H- ion sources for CERN's Linac4
NASA Astrophysics Data System (ADS)
Lettry, J.; Aguglia, D.; Coutron, Y.; Chaudet, E.; Dallocchio, A.; Gil Flores, J.; Hansen, J.; Mahner, E.; Mathot, S.; Mattei, S.; Midttun, O.; Moyret, P.; Nisbet, D.; O'Neil, M.; Paoluzzi, M.; Pasquino, C.; Pereira, H.; Arias, J. Sanchez; Schmitzer, C.; Scrivens, R.; Steyaert, D.
2013-02-01
The specifications set to the Linac4 ion source are: H- ion pulses of 0.5 ms duration, 80 mA intensity and 45 keV energy within a normalized emittance of 0.25 mmmrad RMS at a repetition rate of 2 Hz. In 2010, during the commissioning of a prototype based on H- production from the plasma volume, it was observed that the powerful co-extracted electron beam inherent to this type of ion source could destroy its electron beam dump well before reaching nominal parameters. However, the same source was able to provide 80 mA of protons mixed with a small fraction of H2+ and H3+ molecular ions. The commissioning of the radio frequency quadrupole accelerator (RFQ), beam chopper and H- beam diagnostics of the Linac4 are scheduled for 2012 and its final installation in the underground building is to start in 2013. Therefore, a crash program was launched in 2010 and reviewed in 2011 aiming at keeping the original Linac4 schedule with the following deliverables: Design and production of a volume ion source prototype suitable for 20-30 mA H- and 80 mA proton pulses at 45 keV by mid-2012. This first prototype will be dedicated to the commissioning of the low energy components of the Linac4. Design and production of a second prototype suitable for 40-50 mA H- based on an external RF solenoid plasma heating and cesiated-surface production mechanism in 2013 and a third prototype based on BNL's Magnetron aiming at reliable 2 Hz and 80 mA H- operations in 2014. In order to ease the future maintenance and allow operation with Ion sources based on three different production principles, an ion source "front end" providing alignment features, pulsed gas injection, pumping units, beam tuning capabilities and pulsed bipolar high voltage acceleration was designed and is being produced. This paper describes the progress of the Linac4 ion source program, the design of the Front end and first ion source prototype. Preliminary results of the summer 2012 commissioning are presented. The outlook on
Ion chemistry of 1H-1,2,3-triazole.
Ichino, Takatoshi; Andrews, Django H; Rathbone, G Jeffery; Misaizu, Fuminori; Calvi, Ryan M D; Wren, Scott W; Kato, Shuji; Bierbaum, Veronica M; Lineberger, W Carl
2008-01-17
A combination of experimental methods, photoelectron-imaging spectroscopy, flowing afterglow-photoelectron spectroscopy and the flowing afterglow-selected ion flow tube technique, and electronic structure calculations at the B3LYP/6-311++G(d,p) level of density functional theory (DFT) have been employed to study the mechanism of the reaction of the hydroxide ion (HO-) with 1H-1,2,3-triazole. Four different product ion species have been identified experimentally, and the DFT calculations suggest that deprotonation by HO- at all sites of the triazole takes place to yield these products. Deprotonation of 1H-1,2,3-triazole at the N1-H site gives the major product ion, the 1,2,3-triazolide ion. The 335 nm photoelectron-imaging spectrum of the ion has been measured. The electron affinity (EA) of the 1,2,3-triazolyl radical has been determined to be 3.447 +/- 0.004 eV. This EA and the gas-phase acidity of 2H-1,2,3-triazole are combined in a negative ion thermochemical cycle to determine the N-H bond dissociation energy of 2H-1,2,3-triazole to be 112.2 +/- 0.6 kcal mol-1. The 363.8 nm photoelectron spectroscopic measurements have identified the other three product ions. Deprotonation of 1H-1,2,3-triazole at the C5 position initiates fragmentation of the ring structure to yield a minor product, the ketenimine anion. Another minor product, the iminodiazomethyl anion, is generated by deprotonation of 1H-1,2,3-triazole at the C4 position, followed by N1-N2 bond fission. Formation of the other minor product, the 2H-1,2,3-triazol-4-ide ion, can be rationalized by initial deprotonation of 1H-1,2,3-triazole at the N1-H site and subsequent proton exchanges within the ion-molecule complex. The EA of the 2H-1,2,3-triazol-4-yl radical is 1.865 +/- 0.004 eV.
pH- and ion-sensitive polymers for drug delivery
Yoshida, Takayuki; Lai, Tsz Chung; Kwon, Glen S; Sako, Kazuhiro
2013-01-01
Introduction Drug delivery systems (DDSs) are important for effective, safe, and convenient administration of drugs. pH- and ion-responsive polymers have been widely employed in DDS for site-specific drug release due to their abilities to exploit specific pH- or ion-gradients in the human body. Areas covered Having pH-sensitivity, cationic polymers can mask the taste of drugs and release drugs in the stomach by responding to gastric low pH. Anionic polymers responsive to intestinal high pH are used for preventing gastric degradation of drug, colon drug delivery and achieving high bioavailability of weak basic drugs. Tumor-targeted DDSs have been developed based on polymers with imidazole groups or poly(β-amino ester) responsive to tumoral low pH. Polymers with pH-sensitive chemical linkages, such as hydrazone, acetal, ortho ester and vinyl ester, pH-sensitive cell-penetrating peptides and cationic polymers undergoing pH-dependent protonation have been studied to utilize the pH gradient along the endocytic pathway for intracellular drug delivery. As ion-sensitive polymers, ion-exchange resins are frequently used for taste-masking, counterion-responsive drug release and sustained drug release. Polymers responding to ions in the saliva and gastrointestinal fluids are also used for controlled drug release in oral drug formulations. Expert opinion Stimuli-responsive DDSs are important for achieving site-specific and controlled drug release; however, intraindividual, interindividual and intercellular variations of pH should be considered when designing DDSs or drug products. Combination of polymers and other components, and deeper understanding of human physiology are important for development of pH- and ion-sensitive polymeric DDS products for patients. PMID:23930949
H(-) ion source developments at the SNS.
Welton, R F; Stockli, M P; Murray, S N; Pennisi, T R; Han, B; Kang, Y; Goulding, R H; Crisp, D W; Sparks, D O; Luciano, N P; Carmichael, J R; Carr, J
2008-02-01
The U.S. Spallation Neutron Source (SNS) will require substantially higher average and pulse H(-) beam currents than can be produced from conventional ion sources such as the base line SNS source. H(-) currents of 40-50 mA (SNS operations) and 70-100 mA (power upgrade project) with a rms emittance of 0.20-0.35pi mm mrad and a approximately 7% duty factor will be needed. We are therefore investigating several advanced ion source concepts based on rf plasma excitation. First, the performance characteristics of an external antenna source based on an Al(2)O(3) plasma chamber combined with an external multicusp magnetic configuration, an elemental Cs system, and plasma gun will be discussed. Second, the first plasma measurements of a helicon-driven H(-) ion source will also be presented.
H- ion source developments at the SNSa)
NASA Astrophysics Data System (ADS)
Welton, R. F.; Stockli, M. P.; Murray, S. N.; Pennisi, T. R.; Han, B.; Kang, Y.; Goulding, R. H.; Crisp, D. W.; Sparks, D. O.; Luciano, N. P.; Carmichael, J. R.; Carr, J.
2008-02-01
The U.S. Spallation Neutron Source (SNS) will require substantially higher average and pulse H- beam currents than can be produced from conventional ion sources such as the base line SNS source. H- currents of 40-50mA (SNS operations) and 70-100mA (power upgrade project) with a rms emittance of 0.20-0.35πmmmrad and a ˜7% duty factor will be needed. We are therefore investigating several advanced ion source concepts based on rf plasma excitation. First, the performance characteristics of an external antenna source based on an Al2O3 plasma chamber combined with an external multicusp magnetic configuration, an elemental Cs system, and plasma gun will be discussed. Second, the first plasma measurements of a helicon-driven H- ion source will also be presented.
Ion transport in a pH-regulated nanopore.
Yeh, Li-Hsien; Zhang, Mingkan; Qian, Shizhi
2013-08-06
Fundamental understanding of ion transport phenomena in nanopores is crucial for designing the next-generation nanofluidic devices. Due to surface reactions of dissociable functional groups on the nanopore wall, the surface charge density highly depends upon the proton concentration on the nanopore wall, which in turn affects the electrokinetic transport of ions, fluid, and particles within the nanopore. Electrokinetic ion transport in a pH-regulated nanopore, taking into account both multiple ionic species and charge regulation on the nanopore wall, is theoretically investigated for the first time. The model is verified by the experimental data of nanopore conductance available in the literature. The results demonstrate that the spatial distribution of the surface charge density at the nanopore wall and the resulting ion transport phenomena, such as ion concentration polarization (ICP), ion selectivity, and conductance, are significantly affected by the background solution properties, such as the pH and salt concentration.
Recent operation of the FNAL magnetron H- ion source
NASA Astrophysics Data System (ADS)
Karns, P. R.; Bollinger, D. S.; Sosa, A.
2017-08-01
This paper will detail changes in the operational paradigm of the Fermi National Accelerator Laboratory (FNAL) magnetron H- ion source due to upgrades in the accelerator system. Prior to November of 2012 the H- ions for High Energy Physics (HEP) experiments were extracted at ˜18 keV vertically downward into a 90 degree bending magnet and accelerated through a Cockcroft-Walton accelerating column to 750 keV. Following the upgrade in the fall of 2012 the H- ions are now directly extracted from a magnetron at 35 keV and accelerated to 750 keV by a Radio Frequency Quadrupole (RFQ). This change in extraction energy as well as the orientation of the ion source required not only a redesign of the ion source, but an updated understanding of its operation at these new values. Discussed in detail are the changes to the ion source timing, arc discharge current, hydrogen gas pressure, and cesium delivery system that were needed to maintain consistent operation at >99% uptime for HEP, with an increased ion source lifetime of over 9 months.
Plaviak, Alexandra; Osburn, Sandra; Patterson, Khiry; van Stipdonk, Michael J
2016-01-15
Experiments were performed to probe the creation of apparent even-electron, [M-H](+) ions by CID of Ag-cationized peptides with N-terminal imine groups (Schiff bases). Imine-modified peptides were prepared using condensation reactions with aldehydes. Ag(+) -cationized precursors were generated by electrospray ionization (ESI). Tandem mass spectrometry (MS(n) ) and collision-induced dissociation (CID) were performed using a linear ion trap mass spectrometer. Loss of AgH from peptide [M + Ag](+) ions, at the MS/MS stage, creates closed-shell [M-H](+) ions from imine-modified peptides. Isotope labeling unambiguously identifies the imine C-H group as the source of H eliminated in AgH. Subsequent CID of the [M-H](+) ions generated sequence ions that are analogous to those produced from [M + H](+) ions of the imine-modified peptides. Experiments show (a) formation of novel even-electron peptide cations by CID and (b) the extent to which sequence ions (conventional b, a and y ions) are generated from peptides with fixed charge site and thus lacking a conventional mobile proton. Copyright © 2015 John Wiley & Sons, Ltd.
Kinetic modeling of particle dynamics in H- negative ion sources (invited)
NASA Astrophysics Data System (ADS)
Hatayama, A.; Shibata, T.; Nishioka, S.; Ohta, M.; Yasumoto, M.; Nishida, K.; Yamamoto, T.; Miyamoto, K.; Fukano, A.; Mizuno, T.
2014-02-01
Progress in the kinetic modeling of particle dynamics in H- negative ion source plasmas and their comparisons with experiments are reviewed, and discussed with some new results. Main focus is placed on the following two topics, which are important for the research and development of large negative ion sources and high power H- ion beams: (i) Effects of non-equilibrium features of EEDF (electron energy distribution function) on H- production, and (ii) extraction physics of H- ions and beam optics.
Energetic O+ and H+ Ions in the Plasma Sheet: Implications for the Transport of Ionospheric Ions
NASA Technical Reports Server (NTRS)
Ohtani, S.; Nose, M.; Christon, S. P.; Lui, A. T.
2011-01-01
The present study statistically examines the characteristics of energetic ions in the plasma sheet using the Geotail/Energetic Particle and Ion Composition data. An emphasis is placed on the O+ ions, and the characteristics of the H+ ions are used as references. The following is a summary of the results. (1) The average O+ energy is lower during solar maximum and higher during solar minimum. A similar tendency is also found for the average H+ energy, but only for geomagnetically active times; (2) The O+ -to -H+ ratios of number and energy densities are several times higher during solar maximum than during solar minimum; (3) The average H+ and O+ energies and the O+ -to -H+ ratios of number and energy densities all increase with geomagnetic activity. The differences among different solar phases not only persist but also increase with increasing geomagnetic activity; (4) Whereas the average H+ energy increases toward Earth, the average O+ energy decreases toward Earth. The average energy increases toward dusk for both the H+ and O+ ions; (5) The O+ -to -H+ ratios of number and energy densities increase toward Earth during all solar phases, but most clearly during solar maximum. These results suggest that the solar illumination enhances the ionospheric outflow more effectively with increasing geomagnetic activity and that a significant portion of the O+ ions is transported directly from the ionosphere to the near ]Earth region rather than through the distant tail.
A mass spectrometric study of gaseous H4PO+3 and H2PO-3 ions
NASA Astrophysics Data System (ADS)
de Petris, Giulia; Occhiucci, Giorgio; Pepi, Federico
1994-09-01
H4PO+3 ions have been generated in a mass spectrometer by proton-transfer to H3PO3 from different Brønsted acids. The proton affinity of H3PO3 has been estimated by bracketing and kinetic methods to be 198.6 ± 2 kcal mol-1. Gaseous H4PO+3 ions have been structurally assessed by metastable ion kinetic energy (MIKE) and collisionally induced dissociation (CID) mass spectrometry leading to the detection of a single isomeric species. The chemistry of H2PO-3 is characterized by facile addition-elimination reactions leading to formation of polyanions. Species containing up to six P atoms have been detected.
NASA Technical Reports Server (NTRS)
Singh, J. J.; Smith, A. S.; Chan, L. Y.; Yue, G. K.
1982-01-01
Thomson's ion nucleation theory was modified to include the effects of curvature dependence of the microscopic surface tension of field dependent, nonlinear, dielectric properties of the liquid; and of sulfuric acid hydrate formation in binary mixtures of water and sulfuric acid vapors. The modified theory leads to a broadening of the ion cluster spectrum, and shifts it towards larger numbers of H2O and H2SO4 molecules. Whether there is more shifting towards larger numbers of H2O or H2SO4 molecules depends on the relative humidity and relative acidity of the mixture. Usually, a broadening of the spectrum is accompanied by a lowering of the mean cluster intensity. For fixed values of relative humidity and relative acidity, a similar broadening pattern is observed when the temperature is lowered. These features of the modified theory illustrate that a trace of sulfuric acid can facilitate the formation of ultrafine, stable, prenucleation ion clusters as well as the growth of the prenucleation ion clusters towards the critical saddle point conditions, even with low values of relative humidity and relative acidity.
Effect of Ion Escape Velocity and Conversion Surface Material on H- Production
NASA Astrophysics Data System (ADS)
Tarvainen, O.; Kalvas, T.; Komppula, J.; Koivisto, H.; Geros, E.; Stelzer, J.; Rouleau, G.; Johnson, K. F.; Carmichael, J.
2011-09-01
According to generally accepted models surface production of negative ions depends on ion escape velocity and work function of the surface. We have conducted an experimental study addressing the role of the ion escape velocity on H- production. A converter-type ion source at Los Alamos Neutron Science Center was employed for the experiment. The ion escape velocity was affected by varying the bias voltage of the converter electrode. It was observed that due to enhanced stripping of H- no direct gain of extracted beam current can be achieved by increasing the converter voltage. The conversion efficiency of H- was observed to vary with converter voltage and follow the existing theories in qualitative manner. We present calculations predicting relative H- yields from different cesiated surfaces with comparison to experimental observations from different types of H- ion sources. Utilizing materials exhibiting negative electron affinity and exposed to UV-light is considered for Cesium-free H-/D- production.
21 CFR 868.1170 - Indwelling blood hydrogen ion concentration (pH) analyzer.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Indwelling blood hydrogen ion concentration (pH... Indwelling blood hydrogen ion concentration (pH) analyzer. (a) Identification. An indwelling blood hydrogen... used to measure, in vivo, the hydrogen ion concentration (pH) in blood to aid in determining the...
21 CFR 868.1170 - Indwelling blood hydrogen ion concentration (pH) analyzer.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Indwelling blood hydrogen ion concentration (pH... Indwelling blood hydrogen ion concentration (pH) analyzer. (a) Identification. An indwelling blood hydrogen... used to measure, in vivo, the hydrogen ion concentration (pH) in blood to aid in determining the...
21 CFR 868.1170 - Indwelling blood hydrogen ion concentration (pH) analyzer.
Code of Federal Regulations, 2012 CFR
2012-04-01
... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Indwelling blood hydrogen ion concentration (pH... Indwelling blood hydrogen ion concentration (pH) analyzer. (a) Identification. An indwelling blood hydrogen... used to measure, in vivo, the hydrogen ion concentration (pH) in blood to aid in determining the...
21 CFR 868.1170 - Indwelling blood hydrogen ion concentration (pH) analyzer.
Code of Federal Regulations, 2014 CFR
2014-04-01
... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Indwelling blood hydrogen ion concentration (pH... Indwelling blood hydrogen ion concentration (pH) analyzer. (a) Identification. An indwelling blood hydrogen... used to measure, in vivo, the hydrogen ion concentration (pH) in blood to aid in determining the...
21 CFR 868.1170 - Indwelling blood hydrogen ion concentration (pH) analyzer.
Code of Federal Regulations, 2013 CFR
2013-04-01
... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Indwelling blood hydrogen ion concentration (pH... Indwelling blood hydrogen ion concentration (pH) analyzer. (a) Identification. An indwelling blood hydrogen... used to measure, in vivo, the hydrogen ion concentration (pH) in blood to aid in determining the...
Numerical analysis of the spatial nonuniformity in a Cs-seeded H{sup -} ion source
DOE Office of Scientific and Technical Information (OSTI.GOV)
Takado, N.; Hanatani, J.; Mizuno, T.
The H{sup -} ion production and transport processes are numerically simulated to clarify the origin of H{sup -} beam nonuniformity. The three-dimensional transport code using the Monte Carlo method has been applied to H{sup 0} atoms and H{sup -} ions in the large 'JAERI 10A negative ion source' under the Cs-seeded condition, in which negative ions are dominantly produced by the surface production process. The results show that a large fraction of hydrogen atoms is produced in the region with high electron temperature. This leads to a spatial nonuniformity of H{sup 0} atom flux to the plasma grid and themore » resultant H{sup -} ion surface production. In addition, most surface-produced H{sup -} ions are extracted even through the high T{sub e} region without destruction. These results indicate a correlation between the production process of the H{sup -} ion and the spatial nonuniformity of the H{sup -} ion beam.« less
Ion Conduction through the hERG Potassium Channel
Cavalli, Andrea; Recanatini, Maurizio
2012-01-01
The inward rectifier voltage-gated potassium channel hERG is of primary importance for the regulation of the membrane potential of cardiomyocytes. Unlike most voltage-gated K+-channels, hERG shows a low elementary conductance at physiological voltage and potassium concentration. To investigate the molecular features underlying this unusual behavior, we simulated the ion conduction through the selectivity filter at a fully atomistic level by means of molecular dynamics-based methods, using a homology-derived model. According to our calculations, permeation of potassium ions can occur along two pathways, one involving site vacancies inside the filter (showing an energy barrier of about 6 kcal mol−1), and the other characterized by the presence of a knock-on intermediate (about 8 kcal mol−1). These barriers are indeed in accordance with a low conductance behavior, and can be explained in terms of a series of distinctive structural features displayed by the hERG ion permeation pathway. PMID:23133669
Xu, Yuan; Peng, Shixiang; Ren, Haitao; Zhao, Jie; Chen, Jia; Zhang, Ailin; Zhang, Tao; Guo, Zhiyu; Chen, Jia'er
2014-02-01
The permanent magnet 2.45 GHz electron cyclotron resonance ion source at Peking University can produce more than 100 mA hydrogen ion beam working at pulsed mode. For the increasing requirements of cluster ions (H2(+) and H3(+)) in linac and cyclotron, experimental study was carried out to further understand the hydrogen plasma processes in the ion source for the generation of cluster ions. The constituents of extracted beam have been analyzed varying with the pulsed duration from 0.3 ms to 2.0 ms (repetition frequency 100 Hz) at different operation pressure. The fraction of cluster ions dramatically increased when the pulsed duration was lower than 0.6 ms, and more than 20 mA pure H3(+) ions with fraction 43.2% and 40 mA H2(+) ions with fraction 47.7% were obtained when the operation parameters were adequate. The dependence of extracted ion fraction on microwave power was also measured at different pressure as the energy absorbed by plasma will greatly influence electron temperature and electron density then the plasma processes in the ion source. More details will be presented in this paper.
Simulation of RF power and multi-cusp magnetic field requirement for H- ion sources
NASA Astrophysics Data System (ADS)
Pathak, Manish; Senecha, V. K.; Kumar, Rajnish; Ghodke, Dharmraj. V.
2016-12-01
A computer simulation study for multi-cusp RF based H- ion source has been carried out using energy and particle balance equation for inductively coupled uniformly dense plasma considering sheath formation near the boundary wall of the plasma chamber for RF ion source used as high current injector for 1 Gev H- Linac project for SNS applications. The average reaction rates for different reactions responsible for H- ion production and destruction have been considered in the simulation model. The RF power requirement for the caesium free H- ion source for a maximum possible H- ion beam current has been derived by evaluating the required current and RF voltage fed to the coil antenna using transformer model for Inductively Coupled Plasma (ICP). Different parameters of RF based H- ion source like excited hydrogen molecular density, H- ion density, RF voltage and current of RF antenna have been calculated through simulations in the presence and absence of multicusp magnetic field to distinctly observe the effect of multicusp field. The RF power evaluated for different H- ion current values have been compared with the experimental reported results showing reasonably good agreement considering the fact that some RF power will be reflected from the plasma medium. The results obtained have helped in understanding the optimum field strength and field free regions suitable for volume emission based H- ion sources. The compact RF ion source exhibits nearly 6 times better efficiency compare to large diameter ion source.
Pilo, Alice L; Bu, Jiexun; McLuckey, Scott A
2015-07-01
The gas-phase oxidation of doubly protonated peptides is demonstrated here using ion/ion reactions with a suite of reagents derived from persulfate. Intact persulfate anion (HS2O8(-)), peroxymonosulfate anion (HSO5(-)), and sulfate radical anion (SO4(-•)) are all either observed directly upon negative nanoelectrospray ionization (nESI) or easily obtained via beam-type collisional activation of persulfate into the mass spectrometer. Ion/ion reactions between each of these reagents and doubly protonated peptides result in the formation of a long-lived complex. Collisional activation of the complex containing a peroxymonosulfate anion results in oxygen transfer from the reagent to the peptide to generate the [M + H + O](+) species. Activation of the complex containing intact persulfate anion either results in oxygen transfer to generate the [M + H + O](+) species or abstraction of two hydrogen atoms and a proton to generate the [M - H](+) species. Activation of the complex containing sulfate radical anion results in abstraction of one hydrogen atom and a proton to form the peptide radical cation, [M](+•). This suite of reagents allows for the facile transformation of the multiply protonated peptides obtained via nESI into a variety of oxidized species capable of providing complementary information about the sequence and structure of the peptide.
Development and characterization of a high-reliability, extended-lifetime H- ion source
NASA Astrophysics Data System (ADS)
Becerra, Gabriel; Barrows, Preston; Sherman, Joseph
2015-11-01
Phoenix Nuclear Labs (PNL) has designed and constructed a long-lifetime, negative hydrogen (H-) ion source, in partnership with Fermilab for an ion beam injector servicing future Intensity Frontier particle accelerators. The specifications for the low-energy beam transport (LEBT) section are 5-10 mA of continuous H- ion current at 30 keV with <0.2 π-mm-mrad emittance. Existing ion sources at Fermilab rely on plasma-facing electrodes, limiting their lifetime to a few hundred hours, while requiring relatively high gas loads on downstream components. PNL's design features an electron cyclotron resonance (ECR) microwave plasma driver which has been extensively developed in positive ion source systems, having demonstrated 1000+ hours of operation and >99% continuous uptime at PNL. Positive ions and hyperthermal neutrals drift toward a low-work-function surface, where a fraction is converted into H- hydrogen ions, which are subsequently extracted into a low-energy beam using electrostatic lenses. A magnetic filter preferentially removes high-energy electrons emitted by the source plasma, in order to mitigate H- ion destruction via electron-impact detachment. The design of the source subsystems and preliminary diagnostic results will be presented.
The Effects of Hydrogen Band EMIC Waves on Ring Current H+ Ions
NASA Astrophysics Data System (ADS)
Wang, Zhiqiang; Zhai, Hao; Gao, Zhuxiu
2017-12-01
Hydrogen band electromagnetic ion cyclotron (EMIC) waves have received much attention recently because they are found to frequently span larger spatial areas than the other band EMIC waves. Using test particle simulations, we study the nonlinear effects of hydrogen band EMIC waves on ring current H+ ions. A dimensionless parameter R is used to characterize the competition between wave-induced and adiabatic motions. The results indicate that there are three regimes of wave-particle interactions for typical 35 keV H+ ions at L = 5: diffusive (quasi-linear) behavior when αeq ≤ 35° (R ≥ 2.45), the nonlinear phase trapping when 35° < αeq < 50° (0.75 < R < 2.45), and both the nonlinear phase bunching and phase trapping when αeq ≥ 50° (R ≤ 0.75). The phase trapping can transport H+ ions toward large pitch angle, while the phase bunching has the opposite effect. The phase-trapped H+ ions can be significantly accelerated (from 35 keV to over 500 keV) in about 4 min and thus contribute to the formation of high energy components of ring current ions. The results suggest that the effect of hydrogen band EMIC waves is not ignorable in the nonlinear acceleration and resonance scattering of ring current H+ ions.
Cross sections for Scattering and Mobility of OH- and H3 O+ ions in H2 O
NASA Astrophysics Data System (ADS)
Petrovic, Zoran; Stojanovic, Vladimir; Maric, Dragana; Jovanovic, Jasmina
2016-05-01
Modelling of plasmas in liquids and in biological and medical applications requires data for scattering of all charged and energetic particles in water vapour. We present swarm parameters for OH- and H3 O+, as representatives of principal negative and positive ions at low pressures in an attempt to provide the data that are not yet available. We applied Denpoh-Nanbu procedure to calculate cross section sets for collisions of OH- and H3 O+ ions with H2 O molecule. Swarm parameters for OH- and H3 O+ ions in H2 O are calculated by using a well tested Monte Carlo code for a range of E / N(E -electric field, N-gas density) at temperature T = 295 K, in the low pressure limit. Non-conservative processes were shown to strongly influence the transport properties even for OH- ions above the average energy of 0.2 eV(E / N >200 Td). The data are valid for low pressure water vapour or small amounts in mixtures. They will provide a basis for calculating properties of ion-water molecule clusters that are most commonly found at higher pressures and for modelling of discharges in liquids. Acknowledgment to Ministry of Education, Science and Technology of Serbia.
Experimental ion mobility measurements in Xe-C2H6
NASA Astrophysics Data System (ADS)
Perdigoto, J. M. C.; Cortez, A. F. V.; Veenhof, R.; Neves, P. N. B.; Santos, F. P.; Borges, F. I. G. M.; Conde, C. A. N.
2017-10-01
In this paper we present the results of the ion mobility measurements made in gaseous mixtures of xenon (Xe) with ethane (C2H6) for pressures ranging from 6 to 10 Torr (8-10.6 mbar) and for low reduced electric fields in the 10 Td to 25 Td range (2.4-6.1 kVṡcm-1ṡ bar-1), at room temperature. The time of arrival spectra revealed two peaks throughout the entire range studied which were attributed to ion species with 3-carbons (C3H5+, C3H6+ C3H8+ and C3H9+) and with 4-carbons (C4H7+, C4H9+ and C4H10+). Besides these, and for Xe concentrations above 70%, a bump starts to appear at the right side of the main peak for reduced electric fields higher than 20 Td, which was attributed to the resonant charge transfer of C2H6+ to C2H6 that affects the mobility of its ion products (C3H8+ and C3H9+). The time of arrival spectra for Xe concentrations of 20%, 50%, 70% and 90% are presented, together with the reduced mobilities as a function of the Xe concentration calculated from the peaks observed for the low reduced electric fields and pressures studied.
Development of a compact filament-discharge multi-cusp H- ion source.
Jia, XianLu; Zhang, TianJue; Zheng, Xia; Qin, JiuChang
2012-02-01
A 14 MeV medical cyclotron with the external ion source has been designed and is being constructed at China Institute of Atomic Energy. The H(-) ion will be accelerated by this machine and the proton beam will be extracted by carbon strippers in dual opposite direction. The compact multi-cusp H(-) ion source has been developed for the cyclotron. The 79.5 mm long ion source is 48 mm in diameter, which is consisting of a special shape filament, ten columns of permanent magnets providing a multi-cusp field, and a three-electrode extraction system. So far, the 3 mA∕25 keV H(-) beam with an emittance of 0.3 π mm mrad has been obtained from the ion source. The paper gives the design details and the beam test results. Further experimental study is under way and an extracted beam of 5 mA is expected.
H- Ion Sources for High Intensity Proton Drivers
DOE Office of Scientific and Technical Information (OSTI.GOV)
Johnson, Rolland Paul; Dudnikov, Vadim
2015-02-20
Existing RF Surface Plasma Sources (SPS) for accelerators have specific efficiencies for H + and H - ion generation around 3 to 5 mA/cm 2 per kW, where about 50 kW of RF power is typically needed for 50 mA beam current production. The Saddle Antenna (SA) SPS described here was developed to improve H- ion production efficiency, reliability and availability for pulsed operation as used in the ORNL Spallation Neutron Source . At low RF power, the efficiency of positive ion generation in the plasma has been improved to 200 mA/cm 2 per kW of RF power at 13.56more » MHz. Initial cesiation of the SPS was performed by heating cesium chromate cartridges by discharge as was done in the very first versions of the SPS. A small oven to decompose cesium compounds and alloys was developed and tested. After cesiation, the current of negative ions to the collector was increased from 1 mA to 10 mA with RF power 1.5 kW in the plasma (6 mm diameter emission aperture) and up to 30 mA with 4 kW RF power in the plasma and 250 Gauss longitudinal magnetic field. The ratio of electron current to negative ion current was improved from 30 to 2. Stable generation of H- beam without intensity degradation was demonstrated in the aluminum nitride (AlN) discharge chamber for 32 days at high discharge power in an RF SPS with an external antenna. Some modifications were made to improve the cooling and cesiation stability. The extracted collector current can be increased significantly by optimizing the longitudinal magnetic field in the discharge chamber. While this project demonstrated the advantages of the pulsed version of the SA RF SPS as an upgrade to the ORNL Spallation Neutron Source, it led to a possibility for upgrades to CW machines like the many cyclotrons used for commercial applications. Four appendices contain important details of the work carried out under this grant.« less
A table for converting pH to hydrogen ion concentration [H+] over the range 5-9.
DOT National Transportation Integrated Search
1968-10-01
The wider use, in the future, of hydrogen ion concentration (H+) rather than pH to describe and evaluate acid-base status will require interconversion of the two notations until a final standard is adopted. The relationship between pH and (H+) is giv...
Scattered Ion Energetics for H atoms Impinging a Copper Surface
NASA Astrophysics Data System (ADS)
Defazio, J. N.; Stephen, T. M.; Peko, B. L.
2002-05-01
The energy loss and charge state of atomic hydrogen scattered from surfaces is important in a broad range of scientific endeavors. These include the charging of spacecraft, the detection of low energy neutrals in the space environment, energy transfer from magnetically confined plasmas and the modeling of low energy electric discharges. Measurements of scattered ions resulting from low energy (20 - 1000 eV) atomic hydrogen impacting a copper surface have been accomplished. Differential energy distributions and yields for H- and H+ resulting from these collisions are presented. The data show that the energy distributions develop a universal dependence, when scaled by the incident energy. These results are compared with studies involving incident hydrogen ions. For incident energies less than 100eV, there are obvious differences in the scattered ion energy distributions resulting from impacting atoms when compared to those resulting from ions.
Large scale silver nanowires network fabricated by MeV hydrogen (H+) ion beam irradiation
NASA Astrophysics Data System (ADS)
Honey, S.; Naseem, S.; Ishaq, A.; Maaza, M.; Bhatti, M. T.; Wan, D.
2016-04-01
A random two-dimensional large scale nano-network of silver nanowires (Ag-NWs) is fabricated by MeV hydrogen (H+) ion beam irradiation. Ag-NWs are irradiated under H+ ion beam at different ion fluences at room temperature. The Ag-NW network is fabricated by H+ ion beam-induced welding of Ag-NWs at intersecting positions. H+ ion beam induced welding is confirmed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Moreover, the structure of Ag NWs remains stable under H+ ion beam, and networks are optically transparent. Morphology also remains stable under H+ ion beam irradiation. No slicings or cuttings of Ag-NWs are observed under MeV H+ ion beam irradiation. The results exhibit that the formation of Ag-NW network proceeds through three steps: ion beam induced thermal spikes lead to the local heating of Ag-NWs, the formation of simple junctions on small scale, and the formation of a large scale network. This observation is useful for using Ag-NWs based devices in upper space where protons are abandoned in an energy range from MeV to GeV. This high-quality Ag-NW network can also be used as a transparent electrode for optoelectronics devices. Project supported by the National Research Foundation of South Africa (NRF), the French Centre National pour la Recherche Scientifique, iThemba-LABS, the UNESCO-UNISA Africa Chair in Nanosciences & Nanotechnology, the Third World Academy of Science (TWAS), Organization of Women in Science for the Developing World (OWSDW), the Abdus Salam ICTP via the Nanosciences African Network (NANOAFNET), and the Higher Education Commission (HEC) of Pakistan.
Fang, Liwen; Dong, Cheng; Guo, Cheng; Xu, Jianxing; Liu, Qiaoling; Qu, Zhirong; Jiang, Kezhi
2018-06-01
A series of N-(1,3-diphenylallyl)benzenamine derivatives (M) were investigated by electrospray ionization mass spectrometry in the positive-ion mode. Both the anomalous [M-H] + and the regular [M+H] + were observed in the ESI mass spectra. The occurrence of [M-H] + has been supported by accurate mass spectrometry, liquid chromatography mass spectrometry, and tandem mass spectrometry analysis. Calculation results indicated that formation of [M-H] + is attributed to the ion-molecule reaction of M with the protonated ESI solvent molecule (e.g. CH 3 OH 2 + ) via hydride abstraction from a tertiary C sp3 -H. The competing ionization processes leading to [M-H] + or [M+H] + were significantly affected by the concentration of formic acid in the electrospray ionization solvent and the proton affinity of the N atom.
Zeng, Zhenping; Yeh, Li-Hsien; Zhang, Mingkan; Qian, Shizhi
2015-10-28
Inspired by nature, functionalized nanopores with biomimetic structures have attracted growing interests in using them as novel platforms for applications of regulating ion and nanoparticle transport. To improve these emerging applications, we study theoretically for the first time the ion transport and selectivity in short nanopores functionalized with pH tunable, zwitterionic polyelectrolyte (PE) brushes. In addition to background salt ions, the study takes into account the presence of H(+) and OH(-) ions along with the chemistry reactions between functional groups on PE chains and protons. Due to ion concentration polarization, the charge density of PE layers is not homogeneously distributed and depends significantly on the background salt concentration, pH, grafting density of PE chains, and applied voltage bias, thereby resulting in many interesting and unexpected ion transport phenomena in the nanopore. For example, the ion selectivity of the biomimetic nanopore can be regulated from anion-selective (cation-selective) to cation-selective (anion-selective) by diminishing (raising) the solution pH when a sufficiently small grafting density of PE chains, large voltage bias, and low background salt concentration are applied.
A SIFT study of the reactions of H2ONO+ ions with several types of organic molecules
NASA Astrophysics Data System (ADS)
Smith, David; Wang, Tianshu; Spanel, Patrik
2003-11-01
A selected ion flow tube (SIFT) study has been carried out of the reactions of hydrated nitrosonium ions, NO+H2O, which theory has equated to protonated nitrous acid ions, H2ONO+. One objective of this study was to investigate if this ion exhibits the properties of both a cluster ion and a protonated acid in their reactions with a variety of organic molecules. The chosen reactant molecules comprise two each of the following types--amines, terpenes, aromatic hydrocarbons, esters, carboxylic acids, ketones, aldehydes and alcohols. The reactant H2ONO+ (NO+H2O) ions are formed in a discharge ion source and injected into helium carrier gas where they are partially vibrationally excited and partially dissociated to NO+ ions. Hence, the reactions of the H2ONO+ ions had to be studies simultaneously with NO+ ions, the reactions of the latter ions readily being studied by selectively injecting NO+ ions into the carrier gas. The results of this study indicate that the H2ONO+ ions undergo a wide variety of reaction processes that depend on the properties of the reactant molecules such as their ionisation energies and proton affinities. These processes include charge transfer with compounds, M, that have low ionisation energies (producing M+), proton transfer with compounds possessing large proton affinities (MH+), hydride ion transfer (M---H+), alkyl radical (M---R+), alkoxide radical transfer (M---OR+), ion-molecule association (NO+H2OM) and ligand switching (NO+M), producing the ions given in parentheses.
Thermal annealing behavior of hydrogen and surface topography of H 2 + ion implanted tungsten
DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhang, Jiandong; Jiang, Weilin; Zhu, Zihua
2018-01-25
Tungsten (W) has been proposed as a plasma-facing material (PFM) in fusion reactors due to its outstanding properties. Degradation of the material properties is expected to occur as a result of hydrogen (H) isotope permeation and trapping in W. In this study, two polycrystalline W plates were implanted with 80 keV H 2 + ions to a fluence of 2E21 H+/m2 at room temperature (RT). Time-of-flight secondary ion mass spectrometry (ToF-SIMS), focused ion beam (FIB) and scanning electron microscopy (SEM) were used for sample characterization. The SIMS data shows that H atoms are distributed well beyond the ion projected range.more » Isochronal annealing appears to suggest two H release stages that might be associated with the reported activation energies. H release at RT was observed between days 10 and 70 following ion implantation, and the level was maintained over the next 60 days. In addition, FIB/SEM results exhibit H2 blister formation near the surface of the as-implanted W. The blister distribution remains unchanged after thermal annealing up to 600 °C.« less
NASA Astrophysics Data System (ADS)
Yoshimura, Satoru; Sugimoto, Satoshi; Takeuchi, Takae; Murai, Kensuke; Kiuchi, Masato
2018-04-01
We mass-selected SiC3H9+ ions from various fragments produced through the decomposition of hexamethyldisilane, and finally produced low-energy SiC3H9+ ion beams. The ion beams were injected into Si(1 0 0) substrates and the dependence of deposited films on injected ion energy was then investigated. Injected ion energies were 20, 100, or 200 eV. Films obtained were investigated with X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. X-ray diffraction and X-ray photoelectron spectroscopy of the substrates obtained following the injection of 20 eV ions demonstrated the occurrence of silicon carbide film (3C-SiC) deposition. On the other hand, Raman spectroscopy showed that the films deposited by the injection of 100 or 200 eV ions included 3C-SiC plus diamond-like carbon. Ion beam deposition using hexamethyldisilane-derived 20 eV SiC3H9+ ions is an efficient technique for 3C-SiC film formation on Si substrates.
Recombination of H(3+) and D(3+) ions with electrons
NASA Technical Reports Server (NTRS)
Johnsen, R.; Gougousi, T.; Golde, M. F.
1994-01-01
Flowing-afterglow measurements in decaying H3(+) or D3(+) plasmas suggest that de-ionization does not occur by simple binary recombination of a single ion species. We find that vibrational excitation of the ions fails to provide an explanation for the effect, contrary to an earlier suggestion. Instead, we suggest that collisional stabilization of H3** Rydberg molecules by ambient electrons introduces an additional dependence on electron density. The proposed mechanism would permit plasma de-ionization to occur without the need for dissociative recombination by the mechanism of potential-surface crossings.
Next Generation H- Ion Sources for the SNS
NASA Astrophysics Data System (ADS)
Welton, R. F.; Stockli, M. P.; Murray, S. N.; Crisp, D.; Carmichael, J.; Goulding, R. H.; Han, B.; Tarvainen, O.; Pennisi, T.; Santana, M.
2009-03-01
The U.S. Spallation Neutron Source (SNS) is the leading accelerator-based, pulsed neutron-scattering facility, currently in the process of ramping up neutron production. In order to insure meeting operational requirements as well as providing for future facility beam power upgrades, a multifaceted H- ion source development program is ongoing. This work discusses several aspects of this program, specifically the design and first beam measurements of an RF-driven, external antenna H- ion source based on an A1N ceramic plasma chamber, elemental and chromate Cs-systems, and plasma ignition gun. Unanalyzed beam currents of up to ˜100 mA (60 Hz, 1 ms) have been observed and sustained currents >60 mA (60 Hz, 1 ms) have been demonstrated on the test stand. Accelerated beam currents of ˜40 mA have also been demonstrated into the SNS front end. Data are also presented describing the first H- beam extraction experiments from a helicon plasma generator based on the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine design.
Progress in the development of an H{sup −} ion source for cyclotrons
DOE Office of Scientific and Technical Information (OSTI.GOV)
Etoh, H., E-mail: Hrh-Etoh@shi.co.jp; Aoki, Y.; Mitsubori, H.
2015-04-08
A multi-cusp DC H{sup −} ion source has been developed for cyclotrons in medical use. Beam optics of the H{sup −} ion beam is studied using a 2D beam trajectory code. The simulation results are compared with the experimental results obtained in the Mark I source, which has produced up to 16 mA H{sup −} ion beams. The optimum extraction voltages show good agreement between the calculation and the experimental results. A new ion source, Mark II source, is designed to achieve the next goal of producing an H{sup −} beam of 20 mA. The magnetic field configurations and the plasma electrodemore » design are optimized for Cs-seeded operation. Primary electron trajectory simulation shows that primary electrons are confined well and the magnetic filter prevents the primary electrons from entering into the extraction region.« less
Measurements of ion-molecule reactions of He plus, H plus, HeH plus with H sub 2 and D sub 2
NASA Technical Reports Server (NTRS)
Johnsen, R.; Biondi, M. A.
1974-01-01
A drift tube mass spectrometer apparatus has been used to determine the rate coefficient, energy dependence and product ions of the reaction He(+) +H2. The total rate coefficient at 300 K is 1.1 plus or minus 0.1) 10 to minus 13th power cu cm/sec. The reaction proceeds principally by dissociative charge transfer to produce H(+), with the small remainder going by charge transfer to produce H2(+) and by atom rearrangement to produce HeH(+). The rate coefficient increases slowly with increasing ion mean energy, reaching a value of 2.8 x ten to the minus 13th power cu cm sec at 0.18 eV. The corresponding reaction with deuterium, He(+) + D2, exhibits a value (5 plus or minus 1) x 10 to the minus 14th cu cm/sec at 300K. The reaction rates for conversion of H(+) and HeH(+) to H3(+) on collisions with H2 molecules are found to agree well with results of previous investigations.
Tarvainen, O; Rouleau, G; Keller, R; Geros, E; Stelzer, J; Ferris, J
2008-02-01
The converter-type negative ion source currently employed at the Los Alamos Neutron Science Center (LANSCE) is based on cesium enhanced surface production of H(-) ion beams in a filament-driven discharge. In this kind of an ion source the extracted H(-) beam current is limited by the achievable plasma density which depends primarily on the electron emission current from the filaments. The emission current can be increased by increasing the filament temperature but, unfortunately, this leads not only to shorter filament lifetime but also to an increase in metal evaporation from the filament, which deposits on the H(-) converter surface and degrades its performance. Therefore, we have started an ion source development project focused on replacing these thermionic cathodes (filaments) of the converter source by a helicon plasma generator capable of producing high-density hydrogen plasmas with low electron energy. In our studies which have so far shown that the plasma density of the surface conversion source can be increased significantly by exciting a helicon wave in the plasma, and we expect to improve the performance of the surface converter H(-) ion source in terms of beam brightness and time between services. The design of this new source and preliminary results are presented, along with a discussion of physical processes relevant for H(-) ion beam production with this novel design. Ultimately, we perceive this approach as an interim step towards our long-term goal, combining a helicon plasma generator with an SNS-type main discharge chamber, which will allow us to individually optimize the plasma properties of the plasma cathode (helicon) and H(-) production (main discharge) in order to further improve the brightness of extracted H(-) ion beams.
NASA Astrophysics Data System (ADS)
Tarvainen, O.; Rouleau, G.; Keller, R.; Geros, E.; Stelzer, J.; Ferris, J.
2008-02-01
The converter-type negative ion source currently employed at the Los Alamos Neutron Science Center (LANSCE) is based on cesium enhanced surface production of H- ion beams in a filament-driven discharge. In this kind of an ion source the extracted H- beam current is limited by the achievable plasma density which depends primarily on the electron emission current from the filaments. The emission current can be increased by increasing the filament temperature but, unfortunately, this leads not only to shorter filament lifetime but also to an increase in metal evaporation from the filament, which deposits on the H- converter surface and degrades its performance. Therefore, we have started an ion source development project focused on replacing these thermionic cathodes (filaments) of the converter source by a helicon plasma generator capable of producing high-density hydrogen plasmas with low electron energy. In our studies which have so far shown that the plasma density of the surface conversion source can be increased significantly by exciting a helicon wave in the plasma, and we expect to improve the performance of the surface converter H- ion source in terms of beam brightness and time between services. The design of this new source and preliminary results are presented, along with a discussion of physical processes relevant for H- ion beam production with this novel design. Ultimately, we perceive this approach as an interim step towards our long-term goal, combining a helicon plasma generator with an SNS-type main discharge chamber, which will allow us to individually optimize the plasma properties of the plasma cathode (helicon) and H- production (main discharge) in order to further improve the brightness of extracted H- ion beams.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ueno, A.; Oguri, H.; Ikegami, K.
2010-02-15
The following interesting experimental results observed in Japan Proton Accelerator Research Complex (J-PARC) H{sup -} ion-source developments are reviewed. It was proven that almost all of H{sup -} ions were produced with surface reactions in cesium (Cs)-free J-PARC H{sup -} ion-sources. The world's most intense class H{sup -} ion current of 38 mA in Cs-free ion sources for a high-energy linac was attained by an optimal shape and high temperature of the plasma electrode (PE), usage of a lanthanum hexaboride (LaB{sub 6}) filament, and a newly devised high-power constant-current pulsed-arc power supply indispensable for it. It was also proven thatmore » the H{sup -} ion current could be increased to more than 40 mA by optimizing LaB{sub 6}-filament shape. The surface elemental analysis of the PE after operation with a LaB{sub 6}-filament showed that it was coated by boron (B) 95.5%, lanthanum (La) 2.5%, and oxygen (O) 1.9%. The H{sup -} ion current decreased by about 20% when a tungsten (W) filament was used instead of a LaB{sub 6}-filament. The H{sup -} ion current could not be increased by seeding cesium (Cs) if the LaB{sub 6}-filament was used. On the other hand, it was increased to more than 70 mA with much lower arc current of 150 A if Cs was seeded when a W-filament was used.« less
ISFET pH Sensitivity: Counter-Ions Play a Key Role.
Parizi, Kokab B; Xu, Xiaoqing; Pal, Ashish; Hu, Xiaolin; Wong, H S Philip
2017-02-02
The Field Effect sensors are broadly used for detecting various target analytes in chemical and biological solutions. We report the conditions under which the pH sensitivity of an Ion Sensitive Field Effect transistor (ISFET) sensor can be significantly enhanced. Our theory and simulations show that by using pH buffer solutions containing counter-ions that are beyond a specific size, the sensor shows significantly higher sensitivity which can exceed the Nernst limit. We validate the theory by measuring the pH response of an extended gate ISFET pH sensor. The consistency and reproducibility of the measurement results have been recorded in hysteresis free and stable operations. Different conditions have been tested to confirm the accuracy and validity of our experiment results such as using different solutions, various oxide dielectrics as the sensing layer and off-the-shelf versus IC fabricated transistors as the basis of the ISFET sensor.
NASA Astrophysics Data System (ADS)
Cherkashin, N.; Daghbouj, N.; Seine, G.; Claverie, A.
2018-04-01
Sequential He++H+ ion implantation, being more effective than the sole implantation of H+ or He+, is used by many to transfer thin layers of silicon onto different substrates. However, due to the poor understanding of the basic mechanisms involved in such a process, the implantation parameters to be used for the efficient delamination of a superficial layer are still subject to debate. In this work, by using various experimental techniques, we have studied the influence of the He and H relative depth-distributions imposed by the ion energies onto the result of the sequential implantation and annealing of the same fluence of He and H ions. Analyzing the characteristics of the blister populations observed after annealing and deducing the composition of the gas they contain from FEM simulations, we show that the trapping efficiency of He atoms in platelets and blisters during annealing depends on the behavior of the vacancies generated by the two implants within the H-rich region before and after annealing. Maximum efficiency of the sequential ion implantation is obtained when the H-rich region is able to trap all implanted He ions, while the vacancies it generated are not available to favor the formation of V-rich complexes after implantation then He-filled nano-bubbles after annealing. A technological option is to implant He+ ions first at such an energy that the damage it generates is located on the deeper side of the H profile.
Rozendal, R A; Sleutels, T H J A; Hamelers, H V M; Buisman, C J N
2008-01-01
Previous studies have shown that the application of cation exchange membranes (CEMs) in bioelectrochemical systems running on wastewater can cause operational problems. In this paper the effect of alternative types of ion exchange membrane is studied in biocatalyzed electrolysis cells. Four types of ion exchange membranes are used: (i) a CEM, (ii) an anion exchange membrane (AEM), (iii) a bipolar membrane (BPM), and (iv) a charge mosaic membrane (CMM). With respect to the electrochemical performance of the four biocatalyzed electrolysis configurations, the ion exchange membranes are rated in the order AEM > CEM > CMM > BPM. However, with respect to the transport numbers for protons and/or hydroxyl ions (t(H/OH)) and the ability to prevent pH increase in the cathode chamber, the ion exchange membranes are rated in the order BPM > AEM > CMM > CEM.
ISFET pH Sensitivity: Counter-Ions Play a Key Role
Parizi, Kokab B.; Xu, Xiaoqing; Pal, Ashish; Hu, Xiaolin; Wong, H. S. Philip
2017-01-01
The Field Effect sensors are broadly used for detecting various target analytes in chemical and biological solutions. We report the conditions under which the pH sensitivity of an Ion Sensitive Field Effect transistor (ISFET) sensor can be significantly enhanced. Our theory and simulations show that by using pH buffer solutions containing counter-ions that are beyond a specific size, the sensor shows significantly higher sensitivity which can exceed the Nernst limit. We validate the theory by measuring the pH response of an extended gate ISFET pH sensor. The consistency and reproducibility of the measurement results have been recorded in hysteresis free and stable operations. Different conditions have been tested to confirm the accuracy and validity of our experiment results such as using different solutions, various oxide dielectrics as the sensing layer and off-the-shelf versus IC fabricated transistors as the basis of the ISFET sensor. PMID:28150700
Intrinsic H+ ion mobility in the rabbit ventricular myocyte
Vaughan-Jones, R D; Peercy, B E; Keener, J P; Spitzer, K W
2002-01-01
The intrinsic mobility of intracellular H+ ions was investigated by confocally imaging the longitudinal movement of acid inside rabbit ventricular myocytes loaded with the acetoxymethyl ester (AM) form of carboxy-seminaphthorhodafluor-1 (carboxy-SNARF-1). Acid was diffused into one end of the cell through a patch pipette filled with an isotonic KCl solution of pH 3.0. Intracellular H+ mobility was low, acid taking 20-30 s to move 40 μm down the cell. Inhibiting sarcolemmal Na+-H+ exchange with 1 mm amiloride had no effect on this time delay. Net Hi+ movement was associated with a longitudinal intracellular pH (pHi) gradient of up to 0.4 pH units. Hi+ movement could be modelled using the equations for diffusion, assuming an apparent diffusion coefficient for H+ ions (DappH) of 3.78 × 10−7 cm2 s−1, a value more than 300-fold lower than the H+ diffusion coefficient in a dilute, unbuffered solution. Measurement of the intracellular concentration of SNARF (≈400 μM) and its intracellular diffusion coefficient (0.9 × 10−7 cm2 s−1) indicated that the fluorophore itself exerted an insignificant effect (between 0.6 and 3.3 %) on the longitudinal movement of H+ equivalents inside the cell. The longitudinal movement of intracellular H+ is discussed in terms of a diffusive shuttling of H+ equivalents on high capacity mobile buffers which comprise about half (≈11 mm) of the total intrinsic buffering capacity within the myocyte (the other half being fixed buffer sites on low mobility, intracellular proteins). Intrinsic Hi+ mobility is consistent with an average diffusion coefficient for the intracellular mobile buffers (Dmob) of ≈9 × 10−7 cm2 s−1. PMID:12015426
Stationary-Afterglow measurements of dissociative recombination of H2D+ and HD2+ ions
NASA Astrophysics Data System (ADS)
Dohnal, Petr; Kalosi, Abel; Plasil, Radek; Johnsen, Rainer; Glosik, Juraj
2016-09-01
Binary recombination rate coefficients of H2D+ and HD2+ ions have been measured at a temperature of 80 K in an afterglow plasma experiment in which the fractional abundances of H3+, H2D+, HD2+, and D3+ ions were varied by adjusting the [D2]/([D2] + [H2]) ratio of the neutral gas. The fractional abundances of the four ion species during the afterglow and their rotational states were determined in situ by continuous-wave cavity ring-down absorption spectroscopy (CRDS), using overtone transitions from the ground vibrational states of the ions. The experimentally determined recombination rate coefficients will be compared to results of advanced theoretical calculations and to the known H3+ and D3+ recombination rate coefficients. We conclude that the recombination coefficients depend only weakly on the isotopic composition. Astrophysical implications of the measured recombination rate coefficients will be also discussed. Work supported by: Czech Science Foundation projects GACR 14-14649P, GACR 15-15077S, GACR P209/12/0233, and by Charles University in Prague Project Nr. GAUK 692214.
NASA Astrophysics Data System (ADS)
Mensah, Samuel; Abu-Safe, Husam; Naseem, Hameed; Gordon, Matt
2012-02-01
Ion energy distributions of sputtered Si particles have been measured by an energy-resolved mass spectrometer, and we correlate the results with measured thin film properties. The plasmas have been generated in a conventional magnetron chamber powered at 150W, 13.56MHz at hydrogen flow rates ranging from 0-25sccm. Various Hn^+, SiHn^+, SiHn fragments (with n = 1, 2, 3) together with Ar^+ and ArH^+ species were detected in the discharge. The most important species for the film deposition is SiHn with n = 0,1,2, and H fragments affect the hydrogen content in the material. The flux of Ar^+ decreases and that of ArH^+ increases when the hydrogen flow rate was increased. However both fluxes saturate at hydrogen flow rates above 15sccm. Plasma parameters, such as plasma potential Vp, electron density ne and electron energy Te, are measured with the Langmuir probe. The ion energy distribution (IED) of all prominent species in the plasma is measured with an energy resolved mass analyzer. The plasma parameters decreased with increasing hydrogen flow rate; Vp, ne and Te decreased from 36.5V, 7.2x10^15 m-3, 5.6eV to 32.8, 2.2x10^15m-3 and 3.8eV respectively. The ion energy of the heavy species, Ar, Ar^+, ArH, ArH^+, SiHn and SiHn^+ radicals have ion energies comparable to the plasma potential. Analysis of the IEDs shows an inter-dependence of the species and their contribution to the thin film growth and properties.
Vibrational Spectra of Cryogenic Peptide Ions Using H_2 Predissociation Spectroscopy
NASA Astrophysics Data System (ADS)
Leavitt, Christopher M.; Wolk, Arron B.; Kamrath, Michael Z.; Garand, Etienne; Johnson, Mark A.; van Stipdonk, Michael J.
2011-06-01
H_2 predissociation spectroscopy was used to collect the vibrational spectra of the model protonated peptides, GlyGly, GlySar, SarGly and SarSar (Gly=glycine and Sar=sarcosine). H_2 molecules were condensed onto protonated peptide ions in a quadrupole ion trap cooled to approximately 10 K. The resulting spectra yielded clearly resolved vibrational transitions throughout the mid IR region, 600-4200 Cm-1, with linewidths of approximately 6 Cm-1. Protonation nominally occurred on the amino terminus giving rise to an intramolecular H-bond between the protonated amine and the neighboring amide oxygen. The sarcosine containing peptides incorporate a methyl group onto either the amino group or the amide nitrogen causing the peptide backbone to adopt a different structure, resulting in the shifts in the amide I and II bands and the N-H stretches.
Effect of pH on ion current through conical nanopores
NASA Astrophysics Data System (ADS)
Chander, M.; Kumar, R.; Kumar, S.; Kumar, N.
2018-05-01
Here, we examined ionic current behavior of conical nanopores at different pH and a fixed ion concentration of potassium halide (KCl). Conical shaped nanopores have been developed by chemical etching technique in polyethylene terephthalate (PET) membrane/foil of thickness 12 micron. For this we employed a self-assembled electrochemical cell having two chambers and the foil was fitted in the centre of cell. The nanopores were produced in the foil using etching and stopping solutions. The experimental results show that ionic current rectification (ICR) occurs through synthesized conical nanopores. Further, ion current increases significantly with increase of voltage from the base side of nanopores to the tip side at fixed pH of electrolyte.
H.F. emission related to the Li+ ion beam injected into ionosphere - ``PLAZMA'' rocket experiment
NASA Astrophysics Data System (ADS)
Klos, Z.; Zbyszynski, Z.; Agafonov, U. F.; Managadze, G. G.; Mayorov, A. D.
1993-10-01
The H.F. emission generated by artificial ion beam injected into ionosphere was observed either with a wave detector and ion gun attached to the rocket through out the flight, or when the gun was deployed on subpayload. Generally the observations show unstructured shape of the H.F. spectrum. In the PLAZMA active rocket experiment - when ionospheric plasma was perturbed by the operation of impulse ion gun, which injected 300 A, 8.3 eV Li+ions - the waves in the 0.1 - 10 MHz frequency range were observed. The results have shown, that when the wave detector and the ion gun are attached to the rocket the emission enhances in the lower as well as in the upper parts of the spectrum. On the other hand only the lower increase is maintained when ion gun is removing away on the subpayload. The observed sequence of H.F. spectra is presented.
Spatiotemporal pH dynamics in concentration polarization near ion-selective membranes.
Andersen, Mathias B; Rogers, David M; Mai, Junyu; Schudel, Benjamin; Hatch, Anson V; Rempe, Susan B; Mani, Ali
2014-07-08
We present a detailed analysis of the transient pH dynamics for a weak, buffered electrolyte subject to voltage-driven transport through an ion-selective membrane. We show that pH fronts emanate from the concentration polarization zone next to the membrane and that these propagating fronts change the pH in the system several units from its equilibrium value. The analysis is based on a 1D model using the unsteady Poisson-Nernst-Planck equations with nonequilibrium chemistry and without assumptions of electroneutrality or asymptotically thin electric double layers. Nonequilibrium chemical effects, especially for water splitting, are shown to be important for the dynamical and spatiotemporal evolution of the pH fronts. Nonetheless, the model also shows that at steady state the assumption of chemical equilibrium can still lead to good approximations of the global pH distribution. Moreover, our model shows that the transport of the hydronium ion in the extended space charge region is governed by a balance between electromigration and water self-ionization. On the basis of this observation, we present a simple model showing that the net flux of the hydronium ion is proportional to the length of the extended space charge region and the water self-ionization rate. To demonstrate these effects in practice, we have adopted the experiment of Mai et al. (Mai, J.; Miller, H.; Hatch, A. V. Spatiotemporal Mapping of Concentration Polarization Induced pH Changes at Nanoconstrictions. ACS Nano 2012, 6, 10206) as a model problem, and by including the full chemistry and transport, we show that the present model can capture the experimentally observed pH fronts. Our model can, among other things, be used to predict and engineer pH dynamics, which can be essential to the performance of membrane-based systems for biochemical separation and analysis.
Novel H+-Ion Sensor Based on a Gated Lateral BJT Pair
Yuan, Heng; Zhang, Jixing; Cao, Chuangui; Zhang, Gangyuan; Zhang, Shaoda
2015-01-01
An H+-ion sensor based on a gated lateral bipolar junction transistor (BJT) pair that can operate without the classical reference electrode is proposed. The device is a special type of ion-sensitive field-effect transistor (ISFET). Classical ISFETs have the advantage of miniaturization, but they are difficult to fabricate by a single fabrication process because of the bulky and brittle reference electrode materials. Moreover, the reference electrodes need to be separated from the sensor device in some cases. The proposed device is composed of two gated lateral BJT components, one of which had a silicide layer while the other was without the layer. The two components were operated under the metal-oxide semiconductor field-effect transistor (MOSFET)-BJT hybrid mode, which can be controlled by emitter voltage and base current. Buffer solutions with different pH values were used as the sensing targets to verify the characteristics of the proposed device. Owing to their different sensitivities, both components could simultaneously detect the H+-ion concentration and function as a reference to each other. Per the experimental results, the sensitivity of the proposed device was found to be approximately 0.175 μA/pH. This experiment demonstrates enormous potential to lower the cost of the ISFET-based sensor technology. PMID:26703625
A 60 mA DC H- multi cusp ion source developed at TRIUMF
NASA Astrophysics Data System (ADS)
Jayamanna, K.; Ames, F.; Bylinskii, I.; Lovera, M.; Minato, B.
2018-07-01
This paper describes the latest high-current multi cusp type ion source developed at TRIUMF, which is capable of producing a negative hydrogen ion beam (H-) of 60 mA of direct current at 140V and 90A arc. The results achieved to date including emittance measurements and filament lifetime issues are presented. The low current version of this ion source is suitable for medical cyclotrons as well as accelerators and the high current version is intended for producing large neutral hydrogen beams for fusion research. The description of the source magnetic configuration, the electron filter profile and the differential pumping techniques given in the paper will allow the building of an arc discharge H- ion source with similar properties.
Theoretical infrared and electronic absorption spectra of C16H10 isomers, their ions and doubly ions
NASA Astrophysics Data System (ADS)
Naganathappa, Mahadevappa; Chaudhari, Ajay
2012-09-01
Polycyclic aromatic hydrocarbons (PAHs) or PAH-related molecules are considered to be responsible for the unidentified infrared (UIR) emission features at 3.3, 6.2, 7.7, 8.6 and 11.2 μm. However, the exact identification of PAH or PAH-related molecules is difficult. There have been several investigations on the spectroscopic characterization of PAH molecules. But none of them compared the spectra of isomers of PAHs, which might have help in the identification of the UIR emission features. This work presents the infrared and electronic absorption spectra of isomers of C16H10. The aim of the present work is to compare infrared and electronic absorption spectra of four isomers of C16H10 PAH viz. pyrene, aceanthrylene, acephenanthrylene and fluoranthene, their ions and doubly ions. We also compare the spectra of pyrene in the gas-phase and in H2O ice. We have used the density functional theory with B3LYP exchange and correlation functional and 6-311++g** basis set to study the infrared spectra. The time-dependent density functional theory (TDDFT) has been used to obtain the electronic absorption spectra. Significant difference in the CC stretching, CH in-plane bending and CH out-of-plane bending vibration modes is observed for the isomers of C16H10 whereas there is no large difference in the CH stretching vibration band. A significant change in the vibrational band is observed for pyrene in H2O ice compared to gas-phase pyrene. Though isomers of C16H10 PAH have the same number of carbon and hydrogen atoms, their spectroscopic characteristics are different. This study should help in identifying the isomers of C16H10, their ions and doubly cation in the interstellar medium.
Sze, Heven; Chanroj, Salil
2018-04-24
Plants remodel their cells through the dynamic endomembrane system. Intracellular pH is important for membrane trafficking, but the determinants of pH homeostasis are poorly defined in plants. Electrogenic proton (H+) pumps depend on counter-ion fluxes to establish transmembrane pH gradients at the plasma membrane and endomembranes. Vacuolar-type H+-ATPase-mediated acidification of the trans-Golgi network (TGN) is crucial for secretion and membrane recycling. Pump and counter-ion fluxes are unlikely to fine-tune pH; rather, alkali cation/H+ antiporters, which can alter pH and/or cation homeostasis locally and transiently, are prime candidates. Plants have a large family of predicted cation/H+ exchangers (CHX) of obscure function, in addition to the well-studied K+(Na+)/H+ exchangers (NHX). Here, we review the regulation of cytosolic and vacuolar pH, highlighting the similarities and distinctions of NHX and CHX members. In planta, alkalinization of the TGN or vacuole by NHXs promotes membrane trafficking, endocytosis, cell expansion, and growth. CHXs localize to endomembranes and/or the plasma membrane, contribute to male fertility, pollen tube guidance, pollen wall construction, stomatal opening, and in soybean (Glycine max), tolerance to salt stress. Three-dimensional structural models and mutagenesis of Arabidopsis thaliana genes have allowed us to infer that AtCHX17 and AtNHX1 share a global architecture and a translocation core like bacterial Na+/H+ antiporters. Yet the presence of distinct residues suggests some CHXs differ from NHXs in pH sensing and electrogenicity. How H+ pumps, counter-ion fluxes, and cation/H+ antiporters are linked with signaling and membrane trafficking to remodel membranes and cell walls awaits further investigation. {copyright, serif} 2018 American Society of Plant Biologists. All rights reserved.
MARVEL analysis of the rotational-vibrational states of the molecular ions H2D+ and D2H+.
Furtenbacher, Tibor; Szidarovszky, Tamás; Fábri, Csaba; Császár, Attila G
2013-07-07
Critically evaluated rotational-vibrational line positions and energy levels, with associated critically reviewed labels and uncertainties, are reported for two deuterated isotopologues of the H3(+) molecular ion: H2D(+) and D2H(+). The procedure MARVEL, standing for Measured Active Rotational-Vibrational Energy Levels, is used to determine the validated levels and lines and their self-consistent uncertainties based on the experimentally available information. The spectral ranges covered for the isotopologues H2D(+) and D2H(+) are 5.2-7105.5 and 23.0-6581.1 cm(-1), respectively. The MARVEL energy levels of the ortho and para forms of the ions are checked against ones determined from accurate variational nuclear motion computations employing the best available adiabatic ab initio potential energy surfaces of these isotopologues. The number of critically evaluated, validated and recommended experimental (levels, lines) are (109, 185) and (104, 136) for H2D(+) and D2H(+), respectively. The lists of assigned MARVEL lines and levels and variational levels obtained for H2D(+) and D2H(+) as part of this study are deposited in the ESI to this paper.
Autopilot regulation for the Linac4 H- ion source
NASA Astrophysics Data System (ADS)
Voulgarakis, G.; Lettry, J.; Mattei, S.; Lefort, B.; Costa, V. J. Correia
2017-08-01
Linac4 is a 160 MeV H- linear accelerator part of the upgrade of the LHC injector chain. Its cesiated surface H- source is designed to provide a beam intensity of 40-50mA. It is operated with periodical Cs-injection at typically 30 days intervals [1] and this implies that the beam parameters will slowly evolve during operation. Autopilot is a control software package extending CERN developed Inspector framework. The aim of Autopilot is to automatize the mandatory optimization and cesiation processes and to derive performance indicators, thus keeping human intervention minimal. Autopilot has been developed by capitalizing on the experience from manually operating the source. It comprises various algorithms running in real-time, which have been devised to: • Optimize the ion source performance by regulation of H2 injection, RF power and frequency. • Describe the performance of the source with performance indicators, which can be easily understood by operators. • Identify failures, try to recover the nominal operation and send warning in case of deviation from nominal operation. • Make the performance indicators remotely available through Web pages.Autopilot is at the same level of hierarchy as an operator, in the CERN infrastructure. This allows the combination of all ion source devices, providing the required flexibility. Autopilot is executed in a dedicated server, ensuring unique and centralized control, yet allowing multiple operators to interact at runtime, always coordinating between them. Autopilot aims at flexibility, adaptability, portability and scalability, and can be extended to other components of CERN's accelerators. In this paper, a detailed description of the Autopilot algorithms is presented, along with first results of operating the Linac4 H- Ion Source with Autopilot.
Cooperative effect of pH-dependent ion transport within two symmetric-structured nanochannels.
Meng, Zheyi; Chen, Yang; Li, Xiulin; Xu, Yanglei; Zhai, Jin
2015-04-15
A novel and simple design is introduced to construct bichannel nanofluid diodes by combining two poly(ethylene terephthalate) (PET) films with columnar nanochannel arrays varying in size or in surface charge. This type of bichannel device performs obvious ion current rectification, and the pH-dependent tunability and degree of rectification can be improved by histidine modification. The origin of the ion current rectification and its pH-dependent tunability are attributed to the cooperative effect of the two columnar half-channels and the applied bias on the mobile ions. As a result of surface groups on the bichannel being charged with different polarities or degrees at different pH values, the function of the bichannel device can be converted from a nanofluid diode to a normal nanochannel or to a reverse diode.
Measurement of H/H+D Ratio and Recycling in Ion Cyclotron Resonance Heating HT-6M Tokamak
NASA Astrophysics Data System (ADS)
Ding, Liancheng; Jiang, Guangkuan; Wei, Lehan
1994-12-01
A scanning Fabry-Perot interferometer has been used to measure the Hα and Dα lines obtain the H/H+D ratio in ion cyclotron resonance heating HT-6M tokamak for determing the energy absorption mechanism. The recycling is observed by changing the working gas from deuterium to hydrogen.
Smith, David; Chippendale, Thomas W E; Španěl, Patrik
2014-09-15
It has been shown that aldehydes are often present in biogenic media. For their analysis by selected ion flow tube mass spectrometry (SIFT-MS), the rate coefficients and the product ion distributions for the reactions of the analyte ions H3O(+) and NO(+) with volatile aldehydes in the presence of water vapour are required. The reactions of H3O(+) and NO(+) ions have been studied with a series of n-aldehydes ranging from acetaldehyde (designated as C2), through undecanal (C11) under the conditions used for SIFT-MS analyses (1 Torr He, 0.1 Torr air sample, 300 K) and over a range of sample gas absolute humidity from 1% to 7%. For comparison, the C5 pentanal isomer 3-methyl butanal, the unsaturated trans-2-pentenal and trans-2-octenal and the aromatic benzaldehyde were also included in the study. The H3O(+) reactions led to the formation of protonated molecules MH(+) and their hydrates MH(+)(H2O)0,1,2,3 , and (MH(+)-H2O). The NO(+) reactions resulted in the production of NO(+)M adduct ions and of [M-H](+) fragment ions. The percentages of the different product ions for each aldehyde are seen to be dependent on the air sample humidity. Kinetic modelling was used to quantitatively explain these observations and to obtain rate coefficients for the association reactions producing NO(+) M adduct ions. This detailed study has provided the kinetics data, in particular the product ion distributions, for the reactions of a number of volatile aldehydes, which allows their analyses by SIFT-MS in humid air, including exhaled breath, food emanations and other biogenic media. Copyright © 2014 John Wiley & Sons, Ltd.
Evaluation of pH and calcium ion diffusion from calcium hydroxide pastes and MTA.
Sáez, María Del M; López, Gabriela L; Atlas, Diana; de la Casa, María L
2017-04-01
The aim of this ex vivo study was to evaluate changes in pH and calcium ion diffusion through root dentin from calcium hydroxide (Ca (OH) 2 ) and mineral trioxide aggregate (MTA) pastes at 7, 30 and 60 days; and the relationship between pH and ion diffusion. Thirty-two human premolars were used. Crowns were sectioned and root canals instrumented and filled in with the following preparations: 1) Ca(OH) 2 + distilled water (n=7); 2) Ca(OH) 2 + 0.1% chlorhexidine gluconate (n=7); 3) MTA + distilled water (n=7); 4) MTA + 0.1% chlorhexidine gluconate (CHX) (n=7); 5) distilled water (n=2) (control); 6) 0.1% chlorhexidine gluconate (n=2) (control). The apex and coronary opening were sealed with IRM. Roots were placed in Eppendorf tubes with 1 ml distilled water at 37°C and 100% humidity. At baseline, 7, 30 and 60 days, pH was measured with pH meter, and calcium ion content in the solution was analyzed by atomic absorption spectrophotometry. The data were statistically analyzed using ANOVA, simple linear regression analysis and Pearson's correlation test. The highest pH values were achieved with calcium hydroxide pastes at 60 days (p ≤ 0.05). Calcium ions were released in all groups. The calcium hydroxide paste with distilled water at 60 days had the highest calcium ion value (p ≤ 0.01). There was a positive correlation between calcium and pH values. Sociedad Argentina de Investigación Odontológica.
Petrović, Z Lj; Phelps, A V
2009-12-01
Absolute spectral emissivities for Doppler broadened H(alpha) profiles are measured and compared with predictions of energetic hydrogen ion, atom, and molecule behavior in low-current electrical discharges in H2 at very high electric field E to gas density N ratios E/N and low values of Nd , where d is the parallel-plate electrode separation. These observations reflect the energy and angular distributions for the excited atoms and quantitatively test features of multiple-scattering kinetic models in weakly ionized hydrogen in the presence of an electric field that are not tested by the spatial distributions of H(alpha) emission. Absolute spectral intensities agree well with predictions. Asymmetries in Doppler profiles observed parallel to the electric field at 4
Freestanding ultrathin single-crystalline SiC substrate by MeV H ion-slicing
NASA Astrophysics Data System (ADS)
Jia, Qi; Huang, Kai; You, Tiangui; Yi, Ailun; Lin, Jiajie; Zhang, Shibin; Zhou, Min; Zhang, Bin; Zhang, Bo; Yu, Wenjie; Ou, Xin; Wang, Xi
2018-05-01
SiC is a widely used wide-bandgap semiconductor, and the freestanding ultrathin single-crystalline SiC substrate provides the material platform for advanced devices. Here, we demonstrate the fabrication of a freestanding ultrathin single-crystalline SiC substrate with a thickness of 22 μm by ion slicing using 1.6 MeV H ion implantation. The ion-slicing process performed in the MeV energy range was compared to the conventional case using low-energy H ion implantation in the keV energy range. The blistering behavior of the implanted SiC surface layer depends on both the implantation temperature and the annealing temperature. Due to the different straggling parameter for two implant energies, the distribution of implantation-induced damage is significantly different. The impact of implantation temperature on the high-energy and low-energy slicing was opposite, and the ion-slicing SiC in the MeV range initiates at a much higher temperature.
Chemical sputtering by H{sub 2}{sup +} and H{sub 3}{sup +} ions during silicon deposition
DOE Office of Scientific and Technical Information (OSTI.GOV)
Landheer, K., E-mail: c.landheer@uu.nl; Poulios, I.; Rath, J. K.
2016-08-07
We investigated chemical sputtering of silicon films by H{sub y}{sup +} ions (with y being 2 and 3) in an asymmetric VHF Plasma Enhanced Chemical Vapor Deposition (PECVD) discharge in detail. In experiments with discharges created with pure H{sub 2} inlet flows, we observed that more Si was etched from the powered than from the grounded electrode, and this resulted in a net deposition on the grounded electrode. With experimental input data from a power density series of discharges with pure H{sub 2} inlet flows, we were able to model this process with a chemical sputtering mechanism. The obtained chemicalmore » sputtering yields were (0.3–0.4) ± 0.1 Si atom per bombarding H{sub y}{sup +} ion at the grounded electrode and at the powered electrode the yield ranged from (0.4 to 0.65) ± 0.1. Subsequently, we investigated the role of chemical sputtering during PECVD deposition with a series of silane fractions S{sub F} (S{sub F}(%) = [SiH{sub 4}]/[H{sub 2}]*100) ranging from S{sub F} = 0% to 20%. We experimentally observed that the SiH{sub y}{sup +} flux is not proportional to S{sub F} but decreasing from S{sub F} = 3.4% to 20%. This counterintuitive SiH{sub y}{sup +} flux trend was partly explained by an increasing chemical sputtering rate with decreasing S{sub F} and partly by the reaction between H{sub 3}{sup +} and SiH{sub 4} that forms SiH{sub 3}{sup +}.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Petrov, M.P.; Bell, R.; Budny, R.V.
1998-07-01
This paper presents studies of ICRF-driven H+ minority ions in TFTR (Tokamak Fusion Test Reator) deuterium plasmas using primarily passive Ho flux detection in the energy range of 0.2-1.0 MeV with some corroborating active (lithium pellet charge exchange) measurements. It is shown that in the passive mode the main donors for the neutralization of H+ ions in this energy range are C5+ ions. The measured effective H+ tail temperatures range from 0.15 MeV at an ICRF power of 2 MW to 0.35 MeV at 6 MW. Analysis of the ICRF-driven H+ ion energy balance has been performed on the basismore » of the dependence of effective H+ temperatures on the plasma parameters. The analysis showed that H+ confinement times are comparable with their slowing-down times and tended to decrease with increasing ICRF power. Radial redistribution of ICRF-driven H+ ions was detected when giant sawtooth crashes occurred during the ICRF heating. The redistribution affected ions with energy below 0.7-0.8 MeV. The sawtooth crashes displace H+ ions outward along the plasma major radius into the stochastic ripple diffusion domain were those ions are lost in about 10 milliseconds. These observations are consistent with the model of the redistribution of energetic particles developed previously to explain the results of deuterium-tritium alpha-particle redistribution due to sawteeth observed in TFTR. The experimental data are also consistent with ORBIT code simulations of H+ stochastic ripple diffusion losses.« less
H- and He-like Charge-Exchange Induced X-ray Emission due to Ion Collisions with H, He, and H2
NASA Astrophysics Data System (ADS)
Cumbee, Renata; Mullen, Patrick; Miller, Ansley; Lyons, David; Shelton, Robin L.; Schultz, David R.; Stancil, Phillip C.; Leutenegger, Maurice A.
2017-08-01
When a hot plasma collides with a cold neutral gas interactions occur between the microscopic constituents including charge exchange (CX). CX is a process in which an electron can be transferred from a neutral atom or molecule into an excited energy level of an ion. Following this transfer, the excited electron relaxes to lower energy levels, emitting X-rays. This process has been established as a primary source of X-ray emission within our solar system, such as when the solar wind interacts with cometary and planetary atmospheres, and outside of our solar system, such as in the hot outflows of starburst galaxies.Since the CX X-ray emission spectrum varies greatly with collision velocity, it is critical that realistic CX data are included in X-ray spectral models of astrophysical environments in which CX might be significant in order to correctly estimate the ion abundance and plasma velocities. Here, line ratios and spectra are computed using theoretical CX cross sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for a variety of collision energies relevant to various astrophysical environments. Collisions of bare and H-like C, N, O, Ne, Mg, Al, Si, P, S, and Cl ions are shown with H, He, and H2 as the neutral collision targets. An X-ray model using line ratios for C-Si ions is then performed within XSPEC for a region of the Cygnus Loop supernova remnant for 8 collision energies in order to highlight the variation in CX spectral models with collision energy.R. Cumbee’s research was partially supported by an appointment to the NASA Postdoctoral Program at NASA GSFC, administered by Universities Space Research Association under contract with NASA. Work at UGA was partially supported by NASA grants NNX09AC46G and NNG09WF24I.
Investigations on caesium-free alternatives for H{sup −} formation at ion source relevant parameters
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kurutz, U.; Fantz, U.; AG Experimentelle Plasmaphysik, Institut für Physik, Universität Augsburg, 86135 Augsburg
2015-04-08
Negative hydrogen ions are efficiently produced in ion sources by the application of caesium. Due to a thereby induced lowering of the work function of a converter surface a direct conversion of impinging hydrogen atoms and positive ions into negative ions is maintained. However, due to the complex caesium chemistry and dynamics a long-term behaviour is inherent for the application of caesium that affects the stability and reliability of negative ion sources. To overcome these drawbacks caesium-free alternatives for efficient negative ion formation are investigated at the flexible laboratory setup HOMER (HOMogenous Electron cyclotron Resonance plasma). By the usage ofmore » a meshed grid the tandem principle is applied allowing for investigations on material induced negative ion formation under plasma parameters relevant for ion source operation. The effect of different sample materials on the ratio of the negative ion density to the electron density n{sub H{sup −}} /n{sub e} is compared to the effect of a stainless steel reference sample and investigated by means of laser photodetachment in a pressure range from 0.3 to 3 Pa. For the stainless steel sample no surface induced effect on the negative ion density is present and the measured negative ion densities are resulting from pure volume formation and destruction processes. In a first step the dependency of n{sub H{sup −}} /n{sub e} on the sample distance has been investigated for a caesiated stainless steel sample. At a distance of 0.5 cm at 0.3 Pa the density ratio is 3 times enhanced compared to the reference sample confirming the surface production of negative ions. In contrast for the caesium-free material samples, tantalum and tungsten, the same dependency on pressure and distance n{sub H{sup −}} /n{sub e} like for the stainless steel reference sample were obtained within the error margins: A density ratio of around 14.5% is measured at 4.5 cm sample distance and 0.3 Pa, linearly
Wang, Huixin; Wang, Bing; Wei, Zhonglin; Zhang, Hao; Guo, Xinhua
2015-01-01
A good understanding of gas-phase fragmentation chemistry of peptides is important for accurate protein identification. Additional product ions obtained by sodiated peptides can provide useful sequence information supplementary to protonated peptides and improve protein identification. In this work, we first demonstrate that the sodiated a3 ions are abundant in the tandem mass spectra of sodium-cationized peptides although observations of a3 ions have rarely been reported in protonated peptides. Quantum chemical calculations combined with tandem mass spectrometry are used to investigate this phenomenon by using a model tetrapeptide GGAG. Our results reveal that the most stable [a3 + Na - H](+) ion is present as a bidentate linear structure in which the sodium cation coordinates to the two backbone carbonyl oxygen atoms. Due to structural inflexibility, further fragmentation of the [a3 + Na - H](+) ion needs to overcome several relatively high energetic barriers to form [b2 + Na - H](+) ion with a diketopiperazine structure. As a result, low abundance of [b2 + Na - H](+) ion is detected at relatively high collision energy. In addition, our computational data also indicate that the common oxazolone pathway to generate [b2 + Na - H](+) from the [a3 + Na - H](+) ion is unlikely. The present work provides a mechanistic insight into how a sodium ion affects the fragmentation behaviors of peptides. Copyright © 2015 John Wiley & Sons, Ltd.
Fulzele, Punit; Baliga, Sudhindra; Thosar, Nilima; Pradhan, Debaprya
2011-01-01
Aims: Evaluation of calcium ion and hydroxyl ion release and pH levels in various calcium hydroxide based intracanal medicaments. Objective: The purpose of this study was to evaluate calcium and hydroxyl ion release and pH levels of calcium hydroxide based products, namely, RC Cal, Metapex, calcium hydroxide with distilled water, along with the new gutta-percha points with calcium hydroxide. Materials and Methods: The materials were inserted in polyethylene tubes and immersed in deionized water. The pH variation, Ca++ and OH- release were monitored periodically for 1 week. Statistical Analysis Used: Statistical analysis was carried out using one-way analysis of variance and Tukey's post hoc tests with PASW Statistics version 18 software to compare the statistical difference. Results: After 1 week, calcium hydroxide with distilled water and RC Cal raised the pH to 12.7 and 11.8, respectively, while a small change was observed for Metapex, calcium hydroxide gutta-percha points. The calcium released after 1 week was 15.36 mg/dL from RC Cal, followed by 13.04, 1.296, 3.064 mg/dL from calcium hydroxide with sterile water, Metapex and calcium hydroxide gutta-percha points, respectively. Conclusions: Calcium hydroxide with sterile water and RC Cal pastes liberate significantly more calcium and hydroxyl ions and raise the pH higher than Metapex and calcium hydroxidegutta-percha points. PMID:22346155
Numerical modeling of the SNS H{sup −} ion source
DOE Office of Scientific and Technical Information (OSTI.GOV)
Veitzer, Seth A.; Beckwith, Kristian R. C.; Kundrapu, Madhusudhan
Ion source rf antennas that produce H- ions can fail when plasma heating causes ablation of the insulating coating due to small structural defects such as cracks. Reducing antenna failures that reduce the operating capabilities of the Spallation Neutron Source (SNS) accelerator is one of the top priorities of the SNS H- Source Program at ORNL. Numerical modeling of ion sources can provide techniques for optimizing design in order to reduce antenna failures. There are a number of difficulties in developing accurate models of rf inductive plasmas. First, a large range of spatial and temporal scales must be resolved inmore » order to accurately capture the physics of plasma motion, including the Debye length, rf frequencies on the order of tens of MHz, simulation time scales of many hundreds of rf periods, large device sizes on tens of cm, and ion motions that are thousands of times slower than electrons. This results in large simulation domains with many computational cells for solving plasma and electromagnetic equations, short time steps, and long-duration simulations. In order to reduce the computational requirements, one can develop implicit models for both fields and particle motions (e.g. divergence-preserving ADI methods), various electrostatic models, or magnetohydrodynamic models. We have performed simulations using all three of these methods and have found that fluid models have the greatest potential for giving accurate solutions while still being fast enough to perform long timescale simulations in a reasonable amount of time. We have implemented a number of fluid models with electromagnetics using the simulation tool USim and applied them to modeling the SNS H- ion source. We found that a reduced, single-fluid MHD model with an imposed magnetic field due to the rf antenna current and the confining multi-cusp field generated increased bulk plasma velocities of > 200 m/s in the region of the antenna where ablation is often observed in the SNS source. We
The effect of ions on the magnetic moment of vacancy for ion-implanted 4H-SiC
NASA Astrophysics Data System (ADS)
Peng, B.; Zhang, Y. M.; Dong, L. P.; Wang, Y. T.; Jia, R. X.
2017-04-01
The structural properties and the spin states of vacancies in ion implanted silicon carbide samples are analyzed by experimental measurements along with first-principles calculations. Different types and dosages of ions (N+, O+, and B+) were implanted in the 4H-silicon carbide single crystal. The Raman spectra, positron annihilation spectroscopy, and magnetization-magnetic field curves of the implanted samples were measured. The fitting results of magnetization-magnetic field curves reveal that samples implanted with 1 × 1016 cm-2 N+ and O+ ions generate paramagnetic centers with various spin states of J = 1 and J = 0.7, respectively. While for other implanted specimens, the spin states of the paramagnetic centers remain unchanged compared with the pristine sample. According to the positron annihilation spectroscopy and first-principles calculations, the change in spin states originates from the silicon vacancy carrying a magnetic moment of 3.0 μB in the high dosage N-implanted system and 2.0 μB in the O-doped system. In addition, the ratio of the concentration of implanted N ions and silicon vacancies will affect the magnetic moment of VSi. The formation of carbon vacancy which does not carry a local magnetic moment in B-implanted SiC can explain the invariability in the spin states of the paramagnetic centers. These results will help to understand the magnetic moments of vacancies in ion implanted 4H-SiC and provide a possible routine to induce vacancies with high spin states in SiC for the application in quantum technologies and spintronics.
A genetically-encoded chloride and pH sensor for dissociating ion dynamics in the nervous system.
Raimondo, Joseph V; Joyce, Bradley; Kay, Louise; Schlagheck, Theresa; Newey, Sarah E; Srinivas, Shankar; Akerman, Colin J
2013-01-01
Within the nervous system, intracellular Cl(-) and pH regulate fundamental processes including cell proliferation, metabolism, synaptic transmission, and network excitability. Cl(-) and pH are often co-regulated, and network activity results in the movement of both Cl(-) and H(+). Tools to accurately measure these ions are crucial for understanding their role under physiological and pathological conditions. Although genetically-encoded Cl(-) and pH sensors have been described previously, these either lack ion specificity or are unsuitable for neuronal use. Here we present ClopHensorN-a new genetically-encoded ratiometric Cl(-) and pH sensor that is optimized for the nervous system. We demonstrate the ability of ClopHensorN to dissociate and simultaneously quantify Cl(-) and H(+) concentrations under a variety of conditions. In addition, we establish the sensor's utility by characterizing activity-dependent ion dynamics in hippocampal neurons.
Computational Tools for Interpreting Ion Channel pH-Dependence.
Sazanavets, Ivan; Warwicker, Jim
2015-01-01
Activity in many biological systems is mediated by pH, involving proton titratable groups with pKas in the relevant pH range. Experimental analysis of pH-dependence in proteins focusses on particular sidechains, often with mutagenesis of histidine, due to its pKa near to neutral pH. The key question for algorithms that predict pKas is whether they are sufficiently accurate to effectively narrow the search for molecular determinants of pH-dependence. Through analysis of inwardly rectifying potassium (Kir) channels and acid-sensing ion channels (ASICs), mutational effects on pH-dependence are probed, distinguishing between groups described as pH-coupled or pH-sensor. Whereas mutation can lead to a shift in transition pH between open and closed forms for either type of group, only for pH-sensor groups does mutation modulate the amplitude of the transition. It is shown that a hybrid Finite Difference Poisson-Boltzmann (FDPB) - Debye-Hückel continuum electrostatic model can filter mutation candidates, providing enrichment for key pH-coupled and pH-sensor residues in both ASICs and Kir channels, in comparison with application of FDPB alone.
Computational Tools for Interpreting Ion Channel pH-Dependence
Sazanavets, Ivan; Warwicker, Jim
2015-01-01
Activity in many biological systems is mediated by pH, involving proton titratable groups with pKas in the relevant pH range. Experimental analysis of pH-dependence in proteins focusses on particular sidechains, often with mutagenesis of histidine, due to its pKa near to neutral pH. The key question for algorithms that predict pKas is whether they are sufficiently accurate to effectively narrow the search for molecular determinants of pH-dependence. Through analysis of inwardly rectifying potassium (Kir) channels and acid-sensing ion channels (ASICs), mutational effects on pH-dependence are probed, distinguishing between groups described as pH-coupled or pH-sensor. Whereas mutation can lead to a shift in transition pH between open and closed forms for either type of group, only for pH-sensor groups does mutation modulate the amplitude of the transition. It is shown that a hybrid Finite Difference Poisson-Boltzmann (FDPB) – Debye-Hückel continuum electrostatic model can filter mutation candidates, providing enrichment for key pH-coupled and pH-sensor residues in both ASICs and Kir channels, in comparison with application of FDPB alone. PMID:25915903
Apolipoprotein L1 confers pH-switchable ion permeability to phospholipid vesicles.
Bruno, Jonathan; Pozzi, Nicola; Oliva, Jonathan; Edwards, John C
2017-11-03
Apolipoprotein L1 (ApoL1) is a human serum protein conferring resistance to African trypanosomes, and certain ApoL1 variants increase susceptibility to some progressive kidney diseases. ApoL1 has been hypothesized to function like a pore-forming colicin and has been reported to have permeability effects on both intracellular and plasma membranes. Here, to gain insight into how ApoL1 may function in vivo , we used vesicle-based ion permeability, direct membrane association, and intrinsic fluorescence to study the activities of purified recombinant ApoL1. We found that ApoL1 confers chloride-selective permeability to preformed phospholipid vesicles and that this selectivity is strongly pH-sensitive, with maximal activity at pH 5 and little activity above pH 7. When ApoL1 and lipid were allowed to interact at low pH and were then brought to neutral pH, chloride permeability was suppressed, and potassium permeability was activated. Both chloride and potassium permeability linearly correlated with the mass of ApoL1 in the reaction mixture, and both exhibited lipid selectivity, requiring the presence of negatively charged lipids for activity. Potassium, but not chloride, permease activity required the presence of calcium ions in both the association and activation steps. Direct assessment of ApoL1-lipid associations confirmed that ApoL1 stably associates with phospholipid vesicles, requiring low pH and the presence of negatively charged phospholipids for maximal binding. Intrinsic fluorescence of ApoL1 supported the presence of a significant structural transition when ApoL1 is mixed with lipids at low pH. This pH-switchable ion-selective permeability may explain the different effects of ApoL1 reported in intracellular and plasma membrane environments. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
L-H transitions driven by ion heating in scrape-off layer turbulence (SOLT) model simulations
NASA Astrophysics Data System (ADS)
Russell, D. A.; D'Ippolito, D. A.; Myra, J. R.
2015-11-01
The original SOLT model now includes the evolution of ion pressure consistent with drift-ordering. It is a two-dimensional, electrostatic reduced model wherein closure relations, obtained by integrating the equations along the B-field, model parallel physics that includes sheath-mediated current and heat flux in the scrape-off-layer and electron drift waves inside the separatrix. Low (L) and high (H) confinement regimes are observed in SOLT simulations, depending on the strength of an ion pressure (i.e., ion heating) source localized inside the separatrix: With increasing heating, particle and energy confinement times at first decrease in the L-mode then rise in the H-mode. The L-H transition is marked by distinct changes in sheared-flow profiles. The addition of ion pressure dynamics enables modeling the self-consistent interaction between the ion diamagnetic drift and the radial electric field (mean and zonal flows). The roles of these sheared flows in mediating the L-H transition are explored. A new diagnostic, based on the density correlation function, is applied to study blob velocities in different regimes. Work supported by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences, under Award Number DE-FG02-97ER54392.
Recombination of H3(+) and D3(+) Ions in a Flowing Afterglow Plasma
NASA Technical Reports Server (NTRS)
Gougousi, T.; Johnsen, R.; Golde, M. F.
1995-01-01
The analysis of flowing afterglow plasmas containing H3(+) or D3(+) ions indicates that the de-ionization of such plasmas does not occur by simple dissociative recombination of ions with electrons. An alternative model of de-ionization is proposed in which electrons are captured into H3(**) auto-ionization Rydberg states that are stabilized by collisional mixing of the Rydberg molecules' angular momenta. The proposed mechanism would enable de-ionization to occur without the need for dissociative recombination by the mechanisms of potential-surface crossings.
Kim, Tae-Seong; Kim, Jinchoon; In, Sang Ryul; Jeong, Seung Ho
2008-02-01
Prototype long pulse ion sources are being developed and tested toward the goal of a deuterium beam extraction of 120 keV/65 A. The latest prototype source consists of a magnetic bucket plasma generator and a four-grid copper accelerator system with multicircular apertures of 568 holes. To measure the angular divergence and the ion species of the ion beam, an optical multichannel analyzer (OMA) system for a Doppler-shifted H-alpha lights was set up at the end of a gas-cell neutralizer. But the OMA data are very difficult to analyze due to a large background level on the top of the three energy peaks (coming from H(+), H(2) (+), and H(3) (+)). These background spectra in the OMA signals seem to result from partially accelerated ion beams in the accelerator. Extracted ions could undergo a premature charge exchange as the accelerator column tends to have a high hydrogen partial pressure from the unused gas from the plasma generator, resulting in a continuous background of partially accelerated beam particles at the accelerator exit. This effect is calculated by accounting for all the possible atomic collision processes and numerically summing up three ion species across the accelerator column. The collection of all the atomic reaction cross sections and the numerical summing up will be presented. The result considerably depends on the background pressure and the ion beam species ratio (H(+), H(2) (+), and H(3) (+)). This effect constitutes more than 20% of the whole particle distribution. And the energy distribution of those suffering from collisions is broad and shows a broad maximum in the vicinity of the half and the third energy region.
rf improvements for Spallation Neutron Source H- ion sourcea)
NASA Astrophysics Data System (ADS)
Kang, Y. W.; Fuja, R.; Goulding, R. H.; Hardek, T.; Lee, S.-W.; McCarthy, M. P.; Piller, M. C.; Shin, K.; Stockli, M. P.; Welton, R. F.
2010-02-01
The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering ˜38 mA H- beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.
rf improvements for Spallation Neutron Source H- ion source.
Kang, Y W; Fuja, R; Goulding, R H; Hardek, T; Lee, S-W; McCarthy, M P; Piller, M C; Shin, K; Stockli, M P; Welton, R F
2010-02-01
The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering approximately 38 mA H(-) beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.
A genetically-encoded chloride and pH sensor for dissociating ion dynamics in the nervous system
Raimondo, Joseph V.; Joyce, Bradley; Kay, Louise; Schlagheck, Theresa; Newey, Sarah E.; Srinivas, Shankar; Akerman, Colin J.
2013-01-01
Within the nervous system, intracellular Cl− and pH regulate fundamental processes including cell proliferation, metabolism, synaptic transmission, and network excitability. Cl− and pH are often co-regulated, and network activity results in the movement of both Cl− and H+. Tools to accurately measure these ions are crucial for understanding their role under physiological and pathological conditions. Although genetically-encoded Cl− and pH sensors have been described previously, these either lack ion specificity or are unsuitable for neuronal use. Here we present ClopHensorN—a new genetically-encoded ratiometric Cl− and pH sensor that is optimized for the nervous system. We demonstrate the ability of ClopHensorN to dissociate and simultaneously quantify Cl− and H+ concentrations under a variety of conditions. In addition, we establish the sensor's utility by characterizing activity-dependent ion dynamics in hippocampal neurons. PMID:24312004
NASA Astrophysics Data System (ADS)
Tanaka, K.; Nagaoka, K.; Murakami, S.; Takahashi, H.; Osakabe, M.; Yokoyama, M.; Seki, R.; Michael, C. A.; Yamaguchi, H.; Suzuki, C.; Shimizu, A.; Tokuzawa, T.; Yoshinuma, M.; Akiyama, T.; Ida, K.; Yamada, I.; Yasuhara, R.; Funaba, H.; Kobayashi, T.; Yamada, H.; Du, X. D.; Vyacheslavov, L. N.; Mikkelsen, D. R.; Yun, G. S.; the LHD Experimental Group
2017-11-01
Surveys of the ion and electron heat transports of neutral beam (NB) heating plasma were carried out by power balance analysis in He and H rich plasma at LHD. Collisionality was scanned by changing density and heating power. The characteristics of the transport vary depending on collisionality. In low collisionality, with low density and high heating power, an ion internal transport barrier (ITB) was formed. The ion heat conductivity (χ i) is lower than electron heat conductivity (χ e) in the core region at ρ < 0.7. On the other hand, in high collisionality, with high density and low heating power, χ i is higher than χ e across the entire range of plasma. These different confinement regimes are associated with different fluctuation characteristics. In ion ITB, fluctuation has a peak at ρ = 0.7, and in normal confinement, fluctuation has a peak at ρ = 1.0. The two confinement modes change gradually depending on the collisionality. Scans of concentration ratio between He and H were also performed. The ion confinement improvements were investigated using gyro-Bohm normalization, taking account of the effective mass and charge. The concentration ratio affected the normalized χ i only in the edge region (ρ ~ 1.0). This indicates ion species effects vary depending on collisionality. Turbulence was modulated by the fast ion loss instability. The modulation of turbulence is higher in H rich than in He rich plasma.
Ion Irradiation of H2-Laden Porous Water-ice Films: Implications for Interstellar Ices
NASA Astrophysics Data System (ADS)
Raut, U.; Mitchell, E. H.; Baragiola, R. A.
2015-10-01
To understand the effects of cosmic-ray (CR) impacts on interstellar icy grains immersed in H2 gas, we have irradiated porous water-ice films loaded with H2 with 100 keV H+. The ice films were exposed to H2 gas at different pressures following deposition and during irradiation. A net H2 loss is observed during irradiation due to competition between ion-induced sputtering and gas adsorption. The initial H2 loss cross-section, 4(1) × 10-14 cm2, was independent of film thickness, H2, and proton fluxes. In addition to sputtering, irradiation also closes nanopores, trapping H2 in the film with binding that exceeds physical absorption energies. As a result, 2%-7% H2 is retained in the ice following irradiation to high fluences. We find that the trapped H2 concentration increases with decreasing Φ, the ratio of ion to H2 fluxes, suggesting that as high as 8% solid H2 can be trapped in interstellar ice by CR or stellar wind impacts.
NASA Astrophysics Data System (ADS)
Nakai, Yohta; Shirai, Toshizo; Tabata, Tatsuo; Ito, Rinsuke
1989-01-01
A universal analytic formula is given for the total cross sections of single-electron capture by multiply-charged ions colliding with H, H2 or He. Values of constants in the formula have been determined by least-squares fit to experimental data collected from the literature. The formula is applicable to ions of almost all atomic species with charge q greater than 4 (for the H and H2 targets) or 5 (for the He target) in the energy region from about 1 to 107 eV amu-1. The root-mean-square deviation of the data from the formula is 29%. The formula shows that the cross sections are proportional to q1.07 at low energies and to q2.86 at high energies. Other trends of the cross sections that can be derived from the formula are also discussed.
Mathematical Modeling of Ni/H2 and Li-Ion Batteries
NASA Technical Reports Server (NTRS)
Weidner, John W.; White, Ralph E.; Dougal, Roger A.
2001-01-01
The modelling effort outlined in this viewgraph presentation encompasses the following topics: 1) Electrochemical Deposition of Nickel Hydroxide; 2) Deposition rates of thin films; 3) Impregnation of porous electrodes; 4) Experimental Characterization of Nickel Hydroxide; 5) Diffusion coefficients of protons; 6) Self-discharge rates (i.e., oxygen-evolution kinetics); 7) Hysteresis between charge and discharge; 8) Capacity loss on cycling; 9) Experimental Verification of the Ni/H2 Battery Model; 10) Mathematical Modeling Li-Ion Batteries; 11) Experimental Verification of the Li-Ion Battery Model; 11) Integrated Power System Models for Satellites; and 12) Experimental Verification of Integrated-Systems Model.
Aihara, Yuichi; Sonai, Atsuo; Hattori, Mineyuki; Hayamizu, Kikuko
2006-12-14
To understand the behaviors of phosphoric acids in fuel cells, the ion conduction mechanisms of phosphoric acids in condensed states without free water and in a monomer state with water were studied by measuring the ionic conductivity (sigma) using AC impedance, thermal properties, and self-diffusion coefficients (D) and spin-lattice relaxation times (T1) with multinuclear NMR. The self-diffusion coefficient of the protons (H+ or H3O+), H2O, and H located around the phosphate were always larger than the diffusion coefficients of the phosphates and the disparity increased with increasing phosphate concentration. The diffusion coefficients of the samples containing D2O paralleled those in the protonated samples. Since the 1H NMR T1 values exhibited a minimum with temperature, it was possible to determine the correlation times and they were found to be of nanosecond order for a distance of nanometer order for a flip. The agreement of the ionic conductivities measured directly and those calculated from the diffusion coefficients indicates that the ion conduction obeys the Nernst-Einstein equation in the condensed phosphoric acids. The proton diffusion plays a dominant role in the ion conduction, especially in the condensed phosphoric acids.
Electron-temperature dependence of the recombination of H3O+(H2O)n ions with electrons
NASA Technical Reports Server (NTRS)
Johnsen, R.
1993-01-01
The T(e) dependence of the recombination of H3O+(H2O)n cluster-ions with electrons has been measured in an afterglow experiment in which the electrons were heated by a radio-frequency electric field. The recombination coefficients were found to vary with T(e) as about T(e) exp -1/2 in better agreement with theoretical expectations than earlier results of microwave-afterglow measurements.
Pistos, C; Tsantili-Kakoulidou, A; Koupparis, M
2005-09-15
The retention/pH profiles of three fluoroquinolones, ofloxacin, norfloxacin and ciprofloxacin, was investigated by means of reversed-phase high performance liquid chromatography (RP-HPLC) and reversed-phase ion-interaction chromatography (RP-IIC), using an octadecylsilane stationary phase and acetonitrile as organic modifier. Sodium hexanesulphonate and tetrabutylammonium hydroxide were used as sources of counter ions in ion-interaction chromatography. The retention/pH profiles under in RP-HPLC were compared to the corresponding lipophilicity/pH profiles. Despite the rather hydrophilic nature of the three fluoroquinolones positive retention factors were obtained while there was a shift of the retention maximum towards more acidic pH values. This behavior was attributed mainly to non-hydrophobic silanophilic interactions with the silanized silica gel material of the stationary phase. In ion-interaction chromatography the effect of counter ions over a broad pH range was found to be ruled rather by the ion pair formation in the mobile phase which led to a drastic decrease in retention as a consequence of the disruption of the zwitterionic structure and thereupon the deliberation of a net charge in the molecules. At pH values at which zwitterionic structure was not favored both the ion-exchange and ion pair formation mechanisms were assumed to contribute to the retention.
NASA Technical Reports Server (NTRS)
Baragiola, R. A.; Loeffler, M. J.; Raut, U.; Vidal, R. A.; Carlson, R. W.
2004-01-01
The detection of H2O2 on Jupiter's icy satellite Europa by the Galileo NIMS instrument presented a strong evidence for the importance of radiation effects on icy surfaces. A few experiments have investigated whether solar flux of protons incident on Europa ice could cause a significant if any H2O2 production. These published results differ as to whether H2O2 can be formed by ions impacting water at temperatures near 80 K, which are appropriate to Europa. This discrepancy may be a result of the use of different incident ion energies, different vacuum conditions, or different ways of processing the data. The latter possibility comes about from the difficulty of identifying the 3.5 m peroxide OH band on the long wavelength wing of the much stronger water 3.1 m band. The problem is aggravated by using straight line baselines to represent the water OH band with a curvature, in the region of the peroxide band, that increases with temperature. To overcome this problem, we use polynomial baselines that provide good fits to the water band and its derivative.
Conformation-Specific Infrared and Ultraviolet Spectroscopy of Cold [YAPAA +H]+ and [YGPAA +H]+ Ions
NASA Astrophysics Data System (ADS)
Deblase, Andrew; Harrilal, Christopher; Lawler, John; Burke, Nicole; McLuckey, Scott; Timothy, Zwier
Incorporation of the unnatural D-proline stereoisomer into a peptide sequence is a typical strategy to synthesize model β-hairpin loops. Using conformation-specific IR and UV spectroscopy of cold ( 10 K) gas-phase ions, we unravel the inherent conformational preferences of the DP and LP diastereomers in the protonated peptide [YAPAA +H]+ because only intramolecular interactions are possible in this isolated regime. Consistent with the solution phase studies, one of the conformers of [YADPAA +H]+ is folded into a β-hairpin turn. However, a second predominant γ-turn conformer family is identified. The [YALPAA +H]+ stereoisomer discourages β-hairpin formation. We show that the trans(DP) ->cis (LP) isomerization is sterically driven and can be reversed by substituting [YGLPAA +H]+ for [YALPAA +H]+. Therefore, we provide a basis for understanding residue-specific alterations in the potential energy surface and reveal new insights into the origin of β-hairpin formation from the bottom-up. National Science Foundation (NSF CHE 1213289) and the U.S. Department of Energy (Office of Basic Energy Sciences under Award Number FG02-00ER15105).
High-intensity polarized H- ion source for the RHIC SPIN physics
NASA Astrophysics Data System (ADS)
Zelenski, A.; Atoian, G.; Raparia, D.; Ritter, J.; Kolmogorov, A.; Davydenko, V.
2017-08-01
A novel polarization technique had been successfully implemented for the RHIC polarized H- ion source upgrade to higher intensity and polarization. In this technique a proton beam inside the high magnetic field solenoid is produced by ionization of the atomic hydrogen beam (from external source) in the He-gas ionizer cell. Further proton polarization is produced in the process of polarized electron capture from the optically-pumped Rb vapour. The use of high-brightness primary beam and large cross-sections of charge-exchange cross-sections resulted in production of high intensity H- ion beam of 85% polarization. High beam brightness and polarization resulted in 75% polarization at 23 GeV out of AGS and 60-65% beam polarization at 100-250 GeV colliding beams in RHIC. The status of un-polarized magnetron type (Cs-vapour loaded) BNL source is also discussed.
Mutagenesis in human cells with accelerated H and Fe ions
NASA Technical Reports Server (NTRS)
Kronenberg, Amy
1994-01-01
The overall goals of this research were to determine the risks of mutation induction and the spectra of mutations induced by energetic protons and iron ions at two loci in human lymphoid cells. During the three year grant period the research has focused in three major areas: (1) the acquisition of sufficient statistics for human TK6 cell mutation experiments using Fe ions (400 MeV/amu), Fe ions (600 MeV/amu) and protons (250 MeV/amu); (2) collection of thymidine kinase- deficient (tk) mutants or hypoxanthine phosphoribosyltransferase deficient (hprt) mutants induced by either Fe 400 MeV/amu, Fe 600 MeV/amu, or H 250 MeV/amu for subsequent molecular analysis; and (3) molecular characterization of mutants isolated after exposure to Fe ions (600 MeV/amu). As a result of the shutdown of the BEVALAC heavy ion accelerator in December 1992, efforts were rearranged somewhat in time to complete our dose-response studies and to complete mutant collections in particular for the Fe ion beams prior to the shutdown. These goals have been achieved. A major effort was placed on collection, re-screening, and archiving of 3 different series of mutants for the various particle beam exposures: tk-ng mutants, tk-sg mutants, and hprt-deficient mutants. Where possible, groups of mutants were isolated for several particle fluences. Comparative analysis of mutation spectra has occured with characterization of the mutation spectrum for hprt-deficient mutants obtained after exposure of TK6 cells to Fe ions (600 MeV/amu) and a series of spontaneous mutants.
Structural and optical modification in 4H-SiC following 30 keV silver ion irradiation
NASA Astrophysics Data System (ADS)
Kaushik, Priya Darshni; Aziz, Anver; Siddiqui, Azher M.; Lakshmi, G. B. V. S.; Syväjärvi, Mikael; Yakimova, Rositsa; Yazdi, G. Reza
2018-05-01
The market of high power, high frequency and high temperature based electronic devices is captured by SiC due to its superior properties like high thermal conductivity and high sublimation temperature and also due to the limitation of silicon based electronics in this area. There is a need to investigate effect of ion irradiation on SiC due to its application in outer space as outer space is surrounded both by low and high energy ion irradiations. In this work, effect of low energy ion irradiation on structural and optical property of 4H-SiC is investigated. ATR-FTIR is used to study structural modification and UV-Visible spectroscopy is used to study optical modifications in 4H-SiC following 30 keV Ag ion irradiation. FTIR showed decrease in bond density of SiC along the ion path (track) due to the creation of point defects. UV-Visible absorption spectra showed decrease in optical band gap from 3.26 eV to 2.9 eV. The study showed degradation of SiC crystallity and change in optical band gap following low energy ion irradiation and should be addressed while fabricationg devices based on SiC for outer space application. Additionally, this study provides a platform for introducing structural and optical modification in 4H-SiC using ion beam technology in a controlled manner.
Kornilov, Oleg; Toennies, J Peter
2008-05-21
Clusters consisting of normal H2 molecules, produced in a free jet expansion, are size selected by diffraction from a transmission nanograting prior to electron impact ionization. For each neutral cluster (H2)(N) (N=2-40), the relative intensities of the ion fragments Hn+ are measured with a mass spectrometer. H3+ is found to be the most abundant fragment up to N=17. With a further increase in N, the abundances of H3+, H5+, H7+, and H9+ first increase and, after passing through a maximum, approach each other. At N=40, they are about the same and more than a factor of 2 and 3 larger than for H11+ and H13+, respectively. For a given neutral cluster size, the intensities of the ion fragments follow a Poisson distribution. The fragmentation probabilities are used to determine the neutral cluster size distribution produced in the expansion at a source temperature of 30.1 K and a source pressure of 1.50 bar. The distribution shows no clear evidence of a magic number N=13 as predicted by theory and found in experiments with pure para-H2 clusters. The ion fragment distributions are also used to extract information on the internal energy distribution of the H3+ ions produced in the reaction H2+ + H2-->H3+ +H, which is initiated upon ionization of the cluster. The internal energy is assumed to be rapidly equilibrated and to determine the number of molecules subsequently evaporated. The internal energy distribution found in this way is in good agreement with data obtained in an earlier independent merged beam scattering experiment.
Deactivation kinetics of acid-sensing ion channel 1a are strongly pH-sensitive.
MacLean, David M; Jayaraman, Vasanthi
2017-03-21
Acid-sensing ion channels (ASICs) are trimeric cation-selective ion channels activated by protons in the physiological range. Recent reports have revealed that postsynaptically localized ASICs contribute to the excitatory postsynaptic current by responding to the transient acidification of the synaptic cleft that accompanies neurotransmission. In response to such brief acidic transients, both recombinant and native ASICs show extremely rapid deactivation in outside-out patches when jumping from a pH 5 stimulus to a single resting pH of 8. Given that the resting pH of the synaptic cleft is highly dynamic and depends on recent synaptic activity, we explored the kinetics of ASIC1a and 1a/2a heteromers to such brief pH transients over a wider [H + ] range to approximate neuronal conditions better. Surprisingly, the deactivation of ASICs was steeply dependent on the pH, spanning nearly three orders of magnitude from extremely fast (<1 ms) at pH 8 to very slow (>300 ms) at pH 7. This study provides an example of a ligand-gated ion channel whose deactivation is sensitive to agonist concentrations that do not directly activate the receptor. Kinetic simulations and further mutagenesis provide evidence that ASICs show such steeply agonist-dependent deactivation because of strong cooperativity in proton binding. This capacity to signal across such a large synaptically relevant bandwidth enhances the response to small-amplitude acidifications likely to occur at the cleft and may provide ASICs with the ability to shape activity in response to the recent history of the synapse.
NASA Astrophysics Data System (ADS)
Ueno, Akira; Ikegami, Kiyoshi; Kondo, Yasuhiro
2004-05-01
A Cs-free negative hydrogen (H-) ion source driven by pulsed arc plasma with a LaB6 filament is being operated for the beam tests of the Japan Proton Accelerator Research Complex (J-PARC) linac. A peak H- current of 38 mA, which exceeds the requirement of the J-PARC first stage, is stably extracted from the ion source with a beam duty factor of 0.9% (360 μs×25 Hz) by principally optimizing the surface condition and shape of the plasma electrode. The sufficiently small emittance of the beam was confirmed by high transmission efficiency (around 90%) through the following 324 MHz 3 MeV J-PARC radio frequency quadrupole linac (M. Ikegami et al., Proc. 2003 Part. Accel. Conf. 2003, p. 1509). The process of the optimization, which confirms the validity of hypothesis that H- ions are produced by surface reaction on a Mo plasma electrode dominantly in the ion source, is presented.
The 25 mA continuous-wave surface-plasma source of H{sup −} ions
DOE Office of Scientific and Technical Information (OSTI.GOV)
Belchenko, Yu., E-mail: belchenko@inp.nsk.su; Gorbovsky, A.; Sanin, A.
The ion source with the Penning geometry of electrodes producing continuous-wave beam of H{sup −} ions with current up to 25 mA was developed. Several improvements were introduced to increase source intensity, reliability, and lifetime. The collar around the emission aperture increases the electrons filtering. The apertures’ diameters of the ion-optical system electrodes were increased to generate the beam with higher intensity. An optimization of electrodes’ temperature was performed.
Nuclear quantum effects on adsorption of H2 and isotopologues on metal ions
NASA Astrophysics Data System (ADS)
Savchenko, Ievgeniia; Gu, Bing; Heine, Thomas; Jakowski, Jacek; Garashchuk, Sophya
2017-02-01
The nuclear quantum effects on the zero-point energy (ZPE), influencing adsorption of H2 and isotopologues on metal ions, are examined using normal mode analysis of ab initio electronic structure results for complexes with 17 metal cations. The lightest metallic nuclei, Li and Be, are found to be the most 'quantum'. The largest selectivity in adsorption is predicted for Cu, Ni and Co ions. Analysis of the nuclear wavepacket dynamics on the ground state electronic potential energy surfaces (PES) performed for complexes of Li+ and Cu+2 with H2/D2/HD shows that the PES anharmonicity changes the ZPE by up to 9%.
Oxidative stability of egg and soy lecithin as affected by transition metal ions and pH in emulsion.
Wang, Guang; Wang, Tong
2008-12-10
Oxidative stability of egg and soy lecithin in emulsion was evaluated with two transition metal ions, cupric and ferric ion, at two concentration levels (50 and 500 microM). The effect of pH on lipid oxidation was also examined under these two concentrations for each ion. Egg lecithin (EL) had similar peroxide value (PV) development pattern as soy lecithin (SL) when treated with cupric ion under both acidic and neutral pH. Acidic pH of 3 accelerated oxidation of both EL and SL, especially under high concentration of copper. When treated with ferric ion, EL oxidized much faster than SL did. EL had higher value of thiobarbituric acid-reactive substances (TBARS) than SL, possibly because of its higher content of long-chain polyunsaturated fatty acids (PUFA). Acidic pH accelerated TBARS development for both EL and SL, but EL had more significantly increased values. Cupric ion was more powerful than ferric in catalyzing oxidation of both EL and SL under both acidic and neutral pH conditions as measured by PV and TBARS. Linoleic acid may contribute to higher PV production, however, arachidonic acid and docosahexaenoic acid may have contributed more to TBARS production. Overall, SL showed better oxidative stability than EL under the experimental conditions. This study also suggests that using multiple methods is necessary in properly evaluating lipid oxidative stability.
RF H-minus ion source development in China spallation neutron source
NASA Astrophysics Data System (ADS)
Chen, W.; Ouyang, H.; Xiao, Y.; Liu, S.; Lü, Y.; Cao, X.; Huang, T.; Xue, K.
2017-08-01
China Spallation Neutron Source (CSNS) phase-I project currently uses a Penning surface plasma H- ion source, which has a life time of several weeks with occasional sparks between high voltage electrodes. To extend the life time of the ion source and prepare for the CSNS phase-II, we are trying to develop a RF negative hydrogen ion source with external antenna. The configuration of the source is similar to the DESY external antenna ion source and SNS ion source. However several changes are made to improve the stability and the life time. Firstly, Si3N4 ceramic with high thermal shock resistance, and high thermal conductivity is used for plasma chamber, which can endure an average power of 2000W. Secondly, the water-cooled antenna is brazed on the chamber to improve the energy efficiency. Thirdly, cesium is injected directly to the plasma chamber if necessary, to simplify the design of the converter and the extraction. Area of stainless steel exposed to plasma is minimized to reduce the sputtering and degassing. Instead Mo, Ta, and Pt coated materials are used to face the plasma, which makes the self-cleaning of the source possible.
Ovanesyan, Zaven; Aljzmi, Amal; Almusaynid, Manal; Khan, Asrar; Valderrama, Esteban; Nash, Kelly L; Marucho, Marcelo
2016-01-15
One major source of complexity in the implementation of nanoparticles in aqueous electrolytes arises from the strong influence that biological environments has on their physicochemical properties. A key parameter for understanding the molecular mechanisms governing the physicochemical properties of nanoparticles is the formation of the surface charge density. In this article, we present an efficient and accurate approach that combines a recently introduced classical solvation density functional theory for spherical electrical double layers with a surface complexation model to account for ion-ion correlation and excluded volume effects on the surface titration of spherical nanoparticles. We apply the proposed computational approach to account for the charge-regulated mechanisms on the surface chemistry of spherical silica (SiO2) nanoparticles. We analyze the effects of the nanoparticle size, as well as pH level and electrolyte concentration of the aqueous solution on the nanoparticle's surface charge density and Zeta potential. We validate our predictions for 580Å and 200Å nanoparticles immersed in acid, neutral and alkaline mono-valent aqueous electrolyte solutions against experimental data. Our results on mono-valent electrolyte show that the excluded volume and ion-ion correlations contribute significantly to the surface charge density and Zeta potential of the nanoparticle at high electrolyte concentration and pH levels, where the solvent crowding effects and electrostatic screening have shown a profound influence on the protonation/deprotonation reactions at the liquid/solute interface. The success of this approach in describing physicochemical properties of silica nanoparticles supports its broader application to study other spherical metal oxide nanoparticles. Copyright © 2015 Elsevier Inc. All rights reserved.
Ummadi, Jyothir Ganesh; Downs, Corey J; Joshi, Vrushali S; Ferracane, Jack L; Koley, Dipankar
2016-03-15
Solid-state ion-selective electrodes are used as scanning electrochemical microscope (SECM) probes because of their inherent fast response time and ease of miniaturization. In this study, we report the development of a solid-state, low-poly(vinyl chloride), carbon-based calcium ion-selective microelectrode (Ca(2+)-ISME), 25 μm in diameter, capable of performing an amperometric approach curve and serving as a potentiometric sensor. The Ca(2+)-ISME has a broad linear response range of 5 μM to 200 mM with a near Nernstian slope of 28 mV/log[a(Ca(2+))]. The calculated detection limit for Ca(2+)-ISME is 1 μM. The selectivity coefficients of this Ca(2+)-ISME are log K(Ca(2+),A) = -5.88, -5.54, and -6.31 for Mg(2+), Na(+), and K(+), respectively. We used this new type of Ca(2+)-ISME as an SECM probe to quantitatively map the chemical microenvironment produced by a model substrate, bioactive glass (BAG). In acidic conditions (pH 4.5), BAG was found to increase the calcium ion concentration from 0.7 mM ([Ca(2+)] in artificial saliva) to 1.4 mM at 20 μm above the surface. In addition, a solid-state dual SECM pH probe was used to correlate the release of calcium ions with the change in local pH. Three-dimensional pH and calcium ion distribution mapping were also obtained by using these solid-state probes. The quantitative mapping of pH and Ca(2+) above the BAG elucidates the effectiveness of BAG in neutralizing and releasing calcium ions in acidic conditions.
Origin of CH+ in diffuse molecular clouds. Warm H2 and ion-neutral drift
NASA Astrophysics Data System (ADS)
Valdivia, Valeska; Godard, Benjamin; Hennebelle, Patrick; Gerin, Maryvonne; Lesaffre, Pierre; Le Bourlot, Jacques
2017-04-01
Context. Molecular clouds are known to be magnetised and to display a turbulent and complex structure where warm and cold phases are interwoven. The turbulent motions within molecular clouds transport molecules, and the presence of magnetic fields induces a relative velocity between neutrals and ions known as the ion-neutral drift (vd). These effects all together can influence the chemical evolution of the clouds. Aims: This paper assesses the roles of two physical phenomena which have previously been invoked to boost the production of CH+ under realistic physical conditions: the presence of warm H2 and the increased formation rate due to the ion-neutral drift. Methods: We performed ideal magnetohydrodynamical (MHD) simulations that include the heating and cooling of the multiphase interstellar medium (ISM), and where we treat dynamically the formation of the H2 molecule. In a post-processing step we compute the abundances of species at chemical equilibrium using a solver that we developed. The solver uses the physical conditions of the gas as input parameters, and can also prescribe the H2 fraction if needed. We validate our approach by showing that the H2 molecule generally has a much longer chemical evolution timescale compared to the other species. Results: We show that CH+ is efficiently formed at the edge of clumps, in regions where the H2 fraction is low (0.3-30%) but nevertheless higher than its equilibrium value, and where the gas temperature is high (≳ 300 K). We show that warm and out of equilibrium H2 increases the integrated column densities of CH+ by one order of magnitude up to values still 3-10 times lower than those observed in the diffuse ISM. We balance the Lorentz force with the ion-neutral drag to estimate the ion-drift velocities from our ideal MHD simulations. We find that the ion-neutral drift velocity distribution peaks around 0.04 km s-1, and that high drift velocities are too rare to have a significant statistical impact on the
NASA Astrophysics Data System (ADS)
Bordikar, M. R.; Scales, W. A.; Samimi, A. R.; Bernhardt, P. A.; Brizcinski, S.; McCarrick, M. J.
2013-04-01
This work presents the first observations of unique narrowband emissions ordered near the hydrogen ion (H+) gyrofrequency (fcH) in the stimulated electromagnetic emission spectrum when the transmitter is tuned near the second electron gyroharmonic frequency (2fce) during ionospheric modification experiments. The frequency structuring of these newly discovered emission lines is quite unexpected since H+ is known to be a minor constituent in the interaction region which is near 160 km altitude. The spectral lines are typically shifted from the pump wave frequency by harmonics of a frequency about 10% less than fcH (≈ 800 Hz) and have a bandwidth of less than 50 Hz which is near the O+ gyrofrequency fcO. A theory is proposed to explain these emissions in terms of a parametric decay instability in a multi-ion species plasma due to possible proton precipitation associated with the disturbed conditions during the heating experiment. The observations can be explained by including several percent H+ ions into the background plasma. The implications are new possibilities for characterizing proton precipitation events during ionospheric heating experiments.
Kröner, Frieder; Hubbuch, Jürgen
2013-04-12
pH gradient protein separations are widely used techniques in the field of protein analytics, of which isoelectric focusing is the most well known application. The chromatographic variant, based on the formation of pH gradients in ion exchange columns is only rarely applied due to the difficulties to form controllable, linear pH gradients over a broad pH range. This work describes a method for the systematic generation of buffer compositions with linear titration curves, resulting in well controllable pH gradients. To generate buffer compositions with linear titration curves an in silico method was successfully developed. With this tool, buffer compositions for pH gradient ion exchange chromatography with pH ranges spanning up to 7.5 pH units were established and successfully validated. Subsequently, the buffer systems were used to characterize the elution behavior of 22 different model proteins in cation and anion exchange pH gradient chromatography. The results of both chromatographic modes as well as isoelectric focusing were compared to describe differences in between the methods. Copyright © 2013 Elsevier B.V. All rights reserved.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Isaacs, H.S.; Lamaka, S.V.; Taryba, M.
2011-01-01
This work reports a new methodology to measure quasi-simultaneously the local electric fields and the distribution of specific ions in a solution via selective microelectrodes. The field produced by the net electric current was detected using the scanning vibrating electrode technique (SVET) with quasi-simultaneous measurements of pH with an ion-selective microelectrode (pH-SME). The measurements were performed in a validation cell providing a 48 ?m diameter Pt wire cross section as a source of electric current. A time lag between acquiring each current density and pH data-point was 1.5 s due to the response time of pH-SME. The quasi-simultaneous SVET-pH measurementsmore » that correlate electrochemical oxidation-reduction processes with acid-base chemical equilibria are reported for the first time. No cross-talk between the vibrating microelectrode and the ion-selective microelectrode could be detected under given experimental conditions.« less
Muntean, C M; Segers-Nolten, G M J
2003-01-01
In this work a confocal Raman microspectrometer is used to investigate the influence of Na(+) and Mg(2+) ions on the DNA structural changes induced by low pH. Measurements are carried out on calf thymus DNA at neutral pH (7) and pH 3 in the presence of low and high concentrations of Na(+) and Mg(2+) ions, respectively. It is found that low concentrations of Na(+) ions do not protect DNA against binding of H(+). High concentrations of monovalent ions can prevent protonation of the DNA double helix. Our Raman spectra show that low concentrations of Mg(2+) ions partly protect DNA against protonation of cytosine (line at 1262 cm(-1)) but do not protect adenine and guanine N(7) against binding of H(+) (characteristic lines at 1304 and 1488 cm(-1), respectively). High concentrations of Mg(2+) can prevent protonation of cytosine and protonation of adenine (disruption of AT pairs). By analyzing the line at 1488 cm(-1), which obtains most of its intensity from a guanine vibration, high magnesium salt protect the N(7) of guanine against protonation. A high salt concentration can prevent protonation of guanine, cytosine, and adenine in DNA. Higher salt concentrations cause less DNA protonation than lower salt concentrations. Magnesium ions are found to be more effective in protecting DNA against binding of H(+) as compared with calcium ions presented in a previous study. Divalent metal cations (Mg(2+), Ca(2+)) are more effective in protecting DNA against protonation than monovalent ions (Na(+)). Copyright 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 000-000, 2003
A study of H+ production using metal hydride and other compounds by means of laser ion source
DOE Office of Scientific and Technical Information (OSTI.GOV)
Sekine M.; Kondo K.; Okamura, M.
2012-02-22
A laser ion source can provide wide variety of ion beams from solid target materials, however, it has been difficult to create proton beam efficiently. We examined capability of proton production using beeswax, polyethylene, and metal hydrides (MgH2 and ZrH2) as target materials. The results showed that beeswax and polyethylene could not be used to produce protons because these targets are transparent to the laser wavelength of 1064 nm. On the other hand, the metal hydrides could supply protons. Although the obtained particle numbers of protons were less than those of the metal ions, the metal hydrides could be usedmore » as a target for proton laser ion source.« less
High resolution main-ion charge exchange spectroscopy in the DIII-D H-mode pedestal.
Grierson, B A; Burrell, K H; Chrystal, C; Groebner, R J; Haskey, S R; Kaplan, D H
2016-11-01
A new high spatial resolution main-ion (deuterium) charge-exchange spectroscopy system covering the tokamak boundary region has been installed on the DIII-D tokamak. Sixteen new edge main-ion charge-exchange recombination sightlines have been combined with nineteen impurity sightlines in a tangentially viewing geometry on the DIII-D midplane with an interleaving design that achieves 8 mm inter-channel radial resolution for detailed profiles of main-ion temperature, velocity, charge-exchange emission, and neutral beam emission. At the plasma boundary, we find a strong enhancement of the main-ion toroidal velocity that exceeds the impurity velocity by a factor of two. The unique combination of experimentally measured main-ion and impurity profiles provides a powerful quasi-neutrality constraint for reconstruction of tokamak H-mode pedestals.
Sioud, Salim; Kharbatia, Najeh; Amad, Maan H; Zhu, Zhiyong; Cabanetos, Clement; Lesimple, Alain; Beaujuge, Pierre
2014-11-30
The formation of ions during atmospheric pressure photoionization (APPI) mass spectrometry in the positive mode usually provides radical cations and/or protonated species. Intriguingly, during the analysis of some N-alkyl-substituted thieno[3,4-c]pyrrole-4,6-dione (TPD) derivatives synthesized in our laboratory, unusual [M-H](+) ion peaks were observed. In this work we investigate the formation of [M-H](+) ions observed under APPI conditions. Multiple experimental parameters, including the type of ionization source, the composition of the solvent, the type of dopant, the infusion flow rate, and the length of the alkyl side chain were investigated to determine their effects on the formation of [M-H](+) ions. In addition, a comparison study of the gas-phase tandem mass spectrometric (MS/MS) fragmentation of [M + H](+) vs [M-H](+) ions and computational approaches were used. [M-H](+) ions were observed under APPI conditions. The type of dopant and the length of the alkyl chain affected the formation of these ions. MS/MS fragmentation of [M-H](+) and [M + H](+) ions exhibited completely different patterns. Theoretical calculations revealed that the loss of hydrogen molecules from the [M + H](+) ions is the most favourable condition under which to form [M-H](+) ions. [M-H](+) ions were detected in all the TPD derivatives studied here under the special experimental conditions during APPI, using a halogenated benzene dopant, and TPD containing substituted N-alkyl side chains with a minimum of four carbon atoms. Density functional theory calculations showed that for [M-H](+) ions to be formed under these conditions, the loss of hydrogen molecules from the [M + H](+) ions is proposed to be necessary. Copyright © 2014 John Wiley & Sons, Ltd.
NASA Astrophysics Data System (ADS)
Cumbee, R. S.; Mullen, P. D.; Lyons, D.; Shelton, R. L.; Fogle, M.; Schultz, D. R.; Stancil, P. C.
2018-01-01
The fundamental collisional process of charge exchange (CX) has been established as a primary source of X-ray emission from the heliosphere, planetary exospheres, and supernova remnants. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly excited, high-charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays. To provide reliable CX-induced X-ray spectral models to realistically simulate these environments, line ratios and spectra are computed using theoretical CX cross sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, molecular-orbital close-coupling, and classical trajectory Monte Carlo methods for various collisional velocities relevant to astrophysics. X-ray spectra were computed for collisions of bare and H-like C to Al ions with H, He, and H2 with results compared to available experimental data. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant and the heliosphere are shown as examples with ion velocity dependence.
Jasík, Juraj; Zabka, Jan; Feketeova, Linda; Ipolyi, Imre; Märk, Tilmann D; Herman, Zdenek
2005-11-17
Interaction of C2Hn+ (n = 2-5) hydrocarbon ions and some of their isotopic variants with room-temperature and heated (600 degrees C) highly oriented pyrolytic graphite (HOPG) surfaces was investigated over the range of incident energies 11-46 eV and an incident angle of 60 degrees with respect to the surface normal. The work is an extension of our earlier research on surface interactions of CHn+ (n = 3-5) ions. Mass spectra, translational energy distributions, and angular distributions of product ions were measured. Collisions with the HOPG surface heated to 600 degrees C showed only partial or substantial dissociation of the projectile ions; translational energy distributions of the product ions peaked at about 50% of the incident energy. Interactions with the HOPG surface at room temperature showed both surface-induced dissociation of the projectiles and, in the case of radical cation projectiles C2H2+* and C2H4+*, chemical reactions with the hydrocarbons on the surface. These reactions were (i) H-atom transfer to the projectile, formation of protonated projectiles, and their subsequent fragmentation and (ii) formation of a carbon chain build-up product in reactions of the projectile ion with a terminal CH3-group of the surface hydrocarbons and subsequent fragmentation of the product ion to C3H3+. The product ions were formed in inelastic collisions in which the translational energy of the surface-excited projectile peaked at about 32% of the incident energy. Angular distributions of reaction products showed peaking at subspecular angles close to 68 degrees (heated surfaces) and 72 degrees (room-temperature surfaces). The absolute survival probability at the incident angle of 60 degrees was about 0.1% for C2H2+*, close to 1% for C2H4+* and C2H5+, and about 3-6% for C2H3+.
Limandri, Silvina; de Vera, Pablo; Fadanelli, Raul C; Nagamine, Luiz C C M; Mello, Alexandre; Garcia-Molina, Rafael; Behar, Moni; Abril, Isabel
2014-02-01
Ion-beam cancer therapy is a promising technique to treat deep-seated tumors; however, for an accurate treatment planning, the energy deposition by the ions must be well known both in soft and hard human tissues. Although the energy loss of ions in water and other organic and biological materials is fairly well known, scarce information is available for the hard tissues (i.e., bone), for which the current stopping power information relies on the application of simple additivity rules to atomic data. Especially, more knowledge is needed for the main constituent of human bone, calcium hydroxyapatite (HAp), which constitutes 58% of its mass composition. In this work the energy loss of H and He ion beams in HAp films has been obtained experimentally. The experiments have been performed using the Rutherford backscattering technique in an energy range of 450-2000 keV for H and 400-5000 keV for He ions. These measurements are used as a benchmark for theoretical calculations (stopping power and mean excitation energy) based on the dielectric formalism together with the MELF-GOS (Mermin energy loss function-generalized oscillator strength) method to describe the electronic excitation spectrum of HAp. The stopping power calculations are in good agreement with the experiments. Even though these experimental data are obtained for low projectile energies compared with the ones used in hadron therapy, they validate the mean excitation energy obtained theoretically, which is the fundamental quantity to accurately assess energy deposition and depth-dose curves of ion beams at clinically relevant high energies. The effect of the mean excitation energy choice on the depth-dose profile is discussed on the basis of detailed simulations. Finally, implications of the present work on the energy loss of charged particles in human cortical bone are remarked.
Hsu, Fong-Fu
2016-01-01
Ceramide is a huge lipid family consisting of diversified structures including various modifications in the fatty acyl chain and the long chain base (LCB). In this contribution, negative-ion ESI linear ion-trap multiple-stage mass spectrometric method (LIT MSn) towards complete structural determination of ceramides in ten major families characterized as the [M – H]− ions is described. Multiple sets of fragment ions reflecting the fatty acyl chain and LCB were observed in the CID MS2 spectrum, while the sequential MS3 and MS4 spectra contain structural information for locating the double bond and the functional groups, permitting realization of the fragmentation processes. Thereby, differentiation of ceramide molecules varied by chain length, the LCB (sphingosine, phytosphigosine, 6-hydroxy-sphingosine), and by the modification (α-hydroxy-, β-hydroxy-, ω-hydroxy-FA) can be achieved; and many isomeric structures in the biological specimen can be revealed in detail. PMID:27523779
Somogyi, Arpád
2008-12-01
The usefulness of gas-phase H/D exchange is demonstrated to probe heterogeneous fragment and parent ion populations. Singly and multiply protonated peptides/proteins were fragmented by using sustained off-resonance irradiation collision-induced dissociation (SORI-CID). The fragments and the surviving precursor ions then all undergo H/D exchange in the gas-phase with either D(2)O or CD(3)OD under the same experimental conditions. Usually, 10 to 60 s of reaction time is adequate to monitor characteristic differences in the H/D exchange kinetic rates. These differences are then correlated to isomeric ion structures. The SORI-HDX method can be used to rapidly test fragment ion structures and provides useful insights into peptide fragmentation mechanisms.
NASA Astrophysics Data System (ADS)
Li, Hongqi; Zheng, Tao; Zhao, Yong; Xu, Zhenxiang; Dai, Xuhang; Shao, Zhiyu
2018-03-01
A spiropyran-appended polysiloxane (SP-Si) was synthesized and characterized. The pH-responsive behavior of SP-Si was investigated. It was found that with the decrease of the pH of SP-Si solution the intensity of the absorption peak at 440 nm increased and the color of SP-Si solution turned from colorless to yellow gradually. The polymer serves as chemosensor for colorimetric detection of Ag+ and Fe3+ ions. Addition of Ag+ and Fe3+ ions to SP-Si solution induced color change from colorless to brown and earthy yellow, respectively. Sensing of Ag+ ions by SP-Si was not affected by common competitive metal ions except Hg2+ ions. Based on the transformation from colorless SP-Si solution with negligible absorption at 440 nm to brown SP-Si/Ag+ showing extremely strong absorption at 440 nm by addition of Ag+ ions and subsequent transformation from brown to colorless SP-Si/Ag+/Hg2+ with relatively weak absorption at 440 nm after addition of 1 equivalent of Hg2+ ions, SP-Si/Ag+ system serves as a dual colorimetric and spectroscopic probe for highly selective and sensitive detection of Hg2+ ions. The selective detection of Fe3+ ions by SP-Si is not interfered by common competitive metal ions including Na+, K+, Li+, Hg2+, Ni2+, Fe2+, Zn2+, Co2+, Sr2+, Cu2+, Al3+, Ce3+ and Cr3+. The detection limit of Ag+ and Fe3+ ions is 1.45 × 10-6 M and 3.52 × 10-6 M, respectively.
Nanostructural evolution and behavior of H and Li in ion-implanted γ-LiAlO 2
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jiang, Weilin; Zhang, Jiandong; Edwards, Danny J.
In-situ He+ ion irradiation is performed under a helium ion microscope to study nanostructural evolution in polycrystalline gamma-LiAlO2 pellets. Various locations within a grain, across grain boundaries and at a cavity are selected. The results exhibit He bubble formation, grain-boundary cracking, nanoparticle agglomeration, increasing surface brightness with dose, and material loss from the surface. Similar brightening effects at grain boundaries are also observed under a scanning electron microscope. Li diffusion and loss from polycrystalline gamma-LiAlO2 is faster than its monocrystalline counterpart during H2+ ion implantation at elevated temperatures. There is also more significant H diffusion and release from polycrystalline pelletsmore » during thermal annealing of 300 K implanted samples. Grain boundaries and cavities could provide a faster pathway for H and Li diffusion. H release is slightly faster from the 573 K implanted monocrystalline gamma-LiAlO2 during annealing at 773 K. Metal hydrides could be formed preferentially along the grain boundaries to immobilize hydrogen.« less
High resolution main-ion charge exchange spectroscopy in the DIII-D H-mode pedestal
Grierson, B. A.; Burrell, K. H.; Chrystal, C.; ...
2016-09-12
A new high spatial resolution main-ion (deuterium) charge-exchange spectroscopy system covering the tokamak boundary region has been installed on the DIII-D tokamak. Sixteen new edge main-ion charge-exchange recombination sightlines have been combined with nineteen impurity sightlines in a tangentially viewing geometry on the DIII-D midplane with an interleaving design that achieves 8 mm inter-channel radial resolution for detailed profiles of main-ion temperature, velocity, charge-exchange emission, and neutral beam emission. At the plasma boundary, we find a strong enhancement of the main-ion toroidal velocity that exceeds the impurity velocity by a factor of two. Furthermore, the unique combination of experimentally measuredmore » main-ion and impurity profiles provides a powerful quasi-neutrality constraint for reconstruction of tokamak H-mode pedestals.« less
The pH sensitive properties of carboxymethyl chitosan nanoparticles cross-linked with calcium ions.
Kalliola, Simo; Repo, Eveliina; Srivastava, Varsha; Heiskanen, Juha P; Sirviö, Juho Antti; Liimatainen, Henrikki; Sillanpää, Mika
2017-05-01
In environmental applications the applied materials are required to be non-toxic and biodegradable. Carboxymethyl chitosan nanoparticles cross-linked with Ca 2+ ions (CMC-Ca) fulfill these requirements, and they are also renewable. These nanoparticles were applied to oil-spill treatment in our previous study and here we focused on enhancing their properties. It was found that while the divalent Ca 2+ ions are crucial for the formation of the CMC-Ca, the attractive interaction between NH 3 + and COO - groups contributed significantly to the formation and stability of the CMC-Ca. The stability decreased as a function of pH due to the deprotonation of the amino groups. Therefore, the nanoparticles were found to be fundamentally pH sensitive in solution, if the pH deviated from the pH (7-9) that was used in the synthesis of the nanoparticles. The pH sensitive CMC-Ca synthesized in pH 7 and 8 were most stable in the studied conditions and could find applications in oil-spill treatment or controlled-release of substances. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.
Relationship of Cell Sap pH to Organic Acid Change During Ion Uptake 1
Hiatt, A. J.
1967-01-01
Excised roots of barley (Hordeum vulgare, var. Campana) were incubated in KCl, K2SO4, CaCl2, and NaCl solutions at concentrations of 10−5 to 10−2 n. Changes in substrate solution pH, cell sap pH, and organic acid content of the roots were related to differences in cation and anion absorption. The pH of expressed sap of roots increased when cations were absorbed in excess of anions and decreased when anions were absorbed in excess of cations. The pH of the cell sap shifted in response to imbalances in cation and anion uptake in salt solutions as dilute as 10−5 n. Changes in cell sap pH were detectable within 15 minutes after the roots were placed in 10−3 n K2SO4. Organic acid changes in the roots were proportional to expressed sap pH changes induced by unbalanced ion uptake. Changes in organic acid content in response to differential cation and anion uptake appear to be associated with the low-salt component of ion uptake. PMID:16656506
Umadevi, Deivasigamani; Narahari Sastry, G
2015-11-11
Graphane has emerged as a two-dimensional hydrocarbon with interesting physical properties and potential applications. Understanding the interaction of graphane with various molecules and ions is crucial to appreciate its potential applications. We investigated the interaction of nucleobases, aminoacids, saturated and unsaturated heterocycles, small molecules, metal ions and onium ions with graphane by using density functional theory calculations. The preferred orientations of these molecules and ions on the graphane surface have been analysed. The binding energies of graphane with these molecules have been compared with the corresponding binding energies of graphene. Our results reveal that graphane forms stable complexes with all the molecules and ions yet showing lesser binding affinity when compared to graphene. As an exemption, the preferential strong binding of H2O with graphane than graphene reveals the fact that graphane is more hydrophilic than graphene. Charge transfer between graphane and the molecules and ions have been found to be an important factor in determining the binding strength of the complexes. The effect of the interaction of these molecules and ions on the HOMO-LUMO energy gap of graphane has also been investigated.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Zymak, I.; Hejduk, M.; Mulin, D.
2013-05-01
Using a low-temperature 22-pole ion trap apparatus, detailed measurements for the title reaction have been performed between 10 K and 100 K in order to get some state specific information about this fundamental hydrogen abstraction process. The relative population of the two lowest H{sub 2} rotational states, j = 0 and 1, has been varied systematically. NH{sup +} formation is nearly thermo-neutral; however, to date, the energetics are not known with the accuracy required for low-temperature astrochemistry. Additional complications arise from the fact that, so far, there is no reliable theoretical or experimental information on how the reactivity of themore » N{sup +} ion depends on its fine-structure (FS) state {sup 3} P{sub ja} . Since in the present trapping experiment, thermalization of the initially hot FS population competes with hydrogen abstraction, the evaluation of the decay of N{sup +} ions over long storage times and at various He and H{sub 2} gas densities provides information on these processes. First assuming strict adiabatic behavior, a set of state specific rate coefficients is derived from the measured thermal rate coefficients. In addition, by recording the disappearance of the N{sup +} ions over several orders of magnitude, information on nonadiabatic transitions is extracted including FS-changing collisions.« less
Freeman, F; Karchefski, E M
1976-10-04
Uniquely stable manganese intermediates (complexes) are formed from the permanganate ion oxidation of the 5,6-carbon-carbon double bond in several 2,4(1H,3H)-pyrimidinediones [uracil, (compound 7), 5-methyluracil (thymine, compound 5), and 6-methyluracil (compound 8)]. These manganese complexes, which represent some of the most stable intermediate manganese species observed thus far in the oxidation of carbon-carbon double bonds, show absorption maxima in the 285-296 nm region (epsilon max approximately 4500). The relative reactivities of 6-methyluracil: uracil: thymine are 1: 23 : 194 and the bimolecular oxidation process is characterized by relatively small deltaH++ values and large negative deltaS++ values.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Barriga-Carrasco, Manuel D.; Garcia-Molina, Rafael
2004-09-01
This work presents the results of computer simulations for the energy spectra of original versus recombined H{sub 2}{sup +} molecular ions transmitted through thin amorphous carbon foils, for a broad range of incident energies. A detailed description of the projectile motion through the target has been done, including nuclear scattering and Coulomb repulsion as well as electronic self-retarding and wake forces; the two latter are calculated in the dielectric formalism framework. Differences in the energy spectra of recombined and original transmitted H{sub 2}{sup +} molecular ions clearly appear in the simulations, in agreement with the available experimental data. Our simulationmore » code also differentiates the contributions due to original and to recombined H{sub 2}{sup +} molecular ions when the energy spectra contain both contributions, a feature that could be used for experimental purposes in estimating the ratio between the number of original and recombined H{sub 2}{sup +} molecular ions transmitted through thin foils.« less
Felix Spectroscopy of Likely Astronomical Molecular Ions: HC_3O^+, C_2H_3CNH^+, and C_2H_5CNH^+
NASA Astrophysics Data System (ADS)
Thorwirth, Sven; Asvany, Oskar; Brünken, Sandra; Jusko, Pavol; Schlemmer, Stephan; Martin-Drumel, Marie-Aline; McCarthy, Michael C.
2017-06-01
Infrared signatures of three molecular ions of relevance to the interstellar medium and planetary atmospheres have been detected at the Free Electron Laser for Infrared eXperiments, FELIX, at Radboud University (Nijmegen, The Netherlands) in combination with the 4K FELion 22-pole ion trap facility. Mid-infrared vibrational modes of protonated tricarbon monoxide, HC_3O^+, protonated vinyl cyanide, C_2H_3CNH^+, and protonated ethyl cyanide, C_2H_5CNH^+, were detected using resonant photodissociation of the respective Ne-complexes by monitoring the depletion of their cluster mass signal as a function of wavenumber. The infrared fingerprints compare very favorably with results from high-level quantum-chemical calculations performed at the CCSD(T) level of theory.
Struwe, W B; Benesch, J L; Harvey, D J; Pagel, K
2015-10-21
We report collision cross sections (CCS) of high-mannose N-glycans as [M + Na](+), [M + K](+), [M + H](+), [M + Cl](-), [M + H2PO4](-) and [M - H](-) ions, measured by drift tube (DT) ion mobility-mass spectrometry (IM-MS) in helium and nitrogen gases. Further analysis using traveling wave (TW) IM-MS reveal the existence of distinct conformers exclusive to [M - H](-) ions.
Kluters, Simon; Wittkopp, Felix; Jöhnck, Matthias; Frech, Christian
2016-02-01
The mobile phase pH is a key parameter of every ion exchange chromatography process. However, mechanistic insights into the pH influence on the ion exchange chromatography equilibrium are rare. This work describes a mechanistic model capturing salt and pH influence in ion exchange chromatography. The pH dependence of the characteristic protein charge and the equilibrium constant is introduced to the steric mass action model based on a protein net charge model considering the number of amino acids interacting with the stationary phase. This allows the description of the adsorption equilibrium of the chromatographed proteins as a function of pH. The model parameters were determined for a monoclonal antibody monomer, dimer, and a higher aggregated species based on a manageable set of pH gradient experiments. Without further modification of the model parameters the transfer to salt gradient elution at fixed pH is demonstrated. A lumped rate model was used to predict the separation of the monoclonal antibody monomer/aggregate mixture in pH gradient elution and for a pH step elution procedure-also at increased protein loadings up to 48 g/L packed resin. The presented model combines both salt and pH influence and may be useful for the development and deeper understanding of an ion exchange chromatography separation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Cesium and strontium ion exchange on the framework titanium silicate M2Ti2O3SiO4.nH2O (M = H, Na).
Solbrå, S; Allison, N; Waite, S; Mikhalovsky, S V; Bortun, A I; Bortun, L N; Clearfield, A
2001-02-01
The ion exchange properties of the titanium silicate, M2Ti2O3SiO4.nH2O (M = H, Na), toward stable and radioactive 137Cs+ and 89Sr2+, have been examined. By studying the cesium and strontium uptake in the presence of NaNO3, CaCl2, NaOH, and HNO3 (in the range of 0.01-6 M) the sodium titanium silicate was found to be an efficient Cs+ ion exchanger in acid, neutral, and alkaline media and an efficient Sr2+ ion exchanger in neutral and alkaline media, which makes it promising for treatment of contaminated environmental media and biological systems.
Swift heavy ion irradiation of Pt nanocrystals: II. Structural changes and H desorption
DOE Office of Scientific and Technical Information (OSTI.GOV)
Giulian, R.; Araujo, L.L.; Kluth, P.
2014-09-24
The structural properties and H desorption from embedded Pt nanocrystals (NCs) following irradiation with swift heavy ions were investigated as a function of energy and fluence. From x-ray absorption near-edge spectroscopy analysis, Pt-H bonding was identified in NCs annealed in a forming gas (95% N{sub 2} + 5% H{sub 2}) ambient. The H content decreased upon irradiation and the desorption process was NC-size dependent such that larger NCs required a higher fluence to achieve a H-free state. Pt-H bonding and NC dissolution both perturbed the NC structural parameters (coordination number, bond-length and mean-square relative displacement) as determined with extended x-raymore » absorption fine structure measurements.« less
Infrared predissociation spectroscopy of M+ (C6H6)(1-4)(H2O)(1-2)Ar(0-1) cluster ions, M = Li, Na.
Beck, Jordan P; Lisy, James M
2011-05-05
Infrared predissociation (IRPD) spectra of Li(+)(C(6)H(6))(1-4)(H(2)O)(1-2)Ar(0-1) and Na(+)(C(6)H(6))(2-4)(H(2)O)(1-2)Ar(1) are presented along with ab initio calculations. The results indicate that the global minimum energy structure for Li(+)(C(6)H(6))(2)(H(2)O)(2) has each water forming a π-hydrogen bond with the same benzene molecule. This bonding motif is preserved in Li(+)(C(6)H(6))(3-4)(H(2)O)(2)Ar(0-1) with the additional benzene ligands binding to the available free OH groups. Argon tagging allows high-energy Li(+)(C(6)H(6))(2-4)(H(2)O)(2)Ar isomers containing water-water hydrogen bonds to be trapped and detected. The monohydrated, Li(+) containing clusters contain benzene-water interactions with varying strength as indicated by shifts in OH stretching frequencies. The IRPD spectra of M(+)(C(6)H(6))(1-4)(H(2)O)(1-2)Ar are very different for lithium-bearing versus sodium-bearing cluster ions emphasizing the important role of ion size in determining the most favorable balance of competing noncovalent interactions.
NASA Technical Reports Server (NTRS)
Truhlik, Vladimir; Triskova, Ludmila; Benson, Robert F.; Bilitza, Dieter; Grebowsky, Joseph; Richards, Phil G.; Smilauer, Jan
2014-01-01
Orbiting Geophysical Observatory 5 (OGO 5) magnetospheric ion-composition data (H+, He+ and O+) from an ion spectrometer (Sharp, 1969) have been retrieved from old magnetic tapes archived at the National Space Science Data Center (NSSDC). The highly compressed binary format was converted into a user-friendly ASCII format and these data have been made available online. We have inspected reliability and consistency of this data set in state of the art current knowledge. Comparing with the climatological model IRI-2012 and the mathematical model FLIP a shift of absolute and relative ion densities with time was revealed. We have suggested a correction procedure of individual H+, He+ and O+ ion densities. Using the corrected data set, we investigated plasmapause locations based on density gradient in H+, and He+. Correlation coefficient of both locations was determined as approx. 0.886 and the typical difference (Delta)L approx. 0.1. The electron density at the He+ plasmapause location for all cases is >100/cu cm.
NASA Astrophysics Data System (ADS)
Di Giovanni, James P.; Barkley, Robert M.; Jones, David N. M.; Hankin, Joseph A.; Murphy, Robert C.
2018-04-01
Ion mobility measurements of product ions were used to characterize the collisional cross section (CCS) of various complex lipid [M-H]- ions using traveling wave ion mobility mass spectrometry (TWIMS). TWIMS analysis of various product ions derived after collisional activation of mono- and dihydroxy arachidonate metabolites was found to be more complex than the analysis of intact molecular ions and provided some insight into molecular mechanisms involved in product ion formation. The CCS observed for the molecular ion [M-H]- and certain product ions were consistent with a folded ion structure, the latter predicted by the proposed mechanisms of product ion formation. Unexpectedly, product ions from [M-H-H2O-CO2]- and [M-H-H2O]- displayed complex ion mobility profiles suggesting multiple mechanisms of ion formation. The [M-H-H2O]- ion from LTB4 was studied in more detail using both nitrogen and helium as the drift gas in the ion mobility cell. One population of [M-H-H2O]- product ions from LTB4 was consistent with formation of covalent ring structures, while the ions displaying a higher CCS were consistent with a more open-chain structure. Using molecular dynamics and theoretical CCS calculations, energy minimized structures of those product ions with the open-chain structures were found to have a higher CCS than a folded molecular ion structure. The measurement of product ion mobility can be an additional and unique signature of eicosanoids measured by LC-MS/MS techniques. [Figure not available: see fulltext.
Di Giovanni, James P; Barkley, Robert M; Jones, David N M; Hankin, Joseph A; Murphy, Robert C
2018-04-23
Ion mobility measurements of product ions were used to characterize the collisional cross section (CCS) of various complex lipid [M-H] - ions using traveling wave ion mobility mass spectrometry (TWIMS). TWIMS analysis of various product ions derived after collisional activation of mono- and dihydroxy arachidonate metabolites was found to be more complex than the analysis of intact molecular ions and provided some insight into molecular mechanisms involved in product ion formation. The CCS observed for the molecular ion [M-H] - and certain product ions were consistent with a folded ion structure, the latter predicted by the proposed mechanisms of product ion formation. Unexpectedly, product ions from [M-H-H 2 O-CO 2 ] - and [M-H-H 2 O] - displayed complex ion mobility profiles suggesting multiple mechanisms of ion formation. The [M-H-H 2 O] - ion from LTB 4 was studied in more detail using both nitrogen and helium as the drift gas in the ion mobility cell. One population of [M-H-H 2 O] - product ions from LTB 4 was consistent with formation of covalent ring structures, while the ions displaying a higher CCS were consistent with a more open-chain structure. Using molecular dynamics and theoretical CCS calculations, energy minimized structures of those product ions with the open-chain structures were found to have a higher CCS than a folded molecular ion structure. The measurement of product ion mobility can be an additional and unique signature of eicosanoids measured by LC-MS/MS techniques. Graphical Abstract ᅟ.
Solution Dependence of the Collisional Activation of Ubiquitin [M+7H]7+ Ions
Shi, Huilin; Atlasevich, Natalya; Merenbloom, Samuel I.; Clemmer, David E.
2014-01-01
The solution dependence of gas-phase unfolding for ubiquitin [M+7H]7+ ions has been studied by ion mobility spectrometry-mass spectrometry (IMS-MS). Different acidic water:methanol solutions are used to favor the native (N), more helical (A), or unfolded (U) solution states of ubiquitin. Unfolding of gas-phase ubiquitin ions is achieved by collisional heating and newly formed structures are examined by IMS. With an activation voltage of 100 V, a selected distribution of compact structures unfolds, forming three resolvable elongated states (E1-E3). The relative populations of these elongated structures depend strongly on the solution composition. Activation of compact ions from aqueous solutions known to favor N-state ubiquitin produces mostly the E1 type elongated state, whereas, activation of compact ions from methanol containing solutions that populate A-state ubiquitin favors the E3 elongated state. Presumably, this difference arises because of differences in precursor ion structures emerging from solution. Thus, it appears that information about solution populations can be retained after ionization, selection, and activation to produce the elongated states. These data as well as others are discussed. PMID:24658799
Pandey, Kalpana; Dhoke, Reema R; Rathore, Yogendra Singh; Nath, Samir K; Verma, Neha; Bawa, Simranjot; Ashish
2014-05-15
Calmodulin (CaM) regulates numerous cellular functions by sensing Ca(2+) levels inside cells. Although its structure as a function of the Ca(2+)-bound state remains hotly debated, no report is available on how pH independently or in interaction with Ca(2+) ions regulates shape and function of CaM. From SAXS data analysis of CaM at different levels of Ca(2+)-ion concentration and buffer pH, we found that (1) CaM molecules possess a Gaussian-chain-like shape in solution even in the presence of Ca(2+) ion or at low pH, (2) the global shape of apo CaM is very similar to its NMR structure rather than the crystal structures, (3) about 16 Ca(2+) ions or more are required per CaM molecule in solution to achieve the four-Ca(2+)-bound crystal structure, (4) low pH alone can impart shape changes in CaM similar to Ca(2+) ions, and (5) at different [Ca(2+)]/[CaM] ratio or pH values, the predominant shape of CaM is essentially a weighted average of its apo and fully activated shape. Results were further substantiated by analysis of sedimentation coefficient values from analytical ultracentrifugation and peptide binding assays using two peptides, each known to preferentially bind the apo or the Ca(2+)-activated state.
NASA Technical Reports Server (NTRS)
Pouch, J. J.; Alterovitz, S. A.; Warner, J. D.
1986-01-01
The amorphous dielectrics a-C:H and BN were deposited on III-V semiconductors. Optical band gaps as high as 3 eV were measured for a-C:H generated by C4H10 plasmas; a comparison was made with bad gaps obtained from films prepared by CH4 glow discharges. The ion beam deposited BN films exhibited amorphous behavior with band gaps on the order of 5 eV. Film compositions were studied by Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The optical properties were characterized by ellipsometry, UV/VIS absorption, and IR reflection and transmission. Etching rates of a-C:H subjected to O2 dicharges were determined.
NASA Astrophysics Data System (ADS)
Schmidtmayr, M.; Hughes, J. W.; Ryter, F.; Wolfrum, E.; Cao, N.; Creely, A. J.; Howard, N.; Hubbard, A. E.; Lin, Y.; Reinke, M. L.; Rice, J. E.; Tolman, E. A.; Wukitch, S.; Ma, Y.; ASDEX Upgrade Team; Alcator C-Mod Team
2018-05-01
This paper presents investigations on the role of the edge ion heat flux for transitions from L-mode to H-mode in Alcator C-Mod. Previous results from the ASDEX Upgrade tokamak indicated that a critical value of edge ion heat flux per particle is needed for the transition. Analysis of C-Mod data confirms this result. The edge ion heat flux is indeed found to increase linearly with density at given magnetic field and plasma current. Furthermore, the Alcator C-Mod data indicate that the edge ion heat flux at the L-H transition also increases with magnetic field. Combining the data from Alcator C-Mod and ASDEX Upgrade yields a general expression for the edge ion heat flux at the L-H transition. These results are discussed from the point of view of the possible physics mechanism of the L-H transition. They are also compared to the L-H power threshold scaling and an extrapolation for ITER is given.
Rod-filter-field optimization of the J-PARC RF-driven H{sup −} ion source
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.
2015-04-08
In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) second-stage requirements of an H{sup −} ion beam of 60mA within normalized emittances of 1.5πmm•mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500μs×25Hz) and a life-time of longer than 1month, the J-PARC cesiated RF-driven H{sup −} ion source was developed by using an internal-antenna developed at the Spallation Neutron Source (SNS). Although rod-filter-field (RFF) is indispensable and one of the most beam performance dominative parameters for the RF-driven H{sup −} ion source with the internal-antenna, the procedure to optimize it is not established. Inmore » order to optimize the RFF and establish the procedure, the beam performances of the J-PARC source with various types of rod-filter-magnets (RFMs) were measured. By changing RFM’s gap length and gap number inside of the region projecting the antenna inner-diameter along the beam axis, the dependence of the H{sup −} ion beam intensity on the net 2MHz-RF power was optimized. Furthermore, the fine-tuning of RFM’s cross-section (magnetmotive force) was indispensable for easy operation with the temperature (T{sub PE}) of the plasma electrode (PE) lower than 70°C, which minimizes the transverse emittances. The 5% reduction of RFM’s cross-section decreased the time-constant to recover the cesium effects after an slightly excessive cesiation on the PE from several 10 minutes to several minutes for T{sub PE} around 60°C.« less
NASA Astrophysics Data System (ADS)
Hayashizaki, Noriyosu; Hattori, Toshiyuki; Matsui, Shinjiro; Tomizawa, Hiromitsu; Yoshida, Toru; Isokawa, Katsushi; Kitagawa, Atsushi; Muramatsu, Masayuki; Yamada, Satoru; Okamura, Masahiro
2000-02-01
We have researched a compact medical accelerator with low investment and running cost for the popularization of heavy ion cancer therapy. As the first step, the compact injector system has been investigated for a Heavy Ion Medical Accelerator in Chiba at National Institute of Radiological Sciences. The proposed new injector system consists of a 6 MeV/u interdigital H-mode (IH) linac of 3.1 m long and a 18 GHz superconducting electron cyclotron resonance (ECR) (SC-ECR) ion source. The IH linac with high power efficiency is appropriate to a medical and industrial injector system. Its beam trajectory was simulated and a prototype has been constructed. The SC-ECR ion source has been designed to realize lightweight and low power consumption and the mirror field distribution was estimated.
Studies on the Extraction Region of the Type VI RF Driven H- Ion Source
NASA Astrophysics Data System (ADS)
McNeely, P.; Bandyopadhyay, M.; Franzen, P.; Heinemann, B.; Hu, C.; Kraus, W.; Riedl, R.; Speth, E.; Wilhelm, R.
2002-11-01
IPP Garching has spent several years developing a RF driven H- ion source intended to be an alternative to the current ITER (International Thermonuclear Experimental Reactor) reference design ion source. A RF driven source offers a number of advantages to ITER in terms of reduced costs and maintenance requirements. Although the RF driven ion source has shown itself to be competitive with a standard arc filament ion source for positive ions many questions still remain on the physics behind the production of the H- ion beam extracted from the source. With the improvements that have been implemented to the BATMAN (Bavarian Test Machine for Negative Ions) facility over the last two years it is now possible to study both the extracted ion beam and the plasma in the vicinity of the extraction grid in greater detail. This paper will show the effect of changing the extraction and acceleration voltage on both the current and shape of the beam as measured on the calorimeter some 1.5 m downstream from the source. The extraction voltage required to operate in the plasma limit is 3 kV. The perveance optimum for the extraction system was determined to be 2.2 x 10-6 A/V3/2 and occurs at 2.7 kV extraction voltage. The horizontal and vertical beam half widths vary as a function of the extracted ion current and the horizontal half width is generally smaller than the vertical. The effect of reducing the co-extracted electron current via plasma grid biasing on the H- current extractable and the beam profile from the source is shown. It is possible in the case of a silver contaminated plasma to reduce the co-extracted electron current to 20% of the initial value by applying a bias of 12 V. In the case where argon is present in the plasma, biasing is observed to have minimal effect on the beam half width but in a pure hydrogen plasma the beam half width increases as the bias voltage increases. New Langmuir probe studies that have been carried out parallel to the plasma grid (in the
Leem, Yea-Hyun; Lee, Kang-Sik; Kim, Jung-Hwa; Seok, Hyun-Kwang; Chang, Jae-Suk; Lee, Dong-Ho
2016-10-01
Magnesium metal and its alloys have been proposed as a novel class of bone implant biomaterials because of their biodegradability and mechanical properties. The purpose of this study was to determine whether magnesium ions, which are released abundantly from alloys, affect proliferation and differentiation of human bone marrow-derived stromal cells (hBMSCs). High levels of magnesium ions did not induce cytotoxicity in hBMSCs, but treatment with 2.5-10 mm magnesium ions for 48-72 h significantly increased hBMSC proliferation. The expression of integrins α2 and α3, but not β1, was upregulated compared with the control and shifted from α3 to α2 in hBMSCs treated with magnesium ions. Knockdown of integrins α2 and/or α3 significantly reduced magnesium-induced proliferation of hBMSCs. Magnesium exposure profoundly enhanced alkaline phosphatase (ALP) gene expression and activity even at a relatively low magnesium concentration (2.5 mm). Exposure to magnesium ions facilitated hBMSC proliferation via integrin α2 and α3 expression and partly promoted differentiation into osteoblasts via the alteration of ALP expression and activity. Accordingly, magnesium could be a useful biomaterial for orthopaedic applications such as bone implant biomaterials for repair and regeneration of bone defects in orthopaedic and dental fields. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.
Improvements to the internal and external antenna H(-) ion sources at the Spallation Neutron Source.
Welton, R F; Dudnikov, V G; Han, B X; Murray, S N; Pennisi, T R; Pillar, C; Santana, M; Stockli, M P; Turvey, M W
2014-02-01
The Spallation Neutron Source (SNS), a large scale neutron production facility, routinely operates with 30-40 mA peak current in the linac. Recent measurements have shown that our RF-driven internal antenna, Cs-enhanced, multi-cusp ion sources injects ∼55 mA of H(-) beam current (∼1 ms, 60 Hz) at 65-kV into a Radio Frequency Quadrupole (RFQ) accelerator through a closely coupled electrostatic Low-Energy Beam Transport system. Over the last several years a decrease in RFQ transmission and issues with internal antennas has stimulated source development at the SNS both for the internal and external antenna ion sources. This report discusses progress in improving internal antenna reliability, H(-) yield improvements which resulted from modifications to the outlet aperture assembly (applicable to both internal and external antenna sources) and studies made of the long standing problem of beam persistence with the external antenna source. The current status of the external antenna ion source will also be presented.
NASA Astrophysics Data System (ADS)
Ghaffour, M.; Abdellaoui, A.; Bouslama, M.; Ouerdane, A.; Abidri, B.
2012-06-01
Auger Electron Spectroscopy (AES) and Electron Energy Loss Spectroscopy (EELS) have been performed in order to investigate the InP(100) surface subjected to ions bombardment. The InP(100) surface is always contaminated by carbon and oxygen revealed by C-KLL and O-KLL AES spectra recorded just after introduction of the sample in the UHV spectrometer chamber. The usually cleaning process of the surface is the bombardment by argon ions. However, even at low energy of ions beam (300 eV) indium clusters and phosphorus vacancies are usually formed on the surface. The aim of our study is to compare the behaviour of the surface when submitted to He+ or H+ ions bombardment. The helium ions accelerated at 500V voltage and for 45 mn allow removing contaminants but induces damaged and no stoichiometric surface. The proton ions were accelerated at low energy of 500 eV to bombard the InP surface at room temperature. The proton ions broke the In-P chemical bonds to induce the formation of In metal islands. Such a chemical reactivity between hydrogen and phosphorus led to form chemical species such as PH and PH3, which desorbed from the surface. The chemical susceptibly and the small size of H+ advantaged their diffusion into bulk. Since the experimental methods alone were not able to give us with accuracy the disturbed depth of the target by these ions. We associate to the AES and EELS spectroscopies, the TRIM (Transport and Range of Ions in Matter) simulation method in order to show the mechanism of interaction between Ar+, He+ or H+ ions and InP and determine the disturbed depth of the target by argon, helium or proton ions.
Sun, Pengzhan; Sasaki, Takayoshi
2017-01-01
Ion conducting membranes/electrolytes have been employed extensively in some important industrial and biological systems, especially in fuel cells, water electrolyzers, gas separation, sensors and biological selective ion transport, acting as one of the core components and sometimes directly determining the device performance. However, the traditional polymeric proton exchange membranes (PEMs)/anion exchange membranes (AEMs) suffer from highly toxic preparation procedures, poor thermal and chemical stabilities, and unsatisfactory ion conductivities. This has triggered researchers worldwide to explore alternative inorganic building blocks with high ion conductivities and stabilities from the new materials library, hoping to solve the above long-lasting problems. The recent burgeoning research on two-dimensional (2D) materials has unveiled exceptionally high ionic conductivities, which raises the feasibility of fabricating high-performance nanosheet-based ion conductors/membranes. In this perspective, the recent advances in measuring and understanding the exceptionally high and anisotropic H+/OH– ion conductivities of representative 2D materials, e.g. graphene oxide (GO), vermiculite and layered double hydroxide (LDH) nanosheets, are reviewed. In particular, regarding the anisotropic ionic conduction in 2D nanosheets, possible design strategies and technological innovations for fabricating macroscopic nanosheet-based ionic conductors/membranes are proposed for maximizing the high in-plane conduction, which may serve to guide future development of high-performance industrial and biological systems relying on H+/OH– conducting membranes. PMID:29629071
Sun, Pengzhan; Ma, Renzhi; Sasaki, Takayoshi
2018-01-07
Ion conducting membranes/electrolytes have been employed extensively in some important industrial and biological systems, especially in fuel cells, water electrolyzers, gas separation, sensors and biological selective ion transport, acting as one of the core components and sometimes directly determining the device performance. However, the traditional polymeric proton exchange membranes (PEMs)/anion exchange membranes (AEMs) suffer from highly toxic preparation procedures, poor thermal and chemical stabilities, and unsatisfactory ion conductivities. This has triggered researchers worldwide to explore alternative inorganic building blocks with high ion conductivities and stabilities from the new materials library, hoping to solve the above long-lasting problems. The recent burgeoning research on two-dimensional (2D) materials has unveiled exceptionally high ionic conductivities, which raises the feasibility of fabricating high-performance nanosheet-based ion conductors/membranes. In this perspective, the recent advances in measuring and understanding the exceptionally high and anisotropic H + /OH - ion conductivities of representative 2D materials, e.g. graphene oxide (GO), vermiculite and layered double hydroxide (LDH) nanosheets, are reviewed. In particular, regarding the anisotropic ionic conduction in 2D nanosheets, possible design strategies and technological innovations for fabricating macroscopic nanosheet-based ionic conductors/membranes are proposed for maximizing the high in-plane conduction, which may serve to guide future development of high-performance industrial and biological systems relying on H + /OH - conducting membranes.
Characterization of faulted dislocation loops and cavities in ion irradiated alloy 800H
NASA Astrophysics Data System (ADS)
Ulmer, Christopher J.; Motta, Arthur T.
2018-01-01
Alloy 800H is a high nickel austenitic stainless steel with good high temperature mechanical properties which is considered for use in current and advanced nuclear reactor designs. The irradiation response of 800H was examined by characterizing samples that had been bulk ion irradiated at the Michigan Ion Beam Laboratory with 5 MeV Fe2+ ions to 1, 10, and 20 dpa at 440 °C. Transmission electron microscopy was used to measure the size and density of both {111} faulted dislocation loops and cavities as functions of depth from the irradiated surface. The faulted loop density increased with dose from 1 dpa up to 10 dpa where it saturated and remained approximately the same until 20 dpa. The faulted loop average diameter decreased between 1 dpa and 10 dpa and again remained approximately constant from 10 dpa to 20 dpa. Cavities were observed after irradiation doses of 10 and 20 dpa, but not after 1 dpa. The average diameter of cavities increased with dose from 10 to 20 dpa, with a corresponding small decrease in density. Cavity denuded zones were observed near the irradiated surface and near the ion implantation peak. To further understand the microstructural evolution of this alloy, FIB lift-out samples from material irradiated in bulk to 1 and 10 dpa were re-irradiated in-situ in their thin-foil geometry with 1 MeV Kr2+ ions at 440 °C at the Intermediate Voltage Electron Microscope. It was observed that the cavities formed during bulk irradiation shrank under thin-foil irradiation in-situ while dislocation loops were observed to grow and incorporate into the dislocation network. The thin-foil geometry used for in-situ irradiation is believed to cause the cavities to shrink.
Żurawik, Tomasz Michał; Pomorski, Adam; Belczyk-Ciesielska, Agnieszka; Goch, Grażyna; Niedźwiedzka, Katarzyna; Kucharczyk, Róża; Krężel, Artur; Bal, Wojciech
2016-01-01
Fluorescence measurements of pH and other analytes in the cell rely on accurate calibrations, but these have routinely used algorithms that inadequately describe the properties of indicators. Here, we have established a more accurate method for calibrating and analyzing data obtained using the ratiometric probe 5(6)-carboxy-SNARF-1. We tested the implications of novel approach to measurements of pH in yeast mitochondria, a compartment containing a small number of free H+ ions. Our findings demonstrate that 5(6)-carboxy-SNARF-1 interacts with H+ ions inside the mitochondria in an anticooperative manner (Hill coefficient n of 0.5) and the apparent pH inside the mitochondria is ~0.5 unit lower than had been generally assumed. This result, at odds with the current consensus on the mechanism of energy generation in the mitochondria, is in better agreement with theoretical considerations and warrants further studies of organellar pH. PMID:27557123
Hydride ions in oxide hosts hidden by hydroxide ions
Hayashi, Katsuro; Sushko, Peter V.; Hashimoto, Yasuhiro; Shluger, Alexander L.; Hosono, Hideo
2014-01-01
The true oxidation state of formally ‘H−’ ions incorporated in an oxide host is frequently discussed in connection with chemical shifts of 1H nuclear magnetic resonance spectroscopy, as they can exhibit values typically attributed to H+. Here we systematically investigate the link between geometrical structure and chemical shift of H− ions in an oxide host, mayenite, with a combination of experimental and ab initio approaches, in an attempt to resolve this issue. We demonstrate that the electron density near the hydrogen nucleus in an OH− ion (formally H+ state) exceeds that in an H− ion. This behaviour is the opposite to that expected from formal valences. We deduce a relationship between the chemical shift of H− and the distance from the H− ion to the coordinating electropositive cation. This relationship is pivotal for resolving H− species that are masked by various states of H+ ions. PMID:24662678
Christian, Eric L; Anderson, Vernon E.; Harris, Michael E
2011-01-01
Quantitative analysis of metal ion-phosphodiester interactions is a significant experimental challenge due to the complexities introduced by inner-sphere, outer-sphere (H-bonding with coordinated water), and electrostatic interactions that are difficult to isolate in solution studies. Here, we provide evidence that inner-sphere, H-bonding and electrostatic interactions between ions and dimethyl phosphate can be deconvoluted through peak fitting in the region of the Raman spectrum for the symmetric stretch of non-bridging phosphate oxygens (νsPO 2-). An approximation of the change in vibrational spectra due to different interaction modes is achieved using ions capable of all or a subset of the three forms of metal ion interaction. Contribution of electrostatic interactions to ion-induced changes to the Raman νsPO2- signal could be modeled by monitoring attenuation of νsPO2- in the presence of tetramethylammonium, while contribution of H-bonding and inner-sphere coordination could be approximated from the intensities of altered νsPO2- vibrational modes created by an interaction with ammonia, monovalent or divalent ions. A model is proposed in which discrete spectroscopic signals for inner-sphere, H-bonding, and electrostatic interactions are sufficient to account for the total observed change in νsPO2- signal due to interaction with a specific ion capable of all three modes of interaction. Importantly, the quantitative results are consistent with relative levels of coordination predicted from absolute electronegativity and absolute hardness of alkali and alkaline earth metals. PMID:21334281
Energy transfer between energetic ring current H(+) and O(+) by electromagnetic ion cyclotron waves
NASA Technical Reports Server (NTRS)
Thorne, Richard M.; Horne, Richard B.
1994-01-01
Electromagnetic ion cyclotron (EMIC) waves in the frequency range below the helium gyrofrequency can be excited in the equatorial region of the outer magnetosphere by cyclotron resonant instability with anisotropic ring current H(+) ions. As the unducted waves propagate to higher latitudes, the wave normal should become highly inclined to the ambient magnetic field. Under such conditions, wave energy can be absorbed by cyclotron resonant interactions with ambient O(+), leading to ion heating perpendicular to the ambient magnetic field. Resonant wave absorption peaks in the vicinity of the bi-ion frequency and the second harmonic of the O(+) gyrofrequrency. This absorption should mainly occur at latitudes between 10 deg and 30 deg along auroral field lines (L is greater than or equal to 7) in the postnoon sector. The concomitant ion heating perpendicular to the ambient magnetic field can contribute to the isotropization and geomagnetic trapping of collapsed O(+) ion conics (or beams) that originate from a low-altitude ionospheric source region. During geomagnetic storms when the O(+) content of the magnetosphere is significantly enhanced, the absorption of EMIC waves should become more efficient, and it may contribute to the observed acceleration of O(+) ions of ionospheric origin up to ring current energies.
NASA Astrophysics Data System (ADS)
Lawrie, S. R.; Faircloth, D. C.; Smith, J. D.; Sarmento, T. M.; Whitehead, M. O.; Wood, T.; Perkins, M.; Macgregor, J.; Abel, R.
2018-05-01
A vessel for extraction and source plasma analyses is being used for Penning H- ion source development at the Rutherford Appleton Laboratory. A new set of optical elements including an einzel lens has been installed, which transports over 80 mA of H- beam successfully. Simultaneously, a 2X scaled Penning source has been developed to reduce cathode power density. The 2X source is now delivering a 65 mA H- ion beam at 10% duty factor, meeting its design criteria. The long-term viability of the einzel lens and 2X source is now being evaluated, so new diagnostic devices have been installed. A pair of electrostatic deflector plates is used to correct beam misalignment and perform fast chopping, with a voltage rise time of 24 ns. A suite of four quartz crystal microbalances has shown that the cesium flux in the vacuum vessel is only increased by a factor of two, despite the absence of a dedicated cold trap. Finally, an infrared camera has demonstrated good agreement with thermal simulations but has indicated unexpected heating due to beam loss on the downstream electrode. These types of diagnostics are suitable for monitoring all operational ion sources. In addition to experimental campaigns and new diagnostic tools, the high-performance VSim and COMSOL software packages are being used for plasma simulations of two novel ion thrusters for space propulsion applications. In parallel, a VSim framework has been established to include arbitrary temperature and cesium fields to allow the modeling of surface physics in H- ion sources.
Shul'pin, Georgiy B
2013-09-28
This brief essay consists of a few "exciting stories" devoted to relations within a metal-complex catalyst between a metal ion and a coordinated ligand. When, as in the case of a human couple, the rapport of the partners is cordial and a love cements these relations, a chemist finds an ideal married couple, in other words he obtains a catalyst of choice which allows him to functionalize C-H bonds very efficiently and selectively. Examples of such lucky marriages in the catalytic world of ions and ligands are discussed here. Activity of the catalyst is characterized by turnover number (TON) or turnover frequency (TOF) as well as by yield of a target product. Introducing a chelating N,N- or N,O-ligand to the catalyst molecule (this can be an iron or manganese derivative) sharply enhances its activity. However, the activity of vanadium derivatives (with additionally added to the solution pyrazinecarboxylic acid, PCA) as well as of various osmium complexes does not dramatically depend on the nature of ligands surrounding metal ions. Complexes of these metals are very efficient catalysts in oxidations with H2O2. Osmium derivatives are record-holders exhibiting extremely high TONs whereas vanadium complexes are on the second position. Finally, elegant examples of alkane functionalization on the ions of non-transition metals (aluminium, gallium etc.) are described when one ligand within the metal complex (namely, hydroperoxyl ligand HOO(-)) helps other ligand of this complex (H2O2 molecule coordinated to the metal) to disintegrate into two species, generating very reactive hydroxyl radical. Hydrogen peroxide molecule, even ligated to the metal ion, is perfectly stable without the assistance of the neighboring HOO(-) ligand. This ligand can be easily oxidized donating an electron to its partner ligand (H2O2). In an analogous case, when the central ion in the catalyst is a transition metal, this ion changing its oxidation state can donate an electron to the coordinated H2O2
NASA Astrophysics Data System (ADS)
Dostanko, A. P.; Golosov, D. A.
2009-10-01
The possibility of using a plasma electron source (PES) with a discharge in crossed E × H field for compensating the ion beam from an end-Hall ion source (EHIS) is analyzed. The PES used as a neutralizer is mounted in the immediate vicinity of the EHIS ion generation and acceleration region at 90° to the source axis. The behavior of the discharge and emission parameters of the EHIS is determined for operation with a filament neutralizer and a plasma electron source. It is found that the maximal discharge current from the ion source attains a value of 3.8 A for operation with a PES and 4 A for operation with a filament compensator. It is established that the maximal discharge current for the ion source strongly depends on the working gas flow rate for low flow rates (up to 10 ml/min) in the EHIS; for higher flow rates, the maximum discharge current in the EHIS depends only on the emissivity of the PES. Analysis of the emission parameters of EHISs with filament and plasma neutralizers shows that the ion beam current and the ion current density distribution profile are independent of the type of the electron source and the ion current density can be as high as 0.2 mA/cm2 at a distance of 25 cm from the EHIS anode. The balance of currents in the ion source-electron source system is considered on the basis of analysis of operation of EHISs with various sources of electrons. It is concluded that the neutralization current required for operation of an ion source in the discharge compensation mode must be equal to or larger than the discharge current of the ion source. The use of PES for compensating the ion beam from an end-Hall ion source proved to be effective in processes of ion-assisted deposition of thin films using reactive gases like O2 or N2. The application of the PES technique makes it possible to increase the lifetime of the ion-assisted deposition system by an order of magnitude (the lifetime with a Ti cathode is at least 60 h and is limited by the
Method for the production of atomic ion species from plasma ion sources
Spence, David; Lykke, Keith
1998-01-01
A technique to enhance the yield of atomic ion species (H.sup.+, D.sup.+, O.sup.+, N.sup.+, etc.) from plasma ion sources. The technique involves the addition of catalyzing agents to the ion discharge. Effective catalysts include H.sub.2 O, D.sub.2 O, O.sub.2, and SF.sub.6, among others, with the most effective being water (H.sub.2 O) and deuterated water (D.sub.2 O). This technique has been developed at Argonne National Laboratory, where microwave generated plasmas have produced ion beams comprised of close to 100% purity protons (H.sup.+) and close to 100% purity deuterons (D.sup.+). The technique also increases the total yield of protons and deuterons by converting unwanted ion species, namely, H.sub.2.sup.+,H.sub.3.sup.+ and D.sub.2.sup.+, D.sub.3.sup.+, into the desired ion species, H.sup.+ and D.sup.+, respectively.
Olah, George A; Surya Prakash, G K; Rasul, Golam
2008-07-16
The structures and energies of the carbocations C 4H 7 (+) and C 5H 9 (+) were calculated using the ab initio method. The (13)C NMR chemical shifts of the carbocations were calculated using the GIAO-CCSD(T) method. The pisigma-delocalized bisected cyclopropylcarbinyl cation, 1 and nonclassical bicyclobutonium ion, 2 were found to be the minima for C 4H 7 (+) at the MP2/cc-pVTZ level. At the MP4(SDTQ)/cc-pVTZ//MP2/cc-pVTZ + ZPE level the structure 2 is 0.4 kcal/mol more stable than the structure 1. The (13)C NMR chemical shifts of 1 and 2 were calculated by the GIAO-CCSD(T) method. Based on relative energies and (13)C NMR chemical shift calculations, an equilibrium involving the 1 and 2 in superacid solutions is most likely responsible for the experimentally observed (13)C NMR chemical shifts, with the latter as the predominant equilibrating species. The alpha-methylcyclopropylcarbinyl cation, 4, and nonclassical bicyclobutonium ion, 5, were found to be the minima for C 5H 9 (+) at the MP2/cc-pVTZ level. At the MP4(SDTQ)/cc-pVTZ//MP2/cc-pVTZ + ZPE level ion 5 is 5.9 kcal/mol more stable than the structure 4. The calculated (13)C NMR chemical shifts of 5 agree rather well with the experimental values of C 5H 9 (+).
Girme, Tejashree Suresh; Agrawal, Jiwanasha Manish; Agrawal, Manish Suresh; Fulari, Sangamesh Gurunath; Shetti, Shraddha Subhash; Kagi, Vishwal Ajith
2017-01-01
Introduction Hand held mobile phones are presently the most popular means of communication worldwide and have transformed our lives in many aspects. The widespread use of such devices have resulted in growing concerns regarding harmful effects of radiations emitted by them. This study was designed to evaluate the effects of mobile phone usage on nickel ion release as well as pH of saliva in patients with fixed orthodontic appliances. Aim To assess the level of nickel ions in saliva and pH of saliva in mobile phone users undergoing fixed orthodontic treatment using inductively coupled plasma atomic emission spectrometry. Materials and Methods A total of 42 healthy patients with fixed orthodontic appliance in mouth for a duration of six to nine months were selected for the study. They were divided into experimental group (n=21) consisting of mobile phone users and control group (n=21) of non mobile phone users. Saliva samples were collected from both the groups and nickel ion levels were measured using inductively coupled plasma-mass spectroscopy. The pH values were also assessed for both groups using pH meter. Unpaired t-test was used for the data analysis. Results Statistical analysis revealed that though the pH levels were reduced and the nickel ion levels were higher in the experimental group compared to the control group, the results were non significant. Conclusion Mobile phone usage may affect the pH of saliva and result in increased release of nickel ions in saliva of patients with fixed orthodontic appliances in the oral cavity. PMID:29207841
Nanjannawar, Lalita Girish; Girme, Tejashree Suresh; Agrawal, Jiwanasha Manish; Agrawal, Manish Suresh; Fulari, Sangamesh Gurunath; Shetti, Shraddha Subhash; Kagi, Vishwal Ajith
2017-09-01
Hand held mobile phones are presently the most popular means of communication worldwide and have transformed our lives in many aspects. The widespread use of such devices have resulted in growing concerns regarding harmful effects of radiations emitted by them. This study was designed to evaluate the effects of mobile phone usage on nickel ion release as well as pH of saliva in patients with fixed orthodontic appliances. To assess the level of nickel ions in saliva and pH of saliva in mobile phone users undergoing fixed orthodontic treatment using inductively coupled plasma atomic emission spectrometry. A total of 42 healthy patients with fixed orthodontic appliance in mouth for a duration of six to nine months were selected for the study. They were divided into experimental group (n=21) consisting of mobile phone users and control group (n=21) of non mobile phone users. Saliva samples were collected from both the groups and nickel ion levels were measured using inductively coupled plasma-mass spectroscopy. The pH values were also assessed for both groups using pH meter. Unpaired t-test was used for the data analysis. Statistical analysis revealed that though the pH levels were reduced and the nickel ion levels were higher in the experimental group compared to the control group, the results were non significant. Mobile phone usage may affect the pH of saliva and result in increased release of nickel ions in saliva of patients with fixed orthodontic appliances in the oral cavity.
Enhancing the luminescence efficiency of silicon-nanocrystals by interaction with H+ ions.
Cannas, Marco; Camarda, Pietro; Vaccaro, Lavinia; Amato, Francesco; Messina, Fabrizio; Fiore, Tiziana; Li Vigni, Maria
2018-04-18
The emission of silicon nanocrystals (Si-NCs), synthesized by pulsed laser ablation in water, was investigated on varying the pH of the solution. These samples emit μs decaying orange photoluminescence (PL) associated with radiative recombination of quantum-confined excitons. Time-resolved spectra reveal that both the PL intensity and the lifetime increase by a factor of ∼20 when the pH decreases from 10 to 1 thus indicating that the emission quantum efficiency increases by inhibiting nonradiative decay rates. Infrared (IR) absorption and electron paramagnetic resonance (EPR) experiments allow addressing the origin of defects on which the excitons nonradiatively recombine. The linear correlation between the PL and the growth of SiH groups demonstrates that H+ ions passivate the nonradiative defects that are located in the interlayer between the Si-NC core and the amorphous SiO2 shell.
pH-sensitive ion-selective field-effect transistor with zirconium dioxide film
DOE Office of Scientific and Technical Information (OSTI.GOV)
Vlasov, Yu.G.; Bratov, A.V.; Tarantov, Yu.A.
1988-09-20
Miniature semiconductor pH sensors for liquid media, i.e., ion-selective field-effect transistors (ISFETs), are silicon field-effect transistors with a two-layer dielectric consisting of a passivating SiO/sub 2/ layer adjoining the silicon and a layer of pH-sensitive material in contact with the electrolyte solution to be tested. This study was devoted to the characteristics of pH-sensitive ISFETs with ZrO/sub 2/ films. The base was p-type silicon (KDB-10) with a (100) surface orientation. A ZrO/sub 2/ layer 10-50 nm thick was applied over the SiO/sub 2/ layer by electron-beam deposition. The measurements were made in aqueous KNO/sub 3/ or KCl solutions.
NASA Astrophysics Data System (ADS)
Stevens, Amy E.; Beauchamp, J. L.
1981-03-01
ICR trapped ion techniques are used to examine the kinetics of proton transfer from MnH + (formed as a fragment ion from HMn (CO) 5 by electron impact) to bases of varying strength. Deprotonation is rapid with bases whose proton affinity exceeds 196±3 kcal mol -1. This value for PA (Mn) yields the homolytic bond dissociation energy D0(Mn +-H) = 53±5 kcal mol -1.
Method for the production of atomic ion species from plasma ion sources
Spence, D.; Lykke, K.
1998-08-04
A technique to enhance the yield of atomic ion species (H{sup +}, D{sup +}, O{sup +}, N{sup +}, etc.) from plasma ion sources. The technique involves the addition of catalyzing agents to the ion discharge. Effective catalysts include H{sub 2}O, D{sub 2}O, O{sub 2}, and SF{sub 6}, among others, with the most effective being water (H{sub 2}O) and deuterated water (D{sub 2}O). This technique has been developed at Argonne National Laboratory, where microwave generated plasmas have produced ion beams comprised of close to 100% purity protons (H{sup +}) and close to 100% purity deuterons (D{sup +}). The technique also increases the total yield of protons and deuterons by converting unwanted ion species, namely, H{sub 2}{sup +}, H{sub 3}{sup +} and D{sub 2}{sup +}, D{sub 3}{sup +}, into the desired ion species, H{sup +} and D{sup +}, respectively. 4 figs.
Alternative RF coupling configurations for H- ion sources
NASA Astrophysics Data System (ADS)
Briefi, S.; Gutmann, P.; Fantz, U.
2015-04-01
RF heated sources for negative hydrogen ions both for fusion and accelerators require very high RF powers in order to achieve the required H- current what poses high demands on the RF generators and the RF circuit. Therefore it is highly desirable to improve the RF efficiency of the sources. This could be achieved by applying different RF coupling concepts than the currently used inductive coupling via a helical antenna, namely Helicon coupling or coupling via a planar ICP antenna enhanced with ferrites. In order to investigate the feasibility of these concepts, two small laboratory experiments have been set up. The PlanICE experiment, where the enhanced inductive coupling is going to be investigated, is currently under assembly. At the CHARLIE experiment systematic measurements concerning Helicon coupling in hydrogen and deuterium are carried out. The investigations show that a prominent feature of Helicon discharges occurs: the so-called low-field peak. This is a local improvement of the coupling efficiency at a magnetic field strength of a few mT which results in an increased electron density and dissociation degree. The full Helicon mode has not been achieved yet due to the limited available RF power and magnetic field strength but it might be sufficient for the application of the coupling concept to ion sources to operate the discharge in the low-field-peak region.
Rajasekharan, Sivaprakash; Vercruysse, Chris; Martens, Luc; Verbeeck, Ronald
2018-01-13
Tricalcium silicate cements (TSC) are used in dental traumatology and endodontics for their bioactivity which is mostly attributed to formation of calcium hydroxide during TSC hydration and its subsequent release of calcium and hydroxide ions. The aim of this study was to determine the effect of volume (Vol), exposed surface area (ESA) and pH of surrounding medium on calcium ion release. Three commercially available hydraulic alkaline dental cements were mixed and condensed into cylindrical tubes of varying length and diameter ( n = 6/group). For the effect of ESA and Vol, tubes were immersed in 10 mL of deionized water. To analyze the effect of environmental pH, the tubes were randomly immersed in 10 mL of buffer solutions with varying pH (10.4, 7.4 or 4.4). The solutions were collected and renewed at various time intervals. pH and/or calcium ion release was measured using a pH glass electrode and atomic absorption spectrophotometer respectively. The change of pH, short-term calcium ion release and rate at which calcium ion release reaches maximum were dependent on ESA ( p < 0.05) while maximum calcium ion release was dependent on Vol of TSC ( p < 0.05). Maximum calcium ion release was significantly higher in acidic solution followed by neutral and alkaline solution ( p < 0.05).
Rajasekharan, Sivaprakash; Vercruysse, Chris; Martens, Luc; Verbeeck, Ronald
2018-01-01
Tricalcium silicate cements (TSC) are used in dental traumatology and endodontics for their bioactivity which is mostly attributed to formation of calcium hydroxide during TSC hydration and its subsequent release of calcium and hydroxide ions. The aim of this study was to determine the effect of volume (Vol), exposed surface area (ESA) and pH of surrounding medium on calcium ion release. Three commercially available hydraulic alkaline dental cements were mixed and condensed into cylindrical tubes of varying length and diameter (n = 6/group). For the effect of ESA and Vol, tubes were immersed in 10 mL of deionized water. To analyze the effect of environmental pH, the tubes were randomly immersed in 10 mL of buffer solutions with varying pH (10.4, 7.4 or 4.4). The solutions were collected and renewed at various time intervals. pH and/or calcium ion release was measured using a pH glass electrode and atomic absorption spectrophotometer respectively. The change of pH, short-term calcium ion release and rate at which calcium ion release reaches maximum were dependent on ESA (p < 0.05) while maximum calcium ion release was dependent on Vol of TSC (p < 0.05). Maximum calcium ion release was significantly higher in acidic solution followed by neutral and alkaline solution (p < 0.05). PMID:29342837
Effect of Coulomb collision on the negative ion extraction mechanism in negative ion sources.
Goto, I; Miyamoto, K; Nishioka, S; Mattei, S; Lettry, J; Abe, S; Hatayama, A
2016-02-01
To improve the H(-) ion beam optics, it is necessary to understand the energy relaxation process of surface produced H(-) ions in the extraction region of Cs seeded H(-) ion sources. Coulomb collisions of charged particles have been introduced to the 2D3V-PIC (two dimension in real space and three dimension in velocity space particle-in-cell) model for the H(-) extraction by using the binary collision model. Due to Coulomb collision, the lower energy part of the ion energy distribution function of H(-) ions has been greatly increased. The mean kinetic energy of the surface produced H(-) ions has been reduced to 0.65 eV from 1.5 eV. It has been suggested that the beam optics of the extracted H(-) ion beam is strongly affected by the energy relaxation process due to Coulomb collision.
Long-pulse beam acceleration of MeV-class H(-) ion beams for ITER NB accelerator.
Umeda, N; Kashiwagi, M; Taniguchi, M; Tobari, H; Watanabe, K; Dairaku, M; Yamanaka, H; Inoue, T; Kojima, A; Hanada, M
2014-02-01
In order to realize neutral beam systems in International Thermonuclear Experimental Reactor whose target is to produce a 1 MeV, 200 A/m(2) during 3600 s D(-) ion beam, the electrostatic five-stages negative ion accelerator so-called "MeV accelerator" has been developed at Japan Atomic Energy Agency. To extend pulse length, heat load of the acceleration grids was reduced by controlling the ion beam trajectory. Namely, the beam deflection due to the residual magnetic field of filter magnet was suppressed with the newly developed extractor with a 0.5 mm off-set aperture displacement. The new extractor improved the deflection angle from 6 mrad to 1 mrad, resulting in the reduction of direct interception of negative ions from 23% to 15% of the total acceleration power, respectively. As a result, the pulse length of 130 A/m(2), 881 keV H(-) ion beam has been successfully extended from a previous value of 0.4 s to 8.7 s. This is the first long pulse negative ion beam acceleration over 100 MW/m(2).
Tattoo-based potentiometric ion-selective sensors for epidermal pH monitoring.
Bandodkar, Amay J; Hung, Vinci W S; Jia, Wenzhao; Valdés-Ramírez, Gabriela; Windmiller, Joshua R; Martinez, Alexandra G; Ramírez, Julian; Chan, Garrett; Kerman, Kagan; Wang, Joseph
2013-01-07
This article presents the fabrication and characterization of novel tattoo-based solid-contact ion-selective electrodes (ISEs) for non-invasive potentiometric monitoring of epidermal pH levels. The new fabrication approach combines commercially available temporary transfer tattoo paper with conventional screen printing and solid-contact polymer ISE methodologies. The resulting tattoo-based potentiometric sensors exhibit rapid and sensitive response to a wide range of pH changes with no carry-over effects. Furthermore, the tattoo ISE sensors endure repetitive mechanical deformation, which is a key requirement of wearable and epidermal sensors. The flexible and conformal nature of the tattoo sensors enable them to be mounted on nearly any exposed skin surface for real-time pH monitoring of the human perspiration, as illustrated from the response during a strenuous physical activity. The resulting tattoo-based ISE sensors offer considerable promise as wearable potentiometric sensors suitable for diverse applications.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Cho, Won-Hwi; Dang, Jeong-Jeung; Kim, June Young
2016-02-15
Transverse magnetic filter field as well as operating pressure is considered to be an important control knob to enhance negative hydrogen ion production via plasma parameter optimization in volume-produced negative hydrogen ion sources. Stronger filter field to reduce electron temperature sufficiently in the extraction region is favorable, but generally known to be limited by electron density drop near the extraction region. In this study, unexpected electron density increase instead of density drop is observed in front of the extraction region when the applied transverse filter field increases monotonically toward the extraction aperture. Measurements of plasma parameters with a movable Langmuirmore » probe indicate that the increased electron density may be caused by low energy electron accumulation in the filter region decreasing perpendicular diffusion coefficients across the increasing filter field. Negative hydrogen ion populations are estimated from the measured profiles of electron temperatures and densities and confirmed to be consistent with laser photo-detachment measurements of the H{sup −} populations for various filter field strengths and pressures. Enhanced H{sup −} population near the extraction region due to the increased low energy electrons in the filter region may be utilized to increase negative hydrogen beam currents by moving the extraction position accordingly. This new finding can be used to design efficient H{sup −} sources with an optimal filtering system by maximizing high energy electron filtering while keeping low energy electrons available in the extraction region.« less
Stopping force and straggling of 0.6-4.7 MeV H, He and Li ions in the polyhydroxybutyrate foil
NASA Astrophysics Data System (ADS)
Hsu, J. Y.; Yu, Y. C.; Chen, K. M.
2010-06-01
Stopping force and straggling of 0.6-3.5 MeV 1H ions, 2.0-4.7 MeV 4He ions and 1.4-4.4 MeV 7Li ions in the polyhydroxybutyrate (PHB) foil were measured by means of a transmission technique. The measured stopping forces are in well agreement with the SRIM 2008 calculation and the ICRU Report tables, except for the lower energy region. The obtained energy loss straggling deviates from the Bohr's value by as much as 23.6% for the energies under study. The validity of the Bragg's rule has also been demonstrated in the stopping force and straggling for 1H, 4He and 7Li ions in the PHB foil.
Different approaches to modeling the LANSCE H- ion source filament performance
NASA Astrophysics Data System (ADS)
Draganic, I. N.; O'Hara, J. F.; Rybarcyk, L. J.
2016-02-01
An overview of different approaches to modeling of hot tungsten filament performance in the Los Alamos Neutron Science Center (LANSCE) H- surface converter ion source is presented. The most critical components in this negative ion source are two specially shaped wire filaments heated up to the working temperature range of 2600 K-2700 K during normal beam production. In order to prevent catastrophic filament failures (creation of hot spots, wire breaking, excessive filament deflection towards source body, etc.) and to improve understanding of the material erosion processes, we have simulated the filament performance using three different models: a semi-empirical model, a thermal finite-element analysis model, and an analytical model. Results of all three models were compared with data taken during LANSCE beam production. The models were used to support the recent successful transition from the beam pulse repetition rate of 60 Hz-120 Hz.
NASA Technical Reports Server (NTRS)
Smyth, William H.
2001-01-01
This project has two overall objectives. One objective is to advance our general understanding of both the comet neutral atmosphere and the cometary plasma in the atmosphere and ion tall. The other objective is to obtain specific key information about comet Hale-Bopp that is generally important for Hale-Bopp studies. The primary emphasis in this project is to analyze, in a self-consistent manner, excellent quality high resolution image and line profile observations obtained by the University of Wisconsin for H, O, OH, and H2O+ emissions from the inner coma, outer coma, and ion tail of Hale-Bopp. The information on the spatial and velocity distributions of H2O neutral and ionized photo-products in the inner coma, outer coma, and in the H2O+ ion tail is of substantial and direct importance in the development of an integrated understanding of the complex structure and dynamics of the neutral and plasma species in the atmosphere of Hale-Bopp in particular and comets in general. The H2O production rate of Hale-Bopp is determined and, together with the other information related to the structure and dynamics of the neutral and plasma atmospheres obtained in this study, provide critical information important for a wide variety of research conducted by other groups.
Effect of H+ ion activity and Ca2+ on the toxicity of metals in the environment.
Hutchinson, T C; Collins, F W
1978-01-01
The role of acidity in determining and restricting plant distribution and performance is discussed. In soils especially, a key effect of H+ ion concentration is on the solubility of potentially toxic heavy metals such as aluminum, managenese, zinc, iron, copper, and nickel. Al has been reported from many studies since the 1920's as the key determining toxic factor in acid soils. Some acid-tolerant species have been shown to be especially tolerant of Al, and mechanisms of tolerance have been suggested. Mn is also a commonly toxic factor at soil pH less than 5.0. Calcium has been shown to alleviate Mn toxicity. Low pH soils are also generally low in Ca, K, Na, and P; all essential major elements for plant growth. In lakes and marine situations acidic waters are uncommon as the waters are buffered. Calcium is again ameliorative of metal toxicities. The pH, redox, and valency state are critical in determining nutrient availability and metal speciation. Recent increases in the H+ ion content of precipitation have caused increased acidities of freshwater lakes in Scandinavia and eastern North America, which have depleted biota, including fish populations. PMID:31277
Modeling of salt and pH gradient elution in ion-exchange chromatography.
Schmidt, Michael; Hafner, Mathias; Frech, Christian
2014-01-01
The separation of proteins by internally and externally generated pH gradients in chromatofocusing on ion-exchange columns is a well-established analytical method with a large number of applications. In this work, a stoichiometric displacement model was used to describe the retention behavior of lysozyme on SP Sepharose FF and a monoclonal antibody on Fractogel SO3 (S) in linear salt and pH gradient elution. The pH dependence of the binding charge B in the linear gradient elution model is introduced using a protein net charge model, while the pH dependence of the equilibrium constant is based on a thermodynamic approach. The model parameter and pH dependences are calculated from linear salt gradient elutions at different pH values as well as from linear pH gradient elutions at different fixed salt concentrations. The application of the model for the well-characterized protein lysozyme resulted in almost identical model parameters based on either linear salt or pH gradient elution data. For the antibody, only the approach based on linear pH gradients is feasible because of the limited pH range useful for salt gradient elution. The application of the model for the separation of an acid variant of the antibody from the major monomeric form is discussed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Iijima, Mayumi; Moriwaki, Yutaka
1989-05-01
The crystal growth of octacalcium phosphate (OCP) is of particular interest, since there is a possibility that OCP is formed in the early stage of tooth enamel formation. In this study, the effects of CO2-3, Mg2+ and F-ions on the morphology of OCP were investigated in a membrane system, where a cation selective membrane was used to simulate amelogenesis. Reactions were carried out at pH 6.3, 6.5 and 6.8 for 3 days at 37°C. In most cases, these ions suppressed the crystal growth in the c-axis direction of OCP, particularly when they coexisted. The morphology of OCP crystal changed from ribbon-like to flake-like, depending on the inhibitory activity. The inhibitory activity, particularly that of F - ion, was suppressed at pH lower than pH 6.8. Antagonistic effect of Mg2+ and F-ion was observed at pH 6.5. In the case of F - ion, OCP crystals showed a unique pattern, which suggests hydrolysis of OCP and subsequent growth of apatite. These findings indicate that inorganic ions, particularly F - ion, influence the growth of OCP. Although CO2-3, Mg2+andF-ions coexisted, extended growth in the c-axis direction of OCP took place at pH 6.0.
Photoionization and ion cyclotron resonance studies of the ion chemistry of ethylene oxide
NASA Technical Reports Server (NTRS)
Corderman, R. R.; Williamson, A. D.; Lebreton, P. R.; Buttrill, S. E., Jr.; Beauchamp, J. L.
1976-01-01
The formation of the ethylene oxide molecular ion and its subsequent ion-molecule reactions leading to the products C2H5O(+) and C3H5O(+) have been studied using time-resolved photoionization mass spectroscopy, ion cyclotron resonance spectroscopy, and photoelectron spectroscopy. An examination of the effects of internal energy on reactivity shows that the ratio of C3H5O(+) to C2H5O(+) increases by an order of magnitude with a single quantum of vibrational energy. The formation of (C2H4O/+/)-asterisk in a collision-induced isomerization is found which yields a ring-opened structure by C-C bond cleavage. The relaxed ring-opened C2H4O(+) ion reacts with neutral ethylene oxide by CH2(+) transfer to yield an intermediate product ion C3H6O(+) which gives C3H5O(+) by loss of H.
Photoinduced currents in pristine and ion irradiated kapton-H polyimide
NASA Astrophysics Data System (ADS)
Sharma, Anu; Sridharbabu, Y.; Quamara, J. K.
2014-10-01
The photoinduced currents in pristine and ion irradiated kapton-H polyimide have been investigated for different applied electric fields at 200°C. Particularly the effect of illumination intensity on the maximum current obtained as a result of photoinduced polarization has been studied. Samples were irradiated by using PELLETRON facility, IUAC, New Delhi. The photo-carrier charge generation depends directly on intensity of illumination. The samples irradiated at higher fluence show a decrease in the peak current with intensity of illumination. The secondary radiation induced crystallinity (SRIC) is responsible for the increase in maximum photoinduced currents generated with intensity of illumination.
Photoinduced currents in pristine and ion irradiated kapton-H polyimide
DOE Office of Scientific and Technical Information (OSTI.GOV)
Sharma, Anu, E-mail: sharmaanu81@gmail.com; Sridharbabu, Y., E-mail: sharmaanu81@gmail.com; Quamara, J. K., E-mail: sharmaanu81@gmail.com
2014-10-15
The photoinduced currents in pristine and ion irradiated kapton-H polyimide have been investigated for different applied electric fields at 200°C. Particularly the effect of illumination intensity on the maximum current obtained as a result of photoinduced polarization has been studied. Samples were irradiated by using PELLETRON facility, IUAC, New Delhi. The photo-carrier charge generation depends directly on intensity of illumination. The samples irradiated at higher fluence show a decrease in the peak current with intensity of illumination. The secondary radiation induced crystallinity (SRIC) is responsible for the increase in maximum photoinduced currents generated with intensity of illumination.
NASA Astrophysics Data System (ADS)
Yamamoto, T.; Shibata, T.; Ohta, M.; Yasumoto, M.; Nishida, K.; Hatayama, A.; Mattei, S.; Lettry, J.; Sawada, K.; Fantz, U.
2014-02-01
To control the H0 atom production profile in the H- ion sources is one of the important issues for the efficient and uniform surface H- production. The purpose of this study is to construct a collisional radiative (CR) model to calculate the effective production rate of H0 atoms from H2 molecules in the model geometry of the radio-frequency (RF) H- ion source for Linac4 accelerator. In order to validate the CR model by comparison with the experimental results from the optical emission spectroscopy, it is also necessary for the model to calculate Balmer photon emission rate in the source. As a basic test of the model, the time evolutions of H0 production and the Balmer Hα photon emission rate are calculated for given electron energy distribution functions in the Linac4 RF H- ion source. Reasonable test results are obtained and basis for the detailed comparisons with experimental results have been established.
Status of the RF-driven H{sup −} ion source for J-PARC linac
DOE Office of Scientific and Technical Information (OSTI.GOV)
Oguri, H., E-mail: oguri.hidetomo@jaea.go.jp; Ohkoshi, K.; Ikegami, K.
2016-02-15
For the upgrade of the Japan Proton Accelerator Research Complex linac beam current, a cesiated RF-driven negative hydrogen ion source was installed during the 2014 summer shutdown period, with subsequent operations commencing on September 29, 2014. The ion source has been successfully operating with a beam current and duty factor of 33 mA and 1.25% (500 μs and 25 Hz), respectively. The result of recent beam operation has demonstrated that the ion source is capable of continuous operation for approximately 1100 h. The spark rate at the beam extractor was observed to be at a frequency of less than oncemore » a day, which is an acceptable level for user operation. Although an antenna failure occurred during operation on October 26, 2014, no subsequent serious issues have occurred since then.« less
Spherical ion acoustic waves in pair ion plasmas with nonthermal electrons
NASA Astrophysics Data System (ADS)
Selim, M. M.
2016-04-01
Propagation of nonplanar ion acoustic waves in a plasma composed of negative and positive ions and nonthermally distributed electrons is investigated using reductive perturbation theory. The spherical Kadomtsev-Petviashvili (SKP) equation which describes the dynamics of the nonlinear spherical ion acoustic waves is derived. It is found that compressive and rarefactive ion-acoustic solitary wave characteristics significantly depend on the density and mass ratios of the positive to negative ions, the nonthermal electron parameter, and the geometry factor. The possible regions for the existence of spherical ion acoustic waves are defined precisely for typical parameters of (H+, O2 -) and (H+, H-) plasmas in the D and F-regions of the Earth's ionosphere, as well as for laboratory plasma (Ar+, F-).
NASA Astrophysics Data System (ADS)
Kokoouline, Viatcheslav; Fonseca Dos Santos, Samantha; Douguet, Nicolas; Orel, Ann
2013-05-01
The methylene amidogen radical (H2CN) was first discovered, in 1962 by Cochran et al ., and since then it has received considerable attention from both experimentalists and theoreticians. It is considered an important intermediate in the combustion of nitramine propellants and proposed to play a role in extraterrestrial atmospheres. It was detected in interstellar clouds in 1994, and its dissociative electron attachment (DEA) process may be responsible for the formation of the CN- and the H- negative ions: e-+H2CN --> CN- + H2; e-+H2CN --> H- + HCN. We report here the results of our ab initio quantum chemical studies of the geometrical and electronic structure of the methylene amidogen and and its negative ion H2CN- in the theoretical of DEA in H2CN. The scattering calculations are carried out using the complex Kohn variational method. The nuclear dynamics, including dissociation, will later be treated using the MCTDH code with a three-dimensional potential energy surface, in which the distance of CN is kept frozen. This work is supported by the DOE Office of Basic Energy Science and the National Science Foundation, Grant No's PHY-11-60611 and PHY-10-68785.
Effects of acidic pH on voltage-gated ion channels in rat trigeminal mesencephalic nucleus neurons.
Han, Jin-Eon; Cho, Jin-Hwa; Choi, In-Sun; Kim, Do-Yeon; Jang, Il-Sung
2017-03-01
The effects of acidic pH on several voltage-dependent ion channels, such as voltage-dependent K + and Ca 2+ channels, and hyperpolarization-gated and cyclic nucleotide-activated cation (HCN) channels, were examined using a whole-cell patch clamp technique on mechanically isolated rat mesencephalic trigeminal nucleus neurons. The application of a pH 6.5 solution had no effect on the peak amplitude of voltage-dependent K + currents. A pH 6.0 solution slightly, but significantly inhibited the peak amplitude of voltage-dependent K + currents. The pH 6.0 also shifted both the current-voltage and conductance-voltage relationships to the depolarization range. The application of a pH 6.5 solution scarcely affected the peak amplitude of membrane currents mediated by HCN channels, which were profoundly inhibited by the general HCN channel blocker Cs + (1 mM). However, the pH 6.0 solution slightly, but significantly inhibited the peak amplitude of HCN-mediated currents. Although the pH 6.0 solution showed complex modulation of the current-voltage and conductance-voltage relationships, the midpoint voltages for the activation of HCN channels were not changed by acidic pH. On the other hand, voltage-dependent Ca 2+ channels were significantly inhibited by an acidic pH. The application of an acidic pH solution significantly shifted the current-voltage and conductance-voltage relationships to the depolarization range. The modulation of several voltage-dependent ion channels by an acidic pH might affect the excitability of mesencephalic trigeminal nucleus neurons, and thus physiological functions mediated by the mesencephalic trigeminal nucleus could be affected in acidic pH conditions.
On Directly Solving SCHRÖDINGER Equation for H+2 Ion by Genetic Algorithm
NASA Astrophysics Data System (ADS)
Saha, Rajendra; Bhattacharyya, S. P.
Schrödinger equation (SE) is sought to be solved directly for the ground state of H+2 ion by invoking genetic algorithm (GA). In one approach the internuclear distance (R) is kept fixed, the corresponding electronic SE for H+2 is solved by GA at each R and the full potential energy curve (PEC) is constructed. The minimum of the PEC is then located giving Ve and Re. Alternatively, Ve and Re are located in a single run by allowing R to vary simultaneously while solving the electronic SE by genetic algorithm. The performance patterns of the two strategies are compared.
Improvement of Ion/Ioff for h-BN encapsulated bilayer graphene by graphite local back gate electrode
NASA Astrophysics Data System (ADS)
Uwanno, Teerayut; Taniguchi, Takashi; Watanabe, Kenji; Nagashio, Kosuke
The critical issue for bilayer graphene (BLG) devices is low Ion/Ioff even at the band gap of 0.3eV. Band gap in BLG can be formed by creating potential difference between the two layers of BLG. This can be done by applying external electric field perpendicularly to BLG to induce different carrier densities in the two layers. Due to such origin, the spatial uniformity of band gap in the channel is quite sensitive to charge inhomogeneity in BLG. In order to apply electric field of 3V/nm to open the maximum band gap of 0.3eV, high- k gate stack has been utilized so far. However, oxide dielectrics usually have large charge inhomogeneity causing in-plane potential fluctuation in BLG channel. Due to surface flatness and small charge inhomogeneity, h-BN has been used as dielectrics to achieve high quality graphene devices, however, Ion/Iofffor BLG/ h-BN heterostuctures has not been reported yet. In this study, we used graphite as local back gate electrode to BLG encapsulated with h-BN. This resulted in much higher Ion/Ioff, indicating the importance of screening of charge inhomogeneity from SiO2 substrate surface by local graphite back gate electrode. This research was partly supported by JSPS Core-to-Core Program, A. Advanced Research Networks.
Quantitative accuracy of the simplified strong ion equation to predict serum pH in dogs.
Cave, N J; Koo, S T
2015-01-01
Electrochemical approach to the assessment of acid-base states should provide a better mechanistic explanation of the metabolic component than methods that consider only pH and carbon dioxide. Simplified strong ion equation (SSIE), using published dog-specific values, would predict the measured serum pH of diseased dogs. Ten dogs, hospitalized for various reasons. Prospective study of a convenience sample of a consecutive series of dogs admitted to the Massey University Veterinary Teaching Hospital (MUVTH), from which serum biochemistry and blood gas analyses were performed at the same time. Serum pH was calculated (Hcal+) using the SSIE, and published values for the concentration and dissociation constant for the nonvolatile weak acids (Atot and Ka ), and subsequently Hcal+ was compared with the dog's actual pH (Hmeasured+). To determine the source of discordance between Hcal+ and Hmeasured+, the calculations were repeated using a series of substituted values for Atot and Ka . The Hcal+ did not approximate the Hmeasured+ for any dog (P = 0.499, r(2) = 0.068), and was consistently more basic. Substituted values Atot and Ka did not significantly improve the accuracy (r(2) = 0.169 to <0.001). Substituting the effective SID (Atot-[HCO3-]) produced a strong association between Hcal+ and Hmeasured+ (r(2) = 0.977). Using the simplified strong ion equation and the published values for Atot and Ka does not appear to provide a quantitative explanation for the acid-base status of dogs. Efficacy of substituting the effective SID in the simplified strong ion equation suggests the error lies in calculating the SID. Copyright © 2015 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.
Nuclear quantum effects on adsorption of H 2 and isotopologues on metal ions
Savchenko, Ievgeniia; Gu, Bing; Heine, Thomas; ...
2017-01-03
The nuclear quantum effects on the zero-point energy (ZPE), influencing adsorption of Hmore » $$_2$$ and isotopologues on metal ions, are examined in this study using normal mode analysis of ab initio electronic structure results for complexes with 17 metal cations. To estimate for the anharmonicity, a nuclear wavepacket dynamics on the ground state electronic potential energy surfaces (PES) have been employed for complexes of Li$^+$ and Cu$$^{+2}$$ with H$$_2$$, D$$_2$$, HD. The dynamics analysis shows that incorporation of the PES anharmonicity changes the ZPE by up to 9%. Finally, the lightest metallic nuclei, Li and Be, are found to be the most 'quantum'. The largest selectivity in adsorption is predicted for Cu, Ni and Co ions.« less
Plasma ignition and steady state simulations of the Linac4 H- ion source
NASA Astrophysics Data System (ADS)
Mattei, S.; Ohta, M.; Yasumoto, M.; Hatayama, A.; Lettry, J.; Grudiev, A.
2014-02-01
The RF heating of the plasma in the Linac4 H- ion source has been simulated using a particle-in-cell Monte Carlo collision method. This model is applied to investigate the plasma formation starting from an initial low electron density of 1012 m-3 and its stabilization at 1018 m-3. The plasma discharge at low electron density is driven by the capacitive coupling with the electric field generated by the antenna, and as the electron density increases the capacitive electric field is shielded by the plasma and induction drives the plasma heating process. Plasma properties such as e-/ion densities and energies, sheath formation, and shielding effect are presented and provide insight to the plasma properties of the hydrogen plasma.
Rotationally inelastic collisions of H2+ ions with He buffer gas: Computing cross sections and rates
NASA Astrophysics Data System (ADS)
Hernández Vera, Mario; Gianturco, F. A.; Wester, R.; da Silva, H.; Dulieu, O.; Schiller, S.
2017-03-01
We present quantum calculations for the inelastic collisions between H2+ molecules, in rotationally excited internal states, and He atoms. This work is motivated by the possibility of experiments in which the molecular ions are stored and translationally cooled in an ion trap and a He buffer gas is added for deactivation of the internal rotational population, in particular at low (cryogenic) translational temperatures. We carry out an accurate representation of the forces at play from an ab initio description of the relevant potential energy surface, with the molecular ion in its ground vibrational state, and obtain the cross sections for state-changing rotationally inelastic collisions by solving the coupled channel quantum scattering equations. The presence of hyperfine and fine structure effects in both ortho- and para-H2+ molecules is investigated and compared to the results where such a contribution is disregarded. An analysis of possible propensity rules that may predict the relative probabilities of inelastic events involving rotational state-changing is also carried out, together with the corresponding elastic cross sections from several initial rotational states. Temperature-dependent rotationally inelastic rates are then computed and discussed in terms of relative state-changing collisional efficiency under trap conditions. The results provide the essential input data for modeling different aspects of the experimental setups which can finally produce internally cold molecular ions interacting with a buffer gas.
NASA Technical Reports Server (NTRS)
Orient, O. J.; Chutjian, A.; Leung, K. N.
1987-01-01
Effects of H(-) production in a multicusp ion source are measured by separately mixing with hydrogen small amounts (0.33-10 percent) of water, ammonia, methane, and hydrazine these are molecules which produce large amounts of H(-) via dissociative attachment (DA) resonances at higher electron energies. The mixing was done in a separate reservoir, with careful measurement of individual pressures. Experimental enhancements of 1.4 and less were observed, whereas calculated enhancements, using accurate DA cross sections for ground-state H2, should have produced factors of 1.5, 3.0, 1.3, and 2.4 enhancements for water, ammonia methane, and hydrazine, respectively, at a mean electron energy of 1.0 eV in the extraction region. The difference is accounted for by including, in the enhancement calculation, vibrationally and rotationally excited H2 molecules, with v-double prime = 5-11, and J-double prime = 0-5, and the large DA cross sections for the excited H2 (v-double prime, J-double prime). The relative populations of H2 (v-double prime, J-double prime) thus obtained are found to be substantially smaller than those predicted by theoretical calculations. The effect on H(-) current was also studied by mixing small amounts of SF6 with H2. A 1.5 percent mixture was found to reduce the H(-) output by one half.
Gas-Phase Oxidation via Ion/Ion Reactions: Pathways and Applications
NASA Astrophysics Data System (ADS)
Pilo, Alice L.; Zhao, Feifei; McLuckey, Scott A.
2017-06-01
Here, we provide an overview of pathways available upon the gas-phase oxidation of peptides and DNA via ion/ion reactions and explore potential applications of these chemistries. The oxidation of thioethers (i.e., methionine residues and S-alkyl cysteine residues), disulfide bonds, S-nitrosylated cysteine residues, and DNA to the [M+H+O]+ derivative via ion/ion reactions with periodate and peroxymono-sulfate anions is demonstrated. The oxidation of neutral basic sites to various oxidized structures, including the [M+H+O]+, [M-H]+, and [M-H-NH3]+ species, via ion/ion reactions is illustrated and the oxidation characteristics of two different oxidizing reagents, periodate and persulfate anions, are compared. Lastly, the highly efficient generation of molecular radical cations via ion/ion reactions with sulfate radical anion is summarized. Activation of the newly generated molecular radical peptide cations results in losses of various neutral side chains, several of which generate dehydroalanine residues that can be used to localize the amino acid from which the dehydroalanine was generated. The chemistries presented herein result in a diverse range of structures that can be used for a variety of applications, including the identification and localization of S-alkyl cysteine residues, the oxidative cleavage of disulfide bonds, and the generation of molecular radical cations from even-electron doubly protonated peptides. [Figure not available: see fulltext.
Microstructure of a-C:H films prepared on a microtrench and analysis of ions and radicals behavior
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hirata, Yuki; Choi, Junho, E-mail: choi@mech.t.u-tokyo.ac.jp
2015-08-28
Amorphous carbon films (a-C:H) were prepared on a microtrench (4-μm pitch and 4-μm depth), and the uniformity of film thickness and microstructure of the films on the top, sidewall, and bottom surfaces of the microtrench were evaluated by scanning electron microscopy and Raman spectroscopy. The a-C:H films were prepared by bipolar-type plasma based ion implantation and deposition (bipolar PBII&D), and the negative pulse voltage, which is the main parameter dominating the film structure, was changed from −1.0 to −15 kV. Moreover, the behavior of ions and radicals was analyzed simultaneously by combining the calculation methods of Particle-In-Cell/Monte Carlo Collision (PIC-MCC) andmore » Direct Simulation Monte Carlo (DSMC) to investigate the coating mechanism for the microtrench. The results reveal that the thickness uniformity of a-C:H films improves with decreasing negative pulse voltage due to the decreasing inertia of incoming ions from the trench mouth, although the film thickness on the sidewall tends to be much smaller than that on the top and bottom surfaces of the trench. The normalized flux and the film thickness show similar behavior, i.e., the normalized flux or thickness at the bottom surface increases at low negative pulse voltages and then saturates at a certain value, whereas at the sidewall it monotonically decreases with increasing negative voltage. The microstructure of a-C:H films on the sidewall surface is very different from that on the top and bottom surfaces. The film structure at a low negative pulse voltage shifts to more of a polymer-like carbon (PLC) structure due to the lower incident energy of ions. Although the radical flux on the sidewall increases slightly, the overall film structure is not significantly changed because this film formation at a low negative voltage is originally dominated by radicals. On the other hand, the flux of radicals is dominant on the sidewall in the case of high negative pulse voltage, resulting
Microstructure of a-C:H films prepared on a microtrench and analysis of ions and radicals behavior
NASA Astrophysics Data System (ADS)
Hirata, Yuki; Choi, Junho
2015-08-01
Amorphous carbon films (a-C:H) were prepared on a microtrench (4-μm pitch and 4-μm depth), and the uniformity of film thickness and microstructure of the films on the top, sidewall, and bottom surfaces of the microtrench were evaluated by scanning electron microscopy and Raman spectroscopy. The a-C:H films were prepared by bipolar-type plasma based ion implantation and deposition (bipolar PBII&D), and the negative pulse voltage, which is the main parameter dominating the film structure, was changed from -1.0 to -15 kV. Moreover, the behavior of ions and radicals was analyzed simultaneously by combining the calculation methods of Particle-In-Cell/Monte Carlo Collision (PIC-MCC) and Direct Simulation Monte Carlo (DSMC) to investigate the coating mechanism for the microtrench. The results reveal that the thickness uniformity of a-C:H films improves with decreasing negative pulse voltage due to the decreasing inertia of incoming ions from the trench mouth, although the film thickness on the sidewall tends to be much smaller than that on the top and bottom surfaces of the trench. The normalized flux and the film thickness show similar behavior, i.e., the normalized flux or thickness at the bottom surface increases at low negative pulse voltages and then saturates at a certain value, whereas at the sidewall it monotonically decreases with increasing negative voltage. The microstructure of a-C:H films on the sidewall surface is very different from that on the top and bottom surfaces. The film structure at a low negative pulse voltage shifts to more of a polymer-like carbon (PLC) structure due to the lower incident energy of ions. Although the radical flux on the sidewall increases slightly, the overall film structure is not significantly changed because this film formation at a low negative voltage is originally dominated by radicals. On the other hand, the flux of radicals is dominant on the sidewall in the case of high negative pulse voltage, resulting in a deviation
The continued development of the Spallation Neutron Source external antenna H- ion sourcea)
NASA Astrophysics Data System (ADS)
Welton, R. F.; Carmichael, J.; Desai, N. J.; Fuga, R.; Goulding, R. H.; Han, B.; Kang, Y.; Lee, S. W.; Murray, S. N.; Pennisi, T.; Potter, K. G.; Santana, M.; Stockli, M. P.
2010-02-01
The U.S. Spallation Neutron Source (SNS) is an accelerator-based, pulsed neutron-scattering facility, currently in the process of ramping up neutron production. In order to ensure that the SNS will meet its operational commitments as well as provide for future facility upgrades with high reliability, we are developing a rf-driven, H- ion source based on a water-cooled, ceramic aluminum nitride (AlN) plasma chamber. To date, early versions of this source have delivered up to 42 mA to the SNS front end and unanalyzed beam currents up to ˜100 mA (60 Hz, 1 ms) to the ion source test stand. This source was operated on the SNS accelerator from February to April 2009 and produced ˜35 mA (beam current required by the ramp up plan) with availability of ˜97%. During this run several ion source failures identified reliability issues, which must be addressed before the source re-enters production: plasma ignition, antenna lifetime, magnet cooling, and cooling jacket integrity. This report discusses these issues, details proposed engineering solutions, and notes progress to date.
Dissociative charge transfer of H/+/ ions with H2 and D2 molecules from 78 to 330 K
NASA Technical Reports Server (NTRS)
Johnsen, R.; Chen, A.; Biondi, M. A.
1980-01-01
The dissociative charge transfer of He(+) ions with H2 and D2 molecules has been studied using a temperature-variable drift-tube mass-spectrometer apparatus over the temperature range 78 to 330 K. The binary rate coefficients are small at 300 K, approximately 10 to the -13th to 10 to the -14th cu cm/sec, and only slightly larger at 78 K. Termolecular contributions to the binary rate coefficients are found to be small at 330 K but increase substantially with decreasing temperature. Two-body charge transfer with D2 is found to be slower than with H2 by a factor of 10, in good agreement with recent theoretical predictions, although the measured values of the rate coefficients are larger by a factor of about 4 than the predicted values.
Modulation of Connexin-36 Gap Junction Channels by Intracellular pH and Magnesium Ions.
Rimkute, Lina; Kraujalis, Tadas; Snipas, Mindaugas; Palacios-Prado, Nicolas; Jotautis, Vaidas; Skeberdis, Vytenis A; Bukauskas, Feliksas F
2018-01-01
Connexin-36 (Cx36) protein forms gap junction (GJ) channels in pancreatic beta cells and is also the main Cx isoform forming electrical synapses in the adult mammalian brain. Cx36 GJs can be regulated by intracellular pH (pH i ) and cytosolic magnesium ion concentration ([Mg 2+ ] i ), which can vary significantly under various physiological and pathological conditions. However, the combined effect and relationship of these two factors over Cx36-dependent coupling have not been previously studied in detail. Our experimental results in HeLa cells expressing Cx36 show that changes in both pH i and [Mg 2+ ] i affect junctional conductance (g j ) in an interdependent manner; in other words, intracellular acidification cause increase or decay in g j depending on whether [Mg 2+ ] i is high or low, respectively, and intracellular alkalization cause reduction in g j independently of [Mg 2+ ] i . Our experimental and modelling data support the hypothesis that Cx36 GJ channels contain two separate gating mechanisms, and both are differentially sensitive to changes in pH i and [Mg 2+ ] i . Using recombinant Cx36 we found that two glutamate residues in the N-terminus could be partly responsible for the observed interrelated effect of pH i and [Mg 2+ ] i . Mutation of glutamate at position 8 attenuated the stimulatory effect of intracellular acidification at high [Mg 2+ ] i , while mutation at position 12 and double mutation at both positions reversed stimulatory effect to inhibition. Moreover, Cx36 * E8Q lost the initial increase of g j at low [Mg 2+ ] i and double mutation lost the sensitivity to high [Mg 2+ ] i . These results suggest that E8 and E12 are involved in regulation of Cx36 GJ channels by Mg 2+ and H + ions.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.
2015-04-08
In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) second stage requirements of an H{sup −} ion beam of 60mA within normalized emittances of 1.5πmm•mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500μs×25Hz) and a life-time of longer than 1month, the J-PARC cesiated RF-driven H{sup −} ion source was developed by using an internal-antenna developed at the Spallation Neutron Source (SNS). The maintenance and operation procedure to minimize the plasma chamber (PCH) replacement time on the beam line, which is very important to maximize the J-PARC beam time especially for an antenna failure,more » is presented in this paper. The PCH preserved by filling argon (Ar) gas inside after pre-conditioning including pre-cesiation to produce the required beam at a test-stand successfully produced the required beam on the beam line with slight addition of cesium (Cs). The methods of the feedback controls of a 2MHz-RF-matching, an H{sup −} ion beam intensity and the addition of Cs are also presented. The RF-matching feedback by using two vacuum variable capacitors (VVCs) and RF-frequency shift produced the almost perfect matching with negligibly small reflected RF-power. The H{sup −} ion beam intensity was controlled within errors of ±0.1mA by the RF-power feedback. The amount of Cs was also controlled by remotely opening a Cs-valve to keep the RF-power lower than a settled value.« less
The ins and outs of intracellular ion homeostasis: NHX-type cation/H(+) transporters.
Bassil, Elias; Blumwald, Eduardo
2014-12-01
The biochemical characterization of cation/H(+) exchange has been known since 1985 [1], yet only recently have we begun to understand the contribution of individual exchangers to ion homeostasis in plants. One particularly important class of exchangers is the NHX-type that is associated with Na(+) transport and therefore salinity tolerance. New evidence suggests that under normal growth conditions NHXs are critical regulators of K(+) and pH homeostasis and have important roles, depending on their cellular localization, in the generation of turgor as well as in vesicular trafficking. Recent advances highlight novel and exciting functions of intracellular NHXs in growth and development, stress adaptation and osmotic adjustment. Here, we elaborate on new and emerging cellular and physiological functions of this group of H(+)-coupled cation exchangers. Copyright © 2014 Elsevier Ltd. All rights reserved.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Draganic, I. N., E-mail: draganic@lanl.gov
Basic vacuum calculations were performed for various operating conditions of the Los Alamos National Neutron Science H{sup −} Cockcroft-Walton (CW) injector and the Ion Source Test Stand (ISTS). The vacuum pressure was estimated for both the CW and ISTS at five different points: (1) inside the H{sup −} ion source, (2) in front of the Pierce electrode, (3) at the extraction electrode, (4) at the column electrode, and (5) at the ground electrode. A static vacuum analysis of residual gases and the working hydrogen gas was completed for the normal ion source working regime. Gas density and partial pressure weremore » estimated for the injected hydrogen gas. The attenuation of H{sup −} beam current and generation of electron current in the high voltage acceleration columns and low energy beam transport lines were calculated. The interaction of H{sup −} ions on molecular hydrogen (H{sub 2}) is discussed as a dominant collision process in describing electron stripping rates. These results are used to estimate the observed increase in the ratio of electrons to H{sup −} ion beam in the ISTS beam transport line.« less
Biosorption of heavy metal ions on Rhodobacter sphaeroides and Alcaligenes eutrophus H16
DOE Office of Scientific and Technical Information (OSTI.GOV)
Seki, Hideshi; Suzuki, Akira; Mitsueda, Shinichiro
1998-01-15
A fundamental study of the application of bacteria to the recovery of toxic heavy metals from aqueous environments was carried out. The biosorption characteristics of cadmium and lead ions were determined with purple nonsulfur bacteria, Rhodobacter sphaeroides and hydrogen bacteria, Alcaligenes eutrophus H16 that were inactivated by steam sterilization. A simplified version of the metal binding model proposed by Plette et al. was used for the description of meal binding data. The results showed that the biosorption of bivalent metal ions to whole cell bodies of the bacteria was due to monodentate binding to two different types of acidic sites:more » carboxilic and phosphatic-type sites. The number of metal binding sites of A. eutrophus was 2.4-fold larger than that of R. sphaeroides.« less
Oxidation of Methionine Residues in Polypeptide Ions via Gas-Phase Ion/Ion Chemistry
Pilo, Alice L.; McLuckey, Scott A.
2014-01-01
The gas-phase oxidation of methionine residues is demonstrated here using ion/ion reactions with periodate anions. Periodate anions are observed to attach to varying degrees to all polypeptide ions irrespective of amino acid composition. Direct proton transfer yielding a charge reduced peptide ion is also observed. In the case of methionine and, to a much lesser degree, tryptophan containing peptide ions, collisional activation of the complex ion generated by periodate attachment yields an oxidized peptide product (i.e., [M+H+O]+), in addition to periodic acid detachment. Detachment of periodic acid takes place exclusively for peptides that do not contain either a methionine or tryptophan side-chain. In the case of methionine containing peptides, the [M+H+O]+ product is observed at a much greater abundance than the proton transfer product (viz., [M+H]+). Collisional activation of oxidized Met-containing peptides yields a signature loss of 64 Da from the precursor and/or product ions. This unique loss corresponds to the ejection of methanesulfenic acid from the oxidized methionine side chain and is commonly used in solution-phase proteomics studies to determine the presence of oxidized methionine residues. The present work shows that periodate anions can be used to ‘label’ methionine residues in polypeptides in the gas-phase. The selectivity of the periodate anion for the methionine side chain suggests several applications including identification and location of methionine residues in sequencing applications. PMID:24671696
Ion cyclotron resonance heating for tungsten control in various JET H-mode scenarios
NASA Astrophysics Data System (ADS)
Goniche, M.; Dumont, R. J.; Bobkov, V.; Buratti, P.; Brezinsek, S.; Challis, C.; Colas, L.; Czarnecka, A.; Drewelow, P.; Fedorczak, N.; Garcia, J.; Giroud, C.; Graham, M.; Graves, J. P.; Hobirk, J.; Jacquet, P.; Lerche, E.; Mantica, P.; Monakhov, I.; Monier-Garbet, P.; Nave, M. F. F.; Noble, C.; Nunes, I.; Pütterich, T.; Rimini, F.; Sertoli, M.; Valisa, M.; Van Eester, D.; Contributors, JET
2017-05-01
Ion cyclotron resonance heating (ICRH) in the hydrogen minority scheme provides central ion heating and acts favorably on the core tungsten transport. Full wave modeling shows that, at medium power level (4 MW), after collisional redistribution, the ratio of power transferred to the ions and the electrons vary little with the minority (hydrogen) concentration n H/n e but the high-Z impurity screening provided by the fast ions temperature increases with the concentration. The power radiated by tungsten in the core of the JET discharges has been analyzed on a large database covering the 2013-2014 campaign. In the baseline scenario with moderate plasma current (I p = 2.5 MA) ICRH modifies efficiently tungsten transport to avoid its accumulation in the plasma centre and, when the ICRH power is increased, the tungsten radiation peaking evolves as predicted by the neo-classical theory. At higher current (3-4 MA), tungsten accumulation can be only avoided with 5 MW of ICRH power with high gas injection rate. For discharges in the hybrid scenario, the strong initial peaking of the density leads to strong tungsten accumulation. When this initial density peaking is slightly reduced, with an ICRH power in excess of 4 MW,very low tungsten concentration in the core (˜10-5) is maintained for 3 s. MHD activity plays a key role in tungsten transport and modulation of the tungsten radiation during a sawtooth cycle is correlated to the fishbone activity triggered by the fast ion pressure gradient.
TANOMARU-FILHO, Mário; SAÇAKI, Juliana Nogueira; FALEIROS, Frederico Bordini Chaves; GUERREIRO-TANOMARU, Juliane Maria
2011-01-01
Objective Hydroxyl (OH-) and calcium (Ca++) ion release was evaluated in six materials: G1) Sealer 26, G2) White mineral trioxide aggregate (MTA), G3) epiphany, G4) epiphany + 10% calcium hydroxide (CH), G5) epiphany + 20% CH, and G6) zinc oxide and eugenol. Material and Methods Specimens were placed in polyethylene tubes and immersed in distilled water. After 3, 6, 12, 24, and 48 h, 7, 14, and 28 days, the water was assessed for pH with a pH meter and for Ca++ release by atomic absorption spectrophotometry. Results G1, G2, G4, and G5 had the highest pH until 14 days (p<0.05). G1 presented the highest Ca++ release until 6 h, and G4 and G5, from 12 h through 14 days. Ca++ release was greater for G1 and G2 at 28 days. G6 released the least Ca++. Conclusion MTA, Sealer 26, epiphany, and epiphany + CH release OH - and Ca++ ions. Epiphany + CH may be an alternative as retrofilling material. PMID:21437461
Measurements of the cesium flow from a surface-plasma H/sup -/ ion source
DOE Office of Scientific and Technical Information (OSTI.GOV)
Smith, H.V.; Allison, P.W.
1979-01-01
A surface ionization gauge (SIG) was constructed and used to measure the Cs/sup 0/ flow rate through the emission slit of a surface-plasma source (SPS) of H/sup -/ ions with Penning geometry. The equivalent cesium density in the SPS discharge is deduced from these flow measurements. For dc operation the optimum H/sup -/ current occurs at an equivalent cesium density of approx. 7 x 10/sup 12/ cm/sup -3/ (corresponding to an average cesium consumption rate of 0.5 mg/h). For pulsed operation the optimum H/sup -/ current occurs at an equivalent cesium density of approx. 2 x 10/sup 13/ cm/sup -3/more » (1-mg/h average cesium consumption rate). Cesium trapping by the SPS discharge was observed for both dc and pulsed operation. A cesium energy of approx. 0.1 eV is deduced from the observed time of flight to the SIG. In addition to providing information on the physics of the source, the SIG is a useful diagnostic tool for source startup and operation.« less
NASA Astrophysics Data System (ADS)
Engebretson, M. J.; Kahlstorf, C. R. G.; Murr, D. L.; Posch, J. L.; Keiling, A.; Lavraud, B.; Rème, H.; Lessard, M. R.; Kim, E.-H.; Johnson, J. R.; Dombeck, J.; Grison, B.; Robert, P.; Glassmeier, K.-H.; Décréau, P. M. E.
2012-10-01
Bursts of band-limited Pc 1 waves (0.2 to ˜1.0 Hz) with normalized frequency f/fH+ ˜ 0.5 have been observed by the Cluster spacecraft during many passes through the high-latitude plasma mantle. These transverse, left-hand polarized waves are associated with regions of H+ and O+ ions streaming away from Earth along magnetic field lines at the same velocity (˜140 km/s). Waves were observed only when H+ fluxes increased by factors of 10-1000 and energies of both ion species increased by factors of up to 10. We present two satellite-ground conjunctions to demonstrate the high latitude localization of these waves and their ability to reach the polar ionosphere and two extended examples of waves and associated ion distribution functions near the southern dusk flank magnetopause. We also present the results of a search for all such events during Cluster's 2002 and 2003 passages through the magnetotail, with orbital precession covering dawn to dusk on Earth's night side (June through December). A total of 46 events (band-limited Pc 1-2 waves accompanied by a sustained population of streaming H+ and O+ ions, separated by at least 12 min) were observed on 29 days. The waves were generally associated with intervals of southward IMF Bz and/or large IMF By (times of active cusp reconnection), and often but not always occurred during the main phase or early recovery phase of magnetic storms. Analysis of selected events shows that the waves are associated with large H+ temperature anisotropy, and that the waves propagate opposite to the direction of the streaming ions. A wave instability analysis using the WHAMP code confirms that the generation of these waves, via the ion cyclotron instability, is basically consistent with known physics. Their extended region of wave growth is likely, however, to reach tailward significantly beyond the Cluster orbit.
Synergistic Effects of Iodine and Silver Ions Co-Implanted in 6H-SiC
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kuhudzai, Remeredzai J.; Malherbe, Johan; Hlatshwayo, T. T.
2015-10-23
Motivated by the aim of understanding the release of fission products through the SiC coating of fuel kernels in modern high temperature nuclear reactors, a fundamental investigation is conducted to understand the synergistic effects of implanted silver (Ag) and iodine (I) in 6H-SiC. The implantation of the individual species, as well as the co-implantation of 360 keV ions of I and Ag at room temperature in 6H-SiC and their subsequent annealing behavior has been investigated by Secondary Ion Mass Spectrometry (SIMS), Atom Probe Tomography (APT) and X-ray Photoelectron Spectroscopy (XPS). SIMS and APT measurements indicated the presence of Ag inmore » the co-implanted samples after annealing at 1500 ºC for 30 hours in sharp contrast to the samples implanted with Ag only. In samples implanted with Ag only, complete loss of the implanted Ag was observed. However, for I only implanted samples, some iodine was retained. APT of annealed co-implanted 6H-SiC showed clear spatial association of Ag and I clusters in SiC, which can be attributed to the observed I assisted retention of Ag after annealing. Such detailed studies will be necessary to identify the fundamental mechanism of fission products migration through SiC coatings.« less
A Particle-In-Cell Gun Code for Surface-Converter H- Ion Source Modeling
DOE Office of Scientific and Technical Information (OSTI.GOV)
Chacon-Golcher, Edwin; Bowers, Kevin J.
2007-08-10
We present the current status of a particle-in-cell with Monte Carlo collisions (PIC-MCC) gun code under development at Los Alamos for the study of surface-converter H- ion sources. The program preserves a first-principles approach to a significant extent and simulates the production processes without ad hoc models within the plasma region. Some of its features include: solution of arbitrary electrostatic and magnetostatic fields in an axisymmetric (r,z) geometry to describe the self-consistent time evolution of a plasma; simulation of a multi-species (e-,H+,H{sub 2}{sup +},H{sub 3}{sup +},H-) plasma discharge from a neutral hydrogen gas and filament-originated seed electrons; full 2-dimensional (r,z)more » 3-velocity (vr,vz,v{phi}) dynamics for all species with exact conservation of the canonical angular momentum p{phi}; detailed collision physics between charged particles and neutrals and the ability to represent multiple smooth (not stair-stepped) electrodes of arbitrary shape and voltage whose surfaces may be secondary-particle emitters (H- and e-). The status of this development is discussed in terms of its physics content and current implementation details.« less
Ion Electrodiffusion Governs Silk Electrogelation.
Kojic, Nikola; Panzer, Matthew J; Leisk, Gary G; Raja, Waseem K; Kojic, Milos; Kaplan, David L
2012-07-14
Silk electrogelation involves the transition of an aqueous silk fibroin solution to a gel state (E-gel) in the presence of an electric current. The process is based on local pH changes as a result of water electrolysis - generating H(+) and OH(-) ions at the (+) and (-) electrodes, respectively. Silk fibroin has a pI=4.2 and when local pH
NASA Astrophysics Data System (ADS)
Ohta, M.; Mattei, S.; Yasumoto, M.; Hatayama, A.; Lettry, J.
2014-02-01
In the Linac4 H- ion source, the plasma is generated by an RF antenna operated at 2 MHz. In order to investigate the conditions necessary for ramping up the plasma density of the Linac4 H- ion source in the low plasma density, a numerical study has been performed for a wide range of parameter space of RF coil current and initial pressure from H2 gas injection. We have employed an Electromagnetic Particle in Cell model, in which the collision processes have been calculated by a Monte Carlo method. The results have shown that the range of initial gas pressure from 2 to 3 Pa is suitable for ramping up plasma density via inductive coupling.
NASA Astrophysics Data System (ADS)
Anah, L.; Astrini, N.
2017-03-01
The major problem in heavy metal pollution is that these metals are not biodegradable and accordingly accumulate in the bodies of living organisms, causing dangerous diseases and serious cell disorder. According to World Health Organization (WHO), the long term exposure of Cr(VI) levels of over 0.1 ppm causes respiratory problems, liver and kidney damage, and carcinogenicity.Due to its easy operation and of various cheap adsorbents development, adsorption has been proved to be efficient and most economically attractive technique and feasible to the removal of toxic heavy metal from wastewater. The study aimed to report the removal of Cr(VI) ions from aqueous solutions through adsorption process using carboxymethyl cellulose-graft-poly(acrylic acid) (CMC-g-PAA) hydrogel as adsorbent.Effect of pH was studied to remove hexavalent chromium.Graft copolymerization of poly(acrylic acid) onto carboxymethyl cellulose was carried out in the presence of benzoyl peroxide redox initiator and methylenbisacrylamide as crosslinker agent. Batch experiments were carried out to investigate the effects ofinitial pH.The adsorption of Cr(VI) ions as a function of pH was conducted in the initial pH range of 1 to 8. The results indicated that acidic pH strongly favored the adsorption. The optimum pH for adsorption of Cr(VI) ranged from 1 to 3, and the maximum uptake of Cr(VI) from the solution was 6.53 mg/g at pH 1 and 30°C. FTIR spectroscopy, SEM analyses were performed on the adsorbent before and after Cr(VI) binding. All analyses confirmed the complexation of Cr(VI) ions on the adsorbent.
NASA Astrophysics Data System (ADS)
van den Berg, Klaas Jan; Ingemann, Steen; Nibbering, Nico M. M.
1994-06-01
The gas-phase reactions of the O- ion with ([eta]5-cyclopentadienyl)tricarbonylmanganese(I), CpMn(CO)3, and ([eta]5-methylcyclopentadienyl)tricarbonylmanganese(I), CH3CpMn(CO)3, have been studied with Fourier transform ion cyclotron resonance. The main reactions are (i) proton abstraction, (ii) loss of CO2, and (iii) expulsion of two or three CO molecules from the collision complex. Initial attack on a CO ligand is the main process as indicated by experiments with 18O- and the ion/molecule reactions of the product ions resulting from the loss of three CO molecules with water, aliphatic alcohols, methanethiol and SO2. The attack on a CO ligand followed by loss of three CO molecules is suggested to yield C5H5MnO- ions with a (cyclopentadienone)MnH- structure in the reaction with CpMn(CO)3 and (methylcyclopentadienone)MnH- ions if CH3CpMn(CO)3 is the substrate. A possible mechanism for the process leading to the indicated transformation of the Cp and CH3Cp ligands into C5H4O and CH3C5H3O ligands, respectively, is discussed together with the formation of (fulvene)Mn(OH)- ions following attack of O- on CH3CpMn(CO)3. The (cyclopentadienone)MnH- and (methylcyclopentadienone)MnH- ions react with N2O by oxygen atom abstraction to form C5H5MnO-2 and C6H7MnO-2 ions, respectively.
NASA Astrophysics Data System (ADS)
Tsumori, K.; Takeiri, Y.; Ikeda, K.; Nakano, H.; Geng, S.; Kisaki, M.; Nagaoka, K.; Tokuzawa, T.; Wada, M.; Sasaki, K.; Nishiyama, S.; Goto, M.; Osakabe, M.
2017-08-01
Total power of 16 MW has been successfully delivered to the plasma confined in the Large Helical Device (LHD) from three Neutral Beam Injectors (NBIs) equipped with negative hydrogen (H-) ion sources. However, the detailed mechanisms from production through extraction of H- ions are still yet to be clarified and a similar size ion source on an independent acceleration test bench called Research and development Negative Ion Source (RNIS) serves as the facility to study physics related to H- production and transport for further improvement of NBI. The production of negative-ion-rich plasma and the H- ions behavior in the beam extraction region in RNIS is being investigated by employing an integrated diagnostic system. Flow patterns of electrons, positive ions and H- ions in the extraction region are described in a two-dimensional map. The measured flow patterns indicate the existence a stagnation region, where the H- flow changes the direction at a distance about 20 mm from the plasma grid. The pattern also suggested the H- flow originated from plasma grid (PG) surface that turned back toward extraction apertures. The turning region seems formed by a layer of combined magnetic field produced by the magnetic filter field and the Electron-Deflection Magnetic (EDM) field created by magnets installed in the extraction electrode.
Minority heating scenarios in ^4He(H) and ^3He(H) SST-1 plasmas
NASA Astrophysics Data System (ADS)
Chattopadhyay, Asim Kumar
2018-01-01
A numerical analysis of ion cyclotron resonance heating scenarios in two species of low ion temperature plasma has been done to elucidate the physics and possibility to achieve H-mode in tokamak plasma. The analysis is done in the steady-state superconducting tokamak, SST-1, using phase-I plasma parameters which is basically L-mode plasma parameters having low ion temperature and magnetic field with the help of the ion cyclotron heating code TORIC combined with `steady state Fokker-Planck quasilinear' (SSFPQL) solver. As a minority species hydrogen has been used in ^3He and ^4He plasmas to make two species ^3He(H) and ^4He(H) plasmas to study the ion cyclotron wave absorption scenarios. The minority heating is predominant in ^3He(H) and ^4He(H) plasmas as minority resonance layers are not shielded by ion-ion resonance and cut-off layers in both cases, and it is better in ^4He(H) plasma due to the smooth penetration of wave through plasma-vacuum surface. In minority concentration up to 15%, it has been observed that minority ion heating is the principal heating mechanism compared to electron heating and heating due to mode conversion phenomena. Numerical analysis with the help of SSFPQL solver shows that the tail of the distribution function of the minority ion is more energetic than that of the majority ion and therefore, more anisotropic. Due to good coupling of the wave and predominance of the minority heating regime, producing energetic ions in the tail region of the distribution function, the ^4He(H) and ^3He(H) plasmas could be studied in-depth to achieve H-mode in two species of low-temperature plasma.
Use of predissociation to enhance the atomic hydrogen ion fraction in ion sources
Kim, Jinchoon
1979-01-01
A duopigatron ion source is modified by replacing the normal oxide-coated wire filament cathode of the ion source with a hot tungsten oven through which hydrogen gas is fed into the arc chamber. The hydrogen gas is predissociated in the hot oven prior to the arc discharge, and the recombination rate is minimized by hot walls inside of the arc chamber. With the use of the above modifications, the atomic H.sub.1.sup.+ ion fraction output can be increased from the normal 50% to greater than 70% with a corresponding decrease in the H.sub.2.sup.+ and H.sub.3.sup.+ molecular ion fraction outputs from the ion source.
Sekimoto, Kanako; Takayama, Mitsuo
2011-01-01
Reliable mass spectrometry data from large water clusters Y(-)(H(2)O)(n) with various negative core ions Y(-) such as O(2)(-), HO(-), HO(2)(-), NO(2)(-), NO(3)(-), NO(3)(-)(HNO(3))(2), CO(3)(-) and HCO(4)(-) have been obtained using atmospheric pressure negative corona discharge mass spectrometry. All the core Y(-) ions observed were ionic species that play a central role in tropospheric ion chemistry. These mass spectra exhibited discontinuities in ion peak intensity at certain size clusters Y(-)(H(2)O)(m) indicating specific thermochemical stability. Thus, Y(-)(H(2)O)(m) may correspond to the magic number or first hydrated shell in the cluster series Y(-)(H(2)O)(n). The high intensity discontinuity at HO(-)(H(2)O)(3) observed was the first mass spectrometric evidence for the specific stability of HO(-)(H(2)O)(3) as the first hydrated shell which Eigen postulated in 1964. The negative ion water clusters Y(-)(H(2)O)(n) observed in the mass spectra are most likely to be formed via core ion formation in the ambient discharge area (760 torr) and the growth of water clusters by adiabatic expansion in the vacuum region of the mass spectrometers (≈1 torr). The detailed mechanism of the formation of the different core water cluster ions Y(-)(H(2)O)(n) is described. Copyright © 2010 John Wiley & Sons, Ltd.
Oxidative aliphatic C-H fluorination with manganese catalysts and fluoride ion
Liu, Wei; Huang, Xiongyi; Groves, John T
2014-01-01
Fluorination is a reaction that is useful in improving the chemical stability and changing the binding affinity of biologically active compounds. The protocol described here can be used to replace aliphatic, C(sp3)-H hydrogen in small molecules with fluorine. Notably, isolated methylene groups and unactivated benzylic sites are accessible. The method uses readily available manganese porphyrin and manganese salen catalysts and various fluoride ion reagents, including silver fluoride (AgF), tetrabutylammonium fluoride and triethylamine trihydrofluoride (TREAT·HF), as the source of fluorine. Typically, the reactions afford 50–70% yield of mono-fluorinated products in one step. Two representative examples, the fragrance component celestolide and the nonsteroidal anti-inflammatory drug ibuprofen, are described; they produced useful isolated quantities (250–300 mg, ~50% yield) of fluorinated material over periods of 1–8 h. The procedures are performed in a typical fume hood using ordinary laboratory glassware. No special precautions to rigorously exclude water are required. PMID:24177292
NASA Astrophysics Data System (ADS)
Dou, Ming-Yu; Lu, Jing
2017-12-01
A novel coordination polymer containing hetero-metal ions, [NiNa2(PDC)2(μ-H2O)(H2O)2] n , where PDC is 2,3-pyridine dicarboxylate ion, has been synthesized. In the structure, the PDC ligand chelates and bridges two Ni(II) and two Na(I) centers. Two kinds of metal centers are connected by μ4-PDC and μ2-H2O to form 2D coordination layers. Hydrogen bonds between coordination water molecules and carboxylate oxygen atoms further link these 2D coordination layers to form 3D supramolecular network.
Chang, Soyoung; Kilic, Tugba; Lee, Chang Kee; Avci, Huseyin; Bae, Hojae; Oskui, Shirin Mesbah; Jung, Sung Mi; Shin, Su Ryon; Kim, Seon Jeong
2018-04-08
The unique biological features of supramolecular DNA have led to an increasing interest in biomedical applications such as biosensors. We have developed an i-motif and G-rich DNA conjugated single-walled carbon nanotube hybrid materials, which shows reversible conformational switching upon external stimuli such as pH (5 and 8) and presence of ions (Li⁺ and K⁺). We observed reversible electrochemical redox activity upon external stimuli in a quick and robust manner. Given the ease and the robustness of this method, we believe that pH- and ion-driven reversible DNA structure transformations will be utilized for future applications for developing novel biosensors.
NASA Astrophysics Data System (ADS)
Jang, Jungkyu; Choi, Sungju; Kim, Jungmok; Park, Tae Jung; Park, Byung-Gook; Kim, Dong Myong; Choi, Sung-Jin; Lee, Seung Min; Kim, Dae Hwan; Mo, Hyun-Sun
2018-02-01
In this study, we investigate the effect of rising time (TR) of liquid gate bias (VLG) on transient responses in pH sensors based on Si nanowire ion-sensitive field-effect transistors (ISFETs). As TR becomes shorter and pH values decrease, the ISFET current takes a longer time to saturate to the pH-dependent steady-state value. By correlating VLG with the internal gate-to-source voltage of the ISFET, we found that this effect occurs when the drift/diffusion of mobile ions in analytes in response to VLG is delayed. This gives us useful insight on the design of ISFET-based point-of-care circuits and systems, particularly with respect to determining an appropriate rising time for the liquid gate bias.
Kim, Kwang-Wook; Kim, Yeon-Hwa; Lee, Se-yoon; Lee, Jae-Won; Joe, Kih-Soo; Lee, Eil-Hee; Kim, Jong-Seung; Song, Kyuseok; Song, Kee-Chan
2009-04-01
This work studied the dissolution of uranium dioxide and precipitation characteristics of uranyl ions in alkaline and acidic solutions depending on the presence of carbonate ions and H2O2 in the solutions at different pHs controlled by adding HNO3 or NaOH in the solution. The chemical structures of the precipitates generated in different conditions were evaluated and compared by using XRD, SEM, TG-DT, and IR analyses together. The sizes and forms of the precipitates in the solutions were evaluated, as well. The uranyl ions were precipitated in the various forms, depending on the solution pH and the presences of hydrogen peroxide and carbonate ions in the solution. In a 0.5 M Na2CO3 solution with H2O2, where the uranyl ions formed mixed uranyl peroxy-carbonato complexes, the uranyl ions were precipitated as a uranium peroxide of UO4(H20)4 at pH 3-4, and precipitated as a clarkeite of Na2U2Ox(OH)y(H2O)z above pH 13. In the same carbonate solution without H2O2, where the uranyl ions formed uranyl tris-carbonato complex, the uranyl ions were observed to be precipitated as a different form of clarkeite above pH 13. The precipitate of uranyl ions in a nitrate solution without carbonate ions and H2O2 at a high pH were studied together to compare the precipitate forms in the carbonate solutions.
Electrocatalytic transformation of HF impurity to H 2 and LiF in lithium-ion batteries
DOE Office of Scientific and Technical Information (OSTI.GOV)
Strmcnik, Dusan; Castelli, Ivano E.; Connell, Justin G.
The formation of solid electrolyte interphase on graphite anodes plays a key role in the efficiency of Li-ion batteries. However, to date, fundamental understanding of the formation of LiF as one of the main solid electrolyte interphase components in hexafluorophosphate-based electrolytes remains elusive. In this paper, we present experimental and theoretical evidence that LiF formation is an electrocatalytic process that is controlled by the electrochemical transformation of HF impurity to LiF and H 2. Although the kinetics of HF dissociation and the concomitant production of LiF and H 2 is dependent on the structure and nature of surface atoms, themore » underlying electrochemistry is the same. The morphology, and thus the role, of the LiF formed is strongly dependent on the nature of the substrate and HF inventory, leading to either complete or partial passivation of the interface. Finally, our finding is of general importance and may lead to new opportunities for the improvement of existing, and design of new, Li-ion technologies.« less
Electrocatalytic transformation of HF impurity to H 2 and LiF in lithium-ion batteries
Strmcnik, Dusan; Castelli, Ivano E.; Connell, Justin G.; ...
2018-04-09
The formation of solid electrolyte interphase on graphite anodes plays a key role in the efficiency of Li-ion batteries. However, to date, fundamental understanding of the formation of LiF as one of the main solid electrolyte interphase components in hexafluorophosphate-based electrolytes remains elusive. In this paper, we present experimental and theoretical evidence that LiF formation is an electrocatalytic process that is controlled by the electrochemical transformation of HF impurity to LiF and H 2. Although the kinetics of HF dissociation and the concomitant production of LiF and H 2 is dependent on the structure and nature of surface atoms, themore » underlying electrochemistry is the same. The morphology, and thus the role, of the LiF formed is strongly dependent on the nature of the substrate and HF inventory, leading to either complete or partial passivation of the interface. Finally, our finding is of general importance and may lead to new opportunities for the improvement of existing, and design of new, Li-ion technologies.« less
NASA Technical Reports Server (NTRS)
Smyth, K. C.; Brauman, J. I.
1972-01-01
The relative cross section for the gas-phase photodetachment of electrons has been determined for NH2(-) in the wavelength region of 1195 to 1695 nm and for AsH2(-) in the region from 620 to 1010 nm. An ion cyclotron resonance spectrometer was used to generate, trap, and detect negative ions. A 1000-W xenon arc lamp with a grating monochromator was used as the light source, except for one series of experiments in which a tunable laser was employed. Single sharp thresholds were observed in both cross sections, and the following electron affinity values were determined: 0.744 (plus or minus 0.022) eV for NH2. and 1.27 (plus or minus 0.03) eV for AsH2.
Energy recovery from mixed H-/H0/H+ beams and collector simulations
NASA Astrophysics Data System (ADS)
Variale, V.; Cavenago, M.; Baltador, C.; Serianni, G.; Veltri, P.; Sartori, E.; Agostinetti, P.
2017-08-01
An axisymmetric system to recover beam energy from partially neutralized H- beams was recently proposed, for a given beam acceleration voltage Vs. In the case of ion source NIO1 Vs may range from 20 to 60 kV. A realistic beam with 3 mrad divergence, and a composition of 25 : 50 : 25 of H-, H0 and H+ has been considered. The collector works by decelerating the H- ions (into a system similar to a Faraday cup provided with an exit hole electrode), so that they are radially deflected by space charge and anode lens effects, and collected to a low kinetic energy Kc (less than 1 keV), while neutral and H+ ions can pass through the exit hole electrode. A following collector can recover H+ energy. Since the space charge calculations are challenging for highly nonlinear problem and for a possible (numerically unstable) virtual cathode phenomena different computation tools were compared for simulations. Stabilization techniques are compared. Limits for local perveance are discussed. Also mesh asymmetry effects and the related transverse oscillations of H+ beam may be observed. Efficiency over 90 % can be reached in typical conditions. The secondary yield (which is low thanks to low impact energy Kc and Faraday cup concept) is estimated.
Ion Kinetics in Silane Plasmas
1988-02-01
stimulated emission. Rg2 + is then a classical excimer laser scheme which ought to apply generally to the homonuclear and heteronuclear rare- gas dimer...kinetics of ion formation by electron impact and subsequent reaction in silane:noble- gas mixtures have been examined using pulsed ion cyclotron reso...charge transfer reactions such as X + + SiH4 -- SiH + + X + (4 - n)(H, H2) where X+ is a rare- gas or s:licon-hydride ion. Room-temperature rate constants
Clegg, S L; Wexler, A S
2011-04-21
A Pitzer ion interaction model has been applied to the systems H(2)SO(4)-H(2)O (0-3 mol kg(-1), 0-55 °C) and H(2)SO(4)-(NH(4))(2)SO(4)-H(2)O (0-6 mol kg(-1), 25 °C) for the calculation of apparent molar volume and density. The dissociation reaction HSO(4)(-)((aq)) ↔ H(+)((aq)) + SO(4)(2-)((aq)) is treated explicitly. Apparent molar volumes of the SO(4)(2-) ion at infinite dilution were obtained from part 1 of this work, (1) and the value for the bisulfate ion was determined in this study from 0 to 55 °C. In dilute solutions of both systems, the change in the degree of dissociation of the HSO(4)(-) ion with concentration results in much larger variations of the apparent molar volumes of the solutes than for conventional strong (fully dissociated) electrolytes. Densities and apparent molar volumes are tabulated. Apparent molar volumes calculated using the model are combined with other data for the solutes NH(4)HSO(4) and (NH(4))(3)H(SO(4))(2) at 25 °C to obtain apparent molar volumes and densities over the entire concentration range (including solutions supersaturated with respect to the salts).
DOE Office of Scientific and Technical Information (OSTI.GOV)
Onai, M., E-mail: onai@ppl.appi.keio.ac.jp; Fujita, S.; Hatayama, A.
2016-02-15
Recently, a filament driven multi-cusp negative ion source has been developed for proton cyclotrons in medical applications. In this study, numerical modeling of the filament arc-discharge source plasma has been done with kinetic modeling of electrons in the ion source plasmas by the multi-cusp arc-discharge code and zero dimensional rate equations for hydrogen molecules and negative ions. In this paper, main focus is placed on the effects of the arc-discharge power on the electron energy distribution function and the resultant H{sup −} production. The modelling results reasonably explains the dependence of the H{sup −} extraction current on the arc-discharge powermore » in the experiments.« less
Polymorphism in the nitrate salt of the [Mn(acetylacetonate)2(H2O)2]+ ion.
Biju, A R; Rajasekharan, M V
2010-06-01
The crystallization of [Mn(acac)(2)(H(2)O)(2)](+) from solutions containing excess nitrate leads to the formation of four polymorphs. All polymorphs contain two different types of complex ions, one containing essentially coplanar acac ligands and the other in which the two acac ligands together assume a chair conformation. Molecular modelling using DFT (density-functional theory) calculations shows that the coplanar conformation is the electronically stable one. The hydrogen bonding between the trans-water molecules and the nitrate ion produces a one-dimensional chain of 12-membered rings, which are further organized into a two-dimensional network via a lattice water molecule. Lattice-energy calculations have been carried out to compare the stabilities of the four polymorphs.
Guo, Mengzhe; Guo, Cheng; Pan, Yuanjiang
2014-08-01
The fragmentation of b3 ions derived from protonated Arg-Xxx-Asp-Ala-Ala (Xxx = Ala, Asp, Glu, Cys) and Arg-Xxx-Glu-Ala-Ala was investigated by electrospray ionization tandem mass spectrometry (MS (n) ) with collision-induced dissociation. A particular ion, which is 1 Da less than b2 ion, is shown to be the c2-H2O ion. The mechanism for its formation involved the aspartic acid in the third position easily losing anhydride to form a c2 ion, which then lost water to form an eight-membered ring of azacyclooctane derivative under the participation of the guanidine of the N-terminal arginine. However, this phenomenon was not observed when the aspartic acid was replaced by glutamic acid. The Amber program was used to determine the conformation of the original c2 residue from the dynamic energy perspective, and then density functional theory-based calculations and changing N-terminal amino acid from arginine to phenylalanine supported this mechanism.
Highly Durable Na2V6O16·1.63H2O Nanowire Cathode for Aqueous Zinc-Ion Battery.
Hu, Ping; Zhu, Ting; Wang, Xuanpeng; Wei, Xiujuan; Yan, Mengyu; Li, Jiantao; Luo, Wen; Yang, Wei; Zhang, Wencui; Zhou, Liang; Zhou, Zhiqiang; Mai, Liqiang
2018-03-14
Rechargeable aqueous zinc-ion batteries are highly desirable for grid-scale applications due to their low cost and high safety; however, the poor cycling stability hinders their widespread application. Herein, a highly durable zinc-ion battery system with a Na 2 V 6 O 16 ·1.63H 2 O nanowire cathode and an aqueous Zn(CF 3 SO 3 ) 2 electrolyte has been developed. The Na 2 V 6 O 16 ·1.63H 2 O nanowires deliver a high specific capacity of 352 mAh g -1 at 50 mA g -1 and exhibit a capacity retention of 90% over 6000 cycles at 5000 mA g -1 , which represents the best cycling performance compared with all previous reports. In contrast, the NaV 3 O 8 nanowires maintain only 17% of the initial capacity after 4000 cycles at 5000 mA g -1 . A single-nanowire-based zinc-ion battery is assembled, which reveals the intrinsic Zn 2+ storage mechanism at nanoscale. The remarkable electrochemical performance especially the long-term cycling stability makes Na 2 V 6 O 16 ·1.63H 2 O a promising cathode for a low-cost and safe aqueous zinc-ion battery.
Dose dependence of nano-hardness of 6H-SiC crystal under irradiation with inert gas ions
NASA Astrophysics Data System (ADS)
Yang, Yitao; Zhang, Chonghong; Su, Changhao; Ding, Zhaonan; Song, Yin
2018-05-01
Single crystal 6H-SiC was irradiated by inert gas ions (He, Ne, Kr and Xe ions) to various damage levels at room temperature. Nano-indentation test was performed to investigate the hardness change behavior with damage. The depth profile of nano-hardness for 6H-SiC decreased with increasing depth for both the pristine and irradiated samples, which was known as indentation size effect (ISE). Nix-Gao model was proposed to determine an asymptotic value of nano-hardness by taking account of ISE for both the pristine and irradiated samples. In this study, nano-hardness of the irradiated samples showed a strong dependence on damage level and showed a weak dependence on ions species. From the dependence of hardness on damage, it was found that the change of hardness demonstrated three distinguishable stages with damage: (I) The hardness increased with damage from 0 to 0.2 dpa and achieved a maximum of hardening fraction ∼20% at 0.2 dpa. The increase of hardness in this damage range was contributed to defects produced by ion irradiation, which can be described well by Taylor relation. (II) The hardness reduced rapidly with large decrement in the damage range from 0.2 to 0.5 dpa, which was considered to be from the covalent bond breaking. (III) The hardness reduced with small decrement in the damage range from 0.5 to 2.2 dpa, which was induced by extension of the amorphous layer around damage peak.
Wisnewski, Adam V; Liu, Jian; Redlich, Carrie A; Nassar, Ala F
2018-02-15
Hexamethylene diisocyanate (HDI) is an important industrial chemical that can cause asthma, however pathogenic mechanisms remain unclear. Upon entry into the respiratory tract, HDI's N=C=O groups may undergo nucleophilic addition (conjugate) to host molecules (e.g. proteins), or instead react with water (hydrolyze), releasing CO 2 and leaving a primary amine in place of the original N=C=O. We hypothesized that (primary amine groups present on) hydrolyzed or partially hydrolyzed HDI may compete with proteins and water as a reaction target for HDI in solution, resulting in polymers that could be identified and characterized using LC-MS and LC-MS/MS. Analysis of the reaction products formed when HDI was mixed with a pH buffered, isotonic, protein containing solution identified multiple [M+H] + ions with m/z's and collision-induced dissociation (CID) fragmentation patterns consistent with those expected for dimers (259.25/285.23 m/z), and trimers (401.36/427.35 m/z) of partially hydrolyzed HDI (e.g. ureas/oligoureas). Human peripheral blood mononuclear cells (PBMCs) and monocyte-like U937, but not airway epithelial NCI-H292 cell lines cultured with these HDI ureas contained a novel 260.23 m/z [M+H] + ion. LC-MS/MS analysis of the 260.23 m/z [M+H] + ion suggest the formula C 13 H 29 N 3 O 2 and a structure containing partially hydrolyzed HDI, however definitive characterization will require further orthogonal analyses. Copyright © 2017 Elsevier Inc. All rights reserved.
Liang, Shijing; Zhu, Shuying; Zhu, Jia; Chen, Yan; Zhang, Yongfan; Wu, Ling
2012-01-21
A series of group IIIA metal ion electron acceptors doped into Sr(0.25)H(1.5)Ta(2)O(6)·H(2)O (HST) samples have been prepared by an impregnation and calcination method for the first time. The samples are characterized by XRD, TEM, DRS and XPS. The variations in the electronic structure and photoelectric response after metal ion doping are investigated by theoretical calculations and photocurrent experiments, respectively. Results show that the metal ions can be efficiently incorporated into the HST crystal structure, which is reflected in the lattice contraction. Meanwhile, the photoabsorption edges of the metal-doped HST samples are red shifted to a longer wavelength. Taking into account the ionic radii and electronegativities of the dopants, as well as the XRD and XPS results, it is concluded that Ta(5+) ions may be partially substituted by the Al(3+) and Ga(3+) ions in the framework, while In(3+) ions are the favourable substitutes for Sr(2+) sites in the cavity. The first-principles DFT calculations confirm that the variation of the band structure is sensitive to the type of group IIIA metal ion. Introducing the dopant only at the Ta site induces an obvious variation in the band structure and the band gap becomes narrow. Meanwhile, an ''extra step'' appeared in the band gap, which can trap photogenerated electrons from the valance band (VB) and could enhance the charge mobility and the photocurrent. For the photocatalytic degradation of methyl orange in an aqueous solution and in benzene in the gas phase, the doped samples show superior photocatalytic activities compared with both undoped samples and TiO(2). The enhanced photocatalytic activities can be well explained by their electronic structure, photoabsorption performance, photoelectric response, and the concentration of the active species. Due to the fact that Ga ion doping can create an acceptor impurity level and change the electronic band, efficiently narrowing the band gap, the Ga-doped sample shows
Lee, Younghyun; Li, Huizi Keiko; Masaoka, Aya; Sunada, Shigeaki; Hirakawa, Hirokazu; Fujimori, Akira; Nickoloff, Jac A; Okayasu, Ryuichi
2016-10-01
PU-H71 is a purine-scaffold Hsp90 inhibitor developed to overcome limitations of conventional Hsp90 inhibitors. This study was designed to investigate the combined effect of PU-H71 and heavy ion irradiation on human tumor and normal cells. The effects of PU-H71 were determined by monitoring cell survival by colony formation, and DNA double-strand break (DSB) repair by γ-H2AX foci and immuno-blotting DSB repair proteins. The mode of cell death was evaluated by sub-G1 DNA content (as an indicator for apoptosis), and mitotic catastrophe. PU-H71 enhanced heavy ion irradiation-induced cell death in three human cancer cell lines, but the drug did not radiosensitize normal human fibroblasts. In irradiated tumor cells, PU-H71 increased the persistence of γ-H2AX foci, and it reduced RAD51 foci and phosphorylated DNA-PKcs, key DSB repair proteins involved in homologous recombination (HR) and non-homologous end joining (NHEJ). In some tumor cell lines, PU-H71 altered the sub-G1 cell fraction and mitotic catastrophe following carbon ion irradiation. Our results demonstrate that PU-H71 sensitizes human cancer cells to heavy ion irradiation by inhibiting both HR and NHEJ DSB repair pathways. PU-H71 holds promise as a radiosensitizer for enhancing the efficacy of heavy ion radiotherapy. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
Yang, Yanli; Mengran Yu; Zhang, Songping; Ma, Guanghui; Su, Zhiguo
2015-08-21
Disassembling of virus-like particles (VLPs) like hepatitis B virus surface antigen (HB-VLPs) during chromatographic process has been identified as a major cause of loss of antigen activity. In this study, dual polarization interferometry (DPI) measurement, together with chromatography experiments, were performed to study the adsorption and conformational change of HB-VLPs on ion exchange surface at three different pHs. Changes in pH values of buffer solution showed only minimal effect on the HB-VLPs assembly and antigen activity, while significantly different degree of HB-VLPs disassembling was observed after ion exchange chromatography (IEC) at different pHs, indicating the conformational change of HB-VLPs caused mainly by its interactions with the adsorbent surface. By creating an ion exchange surface on chip surface, the conformational changes of HB-VLPs during adsorption to the surface were monitored in real time by DPI for the first time. As pH increased from 7.0 to 9.0, strong electrostatic interactions between oppositely charged HB-VLPs and the ion exchange surface make the HB-VLPs spread thinly or even adsorbed in disassembled formation on the surface as revealed by significant decrease in thickness of the adsorbed layer measured by DPI. Such findings were consistent with the results of IEC experiments operated at different pHs, that more disassembled HB-VLPs were detected in the eluted proteins at pH 9.0. At low pH like pH 5.0, however, possible bi-layer adsorption was involved as evidenced by an adsorbed layer thickness higher than average diameter of the HB-VLPs. The "lateral" protein-protein interactions might be unfavorable and would make additional contribution to the disassembling of HB-VLPs besides the primary mechanism related to the protein-surface interactions; therefore, the lowest antigen activity was observed after IEC at pH 5.0. Such real-time information on conformational change of VLPs is helpful for better understanding the real mechanism
Improvements on the stability and operation of a magnetron H - ion source
Sosa, A.; Bollinger, D. S.; Karns, P. R.; ...
2017-05-31
The magnetron H - ion sources developed in the 1970s currently in operation at Fermilab provide beam to the rest of the accelerator complex. A series of modifications to these sources have been tested in a dedicated offline test stand with the aim of improving different operational issues. The solenoid type gas valve was tested as an alternative to the piezoelectric gas valve in order to avoid its temperature dependence. A new cesium oven was designed and tested in order to avoid glass pieces that were present with the previous oven, improve thermal insulation and fine tune its temperature. Amore » current-regulated arc modulator was developed to run the ion source at a constant arc current, providing very stable beam outputs during operations. In order to reduce beam noise, the addition of small amounts of N 2 gas was explored, as well as testing different cathode shapes with increasing plasma volume. This study summarizes the studies and modifications done in the source over the last three years with the aim of improving its stability, reliability and overall performance.« less
Improvements on the stability and operation of a magnetron H- ion source
NASA Astrophysics Data System (ADS)
Sosa, A.; Bollinger, D. S.; Karns, P. R.; Tan, C. Y.
2017-05-01
The magnetron H- ion sources developed in the 1970s currently in operation at Fermilab provide beam to the rest of the accelerator complex. A series of modifications to these sources have been tested in a dedicated off-line test stand with the aim of improving different operational issues. The solenoid type gas valve was tested as an alternative to the piezoelectric gas valve in order to avoid its temperature dependence. A new cesium oven was designed and tested in order to avoid glass pieces that were present with the previous oven, improve thermal insulation and fine-tune its temperature. A current-regulated arc modulator was developed to run the ion source at a constant arc current, providing very stable beam outputs during operations. In order to reduce beam noise, the addition of small amounts of N2 gas was explored, as well as testing different cathode shapes with increasing plasma volume. This paper summarizes the studies and modifications done in the source over the past three years with the aim of improving its stability, reliability and overall performance.
Improvements on the stability and operation of a magnetron H - ion source
DOE Office of Scientific and Technical Information (OSTI.GOV)
Sosa, A.; Bollinger, D. S.; Karns, P. R.
The magnetron H - ion sources developed in the 1970s currently in operation at Fermilab provide beam to the rest of the accelerator complex. A series of modifications to these sources have been tested in a dedicated offline test stand with the aim of improving different operational issues. The solenoid type gas valve was tested as an alternative to the piezoelectric gas valve in order to avoid its temperature dependence. A new cesium oven was designed and tested in order to avoid glass pieces that were present with the previous oven, improve thermal insulation and fine tune its temperature. Amore » current-regulated arc modulator was developed to run the ion source at a constant arc current, providing very stable beam outputs during operations. In order to reduce beam noise, the addition of small amounts of N 2 gas was explored, as well as testing different cathode shapes with increasing plasma volume. This study summarizes the studies and modifications done in the source over the last three years with the aim of improving its stability, reliability and overall performance.« less
Pysanenko, Andriy; Zabka, Jan; Feketeová, Linda; Märk, Tilmann D; Herman, Zdenek
2008-01-01
Collisions of C3Hn+ (n = 2-8) ions and some of their per- deuterated analogs with room temperature carbon (HOPG) surfaces (hydrocarbon-covered) were investigated over the incident energy range 13-45 eV in beam scattering experiments. The mass spectra of product ions were measured and main fragmentation paths of the incident projectile ions, energized in the surface collision, were determined. The extent of fragmentation increased with increasing incident energy. Mass spectra of even-electron ions C3H7+ and C3H5+ showed only fragmentations, mass spectra of radical cations C3H8*+ and C3H6*+ showed both simple fragmentations of the projectile ion and formation of products of its surface chemical reaction (H-atom transfer between the projectile ion and hydrocarbons on the surface). No carbon-chain build-up reaction (formation of C4 hydrocarbons) was detected. The survival probability of the incident ions, S(a), was usually found to be about 1-2% for the radical cation projectile ions C3H8*+, C3H6*+, C3H4*+ and C3H2*+ and several percent up to about 20% for the even-electron projectile ions C3H7+, C3H5+, C3H3+. A plot of S(a) values of C1, C2, C3, some C7 hydrocarbon ions, Ar+ and CO2+ on hydrocarbon-covered carbon surfaces as a function of the ionization energies (IE) of the projectile species showed a drop from about 10% to about 1% and less at IE 8.5-9.5 eV and further decrease with increasing IE. A strong correlation was found between log S(a) and IE, a linear decrease over the entire range of IE investigated (7-16 eV), described by log S(a) = (3.9 +/- 0.5)-(0.39 +/- 0.04) IE.
NASA Astrophysics Data System (ADS)
Paty, C.; Paterson, W.; Winglee, R.
2008-06-01
We investigate the ion population and energy distribution within Ganymede's magnetosphere by examining Ganymede's ionospheric outflow as a source of heavy (O+) and light (H+) ions and the Jovian magnetospheric plasma as an external source of heavy ions. We develop a method for examining the energy distributions of each ion species in a three-dimensional multifluid simulation in a way directly comparable to the observations of the Plasma Experiment on the Galileo spacecraft. This is used to provide new insight to the existing controversy over the composition of Ganymede's observed ionospheric outflow, and enables further examination of the energetic signatures of the ion population trapped within Ganymede's magnetosphere. The model-predicted ionospheric outflow is consistent with the in situ ion energy spectrograms observed by the Galileo Plasma Experiment at closest approach, and requires that both ionospheric H+ and O+ are present in the population of ions exiting Ganymede's ionosphere over the polar cap. The outward flux of ionospheric ions was calculated to be ~1026 ions/cm2/s, which is in agreement with independently calculated sputtering rates of Ganymede's icy surface. The modeled spectrograms define characteristic energy signatures and populations for various regions of Ganymede's magnetosphere, which illustrate the major sources of ions trapped within the magnetosphere are Ganymede's ionospheric O+ and H+. The fact that very little plasma was observed inside Ganymede's magnetosphere during the G8 flyby is attributed to the region being shadowed from the sun for ~60 h, which may indicate the importance of photoionization for sustaining Ganymede's ionospheric plasma source.
The negative hydrogen Penning ion gauge ion source for KIRAMS-13 cyclotron
DOE Office of Scientific and Technical Information (OSTI.GOV)
An, D. H.; Jung, I. S.; Kang, J.
2008-02-15
The cold-cathode-type Penning ion gauge (PIG) ion source for the internal ion source of KIRAMS-13 cyclotron has been used for generation of negative hydrogen ions. The dc H-beam current of 650 {mu}A from the PIG ion source with the Dee voltage of 40 kV and arc current of 1.0 A is extrapolated from the measured dc extraction beam currents at the low extraction dc voltages. The output optimization of PIG ion source in the cyclotron has been carried out by using various chimneys with different sizes of the expansion gap between the plasma boundary and the chimney wall. This papermore » presents the results of the dc H-extraction measurement and the expansion gap experiment.« less
Effects of the plasma-facing materials on the negative ion H ‑ density in an ECR (2.45 GHz) plasma
NASA Astrophysics Data System (ADS)
Bentounes, J.; Béchu, S.; Biggins, F.; Michau, A.; Gavilan, L.; Menu, J.; Bonny, L.; Fombaron, D.; Bès, A.; Lebedev, Yu A.; Shakhatov, V. A.; Svarnas, P.; Hassaine, T.; Lemaire, J. L.; Lacoste, A.
2018-05-01
Within the framework of fundamental research, the present work focuses on the role of surface material in the production of H ‑ negative ion, with a potential application of designing cesium-free H ‑ negative ion sources oriented to fusion application. It is widely accepted that the main reaction leading to H ‑ production, in the plasma volume, is the dissociative attachment of low-energy electrons (T e ≤ 1 eV) on highly ro-vibrationally excited hydrogen molecules. In parallel with other mechanisms, the density of these excited molecules may be enhanced by means of the recombinative desorption, i.e. the interaction between surface absorbed atoms with other atoms (surface adsorbed or not) through the path {H}{{ads}}+{H}{{gas}/{{ads}}}\\to {H}2{(v,J)}{{gas}}+{{Δ }}E. Accordingly, a systematic study on the role played by the surface in this reaction, with respect to the production of H ‑ ion in the plasma volume, is here performed. Thus, tantalum and tungsten (already known as H ‑ enhancers) and quartz (inert surface) materials are employed as inner surfaces of a test bench chamber. The plasma inside the chamber is produced by electron cyclotron resonance (ECR) driving and it is characterized with conventional electrostatic probes, laser photodetachment, and emission and absorption spectroscopy. Two different positions (close to and away from the ECR driving zone) are investigated under various conditions of pressure and power. The experimental results are supported by numerical data generated by a 1D model. The latter couples continuity and electron energy balance equations in the presence of magnetic field, and incorporates vibrational kinetics, H2 molecular reactions, H electronically excited states and ground-state species kinetics. In the light of this study, recombinative desorption has been evidenced as the most probable mechanism, among others, responsible for an enhancement by a factor of about 3.4, at 1.6 Pa and 175 W of microwave power, in the
Denton, M. H.; Thomsen, M. F.; Reeves, G. D.; ...
2017-10-03
The ion plasma sheet (~few hundred eV to ~few 10s keV) is usually dominated by H + ions. Here, changes in ion composition within the plasma sheet are explored both during individual events, and statistically during 54 calm-to-storm events and during 21 active-to-calm events. Ion composition data from the HOPE (Helium, Oxygen, Proton, Electron) instruments onboard Van Allen Probes satellites provide exceptional spatial and temporal resolution of the H +, O +, and He + ion fluxes in the plasma sheet. H+ shown to be the dominant ion in the plasma sheet in the calm-to-storm transition. However, the energy-flux ofmore » each ion changes in a quasi-linear manner during extended calm intervals. Heavy ions (O + and He +) become increasingly important during such periods as charge-exchange reactions result in faster loss for H + than for O + or He +. Results confirm previous investigations showing that the ion composition of the plasma sheet can be largely understood (and predicted) during calm intervals from knowledge of: (a) the composition of previously injected plasma at the onset of calm conditions, and (b) use of simple drift-physics models combined with calculations of charge-exchange losses.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Denton, M. H.; Thomsen, M. F.; Reeves, G. D.
The ion plasma sheet (~few hundred eV to ~few 10s keV) is usually dominated by H + ions. Here, changes in ion composition within the plasma sheet are explored both during individual events, and statistically during 54 calm-to-storm events and during 21 active-to-calm events. Ion composition data from the HOPE (Helium, Oxygen, Proton, Electron) instruments onboard Van Allen Probes satellites provide exceptional spatial and temporal resolution of the H +, O +, and He + ion fluxes in the plasma sheet. H+ shown to be the dominant ion in the plasma sheet in the calm-to-storm transition. However, the energy-flux ofmore » each ion changes in a quasi-linear manner during extended calm intervals. Heavy ions (O + and He +) become increasingly important during such periods as charge-exchange reactions result in faster loss for H + than for O + or He +. Results confirm previous investigations showing that the ion composition of the plasma sheet can be largely understood (and predicted) during calm intervals from knowledge of: (a) the composition of previously injected plasma at the onset of calm conditions, and (b) use of simple drift-physics models combined with calculations of charge-exchange losses.« less
Different approaches to modeling the LANSCE H{sup −} ion source filament performance
DOE Office of Scientific and Technical Information (OSTI.GOV)
Draganic, I. N., E-mail: draganic@lanl.gov; O’Hara, J. F.; Rybarcyk, L. J.
2016-02-15
An overview of different approaches to modeling of hot tungsten filament performance in the Los Alamos Neutron Science Center (LANSCE) H{sup −} surface converter ion source is presented. The most critical components in this negative ion source are two specially shaped wire filaments heated up to the working temperature range of 2600 K–2700 K during normal beam production. In order to prevent catastrophic filament failures (creation of hot spots, wire breaking, excessive filament deflection towards source body, etc.) and to improve understanding of the material erosion processes, we have simulated the filament performance using three different models: a semi-empirical model,more » a thermal finite-element analysis model, and an analytical model. Results of all three models were compared with data taken during LANSCE beam production. The models were used to support the recent successful transition from the beam pulse repetition rate of 60 Hz–120 Hz.« less
NASA Astrophysics Data System (ADS)
Cowles, Chad L.; Zhu, Xiaoshan; Pai, Chi-Yun
2011-10-01
In this study, an alternative approach using ZnS nanoparticle biolabels as fluorescence signal transducers is reported for the immunoassay of E. coli O157:H7 in tap water samples. Instead of measuring the fluorescence of ZnS nanoparticles in the assay, the fluorescence signal is generated through the binding of zinc ions released from nanoparticle labels with zinc-ion sensitive fluorescence indicator Fluozin-3. In the assay, ZnS nanoparticles around 50 nm in diameter were synthesized, bioconjugated, and applied for the detection of E. coli O157:H7. The assay shows a detection range over two orders of magnitude and a detection limit around 1000 colony-forming units (cfu) of E. coli O157:H7.
Sun, Fuhong; Yan, Yuanbo; Liao, Haiqing; Bai, Yingchen; Xing, Baoshan; Wu, Fengchang
2014-05-01
There is limited knowledge available on metalloid biosorption by freshwater algae. In this study, biosorption properties of anionic Sb(OH) 6 (-) by naturally occurring cyanobacteria Microcystis were investigated as a function of initial pH, biosorbent dosage, contact time, and addition sequences of competitive ions, and their binding mechanisms were discussed. The biosorption process was fast and equilibrium was reached at 2 h. Sb(V) biosorption decreased with the increase of pH and the optimum pH range was 2.5-3.0, which corresponded with the changes of surface charges of the cell wall of Microcystis. The biosorption data satisfactorily followed the Freundlich model. The simultaneous addition of H2PO4 (-) and Ca(2+) enhanced Sb(V) biosorption, while NO3 (-) greatly inhibited the biosorption, compared with single Sb(V) addition. The initial addition of the competitive ions reduced Sb(V) biosorption at higher Sb(V) concentrations, compared with simultaneous addition. A fraction of biosorbed Sb(V) was replaced by the competitive ions which were added subsequently, and the exchange only occurred at higher concentrations of Sb(V). 1.0 mol/L HCl demonstrated the highest desorption efficiency. Speciation analyses indicated that no reduction of Sb(V) into Sb(III) occurred. Based on the results of zeta potential and attenuated total reflection infrared spectroscopy spectra, Sb(OH) 6 (-) bound to the biomass through electrostatic attraction and surface complexation, and amino, carboxyl, and hydroxyl groups were involved in the biosorption process. The study suggest that Microcystis from cyanobacteria blooms could be used as a potential biosorbent to remove Sb(V) from effluents at environmentally relevant concentrations (≤10.0 mg/L).
Theoretical mechanistic study on the ion-molecule reaction of SiCN+/SiNC+ with H2O.
Wang, Jian; Ding, Yi-hong; Sun, Chia-chung
2005-02-15
The gas-phase ion-molecule reactions play very important roles in interstellar and in plasma chemistry. Motivated by recent astrophysical detection of the SiCN/SiNC radicals and laboratory characterization of some SiCN-containing species, we carried out a detailed potential energy survey on the SiCN+/SiNC(+) + H2O reaction at the Becke's three-parameter Lee-Yang-Parr-B3LYP/6-311G(d,p) and coupled cluster with single, double, and triple excitations-CCSD(T)/6-311 + G(2df,p) (single-point) levels as an attempt towards understanding the SiCN+/SiNC+ reaction mechanisms. In contrast to the carbene-featured analogous CCN+/CNC(+) + H2X (X=O,S) reactions, the title reaction SiCN+/SiNC(+) + H2O are not associated with any competitive silylene-insertion characters. Moreover, the -CN <--> -NC interconversion has a low barrier and plays an important role in determining the final product distributions. This is also in marked difference from the CCN+/CNC+ reaction. It is shown that the isomeric sila-cations SiCN+ and SiNC+ can both react with H2O to barrierlessly generate the major product P1 HOSi(+) + HCN and the minor one P3 HOSi(+) + HNC, whereas other low-lying products such as P2 SiNCO(+) + H2, and P(0) H2NSi(+) + CO are kinetically unfeasible. The high efficiency of the SiCN+/SiNC+ reaction towards H2O and the potential importance of SiCN+/SiNC+ ion chemistry in interstellar and SiCN-based microelectric and photoelectric processes strongly appeals for future laboratory investigations on the SiCN+/SiNC+ chemical reactivity.
NASA Astrophysics Data System (ADS)
Mostafavi, Najmeh; Ebrahimi, Ali
2018-06-01
In order to characterize various interactions in the G-quadruplex ⋯ Mn+ (G-Q ⋯ Mn+) complexes, the individual H-bond (EHB) and metal ion-ligand interaction (EMO) energies have been estimated using the electron charge densities (ρs) calculated at the X ⋯ H (X = N and O) and Mn+ ⋯ O (Mn+ is an alkaline, alkaline earth and transition metal ion) bond critical points (BCPs) obtained from the atoms in molecules (AIM) analysis. The estimated values of EMO and EHB were evaluated using the structural parameters, results of natural bond orbital analysis (NBO), aromaticity indexes and atomic charges. The EMO value increase with the ratio of ionic charge to radius, e/r, where a linear correlation is observed between EMO and e/r (R = 0.97). Meaningful relationships are also observed between EMO and indexes used for aromaticity estimation. The ENH value is higher than EOH in the complexes; this is in complete agreement with the trend of N⋯Hsbnd N and O⋯Hsbnd N angles, the E (2) value of nN → σ*NH and nO → σ*NH interactions and the difference between the natural charges on the H-bonded atom and the hydrogen atom of guanine (Δq). In general, the O1MO2 angle becomes closer to 109.5° with the increase in EMO and decrease in EHB in the presence of metal ion.
Alternative RF coupling configurations for H{sup −} ion sources
DOE Office of Scientific and Technical Information (OSTI.GOV)
Briefi, S.; Fantz, U.; AG Experimentelle Plasmaphysik, Universität Augsburg, 86135 Augsburg
2015-04-08
RF heated sources for negative hydrogen ions both for fusion and accelerators require very high RF powers in order to achieve the required H{sup −} current what poses high demands on the RF generators and the RF circuit. Therefore it is highly desirable to improve the RF efficiency of the sources. This could be achieved by applying different RF coupling concepts than the currently used inductive coupling via a helical antenna, namely Helicon coupling or coupling via a planar ICP antenna enhanced with ferrites. In order to investigate the feasibility of these concepts, two small laboratory experiments have been setmore » up. The PlanICE experiment, where the enhanced inductive coupling is going to be investigated, is currently under assembly. At the CHARLIE experiment systematic measurements concerning Helicon coupling in hydrogen and deuterium are carried out. The investigations show that a prominent feature of Helicon discharges occurs: the so-called low-field peak. This is a local improvement of the coupling efficiency at a magnetic field strength of a few mT which results in an increased electron density and dissociation degree. The full Helicon mode has not been achieved yet due to the limited available RF power and magnetic field strength but it might be sufficient for the application of the coupling concept to ion sources to operate the discharge in the low-field-peak region.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Haeberli, W.
1981-04-01
This paper presents a survey of methods, commonly in use or under development, to produce beams of polarized negative ions for injection into accelerators. A short summary recalls how the hyperfine interaction is used to obtain nuclear polarization in beams of atoms. Atomic-beam sources for light ions are discussed. If the best presently known techniques are incorporated in all stages of the source, polarized H/sup -/ and D/sup -/ beams in excess of 10 ..mu..A can probably be achieved. Production of polarized ions from fast (keV) beams of polarized atoms is treated separately for atoms in the H(25) excited statemore » (Lamb-Shift source) and atoms in the H(1S) ground state. The negative ion beam from Lamb-Shift sources has reached a plateau just above 1 ..mu..A, but this beam current is adequate for many applications and the somewhat lower beam current is compensated by other desirable characteristics. Sources using fast polarized ground state atoms are in a stage of intense development. The next sections summarize production of polarized heavy ions by the atomic beam method, which is well established, and by optical pumping, which has recently been demonstrated to yield very large nuclear polarization. A short discussion of proposed ion sources for polarized /sup 3/He/sup -/ ions is followed by some concluding remarks.« less
RF plasma modeling of the Linac4 H- ion source
NASA Astrophysics Data System (ADS)
Mattei, S.; Ohta, M.; Hatayama, A.; Lettry, J.; Kawamura, Y.; Yasumoto, M.; Schmitzer, C.
2013-02-01
This study focuses on the modelling of the ICP RF-plasma in the Linac4 H- ion source currently being constructed at CERN. A self-consistent model of the plasma dynamics with the RF electromagnetic field has been developed by a PIC-MCC method. In this paper, the model is applied to the analysis of a low density plasma discharge initiation, with particular interest on the effect of the external magnetic field on the plasma properties, such as wall loss, electron density and electron energy. The employment of a multi-cusp magnetic field effectively limits the wall losses, particularly in the radial direction. Preliminary results however indicate that a reduced heating efficiency results in such a configuration. The effect is possibly due to trapping of electrons in the multi-cusp magnetic field, preventing their continuous acceleration in the azimuthal direction.
NASA Astrophysics Data System (ADS)
Yuan, Bin; Koss, Abigail; Warneke, Carsten; Gilman, Jessica B.; Lerner, Brian M.; Stark, Harald; de Gouw, Joost A.
2016-07-01
Proton transfer reactions between hydronium ions (H3O+) and volatile organic compounds (VOCs) provide a fast and highly sensitive technique for VOC measurements, leading to extensive use of proton-transfer-reaction mass spectrometry (PTR-MS) in atmospheric research. Based on the same ionization approach, we describe the development of a high-resolution time-of-flight chemical ionization mass spectrometer (ToF-CIMS) utilizing H3O+ as the reagent ion. The new H3O+ ToF-CIMS has sensitivities of 100-1000 cps ppb-1 (ion counts per second per part-per-billion mixing ratio of VOC) and detection limits of 20-600 ppt at 3σ for a 1 s integration time for simultaneous measurements of many VOC species of atmospheric relevance. The ToF analyzer with mass resolution (m/Δm) of up to 6000 allows the separation of isobaric masses, as shown in previous studies using similar ToF-MS. While radio frequency (RF)-only quadrupole ion guides provide better overall ion transmission than ion lens system, low-mass cutoff of RF-only quadrupole causes H3O+ ions to be transmitted less efficiently than heavier masses, which leads to unusual humidity dependence of reagent ions and difficulty obtaining a humidity-independent parameter for normalization. The humidity dependence of the instrument was characterized for various VOC species and the behaviors for different species can be explained by compound-specific properties that affect the ion chemistry (e.g., proton affinity and dipole moment). The new H3O+ ToF-CIMS was successfully deployed on the NOAA WP-3D research aircraft for the SONGNEX campaign in spring of 2015. The measured mixing ratios of several aromatics from the H3O+ ToF-CIMS agreed within ±10 % with independent gas chromatography measurements from whole air samples. Initial results from the SONGNEX measurements demonstrate that the H3O+ ToF-CIMS data set will be valuable for the identification and characterization of emissions from various sources, investigation of secondary
NASA Astrophysics Data System (ADS)
Ghasemi, Khaled; Rezvani, Ali Reza; Shokrollahi, Ardeshir; Abdul Razak, Ibrahim; Refahi, Masoud; Moghimi, Abolghasem; Rosli, Mohd Mustaqim
2015-09-01
The complex [DAPH][H3O][Cu(dipic)2]·3H2O, (1) (dipicH2 = 2,6-pyridinedicarboxylic acid and DAP = 2,3-diaminophenazine) was prepared from the reaction of Cu(NO3)2·2H2O with mixture of o-phenylenediamine (OPD) and 2,6-pyridinedicarboxylic acid in water. The complex was characterized by FTIR, elemental analysis, UV-Vis and the single-crystal X-ray diffraction. The crystal system is monoclinic with the space group P21/c. This complex is stabilized in the solid state by an extensive network of hydrogen bonds between crystallized water, anionic and cationic fragments, which form a three-dimensional network. Furthermore, hydrogen bonds, π⋯π and Csbnd O⋯π stacking interactions seem to be effective in stabilizing the crystal structures. The protonation constants of dipic (L) and DAP (Q), the equilibrium constants for the dipic-DAP proton transfer system and the stoichiometry and stability constants of binary complexes including each of ligands (dipic, DAP) in presence Cu2+ ion, ternary complexes including, both of ligands (dipic-DAP) in presence of metal ion were calculated in aqueous solutions by potentiometric pH titration method using the Hyperquad2008 program. The stoichiometry of the most complexes species in solution was found to be very similar to the solid-state of cited metal ion complex.
Effect of cerium ions on corrosion inhibition of PANI for iron in 0.5 M H 2SO 4
NASA Astrophysics Data System (ADS)
Jeyaprabha, C.; Sathiyanarayanan, S.; Venkatachari, G.
2006-11-01
In recent years conducting polymers such as polyaniline are used as corrosion inhibitors for metals in acids. The performance of the inhibitor can be enhanced either by the addition of halide ions or metal cations. A study has been made on the effect of addition of ceric ions on the corrosion inhibition performance of polyaniline for iron in 0.5 M H2SO4. Techniques such as electrochemical impedance spectroscopy, potentiodynamic polarization and linear polarization resistance methods have been employed to study the corrosion inhibition. The polyaniline has been used in the concentration range of 10-100 ppm and the ceric ions concentration has been maintained at 1 × 10-3 M. The inhibition efficiency of polyaniline at 10 ppm has been increased from 53 to 88% and for 50 ppm from 71 to 90% in the presence of ceric ions. The enhanced inhibition of polyaniline in presence of ceric ions is due to the higher coverage of polyaniline-cerium complex.
Ion-molecule reactions relevant to Titan's ionosphere.
NASA Astrophysics Data System (ADS)
McEwan, M. J.; Scott, G. B. I.; Anicich, V. G.
1998-02-01
Twenty four new ion-molecule reactions are presented for inclusion in the modeling of the ionosphere of Saturn's satellite Titan. Sixteen reactions were re-examined to reduce uncertainties in the previous literature results. In this study the authors have examined the reactions of N+ and N2+ with CH4, C2H2, C2H4, C2H6, HCN, CH2CHCN and HC3N; the reaction of N+ with CH3CN; the reactions of C3H5+ with CH4, C2H2 C2H4, C2H6, H2, HCN, HC3N and CH2CHCN; the reactions of C2N2+ with C2H2; C2H2+ and C2N2; C2H4 with C2H3+, C2H4+, CHCCNH+, and HC5N+; HCNH+ with C2H6; C3H6+ with C3H6; HCN with C2H6+, C3H6+, c-C3H6+, C2N2+ and NO+; N2 with C2H2+ and C2H5+; C2H4+ and HC3N. The ions selected for this study were derived either from nitrogen, appropriate hydrocarbons or nitriles. The reactant neutrals were selected on the basis of their known presence in Titan's atmosphere. The reaction products are consistent with the expected increase in ion size through ion-molecule reaction processing. Data are also presented for the reactions of 23 ions with molecular nitrogen. Almost all of these ions are unreactive with N2.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yamazaki, Takao; Watanabe, Yusuke; Kanya, Reika
2016-01-14
Decomposition of cyclohexane cations induced by intense femtosecond laser fields at the wavelength of 800 nm is investigated by ion-trap time-of-flight mass spectrometry in which cyclohexane cations C{sub 6}H{sub 12}{sup +} stored in an ion trap are irradiated with intense femtosecond laser pulses and the generated fragment ions are recorded by time-of-flight mass spectrometry. The various fragment ion species, C{sub 5}H{sub n}{sup +} (n = 7, 9), C{sub 4}H{sub n}{sup +} (n = 5–8), C{sub 3}H{sub n}{sup +} (n = 3–7), C{sub 2}H{sub n}{sup +} (n = 2–6), and CH{sub 3}{sup +}, identified in the mass spectra show that decompositionmore » of C{sub 6}H{sub 12}{sup +} proceeds efficiently by the photo-irradiation. From the laser intensity dependences of the yields of the fragment ion species, the numbers of photons required for producing the respective fragment ions are estimated.« less
X-ray transitions studied for decelerated bare and H-like uranium ions at the ESR electron cooler
NASA Astrophysics Data System (ADS)
Gumberidze, A.; Stöhlker, Th.; Bednarz, G.; Beyer, H. F.; Bosch, F.; Cai, X.; Hagmann, S.; Klepper, O.; Kozhuharov, C.; Liesen, D.; Ma, X.; Mokler, P. H.; Sierpowski, D.; Stachura, Z.; Steck, M.; Toleikis, S.; Warczak, A.; Zou, Y.
2003-05-01
Here we report on X-ray spectra induced by spontaneous capture of free electrons into decelerated bare- and hydrogen-like uranium ions which we measured recently at the cooler section of the ESR storage ring. The most intense lines observed in spectra can be attributed to direct transition of electrons into the K shell of the projectile ions and to characteristic L → K (Lyα) transitions. Radiative recombination lines into the K shell of bare and H-like uranium can be exploited for measuring the two-electron contribution to the ground state binding energy in helium-like uranium. The goal is to probe for high-Z ions bound-state QED corrections which are of the order of α2. Besides the dominant characteristic L → K transitions, the strongly reduced Bremsstrahlung (due to the low cooler voltage applied to the decelerated ions) allowed us to observe for the very first time RR transitions into the L shell as well as the balmer radiation located at the low-energy part of the spectra.
Suprathermal O(+) and H(+) ion behavior during the March 22, 1979 (CDAW 6), substorms
NASA Technical Reports Server (NTRS)
Ipavich, F. M.; Galvin, A. B.; Gloeckler, G.; Scholer, M.; Hovestadt, D.; Klecker, B.
1985-01-01
The present investigation has the objective to report on the behavior of energetic (approximately 130 keV) O(+) ions in the earth's plasma sheet, taking into account observations by the ISEE 1 spacecraft during a magnetically active time interval encompassing two major substorms on March 22, 1979. Attention is also given to suprathermal H(+) and He(++) ions. ISEE 1 plasma sheet observations of the proton and alpha particle phase space densities as a function of energy per charge during the time interval 0933-1000 UT on March 22, 1979 are considered along with the proton phase space density versus energy in the energy interval approximately 10 to 70 keV for the selected time periods 0933-1000 UT (presubstorm) and 1230-1243 UT (recovery phase) during the 1055 substorm on March 22, 1979. A table listing the proton energy density for presubstorm and recovery periods is also provided.
Laser-stimulated electric quadrupole transitions in the molecular hydrogen ion H2+
NASA Astrophysics Data System (ADS)
Korobov, V. I.; Danev, P.; Bakalov, D.; Schiller, S.
2018-03-01
Molecular hydrogen ions are of metrological relevance due to the possibility of precise theoretical evaluation of their spectrum and of external-field-induced shifts. We report the results of the calculations of the rate of laser-induced electric quadrupole transitions between a large set of ro-vibrational states of H2+. The hyperfine and Zeeman structure of the E 2 transition spectrum and the effects of the laser polarization are treated in detail. The treatment is generally applicable to molecules in 2Σ states. We also present the nuclear spin-electron spin-coupling constants, computed with a precision ten times higher than previously obtained.
NASA Astrophysics Data System (ADS)
Castro, G.; Torrisi, G.; Celona, L.; Mascali, D.; Neri, L.; Sorbello, G.; Leonardi, O.; Patti, G.; Castorina, G.; Gammino, S.
2016-08-01
The versatile ion source is an off-resonance microwave discharge ion source which produces a slightly overdense plasma at 2.45 GHz of pumping wave frequency extracting more than 60 mA proton beams and 50 mA He+ beams. DAEδALUS and IsoDAR experiments require high intensities for H2+ beams to be accelerated by high power cyclotrons for neutrinos generation. In order to fulfill the new requirements, a new plasma chamber and injection system has been designed and manufactured for increasing the H2+ beam intensity. In this paper the studies for the increasing of the H2+/p ratio and for the design of the new plasma chamber and injection system will be shown and discussed together with the experimental tests carried out at Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS) and at Best Cyclotron Systems test-bench in Vancouver, Canada.
NASA Astrophysics Data System (ADS)
Ohtani, S.; Nose, M.; Miyashita, Y.; Lui, A.
2014-12-01
We investigate the responses of different ion species (H+, He+, He++, and O+) to fast plasma flows and local dipolarization in the plasma sheet in terms of energy density. We use energetic (9-210 keV) ion composition measurements made by the Geotail satellite at r = 10~31 RE. The results are summarized as follows: (1) whereas the O+-to-H+ ratio decreases with earthward flow velocity, it increases with tailward flow velocity with Vx dependence steeper for perpendicular flows than for parallel flows; (2) for fast earthward flows, the energy density of each ion species increases without any clear preference for heavy ions; (3) for fast tailward flows the ion energy density increases initially, then it decreases to below pre-flow levels except for O+; (4) the O+-to-H+ ratio does not increase through local dipolarization irrespective of dipolarization amplitude, background BZ, X distance, and VX; (5) in general, the H+ and He++ ions behave similarly. Result (1) can be attributed to radial transport along with the earthward increase of the background O+-to-H+ ratio. Results (2) and (4) indicate that ion energization associated with local dipolarization is not mass-dependent possibly because in the energy range of our interest the ions are not magnetized irrespective of species. In the tailward outflow region of reconnection, where the plasma sheet becomes thinner, the H+ ions escape along the field line more easily than the O+ ions, which possibly explains result (3). Result (5) suggests that the solar wind is the primary source of the high-energy H+ ions.
Calculations on the rate of the ion-molecule reaction between NH3(+) and H2
NASA Technical Reports Server (NTRS)
Herbst, Eric; Defrees, D. J.; Talbi, D.; Pauzat, F.; Koch, W.
1991-01-01
The rate coefficient for the ion-molecule reaction NH3(+) + H2 yields NH4(+) + H has been calculated as a function of temperature with the use of the statistical phase space approach. The potential surface and reaction complex and transition state parameters used in the calculation have been taken from ab initio quantum chemical calculations. The calculated rate coefficient has been found to mimic the unusual temperature dependence measured in the laboratory, in which the rate coefficient decreases with decreasing temperature until 50-100 K and then increases at still lower temperatures. Quantitative agreement between experimental and theoretical rate coefficients is satisfactory given the uncertainties in the ab initio results and in the dynamics calculations. The rate coefficient for the unusual three-body process NH3(+) + H2 + He yields NH4(+) + H + He has also been calculated as a function of temperature and the result found to agree well with a previous laboratory determination.
Oppenheimer, F.F.
1959-06-01
A shielding arrangement for eliminating oscillating electrons in the ion source region of calutrons is offered. Metal plates are attached to the ion generator so as to intercept the magnetic field between ion generator and accelerating electrode. The oscillating electrons are discharged on the plates. (T.R.H.)
Ion energy distributions in silane-hydrogen plasmas
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hamers, E.A.G.; Sark, W.G.J.H.M. van; Bezemer, J.
1996-12-31
For the first time ion energy distributions (IED) of different ions from silane-hydrogen (SiH{sub 4}-H{sub 2}) RF plasmas are presented, i.e., the distributions of SiH{sub 3}{sup +}, SiH{sub 2}{sup +} and Si{sub 2}H{sub 4}{sup +}. The energy distributions of SiH{sub 3}{sup +} and SiH{sub 2}{sup +} ions show peaks, which are caused by a charge exchange process in the sheath. A method is presented by which the net charge density in the sheath is determined from the plasma potential and the energy positions of the charge exchange peaks. Knowing the net charge density in the sheath and the plasma potential,more » the sheath thickness can be determined and an estimation of the absolute ion fluxes can be made. The flux of ions can, at maximum, account for 10% of the observed deposition rate.« less
NASA Technical Reports Server (NTRS)
Wu, Jian; Blanc, Michel; Alcayde, Denis; Barakat, Abdullah R.; Fontanari, Jean; Blelly, Pierre-Louis; Kofman, Wlodek
1992-01-01
EISCAT VHF radar was used to investigate the vertical flows of H(+) and O(+) ions in the topside high-latitude ionosphere. The radar transmitted a single long pulse to probe the ionosphere from 300 to 1200 km altitude. A calculation scheme is developed to deduce the H(+) drift velocity from the coupled momentum equations of H(+), O(+), and the electrons, using the radar data and a neutral atmosphere model. The H(+) vertical drift velocity was expressed as a linear combination of the different forces acting on the plasma. Two nights, one very quiet, one with moderate magnetic activity, were used to test the technique and to provide a first study of the morphology and orders of magnitudes of ion outflow fluxes over Tromso. O(+) vertical flows were found to be downward or close to zero most of the time in the topside ionosphere; they appeared to be strongly correlated with magnetic activity during the disturbed night. H(+) topside ion fluxes were always directed upward, with velocity reaching 500-1000 m/s. A permanent outflow of H(+) ions is inferred.
NASA Astrophysics Data System (ADS)
Sekimoto, K.; Takayama, M.
2010-12-01
Atmospheric ion water clusters have been of long-standing interest in the field of atmospheric sciences, because of them playing a central role in the formation of tropospheric aerosols which affect the photochemistry, radiation budget of the atmosphere and climate. On the basis of a mechanism of aerosol formation in the troposphere proposed by Yu and Turco, termed “ion-mediated nucleation” (Geophys. Res. Lett. 2000, 27, 883), atmospheric ion water clusters are most likely to be produced via two processes; 1) direct attachment of polar solvent molecules H2O to atmospheric ions due to them having strong binding energy via ion-dipole interactions, and 2) growth of ion-induced hydrates into larger water clusters bound via hydrogen-bonding networks by condensation with H2O molecules. The stability and growth rates of water clusters are strongly dependent on the thermochemical properties of individual atmospheric core ions. A large number of thermochemical information of the positive atmospheric ion H3O+ and its hydrates H3O+(H2O)n have been reported so far, while there has been little information of the water clusters with the negative atmospheric core ions. Therefore, fundamental studies of the thermochemistry of various negative atmospheric ion water clusters will contribute towards furthering an understanding of their unique role in atmospheric sciences and climate change. We have recently established an atmospheric pressure DC corona discharge device containing a specific corona needle electrode that made it possible to reproducibly generate negative core ions Y- originating from ambient air (Int. J. Mass Spectrom. 2007, 261, 38; Eur. Phys. J. D 2008, 50, 297). The change in electric field strength on the needle tip resulted in the formation of negative atmospheric core ions Y- with various different lifetimes in air. The low field strength brought about the dominant formation of core ions with short lifetimes in air such as O2- and HOx-, while the longer
Zeng, Liang; Ichikawa, Takayuki; Kawahito, Koji; Miyaoka, Hiroki; Kojima, Yoshitsugu
2017-01-25
Magnesium hydride, MgH 2 , a recently developed compound for lithium-ion batteries, is considered to be a promising conversion-type negative electrode material due to its high theoretical lithium storage capacity of over 2000 mA h g -1 , suitable working potential, and relatively small volume expansion. Nevertheless, it suffers from unsatisfactory cyclability, poor reversibility, and slow kinetics in conventional nonaqueous electrolyte systems, which greatly limit the practical application of MgH 2 . In this work, a vapor-grown carbon nanofiber was used to enhance the electrical conductivity of MgH 2 using LiBH 4 as the solid-state electrolyte. It shows that a reversible capacity of over 1200 mA h g -1 with an average voltage of 0.5 V (vs Li/Li + ) can be obtained after 50 cycles at a current density of 1000 mA g -1 . In addition, the capacity of MgH 2 retains over 1100 mA h g -1 at a high current density of 8000 mA g -1 , which indicates the possibility of using MgH 2 as a negative electrode material for high power and high capacity lithium-ion batteries in future practical applications. Moreover, the widely studied sulfide-based solid electrolyte was also used to assemble battery cells with MgH 2 electrode in the same system, and the electrochemical performance was as good as that using LiBH 4 electrolyte.
Wang, T; Yang, Z; Dong, P; long, J D; He, X Z; Wang, X; Zhang, K Z; Zhang, L W
2012-06-01
The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H(-)) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H(-) beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H(-) beam current of about 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.
Effect of pH on H2O2 production in the radiolysis of water.
Roth, Olivia; LaVerne, Jay A
2011-02-10
The yields of hydrogen peroxide have been measured in the radiolysis of aqueous solutions of acrylamide, bromide, nitrate, and air in the pH range of 1-13. Hydrogen peroxide is the main stable oxidizing species formed in the radiolysis of water, and its long-term yield is found to be very sensitive to the system used in the measurements. Experiments with γ-irradiation combined with model calculations show that the primary yields of hydrogen peroxide are nearly independent of pH in the range of 2-12. Slightly higher primary yields are suggested at very low pH in particular when O(2) is present, while the yields seem to decrease at very high pH. Irradiations were performed with 5 MeV H ions, 5 MeV He ions, and 10 MeV C ions to evaluate the intratrack and homogeneous kinetic contributions to H(2)O(2) formation with different ions. Many of the trends in hydrogen peroxide yields with pH observed with γ-irradiations are observed with irradiation by the heavy ions. The lower yields of radicals in the homogeneous phase with the heavier ions tend to minimize the effects of radicals on the hydrogen peroxide yields at long times.
Wingen, Andreas; Schmitz, Oliver; Evans, Todd E.; ...
2014-01-01
The heat flux patterns measured in low-collisionality DIII-D H-mode plasmas strongly deviate from simultaneously measured CII emission patterns, used as indicator of particle flux, during applied resonant magnetic perturbations. While the CII emission clearly shows typical striations, which are similar to magnetic footprint patterns obtained from vacuum field line tracing, the heat flux is usually dominated by one large peak at the strike point position. The vacuum approximation, which only considers applied magnetic fields and neglects plasma response and plasma effects, cannot explain the shape of the observed heat flux pattern. One possible explanation is the effect of particle drifts.more » This is included in the field line equations and the results are discussed with reference to the measurement. Electrons and ions show di fferent drift motions at thermal energy levels in a guiding center approximation. While electrons hardly deviate from the field lines, ions can drift several centimetres away from field line flux surfaces. A model is presented in which an ion heat flux, based on the ion drift motion from various kinetic energies as they contribute to a thermal Maxwellian distribution, is calculated. The simulated heat flux is directly compared to measurements with a varying edge safety factor q95. This analysis provides evidence for the dominate e ect of high-energy ions in carrying heat from the plasma inside the separatrix to the target. High-energy ions are deposited close to the unperturbed strike line while low-energy ions can travel into the striated magnetic topology.« less
Failure Mechanisms of Ni-H2 and Li-Ion Batteries Under Hypervelocity Impacts
NASA Technical Reports Server (NTRS)
Miller, J. E.; Lyons, F.; Christiansen, E. L.; Lear, D. M.
2017-01-01
Lithium-Ion (Li-Ion) batteries have yielded significant performance advantages for many industries, including the aerospace industry, and have been selected to replace nickel hydrogen (Ni-H2) batteries for the International Space Station (ISS) program to meet the energy storage demands. As the ISS uses its vast solar arrays to generate its power, the solar ar-rays meet their sunlit power demands and supply excess power to battery packs for power de-livery on the sun obscured phase of the approximate 90 minute low Earth orbit. These large battery packs are located on the exterior of the ISS, and as such, the battery packs are ex-posed to external environment threats like naturally occurring meteoroids and artificial orbital debris (MMOD). While the risks from these solid particle environments has been known and addressed to an acceptable risk of failure through shield design, it is not possible to completely eliminate the risk of loss of these assets on orbit due to MMOD, and as such, failure consequences to the ISS have been considered.
Failure Mechanisms of Ni-H2 and Li-Ion Batteries Under Hypervelocity Impacts
NASA Technical Reports Server (NTRS)
Miller, J. E.; Lyons, F.; Christiansen, E. L.; Lear, D. M.
2017-01-01
Lithium-Ion (Li-Ion) batteries have yielded significant performance advantages for many industries, including the aerospace industry, and have been selected to replace nickel hydrogen (Ni-H2) batteries for the International Space Station (ISS) program to meet the energy storage demands. As the ISS uses its vast solar arrays to generate its power, the solar arrays meet their sunlit power demands and supply excess power to battery packs for power delivery on the sun obscured phase of the approximate 90 minute low Earth orbit. These large battery packs are located on the exterior of the ISS, and as such, the battery packs are exposed to external environment threats like naturally occurring meteoroids and artificial orbital debris (MMOD). While the risks from these solid particle environments has been known and addressed to an acceptable risk of failure through shield design, it is not possible to completely eliminate the risk of loss of these assets on orbit due to MMOD, and as such, failure consequences to the ISS have been considered.
International Space Station Lithium-Ion Battery
NASA Technical Reports Server (NTRS)
Dalton, Penni J.; Balcer, Sonia
2016-01-01
The International Space Station (ISS) Electric Power System (EPS) currently uses Nickel-Hydrogen (Ni-H2) batteries to store electrical energy. The batteries are charged during insolation and discharged during eclipse. The Ni-H2 batteries are designed to operate at a 35 depth of discharge (DOD) maximum during normal operation in a Low Earth Orbit. Since the oldest of the 48 Ni-H2 battery Orbital Replacement Units (ORUs) has been cycling since September 2006, these batteries are now approaching their end of useful life. In 2010, the ISS Program began the development of Lithium-Ion (Li-ion) batteries to replace the Ni-H2 batteries and concurrently funded a Li-ion cell life testing project. This paper will include an overview of the ISS Li-Ion battery system architecture and the progress of the Li-ion battery design and development.
Byles, B. W.; West, P.; Cullen, D. A.; ...
2015-12-03
Extended hydrothermal treatment at an elevated temperature of 220 °C allowed high yield synthesis of manganese oxide nanowires with a todorokite crystal structure suitable for ions intercalation. The flexible, high aspect ratio nanowires are 50–100 nm in diameter and up to several microns long, with 3 × 3 structural tunnels running parallel to the nanowire longitudinal axis. Moreover, the tunnels are occupied by magnesium ions and water molecules, with the chemical composition found to be Mg 0.2MnO 2·0.5H 2O. The todorokite nanowires were, for the first time, electrochemically tested in both Li-ion and Na-ion cells. A first discharge capacity ofmore » 158 mA h g -1 was achieved in a Na-ion system, which was found to be greater than the first discharge capacity in a Li-ion system (133 mA h g -1). In spite of the large structural tunnel dimensions, todorokite showed a significant first cycle capacity loss in a Na-ion battery. After 20 cycles, the capacity was found to stabilize around 50 mA h g -1 and remained at this level for 100 cycles. In a Li-ion system, todorokite nanowires showed significantly better capacity retention with 78% of its initial capacity remaining after 100 cycles. Rate capability tests also showed superior performance of todorokite nanowires in Li-ion cells compared to Na-ion cells at higher current rates. Finally, these results highlight the difference in electrochemical cycling behavior of Li-ion and Na-ion batteries for a host material with spacious 3 × 3 tunnels tailored for large Na + ion intercalation.« less
Ultrafast Scavenging of the Precursor of H(•) Atom, (e(-), H3O(+)), in Aqueous Solutions.
Balcerzyk, Anna; Schmidhammer, Uli; Wang, Furong; de la Lande, Aurélien; Mostafavi, Mehran
2016-09-01
Picosecond pulse radiolysis measurements have been performed in several highly concentrated HClO4 and H3PO4 aqueous solutions containing silver ions at different concentrations. Silver ion reduction is used to unravel the ultrafast reduction reactions observed at the end of a 7 ps electron pulse. Solvated electrons and silver atoms are observed by the pulse (electron beam)-probe (supercontinuum light) method. In highly acidic solutions, ultrafast reduction of silver ions is observed, a finding that is not compatible with a reaction between the H(•) atom and silver ions, which is known to be thermally activated. In addition, silver ion reduction is found to be even more efficient in phosphoric acid solution than that in neutral solution. In the acidic solutions investigated here, the species responsible for the reduction of silver atoms is considered to be the precursor of the H(•) atom. This precursor, denoted (e(-), H3O(+)), is a pair constituting an electron (not fully solvated) and H3O(+). Its structure differs from that of the pair of a solvated electron and a hydronium ion (es(-), H3O(+)), which absorbs in the visible region. The (e(-), H3O(+)) pair , called the pre-H(•) atom here, undergoes ultrafast electron transfer and can, like the presolvated electron, reduce silver ions much faster than the H(•) atom. Moreover, it is found that with the same concentration of H3O(+) the reduction reaction is favored in the phosphoric acid solution compared to that in the perchloric acid solution because of the less-efficient electron solvation process. The kinetics show that among the three reducing species, (e(-), H3O(+)), (es(-), H3O(+)), and H(•) atom, the first one is the most efficient.
Liu, Fenwu; Zhou, Jun; Zhang, Shasha; Liu, Lanlan; Zhou, Lixiang; Fan, Wenhua
2015-01-01
Schwertmannite-mediated removal of arsenic from contaminated water has attracted increasing attention. However, schwertmannite chemical synthesis behavior under different H2O2 supply rates for ferrous ions oxidation is unclear. This study investigated pH, ferrous ions oxidation efficiency, and total iron precipitation efficiency during schwertmannite synthesis by adding H2O2 into FeSO4 · 7H2O solution at different supply rates. Specific surface area and arsenic (III) removal capacity of schwertmannite have also been studied. Results showed that pH decreased from ~3.48 to ~1.96, ~2.06, ~2.12, ~2.14, or ~2.17 after 60 h reaction when the ferrous ions solution received the following corresponding amounts of H2O2: 1.80 mL at 2 h (treatment 1); 0.90 mL at 2 h and 14 h (treatment 2); 0.60 mL at 2, 14, and 26 h (treatment 3); 0.45 mL at 2, 14, 26, and 38 h (treatment 4), or 0.36 mL at 2, 14, 26, 38, and 50 h (treatment 5). Slow H2O2 supply significantly inhibited the total iron precipitation efficiency but improved the specific surface area or arsenic (III) removal capacity of schwertmannite. For the initial 50.0 μg/L arsenic (III)-contaminated water under pH ~7.0 and using 0.25 g/L schwertmannite as an adsorbent, the total iron precipitation efficiency, specific surface area of the harvested schwertmannite, and schwertmannite arsenic(III) removal efficiency were 29.3%, 2.06 m2/g, and 81.1%, respectively, in treatment 1. However, the above parameters correspondingly changed to 17.3%, 16.30 m2/g, and 96.5%, respectively, in treatment 5.
Efficiency of Cs-free materials for negative ion production in H2 and D2 plasmas
NASA Astrophysics Data System (ADS)
Friedl, R.; Kurutz, U.; Fantz, U.
2017-08-01
High power negative ion sources use caesium to reduce the work function of the converter surface which significantly increases the negative ion yield. Caesium, however, is a very reactive alkali-metal and shows complex redistribution dynamics in consequence of plasma-surface-interaction. Thus, maintaining a stable and homogenous low work function surface is a demanding task, which is not easily compatible with the RAMI issues (reliability, availability, maintainability, inspectability) for a future DEMO fusion reactor. Hence, Cs-free alternative materials for efficient negative ion formation are desirable. At the laboratory experiment HOMER materials which are referred to as promising are investigated under identical and ion source relevant parameters: the refractory metals Ta and W, non-doped and boron-doped diamond as well as materials with inherent low work function (lanthanum-doped molybdenum, MoLa and lanthanum hexaboride, LaB6). The results are compared to the effect of in-situ caesiation, which at HOMER leads to a maximal increase of the negative ion density by a factor of 2.5. Among the examined samples low work function materials are most efficient. In particular, MoLa leads to an increase of almost 50 % compared to pure volume formation. The difference to a caesiated surface can be attributed to the still higher work function of MoLa, which is expected to be slightly below 3 eV. Using deuterium instead of hydrogen leads to increased atomic and positive ion densities, while comparable negative ion densities are achieved. In contrast to the low work function materials, bulk samples of the refractory metals as well as carbon based materials have no enhancing effect on H-, where the latter materials furthermore show severe erosion due to the hydrogen plasma.
Ion exchange selectivity for cross-linked polyacrylic acid
NASA Technical Reports Server (NTRS)
May, C. E.; Philipp, W. H.
1983-01-01
The ion separation factors for 21 common metal ions with cross-linked polyacrylic acid were determined as a function of pH and the percent of the cross-linked polyacrylic acid neutralized. The calcium ion was used as a reference. At a pH of 5 the decreasing order of affinity of the ions for the cross-linked polyacrylic acid was found to be: Hg++, Fe+++, Pb++, Cr+++, Cu++, Cd++, Al+++, Ag+, Zn++, Ni++, Mn++, Co++, Ca++, Sr++, Ba++, Mg++, K+, Rb+, Cs+, Na+, and Li+. Members of a chemical family exhibited similar selectivities. The Hg++ ion appeared to be about a million times more strongly bound than the alkali metal ions. The relative binding of most of the metal ions varied with pH; the very tightly and very weakly bound ions showed the largest variations with pH. The calcium ion-hydrogen ion equilibrium was perturbed very little by the presence of the other ions. The separation factors and selectivity coefficients are discussed in terms of equilibrium and thermodynamic significance.
Peng, Liying; Jiang, Dandan; Wang, Zhenxin; Hua, Lei; Li, Haiyang
2016-06-01
Malodorous hydrogen sulfide (H2S) gas often exists in the sewer system and associates with the problems of releasing the dangerous odor to the atmosphere and causing sewer pipe to be corroded. A simple method is in demand for real-time measuring H2S level in the sewer gas. In this paper, an innovated method based on dopant-assisted negative photoionization ion mobility spectrometry (DANP-IMS) with on-line semiconductor cooling inlet was put forward and successfully applied for the real-time measurement of H2S in sewer gas. The influence of moisture was effectively reduced via an on-line cooling method and a non-equilibrium dilution with drift gas. The limits of quantitation for the H2S in ≥60% relative humidity air could be obtained at ≤79.0ng L(-1) with linear ranges of 129-2064ng L(-1). The H2S concentration in a sewer manhole was successfully determined while its product ions were identified by an ion-mobility time-of-fight mass spectrometry. Finally, the correlation between sewer H2S concentration and the daily routines and habits of residents was investigated through hourly or real-time monitoring the variation of sewer H2S in manholes, indicating the power of this DANP-IMS method in assessing the H2S concentration in sewer system. Copyright © 2016 Elsevier B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Turmuzi, M.; Tarigan, Z. N.; Nadapdap, L.; Batubara, F.
2018-02-01
The total nitrogen content in water bodies should be below 50 mg NO3 -/L (11.3 mgN/l) World Health Organization (WHO) 2006. The content of nitrogen exceeding the quality standard threshold will cause damage to the aquatic ecosystem and be carcinogenic to humans. The Purolite A-400 resin will be modified with Cu metal by batch method to see the adsorption allowance of nitrate in synthetic liquid waste with nitrate concentration of 50 mg/l. This study will evaluate the effect of pH and complementary ions on the adsorption process. From the result of the research, the second order pseudo model is the most suitable adsorption kinetics model. For the adsorption isotherms the most suitable model is the Freundlich adsorption isotherm model. The optimum pH conditions were at the range of 8.5. The addition of complementary ions sulfate and phosphate did not show any significant change, but sulfate is the most effective complementary ion with a content of 20 mg/l.
Shi, Haotian; Poudel, Nirakar; Hou, Bingya; Shen, Lang; Chen, Jihan; Benderskii, Alexander V; Cronin, Stephen B
2018-02-01
We report a novel approach to probe the local ion concentration at graphene/water interfaces using in situ Raman spectroscopy. Here, the upshifts observed in the G band Raman mode under applied electrochemical potentials are used to determine the charge density in the graphene sheet. For voltages up to ±0.8 V vs. NHE, we observe substantial upshifts in the G band Raman mode by as much as 19 cm -1 , which corresponds to electron and hole carrier densities of 1.4 × 10 13 cm -2 and Fermi energy shifts of ±430 meV. The charge density in the graphene electrode is also measured independently using the capacitance-voltage characteristics (i.e., Q = CV), and is found to be consistent with those measured by Raman spectroscopy. From charge neutrality requirements, the ion concentration in solution per unit area must be equal and opposite to the charge density in the graphene electrode. Based on these charge densities, we estimate the local ion concentration as a function of electrochemical potential in both pure DI water and 1 M KCl solutions, which span a pH range from 3.8 to 10.4 for pure DI water and net ion concentrations of ±0.7 mol L -1 for KCl under these applied voltages.
The Role of Oxygen in the Formation of TNT Product Ions in Ion Mobility Spectrometry
DOE Office of Scientific and Technical Information (OSTI.GOV)
Daum, Keith Alvin; Atkinson, David Alan; Ewing, Robert Gordon
2002-03-01
The atmospheric pressure ionization of 2,4,6-trinitrotoluene (TNT) in air yields the (TNT-H)- product ion. It is generally accepted that this product ion is formed by the direct proton abstraction of neutral TNT by O2- reactant ions. Data presented here demonstrate the reaction involves the formation of an intermediate (TNT·O2)-, from the association of either TNT+O2- or TNT-+O2. This intermediate has two subsequent reaction branches. One of these branches involves simple dissociation of the intermediate to TNT-; the other branch is a terminal reaction that forms the typically observed (TNT-H)- ion via proton abstraction. The dissociation reaction involving electron transfer tomore » TNT- appeared to be kinetically favored and prevailed at low concentrations of oxygen (less than 2%). The presence of significant amounts of oxygen, however, resulted in the predominant formation of the (TNT-H)- ion by the terminal reaction branch. With TNT- in the system, either from direct electron attachment or by simple dissociation of the intermediate, increasing levels of oxygen in the system will continue to reform the intermediate, allowing the cycle to continue until proton abstraction occurs. Key to understanding this complex reaction pathway is that O2- was observed to transfer an electron directly to neutral TNT to form the TNT-. At oxygen levels of less than 2%, the TNT- ion intensity increased with increasing levels of oxygen (and O2-) and was larger than the (TNT-H)- ion intensity. As the oxygen level increased from 2 to 10%, the (TNT-H)- product ion became predominant. The potential reaction mechanisms were investigated with an ion mobility spectrometer, which was configured to independently evaluate the ionization pathways.« less
International Space Station Lithium-Ion Battery
NASA Technical Reports Server (NTRS)
Dalton, Penni J.; Schwanbeck, Eugene; North, Tim; Balcer, Sonia
2016-01-01
The International Space Station (ISS) primary Electric Power System (EPS) currently uses Nickel-Hydrogen (Ni-H2) batteries to store electrical energy. The electricity for the space station is generated by its solar arrays, which charge batteries during insolation for subsequent discharge during eclipse. The Ni-H2 batteries are designed to operate at a 35 depth of discharge (DOD) maximum during normal operation in a Low Earth Orbit. Since the oldest of the 48 Ni-H2 battery Orbital Replacement Units (ORUs) has been cycling since September 2006, these batteries are now approaching their end of useful life. In 2010, the ISS Program began the development of Lithium-Ion (Li-Ion) batteries to replace the Ni-H2 batteries and concurrently funded a Li-Ion ORU and cell life testing project. When deployed, they will be the largest Li-Ion batteries ever utilized for a human-rated spacecraft. This paper will include an overview of the ISS Li-Ion battery system architecture, the Li-Ion battery design and development, controls to limit potential hazards from the batteries, and the status of the Li-Ion cell and ORU life cycle testing.
Modeling the ion transfer and polarization of ion exchange membranes in bioelectrochemical systems.
Harnisch, Falk; Warmbier, Robert; Schneider, Ralf; Schröder, Uwe
2009-06-01
An explicit numerical model for the charge balancing ion transfer across monopolar ion exchange membranes under conditions of bioelectrochemical systems is presented. Diffusion and migration equations have been solved according to the Nernst-Planck Equation and the resulting ion concentrations, pH values and the resistance values of the membrane for different conditions were computed. The modeling results underline the principle limitations of the application of ion exchange membranes in biological fuel cells and electrolyzers, caused by the inherent occurrence of a pH-gradient between anode and cathode compartment, and an increased ohmic membrane resistance at decreasing electrolyte concentrations. Finally, the physical and numerical limitations of the model are discussed.
Gerrard, Andrew; Lanzerotti, Louis; Gkioulidou, Matina; Mitchell, Donald; Manweiler, Jerry; Bortnik, Jacob; Keika, Kunihiro
2014-01-01
H-ion (∼45 keV to ∼600 keV), He-ion (∼65 keV to ∼520 keV), and O-ion (∼140 keV to ∼1130 keV) integral flux measurements, from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft B, are reported. These abundance data form a cohesive picture of ring current ions during the first 9 months of measurements. Furthermore, the data presented herein are used to show injection characteristics via the He-ion/H-ion abundance ratio and the O-ion/H-ion abundance ratio. Of unique interest to ring current dynamics are the spatial-temporal decay characteristics of the two injected populations. We observe that He-ions decay more quickly at lower L shells, on the order of ∼0.8 day at L shells of 3–4, and decay more slowly with higher L shell, on the order of ∼1.7 days at L shells of 5–6. Conversely, O-ions decay very rapidly (∼1.5 h) across all L shells. The He-ion decay time are consistent with previously measured and calculated lifetimes associated with charge exchange. The O-ion decay time is much faster than predicted and is attributed to the inclusion of higher-energy (> 500 keV) O-ions in our decay rate estimation. We note that these measurements demonstrate a compelling need for calculation of high-energy O-ion loss rates, which have not been adequately studied in the literature to date. Key Points We report initial observations of ring current ions We show that He-ion decay rates are consistent with theory We show that O-ions with energies greater than 500 keV decay very rapidly PMID:26167435
NASA Astrophysics Data System (ADS)
Schiller, S.; Kortunov, I.; Hernández Vera, M.; Gianturco, F.; da Silva, H.
2017-04-01
Precision vibrational spectroscopy of the molecular hydrogen ions is of significant interest for determining fundamental constants, for searching for new forces, and for testing quantum electrodynamics calculations. Future experiments can profit from the ability of preparing molecular hydrogen ions at ultralow kinetic energy and in preselected internal states, with respect to vibration, rotation, and spin degrees of freedom. For the homonuclear ions (H2+ , D2+ ), direct laser cooling of the rotational degree of freedom is not feasible. We show by quantum calculations that rotational cooling by cold He buffer gas is an effective approach. For this purpose we have computed the energy-dependent cross sections for rotationally elastic and inelastic collisions, h2+ (v =0 ,N ) +He → h2+ (v =0 ,N') +He (where h =H ,D ) , using ab initio coupled-channel calculations. We find that rotational cooling to the lowest rotational state is possible within tens of seconds under experimentally realistic conditions. We furthermore describe possible protocols for the preparation of a single quantum state, where also the spin state is well defined.
Zschornack, G; Schwan, A; Ullmann, F; Grossmann, F; Ovsyannikov, V P; Ritter, E
2012-02-01
We report on experiments with a new superconducting electron beam ion source (EBIS-SC), the Dresden EBIS-SC, with the objective to meet the main requirements for their application in particle-therapy facilities. Synchrotrons as well as innovative accelerator concepts, such as high-gradient linacs which are driven by a large-current cyclotron (CYCLINACS) and direct drive RF linear accelerators may benefit from the advantages of EBISs in regard to their functional principle. First experimental studies of the production of low-Z ions such as H(+), H(2)(+), H(3)(+), C(4+), and C(6+) are presented. Particular attention is paid to the ion output, i.e., the number of ions per pulse and per second, respectively. Important beam parameters in this context are, among others, ion pulse shaping, pulse repetition rates, beam emittance, and ion energy spread.
Flores-Alsina, Xavier; Kazadi Mbamba, Christian; Solon, Kimberly; Vrecko, Darko; Tait, Stephan; Batstone, Damien J; Jeppsson, Ulf; Gernaey, Krist V
2015-11-15
There is a growing interest within the Wastewater Treatment Plant (WWTP) modelling community to correctly describe physico-chemical processes after many years of mainly focusing on biokinetics. Indeed, future modelling needs, such as a plant-wide phosphorus (P) description, require a major, but unavoidable, additional degree of complexity when representing cationic/anionic behaviour in Activated Sludge (AS)/Anaerobic Digestion (AD) systems. In this paper, a plant-wide aqueous phase chemistry module describing pH variations plus ion speciation/pairing is presented and interfaced with industry standard models. The module accounts for extensive consideration of non-ideality, including ion activities instead of molar concentrations and complex ion pairing. The general equilibria are formulated as a set of Differential Algebraic Equations (DAEs) instead of Ordinary Differential Equations (ODEs) in order to reduce the overall stiffness of the system, thereby enhancing simulation speed. Additionally, a multi-dimensional version of the Newton-Raphson algorithm is applied to handle the existing multiple algebraic inter-dependencies. The latter is reinforced with the Simulated Annealing method to increase the robustness of the solver making the system not so dependent of the initial conditions. Simulation results show pH predictions when describing Biological Nutrient Removal (BNR) by the activated sludge models (ASM) 1, 2d and 3 comparing the performance of a nitrogen removal (WWTP1) and a combined nitrogen and phosphorus removal (WWTP2) treatment plant configuration under different anaerobic/anoxic/aerobic conditions. The same framework is implemented in the Benchmark Simulation Model No. 2 (BSM2) version of the Anaerobic Digestion Model No. 1 (ADM1) (WWTP3) as well, predicting pH values at different cationic/anionic loads. In this way, the general applicability/flexibility of the proposed approach is demonstrated, by implementing the aqueous phase chemistry module in some
Duarte, Rafael M; Wood, Chris M; Val, Adalberto L; Smith, D Scott
2018-06-11
Dissolved organic carbon (DOC) represents a heterogeneous group of naturally-occurring molecules in aquatic environments, and recent studies have evidenced that optically dark DOCs can exert some positive effects on ionoregulatory homeostasis of aquatic organisms in acidic waters. We investigated the effects of Luther Marsh DOC, a dark allochthonous DOC, on ion regulation and N-waste excretion of zebrafish acutely exposed to either neutral or low pH in ion-poor water. In the first experiment, simultaneous exposure to pH 4.0 and DOC greatly attenuated the stimulation of Na + diffusive losses (J out Na ), and prevented the blockade of Na + uptake (J in Na ) seen in zebrafish exposed to pH 4.0 alone, resulting in much smaller disturbances in Na + net losses (J net Na ). DOC also attenuated the stimulation of net Cl - losses (J net Cl ) and ammonia excretion (J net Amm ) during acidic challenge. In the second experiment, zebrafish acclimated to DOC displayed similar regulation of J in Na and J out Na , and, therefore, reduced J net Na at pH 4.0, effects which persisted even when DOC was no longer present. Protective effects of prior acclimation to DOC on J net Cl and J net Amm at pH 4.0 also occurred, but were less marked than those on Na + balance. Urea fluxes were unaffected by the experimental treatments. Overall, these effects were clearly beneficial to the ionoregulatory homeostasis of zebrafish at low pH, and were quite similar to those seen in a recent parallel study using darker DOC from the upper Rio Negro. This suggests that dark allochthonous DOCs share some chemical properties that render fish tolerant to ionoregulatory disturbances during acidic challenge.
NASA Astrophysics Data System (ADS)
Johansen, K. M.; Zubiaga, A.; Tuomisto, F.; Monakhov, E. V.; Kuznetsov, A. Yu.; Svensson, B. G.
2011-09-01
The interaction of hydrogen (H) with lithium (Li) and zinc vacancies (VZn) in hydrothermally grown n-type zinc oxide (ZnO) has been investigated by positron annihilation spectroscopy (PAS) and secondary ion mass spectrometry. Li on Zn-site (LiZn) is found to be the dominant trap for migrating H atoms, while the trapping efficiency of VZn is considerably smaller. After hydrogenation, where the LiZn acceptor is passivated via formation of neutral LiZn-H pairs, VZn occurs as the prime PAS signature and with a concentration similar to that observed in nonhydrogenated Li-poor samples. Despite a low efficiency as an H trap, the apparent concentration of VZn in Li-poor samples decreases after hydrogenation, as detected by PAS, and evidence for formation of the neutral VZnH2 complex is presented.
Imaoka, Tatsuhiko; Nishimura, Mayumi; Kakinuma, Shizuko; Hatano, Yukiko; Ohmachi, Yasushi; Yoshinaga, Shinji; Kawano, Akihiro; Maekawa, Akihiko; Shimada, Yoshiya
2007-09-01
The high relative biologic effectiveness (RBE) of high-linear energy transfer (LET) heavy-ion radiation has enabled powerful radiotherapy. The potential risk of later onset of secondary cancers, however, has not been adequately studied. We undertook the present study to clarify the RBE of therapeutic carbon ion radiation and molecular changes that occur in the rat mammary cancer model. We observed 7-8-week-old rats (ACI, F344, Wistar, and Sprague-Dawley) until 1 year of age after irradiation (0.05-2 Gy) with either 290 MeV/u carbon ions with a spread out Bragg peak (LET 40-90 keV/mum) generated from the Heavy-Ion Medical Accelerator in Chiba or (137)Cs gamma-rays. Carbon ions significantly induced mammary carcinomas in Sprague-Dawley rats but less so in other strains. The dose-effect relationship for carcinoma incidence in the Sprague-Dawley rats was concave downward, providing an RBE of 2 at a typical therapeutic dose per fraction. In contrast, approximately 10 should be considered for radiation protection at low doses. Immunohistochemically, 14 of 18 carcinomas were positive for estrogen receptor alpha. All carcinomas examined were free of common H-ras and Tp53 mutations. Importantly, lung metastasis (7%) was characteristic of carbon ion-irradiated rats. We found clear genetic variability in the susceptibility to carbon ion-induced mammary carcinomas. The high RBE for carbon ion radiation further supports the importance of precise dose localization in radiotherapy. Common point mutations in H-ras and Tp53 were not involved in carbon ion induction of rat mammary carcinomas.
Experimental benchmark of the NINJA code for application to the Linac4 H- ion source plasma
NASA Astrophysics Data System (ADS)
Briefi, S.; Mattei, S.; Rauner, D.; Lettry, J.; Tran, M. Q.; Fantz, U.
2017-10-01
For a dedicated performance optimization of negative hydrogen ion sources applied at particle accelerators, a detailed assessment of the plasma processes is required. Due to the compact design of these sources, diagnostic access is typically limited to optical emission spectroscopy yielding only line-of-sight integrated results. In order to allow for a spatially resolved investigation, the electromagnetic particle-in-cell Monte Carlo collision code NINJA has been developed for the Linac4 ion source at CERN. This code considers the RF field generated by the ICP coil as well as the external static magnetic fields and calculates self-consistently the resulting discharge properties. NINJA is benchmarked at the diagnostically well accessible lab experiment CHARLIE (Concept studies for Helicon Assisted RF Low pressure Ion sourcEs) at varying RF power and gas pressure. A good general agreement is observed between experiment and simulation although the simulated electron density trends for varying pressure and power as well as the absolute electron temperature values deviate slightly from the measured ones. This can be explained by the assumption of strong inductive coupling in NINJA, whereas the CHARLIE discharges show the characteristics of loosely coupled plasmas. For the Linac4 plasma, this assumption is valid. Accordingly, both the absolute values of the accessible plasma parameters and their trends for varying RF power agree well in measurement and simulation. At varying RF power, the H- current extracted from the Linac4 source peaks at 40 kW. For volume operation, this is perfectly reflected by assessing the processes in front of the extraction aperture based on the simulation results where the highest H- density is obtained for the same power level. In surface operation, the production of negative hydrogen ions at the converter surface can only be considered by specialized beam formation codes, which require plasma parameters as input. It has been demonstrated that
Measurement of H/D ratio and ion temperature on a HT-6M Tokamak
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wei, L.; Lin, X.
1997-01-01
By combining optical fibers with piezoelectric scanning Fabry{endash}Perot interferometer, the profiles of H{sub {alpha}} and D{sub {alpha}} have been determined simultaneously in a single Tokamak discharge. Consequently, the ratio of hydrogen to deuterium and ion temperature are obtained. Not only is the uncertainty of shot-to-shot avoided, the results of the experiment indicate that this instrumentation has the advantage of rapid wavelength scanning, large dispersion, high resolution, and good adaptability of working in adverse circumstances such as at a Tokamak site. {copyright} {ital 1997 American Institute of Physics.}
NASA Astrophysics Data System (ADS)
Expósito, E.; Sánchez-Sánchez, C. M.; Solla-Gullón, J.; Montiel, V.
The influence of Pb 2+ ions in sulfuric acid medium on the behavior of a platinum catalyzed hydrogen diffusion electrode (HDE) in a filter press reactor has been studied. A voltammetric study of the H 2 oxidation reaction on a polyoriented platinum electrode and a platinum rotating disk electrode (RDE) in presence of lead ions in solution has also been carried out. Potential oscillations were found in galvanostatic experiments of H 2 oxidation using a HDE catalyzed with platinum when Pb 2+ ions are present in solution. This oscillatory phenomenon was also observed when hydrogen oxidation was carried out in presence of Pb 2+ ions using a platinum RDE. The oscillatory behavior observed has been attributed to an adsorption-oxidation-desorption process of lead on the platinum surface. Due to the low solubility of Pb 2+ in sulfuric acid, at high values of coverage, lead is oxidised to insoluble lead sulfate that blocks the Pt surface. The coupling of the dissolution of lead sulfate and the Pb electrochemical adsorption-oxidation processes cause the oscillatory phenomenon.
NASA Astrophysics Data System (ADS)
Lucca, D. A.; Qi, Y.; Harriman, T. A.; Prenzel, T.; Wang, Y. Q.; Nastasi, M.; Dong, J.; Mehner, A.
2010-10-01
A study of the effects of ion irradiation of hybrid organic/inorganic modified silicate thin films on their mechanical properties is presented. NaOH catalyzed SiNa wO xC yH z thin films were synthesized by sol-gel processing from tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto Si substrates. After drying at 300 °C, the films were irradiated with 125 keV H + or 250 keV N 2+ at fluences ranging from 1 × 10 14 to 2.5 × 10 16 ions/cm 2. Nanoindentation was used to characterize the films. Changes in hardness and reduced elastic modulus were examined as a function of ion fluence and irradiating species. The resulting increases in hardness and reduced elastic modulus are compared to similarly processed acid catalyzed silicate thin films.
DOE Office of Scientific and Technical Information (OSTI.GOV)
López, E.; Lucas, J. M.; Andrés, J. de
2014-10-28
Collisions between potassium ions and neutral i-C{sub 3}H{sub 7}Br and i-C{sub 3}H{sub 7}OH, all in their electronic ground state, have been studied in the 0.10–10.00 eV center of mass (CM) collision energy range, using the radiofrequency-guided ion beam technique. In K{sup +} + i-C{sub 3}H{sub 7}Br collisions KHBr{sup +} formation was observed and quantified, while the analogous KH{sub 2}O{sup +} formation in K{sup +} + i-C{sub 3}H{sub 7}OH was hardly detected. Moreover, formation of the ion-molecule adducts and their decomposition leading to C{sub 3}H{sub 7}{sup +} and either KBr or KOH, respectively, have been observed. For all these processes, absolutemore » cross-sections were measured as a function of the CM collision energy. Ab initio structure calculations at the MP2 level have given information about the potential energy surfaces (PESs) involved. In these, different stationary points have been characterized using the reaction coordinate method, their connectivity being ensured by using the intrinsic-reaction-coordinate method. From the measured excitation function for KHBr{sup +} formation the corresponding thermal rate constant at 303 K has been calculated. The topology of the calculated PESs allows an interpretation of the main features of the reaction dynamics of both systems, and in particular evidence the important role played by the potential energy wells in controlling the reactivity for the different reaction channels.« less
Localization of Hydrogen Ion and Chloride Ion Fluxes in Nitella
Spear, Donald G.; Barr, June K.; Barr, C. E.
1969-01-01
Alternating bands of acid and base formation have been detected along the length of the internodal cell of Nitella clavata when it is illuminated, while in the dark this phenomenon is minimal. Chloride influx occurs only or largely in the acid-extruding regions, and this is also a light-dependent ion movement. Chloride efflux is slightly dependent on illumination and is not localized as are H+ efflux and Cl- influx. The results obtained support Kitasato's (1968) proposal that a large passive H+ influx is balanced by an active efflux of this ion. Transport mechanisms suggested by the correlations of Cl- and HCO3 - influxes with H+ extrusion are discussed. PMID:5806597
Photon Stimulated Ion Desorption.
1982-03-03
1978) 1997.(181 T. Shibaguchi, H . Onuki and R. Onaka, J. Phys. Soc. Contract DE.AC04.76-DPO0789. Experiments were Japan 42 (1977) S51. conducted at...University of California and the Naval Weapons Center. Sincerely COPY ovoikoble to DTIC doee 00t pe m i jully legible rep oductC r h Christopher C... H 20 is studied; only hydrogen ions are observed. Desorption of hydrogen ions from amorphous ice 7 is part of an ongoing study of condensed gases
NASA Astrophysics Data System (ADS)
McLain, J. L.; Molek, C. D.; , D. Osborne, Jr.; Adams, N. G.
2009-05-01
A study has been made of the electron-ion dissociative recombination of the protonated cyanides (RCNH+, R = H, CH3, C2H5) and their proton-bound dimers (RCN)2H+ at 300 K. This has been accomplished with the flowing afterglow technique using an electrostatic Langmuir probe to determine the electron density decay along the flow tube. For the protonated species, the recombination coefficients, [alpha]e(cm3 s-1), are (3.6 +/- 0.5) × 10-7, (3.4 +/- 0.5) × 10-7, (4.6 +/- 0.7) × 10-7 for R = H, CH3, C2H5, respectively. For the proton-bound dimers, the [alpha]e are substantially greater being (2.4 +/- 0.4) × 10-6, (2.8 +/- 0.4) × 10-6, (2.3 +/- 0.3) × 10-6 for R = H, CH3, C2H5, respectively. Fitting of the electron density decay data to a simple model has shown that the rate coefficients for the three-body association of RCNH+ with RCN are very large being (2.0 +/- 0.5) × 10-26 cm6 s-1. The significance of these data to the Titan ionosphere is discussed.
Irradiation of 4H-SiC UV detectors with heavy ions
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kalinina, E. V., E-mail: evk@mail.ioffe.ru; Lebedev, A. A.; Bogdanova, E.
Ultraviolet (UV) photodetectors based on Schottky barriers to 4H-SiC are formed on lightly doped n-type epitaxial layers grown by the chemical vapor deposition method on commercial substrates. The diode structures are irradiated at 25°C by 167-MeV Xe ions with a mass of 131 amu at a fluence of 6 × 10{sup 9} cm{sup −2}. Comparative studies of the optical and electrical properties of as-grown and irradiated structures with Schottky barriers are carried out in the temperature range 23–180°C. The specific features of changes in the photosensitivity and electrical characteristics of the detector structures are accounted for by the capture ofmore » photogenerated carriers into traps formed due to fluctuations of the conduction-band bottom and valence-band top, with subsequent thermal dissociation.« less
Response of thermal ions to electromagnetic ion cyclotron waves
NASA Technical Reports Server (NTRS)
Anderson, B. J.; Fuselier, S. A.
1994-01-01
Electromagnetic ion cyclotron waves generated by 10 - 50 keV protons in the Earth's equatorial magnetosphere will interact with the ambient low-energy ions also found in this region. We examine H(+) and He(+) distribution functions from approx. equals 1 to 160 eV using the Hot Plasma Composition Experiment instrument on AMPTE/CCE to investigate the thermal ion response to the waves. A total of 48 intervals were chosen on the basis of electromagnetic ion cyclotron (EMIC) wave activity: 24 with prevalent EMIC waves and 24 with no EMIC waves observed on the orbit. There is a close correlation between EMIC waves and perpendicular heated ion distributions. For protons the perpendicular temperature increase is modest, about 5 eV, and is always observed at 90 deg pitch angles. This is consistent with a nonresonant interaction near the equator. By contrast, He(+) temperatures during EMIC wave events averaged 35 eV and sometimes exceeded 100 eV, indicating stronger interaction with the waves. Furthermore, heated He(+) ions have X-type distributions with maximum fluxes occurring at pitch angles intermediate between field-aligned and perpendicular directions. The X-type He(+) distributions are consistent with a gyroresonant interaction off the equator. The concentration of He(+) relative to H(+) is found to correlate with EMIC wave activity, but it is suggested that the preferential heating of He(+) accounts for the apparent increase in relative He(+) concentration by increasing the proportion of He(+) detected by the ion instrument.
NASA Astrophysics Data System (ADS)
Harrilal, Christopher P.; DeBlase, Andrew F.; Burke, Nicole L.; McLuckey, Scott A.; Zwier, Timothy S.
2016-06-01
The "proline effect" is a well-known fragmentation phenomenon in mass spectrometry, in which y-fragments are produced preferentially over b-fragments during the collision induced dissociation of protonated L-proline containing peptide ions. This specific fragmentation channel is favored because of the high basicity of the secondary amine intermediate and the ring instability in alternative bn+ products [ASMS 2014, 25, 1705]. In contrast, peptides containing the D-Pro stereoisomer have been shown to largely favor the production of b4+ ions over y3+ ions. This strongly suggests that differences in the conformational preferences between the D-Pro and L-Pro diastereomers are likely to be responsible but structural evidence has been lacking to date. Using tandem mass spectrometry and IR-UV double resonant action spectroscopy we are able to compare the 3D structures of cold [YA(D-Pro)AA+H]+ to [YA(L-Pro)AA+H]+ ions. The UV action spectra reveals two major conformers in [YA(D-Pro)AA+H]+ and one major conformer in [YA(L-Pro)AA+H]+. Clear differences in the hydrogen bonding patterns are apparent between the two conformers observed in the D-Pro specie which are both distinct from the L-Pro diastereomer. Furthermore, conformer and diastereomer specific photofragmentation patterns are observed. It is also noted that a ten-fold photofragment enhancement unique to one of the D-Pro conformers is observed upon absorption of a resonant IR photon after UV excitation. Differences in the excited state photophysics between the two D-Pro conformers suggest that vibrational excitation of S1 turns on coupling to the dissociative -Tyr channel in one conformer, while this coupling is already present in the vibronic ground state of the other. Calculated harmonic spectra (M052X/6-31+G*) of conformers obtained from Monte Carlo searches to the experimental spectra.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Imaoka, Tatsuhiko; Nishimura, Mayumi; Kakinuma, Shizuko
2007-09-01
Purpose: The high relative biologic effectiveness (RBE) of high-linear energy transfer (LET) heavy-ion radiation has enabled powerful radiotherapy. The potential risk of later onset of secondary cancers, however, has not been adequately studied. We undertook the present study to clarify the RBE of therapeutic carbon ion radiation and molecular changes that occur in the rat mammary cancer model. Methods and Materials: We observed 7-8-week-old rats (ACI, F344, Wistar, and Sprague-Dawley) until 1 year of age after irradiation (0.05-2 Gy) with either 290 MeV/u carbon ions with a spread out Bragg peak (LET 40-90 keV/{mu}m) generated from the Heavy-Ion Medical Acceleratormore » in Chiba or {sup 137}Cs {gamma}-rays. Results: Carbon ions significantly induced mammary carcinomas in Sprague-Dawley rats but less so in other strains. The dose-effect relationship for carcinoma incidence in the Sprague-Dawley rats was concave downward, providing an RBE of 2 at a typical therapeutic dose per fraction. In contrast, {approx}10 should be considered for radiation protection at low doses. Immunohistochemically, 14 of 18 carcinomas were positive for estrogen receptor {alpha}. All carcinomas examined were free of common H-ras and Tp53 mutations. Importantly, lung metastasis (7%) was characteristic of carbon ion-irradiated rats. Conclusions: We found clear genetic variability in the susceptibility to carbon ion-induced mammary carcinomas. The high RBE for carbon ion radiation further supports the importance of precise dose localization in radiotherapy. Common point mutations in H-ras and Tp53 were not involved in carbon ion induction of rat mammary carcinomas.« less
Interstellar Pickup Ion Observations to 38 au
NASA Astrophysics Data System (ADS)
McComas, D. J.; Zirnstein, E. J.; Bzowski, M.; Elliott, H. A.; Randol, B.; Schwadron, N. A.; Sokół, J. M.; Szalay, J. R.; Olkin, C.; Spencer, J.; Stern, A.; Weaver, H.
2017-11-01
We provide the first direct observations of interstellar H+ and He+ pickup ions in the solar wind from 22 to 38 au. We use the Vasyliunas and Siscoe model functional form to quantify the pickup ion distributions, and while the fit parameters generally lie outside their physically expected ranges, this form allows fits that quantify variations in the pickup H+ properties with distance. By ˜20 au, the pickup ions already provide the dominant internal pressure in the solar wind. We determine the radial trends and extrapolate them to the termination shock at ˜90 au, where the pickup H+ to core solar wind density reaches ˜0.14. The pickup H+ temperature and thermal pressure increase from 22 to 38 au, indicating additional heating of the pickup ions. This produces very large extrapolated ratios of pickup H+ to solar wind temperature and pressure, and an extrapolated ratio of the pickup ion pressure to the solar wind dynamic pressure at the termination shock of ˜0.16. Such a large ratio has profound implications for moderating the termination shock and the overall outer heliospheric interaction. We also identify suprathermal tails in the H+ spectra and complex features in the He+ spectra, likely indicating variations in the pickup ion history and processing. Finally, we discover enhancements in both H+ and He+ populations just below their cutoff energies, which may be associated with enhanced local pickup. This study serves to document the release and serves as a citable reference of these pickup ion data for broad community use and analysis.
NASA Astrophysics Data System (ADS)
Tsuji, H.; Ebihara, Y.; Tanaka, T.
2017-04-01
An interplanetary (IP) shock has a large impact on magnetospheric ions. Satellite observations have shown that soon after arrival of the IP shock, overall intensity of the ions rapidly increases and multiple energy dispersion appears in an energy-time spectrogram of the ions. In order to understand the response of the magnetospheric ions to IP shock, we have performed test particle simulation under the electric and magnetic fields provided by the global magnetohydrodynamic simulation. We reconstructed the differential flux of H+, He+, and O+ ions at (7, 0, 0) Re in GSM coordinates by means of the semi-Lagrangian (phase space mapping) method. Simulation results show that the ions respond to the IP shock in two different ways. First, overall intensity of the flux gradually increases at all pitch angles. As the compressional wave propagates tailward, the magnetic field increases, which accelerates the ions due to the gyrobetatron. Second, multiple energy-time dispersion appears in the reconstructed spectrograms of the ion flux. The energy-time dispersion is caused by the ion moving toward mirror point together with tailward propagating compressional wave at off-equator. The ions are primarily accelerated by the drift betatron under the strong electric field looking dawnward. The dispersion is absent in the spectrogram of equatorially mirroring ions. The dispersion appears at higher energy for heavier ions. These features are consistent with the satellite observations. Because the acceleration depends on bounce phase, the bounce-averaged approximation is probably invalid for the ions during the interval of geomagnetic sudden commencement.
Inner Source Pickup Ions Observed by Ulysses
NASA Astrophysics Data System (ADS)
Gloeckler, G.
2016-12-01
The existence of an inner source of pickup ions close to the Sun was proposed in order to explain the unexpected discovery of C+ in the high-speed polar solar wind. Here I report on detailed analyses of the composition and the radial and latitudinal variations of inner source pickup ions measured with the Solar Wind Ion Composition Spectrometer on Ulysses from 1991 to 1998, approaching and during solar minimum. We find that the C+ intensity drops off with radial distance R as R-1.53, peaks at mid latitudes and drops to its lowest value in the ecliptic. Not only was C+ observed, but also N+, O+, Ne+, Na+, Mg+, Ar+, S+, K+, CH+, NH+, OH+, H2O+, H3O+, MgH+, HCN+, C2H4+, SO+ and many other singly-charged heavy ions and molecular ions. The measured velocity distributions of inner source pickup C+ and O+ indicate that these inner source pickup ions are most likely produced by charge exchange, photoionization and electron impact ionization of neutrals close to the Sun (within 10 to 30 solar radii). Possible causes for the unexpected latitudinal variations and the neutral source(s) producing the inner source pickup ions as well as plausible production mechanisms for inner source pickup ions will be discussed.
The short range anion-H interaction is the driving force for crystal formation of ions in water.
Alejandre, José; Chapela, Gustavo A; Bresme, Fernando; Hansen, Jean-Pierre
2009-05-07
The crystal formation of NaCl in water is studied by extensive molecular dynamics simulations. Ionic solutions at room temperature and various concentrations are studied using the SPC/E and TIP4P/2005 water models and seven force fields of NaCl. Most force fields of pure NaCl fail to reproduce the experimental density of the crystal, and in solution some favor dissociation at saturated conditions, while others favor crystal formation at low concentration. A new force field of NaCl is proposed, which reproduces the experimental phase diagram in the solid, liquid, and vapor regions. This force field overestimates the solubility of NaCl in water at saturation conditions when used with standard Lorentz-Berthelot combining rules for the ion-water pair potentials. It is shown that precipitation of ions is driven by the short range interaction between Cl-H pairs, a term which is generally missing in the simulation of ionic solutions. The effects of intramolecular flexibility of water on the solubility of NaCl ions are analyzed and is found to be small compared to rigid models. A flexible water model, extending the rigid SPC/E, is proposed, which incorporates Lennard-Jones interactions centered on the hydrogen atoms. This force field gives liquid-vapor coexisting densities and surface tensions in better agreement with experimental data than the rigid SPC/E model. The Cl-H, Na-O, and Cl-O pair distribution functions of the rigid and flexible models agree well with experiment. The predicted concentration dependence of the electric conductivity is in fair agreement with available experimental data.
NASA Astrophysics Data System (ADS)
Dialynas, K.; Paranicas, C.; Roussos, E.; Krimigis, S. M.; Kane, M.; Mitchell, D. G.
2015-12-01
We present a composite analysis (H+ and O+) of energetic ion spectra and kappa distribution fits, using combined ion measurements from Charge Energy Mass Spectrometer (CHEMS, 3 to 236 keV/e), Low Energy Magnetospheric Measurements System (LEMMS, 0.024 < E < 18 MeV), and the Ion Neutral Camera (INCA, ~5.2 to >220 keV for H+). The modeled expressions of these energetic ion distributions are then used to obtain the four integral particle moments (from zeroth to 3rd moment: n, In, P, IE, i.e. Density, Integral number intensity, Pressure, Integral energy intensity) as well as the characteristic energy (EC=IE/In) of these ions as a function of Local Time and L-Shell. We find that a) protons dominate the energetic ion (>30 keV) integral number and energy intensity at all radial distances (L>5 Rs) and local times, while the H+ and O+ partial pressures and densities are comparable; b) the 12
NASA Astrophysics Data System (ADS)
Kitajima, Kensei; Majima, Takuya; Nishio, Tatsuya; Oonishi, Yoshiki; Mizutani, Shiori; Kohno, Jun-ya; Saito, Manabu; Tsuchida, Hidetsugu
2018-06-01
We have investigated the negative and positive secondary ions emitted from ethanol droplets by 4.0-MeV C3+ impact to reveal the characteristic features of the reaction processes induced by fast heavy ions at the liquid ethanol surface. Analysis of the secondary ions was performed by time-of-flight mass spectrometry for microdroplet targets in a high vacuum environment. Fragment ions, deprotonated cluster ions, and trace amounts of the reaction product ions are observed in the negative secondary ions. The main fragment anions are C2HmO- (m = 1, 3, and 5) and C2H- generated by loss of hydrogen and oxygen atoms. The reaction product anions include deprotonated glycols, larger alcohols, and their dehydrated and dehydrogenated forms generated by secondary reactions between fragments and radicals. Furthermore, C3Hm- (m = 0-2) and C4Hm- (m = 0 and 1) are observed, which could be produced through a plasma state generated in the heavy ion track. Deprotonated ethanol cluster ions, [(EtOH)n - H]-, are observed up to about n = 25. [(EtOH)n - H]- have smaller kinetic energies than the protonated cluster ions (EtOH)nH+. This probably represents the effect of the positive Coulomb potential transiently formed in the ion track. We also discuss the size distributions and structures of the water- and CH2OH-radical-attached ethanol cluster ions.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kawasaki, Yoji; Shibahara, Kentaro; Research Institute for Nanodevice and Bio Systems, Hiroshima University, 1-4-2 Kagamiyama, Higashihiroshima, Hiroshima 739-8527
2012-01-15
The effects of B{sub 18}H{sub x}{sup +} and B{sub 18}H{sub x} dimer ion (B{sub 36}H{sub y}{sup +}) implantations on Si crystallinity and the retained B dose in Si were investigated using B{sub 18}H{sub x} bombardment and compared with the effects of B{sup +} implantation. Crystallinity was estimated for the implantation dose using molecular dynamic simulations (MDSs) and was quantified using the optical thickness obtained from spectroscopic ellipsometry. The authors focused on the crystallinity at a low B dose and compared the amorphized zones predicted by MDS for B{sub 18}H{sub x}{sup +} implantation with those measured using transmission electron microscopy; themore » predicted and measured results were in reasonable agreement. The authors then used their understanding of B{sub 18}H{sub x} bombardment to discuss the process for the generation of larger amorphized zones and thicker amorphized layers, as observed in B{sub 36}H{sub y}{sup +} implantation. The retained B dose and the sputtering were examined with secondary ion mass spectroscopy, focusing on a comparison of the retained B and the sputtering of Si and SiO{sub 2} surfaces. The retained B dose was lower for B{sub 18}H{sub x}{sup +} and B{sub 36}H{sub y}{sup +} implantations, with and without surface SiO{sub 2}, than for B{sup +} implantation, although no sputtering was observed. The reduction of the retained B dose was more severe in the samples with SiO{sub 2}. The origin of the differences between Si and SiO{sub 2} surfaces was considered to be Si melting; this was predicted by the MDSs, and observed indirectly as flat B profiles in the Si region. To examine the effects of both crystallinity and retained B dose on the electrical characteristics, the sheet resistance (R{sub S}) was measured. The R{sub S} for B{sub 18}H{sub x}{sup +} implantation was lower than that for B{sup +} implantation at both B doses studied. Additionally, the B{sub 36}H{sub y}{sup +} implantation under conditions that produced
Measurements of positive ion conversion and removal reactions relating to the Jovian ionosphere
NASA Technical Reports Server (NTRS)
Johnsen, R.; Biondi, M. A.
1974-01-01
Measured rates are presented for the reaction of He(+) ions with H2 (and D2) molecules to form H(+), H2(+), and HeH(+) ions, as well as for the subsequent reactions of H(+) and HeH(+) ions with H2 to form H3(+). The neutralization of H3(+) /and H5(+)/ ions by dissociative recombination with electrons is shown to be fast. The reaction He(+) + H2 is slow (k 1.1 x 10 to the minus 13th cu cm/sec at 300 K) and produces principally H(+) by the dissociative charge transfer branch. It is concluded that there may be a serious bottleneck in the conversion of two of the primary ions of the upper Jovian ionosphere, H(+) and He(+) (which recombine slowly), to the rapidly recombining H3(+) ion.
Burch, J L; Cravens, T E; Llera, K; Goldstein, R; Mokashi, P; Tzou, C-Y; Broiles, T
2015-07-16
As Rosetta was orbiting comet 67P/Churyumov-Gerasimenko, the Ion and Electron Sensor detected negative particles with angular distributions like those of the concurrently measured solar wind protons but with fluxes of only about 10% of the proton fluxes and energies of about 90% of the proton energies. Using well-known cross sections and energy-loss data, it is determined that the fluxes and energies of the negative particles are consistent with the production of H - ions in the solar wind by double charge exchange with molecules in the coma.
Conversion electron Mössbauer spectroscopy of plasma immersion ion implanted H13 tool steel
NASA Astrophysics Data System (ADS)
Terwagne, G.; Collins, G. A.; Hutchings, R.
1994-12-01
Conversion electron Mössbauer spectroscopy (CEMS) has been used to investigate nitride formation in AISI-H13 tool steel after treatment by plasma immersion ion implantation (PI3) at 350 °C. With only slight variation in the plasma conditions, it is possible to influence the kinetics of nitride precipitation so as to obtain nitrogen concentrations that range from those associated with ɛ-Fe2N through ɛ-Fe3N to γ'-Fe4N. The CEMS results enable a more definite identification of the nitrides than that obtained by glancing-angle X-ray diffraction and nuclear reaction analysis alone.
Rashad, Muhammad; Li, Xianfeng; Zhang, Huamin
2018-06-27
Recently, magnesium-ion batteries (MIBs) have been under remarkable research focus owing to their appealingly high energy density and natural abundance of magnesium. Nevertheless, MIBs exhibit a very limited performance because of sluggish solid-state Mg 2+ ion diffusion and high polarizability, which hinder their progress toward commercialization. Herein, we report a Mg 2+ /Li + hybrid-ion battery (MLIB) with NaV 3 O 8 ·1.69H 2 O (NVO) nanobelts synthesized at room temperature working as the positive electrode. In the hybrid-ion system, Li + intercalates/deintercalates along with a small amount of Mg 2+ adsorption at the NVO cathode, whereas the anode side of the cell is dominated by Mg 2+ deposition/dissolution. As a result, the MLIB exhibits a much higher rate capability (i.e., 446 mA h g -1 at 20 mA g -1 ) than the previously reported MLIBs. MLIB maintains a high specific capacity of 200 mA h g -1 at 80 mA g -1 for 150 cycles, showing excellent stability. Moreover, the effect of different Li-ion concentrations (i.e., 0.5-2.0 M) in the electrolyte and cutoff voltage (ranging from 2 to 2.6 V) on the specific capacities are investigated. The current study highlights a strategy to exploit the Mg 2+ /Li + hybrid electrolyte system with various electrode materials for high-performance MIBs.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ayedh, H. M.; Svensson, B. G.; Hallén, A.
The carbon vacancy (V{sub C}) is a prevailing point defect in high-purity 4H-SiC epitaxial layers, and it plays a decisive role in controlling the charge carrier lifetime. One concept of reducing the V{sub C}-concentration is based on carbon self-ion implantation in a near surface layer followed by thermal annealing. This leads to injection of carbon interstitials (C{sub i}'s) and annihilation of V{sub C}'s in the epi-layer “bulk”. Here, we show that the excess of C atoms introduced by the self-ion implantation plays a negligible role in the V{sub C} annihilation. Actually, employing normalized implantation conditions with respect to displaced Cmore » atoms, other heavier ions like Al and Si are found to be more efficient in annihilating V{sub C}'s. Concentrations of V{sub C} below ∼2 × 10{sup 11} cm{sup −3} can be reached already after annealing at 1400 °C, as monitored by deep-level transient spectroscopy. This corresponds to a reduction in the V{sub C}-concentration by about a factor of 40 relative to the as-grown state of the epi-layers studied. The negligible role of the implanted species itself can be understood from simulation results showing that the concentration of displaced C atoms exceeds the concentration of implanted species by two to three orders of magnitude. The higher efficiency for Al and Si ions is attributed to the generation of collision cascades with a sufficiently high energy density to promote C{sub i}-clustering and reduce dynamic defect annealing. These C{sub i}-related clusters will subsequently dissolve during the post-implant annealing giving rise to enhanced C{sub i} injection. However, at annealing temperatures above 1500 °C, thermodynamic equilibrium conditions start to apply for the V{sub C}-concentration, which limit the net effect of the C{sub i} injection, and a competition between the two processes occurs.« less
The Great Fallacy of the H Plus Ion and the True Nature of H30 Plus.
ERIC Educational Resources Information Center
Giguere, Paul A.
1979-01-01
Experimental and theoretical data are presented which verifies the existence of the hydronium ion. This existence was confirmed directly by x-ray and neutron diffraction in hydrochloric acid. Recommended is the abandonment of the erroneous hydrogen ion formulation and names such as proton hydrate. (BT)
Tsonev, Latchezar I; Hirsh, Allen G
2008-07-25
pISep is a major new advance in low ionic strength ion exchange chromatography. It enables the formation of externally controlled pH gradients over the very broad pH range from 2 to 12. The gradients can be generated on either cationic or anionic exchangers over arbitrary pH ranges wherein the stationary phases remain totally charged. Associated pISep software makes possible the calculation of either linear, nonlinear or combined, multi-step, multi-slope pH gradients. These highly reproducible pH gradients, while separating proteins and glycoproteins in the order of their electrophoretic pIs, provide superior chromatographic resolution compared to salt. This paper also presents a statistical mechanical model for protein binding to ion exchange stationary phases enhancing the electrostatic interaction theory for the general dependence of retention factor k, on both salt and pH simultaneously. It is shown that the retention factors computed from short time isocratic salt elution data of a model protein can be used to accurately predict its salt elution concentration in varying slope salt elution gradients formed at varying isocratic pH as well as the pH at which it will be eluted from an anionic exchange column by a pISep pH gradient in the absence of salt.
Nam, Ki Min; Choi, Young Cheol; Jung, Sung Chul; Kim, Yong-Il; Jo, Mi Ru; Park, Se Ho; Kang, Yong-Mook; Han, Young-Kyu; Park, Joon T
2012-01-21
Thermal decomposition of Co(acac)(3) and Cu(acac)(2) in benzylamine leads to the formation of [100] directed Cu-doped h-CoO nanorods, which are very stable in an aqueous solution. The formation mechanism of the [100] directed Cu-doped h-CoO nanorods is fully elucidated by using first-principles calculations, demonstrating that Cu-doping not only changes the growth direction but also enhances the stability of the nanorods significantly. Evaluation of the electrochemical performance of Cu-doped h-CoO nanorods shows high initial Coulombic efficiency and ultrahigh capacity with excellent cycling performance, indicating their suitability as an anode material for next generation lithium-ion batteries.
Lattice sites of ion-implanted Mn, Fe and Ni in 6H-SiC
NASA Astrophysics Data System (ADS)
Costa, A. R. G.; Wahl, U.; Correia, J. G.; David-Bosne, E.; Amorim, L. M.; Augustyns, V.; Silva, D. J.; da Silva, M. R.; Pereira, L. M. C.
2018-01-01
Using radioactive isotopes produced at the CERN-ISOLDE facility, the lattice location of the implanted transition metal (TM) ions 56Mn, 59Fe and 65Ni in n-type single-crystalline hexagonal 6H-SiC was studied by means of the emission channeling technique. TM probes on carbon coordinated tetrahedral interstitial sites (T C) and on substitutional silicon sites (S Si,h+k ) were identified. We tested for but found no indication that the TM distribution on S Si sites deviates from the statistical mixture of 1/3 hexagonal and 2/3 cubic sites present in the 6H crystal. The TM atoms partially disappear from T C positions during annealing at temperatures between 500 °C and 700 °C which is accompanied by an increase on S Si and random sites. From the temperature associated with these site changes, interstitial migration energies of 1.7-2.7 eV for Mn and Ni, and 2.3-3.2 eV for Fe were estimated. TM lattice locations are compared to previous results obtained in 3C-SiC using the same technique.
Kaplan, Anne R; Brady, Megan R; Maciejewski, Mark W; Kammerer, Richard A; Alexandrescu, Andrei T
2017-03-21
To understand the roles ion pairs play in stabilizing coiled coils, we determined nuclear magnetic resonance structures of GCN4p at three pH values. At pH 6.6, all acidic residues are fully charged; at pH 4.4, they are half-charged, and at pH 1.5, they are protonated and uncharged. The α-helix monomer and coiled coil structures of GCN4p are largely conserved, except for a loosening of the coiled coil quaternary structure with a decrease in pH. Differences going from neutral to acidic pH include (i) an unwinding of the coiled coil superhelix caused by the loss of interchain ion pair contacts, (ii) a small increase in the separation of the monomers in the dimer, (iii) a loosening of the knobs-into-holes packing motifs, and (iv) an increased separation between oppositely charged residues that participate in ion pairs at neutral pH. Chemical shifts (HN, N, C', Cα, and Cβ) of GCN4p display a seven-residue periodicity that is consistent with α-helical structure and is invariant with pH. By contrast, periodicity in hydrogen exchange rates at neutral pH is lost at acidic pH as the exchange mechanism moves into the EX1 regime. On the basis of 1 H- 15 N nuclear Overhauser effect relaxation measurements, the α-helix monomers experience only small increases in picosecond to nanosecond backbone dynamics at acidic pH. By contrast, 13 C rotating frame T 1 relaxation (T 1ρ ) data evince an increase in picosecond to nanosecond side-chain dynamics at lower pH, particularly for residues that stabilize the coiled coil dimerization interface through ion pairs. The results on the structure and dynamics of GCNp4 over a range of pH values help rationalize why a single structure at neutral pH poorly predicts the pH dependence of the unfolding stability of the coiled coil.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Castro, G., E-mail: Giuseppe.Castro@lns.infn.it; Celona, L.; Mascali, D.
2016-08-15
The versatile ion source is an off-resonance microwave discharge ion source which produces a slightly overdense plasma at 2.45 GHz of pumping wave frequency extracting more than 60 mA proton beams and 50 mA He{sup +} beams. DAEδALUS and IsoDAR experiments require high intensities for H{sub 2}{sup +} beams to be accelerated by high power cyclotrons for neutrinos generation. In order to fulfill the new requirements, a new plasma chamber and injection system has been designed and manufactured for increasing the H{sub 2}{sup +} beam intensity. In this paper the studies for the increasing of the H{sub 2}{sup +}/p ratiomore » and for the design of the new plasma chamber and injection system will be shown and discussed together with the experimental tests carried out at Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS) and at Best Cyclotron Systems test-bench in Vancouver, Canada.« less
NASA Astrophysics Data System (ADS)
Wang, Yi-Sheng; Sabu, Sahadevan; Wei, Shih-Chia; Josh Kao, C.-M.; Kong, Xianglei; Liau, Shing-Chih; Han, Chau-Chung; Chang, Huan-Cheng; Tu, Shih-Yu; Kung, A. H.; Zhang, John Z. H.
2006-10-01
Detachment of heme prosthetic groups from gaseous myoglobin ions has been studied by collision-induced dissociation and infrared multiphoton dissociation in combination with Fourier-transform ion cyclotron resonance mass spectrometry. Multiply charged holomyoglobin ions (hMbn +) were generated by electrospray ionization and transferred to an ion cyclotron resonance cell, where the ions of interest were isolated and fragmented by either collision with Ar atoms or irradiation with 3μm photons, producing apomyoglobin ions (aMbn +). Both charged heme loss (with [Fe(III)-heme]+ and aMb(n-1)+ as the products) and neutral heme loss (with [Fe(II)-heme] and aMbn + as the products) were detected concurrently for hMbn + produced from a myoglobin solution pretreated with reducing reagents. By reference to Ea=0.9eV determined by blackbody infrared radiative dissociation for charged heme loss of ferric hMbn +, an activation energy of 1.1eV was deduced for neutral heme loss of ferrous hMbn + with n =9 and 10.
Schnier, P D; Price, W D; Strittmatter, E F; Williams, E R
1997-08-01
The dissociation kinetics of protonated leucine enkephalin and its proton and alkali metal bound dimers were investigated by blackbody infrared radiative dissociation in a Fourier-transform mass spectrometer. From the temperature dependence of the unimolecular dissociation rate constants, Arrhenius activation parameters in the zero-pressure limit are obtained. Protonated leucine enkephalin dissociates to form b(4) and (M-H(2)O)(+) ions with an average activation energy (E(a)) of 1.1 eV and an A factor of 10(10.5) s(-1). The value of the A factor indicates that these dissociation processes are rearrangements. The b(4) ions subsequently dissociate to form a(4) ions via a process with a relatively high activation energy (1.3 eV), but one that is entropically favored. For the cationized dimers, the thermal stability decreases with increasing cation size, consistent with a simple electrostatic interaction in these noncovalent ion-molecule complexes. The E(a) and A factors are indistinguishable within experimental error with values of approximately 1.5 eV and 10(17) s(-1), respectively. Although not conclusive, results from master equation modeling indicate that all these BIRD processes, except for b(4) --> a(4), are in the rapid energy exchange limit. In this limit, the internal energy of the precursor ion population is given by a Boltzmann distribution and information about the energetics and dynamics of the reaction are obtained directly from the measured Arrhenius parameters.
Calculation of Dose Deposition in 3D Voxels by Heavy Ions and Simulation of gamma-H2AX Experiments
NASA Technical Reports Server (NTRS)
Plante, I.; Ponomarev, A. L.; Wang, M.; Cucinotta, F. A.
2011-01-01
The biological response to high-LET radiation is different from low-LET radiation due to several factors, notably difference in energy deposition and formation of radiolytic species. Of particular importance in radiobiology is the formation of double-strand breaks (DSB), which can be detected by -H2AX foci experiments. These experiments has revealed important differences in the spatial distribution of DSB induced by low- and high-LET radiations [1,2]. To simulate -H2AX experiments, models based on amorphous track with radial dose are often combined with random walk chromosome models [3,4]. In this work, a new approach using the Monte-Carlo track structure code RITRACKS [5] and chromosome models have been used to simulate DSB formation. At first, RITRACKS have been used to simulate the irradiation of a cubic volume of 5 m by 1) 450 1H+ ions of 300 MeV (LET 0.3 keV/ m) and 2) by 1 56Fe26+ ion of 1 GeV/amu (LET 150 keV/ m). All energy deposition events are recorded to calculate dose in voxels of 20 m. The dose voxels are distributed randomly and scattered uniformly within the volume irradiated by low-LET radiation. Many differences are found in the spatial distribution of dose voxels for the 56Fe26+ ion. The track structure can be distinguished, and voxels with very high dose are found in the region corresponding to the track "core". These high-dose voxels are not found in the low-LET irradiation simulation and indicate clustered energy deposition, which may be responsible for complex DSB. In the second step, assuming that DSB will be found only in voxels where energy is deposited by the radiation, the intersection points between voxels with dose > 0 and simulated chromosomes were obtained. The spatial distribution of the intersection points is similar to -H2AX foci experiments. These preliminary results suggest that combining stochastic track structure and chromosome models could be a good approach to understand radiation-induced DSB and chromosome aberrations.
The effect of axial ion parameters on the properties of glow discharge polymer in T2B/H2 plasma
NASA Astrophysics Data System (ADS)
Ai, Xing; He, Xiao-Shan; Huang, Jing-Lin; He, Zhi-Bing; Du, Kai; Chen, Guo
2018-03-01
Glow discharge polymer (GDP) films were fabricated using plasma-enhanced chemical vapor deposition. The main purpose of this work was to explore the correlations of plasma parameters with the surface morphology and chemical structure of GDP films. The intensities of main positive ions and ion energy as functions of axial distances in T2B/H2 plasma were diagnosed using energy-resolved mass spectrometry. The surface morphology and chemical structure were characterized as functions of axial distances using a scanning electron microscope and Fourier transform infrared spectroscopy, respectively. As the axial distance increases, both the intensities of positive ions and high energy ions decreases, and dissociation weakens while polymerization enhances. This leads to the weakening of the cross-linking structure of GDP films and the formation of dome defects on films. Additionally, high energy ions could introduce a strong etching effect to form etching pits. Therefore, an axial distance of about 20 mm was found to be the optimal plasma parameter to prepare the defect-free GDP films. These results could help one to find the optimal plasma parameters for GDP film deposition.
NASA Astrophysics Data System (ADS)
Kovács, Tamás; Plane, John M. C.; Feng, Wuhu; Nagy, Tibor; Chipperfield, Martyn P.; Verronen, Pekka T.; Andersson, Monika E.; Newnham, David A.; Clilverd, Mark A.; Marsh, Daniel R.
2016-09-01
This study presents a new ion-neutral chemical model coupled into the Whole Atmosphere Community Climate Model (WACCM). The ionospheric D-region (altitudes ˜ 50-90 km) chemistry is based on the Sodankylä Ion Chemistry (SIC) model, a one-dimensional model containing 307 ion-neutral and ion recombination, 16 photodissociation and 7 photoionization reactions of neutral species, positive and negative ions, and electrons. The SIC mechanism was reduced using the simulation error minimization connectivity method (SEM-CM) to produce a reaction scheme of 181 ion-molecule reactions of 181 ion-molecule reactions of 27 positive and 18 negative ions. This scheme describes the concentration profiles at altitudes between 20 km and 120 km of a set of major neutral species (HNO3, O3, H2O2, NO, NO2, HO2, OH, N2O5) and ions (O2+, O4+, NO+, NO+(H2O), O2+(H2O), H+(H2O), H+(H2O)2, H+(H2O)3, H+(H2O)4, O3-, NO2-, O-, O2, OH-, O2-(H2O), O2-(H2O)2, O4-, CO3-, CO3-(H2O), CO4-, HCO3-, NO2-, NO3-, NO3-(H2O), NO3-(H2O)2, NO3-(HNO3), NO3-(HNO3)2, Cl-, ClO-), which agree with the full SIC mechanism within a 5 % tolerance. Four 3-D model simulations were then performed, using the impact of the January 2005 solar proton event (SPE) on D-region HOx and NOx chemistry as a test case of four different model versions: the standard WACCM (no negative ions and a very limited set of positive ions); WACCM-SIC (standard WACCM with the full SIC chemistry of positive and negative ions); WACCM-D (standard WACCM with a heuristic reduction of the SIC chemistry, recently used to examine HNO3 formation following an SPE); and WACCM-rSIC (standard WACCM with a reduction of SIC chemistry using the SEM-CM method). The standard WACCM misses the HNO3 enhancement during the SPE, while the full and reduced model versions predict significant NOx, HOx and HNO3 enhancements in the mesosphere during solar proton events. The SEM-CM reduction also identifies the important ion-molecule reactions that affect the partitioning of
Saddle antenna radio frequency ion sources
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dudnikov, V., E-mail: vadim@muonsinc.com; Johnson, R.; Murray, S.
Existing RF ion sources for accelerators have specific efficiencies for H{sup +} and H{sup −} ion generation ∼3–5 mA/cm{sup 2} kW, where about 50 kW of RF power is typically needed for 50 mA beam current production. The Saddle Antenna (SA) surface plasma source (SPS) described here was developed to improve H{sup −} ion production efficiency, reliability, and availability. In SA RF ion source, the efficiency of positive ion generation in the plasma has been improved to 200 mA/cm{sup 2} kW. After cesiation, the current of negative ions to the collector was increased from 1 mA to 10 mA withmore » RF power ∼1.5 kW in the plasma (6 mm diameter emission aperture) and up to 30 mA with ∼4 kW RF. Continuous wave (CW) operation of the SA SPS has been tested on the test stand. The general design of the CW SA SPS is based on the pulsed version. Some modifications were made to improve the cooling and cesiation stability. CW operation with negative ion extraction was tested with RF power up to ∼1.2 kW in the plasma with production up to Ic = 7 mA. A stable long time generation of H{sup −} beam without degradation was demonstrated in RF discharge with AlN discharge chamber.« less
Investigations of negative and positive cesium ion species
NASA Technical Reports Server (NTRS)
Chanin, L. M.
1978-01-01
A direct test is provided of the hypothesis of negative ion creation at the anode or collector of a diode operating under conditions simulating a cesium thermionic converter. The experimental technique involves using direct ion sampling through the collector electrode with mass analysis using a quadrupole mass analyzer. Similar measurements are undertaken on positive ions extracted through the emitter electrode. Measurements were made on a variety of gases including pure cesium, helium-cesium mixtures and cesium-hydrogen as well as cesium-xenon mixtures. The gas additive was used primarily to aid in understanding the negative ion formation processes. Measurements were conducted using emitter (cathode) temperatures up to about 1000 F. The major negative ion identified through the collector was Cs(-) with minor negative ion peaks tentatively identified as H(-), H2(-), H3(-), He(-) and a mass 66. Positive ions detected were believed to be Cs(+), Cs2(+) and Cs3(+).
Gilbert, Hamish T J; Hodson, Nathan; Baird, Pauline; Richardson, Stephen M; Hoyland, Judith A
2016-11-17
The aetiology of intervertebral disc (IVD) degeneration remains poorly understood. Painful IVD degeneration is associated with an acidic intradiscal pH but the response of NP cells to this aberrant microenvironmental factor remains to be fully characterised. The aim here was to address the hypothesis that acidic pH, similar to that found in degenerate IVDs, leads to the altered cell/functional phenotype observed during IVD degeneration, and to investigate the involvement of acid-sensing ion channel (ASIC) -3 in the response. Human NP cells were treated with a range of pH, from that of a non-degenerate (pH 7.4 and 7.1) through to mildly degenerate (pH 6.8) and severely degenerate IVD (pH 6.5 and 6.2). Increasing acidity of pH caused a decrease in cell proliferation and viability, a shift towards matrix catabolism and increased expression of proinflammatory cytokines and pain-related factors. Acidic pH resulted in an increase in ASIC-3 expression. Importantly, inhibition of ASIC-3 prevented the acidic pH induced proinflammatory and pain-related phenotype in NP cells. Acidic pH causes a catabolic and degenerate phenotype in NP cells which is inhibited by blocking ASIC-3 activity, suggesting that this may be a useful therapeutic target for treatment of IVD degeneration.
Emittance measurements for optimum operation of the J-PARC RF-driven H{sup −} ion source
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.
2015-04-08
In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) second stage requirements of an H{sup −} ion beam of 60mA within normalized emittances of 1.5πmm•mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500μs×25Hz) and a life-time of longer than 1month, the J-PARC cesiated RF-driven H{sup −} ion source was developed by using an internal-antenna developed at the Spallation Neutron Source (SNS). The transverse emittances of the source were measured with various conditions to find out the optimum operation conditions minimizing the horizontal and vertical rms normalized emittances. The transverse emittances were most effectivelymore » reduced by operating the source with the plasma electrode temperature lower than 70°C. The optimum value of the cesium (Cs) density around the beam hole of the plasma electrode seems to be proportional to the plasma electrode temperature. The fine control of the Cs density is indispensable, since the emittances seem to increase proportionally to the excessiveness of the Cs density. Furthermore, the source should be operated with the Cs density beyond a threshold value, since the plasma meniscus shape and the ellipse parameters of the transverse emittances seem to be changed step-function-likely on the threshold Cs value.« less
Gadolinium-hydrogen ion exchange of zirconium phosphate
NASA Technical Reports Server (NTRS)
Liu, D. C.; Power, J. L.
1972-01-01
The Gd(+3)/H(+) ion exchange on a commercial zirconium phosphate ion exchanger was investigated in chloride, sulfate, and phosphate solutions of Gd(+3) at gadolinium concentrations of 0.001 to 1 millimole per cc and in the pH range of 0 to 3.5. Relatively low Gd(+3) capacities, in the range of 0.01 to 0.1 millimole per g of ion exchanger were found at room temperature. A significant difference in Gd(+3) sorption was observed, depending on whether the ion exchanger was converted from initial conditions of greater or lesser Gd(+3) sorption than the specific final conditions. Correlations were found between decrease in Gd(+3) capacity and loss of exchanger phosphate groups due to hydrolysis during washing and between increase in capacity and treatment with H3PO4. Fitting of the experimental data to ideal ion exchange equilibrium expressions indicated that each Gd(+3) ion is sorbed on only one site of the ion exchanger. The selectivity quotient was determined to be 2.5 + or - 0.4 at room temperature on gadolinium desorption in chloride solutions.
Mech, Agnieszka; Gajek, Zbigniew; Karbowiak, Mirosław; Rudowicz, Czesław
2008-09-24
Optical absorption measurements of Nd(3+) ions in single crystals of [Nd(hfa)(4)(H(2)O)](N(C(2)H(5))(4)) (hfa = hexafluoroacetyloacetonate), denoted Nd(hfa) for short, have been carried out at 4.2 and 298 K. This compound crystallizes in the monoclinic system (space group P 2(1)/n). Each Nd ion is coordinated to eight oxygen atoms that originate from the hexafluoroacetylacetonate ligands and one oxygen atom from the water molecule. A total of 85 experimental crystal-field (CF) energy levels arising from the Nd(3+) (4f(3)) electronic configuration were identified in the optical spectra and assigned. A three-step CF analysis was carried out in terms of a parametric Hamiltonian for the actual C(1) symmetry at the Nd(3+) ion sites. In the first step, a total of 27 CF parameters (CFPs) in the Wybourne notation B(kq), admissible by group theory, were determined in a preliminary fitting constrained by the angular overlap model predictions. The resulting CFP set was reduced to 24 specific independent CFPs using appropriate standardization transformations. Optimizations of the second-rank CFPs and extended scanning of the parameter space were employed in the second step to improve reliability of the CFP sets, which is rather a difficult task in the case of no site symmetry. Finally, seven free-ion parameters and 24 CFPs were freely varied, yielding an rms deviation between the calculated energy levels and the 85 observed ones of 11.1 cm(-1). Our approach also allows prediction of the energy levels of Nd(3+) ions that are hidden in the spectral range overlapping with strong ligand absorption, which is essential for understanding the inter-ionic energy transfer. The orientation of the axis system associated with the fitted CF parameters w.r.t. the crystallographic axes is established. The procedure adopted in our calculations may be considered as a general framework for analysis of CF levels of lanthanide ions at low (triclinic) symmetry sites.
NASA Astrophysics Data System (ADS)
Mech, Agnieszka; Gajek, Zbigniew; Karbowiak, Mirosław; Rudowicz, Czesław
2008-09-01
Optical absorption measurements of Nd3+ ions in single crystals of [Nd(hfa)4(H2O)](N(C2H5)4) (hfa = hexafluoroacetyloacetonate), denoted Nd(hfa) for short, have been carried out at 4.2 and 298 K. This compound crystallizes in the monoclinic system (space group P 21/n). Each Nd ion is coordinated to eight oxygen atoms that originate from the hexafluoroacetylacetonate ligands and one oxygen atom from the water molecule. A total of 85 experimental crystal-field (CF) energy levels arising from the Nd3+ (4f3) electronic configuration were identified in the optical spectra and assigned. A three-step CF analysis was carried out in terms of a parametric Hamiltonian for the actual C1 symmetry at the Nd3+ ion sites. In the first step, a total of 27 CF parameters (CFPs) in the Wybourne notation Bkq, admissible by group theory, were determined in a preliminary fitting constrained by the angular overlap model predictions. The resulting CFP set was reduced to 24 specific independent CFPs using appropriate standardization transformations. Optimizations of the second-rank CFPs and extended scanning of the parameter space were employed in the second step to improve reliability of the CFP sets, which is rather a difficult task in the case of no site symmetry. Finally, seven free-ion parameters and 24 CFPs were freely varied, yielding an rms deviation between the calculated energy levels and the 85 observed ones of 11.1 cm-1. Our approach also allows prediction of the energy levels of Nd3+ ions that are hidden in the spectral range overlapping with strong ligand absorption, which is essential for understanding the inter-ionic energy transfer. The orientation of the axis system associated with the fitted CF parameters w.r.t. the crystallographic axes is established. The procedure adopted in our calculations may be considered as a general framework for analysis of CF levels of lanthanide ions at low (triclinic) symmetry sites.
Performance test of electron cyclotron resonance ion sources for the Hyogo Ion Beam Medical Center
NASA Astrophysics Data System (ADS)
Sawada, K.; Sawada, J.; Sakata, T.; Uno, K.; Okanishi, K.; Harada, H.; Itano, A.; Higashi, A.; Akagi, T.; Yamada, S.; Noda, K.; Torikoshi, M.; Kitagawa, A.
2000-02-01
Two electron cyclotron resonance (ECR) ion sources were manufactured for the accelerator facility at the Hyogo Ion Beam Medical Center. H2+, He2+, and C4+ were chosen as the accelerating ions because they have the highest charge to mass ratio among ion states which satisfy the required intensity and quality. The sources have the same structure as the 10 GHz ECR source at the Heavy Ion Medical Accelerator in Chiba except for a few improvements in the magnetic structure. Their performance was investigated at the Sumitomo Heavy Industries factory before shipment. The maximum intensity was 1500 μA for H2+, 1320 μA for He2+, and 580 μA for C4+ at the end of the ion source beam transport line. These are several times higher than required. Sufficient performance was also observed in the flatness and long-term stability of the pulsed beams. These test results satisfy the requirements for medical use.
International Space Station Lithium-Ion Battery Start-Up
NASA Technical Reports Server (NTRS)
Dalton, Penni J.; North, Tim; Bowens, Ebony; Balcer, Sonia
2017-01-01
International Space Station Lithium-Ion Battery Start-Up.The International Space Station (ISS) primary Electric Power System (EPS) was originally designed to use Nickel-Hydrogen (Ni-H2) batteries to store electrical energy. The electricity for the space station is generated by its solar arrays, which charge batteries during insolation for subsequent discharge during eclipse. The Ni-H2 batteries are designed to operate at a 35 depth of discharge (DOD) maximum during normal operation in a Low Earth Orbit. As the oldest of the 48 Ni-H2 battery Orbital Replacement Units (ORUs) has been cycling since September 2006, these batteries are now approaching their end of useful life. In 2010, the ISS Program began the development of Lithium-Ion (Li-ion) batteries to replace the Ni-H2 batteries and concurrently funded a Li-Ion ORU and cell life testing project. The first set of 6 Li-ion battery replacements were launched in December 2016 and deployed in January 2017. This paper will discuss the Li-ion battery on-orbit start-up and the status of the Li-Ion cell and ORU life cycle testing.
Pickup Ion Distributions from Three Dimensional Neutral Exospheres
NASA Technical Reports Server (NTRS)
Hartle, R. E.; Sarantos, M.; Sittler, E. C., Jr.
2011-01-01
Pickup ions formed from ionized neutral exospheres in flowing plasmas have phase space distributions that reflect their source's spatial distributions. Phase space distributions of the ions are derived from the Vlasov equation with a delta function source using three.dimensional neutral exospheres. The ExB drift produced by plasma motion picks up the ions while the effects of magnetic field draping, mass loading, wave particle scattering, and Coulomb collisions near a planetary body are ignored. Previously, one.dimensional exospheres were treated, resulting in closed form pickup ion distributions that explicitly depend on the ratio rg/H, where rg is the ion gyroradius and H is the neutral scale height at the exobase. In general, the pickup ion distributions, based on three.dimensional neutral exospheres, cannot be written in closed form, but can be computed numerically. They continue to reflect their source's spatial distributions in an implicit way. These ion distributions and their moments are applied to several bodies, including He(+) and Na(+) at the Moon, H(+2) and CH(+4) at Titan, and H+ at Venus. The best places to use these distributions are upstream of the Moon's surface, the ionopause of Titan, and the bow shock of Venus.
Measurement of the H3Λ lifetime in Au+Au collisions at the BNL Relativistic Heavy Ion Collider
NASA Astrophysics Data System (ADS)
Adamczyk, L.; Adams, J. R.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Ajitanand, N. N.; Alekseev, I.; Alford, J.; Anderson, D. M.; Aoyama, R.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Barish, K.; Behera, A.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Brown, D.; Bryslawskyj, J.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chankova-Bunzarova, N.; Chatterjee, A.; Chattopadhyay, S.; Chen, X.; Chen, X.; Chen, J. H.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; Dedovich, T. G.; Deng, J.; Deppner, I. M.; Derevschikov, A. A.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Dunlop, J. C.; Efimov, L. G.; Elsey, N.; Engelage, J.; Eppley, G.; Esha, R.; Esumi, S.; Evdokimov, O.; Ewigleben, J.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Federicova, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Fujita, J.; Fulek, L.; Gagliardi, C. A.; Geurts, F.; Gibson, A.; Girard, M.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Guryn, W.; Hamad, A. I.; Hamed, A.; Harlenderova, A.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Herrmann, N.; Hirsch, A.; Horvat, S.; Huang, B.; Huang, T.; Huang, X.; Huang, H. Z.; Humanic, T. J.; Huo, P.; Igo, G.; Jacobs, W. W.; Jentsch, A.; Jia, J.; Jiang, K.; Jowzaee, S.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kapukchyan, D.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z.; Kikoła, D. P.; Kim, C.; Kisel, I.; Kisiel, A.; Kochenda, L.; Kocmanek, M.; Kollegger, T.; Kosarzewski, L. K.; Kraishan, A. F.; Krauth, L.; Kravtsov, P.; Krueger, K.; Kulathunga, N.; Kumar, L.; Kvapil, J.; Kwasizur, J. H.; Lacey, R.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, X.; Li, W.; Li, Y.; Li, C.; Lidrych, J.; Lin, T.; Lisa, M. A.; Liu, F.; Liu, P.; Liu, Y.; Liu, H.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Luo, S.; Ma, G. L.; Ma, L.; Ma, R.; Ma, Y. G.; Magdy, N.; Majka, R.; Mallick, D.; Margetis, S.; Markert, C.; Matis, H. S.; Mayes, D.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mizuno, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nemes, D. B.; Nie, M.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Nonaka, T.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Reed, R.; Rehbein, M. J.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Roth, J. D.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Salur, S.; Sandweiss, J.; Saur, M.; Schambach, J.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Schweid, B. R.; Seger, J.; Sergeeva, M.; Seto, R.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Shen, W. Q.; Shi, S. S.; Shi, Z.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stewart, D. J.; Strikhanov, M.; Stringfellow, B.; Suaide, A. A. P.; Sugiura, T.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, X.; Sun, X. M.; Surrow, B.; Svirida, D. N.; Tang, A. H.; Tang, Z.; Taranenko, A.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Trzeciak, B. A.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vasiliev, A. N.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, G.; Wang, Y.; Wang, F.; Wang, Y.; Webb, G.; Webb, J. C.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, G.; Xie, W.; Xu, Y. F.; Xu, J.; Xu, Q. H.; Xu, N.; Xu, Z.; Yang, S.; Yang, Y.; Yang, C.; Yang, Q.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, Z.; Zhang, J.; Zhang, S.; Zhang, S.; Zhang, J.; Zhang, Y.; Zhang, X. P.; Zhang, J. B.; Zhao, J.; Zhong, C.; Zhou, L.; Zhou, C.; Zhu, X.; Zhu, Z.; Zyzak, M.; STAR Collaboration
2018-05-01
An improved measurement of the H3Λ lifetime is presented. In this paper, the mesonic decay modes H3Λ→3He + π- and H3Λ→d +p +π- are used to reconstruct the H3Λ from Au+Au collision data collected by the STAR collaboration at Relativistic Heavy Ion Collider (RHIC). A minimum χ2 estimation is used to determine the lifetime of τ = 142-21+24(stat .) ±29 (syst .) ps. This lifetime is about 50% shorter than the lifetime τ =263 ±2 ps of a free Λ , indicating strong hyperon-nucleon interaction in the hypernucleus system. The branching ratios of the mesonic decay channels are also determined to satisfy B.R . (3He+π-)/(B.R . (3He+π-)+B.R . (d +p +π-)) = 0.32 ±0.05 (stat .) ±0.08 (syst .) . Our ratio result favors the assignment J (H3Λ) =1/2 over J (H3Λ) =3/2 . These measurements will help to constrain models of hyperon-baryon interactions.
Influence of pH on Transungual Passive and Iontophoretic Transport
SMITH, KELLY A.; HAO, JINSONG; LI, S. KEVIN
2010-01-01
The present study investigated the effects of pH on nail permeability and the transport of ions such as sodium (Na) and chloride (Cl) ions endogenous to nail and hydronium and hydroxide ions present at low and high pH, which might compete with drug transport across hydrated nail plate during iontophoresis. Nail hydration and passive transport of water across the nail at pH 1–13 were assessed. Subsequently, passive and iontophoretic transport experiments were conducted using 22Na and 36Cl ions under various pH conditions. Nail hydration was independent of pH under moderate pH conditions and increased significantly under extreme pH conditions (pH>11). Likewise, nail permeability for water was pH independent at pH 1–10 and an order of magnitude higher at pH 13. The results of passive and iontophoretic transport of Na and Cl ions are consistent with the permselective property of nail. Interestingly, extremely acidic conditions (e.g., pH 1) altered nail permselectivity with the effect lasting several days at the higher pH conditions. Hydronium and hydroxide ion competition in iontophoretic transport was generally negligible at pH 3–11 was significant at the extreme pH conditions studied. PMID:19904826
Tran, T T Nha; Wang, Tianfang; Hack, Sandra; Hoffmann, Peter; Bowie, John H
2011-12-15
A joint experimental and theoretical investigation of the fragmentation behaviour of energised [M-H](-) anions from selected phosphorylated peptides has confirmed some of the most complex rearrangement processes yet to be reported for peptide negative ions. In particular: pSer and pThr (like pTyr) may transfer phosphate groups to C-terminal carboxyl anions and to the carboxyl anion side chains of Asp and Glu, and characteristic nucleophilic/cleavage reactions accompany or follow these rearrangements. pTyr may transfer phosphate to the side chains of Ser and Thr. The reverse reaction, namely transfer of a phosphate group from pSer or pThr to Tyr, is energetically unfavourable in comparison. pSer can transfer phosphate to a non-phosphorylated Ser. The non-rearranged [M-H](-) species yields more abundant product anions than its rearranged counterpart. If a peptide containing any or all of Ser, Thr and Tyr is not completely phosphorylated, negative-ion cleavages can determine the number of phosphated residues, and normally the positions of Ser, Thr and Tyr, but not which specific residues are phosphorylated. This is in accord with comments made earlier by Lehmann and coworkers. Copyright © 2011 John Wiley & Sons, Ltd.
Apparatus for neutralization of accelerated ions
Fink, Joel H.; Frank, Alan M.
1979-01-01
Apparatus for neutralization of a beam of accelerated ions, such as hydrogen negative ions (H.sup.-), using relatively efficient strip diode lasers which emit monochromatically at an appropriate wavelength (.lambda. = 8000 A for H.sup.- ions) to strip the excess electrons by photodetachment. A cavity, formed by two or more reflectors spaced apart, causes the laser beams to undergo multiple reflections within the cavity, thus increasing the efficiency and reducing the illumination required to obtain an acceptable percentage (.about. 85%) of neutralization.
[Effects of thiourea on pH and availability of metal ions in acid red soil].
Yang, Bo; Wang, Wen; Zeng, Qing-Ru; Zhou, Xi-Hong
2014-03-01
Through the simulation research, the effects of application of thiourea and urea on pH and availability of metal ions in acid red soil were studied, and the results showed that after applying urea, the soil pH increased in the first experimental stage and then reduced gradually to a low level, however, decreased trends of soil pH values were inhibited by the application of thiourea, especially when the concentration of thiourea reached to 5.0 mmol x kg(-1) dry soil, the soil pH was stable at high level, which exceeded to 6.0. It proved that the application of thiourea could inhibit the soil acidification due to urea application. After applying urea with different concentrations of thiourea, the available contents of Zn and Al decreased with the increasing concentration of thiourea, nevertheless, when the concentration of thiourea reached to 5.0 mmol x kg(-1), the available content of Mn was stable at high level which was over 110 mg x kg(-1). In addition, the results showed a highly significant negative correlation between the soil pH and the available content of Cu, Zn and Al, but for Mn, no discipline was found between the soil pH and the availability after applying thiourea. Moreover, the soil pH became higher after applying urea with thiourea compared to add urea only, which led to the decreasing of available content of Al, and it was benefited for the control of the phytotoxic effect of Al. The available content of Mn in the soil not only depended on soil pH but also the content of thiourea due to its redox and complexing reaction with Mn.
Accessing the Vibrational Signatures of Amino Acid Ions Embedded in Water Clusters
Voss, Jonathan M.; Fischer, Kaitlyn C.; Garand, Etienne
2018-04-16
We present an infrared predissociation (IRPD) study of microsolvated GlyH +(H 2O) n and GlyH +(D 2O) n clusters, formed inside of a cryogenic ion trap via condensation of H 2O or D 2O onto the protonated glycine ions. The resulting IRPD spectra, showing characteristic O–H and O–D stretches, indicate that H/D exchange reactions are quenched when the ion trap is held at 80 K, minimizing the presence of isotopomers. Comparisons of GlyH +(H 2O) n and GlyH +(D 2O) n spectra clearly highlight and distinguish the vibrational signatures of the water solvent molecules from those of the core GlyHmore » + ion, allowing for quick assessment of solvation structures. Without the aid of calculations, we can already infer solvation motifs and the presence of multiple conformations. Furthermore, the use of a cryogenic ion trap to cluster solvent molecules around ions of interest and control H/D exchange reactions is broadly applicable and should be extendable to studies of more complex peptidic ions in large solvated clusters.« less
Accessing the Vibrational Signatures of Amino Acid Ions Embedded in Water Clusters
DOE Office of Scientific and Technical Information (OSTI.GOV)
Voss, Jonathan M.; Fischer, Kaitlyn C.; Garand, Etienne
We present an infrared predissociation (IRPD) study of microsolvated GlyH +(H 2O) n and GlyH +(D 2O) n clusters, formed inside of a cryogenic ion trap via condensation of H 2O or D 2O onto the protonated glycine ions. The resulting IRPD spectra, showing characteristic O–H and O–D stretches, indicate that H/D exchange reactions are quenched when the ion trap is held at 80 K, minimizing the presence of isotopomers. Comparisons of GlyH +(H 2O) n and GlyH +(D 2O) n spectra clearly highlight and distinguish the vibrational signatures of the water solvent molecules from those of the core GlyHmore » + ion, allowing for quick assessment of solvation structures. Without the aid of calculations, we can already infer solvation motifs and the presence of multiple conformations. Furthermore, the use of a cryogenic ion trap to cluster solvent molecules around ions of interest and control H/D exchange reactions is broadly applicable and should be extendable to studies of more complex peptidic ions in large solvated clusters.« less
A CW radiofrequency ion source for production of negative hydrogen ion beams for cyclotrons
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kalvas, T.; Tarvainen, O.; Komppula, J.
2015-04-08
A CW 13.56 MHz radiofrequency-driven ion source RADIS for production of H{sup −} and D{sup −} beams is under development for replacing the filament-driven ion source of the MCC30/15 cyclotron. The RF ion source has a 16-pole multicusp plasma chamber, an electromagnet-based magnetic filter and an external planar spiral RF antenna behind an AlN window. The extraction is a 5-electrode system with an adjustable puller electrode voltage for optimizing the beam formation, a water-cooled electron dump electrode and an accelerating einzel lens. At 2650 W of RF power, the source produces 1 mA of H{sup −} (2.6 mA/cm{sup 2}), which is the intensity neededmore » at injection for production of 200 µA H{sup +} with the filament-driven ion source. A simple pepperpot device has been developed for characterizing the beam emittance. Plans for improving the power efficiency with the use of a new permanent magnet front plate is discussed.« less
Photolysis of H2O-H2O2 Mixtures: The Destruction of H2O2
NASA Technical Reports Server (NTRS)
Loeffler, M. J.; Fama, M.; Baragiola, R. A.; Carlson, R. W.
2013-01-01
We present laboratory results on the loss of H2O2 in solid H2O + H2O2 mixtures at temperatures between 21 and 145 K initiated by UV photolysis (193 nm). Using infrared spectroscopy and microbalance gravimetry, we measured the decrease of the 3.5 micrometer infrared absorption band during UV irradiation and obtained a photodestruction cross section that varies with temperature, being lowest at 70 K. We use our results, along with our previously measured H2O2 production rates via ionizing radiation and ion energy fluxes from the spacecraft to compare H2O2 creation and destruction at icy satellites by ions from their planetary magnetosphere and from solar UV photons. We conclude that, in many cases, H2O2 is not observed on icy satellite surfaces because the H2O2 photodestruction rate is much higher than the production rate via energetic particles, effectively keeping the H2O2 infrared signature at or below the noise level.
Humic Acid Isolations from Lignite by Ion Exchange Method
NASA Astrophysics Data System (ADS)
Kurniati, E.; Muljani, S.; Virgani, D. G.; Neno, B. P.
2018-01-01
The humic liquid is produced from lignite extraction using alkali solution. Conventional humic acid is obtained by acidifying a humic solution using HCl. The purpose of this research is the formation of solid humic acid from lignite by ion exchange method using cation resin. The results showed that the addition of cation resin was able to reduce the pH from 14 to pH 2 as well as the addition of acid (HCl), indicating the exchange of Na + ions with H + ions. The reduction of pH in the humic solution is influenced by the concentration of sodium ions in the humic solution, the weight of the cation resin, and the ion exchange time. The IR spectra results are in good agreement for humic acid from lignite characterization.
Santa Rosa, P; Parker, H M; Kiess, A S; McDaniel, C D
2016-01-15
Parthenogenesis is a form of embryonic development that occurs without fertilization. Recently, parthenogenesis has been reported in Chinese painted quail eggs. In Japanese quail, it has been shown that albumen pH of incubated fertile eggs is lower than that of incubated infertile eggs. However, it is unknown if alterations, similar to those in incubated fertile eggs, occur in albumen pH, gases, or ion concentrations from unfertilized eggs exhibiting parthenogenetic development. Therefore, the objective of this study was to determine if any differences in pH, gases, or ion concentrations exist between incubated unfertilized eggs exhibiting parthenogenetic development versus unfertilized eggs with no development over incubation. In this study, eggs were collected daily from Chinese painted quail hens that were separated from males at 4 weeks of age, before sexual maturity. Eggs were stored for 0 to 3 days at 20 °C and incubated at 37.5 °C for 12 days. Eggs were weighed before and after incubation to obtain percentage egg weight loss. After incubation, embryo size and albumen O2, CO2, Ca(2+), Na(+), and Cl(-) concentrations as well as pH were obtained from each incubated egg. Over incubation, albumen from unfertilized eggs exhibiting parthenogenetic development had a lower pH as well as less O2 and Cl(-), yet a higher Ca(2+) and Na(+) concentration as compared with the albumen of unfertilized eggs with no development. Also, eggs exhibiting parthenogenetic development had a higher albumen CO2 concentration as compared with eggs without development. The rate of egg weight loss was much lower in eggs exhibiting parthenogenetic development as compared with eggs without development. Also, as parthenogen size increased, there was a decrease in albumen pH, O2, and Cl(-), yet an increase in CO2 and Ca(2+). In conclusion, it appears that, over incubation, parthenogenetic development from unfertilized eggs alters the composition of albumen as compared with the albumen
Krüger, Julia; Bohrmann, Johannes
2015-01-16
Bioelectric phenomena have been found to exert influence on various developmental and regenerative processes. Little is known about their possible functions and the cellular mechanisms by which they might act during Drosophila oogenesis. In developing follicles, characteristic extracellular current patterns and membrane-potential changes in oocyte and nurse cells have been observed that partly depend on the exchange of protons, potassium ions and sodium ions. These bioelectric properties have been supposed to be related to various processes during oogenesis, e. g. pH-regulation, osmoregulation, cell communication, cell migration, cell proliferation, cell death, vitellogenesis and follicle growth. Analysing in detail the spatial distribution and activity of the relevant ion-transport mechanisms is expected to elucidate the roles that bioelectric phenomena play during oogenesis. To obtain an overview of bioelectric patterning along the longitudinal and transversal axes of the developing follicle, the spatial distributions of membrane potentials (Vmem), intracellular pH (pHi) and various membrane-channel proteins were studied systematically using fluorescent indicators, fluorescent inhibitors and antisera. During mid-vitellogenic stages 9 to 10B, characteristic, stage-specific Vmem-patterns in the follicle-cell epithelium as well as anteroposterior pHi-gradients in follicle cells and nurse cells were observed. Corresponding distribution patterns of proton pumps (V-ATPases), voltage-dependent L-type Ca(2+)-channels, amiloride-sensitive Na(+)-channels and Na(+),H(+)-exchangers (NHE) and gap-junction proteins (innexin 3) were detected. In particular, six morphologically distinguishable follicle-cell types are characterized on the bioelectric level by differences concerning Vmem and pHi as well as specific compositions of ion channels and carriers. Striking similarities between Vmem-patterns and activity patterns of voltage-dependent Ca(2+)-channels were found, suggesting
Zhu, Yaqiong; Ni, Yonghong; Sheng, Enhong
2016-06-07
LaVO4:Eu(3+) micro/nanocrystals with various shapes were hydrothermally synthesized by adjusting the pH of the system at 180 °C for 12 h in the presence of ethylenediaminetetraacetic acid (EDTA). The shape and phase of the final product were characterized by field emission scanning electron microscopy (FESEM) and X-ray powder diffraction (XRD). Experiments showed that when the other conditions were kept unchanged, the shape of the final product changed from hollow microspheres constructed by nanorods to long nanorods, to short nanorods and finally to grains with microscale sizes with the pH increase from 4.0, 7.0, 11.0 to 13.0 in the system. Meanwhile, the t-LaVO4 phase was always obtained from the system at pH below 13.0 and the m-LaVO4 phase was formed at pH 13.0. It was found that the final product with various shapes presented different luminescence performances. LaVO4:Eu(3+) nanorods obtained from the system at pH 11.0 displayed the strongest luminescence and good fluorescence stability in water. Also, the above strong PL spectrum could be quenched by Fe(3+) ions without the interference of other ions, indicating that the present product could be used as an efficient fluorescent probe for highly selective detection of Fe(3+) ions in water systems. The fluorescence quenching mechanism was investigated simultaneously.
NASA Astrophysics Data System (ADS)
Zheng, Jun; Yang, Dongsen; Ma, Yan; Chen, Mindong; Cheng, Jin; Li, Shizheng; Wang, Ming
2015-10-01
A new corona discharge (CD) based ion source was developed for a commercial high-resolution time-of-flight chemical ionization mass spectrometer (HRToF-CIMS) (Aerodyne Research Inc.) to measure both gaseous sulfuric acid (H2SO4) and aerosol sulfate after thermal desorption. Nitrate core ions (NO3-) were used as reagent ions and were generated by a negative discharge in zero air followed by addition of excess nitrogen dioxide (NO2) to convert primary ions and hydroxyl radicals (OH) into NO3- ions and nitric acid (HNO3). The CD-HRToF-CIMS showed no detectable interference from hundreds parts per billion by volume (ppbv) of sulfur dioxide (SO2). Unlike the atmospheric pressure ionization (API) ToF-CIMS, the CD ion source was integrated onto the ion-molecule reaction (IMR) chamber and which made it possible to measure aerosol sulfate by coupling to a filter inlet for gases and aerosols (FIGAERO). Moreover, compared with a quadrupole-based mass spectrometer, the desired HSO4- signal was detected by its exact mass of m/z 96.960, which was well resolved from the potential interferences of HCO3-ṡ(H2O)2 (m/z 97.014) and O-ṡH2OṡHNO3 (m/z 97.002). In this work, using laboratory-generated standards the CD-HRToF-CIMS was demonstrated to be able to detect as low as 3.1 × 105 molecules cm-3 gaseous H2SO4 and 0.5 μg m-3 ammonium sulfate based on 10-s integration time and two times of the baseline noise. The CD ion source had the advantages of low cost and a simple but robust structure. Since the system was non-radioactive and did not require corrosive HNO3 gas, it can be readily field deployed. The CD-HRToF-CIMS can be a powerful tool for both field and laboratory studies of aerosol formation mechanism and the chemical processes that were critical to understand the evolution of aerosols in the atmosphere.
The extraction of negative carbon ions from a volume cusp ion source
NASA Astrophysics Data System (ADS)
Melanson, Stephane; Dehnel, Morgan; Potkins, Dave; McDonald, Hamish; Hollinger, Craig; Theroux, Joseph; Martin, Jeff; Stewart, Thomas; Jackle, Philip; Philpott, Chris; Jones, Tobin; Kalvas, Taneli; Tarvainen, Olli
2017-08-01
Acetylene and carbon dioxide gases are used in a filament-powered volume-cusp ion source to produce negative carbon ions for the purpose of carbon implantation for gettering applications. The beam was extracted to an energy of 25 keV and the composition was analyzed with a spectrometer system consisting of a 90° dipole magnet and a pair of slits. It is found that acetylene produces mostly C2- ions (up to 92 µA), while carbon dioxide produces mostly O- with only trace amounts of C-. Maximum C2- current was achieved with 400 W of arc power and, the beam current and composition were found to be highly dependent on the pressure in the source. The beam properties as a function of source settings are analyzed, and plasma properties are measured with a Langmuir probe. Finally, we describe testing of a new RF H- ion source, found to produce more than 6 mA of CW H- beam.
Hershcovitch, Ady
1987-01-01
A process for selectively neutralizing H.sup.- ions in a magnetic field to produce an intense negative hydrogen ion beam with spin polarized protons. Characteristic features of the process include providing a multi-ampere beam of H.sup.- ions that are intersected by a beam of laser light. Photodetachment is effected in a uniform magnetic field that is provided around the beam of H.sup.- ions to spin polarize the H.sup.- ions and produce first and second populations or groups of ions, having their respective proton spin aligned either with the magnetic field or opposite to it. The intersecting beam of laser light is directed to selectively neutralize a majority of the ions in only one population, or given spin polarized group of H.sup.- ions, without neutralizing the ions in the other group thereby forming a population of H.sup.- ions each of which has its proton spin down, and a second group or population of H.sup.o atoms having proton spin up. Finally, the two groups of ions are separated from each other by magnetically bending the group of H.sup.- ions away from the group of neutralized ions, thereby to form an intense H.sup.- ion beam that is directed toward a predetermined objective.
Xu, Ling; Yan, Shihai; Choi, Eun-Young; Lee, Jin Yong; Kwon, Young-Uk
2009-06-21
Ni(OAc)(2)-H(3)BTC system in various ionic liquids, [RMI]X (R = ethyl, n-propyl, n-butyl; X = Cl, Br, I), produced five MOFs in two structure types; their relative thermodynamic stability varies with the size of RMI(+), and the X(-) ions govern the kinetic factors so that their combination effects determine the final product.
Two mechanisms of oral malodor inhibition by zinc ions.
Suzuki, Nao; Nakano, Yoshio; Watanabe, Takeshi; Yoneda, Masahiro; Hirofuji, Takao; Hanioka, Takashi
2018-01-18
The aim of this study was to reveal the mechanisms by which zinc ions inhibit oral malodor. The direct binding of zinc ions to gaseous hydrogen sulfide (H2S) was assessed in comparison with other metal ions. Nine metal chlorides and six metal acetates were examined. To understand the strength of H2S volatilization inhibition, the minimum concentration needed to inhibit H2S volatilization was determined using serial dilution methods. Subsequently, the inhibitory activities of zinc ions on the growth of six oral bacterial strains related to volatile sulfur compound (VSC) production and three strains not related to VSC production were evaluated. Aqueous solutions of ZnCl2, CdCl2, CuCl2, (CH3COO)2Zn, (CH3COO)2Cd, (CH3COO)2Cu, and CH3COOAg inhibited H2S volatilization almost entirely. The strengths of H2S volatilization inhibition were in the order Ag+ > Cd2+ > Cu2+ > Zn2+. The effect of zinc ions on the growth of oral bacteria was strain-dependent. Fusobacterium nucleatum ATCC 25586 was the most sensitive, as it was suppressed by medium containing 0.001% zinc ions. Zinc ions have an inhibitory effect on oral malodor involving the two mechanisms of direct binding with gaseous H2S and suppressing the growth of VSC-producing oral bacteria.
Han, Yingying; Ding, Changqin; Zhou, Jie; Tian, Yang
2015-01-01
It is very essential to disentangle the complicated inter-relationship between pH and Cu in the signal transduction and homeostasis. To this end, reporters that can display distinct signals to pH and Cu are highly valuable. Unfortunately, there is still no report on the development of biosensors that can simultaneously respond to pH and Cu(2+), to the best of our knowledge. In this work, we developed a single fluorescent probe, AuNC@FITC@DEAC (AuNC, gold cluster; FITC, fluorescein isothiocyanate; DEAC, 7-diethylaminocoumarin-3-carboxylic acid), for biosensing of pH, Cu(2+), and pH/Cu(2+) with different ratiometric fluorescent signals. First, 2,2',2″-(2,2',2″-nitrilotris(ethane-2,1-diyl)tris((pyridin-2-yl-methyl)azanediyl))triethanethiol (TPAASH) was designed for specific recognition of Cu(2+), as well as for organic ligand to synthesize fluorescent AuNCs. Then, pH-sensitive molecule, FITC emitting at 518 nm, and inner reference molecule, DEAC with emission peak at 472 nm, were simultaneously conjugated on the surface of AuNCs emitting at 722 nm, thus, constructing a single fluorescent probe, AuNC@FITC@DEAC, to sensing pH, Cu(2+), and pH/Cu(2+) excited by 405 nm light. The developed probe exhibited high selectivity and accuracy for independent determination of pH and Cu(2+) against reactive oxygen species (ROS), other metal ions, amino acids, and even copper-containing proteins. The AuNC-based inorganic-organic probe with good cell-permeability and high biocompatibility was eventually applied in monitoring both pH and Cu(2+) and in understanding the interplaying roles of Cu(2+) and pH in live cells by ratiometric multicolor fluorescent imaging.
Michael, Katharina; Kreiss, Cornelia M; Hu, Marian Y; Koschnick, Nils; Bickmeyer, Ulf; Dupont, Sam; Pörtner, Hans-O; Lucassen, Magnus
2016-03-01
Marine teleost fish sustain compensation of extracellular pH after exposure to hypercapnia by means of efficient ion and acid-base regulation. Elevated rates of ion and acid-base regulation under hypercapnia may be stimulated further by elevated temperature. Here, we characterized the regulation of transepithelial ion transporters (NKCC1, NBC1, SLC26A6, NHE1 and 2) and ATPases (Na(+)/K(+) ATPase and V-type H(+) ATPase) in gills of Atlantic cod (Gadus morhua) after 4 weeks of exposure to ambient and future PCO2 levels (550 μatm, 1200 μatm, 2200 μatm) at optimum (10 °C) and summer maximum temperature (18 °C), respectively. Gene expression of most branchial ion transporters revealed temperature- and dose-dependent responses to elevated PCO2. Transcriptional regulation resulted in stable protein expression at 10 °C, whereas expression of most transport proteins increased at medium PCO2 and 18 °C. mRNA and protein expression of distinct ion transport proteins were closely co-regulated, substantiating cellular functional relationships. Na(+)/K(+) ATPase capacities were PCO2 independent, but increased with acclimation temperature, whereas H(+) ATPase capacities were thermally compensated but decreased at medium PCO2 and 10 °C. When functional capacities of branchial ATPases were compared with mitochondrial F1Fo ATP-synthase strong correlations of F1Fo ATP-synthase and ATPase capacities generally indicate close coordination of branchial aerobic ATP demand and supply. Our data indicate physiological plasticity in the gills of cod to adjust to a warming, acidifying ocean within limits. In light of the interacting and non-linear, dose-dependent effects of both climate factors the role of these mechanisms in shaping resilience under climate change remains to be explored. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
[Partitioning of taxifolin-iron ions complexes in octanol-water system].
Shatalin, Iu V; Shubina, V S
2014-01-01
The composition of taxifolin-iron ions complexes in an octanol-water biphasic system was studied using the method of absorption spectrophotometry. It was found that at pH 5.0 in an aqueous biphasic system the complex of [Tf2 x Fe x (OH)k(H2O)8-k] is present, but at pH 7.0 and 9.0 the complexes of [Tf2 x Fe x (OH)k(H2O)2-k] and [Tf x Fe x OH)k(H2O)4-k] are predominantly observed. The formation of a stable [Tf3 x Fe] complex occurred in octanol phase. The charged iron ion of this complex is surrounded by taxifolin molecules, which shield the iron ion from lipophilic solvent. During transition from water to octanol phase the changes of the composition of complexes are accompanied by reciprocal changes in portion of taxifolin and iron ions in these phases. It was shown that the portion of taxifolin in aqueous solution in the presence of iron ions is increased at high pH values, and the portion of iron ions is minimal at pH 7.0. In addition, the parameters of solubility limits of taxifolin-iron ions complexes in an aqueous solution were determined. The data obtained gain a better understanding of the role of complexation of polyphenol with metal of variable valency in passive transport of flavonoids and metal ions across lipid membranes.
ION BEAM FOCUSING MEANS FOR CALUTRON
Backus, J.G.
1959-06-01
An ion beam focusing arrangement for calutrons is described. It provides a virtual focus of origin for the ion beam so that the ions may be withdrawn from an arc plasma of considerable width providing greater beam current and accuracy. (T.R.H.)
Carbon Mineralization Using Phosphate and Silicate Ions
NASA Astrophysics Data System (ADS)
Gokturk, H.
2013-12-01
ions would enhance the absorption of CO2 into the aerosol even more than the singly or doubly charged ions. Ion containing aerosols also help to catalyze reactions between water and CO2. Hydrated phosphate and silicate ions tend to attract hydrogen atoms from neighboring water molecules to reduce the charged state. When there is CO2 in the vicinity of the ion, the remainder of the water molecule which loses the hydrogen(s) reacts with CO2 to form carbonates. (PO4---) + H2O + CO2 -> (HPO3--) + (HCO3-) (SiO4----) + H2O + CO2 -> (HSiO4---) + (HCO3-) (SiO4----) + H2O + CO2 -> (H2SiO4--) + (CO3--) In conclusion, highly charged phosphate and silicate ions dissolved in water and aerosolized into small droplets can facilitate both the capture and the mineralization of CO2. This method would be especially effective in a CO2 rich environment such as the exhaust gas of a combustion process. [1] H. Gokturk, "Geoengineering with Charged Droplets," AGU Fall Meeting, San Francisco 2011 [2] H. Gokturk, "Atomistic Simulation of Sea Spray Particles," AGU Fall Meeting, San Francisco 2012
NASA Technical Reports Server (NTRS)
Marconi, M. L.; Mendis, D. A.; Korth, A.; Lin, R. P.; Mitchell, D. L.
1990-01-01
A sharp peak in the mass spectrum at 35 amu is observed by the heavy ion analyzer on board the Giotto spacecraft just inside the ionopause. This peak is identified with H3S(+) and it is argued that the dominant source of its likely parent molecule (H2S) is the observed distributed source of circumnuclear dust, rather than the central nucleus. In this case, the total production rate of H2S is more than about 0.5 percent that of the dominant cometary molecule H2O.
Fujimoto, S; Okano, I; Tanaka, Y; Sumida, Y; Tsuda, J; Kawakami, N; Shimohama, S
1996-06-01
We have purified bovine brain Zn(2+)-dependent acid phosphatase (Zn(2+)-APase), which requires Zn2+ ions to hydrolyze the substrate p-nitrophenyl phosphate (pNPP) in an acidic environment. The substrate specificity and metal requirement of Zn(2+)-APase at a physiological pH was also studied. The enzyme exhibited hydrolytic activity on myo-inositol-1- and -2-monophosphates, 2'-adenosine monophosphate, 2'-guanosine monophosphate, and the alpha- and beta-glycerophosphates, glucose-1-phosphate, and fructose-6-phosphate in 50 mM Tris-HCl buffer (pH 7.4) in the presence of Mg2+ ions, but not on pNPP and phosphotyrosine. Zn2+, Mn2+ and Co2+ ions were less effective for activation. Among the above substrates, myo-inositol-1-phosphate was the most susceptible to hydrolysis by the enzyme in the presence of 3 mM Mg2+ ions. The enzyme exhibited an optimum pH at around 8 for myo-inositol-1-phosphate in the presence of 3 mM Mg2+ ions. The Mg(2+)-dependent myo-inositol-1-phosphatase activity of the enzyme was significantly inhibited by Li+ ions. The Zn(2+)-dependent p-nitrophenyl phosphatase activity and Mg(2+)-dependent myo-inositol-1-phosphatase activity of the purified enzyme fraction exhibited similar behavior on Sephadex G-100 and Mono Q colomns. These findings suggest that Zn(2+)-APase also exhibits Mg(2+)-dependent myo-inositol-1-phosphatase activity under physiological conditions.
Modulation of Connexin-36 Gap Junction Channels by Intracellular pH and Magnesium Ions
Rimkute, Lina; Kraujalis, Tadas; Snipas, Mindaugas; Palacios-Prado, Nicolas; Jotautis, Vaidas; Skeberdis, Vytenis A.; Bukauskas, Feliksas F.
2018-01-01
Connexin-36 (Cx36) protein forms gap junction (GJ) channels in pancreatic beta cells and is also the main Cx isoform forming electrical synapses in the adult mammalian brain. Cx36 GJs can be regulated by intracellular pH (pHi) and cytosolic magnesium ion concentration ([Mg2+]i), which can vary significantly under various physiological and pathological conditions. However, the combined effect and relationship of these two factors over Cx36-dependent coupling have not been previously studied in detail. Our experimental results in HeLa cells expressing Cx36 show that changes in both pHi and [Mg2+]i affect junctional conductance (gj) in an interdependent manner; in other words, intracellular acidification cause increase or decay in gj depending on whether [Mg2+]i is high or low, respectively, and intracellular alkalization cause reduction in gj independently of [Mg2+]i. Our experimental and modelling data support the hypothesis that Cx36 GJ channels contain two separate gating mechanisms, and both are differentially sensitive to changes in pHi and [Mg2+]i. Using recombinant Cx36 we found that two glutamate residues in the N-terminus could be partly responsible for the observed interrelated effect of pHi and [Mg2+]i. Mutation of glutamate at position 8 attenuated the stimulatory effect of intracellular acidification at high [Mg2+]i, while mutation at position 12 and double mutation at both positions reversed stimulatory effect to inhibition. Moreover, Cx36*E8Q lost the initial increase of gj at low [Mg2+]i and double mutation lost the sensitivity to high [Mg2+]i. These results suggest that E8 and E12 are involved in regulation of Cx36 GJ channels by Mg2+ and H+ ions. PMID:29706896
NASA Astrophysics Data System (ADS)
Amelynck, C.; Schoon, N.; Kuppens, T.; Bultinck, P.; Arijs, E.
2005-12-01
The rate constants and product ion distributions of the reactions of H3O+, NO+ and O2+ with 2-methyl-3-buten-2-ol, cis-3-hexen-1-ol, cis-3-hexenyl acetate, 1,8-cineole, 6-methyl-5-hepten-2-one, camphor and linalool have been determined at 150 Pa and 297 K using a selected ion flow tube (SIFT). All reactions were found to proceed at a rate close to the collision rate, calculated with the Su and Chesnavich model, using the polarizability and electric dipole moment of the compounds derived from B3LYP/aug-cc-pVDZ quantum chemical calculations. Additionally the product ion distributions of the reactions of these three ions with the terpenoid alcohols nerol and geraniol have been obtained.
Shinto, K; Senée, F; Ayala, J-M; Bolzon, B; Chauvin, N; Gobin, R; Ichimiya, R; Ihara, A; Ikeda, Y; Kasugai, A; Kitano, T; Kondo, K; Marqueta, A; Okumura, Y; Takahashi, H; Valette, M
2016-02-01
Ion species ratio of high current positive hydrogen/deuterium ion beams extracted from an electron-cyclotron-resonance ion source for International Fusion Materials Irradiation Facility accelerator was measured by the Doppler shift Balmer-α line spectroscopy. The proton (H(+)) ratio at the middle of the low energy beam transport reached 80% at the hydrogen ion beam extraction of 100 keV/160 mA and the deuteron (D(+)) ratio reached 75% at the deuterium ion beam extraction of 100 keV/113 mA. It is found that the H(+) ratio measured by the spectroscopy gives lower than that derived from the phase-space diagram measured by an Allison scanner type emittance monitor. The H(+)/D(+) ratio estimated by the emittance monitor was more than 90% at those extraction currents.
Jia, Xianlu; Zhang, Tianjue; Luo, Shan; Wang, Chuan; Zheng, Xia; Yin, Zhiguo; Zhong, Junqing; Wu, Longcheng; Qin, Jiuchang
2010-02-01
A 2.45 GHz microwave ion source was developed at China Institute of Atomic Energy (CIAE) for proton beam production of over 60 mA [B.-Q. Cui, Y.-W. Bao, L.-Q. Li, W.-S. Jiang, and R.-W. Wang, Proceedings of the High Current Electron Cyclotron Resonance (ECR) Ion Source for Proton Accelerator, APAC-2001, 2001 (unpublished)]. For various proton beam applications, another 2.45 GHz microwave ion source with a compact structure is designed and will be built at CIAE as well for high current proton beam production. It is also considered to be used for the test of H(2)(+) beam, which could be injected into the central region model cyclotron at CIAE, and accelerated to 5 MeV before extraction by stripping. The required ECR magnetic field is supplied by all the permanent magnets rather than electrical solenoids and six poles. The magnetic field distribution provided by this permanent magnets configuration is a large and uniformly volume of ECR zone, with central magnetic field of a magnitude of approximately 875 Gs [T. Taylor and J. S. C. Wills, Nucl. Instrum. Methods Phys. Res. A 309, 37 (1991)]. The field adjustment at the extraction end can be implemented by moving the position of the magnet blocks. The results of plasma, coupling with 2.45 GHz microwave in the ECR zone inside the ion source are simulated by particle-in-cell code to optimize the density by adjusting the magnetic field distribution. The design configuration of the ion source will be summarized in the paper.
Long pulse acceleration of MeV class high power density negative H{sup −} ion beam for ITER
DOE Office of Scientific and Technical Information (OSTI.GOV)
Umeda, N., E-mail: umeda.naotaka@jaea.go.jp; Kojima, A.; Kashiwagi, M.
2015-04-08
R and D of high power density negative ion beam acceleration has been carried out at MeV test facility in JAEA to realize ITER neutral beam accelerator. The main target is H{sup −} ion beam acceleration up to 1 MeV with 200 A/m{sup 2} for 60 s whose pulse length is the present facility limit. For long pulse acceleration at high power density, new extraction grid (EXG) has been developed with high cooling capability, which electron suppression magnet is placed under cooling channel similar to ITER. In addition, aperture size of electron suppression grid (ESG) is enlarged from 14 mmmore » to 16 mm to reduce direct interception on the ESG and emission of secondary electron which leads to high heat load on the upstream acceleration grid. By enlarging ESG aperture, beam current increased 10 % at high current beam and total acceleration grid heat load reduced from 13 % to 10 % of input power at long pulse beam. In addition, heat load by back stream positive ion into the EXG is measured for the first time and is estimated as 0.3 % of beam power, while heat load by back stream ion into the source chamber is estimated as 3.5 ~ 4.0 % of beam power. Beam acceleration up to 60 s which is the facility limit, has achieved at 683 keV, 100 A/m{sup 2} of negative ion beam, whose energy density increases two orders of magnitude since 2011.« less
NASA Astrophysics Data System (ADS)
Kano, Sho; Yang, Huilong; Shen, Jingjie; Zhao, Zishou; McGrady, John; Hamaguchi, Dai; Ando, Mamami; Tanigawa, Hiroyasu; Abe, Hiroaki
2018-04-01
In order to clarify the instability of M23C6 in F82H steel under irradiation, both electron irradiation using a high voltage electron microscope (HVEM) and ion irradiation using an ion accelerator were performed. For the electron irradiation, in-situ observation under 2 MV electron irradiation and ex-situ high resolution electron microscopic (HREM) analysis were utilized to evaluate the response of M23C6 against irradiation. The temperature dependence of the irradiation induced instability of the carbide was first confirmed: 293 K < T < 573 K, by observation of lowering in contrast at the periphery of carbides, 698 K < T < 773 K, fragmentation at the interface between carbides and matrix, and at 773 K, formation and coarsening of new particles near the periphery of M23C6. HREM analysis showed the loss of the lattice fringe contrast at the pre-existing M23C6 precipitates at temperatures ranging from 473 to 773 K, indicating severe loss of crystallinity due to dissolution of the constituent atoms though irradiation-enhanced diffusion under the vacancy diffusion by the focused electron beam irradiation. For the ion irradiation, 10.5 MeV-Fe3+ ion was applied to bombard the F82H steel at 673 K to achieve the displacement damage of ≈20 dpa at the depth of 1.0 μm from surface. Cross-section TEM specimens were prepared by a focused ion beam technique. The shrinkage of carbide particles was observed especially near the irradiation surface. Besides, the lattice fringes at the periphery of carbide were observed in the irradiated M23C6 by the HREM analysis, which is different from that observed in the electron irradiation. It was clarified that the instability of M23C6 is dependent on the irradiation conditions, indicating that the flow rate of vacancy type defects might be the key factor to cause the dissolution of constituent atoms of carbide particles into matrix under irradiation.
First principles study of cobalt hydride, CoH, and its ions CoH+ and CoH-
NASA Astrophysics Data System (ADS)
Sakellaris, Constantine N.; Mavridis, Aristides
2012-07-01
The electronic structure of the diatomic species CoH, CoH+, and CoH- have been studied mainly by multireference configuration interaction (MRCI) methods and basis sets of quintuple quality. The restricted coupled-cluster with iterative singles + doubles + quasi-perturbative connected triples, RCCSD(T), approach was also employed, limited however to the ground states only. At the MRCI level we have constructed 27 (CoH), 24 (CoH+), and 12 (CoH-) potential energy curves correlating adiabatically to six, seven, and two energy channels, respectively. For the ground states scalar relativistic and core-subvalence effects have been taken into account. We report energetics, spectroscopic parameters, dipole moments, excitation energies, and spin-orbit coupling constants. Our CoH calculated results are in accord with experiment, but there is an interesting discrepancy between theory and experiment concerning the dipole moment, the former being significantly larger than the latter. Experimental results on CoH+ and CoH- are scarce. The ground state of CoH, CoH+, and CoH- are definitely of 3Φ, 4Φ, and 4Φ symmetries with calculated (experimental) dissociation energies D_0^0 = 46.4 ± 0.5(45.0 ± 1.2), 49.6(47 ± 2), and 45.6(43.1 ± 1.2) kcal/mol, respectively. In all 24 calculated CoH states, a Co-to-H charge transfer of 0.2-0.3 e- is recorded; in CoH-, however, the negative charge resides almost exclusively on the Co atom.
Zhao, Yufei; Zhang, Yuxia; Yang, Zhiyu; Yan, Yiming; Sun, Kening
2013-08-01
Scientists increasingly witness the applications of MoS 2 and MoO 2 in the field of energy conversion and energy storage. On the one hand, MoS 2 and MoO 2 have been widely utilized as promising catalysts for electrocatalytic or photocatalytic hydrogen evolution in aqueous solution. On the other hand, MoS 2 and MoO 2 have also been verified as efficient electrode material for lithium ion batteries. In this review, the synthesis, structure and properties of MoS 2 and MoO 2 are briefly summarized according to their applications for H 2 generation and lithium ion batteries. Firstly, we overview the recent advancements in the morphology control of MoS 2 and MoO 2 and their applications as electrocatalysts for hydrogen evolution reactions. Secondly, we focus on the photo-induced water splitting for H 2 generation, in which MoS 2 acts as an important co-catalyst when combined with other semiconductor catalysts. The newly reported research results of the significant functions of MoS 2 nanocomposites in photo-induced water splitting are presented. Thirdly, we introduce the advantages of MoS 2 and MoO 2 for their enhanced cyclic performance and high capacity as electrode materials of lithium ion batteries. Recent key achievements in MoS 2 - and MoO 2 -based lithium ion batteries are highlighted. Finally, we discuss the future scope and the important challenges emerging from these fascinating materials.
NASA Astrophysics Data System (ADS)
DeBlase, Andrew F.; Harrilal, Christopher P.; Lawler, John T.; Burke, Nicole L.; McLuckey, Scott A.; Zwier, Timothy S.
2017-06-01
Incorporation of the unnatural D-proline (^{D}P) stereoisomer into a polypeptide sequence is a typical strategy to encourage formation of β-hairpin loops because natural sequences are often unstructured in solution. Using conformation-specific IR and UV spectroscopy of cold (10 K) gas-phase ions, we probe the inherent conformational preferences of the ^{D}P and ^{L}P diastereomers in the protonated peptide [YAPAA+H]^{+}, where only intramolecular interactions are possible. Consistent with the solution phase studies, one of the conformers of [YADPAA+H]^{+} is folded into a charge-stabilized β-hairpin turn. However, a second predominant conformer family containing two sequential γ-turns is also identified, with similar energetic stability. A single conformational isomer of the ^{L}P diastereomer, [YALPAA+H]^{+}, is found and assigned to a structure that is not the anticipated "mirror image" β-turn. Instead, the ^{L}P stereo center promotes a cis alanine-proline amide bond. The assigned structures contain clues that the preference of the ^{D}P diastereomer to support a trans-amide bond and the proclivity of ^{L}P for a cis-amide bond is sterically driven and can be reversed by substituting glycine for alanine in position 2, forming [YGLPAA+H]^{+}. These results provide a basis for understanding the residue-specific and stereo-specific alterations in the potential energy surface that underlie these changing preferences, providing insights to the origin of β-hairpin formation.
Nakai, Yoichi; Hidaka, Hiroshi; Watanabe, Naoki; Kojima, Takao M
2016-06-14
We measured equilibrium constants for H3O(+)(H2O)n-1 + H2O↔H3O(+)(H2O)n (n = 4-9) reactions taking place in an ion drift tube with various applied electric fields at gas temperatures of 238-330 K. The zero-field reaction equilibrium constants were determined by extrapolation of those obtained at non-zero electric fields. From the zero-field reaction equilibrium constants, the standard enthalpy and entropy changes, ΔHn,n-1 (0) and ΔSn,n-1 (0), of stepwise association for n = 4-8 were derived and were in reasonable agreement with those measured in previous studies. We also examined the electric field dependence of the reaction equilibrium constants at non-zero electric fields for n = 4-8. An effective temperature for the reaction equilibrium constants at non-zero electric field was empirically obtained using a parameter describing the electric field dependence of the reaction equilibrium constants. Furthermore, the size dependence of the parameter was thought to reflect the evolution of the hydrogen-bond structure of H3O(+)(H2O)n with the cluster size. The reflection of structural information in the electric field dependence of the reaction equilibria is particularly noteworthy.
Van Stipdonk, Michael J; Kerstetter, Dale R; Leavitt, Christopher M; Groenewold, Gary S; Steill, Jeffrey; Oomens, Jos
2008-06-14
Wavelength-selective infrared multiple-photon photodissociation (WS-IRMPD) was used to study isotopically-labeled ions generated by McLafferty rearrangement of nicotinyl-glycine-tert-butyl ester and betaine-glycine-tert-butyl ester. The tert-butyl esters were incubated in a mixture of D(2)O and CH(3)OD to induce solution-phase hydrogen-deuterium exchange and then converted to gas-phase ions using electrospray ionization. McLafferty rearrangement was used to generate the free-acid forms of the respective model peptides through transfer of an H atom and elimination of butene. The specific aim was to use vibrational spectra generated by WS-IRMPD to determine whether the H atom remains at the acid group, or migrates to one or more of the other exchangeable sites. Comparison of the IRMPD results in the region from 1200-1900 cm(-1) to theoretical spectra for different isotopically-labeled isomers clearly shows that the H atom is situated at the C-terminal acid group and migration to amide positions is negligible on the time scale of the experiment. The results of this study suggest that use of the McLafferty rearrangement for peptide esters could be an effective approach for generation of H-atom isotope tracers, in situ, for subsequent investigation of intramolecular proton migration during peptide fragmentation studies.
Two mechanisms of oral malodor inhibition by zinc ions
Suzuki, Nao; Nakano, Yoshio; Watanabe, Takeshi; Yoneda, Masahiro; Hirofuji, Takao; Hanioka, Takashi
2018-01-01
Abstract Objectives The aim of this study was to reveal the mechanisms by which zinc ions inhibit oral malodor. Material and Methods The direct binding of zinc ions to gaseous hydrogen sulfide (H2S) was assessed in comparison with other metal ions. Nine metal chlorides and six metal acetates were examined. To understand the strength of H2S volatilization inhibition, the minimum concentration needed to inhibit H2S volatilization was determined using serial dilution methods. Subsequently, the inhibitory activities of zinc ions on the growth of six oral bacterial strains related to volatile sulfur compound (VSC) production and three strains not related to VSC production were evaluated. Results Aqueous solutions of ZnCl2, CdCl2, CuCl2, (CH3COO)2Zn, (CH3COO)2Cd, (CH3COO)2Cu, and CH3COOAg inhibited H2S volatilization almost entirely. The strengths of H2S volatilization inhibition were in the order Ag+ > Cd2+ > Cu2+ > Zn2+. The effect of zinc ions on the growth of oral bacteria was strain-dependent. Fusobacterium nucleatum ATCC 25586 was the most sensitive, as it was suppressed by medium containing 0.001% zinc ions. Conclusions Zinc ions have an inhibitory effect on oral malodor involving the two mechanisms of direct binding with gaseous H2S and suppressing the growth of VSC-producing oral bacteria. PMID:29364345
Broadley, Sarah; Vondrak, Tomas; Wright, Timothy G; Plane, John M C
2008-09-14
A series of gas-phase reactions involving molecular Ca-containing ions was studied by the pulsed laser ablation of a calcite target to produce Ca+ in a fast flow of He, followed by the addition of reagents downstream and detection of ions by quadrupole mass spectrometry. Most of the reactions that were studied are important for describing the chemistry of meteor-ablated calcium in the earth's upper atmosphere. The following rate coefficients were measured: k(CaO+ + O --> Ca+ + O2) = (4.2 +/- 2.8) x 10(-11) at 197 K and (6.3 +/- 3.0) x 10(-11) at 294 K; k(CaO+ + CO --> Ca+ + CO2, 294 K) = (2.8 +/- 1.5) x 10(-10); k(Ca+.CO2 + O2 --> CaO2+ + CO2, 294 K) = (1.2 +/- 0.5) x10(-10); k(Ca+.CO2 + H2O --> Ca+.H2O + CO2) = (13.0 +/- 4.0) x 10(-10); and k(Ca+.H2O + O2 --> CaO2+ + H2O, 294 K) = (4.0 +/- 2.5) x 10(-10) cm3 molecule(-1) s(-1). The quoted uncertainties are a combination of the 1 sigma standard errors in the kinetic data and the systematic errors in the models used to extract the rate coefficients. Rate coefficients were also obtained for the following recombination (also termed association) reactions in He bath gas: k(Ca+.CO2 + CO2 --> Ca+.(CO2)2, 294 K) = (2.6 +/- 1.0) x 10(-29); k(Ca+.H2O + H2O --> Ca+.(H2O)2) = (1.6 +/- 1.1) x 10(-27); and k(CaO2+ + O2 --> CaO2+.O2) < 1 x 10(-31) cm6 molecule(-2) s(-1). These recombination rate coefficients, as well as those for the ligand-switching reactions listed above, were then interpreted using a combination of high level quantum chemistry calculations and RRKM theory using an inverse Laplace transform solution of the master equation. The surprisingly slow reaction between CaO+ and O was explained using quantum chemistry calculations on the lowest 2A', 2A'' and 4A'' potential energy surfaces. These calculations indicate that reaction mostly occurs on the 2A' surface, leading to production of Ca+ (2S) + O2(1 Delta g). The importance of this reaction for controlling the lifetime of Ca+ in the upper mesosphere and lower
Lu, W; Li, J Y; Kang, L; Liu, H P; Li, H; Li, J D; Sun, L T; Ma, X W
2014-02-01
The 320 kV platform for multi-discipline research with highly charged ions is a heavy ion beam acceleration instrument developed by Institute of Modern Physics, which is dedicated to basic scientific researches such as plasma, atom, material physics, and astrophysics, etc. The platform has delivered ion beams of 400 species for 36,000 h. The average operation time is around 5000 h/year. With the beams provided by the platform, lots of outstanding progresses were made in various research fields. The ion source of the platform is an all-permanent magnet electron cyclotron resonance ion source, LAPECR2 (Lanzhou All Permanent ECR ion source No. 2). The maximum axial magnetic fields are 1.28 T at injection and 1.07 T at extraction, and the radial magnetic field is up to 1.21 T at the inner wall of the plasma chamber. The ion source is capable to produce low, medium, and high charge state gaseous and metallic ion beams, such as H(+), (40)Ar(8+), (129)Xe(30+), (209)Bi(33+), etc. This paper will present the latest result of LAPECR2 and the routine operation status for the high voltage platform.
Kinetics and Equilibrium of Fe3+ Ions Adsorption on Carbon Nanofibers
NASA Astrophysics Data System (ADS)
Alimin; Agusu, La; Ahmad, L. O.; Kadidae, L. O.; Ramadhan, L.; Nurdin, M.; Isdayanti, N.; Asria; Aprilia M, P.; Hasrudin
2018-05-01
Generally, the interaction between metal ions and adsorbent is governed by many factors including; concentration of metal ions, interaction time and solution pH. In this work, we applied liquid phase adsorption for studying the interaction between Fe3+ ions and Carbon Nanofibers (CNFs) irradiated by ultrasonic waves. Kinetics and isotherms model of the Fe3+ ion adsorption was investigated by varying contact time and pH. We found that the Fe3+ ions were efficiently adsorbed on CNFs for 0.5 h in acidic pH of around 5. In order to obtain the best-fitted isotherms model, Langmuir and Freundlich’s isotherms were used in this work. The adsorption equilibrium Fe3+ metal ions on CNFs tend to follow Langmuir. Adsorption kinetics of Fe3+ ions on CNFs were investigated by using both pseudo-first and pseudo-second orders. The adsorption kinetics coincided well with the pseudo-second-order.
Hydrogen ion block of the sodium pore in squid giant axons
1983-01-01
The block of squid axon sodium channels by H ions was studied using voltage-clamp and internal perfusion techniques. An increase in the concentration of internal permeant ions decreased the block produced by external H ions. The voltage dependence of the block was found to be nonmonotonic: it was reduced by both large positive and large negative potentials. The ability of internal ions to modify the block by external H+ is explained by a competition among these ions for a binding site within the pore. The nonmonotonic voltage dependence is consistent with this picture if the hydrogen ions are allowed to be permeant. PMID:6315859
NASA Astrophysics Data System (ADS)
Adebiyi, Babatunde Mattew
Material properties and performance are governed by material molecular chemistry structures and molecular level interactions. Methods to understand relationships between the material properties and performance and their correlation to the molecular level chemistry and morphology, and thus find ways of manipulating and adjusting matters at the atomistic level in order to improve material performance, are required. A computational material modeling methodology is investigated and demonstrated for a key cement hydrated component material chemistry structure of Calcium-Silicate-Hydrate (C-S-H) Jennite in this work. The effect of material ion exchanges on the mechanical stiffness properties and shear deformation behavior of hydrated cement material chemistry structure of Calcium Silicate Hydrate (C-S-H) Jennite was studied. Calcium ions were replaced with Magnesium ions in Jennite structure of the C-S-H gel. Different level of substitution of the ions was used. The traditional Jennite structure was obtained from the American Mineralogist Crystal Structure Database and super cells of the structures were created using a Molecular Dynamics Analyzer and Visualizer Material Studio. Molecular dynamics parameters used in the modeling analysis were determined by carrying out initial dynamic studies. 64 unit cell of C-S-H Jennite was used in material modeling analysis studies based on convergence results obtained from the elastic modulus and total energies. NVT forcite dynamics using COMPASS force field based on 200 ps dynamics time was used to determine mechanical modulus of the traditional C-S-H gel and the Magnesium ion modified structures. NVT Discover dynamics using COMPASS forcefield was used in the material modeling studies to investigate the influence of ionic exchange on the shear deformation of the associated material chemistry structures. A prior established quasi-static deformation method to emulate shear deformation of C-S-H material chemistry structure that is
Schnier, Paul D.; Price, William D.; Strittmatter, Eric F.; Williams, Evan R.
2005-01-01
The dissociation kinetics of protonated leucine enkephalin and its proton and alkali metal bound dimers were investigated by blackbody infrared radiative dissociation in a Fourier-transform mass spectrometer. From the temperature dependence of the unimolecular dissociation rate constants, Arrhenius activation parameters in the zero-pressure limit are obtained. Protonated leucine enkephalin dissociates to form b4 and (M−H2O)+ ions with an average activation energy (Ea) of 1.1 eV and an A factor of 1010.5 s−1. The value of the A factor indicates that these dissociation processes are rearrangements. The b4 ions subsequently dissociate to form a4 ions via a process with a relatively high activation energy (1.3 eV), but one that is entropically favored. For the cationized dimers, the thermal stability decreases with increasing cation size, consistent with a simple electrostatic interaction in these noncovalent ion–molecule complexes. The Ea and A factors are indistinguishable within experimental error with values of ~1.5 eV and 1017 s−1, respectively. Although not conclusive, results from master equation modeling indicate that all these BIRD processes, except for b4 → a4, are in the rapid energy exchange limit. In this limit, the internal energy of the precursor ion population is given by a Boltzmann distribution and information about the energetics and dynamics of the reaction are obtained directly from the measured Arrhenius parameters. PMID:16554908
Electron cyclotron resonance ion sources in use for heavy ion cancer therapy.
Tinschert, K; Iannucci, R; Lang, R
2008-02-01
The use of electron cyclotron resonance (ECR) ion sources for producing ion beams for heavy ion cancer therapy has been established for more than ten years. After the Heavy Ion Medical Accelerator (HIMAC) at Chiba, Japan started therapy of patients with carbon ions in 1994 the first carbon ion beam for patient treatment at the accelerator facility of GSI was delivered in 1997. ECR ion sources are the perfect tool for providing the required ion beams with good stability, high reliability, and easy maintenance after long operating periods. Various investigations were performed at GSI with different combinations of working gas and auxiliary gas to define the optimal beam conditions for an extended use of further ion species for the dedicated Heidelberg Ion Beam Therapy (HIT) facility installed at the Radiological University Hospital Heidelberg, Germany. Commercially available compact all permanent magnet ECR ion sources operated at 14.5 GHz were chosen for this facility. Besides for (12)C(4+) these ion sources are used to provide beams of (1)H(3)(1+), (3)He(1+), and (16)O(6+). The final commissioning at the HIT facility could be finished at the end of 2006.
Maity, Shubhra B; Banerjee, Saikat; Sunwoo, Kyoung; Kim, Jong Seung; Bharadwaj, Parimal K
2015-04-20
A new BODIPY derivative with 2,2'-(ethane-1,2-diylbis(oxy))bis(N,N-bis(pyridine-2-ylmethyl)aniline unit as the metal receptor has been designed and synthesized. The dye selectively detects either Cd(2+) or Hg(2+) ions in the presence of hosts of other biologically important and environmentally relevant metal ions in aqueous medium at physiological pH. Binding of metal ions causes a change in the emission behavior of the dye from weakly fluorescent to highly fluorescent. Confocal microscopic experiments validate that the dye can be used to identify changes in either Hg(2+) or Cd(2+) levels in living cells.
A pure inorganic 1D chain based on {Mo8O28} clusters and Mn(II) ions: [Mn(H2O)2Mo8O28 ] n 6 n -
NASA Astrophysics Data System (ADS)
Zhang, Xiaofen; Yan, Yonghong; Wu, Lizhou; Yu, Chengxin; Dong, Xinbo; Hu, Huaiming; Xue, Ganglin
2016-01-01
A new pure inorganic polymer, (NH4)6n[Mn(H2O)2Mo8O28)]n(H2O)2n(1), has been synthesized and characterized by elemental analyses, IR spectrum, UV-vis absorption spectra, TG-DSC and electrochemical studies. In 1, [Mo8O28]8- anions act as tetradentate ligands and are alternately linked by Mn(H2O)2 2 + ions into a one-dimensional chain structure. It is interesting that 1 represents the first example of pure inorganic-inorganic hybrid based on octamolybdate and transition metal ions. Moreover, it was indicated that 1 had definite catalytic activities on the probe reaction of benzyl alcohol oxidation to benzaldehyde with H2O2.
Determining fluoride ions in ammonium desulfurization slurry using an ion selective electrode method
NASA Astrophysics Data System (ADS)
Luo, Zhengwei; Guo, Mulin; Chen, Huihui; Lian, Zhouyang; Wei, Wuji
2018-02-01
Determining fluoride ions in ammonia desulphurization slurry using a fluoride ion selective electrode (ISE) is investigated. The influence of pH was studied and the appropriate total ionic strength adjustment buffer and its dosage were optimized. The impact of Fe3+ concentration on the detection results was analyzed under preferable conditions, and the error analysis of the ISE method’s accuracy and precision for measuring fluoride ion concentration in the range of 0.5-2000 mg/L was conducted. The quantitative recovery of F- in ammonium sulfate slurry was assessed. The results showed that when pH ranged from 5.5˜6 and the Fe3+ concentration was less than 750 mg/L, the accuracy and precision test results with quantitative recovery rates of 92.0%-104.2% were obtained.
NASA Astrophysics Data System (ADS)
Chen, X.; Romaniello, S. J.; Herrmann, A. D.; Wasylenki, L. E.; Anbar, A. D.
2015-12-01
abiotic CaCO3 reflect changes in aqueous U(VI) speciation, which are in turn a function of carbonate ion chemistry and pH. Hence, the door is opened to the development of a possible 238U/235U proxy for the carbonate ion system. [1] DeCarlo et al., (2015), GCA, 162,151-165. [2] Reeder et a., (2001), GCA, 65, 3491-3503. [3] Weyer et al., (2008) GCA 72, 345-359.
Proton transfer and the diffusion of H+ and OH- ions along water wires.
Lee, Song Hi; Rasaiah, Jayendran C
2013-09-28
Hydrogen and hydroxide ion transport in narrow carbon nanotubes (CNTs) of diameter 8.1 Å and lengths up to 582 Å are investigated by molecular dynamics simulations using a dissociating water model. The diffusion coefficients of the free ions in an open chain are significantly larger than in periodically replicated wires that necessarily contain D or L end defects, and both are higher than they are in bulk water. The free hydroxide ion diffuses faster than the free hydronium ion in short CNTs, unlike diffusion in liquid water, and both coefficients increase and converge to nearly the same value with increasing tube length. The diffusion coefficients of the two ions increase further when the tubes are immersed in a water reservoir and they move easily out of the tube, suggesting an additional pathway for proton transport via OH(-) ions in biological channels.
Gatto, C; Lutsenko, S; Shin, J M; Sachs, G; Kaplan, J H
1999-05-14
The integral membrane protein, the gastric H,K-ATPase, is an alpha-beta heterodimer, with 10 putative transmembrane segments in the alpha-subunit and one such segment in the beta-subunit. All transmembrane segments remain within the membrane domain following trypsinization of the intact gastric H,K-ATPase in the presence of K+ ions, identified as M1M2, M3M4, M5M6, and M7, M8, M9, and M10. Removal of K+ ions from this digested preparation results in the selective loss of the M5M6 hairpin from the membrane. The release of the M5M6 fragment is directed to the extracellular phase as evidenced by the accumulation of the released M5M6 hairpin inside the sealed inside out vesicles. The stabilization of the M5M6 hairpin in the membrane phase by the transported cation as well as loss to the aqueous phase in the absence of the transported cation has been previously observed for another P2-type ATPase, the Na, K-ATPase (Lutsenko, S., Anderko, R., and Kaplan, J. H. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 7936-7940). Thus, the effects of the counter-transported cation on retention of the M5M6 segment in the membrane as compared with the other membrane pairs may be a general feature of P2-ATPase ion pumps, reflecting a flexibility of this region that relates to the mechanism of transport.
NASA Astrophysics Data System (ADS)
Tanarro, I.; Herrero, V. J.; Islyaikin, A.; Tabarés, F. L.; Tafalla, D.
En este trabajo se presenta el estudio espectrométrico de los plasmas levemente ionizados generados en una descarga continua a baja presión de H2 con trazas de N2 y CH4, orientado principalmente a identificar la naturaleza y distribución energética de los iones que en ella se producen, y a asignar algunos de los mecanismos cinéticos elementales de formación y destrucción de tales especies. Alguno de los iones mayoritarios de estos plasmas, como el H3+, presenta gran interés desde el punto de vista de la Astrofísica por su prevista intervención en la química de las ionosferas planetarias y del medio interestelar, al actuar como sustancia intermedia en la formación de gran variedad de especies moleculares; si bien, dada su pequeña concentración, su observación real en el espacio se demoró hasta la pasada década de los años 90, cuando fue detectado por primera vez en la atmósfera de Júpiter y en otros objetos estelares. Del mismo modo que los trabajos espectroscópicos de laboratorio resultan indispensables para la posterior identificación de las especies observadas en el espacio, es de esperar que la asignación de los procesos cinéticos más importantes que tienen lugar en los plasmas generados en reactores de descarga, como los aquí presentados, permitan extrapolar los resultados así obtenidos al esclarecimiento de los mecanismos fisico-químicos participantes en otros medios observables únicamente a larga distancia.
Modeling of negative ion transport in a plasma source
NASA Astrophysics Data System (ADS)
Riz, David; Paméla, Jérôme
1998-08-01
A code called NIETZSCHE has been developed to simulate the negative ion transport in a plasma source, from their birth place to the extraction holes. The ion trajectory is calculated by numerically solving the 3-D motion equation, while the atomic processes of destruction, of elastic collision H-/H+ and of charge exchange H-/H0 are handled at each time step by a Monte-Carlo procedure. This code can be used to calculate the extraction probability of a negative ion produced at any location inside the source. Calculations performed with NIETZSCHE have allowed to explain, either quantitatively or qualitatively, several phenomena observed in negative ion sources, such as the isotopic H-/D- effect, and the influence of the plasma grid bias or of the magnetic filter on the negative ion extraction. The code has also shown that in the type of sources contemplated for ITER, which operate at large arc power densities (>1 W cm-3), negative ions can reach the extraction region provided if they are produced at a distance lower than 2 cm from the plasma grid in the case of «volume production» (dissociative attachment processes), or if they are produced at the plasma grid surface, in the vicinity of the extraction holes.
Amadei, Gianluca; Ross, Brian M
2011-01-15
The reactions of H(3) O(+) , NO(+) and O 2+ with twelve terpenoids and one terpene, all of which occur naturally in plants and which possess important smell and flavourant properties, were characterized using Selected Ion Flow Tube Mass Spectrometry (SIFT-MS). The H(3) O(+) reactions resulted primarily in the formation of the proton transfer product and occasionally in a water elimination product. The NO(+) reactions instead generated the charge transfer product or NO(+) adducts, and occasionally alkyl fragments, or resulted in hydride abstraction. Reaction with O 2+ caused a higher fragmentation of the terpenoids with the molecular ion being the minor product of most reactions. Identification and quantification of each compound in complex mixtures are probably possible in most cases using the H(3) O(+) and/or NO(+) precursors while O 2+ may be useful for isomer discrimination. Our data suggests that SIFT-MS may be a useful tool for the rapid analysis of these compounds in plants and derived foodstuffs. Copyright © 2010 John Wiley & Sons, Ltd.
Ion composition variety and variability around perihelion
NASA Astrophysics Data System (ADS)
Beth, Arnaud; Altwegg, Kathrin; Behar, Étienne; Broiles, Tom; Burch, Jim; Carr, Christopher; Eriksson, Anders; Galand, Marina; Goetz, Charlotte; Henri, Pierre; Heritier, Kévin; Nilsson, Hans; Odelstad, Elias; Richter, Ingo; Rubin, Martin; Vallieres, Xavier
2017-04-01
For two years, the Double Focusing Mass Spectrometer (DFMS), one of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) onboard Rosetta probed the neutral gas and the plasma composition of the comet 67P/Churyumov-Gerasimenko's coma (67P). Major ion species detected include water ions (e.g, H2O+, H3O+, HO+) observed throughout the escorting phase. The analysis of DFMS data revealed a large zoo of ion species near perihelion (summer 2015). In particular, protonated versions of high proton affinity neutrals (e.g., NH4+) were detected, but also hydrocarbon and organic ion species. Near perihelion, ion composition was also highly variable and showed interesting variations in the complexity of the observed ion species. We will first present an overview of the rich variety of ion species observed during perihelion. This study will be supported by ionospheric modeling of ion composition below the ion exobase. We will then show an intercomparison between DFMS data and Rosetta Plasma Consortium (RPC) plasma and particle data to interpret the DFMS ion composition variability. Our primary goal is to highlight any correlation between observations from these different instruments (i.e. ion composition, ion and electron number density, energy distribution, magnetic field) and to find relevant signatures of physical processes which can affect the chemistry and dynamics (e.g., acceleration and deflection) of the involved neutral and ion species.
Fortunato, Angelo
2017-08-01
The transition of cells from the epithelial to the mesenchymal state (EMT) plays an important role in tumor progression. EMT allows cells to acquire mobility, stem-like behavior and resistance to apoptosis and drug treatment. These features turn EMT into a central process in tumor biology. Ion channels are attractive targets for the treatment of cancer since they play critical roles in controlling a wide range of physiological processes that are frequently deregulated in cancer. Here, we investigated the role of ether-a-go-go-related 1 (hERG1) ion channels in the EMT of colorectal cancer cells. We studied the epithelial-mesenchymal profile of different colorectal cancer-derived cell lines and the expression of hERG1 potassium channels in these cell lines using real-time PCR. Next, we knocked down hERG1 expression in HCT116 cells using lentivirus mediated RNA interference and characterized the hERG1 silenced cells in vitro and in vivo. Finally, we investigated the capacity of riluzole, an ion channel-modulating drug used in humans to treat amyotrophic lateral sclerosis, to reduce the resistance of the respective colorectal cancer cells to the chemotherapeutic drug cisplatin. We found that of the colorectal cancer-derived cell lines tested, HCT116 showed the highest mesenchymal profile and a high hERG1 expression. Subsequent hERG1 expression knockdown induced a change in cell morphology, which was accompanied by a reduction in the proliferative and tumorigenic capacities of the cells. Notably, we found that hERG1expression knockdown elicited a reversion of the EMT profile in HCT116 cells with a reacquisition of the epithelial-like profile. We also found that riluzole increased the sensitivity of HCT116 cisplatin-resistant cells to cisplatin. Our data indicate that hERG1 plays a role in the EMT of colorectal cancer cells and that its knockdown reduces the proliferative and tumorigenic capacities of these cells. In addition, we conclude that riluzole may be used in
An all permanent magnet electron cyclotron resonance ion source for heavy ion therapy.
Cao, Yun; Li, Jia Qing; Sun, Liang Ting; Zhang, Xue Zhen; Feng, Yu Cheng; Wang, Hui; Ma, Bao Hua; Li, Xi Xia
2014-02-01
A high charge state all permanent Electron Cyclotron Resonance ion source, Lanzhou All Permanent ECR ion source no. 3-LAPECR3, has been successfully built at IMP in 2012, which will serve as the ion injector of the Heavy Ion Medical Machine (HIMM) project. As a commercial device, LAPECR3 features a compact structure, small size, and low cost. According to HIMM scenario more than 100 eμA of C(5+) ion beam should be extracted from the ion source, and the beam emittance better than 75 π*mm*mrad. In recent commissioning, about 120 eμA of C(5+) ion beam was got when work gas was CH4 while about 262 eμA of C(5+) ion beam was obtained when work gas was C2H2 gas. The design and construction of the ion source and its low-energy transportation beam line, and the preliminary commissioning results will be presented in detail in this paper.
Ion-ion charge exchange processes. Final technical report, June 1, 1977-May 31, 1978
DOE Office of Scientific and Technical Information (OSTI.GOV)
Poe, R.T.; Choi, B.H.
Under the auspices of ERDA, we have undertaken a vigorous study of ion-ion charge exchange process pertinent to the storage-ring configurations in the heavy-ion fusion program. One particular reaction, singly charged helium charge exchange, was investigated in detail. General trend of the singly charged heavy-ion charge exchange reaction can be inferred from the present study. Some of our results were presented at Proceedings of the Heavy-Ion Fusion Workshop, Argonne National Laboratory (September 1978) as a paper entitled Charge Exchange Between Singly Ionized Helium Ions, by B.H. Choi, R.T. Poe and K.T. Tang. Here, we briefly describe our method and reportmore » the results.« less
NASA Astrophysics Data System (ADS)
Peko, B. L.; Stephen, T. M.
2000-12-01
Measured absolute detection efficiencies are presented for H, H - and H n+ ( n=1,2,3) impacting a commercially available, dual multichannel plate (MCP) electron multiplier at kinetic energies ranging from 30 to 1000 eV. Measurements involving isotopic substitutions (D, D -, D n+) and Ar + are also presented. In addition, atomic hydrogen detection efficiencies relative to those of H + and H - are given, as they may have a more universal application. For the three charge states, H, H + and H -, the absolute detection efficiencies are markedly different at low energies and converge to a nearly uniform value of ˜70% with increasing projectile energy. The energy dependence is strongest for H +, varying nearly three orders of magnitude over the energy range studied, and weakest for H -, varying by less than one order of magnitude. In general, for the low energy positive ions at a given energy, the lighter the incident particle mass, the greater the probability of its detection.
NASA Astrophysics Data System (ADS)
Okada, Katsuyuki; Komatsu, Shojiro; Matsumoto, Seiichiro
2003-11-01
Ion energy distributions (IEDs) and the density of CH3 radicals (n) in a 13.56 MHz radio frequency (rf) low pressure inductively coupled CH4/H2 plasma used for nanocrystalline diamond deposition have been investigated with a quadrupole mass spectrometer. The energy distributions of positive ions were measured in a CH4/H2 plasma with 50 mTorr of the gas pressure at 500 W of the plasma input power, and were compared with those of an Ar plasma. We have found that the IEDs of Ar+, CH4+, and C2H5+ have a nearly monoenergetic peak, and a hump due to a small degree of capacitive coupling. The plasma potentials obtained from the peaks are consistent with the previously reported values measured with a Langmuir probe. On the other hand, the IEDs of H+, H2+, and H3+ have a clear asymmetric double peak due to the modulation of rf driven glow discharge. The n monotonously increases with increasing pressure. The n indicates that CH3 radicals are main precursors for the growth of nanocrystalline diamond. The estimated sticking coefficient of the CH3 radical is comparable with the reported value.
Shi, Ruili; Li, Keyao; Su, Yan; Tang, Lingli; Huang, Xiaoming; Sai, Linwei; Zhao, Jijun
2018-05-07
Using a genetic algorithm incorporated with density functional theory, we explore the ground state structures of protonated water clusters H + (H 2 O) n with n = 10-17. Then we re-optimize the isomers at B97-D/aug-cc-pVDZ level of theory. The extra proton connects with a H 2 O molecule to form a H 3 O + ion in all H + (H 2 O) 10-17 clusters. The lowest-energy structures adopt a monocage form at n = 10-16 and core-shell structure at n = 17 based on the MP2/aug-cc-pVTZ//B97-D/aug-cc-pVDZ+ZPE single-point-energy calculation. Using second-order vibrational perturbation theory, we further calculate the infrared spectra with anharmonic correction for the ground state structures of H + (H 2 O) 10-17 clusters at the PBE0/aug-cc-pVDZ level. The anharmonic correction to the spectra is crucial since it reproduces the experimental results quite well. The extra proton weakens the O-H bond strength in the H 3 O + ion since the Wiberg bond order of the O-H bond in the H 3 O + ion is smaller than that in H 2 O molecules, which causes a red shift of the O-H stretching mode in the H 3 O + ion.
NASA Astrophysics Data System (ADS)
Shi, Ruili; Li, Keyao; Su, Yan; Tang, Lingli; Huang, Xiaoming; Sai, Linwei; Zhao, Jijun
2018-05-01
Using a genetic algorithm incorporated with density functional theory, we explore the ground state structures of protonated water clusters H+(H2O)n with n = 10-17. Then we re-optimize the isomers at B97-D/aug-cc-pVDZ level of theory. The extra proton connects with a H2O molecule to form a H3O+ ion in all H+(H2O)10-17 clusters. The lowest-energy structures adopt a monocage form at n = 10-16 and core-shell structure at n = 17 based on the MP2/aug-cc-pVTZ//B97-D/aug-cc-pVDZ+ZPE single-point-energy calculation. Using second-order vibrational perturbation theory, we further calculate the infrared spectra with anharmonic correction for the ground state structures of H+(H2O)10-17 clusters at the PBE0/aug-cc-pVDZ level. The anharmonic correction to the spectra is crucial since it reproduces the experimental results quite well. The extra proton weakens the O-H bond strength in the H3O+ ion since the Wiberg bond order of the O-H bond in the H3O+ ion is smaller than that in H2O molecules, which causes a red shift of the O-H stretching mode in the H3O+ ion.
NASA Astrophysics Data System (ADS)
Fakih, Ibrahim; Sabri, Shadi; Mahvash, Farzaneh; Nannini, Matthieu; Siaj, Mohamed; Szkopek, Thomas
2014-08-01
We have fabricated and characterized large area graphene ion sensitive field effect transistors (ISFETs) with tantalum pentoxide sensing layers and demonstrated pH sensitivities approaching the Nernstian limit. Low temperature atomic layer deposition was used to deposit tantalum pentoxide atop large area graphene ISFETs. The charge neutrality point of graphene, inferred from quantum capacitance or channel conductance, was used to monitor surface potential in the presence of an electrolyte with varying pH. Bare graphene ISFETs exhibit negligible response, while graphene ISFETs with tantalum pentoxide sensing layers show increased sensitivity reaching up to 55 mV/pH over pH 3 through pH 8. Applying the Bergveld model, which accounts for site binding and a Guoy-Chapman-Stern picture of the surface-electrolyte interface, the increased pH sensitivity can be attributed to an increased buffer capacity reaching up to 1014 sites/cm2. ISFET response was found to be stable to better than 0.05 pH units over the course of two weeks.
Zhang, Huacheng; Hou, Xu; Yang, Zhe; Yan, Dadong; Li, Lin; Tian, Ye; Wang, Huanting; Jiang, Lei
2015-02-18
Inspired by biological asymmetric ion channels, new shape-tunable and pH-responsive asymmetric hourglass single nanochannel systems demonstrate unique ion-transport properties. It is found that the change in shape and pH cooperatively control the ion transport within the nanochannel ranging from asymmetric shape with asymmetric ion transport, to asymmetric shape with symmetric ion transport and symmetric shape with symmetric ion transport. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Progress Towards a High-Precision Infrared Spectroscopic Survey of the H_3^+ Ion
NASA Astrophysics Data System (ADS)
Perry, Adam J.; Hodges, James N.; Markus, Charles R.; Kocheril, G. Stephen; Jenkins, Paul A., II; McCall, Benjamin J.
2015-06-01
The trihydrogen cation, H_3^+, represents one of the most important and fundamental molecular systems. Having only two electrons and three nuclei, H_3^+ is the simplest polyatomic system and is a key testing ground for the development of new techniques for calculating potential energy surfaces and predicting molecular spectra. Corrections that go beyond the Born-Oppenheimer approximation, including adiabatic, non-adiabatic, relativistic, and quantum electrodynamic corrections are becoming more feasible to calculate. As a result, experimental measurements performed on the H_3^+ ion serve as important benchmarks which are used to test the predictive power of new computational methods. By measuring many infrared transitions with precision at the sub-MHz level it is possible to construct a list of the most highly precise experimental rovibrational energy levels for this molecule. Until recently, only a select handful of infrared transitions of this molecule have been measured with high precision (˜ 1 MHz). Using the technique of Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy, we are aiming to produce the largest high-precision spectroscopic dataset for this molecule to date. Presented here are the current results from our survey along with a discussion of the combination differences analysis used to extract the experimentally determined rovibrational energy levels. O. Polyansky, et al., Phil. Trans. R. Soc. A (2012), 370, 5014. M. Pavanello, et al., J. Chem. Phys. (2012), 136, 184303. L. Diniz, et al., Phys. Rev. A (2013), 88, 032506. L. Lodi, et al., Phys. Rev. A (2014), 89, 032505. J. Hodges, et al., J. Chem. Phys (2013), 139, 164201.
NASA Technical Reports Server (NTRS)
Thorne, L. R.; Anicich, V. G.; Huntress, W. T.
1983-01-01
The reactions of PH(n)+ ions (n = 0-3) were examined with a number of neutrals using ion-cyclotron-resonance techniques. The reactions examined have significance for the distribution of phosphorus in interstellar molecules. The results indicate that interstellar molecules containing the P-O bond are likely to be more abundant than those containing the P-H bond.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lu, W., E-mail: luwang@impcas.ac.cn; University of Chinese Academy of Sciences, Beijing 100049; Li, J. Y.
2014-02-15
The 320 kV platform for multi-discipline research with highly charged ions is a heavy ion beam acceleration instrument developed by Institute of Modern Physics, which is dedicated to basic scientific researches such as plasma, atom, material physics, and astrophysics, etc. The platform has delivered ion beams of 400 species for 36 000 h. The average operation time is around 5000 h/year. With the beams provided by the platform, lots of outstanding progresses were made in various research fields. The ion source of the platform is an all-permanent magnet electron cyclotron resonance ion source, LAPECR2 (Lanzhou All Permanent ECR ion source No.more » 2). The maximum axial magnetic fields are 1.28 T at injection and 1.07 T at extraction, and the radial magnetic field is up to 1.21 T at the inner wall of the plasma chamber. The ion source is capable to produce low, medium, and high charge state gaseous and metallic ion beams, such as H{sup +}, {sup 40}Ar{sup 8+}, {sup 129}Xe{sup 30+}, {sup 209}Bi{sup 33+}, etc. This paper will present the latest result of LAPECR2 and the routine operation status for the high voltage platform.« less
NASA Technical Reports Server (NTRS)
Elliott, H. A.; Comfort, R. H.; Craven, P. D.; Moore, T. E.; Russell, C. T.; Rose, M. Franklin (Technical Monitor)
2001-01-01
We examine ionospheric outflows in the high altitude magnetospheric polar cap during the POLAR satellite's apogee on April 19, 1996 using the Thermal Ion Dynamics Experiment (TIDE) instrument. The elevated levels of O(+) observed in this pass may be due to the geophysical conditions during and prior to the apogee pass. In addition to the high abundance of O(+) relative to H(+), several other aspects of this data are noteworthy. We observe relationships between the density, velocity, and temperature which appear to be associated with perpendicular heating and the mirror force, rather than adiabatic expansion. The H(+) outflow is at a fairly constant flux which is consistent with being source limited by charge exchange at lower altitudes. Local centrifugal acceleration in the polar cap is found to be insufficient to account for the main variations we observe in the outflow velocity. The solar wind speed is high during this pass approximately 700 kilometers per second, and there are Alfve'n waves present in the solar wind such that the solar wind speed and IMF Bx are correlated. In this pass both the H(+) and O(+) outflow velocities correlate with both the solar wind speed and IMF fluctuations. Polar cap magnetometer and Hydra electron data show the same long period wave structure as found in the solar wind and polar cap ion outflow. In addition, the polar cap Poynting flux along the magnetic field direction correlates well with the H(+) temperature (R=0.84). We conclude that the solar wind can drive polar cap ion outflow particularly during polar squalls by setting up a parallel drop that is tens of eV which then causes the ion outflow velocity of O(+) and H(+), the electrons, and magnetic perturbations to vary in a similar fashion.
Coexisting stable conformations of gaseous protein ions.
Suckau, D; Shi, Y; Beu, S C; Senko, M W; Quinn, J P; Wampler, F M; McLafferty, F W
1993-01-01
For further insight into the role of solvent in protein conformer stabilization, the structural and dynamic properties of protein ions in vacuo have been probed by hydrogen-deuterium exchange in a Fourier-transform mass spectrometer. Multiply charged ions generated by electrospray ionization of five proteins show exchange reactions with 2H2O at 10(-7) torr (1 torr = 133.3 Pa) exhibiting pseudo-first-order kinetics. Gas-phase compactness of the S-S cross-linked RNase A relative to denatured S-derivatized RNase A is indicated by exchange of 35 and 135 hydrogen atoms, respectively. For pure cytochrome c ions, the existence of at least three distinct gaseous conformers is indicated by the substantially different values--52, 113, and 74--of reactive H atoms; the observation of these same values for ions of a number--2, 7, and 5, respectively--of different charge states indicates conformational insensitivity to coulombic forces. For each of these conformers, the compactness in vacuo indicated by these values corresponds directly to that of a known conformer structure in the solution from which the conformer ions are produced by electrospray. S-derivatized RNase A ions also exist as at least two gaseous conformers exchanging 50-140 H atoms. Gaseous conformer ions are isometrically stable for hours; removal of solvent greatly increases conformational rigidity. More specific ion-molecule reactions could provide further details of conformer structures. Images PMID:8381533
DOE Office of Scientific and Technical Information (OSTI.GOV)
Schiesko, L., E-mail: loic.schiesko@ipp.mpg.de; Hopf, C.; Höschen, T.
2015-04-08
In a proof-of-principle study, molybdenum samples were implanted with a very small dose of Cs in order to test the properties of the compound as a surface converter for negative hydrogen ion production. First results on the properties of Cs doped Mo compounds show a reduction of the work function and a stable H{sup −} yield up to four hours in low density hydrogen plasma. The implanted Cs atoms were stable in the Mo lattice over one year for samples stored in vacuum and not exposed to the plasma. The surface H{sup −} generation mechanisms were identified and a comparisonmore » of the negative ion yield with pure Mo showed that the Cs doped Mo sample’s yield was much larger.« less
Hu, Xia; Wang, Chunyan; Wang, Le; Zhang, Ranran; Chen, Hui
2014-04-01
The bark beetle Dendroctonus armandi is able to kill living Pinus armandi and has caused serious damage to pine forest in Northern China. As the most important symbiotic fungus of D. armandi, Leptographium qinlingensis plays an important role in the invasion process of the bark beetle. The laccase secreted by it are involved in lignin degradation to provide utilizable nutrition for D. armandi, and catalyze some biochemical reactions, causing the damages of tree tissue. In present study, the extracellular laccase of L. qinlingensis was purified by using the ammonium sulfate precipitation and DEAE-cellulose (DE-52) column chromatography. Furthermore, the effects of temperature, pH value and metal ions on it were investigated and characterized. The purified enzyme exerted its optimal activity with guaiacol. The catalytic efficiencies K(m) and V(max) determined for substrate guaiacol were 15.4 μM and 372.9 IU mg⁻¹, respectively. The optimum pH and temperature for the purified enzyme was 4.4 and 45 °C, respectively, with the highest enzyme specific activity of 7,000 IU mg⁻¹. Moreover, the metal ions, Co²⁺, Mn²⁺, Ca²⁺, Mg²⁺, Fe²⁺ and Cd²⁺, especially Hg²⁺, showed significantly inhibition effects on its activity. To understand the characteristics of this laccase might provide an opportunity and theoretical basis to promote integrated pest management of D. armandi.
NASA Technical Reports Server (NTRS)
Grebowsky, J. M.; Hartle, R. E.; Kar, J.; Cloutier, P. A.; Taylor, H. A., Jr.; Brace, L. H.
1993-01-01
During the final, low solar activity phase of the Pioneer Venus (PV) mission, the Orbiter Ion Mass Spectrometer (OIMS) measurements found all ion species, in the midnight-dusk sector, reduced in concentration relative to that observed at solar maximum. Molecular ion species comprised a greater part of the total ion concentration as O(+) and H(+) had the greatest depletions. The nightside ionospheric states were strikingly similar to the isolated solar maximum 'disappearing' ionospheres. Both are very dynamic states characterized by a rapidly drifting plasma and 30-100 eV superthermal O(+) ions.
Ion Exchange Method - Diffusion Barrier Investigations
NASA Astrophysics Data System (ADS)
Pielak, G.; Szustakowski, M.; Kiezun, A.
1990-01-01
Ion exchange method is used to GRIN-rod lenses manufacturing. In this process the ion exchange occurs between bulk glass (rod) and a molten salt. It was find that diffusion barrier exists on a border of glass surface and molten salt. The investigations of this barrier show that it value varies with ion exchange time and process temperature. It was find that in the case when thalium glass rod was treated in KNO3, bath, the minimum of the potential after 24 h was in temperature of 407°C, after 48 h in 422°C, after 72 h in 438°C and so on. So there are the possibility to keep the minimum of diffusion barrier by changing the temperature of the process and then the effectiveness of ion exchange process is the most effective. The time needed to obtain suitable refractive index distribution in a process when temperature was linearly changed from 400°C to 460°C was shorter of about 30% compare with the process in which temperature was constant and equal 450°C.
Negative hydrogen ion sources for accelerators
DOE Office of Scientific and Technical Information (OSTI.GOV)
Moehs, D.P.; /Fermilab; Peters, J.
2005-08-01
A variety of H{sup -} ion sources are in use at accelerator laboratories around the world. A list of these ion sources includes surface plasma sources with magnetron, Penning and surface converter geometries as well as magnetic-multipole volume sources with and without cesium. Just as varied is the means of igniting and maintaining magnetically confined plasmas. Hot and cold cathodes, radio frequency, and microwave power are all in use, as well as electron tandem source ignition. The extraction systems of accelerator H{sup -} ion sources are highly specialized utilizing magnetic and electric fields in their low energy beam transport systemsmore » to produce direct current, as well as pulsed and/or chopped beams with a variety of time structures. Within this paper, specific ion sources utilized at accelerator laboratories shall be reviewed along with the physics of surface and volume H{sup -} production in regard to source emittance. Current research trends including aperture modeling, thermal modeling, surface conditioning, and laser diagnostics will also be discussed.« less
NASA Astrophysics Data System (ADS)
Heikes, Brian G.; Treadaway, Victoria; McNeill, Ashley S.; Silwal, Indira K. C.; O'Sullivan, Daniel W.
2018-04-01
An ion-neutral chemical kinetic model is described and used to simulate the negative ion chemistry occurring within a mixed-reagent ion chemical ionization mass spectrometer (CIMS). The model objective was the establishment of a theoretical basis to understand ambient pressure (variable sample flow and reagent ion carrier gas flow rates), water vapor, ozone and oxides of nitrogen effects on ion cluster sensitivities for hydrogen peroxide (H2O2), methyl peroxide (CH3OOH), formic acid (HFo) and acetic acid (HAc). The model development started with established atmospheric ion chemistry mechanisms, thermodynamic data and reaction rate coefficients. The chemical mechanism was augmented with additional reactions and their reaction rate coefficients specific to the analytes. Some existing reaction rate coefficients were modified to enable the model to match laboratory and field campaign determinations of ion cluster sensitivities as functions of CIMS sample flow rate and ambient humidity. Relative trends in predicted and observed sensitivities are compared as instrument specific factors preclude a direct calculation of instrument sensitivity as a function of sample pressure and humidity. Predicted sensitivity trends and experimental sensitivity trends suggested the model captured the reagent ion and cluster chemistry and reproduced trends in ion cluster sensitivity with sample flow and humidity observed with a CIMS instrument developed for atmospheric peroxide measurements (PCIMSs). The model was further used to investigate the potential for isobaric compounds as interferences in the measurement of the above species. For ambient O3 mixing ratios more than 50 times those of H2O2, O3-(H2O) was predicted to be a significant isobaric interference to the measurement of H2O2 using O2-(H2O2) at m/z 66. O3 and NO give rise to species and cluster ions, CO3-(H2O) and NO3-(H2O), respectively, which interfere in the measurement of CH3OOH using O2-(CH3OOH) at m/z 80. The CO3-(H2O
NASA Technical Reports Server (NTRS)
Taylor, H. A., Jr.; Mayr, H.; Brinton, H.; Niemann, H.; Hartle, R.; Daniell, R. E., Jr.
1982-01-01
A comparison of ion and neutral composition measurements at Venus for periods of greatly different solar activity provides qualitative evidence of solar control of the day-to-night transport of light ion and neutral species. Concentrations of H(+) and He in the predawn bulge near solar maximum in November, 1979, exhibit a depletion signature correlated with a pronounced modulation in the solar F10.7 and EUV fluxes. This perturbation, not observed in the predawn region during an earlier period of relative quiet solar conditions, is interpreted as resulting from pronounced changes in solar heating and photoionization on the dayside, which in turn modulate the transport of ions and neutrals into the bulge region.
NASA Technical Reports Server (NTRS)
Dominquez, Jesus; Barile, Ron
2006-01-01
Polarography is the measurement of the current that flows in solution as a function of an applied voltage. The actual form of the observed polarographic current depends upon the manner in which the voltage is applied and on the characteristics of the working electrode. The new gas polarographic H2 sensor shows a current level increment with concentration of the gaseous H2 similar to those relating to metal ions in liquid electrolytes in well-known polarography. This phenomenon is caused by the fact that the diffusion of the gaseous H2 through a gas diffusion hole built in the sensor is a rate-determining step in the gaseous-hydrogen sensing mechanism. The diffusion hole artificially limits the diffusion of the gaseous H2 toward the electrode located at the sensor cavity. This gas polarographic H2 sensor is actually an electrochemical-pumping cell since the gaseous H2 is in fact pumped via the electrochemical driving force generated between the electrodes. Gaseous H2 enters the diffusion hole and reaches the first electrode (anode) located in the sensor cavity to be transformed into an H ions or protons; H ions pass through the electrolyte and reach the second electrode (cathode) to be reformed to gaseous H2. Gas polarographic O2 sensors are commercially available; a gas polarographic O2 sensor was used to prove the feasibility of building a new gas polarographic H2 sensor.
Ajji, Zaki; Ali, Ali M
2010-01-15
Acrylic acid (AAc), N-vinyl imidazole (Azol) and their binary mixtures were graft copolymerized onto poly(vinyl alcohol) membranes using gamma irradiation. The ability of the grafted membranes to separate Cu ions from Fe ions was investigated with respect to the grafting yield and the pH of the feed solution. The data showed that the diffusion of copper ions from the feed compartment to the receiver compartment depends on the grafting yield of the membranes and the pH of the feed solution. To the contrary, iron ions did not diffuse through the membranes of all grafting yields. However, a limited amount of iron ions diffused in strong acidic medium. This study shows that the prepared membranes could be considered for the separation of copper ions from iron ions. The temperature of thermal decomposition of pure PVA-g-AAc/Azol membrane, PVA-g-AAc/Azol membrane containing copper ions, and PVA-g-AAc/Azol membrane containing iron ions were determined using TGA analyzer. It was shown that the presence of Cu and Fe ions increases the decomposition temperature, and the membranes bonded with iron ions are more stable than those containing copper ions.
Leite, Andreia; Silva, Ana M G; Cunha-Silva, Luís; de Castro, Baltazar; Gameiro, Paula; Rangel, Maria
2013-05-07
In the present work we describe the structure and the spectroscopic characterization of a spirocyclic derivative of a rhodamine B ligand whose properties allow discrimination of light-up effects induced by metal ion chelation and variation of pH. Distinction of the two effects is important for the use of this type of ligand to detect and monitor metal ions in aqueous solutions. The synthesis of the ligand was performed in two steps, which involve the reaction of rhodamine B with hydrazine hydrate to form rhodamine B hydrazide followed by condensation with 2-pyridinecarboxaldehyde and was successfully optimized using a solvent free approach under microwave irradiation. The ligand was obtained in the expected spirolactam form and was characterized in the solid state by EA, MS and single-crystal X-ray diffraction. The ligand was characterized in solution by NMR and absorption and fluorescence spectroscopies and its properties were found to be sensitive to pH and concentration of iron(III). The study of the fluorescence properties at variable pH shows that the compound is fluorescent in the range 2 < pH < 4 with maximum intensity at pH 3 and allowed the determination of two pK(a) values (pK(a1) = 2.98, pK(a2) = 2.89) and establishment of the corresponding distribution diagram. The very low pK(a) values guarantee that above pH equal to 4 the ligand is mostly present in the fully non-protonated and non-fluorescent form L. The study of the interaction of the ligand with iron(iii) was performed in DMSO and DMSO-H(2)O to exclude the influence of pH and due to the low solubility of the compound. The results indicate that the presence of iron(III) triggers the opening of the spirolactam form of the ligand and the maximum intensity obtained at a metal : ligand ratio of 1 : 2 is consistent with the formation of an iron(III) complex with the tridentate ligand.
Fournier, Joseph A.; Wolke, Conrad T.; Johnson, Christopher J.; Johnson, Mark A.; Heine, Nadja; Gewinner, Sandy; Schöllkopf, Wieland; Esser, Tim K.; Fagiani, Matias R.; Knorke, Harald; Asmis, Knut R.
2014-01-01
Theoretical models of proton hydration with tens of water molecules indicate that the excess proton is embedded on the surface of clathrate-like cage structures with one or two water molecules in the interior. The evidence for these structures has been indirect, however, because the experimental spectra in the critical H-bonding region of the OH stretching vibrations have been too diffuse to provide band patterns that distinguish between candidate structures predicted theoretically. Here we exploit the slow cooling afforded by cryogenic ion trapping, along with isotopic substitution, to quench water clusters attached to the H3O+ and Cs+ ions into structures that yield well-resolved vibrational bands over the entire 215- to 3,800-cm−1 range. The magic H3O+(H2O)20 cluster yields particularly clear spectral signatures that can, with the aid of ab initio predictions, be traced to specific classes of network sites in the predicted pentagonal dodecahedron H-bonded cage with the hydronium ion residing on the surface. PMID:25489068
Fournier, Joseph A.; Wolke, Conrad T.; Johnson, Christopher J.; ...
2014-12-08
Here, theoretical models of proton hydration with tens of water molecules indicate that the excess proton is embedded on the surface of clathrate-like cage structures with one or two water molecules in the interior. The evidence for these structures has been indirect, however, because the experimental spectra in the critical H-bonding region of the OH stretching vibrations have been too diffuse to provide band patterns that distinguish between candidate structures predicted theoretically. Here we exploit the slow cooling afforded by cryogenic ion trapping, along with isotopic substitution, to quench water clusters attached to the H 3O + and Cs +more » ions into structures that yield well-resolved vibrational bands over the entire 215- to 3,800-cm -1 range. The magic H 3O +(H 2O) 20 cluster yields particularly clear spectral signatures that can, with the aid of ab initio predictions, be traced to specific classes of network sites in the predicted pentagonal dodecahedron H-bonded cage with the hydronium ion residing on the surface.« less
Modeling of negative ion transport in a plasma source
DOE Office of Scientific and Technical Information (OSTI.GOV)
Riz, David; Departement de Recherches sur la Fusion Controelee CE Cadarache, 13108 St Paul lez Durance; Pamela, Jerome
1998-08-20
A code called NIETZSCHE has been developed to simulate the negative ion transport in a plasma source, from their birth place to the extraction holes. The ion trajectory is calculated by numerically solving the 3-D motion equation, while the atomic processes of destruction, of elastic collision H{sup -}/H{sup +} and of charge exchange H{sup -}/H{sup 0} are handled at each time step by a Monte-Carlo procedure. This code can be used to calculate the extraction probability of a negative ion produced at any location inside the source. Calculations performed with NIETZSCHE have allowed to explain, either quantitatively or qualitatively, severalmore » phenomena observed in negative ion sources, such as the isotopic H{sup -}/D{sup -} effect, and the influence of the plasma grid bias or of the magnetic filter on the negative ion extraction. The code has also shown that in the type of sources contemplated for ITER, which operate at large arc power densities (>1 W cm{sup -3}), negative ions can reach the extraction region provided if they are produced at a distance lower than 2 cm from the plasma grid in the case of 'volume production' (dissociative attachment processes), or if they are produced at the plasma grid surface, in the vicinity of the extraction holes.« less
Fine-tuning to minimize emittances of J-PARC RF-driven H{sup −} ion source
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.
2016-02-15
The Japan Proton Accelerator Research Complex (J-PARC) cesiated RF-driven H{sup −} ion source has been successfully operated for about one year. By the world’s brightest level beam, the J-PARC design beam power of 1 MW was successfully demonstrated. In order to minimize the transverse emittances, the rod-filter-field (RFF) was optimized by changing the triple-gap-lengths of each of pairing five piece rod-filter-magnets. The larger emittance degradation seems to be caused by impurity-gases than the RFF. The smaller beam-hole-diameter of the extraction electrode caused the more than expected improvements on not only the emittances but also the peak beam intensity.
Ion Composition of Comet 19P/Borrelly as Measured by the PEPE Ion Mass Spectrometer on DS1
NASA Astrophysics Data System (ADS)
Nordholt, J. E.; Reisenfeld, D. B.; Wiens, R. C.; Gary, P.
2002-12-01
Cometary compositions are of great interest because they hold important clues to the formation of the outer solar system, and to the sources of volatiles in the solar system, including the terrestrial planets. In order to understand the primordial compositions of cometary nuclei, it is important to also understand their evolution, as many of the comets most accessible to spacecraft are highly evolved. It is also important to understand the ion and neutral chemistry that occurs in the coma surrounding the nucleus if the coma ion composition is to be used to determine the original composition of the nucleus. Deep Space One (DS1) was only the second spacecraft, after Giotto, to use an ion mass-resolving instrument to explore cometary coma compositions in-situ, which it did during the flyby of Comet Borrelly on September 22, 2001. Borrelly is significantly more evolved than Halley. In addition, the encounter occurred at a significantly greater distance from the sun (1.36 AU vs 0.9 AU for Giotto at Halley). The Plasma Experiment for Planetary Exploration (PEPE) on board DS1 was capable of resolving electron and ion energy, angle of incidence, and ion mass composition. The PEPE ion data from the seven minutes surrounding closest approach (2171 km) have been extensively analyzed. The instrument response was modeled using SIMION and TRIM codes for all of the major species through 20 AMU plus CO (at its operating voltage PEPE was very insensitive to heavier molecules). Chi-squared minimization analysis is being carried out to determine the best fit and the uncertainties. Preliminary results for the predominant heavy ions are OH+ at (72 +/- 9)% of the total water-group ion density, H2O+ at (25 +/- 7)%, CH3+ at (5 +/- 3)%, and O+ at (4 +/- 5)%. Uncertainties are quoted at the 90% confidence level. Comparison with reported Halley compositions from Giotto shows that Borrelly clearly has a lower H3O+ abundance (< 9%), consistent with a more evolved comet. The presence of
Supramolecular gating of ion transport in nanochannels.
Kumar, B V V S Pavan; Rao, K Venkata; Sampath, S; George, Subi J; Eswaramoorthy, Muthusamy
2014-11-24
Several covalent strategies towards surface charge-reversal in nanochannels have been reported with the purpose of manipulating ion transport. However, covalent routes lack dynamism, modularity and post-synthetic flexibility, and hence restrict their applicability in different environments. Here, we introduce a facile non-covalent approach towards charge-reversal in nanochannels (<10 nm) using strong charge-transfer interactions between dicationic viologen (acceptor) and trianionic pyranine (donor). The polarity of ion transport was switched from anion selective to ambipolar to cation selective by controlling the extent of viologen bound to the pyranine. We could also regulate the ion transport with respect to pH by selecting a donor with pH-responsive functional groups. The modularity of this approach further allows facile integration of various functional groups capable of responding to stimuli such as light and temperature to modulate the transport of ions as well as molecules. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Si Oxidation and H 2 Gassing During Aqueous Slurry Preparation for Li-Ion Battery Anodes
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hays, Kevin A.; Key, Baris; Li, Jianlin
Si has the possibility to greatly increase the energy density of Li-ion battery anodes, though it is not without its problems. One issue often overlooked is the decomposition of Si during large scale slurry formulation and battery fabrication. Here, we investigate the mechanism of H 2 production to understand the role of different slurry components and their impact on the Si oxidation and surface chemistry. Mass spectrometry and in situ pressure monitoring identifies that carbon black plays a major role in promoting the oxidation of Si and generation of H 2. Si oxidation also occurs through atmospheric O 2 consumption.more » Both pathways, along with solvent choice, impact the surface silanol chemistry, as analyzed by 1H– 29Si cross-polarization magic angle spinning nuclear magnetic resonance (MAS NMR) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR). An understanding of the oxidation of Si, during slurry processing, provides a pathway toward improving the manufacturing of Si based anodes by maximizing its capacity and minimizing safety hazards.« less
Si Oxidation and H 2 Gassing During Aqueous Slurry Preparation for Li-Ion Battery Anodes
Hays, Kevin A.; Key, Baris; Li, Jianlin; ...
2018-04-24
Si has the possibility to greatly increase the energy density of Li-ion battery anodes, though it is not without its problems. One issue often overlooked is the decomposition of Si during large scale slurry formulation and battery fabrication. Here, we investigate the mechanism of H 2 production to understand the role of different slurry components and their impact on the Si oxidation and surface chemistry. Mass spectrometry and in situ pressure monitoring identifies that carbon black plays a major role in promoting the oxidation of Si and generation of H 2. Si oxidation also occurs through atmospheric O 2 consumption.more » Both pathways, along with solvent choice, impact the surface silanol chemistry, as analyzed by 1H– 29Si cross-polarization magic angle spinning nuclear magnetic resonance (MAS NMR) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR). An understanding of the oxidation of Si, during slurry processing, provides a pathway toward improving the manufacturing of Si based anodes by maximizing its capacity and minimizing safety hazards.« less
Kanagaraj, Kuppusamy; Pitchumani, Kasi
2014-01-01
A simple, highly selective and sensitive colorimetric system for the detection of fluoride ion in an aqueous medium has been developed using 2-(2-hydroxyphenyl)-2,3-dihydroquinolin-4(1H)-one. This system allows selective "turn-on" fluorescence detection of fluoride ion, which is found to be dependent upon guest basicity. An excited-state proton transfer is proposed to be the signaling mechanism, which is rationalized by DFT and TD-DFT calculations. The present sensor can also be applied to detect fluoride levels in real water samples. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Vo, V. T.; Koon, K. L.; Hu, Z. R.; Dharmasiri, C. N.; Subramaniam, S. C.; Rezazadeh, A. A.
2004-04-01
Electrical isolation in multilayer GaAs planar doped barrier (PDB) diode structures produced by H+ and Fe+ ion implantation were investigated. For an H+ bombardment with a dose of 1×1015cm-2, a sheet resistivity as high as 3×108 Ω/sq and thermal stability up to 400 °C has been achieved. For samples bombarded by Fe+ ions, a similar high sheet resistivity has also been achieved although a longer annealing time (15 min) and a higher annealing temperature (550 °C) were needed. The rf dissipation losses of coplanar waveguide (CPW) "thru" lines fabricated on bombarded multilayer PDBD structure samples were also examined. The measured rf losses were 1.65 dB/cm at 10 GHz and 3 dB/cm at 40 GHz, similar to the values that a CPW line exhibits on a semi-isolating GaAs substrate.
Meot-Ner, M
1978-12-01
The CH3+ ion, formed in ionized methane, undergoes consecutive eliminative condensation reactions with methane to form the carbonium ions C2H5+, i-C3H7+ and t-C4H9+. At T smaller than 500 degrees K, NCH4 greater than 10(16) cm-3 these ions react with NH3 in competitive condensation -- H+ transfer reactions, e.g. C2H5 + NH3 M leads to C2H5NH3+ leads to NH4+ + C2H4 At particle densities of NCH4 smaller than 10(16) cm-3 proton transfer is the only significant reaction channel. At NCH4 greater than 10(17) cm-3 condensation constitutes 5--20% of the overall reactions. The product of the condensation reaction further associates with CO2 to form C2H5NH3+ . CO2; the atomic composition of this cluster ion is identical with the protonated amino acid alanine. The carbonium ions i-C3H7+ and t-C4H9+ condense also with HCN to yield protonated isocyanides. HCNH% also appears to condense with HCN at T greater than 570 degrees K, and form cluster ions with HCN at lower temperatures. The rate constants of the condensation reactions vary with temperature and pressure in a complex manner. Under conditions similar to those on Titan at an altitude of 100 km (T = 100--150 degrees K, NCH4 approximately 10(18) cm-3), with a methane atmosphere containing 1% H2 and traces of NH3 and H2O, ion-molecule condensation reactions followed by H+ transfer are expected to lead to the atmospheric synthesis of C2H6, C3H8, CH3OH, C2H5OH and the terminal ions NH4+, CH3NH3+ and C2H5NH3+. At higher temperatures (250 degrees K smaller than T smaller than 400 degrees K), the synthesis of i-C4H10, i-C3H7OH and t-C4H9OH and of the ions i-C3H7NH3+ and t-C4H9NH3+ is also expected. Electron recombination of the terminal ions may yield amines, imines and nitriles. Cycles of protonation and dissociative recombination of the alkanes and alcohols produced in condensation reactions will also produce unsaturated hydrocarbons, ketones and aldehydes in the ionized atmosphere.
NASA Astrophysics Data System (ADS)
Manikandan, Irulappan; Chang, Chien-Huei; Chen, Chia-Ling; Sathish, Veerasamy; Li, Wen-Shan; Malathi, Mahalingam
2017-07-01
Novel benzimidazoquinoline derivative (AVT) was synthesized through a substitution reaction and characterized by various spectral techniques. Analyzing the optical properties of AVT under absorption and emission spectral studies in different environments exclusively with respect to solvents and pH, intriguing characteristics viz. aggregation induced emission enhancement (AIEE) in the THF solvent and 'On-Off' pH sensing were found at neutral pH. Sensing nature of AVT with diverse metal ions and bovine serum albumin (BSA) was also studied. Among the metal ions, Fe3 + ion alone tunes the fluorescence intensity of AVT probe in aqueous medium from ;turn-on; to ;turn-off; through ligand (probe) to metal charge transfer (LMCT) mechanism. The probe AVT in aqueous medium interacts strongly with BSA due to Fluorescence Resonance Energy Transfer (FRET) and the conformational change in BSA was further analyzed using synchronous fluorescence techniques. Docking study of AVT with BSA reveals that the active site of binding is tryptophan residue which is also supported by the experimental results. Interestingly, fluorescent AVT probe in cells was examined through cellular imaging studies using BT-549 and MDA-MB-231 cells. Thus, the single molecule probe based detection of multiple species and stimuli were described.
NASA Astrophysics Data System (ADS)
Kurin-Csörgei, Krisztina; Poros, Eszter; Csepiova, Julianna; Orbán, Miklós
2018-05-01
The coupling of acid-base type pH-dependent equilibria to pH-oscillators expanded significantly the number and type of species which can participate in oscillatory chemical processes. Here, we report a new version of oscillatory phenomena that can appear in coupled oscillators. Oscillations in the oxidation states of the center ion bound in a chelate complex were generated in a combined system, when the participants of the oscillator as dynamical unit and the components of the complex formation interacted with each other through redox reaction. It was demonstrated, when the BrO3- - SO32- pH-oscillator and the Co2+ - histidine complex were mixed in a continuous stirred tank reactor, periodic changes in the pH were accompanied with periodic transitions in the oxidation number of the cobalt ion between +2 and +3. The oscillatory build up and removal of the Co(III)-complex were followed by recording the light absorption at the wavelength characteristic for this species with simultaneous monitoring the pH-oscillations. The dual role of the SO32- ion in the explanation of this observation was pointed out. Its partial and consecutive total oxidations by BrO3- give rise to and maintain sustained pH-oscillations in the combined system and its presence induces the rapid conversion of the Co2+ to a highly inert Co(III)-histidine chelate when the system jumps to and remains in the high pH-state. The oscillatory cycle is completed when the Co(III)-complex is washed out from the reactor and the reagents are replenished by the flow during the time the system spends in the acidic range of pH. The idea, to couple a core oscillator to an equilibrium through a redox reaction that takes place between the constituents of the oscillator and the target species of the linked subsystem, may be generally used to bring about forced oscillations in many other combined chemical systems.
An all permanent magnet electron cyclotron resonance ion source for heavy ion therapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Cao, Yun, E-mail: caoyun@impcas.ac.cn; Li, Jia Qing; Sun, Liang Ting
2014-02-15
A high charge state all permanent Electron Cyclotron Resonance ion source, Lanzhou All Permanent ECR ion source no. 3-LAPECR3, has been successfully built at IMP in 2012, which will serve as the ion injector of the Heavy Ion Medical Machine (HIMM) project. As a commercial device, LAPECR3 features a compact structure, small size, and low cost. According to HIMM scenario more than 100 eμA of C{sup 5+} ion beam should be extracted from the ion source, and the beam emittance better than 75 π*mm*mrad. In recent commissioning, about 120 eμA of C{sup 5+} ion beam was got when work gasmore » was CH{sub 4} while about 262 eμA of C{sup 5+} ion beam was obtained when work gas was C{sub 2}H{sub 2} gas. The design and construction of the ion source and its low-energy transportation beam line, and the preliminary commissioning results will be presented in detail in this paper.« less
Spectrophotometric estimation of bromide ion in excess chloride media.
Adimurthy, S; Susarla, V R K S; Reddy, M P; Ramachandraiah, G
2005-10-31
The redox reaction between bromate and chloride ions in the presence and the absence of two or less equivalents of bromide ion ascertaining the formation of bromine chloride species of type BrCl and BrCl(2)(-) in subsequent reactions in 4% H(2)SO(4), has been studied by spectrophotometry. Calibration graphs for the bromide ion estimation in 0.1% KBrO(3)-4% H(2)SO(4) medium are determined separately in the presence of known amounts of NaCl. The effect of Cl(-) ion percentage on the determination of Br(-) ion is studied and reported herewith a suitable equation for a precise, reliable and quick spectrophotometric estimation.
In situ gas and ion measurements at comet Halley
NASA Astrophysics Data System (ADS)
Krankowsky, D.; Lammerzahl, P.; Herrwerth, I.; Woweries, J.; Eberhardt, P.; Dolder, U.; Herrmann, U.; Schulte, W.; Berthelier, J. J.; Illiano, J. M.; Hodges, R. R.; Hoffman, J. H.
1986-05-01
The neutral mass spectrometer experiment carried by the Giotto spacecraft was designed to determine the abundances and the chemical, elemental and isotopic composition of the gases and low-energy ions in the coma of comet Halley. Its first results show the predominance of water vapour with an H2O density of 4.7x107molecules cm-3 at 1,000 km. Limits on the abundances of CO2, NH3 and CH4 relative to H2O are given. The water-group ions H3O+, H2O+ and OH+ have been unambiguously identified, along with the ions 12C+, 12CH+, 16O+, Na+, 12C2+, 32S+, 34S+ and 56Fe+.
Bythell, Benjamin J; Dain, Ryan P; Curtice, Stephanie S; Oomens, Jos; Steill, Jeffrey D; Groenewold, Gary S; Paizs, Béla; Van Stipdonk, Michael J
2010-04-22
Multiple-stage tandem mass spectrometry and collision-induced dissociation were used to investigate loss of H(2)O or CH(3)OH from protonated versions of GGGX (where X = G, A, and V), GGGGG, and the methyl esters of these peptides. In addition, wavelength-selective infrared multiple photon dissociation was used to characterize the [M + H - H(2)O](+) product derived from protonated GGGG and the major MS(3) fragment, [M + H - H(2)O - 29](+) of this peak. Consistent with the earlier work [ Ballard , K. D. ; Gaskell , S. J. J. Am. Soc. Mass Spectrom. 1993 , 4 , 477 - 481 ; Reid , G. E. ; Simpson , R. J. ; O'Hair , R. A. J. Int. J. Mass Spectrom. 1999 , 190/191 , 209 -230 ], CID experiments show that [M + H - H(2)O](+) is the dominant peak generated from both protonated GGGG and protonated GGGG-OMe. This strongly suggests that the loss of the H(2)O molecule occurs from a position other than the C-terminal free acid and that the product does not correspond to formation of the b(4) ion. Subsequent CID of [M + H - H(2)O](+) supports this proposal by resulting in a major product that is 29 mass units less than the precursor ion. This is consistent with loss of HN horizontal lineCH(2) rather than loss of carbon monoxide (28 mass units), which is characteristic of oxazolone-type b(n) ions. Comparison between experimental and theoretical infrared spectra for a group of possible structures confirms that the [M + H - H(2)O](+) peak is not a substituted oxazolone but instead suggests formation of an ion that features a five-membered ring along the peptide backbone, close to the amino terminus. Additionally, transition structure calculations and comparison of theoretical and experimental spectra of the [M + H - H(2)O - 29](+) peak also support this proposal.
The Narodny ion accelerator as an injector for a small cyclotron
NASA Astrophysics Data System (ADS)
Derenchuk, V.
1985-01-01
A 120 keV electrostatic accelerator is currently in use at the University of Manitoba as an ion implanter. It is proposed to use this accelerator (called the Narodny ion accelerator or NIA), upgraded to 200 keV, as an injector for a small light ion cyclotron. This "minicyclotron" will consist of 6 sectors with four dees operating at 60 kV and variable frequency. The ions will be extracted at about 50 cm radius. The types of ions to be accelerated are H -, H +, D -1, 3He 2+, 4He 2+, 6Li 3+, and 7Li 3+ with a maximum energy of about 4 MeV for the Li ions and between 2 and 3 MeV for the He ions. A beam current of close to 0.5 mA is anticipated for H + and D + ions and high energy resolution ( ΔE/ E ~ 10 -3) is expected for all ions. The marriage of these two accelerators will give a very wide range of ion implantation energies (for certain ion species) as well as a source of particles for Rutherford backscatter analysis.
Ternary recombination of H3+, H2D+, HD2+, and D3+ with electrons in He/Ar/H2/D2 gas mixtures
NASA Astrophysics Data System (ADS)
Kalosi, Abel; Dohnal, Petr; Plasil, Radek; Johnsen, Rainer; Glosik, Juraj
2016-09-01
The temperature dependence of the ternary recombination rate coefficients of H2D+ and HD2+ ions has been studied in the temperature range of 80-150 K at pressures from 500 to 1700 Pa in a stationary afterglow apparatus equipped with a cavity ring-down spectrometer. Neutral gas mixtures consisting of He/Ar/H2/D2 (with typical number densities 1017 /1014 /1014 /1014 cm-3) were employed to produce the desired ionic species and their fractional abundances were monitored as a function of helium pressure and the [D2]/[H2] ratio of the neutral gas. In addition, the translational and the rotational temperature and the ortho to para ratio were monitored for both H2D+ and HD2+ ions. A fairly strong pressure dependence of the effective recombination rate coefficient was observed for both ion species, leading to ternary recombination rate coefficients close to those previously found for (helium assisted) ternary recombination of H3+ and D3+. Work supported by: Czech Science Foundation projects GACR 14-14649P, GACR 15-15077S, GACR P209/12/0233, and by Charles University in Prague Project Nr. GAUK 692214.
NASA Astrophysics Data System (ADS)
Hill, Nicholas C.; Limbach, Patrick A.; Shomo, Ronald E., II; Marshall, Alan G.; Appelhans, Anthony D.; Delmore, James E.
1991-11-01
The coupling of an autoneutralizing SF-6 fast ion-beam gun to a Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometer is described. The fast neutral beam provides for secondary-ion-type FT/ICR mass analysis [e.g., production of abundant pseudomolecular (M+H)+ ions] of involatile samples without the need for external ion injection, since ions are formed at the entrance to the ICR ion trap. The design, construction, and testing of the hybrid instrument are described. The feasibility of the experiment (for both broadband and high-resolution FT/ICR positive-ion mass spectra) is demonstrated with tetra-butylammonium bromide and a Tylenol■ sample. The ability to analyze high molecular weight polymers with high mass resolution is demonstrated for Teflon■. All of the advantages of the fast neutral beam ion source previously demonstrated with quadrupole mass analysis are preserved, and the additional advantages of FT/ICR mass analysis (e.g., high mass resolving power, ion trapping) are retained.
The charge spectrum of positive ions in a hydrogen aurora
NASA Technical Reports Server (NTRS)
Lynch, J.; Pulliam, D.; Leach, R.; Scherb, F.
1976-01-01
An auroral ion charge spectrometer was flown into a hydrogen aurora on a Javelin sounding rocket launched from Churchill, Manitoba. The instrument contained an electrostatic analyzer which selected particles with incident energy per unit charge up to 20 keV/charge and an 80-kV power supply which accelerated these ions onto an array of solid state detectors. Ions tentatively identified as H(+), He(+2), and O(+) were detected from 225 to 820 km in altitude. The experiment did not discriminate between H(+) and He(+), or between O(+), N(+), and C(+). Upper limits of highly charged heavy ion abundances have been set at 20% of the He(+2) and 0.15% of the H(+). It is concluded that both terrestrial and solar wind sources play significant roles in auroral ion precipitation.
NASA Astrophysics Data System (ADS)
Büyükyıldız, M.
2017-09-01
The radiological properties of some vitamins such as Retinol, Beta-carotene, Riboflavin, Niacin, Niacinamide, Pantothenic acid, Pyridoxine, Pyridoxamine, Pyridoxal, Biotin, Folic acid, Ascorbic acid, Cholecalciferol, Alpha-tocopherol, Gamma-tocopherol, Phylloquinone have been investigated with respect to total electron interaction and some heavy charged particle interaction as means of effective atomic numbers (Z_{eff}) and electron densities (N_{eff}) for the first time. Calculations were performed for total electron interaction and heavy ions such as H, He and C ion interactions in the energy region 10keV-10MeV by using a logarithmic interpolation method. Variations in Z_{eff}'s and N_{eff}'s of given vitamins have been studied according to the energy of electron or heavy charged particles, and significant variations have been observed for all types of interaction in the given energy region. The maximum values of Z_{eff} have been found in the different energy regions for different interactions remarkably and variations in N_{eff} seem approximately to be the same with variation in Z_{eff} for the given vitamins as expected. Z_{eff} values of some vitamins were plotted together and compared with each other for electron, H, He and C interactions and the ratios of Z_{eff}/ < A > have been changed in the range of 0.25-0.36, 0.20-0.36, 0.22-0.35 and 0.20-0.35 for electron, H, He and C interactions, respectively.
The effects of CO2 on the negative reactant ions of IMS
NASA Technical Reports Server (NTRS)
Spangler, Glenn E.
1995-01-01
In the presence of CO2, the negative reactant ions of ion mobility spectrometry (IMS) are ion clusters of CO4(-) and CO3(-). Methyl salicylate is ionized by the CO4(-)(H2O(n))(N2(m)) reactant ions, but not by the CO3(-)(H2O(n))(N2(m)) reactant ions. While the CO4(-) ions are formed by direct association, the CO3(-) ions require additional energy to be formed. The additional energy is provided by either excited neutral gas molecules in a metastable state or UV (ultraviolet) radiation.
Extrinsic ion migration in perovskite solar cells
Li, Zhen; Xiao, Chuanxiao; Yang, Ye; ...
2017-04-10
In this study, the migration of intrinsic ions (e.g., MA +, Pb 2+, I –) in organic–inorganic hybrid perovskites has received significant attention with respect to the critical roles of these ions in the hysteresis and degradation in perovskite solar cells (PSCs). Here, we demonstrate that extrinsic ions (e.g., Li +, H +, Na +), when used in the contact layers in PSCs, can migrate across the perovskite layer and strongly impact PSC operation. In a TiO 2/perovskite/spiro-OMeTAD-based PSC, Li +-ion migration from spiro-OMeTAD to the perovskite and TiO 2 layer is illustrated by time-of-flight secondary-ion mass spectrometry. The movementmore » of Li + ions in PSCs plays an important role in modulating the solar cell performance, tuning TiO 2 carrier-extraction properties, and affecting hysteresis in PSCs. The influence of Li +-ion migration was investigated using time-resolved photoluminescence, Kelvin probe force microscopy, and external quantum efficiency spectra. Other extrinsic ions such as H + and Na + also show a clear impact on the performance and hysteresis in PSCs. Understanding the impacts of extrinsic ions in perovskite-based devices could lead to new material and device designs to further advance perovskite technology for various applications.« less
Iverson, Chad D; Gu, Xinyun; Lucy, Charles A
2016-08-05
This work systematically investigates the selectivity changes on many HILIC phases from w(w)pH 3.7-6.8, at 5 and 25mM buffer concentrations. Hydrophilicity (kcytosine/kuracil) vs. ion interaction (kBTMA/kuracil) selectivity plots developed by Ibrahim et al. (J. Chromatogr. A 1260 (2012) 126-131) are used to investigate the effect of mobile phase changes on the selectivity of 18 HILIC columns from various classes. "Selectivity change plots" focus on the change in hydrophilicity and ion interaction that the columns exhibit upon changing mobile phase conditions. In general, the selectivity behavior of most HILIC columns is dominated by silanol activity. Minimal changes in selectivity are observed upon changing pH between w(w)pH 5 and 6.8. However, a reduction in ionic interaction is observed when the buffer concentration is increased at w(w)pH≥5.0 due to ionic shielding. Reduction of the w(w)pH to<5.0 results in decreasing cation exchange activity due to silanol protonation. Under all eluent conditions, the majority of phases show little change in their hydrophilicity. Copyright © 2016 Elsevier B.V. All rights reserved.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fakih, Ibrahim, E-mail: ibrahim.fakih@mail.mcgill.ca; Sabri, Shadi; Szkopek, Thomas, E-mail: thomas.szkopek@mcgill.ca
2014-08-25
We have fabricated and characterized large area graphene ion sensitive field effect transistors (ISFETs) with tantalum pentoxide sensing layers and demonstrated pH sensitivities approaching the Nernstian limit. Low temperature atomic layer deposition was used to deposit tantalum pentoxide atop large area graphene ISFETs. The charge neutrality point of graphene, inferred from quantum capacitance or channel conductance, was used to monitor surface potential in the presence of an electrolyte with varying pH. Bare graphene ISFETs exhibit negligible response, while graphene ISFETs with tantalum pentoxide sensing layers show increased sensitivity reaching up to 55 mV/pH over pH 3 through pH 8. Applying themore » Bergveld model, which accounts for site binding and a Guoy-Chapman-Stern picture of the surface-electrolyte interface, the increased pH sensitivity can be attributed to an increased buffer capacity reaching up to 10{sup 14} sites/cm{sup 2}. ISFET response was found to be stable to better than 0.05 pH units over the course of two weeks.« less
Redox Chemistry of Molybdenum Trioxide for Ultrafast Hydrogen-Ion Storage.
Wang, Xianfu; Xie, Yiming; Tang, Kai; Wang, Chao; Yan, Chenglin
2018-05-11
Hydrogen ions are ideal charge carriers for rechargeable batteries due to their small ionic radius and wide availability. However, little attention has been paid to hydrogen-ion storage devices because they generally deliver relatively low Coulombic efficiency as a result of the hydrogen evolution reaction that occurs in an aqueous electrolyte. Herein, we successfully demonstrate that hydrogen ions can be electrochemically stored in an inorganic molybdenum trioxide (MoO 3 ) electrode with high Coulombic efficiency and stability. The as-obtained electrode exhibits ultrafast hydrogen-ion storage properties with a specific capacity of 88 mA hg -1 at an ultrahigh rate of 100 C. The redox reaction mechanism of the MoO 3 electrode in the hydrogen-ion cell was investigated in detail. The results reveal a conversion reaction of the MoO 3 electrode into H 0.88 MoO 3 during the first hydrogen-ion insertion process and reversible intercalation/deintercalation of hydrogen ions between H 0.88 MoO 3 and H 0.12 MoO 3 during the following cycles. This study reveals new opportunities for the development of high-power energy storage devices with lightweight elements. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Drift wave stabilized by an additional streaming ion or plasma population
NASA Astrophysics Data System (ADS)
Bashir, M. F.; Vranjes, J.
2015-03-01
It is shown that the universally unstable kinetic drift wave in an electron-ion plasma can very effectively be suppressed by adding an extra flowing ion (or plasma) population. The effect of the flow of the added ions is essential, their response is of the type (vp h-vf 0) exp[-(vph-vf 0) 2] , where vf 0 is the flow speed and vp h is the phase speed parallel to the magnetic field vector. The damping is strong and it is mainly due to this ion exponential term, and this remains so for vf 0
New LaMAsH(x) (M = Co, Ni, or Cu) arsenides with covalent M-H chains.
Mizoguchi, Hiroshi; Park, SangWon; Hiraka, Haruhiro; Ikeda, Kazutaka; Otomo, Toshiya; Hosono, Hideo
2014-12-17
A new series of tetragonal LaPtSi-type mixed-anion arsenides, LaMAsH(x) (M = Co, Ni, or Cu), has been synthesized using high-temperature and high-pressure techniques. The crystal structure of these intermetallic compounds determined via powder neutron diffraction is composed of a 3D framework of three connected planes with the La ions filling the cavities in the structure. Each late transition-metal ion M, all of which have relatively large electronegativities, behaves like a main group element and forms a planar coordination configuration with three As ions. The trigonal-bipyramidal coordination adopted by the H in the cavity, HM2La3, is compressed along the C3 axis, and unusual M-H chains run along the x and y directions, reinforcing the covalent framework. These chains, which are unique in solids, are stabilized by covalent interactions between the M 4s and H 1s orbitals.
NASA Technical Reports Server (NTRS)
Taylor, H. A., Jr.
1972-01-01
A distinct feature of the ion composition results from the OGO-2, 4 and 6 satellites is the light ion trough, wherein the mid-latitude concentrations of H+ and He+ decrease sharply with latitude. In contrast to the 'main trough' in electron density observed primarily as a nightside phenomenon, the light ion trough persists during both day and night. For daytime winter hemisphere conditions and for all seasons during night, the mid-latitude light ion concentration decrease is a pronounced feature. In the dayside summer and equinox hemispheres, the rate of light ion decrease with latitude is comparatively gradual, and the trough boundary is less well defined, particularly for quiet magnetic conditions. In response to magnetic storms, the light ion trough minimum moves equatorward, and deepens, consistent with earlier evidence of the contraction of the plasmasphere in response to storm time enhancements in magnetospheric plasma convection.
The pH and ionic composition of stratiform cloud water
NASA Astrophysics Data System (ADS)
Castillo, Raymond A.; Jiusto, James E.; Mclaren, Eugene
Over 50 cloud water samples were collected during five comprehensive case studies of the water chemistry of stratiform clouds at Whiteface Mountain, New York. The water samples were analyzed for pH, conductivity and ions of sodium, potassium, magnesium, calcium, ammonium, sulfate, chloride and nitrate. Trajectory analyses and cloud condensation nucleus concentrations at 0.5 % confirmed that the air masses in all five of these cases represented continental air that was relatively clean (low aerosol concentration) for the northeystern United States. The major ions related to cloud water pH were found to be sulfate, nitrate, potassium, ammonium and calcium. The results revealed a mean hydrogen ion concentration [ H+] = 0.239 meq ℓ -1 ( σ = ± 0.21) which converts to a mean pH = 3.6 for all collected cloud samples. The low pH values are related to a normal background of nitrate ions found in the rural continental air masses plus sulfate ions largely from the industrial emissions of the midwestern United States. The [NO -3], in two of the three cases presented, demonstrates the importance of the nitrate ions' contribution to the pH of cloud water. A dependent means analysis of 40 events yielded a significant difference (0.04 level of significance), with the mean pH of precipitation (4.2) being greater than the mean pH of cloud water (4.0) for event samples. The ion concentrations indicated that the cloud rainout process contributed from 67 % to almost 100% of the total ion concentration of the precipitation. The washout process, i.e. precipitation scavenging below the cloud base, contributed considerably less than the cloud/rainout process of those total precipitation anions associated with air pollution.
Study of wettability and cell viability of H implanted stainless steel
NASA Astrophysics Data System (ADS)
Shafique, Muhammad Ahsan; Ahmad, Riaz; Rehman, Ihtesham Ur
2018-03-01
In the present work, the effect of hydrogen ion implantation on surface wettability and biocompatibility of stainless steel is investigated. Hydrogen ions are implanted in the near-surface of stainless steel to facilitate hydrogen bonding at different doses with constant energy of 500 KeV, which consequently improve the surface wettability. Treated and untreated sample are characterized for surface wettability, incubation of hydroxyapatite and cell viability. Contact angle (CA) study reveals that surface wettability increases with increasing H-ion dose. Raman spectroscopy shows that precipitation of hydroxyapatite over the surface increase with increasing dose of H-ions. Cell viability study using MTT assay describes improved cell viability in treated samples as compared to the untreated sample. It is found that low dose of H-ions is more effective for cell proliferation and the cell count decreases with increasing ion dose. Our study demonstrates that H ion implantation improves the surface wettability and biocompatibility of stainless steel.
Operation and development status of the J-PARC ion source
NASA Astrophysics Data System (ADS)
Yamazaki, S.; Ikegami, K.; Ohkoshi, K.; Ueno, A.; Koizumi, I.; Takagi, A.; Oguri, H.
2014-02-01
A cesium-free H- ion source driven with a LaB6 filament is being operated at the Japan Proton Accelerator Research Complex (J-PARC) without any serious trouble since the restoration from the March 2011 earthquake. The H- ion current from the ion source is routinely restricted approximately 19 mA for the lifetime of the filament. In order to increase the beam power at the linac beam operation (January to February 2013), the beam current from the ion source was increased to 22 mA. At this operation, the lifetime of the filament was estimated by the reduction in the filament current. According to the steep reduction in the filament current, the break of the filament was predicted. Although the filament has broken after approximately 10 h from the steep current reduction, the beam operation was restarted approximately 8 h later by the preparation for the exchange of new filament. At the study time for the 3 GeV rapid cycling synchrotron (April 2013), the ion source was operated at approximately 30 mA for 8 days. As a part of the beam current upgrade plan for the J-PARC, the front end test stand consisting of the ion source and the radio frequency quadrupole is under preparation. The RF-driven H- ion source developed for the J-PARC 2nd stage requirements will be tested at this test stand.
Carbonic Acid by Ion Implantation in Water_solarCarbon Dioxide Ice Mixtures
NASA Astrophysics Data System (ADS)
Brucato, J. R.; Palumbo, M. E.; Strazzulla, G.
1997-01-01
We present the results of experiments performed by keV ion (He and H) bombardment of frozen mixtures of H 2O:CO 2and of pure CO 2ice. Using keV He ions we confirm the already reported measurement of carbonic acid (H 2CO 3) production in an ice mixture of frozen water and carbon dioxide (1:1) after irradiation by 0.7 MeV H ions (Moore, M. H., and R. K. Khanna 1991. Spectrochim. Acta47, 255-262; Moore, M. H., R. K. Khanna, and B. Donn 1991. J. Geophys. Res. E96(2), 17,541-17,545.). Contrary to a previous report (Pirronello, V., W. L. Brown, L. J. Lanzerotti, K. J. Marcantonio, and E. H. Simmons 1982. Astrophys. J.262, 636-640.), formaldehyde (H 2CO), if any, is not a major product. Implantation with hydrogen ions demonstrates that carbonic acid is formed even if the irradiated target is pure CO 2; i.e., the implanted ion is incorporated into the target and forms new bonds. Some possible astrophysical applications on Solar System objects or (pre-solar) interstellar grains are discussed.
NASA Astrophysics Data System (ADS)
Sugimura, Natsuhiko; Igarashi, Yoko; Aoyama, Reiko; Shibue, Toshimichi
2017-09-01
The physical origins of the interactions in the acetophenone cation adducts [M+Na]+, [M+NH4]+, and [M+H]+ were explored by localized molecular orbital-energy decomposition analysis and density functional theory. The analyses highlighted the differences in the interactions in the three adduct ions. Electrostatic energy was important in [M+Na]+ and there was little change in the acetophenone orbital shape. Both electrostatic and polarization energy were important in [M+NH4]+, and a considerable change in the orbital shape occurred to maximize the strength of the hydrogen bond. Polarization energy was the major attractive force in [M+H]+.
Adsorption of heavy metal ions by sawdust of deciduous trees.
Bozić, D; Stanković, V; Gorgievski, M; Bogdanović, G; Kovacević, R
2009-11-15
The adsorption of heavy metal ions from synthetic solutions was performed using sawdust of beech, linden and poplar trees. The adsorption depends on the process time, pH of the solution, type of ions, initial concentration of metals and the sawdust concentration in suspension. The kinetics of adsorption was relatively fast, reaching equilibrium for less than 20 min. The adsorption equilibrium follows Langmuir adsorption model. The ion exchange mechanism was confirmed assuming that the alkali-earth metals from the adsorbent are substituted by heavy metal ions and protons. On lowering the initial pH, the adsorption capacity decreased, achieving a zero value at a pH close to unity. The maximum adsorption capacity (7-8 mg g(-1) of sawdust) was achieved at a pH between 3.5 and 5 for all the studied kinds of sawdust. The initial concentration of the adsorbate and the concentration of sawdust strongly affect the process. No influence of particles size was evidenced. A degree of adsorption higher than 80% can be achieved for Cu(2+) ions but it is very low for Fe(2+) ions, not exceeding 10%.
Ion Transport Processes in Corn Mitochondria 1
Klein, Robert R.; Koeppe, David E.
1985-01-01
The local anesthetic dibucaine inhibited respiration-dependent contraction mediated by the K+/H+ antiport system of isolated corn mitochondria. Respiration declined concurrently. Nigericin, an exogenous K+/H+ exchanger, restored ion efflux in dibucaine-blocked corn mitochondria. It was concluded that dibucaine inhibited ion efflux via blockage of the K+/H+ antiport. Further experiments determined that dibucaine also inhibited proton influx facilitated by protonophores and by the ATPase complex during state III respiration. These results are discussed in relation to the mechanism by which dibucaine inhibits proton translocation across the inner mitochondrial membrane. PMID:16664160
Spin-orbit quenching of the C+(2P) ion by collisions with para- and ortho-H2.
Lique, François; Werfelli, Ghofran; Halvick, Philippe; Stoecklin, Thierry; Faure, Alexandre; Wiesenfeld, Laurent; Dagdigian, Paul J
2013-05-28
Spin-orbit (de-)excitation of C(+)((2)P) by collisions with H2, a key process for astrochemistry, is investigated. Quantum-mechanical calculations of collisions between C(+) ions and para- and ortho-H2 have been performed in order to determine the cross section for the C(+) (2)P3∕2 → (2)P1∕2 fine-structure transition at low and intermediate energies. The calculation are based on new ab initio potential energy surfaces obtained using the multireference configuration interaction method. Corresponding rate coefficients were obtained for temperatures ranging from 5 to 500 K. These rate coefficients are compared to previous estimations, and their impact is assessed through radiative transfer computation. They are found to increase the flux of the (2)P3∕2 → (2)P1∕2 line at 158 μm by up to 30% for typical diffuse interstellar cloud conditions.
Mao, Hailei; Han, Gang; Xu, Longyong; Zhu, Duming; Lin, Hanqing; Cao, Xiongwen; Yu, Yi; Chen, Charlie Degui
2015-07-21
Histone H3 lysine 27 trimethylation (H3K27me3) and H3 lysine 36 trimethylation (H3K36me3) are important epigenetic modifications correlated with transcription repression and activation, respectively. These two opposing modifications rarely co-exist in the same H3 polypeptide. However, a small but significant amount of H3 tails are modified with 5 methyl groups on K27 and K36 in mouse embryonic stem cells (mESCs) and it is unclear how the trimethylation is distributed on K27 or K36. A label-free, bottom-up mass spectrum method, named specific ions of isobaric modification chromatogram (SIMC), was established to quantify the relative abundance of K27me2-K36me3 and K27me3-K36me2 in the same histone H3 tail. By using this method, we demonstrated that the H3K27me3-K36me2 comprises about 85 % of the penta-methylated H3 tails at K27 and K36 in mESCs. Upon mESC differentiation, the abundance of H3K27me3-K36me2 significantly decreased, while the level of H3K27me2-K36me3 remains unchanged. Our study not only revealed the cis-existence of H3K27me3-K36me2 in mESCs, but also suggested that this combinatorial histone modification may assume a specific regulatory function during differentiation.
A segmented ion engine design for solar electric propulsion systems
NASA Technical Reports Server (NTRS)
Brophy, John R.
1992-01-01
A new ion engine design, called a segmented ion engine, is described which is capable of reducing the required ion source life time for small body rendezvous missions from 18,000 h to about 8,000 h. The use of SAND ion optics for the engine accelerator system makes it possible to substantially reduce the cost of demonstrating the required engine endurance. It is concluded that a flight test of a 5-kW xenon ion propulsion system on the ELITE spacecraft would enormously reduce the cost and risk of using ion propulsion on a planetary vehicle by addressing systems level issues associated with flying a spacecraft radically different from conventional planetary vehicles.
Mass-dependent channel electron multiplier operation. [for ion detection
NASA Technical Reports Server (NTRS)
Fields, S. A.; Burch, J. L.; Oran, W. A.
1977-01-01
The absolute counting efficiency and pulse height distributions of a continuous-channel electron multiplier used in the detection of hydrogen, argon and xenon ions are assessed. The assessment technique, which involves the post-acceleration of 8-eV ion beams to energies from 100 to 4000 eV, provides information on counting efficiency versus post-acceleration voltage characteristics over a wide range of ion mass. The charge pulse height distributions for H2 (+), A (+) and Xe (+) were measured by operating the experimental apparatus in a marginally gain-saturated mode. It was found that gain saturation occurs at lower channel multiplier operating voltages for light ions such as H2 (+) than for the heavier ions A (+) and Xe (+), suggesting that the technique may be used to discriminate between these two classes of ions in electrostatic analyzers.
Ion source issues for the DAEδALUS neutrino experiment
DOE Office of Scientific and Technical Information (OSTI.GOV)
Alonso, Jose R., E-mail: JRAlonso@LBL.gov; Barletta, William A.; Toups, Matthew H.
2014-02-15
The DAEδALUS experiment calls for 10 mA of protons at 800 MeV on a neutrino-producing target. To achieve this record-setting current from a cyclotron system, H{sub 2}{sup +} ions will be accelerated. Loosely bound vibrationally excited H{sub 2}{sup +} ions inevitably produced in conventional ion sources will be Lorentz stripped at the highest energies. Presence of these states was confirmed at the Oak Ridge National Laboratory and strategies were investigated to quench them, leading to a proposed R and D effort towards a suitable ion source for these high-power cyclotrons.
Study of the storm time fluxes of heavy ions
NASA Technical Reports Server (NTRS)
1978-01-01
The characteristics of the storm time ring current ions in the energy range of 0.5 to 16 keV were investigated. Data were processed and analyzed from the energetic ion mass spectrometer aboard the S3-3 satellite. Results are used for planning and operating the ion mass spectrometer experiment on the ISEE spacecraft, for selecting and processing the ISEE ion data, and for planning and conducting coordinated satellite experiments in support of the International Magnetospheric Study (IMS). It is established from the S3-3 ion data that relatively large fluxes of energetic (keV) 0(+) and H(+) ions are frequently flowing upward from the ionosphere along magnetic field lines in the polar auroral regions. Also, from investigations with the same instrument during the main phase of three moderate (D sub ST approximately 100) magnetic storms, it is found that the number density of 0(+) ions in the ring current was comparable to H(+) ion density the range 0.5 to 15 keV.
Collisional excitation of ArH+ by hydrogen atoms
NASA Astrophysics Data System (ADS)
Dagdigian, Paul J.
2018-06-01
The rotational excitation of the 36ArH+ ion in collisions with hydrogen atoms is investigated in this work. The potential energy surface (PES) describing the 36ArH+-H interaction, with the ion bond length r fixed at the average of r over the radial v = 0 vibrational state distribution, was obtained with a coupled cluster method that included single, double, and (perturbatively) triple excitations [RCCSD(T)]. A deep minimum (De = 3135 cm-1) in the PES was found in linear H-ArH+ geometry at an ion-atom separation Re = 4.80a0. Energy-dependent cross-sections and rate coefficients as a function of temperature for this collision pair were computed in close-coupling (CC) calculations. Since the PES possesses a deep well, this is a good system to test the performance of the quantum statistical (QS) method developed by Manolopoulos and co-workers as a more efficient method to compute the cross-sections. Good agreement was found between rate coefficients obtained by the CC and QS methods at several temperatures. In a simple application, the excitation of ArH+ is simulated for conditions under which this ion is observed in absorption.
X-ray investigation of molten crystal hydrates H2SO4(nH2O) and HNO3(nH2O)
NASA Technical Reports Server (NTRS)
Romanova, A. V.; Skryshevskiy, A. F.
1979-01-01
Integral analysis of the intensity of the electron density distribution curve in molten crystal hydrates provided by X-ray analysis, permits the following conclusions on the structure of the complex SO and NO ions, and the short-range order in the structure of the solution. The SO4 ion in the solution has a tetrahedral structure with an S to O distance equal to 1.5 A. For the NO3 in the solution, a planar triangular shape is probable, with an N to O distance equal to 1.2 A. Preferential distances between each of the oxygens of the SO ion and the nearest molecules of water proved near to the corresponding distances in solid crystal hydrates. For an (H2SO4)(H2O) solution, the average number of water molecules surrounding each oxygen atom of the SO4 (--) ion was on the order of 1.3 molecules. Hence the preferential distances between the water molecules and the oxygen atoms of the SO ion, and the preference of their mutual position, correspond to the fixed position of these same elements of the structure in the solid crystal hydrate.
Hot magnetospheric O+ and cold ion behavior in magnetopause reconnection: Cluster observations
NASA Astrophysics Data System (ADS)
Wang, S.; Kistler, L. M.; Mouikis, C. G.; Liu, Y.; Genestreti, K. J.
2014-12-01
In reconnection, the presence of heavy ions like O+ increases the ion mass density reducing the fluid's Alfvén speed. In addition, it may modify the reconnection structure, which can also change the reconnection rate. However, because O+ ions have a larger Larmor radii than H+ ions at the same velocity, they may not be fully entrained in the reconnection flow and may have kinetic effects other than just increasing the mass density. In this study, for the first time, the ion velocity distribution functions of H+ and O+ from one magnetopause reconnection event with a strong guide field are analyzed to determine in detail the behavior of the different ion populations. We show that the hot magnetospheric O+ ions, along with the hot magnetospheric H+ ions almost fully participate in the reconnection exhaust flows. Finite Larmor radius effects are also apparent and control how far the ions extend on the magnetosheath side. Ion signatures consistent with heating after being picked up in the reconnection exhaust flow are observed in the H+ and O+ distribution functions. The dynamics of the cold magnetospheric ions depends on where they enter the reconnection region. If they enter the reconnection region at the downstream separatrix, they will be taken away by the magnetic field in an adiabatic way as analyzed by Drake et al. (2009a); if they enter close to the diffusion region, they behave as pick-up ions.
Vogt, Matthew; Lahiri, Simanti; Hoogstraten, Charles G.; Britt, R. David; DeRose, Victoria J.
2010-01-01
Although site-bound Mg2+ ions have been proposed to influence RNA structure and function, establishing the molecular properties of such sites has been challenging due largely to the unique electrostatic properties of the RNA biopolymer. We have previously determined that, in solution, the hammerhead ribozyme (a self-cleaving RNA) has a high-affinity metal ion binding site characterized by a Kd,app < 10 µM for Mn2+ in 1 M NaCl and speculated that this site has functional importance in the ribozyme cleavage reaction. Here we determine both the precise location and the hydration level of Mn2+ in this site using ESEEM (electron spin–echo envelope modulation) spectroscopy. Definitive assignment of the high-affinity site to the activity-sensitive A9/G10.1 region is achieved by site-specific labeling of G10.1 with 15N guanine. The coordinated metal ion retains four water ligands as measured by 2H ESEEM spectroscopy. The results presented here show that a functionally important, specific metal binding site is uniquely populated in the hammerhead ribozyme even in a background of high ionic strength. Although it has a relatively high thermodynamic affinity, this ion remains partially hydrated and is chelated to the RNA by just two ligands. PMID:17177426
Balaj, O Petru; Siu, Chi-Kit; Balteanu, Iulia; Beyer, Martin K; Bondybey, Vladimir E
2004-10-04
The gas-phase reactions of hydrated electrons with carbon dioxide and molecular oxygen were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Both CO2 and O2 react efficiently with (H2O)n- because they possess low-lying empty pi* orbitals. The molecular CO2- and O2- anions are concurrently solvated and stabilized by the water ligands to form CO2(-)(H2O)n and O2(-)(H2O)n. Core exchange reactions are also observed, in which CO2(-)(H2O)n is transformed into O2(-)(H2O)n upon collision with O2. This is in agreement with the prediction based on density functional theory calculations that O2(-)(H2O)n clusters are thermodynamically favored with respect to CO2(-)(H2O)n. Electron detachment from the product species is only observed for CO2(-)(H2O)2, in agreement with the calculated electron affinities and solvation energies.
In Situ Measurements of Meteoric Ions. Chapter 8
NASA Technical Reports Server (NTRS)
Grebowsky, Joseph M.; Aikin, Arthur C.; Vondrak, Richard R. (Technical Monitor)
2001-01-01
Metal ions found in the atmosphere above 60 km are the result of incoming meteoroid atmospheric ablation. Layers of metal ions are detected by sounding rocket in situ mass spectrometric sampling in the 80 to 130 km region, which coincides with the altitude region where meteors are observed. Enhancements of metal ion concentrations occur during meteor showers. Even outside of shower periods, the metal ion altitude profiles vary from measurement to measurement. Double layers are frequent at middle latitudes. More than 40 different meteoric atomic and molecular ions, including isotopes, have been detected. Atmospheric metal ions on average have an abundance that matches chrondritic material, the same composition as the early solar system. However there are frequently local departures from this composition due to differential ablation, species dependent chemistry and mass dependent ion transport. Metal ions react with atmospheric O2, O, O3, H2O and H2O2 to form oxygenated and hydrogenated ionic compounds. Metal atomic ions at high altitudes have long lifetimes. As a result, these ions, in the presence of Earth's magnetic field, are transported over long distances by upper atmospheric winds and ionospheric electric fields. Satellite measurements have detected metal ions as high as, approximately 1000 km and have revealed circulation of the ions on a global scale.
Heteroditopic receptors for ion-pair recognition.
McConnell, Anna J; Beer, Paul D
2012-05-21
Ion-pair recognition is a new field of research emerging from cation and anion coordination chemistry. Specific types of heteroditopic receptor designs for ion pairs and the complexity of ion-pair binding are discussed to illustrate key concepts such as cooperativity. The importance of this area of research is reflected by the wide variety of potential applications of ion-pair receptors, including applications as membrane transport and salt solubilization agents and sensors. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Hagiwara, Yoshihiko; Niimi, Atsuko; Isono, Mayu; Yamauchi, Motohiro; Yasuhara, Takaaki; Limsirichaikul, Siripan; Oike, Takahiro; Sato, Hiro; Held, Kathryn D.; Nakano, Takashi; Shibata, Atsushi
2017-01-01
DNA double-strand breaks (DSBs) induced by ionising radiation are considered the major cause of genotoxic mutations and cell death. While DSBs are dispersed throughout chromatin after X-rays or γ-irradiation, multiple types of DNA damage including DSBs, single-strand breaks and base damage can be generated within 1–2 helical DNA turns, defined as a complex DNA lesion, after high Linear Energy Transfer (LET) particle irradiation. In addition to the formation of complex DNA lesions, recent evidence suggests that multiple DSBs can be closely generated along the tracks of high LET particle irradiation. Herein, by using three dimensional (3D)-structured illumination microscopy, we identified the formation of 3D widespread γH2AX foci after high LET carbon-ion irradiation. The large γH2AX foci in G2-phase cells encompassed multiple foci of replication protein A (RPA), a marker of DSBs undergoing resection during homologous recombination. Furthermore, we demonstrated by 3D analysis that the distance between two individual RPA foci within γH2AX foci was approximately 700 nm. Together, our findings suggest that high LET heavy-ion particles induce clustered DSB formation on a scale of approximately 1 μm3. These closely localised DSBs are considered to be a risk for the formation of chromosomal rearrangement after heavy-ion irradiation. PMID:29312614
Hagiwara, Yoshihiko; Niimi, Atsuko; Isono, Mayu; Yamauchi, Motohiro; Yasuhara, Takaaki; Limsirichaikul, Siripan; Oike, Takahiro; Sato, Hiro; Held, Kathryn D; Nakano, Takashi; Shibata, Atsushi
2017-12-12
DNA double-strand breaks (DSBs) induced by ionising radiation are considered the major cause of genotoxic mutations and cell death. While DSBs are dispersed throughout chromatin after X-rays or γ-irradiation, multiple types of DNA damage including DSBs, single-strand breaks and base damage can be generated within 1-2 helical DNA turns, defined as a complex DNA lesion, after high Linear Energy Transfer (LET) particle irradiation. In addition to the formation of complex DNA lesions, recent evidence suggests that multiple DSBs can be closely generated along the tracks of high LET particle irradiation. Herein, by using three dimensional (3D)-structured illumination microscopy, we identified the formation of 3D widespread γH2AX foci after high LET carbon-ion irradiation. The large γH2AX foci in G 2 -phase cells encompassed multiple foci of replication protein A (RPA), a marker of DSBs undergoing resection during homologous recombination. Furthermore, we demonstrated by 3D analysis that the distance between two individual RPA foci within γH2AX foci was approximately 700 nm. Together, our findings suggest that high LET heavy-ion particles induce clustered DSB formation on a scale of approximately 1 μm 3 . These closely localised DSBs are considered to be a risk for the formation of chromosomal rearrangement after heavy-ion irradiation.
Sankova, Tatiana P; Orlov, Iurii A; Saveliev, Andrey N; Kirilenko, Demid A; Babich, Polina S; Brunkov, Pavel N; Puchkova, Ludmila V
2017-11-03
There is much interest in effective copper chelators to correct copper dyshomeostasis in neurodegenerative and oncological diseases. In this study, a recombinant fusion protein for expression in Escherichia coli cells was constructed from glutathione-S-transferase (GST) and the N-terminal domain (ectodomain) of human high affinity copper transporter CTR1 (hNdCTR1), which has three metal-bound motifs. Several biological properties of the GST-hNdCTR1 fusion protein were assessed. It was demonstrated that in cells, the protein was prone to oligomerization, formed inclusion bodies and displayed no toxicity. Treatment of E. coli cells with copper and silver ions reduced cell viability in a dose- and time-dependent manner. Cells expressing GST-hNdCTR1 protein demonstrated resistance to the metal treatments. These cells accumulated silver ions and formed nanoparticles that contained AgCl and metallic silver. In this bacterial population, filamentous bacteria with a length of about 10 µm were often observed. The possibility for the fusion protein carrying extracellular metal binding motifs to integrate into the cell's copper metabolism and its chelating properties are discussed.
NASA Astrophysics Data System (ADS)
Irion, M. P.; Selinger, A.; Schnabel, P.
1991-03-01
Fe{/n +} and Pd{/n +} clusters up to n=19 and n=25, respectively, are produced in an external ion source by sputtering of the respective metal foils with Xe+ primary ions at 20 keV. They are transferred to the ICR cell of a home-built Fourier transform mass spectrometer, where they are thermalized to nearly room temperature and stored for several tens of seconds. During this time, their reactions with a gas leaked in at low level are studied. Thus in the presence of ammonia, most Fe{/n +} clusters react by simply adsorbing intact NH3 molecules. Only Fe{4/+} ions show dehydrogenation/adsorption to Fe4(NH){/m +} intermediates ( m=1, 2) that in a complex scheme go on adsorbing complete NH3 units. To clarify the reaction scheme, one has to isolate each species in the ion cell, which often requires the ejection of ions very close in mass. This led to the development of a special isolation technique that avoids the use of isotopically pure metal samples. Pd{n/+} cluster ions ( n=2...9) dehydrogenate C2H4 in general to yield Pd n (C2H2)+, yet Pd{6/+} appear totally unreactive. Towards D2, Pd{7/+} ions seem inert, whereas Pd{8/+} adsorb up to two molecules.
Evans, H.T.
1963-01-01
A review of the known crystal structures containing the uranyl ion shows that plane-pentagon coordination is equally as prevalent as plane-square or plane-hexagon. It is suggested that puckered-hexagon configurations of OH - or H2O about the uranyl group will tend to revert to plane-pentagon coordination. The concept of pentagonal coordination is invoked for possible explanations of the complex crystallography of the natural uranyl hydroxides and the unusual behavior of polynuclear ions in hydrolyzed uranyl solutions.
Electron-ion recombination in low temperature hydrogen/deuterium plasma
NASA Astrophysics Data System (ADS)
Glosík, Juraj; Dohnal, Petr; Kálosi, Ábel; Augustovičová, Lucie D.; Shapko, Dmytro; Roučka, Štěpán; Plašil, Radek
2018-01-01
The stationary afterglow with cavity ring down spectrometer (SA-CRDS) was used to study the recombination of H3+, H2D+, HD2+ and D3+ ions with electrons in low temperature (77-300 K) plasmas in He/Ar/H2/D2 gas mixtures. By measuring effective recombination rate coefficients (αeff) in plasma with mixtures of ions and their dependences on temperature and partial densities of He, H2 and D2, αeff (T, [He],[H2],[D2]), we determined binary (αbinH3, αbinH2D, αbinHD2, αbinD3) and ternary (KH3, KH2D, KHD2, KD3) recombination rate coefficients for H3+, H2D+, HD2+ and D3+ ions. For all four ions we observed very efficient He assisted ternary recombination which is comparable with binary recombination already at [He] =1 × 1017 cm-3. The removal of excited particles in afterglow plasma was monitored to obtain the plasma thermalisation rate at given experimental conditions. The inferred deexcitation rates for reaction of helium metastable atoms with D2 are kD2 (300 K)=(2.1 ± 0.3) × 10-10 cm3 s-1 and kD2 (140 K)=(1.3 ± 0.3) × 10-10 cm3 s-1. Contribution to the topical issue "Plasma Sources and Plasma Processes (PSPP)", edited by Luis Lemos Alves, Thierry Belmonte and Tiberiu Minea.
Release of major ions during rigor mortis development in kid Longissimus dorsi muscle.
Feidt, C; Brun-Bellut, J
1999-01-01
Ionic strength plays an important role in post mortem muscle changes. Its increase is due to ion release during the development of rigor mortis. Twelve alpine kids were used to study the effects of chilling and meat pH on ion release. Free ions were measured in Longissimus dorsi muscle by capillary electrophoresis after water extraction. All free ion concentrations increased after death, but there were differences between ions. Temperature was not a factor affecting ion release in contrast to ultimate pH value. Three release mechanisms are believed to coexist: a passive binding to proteins, which stops as pH decreases, an active segregation which stops as ATP disappears and the production of metabolites due to anaerobic glycolysis.
Cometary coma ions. [which occur when water is the major constituent
NASA Technical Reports Server (NTRS)
Aikin, A. C.
1974-01-01
For comets whose nuclei are composed of water ice conglomerates it is shown that the ion H3O(+) can predominate to distances of 5000 km in the subsolar direction. Beyond this distance H2O(+) is the most important ion. The crossover point is a sensitive function of the rate of evaporation from the nucleus. The presence of ammonia or metals such as sodium, in concentrations greater than 0.1% H2O, can lead to NH4(+) and Na(+) ions.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wiens, Justin P.; Shuman, Nicholas S.; Viggiano, Albert A., E-mail: afrl.rvborgmailbox@kirtland.af.mil
Dissociative recombination (DR) rate coefficients for the naphthalene cation, C{sub 10}H{sub 8}{sup +}, and WF{sub 5}{sup +}, and mutual neutralization (MN) rate coefficients for these species and five C{sub n}F{sub m}{sup +} ions, were determined at 300 K using variable electron and neutral density attachment mass spectrometry (VENDAMS). DR proceeds at 9 ± 3 × 10{sup −7} cm{sup 3} s{sup −1} for C{sub 10}H{sub 8}{sup +} and at 6.1 ± 1.4 × 10{sup −7} cm{sup 3} s{sup −1} for WF{sub 5}{sup +}. Consistent with previous results, MN for the polyatomic cations with the halide anions Cl{sup −}, Br{sup −}, andmore » I{sup −} exhibits an approximate μ{sup −1/2} reduced mass dependence of the reactant partners, demonstrating that ion collision velocities influence the rate coefficients. This work is an extension of VENDAMS to systems, where low reactant concentrations are necessary to avoid significant reaction of product ions with the neutral precursor, i.e., conditions not suitable for traditional flowing afterglow measurements, as well as to ions of masses > ∼ 100 Da, which are not amenable to the study of DR in magnetic storage rings. Our results expand the sparse literature on DR and MN of heavier ions.« less
Stimulation of eryptosis by aluminium ions
DOE Office of Scientific and Technical Information (OSTI.GOV)
Niemoeller, Olivier M.; Kiedaisch, Valentin; Dreischer, Peter
2006-12-01
Aluminium salts are utilized to impede intestinal phosphate absorption in chronic renal failure. Toxic side effects include anemia, which could result from impaired formation or accelerated clearance of circulating erythrocytes. Erythrocytes may be cleared secondary to suicidal erythrocyte death or eryptosis, which is characterized by cell shrinkage and exposure of phosphatidylserine (PS) at the erythrocyte surface. As macrophages are equipped with PS receptors, they bind, engulf and degrade PS-exposing cells. The present experiments have been performed to explore whether Al{sup 3+} ions trigger eryptosis. The PS exposure was estimated from annexin binding and cell volume from forward scatter in FACSmore » analysis. Exposure to Al{sup 3+} ions ({>=} 10 {mu}M Al{sup 3+} for 24 h) indeed significantly increased annexin binding, an effect paralleled by decrease of forward scatter at higher concentrations ({>=} 30 {mu}M Al{sup 3+}). According to Fluo3 fluorescence Al{sup 3+} ions ({>=} 30 {mu}M for 3 h) increased cytosolic Ca{sup 2+} activity. Al{sup 3+} ions ({>=} 10 {mu}M for 24 h) further decreased cytosolic ATP concentrations. Energy depletion by removal of glucose similarly triggered annexin binding, an effect not further enhanced by Al{sup 3+} ions. The eryptosis was paralleled by release of hemoglobin, pointing to loss of cell membrane integrity. In conclusion, Al{sup 3+} ions decrease cytosolic ATP leading to activation of Ca{sup 2+}-permeable cation channels, Ca{sup 2+} entry, stimulation of cell membrane scrambling and cell shrinkage. Moreover, Al{sup 3+} ions lead to loss of cellular hemoglobin, a feature of hemolysis. Both effects are expected to decrease the life span of circulating erythrocytes and presumably contribute to the development of anemia during Al{sup 3+} intoxication.« less
Thwaites, D T; Ford, D; Glanville, M; Simmons, N L
1999-09-01
The intestinal absorption of many nutrients and drug molecules is mediated by ion-driven transport mechanisms in the intestinal enterocyte plasma membrane. Clearly, the establishment and maintenance of the driving forces - transepithelial ion gradients - are vital for maximum nutrient absorption. The purpose of this study was to determine the nature of intracellular pH (pH(i)) regulation in response to H(+)-coupled transport at the apical membrane of human intestinal epithelial Caco-2 cells. Using isoform-specific primers, mRNA transcripts of the Na(+)/H(+) exchangers NHE1, NHE2, and NHE3 were detected by RT-PCR, and identities were confirmed by sequencing. The functional profile of Na(+)/H(+) exchange was determined by a combination of pH(i), (22)Na(+) influx, and EIPA inhibition experiments. Functional NHE1 and NHE3 activities were identified at the basolateral and apical membranes, respectively. H(+)/solute-induced acidification (using glycylsarcosine or beta-alanine) led to Na(+)-dependent, EIPA-inhibitable pH(i) recovery or EIPA-inhibitable (22)Na(+) influx at the apical membrane only. Selective activation of apical (but not basolateral) Na(+)/H(+) exchange by H(+)/solute cotransport demonstrates that coordinated activity of H(+)/solute symport with apical Na(+)/H(+) exchange optimizes the efficient absorption of nutrients and Na(+), while maintaining pH(i) and the ion gradients involved in driving transport.
NASA Astrophysics Data System (ADS)
Cukras, Janusz; Antušek, Andrej; Holka, Filip; Sadlej, Joanna
2009-06-01
Extensive ab initio calculations of static electric properties of molecular ions of general formula RgH + (Rg = He, Ne, Ar, Kr, Xe) involving the finite field method and coupled cluster CCSD(T) approach have been done. The relativistic effects were taken into account by Douglas-Kroll-Hess approximation. The numerical stability and reliability of calculated values have been tested using the systematic sequence of Dunning's cc-pVXZ-DK and ANO-RCC-VQZP basis sets. The influence of ZPE and pure vibrational contribution has been discussed. The component αzz has increasing trend in RgH + while the relativistic effect on αzz leads to a small increase of this molecular parameter.
Paschalidis, Damianos G.; Harrison, William T. A.
2016-01-01
The gel-mediated syntheses and crystal structures of [N′-(pyridin-2-ylmethylidene-κN)benzohydrazide-κ2 N′,O]tris(thiocyanato-κN)praseodymium(III) monohydrate, [Pr(NCS)3(C13H11N3O)2]·H2O, (I), and aqua(nitrato-κ2 O,O′)[N′-(pyridin-2-ylmethylidene-κN)benzohydrazide-κ2 N′,O](thiocyanato-κN)neodymium(III) nitrate 2.33-hydrate, [Nd(NCS)(NO3)(C13H11N3O)2(H2O)]NO3·2.33H2O, (II), are reported. The Pr3+ ion in (I) is coordinated by two N,N,O-tridentate N′-(pyridin-2-ylmethylidene)benzohydrazide (pbh) ligands and three N-bonded thiocyanate ions to generate an irregular PrN7O2 coordination polyhedron. The Nd3+ ion in (II) is coordinated by two N,N,O-tridentate pbh ligands, an N-bonded thiocyanate ion, a bidentate nitrate ion and a water molecule to generate a distorted NdN5O5 bicapped square antiprism. The crystal structures of (I) and (II) feature numerous hydrogen bonds, which lead to the formation of three-dimensional networks in each case. PMID:26958385
Ionized calcium analyzer with a built-in pH correction.
Fogh-Andersen, N
1981-07-01
We describe a new semi-automated apparatus for simultaneously measuring the concentration of free calcium ion and of hydrogen ion (pH) at 37 degrees C. The sample volume is 110 microL. In addition to the actual values for these concentrations in the sample, the apparatus calculates the concentration of free calcium ion at pH 7.40. Mean values for serum from 51 fasting bedridden patients without calcium metabolic disorders and 64 fasting hospital employees were 1.192 and 1.232 mmol/L, respectively, with SD of 0.042 and 0.040 mmol/L, respectively. The within-series analytical SD was 12 mumol/L and the day-to-day SD of the pH-corrected concentration of free calcium ion was 21 mumol/L, as calculated from measurements made on a serum pool after equilibration with a CO2--air mixture. The mean dependency on pH as determined in 120 consecutive patients' sera equalled the built-in pH correction. The accuracy was evaluated by comparison with other calcium ion-selective electrodes.
NASA Astrophysics Data System (ADS)
Zhou, Qinghua; Hua, Lei; Wang, Changsong; Li, Enyou; Li, Haiyang
2015-01-01
On-line monitoring of propofol in exhaled air is a potential way to evaluate the anaesthesia depth for patients during surgery. In this study, a negative 63Ni ionization high resolution ion mobility spectrometer with Bradbury-Nielsen-Gate-Grid structure was built to measure propofol with reactant ions Cl-(H2O) n using dichloromethane as dopant. Instead of forming three propofol ions (M - H)-, M · O2 -, and (M2 - H)- with reactant ions O2 -(H2O) n , only product ion M · Cl- was produced when introducing dichloromethane gas. The peak-to-peak resolution ( R p-p) between reactant ions Cl-(H2O) n and product ion M · Cl- was 17.4, which was 1.6 times larger than that between O2 -(H2O) n and product ion. Furthermore, the linear response range using reactant ions Cl-(H2O) n was 3.5 times wider than that obtained with reactant ions O2 -(H2O) n .
The ionization length in plasmas with finite temperature ion sources
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jelic, N.; Kos, L.; Duhovnik, J.
2009-12-15
The ionization length is an important quantity which up to now has been precisely determined only in plasmas which assume that the ions are born at rest, i.e., in discharges known as 'cold ion-source' plasmas. Presented here are the results of our calculations of the ionization lengths in plasmas with an arbitrary ion source temperature. Harrison and Thompson (H and T) [Proc. Phys. Soc. 74, 145 (1959)] found the values of this quantity for the cases of several ion strength potential profiles in the well-known Tonks-Langmuir [Phys. Rev. 34, 876 (1929)] discharge, which is characterized by 'cold' ion temperature. Thismore » scenario is also known as the 'singular' ion-source discharge. The H and T analytic result covers cases of ion sources proportional to exp(betaPHI) with PHI the normalized plasma potential and beta=0,1,2 values, which correspond to particular physical scenarios. Many years following H and T's work, Bissell and Johnson (B and J) [Phys. Fluids 30, 779 (1987)] developed a model with the so-called 'warm' ion-source temperature, i.e., 'regular' ion source, under B and J's particular assumption that the ionization strength is proportional to the local electron density. However, it appears that B and J were not interested in determining the ionization length at all. The importance of this quantity to theoretical modeling was recognized by Riemann, who recently answered all the questions of the most advanced up-to-date plasma-sheath boundary theory with cold ions [K.-U. Riemann, Phys. Plasmas 13, 063508 (2006)] but still without the stiff warm ion-source case solution, which is highly resistant to solution via any available analytic method. The present article is an extension of H and T's results obtained for a single point only with ion source temperature T{sub n}=0 to arbitrary finite ion source temperatures. The approach applied in this work is based on the method recently developed by Kos et al. [Phys. Plasmas 16, 093503 (2009)].« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kudo, H.; Shima, K.; Seki, S.
1991-06-01
Ion-beam shadowing effects have been observed for secondary electrons induced by various ions in the energy range of 1.8--3.8 MeV/amu, under various channeling conditions in Si and GaAs crystals. From a comparison of the energy spectra of electrons induced by ions of equal velocity, we have found reduced shadowing effects for heavy ions (Si, S, and Cl) as compared with light (H, He, C, and O) ions. It is concluded that the reduction results from the screening of the heavy ion's nuclear charge by bound electrons. By analyzing the reduced shadowing effect, the effective nuclear charges for the heavy ionsmore » within the target crystals have been determined.« less
Nuts and Bolts of the Ion Band State Theory
NASA Astrophysics Data System (ADS)
Chubb, Scott R.
2005-12-01
The nuts and bolts of our ion band state theory of low energy nuclear reactions (LENR's) in palladium-deuteride (PdD) and palladium-hydride (PdH) are the electrons that hold together or tear apart the bonds (or lack of bonds) between deuterons (d's) or protons (p's) and the host material. In PdDx and PdHx, this bonding is strongly correlated with loading. In ambient loading conditions (x ≲ 0.6), bonding inhibits ion band state occupation. As x → 1, slight increases and decreases in loading can induce "vibrations" (which have conventionally been thought to occur from phonons) that can induce potential losses or increases of p/d. Naive assumptions about phonons fail to include these losses and increases. These effects can occur because neither H or D has core electrons and because in either PdD or PdH, the electrons near the Fermi energy have negligible overlap with the nucleus of either D or H. In the past, implicitly, we have used these facts to justify our ion band state theory. Here, we present a more formal justification, based on the relationship between H(D) ion band states (IBS's) and H(D) phonons that includes a microscopic picture that explains why occupation of IBS's can occur in PdD and PdH and how this can lead to nuclear reactions.
Operation Status of the J-PARC Negative Hydrogen Ion Source
NASA Astrophysics Data System (ADS)
Oguri, H.; Ikegami, K.; Ohkoshi, K.; Namekawa, Y.; Ueno, A.
2011-09-01
A cesium-free negative hydrogen ion source driven with a lanthanum hexaboride (LaB6) filament is being operated without any serious trouble for approximately four years in J-PARC. Although the ion source is capable of producing an H- ion current of more than 30 mA, the current is routinely restricted to approximately 16 mA at present for the stable operation of the RFQ linac which has serious discharge problem from September 2008. The beam run is performed during 1 month cycle, which consisted of a 4-5 weeks beam operation and a few days down-period interval. At the recent beam run, approximately 700 h continuous operation was achieved. At every runs, the beam interruption time due to the ion source failure is a few hours, which correspond to the ion source availability of more than 99%. The R&D work is being performed in parallel with the operation in order to enhance the further beam current. As a result, the H- ion current of 61 mA with normalized rms emittance of 0.26 πmm.mrad was obtained by adding a cesium seeding system to a J-PARC test ion source which has the almost same structure with the present J-PARC ion source.
Monitoring and modulating ion traffic in hybrid lipid/polymer vesicles
Paxton, Walter F.; McAninch, Patrick T.; Achyuthan, Komandoor E.; ...
2017-08-01
Controlling the traffic of molecules and ions across membranes is a critical feature in a number of biologically relevant processes and highly desirable for the development of technologies based on membrane materials. In this study, ion transport behavior of hybrid lipid/polymer membranes was studied in the absence and presence of ion transfer agents. A pH-sensitive fluorophore was used to investigate ion (H +/OH -) permeability across hybrid lipid/polymer membranes as a function of the fraction of amphiphilic block copolymer. It was observed that vesicles with intermediate lipid/polymer ratios tend to be surprisingly more permeable to ion transport than the puremore » lipid or pure polymer vesicles. Hybrid vesicle permeability could be further modulated with valinomycin, nigericin, or gramicidin A, which significantly expedite the dissipation of externally-imposed pH gradients by facilitating the transport of the rate-limiting co-ions (e.g. K +) ions across the membrane. For gramicidin A, ion permeability decreased with increasing polymer mole fraction, and the method of introduction of gramicidin A into the membrane played an important role. Finally, strategies to incorporate biofunctional molecules and facilitate their activity in synthetic systems are highly desirable for developing artificial organelles or other synthetic compartmentalized structures requiring control over molecular traffic across biomimetic membranes.« less
Sekiya, Sadanori; Nagoshi, Keishiro; Iwamoto, Shinichi; Tanaka, Koichi; Takayama, Mitsuo
2015-09-01
The fragment ions observed with time-of-flight (TOF) and quadrupole ion trap (QIT) TOF mass spectrometers (MS) combined with matrix-assisted laser desorption/ionization in-source decay (MALDI-ISD) experiments of phosphorylated analytes β-casein and its model peptide were compared from the standpoint of the residence timeframe of analyte and fragment ions in the MALDI ion source and QIT cell. The QIT-TOF MS gave fragment c-, z'-, z-ANL, y-, and b-ions, and further degraded fragments originating from the loss of neutrals such as H(2)O, NH(3), CH(2)O (from serine), C2H4O (from threonine), and H(3)PO(4), whereas the TOF MS merely showed MALDI source-generated fragment c-, z'-, z-ANL, y-, and w-ions. The fragment ions observed in the QIT-TOF MS could be explained by the injection of the source-generated ions into the QIT cell or a cooperative effect of a little internal energy deposition, a long residence timeframe (140 ms) in the QIT cell, and specific amino acid effects on low-energy CID, whereas the source-generated fragments (c-, z'-, z-ANL, y-, and w-ions) could be a result of prompt radical-initiated fragmentation of hydrogen-abundant radical ions [M + H + H](+) and [M + H - H](-) within the 53 ns timeframe, which corresponds to the delayed extraction time. The further degraded fragment b/y-ions produced in the QIT cell were confirmed by positive- and negative-ion low-energy CID experiments performed on the source-generated ions (c-, z'-, and y-ions). The loss of phosphoric acid (98 u) from analyte and fragment ions can be explained by a slow ergodic fragmentation independent of positive and negative charges.
NASA Astrophysics Data System (ADS)
Sekiya, Sadanori; Nagoshi, Keishiro; Iwamoto, Shinichi; Tanaka, Koichi; Takayama, Mitsuo
2015-09-01
The fragment ions observed with time-of-flight (TOF) and quadrupole ion trap (QIT) TOF mass spectrometers (MS) combined with matrix-assisted laser desorption/ionization in-source decay (MALDI-ISD) experiments of phosphorylated analytes β-casein and its model peptide were compared from the standpoint of the residence timeframe of analyte and fragment ions in the MALDI ion source and QIT cell. The QIT-TOF MS gave fragment c-, z'-, z-ANL, y-, and b-ions, and further degraded fragments originating from the loss of neutrals such as H2O, NH3, CH2O (from serine), C2H4O (from threonine), and H3PO4, whereas the TOF MS merely showed MALDI source-generated fragment c-, z'-, z-ANL, y-, and w-ions. The fragment ions observed in the QIT-TOF MS could be explained by the injection of the source-generated ions into the QIT cell or a cooperative effect of a little internal energy deposition, a long residence timeframe (140 ms) in the QIT cell, and specific amino acid effects on low-energy CID, whereas the source-generated fragments (c-, z'-, z-ANL, y-, and w-ions) could be a result of prompt radical-initiated fragmentation of hydrogen-abundant radical ions [M + H + H]+ and [M + H - H]- within the 53 ns timeframe, which corresponds to the delayed extraction time. The further degraded fragment b/y-ions produced in the QIT cell were confirmed by positive- and negative-ion low-energy CID experiments performed on the source-generated ions (c-, z'-, and y-ions). The loss of phosphoric acid (98 u) from analyte and fragment ions can be explained by a slow ergodic fragmentation independent of positive and negative charges.
Regulating NETosis: Increasing pH Promotes NADPH Oxidase-Dependent NETosis.
Khan, Meraj A; Philip, Lijy M; Cheung, Guillaume; Vadakepeedika, Shawn; Grasemann, Hartmut; Sweezey, Neil; Palaniyar, Nades
2018-01-01
Neutrophils migrating from the blood (pH 7.35-7.45) into the surrounding tissues encounter changes in extracellular pH (pH e ) conditions. Upon activation of NADPH oxidase 2 (Nox), neutrophils generate large amounts of H + ions reducing the intracellular pH (pH i ). Nevertheless, how extracellular pH regulates neutrophil extracellular trap (NET) formation (NETosis) is not clearly established. We hypothesized that increasing pH increases Nox-mediated production of reactive oxygen species (ROS) and neutrophil protease activity, stimulating NETosis. Here, we found that raising pH e (ranging from 6.6 to 7.8; every 0.2 units) increased pH i of both activated and resting neutrophils within 10-20 min (Seminaphtharhodafluor dual fluorescence measurements). Since Nox activity generates H + ions, pH i is lower in neutrophils that are activated compared to resting. We also found that higher pH stimulated Nox-dependent ROS production (R123 generation; flow cytometry, plate reader assay, and imaging) during spontaneous and phorbol myristate acetate-induced NETosis (Sytox Green assays, immunoconfocal microscopy, and quantifying NETs). In neutrophils that are activated and not resting, higher pH stimulated histone H4 cleavage (Western blots) and NETosis. Raising pH increased Escherichia coli lipopolysaccharide-, Pseudomonas aeruginosa (Gram-negative)-, and Staphylococcus aureus (Gram-positive)-induced NETosis. Thus, higher pH e promoted Nox-dependent ROS production, protease activity, and NETosis; lower pH has the opposite effect. These studies provided mechanistic steps of pH e -mediated regulation of Nox-dependent NETosis. Raising pH either by sodium bicarbonate or Tris base (clinically known as Tris hydroxymethyl aminomethane, tromethamine, or THAM) increases NETosis. Each Tris molecule can bind 3H + ions, whereas each bicarbonate HCO3 - ion binds 1H + ion. Therefore, the amount of Tris solution required to cause the same increase in pH level is less than that of equimolar
Ion Source Development at the SNS
NASA Astrophysics Data System (ADS)
Welton, R. F.; Stockli, M. P.; Murray, S. N.; Carr, J.; Carmichael, J.; Goulding, R. H.; Baity, F. W.
2007-08-01
The US Spallation Neutron Source (SNS) has recently begun producing neutrons and is currently on track to becoming a world-leading facility for material science based on neutron scattering. The facility is comprised of an H- ion source, a linear accelerator, an accumulator ring, a liquid-Hg target and a suite of neutron scattering instruments. Over the next several years the average H- current from the ion source will be increased in order to meet the baseline facility requirement of providing 1.4 MW of beam-power to the target and the SNS power upgrade power requirement of 2+ MW on target. Meeting the latter goal will require H- currents of 70-100 mA with an RMS emittance of 0.20-0.35 π mm mrad and a ˜7% duty-factor. To date, the RF-driven-multicusp SNS ion source has only been able to demonstrate sustained operation at 33 mA of beam current at a ˜7% duty-factor. This report details our efforts to develop variations of the current ion source which can meet these requirements. Designs and experimental results are presented for helicon plasma drivers, high-power external antennas, glow-discharge plasma guns and advanced Cs systems.
Chen, Shaojiang; Popovich, John; Iannuzo, Natalie; Haydel, Shelley E; Seo, Dong-Kyun
2017-11-15
As antibiotic resistance continues to be a major public health problem, antimicrobial alternatives have become critically important. Nanostructured zeolites have been considered as an ideal host for improving popular antimicrobial silver-ion-exchanged zeolites, because with very short diffusion path lengths they offer advantages in ion diffusion and release over their conventional microsized zeolite counterparts. Herein, comprehensive studies are reported on materials characteristics, silver-ion release kinetics, and antibacterial properties of silver-ion-exchanged nanostructured zeolite X with comparisons to conventional microsized silver-ion-exchanged zeolite (∼2 μm) as a reference. The nanostructured zeolites are submicrometer-sized aggregates (100-700 nm) made up of primary zeolite particles with an average primary particle size of 24 nm. The silver-ion-exchanged nanostructured zeolite released twice the concentration of silver ions at a rate approximately three times faster than the reference. The material exhibited rapid antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) with minimum inhibitory concentration (MIC) values ranging from 4 to 16 μg/mL after 24 h exposure in various growth media and a minimum bactericidal concentration (MBC; >99.9% population reduction) of 1 μg/mL after 2 h in water. While high concentrations of silver-ion-exchanged nanostructured zeolite X were ineffective at reducing MRSA biofilm cell viability, efficacy increased at lower concentrations. In consideration of potential medical applications, cytotoxicity of the silver-ion-exchanged nanostructured zeolite X was also investigated. After 4 days of incubation, significant reduction in eukaryotic cell viability was observed only at concentrations 4-16-fold greater than the 24 h MIC, indicating low cytotoxicity of the material. Our results establish silver-ion-exchanged nanostructured zeolites as an effective antibacterial material against dangerous
Graphene defects induced by ion beam
NASA Astrophysics Data System (ADS)
Gawlik, Grzegorz; Ciepielewski, Paweł; Baranowski, Jacek; Jagielski, Jacek
2017-10-01
The CVD graphene deposited on the glass substrate was bombarded by molecular carbon ions C3+ C6+ hydrocarbon ions C3H4+ and atomic ions He+, C+, N+, Ar+, Kr+ Yb+. Size and density of ion induced defects were estimated from evolution of relative intensities of Raman lines D (∼1350 1/cm), G (∼1600 1/cm), and D‧ (∼1620 1/cm) with ion fluence. The efficiency of defect generation by atomic ions depend on ion mass and energy similarly as vacancy generation directly by ion predicted by SRIM simulations. However, efficiency of defect generation in graphene by molecular carbon ions is essentially higher than summarized efficiency of similar group of separate atomic carbon ions of the same energy that each carbon ion in a cluster. The evolution of the D/D‧ ratio of Raman lines intensities with ion fluence was observed. This effect may indicate evolution of defect nature from sp3-like at low fluence to a vacancy-like at high fluence. Observed ion graphene interactions suggest that the molecular ion interacts with graphene as single integrated object and should not be considered as a group of atomic ions with partial energy.
Liu, Fenwu; Zhou, Jun; Jin, Tongjun; Zhang, Shasha; Liu, Lanlan
2016-01-01
Calcium oxide was added into ferrous ion oxidation system in the presence of Acidithiobacillus ferrooxidans at concentrations of 0-4.00 g/L. The pH, ferrous ion oxidation efficiency, total iron precipitation efficiency, and phase of the solid minerals harvested from different treatments were investigated during the ferrous ion oxidation process. In control check (CK) system, pH of the solution decreased from 2.81 to 2.25 when ferrous ions achieved complete oxidation after 72 h of Acidithiobacillus ferrooxidans incubation without the addition of calcium oxide, and total iron precipitation efficiency reached 20.2%. Efficiency of ferrous ion oxidation and total iron precipitation was significantly improved when the amount of calcium oxide added was ≤1.33 g/L, and the minerals harvested from systems were mainly a mixture of jarosite and schwertmannite. For example, the ferrous ion oxidation efficiency reached 100% at 60 h and total iron precipitation efficiency was increased to 32.1% at 72 h when 1.33 g/L of calcium oxide was added. However, ferrous ion oxidation and total iron precipitation for jarosite and schwertmannite formation were inhibited if the amount of calcium oxide added was above 2.67 g/L, and large amounts of calcium sulfate dihydrate were generated in systems.
Guo, Qiang; Chen, Li; Shan, Zizhao; Lee, Wee Siang Vincent; Xiao, Wen; Liu, Zhifang; Liang, Jingjing; Yang, Gaoli; Xue, Junmin
2018-01-10
H 2 Ti 12 O 25 holds great promise as a high-voltage anode material for advanced lithium-ion battery applications. To enhance its electrochemical performance, control of the crystal orientation and morphology is an effective way to cope with slow Li + -ion diffusion inside H 2 Ti 12 O 25 with severe anisotropy. In this report, Na 2 Ti 6 O 13 nanorods, prepared from Na 2 CO 3 and anatase TiO 2 in molten NaCl medium, were used as a precursor in the synthesis of long single-crystal H 2 Ti 12 O 25 nanorods with reactive facets. The as-prepared H 2 Ti 12 O 25 nanorods with a diameter of 100-200 nm showed higher charge (extraction) specific capacity and better rate performance than previously reported systems. The reversible capacity of H 2 Ti 12 O 25 was 219.8 mAh g -1 at 1C after 100 cycles, 172.1 mAh g -1 at 10C, and 144.4 mAh g -1 at 20C after 200 cycles; these values are higher than those of H 2 Ti 12 O 25 prepared by the conventional soft-chemical method. Moreover, the as-prepared H 2 Ti 12 O 25 nanorods exhibited superior cycle stability with more than 94 % retention of capacity with nearly 100 % coulombic efficiency after 100 cycles at 1C. On the basis of the above results, long single-crystal H 2 Ti 12 O 25 nanorods synthesized in molten NaCl with outstanding electrochemical characteristics hold a significant amount of promise for hybrid electric vehicles and energy-storage systems. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Recrystallization-Induced Surface Cracks of Carbon Ions Irradiated 6H-SiC after Annealing
Ye, Chao; Ran, Guang; Zhou, Wei; Shen, Qiang; Feng, Qijie; Lin, Jianxin
2017-01-01
Single crystal 6H-SiC wafers with 4° off-axis [0001] orientation were irradiated with carbon ions and then annealed at 900 °C for different time periods. The microstructure and surface morphology of these samples were investigated by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Ion irradiation induced SiC amorphization, but the surface was smooth and did not have special structures. During the annealing process, the amorphous SiC was recrystallized to form columnar crystals that had a large amount of twin structures. The longer the annealing time was, the greater the amount of recrystallized SiC would be. The recrystallization volume fraction was accorded with the law of the Johnson–Mehl–Avrami equation. The surface morphology consisted of tiny pieces with an average width of approximately 30 nm in the annealed SiC. The volume shrinkage of irradiated SiC layer and the anisotropy of newly born crystals during annealing process produced internal stress and then induced not only a large number of dislocation walls in the non-irradiated layer but also the initiation and propagation of the cracks. The direction of dislocation walls was perpendicular to the growth direction of the columnar crystal. The longer the annealing time was, the larger the length and width of the formed crack would be. A quantitative model of the crack growth was provided to calculate the length and width of the cracks at a given annealing time. PMID:29068408
Recrystallization-Induced Surface Cracks of Carbon Ions Irradiated 6H-SiC after Annealing.
Ye, Chao; Ran, Guang; Zhou, Wei; Shen, Qiang; Feng, Qijie; Lin, Jianxin
2017-10-25
Single crystal 6H-SiC wafers with 4° off-axis [0001] orientation were irradiated with carbon ions and then annealed at 900 °C for different time periods. The microstructure and surface morphology of these samples were investigated by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Ion irradiation induced SiC amorphization, but the surface was smooth and did not have special structures. During the annealing process, the amorphous SiC was recrystallized to form columnar crystals that had a large amount of twin structures. The longer the annealing time was, the greater the amount of recrystallized SiC would be. The recrystallization volume fraction was accorded with the law of the Johnson-Mehl-Avrami equation. The surface morphology consisted of tiny pieces with an average width of approximately 30 nm in the annealed SiC. The volume shrinkage of irradiated SiC layer and the anisotropy of newly born crystals during annealing process produced internal stress and then induced not only a large number of dislocation walls in the non-irradiated layer but also the initiation and propagation of the cracks. The direction of dislocation walls was perpendicular to the growth direction of the columnar crystal. The longer the annealing time was, the larger the length and width of the formed crack would be. A quantitative model of the crack growth was provided to calculate the length and width of the cracks at a given annealing time.
RF synchronized short pulse laser ion source
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fuwa, Yasuhiro, E-mail: fuwa@kyticr.kuicr.kyoto-u.ac.jp; Iwashita, Yoshihisa; Tongu, Hiromu
A laser ion source that produces shortly bunched ion beam is proposed. In this ion source, ions are extracted immediately after the generation of laser plasma by an ultra-short pulse laser before its diffusion. The ions can be injected into radio frequency (RF) accelerating bucket of a subsequent accelerator. As a proof-of-principle experiment of the ion source, a RF resonator is prepared and H{sub 2} gas was ionized by a short pulse laser in the RF electric field in the resonator. As a result, bunched ions with 1.2 mA peak current and 5 ns pulse length were observed at themore » exit of RF resonator by a probe.« less
Heavy-ion dominance near Cluster perigees
NASA Astrophysics Data System (ADS)
Ferradas, C. P.; Zhang, J.-C.; Kistler, L. M.; Spence, H. E.
2015-12-01
Time periods in which heavy ions dominate over H+ in the energy range of 1-40 keV were observed by the Cluster Ion Spectrometry (CIS)/COmposition DIstribution Function (CODIF) instrument onboard Cluster Spacecraft 4 at L values less than 4. The characteristic feature is a narrow flux peak at around 10 keV that extends into low L values, with He+ and/or O+ dominating. In the present work we perform a statistical study of these events and examine their temporal occurrence and spatial distribution. The observed features, both the narrow energy range and the heavy-ion dominance, can be interpreted using a model of ion drift from the plasma sheet, subject to charge exchange losses. The narrow energy range corresponds to the only energy range that has direct drift access from the plasma sheet during quiet times. The drift time to these locations from the plasma sheet is > 30 h, so that charge exchange has a significant impact on the population. We show that a simple drift/loss model can explain the dependence on L shell and MLT of these heavy-ion-dominant time periods.