Effect on the Lunar Exosphere of a CME Passage

NASA Technical Reports Server (NTRS)

Killen, Rosemary M.; Hurley, Dana M.; Farrell, William M.; Sarantos, Menelaos

2011-01-01

It has long been recognized that solar wind bombardment onto exposed surfaces in the solar system will produce an energetic component to the exospheres about those bodies. Laboratory experiments have shown that the sputter yield can be noticeably increased in the case of a good insulating surface. It is now known that the solar wind composition is highly dependent on the origin of the particular plasma. Using the measured composition of the slow wind, fast wind, solar energetic particle (SEP) population, and coronal mass ejection (CME), broken down into its various components, we have estimated the total sputter yield for each type of solar wind. The heavy ion component, especially the He++ component, greatly enhances the total sputter yield during times when the heavy ion population is enhanced, most notably during a coronal mass ejection. To simulate the effect on the lunar exosphere of a CME passage past the Moon, we ran a Monte Carlo code for the species Na, K, Mg and Ca.

Mechanical properties of ion-beam-textured surgical implant alloys

NASA Technical Reports Server (NTRS)

Weigand, A. J.

1977-01-01

An electron-bombardment Hg ion thruster was used as an ion source to texture surfaces of materials used to make orthopedic and/or dental prostheses or implants. The materials textured include 316 stainless steel, titanium-6% aluminum, 4% vanadium, and cobalt-20% chromium, 15% tungsten. To determine the effect of ion texturing on the ultimate strength and yield strength, stainless steel and Co-Cr-W alloy samples were tensile tested to failure. Three types of samples of both materials were tested. One type was ion-textured (the process also heats each sample to 300 C), another type was simply heated to 300 C in an oven, and the third type was untreated. Stress-strain diagrams, 0.2% offset yield strength data, total elongation data, and area reduction data are presented. Fatigue specimens of ion textured and untextured 316 stainless steel and Ti-6% Al-4% V were tested. Included as an ion textured sample is a Ti-6% Al-4% V sample which was ion machined by means of Ni screen mask so as to produce an array of 140 mu m x 140 mu m x 60 mu m deep pits. Scanning electron microscopy was used to characterize the ion textured surfaces.

A New Poisson-Nernst-Planck Model with Ion-Water Interactions for Charge Transport in Ion Channels.

PubMed

Chen, Duan

2016-08-01

In this work, we propose a new Poisson-Nernst-Planck (PNP) model with ion-water interactions for biological charge transport in ion channels. Due to narrow geometries of these membrane proteins, ion-water interaction is critical for both dielectric property of water molecules in channel pore and transport dynamics of mobile ions. We model the ion-water interaction energy based on realistic experimental observations in an efficient mean-field approach. Variation of a total energy functional of the biological system yields a new PNP-type continuum model. Numerical simulations show that the proposed model with ion-water interaction energy has the new features that quantitatively describe dielectric properties of water molecules in narrow pores and are possible to model the selectivity of some ion channels.

Electron impact ionization of the gas-phase sorbitol

NASA Astrophysics Data System (ADS)

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

2015-03-01

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

On the Heating of Ions in Noncylindrical Z-Pinches

NASA Astrophysics Data System (ADS)

Svirsky, E. B.

2018-01-01

The method proposed here for analyzing processes in a hot plasma of noncylindrical Z-pinches is based on separation of the group of high-energy ions into a special fraction. Such ions constitute an insignificant fraction ( 10%) of the total volume of the Z-pinch plasma, but these ions contribute the most to the formation of conditions in which the pinch becomes a source of nuclear fusion products and X-ray radiation. The method allows a quite correct approach to obtaining quantitative estimates of the plasma parameters, the nuclear fusion energy yield, and the features of neutron fluxes in experiments with Z-pinches.

Correlation between molecular secondary ion yield and cluster ion sputtering for samples with different stopping powers

NASA Astrophysics Data System (ADS)

Heile, A.; Muhmann, C.; Lipinsky, D.; Arlinghaus, H. F.

2012-07-01

In static SIMS, the secondary ion yield, defined as detected ions per primary ion, can be increased by altering several primary ion parameters. For many years, no quantitative predictions could be made for the secondary ion yield enhancement of molecular ions. For thick samples of organic compounds, a power dependency of the secondary ion yield on the sputtering yield was shown. For this article, samples with thick molecular layers and (sub-)monolayers composed of various molecules were prepared on inorganic substrates such as silicon, silver, and gold, and subsequently analyzed. For primary ion bombardment, monoatomic (Ne+, Ar+, Ga+, Kr+, Xe+, Bi+) as well as polyatomic (Bin+, Bin++) primary ions were used within an energy range of 10-50 keV. The power dependency was found to hold true for the different samples; however, the exponent decreased with increasing stopping power. Based on these findings, a rule of thumb is proposed for the prediction of the lower limit of the secondary ion yield enhancement as a function of the primary ion species. Additionally, effects caused by the variation of the energy deposition are discussed, including the degree of molecular fragmentation and the non-linear increase of the secondary ion yield when polyatomic primary ions are used.

An investigation of enhanced secondary ion emission under Au(n)+ (n = 1-7) bombardment.

PubMed

Nagy, G; Gelb, L D; Walker, A V

2005-05-01

We investigate the mechanism of the nonlinear secondary ion yield enhancement using Au(n)+ (n = 1, 2, 3, 5, 7) primary ions bombarding thin films of Irganox 1010, DL-phenylalanine and polystyrene on Si, Al, and Ag substrates. The largest differences in secondary ion yields are found using Au+, Au2+, and Au3+ primary ion beams. A smaller increase in secondary ion yield is observed using Au5+ and Au7+ primary ions. The yield enhancement is found to be larger on Si than on Al, while the ion yield is smaller using an Au+ beam on Si than on Al. Using Au(n)+ ion structures obtained from Density Functional Theory, we demonstrate that the secondary yield enhancement is not simply due to an increase in energy per area deposited into the surface (energy deposition density). Instead, based on simple mechanical arguments and molecular dynamics results from Medvedeva et al, we suggest a mechanism for nonlinear secondary ion yield enhancement wherein the action of multiple concerted Au impacts leads to efficient energy transfer to substrate atoms in the near surface region and an increase in the number of secondary ions ejected from the surface. Such concerted impacts involve one, two, or three Au atoms, which explains well the large nonlinear yield enhancements observed going from Au+ to Au2+ to Au3+ primary ions. This model is also able to explain the observed substrate effect. For an Au+ ion passing through the more open Si surface, it contacts fewer substrate atoms than in the more dense Al surface. Less energy is deposited in the Si surface region by the Au+ primary ion and the secondary ion yield will be lower for adsorbates on Si than on Al. In the case of Au(n)+ the greater density of Al leads to earlier break-up of the primary ion and a consequent reduction in energy transfer to the near-surface region when compared with Si. This results in higher secondary ion yields and yield enhancements on silicon than aluminum substrates.

X-ray absorption spectroscopy and photoluminescence study of rare earth ions doped strontium sulphide phosphors

NASA Astrophysics Data System (ADS)

Vij, Ankush; Gautam, Sanjeev; Kumar, Vinay; Brajpuriya, R.; Kumar, Ravi; Singh, Nafa; Chae, Keun Hwa

2013-01-01

We present here the electronic structure and photoluminescence properties of Sm (0.1-1.0 mol%) doped SrS phosphors. The doping in SrS was probed by near-edge X-ray absorption fine structure (NEXAFS) at M5,4-edges of Sm in total electron yield mode. The simulated absorption edges using atomic multiplet calculations were correlated with experimental results, which clearly reveal the presence of trivalent state of Sm in SrS matrix. However, for Sm (1 mol%), very minor traces of Sm2+ were also observed, which have been explained by comparing the NEXAFS spectra in total electron and florescence yield mode. The PL emission of SrS:Sm comprises of three sharp bands at 567, 602 and 650 nm owing to the well-known intra 4f transitions from 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2) levels of Sm3+ ions in SrS host. The effect of Ce co-doping on SrS:Sm phosphors was also investigated, which exhibits characteristic PL emission of independent ions at their respective excitation wavelengths. However, at an excitation wavelength of 393 nm, SrS:Ce,Sm exhibits the simultaneous characteristic PL emission of both ions spanning into blue-green-red region. The CIE chromaticity coordinates also clearly show the influence of excitation wavelengths on the emission colour of SrS:Ce,Sm.

Dissociative-ionization cross sections for 12-keV-electron impact on CO{sub 2}

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

Bhatt, Pragya; Singh, Raj; Yadav, Namita

The dissociative ionization of a CO{sub 2} molecule is studied at an electron energy of 12 keV using the multiple ion coincidence imaging technique. The absolute partial ionization cross sections and the precursor-specific absolute partial ionization cross sections of resulting fragment ions are obtained and reported. It is found that {approx}75% of single ionization, 22% of double ionization, and {approx}2% of triple ionization of the parent molecule contribute to the total fragment ion yield; quadruple ionization of CO{sub 2} is found to make a negligibly small contribution. Furthermore, the absolute partial ionization cross sections for ion-pair and ion-triple formation aremore » measured for nine dissociative ionization channels of up to a quadruply ionized CO{sub 2} molecule. In addition, the branching ratios for single-ion, ion-pair, and ion-triple formation are also determined.« less

Contribution of energetic and heavy ions to the plasma pressure: The 27 September to 3 October 2002 storm

NASA Astrophysics Data System (ADS)

Kronberg, E. A.; Welling, D.; Kistler, L. M.; Mouikis, C.; Daly, P. W.; Grigorenko, E. E.; Klecker, B.; Dandouras, I.

2017-09-01

Magnetospheric plasma sheet ions drift toward the Earth and populate the ring current. The ring current plasma pressure distorts the terrestrial internal magnetic field at the surface, and this disturbance strongly affects the strength of a magnetic storm. The contribution of energetic ions (>40 keV) and of heavy ions to the total plasma pressure in the near-Earth plasma sheet is not always considered. In this study, we evaluate the contribution of low-energy and energetic ions of different species to the total plasma pressure for the storm observed by the Cluster mission from 27 September until 3 October 2002. We show that the contribution of energetic ions (>40 keV) and of heavy ions to the total plasma pressure is ≃76-98.6% in the ring current and ≃14-59% in the magnetotail. The main source of oxygen ions, responsible for ≃56% of the plasma pressure of the ring current, is located at distances earthward of XGSE ≃ -13.5 RE during the main phase of the storm. The contribution of the ring current particles agrees with the observed Dst index. We model the magnetic storm using the Space Weather Modeling Framework (SWMF). We assess the plasma pressure output in the ring current for two different ion outflow models in the SWMF through comparison with observations. Both models yield reasonable results. The model which produces the most heavy ions agrees best with the observations. However, the data suggest that there is still potential for refinement in the simulations.

Escape of anions from geminate recombination in THF due to charge delocalization

DOE PAGES

Chen, Hung -Cheng; Cook, Andrew R.; Asaoka, Sadayuki; ...

2017-11-24

Geminate recombination of 24 radical anions (M˙ –) with solvated protons (RH 2 +) was studied in tetrahydrofuran (THF) with pulse radiolysis. The recombination has two steps: (1) diffusion of M˙ – and RH 2 + together to form intimate (contact and solvent separated) ion pairs, driven by Coulomb attraction; (2) annihilation of anions due to proton transfer (PT) from RH 2 + to M˙ –. The non-exponential time-dependence of the geminate diffusion was determined. For all molecules protonated on O or N atoms the subsequent PT step is too fast (<0.2 ns) to measure, except for the anion ofmore » TCNE which did not undergo proton transfer. PT to C atoms was as slow as 70 ns and was always slow enough to be observable. A possible effect of charge delocalization on the PT rates could not be clearly separated from other factors. For 21 of the 24 molecules studied here, a free ion yield (71.6 ± 6.2 nmol J –1) comprising ~29% of the total, was formed. This yield of “Type I” free ions is independent of the PT rate because it arises entirely by escape from the initial distribution of ion pair distances without forming intimate ion pairs. Furthermore, three anions of oligo(9,9-dihexyl)fluorenes, F n˙ – (n = 2–4) were able to escape from intimate ion-pairs to form additional yields of “Type II” free ions with escape rate constants near 3 × 10 6 s –1. These experiments find no evidence for an inverted region for proton transfer.« less

Modeling of life limiting phenomena in the discharge chamber of an electron bombardment ion thruster

NASA Technical Reports Server (NTRS)

Handoo, Arvind K.; Ray, Pradosh K.

1991-01-01

An experimental facility to study the low energy sputtering of metal surfaces with ions produced by an ion gun is described. The energy of the ions ranged from 10 to 500 eV. Cesium ions with energies from 100 to 500 eV were used initially to characterize the operation of the ion gun. Next, argon and xenon ions were used to measure the sputtering yields of cobalt (Co), Cadmium (Cd), and Chromium (Cr) at an operating temperature of 2x10(exp -5) Torr. The ion current ranged from 0.0135 micro-A at 500 eV. The targets were electroplated on a copper substrate. The surface density of the electroplated material was approx. 50 micro-g/sq cm. The sputtered atoms were collected on an aluminum foil surrounding the target. Radioactive tracers were used to measure the sputtering yields. The sputtering yields of Cr were found to be much higher than those of Co and Cd. The yields of Co and Cd were comparable, with Co providing the higher yields. Co and Cd targets were observed to sputter at energies as low as 10 eV for both argon and xenon ions. The Cr yields could not be measured below 20 eV for argon ions and 15 eV for xenon ions. On a linear scale the yield energy curves near the threshold energies exhibit a concave nature.

Electronic sputtering of vitreous SiO2: Experimental and modeling results

NASA Astrophysics Data System (ADS)

Toulemonde, M.; Assmann, W.; Trautmann, C.

2016-07-01

The irradiation of solids with swift heavy ions leads to pronounced surface and bulk effects controlled by the electronic energy loss of the projectiles. In contrast to the formation of ion tracks in bulk materials, the concomitant emission of atoms from the surface is much less investigated. Sputtering experiments with different ions (58Ni, 127I and 197Au) at energies around 1.2 MeV/u were performed on vitreous SiO2 (a-SiO2) in order to quantify the emission rates and compare them with data for crystalline SiO2 quartz. Stoichiometry of the sputtering process was verified by monitoring the thickness decreases of a thin SiO2 film deposited on a Si substrate. Angular distributions of the emitted atoms were measured by collecting sputtered atoms on arc-shaped Cu catcher foils. Subsequent analysis of the number of Si atoms deposited on the catcher foils was quantified by elastic recoil detection analysis providing differential as well as total sputtering yields. Compared to existing data for crystalline SiO2, the total sputtering yields for vitreous SiO2 are by a factor of about five larger. Differences in the sputtering rate and track formation characteristics between amorphous and crystalline SiO2 are discussed within the frame of the inelastic thermal spike model.

Enhanced secondary ion emission with a bismuth cluster ion source

NASA Astrophysics Data System (ADS)

Nagy, G.; Walker, A. V.

2007-04-01

We have investigated the mechanism of secondary ion yield enhancement using Bin+ (n = 1-6) primary ions and three different samples - dl-phenylalanine, Irganox 1010 and polystyrene - adsorbed on Al, Si and Ag substrates. The largest changes in secondary ion yields are observed for Bi2+ and Bi3+ primary ions. Smaller increases in secondary ion yield are found using Bi4+, Bi5+ and Bi6+ projectiles. The secondary ion yield enhancements are generally larger on Si than on Al. Using Bin+ structures obtained from density functional theory (DFT) calculations we demonstrate that the yield enhancements cannot be explained by an increase in the deposited energy density (energy per area) into the substrate. These data show that the mechanism of Bin+ sputtering is very similar to that for Aun+ primary ion beams. When a polyatomic primary ion strikes the substrate, its constituent atoms are likely to remain near to each other, and so a substrate atom can be struck simultaneously by multiple atoms. The action of these multiple concerted impacts leads to efficient energy transfer in the near surface region and an increase in the number of secondary ions ejected from the surface. Such concerted impacts involve one, two or three projectile atoms, which explains well the nonlinear yield enhancements observed going from Bi+ to Bi2+ to Bi3+.

Yield and ion distribution for the barium cloud at 31,000 kilometers, September 21, 1971.

NASA Technical Reports Server (NTRS)

Manring, E. R.; Patty, R. R.

1973-01-01

The photon flux density associated with the 4554-A resonance radiation for Ba II was measured at Mount Hopkins, Arizona, and Cerro Morado, Chile, and was determined to be 36,000 photon/sq cm sec outside the atmosphere; this measurement was made when the cloud was optically thin at 120 sec after release. Using this and a photon scattering efficiency of 0.66 photon/ion sec we estimate a 1.7-kg yield of barium ions that are formed from the initially released atomic barium and are thus associated with the main core of the cloud. Photographic and photometric data are combined to obtain preliminary values for the brightness throughout the cloud for two photographs, and isobrightness plots are presented. These plots indicate that the cloud is quite narrow, that a considerable portion of the ionized barium is outside the main core after a few minutes, and that the striations contain only a small fraction of the total material.

Simultaneous biosorption of chromium(VI) and copper(II) on Rhizopus arrhizus in packed column reactor: Application of the competitive Freundlich model

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

Sag, Y.; Atacoglu, I.; Kutsal, T.

1999-12-01

The simultaneous biosorption of Cr(VI) and Cu(II) on free Rhizopus arrhizus in a packed column operated in the continuous mode was investigated and compared to the single metal ion situation. The breakthrough curves were measured as a function of feed flow rate, feed pH, and different combinations of metal ion concentrations in the feed solutions. Column competitive biosorption data were evaluated in terms of the maximum (equilibrium) capacity in the column, the amount of metal loading on the R. arrhizus surface, the adsorption yield, and the total adsorption yield. In the single-ion situation the adsorption isotherms were developed for optimummore » conditions, and it was seen that the adsorption equilibrium data fit the noncompetitive Freundlich model. For the multicomponent adsorption equilibrium the competitive adsorption isotherms were also developed. The competitive Freundlich model for binary metal mixtures represented most the column adsorption equilibrium data of Cr(VI) and Cu(II) on R. arrhizus satisfactorily.« less

Desorption Induced by KEV Molecular and Cluster Projectiles.

NASA Astrophysics Data System (ADS)

Blain, Matthew Glenn

1990-01-01

A new experimental method has been developed for studying negative secondary ion (SI) emission from solid surfaces bombarded by polyatomic primary ions of 5 to 30 keV. The method is based on the time-of-flight (TOF) analysis of primary ions which are produced by either ^ {252}Cf fission fragment induced desorption or by extraction from a liquid metal ion source, and then accelerated into a field free region. The primary ions included organic monomer, dimer, and fragment ions of coronene and phenylalanine, (CsI)_ nCs ^{+} cluster ions, and Au _sp{n}{+} cluster ions. Secondary electrons, emitted from a target surface upon primary ion impact, are used to identify which primary ion has hit the surface. An event-by-event coincidence counting technique allows several secondary ion TOF spectra, correlated to several different primary ions, to be acquired simultaneously. Negative SI yields from organic (phenylalanine and dinitrostilbene), CsI, and Au surfaces have been measured for a number of different mono- and polyatomic primary ions. The results show, for example, yields ranging from 1 to 10% for phenylalanine (M-H) ^{ -}, 1 to 10% for I^{-} , and 1 to 5% for Au^{-} , with Cs_2I^ {+} and Cs_3I _sp{2}{+} clusters as projectiles. Yields for the same surfaces using Cs ^{+} primary ions are much less than 1%, indicating that SI yields are enhanced with clusters. A yield enhancement occurs when the SI yield per atom of a polyatomic projectile is greater than the SI yield of its monoatomic equivalent, at the same velocity. Thus, a (M-H) ^{-} yield increase of a factor of 50, when phenylalanine is bombarded with Cs_3I_sp{2} {+} instead of Cs^{+ }, represents a yield enhancement factor of 10. For the projectiles and samples studied, it was observed that the heavier the mass of the constituents of a projectile, the larger the enhancement effects, and that the largest yield enhancements (with CsI and Au _ n projectiles) occur for the organic target, phenylalanine. One possible explanation for the larger enhancements with organics, namely a thermal spike process, appears unlikely. Experiments with high and low melting point isomers of dinitrostilbene, bombarded with Cs _2I^{+} and Cs^{+} projectiles, showed larger Cs_2I^ {+} yield enhancements for the high melting point isomer.

Quantification of diesel exhaust gas phase organics by a thermal desorption proton transfer reaction mass spectrometer

NASA Astrophysics Data System (ADS)

Erickson, M. H.; Wallace, H. W.; Jobson, B. T.

2012-02-01

A new approach was developed to measure the total abundance of long chain alkanes (C12 and above) in urban air using thermal desorption with a proton transfer reaction mass spectrometer (PTR-MS). These species are emitted in diesel exhaust and may be important precursors to secondary organic aerosol production in urban areas. Long chain alkanes undergo dissociative proton transfer reactions forming a series of fragment ions with formula CnH2n+1. The yield of the fragment ions is a function of drift conditions. At a drift field strength of 80 Townsends, the most abundant ion fragments from C10 to C16 n-alkanes were m/z 57, 71 and 85. The PTR-MS is insensitive to n-alkanes less than C8 but displays an increasing sensitivity for larger alkanes. Higher drift field strengths yield greater normalized sensitivity implying that the proton affinity of the long chain n-alkanes is less than H2O. Analysis of diesel fuel shows the mass spectrum was dominated by alkanes (CnH2n+1), monocyclic aromatics, and an ion group with formula CnH2n-1 (m/z 97, 111, 125, 139). The PTR-MS was deployed in Sacramento, CA during the Carbonaceous Aerosols and Radiative Effects Study field experiment in June 2010. The ratio of the m/z 97 to 85 ion intensities in ambient air matched that found in diesel fuel. Total diesel exhaust alkane concentrations calculated from the measured abundance of m/z 85 ranged from the method detection limit of ~1 μg m-3 to 100 μg m-3 in several air pollution episodes. The total diesel exhaust alkane concentration determined by this method was on average a factor of 10 greater than the sum of alkylbenzenes associated with spark ignition vehicle exhaust.

Considerations about projectile and target X-rays induced during heavy ion bombardment

NASA Astrophysics Data System (ADS)

Fernandes, F.; Bauer, D. V.; Duarte, A.; Ferrari, T. M.; Niekraszewicz, L. A. B.; Amaral, L.; Dias, J. F.

2018-02-01

In this work we present some results concerning the X-rays emitted by heavy ions during target bombardment. In this case, Cl4+ and Cl5+ ions with energies from 4 MeV to 10 MeV were employed to irradiate vitreous carbon planchets. Moreover, total X-ray production cross sections of titanium X-rays induced by chlorine ions were obtained as well for the same energy range. Only inner shell transitions were considered in the present work. The titanium target consisted of a thin film deposited over vitreous carbon planchets. The results indicate that the projectile X-ray yields increase as a function of the bombarding energy for the present energy range. Effects due to projectile charge state appears to be of minor importance at these low ion velocities. It is shown that a simple exponential function can represent the continuum background of such complex spectra. The chlorine transition rates Kβ/Kα obtained from chlorine acting as a projectile interacting with a carbon target are about half the value when compared to the chlorine Kβ/Kα ratios obtained when a LiCl target is bombarded with C+ and C3+ ions with energies from 2 MeV to 6 MeV. As far as the total X-ray production cross sections of Ti induced by chlorine ions are concerned, the ECPSSR theory underestimates the Ti total X-rays production cross sections by several orders of magnitude. The role of electron capture and possible mechanisms responsible for these effects are discussed.

Constrained sheath optics for high thrust density, low specific impulse ion thrusters

NASA Technical Reports Server (NTRS)

Wilbur, Paul J.; Han, Jian-Zhang

1987-01-01

The results of an experimental study showing that a contoured, fine wire mesh attached to the screen grid can be used to control the divergence characteristics of ion beamlets produced at low net-to-total accelerating voltage ratios are presented. The influence of free and constrained-sheath optics systems on beamlet divergence characteristics are found to be similar in the operating regime investigated, but it was found that constrained-sheath optics systems can be operated at higher perveance levels than free-sheath ones. The concept of a fine wire interference probe that can be used to study ion beamlet focusing behavior is introduced. This probe is used to demonstrate beamlet focusing to a diameter about one hundreth of the screen grid extraction aperture diameter. Additional testing is suggested to define an optimally contoured mesh that could yield well focused beamlets at net-to-total accelerating voltage ratios below about 0.1.

Enantioselective total synthesis of (-)-strychnine using the catalytic asymmetric Michael reaction and tandem cyclization.

PubMed

Ohshima, Takashi; Xu, Youjun; Takita, Ryo; Shimizu, Satoshi; Zhong, Dafang; Shibasaki, Masakatsu

2002-12-11

The enantioselective total synthesis of (-)-strychnine was accomplished through the use of the highly practical catalytic asymmetric Michael reaction (0.1 mol % of (R)-ALB, more than kilogram scale, without chromatography, 91% yield and >99% ee) as well as a tandem cyclization that simultaneously constructed B- and D-rings (>77% yield). Moreover, newly developed reaction conditions for thionium ion cyclization, NaBH3CN reduction of the imine moiety in the presence of Lewis acid to prevent ring opening reaction, and chemoselective reduction of the thioether (desulfurization) in the presence of exocyclic olefin were pivotal to complete the synthesis. The described chemistry paves the way for the synthesis of more advanced Strychnos alkaloids.

Suppression of self-organized surface nanopatterning on GaSb/InAs multilayers induced by low energy oxygen ion bombardment by using simultaneously sample rotation and oxygen flooding

NASA Astrophysics Data System (ADS)

Beainy, Georges; Cerba, Tiphaine; Bassani, Franck; Martin, Mickaël; Baron, Thierry; Barnes, Jean-Paul

2018-05-01

Time of flight secondary ion mass spectrometry (ToF-SIMS) is a well-adapted analytical method for the chemical characterization of concentration profiles in layered or multilayered materials. However, under ion beam bombardment, initially smooth material surface becomes morphologically unstable. This leads to abnormal secondary ion yields and depth profile distortions. In this contribution, we explore the surface topography and roughening evolution induced by O2+ ion bombardment on GaSb/InAs multilayers. We demonstrate the formation of nanodots and ripples patterning according to the ion beam energy. Since the latter are undesirable for ToF-SIMS analysis, we managed to totally stop their growth by using simultaneously sample rotation and oxygen flooding. This unprecedented coupling between these two latter mechanisms leads to a significant enhancement in depth profiles resolution.

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

Lacmann, K.; Maneira, M.J.P.; Moutinho, A.M.C.

The reaction K+ACl/sub 4/..-->..K/sup +/+(A-Cl/sub 4/)/sup -/* with A = Sn and C was examined as a function of the collision energy from threshold up to about 40 eV in the c.m. system. Total cross sections of the mass-selected negative ions and doubly differential cross sections (energy and angle) of the K/sup +/ ions have been determined. Electron affinities, bond energies, and electronic excitation were calculated from the appearance potentials. In addition, the total cross sections for SnCl/sub 4/ were measured and are contrasted with the earlier results of CCl/sub 4/ from Dispert and Lacmann. Although both parent molecules havemore » the same electron affinity within their error limits (2.2 eV for SnCl/sub 4/ and 2.0 eV for CCl/sub 4/) and the same dissociation energy for the negative ions of 1.4 +- 0.2 eV, the product ion yields differ drastically. The main negative ion yield in K+SnCl/sub 4/ results from SnCl/sup -//sub 4/ formation (over 80%). Its lowest dissociation channel leads to SnCl/sup -//sub 3/ formation, while Cl/sup -/ ions are the main ions produced (90%) from CCl/sub 4/, with only 7% leading to CCl/sup -//sub 3/+Cl formation at higher energies. These results support orbital energy considerations of electron addition to SnCl/sub 4/ and CCl/sub 4/ as applied to the results of reactive collisions of these molecules. The electron affinity and an electronically excited state of SnCl/sub 3/ have been also determined. Morse potentials of CCl/sup -//sub 4/ and SnCl/sup -//sub 4/ were fitted to the experimental results of energy loss measurements from this work. The vertical electron affinities thus derived are 1.15 eV for SnCl/sub 4/ and -1.0 eV for CCl/sub 4/.« less

Increasing ion and fusion yield in a dense plasma focus by combination of pre-ionization and heavy ion gas admixture

NASA Astrophysics Data System (ADS)

Farmanfarmaei, B.; Yousefi, H. R.; Salem, M. K.; Sari, A. H.

2018-04-01

The results of an experimental study of pre-ionization and heavy gas introduced into driven gas in a plasma focus device are reported. To achieve this purpose, we made use of two methods: first, the pre-ionization method by applying the shunt resistor and second, the admixture of heavy ions. We applied the different shunt resistors and found the optimum amount to be 200 MΩ at an optimum pressure of 0.5 Torr. Ion yield that was measured by array of Faraday cups and the energy of fast ions that was calculated by using the time-of-flight method were raised up to 22% and 45%, and the impurity caused by anode's erosion was reduced approximately by 67% in comparison to when there was no pre-ionization. Also, we have used the admixture of 5% argon ions with nitrogen (working gas) to improve the ion yield up to 45% in comparison with pure nitrogen. Finally, for the first time, we have utilized the combination of these methods together and have, consequently, reached the maximum ion yield and fusion yield. With this new method, ion yield raised up to 70% greater than that of the previous condition, i.e., without pre-ionization and heavy ion admixture.

Relative biological effectiveness in canine osteosarcoma cells irradiated with accelerated charged particles

PubMed Central

Maeda, Junko; Cartwright, Ian M.; Haskins, Jeremy S.; Fujii, Yoshihiro; Fujisawa, Hiroshi; Hirakawa, Hirokazu; Uesaka, Mitsuru; Kitamura, Hisashi; Fujimori, Akira; Thamm, Douglas H.; Kato, Takamitsu A.

2016-01-01

Heavy ions, characterized by high linear energy transfer (LET) radiation, have advantages compared with low LET protons and photons in their biological effects. The application of heavy ions within veterinary clinics requires additional background information to determine heavy ion efficacy. In the present study, comparison of the cell-killing effects of photons, protons and heavy ions was investigated in canine osteosarcoma (OSA) cells in vitro. A total of four canine OSA cell lines with various radiosensitivities were irradiated with 137Cs gamma-rays, monoenergetic proton beams, 50 keV/µm carbon ion spread out Bragg peak beams and 200 keV/µm iron ion monoenergetic beams. Clonogenic survival was examined using colony-forming as says, and relative biological effectiveness (RBE) values were calculated relative to gamma-rays using the D10 value, which is determined as the dose (Gy) resulting in 10% survival. For proton irradiation, the RBE values for all four cell lines were 1.0–1.1. For all four cell lines, exposure to carbon ions yielded a decreased cell survival compared with gamma-rays, with the RBE values ranging from 1.56–2.10. Iron ions yielded the lowest cell survival among tested radiation types, with RBE values ranging from 3.51–3.69 observed in the three radioresistant cell lines. The radiosensitive cell line investigated demonstrated similar cell survival for carbon and iron ion irradiation. The results of the present study suggest that heavy ions are more effective for killing radioresistant canine OSA cells when compared with gamma-rays and protons. This markedly increased efficiency of cell killing is an attractive reason for utilizing heavy ions for radioresistant canine OSA. PMID:27446477

Materials erosion and redeposition studies at the PISCES-facility: net erosion under redeposition

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

Hirooka, Y.; Goebel, D.M.; Conn, R.W.

1986-05-01

Simultaneous erosion and redeposition of copper and 304 stainless steel under controlled and continuous plasma (D,He,Ar) bombardment has been investigated in the PISCES-facility, which generates typical edge-plasma conditions of magnetic fusion devices. The plasma bombardment conditions are: incident ion flux in the range from 10/sup 17/ to 10/sup 18/ ions/sec/cm/sup 2/, ion bombarding energy of 100 eV, electron temperature in the range from 5 to 15 eV, plasma density in the range from 10/sup 11/ to 10/sup 13/ cm/sup -3/, target temperature in the range from 300 to 900K, and the total ion fluence in the range from 10/sup 20/more » to 10/sup 22/ ions/cm/sup 2/. The net erosion yield under redeposition is found to be significantly smaller than the classical sputtering yield data. A first-order modeling is attempted to interpret the erosion and redeposition behavior of materials under plasma bombardment. It is pointed out both theoretically and experimentally that the mean free path for electron impact ionization of the sputtered material is the key parameter to control the overall mechanism of erosion and redeposition. Strongly modified surface morphologies of bombarded targets are observed and indicate a retrapping effect.« less

Sputtering of cobalt and chromium by argon and xenon ions near the threshold energy region

NASA Technical Reports Server (NTRS)

Handoo, A. K.; Ray, P. K.

1993-01-01

Sputtering yields of cobalt and chromium by argon and xenon ions with energies below 50 eV are reported. The targets were electroplated on copper substrates. Measurable sputtering yields were obtained from cobalt with ion energies as low as 10 eV. The ion beams were produced by an ion gun. A radioactive tracer technique was used for the quantitative measurement of the sputtering yield. Co-57 and Cr-51 were used as tracers. The yield-energy curves are observed to be concave, which brings into question the practice of finding threshold energies by linear extrapolation.

Material/element-dependent fluorescence-yield modes on soft X-ray absorption spectroscopy of cathode materials for Li-ion batteries

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

Asakura, Daisuke; Hosono, Eiji; Nanba, Yusuke

2016-03-07

Here, we evaluate the utilities of fluorescence-yield (FY) modes in soft X-ray absorption spectroscopy (XAS) of several cathodematerials for Li-ion batteries. In the case of total-FY (TFY) XAS for LiNi 0.5Mn 1.5O 4, the line shape of the Mn L 3-edge XAS was largely distorted by the self-absorption and saturation effects, while the distortions were less pronounced at the Ni L 3 edge. The distortions were suppressed for the inverse-partial-FY (IPFY) spectra. We found that, in the cathodematerials, the IPFY XAS is highly effective for the Cr, Mn, and Fe L edges and the TFY and PFY modes are usefulmore » enough for the Ni L edge which is far from the O K edge.« less

Effect of cycled combustion ageing on a cordierite burner plate

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

Garcia, Eugenio; Gancedo, J. Ramon; Gracia, Mercedes, E-mail: rocgracia@iqfr.csic.es

2010-11-15

A combination of {sup 57}Fe-Moessbauer spectroscopy and X-ray Powder Diffraction analysis has been employed to study modifications in chemical and mechanical stability occurring in a cordierite burner aged under combustion conditions which simulate the working of domestic boilers. Moessbauer study shows that Fe is distributed into the structural sites of the cordierite lattice as Fe{sup 2+} and Fe{sup 3+} ions located mostly at octahedral sites. Ferric oxide impurities, mainly hematite, are also present in the starting cordierite material accounting for {approx_equal}40% of the total iron phases. From Moessbauer and X-ray diffraction data it can be deduced that, under the combustionmore » conditions used, new crystalline phases were formed, some of the substitutional Fe{sup 3+} ions existing in the cordierite lattice were reduced to Fe{sup 2+}, and ferric oxides underwent a sintering process which results in hematite with higher particle size. All these findings were detected in the burner zone located in the proximity of the flame and were related to possible chemical reactions which might explain the observed deterioration of the burner material. Research Highlights: {yields}Depth profile analyses used as a probe to understand changes in refractory structure. {yields}All changes take place in the uppermost surface of the burner, close to the flame. {yields}Reduction to Fe{sup 2+} of substitutional Fe{sup 3+} ions and partial cordierite decomposition. {yields}Heating-cooling cycling induces a sintering of the existing iron oxide particles. {yields}Chemical changes can explain the alterations observed in the material microstructure.« less

Estimated loads and yields of suspended soils and water-quality constituents in Kentucky streams

USGS Publications Warehouse

Crain, Angela S.

2001-01-01

Loads and yields of suspended solids, nutrients, major ions, trace elements, organic carbon, fecal coliform, dissolved oxygen, and alkalinity were estimated for 22 streams in 11 major river basins in Kentucky. Mean daily discharge was estimated at ungaged stations or stations with incomplete discharge records using drainage-area ratio, regression analysis, or a combination of the two techniques. Streamflow was partitioned into total and base flow and used to estimate loads and yields for suspended solids and water-quality constituents by use of the ESTIMATOR and FLUX computer programs. The relative magnitude of constituent transport to streams from groundand surface-water sources was determined for the 22 stations. Nutrient and suspended solids yields for drainage basins with relatively homogenous land use were used to estimate the total-flow and base-flow yields of nutrient and suspended solids for forested, agricultural, and urban land. Yields of nutrients?nitrite plus nitrate, ammonia plus organic nitrogen, and total phosphorus?in forested drainage basins were generally less than 1 ton per square mile per year ((ton/mi2)/yr) and were generally less than 2 (ton/mi2)/yr in agricultural drainage basins. The smallest total-flow yields for nitrogen (nitrite plus nitrate) was estimated at Levisa Fork at Paintsville in which 95 percent of the land is forested. This site also had one of the smallest total-flow yields for ammonia plus organic nitrogen. In general, nutrient yields from forested lands were lower than those from urban and agricultural land. Some of the largest estimated total-flow yields of nutrients among agricultural basins were for streams in the Licking River Basin, the North Fork Licking River near Milford, and the South Fork Licking River at Cynthiana. Agricultural land constitutes greater than 75 percent of the drainage area in these two basins. Possible sources of nutrients discharging into the Licking River are farm and residential fertilizers. Estimated base-flow yields of suspended solids and nutrients at several basins in the larger Green River and Lower Cumberland River Basins were about half of their estimated total-flow yields. The karst terrain in these basins makes the ground water highly susceptible to contamination, especially if a confining unit is thin or absent.

Analysis of iodinated quorum sensing peptides by LC-UV/ESI ion trap mass spectrometry.

PubMed

Janssens, Yorick; Verbeke, Frederick; Debunne, Nathan; Wynendaele, Evelien; Peremans, Kathelijne; De Spiegeleer, Bart

2018-02-01

Five different quorum sensing peptides (QSP) were iodinated using different iodination techniques. These iodinated peptides were analyzed using a C 18 reversed phase HPLC system, applying a linear gradient of water and acetonitrile containing 0.1% (m/v) formic acid as mobile phase. Electrospray ionization (ESI) ion trap mass spectrometry was used for the identification of the modified peptides, while semi-quantification was performed using total ion current (TIC) spectra. Non-iodinated peptides and mono- and di-iodinated peptides (NIP, MIP and DIP respectively) were well separated and eluted in that order. Depending on the used iodination method, iodination yields varied from low (2%) to high (57%).

Copper fine-structure K-shell electron impact ionization cross sections for fast-electron diagnostic in laser-solid experiments

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

Palmeri, P., E-mail: patrick.palmeri@umons.ac.be; Quinet, P., E-mail: pascal.quinet@umons.ac.be; IPNAS, Université de Liège, B-4000 Liège

2015-03-15

The K-shell electron impact ionization (EII) cross section, along with the K-shell fluorescence yield, is one of the key atomic parameters for fast-electron diagnostic in laser-solid experiments through the K-shell emission cross section. In addition, copper is a material that has been often used in those experiments because it has a maximum total K-shell emission yield. Furthermore, in a campaign dedicated to the modeling of the K lines of astrophysical interest (Palmeri et al., 2012), the K-shell fluorescence yields for the K-vacancy fine-structure atomic levels of all the copper isonuclear ions have been calculated. In this study, the K-shell EII crossmore » sections connecting the ground and the metastable levels of the parent copper ions to the daughter ions K-vacancy levels considered in Palmeri et al. (2012) have been determined. The relativistic distorted-wave (DW) approximation implemented in the FAC atomic code has been used for the incident electron kinetic energies up to 10 times the K-shell threshold energies. Moreover, the resulting DW cross sections have been extrapolated at higher energies using the asymptotic form proposed by Davies et al. (2013)« less

Boron ion beam generation utilizing lanthanum hexaboride cathodes: Comparison of vacuum arc and planar magnetron glow

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

Nikolaev, A. G.; Vizir, A. V.; Yushkov, G. Yu., E-mail: gyushkov@mail.ru

Boron ion beams are widely used for semiconductor ion implantation and for surface modification for improving the operating parameters and increasing the lifetime of machine parts and tools. For the latter application, the purity requirements of boron ion beams are not as stringent as for semiconductor technology, and a composite cathode of lanthanum hexaboride may be suitable for the production of boron ions. We have explored the use of two different approaches to boron plasma production: vacuum arc and planar high power impulse magnetron in self-sputtering mode. For the arc discharge, the boron plasma is generated at cathode spots, whereasmore » for the magnetron discharge, the main process is sputtering of cathode material. We present here the results of comparative test experiments for both kinds of discharge, aimed at determining the optimal discharge parameters for maximum yield of boron ions. For both discharges, the extracted ion beam current reaches hundreds of milliamps and the fraction of boron ions in the total extracted ion beam is as high as 80%.« less

Characterization of Novel Materials with Very Low Secondary Electron Emission Yield for Use in High-Power Microwave Devices

NASA Astrophysics Data System (ADS)

Svimonishvili, Tengiz; Zameroski, Nathan; Gilmore, Mark; Schamiloglu, Edl; Gaudet, John; Yan, Lincan

2004-11-01

Secondary Electron Emission (SEE) results from bombarding materials with electrons, atoms, or ions. The amount of secondary emission depends on factors such as bulk and surface properties of materials, energy of incident particles, and their angle of incidence. Total secondary electron emission yield, defined as the number of secondary electrons ejected per primary electron, is an important material parameter. Materials with high yield find use, for instance, in photomultiplier tubes, whereas materials with low yield, such as graphite, are used for SEE suppression in high-power microwave devices. The lower the SEE yield, the better the performance of high-power microwave devices (for example, gyrotrons). Employing a low-energy electron gun (energy range from 5 eV to 2000 eV), our work aims at characterizing and eventually identifying novel materials (with the lowest possible SEE yield) that will enhance operation and efficiency of high-power microwave devices.

Enhanced etching of tin-doped indium oxide due to surface modification by hydrogen ion injection

NASA Astrophysics Data System (ADS)

Li, Hu; Karahashi, Kazuhiro; Friederich, Pascal; Fink, Karin; Fukasawa, Masanaga; Hirata, Akiko; Nagahata, Kazunori; Tatsumi, Tetsuya; Wenzel, Wolfgang; Hamaguchi, Satoshi

2018-06-01

It is known that the etching yield (i.e., sputtering yield) of tin-doped indium oxide (ITO) by hydrocarbon ions (CH x +) is higher than its corresponding physical sputtering yield [H. Li et al., J. Vac. Sci. Technol. A 33, 060606 (2015)]. In this study, the effects of hydrogen in the incident hydrocarbon ion beam on the etching yield of ITO have been examined experimentally and theoretically with the use of a mass-selected ion beam system and by first-principles quantum mechanical (QM) simulation. As in the case of ZnO [H. Li et al., J. Vac. Sci. Technol. A 35, 05C303 (2017)], mass-selected ion beam experiments have shown that the physical sputtering yield of ITO by chemically inert Ne ions increases after a pretreatment of the ITO film by energetic hydrogen ion injection. First-principles QM simulation of the interaction of In2O3 with hydrogen atoms shows that hydrogen atoms embedded in In2O3 readily form hydroxyl (OH) groups and weaken or break In–O bonds around the hydrogen atoms, making the In2O3 film less resistant to physical sputtering. This is consistent with experimental observation of the enhanced etching yields of ITO by CH x + ions, considering the fact that hydrogen atoms of the incident CH x + ions are embedded into ITO during the etching process.

Kr-86 Ion-Beam Irradiation of Hydrated DNA: Free Radical and Unaltered Base Yields

PubMed Central

Becker, David; Adhikary, Amitava; Tetteh, Smedley T.; Bull, Arthur W.; Sevilla, Michael D.

2012-01-01

This work reports an ESR and product analysis investigation of Kr-86 ion-beam irradiation of hydrated DNA at 77 K. The irradiation results in the formation and trapping of both base radicals and sugar phosphate radicals (DNA backbone radicals). The absolute yields (G, μmol/J) of the base radicals are smaller than the yields found in similarly prepared γ-irradiated DNA samples, and the relative yields of backbone radicals relative to base radicals are much higher than that found in γ-irradiated samples. From these results, we have elaborated our radiation chemical model of the track structure for ion-beam irradiated DNA as it applies to krypton ion-beams. The base radicals, which are trapped as ion radicals or reversibly protonated or deprotonated ion radicals, are formed almost entirely in the track penumbra, a region in which radiation chemical effects are similar to those found in γ-irradiated samples. By comparing the yields of base radicals in ion-beam samples to the yields of the same radicals in γ-irradiated samples, the partition of energy between the low-LET region (penumbra) and the core is experimentally determined. The neutral sugar and other backbone radicals, which are not as susceptible to recombination as are ion radicals, are formed largely in the track core. The backbone radicals show a linear dose response up to very high doses. Unaltered base release yields in Kr-86 irradiated hydrated DNA are equal to sugar radical yields within experimental error limits, consistent with radiation-chemical processes in which all base release originates with sugar radicals. Two phosphorus-centered radicals from fragmentation of the DNA backbone are found in low yields. PMID:23106211

Kr-86 ion-beam irradiation of hydrated DNA: free radical and unaltered base yields.

PubMed

Becker, David; Adhikary, Amitava; Tetteh, Smedley T; Bull, Arthur W; Sevilla, Michael D

2012-12-01

This work reports an ESR and product analysis investigation of Kr-86 ion-beam irradiation of hydrated DNA at 77 K. The irradiation results in the formation and trapping of both base radicals and sugar phosphate radicals (DNA backbone radicals). The absolute yields (G, μmol/J) of the base radicals are smaller than the yields found in similarly prepared γ-irradiated DNA samples, and the relative yields of backbone radicals relative to base radicals are much higher than that found in γ-irradiated samples. From these results, we have elaborated our radiation chemical model of the track structure for ion-beam irradiated DNA as it applies to krypton ion-beams. The base radicals, which are trapped as ion radicals or reversibly protonated or deprotonated ion radicals, are formed almost entirely in the track penumbra, a region in which radiation chemical effects are similar to those found in γ-irradiated samples. By comparing the yields of base radicals in ion-beam samples to the yields of the same radicals in γ-irradiated samples, the partition of energy between the low-LET region (penumbra) and the core is experimentally determined. The neutral sugar and other backbone radicals, which are not as susceptible to recombination as are ion radicals, are formed largely in the track core. The backbone radicals show a linear dose response up to very high doses. Unaltered base release yields in Kr-86 irradiated hydrated DNA are equal to sugar radical yields within experimental error limits, consistent with radiation-chemical processes in which all base release originates with sugar radicals. Two phosphorus-centered radicals from fragmentation of the DNA backbone are found in low yields.

The separation distance distribution in electron-donor-acceptor systems and the wavelength dependence of free ion yields

NASA Astrophysics Data System (ADS)

Zhou, Jinwei; Findley, Bret R.; Braun, Charles L.; Sutin, Norman

2001-06-01

We recently reported that free radical ion quantum yields for electron-donor-acceptor (EDA) systems of alkylbenzenes-tetracyanoethylene (TCNE) exhibit a remarkable wavelength dependence in dichloromethane, a medium polarity solvent. We proposed that weak absorption by long-distance, unassociated or "random" D⋯A pairs is mainly responsible for the free radical ion yield. Here a model for the wavelength dependence of the free ion yield is developed for four systems in which differing degrees of EDA complex formation are present: 1,3,5-tri-tert-butylbenzene-TCNE in which only random pairs exist due to the bulky groups on the electron donor, and toluene—TCNE, 1,3,5-triethylbenzene-TCNE and 1,3,5-trimethylbenzene-TCNE. Mulliken-Hush theory is used to determine the excitation distance distribution of unassociated, random pairs at different wavelengths. For each absorption distribution, free radical ion yields at different wavelengths are then calculated using Onsager's result for the ion separation probability. Encouraging agreement between the calculated yields and our experimental results is obtained. As far as we are aware, this is the first time that photoexcitation of unassociated donor/acceptor pairs has been invoked as the source of separated radical ion pairs.

Molybdenum and carbon atom and carbon cluster sputtering under low-energy noble gas plasma bombardment

NASA Astrophysics Data System (ADS)

Oyarzabal, Eider

Exit-angle resolved Mo atom sputtering yield under Xe ion bombardment and carbon atom and cluster (C2 and C3) sputtering yields under Xe, Kr, Ar, Ne and He ion bombardment from a plasma are measured for low incident energies (75--225 eV). An energy-resolved quadrupole mass spectrometer (QMS) is used to detect the fraction of un-scattered sputtered neutrals that become ionized in the plasma; the angular distribution is obtained by changing the angle between the target and the QMS aperture. A one-dimensional Monte Carlo code is used to simulate the interaction of the plasma and the sputtered particles between the sample and the QMS. The elastic scattering cross-sections of C, C2 and C3 with the different bombarding gas neutrals is obtained by varying the distance between the sample and the QMS and by performing a best fit of the simulation results to the experimental results. Because the results obtained with the QMS are relative, the Mo atom sputtering results are normalized to the existing data in the literature and the total sputtering yield for carbon (C+C 2+C3) for each bombarding gas is obtained from weight loss measurements. The absolute sputtering yield for C, C2 and C 3 is then calculated from the integration of the measured angular distribution, taking into account the scattering and ionization of the sputtered particles between the sample and the QMS. The angular sputtering distribution for Mo has a maximum at theta=60°, and this maximum becomes less pronounced as the incident ion energy increases. The results of the Monte Carlo TRIDYN code simulation for the angular distribution of Mo atoms sputtered by Xe bombardment are in agreement with the experiments. For carbon sputtering under-cosine angular distributions of the sputtered atoms and clusters for all the studied bombarding gases are also observed. The C, C2 and C3 sputtering yield data shows a clear decrease of the atom to cluster (C/C2 and C/C3) sputtering ratio as the incident ion mass increases, changing from a carbon atom preferential erosion for the lower incident ion masses (He, Ne and Ar) to a cluster preferential erosion for the higher incident ion masses (Kr and Xe).

Effect of pH on H2O2 production in the radiolysis of water.

PubMed

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.

Studies of multi-ion-fluid yield anomaly in shock-driven implosions

NASA Astrophysics Data System (ADS)

Rinderknecht, H. G.; Rosenberg, M. J.; Li, C. K.; Zylstra, A. B.; Sio, H.; Gatu Johnson, M.; Frenje, J. A.; Séguin, F. H.; Petrasso, R. D.; Amendt, P. A.; Bellei, C.; Wilks, S. C.; Zimmerman, G.; Hoffman, N. M.; Kagan, G.; Molvig, K.; Glebov, V. Yu.; Stoeckl, C.; Marshall, F. J.; Seka, W.; Delettrez, J. A.; Sangster, T. C.; Betti, R.; Goncharov, V. N.; Meyerhofer, D. D.

2014-10-01

A. NIKROO, GA - Anomalously reduced yields relative to hydrodynamically calculated values have been observed for mixtures of D:3He compared to pure D2 gas-filled implosions in a series of shock-driven implosions at OMEGA. An extensive suite of measurements including temporal and spatial measurements of both the DD- and D3He-fusion reactions were obtained to identify the origin and physics behind this anomalous yield reduction. Measured spectral linewidths of fusion products suggest that the D ions are not thermalized to 3He during the burn, contributing to the reduced yield. The hypothesis that ion-species separation due to diffusive processes contributes to the observed yield reduction is explored using hydrodynamic simulations incorporating ion diffusion. Recent observations by Rosenberg et al. of a yield reduction with increased ion-ion mean free path do not explain the observed anomalous yield trend. Future work that will directly probe species separation with high-precision relative fusion reaction rate measurements between DD-neutrons and D3He-protons using the DualPTD instrument is discussed. This work was supported in part by the U.S. DOE, NLUF, LLE, and LLNL.

RADIATION CHEMISTRY OF HIGH ENERGY CARBON, NEON AND ARGON IONS: INTEGRAL YIELDS FROM FERROUS SULFATE SOLUTIONS

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

Christman, E.A.; Appleby, A.; Jayko, M.

1980-07-01

Chemical yields of Fe{sup 3+} have been measured from FeSO{sub 4} solutions irradiated in the presence and absence of oxygen with carbon, neon, and argon ions from the Berkeley Bevalac facility. G(Fe{sup 3+}) decreases with increasing beam penetration and with increasing atomic number of the incident ion. The results are compared with current theoretical expectations of the behavior of these particles in an aqueous absorber. The chemical yields are consistently higher than theoretically predicted, by amounts varying from <6.2% (carbon ions) to <13.2% (argon ions). The additional yields are possibly attributable to fragmentation of the primary particle beams.

Anorthite sputtering by H + and Ar q+ (q = 1-9) at solar wind velocities

DOE PAGES

Hijazi, Hussein Dib; Bannister, Mark E.; Meyer, III, Harry M.; ...

2014-10-16

Here, we report sputtering measurements of anorthite-like material, taken to be representative of soils found in the lunar highlands, impacted by singly and multicharged ions representative of the solar wind. The ions investigated include protons, as well as singly and multicharged Ar ions (as proxies for the nonreactive heavy solar wind constituents), in the charge state range +1 to +9, at fixed solar wind-relevant impact velocities of 165 and 310 km/s (0.25 keV/amu and 0.5 keV/amu). A quartz microbalance approach (QCM) for determination of total sputtering yields was used. The goal of the measurements was to determine the sputtering contributionmore » of the heavy, multicharged minority solar wind constituents in comparison to that due to the dominant H + fraction. The QCM results show a yield increase of a factor of about 80 for Ar + versus H + sputtering and an enhancement by a factor of 1.67 between Ar 9+ and Ar +, which is a clear indication of a potential sputtering effect.« less

Useful ion yields for Cameca IMS 3f and 6f SIMS: Limits on quantitative analysis

USGS Publications Warehouse

Hervig, R.L.; Mazdab, F.K.; Williams, Pat; Guan, Y.; Huss, G.R.; Leshin, L.A.

2006-01-01

The useful yields (ions detected/atom sputtered) of major and trace elements in NIST 610 glass were measured by secondary ion mass spectrometry (SIMS) using Cameca IMS 3f and 6f instruments. Useful yields of positive ions at maximum transmission range from 10-4 to 0.2 and are negatively correlated with ionization potential. We quantified the decrease in useful yields when applying energy filtering or high mass resolution techniques to remove molecular interferences. The useful yields of selected negative ions (O, S, Au) in magnetite and pyrite were also determined. These data allow the analyst to determine if a particular analysis (trace element contents or isotopic ratio) can be achieved, given the amount of sample available and the conditions of the analysis. ?? 2005 Elsevier B.V. All rights reserved.

Analysis of human serum proteins by liquid phase isoelectric focusing and matrix-assisted laser desorption/ionization-mass spectrometry.

PubMed

Wang, Michael Z; Howard, Brandon; Campa, Michael J; Patz, Edward F; Fitzgerald, Michael C

2003-09-01

Direct matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis of human serum yielded ion signals from only a fraction of the total number of peptides and proteins expected to be in the sample. We increased the number of peptide and protein ion signals observed in the MALDI-TOF mass spectra analysis of human serum by using a prefractionation protocol based on liquid phase isoelectric focusing electrophoresis. This pre-fractionation technique facilitated the MALDI-TOF MS detection of as many as 262 different peptide and protein ion signals from human serum. The results obtained from three replicate fractionation experiments on the same serum sample indicated that 148 different peptide and protein ion signals were reproducibly detected using our isoelectric focusing and MALDI-TOF MS protocol.

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

Adare, A.; Afanasiev, S.; Aidala, C.

Measurements of bottomonium production in heavy-ion and p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three Υ states, Υ(1S + 2S + 3S), was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au+Au and p+p collisions at \\(\\sqrt{s_{\\mathrm{NN}}}=200\\) GeV. The Υ(1S + 2S + 3S) → e⁺e⁻ differential cross section at midrapidity was found to be B eedσ/dy = 108 ± 38 (stat) ± 15 (syst) ± 11 (luminosity) pb in p+p collisions. The nuclear modification factor in the 30% most central Au+Au collisions indicates a suppression ofmore » the total Υ state yield relative to the extrapolation from p+p collision data. Thus, the suppression is consistent with measurements at higher energies by the CMS experiment at the Large Hadron Collider.« less

Measurements of ionic structure in shock compressed lithium hydride from ultrafast x-ray Thomson scattering.

PubMed

Kritcher, A L; Neumayer, P; Brown, C R D; Davis, P; Döppner, T; Falcone, R W; Gericke, D O; Gregori, G; Holst, B; Landen, O L; Lee, H J; Morse, E C; Pelka, A; Redmer, R; Roth, M; Vorberger, J; Wünsch, K; Glenzer, S H

2009-12-11

We present the first ultrafast temporally, spectrally, and angularly resolved x-ray scattering measurements from shock-compressed matter. The experimental spectra yield the absolute elastic and inelastic scattering intensities from the measured density of free electrons. Laser-compressed lithium-hydride samples are well characterized by inelastic Compton and plasmon scattering of a K-alpha x-ray probe providing independent measurements of temperature and density. The data show excellent agreement with the total intensity and structure when using the two-species form factor and accounting for the screening of ion-ion interactions.

Fusion yield rate recovery by escaping hot-spot fast ions in the neighboring fuel layer

NASA Astrophysics Data System (ADS)

Tang, Xian-Zhu; McDevitt, C. J.; Guo, Zehua; Berk, H. L.

2014-02-01

Free-streaming loss by fast ions can deplete the tail population in the hot spot of an inertial confinement fusion (ICF) target. Escaping fast ions in the neighboring fuel layer of a cryogenic target can produce a surplus of fast ions locally. In contrast to the Knudsen layer effect that reduces hot-spot fusion reactivity due to tail ion depletion, the inverse Knudsen layer effect increases fusion reactivity in the neighboring fuel layer. In the case of a burning ICF target in the presence of significant hydrodynamic mix which aggravates the Knudsen layer effect, the yield recovery largely compensates for the yield reduction. For mix-dominated sub-ignition targets, the yield reduction is the dominant process.

Deconstructing Free Energies in the Law of Matching Water Affinities.

PubMed

Shi, Yu; Beck, Thomas

2017-03-09

The law of matching water affinities (LMWA) is explored in classical molecular dynamics simulations of several alkali halide ion pairs, spanning the size range from small kosmotropes to large chaotropes. The ion-ion potentials of mean force (PMFs) are computed using three methods: the local molecular field theory (LMFT), the weighted histogram analysis method (WHAM), and integration of the average force. All three methods produce the same total PMF for a given ion pair. In addition, LMFT-based partitioning into van der Waals and local and far-field electrostatic free energies and assessment of the enthalpic, entropic, and ion-water components yield insights into the origins of the observed free energy profiles in water. The results highlight the importance of local electrostatic interactions in determining the shape of the PMFs, while longer-ranged interactions enhance the overall ion-ion attraction, as expected in a dielectric continuum model. The association equilibrium constants are estimated from the smooth WHAM curves and compared to available experimental conductance data. By examining the variations in the average hydration numbers of ions with ion-ion distance, a correlation of the water structure in the hydration shells with the free energy features is found.

SU-D-BRB-02: Investigations of Secondary Ion Distributions in Carbon Ion Therapy Using the Timepix Detector.

PubMed

Gwosch, K; Hartmann, B; Jakubek, J; Granja, C; Soukup, P; Jaekel, O; Martisikova, M

2012-06-01

Due to the high conformity of carbon ion therapy, unpredictable changes in the patient's geometry or deviations from the planned beam properties can result in changes of the dose distribution. PET has been used successfully to monitor the actual dose distribution in the patient. However, it suffers from biological washout processes and low detection efficiency. The purpose of this contribution is to investigate the potential of beam monitoring by detection of prompt secondary ions emerging from a homogeneous phantom, simulating a patient's head. Measurements were performed at the Heidelberg Ion-Beam Therapy Center (Germany) using a carbon ion pencil beam irradiated on a cylindrical PMMA phantom (16cm diameter). For registration of the secondary ions, the Timepix detector was used. This pixelated silicon detector allows position-resolved measurements of individual ions (256×256 pixels, 55μm pitch). To track the secondary ions we used several parallel detectors (3D voxel detector). For monitoring of the beam in the phantom, we analyzed the directional distribution of the registered ions. This distribution shows a clear dependence on the initial beam energy, width and position. Detectable were range differences of 1.7mm, as well as vertical and horizontal shifts of the beam position by 1mm. To estimate the clinical potential of this method, we measured the yield of secondary ions emerging from the phantom for a beam energy of 226MeV/u. The differential distribution of secondary ions as a function of the angle from the beam axis for angles between 0 and 90° will be presented. In this setup the total yield in the forward hemisphere was found to be in the order of 10 -1 secondary ions per primary carbon ion. The presented measurements show that tracking of secondary ions provides a promising method for non-invasive monitoring of ion beam parameters for clinical relevant carbon ion fluences. Research with the pixel detectors was carried out in frame of the Medipix Collaboration. © 2012 American Association of Physicists in Medicine.

Ion guiding accompanied by formation of neutrals in polyethylene terephthalate polymer nanocapillaries: Further insight into a self-organizing process

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

Juhasz, Z.; Sulik, B.; Racz, R.

2010-12-15

A relatively large yield of neutralized atoms was observed when 3 keV Ar{sup 7+} ions were guided trough polyethylene terephthalate nanocapillaries. Time and deposited-charge dependence of the angular distribution of both the guided ions and the neutrals was measured simultaneously using a two-dimensional multichannel plate detector. The yield of neutrals increased significantly faster than that of guided ions and saturated typically at a few percent level. In accordance with earlier observations, both the yield and the mean emission angle of the guided ions exhibited strong oscillations. For the atoms, the equilibrium was achieved not only faster, but also without significantmore » oscillations in yield and angular position. A phase analysis of these time dependencies provides insight into the dynamic features of the self-organizing mechanisms, which leads to ion guiding in insulating nanocapillaries.« less

Erosion and deuterium retention of CLF-1 steel exposed to deuterium plasma

NASA Astrophysics Data System (ADS)

Qiao, L.; Wang, P.; Hu, M.; Gao, L.; Jacob, W.; Fu, E. G.; Luo, G. N.

2017-12-01

In recent years reduced activation ferritic martensitic steel has been proposed as the plasma-facing material in remote regions of the first wall. This study reports the erosion and deuterium retention behaviours in CLF-1 steel exposed to deuterium (D) plasma in a linear experimental plasma system as function of incident ion energy and fluence. The incident D ion energy ranges from 30 to 180 eV at a flux of 4 × 1021 D m-2 s-1 up to a fluence of 1025 D m-2. SEM images revealed a clear change of the surface morphology as functions of incident fluence and impinging energy. The mass loss results showed a decrease of the total sputtering yield of CLF-1 steel with increasing incident fluence by up to one order of magnitude. The total sputtering yield of CLF-1 steel after 7.2 × 1024 D m-2 deuterium plasma exposure reduced by a factor of 4 compared with that of pure iron, which can be attributed to the enrichment of W at the surface due to preferential sputtering of iron and chromium. After D plasma exposure, the total deuterium retention in CLF-1 steel samples measured by TDS decreased with increasing incident fluence and energy, and a clear saturation tendency as function of incident fluence or energy was also observed.

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

Ward, W.W.; Seliger, H.H.

By methods previously described, the calcium-activated bioluminescent photoproteins were extracted with EDTA from the ctenophores Mnemiopsis sp. and Beroue ovata and then purified extensively. Two forms of the Mnemiopsis photoprotein, mnemiopsin-1 and mnemiopsin-2, and the single Beroue photoprotein, berovin, have been characterized and compared with respect to their physical and spectral properties. Ctenophore photoproteins react in vitro with calcium ions in molar excess of EDTA to produce a rapid flash with first-order decay kinetics. The rates and total light yields of these reactions are differently dependent on pH, temperature, and ionic strength. Mnemiopsin activation is specific for calcium ions. However,more » under certain assay conditions and at low metal ion concentrations a large number of cations appear to activate mnemiopsin. But at higher concentrations, most of these cations are inhibitors. Among these, only Mg/sup 2 +/ and Ba/sup 2 +/ are completely reversible competitive inhibitors of bioluminescence. Total photon yields are enhanced by preincubation with certain hydrophilic alcohols but reduced with long-chain aliphatic alcohols. Molecular weights were estimated by gel filtration on Sephadex and Bio-Gel and by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The most reliable molecular weight estimates were 24,000, 27,500, and 25,000 awu for m-1, m-2, and berovin, respectively. Physical and spectral similarities among these photoproteins and the bioluminescent systems of the jellyfish Aequorea and the sea pansy Renilla suggest that similar biochemical mechanisms may exist among all of the bioluminescent coelenterates.« less

Concentrations, loads, and yields of select constituents from major tributaries of the Mississippi and Missouri Rivers in Iowa, water years 2004-2008

USGS Publications Warehouse

Garrett, Jessica D.

2012-01-01

Excess nutrients, suspended-sediment loads, and the presence of pesticides in Iowa rivers can have deleterious effects on water quality in State streams, downstream major rivers, and the Gulf of Mexico. Fertilizer and pesticides are used to support crop growth on Iowa's highly productive agricultural landscape and for household and commercial lawns and gardens. Water quality was characterized near the mouths of 10 major Iowa tributaries to the Mississippi and Missouri Rivers from March 2004 through September 2008. Stream loads were calculated for select ions, nutrients, and sediment using approximately monthly samples, and samples from storm and snowmelt events. Water-quality samples collected using standard streamflow-integrated protocols were analyzed for major ions, nutrients, carbon, pesticides, and suspended sediment. Statistical data summaries of sample data used parametric and nonparametric techniques to address potential bias related to censored data and multiple levels of censoring of data below analytical detection limits. Constituent stream loads were computed using standard pre-defined models in S-LOADEST that include streamflow and time terms plus additional terms for streamflow variability and streamflow anomalies. Streamflow variability terms describe the difference in streamflow from recent average conditions, whereas streamflow anomaly terms account for deviations from average conditions from long- to short-term sequentially. Streamflow variability or anomaly terms were included in 44 of 80 site/constituent individual models, demonstrating the usefulness of these terms in increasing accuracy of the load estimates. Constituent concentrations in Iowa streams exhibit streamflow, seasonal, and spatial patterns related to the landform and climate gradients across the studied basins. The streamflow-concentration relation indicated dilution for ions such as chloride and sulfate. Other constituent concentrations, such as dissolved organic carbon and suspended sediment, increased with streamflow. Nitrogen concentrations (total nitrogen and nitrate plus nitrite) increased with low and moderate streamflows, but decreased with high streamflows. Seasonal patterns observed in constituent concentrations were affected by streamflow, algae blooms, and pesticide application. The various landform regions produced different water-quality responses across the study basins; for example, total phosphorus, suspended sediment, and turbidity were greatest from the steep, loess-dominated southwestern Iowa basins. Nutrient concentrations, though not regulated for drinking water at the study sites, were high compared to drinking-water limits and criteria for protection of aquatic life proposed for other Midwestern states (Iowa criteria for aquatic life have not been proposed). Nitrate plus nitrite concentrations exceeded the drinking-water limit [10 milligrams per liter (mg/L)] in 11 percent of all samples at the 10 sites, and exceeded Minnesota's proposed aquatic life criteria (4.9 mg/L) in 68 percent of samples. The Wisconsin standard for total phosphorus (0.1 mg/L) was exceeded in 92 percent of samples. Ammonia standards, current during sample collection and at publication of this report, for protection of aquatic life were met for all samples, but draft criteria proposed in 2009 to protect more sensitive species like mussels, were exceeded at three sites. Loads and yields also differed among sites and years. The Big Sioux, Little Sioux, and Des Moines Rivers produced the greatest sulfate yields. Mississippi River tributaries had greater chloride yields than Missouri River tributaries. The Big Sioux River also had the lowest silica yields and total nitrogen and nitrate yields, whereas nitrogen yields were greater in the northeastern rivers. The Boyer and Nishnabotna River total phosphorus yields were the greatest in the study. The Boyer River orthophosphate yields were greatest except in 2008, when the Maquoketa River produced the greatest yield. Rivers in southwestern Iowa's Western Loess Hills and Steeply Rolling Loess Prairie ecoregions had the greatest suspended-sediment yields, whereas the smallest yields were in the Big Sioux and Wapsipinicon Rivers. In the 10 Iowa rivers studied, combined annual total nitrogen stream transport ranged from 3.68 to 9.95 tons per square mile per year, and total phosphorus transport ranged from 0.138 to 0.570 tons per square mile per year. Six-month loads relative to fertilizer use ranged from 8 to 56 percent for nitrogen, and 1.0 to 11.1 percent for phosphorus. The smallest loads relative to fertilizer use for both nitrogen and phosphorus occurred in July-December of dry years, and the largest nitrogen and phosphorus loads relative to use were in wet years from January-June.

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

Yusa, Kazuyuki; Yamamoto, Osamu; Fukuda, Masayuki

Highlights: {yields} We isolated the Zn{sup 2+} ions (eluted Zn{sup 2+} ion; EZ) from zinc-incorporated titanium implant. {yields} The EZ promoted the cell viability in hBMCs. {yields} The EZ stimulated preosteoblast and osteoblast marker gene expression in hBMCs. {yields} The hBMCs supplemented with EZ showed typically cell morphology when osteoblast maturing. {yields} It is revealed that the EZ also stimulates the calcium deposition of hBMCs. -- Abstract: Zinc is one of the trace elements which induce the proliferation and the differentiation of the osteoblast. In the previous study, we found that zinc ions (Zn{sup 2+} ion)-releasing titanium implants had excellentmore » bone fixation using a rabbit femurs model. In this study, we isolated the Zn{sup 2+} ions (eluted Zn{sup 2+} ion; EZ) released from the implant surface, and evaluated the effect of EZ on the osteogenesis of human bone marrow-derived mesenchymal cells (hBMCs). In the result, it was found that the EZ stimulated cell viability, osteoblast marker gene (type I collagen, osteocalcin (OC), alkaline phosphatase (ALP) and bone sialoprotein (BSP)) expressions and calcium deposition in hBMCs.« less

Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse.

PubMed

Bang, W

2015-07-01

Energetic deuterium ions from large deuterium clusters (>10nm diameter) irradiated by an intense laser pulse (>10(16)W/cm(2)) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We present an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the available experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10-keV deuterium fusion plasma for 10ns.

Photoionization and photofragmentation of the C 60 + molecular ion

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

Baral, K. K.; Aryal, N. B.; Esteves-Macaluso, D. A.

2016-03-01

Cross-section measurements are reported for single and double photoionization of Cmore » $$+\\atop{60}$$ ions in the photon energy range 18-150 eV accompanied by the loss of zero to seven pairs of carbon atoms, as well as for fragmentation without ionization resulting in loss of two to eight pairs of C atoms in the photon energy range 18-65 eV. Absolute measurements were performed by merging a beam of C$$+\\atop{60}$$ molecular ions with a beam of monochromatized synchrotron radiation. Product channels involving dissociation yielding smaller fullerene fragment ions account for nearly half of the total measured oscillator strength in this energy range. The sum of cross sections for the measured product channels is compared to a published calculation of the total photoabsorption cross section of neutral C 60 based on time-dependent density-functional theory. Lastly, this comparison and an accounting of oscillator strengths indicate that with the exception of C$$+\\atop{58}$$, the most important product channels resulting from photoabsorption were accounted for in the experiment. Threshold energies for the successive removal of carbon atom pairs accompanying photoionization are also determined from the measurements.« less

Metal-assisted SIMS and cluster ion bombardment for ion yield enhancement

NASA Astrophysics Data System (ADS)

Heile, A.; Lipinsky, D.; Wehbe, N.; Delcorte, A.; Bertrand, P.; Felten, A.; Houssiau, L.; Pireaux, J.-J.; De Mondt, R.; Van Vaeck, L.; Arlinghaus, H. F.

2008-12-01

In addition to structural information, a detailed knowledge of the local chemical environment proves to be of ever greater importance, for example for the development of new types of materials as well as for specific modifications of surfaces and interfaces in multiple fields of materials science or various biomedical and chemical applications. But the ongoing miniaturization and therefore reduction of the amount of material available for analysis constitute a challenge to the detection limits of analytical methods. In the case of time-of-flight secondary ion mass spectrometry (TOF-SIMS), several methods of secondary ion yield enhancement have been proposed. This paper focuses on the investigation of the effects of two of these methods, metal-assisted SIMS and polyatomic primary ion bombardment. For this purpose, thicker layers of polystyrene (PS), both pristine and metallized with different amounts of gold, were analyzed using monoatomic (Ar +, Ga +, Xe +, Bi +) and polyatomic (SF 5+, Bi 3+, C 60+) primary ions. It was found that polyatomic ions generally induce a significant increase of the secondary ion yield. On the other hand, with gold deposition, a yield enhancement can only be detected for monoatomic ion bombardment.

Surface-Water Quality and Nutrient Loads in the Nepaug Reservoir Watershed, Northwestern Connecticut, 1999-2001

USGS Publications Warehouse

Morrison, Jonathan; Colombo, Michael J.

2006-01-01

Water quality was characterized at three tributary watersheds to the Nepaug Reservoir-Nepaug River, Phelps Brook, and Clear Brook-from October 1998 through September 2001 to document existing water-quality conditions and evaluate potential future effects of the removal of sand and gravel from areas of the watershed. Some removal operations may include removal of vegetation and top soil and steepening of slopes. Routine water samples collected monthly in all three watersheds were analyzed for nutrients, organic carbon, major ions, and fecal indicator bacteria. Results of the analyses indicate that, in general, the water quality in all three tributary watersheds is good and meets standards established for drinking-water supplies for nitrate, but does not always meet contact-recreation standards for bacteria. Median concentrations of total nitrogen, total phosphorus, and total organic carbon were highest in the routine monthly samples from Phelps Brook and lowest from Clear Brook. Samples also were collected during selected storms to examine changes in concentrations of nutrients during periods of high streamflow. The maximum values measured for total nitrogen, total phosphorus, and total organic carbon were in storm samples from Clear Brook. The Nepaug River watershed delivered the largest loads of total nitrogen, total phosphorus, and total organic carbon to the reservoir. Yields of nutrients and organic carbon differed significantly from year to year and among the three watersheds. Yields of total nitrogen and total organic carbon were largest from Phelps Brook and smallest from Clear Brook. The yields of total phosphorus were largest from Nepaug River and smallest from Phelps Brook. In comparison to other watersheds in Connecticut, annual loads and yields from the three streams were lower than those of developed urban areas and comparable to those of other rural and forested basins. Delivery of nutrients and organic carbon to the reservoir took place mostly during the spring with the exception of those constituents delivered during Tropical Storm Floyd, a large fall storm.

Measurements and Modelling of Sputtering Rates with Low Energy Ions

NASA Astrophysics Data System (ADS)

Ruzic, David N.; Smith, Preston C.; Turkot, Robert B., Jr.

1996-10-01

The angular-resolved sputtering yield of Be by D+, and Al by Ar+ was predicted and then measured. A 50 to 1000 eV ion beam from a Colutron was focused on to commercial grade and magnetron target grade samples. The S-65 C grade beryllium samples were supplied by Brush Wellman and the Al samples from TOSOH SMD. In our vacuum chamber the samples can be exposed to a dc D or Ar plasma to remove oxide, load the surface and more-nearly simulate steady state operating conditions in the plasma device. The angular distribution of the sputtered atoms was measured by collection on a single crystal graphite witness plate. The areal density of Be or Al (and BeO2 or Al2O3, after exposure to air) was then measured using a Scanning Auger Spectrometer. Total yield was also measured by deposition onto a quartz crystal oscillator simultaneously to deposition onto the witness plate. A three dimensional version of vectorized fractal TRIM (VFTRIM3D), a Monte-Carlo computer code which includes surface roughness characterized by fractal geometry, was used to predict the angular distribution of the sputtered particles and a global sputtering coefficient. Over a million trajectories were simulated for each incident angle to determine the azimuthal and polar angle distributions of the sputtered atoms. The experimental results match closely with the simulations for total yield, while the measured angular distributions depart somewhat from the predicted cosine curve.

Dissociation of biomolecules in liquid environments during fast heavy-ion irradiation

NASA Astrophysics Data System (ADS)

Nomura, Shinji; Tsuchida, Hidetsugu; Kajiwara, Akihiro; Yoshida, Shintaro; Majima, Takuya; Saito, Manabu

2017-12-01

The effect of aqueous environment on fast heavy-ion radiation damage of biomolecules was studied by comparative experiments using liquid- and gas-phase amino acid targets. Three types of amino acids with different chemical structures were used: glycine, proline, and hydroxyproline. Ion-induced reaction products were analyzed by time-of-flight secondary-ion mass spectrometry. The results showed that fragments from the amino acids resulting from the C—Cα bond cleavage were the major products for both types of targets. For liquid-phase targets, specific products originating from chemical reactions in solutions were observed. Interestingly, multiple dissociated atomic fragments were negligible for the liquid-phase targets. We found that the ratio of multifragment to total fragment ion yields was approximately half of that for gas-phase targets. This finding agreed with the results of other studies on biomolecular cluster targets. It is concluded that the suppression of molecular multifragmentation is caused by the energy dispersion to numerous water molecules surrounding the biomolecular solutes.

Erosion and modification of SO2 ice by ion bombardment of the surface of Io

NASA Technical Reports Server (NTRS)

Johnson, R. E.; Garrett, J. W.; Boring, J. W.; Barton, L. A.; Brown, W. L.

1984-01-01

New measurements on the effect of slow ion bombardment of SO2 ice using Ar(+) in the 15-45 keV range are presented. Total yields for loss of SO2 are given along with the energy spectra of the ejected molecules and molecular fragments and information on the chemical changes induced by the ion bombardment. These data are used to estimate that the direct sputter ejection rate of sulfur into the Jovian plasma is of the order of 10 billion atoms/sq cm/s, that the erosion rate of fresh SO2 deposits due to sputtering is of the order of 0.001 cm/yr, and that a significant and possibly observable column density of SO3 can be produced in an SO2 front only for penetrating ion bombardment. Chemical activity occurs even in rather low-temperature SO2 ice bombardment by ions in the nuclear stopping region, and this activity is likely to increase with increasing temperature.

Effects of metal ions on biomass and 5-aminolevulinic acid production in Rhodopseudomonas palustris wastewater treatment.

PubMed

Liu, Shuli; Zhang, Guangming; Li, Jianzheng; Li, Xiangkun; Zhang, Jie

2016-01-01

This work investigated the effects of eight metal ions on Rhodopseudomonas palustris growth and 5-aminolevulinic acid (ALA) yield in wastewater treatment. Results show that metal ions (Mg(2+) of 15 mmol/L, Fe(2+) of 400 μmol/L, Co(2+) of 4 μmol/L, Ni(2+) of 8 μmol/L and Zn(2+) of 4 μmol/L) could effectively improve the chemical oxygen demand (COD) removal, Rp. palustris biomass and ALA yield. The highest ALA yield of 13.1 mg/g-biomass was achieved with Fe(2+) of 400 μmol/L. ALA yields were differentially increased under different metal ions in the following order: Fe(2+) group > Mg(2+) group > Co(2+) group = Ni(2+) group > Zn(2+) group = Mo(2+) group > control. Cu(2+) and Mn(2+) inhibited Rp. palustris growth and ALA production. Mechanism analysis revealed that metal ions changed ALA yields by influencing the activities of ALA synthetase and ALA dehydratase.

Sputtering yields and surface chemical modification of tin-doped indium oxide in hydrocarbon-based plasma etching

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

Li, Hu; Karahashi, Kazuhiro; Hamaguchi, Satoshi, E-mail: hamaguch@ppl.eng.osaka-u.ac.jp

2015-11-15

Sputtering yields and surface chemical compositions of tin-doped indium oxide (or indium tin oxide, ITO) by CH{sup +}, CH{sub 3}{sup +}, and inert-gas ion (He{sup +}, Ne{sup +}, and Ar{sup +}) incidence have been obtained experimentally with the use of a mass-selected ion beam system and in-situ x-ray photoelectron spectroscopy. It has been found that etching of ITO is chemically enhanced by energetic incidence of hydrocarbon (CH{sub x}{sup +}) ions. At high incident energy incidence, it appears that carbon of incident ions predominantly reduce indium (In) of ITO and the ITO sputtering yields by CH{sup +} and CH{sub 3}{sup +}more » ions are found to be essentially equal. At lower incident energy (less than 500 eV or so), however, a hydrogen effect on ITO reduction is more pronounced and the ITO surface is more reduced by CH{sub 3}{sup +} ions than CH{sup +} ions. Although the surface is covered more with metallic In by low-energy incident CH{sub 3}{sup +} ions than CH{sup +} ions and metallic In is in general less resistant against physical sputtering than its oxide, the ITO sputtering yield by incident CH{sub 3}{sup +} ions is found to be lower than that by incident CH{sup +} ions in this energy range. A postulation to account for the relation between the observed sputtering yield and reduction of the ITO surface is also presented. The results presented here offer a better understanding of elementary surface reactions observed in reactive ion etching processes of ITO by hydrocarbon plasmas.« less

High yield antibiotic producing mutants of Streptomyces erythreus induced by low energy ion implantation

NASA Astrophysics Data System (ADS)

Yu, Chen; Zhixin, Lin; Zuyao, Zou; Feng, Zhang; Duo, Liu; Xianghuai, Liu; Jianzhong, Tang; Weimin, Zhu; Bo, Huang

1998-05-01

Conidia of Streptomyces erythreus, an industrial microbe, were implanted by nitrogen ions with energy of 40-60 keV and fluence from 1 × 10 11 to 5 × 10 14 ions/cm 2. The logarithm value of survival fraction had good linear relationship with the logarithm value of fluence. Some mutants with a high yield of erythromycin were induced by ion implantation. The yield increment was correlated with the implantation fluence. Compared with the mutation results induced by ultraviolet rays, mutation effects of ion implantation were obvious having higher increasing erythromycin potency and wider mutation spectrum. The spores of Bacillus subtilis were implanted by arsenic ions with energy of 100 keV. The distribution of implanted ions was measured by Rutherford Backscattering Spectrometry (RBS) and calculated in theory. The mechanism of mutation induced by ion implantation was discussed.

Cytogenetic effects of high-energy iron ions: dependence on shielding thickness and material.

PubMed

Durante, M; George, K; Gialanella, G; Grossi, G; La Tessa, C; Manti, L; Miller, J; Pugliese, M; Scampoli, P; Cucinotta, F A

2005-10-01

We report results for chromosomal aberrations in human peripheral blood lymphocytes after they were exposed to high-energy iron ions with or without shielding at the HIMAC, AGS and NSRL accelerators. Isolated lymphocytes were exposed to iron ions with energies between 200 and 5000 MeV/nucleon in the 0.1-1-Gy dose range. Shielding materials consisted of polyethylene, lucite (PMMA), carbon, aluminum and lead, with mass thickness ranging from 2 to 30 g/cm2. After exposure, lymphocytes were stimulated to grow in vitro, and chromosomes were prematurely condensed using a phosphatase inhibitor (calyculin A). Aberrations were scored using FISH painting. The yield of total interchromosomal exchanges (including dicentrics, translocations and complex rearrangements) increased linearly with dose or fluence in the range studied. Shielding decreased the effectiveness per unit dose of iron ions. The highest RBE value was measured with the 1 GeV/nucleon iron-ion beam at NSRL. However, the RBE for the induction of aberrations apparently is not well correlated with the mean LET. When shielding thickness was increased, the frequency of aberrations per particle incident on the shield increased for the 500 MeV/nucleon ions and decreased for the 1 GeV/nucleon ions. Maximum variation at equal mass thickness was obtained with light materials (polyethylene, carbon or PMMA). Variations in the yield of chromosomal aberrations per iron particle incident on the shield follow variations in the dose per incident particle behind the shield but can be modified by the different RBE of the mixed radiation field produced by nuclear fragmentation. The results suggest that shielding design models should be benchmarked using both physics and biological data.

Production yield of rare-earth ions implanted into an optical crystal

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

Kornher, Thomas, E-mail: t.kornher@physik.uni-stuttgart.de; Xia, Kangwei; Kolesov, Roman

2016-02-01

Rare-earth (RE) ions doped into desired locations of optical crystals might enable a range of novel integrated photonic devices for quantum applications. With this aim, we have investigated the production yield of cerium and praseodymium by means of ion implantation. As a measure, the collected fluorescence intensity from both implanted samples and single centers was used. With a tailored annealing procedure for cerium, a yield up to 53% was estimated. Praseodymium yield amounts up to 91%. Such high implantation yield indicates a feasibility of creation of nanopatterned rare-earth doping and suggests strong potential of RE species for on-chip photonic devices.

Yield degradation in inertial-confinement-fusion implosions due to shock-driven kinetic fuel-species stratification and viscous heating

DOE PAGES

Taitano, William T.; Simakov, Andrei N.; Chacon, Luis; ...

2018-04-09

Anomalous thermonuclear yield degradation (i.e., that not describable by single-fluid radiation hydrodynamics) in Inertial Confinement Fusion (ICF) implosions is ubiquitously observed in both Omega and National Ignition experiments. Multiple experimental and theoretical studies have been carried out to investigate the origin of such a degradation. Relative concentration changes of fuel-ion species, as well as kinetically enhanced viscous heating, have been among possible explanations proposed for certain classes of ICF experiments. In this study, we investigate the role of such kinetic plasma effects in detail. To this end, we use the iFP code to perform multi-species ion Vlasov-Fokker-Planck simulations of ICFmore » capsule implosions with the fuel comprising various hydrodynamically equivalent mixtures of deuterium (D) and helium-3 (3He), as in the original. We employ the same computational setup as in O. Larroche, which was the first to simulate the experiments kinetically. However, unlike the Larroche study, and in partial agreement with experimental data, we find a systematic yield degradation in multi-species simulations versus averaged-ion simulations when the D-fuel fraction is decreased. This yield degradation originates in the fuel-ion species stratification induced by plasma shocks, which imprints the imploding system and results in the relocation of the D ions from the core of the capsule to its periphery, thereby reducing the yield relative to a non-separable averaged-ion case. By comparing yields from the averaged-ion kinetic simulations and from the hydrodynamic scaling, we also observe yield variations associated with ion kinetic effects other than fuel-ion stratification, such as ion viscous heating, which is typically neglected in hydrodynamic implosions' simulations. Since our kinetic simulations are driven by hydrodynamic boundary conditions at the fuel-ablator interface, they cannot capture the effects of ion viscosity on the capsule compression, or effects associated with the interface, which are expected to be important. As a result, studies of such effects are left for future work.« less

Yield degradation in inertial-confinement-fusion implosions due to shock-driven kinetic fuel-species stratification and viscous heating

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

Taitano, William T.; Simakov, Andrei N.; Chacon, Luis

Anomalous thermonuclear yield degradation (i.e., that not describable by single-fluid radiation hydrodynamics) in Inertial Confinement Fusion (ICF) implosions is ubiquitously observed in both Omega and National Ignition experiments. Multiple experimental and theoretical studies have been carried out to investigate the origin of such a degradation. Relative concentration changes of fuel-ion species, as well as kinetically enhanced viscous heating, have been among possible explanations proposed for certain classes of ICF experiments. In this study, we investigate the role of such kinetic plasma effects in detail. To this end, we use the iFP code to perform multi-species ion Vlasov-Fokker-Planck simulations of ICFmore » capsule implosions with the fuel comprising various hydrodynamically equivalent mixtures of deuterium (D) and helium-3 (3He), as in the original. We employ the same computational setup as in O. Larroche, which was the first to simulate the experiments kinetically. However, unlike the Larroche study, and in partial agreement with experimental data, we find a systematic yield degradation in multi-species simulations versus averaged-ion simulations when the D-fuel fraction is decreased. This yield degradation originates in the fuel-ion species stratification induced by plasma shocks, which imprints the imploding system and results in the relocation of the D ions from the core of the capsule to its periphery, thereby reducing the yield relative to a non-separable averaged-ion case. By comparing yields from the averaged-ion kinetic simulations and from the hydrodynamic scaling, we also observe yield variations associated with ion kinetic effects other than fuel-ion stratification, such as ion viscous heating, which is typically neglected in hydrodynamic implosions' simulations. Since our kinetic simulations are driven by hydrodynamic boundary conditions at the fuel-ablator interface, they cannot capture the effects of ion viscosity on the capsule compression, or effects associated with the interface, which are expected to be important. As a result, studies of such effects are left for future work.« less

Yield degradation in inertial-confinement-fusion implosions due to shock-driven kinetic fuel-species stratification and viscous heating

NASA Astrophysics Data System (ADS)

Taitano, W. T.; Simakov, A. N.; Chacón, L.; Keenan, B.

2018-05-01

Anomalous thermonuclear yield degradation (i.e., that not describable by single-fluid radiation hydrodynamics) in Inertial Confinement Fusion (ICF) implosions is ubiquitously observed in both Omega and National Ignition experiments. Multiple experimental and theoretical studies have been carried out to investigate the origin of such a degradation. Relative concentration changes of fuel-ion species, as well as kinetically enhanced viscous heating, have been among possible explanations proposed for certain classes of ICF experiments. In this study, we investigate the role of such kinetic plasma effects in detail. To this end, we use the iFP code to perform multi-species ion Vlasov-Fokker-Planck simulations of ICF capsule implosions with the fuel comprising various hydrodynamically equivalent mixtures of deuterium (D) and helium-3 (3He), as in the original Rygg experiments [J. R. Rygg et al., Phys. Plasmas 13, 052702 (2006)]. We employ the same computational setup as in O. Larroche [Phys. Plasmas 19, 122706 (2012)], which was the first to simulate the experiments kinetically. However, unlike the Larroche study, and in partial agreement with experimental data, we find a systematic yield degradation in multi-species simulations versus averaged-ion simulations when the D-fuel fraction is decreased. This yield degradation originates in the fuel-ion species stratification induced by plasma shocks, which imprints the imploding system and results in the relocation of the D ions from the core of the capsule to its periphery, thereby reducing the yield relative to a non-separable averaged-ion case. By comparing yields from the averaged-ion kinetic simulations and from the hydrodynamic scaling, we also observe yield variations associated with ion kinetic effects other than fuel-ion stratification, such as ion viscous heating, which is typically neglected in hydrodynamic implosions' simulations. Since our kinetic simulations are driven by hydrodynamic boundary conditions at the fuel-ablator interface, they cannot capture the effects of ion viscosity on the capsule compression, or effects associated with the interface, which are expected to be important. Studies of such effects are left for future work.

Separation of copper ions from iron ions using PVA-g-(acrylic acid/N-vinyl imidazole) membranes prepared by radiation-induced grafting.

PubMed

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.

Step edge sputtering yield at grazing incidence ion bombardment.

PubMed

Hansen, Henri; Polop, Celia; Michely, Thomas; Friedrich, Andreas; Urbassek, Herbert M

2004-06-18

The surface morphology of Pt(111) was investigated by scanning tunneling microscopy after 5 keV Ar+ ion bombardment at grazing incidence in dependence of the ion fluence and in the temperature range between 625 and 720 K. The average erosion rate was found to be strongly dependent on the ion fluence and the substrate temperature during bombardment. This dependence is traced back to the variation of step concentration with temperature and fluence. We develop a simple model allowing us to determine separately the constant sputtering yields for terraces and for impact area stripes in front of ascending steps. The experimentally determined yield of these stripes--the step-edge sputtering yield--is in excellent agreement with our molecular dynamics simulations performed for the experimental situation.

A thermal extrapolation method for the effective temperatures and internal energies of activated ions

NASA Astrophysics Data System (ADS)

Meot-Ner (Mautner), Michael; Somogyi, Árpád

2007-11-01

The internal energies of dissociating ions, activated chemically or collisionally, can be estimated using the kinetics of thermal dissociation. The thermal Arrhenius parameters can be combined with the observed dissociation rate of the activated ions using kdiss = Athermalexp(-Ea,thermal/RTeff). This Arrhenius-type relation yields the effective temperature, Teff, at which the ions would dissociate thermally at the same rate, or yield the same product distributions, as the activated ions. In turn, Teff is used to calculate the internal energy of the ions and the energy deposited by the activation process. The method yields an energy deposition efficiency of 10% for a chemical ionization proton transfer reaction and 8-26% for the surface collisions of various peptide ions. Internal energies of ions activated by chemical ionization or by gas phase collisions, and of ions produced by desorption methods such as fast atom bombardment, can be also evaluated. Thermal extrapolation is especially useful for ion-molecule reaction products and for biological ions, where other methods to evaluate internal energies are laborious or unavailable.

Secondary ion emission from phosphatidic acid sandwich films under atomic and molecular primary ion bombardment

NASA Astrophysics Data System (ADS)

Stapel, D.; Benninghoven, A.

2001-11-01

Secondary ion yields increase considerably when changing from atomic to molecular primary ions. Since secondary ion emission from deeper layers could result in a pronounced yield increase, the secondary ion emission depth of molecular fragments was investigated. A phosphatidic acid Langmuir-Blodgett (LB) sandwich system was applied. The well-defined layer structure of the applied sample allows the assignment of different depths of origin to the selected fragment ions. At least 93% of the detected characteristic molecular fragment ions originate from the first and second layers. This holds true for all applied atomic and molecular primary ions.

Dipeptide Formation from Amino Acid Monomer Induced by keV Ion Irradiation: An Implication for Physicochemical Repair by Radiation Itself

NASA Astrophysics Data System (ADS)

Wang, Wei; Yuan, Hang; Wang, Xiangqin; Yu, Zengliang

2008-02-01

An identification of Phe dipeptide from L-phenylalanine monomers after keV nitrogen and argon ion implantation, by using the HPLC (high performance liquid chromatography) and LC-MS(liquid chromatography mass spectrometer) methods is reported. The results showed a similar yield behavior for both ion species, namely: 1) the yield of dipeptides under alkalescent conditions was distinctly higher than that under acidic or neutral conditions; 2) for different ion species, the dose-yield curves tracked a similar trend which was called a counter-saddle curve. The dipeptide formation may implicate a recombination repair mechanism of damaged biomolecules that energetic ions have left in their wake. Accordingly a physicochemical self-repair mechanism by radiation itself for the ion-beam radiobiological effects is proposed.

Arguments for fundamental emission by the parametric process L yields T + S in interplanetary type III bursts. [langmuir, electromagnetic, ion acoustic waves (L, T, S)

NASA Technical Reports Server (NTRS)

Cairns, I. H.

1984-01-01

Observations of low frequency ion acoustic-like waves associated with Langmuir waves present during interplanetary Type 3 bursts are used to study plasma emission mechanisms and wave processes involving ion acoustic waves. It is shown that the observed wave frequency characteristics are consistent with the processes L yields T + S (where L = Langmuir waves, T = electromagnetic waves, S = ion acoustic waves) and L yields L' + S proceeding. The usual incoherent (random phase) version of the process L yields T + S cannot explain the observed wave production time scale. The clumpy nature of the observed Langmuir waves is vital to the theory of IP Type 3 bursts. The incoherent process L yields T + S may encounter difficulties explaining the observed Type 3 brightness temperatures when Langmuir wave clumps are incorporated into the theory. The parametric process L yields T + S may be the important emission process for the fundamental radiation of interplanetary Type 3 bursts.

MALDI-MS/MS with Traveling Wave Ion Mobility for the Structural Analysis of N-Linked Glycans

NASA Astrophysics Data System (ADS)

Harvey, David J.; Scarff, Charlotte A.; Crispin, Max; Scanlan, Christopher N.; Bonomelli, Camille; Scrivens, James H.

2012-11-01

The preference for singly charged ion formation by MALDI makes it a better choice than electrospray ionization for profiling mixtures of N-glycans. For structural analysis, fragmentation of negative ions often yields more informative spectra than fragmentation of positive ones but such ions are more difficult to produce from neutral glycans under MALDI conditions. This work investigates conditions for the formation of both positive and negative ions by MALDI from N-linked glycans released from glycoproteins and their subsequent MS/MS and ion mobility behaviour. 2,4,6-Trihydroxyacetophenone (THAP) doped with ammonium nitrate was found to give optimal ion yields in negative ion mode. Ammonium chloride or phosphate also yielded prominent adducts but anionic carbohydrates such as sulfated N-glycans tended to ionize preferentially. Carbohydrates adducted with all three adducts (phosphate, chloride, and nitrate) produced good negative ion CID spectra but those adducted with iodide and sulfate did not yield fragment ions although they gave stronger signals. Fragmentation paralleled that seen following electrospray ionization providing superior spectra than could be obtained by PSD on MALDI-TOF instruments or with ion traps. In addition, ion mobility drift times of the adducted glycans and the ability of this technique to separate isomers also mirrored those obtained following ESI sample introduction. Ion mobility also allowed profiles to be obtained from samples whose MALDI spectra showed no evidence of such ions allowing the technique to be used in conditions where sample amounts were limiting. The method was applied to N-glycans released from the recombinant human immunodeficiency virus glycoprotein, gp120.

Carbon atom and cluster sputtering under low-energy noble gas plasma bombardment

NASA Astrophysics Data System (ADS)

Oyarzabal, E.; Doerner, R. P.; Shimada, M.; Tynan, G. R.

2008-08-01

Exit-angle resolved carbon atom and cluster (C2 and C3) sputtering yields are measured during different noble gas (Xe, Kr, Ar, Ne, and He) ion bombardments from a plasma, for low incident energies (75-225 eV). A quadrupole mass spectrometer (QMS) is used to detect the fraction of sputtered neutrals that is ionized in the plasma and to obtain the angular distribution by changing the angle between the target normal and the QMS aperture. A one-dimensional Monte Carlo code is used to simulate the interaction of the plasma and the sputtered particles in the region between the sample and the QMS. The effective elastic scattering cross sections of C, C2, and C3 with the different bombarding gas neutrals are obtained by varying the distance between the sample and the QMS and by performing a best fit of the simulation results to the experimental results. The total sputtering yield (C+C2+C3) for each bombarding gas is obtained from weight-loss measurements and the sputtering yield for C, C2, and C3 is then calculated from the integration of the measured angular distribution, taking into account the scattering and ionization of the sputtered particles between the sample and the QMS. We observe undercosine angular distributions of the sputtered atoms and clusters for all the studied bombarding gases and a clear decrease of the atom to cluster (C2 and C3) sputtering ratio as the incident ion mass increases, changing from a carbon atom preferential erosion for the lower incident ion masses (He, Ne, and Ar) to a cluster preferential erosion for the higher incident ion masses (Kr and Xe).

Experimental research of neutron yield and spectrum from deuterium gas-puff z-pinch on the GIT-12 generator at current above 2 MA

NASA Astrophysics Data System (ADS)

Cherdizov, R. K.; Fursov, F. I.; Kokshenev, V. A.; Kurmaev, N. E.; Labetsky, A. Yu; Ratakhin, N. A.; Shishlov, A. V.; Cikhardt, J.; Cikhardtova, B.; Klir, D.; Kravarik, J.; Kubes, P.; Rezac, K.; Dudkin, G. N.; Garapatsky, A. A.; Padalko, V. N.; Varlachev, V. A.

2017-05-01

The Z-pinch experiments with deuterium gas-puff surrounded by an outer plasma shell were carried out on the GIT-12 generator (Tomsk, Russia) at currents of 2 MA. The plasma shell consisting of hydrogen and carbon ions was formed by 48 plasma guns. The deuterium gas-puff was created by a fast electromagnetic valve. This configuration provides an efficient mode of the neutron production in DD reaction, and the neutron yield reaches a value above 1012 neutrons per shot. Neutron diagnostics included scintillation TOF detectors for determination of the neutron energy spectrum, bubble detectors BD-PND, a silver activation detector, and several activation samples for determination of the neutron yield analysed by a Sodium Iodide (NaI) and a high-purity Germanium (HPGe) detectors. Using this neutron diagnostic complex, we measured the total neutron yield and amount of high-energy neutrons.

Phosphorus-zinc interactive effects on growth by Selenastrum capricornutum (chlorophyta)

USGS Publications Warehouse

Kuwabara, J.S.

1985-01-01

Culturing experiments in chemically defined growth media were conducted to observe possible Zn and P interactions on Selenastrum capricornutum Printz growth indexes. Elevated Zn concentrations (7.5 ?? 10-8 and 1.5 ?? 10-7 M [Zn2+]) were highly detrimental to algal growth, affecting lag, exponential, and stationary growth phases. P behaved as a yield-limiting nutrient with maximum cell densities increasing linearly with total P. This yield limitation was intensified at elevated Zn concentrations. Although calculated cellular phosphorus concentrations increased markedly with Zn ion activity, elevated Zn concentrations had no apparent effect on rates of phosphorus uptake estimated for Selenastrum during exponential growth. Results indicated that P-Zn interactions were significant in describing Selenastrum cell yield results and are consistent with previous Zn studies on chlorophytes. These P-Zn interactions and the observed inhibitory growth effects of submicromolar Zn concentrations suggest that in nature an apparent P yield-limiting condition may result from elevated Zn concentrations.

Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse

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

Bang, W.

Energetic deuterium ions from large deuterium clusters (>10 nm diameter) irradiated by an intense laser pulse (>10¹⁶ W/cm²) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We show an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the availablemore » experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10 - keV deuterium fusion plasma for 10 ns.« less

Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse

DOE PAGES

Bang, W.

2015-07-02

Energetic deuterium ions from large deuterium clusters (>10 nm diameter) irradiated by an intense laser pulse (>10¹⁶ W/cm²) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We show an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the availablemore » experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10 - keV deuterium fusion plasma for 10 ns.« less

Ab-initio Calculation of the XANES of Lithium Phosphates and LiFePO4

NASA Astrophysics Data System (ADS)

Yiu, Y. M.; Yang, Songlan; Wang, Dongniu; Sun, Xueliang; Sham, T. K.

2013-04-01

Lithium iron phosphate has been regarded as a promising cathode material for the next generation lithium ion batteries due to its high specific capacity, superior thermal and cyclic stability [1]. In this study, the XANES (X-ray Absorption Near Edge Structure) spectra of lithium iron phosphate and lithium phosphates of various compositions at the Li K, P L3,2, Fe M3,2 and O K-edges have been simulated self-consistently using ab-initio calculations based on multiple scattering theory (the FEFF9 code) and DFT (Density Functional Theory, the Wien2k code). The lithium phosphates under investigation include LiFePO4, γ-Li3PO4, Li4P2O7 and LiPO3. The calculated spectra are compared to the experimental XANES recorded in total electron yield (TEY) and fluorescence yield (FLY). This work was carried out to assess the XANES of possible phases presented in LiFePO4 based Li ion battery applications [2].

Measurement of Υ (1 S +2 S +3 S ) production in p +p and Au + Au collisions at √{sNN}=200 GeV

NASA Astrophysics Data System (ADS)

Adare, A.; Afanasiev, S.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Al-Bataineh, H.; Al-Ta'Ani, H.; Alexander, J.; Angerami, A.; Aoki, K.; Apadula, N.; Aphecetche, L.; Aramaki, Y.; Asai, J.; Asano, H.; Aschenauer, E. C.; Atomssa, E. T.; Averbeck, R.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Baksay, G.; Baksay, L.; Baldisseri, A.; Bannier, B.; Barish, K. N.; Barnes, P. D.; Bassalleck, B.; Basye, A. T.; Bathe, S.; Batsouli, S.; Baublis, V.; Baumann, C.; Baumgart, S.; Bazilevsky, A.; Belikov, S.; Belmont, R.; Bennett, R.; Berdnikov, A.; Berdnikov, Y.; Bickley, A. A.; Bing, X.; Blau, D. S.; Boissevain, J. G.; Bok, J. S.; Borel, H.; Boyle, K.; Brooks, M. L.; Buesching, H.; Bumazhnov, V.; Bunce, G.; Butsyk, S.; Camacho, C. M.; Campbell, S.; Castera, P.; Chang, B. S.; Chang, W. C.; Charvet, J.-L.; Chen, C.-H.; Chernichenko, S.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choi, J. B.; Choi, S.; Choudhury, R. K.; Christiansen, P.; Chujo, T.; Chung, P.; Churyn, A.; Chvala, O.; Cianciolo, V.; Citron, Z.; Cole, B. A.; Connors, M.; Constantin, P.; Csanád, M.; Csörgő, T.; Dahms, T.; Dairaku, S.; Das, K.; Datta, A.; Daugherity, M. S.; David, G.; Denisov, A.; D'Enterria, D.; Deshpande, A.; Desmond, E. J.; Dharmawardane, K. V.; Dietzsch, O.; Ding, L.; Dion, A.; Donadelli, M.; Drapier, O.; Drees, A.; Drees, K. A.; Dubey, A. K.; Durham, J. M.; Durum, A.; Dutta, D.; Dzhordzhadze, V.; D'Orazio, L.; Edwards, S.; Efremenko, Y. V.; Ellinghaus, F.; Engelmore, T.; Enokizono, A.; En'yo, H.; Esumi, S.; Eyser, K. O.; Fadem, B.; Fields, D. E.; Finger, M.; Finger, M.; Fleuret, F.; Fokin, S. L.; Fraenkel, Z.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fujiwara, K.; Fukao, Y.; Fusayasu, T.; Gainey, K.; Gal, C.; Garishvili, A.; Garishvili, I.; Glenn, A.; Gong, H.; Gong, X.; Gonin, M.; Gosset, J.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gunji, T.; Guo, L.; Gustafsson, H.-Å.; Hachiya, T.; Hadj Henni, A.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Han, R.; Hanks, J.; Hartouni, E. P.; Haruna, K.; Hashimoto, K.; Haslum, E.; Hayano, R.; He, X.; Heffner, M.; Hemmick, T. K.; Hester, T.; Hill, J. C.; Hohlmann, M.; Hollis, R. S.; Holzmann, W.; Homma, K.; Hong, B.; Horaguchi, T.; Hori, Y.; Hornback, D.; Huang, S.; Ichihara, T.; Ichimiya, R.; Iinuma, H.; Ikeda, Y.; Imai, K.; Imrek, J.; Inaba, M.; Iordanova, A.; Isenhower, D.; Ishihara, M.; Isobe, T.; Issah, M.; Isupov, A.; Ivanischev, D.; Ivanishchev, D.; Jacak, B. V.; Javani, M.; Jia, J.; Jiang, X.; Jin, J.; Johnson, B. M.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kajihara, F.; Kametani, S.; Kamihara, N.; Kamin, J.; Kaneti, S.; Kang, B. H.; Kang, J. H.; Kang, J. S.; Kapustinsky, J.; Karatsu, K.; Kasai, M.; Kawall, D.; Kazantsev, A. V.; Kempel, T.; Khanzadeev, A.; Kijima, K. M.; Kikuchi, J.; Kim, B. I.; Kim, C.; Kim, D. H.; Kim, D. J.; Kim, E.; Kim, E.-J.; Kim, H. J.; Kim, K.-B.; Kim, S. H.; Kim, Y.-J.; Kim, Y. K.; Kinney, E.; Kiriluk, K.; Kiss, Á.; Kistenev, E.; Klatsky, J.; Klay, J.; Klein-Boesing, C.; Kleinjan, D.; Kline, P.; Kochenda, L.; Komatsu, Y.; Komkov, B.; Konno, M.; Koster, J.; Kotchetkov, D.; Kotov, D.; Kozlov, A.; Král, A.; Kravitz, A.; Krizek, F.; Kunde, G. J.; Kurita, K.; Kurosawa, M.; Kweon, M. J.; Kwon, Y.; Kyle, G. S.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Layton, D.; Lebedev, A.; Lee, B.; Lee, D. M.; Lee, J.; Lee, K. B.; Lee, K. S.; Lee, S. H.; Lee, S. R.; Lee, T.; Leitch, M. J.; Leite, M. A. L.; Leitgab, M.; Lenzi, B.; Lewis, B.; Li, X.; Liebing, P.; Lim, S. H.; Linden Levy, L. A.; Liška, T.; Litvinenko, A.; Liu, H.; Liu, M. X.; Love, B.; Lynch, D.; Maguire, C. F.; Makdisi, Y. I.; Makek, M.; Malakhov, A.; Malik, M. D.; Manion, A.; Manko, V. I.; Mannel, E.; Mao, Y.; Mašek, L.; Masui, H.; Masumoto, S.; Matathias, F.; McCumber, M.; McGaughey, P. L.; McGlinchey, D.; McKinney, C.; Means, N.; Mendoza, M.; Meredith, B.; Miake, Y.; Mibe, T.; Mignerey, A. C.; Mikeš, P.; Miki, K.; Milov, A.; Mishra, D. K.; Mishra, M.; Mitchell, J. T.; Miyachi, Y.; Miyasaka, S.; Mohanty, A. K.; Moon, H. J.; Morino, Y.; Morreale, A.; Morrison, D. P.; Motschwiller, S.; Moukhanova, T. V.; Mukhopadhyay, D.; Murakami, T.; Murata, J.; Nagae, T.; Nagamiya, S.; Nagle, J. L.; Naglis, M.; Nagy, M. I.; Nakagawa, I.; Nakamiya, Y.; Nakamura, K. R.; Nakamura, T.; Nakano, K.; Nattrass, C.; Nederlof, A.; Newby, J.; Nguyen, M.; Nihashi, M.; Niida, T.; Nouicer, R.; Novitzky, N.; Nyanin, A. S.; O'Brien, E.; Oda, S. X.; Ogilvie, C. A.; Oka, M.; Okada, K.; Onuki, Y.; Oskarsson, A.; Ouchida, M.; Ozawa, K.; Pak, R.; Palounek, A. P. T.; Pantuev, V.; Papavassiliou, V.; Park, B. H.; Park, I. H.; Park, J.; Park, S. K.; Park, W. J.; Pate, S. F.; Patel, L.; Pei, H.; Peng, J.-C.; Pereira, H.; Peresedov, V.; Peressounko, D. Yu.; Petti, R.; Pinkenburg, C.; Pisani, R. P.; Proissl, M.; Purschke, M. L.; Purwar, A. K.; Qu, H.; Rak, J.; Rakotozafindrabe, A.; Ravinovich, I.; Read, K. F.; Rembeczki, S.; Reygers, K.; Reynolds, D.; Riabov, V.; Riabov, Y.; Richardson, E.; Riveli, N.; Roach, D.; Roche, G.; Rolnick, S. D.; Rosati, M.; Rosendahl, S. S. E.; Rosnet, P.; Rukoyatkin, P.; Ružička, P.; Rykov, V. L.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sakai, S.; Sakashita, K.; Samsonov, V.; Sano, M.; Sarsour, M.; Sato, T.; Sawada, S.; Sedgwick, K.; Seele, J.; Seidl, R.; Semenov, A. Yu.; Semenov, V.; Sen, A.; Seto, R.; Sharma, D.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Silvestre, C.; Sim, K. S.; Singh, B. K.; Singh, C. P.; Singh, V.; Slunečka, M.; Soldatov, A.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Soumya, M.; Sourikova, I. V.; Staley, F.; Stankus, P. W.; Stenlund, E.; Stepanov, M.; Ster, A.; Stoll, S. P.; Sugitate, T.; Suire, C.; Sukhanov, A.; Sun, J.; Sziklai, J.; Takagui, E. M.; Takahara, A.; Taketani, A.; Tanabe, R.; Tanaka, Y.; Taneja, S.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tarján, P.; Tennant, E.; Themann, H.; Thomas, T. L.; Todoroki, T.; Togawa, M.; Toia, A.; Tomášek, L.; Tomášek, M.; Tomita, Y.; Torii, H.; Towell, R. S.; Tram, V.-N.; Tserruya, I.; Tsuchimoto, Y.; Tsuji, T.; Vale, C.; Valle, H.; van Hecke, H. W.; Vargyas, M.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Vinogradov, A. A.; Virius, M.; Vossen, A.; Vrba, V.; Vznuzdaev, E.; Wang, X. R.; Watanabe, D.; Watanabe, K.; Watanabe, Y.; Watanabe, Y. S.; Wei, F.; Wei, R.; Wessels, J.; Whitaker, S.; White, S. N.; Winter, D.; Wolin, S.; Woody, C. L.; Wysocki, M.; Xie, W.; Yamaguchi, Y. L.; Yamaura, K.; Yang, R.; Yanovich, A.; Ying, J.; Yokkaichi, S.; You, Z.; Young, G. R.; Younus, I.; Yushmanov, I. E.; Zajc, W. A.; Zaudtke, O.; Zelenski, A.; Zhang, C.; Zhou, S.; Zolin, L.; Phenix Collaboration

2015-02-01

Measurements of bottomonium production in heavy-ion and p +p collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three Υ states, Υ (1 S +2 S +3 S ) , was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au +Au and p +p collisions at √{sNN}=200 GeV. The Υ (1 S +2 S +3 S ) →e+e- differential cross section at midrapidity was found to be Beed σ /d y =108 ±38 (stat) ±15 (syst) ±11 (luminosity) pb in p +p collisions. The nuclear modification factor in the 30% most central Au +Au collisions indicates a suppression of the total Υ state yield relative to the extrapolation from p +p collision data. The suppression is consistent with measurements made by STAR at RHIC and at higher energies by the CMS experiment at the Large Hadron Collider.

Measurement of Υ(1S + 2S +3S) production in p + p and Au + Au collisions at \\(\\sqrt{s_{\\mathrm{NN}}}=200\\) GeV

DOE PAGES

Adare, A.; Afanasiev, S.; Aidala, C.; ...

2015-02-24

Measurements of bottomonium production in heavy-ion and p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three Υ states, Υ(1S + 2S + 3S), was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au+Au and p+p collisions at \\(\\sqrt{s_{\\mathrm{NN}}}=200\\) GeV. The Υ(1S + 2S + 3S) → e⁺e⁻ differential cross section at midrapidity was found to be B eedσ/dy = 108 ± 38 (stat) ± 15 (syst) ± 11 (luminosity) pb in p+p collisions. The nuclear modification factor in the 30% most central Au+Au collisions indicates a suppression ofmore » the total Υ state yield relative to the extrapolation from p+p collision data. Thus, the suppression is consistent with measurements at higher energies by the CMS experiment at the Large Hadron Collider.« less

Absolute prompt-gamma yield measurements for ion beam therapy monitoring

NASA Astrophysics Data System (ADS)

Pinto, M.; Bajard, M.; Brons, S.; Chevallier, M.; Dauvergne, D.; Dedes, G.; De Rydt, M.; Freud, N.; Krimmer, J.; La Tessa, C.; Létang, J. M.; Parodi, K.; Pleskač, R.; Prieels, D.; Ray, C.; Rinaldi, I.; Roellinghoff, F.; Schardt, D.; Testa, E.; Testa, M.

2015-01-01

Prompt-gamma emission detection is a promising technique for hadrontherapy monitoring purposes. In this regard, obtaining prompt-gamma yields that can be used to develop monitoring systems based on this principle is of utmost importance since any camera design must cope with the available signal. Herein, a comprehensive study of the data from ten single-slit experiments is presented, five consisting in the irradiation of either PMMA or water targets with lower and higher energy carbon ions, and another five experiments using PMMA targets and proton beams. Analysis techniques such as background subtraction methods, geometrical normalization, and systematic uncertainty estimation were applied to the data in order to obtain absolute prompt-gamma yields in units of prompt-gamma counts per incident ion, unit of field of view, and unit of solid angle. At the entrance of a PMMA target, where the contribution of secondary nuclear reactions is negligible, prompt-gamma counts per incident ion, per millimetre and per steradian equal to (124 ± 0.7stat ± 30sys) × 10-6 for 95 MeV u-1 carbon ions, (79 ± 2stat ± 23sys) × 10-6 for 310 MeV u-1 carbon ions, and (16 ± 0.07stat ± 1sys) × 10-6 for 160 MeV protons were found for prompt gammas with energies higher than 1 MeV. This shows a factor 5 between the yields of two different ions species with the same range in water (160 MeV protons and 310 MeV u-1 carbon ions). The target composition was also found to influence the prompt-gamma yield since, for 300/310 MeV u-1 carbon ions, a 42% greater yield ((112 ± 1stat ± 22sys) × 10-6 counts ion-1 mm-1 sr-1) was obtained with a water target compared to a PMMA one.

Sputtering Erosion in the Ion Thruster

NASA Technical Reports Server (NTRS)

Ray, Pradosh K.; Mantenieks, Maris A. (Technical Monitor)

2000-01-01

During the first phase of this research, the sputtering yields of molybdenum by low energy (100 eV and higher) xenon ions were measured by using the methods of secondary neutral mass spectrometry (SNMS) and Rutherford backscattering spectrometry (RBS). However, the measured sputtering yields were found to be far too low to explain the sputtering erosions observed in the long-duration tests of ion thrusters. The only difference between the sputtering yield measurement experiments and the ion thruster tests was that the later are conducted at high ion fluences. Hence, a study was initiated to investigate if any linkage exists between high ion fluence and an enhanced sputtering yield. The objective of this research is to gain an understanding of the causes of the discrepancies between the sputtering rates of molybdenum grids in an ion thruster and those measured from our experiments. We are developing a molecular dynamics simulation technique for studying low-energy xenon ion interactions with molybdenum. It is difficult to determine collision sequences analytically for primary ions below the 200 eV energy range where the ion energy is too low to be able to employ a random cascade model with confidence and it is too high to have to consider only single collision at or near the surface. At these low energies, the range of primary ions is about 1 to 2 nm from the surface and it takes less than 4 collisions on the average to get an ion to degrade to such an energy that it can no longer migrate. The fine details of atomic motion during the sputtering process are revealed through computer simulation schemes. By using an appropriate interatomic potential, the positions and velocities of the incident ion together with a sufficient number of target atoms are determined in small time steps. Hence, it allows one to study the evolution of damages in the target and its effect on the sputtering yield. We are at the preliminary stages of setting up the simulation program.

Influence of Boiling Duration of GCSB-5 on Index Compound Content and Antioxidative and Anti-inflammatory Activity.

PubMed

Lee, In-Hee; Chung, Hwa-Jin; Shin, Joon-Shik; Ha, In-Hyuk; Kim, Me-Riong; Koh, Wonil; Lee, Jinho

2017-01-01

GCSB-5, an herbal drug composition with an anti-inflammatory effect, is prepared by boiling, which is the most common herbal extraction method in traditional Korean medicine. Several parameters are involved in the process, i.e., extractant type, herb-to-extractant ratio, extraction temperature and pressure, and total boiling time. The aim of this study was to examine the influence of boiling time on index compound amount and the antioxidative and anti-inflammatory activities of GCSB-5. Different samples of GCSB-5 were obtained by decocting for 30, 60, 90, 120, 150, and 240 min. Each sample was tested for hydrogen ion concentration (pH), total soluble solid content (TSSC), marker compound profiles, and antioxidative and anti-inflammatory activity. pH was found to decrease while TSSC increased with extended decoction. Marker compound contents for GCSB-5 (acanthoside D for Acanthopanax sessiliflorus Seem, 20-hydroxyecdysone for Achyranthes japonica Nakai, and pinoresinol diglucoside for Eucommia ulmoides Oliver) remained relatively constant regardless of the length of boiling. Total D-glucose amount increased with longer boiling. The antioxidative and anti-inflammatory potentials of GCSB-5 were not substantially affected by decoction duration. Biological characteristics and marker compound content of GCSB-5 were not altered significantly in prolonged boiling. Longer boiling duration of GCSB-5 did not increase yield in a time-dependent manner, but yields of 210 and 240 min samples were significantly higherHydrogen ion concentration of GCSB-5 samples decreased while total soluble solid content and D-glucose concentration levels increased with boiling durationAlthough concentrations of some index compounds increased with extended boiling duration of GCSB-5, increase was small and not in a direct proportional relationshipAntioxidative and anti-inflammatory properties of GCSB-5 were not substantially affected by decoction duration. Abbreviations used: CAM: Complementary and alternative medicine; KIOM: Korea Institute of Oriental Medicine; KMD: Korean medicine doctor; TSSC: Total soluble solid content; pH: Hydrogen ion concentration; HPLC: High-performance liquid chromatography; NO: Nitric oxide; NO 2 : Nitric dioxide; LPS: Lipopolysaccharide; DMSO: Dimethyl sulfoxide.

Evolution of ion emission yield of alloys with the nature of the solute. 2: Interpretation

NASA Technical Reports Server (NTRS)

Blaise, G.; Slodzian, G.

1977-01-01

Solid solutions of transition elements in copper, nickel, cobalt, iron, and aluminum matrices were analyzed by observing secondary ion emissions under bombardment with 6.2-keV argon ions. Enchancement of the production of solute-element ions was observed. An ion emission model is proposed according to which the ion yield is governed by the probability of an atom leaving the metal in a preionized state. The energy distribution of the valence electrons of the solute atoms is the bases of the probability calculation.

Dynamic of negative ions in potassium-D-ribose collisions.

PubMed

Almeida, D; Ferreira da Silva, F; García, G; Limão-Vieira, P

2013-09-21

We present negative ion formation from collisions of neutral potassium atoms with D-ribose (C5H10O5), the sugar unit in the DNA/RNA molecule. From the negative ion time-of-flight (TOF) mass spectra, OH(-) is the main fragment detected in the collision range 50-100 eV accounting on average for 50% of the total anion yield. Prominence is also given to the rich fragmentation pattern observed with special attention to O(-) (16 m/z) formation. These results are in sharp contrast to dissociative electron attachment experiments. The TOF mass spectra assignments show that these channels are also observed, albeit with a much lower relative intensity. Branching ratios of the most abundant fragment anions as a function of the collision energy are obtained, allowing to establish a rationale on the collision dynamics.

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.

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

Rudeck, P.J.; Harper, J.M.E.; Fryer, P.M.

The copper concentration in aluminum--copper alloys can be altered by ion bombardment during film deposition. We have measured the sputtering yields of aluminum and copper in Al--Cu alloys as a function of the Cu concentration (5--13 at. %) and the angle of ion incidence (0--40/sup 0/ from normal). During deposition, the films were partially resputtered by 500-eV Ar/sup +/ ion bombardment from a Kaufman ion source. We found that the Cu sputtering yield decreases by up to a factor of 10 in the alloy, relative to elemental Cu. The Al sputtering yield remains close to the elemental value. The netmore » effect is a strong preferential sputtering of Al relative to Cu, which enhances the Cu concentration in an ion bombarded film. The Al/Cu sputtering yield ratio for normal incidence ion bombardment ranges from 3 to 5 as a function of Cu concentration. This ratio decreases with increasing angle of incidence to as low as 2 for 40/sup 0/ incident ions. However, since a higher fraction of the film is resputtered from a sloping surface, a higher Cu concentration is found on a sloping surface relative to a flat surface. These results show that in multicomponent film deposition under ion bombardment, the film composition will vary as a function of the surface topography. We will also show how the level of argon left trapped in the films varies inversely with respect to the ion flux.« less

Total angular momenta of high-lying odd levels of U I at ∼ 4 eV using resonance ionization laser polarization spectroscopy

NASA Astrophysics Data System (ADS)

Rath, Asawari D.; Kundu, S.; Ray, A. K.

2018-02-01

Laser induced photoionization of atoms shows significant dependence on the choice of polarizations of lasers. In multi-step, multi-photon excitation and subsequent ionization of atoms different polarization combinations of the exciting lasers lead to distinctly different ion yields. This fact is exploited in this work to determine total angular momenta of odd-parity energy levels of U I lying at ∼ 4 eV from its ground level using resonance ionization laser polarization spectroscopy in time of flight mass spectrometer. These levels are populated by two-step resonant excitation using two pulsed dye lasers with preset polarizations of choice followed by nonresonant ionization by third laser. The dependence of ionization yield on specific polarizations of the first two lasers is studied experimentally for each level under consideration. This dependence when compared to simulations makes possible unambiguous assignment of J angular momenta to these levels.

Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

DOE PAGES

Hatarik, R.; Sayre, D. B.; Caggiano, J. A.; ...

2015-11-12

For a long time, neutron time-of-flight diagnostics been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d+t→n+α (DT) and d+d→n+³He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, which is also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (T ion) and cold fuel areal density. We explain such novel methodologies used to determine neutron yield, apparent T ion and DSR.

Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

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

Hatarik, R., E-mail: hatarik1@llnl.gov; Sayre, D. B.; Caggiano, J. A.

2015-11-14

Neutron time-of-flight diagnostics have long been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d + t → n + α (DT) and d + d → n + {sup 3}He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (T{sub ion}) and cold fuel areal density. We report on novel methodologies used to determine neutron yield, apparent T{sub ion}, and DSR. These methods invoke a single temperature,more » static fluid model to describe the neutron peaks from DD and DT reactions and a spline description of the DT spectrum to determine the DSR. Both measurements are performed using a forward modeling technique that includes corrections for line-of-sight attenuation and impulse response of the detection system. These methods produce typical uncertainties for DT T{sub ion} of 250 eV, 7% for DSR, and 9% for the DT neutron yield. For the DD values, the uncertainties are 290 eV for T{sub ion} and 10% for the neutron yield.« less

Factors Affecting the Production of Aromatic Immonium Ions in MALDI 157 nm Photodissociation Studies

NASA Astrophysics Data System (ADS)

DeGraan-Weber, Nick; Ashley, Daniel C.; Keijzer, Karlijn; Baik, Mu-Hyun; Reilly, James P.

2016-05-01

Immonium ions are commonly observed in the high energy fragmentation of peptide ions. In a MALDI-TOF/TOF mass spectrometer, singly charged peptides photofragmented with 157 nm VUV light yield a copious abundance of immonium ions, especially those from aromatic residues. However, their intensities may vary from one peptide to another. In this work, the effect of varying amino acid position, peptide length, and peptide composition on immonium ion yield is investigated. Internal immonium ions are found to have the strongest intensity, whereas immonium ions arising from C-terminal residues are the weakest. Peptide length and competition among residues also strongly influence the immonium ion production. Quantum calculations provide insights about immonium ion structures and the fragment ion conformations that promote or inhibit immonium ion formation.

Negative-hydrogen-ion production from a nanoporous 12CaO • 7Al2O3 electride surface

NASA Astrophysics Data System (ADS)

Sasao, Mamiko; Moussaoui, Roba; Kogut, Dmitry; Ellis, James; Cartry, Gilles; Wada, Motoi; Tsumori, Katsuyoshi; Hosono, Hideo

2018-06-01

A high production rate of negative hydrogen ions (H‑) was observed from a nanoporous 12CaO • 7Al2O3 (C12A7) electride surface immersed in hydrogen/deuterium low-pressure plasmas. The target was negatively biased at 20–130 V, and the target surface was bombarded by H3 + ions from the plasma. The production rate was compared with that from a clean molybdenum surface. Using the pseudo-exponential work-function dependence of the H‑ production rate, the total H‑ yield from the C12A7 electride surface bombarded at 80 V was evaluated to be 25% of that from a cesiated molybdenum surface with the lowest work-function. The measured H‑ energy spectrum indicates that the major production mechanism is desorption by sputtering. This material has potential to be used as a production surface of cesium-free negative ion sources for accelerators, heating beams in nuclear fusion, and surface modification for industrial applications.

Monte Carlo simulations of nanoscale focused neon ion beam sputtering.

PubMed

Timilsina, Rajendra; Rack, Philip D

2013-12-13

A Monte Carlo simulation is developed to model the physical sputtering of aluminum and tungsten emulating nanoscale focused helium and neon ion beam etching from the gas field ion microscope. Neon beams with different beam energies (0.5-30 keV) and a constant beam diameter (Gaussian with full-width-at-half-maximum of 1 nm) were simulated to elucidate the nanostructure evolution during the physical sputtering of nanoscale high aspect ratio features. The aspect ratio and sputter yield vary with the ion species and beam energy for a constant beam diameter and are related to the distribution of the nuclear energy loss. Neon ions have a larger sputter yield than the helium ions due to their larger mass and consequently larger nuclear energy loss relative to helium. Quantitative information such as the sputtering yields, the energy-dependent aspect ratios and resolution-limiting effects are discussed.

Local formation of nitrogen-vacancy centers in diamond by swift heavy ions

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

Schwartz, J.; Aloni, S.; Ogletree, D. F.

2014-12-03

In this paper, we exposed nitrogen-implanted diamonds to beams of swift heavy ions (~1 GeV, ~4 MeV/u) and find that these irradiations lead directly to the formation of nitrogen vacancy (NV) centers, without thermal annealing. We compare the photoluminescence intensities of swift heavy ion activated NV - centers to those formed by irradiation with low-energy electrons and by thermal annealing. NV - yields from irradiations with swift heavy ions are 0.1 of yields from low energy electrons and 0.02 of yields from thermal annealing. We discuss possible mechanisms of NV center formation by swift heavy ions such as electronic excitationsmore » and thermal spikes. While forming NV centers with low efficiency, swift heavy ions could enable the formation of three dimensional NV - assemblies over relatively large distances of tens of micrometers. Finally and further, our results show that NV center formation is a local probe of (partial) lattice damage relaxation induced by electronic excitations from swift heavy ions in diamond.« less

Retention of neon in graphite after ion beam implantation or exposures to the scrape-off layer plasma in the TEXTOR tokamak

NASA Astrophysics Data System (ADS)

Kim, Y. M.; Philipps, V.; Rubel, M.; Vietzke, E.; Pospieszczyk, A.; Unterberg, B.; Jaspers, R.

2002-01-01

The interaction of neon ions with graphite was investigated for targets either irradiated with ion beams (2-10 keV range) or exposed to the scrape-off layer plasma in the TEXTOR tokamak during discharges with neon edge cooling. The emphasis was on the influence of the target temperature (300-1200 K) and the implantation dose on the neon retention and reemission. The influence of deuterium impact on the retention of neon implanted into graphite has also been addressed. In ion beam experiments saturation is observed above a certain ion dose with a saturation level, which decreases with increasing target temperature. The temperature dependence of the thermal desorption corresponds to an apparent binding energy of about 2.06 eV. The retention of neon (CNe/CC) decreases with increasing ion energy with values from 0.55 to 0.15 following irradiation with 2 and 10 keV ions, respectively. The reemission yield during the irradiation increases with target temperature and above 1200 K all impinging ions are reemitted instantaneously. The retention densities measured using the sniffer probe at the TEXTOR tokamak are less than 1% of the total neon fluence and are over one order of magnitude smaller than those observed in ion beam experiments. The results are discussed in terms of different process decisive for ion deposition and release under the two experimental conditions.

Extending Ion Engine Technology to NEXT and Beyond

NASA Technical Reports Server (NTRS)

Domonkos, Matthew T.; Patterson, Michael J.; Foster, John E.; Rawlin, Vince K.; Soulas, George C.; Sovey, James S.; Kovaleski, Scott D.; Roman, Robert F.; Williams, George J., Jr.; Lyons, Valerie J. (Technical Monitor)

2002-01-01

Extending ion engine technology beyond the current state-of-the art primary interplanetary electric propulsion system, the 2.3-kW NASA Solar Electric Propulsion Technology and Applications Readiness (NSTAR) system, will require thrusters with improved propellant throughput and total impulse capability. Many of the design choices that culminated in the NSTAR thrusters must be revisited, and their application to next generation ion engine technology must be evaluated. The concept of derating, which was successfully employed in NSTAR, has been applied to the 40 cm NASA Evolutionary Xenon Thruster (NEXT) currently under development at NASA Glenn Research Center (GRC). At 5-kW, NEXT operates with the same average beam current density as NSTAR, and at 10-kW, the peak beam current density is only ten percent greater than NSTAR. The result is that similar Ion optics technology is expected to yield comparable lifetime. Thick-accelerator- grid ion optics are also being tested to realize additional lifetime benefits. A 40-A discharge cathode is being developed for NEXT based on scaling the NSTAR design. Nevertheless, the experiences of the NSTAR ground tests and the thruster on the Deep Space One spacecraft indicate that the discharge cathode wear must be studied experimentally and theoretically to ensure that it meets the lifetime requirements. Although NEXT is in its infancy, investigations have already begun to examine possible modifications to engine design for even higher-power and higher-specific impulse engines. Ion optics using alternate materials such as titanium, graphite, or carbon-carbon composite are currently being investigated due to their low sputter yields at high voltage. To avoid the difficulties encountered using electrodes at high-currents, the use of a microwave-based ion thruster is under investigation for potential high-power ion thruster systems requiring long lifetimes. Additionally, alternative propellants are being considered for applications requiring high-specific impulse (>> 5000 s) and extremely long-life (>> 15,000 hr). Testing requirements make condensable propellants attractive for high-power engines. Although the NSTAR ion engine demonstrated the flight maturity of ion thruster technology, many challenges remain for the development of thrusters with improved propellant throughput and power handling capabilities.

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

Rudeck, P.J.; Harper, J.M.E.; Fryer, P.M.

The copper concentration in aluminum-copper alloys can be altered by ion bombardment during film deposition. We have measured the sputtering yields of aluminum and copper in Al-Cu alloys as a function of the Cu concentration (5--13 at. %) and the angle of ion incidence (0/sup 0/--40/sup 0/ from normal). During deposition, the films were partially resputtered by 500 eV Ar/sup +/ ion bombardment from a Kaufman ion source. We found that the Cu sputtering yield decreases by up to a factor of 10 in the alloy, relative to elemental Cu. The Al sputtering yield remains close to the elemental value.more » The net effect is a strong preferential sputtering of Al relative to Cu, which enhances the Cu concentration in an ion-bombarded film. The Al/Cu sputtering yield ratio for normal incidence ion bombardment ranges from 3 to 5 as a function of Cu concentration. This ratio decreases with increasing angle of incidence to as low as 2 for 40/sup 0/ incident ions. However, since a higher fraction of the film is resputtered from a sloping surface, a higher Cu concentration is found on a sloping surface relative to a flat surface. These results show that the film composition will vary as a function of the surface topography.« less

Radiation dose-response curves: cell repair mechanisms vs. ion track overlapping

NASA Astrophysics Data System (ADS)

Kowalska, Agata; Czerski, Konrad; Nasonova, Elena; Kutsalo, Polina; Krasavin, Eugen

2017-12-01

Chromosome aberrations in human lymphocytes exposed to different doses of particle radiation: 150 MeV and spread out Bragg peak proton beams, 22 MeV/u boron beam and 199 V/u carbon beam were studied. For comparison, an experiment with 60Co γ-rays was also performed. We investigated distributions of aberration frequency and the shape of dose-response curves for the total aberration yield as well as for exchange and non-exchange aberrations, separately. Applying the linear-quadratic model, we could derive a relation between the fitted parameters and the ion track radius which could explain experimentally observed curvature of the dose-response curves. The results compared with physical expectations clearly show that the biological effects of cell repair are much more important than the ion track overlapping. Contribution to the Topical Issue "Dynamics of Systems at the Nanoscale", edited by Andrey Solov'yov and Andrei Korol.

Heavy Ion Fragmentation Experiments at the Bevatron

NASA Technical Reports Server (NTRS)

Heckman, H. H.

1975-01-01

Fragmentation processes of heavy nuclei in matter using the heavy-ion capability of the Bevatron were studied. The purpose was to obtain the single particle inclusive spectra of secondary nuclei produced at 0 deg by the fragmentation of heavy ion beam projectiles. The process being examined is B+T yields F + anything, where B is the beam nucleus, T is the target nucleus, and F is the detected fragment. The fragments F are isotopically identified by experimental procedures involving magnetic analysis, energy loss and time-of-flight measurements. Attempts were also made to: (1) measure the total and partial production cross section for all isotopes, (2) test the applicability of high-energy multi-particle interaction theory to nuclear fragmentation, (3) apply the cross-section data and fragmentation probabilities to cosmic ray transport theory, and (4) search for systematic behavior of fragment production as a means to improve existing semi-empirical theories of cross sections.

Recombination of open-f-shell tungsten ions

NASA Astrophysics Data System (ADS)

Krantz, C.; Badnell, N. R.; Müller, A.; Schippers, S.; Wolf, A.

2017-03-01

We review experimental and theoretical efforts aimed at a detailed understanding of the recombination of electrons with highly charged tungsten ions characterised by an open 4f sub-shell. Highly charged tungsten occurs as a plasma contaminant in ITER-like tokamak experiments, where it acts as an unwanted cooling agent. Modelling of the charge state populations in a plasma requires reliable thermal rate coefficients for charge-changing electron collisions. The electron recombination of medium-charged tungsten species with open 4f sub-shells is especially challenging to compute reliably. Storage-ring experiments have been conducted that yielded recombination rate coefficients at high energy resolution and well-understood systematics. Significant deviations compared to simplified, but prevalent, computational models have been found. A new class of ab initio numerical calculations has been developed that provides reliable predictions of the total plasma recombination rate coefficients for these ions.

LIF standoff research

NASA Astrophysics Data System (ADS)

Olson, C. L.; Cuneo, M. E.; Desjarlais, M. P.; Filuk, A. B.; Greenly, J. B.; Hanson, D. L.; Hinshelwood, D. D.; Hubbard, R. F.; Lampe, M.; Lockner, T. R.

Present Light Ion Fusion (LIF) target experiments on PBFA 2 use a barrel diode in which the total transport length from the anode to the target is less than or equal to 15 cm. Future LIF development includes high yield applications (LMF) and energy production (ETF and LIBRA power plants) that require standoff - the generation of extracted ion beams and transport of these beams over distances of several meters. Standoff research includes the development of high efficiency extraction diodes (single stage and two-stage), improvements in beam quality (divergence, purity, uniformity, etc.), and the efficient transport and focusing of these beams over distances of several meters to a fusion target. Progress in all of these areas is discussed, as well as a strategy to reduce the divergence from the present 17 mrad for 5 MeV protons on SABRE to the required mrad for 35 MeV Li ions for LMF. The status of experiments is summarized, and future directions are indicated.

Ejection of sodium from sodium sulfide by the sputtering of the surface of Io

NASA Technical Reports Server (NTRS)

Chrisey, D. B.; Johnson, R. E.; Boring, J. W.; Phipps, J. A.

1988-01-01

The mechanism by which Na is removed from the surface of Io prior to its injection into the plasma torus is investigated experimentally. Na2S films of thickness 3-8 microns were produced by spray coating an Ni substrate in a dry N2 atmosphere and subjected to sputtering by 34-keV Ar(+), Ne(+), Kr(+), or Xe(+) ions up to total doses of about 5 x 10 to the 18th ions/sq cm. The sputtering yields and mass spectra are found to be consistent with ejection of only small amounts of atomic Na and somewhat larger amounts of Na-containing molecules. It is concluded that the amount of Na ejected by magnetospheric-ion sputtering of Na2S would be insufficient to account for the amounts observed in the Io neutral cloud. A scenario involving sputtering of larger polysulfide molecules is considered.

Using fluorometry and ion-sensitive microelectrodes to study the functional expression of heterologously-expressed ion channels and transporters in Xenopus oocytes

PubMed Central

Musa-Aziz, Raif; Boron, Walter F.; Parker, Mark D.

2010-01-01

The Xenopus laevis oocyte is a model system for the electrophysiological study of exogenous ion transporters. Three main reasons make the oocyte suitable for this purpose: (a) it has a large cell size (~1 mm diameter), (b) it has an established capacity to produce—from microinjected mRNAs or cRNAs—exogenous ion transporters with close-to-physiological post-translational modifications and actions, and (c) its membranes contain endogenous ion-transport activities which are usually smaller in magnitude than the activities of exogenously-expressed ion transporters. The expression of ion-transporters as green-fluorescent-protein fusions allows the fluorometric assay of transporter yield in living oocytes. Monitoring of transporter-mediated movement of ions such as Cl−, H+ (and hence base equivalents like OH−1 and HCO3−), K+, and Na+ is achieved by positioning the tips of ion-sensitive microelectrodes inside the oocyte and/or at the surface of the oocyte plasma membrane. The use of ion-sensitive electrodes is critical for studying net ion-movements mediated by electroneutral transporters. The combined use of fluorometry and electrophysiology expedites transporter study by allowing measurement of transporter yield prior to electrophysiological study and correlation of relative transporter yield with transport rates. PMID:20051266

Highly charged ion based time of flight emission microscope

DOEpatents

Barnes, Alan V.; Schenkel, Thomas; Hamza, Alex V.; Schneider, Dieter H.; Doyle, Barney

2001-01-01

A highly charged ion based time-of-flight emission microscope has been designed, which improves the surface sensitivity of static SIMS measurements because of the higher ionization probability of highly charged ions. Slow, highly charged ions are produced in an electron beam ion trap and are directed to the sample surface. The sputtered secondary ions and electrons pass through a specially designed objective lens to a microchannel plate detector. This new instrument permits high surface sensitivity (10.sup.10 atoms/cm.sup.2), high spatial resolution (100 nm), and chemical structural information due to the high molecular ion yields. The high secondary ion yield permits coincidence counting, which can be used to enhance determination of chemical and topological structure and to correlate specific molecular species.

Fabrication and characterization of a co-planar detector in diamond for low energy single ion implantation

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

Abraham, John Bishoy Sam; Pacheco, Jose L.; Aguirre, Brandon Adrian

2016-08-09

We demonstrate low energy single ion detection using a co-planar detector fabricated on a diamond substrate and characterized by ion beam induced charge collection. Histograms are taken with low fluence ion pulses illustrating quantized ion detection down to a single ion with a signal-to-noise ratio of approximately 10. We anticipate that this detection technique can serve as a basis to optimize the yield of single color centers in diamond. In conclusion, the ability to count ions into a diamond substrate is expected to reduce the uncertainty in the yield of color center formation by removing Poisson statistics from the implantationmore » process.« less

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

Mattox, D.M.; Sharp, D.J.

A Veeco microetch system which uses a Kaufman type ion source has been used to study ion erosion yields for a variety of materials of possible interest in CTR wall coating applications. A schematic diagram of the Kaufman gun and etching chamber are given. The ion beam is nearly monoenergetic (within several eV). The extracted ion beam consists of a mixture of H/sub 2//sup +/ and H/sup +/. A H/sub 2//sup +/ ion will have a sputtering yield equivalent to 2H/sup +/ ions with one-half the energy of the H/sub 2//sup +/ ion. For most of these investigations, the chargemore » compensation filament is removed to avoid sputtering of the tungsten filament.« less

Maximization of DRAM yield by control of surface charge and particle addition during high dose implantation

NASA Astrophysics Data System (ADS)

Horvath, J.; Moffatt, S.

1991-04-01

Ion implantation processing exposes semiconductor devices to an energetic ion beam in order to deposit dopant ions in shallow layers. In addition to this primary process, foreign materials are deposited as particles and surface films. The deposition of particles is a major cause of IC yield loss and becomes even more significant as device dimensions are decreased. Control of particle addition in a high-volume production environment requires procedures to limit beamline and endstation sources, control of particle transport, cleaning procedures and a well grounded preventative maintenance philosophy. Control of surface charge by optimization of the ion beam and electron shower conditions and measurement with a real-time charge sensor has been effective in improving the yield of NMOS and CMOS DRAMs. Control of surface voltages to a range between 0 and -20 V was correlated with good implant yield with PI9200 implanters for p + and n + source-drain implants.

Studies of Ion Acceleration from Thin Solid-Density Targets on High-Intensity Lasers

NASA Astrophysics Data System (ADS)

Willis, Christopher R.

Over the past two decades, a number of experiments have been performed demonstrating the acceleration of ions from the interaction of an intense laser pulse with a thin, solid density target. These ions are accelerated by quasi-static electric fields generated by energetic electrons produced at the front of the target, resulting in ion energies up to tens of MeV. These ions have been widely studied for a variety of potential applications ranging from treatment of cancer to the production of neutrons for advanced radiography techniques. However, realization of these applications will require further optimization of the maximum energy, spectrum, or species of the accelerated ions, which has been a primary focus of research to date. This thesis presents two experiments designed to optimize several characteristics of the accelerated ion beam. The first of these experiments took place on the GHOST laser system at the University of Texas at Austin, and was designed to demonstrate reliable acceleration of deuterium ions, as needed for the most efficient methods of neutron generation from accelerated ions. This experiment leveraged cryogenically cooled targets coated in D2 O ice to suppress the protons which typically dominate the accelerated ions, producing as many as 2 x 1010 deuterium ions per 1 J laser shot, exceeding the proton yield by an average ratio of 5:1. The second major experiment in this work was performed on the Scarlet laser system at The Ohio State University, and studied the accelerated ion energy, yield, and spatial distribution as a function of the target thickness. In principle, the peak energy increases with decreasing target thickness, with the thinnest targets accessing additional acceleration mechanisms which provide favorable scaling with the laser intensity. However, laser prepulse characteristics provide a lower bound for the target thickness, yielding an optimum target thickness for ion acceleration which is dependent on the laser system. This experiment utilized new liquid crystal film targets developed at OSU, which may be formed at variable thicknesses from tens of nanometers to several microns. On this experiment, an optimum ion energy and flux was reached for targets of 600-900 nm, providing a peak proton energy of 24 MeV, and total ion flux of > 109 protons over 3.4 MeV from 5.5 J of laser energy at an intensity of 1 x 1020 W cm -2. The primary ion diagnostics for these two experiments are described in detail, including the analysis techniques needed to extract absolutely calibrated spatial and spectral distributions of the accelerated ions. Additionally, a new technique for target alignment is presented, providing repeatable target alignment on the micron scale. This allows for a repeatable laser intensity on target, allowing improved shot to shot consistency on high intensity experiments. In addition to these two experiments, work on the upgrade and characterization of the 400 TW Scarlet laser is discussed, including several calculations critical to the design and upgrade of the laser system, as well as prepulse characterization needed for experiments on thin targets.

Comparison of ion-exchange resin counterions in the nutrient measurement of calcareous soils: implications for correlative studies of plant-soil relationships

USGS Publications Warehouse

Sherrod, S.K.; Belnap, Jayne; Miller, M.E.

2003-01-01

For more than 40 years, ion-exchange resins have been used to characterize nutrient bioavailability in terrestrial and aquatic ecosystems. To date, however, no standardized methodology has been developed, particularly with respect to the counterions that initially occupy resin exchange sites. To determine whether different resin counterions yield different measures of soil nutrients and rank soils differently with respect to their measured nutrient bioavailability, we compared nutrient measurements by three common counterion combinations (HCl, HOH, and NaHCO3). Five sandy calcareous soils were chosen to represent a range of soil characteristics at Canyonlands National Park, Utah, and resin capsules charged with the different counterions equilibrated in saturated pastes of these soils for one week. Data were converted to proportions of total ions of corresponding charge for ANOVA. Results from the different methods were not comparable with respect to any nutrient. Of eleven nutrients measured, all but iron (Fe2+), manganese (Mn2+), and zinc (Zn2+) differed significantly (pa??0.05) as a function of soilcounterion interactions; Fe2+ and Zn2+ varied as functions of counterion alone. Of the counterion combinations, HCl-resins yielded the most net ion exchange with all measured nutrients except Na+, and the three of which desorbed in the greatest quantities from HOH-resins. Conventional chemical extractions using ammonium acetate generally yielded high proportional values of Ca2+, K+, and Na+. Further, among-soil rankings of nutrient bioavailability varied widely among methods. This study highlights the fact that various ion-exchange resin techniques for measuring soil nutrients may have differential effects on the soil-resin environment and yield data that should not be compared nor considered interchangeable. The most appropriate methods for characterizing soil-nutrient bioavailability depends on soil characteristics and likely on the physiological uptake mechanisms of plants or functional groups of interest. The effects of different extraction techniques on nutrient measures should be understood before selecting an extraction method. For example, in the calcareous soils used for this experiment, nutrient extraction methods that alter soil carbonates through dissolution or precipitation could compromise the accurate measurement of plant-available nutrients. The implications of this study emphasize the universal importance of understanding the differential effects of alternate methods on soil chemistry.

Comparison of ion-exchange resin counterions in the nutrient measurement of calcareous soils: Implications for correlative studies of plant-soil relationships

USGS Publications Warehouse

Sherrod, S.K.; Belnap, J.; Miller, M.E.

2003-01-01

For more than 40 years, ion-exchange resins have been used to characterize nutrient bioavailability in terrestrial and aquatic ecosystems. To date, however, no standardized methodology has been developed, particularly with respect to the counterions that initially occupy resin exchange sites. To determine whether different resin counterions yield different measures of soil nutrients and rank soils differently with respect to their measured nutrient bioavailability, we compared nutrient measurements by three common counterion combinations (HCl, HOH, and NaHCO3). Five sandy calcareous soils were chosen to represent a range of soil characteristics at Canyonlands National Park, Utah, and resin capsules charged with the different counterions equilibrated in saturated pastes of these soils for one week. Data were converted to proportions of total ions of corresponding charge for ANOVA. Results from the different methods were not comparable with respect to any nutrient. Of eleven nutrients measured, all but iron (Fe2+), manganese (Mn2+), and zinc (Zn2+) differed significantly (p ??? 0.05) as a function of soil x counterion interactions; Fe2+ and Zn2+ varied as functions of counterion alone. Of the counterion combinations, HCl-resins yielded the most net ion exchange with all measured nutrients except Na+, NH4+, and HPO42-, the three of which desorbed in the greatest quantities from HOH-resins. Conventional chemical extractions using ammonium acetate generally yielded high proportional values of Ca2+, K+, and Na+. Further, among-soil rankings of nutrient bioavailability varied widely among methods. This study highlights the fact that various ion-exchange resin techniques for measuring soil nutrients may have differential effects on the soil-resin environment and yield data that should not be compared nor considered interchangeable. The most appropriate methods for characterizing soil-nutrient bioavailability depends on soil characteristics and likely on the physiological uptake mechanisms of plants or functional groups of interest. The effects of different extraction techniques on nutrient measures should be understood before selecting an extraction method. For example, in the calcareous soils used for this experiment, nutrient extraction methods that alter soil carbonates through dissolution or precipitation could compromise the accurate measurement of plant-available nutrients. The implications of this study emphasize the universal importance of understanding the differential effects of alternate methods on soil chemistry.

Utilization of High-Fructose Corn Syrup for Biomass Production Containing High Levels of Docosahexaenoic Acid by a Newly Isolated Aurantiochytrium sp. YLH70.

PubMed

Yu, Xin-Jun; Yu, Zhi-Qiang; Liu, Ying-Liang; Sun, Jie; Zheng, Jian-Yong; Wang, Zhao

2015-11-01

High-fructose corn syrup (HFCS) is an agro-source product and has been the most commonly used substitute for sugar as sweetener in food industry due to its low price and high solution property. In this study, the F55 HFCS, rich in fructose and glucose, was first tested for biomass and docosahexaenoic acid productions as a mixed carbon source by a newly isolated Aurantiochytrium sp.YLH70. After the compositions of the HFCS media were optimized, the results showed that the HFCS with additions of metal ion and vitamin at low concentrations was suitable for biomass and docosahexaenoic acid productions and the metal ion and sea salt had the most significant effects on biomass production. During the 5-l fed-batch fermentation, total HFCS containing 180 g l(-1) reducing sugar was consumed and yields of biomass, lipid, and DHA could reach 78.5, 51, and 20.1 g l(-1), respectively, at 114 h. Meanwhile, the daily productivity and the reducing sugar conversion yield for docosahexaenoic acid were up to 4.23 g l(-1)day(-1) and 0.11 g g(-1). The fatty acid profile of Aurantiochytrium sp.YLH70 showed that 46.4% of total fatty acid was docosahexaenoic acid, suggesting that Aurantiochytrium sp.YLH70 was a promising DHA producer.

Characterization of charge and kinetic energy distribution of ions emitted during nanosecond pulsed laser ablation of several metals

NASA Astrophysics Data System (ADS)

Dogar, A. H.; Ullah, S.; Qayyum, H.; Rehman, Z. U.; Qayyum, A.

2017-09-01

The ion flux from various metals (Al, Ti, Cu, Sn and W) ablated with 20 ns Nd:YAG laser radiation at a wavelength of 1064 nm was investigated by an ion collector operating in time-of-flight (TOF) configuration. The laser irradiance at the target was varied in the range of 1.7  ×  108-5.73  ×  108 W cm-2. Ion yield from various metals showed a linearly increasing trend with increasing laser irradiance, whereas ion yield was found to decrease with an increasing atomic mass of the target. Our results clearly indicate that ion yield is not a function of the volatility of the metal. TOF ion spectra showed at least two groups of low intensity peaks due to fast ions. The first group of ion peaks, which was present in the spectra of all five metals, was due to surface contamination. The additional fast ion structures in the spectra of Sn and W can be related to the ion acceleration due to the prompt electron emission from these high-Z metals. The ion velocity follows the anticipated inverse square root dependence on the ion mass. For the range of laser irradiance investigated here, the most probable energy of the Cu ions increases from about 100-600 eV. The fast increase in ion energy above ~3  ×  108 W cm-2 is related to the increase of the Columb part of the ion energy due to the production of multiply charged ions.

Channeling effect in polycrystalline deuterium-saturated CVD diamond target bombarded by deuterium ion beam

NASA Astrophysics Data System (ADS)

Bagulya, A. V.; Dalkarov, O. D.; Negodaev, M. A.; Rusetskii, A. S.; Chubenko, A. P.; Ralchenko, V. G.; Bolshakov, A. P.

2015-07-01

At the ion accelerator HELIS at LPI, the neutron yield is investigated in DD reactions within a strongly textured polycrystalline deuterium-saturated CVD diamond under irradiation by a deuterium ion beam with the energy of less than 30 keV. The measurements of the neutron flux in the beam direction are performed using a multichannel detector based on 3He counters, in dependence on the target angle, β, with respect to the beam axis. A significant anisotropy in the neutron yield is observed. At β = 0° the yield is higher by a factor of 3 as compared to that at β = ±45°. The possible reasons for the anisotropy, including ion channeling, are discussed.

High Useful Yield and Isotopic Analysis of Uranium by Resonance Ionization Mass Spectrometry

DOE PAGES

Savina, Michael R.; Isselhardt, Brett H.; Kucher, Andrew; ...

2017-05-09

Useful yields from resonance ionization mass spectrometry can be extremely high compared to other mass spectrometry techniques, but uranium analysis shows strong matrix effects arising from the tendency of uranium to form strongly bound oxide molecules that do not dissociate appreciably on energetic ion bombardment. Here, we demonstrate a useful yield of 24% for metallic uranium. Modeling the laser ionization and ion transmission processes shows that the high useful yield is attributable to a high ion fraction achieved by resonance ionization. We quantify the reduction of uranium oxide surface layers by Ar + and Ga + sputtering. The useful yieldmore » for uranium atoms from a uranium dioxide matrix is 0.4% and rises to 2% when the surface is in sputter equilibrium with the ion beam. The lower useful yield from the oxide is almost entirely due to uranium oxide molecules reducing the neutral atom content of the sputtered flux. We also demonstrate rapid isotopic analysis of solid uranium oxide at a precision of <0.5% relative standard deviation using relatively broadband lasers to mitigate spectroscopic fractionation.« less

High Useful Yield and Isotopic Analysis of Uranium by Resonance Ionization Mass Spectrometry

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

Savina, Michael R.; Isselhardt, Brett H.; Kucher, Andrew

Useful yields from resonance ionization mass spectrometry can be extremely high compared to other mass spectrometry techniques, but uranium analysis shows strong matrix effects arising from the tendency of uranium to form strongly bound oxide molecules that do not dissociate appreciably on energetic ion bombardment. Here, we demonstrate a useful yield of 24% for metallic uranium. Modeling the laser ionization and ion transmission processes shows that the high useful yield is attributable to a high ion fraction achieved by resonance ionization. We quantify the reduction of uranium oxide surface layers by Ar + and Ga + sputtering. The useful yieldmore » for uranium atoms from a uranium dioxide matrix is 0.4% and rises to 2% when the surface is in sputter equilibrium with the ion beam. The lower useful yield from the oxide is almost entirely due to uranium oxide molecules reducing the neutral atom content of the sputtered flux. We also demonstrate rapid isotopic analysis of solid uranium oxide at a precision of <0.5% relative standard deviation using relatively broadband lasers to mitigate spectroscopic fractionation.« less

Local formation of nitrogen-vacancy centers in diamond by swift heavy ions

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

Schwartz, J.; Ilmenau University of Technology, Department of Microelectronics and Nanoelectric Systems, 98684 Ilmenau; Aloni, S.

2014-12-07

We exposed nitrogen-implanted diamonds to beams of swift heavy ions (∼1 GeV, ∼4 MeV/u) and find that these irradiations lead directly to the formation of nitrogen vacancy (NV) centers, without thermal annealing. We compare the photoluminescence intensities of swift heavy ion activated NV{sup −} centers to those formed by irradiation with low-energy electrons and by thermal annealing. NV{sup −} yields from irradiations with swift heavy ions are 0.1 of yields from low energy electrons and 0.02 of yields from thermal annealing. We discuss possible mechanisms of NV center formation by swift heavy ions such as electronic excitations and thermal spikes. While formingmore » NV centers with low efficiency, swift heavy ions could enable the formation of three dimensional NV{sup −} assemblies over relatively large distances of tens of micrometers. Further, our results show that NV center formation is a local probe of (partial) lattice damage relaxation induced by electronic excitations from swift heavy ions in diamond.« less

Effects of crystallographic and geometric orientation on ion beam sputtering of gold nanorods

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

Hinks, J. A.; Hibberd, F.; Hattar, K.

Nanostructures may be exposed to irradiation during their manufacture, their engineering and whilst in-service. The consequences of such bombardment can be vastly different from those seen in the bulk. In this paper, we combine transmission electron microscopy with in situ ion irradiation with complementary computer modelling techniques to explore the physics governing the effects of 1.7 MeV Au ions on gold nanorods. Phenomena surrounding the sputtering and associated morphological changes caused by the ion irradiation have been explored. In both the experiments and the simulations, large variations in the sputter yields from individual nanorods were observed. These sputter yields havemore » been shown to correlate with the strength of channelling directions close to the direction in which the ion beam was incident. Finally, craters decorated by ejecta blankets were found to form due to cluster emission thus explaining the high sputter yields.« less

Effects of crystallographic and geometric orientation on ion beam sputtering of gold nanorods

DOE PAGES

Hinks, J. A.; Hibberd, F.; Hattar, K.; ...

2018-01-11

Nanostructures may be exposed to irradiation during their manufacture, their engineering and whilst in-service. The consequences of such bombardment can be vastly different from those seen in the bulk. In this paper, we combine transmission electron microscopy with in situ ion irradiation with complementary computer modelling techniques to explore the physics governing the effects of 1.7 MeV Au ions on gold nanorods. Phenomena surrounding the sputtering and associated morphological changes caused by the ion irradiation have been explored. In both the experiments and the simulations, large variations in the sputter yields from individual nanorods were observed. These sputter yields havemore » been shown to correlate with the strength of channelling directions close to the direction in which the ion beam was incident. Finally, craters decorated by ejecta blankets were found to form due to cluster emission thus explaining the high sputter yields.« less

A Survey of Xenon Ion Sputter Yield Data and Fits Relevant to Electric Propulsion Spacecraft Integration

NASA Technical Reports Server (NTRS)

Yim, John T.

2017-01-01

A survey of low energy xenon ion impact sputter yields was conducted to provide a more coherent baseline set of sputter yield data and accompanying fits for electric propulsion integration. Data uncertainties are discussed and different available curve fit formulas are assessed for their general suitability. A Bayesian parameter fitting approach is used with a Markov chain Monte Carlo method to provide estimates for the fitting parameters while characterizing the uncertainties for the resulting yield curves.

Product ion tandem mass spectrometric differentiation of regioisomeric side-chain groups in cathinone derivatives.

PubMed

Abiedalla, Younis; DeRuiter, Jack; Clark, C Randall

2016-07-30

Precursor materials are available to prepare aminoketone drugs containing regioisomeric propyl and isopropyl side-chain groups related to the drug alpha-pyrrovalerone (Flakka) and MDPV (3,4-methylenedioxypyrrovalerone). These compounds yield equivalent regioisomeric iminium cation base peaks in electron ionization mass spectrometry (EI-MS). The propyl and isopropyl side-chain groups related to alpha-pyrrovalerone and MDPV were prepared and evaluated in EI-MS and tandem mass spectrometry (MS/MS) product ion experiments. Deuterium labeling in both the pyrrolidine and alkyl side-chain groups allowed for the confirmation of the structures for the major product ions formed from the regioisomeric EI-MS iminium cation base peaks. These iminium cation base peaks show characteristic product ion spectra which allow differentiation of the side-chain propyl and isopropyl groups in the structure. The n-propyl side chain containing iminium cation base peak (m/z 126) in the EI-MS spectrum yields a major product ion at m/z 84 while the regioisomeric m/z 126 base peak for the isopropyl side chain yields a characteristic product ion at m/z 70. Deuterium labeling in both the pyrrolidine ring and the alkyl side chain confirmed the process for the formation of these major product ions. Product ion fragmentation provides useful data for differentiation of n-propyl and isopropyl side-chain iminium cations from cathinone derivative drugs of abuse. Regioisomeric n-propyl and isopropyl iminium cations of equal mass yield characteristic product ions identifying the alkyl side-chain regioisomers in the pyrrolidine cathinone derivatives. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Higher sensitivity secondary ion mass spectrometry of biological molecules for high resolution, chemically specific imaging.

PubMed

McDonnell, Liam A; Heeren, Ron M A; de Lange, Robert P J; Fletcher, Ian W

2006-09-01

To expand the role of high spatial resolution secondary ion mass spectrometry (SIMS) in biological studies, numerous developments have been reported in recent years for enhancing the molecular ion yield of high mass molecules. These include both surface modification, including matrix-enhanced SIMS and metal-assisted SIMS, and polyatomic primary ions. Using rat brain tissue sections and a bismuth primary ion gun able to produce atomic and polyatomic primary ions, we report here how the sensitivity enhancements provided by these developments are additive. Combined surface modification and polyatomic primary ions provided approximately 15.8 times more signal than using atomic primary ions on the raw sample, whereas surface modification and polyatomic primary ions yield approximately 3.8 and approximately 8.4 times more signal. This higher sensitivity is used to generate chemically specific images of higher mass biomolecules using a single molecular ion peak.

The Au(n) cluster probe in secondary ion mass spectrometry: influence of the projectile size and energy on the desorption/ionization rate from biomolecular solids.

PubMed

Novikov, Alexey; Caroff, Martine; Della-Negra, Serge; Depauw, Joël; Fallavier, Mireille; Le Beyec, Yvon; Pautrat, Michèle; Schultz, J Albert; Tempez, Agnès; Woods, Amina S

2005-01-01

A Au-Si liquid metal ion source which produces Au(n) clusters over a large range of sizes was used to study the dependence of both the molecular ion desorption yield and the damage cross-section on the size (n = 1 to 400) and on the kinetic energy (E = 10 to 500 keV) of the clusters used to bombard bioorganic surfaces. Three pure peptides with molecular masses between 750 and 1200 Da were used without matrix. [M+H](+) and [M+cation](+) ion emission yields were enhanced by as much as three orders of magnitude when bombarding with Au(400) (4+) instead of monatomic Au(+), yet very little damage was induced in the samples. A 100-fold increase in the molecular ion yield was observed when the incident energy of Au(9) (+) was varied from 10 to 180 keV. Values of emission yields and damage cross-sections are presented as a function of cluster size and energy. The possibility to adjust both cluster size and energy, depending on the application, makes the analysis of biomolecules by secondary ion mass spectrometry an extremely powerful and flexible technique, particularly when combined with orthogonal time-of-flight mass spectrometry that then allows fast measurements using small primary ion beam currents. Copyright (c) 2005 John Wiley & Sons, Ltd.

An investigation on the mechanism of sublimed DHB matrix on molecular ion yields in SIMS imaging of brain tissue.

PubMed

Dowlatshahi Pour, Masoumeh; Malmberg, Per; Ewing, Andrew

2016-05-01

We have characterized the use of sublimation to deposit matrix-assisted laser desorption/ionization (MALDI) matrices in secondary ion mass spectrometry (SIMS) analysis, i.e. matrix-enhanced SIMS (ME-SIMS), a common surface modification method to enhance sensitivity for larger molecules and to increase the production of intact molecular ions. We use sublimation to apply a thin layer of a conventional MALDI matrix, 2,5-dihydroxybenzoic acid (DHB), onto rat brain cerebellum tissue to show how this technique can be used to enhance molecular yields in SIMS while still retaining a lateral resolution around 2 μm and also to investigate the mechanism of this enhancement. The results here illustrate that cholesterol, which is a dominant lipid species in the brain, is decreased on the tissue surface after deposition of matrix, particularly in white matter. The decrease of cholesterol is followed by an increased ion yield of several other lipid species. Depth profiling of the sublimed rat brain reveals that the lipid species are de facto extracted by the DHB matrix and concentrated in the top most layers of the sublimed matrix. This extraction/concentration of lipids directly leads to an increase of higher mass lipid ion yield. It is also possible that the decrease of cholesterol decreases the potential suppression of ion yield caused by cholesterol migration to the tissue surface. This result provides us with significant insights into the possible mechanisms involved when using sublimation to deposit this matrix in ME-SIMS.

Degradation of paracetamol by Pseudomonas aeruginosa strain HJ1012.

PubMed

Hu, Jun; Zhang, Li L; Chen, Jian M; Liu, Yu

2013-01-01

Pseudomonas aeruginosa strain HJ1012 was isolated on paracetamol as a sole carbon and energy source. This organism could completely degrade paracetamol as high as 2200 mg/L. Following paracetamol consumption, a CO₂ yield rate up to 71.4% proved that the loss of paracetamol was mainly via mineralization. Haldane's equation adequately described the relationship between the specific growth rate and substrate concentration. The maximum specific growth rate and yield coefficient were 0.201 g-Paracetamol/g-VSS·h and 0.101 mg of biomass yield/mg of paracetamol consumed, respectively. A total of 8 metabolic intermediates was identified and classified into aromatic compounds, carboxylic acids, and inorganic species (nitrite and nitrate ions). P-aminophenol and hydroquinone are the two key metabolites of the initial steps in the paracetamol catabolic pathway. Paracetamol is degraded predominantly via p-aminophenol to hydroquinone with subsequent ring fission, suggesting partially new pathways for paracetamol-degrading bacteria.

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

Frenje, J. A.; Hilsabeck, T. J.; Wink, C. W.

The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (T i), yield (Y n), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate datamore » with a time resolution of ~20 ps and energy resolution of ~100 keV for total neutron yields above ~10 16. Lastly, at lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ~20 ps.« less

Effects of anode geometry on forward wide-angle neon ion emissions in 3.5 kJ plasma focus device by novel mega-size panorama polycarbonate image detectors

NASA Astrophysics Data System (ADS)

Sohrabi, M.; Soltani, Z.; Sarlak, Z.

2018-03-01

Forward wide-angle neon ion emissions in a 3.5 kJ plasma focus device (PFD) were studied using 5 different anode top geometries; hollow-end cylinder, solid triangle, solid hemisphere, hollow-end cone and flat-end cone. Position-sensitive mega-size panorama polycarbonate ion image detectors (MS-PCID) developed by dual-cell circular mega-size electrochemical etching (MS-ECE) systems were applied for processesing wide-angle neon ion images on MS-PCIDs exposed on the PFD cylinder top base under a single pinch shot. The images can be simply observed, analyzed and relatively quantified in terms of ion emission angular distributions even by the unaided eyes. By analysis of the forward neon ion emission images, the ion emission yields, ion emission angular distributions, iso-fluence ion contours and solid angles of ion emissions in 4π PFD space were determined. The neon ion emission yields on the PFD cylinder top base are in an increasing order ~2.1×109, ~2.2 ×109, ~2.8×109, ~2.9×109, and ~3.5×109 neon ions/shot for the 5 stated anode top geometries respectively. The panorama neon ion images as diagnosed even by the unaided eyes demonstrate the lowest and highest ion yields from the hollow-end cylinder and flat-end cone anode tops respectively. Relative dynamic qualitative neon ion spectrometry was made by the unaided eyes demonstrating relative neon ion energy as they appear. The study also demonstrates the unique power of the MS-PCID/MS-ECE imaging system as an advanced state-of-the-art ion imaging method for wide-angle dynamic parametric studies in PFD space and other ion study applications.

FTMS studies of sputtered metal cluster ions (IV): size-selective effects in the chemistry of Fe{/n +} with NH3 and Pd{/n +} with D2 or C2H4

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.

Low energy sputtering of cobalt by cesium ions

NASA Technical Reports Server (NTRS)

Handoo, A.; Ray, Pradosh K.

1989-01-01

An experimental facility to investigate low energy (less than 500 eV) sputtering of metal surfaces with ions produced by an ion gun is described. Results are reported on the sputtering yield of cobalt by cesium ions in the 100 to 500 eV energy range at a pressure of 1 times 10(exp -6) Torr. The target was electroplated on a copper substrate. The sputtered atoms were collected on a cobalt foil surrounding the target. Co-57 was used as a tracer to determine the sputtering yield.

Estimates of Sputter Yields of Solar-Wind Heavy Ions of Lunar Regolith Materials

NASA Technical Reports Server (NTRS)

Barghouty, Abdulmasser F.; Adams, James H., Jr.

2008-01-01

At energies of approximately 1 keV/amu, solar-wind protons and heavy ions interact with the lunar surface materials via a number of microscopic interactions that include sputtering. Solar-wind induced sputtering is a main mechanism by which the composition of the topmost layers of the lunar surface can change, dynamically and preferentially. This work concentrates on sputtering induced by solar-wind heavy ions. Sputtering associated with slow (speeds the electrons speed in its first Bohr orbit) and highly charged ions are known to include both kinetic and potential sputtering. Potential sputtering enjoys some unique characteristics that makes it of special interest to lunar science and exploration. Unlike the yield from kinetic sputtering where simulation and approximation schemes exist, the yield from potential sputtering is not as easy to estimate. This work will present a preliminary numerical scheme designed to estimate potential sputtering yields from reactions relevant to this aspect of solar-wind lunar-surface coupling.

Improved yields for MOST’s using ion implantation

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

Brockman, H. E.

1976-04-01

Conventionally diffused source and drain polysilicon gate MOST's commonly exhibit one type of fault, namely, that of polysilicon-to-diffusion short circuits. Investigations into the yields of large-area devices fabricated using ion-implanted sources and drains are compared with those of diffused structures. An improved technology for the chemical shaping of the polysilicon gates, which improves the yields for both types of devices, is also described. (AIP)

Analyzing Internal Fragmentation of Electrosprayed Ubiquitin Ions During Beam-Type Collisional Dissociation

NASA Astrophysics Data System (ADS)

Durbin, Kenneth R.; Skinner, Owen S.; Fellers, Ryan T.; Kelleher, Neil L.

2015-05-01

Gaseous fragmentation of intact proteins is multifaceted and can be unpredictable by current theories in the field. Contributing to the complexity is the multitude of precursor ion states and fragmentation channels. Terminal fragment ions can be re-fragmented, yielding product ions containing neither terminus, termed internal fragment ions. In an effort to better understand and capitalize upon this fragmentation process, we collisionally dissociated the high (13+), middle (10+), and low (7+) charge states of electrosprayed ubiquitin ions. Both terminal and internal fragmentation processes were quantified through step-wise increases of voltage potential in the collision cell. An isotope fitting algorithm matched observed product ions to theoretical terminal and internal fragment ions. At optimal energies for internal fragmentation of the 10+, nearly 200 internal fragments were observed; on average each of the 76 residues in ubiquitin was covered by 24.1 internal fragments. A pertinent finding was that formation of internal ions occurs at similar energy thresholds as terminal b- and y-ion types in beam-type activation. This large amount of internal fragmentation is frequently overlooked during top-down mass spectrometry. As such, we present several new approaches to visualize internal fragments through modified graphical fragment maps. With the presented advances of internal fragment ion accounting and visualization, the total percentage of matched fragment ions increased from approximately 40% to over 75% in a typical beam-type MS/MS spectrum. These sequence coverage improvements offer greater characterization potential for whole proteins with no needed experimental changes and could be of large benefit for future high-throughput intact protein analysis.

On the Possibility of Creating a Point-Like Neutron Source

NASA Astrophysics Data System (ADS)

Golubev, S. V.; Skalyga, V. A.; Izotov, I. V.; Sidorov, A. V.; Razin, S. V.; Shaposhnikov, R. A.; Lapin, R. L.; Bokhanov, A. F.; Kazakov, M. Yu.

2018-03-01

We consider the possibility of creating a compact high-power neutron generator with a small emitting area (of the order of 100 μm) and a neutron yield of 1010s-1 on the basis of a deuterium-deuterium fusion reaction (or 1012 s-1 on the basis of a deuterium-tritium fusion reaction). The fusion takes place under bombardment of a deuterium- (or tritium-) saturated target by a high-current (about 100 mA) focused deuterium ion beam with an energy of 100 keV. The ion beam with total current at a level of hundreds of milliamperes and small emittance (less than 0.1 π·mm·mrad), which is crucial for sharp focusing, can be generated by a quasi-gas-dynamic ion source of a new generation created on the basis of a discharge in an open magnetic trap sustained by high-power electromagnetic radiation of the millimeter wavelength range under electron cyclotron resonance conditions. Simulations of the focusing system for the experimentally obtained ion beam show the possibility to create a deuterium ion beam with a transverse size of 200 μm on the neutron-forming target. Prospects for using such a neutron source for neutron tomography are discussed.

Influences of coal mining water irrigation on the maize losses in the Xingdong Mine area, China.

PubMed

Sun, Yuzhuang; Ling, Pei; Li, Yanheng; Li, Qingxue; Sun, Quande; Wang, Jinxi

2014-02-01

In 2008, a maize underproduction disaster occurred in the Xianyu village after irrigation using the coal mining water from the Xingdong Mine, China. This disaster resulted in about 40 hectare maize underproduction and 20 hectare total loss of the maize yields. In order to study the reason, a total of 25 soil, water and plant samples were taken from the study area. These samples were analysed by inductively coupled plasma mass spectrometry and ion chromatography. The results indicate that the contents of both water-soluble fluorine and total fluorine are very high and resulting of maize underproduction and total loss of production. The possible pollution sources of fluorine in the study area could be from the coal mine water used for irrigation and glass chemical factory near the study area.

Progress in obtaining an absolute calibration of a total deuterium-tritium neutron yield diagnostic based on copper activationa)

NASA Astrophysics Data System (ADS)

Ruiz, C. L.; Chandler, G. A.; Cooper, G. W.; Fehl, D. L.; Hahn, K. D.; Leeper, R. J.; McWatters, B. R.; Nelson, A. J.; Smelser, R. M.; Snow, C. S.; Torres, J. A.

2012-10-01

The 350-keV Cockroft-Walton accelerator at Sandia National laboratory's Ion Beam facility is being used to calibrate absolutely a total DT neutron yield diagnostic based on the 63Cu(n,2n)62Cu(β+) reaction. These investigations have led to first-order uncertainties approaching 5% or better. The experiments employ the associated-particle technique. Deuterons at 175 keV impinge a 2.6 μm thick erbium tritide target producing 14.1 MeV neutrons from the T(d,n)4He reaction. The alpha particles emitted are measured at two angles relative to the beam direction and used to infer the neutron flux on a copper sample. The induced 62Cu activity is then measured and related to the neutron flux. This method is known as the F-factor technique. Description of the associated-particle method, copper sample geometries employed, and the present estimates of the uncertainties to the F-factor obtained are given.

Progress in obtaining an absolute calibration of a total deuterium-tritium neutron yield diagnostic based on copper activation.

PubMed

Ruiz, C L; Chandler, G A; Cooper, G W; Fehl, D L; Hahn, K D; Leeper, R J; McWatters, B R; Nelson, A J; Smelser, R M; Snow, C S; Torres, J A

2012-10-01

The 350-keV Cockroft-Walton accelerator at Sandia National laboratory's Ion Beam facility is being used to calibrate absolutely a total DT neutron yield diagnostic based on the (63)Cu(n,2n)(62)Cu(β+) reaction. These investigations have led to first-order uncertainties approaching 5% or better. The experiments employ the associated-particle technique. Deuterons at 175 keV impinge a 2.6 μm thick erbium tritide target producing 14.1 MeV neutrons from the T(d,n)(4)He reaction. The alpha particles emitted are measured at two angles relative to the beam direction and used to infer the neutron flux on a copper sample. The induced (62)Cu activity is then measured and related to the neutron flux. This method is known as the F-factor technique. Description of the associated-particle method, copper sample geometries employed, and the present estimates of the uncertainties to the F-factor obtained are given.

Hydrologic conditions and quality of rainfall and storm runoff for two agricultural areas of the Oso Creek Watershed, Nueces County, Texas, 2005-07

USGS Publications Warehouse

Ockerman, Darwin J.

2008-01-01

The U.S. Geological Survey, in cooperation with the Texas State Soil and Water Conservation Board, Coastal Bend Bays and Estuaries Program, and Texas AgriLife Research and Extension Center at Corpus Christi, studied hydrologic conditions and quality of rainfall and storm runoff of two (primarily) agricultural areas (subwatersheds) of the Oso Creek watershed in Nueces County, Texas. One area, the upper West Oso Creek subwatershed, is 5,145 acres. The other area, a subwatershed drained by an unnamed Oso Creek tributary (hereinafter, Oso Creek tributary), is 5,287 acres. Rainfall and runoff (streamflow) were continuously monitored at the outlets of the two subwatersheds during October 2005-September 2007. Fourteen rainfall samples were collected and analyzed for nutrients and major inorganic ions. Nineteen composite runoff samples (10 West Oso Creek, nine Oso Creek tributary) were collected and analyzed for nutrients, major inorganic ions, and pesticides. Twenty-two discrete suspended-sediment samples (10 West Oso Creek, 12 Oso Creek tributary) and 13 bacteria samples (eight West Oso Creek, five Oso Creek tributary) were collected and analyzed. These data were used to estimate, for selected constituents, rainfall deposition to and runoff loads and yields from the study subwatersheds. Quantities of fertilizers and pesticides applied in the subwatersheds were compared with quantities of nutrients and pesticides in rainfall and runoff. For the study period, total rainfall was greater than average. Most of the runoff at both subwatershed outlet sites occurred in response to a few specific storm periods. The West Oso Creek subwatershed produced more runoff during the study period than the Oso Creek tributary subwatershed, 10.83 inches compared with 7.28 inches. Runoff response was quicker and peak flows were higher in the West Oso Creek subwatershed than in the Oso Creek tributary subwatershed. Total nitrogen runoff yield for the 2-year study period averaged 2.61 pounds per acre per year from the West Oso Creek subwatershed and 0.966 pound per acre per year from the Oso Creek tributary subwatershed. Total phosphorus yields from the West Oso Creek and the Oso Creek tributary subwatersheds for the 2-year period were 0.776 and 0.498 pound per acre per year. Runoff yields of nitrogen and phosphorus were relatively small compared to inputs of nitrogen in fertilizer and rainfall deposition. Average annual runoff yield of total nitrogen (subwatersheds combined) represents about 2.4 percent of nitrogen applied as fertilizer and nitrogen entering the subwatersheds through rainfall deposition. Average annual runoff yield of total phosphorus (subwatersheds combined) represents about 4.4 percent of the phosphorus in applied fertilizer and rainfall deposition. Suspended-sediment yields from the West Oso Creek subwatershed were more than twice those from the Oso Creek tributary subwatershed. The average suspended-sediment yield from the West Oso Creek subwatershed was 582 pounds per acre per year. The average suspended-sediment yield from the Oso Creek tributary subwatershed was 257 pounds per acre per year. Twenty-two herbicides and eight insecticides were detected in runoff samples collected from the two subwatershed outlet sites. At the West Oso Creek site, 18 herbicides and four insecticides were detected, and at the Oso Creek tributary site, 17 herbicides and six insecticides. Seventeen pesticides were detected in only one sample at low concentrations (near the laboratory reporting level). Atrazine, atrazine degradation byproducts 2-chloro-4-isopropylamino-6-amino-s-triazine (CIAT) and 2-hydroxy-4-isopropylamino-6-ethylamino-s-triazine (OIET), glyphosate, and glyphosate byproduct aminomethylphosphonic acid (AMPA) were detected in all samples. Of all pesticides detected in runoff, the highest runoff yields were for glyphosate, 0.013 pound per acre per year for the West Oso Creek subwatershed and 0.001 pound per acre per year for the Oso Creek t

Structural characterization of saturated branched chain fatty acid methyl esters by collisional dissociation of molecular ions generated by electron ionization.

PubMed

Ran-Ressler, Rinat R; Lawrence, Peter; Brenna, J Thomas

2012-01-01

Saturated branched chain fatty acids (BCFA) are present as complex mixtures in numerous biological samples. The traditional method for structure elucidation, electron ionization (EI) mass spectrometry, sometimes does not unambiguously enable assignment of branching in isomeric BCFA. Zirrolli and Murphy (Zirrolli , J. A. , and R. A. Murphy. 1993. Low-energy tandem mass spectrometry of the molecular ion derived from fatty acid methyl esters: a novel method for analysis of branched-chain fatty acids. J. Am. Soc. Mass Spectrom. 4: 223-229.) showed that the molecular ions of four BCFA methyl ester (BCFAME) yield highly characteristic fragments upon collisional dissociation using a triple quadrupole instrument. Here, we confirm and extend these results by analysis using a tabletop 3-D ion trap for activated molecular ion EI-MS/MS to 30 BCFAME. iso-BCFAME produces a prominent ion (30-100% of base peak) for [M-43] (M-C₃H₇), corresponding to the terminal isopropyl moiety in the original iso-BCFAME. Anteiso-FAME yield prominent ions (20-100% of base peak) corresponding to losses on both side of the methyl branch, [M-29] and [M-57], and tend to produce more prominent m/z 115 peaks corresponding to a cyclization product around the ester. Dimethyl and tetramethyl FAME, with branches separated by at least one methylene group, yield fragment on both sides of the sites of methyl branches that are more than 6 C away from the carboxyl carbon. EI-MS/MS yields uniquely specific ions that enable highly confident structural identification and quantification of BCFAME.

Structural characterization of saturated branched chain fatty acid methyl esters by collisional dissociation of molecular ions generated by electron ionization[S

PubMed Central

Ran-Ressler, Rinat R.; Lawrence, Peter; Brenna, J. Thomas

2012-01-01

Saturated branched chain fatty acids (BCFA) are present as complex mixtures in numerous biological samples. The traditional method for structure elucidation, electron ionization (EI) mass spectrometry, sometimes does not unambiguously enable assignment of branching in isomeric BCFA. Zirrolli and Murphy (Zirrolli , J. A. , and R. A. Murphy. 1993. Low-energy tandem mass spectrometry of the molecular ion derived from fatty acid methyl esters: a novel method for analysis of branched-chain fatty acids. J. Am. Soc. Mass Spectrom. 4: 223–229.) showed that the molecular ions of four BCFA methyl ester (BCFAME) yield highly characteristic fragments upon collisional dissociation using a triple quadrupole instrument. Here, we confirm and extend these results by analysis using a tabletop 3-D ion trap for activated molecular ion EI-MS/MS to 30 BCFAME. iso-BCFAME produces a prominent ion (30-100% of base peak) for [M-43] (M-C3H7), corresponding to the terminal isopropyl moiety in the original iso-BCFAME. Anteiso-FAME yield prominent ions (20-100% of base peak) corresponding to losses on both side of the methyl branch, [M-29] and [M-57], and tend to produce more prominent m/z 115 peaks corresponding to a cyclization product around the ester. Dimethyl and tetramethyl FAME, with branches separated by at least one methylene group, yield fragment on both sides of the sites of methyl branches that are more than 6 C away from the carboxyl carbon. EI-MS/MS yields uniquely specific ions that enable highly confident structural identification and quantification of BCFAME. PMID:22021637

Design and qualification of the SEU/TD Radiation Monitor chip

NASA Technical Reports Server (NTRS)

Buehler, Martin G.; Blaes, Brent R.; Soli, George A.; Zamani, Nasser; Hicks, Kenneth A.

1992-01-01

This report describes the design, fabrication, and testing of the Single-Event Upset/Total Dose (SEU/TD) Radiation Monitor chip. The Radiation Monitor is scheduled to fly on the Mid-Course Space Experiment Satellite (MSX). The Radiation Monitor chip consists of a custom-designed 4-bit SRAM for heavy ion detection and three MOSFET's for monitoring total dose. In addition the Radiation Monitor chip was tested along with three diagnostic chips: the processor monitor and the reliability and fault chips. These chips revealed the quality of the CMOS fabrication process. The SEU/TD Radiation Monitor chip had an initial functional yield of 94.6 percent. Forty-three (43) SEU SRAM's and 14 Total Dose MOSFET's passed the hermeticity and final electrical tests and were delivered to LL.

Grain size effect on yield strength of titanium alloy implanted with aluminum ions

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

Popova, Natalya, E-mail: natalya-popova-44@mail.ru; Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk; Nikonenko, Elena, E-mail: vilatomsk@mail.ru

2016-01-15

The paper presents a transmission electron microscopy (TEM) study of the microstructure and phase state of commercially pure titanium VT1-0 implanted by aluminum ions. This study has been carried out before and after the ion implantation for different grain size, i.e. 0.3 µm (ultra-fine grain condition), 1.5 µm (fine grain condition), and 17 µm (polycrystalline condition). This paper presents details of calculations and analysis of strength components of the yield stress. It is shown that the ion implantation results in a considerable hardening of the entire thickness of the implanted layer in the both grain types. The grain size has, however, a differentmore » effect on the yield stress. So, both before and after the ion implantation, the increase of the grain size leads to the decrease of the alloy hardening. Thus, hardening in ultra-fine and fine grain alloys increased by four times, while in polycrystalline alloy it increased by over six times.« less

Sputtering of sodium and potassium from nepheline: Secondary ion yields and velocity spectra

NASA Astrophysics Data System (ADS)

Martinez, R.; Langlinay, Th.; Ponciano, C. R.; da Silveira, E. F.; Palumbo, M. E.; Strazzulla, G.; Brucato, J. R.; Hijazi, H.; Agnihotri, A. N.; Boduch, P.; Cassimi, A.; Domaracka, A.; Ropars, F.; Rothard, H.

2017-09-01

Silicates are the dominant surface material of many Solar System objects, which are exposed to ion bombardment by solar wind ions and cosmic rays. Induced physico-chemical processes include sputtering which can contribute to the formation of an exosphere. We have measured sputtering yields and velocity spectra of secondary ions ejected from nepheline, an aluminosilicate thought to be a good analogue for Mercury's surface, as a laboratory approach to understand the evolution of silicate surfaces and the presence of Na and K vapor in the exosphere. Experiments were performed with highly charged ion beams (keV/u-MeV/u) delivered by GANIL using an imaging XY-TOF-SIMS device under UHV conditions. The fluence dependence of sputtering yields gives information about the evolution of surface stoichiometry during irradiation. From the energy distributions N(E) of sputtered particles, the fraction of particles which could escape from the gravitational field of Mercury, and of those falling back and possibly contributing to populate the exosphere can be roughly estimated.

Ion-irradiation-induced densification of zirconia sol-gel thin films

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

Levine, T.E.; Giannelis, E.P.; Kodali, P.

1994-02-01

We have investigated the densification behavior of sol-gel zirconia films resulting from ion irradiation. Three sets of films were implanted with neon, krypton, or xenon. The ion energies were chosen to yield approximately constant energy loss through the film and the doses were chosen to yield similar nuclear energy deposition. Ion irradiation of the sol-gel films resulted in carbon and hydrogen loss as indicated by Rutherford backscattering spectrometry and forward recoil energy spectroscopy. Although the densification was hypothesized to result from target atom displacement, the observed densification exhibits a stronger dependence on electronic energy deposition.

Efficient Generation of Chemiluminescence during the reduction of manganese(IV) ions with lactic acid

NASA Astrophysics Data System (ADS)

Tsaplev, Yu. B.

2016-12-01

The kinetics and mechanism of chemiluminescence during the reduction of manganese(IV) ions with lactic acid in an H2SO4-AcOH medium are studied. Kinetic spectrophotometric measurements are used to determine the profiles of change in the concentrations of Mn(IV) and Mn(III) ions during the reaction. The results from kinetic spectrophotometric measurements are compared to the light yield kinetics. The quantum chemiluminescence and chemiexcitation yields reach record values.

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

Yin Yunpeng; Sawin, Herbert H.

The surface roughness evolutions of single crystal silicon, thermal silicon dioxide (SiO{sub 2}), and low dielectric constant film coral in argon plasma have been measured by atomic force microscopy as a function of ion bombardment energy, ion impingement angle, and etching time in an inductively coupled plasma beam chamber, in which the plasma chemistry, ion energy, ion flux, and ion incident angle can be adjusted independently. The sputtering yield (or etching rate) scales linearly with the square root of ion energy at normal impingement angle; additionally, the angular dependence of the etching yield of all films in argon plasma followedmore » the typical sputtering yield curve, with a maximum around 60 deg. -70 deg. off-normal angle. All films stayed smooth after etching at normal angle but typically became rougher at grazing angles. In particular, at grazing angles the rms roughness level of all films increased if more material was removed; additionally, the striation structure formed at grazing angles can be either parallel or transverse to the beam impingement direction, which depends on the off-normal angle. More interestingly, the sputtering caused roughness evolution at different off-normal angles can be qualitatively explained by the corresponding angular dependent etching yield curve. In addition, the roughening at grazing angles is a strong function of the type of surface; specifically, coral suffers greater roughening compared to thermal silicon dioxide.« less

The structural influence of aluminium ions on emission characteristics of Sm{sup 3+} ions in lead aluminium silicate glass system

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

Bhargavi, K.; Srinivasa Reddy, M.; Raghava Rao, P.

Graphical abstract: The optical absorption and photoluminescence spectra of Sm ions in PbO-Al{sub 2}O{sub 3}-SiO{sub 2} glasses mixed with different concentrations of Al{sub 2}O{sub 3} have been investigated. From these spectra, the emission probabilities and also fluorescence lifetime principal transition viz., {sup 4}G{sub 5/2} {yields} {sup 6}H{sub 7/2} of Sm{sup 3+} ions of has been evaluated. The analysis of results of these studies has indicated that there is a less radiative trapping and enhanced fluorescence lifetime and high quantum efficiency in the glasses mixed with 8.0 mol% of Al{sub 2}O{sub 3}. Highlights: Black-Right-Pointing-Pointer Glasses of the composition (40 - x)PbO-(5more » + x)Al{sub 2}O{sub 3}-54SiO{sub 2}:1.0Sm{sub 2}O{sub 3} with x = 5-10 mol% were prepared. Black-Right-Pointing-Pointer Spectroscopic properties (OA, PL and IR) were investigated. Black-Right-Pointing-Pointer Emission probability, lifetime, branching ratio of {sup 4}G{sub 5/2} {yields} {sup 6}H{sub 7/2} transition of Sm{sup 3+} have been evaluated. Black-Right-Pointing-Pointer Analysis of the results indicated that glass mixed with 8.0 mol% exhibits high luminescence efficiency. -- Abstract: Optical absorption and photoluminescence characteristics of Sm{sup 3+} ions in lead silicate glasses mixed with different concentrations of Al{sub 2}O{sub 3} (5-10 mol%) have been investigated. From these studies, the radiative properties viz., spontaneous emission probability A, the total emission probability, the radiative lifetime {tau}{sub R}, the fluorescent branching ratio {beta} of emission transition of {sup 4}G{sub 5/2} {yields} {sup 6}H{sub 7/2} along with other transitions for Sm{sup 3+} have been evaluated and found to be the highest for the glass mixed with 8.0 mol% of Al{sub 2}O{sub 3}.The IR spectral studies have indicated that Al{sup 3+} ions do participate in the glass network with AlO{sub 4} and AlO{sub 6} structural units and further revealed that the concentration of octahedral aluminium ions induce bonding defects in the glass network. Such bonding defects are assumed to be responsible for low phonon losses in these glasses and lead to higher values of radiative parameters for the glass mixed with 8.0 mol% of Al{sub 2}O{sub 3}.« less

Ultraperformance convergence chromatography-high resolution tandem mass spectrometry for lipid biomarker profiling and identification.

PubMed

Jones, Jace W; Carter, Claire L; Li, Fei; Yu, Jianshi; Pierzchalski, Keely; Jackson, Isabel L; Vujaskovic, Zeljko; Kane, Maureen A

2017-03-01

Lipids represent biologically ubiquitous and highly dynamic molecules in terms of abundance and structural diversity. Whereas the potential for lipids to inform on disease/injury is promising, their unique characteristics make detection and identification of lipids from biological samples analytically demanding. We report the use of ultraperformance convergence chromatography (UPC 2 ), a variant of supercritical fluid chromatography, coupled to high-resolution, data-independent tandem mass spectrometry for characterization of total lipid extracts from mouse lung tissue. The UPC 2 platform resulted in lipid class separation and when combined with orthogonal column chemistries yielded chromatographic separation of intra-class species based on acyl chain hydrophobicity. Moreover, the combined approach of using UPC 2 with orthogonal column chemistries, accurate mass measurements, time-aligned low- and high-collision energy total ion chromatograms, and positive and negative ion mode product ion spectra correlation allowed for confident lipid identification. Of great interest was the identification of differentially expressed ceramides that were elevated 24 h post whole thorax lung irradiation. The identification of lipids that were elevated 24 h post-irradiation signifies a unique opportunity to investigate early mechanisms of action prior to the onset of clinical symptoms in the whole thorax lung irradiation mouse model. Copyright © 2016 John Wiley & Sons, Ltd.

The Effect on the Lunar Exosphere of a Coroual Mass Ejection Passage

NASA Technical Reports Server (NTRS)

Killen, R. M.; Hurley, D. M.; Farrell, W. M.

2011-01-01

Solar wind bombardment onto exposed surfaces in the solar system produces an energetic component to the exospheres about those bodies. The solar wind energy and composition are highly dependent on the origin of the plasma. Using the measured composition of the slow wind, fast wind, solar energetic particle (SEP) population, and coronal mass ejection (CME), broken down into their various components, we have estimated the total sputter yield for each type of solar wind. We show that the heavy ion component, especially the He++ and 0+7 can greatly enhance the total sputter yield during times when the heavy ion population is enhanced. Folding in the flux, we compute the source rate for several species during different types of solar wind. Finally, we use a Monte Carlo model developed to simulate the time-dependent evolution of the lunar exosphere to study the sputtering component of the exosphere under the influence of a CME passage. We simulate the background exosphere of Na, K, Ca, and Mg. Simulations indicate that sputtering increases the mass of those constituents in the exosphere a few to a few tens times the background values. The escalation of atmospheric density occurs within an hour of onset The decrease in atmospheric density after the CME passage is also rapid, although takes longer than the increase, Sputtered neutral particles have a high probability of escaping the moon,by both Jeans escape and photo ionization. Density and spatial distribution of the exosphere can be tested with the LADEE mission.

Heavy ion fragmentation experiments at the bevatron

NASA Technical Reports Server (NTRS)

Heckman, H. H.

1976-01-01

Collaborative research efforts to study the fragmentation processes of heavy nuclei in matter using heavy ion beams of the Bevatron/Bevalac are described. The goal of the program is to obtain the single particle inclusive spectra of secondary nuclei produced at 0 deg by the fragmentation of heavy ion beam projectiles. The process being examined is B+T yields F + anything, where B is the beam nucleus, T is the target nucleus, and F is the detected fragment. The fragments F are isotopically identified by experimental procedures involving magnetic analysis, energy loss and time-of-flight measurements. Effects were also made to: (a) study processes of heavy nuclei in matter, (b) measure the total and partial production cross section for all isotopes, (c) test the applicability of high energy multiparticle interaction theory to nuclear fragmentation, (d) apply the cross section data and fragmentation probabilities to cosmic ray transport theory, and (e) search for systematic behavior of fragment production as a means to improve existing semi-empirical theories of cross-sections.

L x-ray production cross sections in high-Z atoms by 3-5 MeV/u silicon ions

NASA Astrophysics Data System (ADS)

Oswal, M.; Kumar, Sunil; Singh, Udai; Singh, G.; Singh, K. P.; Mehta, D.; Mitnik, D.; Montanari, C. C.; Nandi, T.

2018-02-01

Total L x-ray production cross sections have been measured in 74W, 79Au, 82Pb, and 83Bi by impact of 3-5 MeV/u 28Si ions, with different charge states q = 8+ up to 12+. We find that the measured cross sections do not differ with the charge state of the projectile ions, but they vary with the beam energies. The experimental data has been compared with three theoretical results, ECUSAR, ECPSSR and SLPA by using the multiple-hole fluorescence and Coster-Kronig yields. The comparison has showed the best agreement with the ECUSAR. The SLPA results also describe the experiments quite well for 74W, 79Au and 83Bi, but certain differences are observed for 82Pb, while the ECPSSR values underestimate by up to a factor two. Surprisingly, the theoretical-experimental agreement is better at low beam energies than in the high beam energy side.

Calculation of the fast ion tail distribution for a spherically symmetric hot spot

NASA Astrophysics Data System (ADS)

McDevitt, C. J.; Tang, X.-Z.; Guo, Z.; Berk, H. L.

2014-10-01

The fast ion tail for a spherically symmetric hot spot is computed via the solution of a simplified Fokker-Planck collision operator. Emphasis is placed on describing the energy scaling of the fast ion distribution function in the hot spot as well as the surrounding cold plasma throughout a broad range of collisionalities and temperatures. It is found that while the fast ion tail inside the hot spot is significantly depleted, leading to a reduction of the fusion yield in this region, a surplus of fast ions is observed in the neighboring cold plasma region. The presence of this surplus of fast ions in the neighboring cold region is shown to result in a partial recovery of the fusion yield lost in the hot spot.

Oxidation of Methionine Residues in Polypeptide Ions via Gas-Phase Ion/Ion Chemistry

PubMed Central

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

Color matters--material ejection and ion yields in UV-MALDI mass spectrometry as a function of laser wavelength and laser fluence.

PubMed

Soltwisch, Jens; Jaskolla, Thorsten W; Dreisewerd, Klaus

2013-10-01

The success of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) as a widely employed analytical tool in the biomolecular sciences builds strongly on an effective laser-material interaction that is resulting in a soft co-desorption and ionization of matrix and imbedded biomolecules. To obtain a maximized ion yield for the analyte(s) of interest, in general both wavelength and fluence need to be tuned to match the specific optical absorption profile of the used matrix. However, commonly only lasers with fixed emission wavelengths of either 337 or 355 nm are used for MALDI-MS. Here, we employed a wavelength-tunable dye laser and recorded both the neutral material ejection and the MS ion data in a wide wavelength and fluence range between 280 and 377.5 nm. α-Cyano-4-hydroxycinnamic acid (HCCA), 4-chloro-α-cyanocinnamic acid (ClCCA), α-cyano-2,4-difluorocinnamic acid (DiFCCA), and 2,5-dihydroxybenzoic acid (DHB) were investigated as matrices, and several peptides as analytes. Recording of the material ejection was achieved by adopting a photoacoustic approach. Relative ion yields were derived by division of photoacoustic and ion signals. In this way, distinct wavelength/fluence regions can be identified for which maximum ion yields were obtained. For the tested matrices, optimal results were achieved for wavelengths corresponding to areas of high optical absorption of the respective matrix and at fluences about a factor of 2-3 above the matrix- and wavelength-dependent ion detection threshold fluences. The material ejection as probed by the photoacoustic method is excellently fitted by the quasithermal model, while a sigmoidal function allows for an empirical description of the ion signal-fluence relationship.

Study of the Insulating Magnetic Field in an Accelerating Ion Diode

NASA Astrophysics Data System (ADS)

Kozlovsky, K. I.; Martynenko, A. S.; Vovchenko, E. D.; Lisovsky, M. I.; Isaev, A. A.

2017-12-01

The results of examination of the insulating magnetic field in an accelerating ion diode are presented. This field is produced in order to suppress the electron current and thus enhance the neutron yield of the D( d, n)3He nuclear reaction. The following two designs are discussed: a gas-filled diode with inertial electrostatic confinement of ions and a vacuum diode with a laser-plasma ion source and pulsed magnetic insulation. Although the insulating field of permanent magnets is highly nonuniform, it made it possible to extend the range of accelerating voltages to U = 200 kV and raise the neutron yield to Q = 107 in the first design. The nonuniform field structure is less prominent in the device with pulsed magnetic insulation, which demonstrated efficient deuteron acceleration with currents up to 1 kA at U = 400 kV. The predicted neutron yield is as high as 109 neutrons/pulse.

Hydrologic conditions and water quality of rainfall and storm runoff for two agricultural areas of the Oso Creek watershed, Nueces County, Texas, 2005-08

USGS Publications Warehouse

Ockerman, Darwin J.; Fernandez, Carlos J.

2010-01-01

The U.S. Geological Survey, in cooperation with the Texas State Soil and Water Conservation Board, Coastal Bend Bays and Estuaries Program, and Texas AgriLife Research and Extension Center at Corpus Christi, studied hydrologic conditions and water quality of rainfall and storm runoff of two primarily agricultural subwatersheds of the Oso Creek watershed in Nueces County, Texas. One area, the upper West Oso Creek subwatershed, is about 5,145 acres. The other area, a subwatershed drained by an unnamed tributary to Oso Creek (hereinafter, Oso Creek tributary), is about 5,287 acres. Rainfall and runoff (streamflow) were continuously monitored at the outlets of the two subwatersheds during the study period October 2005-September 2008. Seventeen rainfall samples were collected and analyzed for nutrients and major inorganic ions. Twenty-four composite runoff water-quality samples (12 at West Oso Creek, 12 at Oso Creek tributary) were collected and analyzed for nutrients, major inorganic ions, and pesticides. Twenty-six discrete suspended-sediment samples (12 West Oso Creek, 14 Oso Creek tributary) and 17 bacteria samples (10 West Oso Creek, 7 Oso Creek tributary) were collected and analyzed. These data were used to estimate, for selected constituents, rainfall deposition to and runoff loads and yields from the two subwatersheds. Quantities of fertilizers and pesticides applied in the two subwatersheds were compared with quantities of nutrients and pesticides in rainfall and runoff. For the study period, total rainfall was greater than average. Most of the runoff from the two subwatersheds occurred in response to a few specific storm periods. The West Oso Creek subwatershed produced more runoff during the study period than the Oso Creek tributary subwatershed, 13.95 inches compared with 9.45 inches. Runoff response was quicker and peak flows were higher in the West Oso Creek subwatershed than in the Oso Creek tributary subwatershed. Total nitrogen runoff yield for the 3-year study period averaged 2.62 pounds per acre per year from the West Oso Creek subwatershed and 0.839 pound per acre per year from the Oso Creek tributary subwatershed. Total phosphorus yields from the West Oso Creek and Oso Creek tributary subwatersheds for the 3-year period were 0.644 and 0.419 pound per acre per year, respectively. Runoff yields of nitrogen and phosphorus were relatively small compared to inputs of nitrogen in fertilizer and rainfall deposition. Average annual runoff yield of total nitrogen (subwatersheds combined) represents about 2.5 percent of nitrogen applied as fertilizer to cropland in the watershed and nitrogen entering the subwatersheds through rainfall deposition. Average annual runoff yield of total phosphorus (subwatersheds combined) represents about 4.0 percent of the phosphorus in applied fertilizer and rainfall deposition. Suspended-sediment yields from the West Oso Creek subwatershed were more than twice those from the Oso Creek tributary subwatershed. The average suspended-sediment yield from the West Oso Creek subwatershed was 522 pounds per acre per year and from the Oso Creek tributary subwatershed was 139 pounds per acre per year. Twenty-four herbicides and eight insecticides were detected in runoff samples collected at the two subwatershed outlets. At the West Oso Creek site, 19 herbicides and 4 insecticides were detected; at the Oso Creek tributary site, 18 herbicides and 6 insecticides were detected. Fourteen pesticides were detected in only one sample at low concentrations (near the laboratory reporting level). Atrazine and atrazine degradation byproduct 2-chloro-4-isopropylamino-6-amino-s-triazine (CIAT) were detected in all samples. Glyphosate and glyphosate byproduct aminomethylphosphonic acid (AMPA) were detected in all samples collected and analyzed during water years 2006-07 but were not included in analysis for samples collected in water year 2008. Of all pesticides detected in runoff, the highest runoff yields w

Non-thermal Processes in the Formation of Mercury's Tenuous Exosphere

NASA Astrophysics Data System (ADS)

Schaible, M. J.; Bennett, C.; Jones, B. M.; Orlando, T. M.

2017-12-01

Recent observations from the MESSENGER spacecraft orbiting Mercury have established that a quasi-trapped population of ions and electrons with 1-10 keV energy exists at a distance of about 1.5 RM (RM is Mercury's radius) around much of the planet. Recent observations from the Fast Imaging Plasma Spectrometer (FIPS), taken < 400 km from the surface, have shown a plasma cusp with energetic heavy ions (i.e. Na+ and O+ groups). The sources of these ions are not clear. A newly developed global kinetic transport model suggests that electron-stimulated desorption (ESD), and possibly light ion stimulated desorption (ISD), can directly yield ions that can be transported and dynamically accelerated to the plasma cusp regions observed by FIPS. Neutrals desorbed from the surface by ESD, ISD, photon-stimulated desorption (PSD) and meteorite impact may also be photoionized and transported/injected into the cusp region. Though the relative importance of these mechanisms in the formation of Mercury's tenuous atmosphere and the subsequent effects on the exosphere/magnetosphere dynamics are not known, it is likely that all of these contribute significantly. The goals of this work are to measure desorption cross-sections and ejection velocities for Na+, O+, and water group ions under relevant electron and ion bombardment energies. This program utilizes state-of-the art surface science capabilities to probe the role of ESD and ISD as a source of ions and neutrals present in the exosphere of Mercury. The experimental chamber is equipped with a dosing system, a cryogenic cooled temperature controlled sample holder, as well as pulsed ion and electron sources. The ESD and ISD ion yields and velocity measurements are obtained directly by sampling with a time-of-flight mass spectrometer. The measured ESD ion yields from adsorbate covered Mercury surface analogs such as the sulfur bearing minerals MgS, Na2S and K2S are low. Additionally, ISD experiments using incident protons also yielded low ion signals. These results implicate PSD and neutral desorption as dominant processes. The information obtained from these experiments can be directly incorporated into model simulations for comparison with data recently obtained by the FIPS instrument.

Optical field ionization of atoms and ions using ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Fittinghoff, D. N.

1993-12-01

This dissertation research is an investigation of the strong optical field ionization of atoms and ions by 120-fs, 614-run laser pulses and 130-fs, 800-nm laser pulses. The experiments have shown ionization that is enhanced above the predictions of sequential tunneling models for He(+2), Ne(+2), and Ar(+2). The ion yields for He(+1), Ne(sup +1) and Ar(sup +1) agree well with the theoretical predictions of optical tunneling models. Investigation of the polarization dependence of the ionization indicates that the enhancements are consistent with a nonsequential ionization mechanism in which the linearly polarized field drives the electron wavefunction back toward the ion core and causes double ionization through inelastic e-2e scattering. These investigations have initiated a number of other studies by other groups and are of current scientific interest in the fields of high-irradiance laser-matter interactions and production of high-density plasmas. This work involved the following: (1) Understanding the characteristic nature of the ion yields produced by tunneling ionization through investigation of analytic solutions for tunneling at optical frequencies. (2) Extensive characterization of the pulses produced by 614-nm and 800-ran ultrashort pulse lasers. Absolute calibration of the irradiance scale produced shows the practicality of the inverse problem--measuring peak laser irradiance using ion yields. (3) Measuring the ion yields for three noble gases using linear, circular and elliptical polarizations of laser pulses at 614-nm and 800-nm. The measurements are some of the first measurements for pulse widths as low as 120-fs.

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.

A routine high-precision method for Lu-Hf isotope geochemistry and chronology

USGS Publications Warehouse

Patchett, P.J.; Tatsumoto, M.

1981-01-01

A method for chemical separation of Lu and Hf from rock, meteorite and mineral samples is described, together with a much improved mass spectrometric running technique for Hf. This allows (i) geo- and cosmochronology using the176Lu???176Hf+??- decay scheme, and (ii) geochemical studies of planetary processes in the earth and moon. Chemical yields for the three-stage ion-exchange column procedure average 90% for Hf. Chemical blanks are <0.2 ng for Lu and Hf. From 1 ??g of Hf, a total ion current of 0.5??10-11 Ampere can be maintained for 3-5 h, yielding 0.01-0.03% precision on the ratio176Hf/177Hf. Normalisation to179Hf/177Hf=0.7325 is used. Extensive results for the Johnson Matthey Hf standard JMC 475 are presented, and this sample is urged as an international mass spectrometric standard; suitable aliquots, prepared from a single batch of JMC 475, are available from Denver. Lu-Hf analyses of the standard rocks BCR-1 and JB-1 are given. The potential of the Lu-Hf method in isotope geochemistry is assessed. ?? 1980 Springer-Verlag.

Suboxide/subnitride formation on Ta masks during magnetic material etching by reactive plasmas

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

Li, Hu; Muraki, Yu; Karahashi, Kazuhiro

2015-07-15

Etching characteristics of tantalum (Ta) masks used in magnetoresistive random-access memory etching processes by carbon monoxide and ammonium (CO/NH{sub 3}) or methanol (CH{sub 3}OH) plasmas have been examined by mass-selected ion beam experiments with in-situ surface analyses. It has been suggested in earlier studies that etching of magnetic materials, i.e., Fe, Ni, Co, and their alloys, by such plasmas is mostly due to physical sputtering and etch selectivity of the process arises from etch resistance (i.e., low-sputtering yield) of the hard mask materials such as Ta. In this study, it is shown that, during Ta etching by energetic CO{sup +}more » or N{sup +} ions, suboxides or subnitrides are formed on the Ta surface, which reduces the apparent sputtering yield of Ta. It is also shown that the sputtering yield of Ta by energetic CO{sup +} or N{sup +} ions has a strong dependence on the angle of ion incidence, which suggests a correlation between the sputtering yield and the oxidation states of Ta in the suboxide or subnitride; the higher the oxidation state of Ta, the lower is the sputtering yield. These data account for the observed etch selectivity by CO/NH{sub 3} and CH{sub 3}OH plasmas.« less

High energy primary knock-on process in metal deuterium systems initiated by bombardment with noble gas ions

NASA Astrophysics Data System (ADS)

Gann, V. V.; Tolstolutskaya, G. D.

2008-08-01

An experimental study confirms the possibility of nuclear fusion reactions initiating in metal-deuterium targets by bombarding them with ions that are not the reagents of the fusion reaction, in particular, with noble gas ions. The yields of (d,d) and (d,t) reactions were measured as functions of energy (0.4-3.2 MeV) and mass of incident ions (He +, Ne +, Ar +, Kr + and Xe +). Irradiation by heavy ions produced a number of energetic deuterium atoms in the deuteride and deuterium + tritium metal targets. At ion energies of ˜0.1-1 MeV the d-d reaction yields are relatively high. A model of nuclear fusion reaction cross-sections in atomic collision cascades initiated by noble gas ion beam in metal-deuterium target is developed. The method for calculation tritium or deuterium recoil fluxes and the yield of d-d fusion reaction in subsequent collisions was proposed. It was shown that D(d,p)t and D(t,n) 4He reactions mainly occur in energy region of the recoiled D-atom from 10 keV to 250 keV. The calculated probabilities of d-d and d-t fusion reactions were found to be in a good agreement with the experimental data.

Secondary-electron emission by 0.5-MeV/u H, He, and Li ions specularly reflected from a SnTe(001) surface: Possibility of the surface track potential reducing the secondary-electron yield at a semiconductor surface

NASA Astrophysics Data System (ADS)

Kimura, Kenji; Usui, Satoshi; Nakajima, Kaoru

2000-12-01

We have measured secondary-electron (SE) yield γ induced by 0.5 MeV/u H, He, and Li ions specularly reflected from a SnTe(001) surface. The position-dependent SE production rate is derived from the observed γ. The SE production rate normalized by the observed mean square charge of the reflected ions is almost independent of the atomic number of the projectile ion. This indicates that the surface track potential induced by the projectile ion is negligibly small to affect the SE emission at semiconductor surfaces probably due to rapid relaxation processes.

Unravelling the secrets of Cs controlled secondary ion formation: Evidence of the dominance of site specific surface chemistry, alloying and ionic bonding

NASA Astrophysics Data System (ADS)

Wittmaack, Klaus

2013-03-01

Exposure of ion bombarded solids to Cs gives rise to a very strong enhancement of the yields of negatively charged secondary ions and, concurrently, to a lowering of positive ion yields. The phenomena have been explored in a large number of experimental and theoretical studies but attempts to clarify the mechanism of ion formation were not as successful as assumed. This review examines the state of the art in Cs controlled secondary ion mass spectrometry (SIMS) in great detail, with due consideration of low-energy alkali-ion scattering. In very basic studies on alkali induced secondary ion yield changes, sub-monolayer quantities of Cs or Li were deposited on the sample surface, followed by low-fluence ion bombardment, to avoid significant damage. If SIMS is applied to characterise the composition of solid materials, the simplest approach to achieving sample erosion as well as high negative-ion yields is bombardment with primary ions of Cs. Two other methods of sample loading with Cs provide more flexibility, (i) exposure to a collimated beam of Cs vapour and concurrent bombardment with high-energy non-Cs ions and (ii) the mixed-beam approach involving quasi-simultaneous bombardment with Cs and Xe ions. Both concepts have the advantage that undesirable sample overload with Cs can be avoided. High Cs concentrations reduce the formation probability of target specific molecular ions and lower the yields of all types of positive secondary ions, including Cs+, M+, X+, MCs+ and XCs+ (M and X denoting matrix and impurity elements). Quantitative SIMS analysis using MCs+ and XCs+ ions appears feasible, provided the Cs coverage is kept below about 5%. The semi-classical model of resonant charge transfer, also known as the tunnelling model, has long been considered a solid framework for the interpretation of Cs and Li based SIMS data. The model predicts ionisation probabilities for cases in which, at shallow distances from the surface, the affinity (ionisation) level of the departing atom is shifted below (above) the Fermi level. Ion yields should be controlled by the work function (WF) of the sample, Φ, and the normal velocity of the ejected ions. To explore the predicted velocity dependence, the performance characteristics of the employed SIMS instrument need to be known. The Cs induced negative-ion yield enhancement observed with pure metal and alloy targets often exceeded five orders of magnitude, with enhancement factors essentially independent of the emission energy. This absence of a velocity dependence is at variance with the predictions of the tunnelling model. Previous theoretical attempts to model the Φ-dependence and the apparent velocity effect for the overrated case of O-emission from Li and Cs exposed oxidised metal surfaces must be considered a meander. The experimental data, recorded with a quadrupole based instrument of inadequate extraction geometry, may alternatively be rationalised in terms of alkali induced changes in the energy spectrum of sputtered atoms. Another important finding is that secondary ion yield changes do not correlate with the absolute magnitude of the (macroscopic) WF but often with WF changes, ΔΦ. The frequently used method of determining ΔΦ in situ from the shift of the leading edge of secondary ion energy spectra rests on the assumption, taken for granted or not even appreciated, that Cs induced yield changes are independent of the ion's emission velocity. Hence the approach is only applicable if the tunnelling model is not valid. The local character of alkali induced WF changes, which might provide a route to an understanding of previously unexplained phenomena, has been explored using photoemission of adsorbed inert gases, scanning tunneling microscopy and low-energy ion scattering spectrometry. At room temperature, the Cs coverage is limited to one layer of adatoms. Close similarities are identified between WF changes generated by Cs vapour deposition and by bombardment with Cs ions. This finding implies that sub-monolayer quantities of Cs adatoms grow at the surface of Cs bombarded samples. The process has been studied in-situ by medium-energy ion scattering spectrometry. The stationary Cs coverage, NCs, is controlled by the efficiency of active transport of implanted atoms to the surface, the bulk retention properties of the sample and the cross section for sputtering of adatoms. Unearthing immobile implanted Cs atoms by sputter erosion usually provides only a minor contribution to the stationary coverage. Cs adatoms are mobile; the time required for final adatom rearrangement may be on the order of minutes at room temperature. Exposure of Cs bombarded samples to oxygen gives rise to oxidation of the substrate as well as to the formation of oxide layers of complex composition. Intercalation should be taken into account as a possible route of alkali transport into analysed samples. An important aspect ignored in prior work is that the alkali coverage required to produce a certain WF change is five to seven times higher if Li is deposited instead of Cs. Studies involving the use of Li thus provide no advantage compared to Cs. Furthermore, migration of the tiny Li atoms into the sample and metallisation effects aggrevate data interpretation. Literature data for ΔΦ (NCs), measured using Cs vapour deposition, can be converted to calibration curves, NCs (ΔΦ), for calculating the coverage established in implantation studies, a method referred to as ΔΦ→NCs conversion. This concept may be carried even further, as shown convincingly for silicon, the material examined most frequently in basic SIMS studies: Si- ion fractions, P(Si-), derived from yields measured under vastly different conditions of Cs supply, exhibit essentially the same ΔΦ dependence. Inverting the data one can produce calibration functions for ΔΦ versus P(Si-), denoted P(Si-)→ΔΦ, or, more generally, P(M-)→ΔΦ conversion. On this basis, transient yields measured during Cs implantation can be evaluated as a function of Cs coverage. The summarised results imply that secondary ions are commonly not formed by charge transfer between an escaping atom and the electronic system of the sample but are already emitted as ions. The probability of ion formation appears to be controlled by the local ionic character of the alkali-target atom bonds, i.e., by the difference in electronegativity between the involved elements as well as by the electron affinity and the ionisation potential of the departing atom. This idea is supported by the finding that Si- yields exhibit the same very strong dependence on Cs coverage as Si+ and O- yields on the oxygen fraction in oxygen loaded Si. Most challenging to theoreticians is the finding that the ionisation probability is independent of the emission velocity of sputtered ions. This phenomenon cannot be rationalised along established routes of thinking. Different concepts need to be explored. An old, somewhat exotic idea takes account of the heavy perturbation created for a very short period of time at the site of ion emission (dynamic randomisation). Molecular dynamics simulations are desirable to clarify the issue. Ultimately it may be possible to describe all phenomena of enhanced or suppressed secondary ion formation, produced either by surface loading with alkali atoms or by enforced surface oxidation, on the basis of a single universal model. There is plenty of room for exciting new studies.

Urban dew and rain in Paris, France: Occurrence and physico-chemical characteristics

NASA Astrophysics Data System (ADS)

Beysens, D.; Mongruel, A.; Acker, K.

2017-06-01

This paper summarizes one year (April 2011 to March 2012) measurements on planar condensing surfaces of dew and rain events and related physico-chemical characteristics in the urban environment of Paris (city center). Yearly collected water was 3.48 mm for dew (63 events) and 593 mm for rain (146 events). The latter value compares well with rain data (547 mm and 107 events) collected within 12 km at Paris-Orly airport. An estimation of dew yield based on meteo data gives 2.35 mm and 74 events, to be compared with 17.11 mm and 196 events at Paris-Orly. These differences highlight the large reduction in dew events and dew yields in an urban area as compared to a close rural-like area. This reduction is not due to a sky view reduction but to heat island that increases air temperature and decreases relative humidity. Analysis of dew (34) and rain (77) samples were done concerning pH, electrical conductivity (EC), major anions and cations as well as selected trace metals and other minor ions. Mean pH values are found similar for both, dew (6.5) and rain (6.1), rain being slightly more acidic than dew. The mean dew total ionic content (TIC 1.8 meq/l) and EC value (124 μS/cm) are about four times that of rain (0.45 meq/l; 35 μS/cm), meaning that total dissolved solids in dew is nearly four times that in rain. Sulfate and nitrate are the most acidifying components, calcium the most neutralizing constituent with ratio of mean total acidity/total alkalinity comparable for dew and rain ( 0.9). Sulfate and nitrate have mainly anthropogenic sources, whereas chloride and magnesium are mostly connected with marine air masses. Dew is a considerable factor of wet deposition of pollutants; dew and rain ion concentrations, however, meet the WHO requirements for drinking water.

Ion kinetic dynamics in strongly-shocked plasmas relevant to ICF

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

Rinderknecht, H. G.; Amendt, P. A.; Rosenberg, M. J.

Implosions of thin-shell capsules produce strongly-shocked (M > 10), low-density (ρ ~1 mg/cc -1), high-temperature (T i ~keV) plasmas, comparable to those produced in the strongly-shocked DT-vapor in inertial confinement fusion (ICF) experiments. A series of thin-glass targets filled with mixtures of deuterium and Helium-3 gas ranging from 7% to 100% deuterium was imploded to investigate the impact of multi-species ion kinetic mechanisms in ICF-relevant plasmas over a wide range of Knudsen numbers (N K ≡ λ ii/R). Anomalous trends in nuclear yields and burn-averaged ion temperatures in implosions with N K > 0.5, which have been interpreted as signaturesmore » of ion species separation and ion thermal decoupling, are found not to be consistent with single-species ion kinetic effects alone. Experimentally inferred Knudsen numbers predict an opposite yield trend to those observed, confirming the dominance of multi-species physics in these experiments. In contrast, implosions with N K ~ 0.01 follow the expected yield trend, suggesting single-species kinetic effects are dominant. In conclusion, the impact of the observed kinetic physics mechanisms on the formation of the hotspot in ICF experiments is discussed.« less

Ion kinetic dynamics in strongly-shocked plasmas relevant to ICF

DOE PAGES

Rinderknecht, H. G.; Amendt, P. A.; Rosenberg, M. J.; ...

2017-04-20

Implosions of thin-shell capsules produce strongly-shocked (M > 10), low-density (ρ ~1 mg/cc -1), high-temperature (T i ~keV) plasmas, comparable to those produced in the strongly-shocked DT-vapor in inertial confinement fusion (ICF) experiments. A series of thin-glass targets filled with mixtures of deuterium and Helium-3 gas ranging from 7% to 100% deuterium was imploded to investigate the impact of multi-species ion kinetic mechanisms in ICF-relevant plasmas over a wide range of Knudsen numbers (N K ≡ λ ii/R). Anomalous trends in nuclear yields and burn-averaged ion temperatures in implosions with N K > 0.5, which have been interpreted as signaturesmore » of ion species separation and ion thermal decoupling, are found not to be consistent with single-species ion kinetic effects alone. Experimentally inferred Knudsen numbers predict an opposite yield trend to those observed, confirming the dominance of multi-species physics in these experiments. In contrast, implosions with N K ~ 0.01 follow the expected yield trend, suggesting single-species kinetic effects are dominant. In conclusion, the impact of the observed kinetic physics mechanisms on the formation of the hotspot in ICF experiments is discussed.« less

Ion Thermal Decoupling and Species Separation in Shock-Driven Implosions

DOE PAGES

Rinderknecht, Hans G.; Rosenberg, M. J.; Li, C. K.; ...

2015-01-14

Here, anomalous reduction of the fusion yields by 50% and anomalous scaling of the burn-averaged ion temperatures with the ion-species fraction has been observed for the first time in D 3He-filled shock-driven inertial confinement fusion implosions. Two ion kinetic mechanisms are used to explain the anomalous observations: thermal decoupling of the D and 3He populations and diffusive species separation. The observed insensitivity of ion temperature to a varying deuterium fraction is shown to be a signature of ion thermal decoupling in shock-heated plasmas. The burn-averaged deuterium fraction calculated from the experimental data demonstrates a reduction in the average core deuteriummore » density, as predicted by simulations that use a diffusion model. Accounting for each of these effects in simulations reproduces the observed yield trends.« less

Molecular ion yield enhancement induced by gold deposition in static secondary ion mass spectrometry

NASA Astrophysics Data System (ADS)

Wehbe, Nimer; Delcorte, Arnaud; Heile, Andreas; Arlinghaus, Heinrich F.; Bertrand, Patrick

2008-12-01

Static ToF-SIMS was used to evaluate the effect of gold condensation as a sample treatment prior to analysis. The experiments were carried out with a model molecular layer (Triacontane M = 422.4 Da), upon atomic (In +) and polyatomic (Bi 3+) projectile bombardment. The results indicate that the effect of molecular ion yield improvement using gold metallization exists only under atomic projectile impact. While the quasi-molecular ion (M+Au) + signal can become two orders of magnitude larger than that of the deprotonated molecular ion from the pristine sample under In + bombardment, it barely reaches the initial intensity of (M-H) + when Bi 3+ projectiles are used. The differences observed for mono- and polyatomic primary ion bombardment might be explained by differences in near-surface energy deposition, which influences the sputtering and ionization processes.

Kinetic and Potential Sputtering of Lunar Regolith: The Contribution of the Heavy Highly Charged (Minority) Solar Wind Ions

NASA Technical Reports Server (NTRS)

Meyer, F. W.; Barghouty, A. F.

2012-01-01

Solar wind sputtering of the lunar surface helps determine the composition of the lunar exosphere and contributes to surface weathering. To date, only the effects of the two dominant solar wind constituents, H+ and He+, have been considered. The heavier, less abundant solar wind constituents have much larger sputtering yields because they have greater mass (kinetic sputtering) and they are highly charged (potential sputtering) Their contribution to total sputtering can therefore be orders of magnitude larger than their relative abundances would suggest

Evaluating the Development of Biocatalytic Technology for the Targeted Removal of Perchlorate from Drinking Water.

PubMed

Hutchison, Justin M; Guest, Jeremy S; Zilles, Julie L

2017-06-20

Removing micropollutants is challenging in part because of their toxicity at low concentrations. A biocatalytic approach could harness the high affinity of enzymes for their substrates to address this challenge. The potential of biocatalysis relative to mature (nonselective ion exchange, selective ion exchange, and whole-cell biological reduction) and emerging (catalysis) perchlorate-removal technologies was evaluated through a quantitative sustainable design framework, and research objectives were prioritized to advance economic and environmental sustainability. In its current undeveloped state, the biocatalytic technology was approximately 1 order of magnitude higher in cost and environmental impact than nonselective ion exchange. Biocatalyst production was highly correlated with cost and impact. Realistic improvement scenarios targeting biocatalyst yield, biocatalyst immobilization for reuse, and elimination of an electron shuttle could reduce total costs to $0.034 m -3 and global warming potential (GWP) to 0.051 kg CO 2 eq m -3 : roughly 6.5% of cost and 7.3% of GWP of the background from drinking water treatment and competitive with the best performing technology, selective ion exchange. With less stringent perchlorate regulatory limits, ion exchange technologies had increased cost and impact, in contrast to biocatalytic and catalytic technologies. Targeted advances in biocatalysis could provide affordable and sustainable treatment options to protect the public from micropollutants.

Fully kinetic simulations of dense plasma focus Z-pinch devices.

PubMed

Schmidt, A; Tang, V; Welch, D

2012-11-16

Dense plasma focus Z-pinch devices are sources of copious high energy electrons and ions, x rays, and neutrons. The mechanisms through which these physically simple devices generate such high-energy beams in a relatively short distance are not fully understood. We now have, for the first time, demonstrated a capability to model these plasmas fully kinetically, allowing us to simulate the pinch process at the particle scale. We present here the results of the initial kinetic simulations, which reproduce experimental neutron yields (~10(7)) and high-energy (MeV) beams for the first time. We compare our fluid, hybrid (kinetic ions and fluid electrons), and fully kinetic simulations. Fluid simulations predict no neutrons and do not allow for nonthermal ions, while hybrid simulations underpredict neutron yield by ~100x and exhibit an ion tail that does not exceed 200 keV. Only fully kinetic simulations predict MeV-energy ions and experimental neutron yields. A frequency analysis in a fully kinetic simulation shows plasma fluctuations near the lower hybrid frequency, possibly implicating lower hybrid drift instability as a contributor to anomalous resistivity in the plasma.

Secondary ion emission from arachidic acid LB-layers under Ar +, Xe +, Ga + and SF 5+ primary ion bombardment

NASA Astrophysics Data System (ADS)

Stapel, D.; Brox, O.; Benninghoven, A.

1999-02-01

The influence of primary ion energy, mass and composition on sputtering and secondary ion emission of arachidic acid Langmuir-Blodgett mono- and multilayers, deposited on gold substrates, has been investigated. Ga +, Ar +, 129Xe+ and SF 5+ in the energy range 5-25 keV were used as primary ions. Yields Y, damage cross-sections σ, and ion formation efficiencies E have been determined for selected secondary ions, characterizing the molecular overlayer, the overlayer substrate interface and the substrate. We found a strong influence of layer thickness and of primary ion energy, mass and composition on Y, σ and E. Information depth increases with increasing ion energy and decreasing mass of primary ions, being higher for SF 5+ than for Xe +. Y, σ and E increase with increasing primary ion mass. They are considerably higher for a molecular (SF 5+) than for atomic ions of comparable mass ( 129Xe+). The experimental results supply information on the extension of impact cascades, generated in different substrate materials by different primary ion species and different energies. They demonstrate that in analytical SIMS application information depths can be minimized and yields and ion formation efficiencies can be maximized by the use of molecular primary ions.

The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF)

DOE PAGES

Frenje, J. A.; Hilsabeck, T. J.; Wink, C. W.; ...

2016-08-02

The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (T i), yield (Y n), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate datamore » with a time resolution of ~20 ps and energy resolution of ~100 keV for total neutron yields above ~10 16. Lastly, at lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ~20 ps.« less

Development of the dense plasma focus for short-pulse applications

NASA Astrophysics Data System (ADS)

Bennett, N.; Blasco, M.; Breeding, K.; Constantino, D.; DeYoung, A.; DiPuccio, V.; Friedman, J.; Gall, B.; Gardner, S.; Gatling, J.; Hagen, E. C.; Luttman, A.; Meehan, B. T.; Misch, M.; Molnar, S.; Morgan, G.; O'Brien, R.; Robbins, L.; Rundberg, R.; Sipe, N.; Welch, D. R.; Yuan, V.

2017-01-01

The dense plasma focus (DPF) has long been considered a compact source for pulsed neutrons and has traditionally been optimized for the total neutron yield. In this paper, we describe the efforts to optimize the DPF for short-pulse applications by introducing a reentrant cathode at the end of the coaxial plasma gun. The resulting neutron pulse widths are reduced by an average of 21 ±9 % from the traditional long-drift DPF design. Pulse widths and yields achieved from deuterium-tritium fusion at 2 MA are 61.8 ±30.7 ns FWHM and 1.84 ±0.49 ×1012 neutrons per shot. Simulations were conducted concurrently to elucidate the DPF operation and confirm the role of the reentrant cathode. A hybrid fluid-kinetic particle-in-cell modeling capability demonstrates correct sheath velocities, plasma instabilities, and fusion yield rates. Consistent with previous findings that the DPF is dominated by beam-target fusion from superthermal ions, we estimate that the thermonuclear contribution is at the 1% level.

The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF).

PubMed

Frenje, J A; Hilsabeck, T J; Wink, C W; Bell, P; Bionta, R; Cerjan, C; Gatu Johnson, M; Kilkenny, J D; Li, C K; Séguin, F H; Petrasso, R D

2016-11-01

The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (T i ), yield (Y n ), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate data with a time resolution of ∼20 ps and energy resolution of ∼100 keV for total neutron yields above ∼10 16 . At lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ∼20 ps.

The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF)

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

Frenje, J. A., E-mail: jfrenje@psfc.mit.edu; Wink, C. W.; Gatu Johnson, M.

The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (T{sub i}), yield (Y{sub n}), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate datamore » with a time resolution of ∼20 ps and energy resolution of ∼100 keV for total neutron yields above ∼10{sup 16}. At lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ∼20 ps.« less

Solar Wind Sputtering of Lunar Surface Materials: Role and Some Possible Implications of Potential Sputtering

NASA Technical Reports Server (NTRS)

Barghouty, A. F.; Adams, J. H., Jr.; Meyer, F.; Reinhold, c.

2010-01-01

Solar-wind induced sputtering of the lunar surface includes, in principle, both kinetic and potential sputtering. The role of the latter mechanism, however, in many focused studies has not been properly ascertained due partly to lack of data but can also be attributed to the assertion that the contribution of solar-wind heavy ions to the total sputtering is quite low due to their low number density compared to solar-wind protons. Limited laboratory measurements show marked enhancements in the sputter yields of slow-moving, highly-charged ions impacting oxides. Lunar surface sputtering yields are important as they affect, e.g., estimates of the compositional changes in the lunar surface, its erosion rate, as well as its contribution to the exosphere as well as estimates of hydrogen and water contents. Since the typical range of solar-wind ions at 1 keV/amu is comparable to the thickness of the amorphous rim found on lunar soil grains, i.e. few 10s nm, lunar simulant samples JSC-1A AGGL are specifically enhanced to have such rims in addition to the other known characteristics of the actual lunar soil particles. However, most, if not all laboratory studies of potential sputtering were carried out in single crystal targets, quite different from the rim s amorphous structure. The effect of this structural difference on the extent of potential sputtering has not, to our knowledge, been investigated to date.

First-principle study of phosphors for white-LED applications : absorption and emission energies for Ce- and Eu-doped hosts.

NASA Astrophysics Data System (ADS)

Gonze, Xavier; Jia, Yongchao; Miglio, Anna; Giantomassi, Matteo; Ponce, Samuel; Mikami, Masayoshi

After the invasion of compact fluorescent lamps, white LED lighting is becoming a major contender in ecofriendly light sources, with a combination of yellow-, green- and/or red-emitting phosphors partly absorbing the blue light emitted by an InGaN LED. After introducing the semi-empirical Dorenbos model for 4f' 5d transition energies of rare earth ions, I present a first-principle study of two dozen compounds, pristine as well as doped with Ce3+ or Eu2+ ions, in view of explaining their different emission color. The neutral excitation of the ions is simulated through a constrained density functional theory method coupled with a delta SCF analysis of total energies, yielding absorption energies. Then, atomic positions in the excited state are relaxed, yielding emission energies and Stokes shifts, and identification of luminescent centers. In case of the Ce doped materials, the first-principle approach matches experimental data within 0.3 eV for both absorption and emission energies, covering a range of values between 2.0 eV and 5.0 eV, and provides Stokes shifts within 30%, with two exceptions. This is significantly better than the semi-empirical Dorenbos model. A similar analysis is performed for Eu-doped materials, also examining the thermal quenching of two oxynitride hosts. The work was supported by the FRS-FNRS Belgium (PDR Grant T.0238.13 - AIXPHO).

State-to-state measurements of low-energy ion-molecule and ion-ion collisions by three dimensional momentum imaging

NASA Astrophysics Data System (ADS)

Urbain, Xavier

2016-09-01

While the measurement of total absolute cross sections remains challenging, the insight provided by differential cross sections and branching ratios is invaluable to assess the quality of theoretical predictions. Satisfactory agreement at the latter level gives better confidence in the proper identification of the reaction mechanism and key parameters. The three dimensional imaging of molecular dissociation, and more generally, the determination of all momentum vectors of the reaction products, gives direct access to the differential quantities of interest. For the prototype reaction of a proton colliding with H2, the secondary H2+current may be recorded to provide the total charge transfer yield. The dissociative charge transfer of the product ions with alkali targets leaves a characteristic signature in the total kinetic energy imparted to the H fragments. Its measurement is readily achieved by coincident detection on position sensitive detectors. This allows us to extract vibrational populations as a function of collision energy. A resonant enhancement of the charge transfer around 45 eV/amu is observed, that leaves the molecular ion in its vibrational ground state. Those observations are supported by state-of-the-art calculations. We have similarly explored the ionization of molecular oxygen by proton and alpha particle impact, at velocities characteristic of the solar wind. A somewhat more involved vibrational analysis of the O2+cations indicates a Franck-Condon like vibrational population of the ground electronic state from 50 eV to 10 keV, unlikely to modify the branching ratios of dissociative recombination, itself responsible for airglow emissions. More interestingly, a significant population of the 4Πu excited state is measured at velocities typical of the fast solar wind. Finally, we shall address the implementation of three dimensional imaging in merged ion-ion beam studies. Mutual neutralization involving anions and cations is a very efficient process, characterized by a uniquely defined initial state and a limited range of final states readily identified by the total kinetic energy released to the products. Detailed branching ratios may be obtained at near zero collision energy where the reaction rate is maximum and the system behaves as a quasi-molecule undergoing in flight dissociation. As an example, we shall discuss the mutual neutralization of C+ and various anions of the second and third row of the periodic table. This work was supported by the Fonds de la Recherche Scientifique - FNRS through IISN Contract No. 4.4504.10.

Rare isotope beam energy measurements and scintillator developments for ReA3

NASA Astrophysics Data System (ADS)

Lin, Ling-Ying

The ReAccelerator for 3 MeV/u beams (ReA3) at the National Superconducting Cyclotron Laboratory (NSCL) in Michigan State University can stop rare isotope beams produced by in-flight fragmentation and reaccelerate them in a superconducting linac. The precise knowledge of the energy and the energy spread of the ion beams extracted from the ReA3 linac is essential for experimental requirement in many applications. Beam energy determination methods such as implantation on a Si detector and/or using calibrated linac settings are precise within a few tens of keV/u. In order to determine beam energies with good resolution of less than 0.5 % FWHM, a 45 degree bending magnet with a movable slit is used to determine the absolute beam energy based on the magnetic rigidity. Two methods have been developed for the energy calibration of the beam analyzing magnet: gamma-ray nuclear resonance reactions and a time-of-flight (TOF) technique. The resonance energies of gamma-ray resonant reactions provide well-known and precise calibration points. The gamma ray yields of the 27Al(p,gamma)28Si at Ep= 992 keV and 632 keV resonances and 58Ni(p,gamma)59Cu at Ep= 1843 keV resonance have been measured with the high efficiency CAESAR (CAESium iodide ARray) and SuN (Summing NaI(Tl)) detectors. By fitting the observed resonant gamma-ray yields, not only the beam energy can be precisely correlated with the magnetic field but also beam energy spread can be obtained. The measured beam energy spread is consistent with beam optics calculations. A time-of-flight system for determining the absolute energy of ion beams and calibrating the 45 degree magnetic analyzer has been developed in ReA3 by using two identical secondary electron monitors (grid-MCP detectors) with appropriate separation. The TOF technique is applicable to the variety of beam energies and ion particles. Velocities of ion beam are determined by simultaneously measuring the arrival time of beam bunches at the two detectors with respect to the acceleration RF clock. The time-of-flight system can provide beam energy information with precision of <0.1%. Scintillators are widely used to reliably measure beam profiles and beam distributions. At low energies, scintillator-based diagnostic devices are more problematic because of their fast light yield degradation under ion bombardment. The degradation of the scintillation yield of single crystal YAG: Ce under He+ irradiation at low energies between 28 and 58 keV has been systematically studied. The scintillator was irradiated at the rare isotope ReAccelerator (ReA) facility. The scintillation emission is attributed to its rapid 5d-4f transition of Ce3+ ions. As the bombardment time increases, an exponential decay of the light output is observed due to the induced radiation damage of the crystal lattice. The decrease of the experimentally observed light yield as a function of particle fluence is found to be in fair agreement with the Birks model. Analysis indicates that the damage cross section of scintillation centers slightly decreases with the ion energy. The scintillator degrades slower under higher-energy irradiation. In order to investigate scintillation degradation over a wide range of irradiation energies and scintillator materials, the scintillation processes for KBr, YAG:Ce, CaF2:Eu and CsI:Tl crystals under H2 + irradiation in the energy range of 600-2150 keV/u have been investigated. The data indicates that YAG:Ce and CsI:Tl can maintain stable luminescence under continuous ion bombardment for at least a total fluence of 1.8x10 12 ions/mm2. On the other hand, the luminescence of CaF2:Eu shows a rapid initial decay but then maintains a nearly constant luminescence yield. The extraordinary scintillation response of KBr is initially enhanced under ion bombardment, approaches a maximum, and then eventually decays. The scintillation efficiency of the CsI:Tl scintillator is superior to the other materials. The low-energy H2+ bombardment (25 keV/u) on the YAG:Ce scintillator can lead to the significant degradation of the scintillation yields. Different scintillation degradation responses for the low- and high-energy bombardments can be attributed to the transmission loss of the emitted light inside the crystal caused by displacement damages.

Formation and reactions of negative ions relevant to chemical ionization mass spectrometry. I. Cl mass spectra of organic compounds produced by F− reactions

PubMed Central

Tiernan, T. O.; Chang, C.; Cheng, C. C.

1980-01-01

A systematic study of the negative-ion chemical ionization mass spectra produced by the reaction of F− with a wide variety of organic compounds has been accomplished. A time-of-flight mass spectrometer fitted with a modified high pressure ion source was employed for these experiments. The F− reagent ion was generated from CF3H or NF3, typically at an ion source pressure of 100 μm. In pure NF3, F− is the major ion formed and constitutes more than 90% of the total ion intensity. While F− is also the major primary ion formed in pure CF3H, it undergoes rapid ion-molecule reactions at elevated source pressures, yielding (HF)nF− (n = 1−3) ions, which makes CF3H less suitable as a chemical ionization reagent gas. Among the organic compounds investigated were carboxylic acids, ketones, aldehydes, esters, alcohols, phenols, halides, nitriles, nitrobenzene, ethers, amines and hydrocarbons. An intense (M − 1)− ion was observed in the F− chemical ionization mass spectra of carboxylic acids, ketones, aldehydes and phenols. Alcohols yield only (M + F)− ions upon reaction with F−. A weaker (M + F)− ion was also detected in the F− chemical ionization spectra of carboxylic acids, aldehydes, ketones and nitriles. The F− chemical ionization mass spectra of esters, halides, nitriles, nitrobenzene and ethers are characterized primarily by the ions, RCOO−, X−, CN−, NO2−, and OR−, respectively. In addition, esters show a very weak (M − 1)− ion (except formates). In the F− chemical ionization spectra of some aliphatic alkanes and o-xylene, a very weak (M + F)− ion was observed. Amines and aliphatic alkenes exhibit only insignificant fragment ions under similar conditions, while aromatic hydrocarbons, such as benzene and toluene are not reactive at all with the F− ion. The mechanisms of the various reactions mentioned are discussed, and several experimental complications are noted. In still other studies, the effects of varying several experimental parameters, including source pressure, relative proportions of the reagent and analyte, and other ion source parameters, on the observed chemical ionization mass spectra were also investigated. In a mixture of NF3 and n-butanol, for example, the ratio of the intensities of the ions characteristic of the alcohol to that of the (HF)nF− ion was found to decrease with increasing sample pressure, with increasing NF3 pressure, and with increasing electron energy. No significant effects on the spectra were observed to result from variation of the source repeller field or the source temperature. The addition of argon to the source as a potential moderator did not alter the F− chemical ionization spectrum significantly, but the use of oxygen appears to inhibit formation of the (HF)nF− cluster ion. The advantages of using F− as a chemical ionization reagent are discussed, and comparisons are made with other reagent ions. PMID:7428746

Double matrix effect in Low Energy Ion Scattering from La surfaces

NASA Astrophysics Data System (ADS)

Zameshin, Andrey A.; Yakshin, Andrey E.; Sturm, Jacobus M.; Brongerma, Hidde H.; Bijkerk, Fred

2018-05-01

Low Energy Ion Scattering (LEIS) has been performed on several lanthanum-based surfaces. Strong subsurface matrix effects - dependence of surface scattered He+ ion yield on the composition of subsurface layer - have been observed. The ion yield of He+ scattered by La differed by a factor of up to 2.5 for different surfaces, while only the La peak was visible in the spectra. To study these effects and enable surface quantification, He+ ion yields have been measured in a range of incident He+ energies from 1000 to 7500 eV for LaB6, La2O3, oxidized La and pure La surfaces. The investigation showed that as many as two simultaneous matrix effects are present, each one driven by a separate charge exchange mechanism. The first one is a resonant neutralization from the conduction band of La to an excited state of the He+ ion. It depends on the work function of the surface, which is lowered significantly when La interacts with O or B. The second mechanism is quasiresonant charge transfer between bound La levels and He 1s, which creates characteristic oscillations in the energy dependence of ion yields. The exact structure of the oscillations depends on small changes in binding energies of interacting La levels. This is the first time quasiresonant charge transfer is proven to be present in La. It is likely that La 5p orbitals participate in this resonance, which can be the first clear observation of a resonance between p and s orbitals in LEIS. This type of resonance was previously believed to be absent because of strong damping. We also demonstrated that despite the complex matrix effect precise measurements over a wide energy range allow quantification of the atomic composition of La-based surfaces.

Simultaneous determination of total nitrogen and total phosphorus in environmental waters using alkaline persulfate digestion and ion chromatography.

PubMed

De Borba, Brian M; Jack, Richard F; Rohrer, Jeffrey S; Wirt, Joan; Wang, Dongmei

2014-11-21

An ion chromatography (IC) method was developed for the simultaneous determination of total nitrogen and total phosphorus after alkaline persulfate digestion. This study takes advantage of advances in construction of high-resolution, high-capacity anion-exchange columns that can better tolerate the matrices typically encountered when a determination of total nitrogen and total phosphorous is required. Here, we used an electrolytically generated hydroxide eluent combined with a high-capacity, hydroxide-selective, anion-exchange column for the determination of total nitrogen (as nitrate-N) and total phosphorus (as phosphate-P) in environmental samples by IC. This method yielded LODs for nitrate-N and phosphate-P of 1.0 and 1.3 μg/L, respectively. The LOQs determined for these analytes were 3.4 and 4.2 μg/L, respectively. Due to the dilution factor required and the blank nitrate-N concentration after the persulfate digestion, the quantification limits increased for nitrate-N and phosphate-P to 171 and 63 μg/L, respectively. The suitability of the method was evaluated by determining the nitrogen and phosphorus concentrations from known concentrations of organic-containing nitrogen and phosphorus compounds. In addition, environmental samples consisting of six different wastewaters and 48 reservoir samples were evaluated for total nitrogen and phosphorus. The recoveries of nitrogen and phosphorus from the organic-containing compounds ranged from 93.1 to 100.1% and 85.2 to 97.1%, respectively. In addition, good correlation between results obtained by the colorimetric method and IC was also observed. The linearity, accuracy, and evaluation of potential interferences for determining TN and TP will be discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Crossed beam studies of ion-molecule reactions in methane and ammonia

NASA Technical Reports Server (NTRS)

Smith, G. P. K.; Saunders, M.; Cross, R. J., Jr.

1976-01-01

A crossed-beam apparatus is used to measure the product ion velocity and angular distributions for the following ion-molecule reactions in the relative energy range from 2 to 9 eV: CH4(+) + NH3 yields NH4(+) + CH3; CH4(+) + NH3 yields CNH5(+) + H2; NH2(+) + CH4 yields CNH4(+) + H2 (or 2H); and CH3(+) + NH3 yields CNH4(+) + H2 (or 2H). These reactions are also studied by means of deuterium labeling as a further probe of the detailed reaction dynamics. Probability contour plots for the four reactions are constructed in Cartesian velocity space, and product peaks in the plots are discussed. Relative cross sections and Q values are computed for two of the reactions as well as for the corresponding deuterium-labelled reactions. The results show that the present ion-neutral condensation reactions are highly exothermic with a deep well for the internal complex, that little hydrogen scrambling occurs, and that the energy of the reactions is released mainly as internal energy, even to the extent of producing two hydrogen atoms in some cases rather than one hydrogen atom or molecule.

Confined ion energy >200 keV and increased fusion yield in a DPF with monolithic tungsten electrodes and pre-ionization

NASA Astrophysics Data System (ADS)

Lerner, Eric J.; Hassan, Syed M.; Karamitsos, Ivana; Von Roessel, Fred

2017-10-01

To reduce impurities in the dense plasma focus FF-1 device, we used monolithic tungsten electrodes with pre-ionization. With this new set-up, we demonstrated a three-fold reduction of impurities by mass and a ten-fold reduction by ion number. FF-1 produced a 50% increase in fusion yield over our previous copper electrodes, both for a single shot and for a mean of ten consecutive shots with the same conditions. These results represent a doubling of fusion yield as compared with any other plasma focus device with the same 60 kJ energy input. In addition, FF-1 produced a new single-shot record of 240 ± 20 keV for mean ion energy, a record for any confined fusion plasma, using any device, and a 50% improvement in ten-shot mean ion energy. With a deuterium-nitrogen mix and corona-discharge pre-ionization, we were also able to reduce the standard deviation in the fusion yield to about 15%, a four-fold reduction over the copper-electrode results. We intend to further reduce impurities with new experiments using microwave treatment of tungsten electrodes, followed by the use of beryllium electrodes.

Ion radiation albedo effect: influence of surface roughness on ion implantation and sputtering of materials

NASA Astrophysics Data System (ADS)

Li, Yonggang; Yang, Yang; Short, Michael P.; Ding, Zejun; Zeng, Zhi; Li, Ju

2017-01-01

In fusion devices, ion retention and sputtering of materials are major concerns in the selection of compatible plasma-facing materials (PFMs), especially in the context of their microstructural conditions and surface morphologies. We demonstrate how surface roughness changes ion implantation and sputtering of materials under energetic ion irradiation. Using a new, sophisticated 3D Monte Carlo (MC) code, IM3D, and a random rough surface model, ion implantation and the sputtering yields of tungsten (W) with a surface roughness varying between 0-2 µm have been studied for irradiation by 0.1-1 keV D+, He+ and Ar+ ions. It is found that both ion backscattering and sputtering yields decrease with increasing roughness; this is hereafter called the ion radiation albedo effect. This effect is mainly dominated by the direct, line-of-sight deposition of a fraction of emitted atoms onto neighboring asperities. Backscattering and sputtering increase with more oblique irradiation angles. We propose a simple analytical formula to relate rough-surface and smooth-surface results.

Ratios of double to single ionization of He and Ne by strong 400-nm laser pulses using the quantitative rescattering theory

NASA Astrophysics Data System (ADS)

Chen, Zhangjin; Li, Xiaojin; Zatsarinny, Oleg; Bartschat, Klaus; Lin, C. D.

2018-01-01

We present numerical simulations of the ratio between double and single ionization of He and Ne by intense laser pulses at wavelengths of 390 and 400 nm, respectively. The yields of doubly charged ions due to nonsequential double ionization (NSDI) are obtained by employing the quantitative rescattering (QRS) model. In this model, the NSDI ionization probability is expressed as a product of the returning electron wave packet (RWP) and the total scattering cross sections for laser-free electron impact excitation and electron impact ionization of the parent ion. According to the QRS theory, the same RWP is also responsible for the emission of high-energy above-threshold ionization photoelectrons. To obtain absolute double-ionization yields, the RWP is generated by solving the time-dependent Schrödinger equation (TDSE) within a one-electron model. The same TDSE results can also be taken to obtain single-ionization yields. By using the TDSE results to calibrate single ionization and the RWP obtained from the strong-field approximation, we further simplify the calculation such that the nonuniform laser intensity distribution in the focused laser beam can be accounted for. In addition, laser-free electron impact excitation and ionization cross sections are calculated using the state-of-the-art many-electron R -matrix theory. The simulation results for double-to-single-ionization ratios are found to compare well with experimental data and support the validity of the nonsequential double-ionization mechanism for the covered intensity region.

Molecular dynamics and dynamic Monte-Carlo simulation of irradiation damage with focused ion beams

NASA Astrophysics Data System (ADS)

Ohya, Kaoru

2017-03-01

The focused ion beam (FIB) has become an important tool for micro- and nanostructuring of samples such as milling, deposition and imaging. However, this leads to damage of the surface on the nanometer scale from implanted projectile ions and recoiled material atoms. It is therefore important to investigate each kind of damage quantitatively. We present a dynamic Monte-Carlo (MC) simulation code to simulate the morphological and compositional changes of a multilayered sample under ion irradiation and a molecular dynamics (MD) simulation code to simulate dose-dependent changes in the backscattering-ion (BSI)/secondary-electron (SE) yields of a crystalline sample. Recent progress in the codes for research to simulate the surface morphology and Mo/Si layers intermixing in an EUV lithography mask irradiated with FIBs, and the crystalline orientation effect on BSI and SE yields relating to the channeling contrast in scanning ion microscopes, is also presented.

Magnetic field affects enzymatic ATP synthesis.

PubMed

Buchachenko, Anatoly L; Kuznetsov, Dmitry A

2008-10-01

The rate of ATP synthesis by creatine kinase extracted from V. xanthia venom was shown to depend on the magnetic field. The yield of ATP produced by enzymes with 24Mg2+ and 26Mg2+ ions in catalytic sites increases by 7-8% at 55 mT and then decreases at 80 mT. For enzyme with 25Mg2+ ion in a catalytic site, the ATP yield increases by 50% and 70% in the fields 55 and 80 mT, respectively. In the Earth field the rate of ATP synthesis by enzyme, in which Mg2+ ion has magnetic nucleus 25Mg, is 2.5 times higher than that by enzymes, in which Mg2+ ion has nonmagnetic, spinless nuclei 24Mg or 26Mg. Both magnetic field effect and magnetic isotope effect demonstrate that the ATP synthesis is an ion-radical process, affected by Zeeman interaction and hyperfine coupling in the intermediate ion-radical pair.

Ion induced electron emission statistics under Agm- cluster bombardment of Ag

NASA Astrophysics Data System (ADS)

Breuers, A.; Penning, R.; Wucher, A.

2018-05-01

The electron emission from a polycrystalline silver surface under bombardment with Agm- cluster ions (m = 1, 2, 3) is investigated in terms of ion induced kinetic excitation. The electron yield γ is determined directly by a current measurement method on the one hand and implicitly by the analysis of the electron emission statistics on the other hand. Successful measurements of the electron emission spectra ensure a deeper understanding of the ion induced kinetic electron emission process, with particular emphasis on the effect of the projectile cluster size to the yield as well as to emission statistics. The results allow a quantitative comparison to computer simulations performed for silver atoms and clusters impinging onto a silver surface.

Note on the artefacts in SRIM simulation of sputtering

NASA Astrophysics Data System (ADS)

Shulga, V. I.

2018-05-01

The computer simulation program SRIM, unlike other well-known programs (MARLOWE, TRIM.SP, etc.), predicts non-zero values of the sputter yield at glancing ion bombardment of smooth amorphous targets and, for heavy ions, greatly underestimates the sputter yield at normal incidence. To understand the reasons for this, the sputtering of amorphous silicon bombarded with different ions was modeled here using the author's program OKSANA. Most simulations refer to 1 keV Xe ions, and angles of incidence cover range from 0 (normal incidence) to almost 90°. It has been shown that SRIM improperly simulates the initial stage of the sputtering process. Some other artefacts in SRIM calculations of sputtering are also revealed and discussed.

Screening and identification of glyceollins and their metabolites by electrospray ionization tandem mass spectrometry with precursor ion scanning

USDA-ARS?s Scientific Manuscript database

A method has been developed for screening glyceollins and their metabolites based upon precursor ion scanning. Under higher-energy collision conditions, employing a triple quadrupole mass spectrometer in the negative ion mode, deprotonated glyceollin precursors yield a diagnostic radical product ion...

Determining the sputter yields of molybdenum in low-index crystal planes via electron backscattered diffraction, focused ion beam and atomic force microscope

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

Huang, H.S., E-mail: 160184@mail.csc.com.tw; Chiu, C.H.; Hong, I.T.

2013-09-15

Previous literature has used several monocrystalline sputtering targets with various crystalline planes, respectively, to investigate the variations of the sputter yield of materials in different crystalline orientations. This study presents a method to measure the sputtered yields of Mo for the three low-index planes (100), (110), and (111), through using an easily made polycrystalline target. The procedure was firstly to use electron backscattered diffraction to identify the grain positions of the three crystalline planes, and then use a focused ion beam to perform the micro-milling of each identified grain, and finally the sputter yields were calculated from the removed volumes,more » which were measured by atomic force microscope. Experimental results showed that the sputter yield of the primary orientations for Mo varied as Y{sub (110)} > Y{sub (100)} > Y{sub (111)}, coincidental with the ranking of their planar atomic packing densities. The concept of transparency of ion in the crystalline substance was applied to elucidate these results. In addition, the result of (110) orientation exhibiting higher sputter yield is helpful for us to develop a Mo target with a higher deposition rate for use in industry. By changing the deformation process from straight rolling to cross rolling, the (110) texture intensity of the Mo target was significantly improved, and thus enhanced the deposition rate. - Highlights: • We used EBSD, FIB and AFM to measure the sputter yields of Mo in low-index planes. • The sputter yield of the primary orientations for Mo varied as Y{sub (110)} > Y{sub (100)} > Y{sub (111)}. • The transparency of ion was used to elucidate the differences in the sputter yield. • We improved the sputter rate of polycrystalline Mo target by adjusting its texture.« less

Secondary electron emission characteristics of ion-textured copper and high-purity isotropic graphite surfaces

NASA Technical Reports Server (NTRS)

Curren, A. N.; Jensen, K. A.

1984-01-01

Experimentally determined values of true secondary electron emission and relative values of reflected primary electron yield for untreated and ion textured oxygen free high conductivity copper and untreated and ion textured high purity isotropic graphite surfaces are presented for a range of primary electron beam energies and beam impingement angles. This investigation was conducted to provide information that would improve the efficiency of multistage depressed collectors (MDC's) for microwave amplifier traveling wave tubes in space communications and aircraft applications. For high efficiency, MDC electrode surfaces must have low secondary electron emission characteristics. Although copper is a commonly used material for MDC electrodes, it exhibits relatively high levels of secondary electron emission if its surface is not treated for emission control. Recent studies demonstrated that high purity isotropic graphite is a promising material for MDC electrodes, particularly with ion textured surfaces. The materials were tested at primary electron beam energies of 200 to 2000 eV and at direct (0 deg) to near grazing (85 deg) beam impingement angles. True secondary electron emission and relative reflected primary electron yield characteristics of the ion textured surfaces were compared with each other and with those of untreated surfaces of the same materials. Both the untreated and ion textured graphite surfaces and the ion treated copper surface exhibited sharply reduced secondary electron emission characteristics relative to those of untreated copper. The ion treated graphite surface yielded the lowest emission levels.

Mutation Breeding of β-carotene Producing Strain B. trispora by Low Energy Ion Implantation

NASA Astrophysics Data System (ADS)

Zhang, Ning; Yu, Long

2009-02-01

Ion beam bioengineering technology as a new mutation approach has been widely used in the biological breeding field. In this paper the application of low energy nitrogen ion implantation in the β-carotene producing strain, Blakeslea trispora(-) was investigated. The effects of different fermentation conditions on β-carotene production by a high yield strain were examined. Results showed that two β-carotene high yielding strains B.trispora(-) BH3-701 and BH3-728 were screened out and the averaged production of β-carotene was raised by 178.7% and 164.6% respectively after five passages in the shaking flasks. Compared with the original strain, the highest yield strain BH3-701 was potent in accumulating β-carotene, especially in the later stage, and greatly increased production efficiency.

Spatially-Resolved Beam Current and Charge-State Distributions for the NEXT Ion Engine

NASA Technical Reports Server (NTRS)

Pollard, James E.; Diamant, Kevin D.; Crofton, Mark W.; Patterson, Michael J.; Soulas, George C.

2010-01-01

Plume characterization tests with the 36-cm NEXT ion engine are being performed at The Aerospace Corporation using engineering-model and prototype-model thrusters. We have examined the beam current density and xenon charge-state distribution as functions of position on the accel grid. To measure the current density ratio j++/j+, a collimated Eprobe was rotated through the plume with the probe oriented normal to the accel electrode surface at a distance of 82 cm. The beam current density jb versus radial position was measured with a miniature planar probe at 3 cm from the accel. Combining the j++/j+ and jb data yielded the ratio of total Xe+2 current to total Xe+1 current (J++/J+) at forty operating points in the standard throttle table. The production of Xe+2 and Xe+3 was measured as a function of propellant utilization to support performance and lifetime predictions for an extended throttle table. The angular dependence of jb was measured at intermediate and far-field distances to assist with plume modeling and to evaluate the thrust loss due to beam divergence. Thrust correction factors were derived from the total doubles-to-singles current ratio and from the far-field divergence data

Fast ion transport at a gas-metal interface

DOE PAGES

McDevitt, Christopher J.; Tang, Xian-Zhu; Guo, Zehua

2017-11-06

Fast ion transport and the resulting fusion yield reduction are computed at a gas-metal interface. The extent of fusion yield reduction is observed to depend sensitively on the charge state of the surrounding pusher material and the width of the atomically mixed region. These sensitivities suggest that idealized boundary conditions often implemented at the gas-pusher interface for the purpose of estimating fast ion loss will likely overestimate fusion reactivity reduction in several important limits. Additionally, the impact of a spatially complex material interface is investigated by considering a collection of droplets of the pusher material immersed in a DT plasma.more » It is found that for small Knudsen numbers, the extent of fusion yield reduction scales with the surface area of the material interface. As the Knudsen number is increased, but, the simple surface area scaling is broken, suggesting that hydrodynamic mix has a nontrivial impact on the extent of fast ion losses.« less

[Low-temperature response and cold tolerance at spike differentiation stage of winter wheat varieties sowed in spring].

PubMed

Xu, Lan; Gao, Zhi-fiang; An, Wei; Yuan, Ya-qi; Li, Yan-liang

2015-06-01

A total of 10 winter wheat varieties were imported from the middle and lower reaches of the Yangtze River region in China. Those varieties were sowed in spring in Xinding basin area of Shanxi Province, and the field trials were performed for two years (2013-2014). The traits and physiological characteristics under low temperature stress including grain yield, total content of chlorophyll, osmotic adjustment, membrane system, ion leakage rate, contents of soluble sugar and soluble protein were investigated, and the cold tolerance levels of the wheat varieties were assessed. The results showed that low temperature stress led to increases in wheat leaf ion leakage rate, soluble sugar and protein contents, but obvious reduction of chlorophyll content. According to principal component analysis and cold tolerance (D value) , Yumai 10, Yangmai 20, and Yunmai 42 were classed as cold sensitive wheat varieties. Yangmai 13, Yumai 12, and Ningmai 13 were classed as stronger cold-resistant wheat genotypes, and showed stability through two-year field trials, with the D values being 0.665-0.659, 0.493-0.495, and 0.471-0.583, respectively, while the D values for the controls Ning 2038 and Xinchun 30 were 0.368-0.397, and 0.328-0.330, respectively. The grain yields of the cold resistant wheat varieties were significantly higher than that of the other varieties tested. Therefore, Yangmai 13, Yumai 12 and Ningmai 13 could be imported and used as the cold tolerant wheat varieties for North Plain of China.

Study and optimisation of SIMS performed with He+ and Ne+ bombardment

NASA Astrophysics Data System (ADS)

Pillatsch, L.; Vanhove, N.; Dowsett, D.; Sijbrandij, S.; Notte, J.; Wirtz, T.

2013-10-01

The combination of the high-brightness He+/Ne+ atomic level ion source with the detection capabilities of secondary ion mass spectrometry (SIMS) opens up the prospect of obtaining chemical information with high lateral resolution and high sensitivity on the Zeiss ORION helium ion microscope (HIM). A feasibility study with He+ and Ne+ ion bombardment is presented in order to determine the performance of SIMS analyses using the HIM. Therefore, the sputtering yields, useful yields and detection limits obtained for metallic (Al, Ni and W) as well as semiconductor samples (Si, Ge, GaAs and InP) were investigated. All the experiments were performed on a Cameca IMS4f SIMS instrument which was equipped with a caesium evaporator and oxygen flooding system. For most of the elements, useful yields in the range of 10-4 to 3 × 10-2 were measured with either O2 or Cs flooding. SIMS experiments performed directly on the ORION with a prototype secondary ion extraction and detection system lead to results that are consistent with those obtained on the IMS4f. Taking into account the obtained useful yields and the analytical conditions, such as the ion current and typical dwell time on the ORION HIM, detection limits in the at% range and better can be obtained during SIMS imaging at 10 nm lateral resolution with Ne+ bombardment and down to the ppm level when a lateral resolution of 100 nm is chosen. Performing SIMS on the HIM with a good detection limit while maintaining an excellent lateral resolution (<50 nm) is therefore very promising.

Analysis of photon emission induced by light and heavy ions in time-of-flight medium energy ion scattering

NASA Astrophysics Data System (ADS)

Lohmann, S.; Sortica, M. A.; Paneta, V.; Primetzhofer, D.

2018-02-01

We present a systematic analysis of the photon emission observed due to impact of pulsed keV ion beams in time-of-flight medium energy ion scattering (ToF-MEIS) experiments. Hereby, hydrogen, helium and neon ions served as projectiles and thin gold and titanium nitride films on different substrates were employed as target materials. The present experimental evidence indicates that a significant fraction of the photons has energies of around 10 eV, i.e. on the order of typical valence and conduction band transitions in solids. Furthermore, the scaling properties of the photon emission with respect to several experimental parameters were studied. A dependence of the photon yield on the projectile velocity was observed in all experiments. The photon yield exhibits a dependence on the film thickness and the scattering angle, which can be explained by photon production along the path of the incident ion through the material. Additionally, a strong dependence on the projectile type was found with the photon emission being higher for heavier projectiles. This difference is larger than the respective difference in electronic stopping cross section. The photon yield shows a strong material dependence, and according to a comparison of SiO2 and Si seems to be subject to matrix effects.

A Permanent-Magnet Microwave Ion Source For A Compact High-Yield Neutron Generator

NASA Astrophysics Data System (ADS)

Waldmann, O.; Ludewigt, B.

2011-06-01

We present recent work on the development of a microwave ion source that will be used in a high-yield compact neutron generator for active interrogation applications. The sealed tube generator will be capable of producing high neutron yields, 5×1011 n/s for D-T and ˜1×1010 n/s for D-D reactions, while remaining transportable. We constructed a microwave ion source (2.45 GHz) with permanent magnets to provide the magnetic field strength of 87.5 mT necessary for satisfying the electron cyclotron resonance (ECR) condition. Microwave ion sources can produce high extracted beam currents at the low gas pressures required for sealed tube operation and at lower power levels than previously used RF-driven ion sources. A 100 mA deuterium/tritium beam will be extracted through a large slit (60×6 mm2) to spread the beam power over a larger target area. This paper describes the design of the permanent-magnet microwave ion source and discusses the impact of the magnetic field design on the source performance. The required equivalent proton beam current density of 40 mA/cm2 was extracted at a moderate microwave power of 400 W with an optimized magnetic field.

Laboratory Studies in UV and EUV Solar Physics

NASA Technical Reports Server (NTRS)

Parkinson, William

2003-01-01

The Ion Beam Experiment at the Center for Astrophysics is dedicated to the study of ion-electron collision processes of importance in solar physics. A paper describing our most recent measurement 'Absolute cross section for Si(2+)(3s3p(sup 3)Rho (sup 0) yields 3s3p(sup 1)Rho(sup 0)) electron-impact excitation' was published during the past year. Dr. Paul Janzen received his PhD. from the Harvard Physics Department on the basis of this and other work, such as the new electron cyclotron resonance (ECR) ion source. The ion source is producing stable beams with large currents for our present work on C(2+), and it also produces stable beams with large currents of more highly charged systems, for future work on systems such as O(4+). The past year has been focussed on our current program to measure absolute cross sections for Electron Impact Excitation (EIE) in C(2+), one of the primary ions used for probing the solar transition region. C(2+) beams produced by the ion source have been transported to the interaction region of the experiment, where the collisions are studied, and Visiting Scientist Dr. Adrian Daw is currently collecting data to measure the C(2+)(2s2p(sup 3)Rho(sup 0) yields 2p(sup 2)(sup 3)Rho) EIE cross section as a function of collision energy, under the guidance of Drs. John Kohl, Larry Gardner and Bill Parkinson. Also this year, modifications were made to the ECR ion source in order to produce greater currents of highly charged ions. Testing of the ion source was completed. Modifications were designed to extend the photon detection capabilities of the apparatus to shorter UV wavelengths, or EUV. Following the work on C(2+)(2s2p(sup 3)Pho(sup 0) yields 2p(sup 2)(sup 3)Rho), the extended UV detection capabilities will be used to measure the C(2+)(2s(sup 2)(sup 1)S yields 2s2p(sup 1)Rho(sup 0)) EIE cross section. The EUV modifications complement those of the new ion source, by enabling detection of EUV light generated by high charge state ions and putting us in a position to measure the excitation cross sections for more highly charged ions as well.

Investigation of argon ion sputtering on the secondary electron emission from gold samples

NASA Astrophysics Data System (ADS)

Yang, Jing; Cui, Wanzhao; Li, Yun; Xie, Guibai; Zhang, Na; Wang, Rui; Hu, Tiancun; Zhang, Hongtai

2016-09-01

Secondary electron (SE) yield, δ, is a very sensitive surface property. The values of δ often are not consistent for even identical materials. The influence of surface changes on the SE yield was investigated experimentally in this article. Argon ion sputtering was used to remove the contamination from the surface. Surface composition was monitored by X-ray photoelectron spectroscopy (XPS) and surface topography was scanned by scanning electron microscope (SEM) and atomic force microscope (AFM) before and after every sputtering. It was found that argon sputtering can remove contamination and roughen the surface. An ;equivalent work function; is presented in this thesis to establish the relationship between SE yield and surface properties. Argon ion sputtering of 1.5keV leads to a significant increase of so called ;work function; (from 3.7 eV to 6.0 eV), and a decrease of SE yield (from 2.01 to 1.54). These results provided a new insight into the influence of surface changes on the SE emission.

Transportation Research News | Transportation News | Transportation

Science.gov Websites

Engineering has yielded new insights for lithium-ion (Li-ion) battery electrodes at the microstructural level -Phase Stochastics in Lithium-Ion Battery Electrodes" detailing the research and resulting revolutionizes the way lithium-ion (Li-ion) batteries are evaluated so designs can be improved before batteries

Static time-of-flight secondary ion mass spectrometry analysis of microelectronics related substrates using a polyatomic ion source

NASA Astrophysics Data System (ADS)

Ravanel, X.; Trouiller, C.; Juhel, M.; Wyon, C.; Kwakman, L. F. Tz.; Léonard, D.

2008-12-01

Recent time-of-flight secondary ion mass spectrometry studies using primary ion cluster sources such as Au n+, SF 5+, Bi n+ or C 60+ have shown the great advantages in terms of secondary ion yield enhancement and ion formation efficiency of polyatomic ion sources as compared to monoatomic ion sources like the commonly used Ga +. In this work, the effective gains provided by such a source in the static ToF-SIMS analysis of microelectronics devices were investigated. Firstly, the influence of the number of atoms in the primary cluster ion on secondary ion formation was studied for physically adsorbed di-isononyl phthalate (DNP) (plasticizer) and perfluoropolyether (PFPE). A drastic increase in secondary ion formation efficiency and a much lower detection limit were observed when using a polyatomic primary ion. Moreover, the yield of the higher mass species was much enhanced indicating a lower degree of fragmentation that can be explained by the fact that the primary ion energy is spread out more widely, or that there is a lower energy per incoming ion. Secondly, the influence of the number of Bi atoms in the Bi n primary ion on the information depth was studied using reference thermally grown silicon oxide samples. The information depth provided by a Bi n cluster was shown to be lowered when the number of atoms in the aggregate was increased.

Investigation of ion kinetic effects in direct-drive exploding-pusher implosions at the NIF

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

Rosenberg, M. J., E-mail: mrosenbe@mit.edu; Zylstra, A. B.; Séguin, F. H.

Measurements of yield, ion temperature, areal density (ρR), shell convergence, and bang time have been obtained in shock-driven, D{sub 2} and D{sup 3}He gas-filled “exploding-pusher” inertial confinement fusion (ICF) implosions at the National Ignition Facility to assess the impact of ion kinetic effects. These measurements probed the shock convergence phase of ICF implosions, a critical stage in hot-spot ignition experiments. The data complement previous studies of kinetic effects in shock-driven implosions. Ion temperature and fuel ρR inferred from fusion-product spectroscopy are used to estimate the ion-ion mean free path in the gas. A trend of decreasing yields relative to themore » predictions of 2D DRACO hydrodynamics simulations with increasing Knudsen number (the ratio of ion-ion mean free path to minimum shell radius) suggests that ion kinetic effects are increasingly impacting the hot fuel region, in general agreement with previous results. The long mean free path conditions giving rise to ion kinetic effects in the gas are often prevalent during the shock phase of both exploding pushers and ablatively driven implosions, including ignition-relevant implosions.« less

DNA damage on nano- and micrometer scales impacts dicentric induction: computer modelling of ion microbeam experiments

NASA Astrophysics Data System (ADS)

Friedland, Werner; Kundrat, Pavel; Schmitt, Elke

2016-07-01

Detailed understanding of the enhanced relative biological effectiveness (RBE) of ions, in particular at high linear energy transfer (LET) values, is needed to fully explore the radiation risk of manned space missions. It is generally accepted that the enhanced RBE of high-LET particles results from the DNA lesion patterns, in particular DNA double-strand breaks (DSB), due to the spatial clustering of energy deposits around their trajectories. In conventional experiments on biological effects of radiation types of diverse quality, however, clustering of energy deposition events on nanometer scale that is relevant for the induction and local complexity of DSB is inherently interlinked with regional (sub-)micrometer-scale DSB clustering along the particle tracks. Due to this limitation, the role of both (nano- and micrometer) scales on the induction of diverse biological endpoints cannot be frankly separated. To address this issue in a unique way, experiments at the ion microbeam SNAKE [1] and corresponding track-structure based model calculations of DSB induction and subsequent repair with the biophysical code PARTRAC [2] have been performed. In the experiments, hybrid human-hamster A_{L} cells were irradiated with 20 MeV (2.6 keV/μm) protons, 45 MeV (60 keV/μm) lithium ions or 55 MeV (310 keV/μm) carbon ions. The ions were either quasi-homogeneously distributed or focused to 0.5 x 1 μm^{2} spots on regular matrix patterns of 5.4 μm, 7.6 μm and 10.6 μm grid size, with pre-defined particle numbers per spot so as to deposit a mean dose of 1.7 Gy for all irradiation patterns. As expected, the induction of dicentrics by homogeneous irradiation increased with LET: lithium and carbon ions induced about two- and four-fold higher yields of dicentrics than protons. The induction of dicentrics is, however, affected by µm-scale, too: focusing 20 lithium ions or 451 protons per spot on a 10.6 μm grid induced two or three times more dicentrics, respectively, than a quasi-homogenous irradiation with these particles [3]. PARTRAC calculations of initial DNA damage showed that the sub-micrometer beam focusing of the ions in these experiments affects neither DSB yields nor local DSB complexity, but considerably enhances the formation of DSB fragments of 10 - 1000 kbp size [4], corresponding to DSB pairs in about 100 - 500 nm distance. Thus, the substantial impact of ion focusing on dicentric induction points out that nanoscale DNA damage clustering can explain only partly the increased RBE of high LET radiation regarding dicentric induction. The measured trends for dicentric induction as a function of grid size (or particle number per spot) were largely reproduced by the calculated induction of total chromosomal aberrations, whereas the calculation of dicentrics yielded apparent discrepancies, such as an overestimation of the focusing effect for protons and of the yield for quasi-homogeneous lithium ions [3]. Since this incongruity was found to be rather robust against model parameter variations, a more basic review of the chromosomal aberration model with in-depth testing of several hypotheses on the origin of misrejoining events of DNA ends has been started considering the reported experimental findings. The results of ongoing parameter studies will be presented at the meeting. Acknowledgement. This work was supported by the German Federal Ministry of Education and Research (Project 'LET-Verbund', Funding no. 02NUK031C). References [1] Schmid et al. 2012 Phys. Med. Biol. 57, 5889-5907 [2] Friedland et al. 2011 Mutat. Res. 711, 28-40 [3] Schmid et al. 2015 Mutat. Res. 793, 30-40 [4] Friedland et al. 2015 Radiat. Prot. Dosim. 166, 34-37

Evolution of L -shell photoabsorption of the molecular-ion series Si Hn + (n =1 ,2 ,3 ): Experimental and theoretical studies

NASA Astrophysics Data System (ADS)

Kennedy, E. T.; Mosnier, J.-P.; van Kampen, P.; Bizau, J.-M.; Cubaynes, D.; Guilbaud, S.; Carniato, S.; Puglisi, A.; Sisourat, N.

2018-04-01

We report on complementary laboratory and theoretical investigations of the 2 p photoexcitation cross sections for the molecular-ion series Si Hn + (n =1 ,2 ,3 ) near the L -shell threshold. The experiments used an electron cyclotron resonance (ECR) plasma molecular-ion source coupled with monochromatized synchrotron radiation in a merged-beam configuration. For all three molecular ions, the S i2 + decay channel appeared dominant, suggesting similar electronic and nuclear relaxation patterns involving resonant Auger and dissociation processes, respectively. The total yields of the S i2 + products were recorded and put on absolute cross-section scales by comparison with the spectrum of the S i+ parent atomic ion. Interpretation of the experimental spectra ensued from a comparison with total photoabsorption cross-sectional profiles calculated using ab initio configuration interaction theoretical methods inclusive of vibrational dynamics and contributions from inner-shell excitations in both ground and valence-excited electronic states. The spectra, while broadly similar for all three molecular ions, moved towards lower energies as the number of screening hydrogen atoms increased from one to three. They featured a wide and shallow region below ˜107 eV due to 2 p →σ* transitions to dissociative states, and intense and broadened peaks in the ˜107 -113 -eV region merging into sharp Rydberg series due to 2 p →n δ ,n π transitions converging on the LII ,III limits above ˜113 eV . This overall spectral shape is broadly replicated by theory in each case, but the level of agreement does not extend to individual resonance structures. In addition to the fundamental interest, the work should also prove useful for the understanding and modeling of astronomical and laboratory plasma sources where silicon hydride molecular species play significant roles.

Distributions of neutron yields and doses around a water phantom bombarded with 290-MeV/nucleon and 430-MeV/nucleon carbon ions

NASA Astrophysics Data System (ADS)

Satoh, D.; Kajimoto, T.; Shigyo, N.; Itashiki, Y.; Imabayashi, Y.; Koba, Y.; Matsufuji, N.; Sanami, T.; Nakao, N.; Uozumi, Y.

2016-11-01

Double-differential neutron yields from a water phantom bombarded with 290-MeV/nucleon and 430-MeV/nucleon carbon ions were measured at emission angles of 15°, 30°, 45°, 60°, 75°, and 90°, and angular distributions of neutron yields and doses around the phantom were obtained. The experimental data were compared with results of the Monte-Carlo simulation code PHITS. The PHITS results showed good agreement with the measured data. On the basis of the PHITS simulation, we estimated the angular distributions of neutron yields and doses from 0° to 180° including thermal neutrons.

Helium ion beam induced electron emission from insulating silicon nitride films under charging conditions

NASA Astrophysics Data System (ADS)

Petrov, Yu. V.; Anikeva, A. E.; Vyvenko, O. F.

2018-06-01

Secondary electron emission from thin silicon nitride films of different thicknesses on silicon excited by helium ions with energies from 15 to 35 keV was investigated in the helium ion microscope. Secondary electron yield measured with Everhart-Thornley detector decreased with the irradiation time because of the charging of insulating films tending to zero or reaching a non-zero value for relatively thick or thin films, respectively. The finiteness of secondary electron yield value, which was found to be proportional to electronic energy losses of the helium ion in silicon substrate, can be explained by the electron emission excited from the substrate by the helium ions. The method of measurement of secondary electron energy distribution from insulators was suggested, and secondary electron energy distribution from silicon nitride was obtained.

High Power, High Energy Density Lithium-Ion Batteries

DTIC Science & Technology

2010-11-29

cells and to provide affordable Lithium - Ion battery packs for the combat and tactical vehicle systems. - To address the manufacturing processes that will...reduce cost of lithium - ion battery packs by one half through the improvement of manufacturing process to enhance production consistency and increase the production yield of high power lithium-ion cells.

Dynamics of nanoparticle morphology under low energy ion irradiation.

PubMed

Holland-Moritz, Henry; Graupner, Julia; Möller, Wolfhard; Pacholski, Claudia; Ronning, Carsten

2018-08-03

If nanostructures are irradiated with energetic ions, the mechanism of sputtering becomes important when the ion range matches about the size of the nanoparticle. Gold nanoparticles with diameters of ∼50 nm on top of silicon substrates with a native oxide layer were irradiated by gallium ions with energies ranging from 1 to 30 keV in a focused ion beam system. High resolution in situ scanning electron microscopy imaging permits detailed insights in the dynamics of the morphology change and sputter yield. Compared to bulk-like structures or thin films, a pronounced shaping and enhanced sputtering in the nanostructures occurs, which enables a specific shaping of these structures using ion beams. This effect depends on the ratio of nanoparticle size and ion energy. In the investigated energy regime, the sputter yield increases at increasing ion energy and shows a distinct dependence on the nanoparticle size. The experimental findings are directly compared to Monte Carlo simulations obtained from iradina and TRI3DYN, where the latter takes into account dynamic morphological and compositional changes of the target.

Higher biomolecules yield in phytoplankton under copper exposure.

PubMed

Silva, Jaqueline Carmo; Echeveste, Pedro; Lombardi, Ana Teresa

2018-05-30

Copper is an important metal for industry, and its toxic threshold in natural ecosystems has increased since the industrial revolution. As an essential nutrient, it is required in minute amounts, being toxic in slightly increased concentrations, causing great biochemical transformation in microalgae. This study aimed at investigating the physiology of Scenedesmus quadricauda, a cosmopolitan species, exposed to copper concentrations including those that trigger intracellular biochemical modifications. The Cu exposure concentrations tested ranged from 0.1 to 25 µM, thus including environmentally important levels. Microalgae cultures were kept under controlled environmental conditions and monitored daily for cell density, in vivo chlorophyll a, and photosynthetic quantum yield (Φ M ). After 24 h growth, free Cu 2+ ions were determined, and after 96 h, cellular Cu concentration, total carbohydrates, proteins, lipids, and cell volume were determined. The results showed that both free Cu 2+ ions and cellular Cu increased with Cu increase in culture medium. Microalgae cell abundance and in vivo chlorophyll a were mostly affected at 2.5 µM Cu exposure (3.8 pg Cu cell -1 ) and above. Approximately 31% decrease of photosynthetic quantum yield was obtained at the highest Cu exposure concentration (25 µM; 25 pg Cu cell -1 ) in comparison with the control. However, at environmentally relevant copper concentrations (0.5 µM Cu; 0.4 pg Cu cell -1 ) cell volume increased in comparison with the control. Considering biomolecules accumulation per unit cell volume, the highest carbohydrates and proteins yield was obtained at 1.0 µM Cu (1.1 pg Cu cell -1 ), while for lipids higher Cu was necessary (2.5 µM Cu; 3.8 pg Cu cell -1 ). This study is a contribution to the understanding of the effects of environmentally significant copper concentrations in the physiology of S. quadricauda, as well as to biotechnological approach to increase biomolecule yield in microalgae production. Copyright © 2018 Elsevier Inc. All rights reserved.

Extreme ultraviolet photoionization of aldoses and ketoses

NASA Astrophysics Data System (ADS)

Shin, Joong-Won; Dong, Feng; Grisham, Michael E.; Rocca, Jorge J.; Bernstein, Elliot R.

2011-04-01

Gas phase monosaccharides (2-deoxyribose, ribose, arabinose, xylose, lyxose, glucose galactose, fructose, and tagatose), generated by laser desorption of solid sample pellets, are ionized with extreme ultraviolet photons (EUV, 46.9 nm, 26.44 eV). The resulting fragment ions are analyzed using a time of flight mass spectrometer. All aldoses yield identical fragment ions regardless of size, and ketoses, while also generating same ions as aldoses, yields additional features. Extensive fragmentation of the monosaccharides is the result the EUV photons ionizing various inner valence orbitals. The observed fragmentation patterns are not dependent upon hydrogen bonding structure or OH group orientation.

Single-crystal and polycrystalline diamond erosion studies in Pilot-PSI

NASA Astrophysics Data System (ADS)

Kogut, D.; Aussems, D.; Ning, N.; Bystrov, K.; Gicquel, A.; Achard, J.; Brinza, O.; Addab, Y.; Martin, C.; Pardanaud, C.; Khrapak, S.; Cartry, G.

2018-03-01

Diamond is a promising candidate for enhancing the negative-ion surface production in the ion sources for neutral injection in fusion reactors; hence evaluation of its reactivity towards hydrogen plasma is of high importance. Single crystal and polycrystalline diamond samples were exposed in Pilot-PSI with the D+ flux of (4‒7)·1024 m-2s-1 and the impact energy of 7-9 eV per deuteron at different surface temperatures; under such conditions physical sputtering is negligible, however chemical sputtering is important. Net chemical sputtering yield Y = 9.7·10-3 at/ion at 800 °C was precisely measured ex-situ using a protective platinum mask (5 × 10 × 2 μm) deposited beforehand on a single crystal followed by the post-mortem analysis using Transmission Electron Microscopy (TEM). The structural properties of the exposed diamond surface were analyzed by Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). Gross chemical sputtering yields were determined in-situ by means of optical emission spectroscopy of the molecular CH A-X band for several surface temperatures. A bell-shaped dependence of the erosion yield versus temperature between 400 °C and 1200 °C was observed, with a maximum yield of ∼1.5·10-2 at/ion attained at 900 °C. The yields obtained for diamond are relatively high (0.5-1.5)·10-2 at/ion, comparable with those of graphite. XPS analysis shows amorphization of diamond surface within 1 nm depth, in a good agreement with molecular dynamics (MD) simulation. MD was also applied to study the hydrogen impact energy threshold for erosion of [100] diamond surface at different temperatures.

A Closer Look at Solar Wind Sputtering of Lunar Surface Materials

NASA Technical Reports Server (NTRS)

Barghouty, A. F.; Adams, J. H., Jr.; Meyer, F.; Mansur, L.; Reinhold, C.

2008-01-01

Solar-wind induced potential sputtering of the lunar surface may be a more efficient erosive mechanism than the "standard" kinetic (or physical) sputtering. This is partly based on new but limited laboratory measurements which show marked enhancements in the sputter yields of slow-moving, highly-charged ions impacting oxides. The enhancements seen in the laboratory can be orders of magnitude for some surfaces and highly charged incident ions, but seem to depend very sensitively on the properties of the impacted surface in addition to the fluence, energy and charge of the impacting ion. For oxides, potential sputtering yields are markedly enhanced and sputtered species, especially hydrogen and light ions, show marked dependence on both charge and dose.

Effects of molten-salt/ionic-liquid mixture on extraction of docosahexaenoic acid (DHA)-rich lipids from Aurantiochytrium sp. KRS101.

PubMed

Choi, Sun-A; Jung, Joo-Young; Kim, Kyochan; Kwon, Jong-Hee; Lee, Jin-Suk; Kim, Seung Wook; Park, Ji-Yeon; Yang, Ji-Won

2014-11-01

In this study, lipid extraction from Aurantiochytrium sp. was performed using a molten-salt/ionic-liquid mixture. The total fatty acid content of Aurantiochytrium sp. was 478.8 mg/g cell, from which 145 mg/g cell (30.3% of total fatty acids) of docosahexaenoic acid (DHA) was obtained. FeCl3·6H2O showed a high lipid extraction yield (207.9 mg/g cell), when compared with that of [Emim]OAc, which was only 118.1 mg/g cell; notably however, when FeCl3·6H2O was mixed with [Emim]OAc (5:1, w/w), the yield was increased to 478.6 mg/g cell. When lipid was extracted by the FeCl3·6H2O/[Emim]OAc mixture at a 5:1 (w/w) blending ratio under 90 °C, 30 min reaction conditions, the fatty acid content of the extracted lipid was a high purity 997.7 mg/g lipid, with most of the DHA having been extracted (30.2% of total fatty acids). Overall, lipid extraction from Aurantiochytrium sp. was enhanced by the synergistic effects of the molten-salt/ionic-liquid mixture with different ions.

Changes in the physiological properties and kinetics of citric acid accumulation via carbon ion irradiation mutagenesis of Aspergillus niger *

PubMed Central

Hu, Wei; Chen, Ji-hong; Wang, Shu-yang; Liu, Jing; Song, Yuan; Wu, Qing-feng; Li, Wen-jian

2016-01-01

The objective of this work was to produce citric acid from corn starch using a newly isolated mutant of Aspergillus niger, and to analyze the relationship between changes in the physiological properties of A. niger induced by carbon ion irradiation and citric acid accumulation. Our results showed that the physiological characteristics of conidia in A. niger were closely related to citric acid accumulation and that lower growth rate and viability of conidia may be beneficial to citric acid accumulation. Using corn starch as a raw material, a high-yielding citric acid mutant, named HW2, was obtained. In a 10-L bioreactor, HW2 can accumulate 118.9 g/L citric acid with a residual total sugar concentration of only 14.4 g/L. This represented an 18% increase in citric acid accumulation and a 12.5% decrease in sugar utilization compared with the original strain.

Molecular dynamics simulations with electronic stopping can reproduce experimental sputtering yields of metals impacted by large cluster ions

NASA Astrophysics Data System (ADS)

Tian, Jiting; Zhou, Wei; Feng, Qijie; Zheng, Jian

2018-03-01

An unsolved problem in research of sputtering from metals induced by energetic large cluster ions is that molecular dynamics (MD) simulations often produce sputtering yields much higher than experimental results. Different from the previous simulations considering only elastic atomic interactions (nuclear stopping), here we incorporate inelastic electrons-atoms interactions (electronic stopping, ES) into MD simulations using a friction model. In this way we have simulated continuous 45° impacts of 10-20 keV C60 on a Ag(111) surface, and found that the calculated sputtering yields can be very close to the experimental results when the model parameter is appropriately assigned. Conversely, when we ignore the effect of ES, the yields are much higher, just like the previous studies. We further expand our research to the sputtering of Au induced by continuous keV C60 or Ar100 bombardments, and obtain quite similar results. Our study indicates that the gap between the experimental and the simulated sputtering yields is probably induced by the ignorance of ES in the simulations, and that a careful treatment of this issue is important for simulations of cluster-ion-induced sputtering, especially for those aiming to compare with experiments.

Improvement of Vitamin K2 Production by Escherichia sp. with Nitrogen Ion Beam Implantation Induction

NASA Astrophysics Data System (ADS)

Liu, Yan; Wang, Li; Zheng, Zhiming; Wang, Peng; Zhao, Genhai; Liu, Hui; Gong, Guohong; Wu, Hefang; Liu, Hongxia; Tan, Mu; Li, Zhemin

2015-02-01

Low-energy ion implantation as a novel mutagen has been increasingly applied in the microbial mutagenesis for its higher mutation frequency and wider mutation spectra. In this work, N+ ion beam implantation was used to enhance Escherichia sp. in vitamin K2 yield. Optimization of process parameters under submerged fermentation was carried out to improve the vitamin K2 yield of mutant FM5-632. The results indicate that an excellent mutant FM5-632 with a yield of 123.2±1.6 μg/L, that is four times that of the original strain, was achieved by eight successive implantations under the conditions of 15 keV and 60×2.6×1013 ions/cm2. A further optimization increased the yield of the mutant by 39.7%, i.e. 172.1±1.2 μg/L which occurred in the mutant cultivated in the optimal fermentation culture medium composed of (per liter): 15.31 g glycerol, 10 g peptone, 2.89 g yeast extract, 5 g K2HPO4, 1 g NaCl, 0.5 g MgSO4·7H2O and 0.04 g cedar wood oil, incubated at 33 °C, pH 7.0 and 180 rpm for 120 h.

Selectivity of peptide bond dissociation on excitation of a core electron: Effects of a phenyl group

NASA Astrophysics Data System (ADS)

Tsai, Cheng-Cheng; Chen, Jien-Lian; Hu, Wei-Ping; Lin, Yi-Shiue; Lin, Huei-Ru; Lee, Tsai-Yun; Lee, Yuan T.; Ni, Chi-Kung; Liu, Chen-Lin

2016-09-01

The selective dissociation of a peptide bond upon excitation of a core electron in acetanilide and N-benzylacetamide was investigated. The total-ion-yield near-edge X-ray absorption fine structure spectra were recorded and compared with the predictions from time-dependent density functional theory. The branching ratios for the dissociation of a peptide bond are observed as 16-34% which is quite significant. This study explores the core-excitation, the X-ray photodissociation pathways, and the theoretical explanation of the NEXAFS spectra of organic molecules containing both a peptide bond and a phenyl group.

Low-energy ion-backscattering spectroscopies applied to the determination of surface structure

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

Yarmoff, J.A.

1985-01-01

Low-Energy Ion Scattering (LEIS) was investigated as a means for determining the geometric structure at a single-crystal surface. A three-dimensional Monte-Carlo computer simulation was developed and applied to existing LEIS data. The binary collision approximation was found to yield satisfactory results in simulating Buck's time-of-flight energy spectra for 2.4 keV Ne/sup +/ scattering from Ni(001). A two-atom-layer model was used in calculations of the azimuthal anisotropy of the ion yield measured by Bernheim and Slodzian for 9.5 keV Ne/sup +/ scattering from Cu(001). The calculations were successful in reproducing most of the features that had been observed in the experiments,more » which shows that this model contained most of the physics required to interpret the data. An apparatus for performing LEIS studies was built, and Low-Energy Ion-Backscattering Angular Distributions (LEIBAD) were collected with 3-20 keV /sup 6/Li/sup +/ incident on Cu(001). For incidence along a low-index Miller axis of the crystal, shadowing effects limited the penetration depth of the elastically scattered ions. However, neutralized Li atoms, which were not filtered out of the scattered yield by the high-pass filter, provided a background characteristic of the bulk. A high-resolution electrostatic analyzer was used to collect impact Collision Ion Scattering Spectroscopy (ICISS) data for 5-keV /sup 6/Li/sup +/ ions to study the Cu(110) and Cu(110) (2 x 1)-0 surfaces.« less

Novel model of negative secondary ion formation and its use to refine the electronegativity of almost fifty elements.

PubMed

Wittmaack, Klaus

2014-06-17

This study aimed to examine the recently proposed idea that the ionic contribution to atomic bonds is essential in determining the charge state of sputtered atoms. Use was made of negative secondary ion yields reported by Wilson for a large number of elements implanted in silicon and then sputter profiled by Cs bombardment. The derived normalized ion yields (or fractions) P vary by 6 orders of magnitude, but the expected exponential dependence on the electron affinity EA is evident only vaguely. Remarkably, a correlation of similar quality is observed if the data are presented as a function of the ionization potential IP. With IP being the dominant (if not sole) contributor to the electronegativity χ, one is led to assume that P depends on the sum χ + EA. About 72% of the "nonsaturated" ion yields are in accordance with a dependence of the form P ∝ exp[(χ + EA)/ε], with ε ≅ 0.2 eV, provided the appropriate value of χ is selected from the electronegativity tables of Pauling (read in eV), Mulliken or Allen. However, each of the three sources contributes only about one-third to the favorable electronegativity data. This unsatisfactory situation initiated the idea to derive the "true" electronegativity χSIMS from the measured ion yields P(χ + EA), verified for 48 elements. Significant negative deviations of χSIMS from a smooth increase with increasing atomic number are evident for elements with special outer-shell electron configurations such as (n-1)d(g-1)ns(1) or (n-1)d(10)ns(2)np(1). The results strongly support the new model of secondary ion formation and provide means for refining electronegativity data.

The Influence of Shielding on the Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage

NASA Technical Reports Server (NTRS)

Goeorge, Kerry; Cucinotta, Francis A.

2007-01-01

Chromosome damage was assessed in human peripheral blood lymphocytes after in vitro exposure to the either Si-28 (490 or 600 MeV/n), Ti-48 (1000 MeV/n), or Fe-56 (600, 1000, or 5000 MeV/n). LET values for these ions ranged from 51 to 184 keV/micron and doses ranged from 10 to 200 cGy. The effect of either aluminum or polyethylene shielding on the induction of chromosome aberrations was investigated for each ion. Chromosome exchanges were measured using fluorescence in situ hybridization (FISH) with whole chromosome probes in cells collected at G2 and mitosis in first division post irradiation after chromosomes were prematurely condensed using calyculin-A. The yield of chromosomal aberrations increased linearly with dose and the relative biological effectiveness (RBE) for the primary beams, estimated from the initial slope of the dose response curve for total chromosomal exchanges with respect to gamma-rays, ranged from 9 to 35. The RBE values increased with LET, reaching a maximum for the 600 MeV/n Fe ions with LET of 184 keV/micron. When the LET of the primary beam was below approximately 100 keV/micron, the addition of shielding material increased the effectiveness per unit dose. Whereas shielding decreased the effectiveness per unit dose when the LET of primary beams was higher than 100 keV/micron. The yield of aberrations correlated with the dose-average LET of the beam after traversal through the shielding.

Structural and electrochemical properties of iron- and nickel-substituted Li2MnO3 cathodes in charged and discharged states

NASA Astrophysics Data System (ADS)

Yuge, Ryota; Kuroshima, Sadanori; Toda, Akio; Miyazaki, Takashi; Tabuchi, Mitsuharu; Doumae, Kyosuke; Shibuya, Hideka; Tamura, Noriyuki

2017-10-01

Structural change and the charge compensation mechanism of lithium-rich layered cathode (Li1.23Fe0.15Ni0.15Mn0.46O2) in charged and discharged states were investigated. Selected area electron diffraction analysis revealed that in discharged state, an initial structure composed of a single phase of monoclinic layered rock-salt changed to a mixture of hexagonal layered rock-salt and spinel-like structures. In charged state, the spinel-like phase became dominant as transition-metal ions migrate. 57Fe Mössbauer spectroscopy, X-ray absorption spectroscopy (XAS), and Soft-XAS showed that the valence of Fe and Ni ions approximately changed from Fe3+ to Fe3.2+ and Ni2+ to Ni3.5+ during charge-discharge, although Mn ions remained as Mn4+. Various oxidation states of oxide ions such as superoxide, peroxide, and hole states have also been detected in charged state. Considering that actual discharge capacity was 255 mAh/g, the contribution to charge compensation from the valence change of Fe and Ni ions was extremely small, and it only contributed to about one-third of total capacity. Therefore, the mechanism to yield high capacity of the Li1.23Fe0.15Ni0.15Mn0.46O2 cathode relates strongly to the redox reaction of oxide ions. Moreover, the decrease in capacity during charge-discharge cycling was mainly due to the irreversible redox reaction of Mn, Fe, and oxide ions.

Ion beam texturing

NASA Technical Reports Server (NTRS)

Hudson, W. R.

1976-01-01

A microscopic surface texture is created by sputter etching a surface while simultaneously sputter depositing a lower sputter yield material onto the surface. A xenon ion beam source has been used to perform this texturing process on samples as large as three centimeters in diameter. Ion beam textured surface structures have been characterized with SEM photomicrographs for a large number of materials including Cu, Al, Si, Ti, Ni, Fe, Stainless steel, Au, and Ag. Surfaces have been textured using a variety of low sputter yield materials - Ta, Mo, Nb, and Ti. The initial stages of the texture creation have been documented, and the technique of ion beam sputter removal of any remaining deposited material has been studied. A number of other texturing parameters have been studied such as the variation of the texture with ion beam power, surface temperature, and the rate of texture growth with sputter etching time.

High Fidelity Ion Beam Simulation of High Dose Neutron Irradiation

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

Was, Gary; Wirth, Brian; Motta, Athur

The objective of this proposal is to demonstrate the capability to predict the evolution of microstructure and properties of structural materials in-reactor and at high doses, using ion irradiation as a surrogate for reactor irradiations. “Properties” includes both physical properties (irradiated microstructure) and the mechanical properties of the material. Demonstration of the capability to predict properties has two components. One is ion irradiation of a set of alloys to yield an irradiated microstructure and corresponding mechanical behavior that are substantially the same as results from neutron exposure in the appropriate reactor environment. Second is the capability to predict the irradiatedmore » microstructure and corresponding mechanical behavior on the basis of improved models, validated against both ion and reactor irradiations and verified against ion irradiations. Taken together, achievement of these objectives will yield an enhanced capability for simulating the behavior of materials in reactor irradiations.« less

Ion irradiation damage in ilmenite at 100 K

USGS Publications Warehouse

Mitchell, J.N.; Yu, N.; Devanathan, R.; Sickafus, K.E.; Nastasi, M.A.; Nord, G.L.

1997-01-01

A natural single crystal of ilmenite (FeTiO3) was irradiated at 100 K with 200 keV Ar2+. Rutherford backscattering spectroscopy and ion channeling with 2 MeV He+ ions were used to monitor damage accumulation in the surface region of the implanted crystal. At an irradiation fluence of 1 ?? 1015 Ar2+/cm2, considerable near-surface He+ ion dechanneling was observed, to the extent that ion yield from a portion of the aligned crystal spectrum reached the yield level of a random spectrum. This observation suggests that the near-surface region of the crystal was amorphized by the implantation. Cross-sectional transmission electron microscopy and electron diffraction on this sample confirmed the presence of a 150 nm thick amorphous layer. These results are compared to similar investigations on geikielite (MgTiO3) and spinel (MgAl2O4) to explore factors that may influence radiation damage response in oxides.

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

Yin Yunpeng; Sawin, Herbert H.

The impact of etching kinetics and etching chemistries on surface roughening was investigated by etching thermal silicon dioxide and low-k dielectric coral materials in C{sub 4}F{sub 8}/Ar plasma beams in an inductive coupled plasma beam reactor. The etching kinetics, especially the angular etching yield curves, were measured by changing the plasma pressure and the feed gas composition which influence the effective neutral-to-ion flux ratio during etching. At low neutral-to-ion flux ratios, the angular etching yield curves are sputteringlike, with a peak around 60 deg. -70 deg. off-normal angles; the surface at grazing ion incidence angles becomes roughened due to ionmore » scattering related ion-channeling effects. At high neutral-to-ion flux ratios, ion enhanced etching dominates and surface roughening at grazing angles is mainly caused by the local fluorocarbon deposition induced micromasking mechanism. Interestingly, the etched surfaces at grazing angles remain smooth for both films at intermediate neutral-to-ion flux ratio regime. Furthermore, the oxygen addition broadens the region over which the etching without roughening can be performed.« less

Electrolyte Suitable for Use in a Lithium Ion Cell or Battery

NASA Technical Reports Server (NTRS)

McDonald, Robert C. (Inventor)

2014-01-01

Electrolyte suitable for use in a lithium ion cell or battery. According to one embodiment, the electrolyte includes a fluorinated lithium ion salt and a solvent system that solvates lithium ions and that yields a high dielectric constant, a low viscosity and a high flashpoint. In one embodiment, the solvent system includes a mixture of an aprotic lithium ion solvating solvent and an aprotic fluorinated solvent.

Quantum treatment of the capture of an atom by a fast nucleus incident on a molecule

NASA Astrophysics Data System (ADS)

Shakeshaft, Robin; Spruch, Larry

1980-04-01

The classical double-scattering model of Thomas for the capture of electrons from atoms by fast ions yields a cross section σ which dominates over the single scattering contribution for sufficiently fast ions. The magnitude of the classical double-scattering σ differs, however, from its quantum-mechanical (second-Born) analog by an order of magnitude. Further, a "fast ion" means an ion of some MeV, and at those energies the cross sections are very low. On the other hand, as noted by Bates, Cook, and Smith, the double-scattering cross section for the capture of atoms from molecules by fast ions dominates over the single-scattering contribution for incident ions of very much lower energy; roughly, one must have the velocity of the incident projectile much larger than a characteristic internal velocity of the particles in the target. It follows that we are in the asymptotic domain not at about 10 MeV but at about 100 eV. For the reaction H+ + CH4-->H+2 + CH3 with incident proton energies of 70 to 150 eV, the peak in the angular distribution as determined experimentally is at almost precisely the value predicted by the classical model, but the theoretical total cross section is about 30 times too large. Using a quantum version of the classical model, which involves the same kinematics and therefore preserves the agreement with the angular distribution, we obtain somewhat better agreement with the experimental total cross section, by a factor of about 5. (To obtain very good agreement, one may have to perform a really accurate calculation of large-angle elastic scattering of protons and H atoms by CH3, and take into account interference effects.) In the center-of-mass frame, for sufficiently high incident energy, the first of the two scatterings involves the scattering of H+ by H through an angle of very close to 90°, and it follows that the nuclei of the emergent H+2 ion will almost all be in the singlet state. We have also calculated the cross section for the reaction D+ + CH4-->(HD)+ + CH3.

Crystal-field energy level analysis for Nd(3+) ions at the low symmetry C(1) site in [Nd(hfa)(4)(H(2)O)](N(C(2)H(5))(4)) single crystals.

PubMed

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.

Crystal-field energy level analysis for Nd3+ ions at the low symmetry C1 site in [Nd(hfa)4(H2O)](N(C2H5)4) single crystals

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.

Modeling of Iron K Lines: Radiative and Auger Decay Data for Fe II-Fe IX

NASA Technical Reports Server (NTRS)

Palmeri, P.; Mendoza, C.; Kallman, T. R.; Bautista, M. A.; Melendez, M.

2003-01-01

A detailed analysis of the radiative and Auger de-excitation channels of K-shell vacancy states in Fe II-Fe IX has been carried out. Level energies, wavelengths, A-values, Auger rates and fluorescence yields have been calculated for the lowest fine-structure levels populated by photoionization of the ground state of the parent ion. Different branching ratios, namely K alpha 2/K alpha 1, K beta/K alpha, KLM/KLL, KMM/KLL, and the total K-shell fluorescence yields, omega(sub k), obtained in the present work have been compared with other theoretical data and solid-state measurements, finding good general agreement with the latter. The Kalpha 2/K alpha l ratio is found to be sensitive to the excitation mechanism. From these comparisons it has been possible to estimate an accuracy of approx.10% for the present transition probabilities.

FORMATION OF AUXIN IN YEAST CULTURES.

PubMed

Robinson, T W; Stier, T J

1941-07-20

We have found far more auxin in the culture media of bakers' yeast than was obtained by Kögl and Kostermans from the cells themselves. The production of auxin by yeast cells resembles the formation observed in other organisms such as Rhizopus and Rhizobium which also form auxins in their culture media. The auxin yield was found to increase with the concentration of sucrose and to decrease with the concentration of peptone. An inverse relation with the rate of cell multiplication was observed. Enlarged and elongated cells appeared only in those media which contained considerable amounts of auxin. The total auxin yield in the various cultures was found to be directly proportional, below pH 5, to the hydrogen ion concentration. Thus, it was proposed that certain growth conditions favor the breakage of the link between auxin and its protein carrier (Skoog and Thimann) 1940) and consequently accelerate the rate of excretion of auxin into the growth medium.

Whole genome sequence analysis of the arctic-lineage strain responsible for distemper in Italian wolves and dogs through a fast and robust next generation sequencing protocol.

PubMed

Marcacci, Maurilia; Ancora, Massimo; Mangone, Iolanda; Teodori, Liana; Di Sabatino, Daria; De Massis, Fabrizio; Camma', Cesare; Savini, Giovanni; Lorusso, Alessio

2014-06-01

Dynamic surveillance and characterization of canine distemper virus (CDV) circulating strains are essential against possible vaccine breakthroughs events. This study describes the setup of a fast and robust next-generation sequencing (NGS) Ion PGM™ protocol that was used to obtain the complete genome sequence of a CDV isolate (CDV2784/2013). CDV2784/2013 is the prototype of CDV strains responsible for severe clinical distemper in dogs and wolves in Italy during 2013. CDV2784/2013 was isolated on cell culture and total RNA was used for NGS sample preparation. A total of 112.3 Mb of reads were assembled de novo using MIRA version 4.0rc4, which yielded a total number of 403 contigs with 12.1% coverage. The whole genome (15,690 bp) was recovered successfully and compared to those of existing CDV whole genomes. CDV2784/2013 was shown to have 92% nt identity with the Onderstepoort vaccine strain. This study describes for the first time a fast and robust Ion PGM™ platform-based whole genome amplification protocol for non-segmented negative stranded RNA viruses starting from total cell-purified RNA. Additionally, this is the first study reporting the whole genome analysis of an Arctic lineage strain that is known to circulate widely in Europe, Asia and USA. Copyright © 2014 Elsevier B.V. All rights reserved.

Upper bound dose values for meson radiation in heavy-ion therapy.

PubMed

Rabin, C; Gonçalves, M; Duarte, S B; González-Sprinberg, G A

2018-06-01

Radiation treatment of cancer has evolved to include massive particle beams, instead of traditional irradiation procedures. Thus, patient doses and worker radiological protection have become issues of constant concern in the use of these new technologies, especially for proton- and heavy-ion-therapy. In the beam energies of interest of heavy-ion-therapy, secondary particle radiation comes from proton, neutron, and neutral and charged pions produced in the nuclear collisions of the beam with human tissue atoms. This work, for the first time, offers the upper bound of meson radiation dose in organic tissues due to secondary meson radiation in heavy-ion therapy. A model based on intranuclear collision has been used to follow in time the nuclear reaction and to determine the secondary radiation due to the meson yield produced in the beam interaction with nuclei in the tissue-equivalent media and water. The multiplicity, energy spectrum, and angular distribution of these pions, as well as their decay products, have been calculated in different scenarios for the nuclear reaction mechanism. The results of the produced secondary meson particles has been used to estimate the energy deposited in tissue using a cylindrical phantom by a transport Monte Carlo simulation and we have concluded that these mesons contribute at most 0.1% of the total prescribed dose.

Fundamental constants and tests of theory in Rydberg states of hydrogenlike ions.

PubMed

Jentschura, Ulrich D; Mohr, Peter J; Tan, Joseph N; Wundt, Benedikt J

2008-04-25

A comparison of precision frequency measurements to quantum electrodynamics (QED) predictions for Rydberg states of hydrogenlike ions can yield information on values of fundamental constants and test theory. With the results of a calculation of a key QED contribution reported here, the uncertainty in the theory of the energy levels is reduced to a level where such a comparison can yield an improved value of the Rydberg constant.

Cs-doped Mo as surface converter for H{sup −}/D{sup −} generation in negative ion sources: First steps and proof of principle

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

Sputtering Erosion in Ion and Plasma Thrusters

NASA Technical Reports Server (NTRS)

Ray, Pradosh K.

1996-01-01

Low energy sputtering of molybdenum, tantalum and boron nitride with xenon ions are being studied using secondary neutral and secondary ion mass spectrometry (SNMS/SIMS). An ultrahigh vacuum chamber was used to conduct the experiment at a base pressure of 1x10(exp -9) torr. The primary ion beam is generated by an ion gun which is capable of delivering ion currents in the range of 20 to 500 nA. The ion beam can be focused to a spot size of approximately 1 mm in diameter. The mass spectrometer is positioned 10 mm from the target and 90 deg to the primary ion beam direction. SNMS and SIMS spectra were collected at various incident angles and different ion energies. For boron nitride sputtering, the target was flooded with an electron beam to neutralize the charge buildup on the surface. In the SNMS mode, sputtering of Mo and Ta can be detected at an ion energy as low as 100 eV whereas in boron nitride the same was observed up to an energy of 300 eV. However, in the positive-SIMS mode, the sputtering of Mo was observed at 10 eV incident ion energy. The SIMS spectra obtained for boron nitride clearly identifies the two isotopes of boron as well as cluster ions such as B2(sup +) and molecular ions such as BN(sup +). From the angle versus yields measurements, it was found that the maximum SNMS yield shifts towards lower incident angles at low ion energies for all three samples.

Adsorbent for metal ions and method of making and using

DOEpatents

White, Lloyd R.; Lundquist, Susan H.

1999-01-01

A method comprises the step of spray-drying a solution or slurry comprising (alkali metal or ammonium) (metal) hexacyanoferrate particles in a liquid, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size in the range of 1 to 500 micrometers, said particles being active towards Cs ions. The particles, which can be of a single salt or a combination of salts, can be used free flowing, in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove Cs ions from aqueous solutions.

Adsorbent for metal ions and method of making and using

DOEpatents

White, L.R.; Lundquist, S.H.

1999-08-10

A method comprises the step of spray-drying a solution or slurry comprising (alkali metal or ammonium) (metal) hexacyanoferrate particles in a liquid, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size in the range of 1 to 500 micrometers, said particles being active towards Cs ions. The particles, which can be of a single salt or a combination of salts, can be used free flowing, in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove Cs ions from aqueous solutions. 2 figs.

Adsorbent for metal ions and method of making and using

DOEpatents

White, Lloyd R.; Lundquist, Susan H.

2000-01-01

A method comprises the step of spray-drying a solution or slurry comprising (alkali metal or ammonium) (metal) hexacyanoferrate particles in a liquid, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size in the range of 1 to 500 micrometers, said particles being active towards Cs ions. The particles, which can be of a single salt or a combination of salts, can be used free flowing, in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove Cs ions from aqueous solutions.

A Major Locus for Chloride Accumulation on Chromosome 5A in Bread Wheat

PubMed Central

Genc, Yusuf; Taylor, Julian; Rongala, Jay; Oldach, Klaus

2014-01-01

Chloride (Cl−) is an essential micronutrient for plant growth, but can be toxic at high concentrations resulting in reduced growth and yield. Although saline soils are generally dominated by both sodium (Na+) and Cl− ions, compared to Na+ toxicity, very little is known about physiological and genetic control mechanisms of tolerance to Cl− toxicity. In hydroponics and field studies, a bread wheat mapping population was tested to examine the relationships between physiological traits [Na+, potassium (K+) and Cl− concentration] involved in salinity tolerance (ST) and seedling growth or grain yield, and to elucidate the genetic control mechanism of plant Cl− accumulation using a quantitative trait loci (QTL) analysis approach. Plant Na+ or Cl− concentration were moderately correlated (genetically) with seedling biomass in hydroponics, but showed no correlations with grain yield in the field, indicating little value in selecting for ion concentration to improve ST. In accordance with phenotypic responses, QTL controlling Cl− accumulation differed entirely between hydroponics and field locations, and few were detected in two or more environments, demonstrating substantial QTL-by-environment interactions. The presence of several QTL for Cl− concentration indicated that uptake and accumulation was a polygenic trait. A major Cl− concentration QTL (5A; barc56/gwm186) was identified in three field environments, and accounted for 27–32% of the total genetic variance. Alignment between the 5A QTL interval and its corresponding physical genome regions in wheat and other grasses has enabled the search for candidate genes involved in Cl− transport, which is discussed. PMID:24893005

Etching of Silicon in HBr Plasmas for High Aspect Ratio Features

NASA Technical Reports Server (NTRS)

Hwang, Helen H.; Meyyappan, M.; Mathad, G. S.; Ranade, R.

2002-01-01

Etching in semiconductor processing typically involves using halides because of the relatively fast rates. Bromine containing plasmas can generate high aspect ratio trenches, desirable for DRAM and MEMS applications, with relatively straight sidewalk We present scanning electron microscope images for silicon-etched trenches in a HBr plasma. Using a feature profile simulation, we show that the removal yield parameter, or number of neutrals removed per incident ion due to all processes (sputtering, spontaneous desorption, etc.), dictates the profile shape. We find that the profile becomes pinched off when the removal yield is a constant, with a maximum aspect ratio (AR) of about 5 to 1 (depth to height). When the removal yield decreases with increasing ion angle, the etch rate increases at the comers and the trench bottom broadens. The profiles have ARs of over 9:1 for yields that vary with ion angle. To match the experimentally observed etched time of 250 s for an AR of 9:1 with a trench width of 0.135 microns, we find that the neutral flux must be 3.336 x 10(exp 17)sq cm/s.

CAEBAT Model Featured on American Chemical Society Journal Tenth

Science.gov Websites

University's School of Mechanical Engineering has yielded new insights for lithium-ion (Li-ion) battery corresponding article, "Secondary-Phase Stochastics in Lithium-Ion Battery Electrodes" detailing the microstructural modifications can greatly improve overall Li-ion battery performance. The value of this work is

Energy Storage News | Transportation | Transportation Research | NREL

Science.gov Websites

NREL/Purdue team's corresponding article, "Secondary-Phase Stochastics in Lithium-Ion Battery by NREL and NASA, the Battery ISC Device revolutionizes the way lithium-ion (Li-ion) batteries are collaboration with Purdue University's School of Mechanical Engineering has yielded new insights for lithium-ion

Spatiospectral Analysis of Accelerated Protons from Sub-Micron Liquid Crystal Films

NASA Astrophysics Data System (ADS)

Willis, Christopher; Poole, Patrick; Cochran, Ginevra; van Woerkom, Linn; Schumacher, Douglass

2017-10-01

Recent studies on ion acceleration have trended towards ultra-thin (<1 μm) targets due to improved ion energies and yields from these targets. As discussed here, ultra-thin targets may exhibit unusual spatial distributions in the accelerated ions, such that ion spectrometer data may not be representative of the overall distribution. More complete characterization of the ions requires spectral unfolding of radiochromic film (RCF) data, yielding spatially dependent spectra. Spatiospectral data will be presented from several experiments using sub-micron liquid crystal film targets at the Scarlet (OSU), Texas Petawatt (UT, Austin) and PHELIX (GSI, Darmstadt) laser facilities, including evidence of >75 MeV protons from 300 nm films at PHELIX. Analysis of RCF data is supported by Monte-Carlo modeling of RCF response to ions and electrons using FLUKA. Trends in the resulting ion distributions will be discussed including spatially varying slope temperature and observation of annular ring features at moderate ion energies on many shots. This material is based upon work supported by the AFOSR under award FA9550-14-1-0085, by the DARPA PULSE program through a Grant from AMRDEC, and by the NNSA under contract DE-NA0003107.

Development of the dense plasma focus for short-pulse applications

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

Bennett, N.; Blasco, M.; Breeding, K.

The dense plasma focus (DPF) has long been considered a compact source for pulsed neutrons and has traditionally been optimized for the total neutron yield. Here, we describe the efforts to optimize the DPF for short-pulse applications by introducing a reentrant cathode at the end of the coaxial plasma gun. We reduced the resulting neutron pulse widths by an average of 21±921±9% from the traditional long-drift DPF design. Pulse widths and yields achieved from deuterium-tritium fusion at 2 MA are 61.8±30.761.8±30.7 ns FWHM and 1.84±0.49×10121.84±0.49×10 12 neutrons per shot. Simulations were conducted concurrently to elucidate the DPF operation and confirmmore » the role of the reentrant cathode. Furthermore, a hybrid fluid-kinetic particle-in-cell modeling capability demonstrates correct sheath velocities, plasma instabilities, and fusion yield rates. Consistent with previous findings that the DPF is dominated by beam-target fusion from superthermal ions, we estimate that the thermonuclear contribution is at the 1% level.« less

Development of the dense plasma focus for short-pulse applications

DOE PAGES

Bennett, N.; Blasco, M.; Breeding, K.; ...

2017-01-05

The dense plasma focus (DPF) has long been considered a compact source for pulsed neutrons and has traditionally been optimized for the total neutron yield. Here, we describe the efforts to optimize the DPF for short-pulse applications by introducing a reentrant cathode at the end of the coaxial plasma gun. We reduced the resulting neutron pulse widths by an average of 21±921±9% from the traditional long-drift DPF design. Pulse widths and yields achieved from deuterium-tritium fusion at 2 MA are 61.8±30.761.8±30.7 ns FWHM and 1.84±0.49×10121.84±0.49×10 12 neutrons per shot. Simulations were conducted concurrently to elucidate the DPF operation and confirmmore » the role of the reentrant cathode. Furthermore, a hybrid fluid-kinetic particle-in-cell modeling capability demonstrates correct sheath velocities, plasma instabilities, and fusion yield rates. Consistent with previous findings that the DPF is dominated by beam-target fusion from superthermal ions, we estimate that the thermonuclear contribution is at the 1% level.« less

Optimization of Ionic Liquid-Assisted Extraction of Biflavonoids from Selaginella doederleinii and Evaluation of Its Antioxidant and Antitumor Activity.

PubMed

Li, Dan; Qian, Yan; Tian, Yu-Jia; Yuan, Shi-Meng; Wei, Wei; Wang, Gang

2017-04-07

As new green solvents, ionic liquids (ILs) have been generally applied in the extraction and separation of natural product. In this study, microwave assisted extraction based on IL (IL-MAE) was firstly employed to extract total biflavonoids from Selaginella doederleinii . Based on single-factor experiment, microwave power (300-700 W), extract time (30-50 min) and extract temperature (40-60 °C) on total bioflavonoids and antioxidant activities of the extracts were further investigated by a Box-Behnken design of response surface methodology (RSM) selecting total bioflavonoids yields and IC 50 of radical scavenging as index. Besides antioxidant activity of the extract was evaluated by a 2,2-diphenyl-1-picrylhydarzyl (DPPH) and 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate (ABTS) radical scavenging assay, ferric reducing power assay and chelation of ferrous ions assay, and then anticaner activity was also researched against A549 cell line and 7721 cell line. The results illustrated that three factors and their interactions could be well suited for second-order polynomial models ( p < 0.05). Through process parameters, optimization of the extract (460 W, 40 min, and 45 °C) and detection of bioactivity, the yield of total bioflavonoids was 16.83 mg/g and IC 50 value was 56.24 μg/mL, respectively, indicating the extract has better anti-oxidation effect and antitumor activity. Furthermore, IL-MAE was the most efficient extracting method compared with MAE and Soxhlet extraction, which could improve extraction efficiency in a shorter time and at a lower temperature. In general, ILs-MAE was first adopted to establish a novel and green extraction process on the yields of total biflavonoids from S. doederleinii . In addition, the extract of containing biflavones showed potent antioxidant and anticancer capacity as a utilized valuable bioactive source for natural medicine.

A survey of analytical methods employed for monitoring of Advanced Oxidation/Reduction Processes for decomposition of selected perfluorinated environmental pollutants.

PubMed

Trojanowicz, Marek; Bobrowski, Krzysztof; Szostek, Bogdan; Bojanowska-Czajka, Anna; Szreder, Tomasz; Bartoszewicz, Iwona; Kulisa, Krzysztof

2018-01-15

The monitoring of Advanced Oxidation/Reduction Processes (AO/RPs) for the evaluation of the yield and mechanisms of decomposition of perfluorinated compounds (PFCs) is often a more difficult task than their determination in the environmental, biological or food samples with complex matrices. This is mostly due to the formation of hundreds, or even thousands, of both intermediate and final products. The considered AO/RPs, involving free radical reactions, include photolytic and photocatalytic processes, Fenton reactions, sonolysis, ozonation, application of ionizing radiation and several wet oxidation processes. The main attention is paid to the most commonly occurring PFCs in the environment, namely PFOA and PFOS. The most powerful and widely exploited method for this purpose is without a doubt LC/MS/MS, which allows the identification and trace quantitation of all species with detectability and resolution power depending on the particular instrumental configurations. The GC/MS is often employed for the monitoring of volatile fluorocarbons, confirming the formation of radicals in the processes of C‒C and C‒S bonds cleavage. For the direct monitoring of radicals participating in the reactions of PFCs decomposition, the molecular spectrophotometry is employed, especially electron paramagnetic resonance (EPR). The UV/Vis spectrophotometry as a detection method is of special importance in the evaluation of kinetics of radical reactions with the use of pulse radiolysis methods. The most commonly employed for the determination of the yield of mineralization of PFCs is ion-chromatography, but there is also potentiometry with ion-selective electrode and the measurements of general parameters such as Total Organic Carbon and Total Organic Fluoride. The presented review is based on about 100 original papers published in both analytical and environmental journals. Copyright © 2017 Elsevier B.V. All rights reserved.

Sputtering yields of carbon based materials under high particle flux with low energy

NASA Astrophysics Data System (ADS)

Nakamura, K.; Nagase, A.; Dairaku, M.; Akiba, M.; Araki, M.; Okumura, Y.

1995-04-01

A new ion source which can produce high particle flux beams at low energies has been developed. This paper presents preliminary results on the sputtering yield of the carbon fiber reinforced composites (CFCs) measured with the new ion source. The sputtering yields of 1D and 2D CFCs, which are candidate materials for the divertor armour tiles, have been measured by the weight loss method under the hydrogen and deuterium particle fluxes of 2 ˜ 7 × 10 20/m 2 s at 50 ˜ 150 eV. Preferential sputtering of the matrix was observed on CFCs which included the matrix of 40 ˜ 60 w%. The energy dependence of the sputtering yields was weak. The sputtering yields of CFCs normally irradiated with deuterium beam were from 0.073 to 0.095, and were around three times larger than those with hydrogen beam.

Electron ionization of SiCl4

NASA Astrophysics Data System (ADS)

King, Simon J.; Price, Stephen D.

2011-02-01

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

Electron ionization of SiCl4.

PubMed

King, Simon J; Price, Stephen D

2011-02-21

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

Direct Heating of a Laser-Imploded Core by Ultraintense Laser-Driven Ions

NASA Astrophysics Data System (ADS)

Kitagawa, Y.; Mori, Y.; Komeda, O.; Ishii, K.; Hanayama, R.; Fujita, K.; Okihara, S.; Sekine, T.; Satoh, N.; Kurita, T.; Takagi, M.; Watari, T.; Kawashima, T.; Kan, H.; Nishimura, Y.; Sunahara, A.; Sentoku, Y.; Nakamura, N.; Kondo, T.; Fujine, M.; Azuma, H.; Motohiro, T.; Hioki, T.; Kakeno, M.; Miura, E.; Arikawa, Y.; Nagai, T.; Abe, Y.; Ozaki, S.; Noda, A.

2015-05-01

A novel direct core heating fusion process is introduced, in which a preimploded core is predominantly heated by energetic ions driven by LFEX, an extremely energetic ultrashort pulse laser. Consequently, we have observed the D (d ,n )He 3 -reacted neutrons (DD beam-fusion neutrons) with the yield of 5 ×108 n /4 π sr . Examination of the beam-fusion neutrons verified that the ions directly collide with the core plasma. While the hot electrons heat the whole core volume, the energetic ions deposit their energies locally in the core, forming hot spots for fuel ignition. As evidenced in the spectrum, the process simultaneously excited thermal neutrons with the yield of 6 ×107 n /4 π sr , raising the local core temperature from 0.8 to 1.8 keV. A one-dimensional hydrocode STAR 1D explains the shell implosion dynamics including the beam fusion and thermal fusion initiated by fast deuterons and carbon ions. A two-dimensional collisional particle-in-cell code predicts the core heating due to resistive processes driven by hot electrons, and also the generation of fast ions, which could be an additional heating source when they reach the core. Since the core density is limited to 2 g /cm3 in the current experiment, neither hot electrons nor fast ions can efficiently deposit their energy and the neutron yield remains low. In future work, we will achieve the higher core density (>10 g /cm3 ); then hot electrons could contribute more to the core heating via drag heating. Together with hot electrons, the ion contribution to fast ignition is indispensable for realizing high-gain fusion. By virtue of its core heating and ignition, the proposed scheme can potentially achieve high gain fusion.

Direct heating of a laser-imploded core by ultraintense laser-driven ions.

PubMed

Kitagawa, Y; Mori, Y; Komeda, O; Ishii, K; Hanayama, R; Fujita, K; Okihara, S; Sekine, T; Satoh, N; Kurita, T; Takagi, M; Watari, T; Kawashima, T; Kan, H; Nishimura, Y; Sunahara, A; Sentoku, Y; Nakamura, N; Kondo, T; Fujine, M; Azuma, H; Motohiro, T; Hioki, T; Kakeno, M; Miura, E; Arikawa, Y; Nagai, T; Abe, Y; Ozaki, S; Noda, A

2015-05-15

A novel direct core heating fusion process is introduced, in which a preimploded core is predominantly heated by energetic ions driven by LFEX, an extremely energetic ultrashort pulse laser. Consequently, we have observed the D(d,n)^{3}He-reacted neutrons (DD beam-fusion neutrons) with the yield of 5×10^{8} n/4π sr. Examination of the beam-fusion neutrons verified that the ions directly collide with the core plasma. While the hot electrons heat the whole core volume, the energetic ions deposit their energies locally in the core, forming hot spots for fuel ignition. As evidenced in the spectrum, the process simultaneously excited thermal neutrons with the yield of 6×10^{7} n/4π sr, raising the local core temperature from 0.8 to 1.8 keV. A one-dimensional hydrocode STAR 1D explains the shell implosion dynamics including the beam fusion and thermal fusion initiated by fast deuterons and carbon ions. A two-dimensional collisional particle-in-cell code predicts the core heating due to resistive processes driven by hot electrons, and also the generation of fast ions, which could be an additional heating source when they reach the core. Since the core density is limited to 2 g/cm^{3} in the current experiment, neither hot electrons nor fast ions can efficiently deposit their energy and the neutron yield remains low. In future work, we will achieve the higher core density (>10 g/cm^{3}); then hot electrons could contribute more to the core heating via drag heating. Together with hot electrons, the ion contribution to fast ignition is indispensable for realizing high-gain fusion. By virtue of its core heating and ignition, the proposed scheme can potentially achieve high gain fusion.

Solution dewatering with concomitant ion removal

DOEpatents

Peterson, Eric S.; Marshall, Douglas W.; Stone, Mark L.

2003-08-05

One of the biggest needs in the separations and waste handling and reduction area is a method for dewatering ion-containing solutions. Unexpectedly, it has been found that phosphazene polymers can discriminate between water and metal ions, allowing water to pass through the membrane while retaining the ions. This unexpected result, along with the inherent chemical and thermal stability of the phosphazene polymers, yields a powerful tool for separating and dewatering metal-ion-containing solutions.

Comparing Benign and Malignant Neoplasia and DSB Induction for Low-and High-LET Radiation

NASA Astrophysics Data System (ADS)

Burns, Fredric; Tang, Moon-Shong Eric; Wu, Feng

One-and 2-stage models based on DNA double strand breaks (DSBs) have been developed to describe the dose and LET dependence of cancer induction in rat skin exposed to the Bragg plateau of several ion beams or electron radiation. Data are presented showing that carcinomas (malignant) and fibromas (benign) are induced differently by low and high LET radiation. DSBs are subject to complex repair processes, including homologous and non-homologous end joining, that slowly eliminate broken chromosome ends but at the expense of elevating genomic instability that increases the risk of neoplasia. In this formulation the initial molecular lesion in radiation carcinogenesis is assumed to be a DNA double strand break (DSB). The 2-event model assumes that pairs of DSBs join to create cellular genomic instability that eventually progresses to malignancy. The 1-event model assumes that joining is insignificant but that unrepaired DSBs remain and are sufficiently destabilizing to produce low-grade neoplasias. The respective expected relationships between neoplasia yield (Y), radiation dose (D) and LET (L) are: Y(D) = CLD + BD2 (A) for 2-events and Y(D) = CLD (B) for 1-event. Respective B and C values have been evaluated empirically for carcinomas, fibromas and DSBs, the latter via the -H2Ax technique in surrogate keratinocytes, for several types of radiations, including, 40Ar ions, 56Fe ions, 20Ne ions, protons, electrons and x-rays. Fibromas outnumber carcinomas by about 6:1 but are more sensitive than carcinomas to the cytolethal effect of the radiations. The 2-event model agrees well with carcinoma yields in rat skin but fails to model fibromas correctly. Instead the fibroma yields best fitted with the 1-event model for the high LET ion radiations, but at very low LET (electron radiation), an empirical D3 component becomes apparent which is not currently incorporated into the theoretical model. At higher LET values, the D3 component was not detected. The overall results are summarized as follows: 1) DSBs predict carcinoma yields in regard to dose and LET in conformity to Equation A, 2) fibroma yields for 40Ar and 20Ne ions conform to Equation B, i.e. yield proportionality to D and L and 3) the positive slope of the fibroma yield to electron radiation is a third order discrepancy suggesting a more complicated response that has yet to be incorporated into the model. The results provide encouragement that once calibrated for humans, a short-term test of DSB yield might be capable of predicting cancer risks for a variety of space radiation exposure scenarios.

Plasma-laser ion discrimination by TOF technique applied to coupled SiC detectors.

NASA Astrophysics Data System (ADS)

Cavallaro, Salvatore

2018-01-01

The rate estimation of nuclear reactions induced in high intensity laser-target interaction (≥1016 W/cm2), is strongly depending on the neutron detection efficiency and ion charge discrimination, according to particles involved in exit open-channels. Ion discrimination is basically performed by means of analysis of pits observed on track detector, which is critically dependent on calibration and/or fast TOF devices based on SiC and diamond detectors. Last setup is used to determine the ion energy and to obtain a rough estimation of yields. However, for each TOF interval, the dependence of yield from the energy deposited in the detector sensitive region, introduces a distortion in the ion spectra. Moreover, if two ion species are present in the same spectrum, the discrimination of their contribution is not attainable. In this paper a new method is described which allows to discriminate the contribution of two ion species in the wide energy range of nuclear reactions induced in laser-target interactions. The method is based on charge response of two TOF-SiC detectors, of suitable thicknesses, placed in adjacent positions. In presence of two ion species, the response of the detectors, associated with different energy losses, can determine the ion specific contribution to each TOF interval.

Proton Energy Optimization and Spatial Distribution Analysis from a Thickness Study Using Liquid Crystal Targets

NASA Astrophysics Data System (ADS)

Willis, Christopher; Poole, Patrick; Schumacher, Douglas; Freeman, Richard; van Woerkom, Linn

2016-10-01

Laser-accelerated ions from thin targets have been widely studied for applications including secondary radiation sources and cancer therapy, with recent studies trending towards thinner targets which can provide improved ion energies and yields. Here we discuss results from an experiment on the Scarlet laser at OSU using variable thickness liquid crystal targets. On this experiment, the spatial and spectral distributions of accelerated ions were measured along target normal and laser axes at varying thicknesses from 150nm to 2000nm at a laser intensity of 1 ×1020W /cm2 . Maximum ion energy was observed for targets in the 600 - 800nm thickness range, with proton energies reaching 24MeV . The ions were further characterized using radiochromic film, revealing an unusual spatial distribution on many laser shots. Here, the peak ion yield falls in an annular ring surrounding the target normal, with an increasing divergence angle as a function of ion energy. Details of these spatial and spectral ion distributions will be presented, including spectral deconvolution of the RCF data, revealing additional trends in the accelerated ion distributions. Supported by the DARPA PULSE program through a Grant from AMRDEC, and by the NNSA under contract DE-NA0001976.

Impact of the track structure of heavy charged particles on cytogenetic damage in human blood lymphocytes

NASA Astrophysics Data System (ADS)

Lee, Ryonfa; Nasonova, Elena; Sommer, Sylwetster; Hartel, Carola; Durante, Marco; Ritter, Sylvia

In space, astronauts are unavoidably exposed to charged particles from protons to irons. For a better estimate of the health risks of astronauts, further knowledge on the biological effects of charged particles, in particular the induction of cytogenetic damage is required. One im-portant factor that determines the biological response is the track structure of particles, i.e. their microscopic dose deposition in cells. The aim of the present study was to assess the influence of track structure of heavy ions on the yield and the quality of cytogenetic damage in human peripheral blood lymphocytes representing normal tissue. Cells were irradiated with 9.5 MeV/u C-ions or 990 MeV/u Fe-ions which have a comparable LET (175 keV/µm and 155 keV/µm, respectively) but a different track radius (2.3 and 6200 µm, respectively). When aberrations were analyzed in first cycle metaphases collected at different post-irradiation times (48-84 h) following fluorescence plus Giemsa staining, an increase in the aberration yield with sampling time was observed for both radiation qualities reflecting a damage dependent cell cycle progression delay to mitosis. The pronounced differences in the aberration frequency per cell are attributable to the stochastic distribution of particle traversals per cell nucleus (radius: 2.8 µm). Following C-ion exposure we found a high fraction of non-aberrant cells in samples collected at 48 h which represent cells not directly hit by a particle and slightly damaged cells that successfully repaired the induced lesions. In addition, at higher C-ion fluences the aberra-tion yield saturated, suggesting that a fraction of lymphocytes receiving multiple particle hits is not able to reach mitosis. On the other hand, at 48 h after Fe-ion exposure the proportion of non-aberrant cells is lower than after C-ion irradiation clearly reflecting the track structure of high energy particles (i.e. more homogeneous dose deposition compared to low energy C-ions). Furthermore, the aberration yield increased linearly with Fe-ion fluence. When aberrations were analyzed in first cycle G2 -PCC cells to account for the prolonged G2 arrest of damaged cells, the same trend was detected. However, the increase in the aberration yield with time and the saturation effect were less pronounced compared to metaphase samples. Altogether, these data show that the aberration analysis with multiple samplings is necessary for a reliable estimate of cytogenetic damage induced by charged particles. In particular, when damage is measured at one early time-point the effectiveness of low energy particles will be considerably underestimated. When the aberration spectrum induced by low energy C-ions and high en-ergy Fe-ions was compared, we did not find a difference. Preliminary data obtained with the high resolution mFISH-technique confirm this observation. (Work supported by BMBF, Bonn, under contract 02S8497)

Structure and reactivity studies of CoHNO{sup +} in the gas phase

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

Chen, H.; Jacobson, D.B.; Freiser, B.S.

1999-12-16

The structure and energetics of three CoHNO{sup +} isomers [HCo(NO){sup +} (1), Co(HNO){sup +} (2), Co(NOH){sup +} (3)] were probed by using density functional theory (DFT). Theory predicts that 2 is the most stable structure with 1 and 3 14.1 and 15.4 kcal/mol less stable. The transition states for 2 {yields} 1 and 2 {yields} 3 conversions were not located. DFT calculations predict D{degree}(CoH{sup +}-NO) = 34.6 kcal/mol and D{degree}(Co{sup +}-HNO) = 45.5 kcal/mol. The gas-phase ion chemistry of CoHNO{sup +} was also studied by using Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. CID and SORI-CID of CoHNO{sup +}more » yield competitive formation of Co{sup +}, CoH{sup +}, and CoNO{sup +}. These results suggest that the barrier for 2 {yields} 1 conversion is less than 45.5 kcal/mol. Reactions with simple molecules were dominated by NO and HNO displacements. Potential energy surface diagrams are presented to explain these displacement reactions. Surprisingly, CoHNO{sup +} reacts with methane by dehydrogenation to yield CoCH{sub 3}NO{sup +}. Studies suggest CH{sub 3}CoNO{sup +} rather than Co(CH{sub 3}NO){sup +}as the structure for this ion.« less

Polymer Electrolyte Through Enzyme Catalysis for High Performance Lithium-Ion Batteries

DTIC Science & Technology

1998-10-16

by block number) FIELD GROUP SUB-GROUP Polymer Electrolyte, Solid State, Enzyme Catalysis, Lithium - Ion Battery , Sol Gel, High Conductivity 19...excellent candidates for lithium - ion battery development. Furthermore, the processes used to achieve the final product yield very good mechanical properties...Objectives This research was initiated to investigate synthesis of improved polymer electrolytes for lithium - ion battery applications. The overall

Cobalt coordination and clustering in alpha-Co(OH)(2) revealed by synchrotron X-ray total scattering.

PubMed

Neilson, James R; Kurzman, Joshua A; Seshadri, Ram; Morse, Daniel E

2010-09-03

Structures of layered metal hydroxides are not well described by traditional crystallography. Total scattering from a synthesis-controlled subset of these materials, as described here, reveals that different cobalt coordination polyhedra cluster within each layer on short length scales, offering new insights and approaches for understanding the properties of these and related layered materials. Structures related to that of brucite [Mg(OH)(2)] are ubiquitous in the mineral world and offer a variety of useful functions ranging from catalysis and ion-exchange to sequestration and energy transduction, including applications in batteries. However, it has been difficult to resolve the atomic structure of these layered compounds because interlayer disorder disrupts the long-range periodicity necessary for diffraction-based structure determination. For this reason, traditional unit-cell-based descriptions have remained inaccurate. Here we apply, for the first time to such layered hydroxides, synchrotron X-ray total scattering methods-analyzing both the Bragg and diffuse components-to resolve the intralayer structure of three different alpha-cobalt hydroxides, revealing the nature and distribution of metal site coordination. The different compounds with incorporated chloride ions have been prepared with kinetic control of hydrolysis to yield different ratios of octahedrally and tetrahedrally coordinated cobalt ions within the layers, as confirmed by total scattering. Real-space analyses indicate local clustering of polyhedra within the layers, manifested in the weighted average of different ordered phases with fixed fractions of tetrahedrally coordinated cobalt sites. These results, hidden from an averaged unit-cell description, reveal new structural characteristics that are essential to understanding the origin of fundamental material properties such as color, anion exchange capacity, and magnetic behavior. Our results also provide further insights into the detailed mechanisms of aqueous hydrolysis chemistry of hydrated metal salts. We emphasize the power of the methods used here for establishing structure-property correlations in functional materials with related layered structures.

Extracting Both Peptide Sequence and Glycan Structural Information by 157 nm Photodissociation of N-Linked Glycopeptides

PubMed Central

Zhang, Liangyi; Reilly, James P.

2009-01-01

157 nm photodissociation of N-linked glycopeptides was investigated in MALDI tandem time-of-flight (TOF) and linear ion trap mass spectrometers. Singly-charged glycopeptides yielded abundant peptide and glycan fragments. The peptide fragments included a series of x-, y-, v- and w- ions with the glycan remaining intact. These provide information about the peptide sequence and the glycosylation site. In addition to glycosidic fragments, abundant cross-ring glycan fragments that are not observed in low-energy CID were detected. These fragments provide insight into the glycan sequence and linkages. Doubly-charged glycopeptides generated by nanospray in the linear ion trap mass spectrometer also yielded peptide and glycan fragments. However, the former were dominated by low-energy fragments such as b- and y- type ions while glycan was primarily cleaved at glycosidic bonds. PMID:19113943

Underlying role of mechanical rigidity and topological constraints in physical sputtering and reactive ion etching of amorphous materials

NASA Astrophysics Data System (ADS)

Bhattarai, Gyanendra; Dhungana, Shailesh; Nordell, Bradley J.; Caruso, Anthony N.; Paquette, Michelle M.; Lanford, William A.; King, Sean W.

2018-05-01

Analytical expressions describing ion-induced sputter or etch processes generally relate the sputter yield to the surface atomic binding energy (Usb) for the target material. While straightforward to measure for the crystalline elemental solids, Usb is more complicated to establish for amorphous and multielement materials due to composition-driven variations and incongruent sublimation. In this regard, we show that for amorphous multielement materials, the ion-driven yield can instead be better understood via a consideration of mechanical rigidity and network topology. We first demonstrate a direct relationship between Usb, bulk modulus, and ion sputter yield for the elements, and then subsequently prove our hypothesis for amorphous multielement compounds by demonstrating that the same relationships exist between the reactive ion etch (RIE) rate and nanoindentation Young's modulus for a series of a -Si Nx :H and a -Si OxCy :H thin films. The impact of network topology is further revealed via application of the Phillips-Thorpe theory of topological constraints, which directly relates the Young's modulus to the mean atomic coordination () for an amorphous solid. The combined analysis allows the trends and plateaus in the RIE rate to be ultimately reinterpreted in terms of the atomic structure of the target material through a consideration of . These findings establish the important underlying role of mechanical rigidity and network topology in ion-solid interactions and provide additional considerations for the design and optimization of radiation-hard materials in nuclear and outer space environments.

Noncontact bimolecular photoionization followed by radical-ions separation and their geminate recombination assisted by coherent HFI induced spin-conversion.

PubMed

Dodin, Dmitry V; Ivanov, Anatoly I; Burshtein, Anatoly I

2008-02-07

The Hamiltonian description of the spin-conversion induced by a hyperfine interaction (HFI) in photogenerated radical-ion pairs is substituted for the rate (incoherent) description of the same conversion provided by the widely used earlier elementary spin model. The quantum yields of the free ions as well as the singlet and triplet products of geminate recombination are calculated using distant dependent ionization and recombination rates, instead of their contact analogs. Invoking the simplest models of these rates, we demonstrate with the example of a spin-less system that the diffusional acceleration of radical-ion pair recombination at lower viscosity gives way to its diffusional deceleration (Angulo effect), accomplished with a kinetic plateau inherent with the primitive exponential model. Qualitatively the same behavior is found in real systems, assuming both ionization and recombination is carried out by the Marcus electron-transfer rates. Neglecting the Coulomb interaction between solvated ions, the efficiencies of radical-ion pair recombination to the singlet and triplet products are well fitted to the available experimental data. The magnetic field dependence of these yields is specified.

Highly charged ion secondary ion mass spectroscopy

DOEpatents

Hamza, Alex V.; Schenkel, Thomas; Barnes, Alan V.; Schneider, Dieter H.

2001-01-01

A secondary ion mass spectrometer using slow, highly charged ions produced in an electron beam ion trap permits ultra-sensitive surface analysis and high spatial resolution simultaneously. The spectrometer comprises an ion source producing a primary ion beam of highly charged ions that are directed at a target surface, a mass analyzer, and a microchannel plate detector of secondary ions that are sputtered from the target surface after interaction with the primary beam. The unusually high secondary ion yield permits the use of coincidence counting, in which the secondary ion stops are detected in coincidence with a particular secondary ion. The association of specific molecular species can be correlated. The unique multiple secondary nature of the highly charged ion interaction enables this new analytical technique.

Indications of flow near maximum compression in layered deuterium-tritium implosions at the National Ignition Facility

DOE PAGES

Gatu Johnson, M.; Knauer, J. P.; Cerjan, C. J.; ...

2016-08-15

Here, an accurate understanding of burn dynamics in implosions of cryogenically layered deuterium (D) and tritium (T) filled capsules, obtained partly through precision diagnosis of these experiments, is essential for assessing the impediments to achieving ignition at the National Ignition Facility. We present measurements of neutrons from such implosions. The apparent ion temperatures T ion are inferred from the variance of the primary neutron spectrum. Consistently higher DT than DD T ion are observed and the difference is seen to increase with increasing apparent DT T ion. The line-of-sight rms variations of both DD and DT T ion are small,more » ~150eV, indicating an isotropic source. The DD neutron yields are consistently high relative to the DT neutron yields given the observed T ion. Spatial and temporal variations of the DT temperature and density, DD-DT differential attenuation in the surrounding DT fuel, and fluid motion variations contribute to a DT Tion greater than the DD T ion, but are in a one-dimensional model insufficient to explain the data. We hypothesize that in a three-dimensional interpretation, these effects combined could explain the results.« less

Indications of flow near maximum compression in layered deuterium-tritium implosions at the National Ignition Facility

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

Gatu Johnson, M.; Knauer, J. P.; Cerjan, C. J.

Here, an accurate understanding of burn dynamics in implosions of cryogenically layered deuterium (D) and tritium (T) filled capsules, obtained partly through precision diagnosis of these experiments, is essential for assessing the impediments to achieving ignition at the National Ignition Facility. We present measurements of neutrons from such implosions. The apparent ion temperatures T ion are inferred from the variance of the primary neutron spectrum. Consistently higher DT than DD T ion are observed and the difference is seen to increase with increasing apparent DT T ion. The line-of-sight rms variations of both DD and DT T ion are small,more » ~150eV, indicating an isotropic source. The DD neutron yields are consistently high relative to the DT neutron yields given the observed T ion. Spatial and temporal variations of the DT temperature and density, DD-DT differential attenuation in the surrounding DT fuel, and fluid motion variations contribute to a DT Tion greater than the DD T ion, but are in a one-dimensional model insufficient to explain the data. We hypothesize that in a three-dimensional interpretation, these effects combined could explain the results.« less

Astrochemistry in TSR and CSR Ion Storage Rings

NASA Astrophysics Data System (ADS)

Novotny, Oldrich

2017-04-01

Dissociative recombination (DR) of molecular ions plays a key role in controlling the charge density and composition of the cold interstellar medium (ISM). Experimental data on DR are required in order to understand the chemical network in the ISM and related processes such as star formation from molecular clouds. Needed data include not only total reaction cross sections, but also the chemical composition and excitation states of the neutral products. Utilizing the TSR storage ring in Heidelberg, Germany, we have carried out DR measurements for astrophysically important molecular ions. We use a merged electron-ion beams technique combined with event-by-event fragment counting and fragment imaging. The count rate of detected neutral DR products yields the absolute DR rate coefficient. Imaging the distribution of fragment distances provides information on the kinetic energy released including the states of both the initial molecule and the final products. Additional kinetic energy sensitivity of the employed detector allows for identification of fragmentation channels by fragment-mass combination within each dissociation event. Such combined information is essential for studies on DR of polyatomic ions with multi-channel breakup. The recently commissioned Cryogenic Storage Ring (CSR) in Heidelberg, Germany, extends the experimental capabilities of TSR by operation at cryogenic temperatures down to 6 K. At these conditions residual gas densities down to 100 cm-3 can be reached resulting in beam storage times of several hours. Long storage in the cold environment allows the ions to relax down to their rotational ground state, thus mimicking well the conditions in the cold ISM. A variety of astrophysically relevant reactions will be investigated at these conditions, such as DR, electron impact excitation, ion-neutral collisions, etc. We report our TSR results on DR of HCl+ and D2Cl+. We also present first results from the CSR commissioning experiments.

Control of femtosecond laser driven retro-Diels-Alder-like reaction of dicyclopentadiene

PubMed Central

Das, Dipak Kumar; Goswami, Tapas; Goswami, Debabrata

2013-01-01

Using femtosecond time resolved degenerate pump-probe mass spectrometry coupled with simple linearly chirped frequency modulated pulse, we elucidate that the dynamics of retro-Diels-Alder-like reaction of diclopentadiene (DCPD) to cyclopentadiene (CPD) in supersonic molecular beam occurs in ultrafast time scale. Negatively chirped pulse enhances the ion yield of CPD, as compared to positively chirped pulse. This indicates that by changing the frequency (chirp) of the laser pulse we can control the ion yield of a chemical reaction. PMID:23814449

Neutron Yield With a Pulsed Surface Flashover Deuterium Source

NASA Astrophysics Data System (ADS)

Guethlein, G.; Falabella, S.; Sampayan, S. E.; Meyer, G.; Tang, V.; Kerr, P.

2009-03-01

As a step towards developing an ultra compact D-D neutron source for various defense and homeland security applications, a compact, low average power ion source is needed. Towards that end, we are testing a high current, pulsed surface flashover ion source, with deuterated titanium as the spark contacts. Neutron yield and source lifetime data will be presented using a low voltage (<100 kV) deuterated target. With 20 ns spark drive pulses we have shown >106 neutrons/s with 1 kHz PRF

Baryonic contributions to the dilepton spectra in relativistic heavy ion collisions

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

Bleicher, M.; Dutt-mazumder, A. K.; Gale, C.

2017-05-09

We investigate the baryonic contributions to the dilepton yield in high energy heavy ion collisions within the context of a transport model. The relative contribution of the baryonic and mesonic sources are examined. It is observed that most dominant among the baryonic channels is the decay of N*(1520) and mostly confined in the region below the rho peak. In a transport theory implementation we find the baryonic contribution to the lepton pair yield to be small.

Capillary ion chromatography with on-column focusing for ultra-trace analysis of methanesulfonate and inorganic anions in limited volume Antarctic ice core samples.

PubMed

Rodriguez, Estrella Sanz; Poynter, Sam; Curran, Mark; Haddad, Paul R; Shellie, Robert A; Nesterenko, Pavel N; Paull, Brett

2015-08-28

Preservation of ionic species within Antarctic ice yields a unique proxy record of the Earth's climate history. Studies have been focused until now on two proxies: the ionic components of sea salt aerosol and methanesulfonic acid. Measurement of the all of the major ionic species in ice core samples is typically carried out by ion chromatography. Former methods, whilst providing suitable detection limits, have been based upon off-column preconcentration techniques, requiring larger sample volumes, with potential for sample contamination and/or carryover. Here, a new capillary ion chromatography based analytical method has been developed for quantitative analysis of limited volume Antarctic ice core samples. The developed analytical protocol applies capillary ion chromatography (with suppressed conductivity detection) and direct on-column sample injection and focusing, thus eliminating the requirement for off-column sample preconcentration. This limits the total sample volume needed to 300μL per analysis, allowing for triplicate sample analysis with <1mL of sample. This new approach provides a reliable and robust analytical method for the simultaneous determination of organic and inorganic anions, including fluoride, methanesulfonate, chloride, sulfate and nitrate anions. Application to composite ice-core samples is demonstrated, with coupling of the capillary ion chromatograph to high resolution mass spectrometry used to confirm the presence and purity of the observed methanesulfonate peak. Copyright © 2015 Elsevier B.V. All rights reserved.

Simulating Salt Movement using a Coupled Salinity Transport Model in a Variably Saturated Agricultural Groundwater System

NASA Astrophysics Data System (ADS)

Tavakoli Kivi, S.; Bailey, R. T.; Gates, T. K.

2017-12-01

Salinization is one of the major concerns in irrigated agricultural fields. Increasing salinity concentrations are due principally to a high water table that results from excessive irrigation, canal seepage, and a lack of efficient drainage systems, and lead to decreasing crop yield. High groundwater salinity loading to nearby river systems also impacts downstream areas, with saline river water diverted for application on irrigated fields. To assess the different strategies for salt remediation, we present a reactive transport model (UZF-RT3D) coupled with a salinity equilibrium chemistry module for simulating the fate and transport of salt ions in a variably-saturated agricultural groundwater system. The developed model accounts not for advection, dispersion, nitrogen and sulfur cycling, oxidation-reduction, sorption, complexation, ion exchange, and precipitation/dissolution of salt minerals. The model is applied to a 500 km2 region within the Lower Arkansas River Valley (LARV) in southeastern Colorado, an area acutely affected by salinization in the past few decades. The model is tested against salt ion concentrations in the saturated zone, total dissolved solid concentrations in the unsaturated zone, and salt groundwater loading to the Arkansas River. The model now can be used to investigate salinity remediation strategies.

Scattering of hydrogen, nitrogen and water ions from micro pore optic plates for application in spaceborne plasma instrumentation

NASA Astrophysics Data System (ADS)

Stude, Joan; Wieser, Martin; Barabash, Stas

2016-10-01

Time-of-flight mass spectrometers for upcoming space missions into enhanced radiation environments need to be small, light weight and energy efficient. Time-of-flight systems using surface interactions as start-event generation can be smaller than foil-type instruments. Start surfaces for such applications need to provide narrow angular scattering, high ionization yields and high secondary electron emissions to be effective. We measured the angular scattering, energy distribution and positive ionization yield of micro pore optics for incident hydrogen, nitrogen and water ions at 2 keV. Positive ionization yields of 2% for H+ , 0.5% for N+ and 0.2% for H2O+ were detected.

Ion-plating of solar cell arrays encapsulation task: LSA project 32

NASA Technical Reports Server (NTRS)

Volkers, J. C.

1983-01-01

An ion plating process by which solar cells can be metallized and AR coated, yielding efficiencies equal to or better than state-of-the-art cells, was developed. It was demonstrated that ion plated AR films may be used as an effective encapsulant, offering primary protection for the metallization. It was also shown that ion plated metallization and AR coatings can be consistent with the project cost goals.

Positron-annihilation-induced ion desorption from TiO2(110)

NASA Astrophysics Data System (ADS)

Tachibana, T.; Hirayama, T.; Nagashima, Y.

2014-05-01

We have investigated the positron-stimulated desorption of ions from a TiO2(110) surface. Desorbed O+ ions were detected in coincidence with the emission of annihilation γ rays. The energy dependence of the ion yields shows that the O+ ions were detected at energies much lower than the previously reported threshold for electron impact desorption corresponding to the excitation energy of Ti(3p) core electrons. These results provide evidence that core-hole creation by positron annihilation with electrons in the core levels leads to ion desorption.

Electron Transfer Dissociation of iTRAQ Labeled Peptide Ions

PubMed Central

Han, Hongling; Pappin, Darryl J.; Ross, Philip L; McLuckey, Scott A.

2009-01-01

Triply and doubly charged iTRAQ (isobaric tagging for relative and absolute quantitation) labeled peptide cations from a tryptic peptide mixture of bovine carbonic anhydrase II were subjected to electron transfer ion/ion reactions to investigate the effect of charge bearing modifications associated with iTRAQ on the fragmentation pattern. It was noted that electron transfer dissociation (ETD) of triply charged or activated ETD (ETD + supplemental collisional activation of intact electron transfer species) of doubly charged iTRAQ tagged peptide ions yielded extensive sequence information, in analogy with ETD of unmodified peptide ions. That is, addition of the fixed charge iTRAQ tag showed relatively little deleterious effect on the ETD performance of the modified peptides. ETD of the triply charged iTRAQ labeled peptide ions followed by collision-induced dissociation (CID) of the product ion at m/z 162 yielded the reporter ion at m/z 116, which is the reporter ion used for quantitation via CID of the same precursor ions. The reporter ion formed via the two-step activation process is expected to provide quantitative information similar to that directly produced from CID. A 103 Da neutral loss species observed in the ETD spectra of all the triply and doubly charged iTRAQ labeled peptide ions is unique to the 116 Da iTRAQ reagent, which implies that this process also has potential for quantitation of peptides/proteins. Therefore, ETD with or without supplemental collisional activation, depending on the precursor ion charge state, has the potential to directly identify and quantify the peptides/proteins simultaneously using existing iTRAQ reagents. PMID:18646790

Practical experience and challenges in the operation of medical cyclotron.

PubMed

Kumar, Rajeev; Sonkawade, Rajendra G; Pandey, Anil K; Tripathi, Madhavi; Damle, Nishikant A; Kumar, Praveen; Bal, Chandra S

2017-01-01

The aim of this article was to share 10 years of operational experience of medical cyclotron and to provide working knowledge on the same. This experience has helped us gain working knowledge on cyclotron operation with practical points, which may help in improving F yield, minimizing the breakdown time, and help in the prevention of the occurrence of unusual events. Our facility has a self-shielded radioisotope delivery system eclipse 111 medical cyclotron with an 11 MeV proton beam in use for the past 10 years to produce positron emitters - namely, F, N, and F-2 gas - for PET imaging. During F production, we have followed a set protocol comprising the following: monitoring target pressure, rinsing the target with O water just immediately after bombardment, ion source feedback, radiofrequency (RF) feedback, and recording any unusual events that occurred during the operation. Besides this, enrichment of O water, target volume, target current, energy of the beam, variation in argon pressure on the target, bombardment duration, target status (new or old target or total number of previous bombardments on the same target), status of the delivery lines from target to the radiochemistry module (old or new) were also recorded. Rinsing with O water immediately after bombardment increases the life of the target and delivery line. The frequent problems encountered were with the ion source, RF, and target foil rupture. These problems were solved by rebuilding the ion source, changing the fuse of RF, and rebuilding the target. F yield can be increased by rinsing with O water immediately after bombardment. The effect of target leak - that is, rupture of vacuum window - can be avoided by immediate stoppage of bombardment.

A chloride tolerant laccase from the plant pathogen ascomycete Botrytis aclada expressed at high levels in Pichia pastoris.

PubMed

Kittl, Roman; Mueangtoom, Kitti; Gonaus, Christoph; Khazaneh, Shima Tahvilda; Sygmund, Christoph; Haltrich, Dietmar; Ludwig, Roland

2012-01-20

Fungal laccases from basidiomycetous fungi are thoroughly investigated in respect of catalytic mechanism and industrial applications, but the number of reported and well characterized ascomycetous laccases is much smaller although they exhibit interesting catalytic properties. We report on a highly chloride tolerant laccase produced by the plant pathogen ascomycete Botrytis aclada, which was recombinantly expressed in Pichia pastoris with an extremely high yield and purified to homogeneity. In a fed-batch fermentation, 495 mg L(-1) of laccase was measured in the medium, which is the highest concentration obtained for a laccase by a yeast expression system. The recombinant B. aclada laccase has a typical molecular mass of 61,565 Da for the amino acid chain. The pI is approximately 2.4, a very low value for a laccase. Glycosyl residues attached to the recombinant protein make up for approximately 27% of the total protein mass. B. aclada laccase exhibits very low K(M) values and high substrate turnover numbers for phenolic and non-phenolic substrates at acidic and near neutral pH. The enzyme's stability increases in the presence of chloride ions and, even more important, its substrate turnover is only weakly inhibited by chloride ions (I(50)=1.4M), which is in sharp contrast to most other described laccases. This high chloride tolerance is mandatory for some applications such as implantable biofuel cells and laccase catalyzed reactions, which suffer from the presence of chloride ions. The high expression yield permits fast and easy production for further basic and applied research. Copyright © 2011 Elsevier B.V. All rights reserved.

Model-independent determination of the astrophysical S factor in laser-induced fusion plasmas

NASA Astrophysics Data System (ADS)

Lattuada, D.; Barbarino, M.; Bonasera, A.; Bang, W.; Quevedo, H. J.; Warren, M.; Consoli, F.; De Angelis, R.; Andreoli, P.; Kimura, S.; Dyer, G.; Bernstein, A. C.; Hagel, K.; Barbui, M.; Schmidt, K.; Gaul, E.; Donovan, M. E.; Natowitz, J. B.; Ditmire, T.

2016-04-01

In this work, we present a new and general method for measuring the astrophysical S factor of nuclear reactions in laser-induced plasmas and we apply it to :mmultiscripts>(d ,n )3He . The experiment was performed with the Texas Petawatt Laser, which delivered 150-270 fs pulses of energy ranging from 90 to 180 J to D2 or CD4 molecular clusters (where D denotes 2H ) . After removing the background noise, we used the measured time-of-flight data of energetic deuterium ions to obtain their energy distribution. We derive the S factor using the measured energy distribution of the ions, the measured volume of the fusion plasma, and the measured fusion yields. This method is model independent in the sense that no assumption on the state of the system is required, but it requires an accurate measurement of the ion energy distribution, especially at high energies, and of the relevant fusion yields. In the :mmultiscripts>(d ,n )3He and 3He(d ,p )4He cases discussed here, it is very important to apply the background subtraction for the energetic ions and to measure the fusion yields with high precision. While the available data on both ion distribution and fusion yields allow us to determine with good precision the S factor in the d +d case (lower Gamow energies), for the d +3He case the data are not precise enough to obtain the S factor using this method. Our results agree with other experiments within the experimental error, even though smaller values of the S factor were obtained. This might be due to the plasma environment differing from the beam target conditions in a conventional accelerator experiment.

Model-independent determination of the astrophysical S factor in laser-induced fusion plasmas

DOE PAGES

Lattuada, D.; Barbarino, M.; Bonasera, A.; ...

2016-04-19

In this paper, we present a new and general method for measuring the astrophysical S factor of nuclear reactions in laser-induced plasmas and we apply it to 2H(d,n) 3He. The experiment was performed with the Texas Petawatt Laser, which delivered 150–270 fs pulses of energy ranging from 90 to 180 J to D 2 or CD 4 molecular clusters (where D denotes 2H). After removing the background noise, we used the measured time-of-flight data of energetic deuterium ions to obtain their energy distribution. We derive the S factor using the measured energy distribution of the ions, the measured volume ofmore » the fusion plasma, and the measured fusion yields. This method is model independent in the sense that no assumption on the state of the system is required, but it requires an accurate measurement of the ion energy distribution, especially at high energies, and of the relevant fusion yields. In the 2H(d,n) 3He and 3He(d,p) 4He cases discussed here, it is very important to apply the background subtraction for the energetic ions and to measure the fusion yields with high precision. While the available data on both ion distribution and fusion yields allow us to determine with good precision the S factor in the d+d case (lower Gamow energies), for the d+ 3He case the data are not precise enough to obtain the S factor using this method. Our results agree with other experiments within the experimental error, even though smaller values of the S factor were obtained. This might be due to the plasma environment differing from the beam target conditions in a conventional accelerator experiment.« less

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

Lattuada, D.; Barbarino, M.; Bonasera, A.

In this paper, we present a new and general method for measuring the astrophysical S factor of nuclear reactions in laser-induced plasmas and we apply it to 2H(d,n) 3He. The experiment was performed with the Texas Petawatt Laser, which delivered 150–270 fs pulses of energy ranging from 90 to 180 J to D 2 or CD 4 molecular clusters (where D denotes 2H). After removing the background noise, we used the measured time-of-flight data of energetic deuterium ions to obtain their energy distribution. We derive the S factor using the measured energy distribution of the ions, the measured volume ofmore » the fusion plasma, and the measured fusion yields. This method is model independent in the sense that no assumption on the state of the system is required, but it requires an accurate measurement of the ion energy distribution, especially at high energies, and of the relevant fusion yields. In the 2H(d,n) 3He and 3He(d,p) 4He cases discussed here, it is very important to apply the background subtraction for the energetic ions and to measure the fusion yields with high precision. While the available data on both ion distribution and fusion yields allow us to determine with good precision the S factor in the d+d case (lower Gamow energies), for the d+ 3He case the data are not precise enough to obtain the S factor using this method. Our results agree with other experiments within the experimental error, even though smaller values of the S factor were obtained. This might be due to the plasma environment differing from the beam target conditions in a conventional accelerator experiment.« less

Heavy ion irradiation of crystalline water ice. Cosmic ray amorphisation cross-section and sputtering yield

NASA Astrophysics Data System (ADS)

Dartois, E.; Augé, B.; Boduch, P.; Brunetto, R.; Chabot, M.; Domaracka, A.; Ding, J. J.; Kamalou, O.; Lv, X. Y.; Rothard, H.; da Silveira, E. F.; Thomas, J. C.

2015-04-01

Context. Under cosmic irradiation, the interstellar water ice mantles evolve towards a compact amorphous state. Crystalline ice amorphisation was previously monitored mainly in the keV to hundreds of keV ion energies. Aims: We experimentally investigate heavy ion irradiation amorphisation of crystalline ice, at high energies closer to true cosmic rays, and explore the water-ice sputtering yield. Methods: We irradiated thin crystalline ice films with MeV to GeV swift ion beams, produced at the GANIL accelerator. The ice infrared spectral evolution as a function of fluence is monitored with in-situ infrared spectroscopy (induced amorphisation of the initial crystalline state into a compact amorphous phase). Results: The crystalline ice amorphisation cross-section is measured in the high electronic stopping-power range for different temperatures. At large fluence, the ice sputtering is measured on the infrared spectra, and the fitted sputtering-yield dependence, combined with previous measurements, is quadratic over three decades of electronic stopping power. Conclusions: The final state of cosmic ray irradiation for porous amorphous and crystalline ice, as monitored by infrared spectroscopy, is the same, but with a large difference in cross-section, hence in time scale in an astrophysical context. The cosmic ray water-ice sputtering rates compete with the UV photodesorption yields reported in the literature. The prevalence of direct cosmic ray sputtering over cosmic-ray induced photons photodesorption may be particularly true for ices strongly bonded to the ice mantles surfaces, such as hydrogen-bonded ice structures or more generally the so-called polar ices. Experiments performed at the Grand Accélérateur National d'Ions Lourds (GANIL) Caen, France. Part of this work has been financed by the French INSU-CNRS programme "Physique et Chimie du Milieu Interstellaire" (PCMI) and the ANR IGLIAS.

Role of isolated and clustered DNA damage and the post-irradiating repair process in the effects of heavy ion beam irradiation.

PubMed

Tokuyama, Yuka; Furusawa, Yoshiya; Ide, Hiroshi; Yasui, Akira; Terato, Hiroaki

2015-05-01

Clustered DNA damage is a specific type of DNA damage induced by ionizing radiation. Any type of ionizing radiation traverses the target DNA molecule as a beam, inducing damage along its track. Our previous study showed that clustered DNA damage yields decreased with increased linear energy transfer (LET), leading us to investigate the importance of clustered DNA damage in the biological effects of heavy ion beam radiation. In this study, we analyzed the yield of clustered base damage (comprising multiple base lesions) in cultured cells irradiated with various heavy ion beams, and investigated isolated base damage and the repair process in post-irradiation cultured cells. Chinese hamster ovary (CHO) cells were irradiated by carbon, silicon, argon and iron ion beams with LETs of 13, 55, 90 and 200 keV µm(-1), respectively. Agarose gel electrophoresis of the cells with enzymatic treatments indicated that clustered base damage yields decreased as the LET increased. The aldehyde reactive probe procedure showed that isolated base damage yields in the irradiated cells followed the same pattern. To analyze the cellular base damage process, clustered DNA damage repair was investigated using DNA repair mutant cells. DNA double-strand breaks accumulated in CHO mutant cells lacking Xrcc1 after irradiation, and the cell viability decreased. On the other hand, mouse embryonic fibroblast (Mef) cells lacking both Nth1 and Ogg1 became more resistant than the wild type Mef. Thus, clustered base damage seems to be involved in the expression of heavy ion beam biological effects via the repair process. © The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Al K x-ray production for incident /sup 16/O ions: The influence of target thickness effects on observed target x-ray yields

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

Gray, T.J.; Richard, P.; Gealy, G.

1979-04-01

Thin solid Al targets ranging in thickness from approx. 1 to 30 ..mu..g/cm/sup 2/ were bombarded by /sup 16/O ions wih incident energies from 0.25 to 2.25 MeV/amu. The effects of target thickness on the measured Al K x-ray yield for ions incident without an initial K-shell vacancy were determined. Comparisons of the data for Al K x-ray production in vanishingly thin targets (and 29-..mu..g/cm/sup 2/ targets) were made to perturbed-stationary-state calculations (PSS) for O ions on Al targets. The PSS calculations contained corrections for Coulomb deflection and binding energy (PSS(CB)) and for Coulomb deflection, binding energy, and polarization (PSS(CBP)).more » Further, two different PSS calculation procedures were employed: calculations without radial cutoffs employed in the binding-energy contribution (PSS), and calculations with radial cutoffs employed in the binding-energy correction (NPSS). The PSS(CBP) calculations agree with the measured Al K x-ray production cross section for data taken in the limit of a vanishingly thin target. The NPSS(CBP) calculations agree with the data taken for a 29-..mu..g/cm/sup 2/ Al target. The latter agreement is fortuitous, as the increase observed in the measured target x-ray yield for the 29-..mu..g/cm/sup 2/ target, in comparison to the yield extracted as rhox ..-->.. 0 at each bombarding energy, is due to K-shell--to--K-shell charge exchange. Comparisons are made with previously published data for /sup 16/O ions incident on finite-thickness Al targets.« less

First observation of HO˙ reactivity in water under high energy ions at elevated temperature.

PubMed

Balcerzyk, A; Boughattas, I; Pin, S; Balanzat, E; Baldacchino, G

2014-11-21

This communication reports the first observation of the formation of HO˙ produced under two different High energy ion beams, (18)O(8+) and (36)Ar(18+) having Linear Energy Transfers (LET) of 65 and 350 eV nm(-1) respectively, at temperatures up to 411 K. Both scavenging with various concentrations of SCN(-) and heavy-ion pulse radiolysis methods are used with an original temperature and pressure regulated optical cell. Deconvolution of kinetics is used to analyze the evolution of HO˙ track segment yields as a function of time and temperature. It takes care of involving the ionic strength effect and Arrhenius expression in the rate constants correction. The results show a fast decay of HO˙ yields in the 10(-10)-10(-8) s range which denotes an efficient reactivity of this species in the track structure of the ion beam. This effect is enhanced with the lowest LET of O(8+). Increasing the temperature also accelerates the decays for both ions. These observations are discussed in terms of temperature activation of reactions and the track structure exhibiting the formation of HO˙ in a "low LET" penumbra around the ionization tracks. HO˙ track segment yields at 100 ns, of 0.4 × 10(-7) and 0.6 × 10(-7) mol J(-1), respectively for 350 and 65 eV nm(-1), are not affected by temperature.

Nanophotonic production, modulation and switching of ions by silicon microcolumn arrays

DOEpatents

Vertes, Akos; Walker, Bennett N.

2013-09-10

The production and use of silicon microcolumn arrays that harvest light from a laser pulse to produce ions are described. The systems of the present invention seem to behave like a quasi-periodic antenna array with ion yields that show profound dependence on the plane of laser light polarization and the angle of incidence. By providing photonic ion sources, this enables enhanced control of ion production on a micro/nano scale and direct integration with miniaturized analytical devices.

Nanophotonic production, modulation and switching of ions by silicon microcolumn arrays

DOEpatents

Vertes, Akos; Walker, Bennett N

2015-04-07

The production and use of silicon microcolumn arrays that harvest light from a laser pulse to produce ions are described. The systems of the present invention seem to behave like a quasi-periodic antenna array with ion yields that show profound dependence on the plane of laser light polarization and the angle of incidence. By providing photonic ion sources, this enables enhanced control of ion production on a micro/nano scale and direct integration with miniaturized analytical devices.

Nanophotonic production, modulation and switching of ions by silicon microcolumn arrays

DOEpatents

Vertes, Akos [Reston, VA; Walker, Bennett N [Washington, DC

2012-02-07

The production and use of silicon microcolumn arrays that harvest light from a laser pulse to produce ions are described. The systems of the present invention seem to behave like a quasi-periodic antenna array with ion yields that show profound dependence on the plane of laser light polarization and the angle of incidence. By providing photonic ion sources, this enables enhanced control of ion production on a micro/nano scale and direct integration with miniaturized analytical devices.

Heavy Ion Current Transients in SiGe HBTs

NASA Technical Reports Server (NTRS)

Pellish, Jonathan A.; Reed, Robert A.; Vizkelethy, Gyorgy; McMorrow, Dale; Ferlet-Cavrois, Veronique; Baggio, Jacques; Paillet, Philipe; Duhanel, Olivier; Phillips, Stanley D.; Sutton, Akil K.;

Addendum: Measurement of charged particle yields from PMMA irradiated by a 220 MeV/u ¹²C beam.

PubMed

Mattei, Ilaria; Battistoni, Giuseppe; Collini, Francesco; De Lucia, Erika; Durante, Marco; Fiore, Salvatore; Latessa, Chiara; Mancini-Terracciano, Carlo; Marafini, Michela; Mirabelli, Riccardo; Muraro, Silvia; Paramatti, Riccardo; Piersanti, Luca; Rucinski, Antoni; Russomando, Andrea; Sarti, Alessio; Schuy, Christoph; Sciubba, Adalberto; Solfaroli Camillocci, Elena; Toppi, Marco; Traini, Giacomo; Valle, Serena Marta; Vanstalle, Marie; Patera, Vincenzo

2017-09-08

In this paper we report the re-analysis of the data published in (Piersanti et al. 2014) documenting the charged secondary particles production induced by the interaction of a 220 MeV/u 12C ion beam impinging on a polymethyl methacrylate (PMMA) target, measured in 2012 at the GSI facility in Darmstadt (Germany). This re-analysis takes into account the inhomogeneous light response of the LYSO crystal in the experimental setup measured in a subsequent experiment (2014) performed in the Heidelberg Ion- Beam Therapy Center. A better description of the detector and re-calculation of the geometrical efficiencies have been implemented as well, based on an improved approach that accounts also for the energy dependence of the emission spectrum. The new analysis has small effect on the total secondary charged flux, but has an impact on the production yield and emission velocity distributions of the different particle species (protons, deuterons and tritons) at different angles with respect to the beam direction (60° and 90°). All these observables indeed depend on the particle identification algorithms and hence on the LYSO detector energy response. The results of the data re-analysis presented here are intended to supersede and replace the results published in (Piersanti et al. 2014). © 2017 Institute of Physics and Engineering in Medicine.

Addendum: Measurement of charged particle yields from PMMA irradiated by a 220 MeV/u 12C beam

NASA Astrophysics Data System (ADS)

Mattei, I.; Battistoni, G.; Collini, F.; De Lucia, E.; Durante, M.; Fiore, S.; La Tessa, C.; Mancini-Terracciano, C.; Marafini, M.; Mirabelli, R.; Muraro, S.; Paramatti, R.; Piersanti, L.; Rucinski, A.; Russomando, A.; Sarti, A.; Schuy, C.; Sciubba, A.; Solfaroli Camillocci, E.; Toppi, M.; Traini, G.; Valle, S. M.; Vanstalle, M.; Patera, V.

2017-11-01

In this paper we report the re-analysis of the data published in Piersanti et al (2014 Phys. Med. Biol. 59 1857) documenting the charged secondary particles production induced by the interaction of a 220 MeV/u 12C ion beam impinging on a polymethyl methacrylate (PMMA) target, measured in 2012 at the GSI facility in Darmstadt (Germany). This re-analysis takes into account the inhomogeneous light response of the LYSO crystal in the experimental setup measured in a subsequent experiment (2014) performed in the Heidelberg Ion-Beam Therapy Center. A better description of the detector and re-calculation of the geometrical efficiencies have been implemented as well, based on an improved approach that accounts also for the energy dependence of the emission spectrum. The new analysis has little effect on the total secondary charged flux, but has an impact on the production yield and emission velocity distributions of the different particle species (protons, deuterons and tritons) at different angles with respect to the beam direction (60^\\circ and 90^\\circ ). All these observables indeed depend on the particle identification algorithms and hence on the LYSO detector energy response. The results of the data re-analysis presented here are intended to supersede and replace the results published in Piersanti et al (2014 Phys. Med. Biol. 59 1857).

Nanopore DNA Sequencing and Genome Assembly on the International Space Station.

PubMed

Castro-Wallace, Sarah L; Chiu, Charles Y; John, Kristen K; Stahl, Sarah E; Rubins, Kathleen H; McIntyre, Alexa B R; Dworkin, Jason P; Lupisella, Mark L; Smith, David J; Botkin, Douglas J; Stephenson, Timothy A; Juul, Sissel; Turner, Daniel J; Izquierdo, Fernando; Federman, Scot; Stryke, Doug; Somasekar, Sneha; Alexander, Noah; Yu, Guixia; Mason, Christopher E; Burton, Aaron S

2017-12-21

We evaluated the performance of the MinION DNA sequencer in-flight on the International Space Station (ISS), and benchmarked its performance off-Earth against the MinION, Illumina MiSeq, and PacBio RS II sequencing platforms in terrestrial laboratories. Samples contained equimolar mixtures of genomic DNA from lambda bacteriophage, Escherichia coli (strain K12, MG1655) and Mus musculus (female BALB/c mouse). Nine sequencing runs were performed aboard the ISS over a 6-month period, yielding a total of 276,882 reads with no apparent decrease in performance over time. From sequence data collected aboard the ISS, we constructed directed assemblies of the ~4.6 Mb E. coli genome, ~48.5 kb lambda genome, and a representative M. musculus sequence (the ~16.3 kb mitochondrial genome), at 100%, 100%, and 96.7% consensus pairwise identity, respectively; de novo assembly of the E. coli genome from raw reads yielded a single contig comprising 99.9% of the genome at 98.6% consensus pairwise identity. Simulated real-time analyses of in-flight sequence data using an automated bioinformatic pipeline and laptop-based genomic assembly demonstrated the feasibility of sequencing analysis and microbial identification aboard the ISS. These findings illustrate the potential for sequencing applications including disease diagnosis, environmental monitoring, and elucidating the molecular basis for how organisms respond to spaceflight.

Cluster size dependence of high-order harmonic generation

NASA Astrophysics Data System (ADS)

Tao, Y.; Hagmeijer, R.; Bastiaens, H. M. J.; Goh, S. J.; van der Slot, P. J. M.; Biedron, S. G.; Milton, S. V.; Boller, K.-J.

2017-08-01

We investigate high-order harmonic generation (HHG) from noble gas clusters in a supersonic gas jet. To identify the contribution of harmonic generation from clusters versus that from gas monomers, we measure the high-order harmonic output over a broad range of the total atomic number density in the jet (from 3×1016 to 3 × 1018 {{cm}}-3) at two different reservoir temperatures (303 and 363 K). For the first time in the evaluation of the harmonic yield in such measurements, the variation of the liquid mass fraction, g, versus pressure and temperature is taken into consideration, which we determine, reliably and consistently, to be below 20% within our range of experimental parameters. By comparing the measured harmonic yield from a thin jet with the calculated corresponding yield from monomers alone, we find an increased emission of the harmonics when the average cluster size is less than 3000. Using g, under the assumption that the emission from monomers and clusters add up coherently, we calculate the ratio of the average single-atom response of an atom within a cluster to that of a monomer and find an enhancement of around 100 for very small average cluster size (∼200). We do not find any dependence of the cut-off frequency on the composition of the cluster jet. This implies that HHG in clusters is based on electrons that return to their parent ions and not to neighboring ions in the cluster. To fully employ the enhanced average single-atom response found for small average cluster sizes (∼200), the nozzle producing the cluster jet must provide a large liquid mass fraction at these small cluster sizes for increasing the harmonic yield. Moreover, cluster jets may allow for quasi-phase matching, as the higher mass of clusters allows for a higher density contrast in spatially structuring the nonlinear medium.

Low-energy N-ion beam biotechnology application in the induction of Thai jasmine rice mutant with improved seed storability

NASA Astrophysics Data System (ADS)

Semsang, Nuananong; Techarang, Jiranat; Yu, Liangdeng; Phanchaisri, Boonrak

2018-06-01

Low-energy heavy-ion beam is a novel biotechnology used for mutation induction in plants. We used a low-energy N-ion beam to induce mutations in Thai jasmine rice (Oryza sativa L. cv. KDML 105) to improve the yield and seed quality. Seeds of BKOS6, a Thai jasmine rice mutant previously induced by ion beams, were re-bombarded with 60-kV-accelerated N-ions (N++N2+) to fluences of 1-2 × 1016 ions/cm2. The resulting mutant, named HyKOS21, exhibited photoperiod insensitivity, semi-dwarfness, and high yield potential. Seed storability of the mutant was studied in natural and accelerated ageing conditions and compared to that of KDML 105 and six other Thai rice varieties. In both testing conditions, HyKOS21 mutant had the highest seed storability among the tested varieties. After storage in the natural condition for 18 months, HyKOS21 had a seed germination percentage nearly two times as that of the original KDML 105. Biochemical analysis showed that the lipid peroxidation level of the mutant seeds was the lowest among those of the tested varieties. Furthermore, an expression analysis of genes encoding lipoxygenase isoenzyme (lox1, lox2, and lox3) revealed that the mutant lacked expression of lox1 and lox2 and expressed only lox3 in seeds. These results may explain the improved seed longevity of the mutant after storage. This work provides further evidence of the modification of biological materials using a low-energy ion beam to produce rice mutants with improved yield and seed storability. The benefits of this technology, to create new varieties with improved values, could serve for local economic development.

Amine-modified magnetic iron oxide nanoparticle as a promising carrier for application in bio self-healing concrete.

PubMed

Seifan, Mostafa; Ebrahiminezhad, Alireza; Ghasemi, Younes; Samani, Ali Khajeh; Berenjian, Aydin

2018-01-01

Self-healing mechanisms are a promising solution to address the concrete cracking issue. Among the investigated self-healing strategies, the biotechnological approach is distinguished itself by inducing the most compatible material with concrete composition. In this method, the potent bacteria and nutrients are incorporated into the concrete matrix. Once cracking occurs, the bacteria will be activated, and the induced CaCO 3 crystals will seal the concrete cracks. However, the effectiveness of a bio self-healing concrete strictly depends on the viability of bacteria. Therefore, it is required to protect the bacteria from the resulted shear forces caused by mixing and drying shrinkage of concrete. Due to the positive effects on mechanical properties and the high compatibility of metallic nanoparticles with concrete composition, for the first time, we propose 3-aminopropyltriethoxy silane-coated iron oxide nanoparticles (APTES-coated IONs) as a biocompatible carrier for Bacillus species. This study was aimed to investigate the effect of APTES-coated IONs on the bacterial viability and CaCO 3 yield for future application in the concrete structures. The APTES-coated IONs were successfully synthesized and characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results show that the presence of 100 μg/mL APTES-coated IONs could increase the bacterial viability. It was also found that the CaCO 3 -specific yield was significantly affected in the presence of APTES-coated IONs. The highest CaCO 3 -specific yield was achieved when the cells were decorated with 50 μg/mL of APTES-coated IONs. This study provides new insights for the application of APTES-coated IONs in designing bio self-healing strategies.

Effect of metal surfaces on matrix-assisted laser desorption/ionization analyte peak intensities.

PubMed

Kancharla, Vidhyullatha; Bashir, Sajid; Liu, Jingbo L; Ramirez, Oscar M; Derrick, Peter J; Beran, Kyle A

2017-10-01

Different metal surfaces in the form of transmission electron microscope grids were examined as support surfaces in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with a view towards enhancement of peptide signal intensity. The observed enhancement between 5-fold and 20-fold relative to the normal stainless steel slide was investigated by applying the thermal desorption model for matrix-assisted laser desorption/ionization. A simple model evaluates the impact that the thermal properties of the metals have on the ion yield of the analyte. It was observed that there was not a direct, or strong, correlation between the thermal properties of the metals and the corresponding ion yield of the peptides. The effects of both fixed and variable laser irradiances versus ion yield were also examined for the respective metals studied. In all cases the use of transmission electron microscope grids required much lower laser irradiances in order to generate similar peak intensities as those observed with a stainless steel surface.

The 15 cm mercury ion thruster research 1975

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1975-01-01

Doubly charged ion current measurements in the beam of a SERT II thruster are shown to introduce corrections which bring its calculated thrust into close agreement with that measured during flight testing. A theoretical model of doubly charged ion production and loss in mercury electron bombardment thrusters is discussed and is shown to yield doubly-to-singly charged ion density ratios that agree with experimental measurements obtained on a 15 cm diameter thruster over a range of operating conditions. Single cusp magnetic field thruster operation is discussed and measured ion beam profiles, performance data, doubly charged ion densities, and discharge plasma characteristics are presented for a range of operating conditions and thruster geometries. Variations in the characteristics of this thruster are compared to those observed in the divergent field thruster and the cusped field thruster is shown to yield flatter ion beam profiles at about the same discharge power and propellant utilization operating point. An ion optics test program is described and the measured effects of grid system dimensions on ion beamlet half angle and diameter are examined. The effectiveness of hollow cathode startup using a thermionically emitting filament within the cathode is examined over a range of mercury flow rates and compared to results obtained with a high voltage tickler startup technique. Results of cathode plasma property measurement tests conducted within the cathode are presented.

Molecular Growth Inside of Polycyclic Aromatic Hydrocarbon Clusters Induced by Ion Collisions.

PubMed

Delaunay, Rudy; Gatchell, Michael; Rousseau, Patrick; Domaracka, Alicja; Maclot, Sylvain; Wang, Yang; Stockett, Mark H; Chen, Tao; Adoui, Lamri; Alcamí, Manuel; Martín, Fernando; Zettergren, Henning; Cederquist, Henrik; Huber, Bernd A

2015-05-07

The present work combines experimental and theoretical studies of the collision between keV ion projectiles and clusters of pyrene, one of the simplest polycyclic aromatic hydrocarbons (PAHs). Intracluster growth processes induced by ion collisions lead to the formation of a wide range of new molecules with masses larger than that of the pyrene molecule. The efficiency of these processes is found to strongly depend on the mass and velocity of the incoming projectile. Classical molecular dynamics simulations of the entire collision process-from the ion impact (nuclear scattering) to the formation of new molecular species-reproduce the essential features of the measured molecular growth process and also yield estimates of the related absolute cross sections. More elaborate density functional tight binding calculations yield the same growth products as the classical simulations. The present results could be relevant to understand the physical chemistry of the PAH-rich upper atmosphere of Saturn's moon Titan.

Utilization of turkey manure as granular activated carbon: physical, chemical and adsorptive properties.

PubMed

Lima, Isabel; Marshall, Wayne E

2005-01-01

The high availability of large quantities of turkey manure generated from turkey production makes it an attractive feedstock for carbon production. Pelletized samples of turkey litter and cake were converted to granular activated carbons (GACs) by steam activation. Water flow rate and activation time were changed to produce a range of activation conditions. The GACs were characterized for select physical (yield, surface area, bulk density, attrition), chemical (pH, surface charge) and adsorptive properties (copper ion uptake). Carbon physical and adsorptive properties were dependent on activation time and quantity of steam used as activant. Yields varied from 23% to 37%, surface area varied from 248 to 472 m(2)/g and copper ion adsorption varied from 0.72 to 1.86 mmol Cu(2+)/g carbon. Copper ion adsorption greatly exceeded the values for two commercial GACs. GACs from turkey litter and cake show considerable potential to remove metal ions from water.

Phase Stabilization of Ammonium Nitrate

DTIC Science & Technology

2008-11-04

substance into the ammonium nitrate crystal structure. Salts containing ions larger or smaller than either ammonium or nitrate ions have been used...introducing another substance into the ammonium nitrate crystal structure. Salts containing ions larger or smaller than either ammonium or nitrate...two ionic attachment points should yield a nonmigrating salt due to difficulty of having simultaneous dissociation of two ionic structures

Assessment of the ion-trap mass spectrometer for routine qualitative and quantitative analysis of drugs of abuse extracted from urine.

PubMed

Vorce, S P; Sklerov, J H; Kalasinsky, K S

2000-10-01

The ion-trap mass spectrometer (MS) has been available as a detector for gas chromatography (GC) for nearly two decades. However, it still occupies a minor role in forensic toxicology drug-testing laboratories. Quadrupole MS instruments make up the majority of GC detectors used in drug confirmation. This work addresses the use of these two MS detectors, comparing the ion ratio precision and quantitative accuracy for the analysis of different classes of abused drugs extracted from urine. Urine specimens were prepared at five concentrations each for amphetamine (AMP), methamphetamine (METH), benzoylecgonine (BZE), delta9-carboxy-tetrahydrocannabinol (delta9-THCCOOH), phencyclidine (PCP), morphine (MOR), codeine (COD), and 6-acetylmorphine (6-AM). Concentration ranges for AMP, METH, BZE, delta9-THCCOOH, PCP, MOR, COD, and 6-AM were 50-2500, 50-5000, 15-800, 1.5-65, 1-250, 500-32000, 250-21000, and 1.5-118 ng/mL, respectively. Sample extracts were injected into a GC-quadrupole MS operating in selected ion monitoring (SIM) mode and a GC-ion-trap MS operating in either selected ion storage (SIS) or full scan (FS) mode. Precision was assessed by the evaluation of five ion ratios for n = 15 injections at each concentration using a single-point calibration. Precision measurements for SIM ion ratios provided coefficients of variation (CV) between 2.6 and 9.8% for all drugs. By comparison, the SIS and FS data yielded CV ranges of 4.0-12.8% and 4.0-11.2%, respectively. The total ion ratio failure rates were 0.2% (SIM), 0.7% (SIS), and 1.2% (FS) for the eight drugs analyzed. Overall, the SIS mode produced stable, comparable mean ratios over the concentration ranges examined, but had greater variance within batch runs. Examination of postmortem and quality-control samples produced forensically accurate quantitation by SIS when compared to SIM. Furthermore, sensitivity of FS was equivalent to SIM for all compounds examined except for 6-AM.

Stochastic properties of radiation-induced DSB: DSB distributions in large scale chromatin loops, the HPRT gene and within the visible volumes of DNA repair foci.

PubMed

Ponomarev, Artem L; Costes, Sylvain V; Cucinotta, Francis A

2008-11-01

We computed probabilities to have multiple double-strand breaks (DSB), which are produced in DNA on a regional scale, and not in close vicinity, in volumes matching the size of DNA damage foci, of a large chromatin loop, and in the physical volume of DNA containing the HPRT (human hypoxanthine phosphoribosyltransferase) locus. The model is based on a Monte Carlo description of DSB formation by heavy ions in the spatial context of the entire human genome contained within the cell nucleus, as well as at the gene sequence level. We showed that a finite physical volume corresponding to a visible DNA repair focus, believed to be associated with one DSB, can contain multiple DSB due to heavy ion track structure and the DNA supercoiled topography. A corrective distribution was introduced, which was a conditional probability to have excess DSB in a focus volume, given that there was already one present. The corrective distribution was calculated for 19.5 MeV/amu N ions, 3.77 MeV/amu alpha-particles, 1000 MeV/amu Fe ions, and X-rays. The corrected initial DSB yield from the experimental data on DNA repair foci was calculated. The DSB yield based on the corrective function converts the focus yield into the DSB yield, which is comparable with the DSB yield based on the earlier PFGE experiments. The distribution of DSB within the physical limits of the HPRT gene was analyzed by a similar method as well. This corrective procedure shows the applicability of the model and empowers the researcher with a tool to better analyze focus statistics. The model enables researchers to analyze the DSB yield based on focus statistics in real experimental situations that lack one-to-one focus-to-DSB correspondance.

Barium-strontium-titanate etching characteristics in chlorinated discharges

NASA Astrophysics Data System (ADS)

Stafford, Luc; Margot, Joëlle; Langlois, Olivier; Chaker, Mohamed

2003-07-01

The etching characteristics of barium-strontium-titanate (BST) were investigated using a high-density plasma sustained by surface waves at 190 MHz in Ar/Cl2 gas mixtures. The etch rate was examined as a function of both the total gas pressure and the Cl2 fraction in Ar/Cl2 using a wafer temperature of 10 °C. The results were correlated to positive ion density and plasma composition obtained from Langmuir probes and mass spectrometry. The BST etch rate was found to increase linearly with the positive ion density and to decrease with increasing chlorine atom concentration. This result indicates that for the temperature conditions used, the interaction between chlorine and BST yields compounds having a volatility that is lower than the original material. As a consequence, the contribution of neutral atomic Cl atoms to the etch mechanism is detrimental, thereby reducing the etch rate. As the wafer temperature increases, the role of chemistry in the etching process is enhanced.

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

Habercorn, Lasse; Merkl, Jan-Philip; Kloust, Hauke Christian

With the polymer encapsulation of quantum dots via seeded emulsion polymerization we present a powerful tool for the preparation of fluorescent nanoparticles with an extraordinary stability in aqueous solution. The method of the seeded emulsion polymerization allows a straightforward and simple in situ functionalization of the polymer shell under preserving the optical properties of the quantum dots. These requirements are inevitable for the application of semiconductor nanoparticles as markers for biomedical applications. Polymer encapsulated quantum dots have shown only a marginal loss of quantum yields when they were exposed to copper(II)-ions. Under normal conditions the quantum dots were totally quenchedmore » in presence of copper(II)-ions. Furthermore, a broad range of in situ functionalized polymer-coated quantum dots were obtained by addition of functional monomers or surfactants like fluorescent dye molecules, antibodies or specific DNA aptamers. Furthermore the emulsion polymerization can be used to prepare multifunctional hybrid systems, combining different nanoparticles within one construct without any adverse effect of the properties of the starting materials.{sup 1,2}.« less

Experimental study of fusion neutron and proton yields produced by petawatt-laser-irradiated D₂-³He or CD₄-³He clustering gases.

PubMed

Bang, W; Barbui, M; Bonasera, A; Quevedo, H J; Dyer, G; Bernstein, A C; Hagel, K; Schmidt, K; Gaul, E; Donovan, M E; Consoli, F; De Angelis, R; Andreoli, P; Barbarino, M; Kimura, S; Mazzocco, M; Natowitz, J B; Ditmire, T

2013-09-01

We report on experiments in which the Texas Petawatt laser irradiated a mixture of deuterium or deuterated methane clusters and helium-3 gas, generating three types of nuclear fusion reactions: D(d,^{3}He)n, D(d,t)p, and ^{3}He(d,p)^{4}He. We measured the yields of fusion neutrons and protons from these reactions and found them to agree with yields based on a simple cylindrical plasma model using known cross sections and measured plasma parameters. Within our measurement errors, the fusion products were isotropically distributed. Plasma temperatures, important for the cross sections, were determined by two independent methods: (1) deuterium ion time of flight and (2) utilizing the ratio of neutron yield to proton yield from D(d,^{3}He)n and ^{3}He(d,p)^{4}He reactions, respectively. This experiment produced the highest ion temperature ever achieved with laser-irradiated deuterium clusters.

Profiling and identification of chlorogenic acid metabolites in rats by ultra-high-performance liquid chromatography coupled with linear ion trap-Orbitrap mass spectrometer.

PubMed

Wang, Fei; Shang, Zhanpeng; Xu, Lulu; Wang, Zhibin; Zhao, Wenjing; Mei, XiaoDan; Lu, Jianqiu; Zhang, Jia Yu

2018-06-01

1. Chlorogenic acids (CGAs), one kind of major bioactive constituents isolated from Flos Lonicera Japonica, possess many biological activities, such as antibacterial, antioxidant and antiviral activities. In this study, we established an efficient strategy using ultra-high-performance liquid chromatography coupled with linear ion trap-Orbitrap mass spectrometry (UHPLC-LTQ-Orbitrap MS) to profile the in vivo metabolic fate of CGAs in rat urine and plasma. 2. The extract from Flos Lonicera Japonica was orally administrated to Sprague-Dawley (SD) rats at a dose of 1000 mg/kg body weight. Then, a combination of various post-acquisition data mining methods, including high-resolution extracted ion chromatogram (HREIC) and multiple mass defect filters (MMDFs) and diagnostic product ions (DPIs), were adopted to characterize the known and unknown CGA metabolites in SD rats. 3. As a result, a total of 68 CGA metabolites were unambiguously or tentatively screened and characterized. These metabolites, including 18 prototype compounds and 50 metabolites, were deduced to be yielded via methylation, hydrogenation, demethylation, dehydration, sulfate conjugation, glucuronide conjugation, glycosylation conjugation and their composite reactions, which mainly occurred to caffeoylquinic acids, dicaffeoylquinic acids, p-coumaroylquinic acids and feruloylquinic acids. 4. In conclusion, this study profiled CGA metabolites, which are useful in understanding the in vivo metabolic fate, effective forms, and pharmacological and toxic actions of CGAs.

Fundamental studies of gas phase ionic reactions by ion mobility spectrometry

NASA Technical Reports Server (NTRS)

Giles, K.; Knighton, W. B.; Sahlstrom, K. E.; Grimsrud, E. P.

1995-01-01

Ion mobility spectrometry (IMS) provides a promising approach to the study of gas phase ionic reactions in buffer gases at unusually high pressures. This point is illustrated here by studies of the Sn2 nucleophilic displacement reaction, Cl(-) + CH3Br yields Br + CH3Br, using IMS at atmospheric pressure. The equilibrium clustering reaction, Cl(-)(CHCI3)(n - 1) + CHCI3 yields Cl(-)(CHCI3)(n), where n = 1 and 2, and the effect of clustering on the Sn2 reaction with CH3Br have also been characterized by this IMS-based kinetic method. Present problems and anticipated improvements in the application of ion mobility spectrometry to studies of other gas phase ionic processes are discussed.

Effect of ion irradiation on the surface, structural and mechanical properties of brass

NASA Astrophysics Data System (ADS)

Ahmad, Shahbaz; Bashir, Shazia; Ali, Nisar; Umm-i-Kalsoom; Yousaf, Daniel; Faizan-ul-Haq; Naeem, Athar; Ahmad, Riaz; Khlaeeq-ur-Rahman, M.

2014-04-01

Modifications to the surface, structural and mechanical properties of brass after ion irradiation have been investigated. Brass targets were bombarded by carbon ions of 2 MeV energy from a Pelletron linear accelerator for various fluences ranging from 56 × 1012 to 26 × 1013 ions/cm2. A scanning electron microscope and X-ray diffractometer were utilized to analyze the surface morphology and crystallographic structure respectively. To explore the mechanical properties e.g., yield stress, ultimate tensile strength and microhardness of irradiated brass, an universal tensile testing machine and Vickers microhardness tester were used. Scanning electron microscopy results revealed an irregular and randomly distributed sputter morphology for a lower ion fluence. With increasing ion fluence, the incoherently shaped structures were transformed into dendritic structures. Nano/micro sized craters and voids, along with the appearance of pits, were observed at the maximum ion fluence. From X-ray diffraction results, no new phases were observed to be formed in the brass upon irradiation. However, a change in the peak intensity and higher and lower angle shifting were observed, which represents the generation of ion-induced defects and stresses. Analyses confirmed modifications in the mechanical properties of irradiated brass. The yield stress, ultimate tensile strength and hardness initially decreased and then increased with increasing ion fluence. The changes in the mechanical properties of irradiated brass are well correlated with surface and crystallographic modifications and are attributed to the generation, augmentation, recombination and annihilation of the ion-induced defects.

Mass spectral analysis and imaging of tissue by ToF-SIMS--The role of buckminsterfullerene, C60+, primary ions

NASA Astrophysics Data System (ADS)

Jones, Emrys A.; Lockyer, Nicholas P.; Vickerman, John C.

2007-02-01

Recent developments in desorption/ionisation mass spectrometry techniques have made their application to biological analysis a realistic and successful proposition. Developments in primary ion source technology, mainly through the advent of polyatomic ion beams, have meant that the technique of secondary ion mass spectrometry (SIMS) can now access the depths of information required to allow biological imaging to be a viable option. Here the role of the primary ion C60+ is assessed with regard to molecular imaging of lipids and pharmaceuticals within tissue sections. High secondary ion yields and low surface damage accumulation are demonstrated on both model and real biological samples, indicating the high secondary ion efficiency afforded to the analyst by this primary ion when compared to other cluster ion beams used in imaging. The newly developed 40 keV C60+ ion source allows the beam to be focused such that high resolution imaging is demonstrated on a tissue sample, and the greater yields allow the molecular signal from the drug raclopride to be imaged within tissue section following in vivo dosing. The localisation shown for this drug alludes to issues regarding the chemical environment affecting the ionisation probability of the molecule; the importance of this effect is demonstrated with model systems and the possibility of using laser post-ionisation as a method for reducing this consequence of bio-sample complexity is demonstrated and discussed.

Effect of calcium oxide on the efficiency of ferrous ion oxidation and total iron precipitation during ferrous ion oxidation in simulated acid mine drainage treatment with inoculation of Acidithiobacillus ferrooxidans.

PubMed

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.

The Biological Effectiveness of Four Energies of Neon Ions for the Induction of Chromosome Damage in Human Lymphocytes

NASA Technical Reports Server (NTRS)

George, Kerry; Hada, Megumi; Cucinotta, F. A.

2011-01-01

Chromosomal aberrations were measured in human peripheral blood lymphocytes after in vitro exposure to neon ions at energies of 64, 89, 142, or 267. The corresponding LET values for these energies of neon ranged from 38-103 keV/micrometers and doses delivered were in the 10 to 80 cGy range. Chromosome exchanges were assessed in metaphase and G2 phase cells at first division after exposure using fluorescence in situ hybridization (FISH) with whole chromosome probes and dose response curves were generated for different types of chromosomal exchanges. The yields of total chromosome exchanges were similar for the 64, 89, and 142 MeV exposures, whereas the 267 MeV/u neon with LET of 38 keV/micrometers produced about half as many exchanges per unit dose. The induction of complex type chromosome exchanges (exchanges involving three or more breaks and two or more chromosomes) showed a clear LET dependence for all energies. The ratio of simple to complex type exchanges increased with LET from 18 to 51%. The relative biological effectiveness (RBE) was estimated from the initial slope of the dose response curve for chromosome damage with respect to gamma-rays. The RBE(sub max) values for total chromosome exchanges for the 64 MeV/u was around 30.

Calibrating ion density profile measurements in ion thruster beam plasma

NASA Astrophysics Data System (ADS)

Zhang, Zun; Tang, Haibin; Ren, Junxue; Zhang, Zhe; Wang, Joseph

2016-11-01

The ion thruster beam plasma is characterized by high directed ion velocity (104 m/s) and low plasma density (1015 m-3). Interpretation of measurements of such a plasma based on classical Langmuir probe theory can yield a large experimental error. This paper presents an indirect method to calibrate ion density determination in an ion thruster beam plasma using a Faraday probe, a retarding potential analyzer, and a Langmuir probe. This new method is applied to determine the plasma emitted from a 20-cm-diameter Kaufman ion thruster. The results show that the ion density calibrated by the new method can be as much as 40% less than that without any ion current density and ion velocity calibration.

Plasma-screening effects on the electron-impact excitation of hydrogenic ions in dense plasmas

NASA Technical Reports Server (NTRS)

Jung, Young-Dae

1993-01-01

Plasma-screening effects are investigated on electron-impact excitation of hydrogenic ions in dense plasmas. Scaled cross sections Z(exp 4) sigma for 1s yields 2s and 1s yields 2p are obtained for a Debye-Hueckel model of the screened Coulomb interaction. Ground and excited bound wave functions are modified in the screened Coulomb potential (Debye-Hueckel model) using the Ritz variation method. The resulting atomic wave functions and their eigenenergies agree well with the numerical and high-order perturbation theory calculations for the interesting domain of the Debye length not less than 10. The Born approximation is used to describe the continuum states of the projectile electron. Plasma screening effects on the atomic electrons cannot be neglected in the high-density cases. Including these effects, the cross sections are appreciably increased for 1s yields 2s transitions and decreased for 1s yields 2p transitions.

Transmission sputtering under diatomic molecule bombardment. Model calculations

NASA Astrophysics Data System (ADS)

Bitensky, I. S.

1996-04-01

Transmission sputtering means that emission of secondary particles is studied from the downstream side of a bombarded foil. Nonlinear effects in sputtering manifest themselves as a deviation of sputtering yield under molecular ion bombardment from the sum of the yields induced by the constituents at the same velocity. In the reflection geometry the overlap of the spike regions reaches maximum, while in transmission the degree of overlap depends on the projectile and on the foil thickness. It has been shown that the transmission sputtering yield can be described by a function of a scaling parameter determined by beam-foil characteristics and a mechanism of nonlinear sputtering. Calculations of the transmission yield have been made in the thermal spike and shock wave models. The results of calculations are compared with experimental data on phenylalanine molecular ion desorption from organic targets induced by Au + and Au 2+ impact. Suggestions for further experimental study are made.

Direct-drive DT implosions with Knudsen number variations

DOE PAGES

Kim, Yong Ho; Herrmann, Hans W.; Hoffman, Nelson M.; ...

2016-05-26

Direct-drive implosions of DT-filled plastic-shells have been conducted at the Omega laser facility, measuring nuclear yields while varying Knudsen numbers (i.e., the ratio of mean free path of fusing ions to the length of fuel region) by adjusting both shell thickness (e.g., 7.5, 15, 20, 30 μm) and fill pressure (e.g., 2, 5, 15 atm). In addition, the fusion reactivity reduction model showed a stronger effect on yield as the Knudsen number increases (or the shell thickness decreases). The Reduced-Ion-Kinetic (RIK) simulation which includes both fusion reactivity reduction and mix model was necessary to provide a better match between themore » observed neutron yields and those simulated.« less

A study of Kapton degradation under simulated shuttle environment

NASA Technical Reports Server (NTRS)

Eck, T. G.; Hoffman, R. W.

1986-01-01

A system was developed which employs a source of low energy oxygen ion to simulate the shuttle low Earth orbit environment. This source, together with diagnostic tools including surface analysis ans mass spectroscopic capability, was used to measure the dependence of ion energy of the oxygen induced CO signals from pyrolytic graphite and Kapton. For graphite the CO signal was examined at energies ranging form 4.5 to 465 eV and for Kapton from 4.5 to 188 eV. While the relative quantum yields inferred from the data are reasonably precise, there are large uncertainties in the absolute yields because of the assumptions necessary to covert the measured signal strengths to quantum yields. These assumptions are discussed in detail.

Ion beam sputtering of fluoropolymers. [etching polymer films and target surfaces

NASA Technical Reports Server (NTRS)

Sovey, J. S.

1978-01-01

Ion beam sputter processing rates as well as pertinent characteristics of etched targets and films are described. An argon ion beam source was used to sputter etch and deposit the fluoropolymers PTFE, FEP, and CTFE. Ion beam energy, current density, and target temperature were varied to examine effects on etch and deposition rates. The ion etched fluoropolymers yield cone or spire-like surface structures which vary depending upon the type of polymer, ion beam power density, etch time, and target temperature. Sputter target and film characteristics documented by spectral transmittance measurements, X-ray diffraction, ESCA, and SEM photomicrographs are included.

Protons from carbon ion fragmentation at 0.3–2.0 GeV/nucleon: Comparison with models of ion-ion interactions

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

Abramov, B. M.; Alekseev, P. N.; Borodin, Yu. A.

2015-05-15

Yields of protons at 3.5° from carbon ion fragmentation at energies of T{sub 0} = 0.3, 0.6, 0.95, and 2.0 GeV/nucleon on a Be target were measured in the FRAGM experiment at TWA-ITEP heavy-ion facility. Proton momentum spectra cover both the region of the fragmentation maximum and the cumulative region. The differential cross sections span six orders of its magnitude. The spectra are compared with the predictions of four models of ion-ion interactions: LAQGSM03.03, SHIELD-HIT, QMD, and BC.

The mechanism of the photochemical oxidation of water to oxygen with silver chloride colloids

NASA Astrophysics Data System (ADS)

Chandrasekaran, K.; Thomas, J. K.

1983-05-01

Photoexcitation of silver chloride colloids in the presence of excess silver ions, leads to the decomposition of water. Hydroxyl radicals were found to be intermediates in the decomposition process. Irradiation leads to hydroxyl radicals, which recombine to give hydrogen peroxide, on the colloidal particle surface. Subsequent decomposition of H 2O 2 to give O 2 is catalyzed by silver ions. Addition of alcohols such as methanol and isopropanol reduce the oxygen yield, as they react with OH radicals and reduce the H 2O 2 yield.

Breeding of D(-)-lactic acid high producing strain by low-energy ion implantation and preliminary analysis of related metabolism.

PubMed

Xu, Ting-Ting; Bai, Zhong-Zhong; Wang, Li-Juan; He, Bing-Fang

2010-01-01

The low-energy nitrogen ion beam implantation technique was used in the breeding of mutant D(-)-lactic-acid-producing strains. The wild strain Sporolactobacillus sp. DX12 was mutated by an N(+) ion beam with energy of 10keV and doses ranging from 0.4 x 10(15) to 6.60 x 10(15) ions/cm(2). Combined with an efficient screening method, an efficient mutant Y2-8 was selected after two times N(+) ion beam implantation. By using the mutant Y2-8, 121.6g/l of D-lactic acid was produced with the molar yields of 162.1% to the glucose. The yield of D-lactic acid by strain Y2-8 was 198.8% higher than the wild strain. Determination of anaerobic metabolism by Biolog MT2 was used to analyze the activities of the concerned enzymes in the lactic acid metabolic pathway. The results showed that the activities of the key enzymes responded on the substrates such as 6-phosphofructokinase, pyruvate kinase, and D-lactate dehydrogenase were considerably higher in the mutants than the wild strain. These might be affected by ion beam implantation.

Small-scale characterisation of irradiated nuclear materials: Part II nanoindentation and micro-cantilever testing of ion irradiated nuclear materials

NASA Astrophysics Data System (ADS)

Armstrong, D. E. J.; Hardie, C. D.; Gibson, J. S. K. L.; Bushby, A. J.; Edmondson, P. D.; Roberts, S. G.

2015-07-01

This paper demonstrates the ability of advanced micro-mechanical testing methods, based on FIB machined micro-cantilevers, to measure the mechanical properties of ion implanted layers without the influence of underlying unimplanted material. The first section describes a study of iron-12 wt% chromium alloy implanted with iron ions. It is shown that by careful cantilever design and finite element modelling that changes in yield stress after implantation can be measured even with the influence of a strong size effect. The second section describes a study of tungsten implanted with both tungsten ions and tungsten and helium ions using spherical and sharp nanoindentation, and micro-cantilevers. The spherical indentation allows yield properties and work hardening behaviour of the implanted layers to be measured. However the brittle nature of the implanted tungsten is only revealed when using micro-cantilevers. This demonstrates that when applying micro-mechanical methods to ion implanted layers care is needed to understand the nature of size effects, careful modelling of experimental procedure is required and multiple experimental techniques are needed to allow the maximum amount of mechanical behaviour information to be collected.

Rapid Screening of Carboxylic Acids from Waste and Surface Waters by ESI-MS/MS Using Barium Ion Chemistry and On-Line Membrane Sampling.

PubMed

Duncan, Kyle D; Volmer, Dietrich A; Gill, Chris G; Krogh, Erik T

2016-03-01

Negative ion tandem mass spectrometric analysis of aliphatic carboxylic acids often yields only non-diagnostic ([M - H](-)) ions with limited selective fragmentation. However, carboxylates cationized with Ba(2+) have demonstrated efficient dissociation in positive ion mode, providing structurally diagnostic product ions. We report the application of barium adducts followed by collision induced dissociation (CID), to improve selectivity for rapid screening of carboxylic acids in complex aqueous samples. The quantitative MS/MS method presented utilizes common product ions of [M - H + Ba](+) precursor ions. The mechanism of product ion formation is investigated using isotopically labeled standards and a series of structurally related carboxylic acids. The results suggest that hydrogen atoms in the β and γ positions yield common product ions ([BaH](+) and [BaOH](+)). Furthermore, the diagnostic product ion at m/z 196 serves as a qualifying ion for carboxylate species. This methodology has been successfully used in conjunction with condensed phase membrane introduction mass spectrometry (CP-MIMS), with barium acetate added directly to the methanol acceptor phase. The combination enables rapid screening of carboxylic acids directly from acidified water samples (wastewater effluent, spiked natural waters) using a capillary hollow fiber PDMS membrane immersion probe. We have applied this technique for the direct analysis of complex naphthenic acid mixtures spiked into natural surface waters using CP-MIMS. Selectivity at the ionization and tandem mass spectrometry level eliminate isobaric interferences from hydroxylated species present within the samples, which have been observed in negative electrospray ionization.

A modified microdosimetric kinetic model for relative biological effectiveness calculation

NASA Astrophysics Data System (ADS)

Chen, Yizheng; Li, Junli; Li, Chunyan; Qiu, Rui; Wu, Zhen

2018-01-01

In the heavy ion therapy, not only the distribution of physical absorbed dose, but also the relative biological effectiveness (RBE) weighted dose needs to be taken into account. The microdosimetric kinetic model (MKM) can predict the RBE value of heavy ions with saturation-corrected dose-mean specific energy, which has been used in clinical treatment planning at the National Institute of Radiological Sciences. In the theoretical assumption of the MKM, the yield of the primary lesion is independent of the radiation quality, while the experimental data shows that DNA double strand break (DSB) yield, considered as the main primary lesion, depends on the LET of the particle. Besides, the β parameter of the MKM is constant with LET resulting from this assumption, which also differs from the experimental conclusion. In this study, a modified MKM was developed, named MMKM. Based on the experimental DSB yield of mammalian cells under the irradiation of ions with different LETs, a RBEDSB (RBE for the induction of DSB)-LET curve was fitted as the correction factor to modify the primary lesion yield in the MKM, and the variation of the primary lesion yield with LET is considered in the MMKM. Compared with the present the MKM, not only the α parameter of the MMKM for mono-energetic ions agree with the experimental data, but also the β parameter varies with LET and the variation trend of the experimental result can be reproduced on the whole. Then a spread-out Bragg peaks (SOBP) distribution of physical dose was simulated with Geant4 Monte Carlo code, and the biological and clinical dose distributions were calculated, under the irradiation of carbon ions. The results show that the distribution of clinical dose calculated with the MMKM is closed to the distribution with the MKM in the SOBP, while the discrepancy before and after the SOBP are both within 10%. Moreover, the MKM might overestimate the clinical dose at the distal end of the SOBP more than 5% because of its constant β value, while a minimal value of β is calculated with the MMKM at this position. Besides, the discrepancy of the averaged cell survival fraction in the SOBP calculated with the two models is more than 15% at the high dose level. The MMKM may provide a reference for the accurate calculation of the RBE value in heavy ion therapy.

Nanofabrication with a helium ion microscope

NASA Astrophysics Data System (ADS)

Maas, Diederik; van Veldhoven, Emile; Chen, Ping; Sidorkin, Vadim; Salemink, Huub; van der Drift, Emile..; Alkemade, Paul

2010-03-01

The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valuable signal for high-resolution imaging as well as a mechanism for very precise nanofabrication. The low proximity effects, due to the low yield of backscattered ions and the confinement of the forward scattered ions into a narrow cone, enable patterning of ultra-dense sub-10 nm structures. This paper presents various nanofabrication results obtained with direct-write, with scanning helium ion beam lithography, and with helium ion beam induced deposition.

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

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

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

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

Non-thermal ion desorption from an acetonitrile (CH3CN) astrophysical ice analogue studied by electron stimulated ion desorption.

PubMed

Ribeiro, F de A; Almeida, G C; Garcia-Basabe, Y; Wolff, W; Boechat-Roberty, H M; Rocco, M L M

2015-11-07

The incidence of high-energy radiation onto icy surfaces constitutes an important route for leading new neutral or ionized molecular species back to the gas phase in interstellar and circumstellar environments, especially where thermal desorption is negligible. In order to simulate such processes, an acetonitrile ice (CH3CN) frozen at 120 K is bombarded by high energy electrons, and the desorbing positive ions are analyzed by time-of-flight mass spectrometry (TOF-MS). Several fragment and cluster ions were identified, including the Hn=1-3(+), CHn=0-3(+)/NHn=0-1(+); C2Hn=0-3(+)/CHn=0-3N(+), C2Hn=0-6N(+) ion series and the ion clusters (CH3CN)n=1-2(+) and (CH3CN)n=1-2H(+). The energy dependence on the positive ion desorption yield indicates that ion desorption is initiated by Coulomb explosion following Auger electronic decay. The results presented here suggest that non-thermal desorption processes, such as desorption induced by electronic transitions (DIET) may be responsible for delivering neutral and ionic fragments from simple nitrile-bearing ices to the gas-phase, contributing to the production of more complex molecules. The derived desorption yields per electron impact may contribute to chemical evolution models in different cold astrophysical objects, especially where the abundance of CH3CN is expected to be high.

Ion-beam technology and applications

NASA Technical Reports Server (NTRS)

Hudson, W. R.; Robson, R. R.; Sovey, J. S.

1977-01-01

Ion propulsion research and development yields a mature technology that is transferable to a wide range of nonpropulsive applications, including terrestrial and space manufacturing. A xenon ion source was used for an investigation into potential ion-beam applications. The results of cathode tests and discharge-chamber experiments are presented. A series of experiments encompassing a wide range of potential applications is discussed. Two types of processes, sputter deposition, and erosion were studied. Some of the potential applications are thin-film Teflon capacitor fabrication, lubrication applications, ion-beam cleaning and polishing, and surface texturing.

Electrolytic Conductance of the Ternary System of Nitric Acid--Nitrogen Dioxide--Water at 32 deg F and Atmospheric Pressure

DTIC Science & Technology

1951-11-12

solutions of nitrogen dioxide in nitric acid where nitrosonium ions (NO+) and nitrate ions (NO-) have been identified (Cf. Ref. 4). The nitrogen...0.97 weight fraction nitric acid, hydrogen and nitrate ions are the predominant conducting species. In the range 0.97 to 1.00 weight fraction nitric...self-ionization to yield nitronium ions (NJ2) and nitratej2 ions (NO3) according to the expression 2HNO3--NO+ + NO- + H2 0 It is evident from this

Physical and chemical characterization of petroleum products by GC-MS.

PubMed

Mendez, A; Meneghini, R; Lubkowitz, J

2007-01-01

There is a need for reliable and fast means of monitoring refining, conversion, and upgrading processes aiming to increase the yield of light distillates, and thus, reducing the oil barrel bottoms. By simultaneously utilizing the FID and mass selective detectors while splitting the column effluent in a controlled way, it is possible to obtain identical gas chromatograms and total ion chromatograms from a single run. This means that besides the intensity vs. time graphs, the intensity vs. mass and boiling point can also be obtained. As a result, physical and chemical characterization can be performed in a simple and rapid manner. Experimental results on middle, heavy distillates, and crude oil fractions show clearly the effect of upgrading processes on the chemical composition and yields of diesel, jet fuels, and high vacuum gasoil fractions. The methodology is fully compliant with ASTM D-2887, D-7213, D-6352, and D7169 for simulated distillation and the previously mentioned mass spectrometry standards. The group type analysis correlated satisfactorily with high-performance liquid chromatography data.

Acetonitrile covalent adduct chemical ionization mass spectrometry for double bond localization in non-methylene-interrupted polyene fatty acid methyl esters.

PubMed

Lawrence, Peter; Brenna, J Thomas

2006-02-15

Covalent adduct chemical ionization (CACI) using a product of acetonitrile self-reaction, (1-methyleneimino)-1-ethenylium (MIE; CH2=C=N+=CH2), has been investigated as a method for localizing double bonds in a series of 16 non-methylene-interrupted fatty acid methyl esters (NMI-FAME) of polyenes with three and more double bonds. As with polyunsaturated homoallylic (methylene-interrupted) FAME and conjugated dienes, MIE (m/z 54) reacts across double bonds to yield molecular ions 54 mass units above the parent analyte. [M + 54]+ ions of several 20- and 22-carbon FAME that include one double bond in the C2-C3 position separated by two to five methylene units from a three, four, or five C homoallylic system dissociated according to rules for the homoallylic system, with an additional fragment corresponding to cleavage between the lone double bond and the carboxyl group and defining the position of the lone double bond. Triene FAME with both methylene and ethylene interruption yielded characteristic fragments distinguishable from homoallylic trienes. Fragmentation of fully conjugated trienes in the MS-1 spectra yields ratios of [M + 54]+/[M + 54 - 32]+ (loss of methanol) near unity, which distinguishes them from homoallylic FAME having a ratio of 8 or more; collisionally activated dissociation of [M + 54]+ yields a series of ions, including some rearrangement products, indicative of double bond position. Unlike conjugated dienes, fully conjugated triene diagnostic ion signal ratios did not follow any pattern based on double bond geometry. Partially conjugated trienes behave similarly to monoenes and conjugated dienes, yielding [M + 54]+/[M + 54 - 32]+ of 2-3 and, permitting them to be assigned as partially conjugated FAME using the MS-1 spectrum. They yield unique MS/MS spectra with weaker but assignable fragment ions, along with a diagnostic fragment that locates the lone double bond and permits 6,10,12-octatrienoate to be distinguished from 6,8,12-octatrienoate. The presence of a triple bond did not affect fragment formation in a methylene-interrupted yne-ene but did change fragments in a conjugated yne-ene. These data extend the principle of double bond localization by acetonitrile CACI-MS/MS to double bond structure in complex FAME found in nature.

The Generation of Dehydroalanine Residues in Protonated Polypeptides: Ion/Ion Reactions for Introducing Selective Cleavages

NASA Astrophysics Data System (ADS)

Peng, Zhou; Bu, Jiexun; McLuckey, Scott A.

2017-09-01

We examine a gas-phase approach for converting a subset of amino acid residues in polypeptide cations to dehydroalanine (Dha). Subsequent activation of the modified polypeptide ions gives rise to specific cleavage N-terminal to the Dha residue. This process allows for the incorporation of selective cleavages in the structural characterization of polypeptide ions. An ion/ion reaction within the mass spectrometer between a multiply protonated polypeptide and the sulfate radical anion introduces a radical site into the multiply protonated polypeptide reactant. Subsequent collisional activation of the polypeptide radical cation gives rise to radical side chain loss from one of several particular amino acid side chains (e.g., leucine, asparagine, lysine, glutamine, and glutamic acid) to yield a Dha residue. The Dha residues facilitate preferential backbone cleavages to produce signature c- and z-ions, demonstrated with cations derived from melittin, mechano growth factor (MGF), and ubiquitin. The efficiencies for radical side chain loss and for subsequent generation of specific c- and z-ions have been examined as functions of precursor ion charge state and activation conditions using cations of ubiquitin as a model for a small protein. It is noted that these efficiencies are not strongly dependent on ion trap collisional activation conditions but are sensitive to precursor ion charge state. Moderate to low charge states show the greatest overall yields for the specific Dha cleavages, whereas small molecule losses (e.g., water/ammonia) dominate at the lowest charge states and proton catalyzed amide bond cleavages that give rise to b- and y-ions tend to dominate at high charge states. [Figure not available: see fulltext.

Method for removing metal ions from solution with titanate sorbents

DOEpatents

Lundquist, Susan H.; White, Lloyd R.

1999-01-01

A method for removing metal ions from solution comprises the steps of providing titanate particles by spray-drying a solution or slurry comprising sorbent titanates having a particle size up to 20 micrometers, optionally in the presence of polymer free of cellulose functionality as binder, said sorbent being active towards heavy metals from Periodic Table (CAS version) Groups IA, IIA, IB, IIB, IIIB, and VIII, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size distribution in the range of 1 to 500 micrometers. The particles can be used free flowing in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove metal ions from aqueous or organic liquid.

Development of 20 GHz monolithic transmit modules

NASA Technical Reports Server (NTRS)

Higgins, J. A.

1988-01-01

The history of the development of a transmit module for the band 17.7 to 20.2 GHz is presented. The module was to monolithically combine, on one chip, five bits of phase shift, a buffer amplifier and a power amplifier to produce 200 mW to the antenna element. The approach taken was MESFET ion implanted device technology. A common pinch-off voltage was decided upon for each application. The beginning of the total integration phases revealed hitherto unencountered hazards of large microwave circuit integration which were successfully overcome. Yield and customer considerations finally led to two separate chips, one containing the power amplifiers and the other containing the complete five bit phase shifter.

Ion accelerator system mounting design and operating characteristics for a 5 kW 30-cm xenon ion engine

NASA Technical Reports Server (NTRS)

Aston, Graeme; Brophy, John R.

1987-01-01

Results from a series of experiments to determine the effect of accelerator grid mount geometry on the performance of the J-series ion optics assembly are described. Three mounting schemes, two flexible and one rigid, are compared for their relative ion extraction capability over a range of total accelerating voltages. The largest ion beam current, for the maximum total voltage investigated, is shown to occur using one of the flexible grid mounting geometries. However, at lower total voltages and reduced engine input power levels, the original rigid J-series ion optics accelerator grid mounts result in marginally better grid system performance at the same cold interelectrode gap.

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

PubMed Central

Moskovets, Eugene

2015-01-01

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

Attraction between like-charged monovalent ions.

PubMed

Zangi, Ronen

2012-05-14

Ions with like-charges repel each other with a magnitude given by the Coulomb law. The repulsion is also known to persist in aqueous solutions albeit factored by the medium's dielectric constant. In this paper, we report results from molecular dynamics simulations of alkali halides salt solutions indicating an effective attraction between some of the like-charged monovalent ions. The attraction is observed between anions, as well as between cations, leading to the formation of dimers with lifetimes on the order of few picoseconds. Two mechanisms have been identified to drive this counterintuitive attraction. The first is exhibited by high-charge density ions, such as fluoride, at low salt concentrations, yielding effective attractions with magnitude up to the order of 1-2 kT. In this case, the stronger local electric field generated when the two ions are in contact augments the alignment of neighboring waters toward the ions. This results in a gain of substantial favorable ion-water interaction energy. For fluorides, this interaction constitutes the major change among the different energy components compensating for the anion-anion repulsion, and therefore, rendering like-charge association possible. The second mechanism involves mediation by counterions, the attractions increase with salt concentration and are characterized by small magnitudes. In particular, clusters of ion triplets, in which a counterion is either bridging the two like-charged ions or is paired to only one of them, are formed. Although these two mechanisms may not yield net attractions in many cases, they might still be operational and significant, explaining effective repulsions between like-charged ions with magnitudes much smaller than expected based on continuum electrostatics.

Study of electronic sputtering of CaF2 thin films

NASA Astrophysics Data System (ADS)

Pandey, Ratnesh K.; Kumar, Manvendra; Khan, Saif A.; Kumar, Tanuj; Tripathi, Ambuj; Avasthi, D. K.; Pandey, Avinash C.

2014-01-01

In the present work thin films of CaF2 deposited on Si substrate by electron beam evaporation have been investigated for swift heavy ions induced sputtering and surface modifications. Glancing angle X-ray Diffraction (GAXRD) measurements show that the pristine films are polycrystalline in nature and the grain size increases with increase in film thickness. Rutherford backscattering spectrometry (RBS) of pristine as well as irradiated films was performed to determine the sputter yield of CaF2 and a decrease in sputter yield has been observed with increase in film thickness. Thermal spike model has been applied to explain this. The confinement of energy in the grains having size smaller than the electron mean free path (λ) results in a higher sputtering yield. Atomic force microscopy (AFM) studies of irradiated CaF2 thin films show formation of cracks on film surface at a fluence of 5 × 1012 ions/cm2. Also RBS results confirm the removal of film from the surface and more exposure of substrate with increasing dose of ions.

Optimization of the neutron yield in fusion plasmas produced by Coulomb explosions of deuterium clusters irradiated by a petawatt laser.

PubMed

Bang, W; Dyer, G; Quevedo, H J; Bernstein, A C; Gaul, E; Donovan, M; Ditmire, T

2013-02-01

The kinetic energy of hot (multi-keV) ions from the laser-driven Coulomb explosion of deuterium clusters and the resulting fusion yield in plasmas formed from these exploding clusters has been investigated under a variety of conditions using the Texas Petawatt laser. An optimum laser intensity was found for producing neutrons in these cluster fusion plasmas with corresponding average ion energies of 14 keV. The substantial volume (1-10 mm(3)) of the laser-cluster interaction produced by the petawatt peak power laser pulse led to a fusion yield of 1.6×10(7) neutrons in a single shot with a 120 J, 170 fs laser pulse. Possible effects of prepulses are discussed.

Sputtering of rough surfaces: a 3D simulation study

NASA Astrophysics Data System (ADS)

von Toussaint, U.; Mutzke, A.; Manhard, A.

2017-12-01

The lifetime of plasma-facing components is critical for future magnetic confinement fusion power plants. A key process limiting the lifetime of the first-wall is sputtering by energetic ions. To provide a consistent modeling of the sputtering process of realistic geometries, the SDTrimSP-code has been extended to enable the processing of analytic as well as measured arbitrary 3D surface morphologies. The code has been applied to study the effect of varying the impact angle of ions on rough surfaces on the sputter yield as well as the influence of the aspect ratio of surface structures on the 2D distribution of the local sputtering yields. Depending on the surface morphologies reductions of the effective sputter yields to less than 25% have been observed in the simulation results.

High-level HIV-1 Nef transient expression in Nicotiana benthamiana using the P19 gene silencing suppressor protein of Artichoke Mottled Crinckle Virus

PubMed Central

2009-01-01

Background In recent years, different HIV antigens have been successfully expressed in plants by either stable transformation or transient expression systems. Among HIV proteins, Nef is considered a promising target for the formulation of a multi-component vaccine due to its implication in the first steps of viral infection. Attempts to express Nef as a single protein product (not fused to a stabilizing protein) in transgenic plants resulted in disappointingly low yields (about 0.5% of total soluble protein). In this work we describe a transient expression system based on co-agroinfiltration of plant virus gene silencing suppressor proteins in Nicotiana benthamiana, followed by a two-step affinity purification protocol of plant-derived Nef. Results The effect of three gene silencing viral suppressor proteins (P25 of Potato Virus X, P19 of either Artichoke Mottled Crinckle virus and Tomato Bushy Stunt virus) on Nef transient expression yield was evaluated. The P19 protein of Artichoke Mottled Crinckle virus (AMCV-P19) gave the highest expression yield in vacuum co-agroinfiltration experiments reaching 1.3% of total soluble protein, a level almost three times higher than that previously reported in stable transgenic plants. The high yield observed in the co-agroinfiltrated plants was correlated to a remarkable decrease of Nef-specific small interfering RNAs (siRNAs) indicating an effective modulation of RNA silencing mechanisms by AMCV-P19. Interestingly, we also showed that expression levels in top leaves of vacuum co-agroinfiltrated plants were noticeably reduced compared to bottom leaves. Moreover, purification of Nef from agroinfiltrated tissue was achieved by a two-step immobilized metal ion affinity chromatography protocol with yields of 250 ng/g of fresh tissue. Conclusion We demonstrated that expression level of HIV-1 Nef in plant can be improved using a transient expression system enhanced by the AMCV-P19 gene silencing suppressor protein. Moreover, plant-derived Nef was purified, with enhanced yield, exploiting a two-step purification protocol. These results represent a first step towards the development of a plant-derived HIV vaccine. PMID:19930574

High-level HIV-1 Nef transient expression in Nicotiana benthamiana using the P19 gene silencing suppressor protein of Artichoke Mottled Crinckle Virus.

PubMed

Lombardi, Raffaele; Circelli, Patrizia; Villani, Maria Elena; Buriani, Giampaolo; Nardi, Luca; Coppola, Valentina; Bianco, Linda; Benvenuto, Eugenio; Donini, Marcello; Marusic, Carla

2009-11-20

In recent years, different HIV antigens have been successfully expressed in plants by either stable transformation or transient expression systems. Among HIV proteins, Nef is considered a promising target for the formulation of a multi-component vaccine due to its implication in the first steps of viral infection. Attempts to express Nef as a single protein product (not fused to a stabilizing protein) in transgenic plants resulted in disappointingly low yields (about 0.5% of total soluble protein). In this work we describe a transient expression system based on co-agroinfiltration of plant virus gene silencing suppressor proteins in Nicotiana benthamiana, followed by a two-step affinity purification protocol of plant-derived Nef. The effect of three gene silencing viral suppressor proteins (P25 of Potato Virus X, P19 of either Artichoke Mottled Crinckle virus and Tomato Bushy Stunt virus) on Nef transient expression yield was evaluated. The P19 protein of Artichoke Mottled Crinckle virus (AMCV-P19) gave the highest expression yield in vacuum co-agroinfiltration experiments reaching 1.3% of total soluble protein, a level almost three times higher than that previously reported in stable transgenic plants. The high yield observed in the co-agroinfiltrated plants was correlated to a remarkable decrease of Nef-specific small interfering RNAs (siRNAs) indicating an effective modulation of RNA silencing mechanisms by AMCV-P19. Interestingly, we also showed that expression levels in top leaves of vacuum co-agroinfiltrated plants were noticeably reduced compared to bottom leaves. Moreover, purification of Nef from agroinfiltrated tissue was achieved by a two-step immobilized metal ion affinity chromatography protocol with yields of 250 ng/g of fresh tissue. We demonstrated that expression level of HIV-1 Nef in plant can be improved using a transient expression system enhanced by the AMCV-P19 gene silencing suppressor protein. Moreover, plant-derived Nef was purified, with enhanced yield, exploiting a two-step purification protocol. These results represent a first step towards the development of a plant-derived HIV vaccine.

Implementation of Dipolar Resonant Excitation for Collision Induced Dissociation with Ion Mobility/Time-of-Flight MS

PubMed Central

Webb, Ian K.; Chen, Tsung-Chi; Danielson, William F.; Ibrahim, Yehia M.; Tang, Keqi; Anderson, Gordon A.; Smith, Richard D.

2014-01-01

An ion mobility/time-of-flight mass spectrometer (IMS/TOF MS) platform that allows for resonant excitation collision induced dissociation (CID) is presented. Highly efficient, mass-resolved fragmentation without additional excitation of product ions was accomplished and over-fragmentation common in beam-type CID experiments was alleviated. A quadrupole ion guide was modified to apply a dipolar AC signal across a pair of rods for resonant excitation. The method was characterized with singly protonated methionine enkephalin and triply protonated peptide angiotensin I, yielding maximum CID efficiencies of 44% and 84%, respectively. The Mathieu qx,y parameter was set at 0.707 for these experiments to maximize pseudopotential well depths and CID efficiencies. Resonant excitation CID was compared to beam-type CID for the peptide mixture. The ability to apply resonant waveforms in mobility-resolved windows is demonstrated with a peptide mixture yielding fragmentation over a range of mass-to-charge (m/z) ratios within a single IMS-MS analysis. PMID:24470195

Photoabsorption of the molecular IH cation at the iodine 3 d absorption edge

NASA Astrophysics Data System (ADS)

Klumpp, Stephan; Guda, Alexander A.; Schubert, Kaja; Mertens, Karolin; Hellhund, Jonas; Müller, Alfred; Schippers, Stefan; Bari, Sadia; Martins, Michael

2018-03-01

Yields of atomic iodine Iq + (q ≥2 ) fragments resulting from photoexcitation and photoionization of the target ions IH+ and I+ have been measured in the photon-energy range 610-680 eV, which comprises the thresholds for iodine 3 d ionization. The measured ion-yield spectra show two strong and broad resonance features due to the excitation of the 3 d3 /2 ,5 /2 electrons into ɛ f states rather similar for both parent ions. In the 3 d pre-edge range, excitations into (n p π ) -like orbitals and into an additional σ* orbital are found for IH+, which have been identified by comparison of the atomic I+ and molecular IH+ data and with the help of (time-dependent) density functional theory (DFT) and atomic Hartree-Fock calculations. The (5 p π ) orbital is almost atomlike, whereas all other resonances of the IH+ primary ion show a more pronounced molecular character, which is deduced from the chemical shifts of the resonances and the theoretical analysis.

Diffusive tunneling for alleviating Knudsen-layer reactivity reduction under hydrodynamic mix

NASA Astrophysics Data System (ADS)

Tang, Xianzhu; McDevitt, Chris; Guo, Zehua

2017-10-01

Hydrodynamic mix will produce small features for intermixed deuterium-tritium fuel and inert pusher materials. The geometrical characteristics of the mix feature have a large impact on Knudsen layer yield reduction. We considered two features. One is planar structure, and the other is fuel cells segmented by inert pusher material which can be represented by a spherical DT bubble enclosed by a pusher shell. The truly 3D fuel feature, the spherical bubble, has the largest degree of yield reduction, due to fast ions being lost in all directions. The planar fuel structure, which can be regarded as 1D features, has modest amount of potential for yield degradation. While the increasing yield reduction with increasing Knudsen number of the fuel region is straightforwardly anticipated, we also show, by a combination of direct simulation and simple model, that once the pusher materials is stretched sufficiently thin by hydrodynamic mix, the fast fuel ions diffusively tunnel through them with minimal energy loss, so the Knudsen layer yield reduction becomes alleviated. This yield recovery can occur in a chunk-mixed plasma, way before the far more stringent, asymptotic limit of an atomically homogenized fuel and pusher assembly. Work supported by LANL LDRD program.

Assessment of ion kinetic effects in shock-driven inertial confinement fusion implosions using fusion burn imaging

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

Rosenberg, M. J., E-mail: mros@lle.rochester.edu; Séguin, F. H.; Rinderknecht, H. G.

The significance and nature of ion kinetic effects in D{sup 3}He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, N{sub K}) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatiallymore » resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (N{sub K} ∼ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.« less

Assessment of ion kinetic effects in shock-driven inertial confinement fusion (ICF) implosions using fusion burn imaging

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

Rosenberg, M. J.; Séguin, F. H.; Amendt, P. A.

The significance and nature of ion kinetic effects in D³He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, N K) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolvedmore » measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (N K ~ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.« less

Assessment of ion kinetic effects in shock-driven inertial confinement fusion implosions using fusion burn imaging

NASA Astrophysics Data System (ADS)

Rosenberg, M. J.; Séguin, F. H.; Amendt, P. A.; Atzeni, S.; Rinderknecht, H. G.; Hoffman, N. M.; Zylstra, A. B.; Li, C. K.; Sio, H.; Gatu Johnson, M.; Frenje, J. A.; Petrasso, R. D.; Glebov, V. Yu.; Stoeckl, C.; Seka, W.; Marshall, F. J.; Delettrez, J. A.; Sangster, T. C.; Betti, R.; Wilks, S. C.; Pino, J.; Kagan, G.; Molvig, K.; Nikroo, A.

2015-06-01

The significance and nature of ion kinetic effects in D3He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, NK) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (NK ˜ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.

Assessment of ion kinetic effects in shock-driven inertial confinement fusion (ICF) implosions using fusion burn imaging

DOE PAGES

Rosenberg, M. J.; Séguin, F. H.; Amendt, P. A.; ...

2015-06-02

The significance and nature of ion kinetic effects in D³He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, N K) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolvedmore » measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (N K ~ 3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects.« less

Structural characterization of phospholipids by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry.

PubMed

Marto, J A; White, F M; Seldomridge, S; Marshall, A G

1995-11-01

Matrix-assisted laser desorption/ionization (MALDI) Fourier transform ion cyclotron resonance mass spectrometry provides for structural analysis of the principal biological phospholipids: glycerophosphatidylcholine, -ethanolamine, -serine, and -inositol. Both positive and negative molecular or quasimolecular ions are generated in high abundance. Isolated molecular ions may be collisionally activated in the source side of a dual trap mass analyzer, yielding fragments serving to identify the polar head group (positive ion mode) and fatty acid side chains (negative ion mode). Azimuthal quadrupolar excitation following collisionally activated dissociation refocuses productions close to the solenoid axis; subsequent transfer of product ions to the analyzer ion trap allows for high-resolution mass analysis. Cyro-cooling of the sample probe with liquid nitrogen greatly reduces matrix adduction encountered in the negative ion mode.

Orthogonal ion injection apparatus and process

DOEpatents

Kurulugama, Ruwan T; Belov, Mikhail E

2014-04-15

An orthogonal ion injection apparatus and process are described in which ions are directly injected into an ion guide orthogonal to the ion guide axis through an inlet opening located on a side of the ion guide. The end of the heated capillary is placed inside the ion guide such that the ions are directly injected into DC and RF fields inside the ion guide, which efficiently confines ions inside the ion guide. Liquid droplets created by the ionization source that are carried through the capillary into the ion guide are removed from the ion guide by a strong directional gas flow through an inlet opening on the opposite side of the ion guide. Strong DC and RF fields divert ions into the ion guide. In-guide orthogonal injection yields a noise level that is a factor of 1.5 to 2 lower than conventional inline injection known in the art. Signal intensities for low m/z ions are greater compared to convention inline injection under the same processing conditions.

Improving the Total Impulse Capability of the NSTAR Ion Thruster With Thick-Accelerator-Grid Ion Optics

NASA Technical Reports Server (NTRS)

Soulas, George C.

2001-01-01

The results of performance tests with thick-accelerator-grid (TAG) ion optics are presented. TAG ion optics utilize a 50 percent thicker accelerator grid to double ion optics' service life. NSTAR ion optics were also tested to provide a baseline performance for comparison. Impingement-limited total voltages for the TAG ion optics were only 0 to 15 V higher than those of the NSTAR ion optics. Electron backstreaming limits for the TAG ion optics were 3 to 9 V higher than those for the NSTAR optics due to the increased accelerator grid thickness for the TAG ion optics. Screen grid ion transparencies for the TAG ion optics were only about 2 percent lower than those for the NSTAR optics, reflecting the lower physical screen grid open area fraction of the TAG ion optics. Accelerator currents for the TAG ion optics were 19 to 43 percent greater than those for the NSTAR ion optics due, in part, to a sudden increase in accelerator current during TAG ion optics' performance tests for unknown reasons and to the lower-than-nominal accelerator aperture diameters. Beam divergence half-angles that enclosed 95 percent of the total beam current and beam divergence thrust correction factors for the TAG ion optics were within 2 degrees and 1 percent, respectively, of those for the NSTAR ion optics.

Aluminum ions induce oat protoplasts to produce an extracellular (1 yields 3). beta. -D-glucan

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

Schaeffer, H.J.; Walton, J.D.

1990-09-01

Aluminum chloride induced mesophyll protoplasts of oat (Avena sativa) to produce an extracellular polysaccharide (EPS). EPS induced by AlCl{sub 3} appeared identical to that produced in response to the phytotoxin victorin. Al ions at 1 millimolar were toxic to protoplasts, but maximum EPS production occurred at a sublethal concentration of 200 micromolar, assayed at pH 6.0. As measured by incorporation of ({sup 14}C)glucose, AlCl{sub 3} stimulated EPS production 10- to 15-fold. Pretreatment of protoplasts with cycloheximide prevented EPS production but not cell death in response to AlCl{sub 3}, indicating that protein synthesis was necessary for EPS production but not formore » the phytotoxicity of Al ions. The trivalent salts of Y, Yb, Gd, and In also induced EPS production but those of Sc, Fe, Ga, Cr, and La did not. Mesophyll protoplasts from an acid-soil tolerant oat cultivar produced less EPS in response to AlCl{sub 3} than the acid-soil sensitive cultivar Fla 501. EPS was also produced by wheat (Triticum aestivum) and barley (Hordeum vulgare) protoplasts in response to AlCl{sub 3}. An Al-tolerant cultivar of wheat, Atlas, produced less EPS than an Al-sensitive cultivar, Scout, but an Al-tolerant cultivar of barley, Dayton, produced more than the Al-sensitive cultivar Kearney. Therefore, production of EPS by protoplasts in response to Al ions did not appear to be related to Al ion tolerance at the level of whole plants. EPS fluoresced in the presence of Calcofluor and Sirofluor and was degraded by purified laminarinase ((1{yields}3){beta}-D-glucanase) but did not pectinase (polygalacturonase). EPS was composed solely of glucose in 1{yields}3 linkages; hence it is a (1{yields}3){beta}-D-glucan (callose).« less

Thermal and log-normal distributions of plasma in laser driven Coulomb explosions of deuterium clusters

NASA Astrophysics Data System (ADS)

Barbarino, M.; Warrens, M.; Bonasera, A.; Lattuada, D.; Bang, W.; Quevedo, H. J.; Consoli, F.; de Angelis, R.; Andreoli, P.; Kimura, S.; Dyer, G.; Bernstein, A. C.; Hagel, K.; Barbui, M.; Schmidt, K.; Gaul, E.; Donovan, M. E.; Natowitz, J. B.; Ditmire, T.

2016-08-01

In this work, we explore the possibility that the motion of the deuterium ions emitted from Coulomb cluster explosions is highly disordered enough to resemble thermalization. We analyze the process of nuclear fusion reactions driven by laser-cluster interactions in experiments conducted at the Texas Petawatt laser facility using a mixture of D2+3He and CD4+3He cluster targets. When clusters explode by Coulomb repulsion, the emission of the energetic ions is “nearly” isotropic. In the framework of cluster Coulomb explosions, we analyze the energy distributions of the ions using a Maxwell-Boltzmann (MB) distribution, a shifted MB distribution (sMB), and the energy distribution derived from a log-normal (LN) size distribution of clusters. We show that the first two distributions reproduce well the experimentally measured ion energy distributions and the number of fusions from d-d and d-3He reactions. The LN distribution is a good representation of the ion kinetic energy distribution well up to high momenta where the noise becomes dominant, but overestimates both the neutron and the proton yields. If the parameters of the LN distributions are chosen to reproduce the fusion yields correctly, the experimentally measured high energy ion spectrum is not well represented. We conclude that the ion kinetic energy distribution is highly disordered and practically not distinguishable from a thermalized one.

Study of genetic effects of high energy radiations with different ionizing capacities on extracellular phages.

PubMed

Bresler, S E; Kalinin, V L; Kopylova, Y U; Krivisky, A S; Rybchin, V N; Shelegedin, V N

1975-07-01

The inactivating and mutagenic action of high-energy radiations with different ionizing capacities (gamma-rays, protons, alpha-particles and accelerated ions of 12C and 20Ne) was studied by using coliphages lambda11 and SD as subjects. In particular the role of irradiation conditions (broth suspension, pure buffer, dry samples) and of the host functions recA, exrA and polA was investigated. The dose-response curve of induced mutagenesis was studied by measuring the yield of vir mutants in lambda11 and plaque mutants in SD. The following results were obtained. (1) The inactivation kinetics of phages under the action of gamma-rays and protons was first order to a survival of 10(-7). Heavy ions also showed exponential inactivation kinetics to a survival of 10(-4). At higher doses of 20Ne ion bombardment some deviation from one-hit kinetics was observed. For dry samples of phages the dimensions of targets for all types of radiation were approximately proportional to the molecular weights of phage DNA's. For densely ionizing radiation (heavy ions) the inactivating action was 3-5 times weaker than for gamma-rays and protons. (2) Mutagenesis was observed for all types of radiation, but heavy ions were 1-5-2 times less efficient than gamma-rays. For both phages studied the dose-response curve of mutagenesis was non-linear. The dependence on the dose was near to parabolic for lambda11. For SD a plateau or maximum of mutagenesis was observed for the relative number of mutants at a survival of about 10(-4). (3) Host-cell functions recA and exrA were practically indifferent for survival of gamma-irradiated phage lambda11, but indispensable for mutagenesis. Mutation recAI3 abolished induced vir mutations totally and exrA- reduced them significantly. The absence of the function polA had a considerable influence on phage survival, but no effect on vir mutation yield (if compared at the same survival level). (4) In conditions of indirect action of gamma-rays no vir mutations were induced. This is regarded as evidence that the single-strand breaks formed under indirect action conditions cannot serve as pre-mutational damage in DNA.

LASER DESORPTION/IONIZATION OF SINGLE ULTRAFINE MULTICOMPONENT AEROSOLS. (R823980)

EPA Science Inventory

Laser desorption/ionization characteristics of single
ultrafine multicomponent aerosols have been investigated.
The results confirm earlier findings that (a) the negative
ion spectra are dominated by free electrons and (b) the ion
yield-to-mass ratio is higher for ...

Kinetic studies of ICF implosions

DOE PAGES

Kagan, Grigory; Herrmann, H. W.; Kim, Y. -H.; ...

2016-05-26

Here, kinetic effects on inertial confinement fusion have been investigated. In particular, inter-ion-species diffusion and suprathermal ion distribution have been analyzed. The former drives separation of the fuel constituents in the hot reacting core and governs mix at the shell/fuel interface. The latter underlie measurements obtained with nuclear diagnostics, including the fusion yield and inferred ion burn temperatures. Basic mechanisms behind and practical consequences from these effects are discussed.

Improved Differential Ion Mobility Separations Using Linked Scans of Carrier Gas Composition and Compensation Field

NASA Astrophysics Data System (ADS)

Santiago, Brandon G.; Harris, Rachel A.; Isenberg, Samantha L.; Ridgeway, Mark E.; Pilo, Alice L.; Kaplan, Desmond A.; Glish, Gary L.

2015-07-01

Differential ion mobility spectrometry (DIMS) separates ions based on differences in their mobilities in low and high electric fields. When coupled to mass spectrometric analyses, DIMS has the ability to improve signal-to-background by eliminating isobaric and isomeric compounds for analytes in complex mixtures. DIMS separation power, often measured by resolution and peak capacity, can be improved through increasing the fraction of helium in the nitrogen carrier gas. However, because the mobility of ions is higher in helium, a greater number of ions collide with the DIMS electrodes or housing, yielding losses in signal intensity. To take advantage of the benefits of helium addition on DIMS separations and reduce ion losses, linked scans were developed. In a linked scan the helium content of the carrier gas is reduced as the compensation field is increased. Linked scans were compared with conventional compensation field scans with constant helium content for the protein ubiquitin and a tryptic digest of bovine serum albumin (BSA). Linked scans yield better separation of ubiquitin charge states and enhanced peak capacities for the analysis of BSA compared with compensation field scans with constant helium carrier gas percentages. Linked scans also offer improved signal intensity retention in comparison to compensation field scans with constant helium percentages in the carrier gas.

Convoy electron emission from resonant coherently excited 390 MeV/u hydrogen-like Ar ions

NASA Astrophysics Data System (ADS)

Azuma, T.; Takabayashi, Y.; Ito, T.; Komaki, K.; Yamazaki, Y.; Takada, E.; Murakami, T.

2003-12-01

Energetic ions traveling through a single crystal are excited by an oscillating crystal field produced by a periodic arrangement of the atomic strings/planes, which is called Resonant Coherent Excitation (RCE). We have observed enhancement of convoy electron yields associated with RCE of 1s electron to the n=2 excited states of 390 MeV/u hydrogen-like Ar 17+ ions passing through a Si crystal in the (2 2¯ 0) planar channeling condition. Lost electrons from projectile ions due to ionization contribute to convoy electrons emitted in the forward direction with the same velocity as the projectile ions. With combination of a magnet and a thick Si solid-state detector, we measured the energy spectra of convoy electrons of about 200 keV emitted at 0°. The convoy electron yield as a function of the transition energy, i.e. the resonance profile, has a similar structure to the resonance profile observed through the ionized fraction of the emerging ions. It is explained by the fact that both enhancements are due to increase in the fraction of the excited states from which electrons are more easily ionized by target electron impact in the crystal than from the ground state.

A Floating Potential Method for Determining Ion Density

NASA Astrophysics Data System (ADS)

Evans, John D.; Chen, Francis F.

2001-10-01

The density n in partially ionized discharges is often found from the saturation ion current Ii of a cylindrical Langmuir probe. Collisionless probe theories, however, disagree with measured I - V curves probably because of collisions^1. We use a heuristic method that yields n from probe data agreeing with microwave interferometry. Probe current I is raised to the 4/3 power and fitted to a straight line on an I^4/3-V plot. The line is extrapolated to the floating potential V_f, thus approximating I_i(V_f). The sheath thickness d_sh for V = Vf is calculated from the Child-Langmuir (CL) law, and applying the Bohm sheath criterion to the surface at r_sh = Rp + d_sh yields n when Ii = I_i(V_f). This method works, but it cannot be justified by theory. Neglected are (a) cylindrical convergence of the ion charge, (b) finite ion energy at r = r_sh, (c) ions orbiting the probe, and (d) escape of ions axially. The Allen-Boyd-Reynolds theory, which treats (a) and (b) and neglects (c) and (d), gives too low n's. Apparently the errors self-cancel, and the simple Vf method gives the right result. ^1 F.F. Chen, Phys. Plasmas 8, 3029 (2001).

Irradiation of DNA loaded with platinum containing molecules by fast atomic ions C(6+) and Fe(26+).

PubMed

Usami, N; Kobayashi, K; Furusawa, Y; Frohlich, H; Lacombe, S; Sech, C Le

2007-09-01

In order to study the role of the Linear Energy Transfer (LET) of fast atomic ions in platinum-DNA complexes inducing breaks, DNA Plasmids were irradiated by C(6+) and Fe(26+) ions. DNA Plasmids (pBR322) loaded with different amounts of platinum contained in a terpyridine-platinum molecule (PtTC) were irradiated by C(6+) ions and Fe(26+) ions. The LET values ranged between 13.4 keV/microm and 550 keV/microm. In some experiments, dimethyl sulfoxide (DMSO) was added. In all experiments, a significant increase in DNA strand breaks was observed when platinum was present. The yield of breaks induced per Gray decreased when the LET increased. The yield of single and double strand breaks per plasmid per track increased with the LET, indicating that the number of DNA breaks per Gray was related to the number of tracks through the medium. These findings show that more DNA breaks are induced by atomic ions when platinum is present. This effect increases for low LET heavy atoms. As DSB induction may induce cell death, these results could open new perspectives with the association of hadrontherapy and chemotherapy. Thus the therapeutic index might be improved by loading the tumour with platinum salts.

Ion/Ion Reactions with "Onium" Reagents: An Approach for the Gas-phase Transfer of Organic Cations to Multiply-Charged Anions

NASA Astrophysics Data System (ADS)

Gilbert, Joshua D.; Prentice, Boone M.; McLuckey, Scott A.

2015-05-01

The use of ion/ion reactions to effect gas-phase alkylation is demonstrated. Commonly used fixed-charge "onium" cations are well-suited for ion/ion reactions with multiply deprotonated analytes because of their tendency to form long-lived electrostatic complexes. Activation of these complexes results in an SN2 reaction that yields an alkylated anion with the loss of a neutral remnant of the reagent. This alkylation process forms the basis of a general method for alkylation of deprotonated analytes generated via electrospray, and is demonstrated on a variety of anionic sites. SN2 reactions of this nature are demonstrated empirically and characterized using density functional theory (DFT). This method for modification in the gas phase is extended to the transfer of larger and more complex R groups that can be used in later gas-phase synthesis steps. For example, N-cyclohexyl- N'-(2-morpholinoethyl)carbodiimide (CMC) is used to transfer a carbodiimide functionality to a peptide anion containing a carboxylic acid. Subsequent activation yields a selective reaction between the transferred carbodiimide group and a carboxylic acid, suggesting the carbodiimide functionality is retained through the transfer process. Many different R groups are transferable using this method, allowing for new possibilities for charge manipulation and derivatization in the gas phase.

Relation of watershed setting and stream nutrient yields at selected sites in central and eastern North Carolina, 1997-2008

USGS Publications Warehouse

Harden, Stephen L.; Cuffney, Thomas F.; Terziotti, Silvia; Kolb, Katharine R.

2013-01-01

Data collected between 1997 and 2008 at 48 stream sites were used to characterize relations between watershed settings and stream nutrient yields throughout central and eastern North Carolina. The focus of the investigation was to identify environmental variables in watersheds that influence nutrient export for supporting the development and prioritization of management strategies for restoring nutrient-impaired streams. Nutrient concentration data and streamflow data compiled for the 1997 to 2008 study period were used to compute stream yields of nitrate, total nitrogen (N), and total phosphorus (P) for each study site. Compiled environmental data (including variables for land cover, hydrologic soil groups, base-flow index, streams, wastewater treatment facilities, and concentrated animal feeding operations) were used to characterize the watershed settings for the study sites. Data for the environmental variables were analyzed in combination with the stream nutrient yields to explore relations based on watershed characteristics and to evaluate whether particular variables were useful indicators of watersheds having relatively higher or lower potential for exporting nutrients. Data evaluations included an examination of median annual nutrient yields based on a watershed land-use classification scheme developed as part of the study. An initial examination of the data indicated that the highest median annual nutrient yields occurred at both agricultural and urban sites, especially for urban sites having large percentages of point-source flow contributions to the streams. The results of statistical testing identified significant differences in annual nutrient yields when sites were analyzed on the basis of watershed land-use category. When statistical differences in median annual yields were noted, the results for nitrate, total N, and total P were similar in that highly urbanized watersheds (greater than 30 percent developed land use) and (or) watersheds with greater than 10 percent point-source flow contributions to streamflow had higher yields relative to undeveloped watersheds (having less than 10 and 15 percent developed and agricultural land uses, respectively) and watersheds with relatively low agricultural land use (between 15 and 30 percent). The statistical tests further indicated that the median annual yields for total P were statistically higher for watersheds with high agricultural land use (greater than 30 percent) compared to the undeveloped watersheds and watersheds with low agricultural land use. The total P yields also were higher for watersheds with low urban land use (between 10 and 30 percent developed land) compared to the undeveloped watersheds. The study data indicate that grouping and examining stream nutrient yields based on the land-use classifications used in this report can be useful for characterizing relations between watershed settings and nutrient yields in streams located throughout central and eastern North Carolina. Compiled study data also were analyzed with four regression tree models as a means of determining which watershed environmental variables or combination of variables result in basins that are likely to have high or low nutrient yields. The regression tree analyses indicated that some of the environmental variables examined in this study were useful for predicting yields of nitrate, total N, and total P. When the median annual nutrient yields for all 48 sites were evaluated as a group (Model 1), annual point-source flow yields had the greatest influence on nitrate and total N yields observed in streams, and annual streamflow yields had the greatest influence on yields of total P. The Model 1 results indicated that watersheds with higher annual point-source flow yields had higher annual yields of nitrate and total N, and watersheds with higher annual streamflow yields had higher annual yields of total P. When sites with high point-source flows (greater than 10 percent of total streamflow) were excluded from the regression tree analyses (Models 2–4), the percentage of forested land in the watersheds was identified as the primary environmental variable influencing stream yields for both total N and total P. Models 2, 3 and 4 did not identify any watershed environmental variables that could adequately explain the observed variability in the nitrate yields among the set of sites examined by each of these models. The results for Models 2, 3, and 4 indicated that watersheds with higher percentages of forested land had lower annual total N and total P yields compared to watersheds with lower percentages of forested land, which had higher median annual total N and total P yields. Additional environmental variables determined to further influence the stream nutrient yields included median annual percentage of point-source flow contributions to the streams, variables of land cover (percentage of forested land, agricultural land, and (or) forested land plus wetlands) in the watershed and (or) in the stream buffer, and drainage area. The regression tree models can serve as a tool for relating differences in select watershed attributes to differences in stream yields of nitrate, total N, and total P, which can provide beneficial information for improving nutrient management in streams throughout North Carolina and for reducing nutrient loads to coastal waters.

Effect of Fe 3+ concentration on MWCNTs formation in liquid arcing method

NASA Astrophysics Data System (ADS)

Shervin, Sh.; Gheytani, S.; Simchi, A.

2010-10-01

The formation of multi-walled carbon nanotubes (MWCNTs) during arc discharge in aqueous solutions of Fe 2(SO 4) 3 and FeCl 3 was studied. The concentration of iron ions changed from zero (deionized water) to 0.25 M and the cathodic products were examined by transmission electron microscopy, Raman spectrometry, and thermal gravimetric analysis. The experimental results showed that the crystallinity of MWCNTs is improved by increasing the concentration of iron ions. Nevertheless, the process yield and overall quality of the produced CNTs were significantly affected by iron concentration in the aqueous solution. This observation suggested that there should be an optimum iron concentration at which the formation of MWCNTs is favored. As compared with the sulfate solution, a higher process yield is obtained in the presence of chloride ions in agreement with previous reports.

Correlation between surface chemistry and ion energy dependence of the etch yield in multicomponent oxides etching

NASA Astrophysics Data System (ADS)

Bérubé, P.-M.; Poirier, J.-S.; Margot, J.; Stafford, L.; Ndione, P. F.; Chaker, M.; Morandotti, R.

2009-09-01

The influence of surface chemistry in plasma etching of multicomponent oxides was investigated through measurements of the ion energy dependence of the etch yield. Using pulsed-laser-deposited CaxBa(1-x)Nb2O6 (CBN) and SrTiO3 thin films as examples, it was found that the etching energy threshold shifts toward values larger or smaller than the sputtering threshold depending on whether or not ion-assisted chemical etching is the dominant etching pathway and whether surface chemistry is enhancing or inhibiting desorption of the film atoms. In the case of CBN films etched in an inductively coupled Cl2 plasma, it is found that the chlorine uptake is inhibiting the etching reaction, with the desorption of nonvolatile NbCl2 and BaCl2 compounds being the rate-limiting step.

Internal friction and vulnerability of mixed alkali glasses.

PubMed

Peibst, Robby; Schott, Stephan; Maass, Philipp

2005-09-09

Based on a hopping model we show how the mixed alkali effect in glasses can be understood if only a small fraction c(V) of the available sites for the mobile ions is vacant. In particular, we reproduce the peculiar behavior of the internal friction and the steep fall ("vulnerability") of the mobility of the majority ion upon small replacements by the minority ion. The single and mixed alkali internal friction peaks are caused by ion-vacancy and ion-ion exchange processes. If c(V) is small, they can become comparable in height even at small mixing ratios. The large vulnerability is explained by a trapping of vacancies induced by the minority ions. Reasonable choices of model parameters yield typical behaviors found in experiments.

Rejoining and misrejoining of radiation-induced chromatin breaks. IV. Charged particles

NASA Technical Reports Server (NTRS)

Durante, M.; Furusawa, Y.; George, K.; Gialanella, G.; Greco, O.; Grossi, G.; Matsufuji, N.; Pugliese, M.; Yang, T. C.

1998-01-01

We have recently reported the kinetics of chromosome rejoining and exchange formation in human lymphocytes exposed to gamma rays using the techniques of fluorescence in situ hybridization (FISH) and premature chromosome condensation (PCC). In this paper, we have extended previous measurements to cells exposed to charged particles. Our goal was to determine differences in chromatin break rejoining and misrejoining after exposure to low- and high-linear energy transfer (LET) radiation. Cells were irradiated with hydrogen, neon, carbon or iron ions in the LET range 0.3-140 keV/microm and were incubated at 37 degrees C for various times after exposure. Little difference was observed in the yield of early prematurely condensed chromosome breaks for the different ions. The kinetics of break rejoining was exponential for all ions and had similar time constants, but the residual level of unrejoined breaks after prolonged incubation was higher for high-LET radiation. The kinetics of exchange formation was also similar for the different ions, but the yield of chromosome interchanges measured soon after exposure was higher for high-LET particles, suggesting that a higher fraction of DNA breaks are misrejoined quickly. On the other hand, the rate of formation of complete exchanges was slightly lower for densely ionizing radiation. The ratios between the yields of different types of aberrations observed at 10 h postirradiation in prematurely condensed chromosome preparations were dependent on LET. We found significant differences between the yields of aberrations measured in interphase (after repair) and metaphase for densely ionizing radiation. This difference might be caused by prolonged mitotic delay and/or interphase death. Overall, the results point out significant differences between low- and high-LET radiation for the formation of chromosome aberrations.

Diels Alder polyphenylene anion exchange membrane for nonaqueous redox flow batteries

DOE PAGES

Small, Leo J.; Pratt, III, Harry D.; Fujimoto, Cy H.; ...

2015-10-23

Here highly conductive, solvent-resistant anionic Diels Alder polyphenylene (DAPP) membranes were synthesized with three different ionic contents and tested in an ionic liquid-based nonaqueous redox flow battery (RFB). These membranes display 3–10× increase in conductivity in propylene carbonate compared to some commercially available (aqueous) anion exchange membranes. The membrane with an ion content of 1.5 meq/g (DAPP1.5) proved too brittle for operation in a RFB, while the membrane with an ion content of 2.5 meq/g (DAPP2.5) allowed excessive movement of solvent and poor electrochemical yields (capacity fade). Despite having lower voltage efficiencies compared to DAPP2.5, the membrane with an intermediatemore » ion content of 2.0 meq/g (DAPP2.0) exhibited higher coulombic efficiencies (96.4% vs. 89.1%) and electrochemical yields (21.6% vs. 10.9%) after 50 cycles. Crossover of the electroactive species was the primary reason for decreased electrochemical yields. Analysis of the anolyte and catholyte revealed degradation of the electroactive species and formation of a film at the membrane-solution interface. Increases in membrane resistance were attributed to mechanical and thermal aging of the membrane; no chemical change was observed. As a result, improvements in the ionic selectivity and ionic conductivity of the membrane will increase the electrochemical yield and voltage efficiency of future nonaqueous redox flow batteries.« less

Benchmark solutions for the galactic heavy-ion transport equations with energy and spatial coupling

NASA Technical Reports Server (NTRS)

Ganapol, Barry D.; Townsend, Lawrence W.; Lamkin, Stanley L.; Wilson, John W.

1991-01-01

Nontrivial benchmark solutions are developed for the galactic heavy ion transport equations in the straightahead approximation with energy and spatial coupling. Analytical representations of the ion fluxes are obtained for a variety of sources with the assumption that the nuclear interaction parameters are energy independent. The method utilizes an analytical LaPlace transform inversion to yield a closed form representation that is computationally efficient. The flux profiles are then used to predict ion dose profiles, which are important for shield design studies.

Ion-beam-induced planarization, densification, and exfoliation of low-density nanoporous silica

NASA Astrophysics Data System (ADS)

Kucheyev, S. O.; Shin, S. J.

2017-09-01

Planarization of low-density nanoporous solids is challenging. Here, we demonstrate that ion bombardment to doses of ˜1015 cm-2 results in significant smoothing of silica aerogels, yielding mirror-like surfaces after metallization. The surface smoothing efficiency scales with the ion energy loss component leading to local lattice heating. Planarization is accompanied by sub-surface monolith densification, resulting in surface exfoliation with increasing ion dose. These findings have implications for the fabrication of graded-density nanofoams, aerogel-based lightweight optical components, and meso-origami.

Water Ice Radiolytic O2, H2, and H2O2 Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

NASA Astrophysics Data System (ADS)

Teolis, B. D.; Plainaki, C.; Cassidy, T. A.; Raut, U.

2017-10-01

O2, H2, and H2O2 radiolysis from water ice is pervasive on icy astrophysical bodies, but the lack of a self-consistent, quantitative model of the yields of these water products versus irradiation projectile species and energy has been an obstacle to estimating the radiolytic oxidant sources to the surfaces and exospheres of these objects. A major challenge is the wide variation of O2 radiolysis yields between laboratory experiments, ranging over 4 orders of magnitude from 5 × 10-7 to 5 × 10-3 molecules/eV for different particles and energies. We revisit decades of laboratory data to solve this long-standing puzzle, finding an inverse projectile range dependence in the O2 yields, due to preferential O2 formation from an 30 Å thick oxygenated surface layer. Highly penetrating projectile ions and electrons with ranges ≳30 Å are therefore less efficient at producing O2 than slow/heavy ions and low-energy electrons (≲ 400 eV) which deposit most energy near the surface. Unlike O2, the H2O2 yields from penetrating projectiles fall within a comparatively narrow range of (0.1-6) × 10-3 molecules/eV and do not depend on range, suggesting that H2O2 forms deep in the ice uniformly along the projectile track, e.g., by reactions of OH radicals. We develop an analytical model for O2, H2, and H2O2 yields from pure water ice for electrons and singly charged ions of any mass and energy and apply the model to estimate possible O2 source rates on several icy satellites. The yields are upper limits for icy bodies on which surface impurities may be present.

Preference for internucleotide linkages as a function of the number of constituents in a mixture

NASA Technical Reports Server (NTRS)

Kanavarioti, A.

1998-01-01

Phosphoimidazolide-activated ribomononucleotides (*pN; see Scheme I) are useful substrates for the nonenzymatic synthesis of oligonucleotides. In the presence of metal ions dilute neutral aqueous solutions of *pN (0.01 M) typically yield only small amounts of dimers and traces of oligomers; most of *pN hydrolyzes to yield nucleoside 5'-monophosphate (5'NMP). An earlier investigation of *pN reactions in highly concentrated aqueous solutions (up to 1.4 M) showed, as expected, that the percentage yield of the condensation products increases and the yield of the hydrolysis product correspondingly decreases with *pN concentration (Kanavarioti 1997). Here we report product distributions in reactions with one, two, or three reactive components at the same total nucleotide concentration. *pN used as substrates were the nucleoside 5'-phosphate 2-methylimidazolides, 2-MeImpN, with N = cytidine (C), uridine (U), or guanosine (G). Reactions were conducted as self-condensations, i. e., one nucleotide only, with two components in the three binary U,C, U,G, and C,G mixtures, and with three components in the ternary U,C, G mixture. The products are 5'NMP, 5',5'-pyrophosphate-, 2',5'-, 3', 5'-linked dimers, cyclic dimers, and a small percentage of longer oligomers. The surprising finding was that, under identical conditions, including the same total monomer concentration, the product distribution differs substantially from one reaction to another, most likely due to changing intermolecular interactions depending on the constituents. Even more unexpected was the observed trend according to which reactions of the U,C,G mixture produce the highest yield of internucleotide-linked dimers, whereas the self-condensations produce the least and the reactions with the binary mixtures produce yields that fall in between. What is remarkable is that the approximately two-fold increase in the percentage yield of internucleotide-linked dimers is not due to a concentration effect or a catalyst, but to the increased complexity of the system from a single to two and three components. These observations, perhaps, provide an example of how increased complexity in relatively simple chemical systems leads to organization of the material and consequently to chemical evolution. A possible link between prebiotic chemistry and the postulated RNA world is discussed.

Measurements and calculations of the Coulomb cross section for the production of direct electron pairs by energetic heavy nuclei in nuclear track emulsion

NASA Technical Reports Server (NTRS)

Derrickson, J. H.; Eby, P. B.; Fountain, W. F.; Parnell, T. A.; Dong, B. L.; Gregory, J. C.; Takahashi, Y.; King, D. T.

1988-01-01

Measurements and theoretical predictions of the Coulomb cross section for the production of direct electron pairs by heavy ions in emulsion have been performed. Nuclear track emulsions were exposed to the 1.8 GeV/amu Fe-56 beam at the Lawrence Berkeley Laboratory bevalac and to the 60 and 200 GeV/amu O-16 and the 200 GeV/amu S-32 beam at the European Center for Nuclear Research Super Proton Synchrotron modified to accelerate heavy ions. The calculations combine the Weizsacker-Williams virtual quanta method applicable to the low-energy transfers and the Kelner-Kotov relativistic treatment for the high-energy transfers. Comparison of the measured total electron pair yield, the energy transfer distribution, and the emission angle distribution with theoretical predictions revealed a discrepancy in the frequency of occurrence of the low-energy pairs (less than or = 10 MeV). The microscope scanning criteria used to identify the direct electron pairs is described and efforts to improve the calculation of the cross section for pair production are also discussed.

Osmotic stress alters the balance between organic and inorganic solutes in flax (Linum usitatissimum).

PubMed

Quéro, Anthony; Molinié, Roland; Elboutachfaiti, Redouan; Petit, Emmanuel; Pau-Roblot, Corinne; Guillot, Xavier; Mesnard, François; Courtois, Josiane

2014-01-01

Flax (Linum usitatissimum) is grown for its oil and its fiber. This crop, cultivated in temperate regions, has seen a renewed interest due to the presence of abundant molecules of interest for many applications. Little information is available about the behavior of flax during osmotic stress; yet this is considered a major stress that causes significant yield losses in most crops. To control the presence of this stress better, flax behavior was investigated following the application of osmotic stress and the response was examined by applying increasing concentrations of PEG 8000. This resulted in the reorganization of 32 metabolites and 6 mineral ions in the leaves. The analysis of these two types of solute highlighted the contrasting behavior between a higher metabolite content (particularly fructose, glucose and proline) and a decrease in mineral ions (especially nitrate and potassium) following PEG treatment. However, this reorganization did not lead to a greater accumulation of solutes, with the total amount remaining unchanged in leaves during osmotic stress. Copyright © 2013 Elsevier GmbH. All rights reserved.

Comparison of simulations with PHITS and HIBRAC with experimental data in the context of particle therapy monitoring

PubMed Central

Rohling, Heide; Sihver, Lembit; Priegnitz, Marlen; Enghardt, Wolfgang; Fiedler, Fine

2014-01-01

Therapeutic irradiation with protons and ions is advantageous over radiotherapy with photons due to its favorable dose deposition. Additionally, ion beams provide a higher relative biological effectiveness than photons. For this reason, an improved treatment of deep-seated tumors is achieved and normal tissue is spared. However, small deviations from the treatment plan can have a large impact on the dose distribution. Therefore, a monitoring is required to assure the quality of the treatment. Particle therapy positron emission tomography (PT-PET) is the only clinically proven method which provides a non-invasive monitoring of dose delivery. It makes use of the β+-activity produced by nuclear fragmentation during irradiation. In order to evaluate these PT-PET measurements, simulations of the β+-activity are necessary. Therefore, it is essential to know the yields of the β+-emitting nuclides at every position of the beam path as exact as possible. We evaluated the three-dimensional Monte-Carlo simulation tool PHITS (version 2.30) [ 1] and the 1D deterministic simulation tool HIBRAC [ 2] with respect to the production of β+-emitting nuclides. The yields of the most important β+-emitting nuclides for carbon, lithium, helium and proton beams have been calculated. The results were then compared with experimental data obtained at GSI Helmholtzzentrum für Schwerionenforschung Darmstadt, Germany. GEANT4 simulations provide an additional benchmark [ 3]. For PHITS, the impact of different nuclear reaction models, total cross-section models and evaporation models on the β+-emitter production has been studied. In general, PHITS underestimates the yields of positron-emitters and cannot compete with GEANT4 so far. The β+-emitters calculated with an extended HIBRAC code were in good agreement with the experimental data for carbon and proton beams and comparable to the GEANT4 results, see [ 4] and Fig. 1. Considering the simulation results and its speed compared with three-dimensional Monte-Carlo tools, HIBRAC is a good candidate for the implementation in clinical routine PT-PET. Fig 1.Depth-dependent yields of the production of 11C and 15O during proton irradiation of a PMMA target with 140 MeV [ 4].

Removal of fluoride ion by bone char produced from animal biomass.

PubMed

Kawasaki, Naohito; Ogata, Fumihiko; Tominaga, Hisato; Yamaguchi, Isao

2009-01-01

Bone char (BC) was prepared by carbonizing four types of animal biomass, and the adsorption of fluoride ions and elution of phosphate ions were investigated. It was found that the BC yield decreased as carbonization temperature increased, and that carbonization temperature had no significant effect on surface pH, base or acid consumptions. Fluoride ion adsorption was increased in BC produced at a low carbonization temperature. The adsorption mechanism of fluoride ion on BCs might be monolayer adsorption. BC can potentially be used to remove fluoride ions in drinking water. However, it was found that phosphate ions from BC are eluted due to adsorption of fluoride ions, and that ingestion of large amounts of phosphate ions inhibits reabsorption of calcium in the human body. Thus there is a need to study the elution behavior of phosphate ions. The adsorption mechanisms of fluoride ions onto BC would be a physical adsorption onto BC and phosphate ion in BC is exchanged to fluoride ion.

Estimating total suspended sediment yield with probability sampling

Treesearch

Robert B. Thomas

1985-01-01

The ""Selection At List Time"" (SALT) scheme controls sampling of concentration for estimating total suspended sediment yield. The probability of taking a sample is proportional to its estimated contribution to total suspended sediment discharge. This procedure gives unbiased estimates of total suspended sediment yield and the variance of the...

Electronic Properties and Dissociative Photoionization of Thiocyanates, Part III. The Effect of the Group's Electronegativity in the Valence and Shallow-Core (Sulfur and Chlorine 2p) Regions of CCl3SCN and CCl2FSCN.

PubMed

Rodríguez Pirani, Lucas S; Della Védova, Carlos O; Geronés, Mariana; Romano, Rosana M; Cavasso-Filho, Reinaldo; Ge, Maofa; Ma, Chunping; Erben, Mauricio F

2017-12-07

Both photoelectron spectroscopy (PES) data and PhotoElectron-PhotoIon-Coincidence (PEPICO) spectra obtained from a synchrotron facility have been used to examine the electronic structure and the dissociative ionization of halomethyl thiocyantes in the valence and shallow-core S 2p and Cl 2p regions. Two simple and closely related molecules, namely, CCl 3 SCN and CCl 2 FSCN, have been analyzed to assess the role of halogen substitution in the electronic properties of thiocyanates. The assignment of the He(I) photoelectron spectra has been achieved with the help of quantum chemical calculations at the outer-valence Green's function (OVGF) level of approximation. The first ionization energies observed at 10.55 and 10.78 eV for CCl 3 SCN and CCl 2 FSCN, respectively, are assigned to ionization processes from the sulfur lone pair orbital [n(S)]. When these molecules are compared with CX 3 SCN (X = H, Cl, F) species, a linear relationship between the vertical first ionization energy and electronegativity of CX 3 group is observed. Irradiation of CCl 3 SCN and CCl 2 FSCN with photons in the valence energy regions leads to the formation of CCl 2 X + and CClXSCN + ions (X = Cl or F). Additionally, the achievement of the fragmentation patterns and the total ion yield spectra obtained from the PEPICO data in the S 2p and Cl 2p regions and several dissociation channels can be inferred for the core-excited species by using the triple coincidence PEPIPICO (PhotoElectron-PhotoIon-PhotoIon-Coincidence) spectra.

Differential Sputtering Behavior of Pyrolytic Graphite and Carbon-Carbon Composite Under Xenon Bombardment

NASA Technical Reports Server (NTRS)

Williams, John D.; Johnson, Mark L.; Williams, Desiree D.

2003-01-01

A differential sputter yield measurement technique is described, which consists of a quartz crystal monitor that is swept at constant radial distance from a small target region where a high current density xenon ion beam is aimed. This apparatus has been used to characterize the sputtering behavior of various forms of carbon including polycrystalline graphite, pyrolytic graphite, and PVD-infiltrated and pyrolized carbon-carbon composites. Sputter yield data are presented for pyrolytic graphite and carbon-carbon composite over a range of xenon ion energies from 200 eV to 1 keV and angles of incidence from 0 deg (normal incidence) to 60 deg .

Temperature dependence of yields from multi-foil SPES target

NASA Astrophysics Data System (ADS)

Corradetti, S.; Biasetto, L.; Manzolaro, M.; Scarpa, D.; Andrighetto, A.; Carturan, S.; Prete, G.; Zanonato, P.; Stracener, D. W.

2011-10-01

The temperature dependence of neutron-rich isotope yields was studied within the framework of the HRIBF-SPES Radioactive Ion Beams (RIB) project. On-line release measurements of fission fragments from a uranium carbide target at ensuremath 1600 {}^{circ}C , ensuremath 1800 {}^{circ}C and ensuremath 2000 {}^{circ}C were performed at ORNL (USA). The fission reactions were induced by a 40MeV proton beam accelerated into a uranium carbide target coupled to a plasma ion source. The experiments allowed for tests of performance of the SPES multi-foil target prototype loaded with seven UC2/graphite discs (ratio C/ U = 4 with density about 4g/cm3.

Effects of fixture rotation on coating uniformity for high-performance optical filter fabrication

NASA Astrophysics Data System (ADS)

Rubin, Binyamin; George, Jason; Singhal, Riju

2018-04-01

Coating uniformity is critical in fabricating high-performance optical filters by various vacuum deposition methods. Simple and planetary rotation systems with shadow masks are used to achieve the required uniformity [J. B. Oliver and D. Talbot, Appl. Optics 45, 13, 3097 (2006); O. Lyngnes, K. Kraus, A. Ode and T. Erguder, in `Method for Designing Coating Thickness Uniformity Shadow Masks for Deposition Systems with a Planetary Fixture', 2014 Technical Conference Proceedings, Optical Coatings, August 13, 2014, DOI: 10.14332/svc14.proc.1817.]. In this work, we discuss the effect of rotation pattern and speed on thickness uniformity in an ion beam sputter deposition system. Numerical modeling is used to determine statistical distribution of random thickness errors in coating layers. The relationship between thickness tolerance and production yield are simulated theoretically and demonstrated experimentally. Production yields for different optical filters produced in an ion beam deposition system with planetary rotation are presented. Single-wavelength and broadband optical monitoring systems were used for endpoint monitoring during filter deposition. Limitations of thickness tolerances that can be achieved in systems with planetary rotation are shown. Paths for improving production yield in an ion beam deposition system are described.

Salinity impact on yield, water use, mineral and essential oil content of fennel (Foeniculum vulgare Mill.)

USDA-ARS?s Scientific Manuscript database

The experimental study was carried out to determine the effects of salinity on water consumption, plant height, fresh and seed yields, biomass production, ion accumulation and essential oil content of fennel (Foeniculum vulgare Mill.) under greenhouse conditions. The experiment was conducted with a ...

Reversible exciplex formation followed charge separation.

PubMed

Petrova, M V; Burshtein, A I

2008-12-25

The reversible exciplex formation followed by its decomposition into an ion pair is considered, taking into account the subsequent geminate and bulk ion recombination to the triplet and singlet products (in excited and ground states). The integral kinetic equations are derived for all state populations, assuming that the spin conversion is performed by the simplest incoherent (rate) mechanism. When the forward and backward electron transfer is in contact as well as all dissociation/association reactions of heavy particles, the kernels of integral equations are specified and expressed through numerous reaction constants and characteristics of encounter diffusion. The solutions of these equations are used to specify the quantum yields of the excited state and exciplex fluorescence induced by pulse or stationary pumping. In the former case, the yields of the free ions and triplet products are also found, while in the latter case their stationary concentrations are obtained.

Parametric estimate of the relative photon yields from the glasma and the quark-gluon plasma in heavy-ion collisions

DOE PAGES

Berges, Jürgen; Reygers, Klaus; Tanji, Naoto; ...

2017-05-09

Recent classical-statistical numerical simulations have established the “bottom-up” thermalization scenario of Baier et al. [Phys. Lett. B 502, 51 (2001)] as the correct weak coupling effective theory for thermalization in ultrarelativistic heavy-ion collisions. In this paper, we perform a parametric study of photon production in the various stages of this bottom-up framework to ascertain the relative contribution of the off-equilibrium “glasma” relative to that of a thermalized quark-gluon plasma. Taking into account the constraints imposed by the measured charged hadron multiplicities at Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), we find that glasma contributions are importantmore » especially for large values of the saturation scale at both energies. Finally, these nonequilibrium effects should therefore be taken into account in studies where weak coupling methods are employed to compute photon yields.« less

Testing and Analysis of NEXT Ion Engine Discharge Cathode Assembly Wear

NASA Technical Reports Server (NTRS)

Domonkos, Matthew T.; Foster, John E.; Soulas, George C.; Nakles, Michael

2003-01-01

Experimental and analytical investigations were conducted to predict the wear of the discharge cathode keeper in the NASA Evolutionary Xenon Thruster. The ion current to the keeper was found to be highly dependent upon the beam current, and the average beam current density was nearly identical to that of the NSTAR thruster for comparable beam current density. The ion current distribution was highly peaked toward the keeper orifice. A deterministic wear assessment predicted keeper orifice erosion to the same diameter as the cathode tube after processing 375 kg of xenon. A rough estimate of discharge cathode assembly life limit due to sputtering indicated that the current design exceeds the qualification goal of 405 kg. Probabilistic wear analysis showed that the plasma potential and the sputter yield contributed most to the uncertainty in the wear assessment. It was recommended that fundamental experimental and modeling efforts focus on accurately describing the plasma potential and the sputtering yield.

Comparison of different substrates for laser-induced electron transfer desorption/ionization of metal complexes

NASA Astrophysics Data System (ADS)

Grechnikov, A. A.; Georgieva, V. B.; Donkov, N.; Borodkov, A. S.; Pento, A. V.; Raicheva, Z. G.; Yordanov, Tc A.

2016-03-01

Four different substrates, namely, graphite, tungsten, amorphous silicon (α-Si) and titanium dioxide (TiO2) films, were compared in view of the laser-induced electron transfer desorption/ionization (LETDI) of metal coordination complexes. A rhenium complex with 8-mercaptoquinoline, a copper complex with diphenylthiocarbazone and chlorophyll A were studied as the test analytes. The dependencies of the ion yield and the surface temperature on the incident radiation fluence were investigated experimentally and theoretically. The temperature was estimated using the numerical solution of a one-dimensional heat conduction problem with a heat source distributed in time and space. It was found that at the same temperature, the ion yield from the different substrates varies in the range of three orders of magnitude. The direct comparison of all studied substrates revealed that LETDI from the TiO2 and α-Si films offer a better choice for producing molecular ions of metal coordination complexes.

Diffusion kinetics of the glucose/glucose oxidase system in swift heavy ion track-based biosensors

NASA Astrophysics Data System (ADS)

Fink, Dietmar; Vacik, Jiri; Hnatowicz, V.; Muñoz Hernandez, G.; Garcia Arrelano, H.; Alfonta, Lital; Kiv, Arik

2017-05-01

For understanding of the diffusion kinetics and their optimization in swift heavy ion track-based biosensors, recently a diffusion simulation was performed. This simulation aimed at yielding the degree of enrichment of the enzymatic reaction products in the highly confined space of the etched ion tracks. A bunch of curves was obtained for the description of such sensors that depend only on the ratio of the diffusion coefficient of the products to that of the analyte within the tracks. As hitherto none of these two diffusion coefficients is accurately known, the present work was undertaken. The results of this paper allow one to quantify the previous simulation and hence yield realistic predictions of glucose-based biosensors. At this occasion, also the influence of the etched track radius on the diffusion coefficients was measured and compared with earlier prediction.

Sputtering of Lunar Regolith Simulant by Protons and Multicharged Heavy Ions at Solar Wind Energies

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

Meyer, Fred W; Harris, Peter R; Taylor, C. N.

2011-01-01

We report preliminary results on sputtering of a lunar regolith simulant at room temperature by singly and multiply charged solar wind ions using quadrupole and time-of-flight (TOF) mass spectrometry approaches. Sputtering of the lunar regolith by solar-wind heavy ions may be an important particle source that contributes to the composition of the lunar exosphere, and is a possible mechanism for lunar surface ageing and compositional modification. The measurements were performed in order to assess the relative sputtering efficiency of protons, which are the dominant constituent of the solar wind, and less abundant heavier multicharged solar wind constituents, which have highermore » physical sputtering yields than same-velocity protons, and whose sputtering yields may be further enhanced due to potential sputtering. Two different target preparation approaches using JSC-1A AGGL lunar regolith simulant are described and compared using SEM and XPS surface analysis.« less

Sensitivity in MALDI MS with small spot sizes

NASA Astrophysics Data System (ADS)

Yamchuk, Andriy

In MALDI, for laser fluences below the saturation point the ion yield per shot follows a cubic dependence on the irradiated area, leading to a conclusion that smaller spots produce overall less ions and therefore are less viable. However, Qiao et al. showed that by decreasing the laser spot size it is possible to raise the saturation point, and thus increase the ion yield per unit area, also known as sensitivity. Here we explore laser spots below 10 micrometer diameter to determine whether they offer any practical advantage. We show that sensitivity is greater for a flat-top 3--4 micrometer spot than for a 10 micrometer spot. The sensitivity is greater for a Gaussian-like 3--5 micrometer spot than for flat-top 5--25 micrometer spots. We also report for the first time sensitivity versus theoretical fluence profile for a Gaussian-like beam focu

Consecutive Fragmentation Mechanisms of Protonated Ferulic Acid Probed by Infrared Multiple Photon Dissociation Spectroscopy and Electronic Structure Calculations

NASA Astrophysics Data System (ADS)

Martens, Sabrina M.; Marta, Rick A.; Martens, Jonathan K.; McMahon, Terry B.

2012-10-01

Protonated ferulic acid and its principle fragment ion have been characterized using infrared multiple photon dissociation spectroscopy and electronic structure calculations at the B3LYP/6-311 + G(d,p) level of theory. Due to its extensively conjugated structure, protonated ferulic acid is observed to yield three stable fragment ions in IRMPD experiments. It is proposed that two parallel fragmentation pathways of protonated ferulic acid are being observed. The first pathway involves proton transfer, resulting in the loss of water and subsequently carbon monoxide, producing fragment ions m/z 177 and 149, respectively. Optimization of m/z 177 yields a species containing an acylium group, which is supported by a diagnostic peak in the IRMPD spectrum at 2168 cm-1. The second pathway involves an alternate proton transfer leading to loss of methanol and rearrangement to a five-membered ring.

Ionization, evaporation and fragmentation of C60 in collisions with highly charged C, O and F ions—effect of projectile charge state.

NASA Astrophysics Data System (ADS)

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

2007-09-01

We study the various inelastic processes such ionization, fragmentation and evaporation of C60 molecule in collisions with fast heavy ions. We have used 2.33 MeV/u C, O and F projectile ion beams. Various ionization and fragmentation products were detected using time-of-flight mass spectrometer. The multiply charged C60r+ ions were detected for maximum r = 4. The projectile charge state (qp) dependence of the single and double ionization cross sections is well reproduced by a model based on the giant dipole plasmon resonance (GDPR). The qp-dependence of the fragmentation yields, was found to be linear. Variation of relative yields of the evaporation products of C602+ (i.e. C582+, C562+ etc) and C603+ (i.e. C583+, C563+ etc) with qp has also been investigated for various projectiles.

Reduction of the K* meson abundance in heavy ion collisions

NASA Astrophysics Data System (ADS)

Cho, Sungtae; Lee, Su Houng

2018-03-01

We study the K* meson reduction in heavy-ion collisions by focusing on the hadronic effects on the K* meson abundance. We evaluate the absorption cross sections of the K* and K meson by light mesons in the hadronic matter, and further investigate the variation in the meson abundances for both particles during the hadronic stage of heavy-ion collisions. We show how the interplay between the interaction of the K* meson and kaon with light mesons in the hadronic medium determines the final yield difference of the statistical hadronization model to the experimental measurements. For the central Au+Au collision at √{sN N}=200 GeV, we find that the K*/K yield ratio at chemical freeze-out decreases by 37 % during the expansion of the hadronic matter, resulting in the final ratio comparable to STAR measurements of 0.23 ±0.05 .

Enhancement of Palmarumycins C(12) and C(13) production in liquid culture of endophytic fungus Berkleasmium sp. Dzf12 after treatments with metal ions.

PubMed

Mou, Yan; Luo, Haiyu; Mao, Ziling; Shan, Tijiang; Sun, Weibo; Zhou, Kaiyi; Zhou, Ligang

2013-01-07

The influences of eight metal ions (i.e., Na+, Ca2+, Ag+, Co2+, Cu2+, Al3+, Zn2+, and Mn4+) on mycelia growth and palmarumycins C(12) and C(13) production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12 were investigated. Three metal ions, Ca2+, Cu2+ and Al3+ were exhibited as the most effective to enhance mycelia growth and palmarumycin production. When calcium ion (Ca2+) was applied to the medium at 10.0 mmol/L on day 3, copper ion (Cu2+) to the medium at 1.0 mmol/L on day 3, aluminum ion (Al3+) to the medium at 2.0 mmol/L on day 6, the maximal yields of palmarumycins C(12) plus C(13) were obtained as 137.57 mg/L, 146.28 mg/L and 156.77 mg/L, which were 3.94-fold, 4.19-fold and 4.49-fold in comparison with that (34.91 mg/L) of the control, respectively. Al3+ favored palmarumycin C(12) production when its concentration was higher than 4 mmol/L. Ca2+ had an improving effect on mycelia growth of Berkleasmium sp. Dzf12. The combination effects of Ca2+, Cu2+ and Al3+ on palmarumycin C(13) production were further studied by employing a statistical method based on the central composite design (CCD) and response surface methodology (RSM). By solving the quadratic regression equation between palmarumycin C(13) and three metal ions, the optimal concentrations of Ca2+, Cu2+ and Al3+ in medium for palmarumycin C(13) production were determined as 7.58, 1.36 and 2.05 mmol/L, respectively. Under the optimum conditions, the predicted maximum palmarumycin C(13) yield reached 208.49 mg/L. By optimizing the combination of Ca2+, Cu2+ and Al3+ in medium, palmarumycin C(13) yield was increased to 203.85 mg/L, which was 6.00-fold in comparison with that (33.98 mg/L) in the original basal medium. The results indicate that appropriate metal ions (i.e., Ca2+, Cu2+ and Al3+) could enhance palmarumycin production. Application of the metal ions should be an effective strategy for palmarumycin production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12.

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

Ghosh, H.N.; Pal, H.; Sapre, A.V.

Photoexcitation of complexes between fullerence C[sub 60] and organic amines in benzene solutions is known to result in charge separation (CS) and subsequent charge recombination (CR) reactions, which lead to varying yields of fullerence triplet formation. Picosecond flash photolysis studies are carried out on C[sub 60]-diphenylamine (DPA), C[sub 60]-triethylamine (TEA), C[sub 60]-diazabicyclooctane (DABCO), and C[sub 60]-triphenylamine (TPA) systems to find out mechanistic details of the triplet formation on CR by inducing heavy atom and polarity effects by using suitable solvents. It is found that in the case of C[sub 60]-DPA, C[sub 60]-TEA, and C[sub 60]-DABCO systems proton transfer from themore » amine cation to the C[sub 60] anion in the ion pair state dominates, leading to poor triplet yields, which improve in heavy atom containing solvents. In TPA, proton transfer is not possible and hence fullerene triplet yields are high. Increase of solvent polarity for this system results in decreased C[sub 60] triplet yields with a consequent increase in the ion dissociation yield. A suitable reaction scheme is proposed to explain the results obtained. 34 refs., 5 figs., 2 tabs.« less

Influence of Nutritional Conditions on Production of l-Glutamine by Flavobacterium rigense

PubMed Central

Nabe, Koichi; Ujimaru, Toshihiko; Yamada, Shigeki; Chibata, Ichiro

1981-01-01

The nutritional conditions for the production of l-glutamine by Flavobacterium rigense strain 703 were investigated. The optimum concentration of ammonia for achieving the highest yield of l-glutamine (25 mg/ml of broth) was relatively broad, from 0.9 to 1.6%, whereas fumaric acid had a narrow optimum range, near 5.5%. High concentration of inorganic ions such as chloride or sulfate ion clearly inhibited cell growth. Therefore, ammonium salts other than (NH4)2-fumarate were unsuitable for the highest production. The optimum concentration of (NH4)2-fumarate was 7%. To reduce the concentration of fumaric acid in the medium, many substances were evaluated as substitutes. The fumaric acid concentration required for highest l-glutamine yield could not be replaced by any one of the compounds tested. However, part of fumaric acid could be replaced with succinic acid and cupric ion; 4% (NH4)2-fumarate plus 2.5% succinic acid or 5% (NH4)2-fumarate plus 1 mM cupric ion produced results similar to 7% (NH4)2-fumarate in the fermentation medium. PMID:16345682

Power generation by a pH-regulated conical nanopore through reverse electrodialysis

NASA Astrophysics Data System (ADS)

Hsu, Jyh-Ping; Lin, Sheng-Chang; Lin, Chih-Yuan; Tseng, Shiojenn

2017-10-01

To assess the possibility of energy harvesting through reverse electrodialysis (RED), we consider the electrokinetic behavior of the ion transport in a pH-regulated conical nanopore connecting two large reservoirs having different bulk salt concentrations, taking account of the effect of osmotic flow. In particular, we examine the influence of the ion diffusion direction, the solution pH, and the bulk concentration ratio on that behavior in detail, and discuss the underlying mechanisms. We show that the geometrically asymmetric nature of the nanopore yields profound and interesting phenomena arising mainly from the distribution of ions in its interior. Assuming a single polymeric nanopore, a power density of 18.2 W/m2 can be generated. We show that the present system has the potential of serving as an ion-selective and a salinity gradient power generation device. The maximum power efficiency which is based on assuming a linear ionic distribution in nanopore can yield appreciable deviation, especially if pH deviates significantly from 7, where the presence of H+ and OH- needs be considered.

Effects of residual kinetic energy on yield degradation and ion temperature asymmetries in inertial confinement fusion implosions

NASA Astrophysics Data System (ADS)

Woo, K. M.; Betti, R.; Shvarts, D.; Bose, A.; Patel, D.; Yan, R.; Chang, P.-Y.; Mannion, O. M.; Epstein, R.; Delettrez, J. A.; Charissis, M.; Anderson, K. S.; Radha, P. B.; Shvydky, A.; Igumenshchev, I. V.; Gopalaswamy, V.; Christopherson, A. R.; Sanz, J.; Aluie, H.

2018-05-01

The study of Rayleigh-Taylor instability in the deceleration phase of inertial confinement fusion implosions is carried out using the three-dimensional (3-D) radiation-hydrodynamic Eulerian parallel code DEC3D. We show that the yield-over-clean is a strong function of the residual kinetic energy (RKE) for low modes. Our analytical models indicate that the behavior of larger hot-spot volumes observed in low modes and the consequential pressure degradation can be explained in terms of increasing the RKE. These results are derived using a simple adiabatic implosion model of the deceleration phase as well as through an extensive set of 3-D single-mode simulations using the code DEC3D. The effect of the bulk velocity broadening on ion temperature asymmetries is analyzed for different mode numbers ℓ=1 -12. The jet observed in low mode ℓ=1 is shown to cause the largest ion temperature variation in the mode spectrum. The vortices of high modes within the cold bubbles are shown to cause lower ion temperature variations than low modes.

Electrospray Post-Ionization Mass Spectrometry of Electrosurgical Aerosols

NASA Astrophysics Data System (ADS)

Guenther, Sabine; Schäfer, Karl-Christian; Balog, Júlia; Dénes, Júlia; Majoros, Tamás; Albrecht, Katalin; Tóth, Miklós; Spengler, Bernhard; Takáts, Zoltán

2011-11-01

The feasibility of electrospray (ES) ionization of aerosols generated by electrosurgical disintegration methods was investigated. Although electrosurgery itself was demonstrated to produce gaseous ions, post-ionization methods were implemented to enhance the ion yield, especially in those cases when the ion current produced by the applied electrosurgical method is not sufficient for MS analysis. Post-ionization was implemented by mounting an ES emitter onto a Venturi pump, which is used for ion transfer. The effect of various parameters including geometry, high voltage setting, flow parameters, and solvent composition was investigated in detail. Experimental setups were optimized accordingly. ES post-ionization was found to yield spectra similar to those obtained by the REIMS technique, featuring predominantly lipid-type species. Signal enhancement was 20- to 50-fold compared with electrosurgical disintegration in positive mode, while no improvement was observed in negative mode. ES post-ionization was also demonstrated to allow the detection of non-lipid type species in the electrosurgical aerosol, including drug molecules. Since the tissue specificity of the MS data was preserved in the ES post-ionization setup, feasibility of tissue identification was demonstrated using different electrosurgical methods.

Spin decoherence of InAs surface electrons by transition metal ions

NASA Astrophysics Data System (ADS)

Zhang, Yao; Soghomonian, V.; Heremans, J. J.

2018-04-01

Spin interactions between a two-dimensional electron system at the InAs surface and transition metal ions, Fe3 +, Co2 +, and Ni2 +, deposited on the InAs surface, are probed by antilocalization measurements. The spin-dependent quantum interference phenomena underlying the quantum transport phenomenon of antilocalization render the technique sensitive to the spin states of the transition metal ions on the surface. The experiments yield data on the magnitude and temperature dependence of the electrons' inelastic scattering rates, spin-orbit scattering rates, and magnetic spin-flip rates as influenced by Fe3 +, Co2 +, and Ni2 +. A high magnetic spin-flip rate is shown to mask the effects of spin-orbit interaction, while the spin-flip rate is shown to scale with the effective magnetic moment of the surface species. The spin-flip rates and their dependence on temperature yield information about the spin states of the transition metal ions at the surface, and in the case of Co2 + suggest either a spin transition or formation of a spin-glass system.

Nanowire dopant measurement using secondary ion mass spectrometry

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

Chia, A. C. E.; Boulanger, J. P.; Wood, B. A.

2015-09-21

A method is presented to improve the quantitative determination of dopant concentration in semiconductor nanowire (NW) arrays using secondary ion mass spectrometry (SIMS). SIMS measurements were used to determine Be dopant concentrations in a Be-doped GaAs thin film and NW arrays of various pitches that were dry-etched from the same film. A comparison of these measurements revealed a factor of 3 to 12 difference, depending on the NW array pitch, between the secondary Be ion yields of the film and the NW arrays, despite being identically doped. This was due to matrix effects and ion beam mixing of Be frommore » the NWs into the surrounding benzocyclobutene that was used to fill the space between the NWs. This indicates the need for etched NWs to be used as doping standards instead of 2D films when evaluating NWs of unknown doping by SIMS. Using the etched NWs as doping standards, NW arrays of various pitches grown by the vapour-liquid-solid mechanism were characterized by SIMS to yield valuable insights into doping mechanisms.« less

Neutron yield when fast deuterium ions collide with strongly charged tritium-saturated dust particles

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

Akishev, Yu. S., E-mail: akishev@triniti.ru; Karal’nik, V. B.; Petryakov, A. V.

2017-02-15

The ultrahigh charging of dust particles in a plasma under exposure to an electron beam with an energy up to 25 keV and the formation of a flux of fast ions coming from the plasma and accelerating in the strong field of negatively charged particles are considered. Particles containing tritium or deuterium atoms are considered as targets. The calculated rates of thermonuclear fusion reactions in strongly charged particles under exposure to accelerated plasma ions are presented. The neutron generation rate in reactions with accelerated deuterium and tritium ions has been calculated for these targets. The neutron yield has been calculatedmore » when varying the plasma-forming gas pressure, the plasma density, the target diameter, and the beam electron current density. Deuterium and tritium-containing particles are shown to be the most promising plasmaforming gas–target material pair for the creation of a compact gas-discharge neutron source based on the ultrahigh charging of dust particles by beam electrons with an energy up to 25 keV.« less

Groundwater transport of strontium 90 in a glacial outwash environment

USGS Publications Warehouse

Kipp, Kenneth L.; Stollenwerk, Kenneth G.; Grove, David B.

1986-01-01

As part of the investigation of groundwater contamination at a uranium-scrap recovery plant at Wood River Junction, Rhode Island, laboratory experiments led to the development of a model for predicting the transport of strontium 90 in glacial outwash sediments based on an approximate mechanism for ion exchange. The multicomponent system was simplified to two components by regarding all exchangeable cations other than strontium 90 as a single component. The binary ion-exchange parameter was a function of the variable, total ion concentration. A one-dimensional solute transport model was formulated to evaluate the time necessary for natural groundwater flow to remove the strontium 90 contamination plume from the groundwater system to the Pawcatuck River. The finite difference transport equations were solved sequentially for total ion concentrations, then strontium 90 concentrations. Clay-free quartz and feldspar sands at the study site have little potential for strontium 90 sorption, and high calcium, magnesium, and sodium concentrations compete for the few ion exchange sites. As the total ion concentration plume moves out of the system, ion exchange of strontium 90 increases, reducing the strontium 90 concentration in the groundwater. Cleanout times predicted using the binary ion exchange mechanism were about two thirds of those predicted using a constant distribution coefficient. It is suggested that this type of model can simulate solute transport more realistically in many groundwater systems where the total ion concentration is not constant.

Ion-induced particle desorption in time-of-flight medium energy ion scattering

NASA Astrophysics Data System (ADS)

Lohmann, S.; Primetzhofer, D.

2018-05-01

Secondary ions emitted from solids upon ion impact are studied in a time-of-flight medium energy ion scattering (ToF-MEIS) set-up. In order to investigate characteristics of the emission processes and to evaluate the potential for surface and thin film analysis, experiments employing TiN and Al samples were conducted. The ejected ions exhibit a low initial kinetic energy of a few eV, thus, requiring a sufficiently high acceleration voltage for detection. Molecular and atomic ions of different charge states originating both from surface contaminations and the sample material are found, and relative yields of several species were determined. Experimental evidence that points towards a predominantly electronic sputtering process is presented. For emitted Ti target atoms an additional nuclear sputtering component is suggested.

Preliminary Results of Low Energy Sputter Yields of Boron Nitride due to Xenon Ion Bombardment (Preprint)

DTIC Science & Technology

2008-07-07

from normal. Comparison with past measurement results are made where possible. I. Nomenclature As = sensor area of QCM E = beam ion...use a combination of weight-loss and QCM deposition sensor and builds upon our previous work 5-7, 9- 10 . In Section III we summarize our experimental...containing the surface normal and the incident ion directions). E. QCM Sensor and Signal Analysis In deposition mode, the QCM allows

Quartz Crystal Microbalance Based System for High-Sensitivity Differential Sputter Yield Measurements (Preprint)

DTIC Science & Technology

2009-08-20

at low ion energies require appropriate ion sources. For example, past work using QCM sensors employed a magnetron as an ion source 32,33 . The...and for data logging. Detailed discussion of the QCM sensor is provided in Section IID. Figure 1. Schematic diagram of the experimental set-up...mass flow rate of 0.5 sccm. The PBN was biased negatively relative to ground potential. D. QCM Sensor and Temperature Control In deposition mode

Adherence and Bonding of the Ion Plated Films.

DTIC Science & Technology

1983-07-01

adhesion strength is, therefore, governed by the physical interactions and van der waals forces yield the lower bound estimates(42). c) Compound interfaces...plasma and 30% for gold- argon plasma, when using high current densities of the or- der of several milliamperes per square centimetere. Buckely et.al...resulted only from ions following the field lines, whereas that on the front surface was the re- sult of both ions and neut ils. In the present work we

Inner-shell photoionization and core-hole decay of Xe and XeF2.

PubMed

Southworth, Stephen H; Wehlitz, Ralf; Picón, Antonio; Lehmann, C Stefan; Cheng, Lan; Stanton, John F

2015-06-14

Photoionization cross sections and partial ion yields of Xe and XeF2 from Xe 3d(5/2), Xe 3d(3/2), and F 1s subshells in the 660-740 eV range are compared to explore effects of the F ligands. The Xe 3d-ϵf continuum shape resonances dominate the photoionization cross sections of both the atom and molecule, but prominent resonances appear in the XeF2 cross section due to nominal excitation of Xe 3d and F 1s electrons to the lowest unoccupied molecular orbital (LUMO), a delocalized anti-bonding MO. Comparisons of the ion products from the atom and molecule following Xe 3d photoionization show that the charge-state distribution of Xe ions is shifted to lower charge states in the molecule along with production of energetic F(+) and F(2+) ions. This suggests that, in decay of a Xe 3d core hole, charge is redistributed to the F ligands and the system dissociates due to Coulomb repulsion. The ion products from excitation of the F 1s-LUMO resonance are different and show strong increases in the yields of Xe(+) and F(+) ions. The subshell ionization thresholds, the LUMO resonance energies, and their oscillator strengths are calculated by relativistic coupled-cluster methods and agree well with measurements.

A laboratory study on the dissociative recombination of vibrationally excited O2/+/ions

NASA Technical Reports Server (NTRS)

Zipf, E. C.

1980-01-01

The dissociative recombination of vibrationally excited O2(+) ions is studied in light of the possible importance of this reaction in upper atmospheric chemistry. A plasma spectroscopy experiment was performed in a microwave cavity filled by an argon-oxygen mixture, with O(1S) production monitored by measurements of the 5577-A afterglow, the O2(+) density and the electron concentration. Plasma and optical data reveal the predominant afterglow ions to be Ar2(+) and O2(+), with an effective O(1S) dissociative recombination coefficient of 2.1 x 10 to the -8th cu cm/sec, corresponding to a quantum yield of 10%. Experiments with an argon-krypton-oxygen mixture reveal that vibrationally excited O2(+) ions are the chief source of the O(1S) atoms, with a specific recombination coefficient for the dissociation of O2(+)(2 pi g) into O(1S) and O(1D) of 4.2 x 10 to the -9th cu cm/sec. A comparison of the laboratory results with Atmospheric Explorer data on the 5577-A airglow implies that O2(+) ions in the sunlit ionosphere are vibrationally excited to the same degree as in the laboratory, with the vibrational relaxation of these ions much slower than dissociative recombination. Results also predict a dawn-twilight asymmetry in the effective O(1S) yield due to the normal variation of electron content.

Inner-shell photoionization and core-hole decay of Xe and XeF 2

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

Southworth, Stephen H.; Wehlitz, Ralf; Picón, Antonio

2015-06-14

Photoionization cross sections and partial ion yields of Xe and XeF2 from Xe 3d5/2, Xe 3d3/2, and F 1s subshells in the 660–740 eV range are compared to explore effects of the F ligands. The Xe 3d-ϵf continuum shape resonances dominate the photoionization cross sections of both the atom and molecule, but prominent resonances appear in the XeF2 cross section due to nominal excitation of Xe 3d and F 1s electrons to the lowest unoccupied molecular orbital (LUMO), a delocalized anti-bonding MO. Comparisons of the ion products from the atom and molecule following Xe 3d photoionization show that the charge-statemore » distribution of Xe ions is shifted to lower charge states in the molecule along with production of energetic F+ and F2+ ions. This suggests that, in decay of a Xe 3d core hole, charge is redistributed to the F ligands and the system dissociates due to Coulomb repulsion. The ion products from excitation of the F 1s-LUMO resonance are different and show strong increases in the yields of Xe+ and F+ ions. The subshell ionization thresholds, the LUMO resonance energies, and their oscillator strengths are calculated by relativistic coupled-cluster methods and agree well with measurements.« less

Superstatistics analysis of the ion current distribution function: Met3PbCl influence study.

PubMed

Miśkiewicz, Janusz; Trela, Zenon; Przestalski, Stanisław; Karcz, Waldemar

2010-09-01

A novel analysis of ion current time series is proposed. It is shown that higher (second, third and fourth) statistical moments of the ion current probability distribution function (PDF) can yield new information about ion channel properties. The method is illustrated on a two-state model where the PDF of the compound states are given by normal distributions. The proposed method was applied to the analysis of the SV cation channels of vacuolar membrane of Beta vulgaris and the influence of trimethyllead chloride (Met(3)PbCl) on the ion current probability distribution. Ion currents were measured by patch-clamp technique. It was shown that Met(3)PbCl influences the variance of the open-state ion current but does not alter the PDF of the closed-state ion current. Incorporation of higher statistical moments into the standard investigation of ion channel properties is proposed.

Change of Monascus pigment metabolism and secretion in different extractive fermentation process.

PubMed

Chen, Gong; Tang, Rui; Tian, Xiaofei; Qin, Peng; Wu, Zhenqiang

2017-06-01

Monascus pigments that were generally produced intracellularly from Monascus spp. are important natural colorants in food industry. In this study, change of pigment metabolism and secretion was investigated through fed-batch extractive fermentation and continuous extractive fermentation. The biomass, secreting rate of pigment and total pigment yield closely correlated with the activated time of extractive fermentation as well as the composition of feeding nutrients. Metal ions played a key role in both the cell growth and pigment metabolism. Nitrogen source was necessary for a high productivity of biomass but not for high pigment yield. Furthermore, fermentation period for the fed-batch extractive fermentation could be reduced by 18.75% with a nitrogen source free feeding medium. Through a 30-day continuous extractive fermentation, the average daily productivity for total pigments reached 74.9 AU day -1 with an increase by 32.6 and 296.3% compared to that in a 6-day conventional batch fermentation and a 16-day fed-batch extractive fermentation, respectively. At the meantime, proportions of extracellular pigments increased gradually from 2.7 to 71.3%, and yellow pigments gradually became dominated in both intracellular and extracellular pigments in the end of continuous extractive fermentation. This findings showed that either fed-batch or continuous extractive fermentation acted as a promising method in the efficient production of Monascus pigments.

Photoionization and Photofragmentation of the Endohedral Xe C60+ Molecular Ion

NASA Astrophysics Data System (ADS)

Aryal, Nagendra Bahadur

An experimental study of photoionization and fragmentation of the Xe C 60+ endohedral molecular ion is presented in the photon energy range of the well-known Xe 4d giant resonance, and evidence of redistribution of the Xe 4d oscillator strength in photon energy due to multipath interference is reported. Experiments were conducted at undulator beamline 10.0.1 of the Advanced Light Source (ALS) using the merged-beams technique. Prior to these measurements, macroscopic samples containing endohedral Xe C60 were prepared using a setup developed at the ALS. Endohedral Xe C60 yields as high as 2.5x10 -4 were synthesized and a pure Xe C60+ ion beam current of up to 5.5 pA was obtained for the merged-beams experiments. Cross sections were measured in the photon energy range 60 - 150 eV in 0.5 eV steps for single, double, and triple photoionization of endohedral Xe C 60+ accompanied by the loss of n pairs of carbon atoms yielding Xe C60-2n2+ (n = 0, 1), Xe C60-2n 3+ (n = 0, 1, 2, 3), and Xe C584+ photoion products. Reference absolute cross-section measurements were made for empty C60+ for the corresponding reaction channels. The spectroscopic measurements with Xe C60+ were placed onto an absolute scale by normalization to the reference cross sections for C60+ in ranges of photon energies where the Xe 4d contributions were negligible. Results for single photoionization and fragmentation of Xe C60+ show no evidence of the presence of the caged Xe atom. The measurements of double and triple photoionization with fragmentation of Xe C60+ exhibit prominent signatures of the Xe 4d resonance and together account for 6.6 +/- 1.5 of the total Xe 4d oscillator strength of 10. Compared to that for a free Xe atom, the Xe oscillator strength in Xe C60+ is redistributed in photon energy due to multipath interference of outgoing Xe 4d photoelectron waves that may be transmitted or reflected by the spherical C60+ molecular cage, yielding so-called confinement resonances. The experimental data are compared with numerous theoretical predictions for this novel single-molecule photoelectron interferometer system. The comparison indicates that the interference structure is sensitive to the geometry of the molecular cage.

Development of a Compact Neutron Generator to be Used For Associated Particle Imaging Utilizing a RF-Driven Ion Source

NASA Astrophysics Data System (ADS)

Wu, Ying

2009-11-01

The development of a prototype compact neutron generator for the application of associated particle imaging (API) to be used for explosive and contraband detection will be presented. The API technique makes use of the 3.5 MeV alpha particles that are produced simultaneously with the 14 MeV neutrons in the deuterium-tritium (^2D(^3T,n)^4α) fusion reaction to determine the direction of the neutrons and reduce background noise. This method determines the spatial position of each neutron interaction and requires the neutrons to be generated from a small spot in order to achieve high spatial resolution. In this work an axial type neutron generator was designed and built with a predicted neutron yield of 10^8 n/s for a 50 μA D/T ion beam current accelerated to 80 kV. It was shown that the measured yield for a D/D gas filled generator was 2x10^5n/s, which scales to 2x10^7 n/s if a D/T gas fill is used. The generator utilizes an RF planar spiral antenna at 13.56 MHz to create a highly efficient inductively coupled plasma at the ion source. Experimental results show that beams with an atomic ion fraction of > 80% can be obtained with only 100 watts of RF power in the ion source. A single acceleration gap with a secondary electron suppression electrode is used in the acceleration column, to suppress secondary backscattered electrons produced at the target. Initial measurements of the neutron generator performance including the beam spot size and neutron yield under sealed operation will be discussed, along with suggestions for future improvements.

Parts-Per-Billion Mass Measurement Accuracy Achieved through the Combination of Multiple Linear Regression and Automatic Gain Control in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer

PubMed Central

Williams, D. Keith; Muddiman, David C.

2008-01-01

Fourier transform ion cyclotron resonance mass spectrometry has the ability to achieve unprecedented mass measurement accuracy (MMA); MMA is one of the most significant attributes of mass spectrometric measurements as it affords extraordinary molecular specificity. However, due to space-charge effects, the achievable MMA significantly depends on the total number of ions trapped in the ICR cell for a particular measurement. Even through the use of automatic gain control (AGC), the total ion population is not constant between spectra. Multiple linear regression calibration in conjunction with AGC is utilized in these experiments to formally account for the differences in total ion population in the ICR cell between the external calibration spectra and experimental spectra. This ability allows for the extension of dynamic range of the instrument while allowing mean MMA values to remain less than 1 ppm. In addition, multiple linear regression calibration is used to account for both differences in total ion population in the ICR cell as well as relative ion abundance of a given species, which also affords mean MMA values at the parts-per-billion level. PMID:17539605

Ion-sculpting of nanopores in amorphous metals, semiconductors, and insulators

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

George, H. Bola; Madi, Charbel S.; Aziz, Michael J.

2010-06-28

We report the closure of nanopores to single-digit nanometer dimensions by ion sculpting in a range of amorphous materials including insulators (SiO{sub 2} and SiN), semiconductors (a-Si), and metallic glasses (Pd{sub 80}Si{sub 20})--the building blocks of a single-digit nanometer electronic device. Ion irradiation of nanopores in crystalline materials (Pt and Ag) does not cause nanopore closure. Ion irradiation of c-Si pores below 100 deg. C and above 600 deg. C, straddling the amorphous-crystalline dynamic transition temperature, yields closure at the lower temperature but no mass transport at the higher temperature. Ion beam nanosculpting appears to be restricted to materials thatmore » either are or become amorphous during ion irradiation.« less

Ion beam sputtering of fluoropolymers

NASA Technical Reports Server (NTRS)

Sovey, J. S.

1978-01-01

Etching and deposition of fluoropolymers are of considerable industrial interest for applications dealing with adhesion, chemical inertness, hydrophobicity, and dielectric properties. This paper describes ion beam sputter processing rates as well as pertinent characteristics of etched targets and films. An argon ion beam source was used to sputter etch and deposit the fluoropolymers PTFE, FEP, and CTFE. Ion beam energy, current density, and target temperature were varied to examine effects on etch and deposition rates. The ion etched fluoropolymers yield cone or spire-like surface structures which vary depending upon the type of polymer, ion beam power density, etch time, and target temperature. Also presented are sputter target and film characteristics which were documented by spectral transmittance measurements, X-ray diffraction, ESCA, and SEM photomicrographs.

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

Schreiber, J.; Max-Planck-Institut für Quantenoptik Garching, Hans-Kopfermann-Str. 1, 85748 Garching bei München; Bolton, P. R.

An overview of progress and typical yields from intense laser-plasma acceleration of ions is presented. The evolution of laser-driven ion acceleration at relativistic intensities ushers prospects for improved functionality and diverse applications which can represent a varied assortment of ion beam requirements. This mandates the development of the integrated laser-driven ion accelerator system, the multiple components of which are described. Relevant high field laser-plasma science and design of controlled optimum pulsed laser irradiation on target are dominant single shot (pulse) considerations with aspects that are appropriate to the emerging petawatt era. The pulse energy scaling of maximum ion energies andmore » typical differential spectra obtained over the past two decades provide guidance for continued advancement of laser-driven energetic ion sources and their meaningful applications.« less

Collision-spike sputtering of Au nanoparticles

DOE PAGES

Sandoval, Luis; Urbassek, Herbert M.

2015-08-06

Ion irradiation of nanoparticles leads to enhanced sputter yields if the nanoparticle size is of the order of the ion penetration depth. While this feature is reasonably well understood for collision-cascade sputtering, we explore it in the regime of collision-spike sputtering using molecular-dynamics simulation. For the particular case of 200-keV Xe bombardment of Au particles, we show that collision spikes lead to abundant sputtering with an average yield of 397 ± 121 atoms compared to only 116 ± 48 atoms for a bulk Au target. Only around 31 % of the impact energy remains in the nanoparticles after impact; themore » remainder is transported away by the transmitted projectile and the ejecta. As a result, the sputter yield of supported nanoparticles is estimated to be around 80 % of that of free nanoparticles due to the suppression of forward sputtering.« less

Bottomonium suppression using a lattice QCD vetted potential

NASA Astrophysics Data System (ADS)

Krouppa, Brandon; Rothkopf, Alexander; Strickland, Michael

2018-01-01

We estimate bottomonium yields in relativistic heavy-ion collisions using a lattice QCD vetted, complex-valued, heavy-quark potential embedded in a realistic, hydrodynamically evolving medium background. We find that the lattice-vetted functional form and temperature dependence of the proper heavy-quark potential dramatically reduces the dependence of the yields on parameters other than the temperature evolution, strengthening the picture of bottomonium as QGP thermometer. Our results also show improved agreement between computed yields and experimental data produced in RHIC 200 GeV /nucleon collisions. For LHC 2.76 TeV /nucleon collisions, the excited states, whose suppression has been used as a vital sign for quark-gluon-plasma production in a heavy-ion collision, are reproduced better than previous perturbatively-motivated potential models; however, at the highest LHC energies our estimates for bottomonium suppression begin to underestimate the data. Possible paths to remedy this situation are discussed.

Spatial and Time Coincidence Detection of the Decay Chain of Short-Lived Radioactive Nuclei

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

Granja, Carlos; Jakubek, Jan; Platkevic, Michal

The quantum counting position sensitive pixel detector Timepix with per-pixel energy and time resolution enables to detect radioactive ions and register the consecutive decay chain by simultaneous position-and time-correlation. This spatial and timing coincidence technique in the same sensor is demonstrated by the registration of the decay chain {sup 8}He{yields}{sup {beta} 8}Li and {sup 8}Li{yields}{sup {beta}-} {sup 8}Be{yields}{alpha}+{alpha} and by the measurement of the {beta} decay half-lives. Radioactive ions, selectively obtained from the Lohengrin fission fragment spectrometer installed at the High Flux Reactor of the ILL Grenoble, are delivered to the Timepix silicon sensor where decays of the implanted ionsmore » and daughter nuclei are registered and visualized. We measure decay lifetimes in the range {>=}{mu}s with precision limited just by counting statistics.« less

The calibration of the intramolecular nitrogen isotope distribution in nitrous oxide measured by isotope ratio mass spectrometry.

PubMed

Westley, Marian B; Popp, Brian N; Rust, Terri M

2007-01-01

Two alternative approaches for the calibration of the intramolecular nitrogen isotope distribution in nitrous oxide using isotope ratio mass spectrometry have yielded a difference in the 15N site preference (defined as the difference between the delta15N of the central and end position nitrogen in NNO) of tropospheric N2O of almost 30 per thousand. One approach is based on adding small amounts of labeled 15N2O to the N2O reference gas and tracking the subsequent changes in m/z 30, 31, 44, 45 and 46, and this yields a 15N site preference of 46.3 +/- 1.4 per thousand for tropospheric N2O. The other involves the synthesis of N2O by thermal decomposition of isotopically characterized ammonium nitrate and yields a 15N site preference of 18.7 +/- 2.2 per thousand for tropospheric N2O. Both approaches neglect to fully account for isotope effects associated with the formation of NO+ fragment ions from the different isotopic species of N2O in the ion source of a mass spectrometer. These effects vary with conditions in the ion source and make it impossible to reproduce a calibration based on the addition of isotopically enriched N2O on mass spectrometers with different ion source configurations. These effects have a much smaller impact on the comparison of a laboratory reference gas with N2O synthesized from isotopically characterized ammonium nitrate. This second approach was successfully replicated and leads us to advocate the acceptance of the site preference value 18.7 +/- 2.2 per thousand for tropospheric N2O as the provisional community standard until further independent calibrations are developed and validated. We present a technique for evaluating the isotope effects associated with fragment ion formation and revised equations for converting ion signal ratios into isotopomer ratios. Copyright 2007 John Wiley & Sons, Ltd.

A variety of characteristic behaviour of resonant KL23L23 Auger decays following Si K-shell photoexcitation of SiCl4

NASA Astrophysics Data System (ADS)

Suzuki, I. H.; Kono, Y.; Sakai, K.; Kimura, M.; Ueda, K.; Tamenori, Y.; Takahashi, O.; Nagaoka, S.

2013-04-01

Spectator resonant Auger electron spectra with the Si 1s photoexcitation of SiCl4 have been measured using an electron spectroscopic technique combined with undulator radiation. The transition with the highest intensity in the total ion yield (TIY) spectrum, coming from excitation of a 1s electron into the 9t2 valence orbital, generates the resonant Auger decay in which the excited electron remains in the 9t2 orbital. A TIY peak positioned slightly above the 1s ionization threshold induces Auger decay in which the slow photoelectron is re-captured into a higher lying Rydberg orbital or the normal Auger peak shape is distorted due to a post-collision interaction effect. Another structure above the threshold, originating from a doubly excited state, yields the normal Auger peak with the distortion of peak shape and a resonant Auger peak with a higher kinetic energy. These findings provide a clear understanding of the properties of the excited orbitals which were ambiguous previously.

Molecular dynamics study of Al and Ni 3Al sputtering by Al clusters bombardment

NASA Astrophysics Data System (ADS)

Zhurkin, Eugeni E.; Kolesnikov, Anton S.

2002-06-01

The sputtering of Al and Ni 3Al (1 0 0) surfaces induced by impact of Al ions and Al N clusters ( N=2,4,6,9,13,55) with energies of 100 and 500 eV/atom is studied at atomic scale by means of classical molecular dynamics (MD). The MD code we used implements many-body tight binding potential splined to ZBL at short distances. Special attention has been paid to model dense cascades: we used quite big computation cells with lateral periodic and damped boundary conditions. In addition, long simulation times (10-25 ps) and representative statistics (up to 1000 runs per each case) were considered. The total sputtering yields, energy and time spectrums of sputtered particles, as well as preferential sputtering of compound target were analyzed, both in the linear and non-linear regimes. The significant "cluster enhancement" of sputtering yield was found for cluster sizes N⩾13. In parallel, we estimated collision cascade features depending on cluster size in order to interpret the nature of observed non-linear effects.

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

Korolev, Yu. D.; Landl, N. V., E-mail: landl@lnp.hcei.tsc.ru; Geyman, V. G.

Results from studies of a low-current glow discharge with a hollow cathode are presented. A specific feature of the discharge conditions was that a highly emissive tablet containing cesium carbonate was placed in the cathode cavity. In the absence of a tablet, the discharge ignition voltage was typically ≥3.5 kV, while the burning voltage was in the range of 500–600 V. The use of the tablet made it possible to decrease the ignition voltage to 280 V and maintain the discharge burning voltage at a level of about 130 V. A model of the current sustainment in a hollow-cathode dischargemore » is proposed. Instead of the conventional secondary emission yield, the model uses a generalized emission yield that takes into account not only ion bombardment of the cathode, but also the emission current from an external source. The model is used to interpret the observed current−voltage characteristics. The results of calculations agree well with the experimental data. It is shown that, in some discharge modes, the external emission current from the cathode can reach 25% of the total discharge current.« less

Extending the analytical window for water-soluble organic matter in sediments by aqueous Soxhlet extraction

NASA Astrophysics Data System (ADS)

Schmidt, Frauke; Koch, Boris P.; Witt, Matthias; Hinrichs, Kai-Uwe

2014-09-01

Dissolved organic matter (DOM) in marine sediments is a complex mixture of thousands of individual constituents that participate in biogeochemical reactions and serve as substrates for benthic microbes. Knowledge of the molecular composition of DOM is a prerequisite for a comprehensive understanding of the biogeochemical processes in sediments. In this study, interstitial water DOM was extracted with Rhizon samplers from a sediment core from the Black Sea and compared to the corresponding water-extractable organic matter fraction (<0.4 μm) obtained by Soxhlet extraction, which mobilizes labile particulate organic matter and DOM. After solid phase extraction (SPE) of DOM, samples were analyzed for the molecular composition by Fourier Transform Ion-Cyclotron Resonance Mass Spectrometry (FT-ICR MS) with electrospray ionization in negative ion mode. The average SPE extraction yield of the dissolved organic carbon (DOC) in interstitial water was 63%, whereas less than 30% of the DOC in Soxhlet-extracted organic matter was recovered. Nevertheless, Soxhlet extraction yielded up to 4.35% of the total sedimentary organic carbon, which is more than 30-times the organic carbon content of the interstitial water. While interstitial water DOM consisted primarily of carbon-, hydrogen- and oxygen-bearing compounds, Soxhlet extracts yielded more complex FT-ICR mass spectra with more peaks and higher abundances of nitrogen- and sulfur-bearing compounds. The molecular composition of both sample types was affected by the geochemical conditions in the sediment; elevated concentrations of HS- promoted the early diagenetic sulfurization of organic matter. The Soxhlet extracts from shallow sediment contained specific three- and four-nitrogen-bearing molecular formulas that were also detected in bacterial cell extracts and presumably represent proteinaceous molecules. These compounds decreased with increasing sediment depth while one- and two-nitrogen-bearing molecules increased, resulting in a higher similarity of both sample types in the deep sediment. In summary, Soxhlet extraction of sediments accessed a larger and more complex pool of organic matter than present in interstitial water DOM.

Effect of driver impedance on dense plasma focus Z-pinch neutron yield

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

Sears, Jason, E-mail: sears8@llnl.gov, E-mail: schmidt36@llnl.gov; Link, Anthony, E-mail: sears8@llnl.gov, E-mail: schmidt36@llnl.gov; Schmidt, Andrea, E-mail: sears8@llnl.gov, E-mail: schmidt36@llnl.gov

2014-12-15

The Z-pinch phase of a dense plasma focus (DPF) heats the plasma by rapid compression and accelerates ions across its intense electric fields, producing neutrons through both thermonuclear and beam-target fusion. Driver characteristics have empirically been shown to affect performance, as measured by neutron yield per unit of stored energy. We are exploring the effect of driver characteristics on DPF performance using particle-in-cell (PIC) simulations of a kJ scale DPF. In this work, our PIC simulations are fluid for the run-down phase and transition to fully kinetic for the pinch phase, capturing kinetic instabilities, anomalous resistivity, and beam formation duringmore » the pinch. The anode-cathode boundary is driven by a circuit model of the capacitive driver, including system inductance, the load of the railgap switches, the guard resistors, and the coaxial transmission line parameters. It is known that the driver impedance plays an important role in the neutron yield: first, it sets the peak current achieved at pinch time; and second, it affects how much current continues to flow through the pinch when the pinch inductance and resistance suddenly increase. Here we show from fully kinetic simulations how total neutron yield depends on the impedance of the driver and the distributed parameters of the transmission circuit. Direct comparisons between the experiment and simulations enhance our understanding of these plasmas and provide predictive design capability for neutron source applications.« less

Fragmentation of DNA components by hyperthermal heavy ion (Ar+ and Xe+) impact in the condensed phase

NASA Astrophysics Data System (ADS)

Sarabipour, Sarvenaz; Sarvenaz Sarabipour, Ms; Michaud, Marc; Deng, Zongwu; Huels, Michael A.

The overriding environmental factor that presently limits human endeavors in space is exposure to heavy ion radiation. While knowledge of its damage to living tissue is essential for radiation protection and risk estimates for astronauts, very little data exists at the molecular level regarding the nascent DNA damage by the primary particle track, or by secondary species during subsequent reaction cascades. This persistent lack of a basic understanding of nascent damage induced by such low dose, high LET radiation, introduces unacceptable errors in radiation risk estimates (based mainly on extrapolation from high dose, low LET radiation), particularly for long term exposure. Mutagenic effects induced by heavy ion radiation to cells are largely due to DNA damage by secondary transient species, i.e. secondary ballistic ions, electrons and radicals generated along the ion tracks; the secondary ions have hyperthermal energies up to several 100 eV, which they will deposit within a few nm in the surrounding medium; thus their LET is very high, and yields lethal clustered DNA lesions. We present measurements of molecular damage induced in films of DNA components by ions with precisely such low energies (1-100 eV) and compare results to conventional electron impact measurements. Experiments are conducted in UHV using a mass selected low energy ion source, and a high-resolution quadrupole MS to monitor ion yields desorbing from molecular films. Among the major fragments, NH4 + is identified in the desorption mass spectra of irradiated films of Adenine, Guanine, Cytosine, indicating efficient deamination; in cells this results in pre-mutagenic lesions. Experiments with 5-amino-Uracil, and comparison to previous results on uracil and thymine show that deamination is a key step in the NH4 + fragment formation. For Adenine, we also observe formation of amine aducts in the films, viz. amination of Adenine, and global fragmentation in all ion impact mass spectra, attributed mainly to kinetic & potential ion scattering.[Funded by NSERC and the Canadian Space Agency].

In situ measurement of surface potential developed on MgO thin film surface under ion irradiation using ion scattering spectroscopy

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

Nagatomi, T.; Kuwayama, T.; Takai, Y.

2009-11-15

The application of ion scattering spectroscopy (ISS) to the in situ measurement of the surface potential developed on an insulator surface under positive ion irradiation was investigated. The ISS spectra measured for a MgO film of 600 nm thickness on a Si substrate by the irradiation of 950 eV He{sup +} ions revealed that the surface is positively charged by approximately 180 V. For accurate measurement of the surface potential, a correction to take into account the angular deflection of primary ions induced by the high surface potential is required. The dependence of the surface potential on the sample temperaturemore » revealed that no charging is induced above 700 deg. C, indicating that accumulated charges can be removed by heating to 700 deg. C. From the measurement of the ion-induced secondary electron yield using a collector electrode located in front of the sample surface, the surface potential and ion-induced secondary electron yield were found to be strongly affected by the experimental setup. Secondary electrons produced by the impact of slow positive secondary ions, the maximum energy of which corresponds to the surface potential, play an important role when the bias voltage applied to the collector electrode is positively high for the present experimental setup. The surface potential developed on the surface of MgO films of 600 and 200 nm thickness was measured in situ, revealing that the amount of accumulated charges and the time required to attain the steady state of charging are slightly dependent on the beam current of primary ions and strongly dependent on the thickness of the MgO film. The present results confirmed that the application of ISS has high potential for investigating charging phenomena and the secondary electron emission from insulator surfaces under positive ion irradiation.« less

Ion chemistry of 1H-1,2,3-triazole.

PubMed

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.

Total ion chromatographic fingerprints combined with chemometrics and mass defect filter to predict antitumor components of Picrasma quassioids.

PubMed

Shi, Yuanyuan; Zhan, Hao; Zhong, Liuyi; Yan, Fangrong; Feng, Feng; Liu, Wenyuan; Xie, Ning

2016-07-01

A method of total ion chromatogram combined with chemometrics and mass defect filter was established for the prediction of active ingredients in Picrasma quassioides samples. The total ion chromatogram data of 28 batches were pretreated with wavelet transformation and correlation optimized warping to correct baseline drifts and retention time shifts. Then partial least squares regression was applied to construct a regression model to bridge the total ion chromatogram fingerprints and the antitumor activity of P. quassioides. Finally, the regression coefficients were used to predict the active peaks in total ion chromatogram fingerprints. In this strategy, mass defect filter was employed to classify and characterize the active peaks from a chemical point of view. A total of 17 constituents were predicted as the potential active compounds, 16 of which were identified as alkaloids by this developed approach. The results showed that the established method was not only simple and easy to operate, but also suitable to predict ultraviolet undetectable compounds and provide chemical information for the prediction of active compounds in herbs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Simple Analytical Model for Predicting the Detectable Ion Current in Ion Mobility Spectrometry Using Corona Discharge Ionization Sources

NASA Astrophysics Data System (ADS)

Kirk, Ansgar Thomas; Kobelt, Tim; Spehlbrink, Hauke; Zimmermann, Stefan

2018-05-01

Corona discharge ionization sources are often used in ion mobility spectrometers (IMS) when a non-radioactive ion source with high ion currents is required. Typically, the corona discharge is followed by a reaction region where analyte ions are formed from the reactant ions. In this work, we present a simple yet sufficiently accurate model for predicting the ion current available at the end of this reaction region when operating at reduced pressure as in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) or most IMS-MS instruments. It yields excellent qualitative agreement with measurement results and is even able to calculate the ion current within an error of 15%. Additional interesting findings of this model are the ion current at the end of the reaction region being independent from the ion current generated by the corona discharge and the ion current in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) growing quadratically when scaling down the length of the reaction region. [Figure not available: see fulltext.

A Simple Analytical Model for Predicting the Detectable Ion Current in Ion Mobility Spectrometry Using Corona Discharge Ionization Sources.

PubMed

Kirk, Ansgar Thomas; Kobelt, Tim; Spehlbrink, Hauke; Zimmermann, Stefan

2018-05-08

Corona discharge ionization sources are often used in ion mobility spectrometers (IMS) when a non-radioactive ion source with high ion currents is required. Typically, the corona discharge is followed by a reaction region where analyte ions are formed from the reactant ions. In this work, we present a simple yet sufficiently accurate model for predicting the ion current available at the end of this reaction region when operating at reduced pressure as in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) or most IMS-MS instruments. It yields excellent qualitative agreement with measurement results and is even able to calculate the ion current within an error of 15%. Additional interesting findings of this model are the ion current at the end of the reaction region being independent from the ion current generated by the corona discharge and the ion current in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) growing quadratically when scaling down the length of the reaction region. Graphical Abstract ᅟ.

Method for selective detection of explosives in mass spectrometer or ion mobility spectrometer at parts-per-quadrillion level

DOEpatents

Ewing, Robert G.; Atkinson, David A.; Clowers, Brian H.

2015-09-01

A method for selective detection of volatile and non-volatile explosives in a mass spectrometer or ion mobility spectrometer at a parts-per-quadrillion level without preconcentration is disclosed. The method comprises the steps of ionizing a carrier gas with an ionization source to form reactant ions or reactant adduct ions comprising nitrate ions (NO.sub.3.sup.-); selectively reacting the reactant ions or reactant adduct ions with at least one volatile or non-volatile explosive analyte at a carrier gas pressure of at least about 100 Ton in a reaction region disposed between the ionization source and an ion detector, the reaction region having a length which provides a residence time (tr) for reactant ions therein of at least about 0.10 seconds, wherein the selective reaction yields product ions comprising reactant ions or reactant adduct ions that are selectively bound to the at least one explosive analyte when present therein; and detecting product ions with the ion detector to determine presence or absence of the at least one explosive analyte.

Organic SIMS: the influence of time on the ion yield enhancement by silver and gold deposition

NASA Astrophysics Data System (ADS)

Adriaensen, L.; Vangaever, F.; Gijbels, R.

2004-06-01

A series of organic dyes and pharmaceuticals was used to study the secondary ion yield enhancement by metal deposition. The molecules were dissolved in methanol and spincasted on silicon substrates. Subsequently, silver or gold was evaporated on the samples to produce a very thin coating. The coated samples, when measured with TOF-SIMS, showed a considerable increase in characteristic secondary ion intensity. Gold-evaporated samples appear to exhibit the highest signal enhancement. These observations apply to organic samples in general, an advantage that allows to use the technique of metal deposition on real-world samples. However, the observed signal increase does not occur at any given moment. The time between metal deposition on the sample surface and the measuring of the sample with TOF-SIMS appears to have an important influence on the enhancement of the secondary ion intensities. In consideration of these observations several experiments were carried out, in which the spincasted samples were measured at different times after sample preparation, i.e., after gold or silver was deposited on the sample surface. The results show that, depending on the sample and the metal deposited, the secondary ion signals reach their maximum at different times. Further study will be necessary to detect the mechanism responsible for the observed enhancement effect.

Exploration of the Transition from the Hydrodynamic-like to the Strongly Kinetic Regime in Shock-Driven Implosions

DOE PAGES

Rosenberg, M. J.; Rinderknecht, H. G.; Hoffman, N. M.; ...

2014-05-05

Clear evidence of the transition from hydrodynamiclike to strongly kinetic shock-driven implosions is, for the first time, revealed and quantitatively assessed. Implosions with a range of initial equimolar D 3He gas densities show that as the density is decreased, hydrodynamic simulations strongly diverge from and increasingly over-predict the observed nuclear yields, from a factor of ~2 at 3.1 mg/cm 3 to a factor of 100 at 0.14 mg/cm 3. (The corresponding Knudsen number, the ratio of ion mean-free path to minimum shell radius, varied from 0.3 to 9; similarly, the ratio of fusion burn duration to ion diffusion time, anothermore » figure of merit of kinetic effects, varied from 0.3 to 14.) This result is shown to be unrelated to the effects of hydrodynamic mix. As a first step to garner insight into this transition, a reduced ion kinetic (RIK) model that includes gradient-diffusion and loss-term approximations to several transport processes was implemented within the framework of a one-dimensional radiation-transport code. After empirical calibration, the RIK simulations reproduce the observed yield trends, largely as a result of ion diffusion and the depletion of the reacting tail ions.« less

Peanut cultivar selection for BLSS in terms of the biomass productivity, nutritional quality, photosynthetic character and mineral ions up-take by PTNDS cultivation

NASA Astrophysics Data System (ADS)

Liu, Hui; Wang, Minjuan; Fu, Yuming; Liu, Hong

2016-11-01

Peanut (Arachis hypogaea L.) has been selected as one of the crop candidates for BLSS, because its seeds have high nutritional value, being rich in vegetable oil and protein. Porous-Tube Nutrient Delivery System (PTNDS) has been successfully used for crop cultivation in controllable environments. In this paper, four peanut cultivars ('HY25', 'HY28', 'HY31' and 'BS1016') were evaluated in terms of yield, photosynthetic efficiency, insoluble fiber and ions uptake efficiency. Besides protein, total oil content and fatty acid composition were monitored in the seeds. 'HY25' plants showed much higher yield and harvest index, in addition to the lower lignin content of inedible biomass. Data showed that 'HY25' had the higher photosynthetic capacity of peanut leaves with regard to highest photosynthetic rate, qP and ΦPSII, lowest energy dissipation (qN) values, whereas instantaneous carboxylation efficiency and water use efficiency carotenoids content were no difference with the other cultivars. 'BS1016‧ showed the lowest photosynthetic capacity contrarily. These suggested that 'HY25‧ could be the most suitable for the cultivation in a closed controlled environment with PTNDS. While, both cations and anions except NH4+ and H2PO4-, were accumulated excessively compared to controls, especially with anions in PTNDS. Hence, further studies are needed in order to improve the nutritional quality of seeds and modify the fertilization strategy of this cultivar in the growth environment feasible during a closed environment and space mission.

preparation of microgram samples on iron wool for radiocarbon analysis via accelerator mass spectrometry: A closed-system approach

NASA Astrophysics Data System (ADS)

Verkouteren, R. Michael; Klouda, George A.; Currie, Lloyd A.; Donahue, Douglas J.; Jull, A. J. Timothy; Linick, T. W.

1987-11-01

A technique has been developed at NBS for the production of high quality targets for radiocarbon analysis by accelerator mass spectrometry (AMS). Our process optimizes chemical yields, ion currents and characterizes the chemical blank. The approach encompasses sample combustion to CO 2, catalytic reduction of CO 2 by Zn to CO, reduction to graphitic carbon on high-purity iron wool and in situ formation of a homogeneous iron-carbon bead; all steps are performed in a closed system. The total measurement system blank and variability are considered in the light of contributions from combustion, iron wool, reduction, bead formation and instrument blank. Additionally, use of this approach provides an increase in throughput, i.e. the effective management of large numbers of samples. Chemical yields for 50-800 μg C samples deposited on 15 mg iron wool were greater than 90%. Integrated 12C - ion currents observed were significant, being 4-64% of those observed in pure graphite. These currents are about an order of magnitude greater than those expected from dilution of graphite with an inert substrate. Isotopic accuracy, precision and blank were assessed by measuring the {14C }/{13C } ratios of a series of targets prepared from dead carbon and oxalic acid (SRM 4990C). Each target was typically measured for one hour; bead consumption was estimated at 5% to 10%. System blank subsequent to combustion was equivalent to (2.2 ± 0.5) μg modern carbon (chemistry + instrument); combustion blank currently stands at (0.4 ± 0.1) (SE, n = 6) μg C.

High Efficiency DNA Extraction by Graphite Oxide/Cellulose/Magnetite Composites Under Na+ Free System

NASA Astrophysics Data System (ADS)

Akceoglu, Garbis Atam; Li, Oi Lun; Saito, Nagahiro

2016-04-01

DNA extraction is the key step at various research areas like biotechnology, diagnostic development, paternity determination, and forensic science . Solid support extraction is the most common method for DNA purification. In this method, Na+ ions have often been applied as binding buffers in order to obtain high extraction efficiency and high quality of DNA; however, the presence of Na+ ions might be interfering with the downstream DNA applications. In this study, we proposed graphite oxide (GO)/magnetite composite/cellulose as an innovative material for Na+-free DNA extraction. The total wt.% of GO was fixed at 4.15% in the GO/cellulose/magnetite composite . The concentration of magnetite within the composites were controlled at 0-3.98 wt.%. The extraction yield of DNA increased with increasing weight percentage of magnetite. The highest yield was achieved at 3.98 wt.% magnetite, where the extraction efficiency was reported to be 338.5 ng/µl. The absorbance ratios between 260 nm and 280 nm (A260/A280) of the DNA elution volume was demonstrated as 1.81, indicating the extracted DNA consisted of high purity. The mechanism of adsorption of DNA was provided by (1) π-π interaction between the aromatic ring in GO and nucleobases of DNA molecule, and (2) surface charge interaction between the positive charge magnetite and anions such as phosphates within the DNA molecules. The results proved that the GO/cellulose/magnetite composite provides a Na+-free method for selective DNA extraction with high extraction efficiency of pure DNA.

Maximizing and stabilizing luminescence from halide perovskites with potassium passivation.

PubMed

Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M; Alsari, Mejd; Booker, Edward P; Hutter, Eline M; Pearson, Andrew J; Lilliu, Samuele; Savenije, Tom J; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H; Stranks, Samuel D

2018-03-21

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield-a quantity that must be maximized to obtain high efficiency-remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

A new strategy for strain improvement of Aurantiochytrium sp. based on heavy-ions mutagenesis and synergistic effects of cold stress and inhibitors of enoyl-ACP reductase.

PubMed

Cheng, Yu-Rong; Sun, Zhi-Jie; Cui, Gu-Zhen; Song, Xiaojin; Cui, Qiu

2016-11-01

Developing a strain with high docosahexaenoic acid (DHA) yield and stable fermenting-performance is an imperative way to improve DHA production using Aurantiochytrium sp., a microorganism with two fatty acid synthesis pathways: polyketide synthase (PKS) pathway and Type I fatty acid synthase (FAS) pathway. This study investigated the growth and metabolism response of Aurantiochytrium sp. CGMCC 6208 to two inhibitors of enoyl-ACP reductase of Type II FAS pathway (isoniazid and triclosan), and proposed a method of screening high DHA yield Aurantiochytrium sp. strains with heavy ion mutagenesis and pre-selection by synergistic usage of cold stress (4°C) and FAS inhibitors (triclosan and isoniazid). Results showed that (1) isoniazid and triclosan have positive effects on improving DHA level of cells; (2) mutants from irradiation dosage of 120Gy yielded more DHA compared with cells from 40Gy, 80Gy treatment and wild type; (3) DHA contents of mutants pre-selected by inhibitors of enoyl-ACP reductase of Type II FAS pathway (isoniazid and triclosan)at 4°C, were significantly higher than that of wild type; (4) compared to the wild type, the DHA productivity and yield of a mutant (T-99) obtained from Aurantiochytrium sp. CGMCC 6208 by the proposed method increased by 50% from 0.18 to 0.27g/Lh and 30% from 21 to 27g/L, respectively. In conclusion, this study developed a feasible method to screen Aurantiochytrium sp. with high DHA yield by a combination of heavy-ion mutagenesis and mutant-preselection by FAS inhibitors and cold stress. Copyright © 2016 Elsevier Inc. All rights reserved.

The use of dialdehyde starch derivatives in the phytoremediation of soils contaminated with heavy metals.

PubMed

Antonkiewicz, Jacek; Para, Andrzej

2016-01-01

Products of the reaction between dialdehyde starch and Y-NH2 compounds (e.g. semicarbazide or hydrazine) are effective ligands for metal ions. The usefulness of these derivatives was tested in the experiment, both in terms of the immobilization of heavy metal ions in soil and the potential application in phytoextraction processes. The experimental model comprised maize and the ions of such metals as: Zn(II), Pb(II), Cu(II), Cd(II), and Ni(II). The amount of maize yield, as well as heavy metal content and uptake by the aboveground parts and roots of maize, were studied during a three-year pot experiment. The results of the study indicate the significant impact of heavy metals on reduced yield and increased heavy metal content in maize. Soil-applied dialdehyde starch derivatives resulted in lower yields, particularly disemicarbazone (DASS), but in heavy metal-contaminated soils they largely limited the negative impact of these metals both on yielding and heavy metal content in plants, particularly dihydrazone (DASH). It was demonstrated that the application of dihydrazone (DASH) to a soil polluted with heavy metals boosted the uptake of Zn, Pb, Cu, and Cd from the soil, hence there is a possibility to use this compound in the phytoextraction of these metals from the soil. Decreased Ni uptake was also determined, hence the possibility of using this compound in the immobilization of this metal. The study showed that dialdehyde starch disemicarbazone was ineffective in the discussed processes.

Neon in ultrashort and intense x-rays from free electron lasers

NASA Astrophysics Data System (ADS)

Buth, Christian; Beerwerth, Randolf; Obaid, Razib; Berrah, Nora; Cederbaum, Lorenz S.; Fritzsche, Stephan

2018-03-01

We theoretically examine neon atoms in ultrashort and intense x-rays from free electron lasers and compare our results with data from experiments conducted at the Linac Coherent Light Source. For this purpose, we treat in detail the electronic structure in all possible nonrelativistic cationic configurations using a relativistic multiconfiguration approach. The interaction with the x-rays is described in rate-equation approximation. To understand the mechanisms of the interaction, a path analysis is devised which allows us to investigate what sequences of photoionization and decay processes lead to a specific configuration and with what probability. Thereby, we uncover a connection to the mathematics of graph theory and formal languages. In detail, we study the ion yields and find that plain rate equations do not provide a satisfactory description. We need to extend the rate equations for neon to incorporate double Auger decay of a K-shell vacancy and photoionization shake off for neutral neon. Shake off is included for valence and core ionization; the former has hitherto been overlooked but has important consequences for the ion yields from an x-ray energy below the core ionization threshold. Furthermore, we predict the photon yields from XUV and x-ray fluorescence these allow one insights into the configurations populated by the interaction with the x-rays. Finally, we discover that inaccuracies in those Auger decay widths employed in previous studies have only a minor influence on ion and photon yields.

Interactive effects of pH, EC and nitrogen on yields and nutrient absorption of rice (Oryza sativa L.)

USDA-ARS?s Scientific Manuscript database

Soil salinity and sodicity can not only directly restrain crop growth by osmotic and specific ion stresses, it also may reduce grain yield indirectly by impacting plant absorption of essential nutrients. Ensuring adequate nitrogen is an important management aspect of rice production in saline-sodic ...

Water-level, recharge, discharge, specific-capacity, well-yield, and aquifer-test data for the Edwards aquifer in the San Antonio area, Texas

USGS Publications Warehouse

Maclay, R.W.; Small, T.A.; Rettman, P.L.

1980-01-01

This report presents data and informat ion, and indicates other sources of data, on water level s, recharge, discharge, spec ifi c capacity, well yields, and aquifer tests for the Edwards aquifer in the Sa n Antonio area, Texas.

Heavy ion mutagenesis combined with triclosan screening provides a new strategy for improving the arachidonic acid yield in Mortierella alpina.

PubMed

Zhang, Huidan; Lu, Dong; Li, Xin; Feng, Yingang; Cui, Qiu; Song, Xiaojin

2018-05-02

Arachidonic acid (ARA), which is a ω-6 polyunsaturated fatty acid, has a wide range of biological activities and is an essential component of cellular membranes in some human tissues. Mortierella alpina is the best strain for industrial production of ARA. To increase its yield of arachidonic acid, heavy ion beam irradiation mutagenesis of Mortierella alpina was carried out in combination with triclosan and octyl gallate treatment. The obtained mutant strain F-23 ultimately achieved an ARA yield of 5.26 g L - 1 , which is 3.24 times higher than that of the wild-type strain. In addition, quantitative real-time PCR confirmed that the expression levels of fatty acid synthase (FAS), Δ5-desaturase, Δ6-desaturase, and Δ9-desaturase were all significantly up-regulated in the mutant F-23 strain, especially Δ6- and Δ9-desaturase, which were up-regulated 3- and 2-fold, respectively. This study confirmed a feasible mutagenesis breeding strategy for improving ARA production and provided a mutant of Mortierella alpina with high ARA yield.

On the Surface Mapping using Individual Cluster Impacts

PubMed Central

Fernandez-Lima, F.A.; Eller, M.J.; DeBord, J.D.; Verkhoturov, S.V.; Della-Negra, S.; Schweikert, E.A.

2011-01-01

This paper describes the advantages of using single impacts of large cluster projectiles (e.g. C60 and Au400) for surface mapping and characterization. The analysis of co-emitted time-resolved photon spectra, electron distributions and characteristic secondary ions shows that they can be used as surface fingerprints for target composition, morphology and structure. Photon, electron and secondary ion emission increases with the projectile cluster size and energy. The observed, high abundant secondary ion emission makes cluster projectiles good candidates for surface mapping of atomic and fragment ions (e.g., yield >1 per nominal mass) and molecular ions (e.g., few tens of percent in the 500 < m/z < 1500 range). PMID:22393269

κ -distributed protons in the solar wind and their charge-exchange coupling to energetic hydrogen

DOE PAGES

Heerikhuisen, J.; Zirnstein, Eric; Pogorelov, Nikolai

2015-03-16

The interaction between the solar wind and the interstellar medium represents a collision between two plasma flows, resulting in a heliosphere with an extended tail. While the solar wind is mostly ionized material from the corona, the interstellar medium is only partially ionized. The ion and neutral populations are coupled through charge-exchange collisions that operate on length scales of tens to hundreds of astronomical units. About half the interstellar hydrogen flows into the heliosphere where it may charge-exchange with solar wind protons. This process gives rise to a nonthermal proton, known as a pickup ion, which joins the plasma. Inmore » this paper we investigate the effects of approximating the total ion distribution of the subsonic solar wind as a generalized Lorentzian, or κ distribution, using an MHD neutral code. We illustrate the effect different values of the κ parameter have on both the structure of the heliosphere and the energetic neutral atom flux at 1 AU. We find that using a κ distribution in our simulations yields levels of energetic neutral atom flux that are within a factor of about 2 or 3 over the IBEX-Hi range of energies from 0.5 to 6 keV. In conclusion, while the presence of a suprathermal tail in the proton distribution leads to the production of high-energy neutrals, the sharp decline in the charge-exchange cross section around 10 keV mitigates the enhanced transfer of energy from the ions to the neutrals that might otherwise be expected.« less

Adsorption of Ions on Zirconium Oxide Surfaces from Aqueous Solutions at High Temperatures.

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

Palmer, Donald; Machesky, Michael L.; Benezeth, Pascale

2009-07-01

Surface titrations were carried out on suspensions of monoclinic ZrO{sub 2} from 25 to 290 C slightly above saturation vapor pressure at ionic strengths of 0.03, 0.1 and 1.0 mol {center_dot} kg{sup -1}(NaCl). A typical increase in surface charge was observed with increasing temperature. There was no correlation between the radius of the cations, Li{sup +}, Na{sup +}, K{sup +} and (CH{sub 3}){sub 4}N{sup +}, and the magnitude of their association with the surface. The combined results were treated with a 1-pK{sub a} MUSIC model, which yielded association constants for the cations (and chloride ion at low pH) at eachmore » temperature. The pH of zero-point-charge, pH{sub zpc}, decreased with increasing temperature as found for other metal oxides, reaching an apparent minimum value of 4.1 by 250 C. Batch experiments were performed to monitor the concentration of LiOH in solutions containing suspended ZrO{sub 2} particles from 200 to 360 C. At 350 and 360 C, Li{sup +} and OH{sup -} ions were almost totally adsorbed when the pressure was lowered to near saturation vapor pressure. This reversible trend has implications not only to pressure-water reactor, PWR, operations, but is also of general scientific and other applied interest. Additional experiments probed the feasibility that boric acid/borate ions adsorb reversibly onto ZrO{sub 2} surfaces at near-neutral pH conditions as indicated in earlier publications.« less

Determination of metal-hydrogen bond dissociation energies by the deprotonation of transition metal hydride ions: application to MnH +

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.

Ion Source Development for a Compact Proton Beam Writing System III

DTIC Science & Technology

2013-06-28

to yield ion beam with energies up to 3 keV. The electrical power required to operate multiple components (like RF Valve , Probe and Extraction...they are powered through an isolation transformer. The required gas, to be ionized in the RF ion source, is fed through a coarse needle valve ...connector, the system can be pumped down to 3×10-2 mbar using an oil roughing pump. Nitrogen gas is feed in by adjusting the gas regulating valve

Measuring the effects of Coulomb repulsion via signal decay in an atmospheric pressure laser ionization ion mobility spectrometer.

PubMed

Ihlenborg, Marvin; Schuster, Ann-Kathrin; Grotemeyer, Juergen; Gunzer, Frank

2018-01-01

Using lasers in ion mobility spectrometry offers a lot of advantages compared to standard ionization sources. Especially, the ion yield can be drastically increased. It can, however, reach levels where the Coulomb repulsion leads to unwanted side effects. Here, we investigate how the Coulomb repulsion can be detected apart from the typical signal broadening by measuring effects created already in the reaction region and comparing them with corresponding finite element method simulations.

Ion charge state distribution effects on elastic X-ray Thomson scattering

NASA Astrophysics Data System (ADS)

Iglesias, Carlos A.

2018-03-01

Analytic models commonly applied in elastic X-ray Thomson scattering cross-section calculations are used to generate results from a discrete ion charge distribution and an average charge description. Comparisons show that interchanging the order of the averaging procedure can appreciably alter the cross-section, especially for plasmas with partially filled K-shell bound electrons. In addition, two common approximations to describe the free electron density around an ion are shown to yield significantly different elastic X-ray Thomson scattering cross-sections.

Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

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

Bradforth, S.E.

1992-11-01

The transition state region of a neutral bimolecular reaction may be experimentally investigated by photoelectron spectroscopy of an appropriate negative ion. The photoelectron spectrum provides information on the spectroscopy and dynamics of the short lived transition state and may be used to develop model potential energy surfaces that are semi-quantitative in this important region. The principles of bound [yields] bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN[sup [minus

Introduction to dissociative recombination

NASA Technical Reports Server (NTRS)

Guberman, Steven L.; Mitchell, J. Brian A.

1989-01-01

Dissociative recombination (DR) of molecular ions with electrons has important consequences in many areas of physical science. Ab-initio calculations coupled with resonant scattering theory and multichannel quantum defect studies have produced detailed results illuminating the role of ion vibrational excitation, the quantum yields of the DR products, and the role of Rydberg states. The theoretical and experimental results are discussed.

Dual-beam focused ion beam/electron microscopy processing and metrology of redeposition during ion-surface 3D interactions, from micromachining to self-organized picostructures.

PubMed

Moberlychan, Warren J

2009-06-03

Focused ion beam (FIB) tools have become a mainstay for processing and metrology of small structures. In order to expand the understanding of an ion impinging a surface (Sigmund sputtering theory) to our processing of small structures, the significance of 3D boundary conditions must be realized. We consider ion erosion for patterning/lithography, and optimize yields using the angle of incidence and chemical enhancement, but we find that the critical 3D parameters are aspect ratio and redeposition. We consider focused ion beam sputtering for micromachining small holes through membranes, but we find that the critical 3D considerations are implantation and redeposition. We consider ion beam self-assembly of nanostructures, but we find that control of the redeposition by ion and/or electron beams enables the growth of nanostructures and picostructures.

Quantitative evaluation of high-energy O- ion particle flux in a DC magnetron sputter plasma with an indium-tin-oxide target

NASA Astrophysics Data System (ADS)

Suyama, Taku; Bae, Hansin; Setaka, Kenta; Ogawa, Hayato; Fukuoka, Yushi; Suzuki, Haruka; Toyoda, Hirotaka

2017-11-01

O- ion flux from the indium tin oxide (ITO) sputter target under Ar ion bombardment is quantitatively evaluated using a calorimetry method. Using a mass spectrometer with an energy analyzer, O- energy distribution is measured with spatial dependence. Directional high-energy O- ion ejected from the target surface is observed. Using a calorimetry method, localized heat flux originated from high-energy O- ion is measured. From absolute evaluation of the heat flux from O- ion, O- particle flux in order of 1018 m-2 s-1 is evaluated at a distance of 10 cm from the target. Production yield of O- ion on the ITO target by one Ar+ ion impingement at a kinetic energy of 244 eV is estimated to be 3.3  ×  10-3 as the minimum value.

Observations of low-energy ions in the wake of a magnetospheric satellite

NASA Technical Reports Server (NTRS)

Samir, U.; Comfort, R. H.; Chappell, C. R.; Stone, N. H.

1986-01-01

Measurements of low-energy ions made by the retarding ion mass spectrometer (RIMS) onboard the Dynamics Explorer 1 (DE 1) satellite are used to study some aspects of 'body-plasma interactions' in the terrestrial plasmasphere. Preliminary results are presented, yielding the degree of H+ and He+ ion depletion in the wake of the satellite in terms of specific and average ion Mach numbers, average ion mass, body size normalized to ionic Debye length, and body potential normalized to ion thermal energy. Some results from the RIMS measurements are compared with relevant results from the Explorer 31 and the Atmosphere Explorer C ionospheric satellites. Wake depletion is found to vary approximately linearly for small bodies (R-sub-Di less than about 12) and exponentially for large bodies (R-sub-Di greater than 50).

Comparison of Se and Te clusters produced by ion bombardment

NASA Astrophysics Data System (ADS)

Trzyna, Małgorzata

2017-01-01

Nanostructures based on tellurium and selenium are materials used as components for the manufacturing topological insulators. Therefore it is crucial to precisely characterize these materials. In this work the emission of selenium and tellurium cluster ions, sputtered by Bi+ primary ion guns, was investigated by using Time-of-Flight Secondary Ion Mass Spectrometry (TOF SIMS). It has been found that BixTex and BixSex clusters appear in addition to Sex and Tex clusters in the mass range up to 1300 m/z. Local maxima or minima (magic numbers) are observed in the ion intensity versus a number of atoms per cluster for both positive and negative ions spectra for all types of clusters and primary ions used. These extrema can be attributed to different yield and stability of certain clusters but also to fragmentation of high-mass clusters.

Structural and electrical characteristics of CoGe(2) alloy films deposited heteroepitaxially on GaAs(100) using partially ionized beam deposition

NASA Astrophysics Data System (ADS)

Mello, Kevin Edward

The partially ionized beam deposition system was utilized to deposit CoGesb2 thin films heteroepitaxially on GaAs(100) substrates in a conventional vacuum. The CoGesb2 films were structurally characterized using conventional 2theta diffraction, reflection X-ray pole figure analysis, and alpha particle channeling techniques. Three distinct crystallographic relationships of the CoGesb2 films to the GaAs(100) substrates were observed, dependent upon the substrate temperature and Gesp+ ion energy used during deposition. The CoGesb2(001) (100)sp°GaAs(100) (001) orientation, which has the smallest lattice mismatch to GaAs(100), was found to occur for depositions performed at a substrate temperature during deposition near 280sp°C with approximately 1160 eV Gesp+ ions. Lowering the substrate temperature or reducing the Gesp+ ion energy results in CoGesb2(100) orientation domination with CoGe2(100) (010)sp°GaAs(100) (001) and CoGesb2(100) (001)sp°GaAs(100) (001). Substrate temperature alone was seen to produce only the CoGesb2(100) orientation. For CoGesb2(001) films, additional energy was required from Gesp+ ions in the evaporant stream. Angular yield profiles for axial Hesp{++} ion channeling yielded values for the minimum yield, Ysb{min}, of 25% for the CoGesb2(001) orientation and 34% for the CoGesb2(100) orientation. The critical angle for channeling, Psisb{c}, was measured to be 1.0sp° for both orientations. Channeling theory was used to predict the minimum yield and critical angle for each orientation. The theoretical values agreed qualitatively with the experimentally measured values, and the theory correctly predicted the lower minimum yield for the CoGesb2(001) orientation. Annealing the films to allow for epitaxial grain growth resulted in orientation selection of CoGesb2(001) at the expense of CoGesb2(100), exposing CoGesb2(100) as a metastable orientation. The CoGesb2(001) films were stable up to 500sp°C, 30 minute anneals, showing no orientation changes and enhanced thermal stability over the CoGesb2(100) films. Current-voltage measurements of CoGesb2 contacts deposited on n-type GaAs(100) were used to determine the electrical nature of the different CoGesb2 orientations. The CoGesb2 (001) (100)sp°GaAs (100) (001) heterostructure deposited at a substrate temperature of 280sp°C with 1160 eV Gesp+ ions was found to exhibit Ohmic behavior, while contacts deposited at lower or higher substrate temperatures displayed non-Ohmic behavior.

Optimization of L-lactic Acid Production of Rhizopus Oryzae Mutant RLC41-6 by Ion Beam Implantation at Low-Energy

NASA Astrophysics Data System (ADS)

Zhou, Xiuhong; Ge, Chunmei; Yao, Jianming; Pan, Renrui; Yu, Zengliang

2005-10-01

In order to obtain an industrial strain with a higher L(+)-lactic acid yield, the strain Rhizopus oryzae RF3608 was mutated by means of nitrogen ion beam implantation and the mutant strain RLC41-6 was isolated. Under optimal conditions the yield of L(+)-lactic acid produced in a shake-flask reached 133 g/L-137 g/L after 36 h cultivation, indicating that the conversion rate based on glucose was as high as 88%-91% and the productivity was 3.75 g/L.h. It was almost a 115% increase in lactic acid production compared with the original strain RF3608.

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

Mourey, Odile; Petit-Etienne, Camille; Cunge, Gilles, E-mail: gilles.cunge@cea.fr

Pulsed plasmas are promising candidates to go beyond limitations of continuous waves' plasma. However, their interaction with surfaces remains poorly understood. The authors investigated the silicon etching mechanism in inductively coupled plasma (ICP) Cl{sub 2} operated either in an ICP-pulsed mode or in a bias-pulsed mode (in which only the bias power is pulsed). The authors observed systematically the development of an important surface roughness at a low duty cycle. By using plasma diagnostics, they show that the roughness is correlated to an anomalously large (Cl atoms flux)/(energetic ion flux) ratio in the pulsed mode. The rational is that themore » Cl atom flux is not modulated on the timescale of the plasma pulses although the ion fluxes and energy are modulated. As a result, a very strong surface chlorination occurs during the OFF period when the surface is not exposed to energetic ions. Therefore, each energetic ion in the ON period will bombard a heavily chlorinated silicon surface, leading to anomalously high etching yield. In the ICP pulsed mode (in which the ion energy is high), the authors report yields as high as 40, which mean that each individual ion impacts will generate a “crater” of about 2 nm depth at the surface. Since the ion flux is very small in the pulsed ICP mode, this process is stochastic and is responsible for the roughness initiation. The roughness expansion can then be attributed partly to the ion channeling effect and is probably enhanced by the formation of a SiClx reactive layer with nonhomogeneous thickness over the topography of the surface. This phenomenon could be a serious limitation of pulsed plasma processes.« less

Sulfonium Ion Derivatization, Isobaric Stable Isotope Labeling and Data Dependent CID- and ETD-MS/MS for Enhanced Phosphopeptide Quantitation, Identification and Phosphorylation Site Characterization

PubMed Central

Lu, Yali; Zhou, Xiao; Stemmer, Paul M.; Reid, Gavin E.

2014-01-01

An amine specific peptide derivatization strategy involving the use of novel isobaric stable isotope encoded ‘fixed charge’ sulfonium ion reagents, coupled with an analysis strategy employing capillary HPLC, ESI-MS, and automated data dependent ion trap CID-MS/MS, -MS3, and/or ETD-MS/MS, has been developed for the improved quantitative analysis of protein phosphorylation, and for identification and characterization of their site(s) of modification. Derivatization of 50 synthetic phosphopeptides with S,S′-dimethylthiobutanoylhydroxysuccinimide ester iodide (DMBNHS), followed by analysis using capillary HPLC-ESI-MS, yielded an average 2.5-fold increase in ionization efficiencies and a significant increase in the presence and/or abundance of higher charge state precursor ions compared to the non-derivatized phosphopeptides. Notably, 44% of the phosphopeptides (22 of 50) in their underivatized states yielded precursor ions whose maximum charge states corresponded to +2, while only 8% (4 of 50) remained at this maximum charge state following DMBNHS derivatization. Quantitative analysis was achieved by measuring the abundances of the diagnostic product ions corresponding to the neutral losses of ‘light’ (S(CH3)2) and ‘heavy’ (S(CD3)2) dimethylsulfide exclusively formed upon CID-MS/MS of isobaric stable isotope labeled forms of the DMBNHS derivatized phosphopeptides. Under these conditions, the phosphate group stayed intact. Access for a greater number of peptides to provide enhanced phosphopeptide sequence identification and phosphorylation site characterization was achieved via automated data-dependent CID-MS3 or ETD-MS/MS analysis due to the formation of the higher charge state precursor ions. Importantly, improved sequence coverage was observed using ETD-MS/MS following introduction of the sulfonium ion fixed charge, but with no detrimental effects on ETD fragmentation efficiency. PMID:21952753

Improved Ion Resistance for III-V Photocathodes in High Current Guns

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

Mulhollan, Gregory, A.

2012-11-16

The two photocathode test systems were modified, baked and recommissioned. The first system was dedicated to ion studies and the second to electron stimulated recovery (ESR) work. The demonstration system for the electron beam rejuvenation was set up, tested and demonstrated to one of the SSRL team (Dr. Kirby) during a site visit. The requisite subsystems were transferred to SSRL, installed and photoemission studies conducted on activated surfaces following electron beam exposure. Little surface chemistry change was detected in the photoemission spectra following the ESR process. The yield mapping system for the ion (and later, the electron beam rejuvenation) studiesmore » was implemented and use made routine. Ion species and flux measurements were performed for H, He, Ne, Ar, Kr and Xe ions at energies of 0.5, 1.0 and 2.0 kV. Gas induced photoyield measurements followed each ion exposure measurement. These data permit the extraction of photoyield induced change per ion (by species) at the measured energies. Electron beam induced rejuvenation was first demonstrated in the second chamber with primary electron beam energy and dependency investigations following. A Hiden quadrupole mass spectrometer for the electron stimulated desorption (ESD) measurements was procured. The UHV test systems needed for subsequent measurements were configured, baked, commissioned and utilized for their intended purposes. Measurements characterizing the desorption products from the ESD process and secondary electron (SE) yield at the surfaces of negative electron affinity GaAs photocathodes have been performed. One US Utility Patent was granted covering the ESR process.« less

Matching the laser wavelength to the absorption properties of matrices increases the ion yield in UV-MALDI mass spectrometry.

PubMed

Wiegelmann, Marcel; Soltwisch, Jens; Jaskolla, Thorsten W; Dreisewerd, Klaus

2013-09-01

A high analytical sensitivity in ultraviolet matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is only achieved if the laser wavelength corresponds to a high optical absorption of the matrix. Laser fluence and the physicochemical properties of the compounds, e.g., the proton affinity, also influence analytical sensitivity significantly. In combination, these parameters determine the amount of material ejected per laser pulse and the ion yield, i.e., the fraction of ionized biomolecules. Here, we recorded peptide ion signal intensities as a function of these parameters. Three cinnamic acid matrices were investigated: α-cyano-4-hydroxycinnamic acid, α-cyano-4-chlorocinnamic acid, and α-cyano-2,4-difluorocinnamic acid. In addition, 2,5-dihydroxybenzoic acid was used in comparison experiments. Ion signal intensities "per laser shot" and integrated ion signal intensities were acquired over 900 consecutive laser pulses applied on distinct positions on the dried-droplet sample preparations. With respect to laser wavelength, the two standard MALDI wavelengths of 337/355 nm were investigated. Also, 305 or 320 nm was selected to account for the blue-shifted absorption profiles of the halogenated derivatives. Maximal peptide ion intensities were obtained if the laser wavelength fell within the peak of the absorption profile of the compound and for fluences two to three times the corresponding ion detection threshold. The results indicate ways for improving the analytical sensitivity in MALDI-MS, and in particular for MALDI-MS imaging applications where a limited amount of material is available per irradiated pixel.

Ion-enhanced oxidation of aluminum as a fundamental surface process during target poisoning in reactive magnetron sputtering

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

Kuschel, Thomas; Keudell, Achim von

2010-05-15

Plasma deposition of aluminum oxide by reactive magnetron sputtering (RMS) using an aluminum target and argon and oxygen as working gases is an important technological process. The undesired oxidation of the target itself, however, causes the so-called target poisoning, which leads to strong hysteresis effects during RMS operation. The oxidation occurs by chemisorption of oxygen atoms and molecules with a simultaneous ion bombardment being present. This heterogenous surface reaction is studied in a quantified particle beam experiment employing beams of oxygen molecules and argon ions impinging onto an aluminum-coated quartz microbalance. The oxidation and/or sputtering rates are measured with thismore » microbalance and the resulting oxide layers are analyzed by x-ray photoelectron spectroscopy. The sticking coefficient of oxygen molecules is determined to 0.015 in the zero coverage limit. The sputtering yields of pure aluminum by argon ions are determined to 0.4, 0.62, and 0.8 at 200, 300, and 400 eV. The variation in the effective sticking coefficient and sputtering yield during the combined impact of argon ions and oxygen molecules is modeled with a set of rate equations. A good agreement is achieved if one postulates an ion-induced surface activation process, which facilitates oxygen chemisorption. This process may be identified with knock-on implantation of surface-bonded oxygen, with an electric-field-driven in-diffusion of oxygen or with an ion-enhanced surface activation process. Based on these fundamental processes, a robust set of balance equations is proposed to describe target poisoning effects in RMS.« less

Exploring the intrinsic polar [4+2(+)] cycloaddition reactivity of gaseous carbosulfonium and carboxonium ions.

PubMed

Basher, Muftah M; Corilo, Yuri E; Sparrapan, Regina; Benassi, Mario; Augusti, Rodinei; Eberlin, Marcos N; Riveros, José M

2012-11-01

Gas-phase reactions of model carbosulfonium ions (CH(3)-S(+)=CH(2;) CH(3)CH(2)-S(+)=CH(2) and Ph-S(+)=CH(2)) and an O-analogue carboxonium ion (CH(3)-O(+)=CH(2)) with acyclic (isoprene, 1,3-butadiene, methyl vinyl ketone) and cyclic (1,3-cyclohexadiene, thiophene, furan) conjugated dienes were systematically investigated by pentaquadrupole mass spectrometry. As corroborated by B3LYP/6-311 G(d,p) calculations, the carbosulfonium ions first react at large extents with the dienes forming adducts via simple addition. The nascent adducts, depending on their stability and internal energy, react further via two competitive channels: (1) in reactions with acyclic dienes via cyclization that yields formally [4+2(+)] cycloadducts, or (2) in reactions with the cyclic dienes via dissociation by HSR loss that yields methylenation (net CH(+) transfer) products. In great contrast to its S-analogues, CH(3)-O(+)=CH(2) (as well as C(2)H(5)-O(+)=CH(2) and Ph-O(+)=CH(2) in reactions with isoprene) forms little or no adduct and proton transfer is the dominant reaction channel. Isomerization to more acidic protonated aldehydes in the course of reaction seems to be the most plausible cause of the contrasting reactivity of carboxonium ions. The CH(2)=CH-O(+)=CH(2) ion forms an abundant [4+2(+)] cycloadduct with isoprene, but similar to the behavior of such α,β-unsaturated carboxonium ions in solution, seems to occur across the C=C bond. Copyright © 2012 John Wiley & Sons, Ltd.

Spallation of Cu by. pi. /sup -/ across the T = 1/2 resonances and at high energy

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

Haustein, P.E.

1979-09-01

Relative yields of 11 selected products (/sup 24/Na, /sup 43,44,46,47,48/Sc, /sup 55,56,57,58,60/Co) have been measured for the interaction of 0.6- and 0.9-GeV negative pions with Cu. In addition, the yields of /sup 24/Na and /sup 58/Co from Cu have been measured for 12-GeV ..pi../sup -/. Results at the two lower energies which correspond to the first two isospin T = 1/2 pion-nucleon resonances are compared with earlier studies of Cu spallation by ..pi../sup -/ at energies across the first T = 3/2 resonance, i.e., 50 to 350 MeV. The 12-GeV ..pi../sup -/ results are compared with similar investigations in whichmore » both energetic protons and heavy ions were used. For E/sub ..pi../ > or = 0.5 GeV no evidence of strong resonance effects can be found in the pattern of the spallation yields. As the pion energy is raised a smooth trend of enhanced yields of deep spallation products to near-target yields closely parallels the same trend observed for both high-energy proton and heavy-ion spallation of Cu. These results indicate that at high energy, pi-mesic spallation exhibits the same features of limiting fragmentation and factorization of the isotopic yields that have been observed previously in hadron induced spallation.« less

Analysis of TOF-SIMS spectra from fullerene compounds

NASA Astrophysics Data System (ADS)

Kato, N.; Yamashita, Y.; Iida, S.; Sanada, N.; Kudo, M.

2008-12-01

We analyzed TOF-SIMS spectra obtained from three different size of fullerenes (C 60, C 70 and C 84) by using Ga +, Au + and Au 3+ primary ion beams and investigated the fragmentation patterns, the enhancement of secondary ion yields and the restraint of fragmentation by using cluster primary ion beams compared with monoatomic primary ion beams. In the TOS-SIMS spectra from C 70 and C 84, it was found that a fragment ion, identified as C 60+ ( m/ z = 720), showed a relatively high intensity compared with that of other fragment ions related to C 2 depletion. It was also found that the Au 3+ bombardment caused intensity enhancement of intact molecules (C 60+, C 70+ and C 84+) and restrained the fragmentation due to C 2 depletion.

Experimental and theoretical studies of nuclear generation of ozone from oxygen and oxygen-sulfur hexafluoride mixtures

NASA Astrophysics Data System (ADS)

Elsayed-Ali, H. E.; Miley, G. H.

1986-08-01

A series of experimental measurements of the yield of O3 in nuclear-induced O2 and O2-SF6 discharges are reported. The discharges were created by bombardment with energetic particles from the 10B(n,α)7Li reaction. Continuous irradiation at dose rates of 1015-1017 eV cm-3 s-1 and pulsed irradiation (˜10 ms FWHM) at a peak dose rate of ˜1020 eV cm-3 s-1 were conducted. At the lower dose rates, the addition of SF6 generally increased the ozone yield due to the slowing of ozone destruction by negative oxygen and ozone ions. In contrast, at the high dose rates, the ozone concentration decreased due to SF6 suppression of atomic oxygen formation by ion-ion recombination. A numerical model was developed and tested against experimental conditions. This model indicates that the steady-state ozone concentration was limited by the reaction O-3+O3→2O2+O-2 with a rate coefficient of ˜1×10-12 cm3 s-1. In addition to dose rate effects, pressure and temperature effects on ozone production are discussed and methods for increasing the ozone yield are suggested.

One-step refolding and purification of recombinant human tumor necrosis factor-α (rhTNF-α) using ion-exchange chromatography.

PubMed

Wang, Yan; Ren, Wenxuan; Gao, Dong; Wang, Lili; Yang, Ying; Bai, Quan

2015-02-01

Protein refolding is a key step for the production of recombinant proteins, especially at large scales, and usually their yields are very low. Chromatographic-based protein refolding techniques have proven to be superior to conventional dilution refolding methods. High refolding yield can be achieved using these methods compared with dilution refolding of proteins. In this work, recombinant human tumor necrosis factor-α (rhTNF-α) from inclusion bodies expressed in Escherichia coli was renatured with simultaneous purification by ion exchange chromatography with a DEAE Sepharose FF column. Several chromatographic parameters influencing the refolding yield of the denatured/reduced rhTNF-α, such as the urea concentration, pH value and concentration ratio of glutathione/oxidized glutathione in the mobile phase, were investigated in detail. Under optimal conditions, rhTNF-α can be renatured and purified simultaneously within 30 min by one step. Specific bioactivity of 2.18 × 10(8) IU/mg, purity of 95.2% and mass recovery of 76.8% of refolded rhTNF-α were achieved. Compared with the usual dilution method, the ion exchange chromatography method developed here is simple and more effective for rhTNF-α refolding in terms of specific bioactivity and mass recovery. Copyright © 2014 John Wiley & Sons, Ltd.

High-dynamic-range neutron time-of-flight detector used to infer the D(t,n){sup 4}He and D(d,n){sup 3}He reaction yield and ion temperature on OMEGA

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

Forrest, C. J., E-mail: cforrest@lle.rochester.edu; Glebov, V. Yu.; Goncharov, V. N.

Upgraded microchannel-plate–based photomultiplier tubes (MCP-PMT’s) with increased stability to signal-shape linearity have been implemented on the 13.4-m neutron time-of-flight (nTOF) detector at the Omega Laser Facility. This diagnostic uses oxygenated xylene doped with diphenyloxazole C{sub 15}H{sub 11}NO + p-bis-(o-methylstyryl)-benzene (PPO + bis-MSB) wavelength shifting dyes and is coupled through four viewing ports to fast-gating MCP-PMT’s, each with a different gain to allow one to measure the light output over a dynamic range of 1 × 10{sup 6}. With these enhancements, the 13.4-m nTOF can measure the D(t,n){sup 4}He and D(d,n){sup 3}He reaction yields and average ion temperatures in a singlemore » line of sight. Once calibrated for absolute neutron sensitivity, the nTOF detectors can be used to measure the neutron yield from 1 × 10{sup 9} to 1 × 10{sup 14} and the ion temperature with an accuracy approaching 5% for both the D(t,n){sup 4}He and D(d,n){sup 3}He reactions.« less

Matrix effects on secondary ion emission from a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis[trifluoromethanesulfonyl]imide

NASA Astrophysics Data System (ADS)

Souda, Ryutaro

2009-06-01

The ionization mechanism of room-temperature ionic liquids has been investigated using time-of-flight secondary ion mass spectrometry in the temperature range of 15-300 K. Analyses of 1-ethyl-3-methylimidazolium bis[trifluoromethanesulfonyl]imide ([emim][Tf2N]) deposited on a Ni(111) substrate revealed that the [emim]+ and [Tf2N]- yields increase together with the Ni+ yield at monolayer coverage; no such increase was observed for the films deposited on a D2O spacer layer. Results indicated that the [emim][Tf2N] molecule is not perfectly ionized; the Ni(111) surface accepts (for [emim]+) or donates (for [Tf2N]-) an electron with higher efficiency than the counterion because of the metal band effect. This phenomenon might be induced by electrostatic interactions between the separated cation and anion during sputtering. It is also suggested that the sputtered Ni atom can be ionized nonadiabatically by the formation of a quasimolecule with adspecies. The multilayer of [emim][Tf2N] deposited at 15 K has a porous structure, resembling that of polar molecules, because of nonionic intermolecular interactions. The phase transition is identifiable, together with the morphological change in the crystalline film, from temperature evolutions of the secondary ion yields.