation at low latitudes (Smith et al 2003, ApJ 586, 432), an effect that spherical models don't include. The N II 1085 feature, the relatively slow wind velocities seen by FUSE, and other details are characteristic of the primary wind, not the secondary. Zanella et al. (1984, A&A 137, 79) suggested that eta Car's far UV disappears during a spectroscopic event due to a shell ejection. The FUSE observations may be regarded as confirmation of that conjecture, which made no reference to a secondary star. The 2003 spectroscopic event was probably a mass ejection or a wind-disturbance episode, not merely an eclipse as assumed by Iping et al. A hot companion star seems likely to account for the ionizing UV and the X-ray variability, but the FUSE data do not confirm its existence.

Experiments on the interaction of heavy ions with dense plasma at GSI-Darmstadt

NASA Astrophysics Data System (ADS)

Stöckl, C.; Boine-Frankenheim, O.; Geißel, M.; Roth, M.; Wetzler, H.; Seelig, W.; Iwase, O.; Spiller, P.; Bock, R.; Süß, W.; Hoffmann, D. H. H.

One of the main objectives of the experimental plasma physics activities at the Gesellschaft für Schwerionenforschung (GSI) are the interaction processes of heavy ions with dense ionized matter. Gas-discharge plasma targets were used for energy loss and charge state measurements in a regime of electron density and temperature up to 10 19 cm -3 and 20 eV, respectively. An improved model of the charge exchange processes in fully ionized hydrogen plasma, taking into account multiple excited electronic configurations which subsequently ionize, has removed the discrepancies of previous theoretical descriptions. The energy loss of the ion beam in partially ionized plasmas such as argon was found to agree very well with our simple theoretical model based on the modified Bethe-Bloch theory. A new setup with a 100 J/5 GW Nd-glass laser now provides access to density ranges up to 10 21 cm -3 and temperatures of up to 100 eV. First results of interaction experiments with laser-produced plasma are presented. To fully exploit the experimental possibilities of the new laser-plasma setup both improved charge state detection systems and better plasma diagnostics are indispensable. Present developments and future possibilities in these fields are presented. This paper summarizes the following contributions: Interaction of heavy-ion beams with laser plasma by C. Stöckl et al. Energy Loss of Heavy Ions in a laser-produced plasma by M. Roth et al. Charge state measurements of heavy ions passing a laser produced plasma with high time resolution by W. Süß et al. Plasma diagnostics for laser-produced plasma by O. Iwase et al. Future possibilities of plasma diagnostics at GSI by M. Geißel et al.

Diamond, titanium dioxide, titanium silicon oxide, and barium strontium titanium oxide nanoparticles as matrixes for direct matrix-assisted laser desorption/ionization mass spectrometry analysis of carbohydrates in plant tissues.

PubMed

Gholipour, Yousef; Giudicessi, Silvana L; Nonami, Hiroshi; Erra-Balsells, Rosa

2010-07-01

Nanoparticles (NPs) of diamond, titanium dioxide, titanium silicon oxide, barium strontium titanium oxide, and silver (Ag) were examined for their potential as MALDI matrixes for direct laser desorption/ionization of carbohydrates, especially fructans, from plant tissue. Two sample preparation methods including solvent-assisted and solvent-free (dry) NPs deposition were performed and compared. All examined NPs except for Ag could desorb/ionize standard sucrose and fructans in positive and in negative ion mode. Ag NPs yielded good signals only for nonsalt-doped samples that were measured in the negative ion mode. In the case of in vivo studies, except for Ag, all NPs studied could desorb/ionize carbohydrates from tissue in both the positive and negative ion modes. Furthermore, compared to the results obtained with soluble sugars extracted from plant tissues, fructans with higher molecular weight intact molecular ions could be detected when the plant tissues were directly profiled. The limit of detection (LOD) of fructans and the ratios between signal intensities and fructan concentrations were analyzed. NPs had similar LODs for standard fructan triose (1-kestose) in the positive ion mode and better LODs in the negative ion mode when compared with the common crystalline organic MALDI matrixes used for carbohydrates (2,5-dihydroxybenzoic acid and nor-harmane) or carbon nanotubes. Solvent-free NP deposition on tissues partially improves the signal acquisition. Although lower signal-to-noise ratio sugar signals were acquired from the tissues when compared to the solvent-assisted method, the reproducibility averaged over all sample was more uniform.

The Mean Metal-line Absorption Spectrum of Damped Ly α Systems in BOSS

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

Mas-Ribas, Lluís; Miralda-Escudé, Jordi; Pérez-Ràfols, Ignasi

We study the mean absorption spectrum of the Damped Ly α (DLA) population at z ∼ 2.6 by stacking normalized, rest-frame-shifted spectra of ∼27,000 DLA systems from the DR12 of the Baryon Oscillation Spectroscopic Survey (BOSS)/SDSS-III. We measure the equivalent widths of 50 individual metal absorption lines in five intervals of DLA hydrogen column density, five intervals of DLA redshift, and overall mean equivalent widths for an additional 13 absorption features from groups of strongly blended lines. The mean equivalent width of low-ionization lines increases with N {sub H} {sub i}, whereas for high-ionization lines the increase is much weaker.more » The mean metal line equivalent widths decrease by a factor ∼1.1–1.5 from z ∼ 2.1 to z ∼ 3.5, with small or no differences between low- and high-ionization species. We develop a theoretical model, inspired by the presence of multiple absorption components observed in high-resolution spectra, to infer mean metal column densities from the equivalent widths of partially saturated metal lines. We apply this model to 14 low-ionization species and to Al iii, S iii, Si iii, C iv, Si iv, N v, and O vi. We use an approximate derivation for separating the equivalent width contributions of several lines to blended absorption features, and infer mean equivalent widths and column densities from lines of the additional species N i, Zn ii, C ii*, Fe iii, and S iv. Several of these mean column densities of metal lines in DLAs are obtained for the first time; their values generally agree with measurements of individual DLAs from high-resolution, high signal-to-noise ratio spectra when they are available.« less

Effect of the dynamic core-electron polarization of CO molecules on high-order harmonic generation

NASA Astrophysics Data System (ADS)

Le, Cam-Tu; Hoang, Van-Hung; Tran, Lan-Phuong; Le, Van-Hoang

2018-04-01

We theoretically investigate the influence of dynamic core-electron polarization (DCeP) of CO molecules on high-order harmonic generation (HHG) by solving the time-dependent Schrödinger equation (TDSE) within the single-active-electron (SAE) approximation. The effect of DCeP is shown to depend strongly on the molecular orientation angle θ . Particularly, compared to the calculations without DCeP, the inclusion of this effect gives rise to an enhancement of harmonic intensity at θ =0° when the electric field aligns along the O-C direction and to a suppression at θ =180° when the field heads in the opposite direction. Meanwhile, when the electric field is perpendicular to the molecular axis, the effect is almost insignificant. The phenomenon is thought to be linked to the ionization process. However, this picture is not completed yet. By solving the TDSE within the SAE approximation and conducting a classical simulation, we are able to obtain the ionization probability as well as the ionization rate and prove that HHG, in fact, receives a major contribution from electrons ionized at only a certain time interval, rather than throughout the whole pulse propagation. Including DCeP, the variation of the ionization rate in this interval highly correlates to that of the HHG intensity. To better demonstrate the origin of this manifestation, we also show the alternation DCeP makes on the effective potential that corresponds to the observed change in the ionization rate and consequently the HHG intensity. Our results confirm previous studies' observations and, more importantly, provide the missing physical explanation. With the role of DCeP now better understood for the entire range of the orientation angle, this effect can be handled more conveniently for calculating the HHG of other targets.

Dynamics of the CRRES barium releases in the magnetosphere

NASA Technical Reports Server (NTRS)

Fuselier, S. A.; Mende, S. B.; Geller, S. P.; Miller, M.; Hoffman, R. A.; Wygant, J. R.; Pongratz, M.; Meredith, N. P.; Anderson, R. R.

1994-01-01

The Combined Release and Radiation Effects Satellite (CRRES) G-2, G-3, and G-4 ionized and neutral barium cloud positions are triangulated from ground-based optical data. From the time history of the ionized cloud motion perpendicular to the magnetic field, the late time coupling of the ionized cloud with the collisionless ambient plasma in the magnetosphere is investigated for each of the releases. The coupling of the ionized clouds with the ambient medium is quantitatively consistent with predictions from theory in that the coupling time increases with increasing distance from the Earth. Quantitative comparison with simple theory for the couping time also yields reasonable agreement. Other effects not predicted by the theory are discussed in the context of the observations.

HF Propagation Effects Caused by an Artificial Plasma Cloud in the Ionosphere

NASA Astrophysics Data System (ADS)

Joshi, D. R.; Groves, K. M.; McNeil, W. J.; Caton, R. G.; Parris, R. T.; Pedersen, T. R.; Cannon, P. S.; Angling, M. J.; Jackson-Booth, N. K.

2014-12-01

In a campaign carried out by the NASA sounding rocket team, the Air Force Research Laboratory (AFRL) launched two sounding rockets in the Kwajalein Atoll, Marshall Islands, in May 2013 known as the Metal Oxide Space Cloud (MOSC) experiment to study the interactions of artificial ionization and the background plasma and measure the effects on high frequency (HF) radio wave propagation. The rockets released samarium metal vapor in the lower F-region of the ionosphere that ionized forming a plasma cloud that persisted for tens of minutes to hours in the post-sunset period. Data from the experiments has been analyzed to understand the impacts of the artificial ionization on HF radio wave propagation. Swept frequency HF links transiting the artificial ionization region were employed to produce oblique ionograms that clearly showed the effects of the samarium cloud. Ray tracing has been used to successfully model the effects of the ionized cloud. Comparisons between observations and modeled results will be presented, including model output using the International Reference Ionosphere (IRI), the Parameterized Ionospheric Model (PIM) and PIM constrained by electron density profiles measured with the ALTAIR radar at Kwajalein. Observations and modeling confirm that the cloud acted as a divergent lens refracting energy away from direct propagation paths and scattering energy at large angles relative to the initial propagation direction. The results confirm that even small amounts of ionized material injected in the upper atmosphere can result in significant changes to the natural propagation environment.

Detection Identification and Quantification of Keto-Hydroperoxides in Low-Temperature Oxidation.

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

Hansen, Nils; Moshammer, Kai; Jasper, Ahren W.

2017-07-01

Keto-hydroperoxides are reactive partially oxidized intermediates that play a central role in chain-branching reactions during the low-temperature oxidation of hydrocarbons. In this Perspective, we outline how these short lived species can be detected, identified, and quantified using integrated experimental and theoretical approaches. The procedures are based on direct molecular-beam sampling from reactive environments, followed by mass spectrometry with single-photon ionization, identification of fragmentation patterns, and theoretical calculations of ionization thresholds, fragment appearance energies, and photoionization cross sections. Using the oxidation of neo-pentane and tetrahydrofuran as examples, the individual steps of the experimental approaches are described in depth together with amore » detailed description of the theoretical efforts. For neo-pentane, the experimental data are consistent with the calculated ionization and fragment appearance energies of the keto-hydroperoxide, thus adding confidence to the analysis routines and the employed levels of theory. For tetrahydrofuran, multiple keto-hydroperoxide isomers are possible due to the presence of nonequivalent O 2 addition sites. Despite this additional complexity, the experimental data allow for the identification of two to four keto-hydroperoxides. Mole fraction profiles of the keto-hydroperoxides, which are quantified using calculated photoionization cross sections, are provided together with estimated uncertainties as function of the temperature of the reactive mixture and can serve as validation targets for chemically detailed mechanisms.« less

A Suzaku, NuSTAR and XMMNewton} view on variable absorption and relativistic reflection in NGC 4151

NASA Astrophysics Data System (ADS)

Beuchert, T.; Markowitz, A.; Dauser, T.; Garcia, J.; Keck, M.; Wilms, J.; Kadler, M.; Brenneman, L.; Zdziarski, A.

2017-10-01

We disentangle X-ray disk reflection from complex line-of-sight absorption in NGC 4151 using Suzaku, NuSTAR, and XMMNewton}. Extending upon Keck et al. (2015), we develop a physically-motivated baseline model using the latest lamp-post reflection code relxillCp_lp, which includes a Comptonization continuum. We identify two components at heights of 1.2 and 15.0 gravitational radii using a long-look simultaneous Suzaku/NuSTAR observation but argue for a vertically extended corona as opposed to distinct primary sources. We also find two neutral absorbers (one full-covering and one partial-covering), an ionized absorber (log ξ=2.8), and a highly-ionized ultra-fast outflow, all reported previously. All analyzed spectra are well described by this baseline model. The bulk of the spectral variability on time-scales from days to years can be attributed to changes of both neutral absorbers, which are inversely correlated with the hard X-ray continuum flux. The observed evolution is either consistent with changes in the absorber structure (clumpy absorber in the outer BLR or a dusty radiatively driven wind) or a geometrically stable neutral absorber that becomes increasingly ionized at a rising flux level. The soft X-rays below 1 keV are dominated by photoionized emission from extended gas, which may act as a warm mirror for the nuclear radiation.

Peas in a Pod: Environment and Ionization in Green Pea Galaxies

NASA Astrophysics Data System (ADS)

Kurtz, Heather; Jaskot, Anne; Drew, Patrick; Pare, Dylan; Griffin, Jon; Petersen, Michael

2016-01-01

The Green Peas are extreme, highly ionized, starburst galaxies with strong [OIII] 5007 emission. Using the Sloan Digital Sky Survey, we present statistics on the environment of Green Peas and investigate its effects on their ionized gas properties. Although most dwarf starburst galaxies are in low-density environments, we identify a sample of Green Peas in dense environments. Emission line observations with the WIYN 0.9-meter telescope at Kitt Peak reveal that one cluster Green Pea is more highly ionized in the direction of the cluster center. Ram pressure stripping likely generates this ionization gradient. We explore the role of the environment in enhancing star formation rates and ionization, and we compare the nebular properties of Green Peas in high-density environments to those in low-density environments.

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

NASA Technical Reports Server (NTRS)

Rubinstein, Robert; Auslender, Aaron H.

1999-01-01

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

Small-signal modeling with direct parameter extraction for impact ionization effect in high-electron-mobility transistors

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

Guan, He; Lv, Hongliang; Guo, Hui, E-mail: hguan@stu.xidian.edu.cn

2015-11-21

Impact ionization affects the radio-frequency (RF) behavior of high-electron-mobility transistors (HEMTs), which have narrow-bandgap semiconductor channels, and this necessitates complex parameter extraction procedures for HEMT modeling. In this paper, an enhanced small-signal equivalent circuit model is developed to investigate the impact ionization, and an improved method is presented in detail for direct extraction of intrinsic parameters using two-step measurements in low-frequency and high-frequency regimes. The practicability of the enhanced model and the proposed direct parameter extraction method are verified by comparing the simulated S-parameters with published experimental data from an InAs/AlSb HEMT operating over a wide frequency range. The resultsmore » demonstrate that the enhanced model with optimal intrinsic parameter values that were obtained by the direct extraction approach can effectively characterize the effects of impact ionization on the RF performance of HEMTs.« less

Total Dose Effects on Single Event Transients in Digital CMOS and Linear Bipolar Circuits

NASA Technical Reports Server (NTRS)

Buchner, S.; McMorrow, D.; Sibley, M.; Eaton, P.; Mavis, D.; Dusseau, L.; Roche, N. J-H.; Bernard, M.

2009-01-01

This presentation discusses the effects of ionizing radiation on single event transients (SETs) in circuits. The exposure of integrated circuits to ionizing radiation changes electrical parameters. The total ionizing dose effect is observed in both complementary metal-oxide-semiconductor (CMOS) and bipolar circuits. In bipolar circuits, transistors exhibit grain degradation, while in CMOS circuits, transistors exhibit threshold voltage shifts. Changes in electrical parameters can cause changes in single event upset(SEU)/SET rates. Depending on the effect, the rates may increase or decrease. Therefore, measures taken for SEU/SET mitigation might work at the beginning of a mission but not at the end following TID exposure. The effect of TID on SET rates should be considered if SETs cannot be tolerated.

Studies of the Twin Helix Parametric-resonance Ionization Cooling Channel with COSY INFINITY

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

J.A. Maloney, K.B. Beard, R.P. Johnson, A. Afanasev, S.A. Bogacz, Y.S. Derbenev, V.S. Morozov, B. Erdelyi

2012-07-01

A primary technical challenge to the design of a high luminosity muon collider is an effective beam cooling system. An epicyclic twin-helix channel utilizing parametric-resonance ionization cooling has been proposed for the final 6D cooling stage. A proposed design of this twin-helix channel is presented that utilizes correlated optics between the horizontal and vertical betatron periods to simultaneously focus transverse motion of the beam in both planes. Parametric resonance is induced in both planes via a system of helical quadrupole harmonics. Ionization cooling is achieved via periodically placed wedges of absorbing material, with intermittent rf cavities restoring longitudinal momentum necessarymore » to maintain stable orbit of the beam. COSY INFINITY is utilized to simulate the theory at first order. The motion of particles around a hyperbolic fixed point is tracked. Comparison is made between the EPIC cooling channel and standard ionization cooling effects. Cooling effects are measured, after including stochastic effects, for both a single particle and a distribution of particles.« less

A Near-Threshold Shape Resonance in the Valence-Shell Photoabsorption of Linear Alkynes

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

Jacovella, U.; Holland, D. M. P.; Boyé-Péronne, S.

2015-12-17

The room-temperature photoabsorption spectra of a number of linear alkynes with internal triple bonds (e.g., 2-butyne, 2-pentyne, and 2- and 3-hexyne) show similar resonances just above the lowest ionization threshold of the neutral molecules. These features result in a substantial enhancement of the photoabsorption cross sections relative to the cross sections of alkynes with terminal triple bonds (e.g., propyne, 1-butyne, 1-pentyne,...). Based on earlier work on 2-butyne [Xu et al., J. Chem. Phys. 2012, 136, 154303], these features are assigned to excitation from the neutral highest occupied molecular orbital (HOMO) to a shape resonance with g (l = 4) charactermore » and approximate pi symmetry. This generic behavior results from the similarity of the HOMOs in all internal alkynes, as well as the similarity of the corresponding g pi virtual orbital in the continuum. Theoretical calculations of the absorption spectrum above the ionization threshold for the 2- and 3-alkynes show the presence of a shape resonance when the coupling between the two degenerate or nearly degenerate pi channels is included, with a dominant contribution from l = 4. These calculations thus confirm the qualitative arguments for the importance of the l = 4 continuum near threshold for internal alkynes, which should also apply to other linear internal alkynes and alkynyl radicals. The 1-alkynes do not have such high partial waves present in the shape resonance. The lower l partial waves in these systems are consistent with the broader features observed in the corresponding spectra.« less

A single-electron picture based on the multiconfiguration time-dependent Hartree-Fock method: application to the anisotropic ionization and subsequent high-harmonic generation of the CO molecule

NASA Astrophysics Data System (ADS)

Ohmura, S.; Kato, T.; Oyamada, T.; Koseki, S.; Ohmura, H.; Kono, H.

2018-02-01

The mechanisms of anisotropic near-IR tunnel ionization and high-order harmonic generation (HHG) in a CO molecule are theoretically investigated by using the multiconfiguration time-dependent Hartree-Fock (MCTDHF) method developed for the simulation of multielectron dynamics of molecules. The multielectron dynamics obtained by numerically solving the equations of motion (EOMs) in the MCTDHF method is converted to a single orbital picture in the natural orbital representation where the first-order reduced density matrix is diagonalized. The ionization through each natural orbital is examined and the process of HHG is classified into different optical paths designated by a combinations of initial, intermediate and final natural orbitals. The EOMs for natural spin-orbitals are also derived within the framework of the MCTDHF, which maintains the first-order reduced density matrix to be a diagonal one throughout the time propagation of a many-electron wave function. The orbital dependent, time-dependent effective potentials that govern the dynamics of respective time-dependent natural orbitals are deduced from the derived EOMs, of which the temporal variation can be used to interpret the motion of the electron density associated with each natural spin-orbital. The roles of the orbital shape, multiorbital ionization, linear Stark effect and multielectron interaction in the ionization and HHG of a CO molecule are revealed by the effective potentials obtained. When the laser electric field points to the nucleus O from C, tunnel ionization from the C atom side is enhanced; a hump structure originating from multielectron interaction is then formed on the top of the field-induced distorted barrier of the HOMO effective potential. This hump formation, responsible for the directional anisotropy of tunnel ionization, restrains the influence of the linear Stark effect on the energy shifts of bound states.

A compact, metal-rich, kpc-scale outflow in FBQS J0209-0438: detailed diagnostics from HST/COS extreme UV observations

NASA Astrophysics Data System (ADS)

Finn, Charles W.; Morris, Simon L.; Crighton, Neil H. M.; Hamann, Fred; Done, Chris; Theuns, Tom; Fumagalli, Michele; Tejos, Nicolas; Worseck, Gabor

2014-06-01

We present HST/COS observations of highly ionized absorption lines associated with a radio-loud quasar (QSO) at z = 1.1319. The absorption system has multiple velocity components, with an overall width of ≈600 km s-1, tracing gas that is largely outflowing from the QSO at velocities of a few 100 km s-1. There is an unprecedented range in ionization, with detections of H I, N III, N IV, N V, O IV, O IV*, O V, O VI, Ne VIII, Mg X, S V and Ar VIII. We estimate the total hydrogen number density from the column density ratio N(OIV*) / N(OIV) to be log(nH/cm-3)˜3. Combined with constraints on the ionization parameter in the O IV bearing gas from photoionization equilibrium models, we derive a distance to the absorbing complex of 2.3≲R≲6.0kpc from the centre of the QSO. A range in ionization parameter, covering ˜two orders of magnitude, suggest absorption path lengths in the range 10-4.5≲labs≲1pc. In addition, the absorbing gas only partially covers the background emission from the QSO continuum, which suggests clouds with transverse sizes ltrans≲10-2.5 pc. Widely differing absorption path lengths, combined with covering fractions less than unity across all ions pose a challenge to models involving simple cloud geometries in associated absorption systems. These issues may be mitigated by the presence of non-equilibrium effects, which can be important in small, dynamically unstable clouds, together with the possibility of multiple gas temperatures. The dynamics and expected lifetimes of the gas clouds suggest that they do not originate from close to the active galactic nuclei, but are instead formed close to their observed location. Their inferred distance, outflow velocities and gas densities are broadly consistent with scenarios involving gas entrainment or condensations in winds driven by either supernovae, or the supermassive black hole accretion disc. In the case of the latter, the present data most likely does not trace the bulk of the outflow by mass, which could instead manifest itself as an accompanying warm absorber, detectable in X-rays.

Fine Substituent Effects in Sandwich Complexes: A Threshold Ionization Study of Monosubstituted Chromium Bisarene Compounds.

PubMed

Ketkov, Sergey Yu; Markin, Gennady V; Tzeng, Sheng Y; Tzeng, Wen B

2016-03-24

Mass-analyzed threshold ionization spectra of jet-cooled [(η(6) -PhMe)(η(6) -PhH)Cr] and [(η(6) -Ph2 )(η(6) -PhH)Cr] reveal with unprecedented accuracy the effects of methyl and phenyl groups on the electronic structure of bis(η(6) -benzene)chromium. These "pure" substituent effects allow quantitative experimental determination of the ionization energy changes caused by the mutual substituent influence in bisarene systems. Two types of such influence have been revealed for the first time in bis(η(6) -toluene)chromium. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In-situ thermal annealing of on-membrane silicon-on-insulator semiconductor-based devices after high gamma dose irradiation.

PubMed

Amor, S; André, N; Kilchytska, V; Tounsi, F; Mezghani, B; Gérard, P; Ali, Z; Udrea, F; Flandre, D; Francis, L A

2017-05-05

In this paper, we investigate the recovery of some semiconductor-based components, such as N/P-type field-effect transistors (FETs) and a complementary metal-oxide-semiconductor (CMOS) inverter, after being exposed to a high total dose of gamma ray radiation. The employed method consists mainly of a rapid, low power and in situ annealing mitigation technique by silicon-on-insulator micro-hotplates. Due to the ionizing effect of the gamma irradiation, the threshold voltages showed an average shift of -580 mV for N-channel transistors, and -360 mV for P-MOSFETs. A 4 min double-cycle annealing of components with a heater temperature up to 465 °C, corresponding to a maximum power of 38 mW, ensured partial recovery but was not sufficient for full recovery. The degradation was completely recovered after the use of a built-in high temperature annealing process, up to 975 °C for 8 min corresponding to a maximum power of 112 mW, which restored the normal operating characteristics for all devices after their irradiation.

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

Filinov, A.V.; Golubnychiy, V.O.; Bonitz, M.

Extending our previous work [A.V. Filinov et al., J. Phys. A 36, 5957 (2003)], we present a detailed discussion of accuracy and practical applications of finite-temperature pseudopotentials for two-component Coulomb systems. Different pseudopotentials are discussed: (i) the diagonal Kelbg potential, (ii) the off-diagonal Kelbg potential, (iii) the improved diagonal Kelbg potential, (iv) an effective potential obtained with the Feynman-Kleinert variational principle, and (v) the 'exact' quantum pair potential derived from the two-particle density matrix. For the improved diagonal Kelbg potential, a simple temperature-dependent fit is derived which accurately reproduces the 'exact' pair potential in the whole temperature range. The derivedmore » pseudopotentials are then used in path integral Monte Carlo and molecular-dynamics (MD) simulations to obtain thermodynamical properties of strongly coupled hydrogen. It is demonstrated that classical MD simulations with spin-dependent interaction potentials for the electrons allow for an accurate description of the internal energy of hydrogen in the difficult regime of partial ionization down to the temperatures of about 60 000 K. Finally, we point out an interesting relationship between the quantum potentials and the effective potentials used in density-functional theory.« less

A Low-Power and In Situ Annealing Technique for the Recovery of Active Devices After Proton Irradiation

NASA Astrophysics Data System (ADS)

Francis, Laurent A.; Sedki, Amor; André, Nicolas; Kilchytska, Valéria; Gérard, Pierre; Ali, Zeeshan; Udrea, Florin; Flandre, Denis

2018-01-01

In this paper, we study the recovery of onmembrane semiconductor components, such as N-type Field-Effect Transistors (FETs) available in two different channel widths and a Complementary Metal-Oxide-Semiconductor (CMOS) inverter, after the exposure to high dose of proton radiation. Due to the ionizing effect, the electrical characteristics of the components established remarkable shifts, where the threshold voltages showed an average shift of -480 mV and -280 mV respectively for 6 μm and 24 μm N-channel transistors, likewise the inversion point of the inverter showed an important shift of -690 mV. The recovery concept is based mainly on a micro-hotplate, fabricated with backside MEMS micromachining structure and a Silicon-On-Insulator (SOI) technology, ensuring rapid, low power and in situ annealing technique, this method proved its reliability in recent works. Annealing the N-channel transistors and the inverter for 16 min with a temperature of the heater up to 385 °C, guaranteed a partial recovery of the semiconductor based components with a maximum power consumption of 66 mW.

In-situ thermal annealing of on-membrane silicon-on-insulator semiconductor-based devices after high gamma dose irradiation

NASA Astrophysics Data System (ADS)

Amor, S.; André, N.; Kilchytska, V.; Tounsi, F.; Mezghani, B.; Gérard, P.; Ali, Z.; Udrea, F.; Flandre, D.; Francis, L. A.

2017-05-01

In this paper, we investigate the recovery of some semiconductor-based components, such as N/P-type field-effect transistors (FETs) and a complementary metal-oxide-semiconductor (CMOS) inverter, after being exposed to a high total dose of gamma ray radiation. The employed method consists mainly of a rapid, low power and in situ annealing mitigation technique by silicon-on-insulator micro-hotplates. Due to the ionizing effect of the gamma irradiation, the threshold voltages showed an average shift of -580 mV for N-channel transistors, and -360 mV for P-MOSFETs. A 4 min double-cycle annealing of components with a heater temperature up to 465 °C, corresponding to a maximum power of 38 mW, ensured partial recovery but was not sufficient for full recovery. The degradation was completely recovered after the use of a built-in high temperature annealing process, up to 975 °C for 8 min corresponding to a maximum power of 112 mW, which restored the normal operating characteristics for all devices after their irradiation.

Organic Lecture Demonstrations of Common-Ion Effect, Ionizing Power of Solvents, and First-Order Reaction Kinetics.

ERIC Educational Resources Information Center

Danen, Wayne C.; Blecha, M. Therese, Sr.

1982-01-01

Background information and experimental procedures are provided for three lecture-demonstrations (involving hydrolysis of tetra-butyl chloride) illustrating: (1) common-ion or mass law effect; (2) effect of changing ionizing power of a solvent on a solvolysis reaction; and (3) collecting/plotting data to illustrate a first-order reaction.…

Electroencephalographic responses to ionizing radiation.

PubMed

GARCIA, J; BUCHWALD, N A; BACH-Y-RITA, G; FEDER, B H; KOELLING, R A

1963-04-19

Electroencephalographic recordings made from chronically implanted cortical electrodes indicate that ionizing radiation has an immediate effect upon brain wave patterns. X-rays delivered at the rate of 0.2 roentgen per second produce an arousal effect resembling that which occurs as a result of stimulation through peripheral receptor systems.

Argon laser phototherapy could eliminate the damage effects induced by the ionizing radiation "gamma radiation" in irradiated rabbits.

PubMed

Abdul-Aziz, Karolin Kamel; Tuorkey, M J

2010-04-02

The ionizing radiations could be taken in considerate as an integral part in our life, since, living organisms are actually exposed to a constant shower of ionizing radiations whether from the natural or artificial resources. The radio-protective efficiency of several chemicals has been confirmed in animal trails, whereas, due to their accumulative toxicity, their clinical utility is limited. Therefore, we aimed in the present work to investigate the possibility of using argon laser to recuperate the damaged tissues due to exposing to the ionizing radiation. The rabbits were used in this study, and they were designed as control, gamma irradiated, laser, and gamma plus laser groups. Lipid peroxidation, reduced glutathione (GSH), glutathione peroxidase (GSH-Px) and glucose-6-phosphate dehydrogenase (G-6-PD) in blood and liver were evaluated. As well as, the level of protein thiol was evaluated in the plasma among each group. Results of this study revealed the potential therapeutic performance of the treatment by laser argon to decline the damaging effect of the ionized radiation whether at systematic or local levels. In conclusion, argon laser therapy appears propitious protective effect against the hazard effects of gamma radiation. Copyright 2010 Elsevier B.V. All rights reserved.

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.

Resveratrol sensitization of DU145 prostate cancer cells to ionizing radiation is associated to ceramide increase.

PubMed

Scarlatti, Francesca; Sala, Giusy; Ricci, Clara; Maioli, Claudio; Milani, Franco; Minella, Marco; Botturi, Marco; Ghidoni, Riccardo

2007-08-08

Radiotherapy is an established therapeutic modality for prostate cancer. Since it is well known that radiotherapy is limited due to its severe toxicity towards normal cells at high dose and minimal effect at low dose, the search for biological compounds that increase the sensitivity of tumors cells to radiation may improve the efficacy of therapy. Resveratrol, a natural antioxidant, was shown to inhibit carcinogenesis in animal models, and to block the process of tumor initiation and progression. The purpose of this study was to examine whether or not resveratrol can sensitize DU145, an androgen-independent human prostate cancer cell line, to ionizing radiation. We report here that DU145 cells are resistant to ionizing radiation-induced cell death, but pretreatment with resveratrol significantly enhances cell death. Resveratrol acts synergistically with ionizing radiation to inhibit cell survival in vitro. Resveratrol also potentiates ionizing radiation-induced ceramide accumulation, by promoting its de novo biosynthesis. This confirms ceramide as an effective mediator of the anticancer potential induced by resveratrol.

Compendium of Current Total Ionizing Dose and Displacement Damage Results from NASA Goddard Space Flight Center and NASA Electronic Parts and Packaging Program

NASA Technical Reports Server (NTRS)

Topper, Alyson D.; Campola, Michael J.; Chen, Dakai; Casey, Megan C.; Yau, Ka-Yen; Cochran, Donna J.; Label, Kenneth A.; Ladbury, Raymond L.; Mondy, Timothy K.; O'Bryan, Martha V.;

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.

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.