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1

Pathway and energetics of xenon migration in uranium dioxide  

NASA Astrophysics Data System (ADS)

Using a combination of density functional theory (DFT), classical potentials, molecular dynamics, and nudged elastic band (NEB) calculations, we explore the diffusion of xenon in uranium dioxide (UO2). We compare migration barriers of empirical potentials with DFT by performing NEB calculations and subsequently we use the DFT-validated empirical potentials to calculate vacancy clusters, with and without xenon, to determine the migration path and barrier of xenon in bulk UO2. We find the following: (i) Two empirical potentials out of four tested agree qualitatively with DFT derived energetics for Schottky defect migration; (ii) through the use of molecular dynamics with empirical potentials, we have found a path for the diffusion of xenon-tetravacancy clusters (Xe+2VU+2VO); (iii) this path has an energy barrier significantly lower than previously reported paths by nearly 1 eV; (iv) we examine the physical contributions to the migration pathway and find the barrier is largely electrostatic and that xenon contributes very little to the barrier height; (v) once a uranium vacancy attaches to a xenon-Schottky defect, the resulting xenon-tetravacancy cluster is strongly bound; and (vi) as xenon in a tetravacancy, a xenon-double Schottky defect can diffuse in a concerted manor with a comparable barrier to xenon in a tetravacancy, but two of the oxygen vacancies are only weakly bound to the defect.

Thompson, Alexander E.; Wolverton, C.

2013-03-01

2

Photoionization of atoms and molecules. [of hydrogen, helium, and xenon  

NASA Technical Reports Server (NTRS)

A literature review on the present state of knowledge in photoionization is presented. Various experimental techniques that have been developed to study photoionization, such as fluorescence and photoelectron spectroscopy, mass spectroscopy, are examined. Various atoms and molecules were chosen to illustrate these techniques, specifically helium and xenon atoms and hydrogen molecules. Specialized photoionization such as in positive and negative ions, excited states, and free radicals is also treated. Absorption cross sections and ionization potentials are also discussed.

Samson, J. A. R.

1976-01-01

3

Migration of defect clusters and xenon-vacancy clusters in uranium dioxide  

NASA Astrophysics Data System (ADS)

The possible transition states, minimum energy paths (MEPs) and migration mechanisms of defect clusters and xenon-vacancy defect clusters in uranium dioxide (UO2) have been investigated using the dimer and the nudged elastic-band (NEB) methods. The nearby O atom can easily hop into the oxygen vacancy position by overcoming a small energy barrier, which is much lower than that for the migration of a uranium vacancy. A simulation for a vacancy cluster consisting of two oxygen vacancies reveals that the energy barrier of the divacancy migration tends to decrease with increasing the separation distance of divacancy. For an oxygen interstitial, the migration barrier for the hopping mechanism is almost three times larger than that for the exchange mechanism. Xe moving between two interstitial sites is unlikely a dominant migration mechanism considering the higher energy barrier. A net migration process of a Xe-vacancy pair containing an oxygen vacancy and a xenon interstitial is identified by the NEB method. We expect the oxygen vacancy-assisted migration mechanism to possibly lead to a long distance migration of the Xe interstitials in UO2. The migration of defect clusters involving Xe substitution indicates that Xe atom migrating away from the uranium vacancy site is difficult.

Chen, Dong; Gao, Fei; Deng, Hui-Qiu; Liu, Bo; Hu, Wang-Yu; Sun, Xin

2014-04-01

4

Physiologic implications of adding small amounts of carbon dioxide to the gas mixture during inhalation of xenon  

Microsoft Academic Search

In addition to being a physiologically active tracer of CBF, xenon (Xe) in subanesthetic concentrations produces a relatively mild lowering of carbon dioxide (CO2) in the blood and elevation of transcranial Doppler (TCD) velocity. The addition of small concentrations of CO2 (0.41.2%) to the inhaled mixture produced no measurable effect on end tidal (Pet) CO2 or TCD velocity. Cerebral blood

E. C. Marks; H. Yonas; M. H. Sanders; J. T. Love; C. Maxwell; S. Schimmerman

1992-01-01

5

Roles of water molecules in trapping carbon dioxide molecules inside the interlayer space of graphene oxides.  

PubMed

Density functional theory (DFT) calculations were employed to investigate the energetics of carbon dioxide migration within hydrated or anhydrous graphene oxides (GOs). When anhydrous GO structures contain a carbon dioxide molecule, the carbon dioxide interacts repulsively with the GO layers to increase the interlayer spacing. The repulsive electrostatic interactions are reduced by the insertion of water molecules into CO2-containing GO structures due to the occurrence of attractive water-layer interactions through hydrogen bonding. Consequently, the interlayer spacings in CO2-containing hydrated structures are shortened compared with those in the anhydrous structures. The results indicate that the intercalated water molecules have the ability to connect the GO layers in the presence of carbon dioxide. Furthermore, the DFT calculations indicated that the GO interlayer spacings, which are influenced by the intercalation of water molecules, control carbon dioxide migration within the GO layers. The importance of the interlayer spacings on the migration of carbon dioxide arises from the occurrence of repulsive interactions between CO2 and oxygen-containing groups attached on the graphene sheets. When the GO interlayer spacings are short due to the presence of intercalated water molecules, the repulsive interactions between carbon dioxide and the GO layers are strong enough to prevent CO2 from migrating from its original position. Such repulsive interactions do not occur during the migration of CO2 within anhydrous GO structures because of the relatively longer interlayer spacing. Accordingly, CO2 migrates within anhydrous GO with a less significant barrier, indicating that carbon dioxide molecules are easily released from the GO. PMID:24733509

Yumura, Takashi; Yamasaki, Ayumi

2014-04-23

6

Direct photo-deposition of silicon dioxide films using a xenon excimer lamp  

NASA Astrophysics Data System (ADS)

Recently excimer lamps have opened up the field of intense vacuum ultra-violet (VUV) light generation. With theoretical efficiencies reaching 40%, the power available from such lamps based on dielectric barrier discharge generation can be superior to those of typical low pressure mercury lamps with shorter UV wavelengths generated. Here we present, for the first time, the use of these lamps for the direct photo-deposition of silicon dioxide from silane and nitrous oxide mixtures. Deposition rates achieved on our unoptimised system are comparable with those obtained with low pressure mercury lamps. The results indicate promising further applications of such lamps towards semiconductor and optoelectronic materials processing.

Bergonzo, P.; Kogelschatz, U.; Boyd, I. W.

1993-05-01

7

Dynamical mean-field theory for transition metal dioxide molecules  

NASA Astrophysics Data System (ADS)

The utility of the dynamical mean-field approximation in quantum chemistry is investigated in the context of transition metal dioxide molecules including TiO2 and CrO2. The choice of correlated orbitals and correlations to treat dynamically is discussed. The dynamical mean field solutions are compared to state of the art quantum chemical calculations. The dynamical mean-field method is found to capture about 50% of the total correlation energy, and to produce very good results for the d-level occupancies and magnetic moments. We also present the excitation spectrum in these molecules which is inaccessible in many wave-function based methods. Conceptual and technical difficulties will be outlined and discussed.

Lin, Nan; Zgid, Dominika; Marianetti, Chris; Reichman, David; Millis, Andrew

2012-02-01

8

Sulfur dioxide molecule sensors based on zigzag graphene nanoribbons with and without Cr dopant  

NASA Astrophysics Data System (ADS)

Structure, electronic, and transport properties of sulfur dioxide (SO2) molecule adsorbed on pure and Cr doped zigzag graphene nanoribbons (ZGNRs) are investigated by means of first principle density functional theory and nonequilibrium Green's function computations. It is found that Cr doped ZGNR is more sensitive to SO2 molecule than pure ZGNR. The pure ZGNRs with and without SO2 molecule show similar I-V curves, but the current of Cr doped ZGNR will significant increase after SO2 molecule adsorption.

Shao, Li; Chen, Guangde; Ye, Honggang; Niu, Haibo; Wu, Yelong; Zhu, Youzhang; Ding, Bingjun

2014-01-01

9

Micelle-hosted palladium nanoparticles catalyze citral molecule hydrogenation in supercritical carbon dioxide.  

PubMed

A new approach of employing metal particles in micelles for the hydrogenation of organic molecules in the presence of fluorinated surfactant and water in supercritical carbon dioxide has very recently been introduced. This is allegedly to deliver many advantages for carrying out catalysis including the use of supercritical carbon dioxide (scCO2) as a greener solvent. Following this preliminary account, the present work aims to provide direct visual evidence on the formation of metal microemulsions and to investigate whether metal located in the soft micellar assemblies could affect reaction selectivity. Synthesis of Pd nanoparticles in perfluorohydrocarboxylate anionic micelles in scCO2 is therefore carried out in a stainless steel batch reactor at 40 degrees C and in a 150 bar CO2/H2 mixture. Homogeneous dispersion of the microemulsion containing Pd nanoparticles in scCO2 is observed through a sapphire window reactor at W0 ratios (molar water-to-surfactant ratios) ranging from 2 to 30. It is also evidenced that the use of micelle assemblies as new metal catalyst nanocarriers could indeed exert a great influence on product selectivity. The hydrogenation of a citral molecule that contains three reducible groups (aldehyde, double bonds at the 2,3-position and the 6,7-position) is studied. An unusually high selectivity toward citronellal (a high regioselectivity toward the reduction of the 2,3-unsaturation) is observed in supercritical carbon dioxide. On the other hand, when the catalysis is carried out in the conventional liquid or vapor phase over the same reaction time, total hydrogenation of the two double bonds is achieved. It is thought that the high kinetic reluctance for double bond hydrogenation of the citral molecule at the hydrophobic end (the 6,7-position) is due to the unique micelle environment that is in close proximity to the metal surface in supercritical carbon dioxide that guides a head-on attack of the molecule toward the core metal particle. PMID:15379472

Meric, Pascal; Yu, Kai Man K; Tsang, Shik Chi

2004-09-28

10

Silicium dioxide nanoparticles as carriers for photoactivatable CO-releasing molecules (PhotoCORMs).  

PubMed

Silicium dioxide nanoparticles of about 20 nm diameter containing azido groups at the surface were prepared by emulsion copolymerization of trimethoxymethylsilane and (3-azidopropyl)triethoxysilane and studied by transmission electron microscopy (TEM). A photoactivatable CO-releasing molecule (PhotoCORM) based on [Mn(CO)(3)(tpm)](+) (tpm = tris(pyrazolyl)methane) containing an alkyne-functionalized tpm ligand was covalently linked to the silicium dioxide nanoparticles via the copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC "click" reaction). The surface functionalization of the particles with azido groups and manganese CORMs was analyzed by UV-vis, IR, (1)H and (13)C CP-MAS NMR spectroscopies as well as energy-dispersive X-ray spectroscopy (EDX). The myoglobin assay was used to demonstrate that the CORM-functionalized nanoparticles have photoinducible CO-release properties very similar to the free complex. In the future, such functionalized silicium dioxide nanoparticles might be utilized as delivery agents for CORMs in solid tumors. PMID:21506524

Drdelmann, Gregor; Pfeiffer, Hendrik; Birkner, Alexander; Schatzschneider, Ulrich

2011-05-16

11

A plan for directional dark matter sensitivity in high-pressure xenon detectors through the addition of wavelength shifting gaseous molecules  

NASA Astrophysics Data System (ADS)

Xenon is an especially attractive candidate for both direct WIMP and 0??? decay searches. Although the current trend has exploited the liquid phase, the gas phase xenon offers remarkable performance advantages for: energy resolution, topology visualization, and discrimination between electron and nuclear recoils. The NEXT-100 experiment, now under construction in the Canfranc Underground Laboratory, Spain, will operate at ~ 15 bars with 100 kg of 136Xe for the 0??? decay search. We will describe recent results with small prototypes, indicating that NEXT-100 can provide about 0.5% FWHM energy resolution at the decay's Q value (2457.83 keV), as well as rejection of ?-rays with topological cuts. However, sensitivity goals for WIMP dark matter and 0??? decay searches indicate the probable need for ton-scale active masses. NEXT-100 provides the springboard to reach this scale with xenon gas. We describe a scenario for performing both searches in a single, high-pressure, ton-scale xenon gas detector, without significant compromise to either. In addition, even in a single ton-scale, high-pressure xenon gas TPC, an intrinsic sensitivity to the nuclear recoil direction may exist. This plausibly offers an advance of more than two orders of magnitude relative to current low-pressure TPC concepts. We argue that, in an era of deepening fiscal austerity, such a dual-purpose detector may be possible at acceptable cost, within the time frame of interest, and deserves our collective attention.

Gehman, V. M.; Goldschmidt, A.; Nygren, D.; Oliveira, C. A. B.; Renner, J.

2013-10-01

12

Chemically-bound xenon in fibrous silica.  

PubMed

High-level quantum chemical calculations reported here predict the existence and remarkable stability, of chemically-bound xenon atoms in fibrous silica. The results may support the suggestion of Sanloup and coworkers that chemically-bound xenon and silica account for the problem of "missing xenon" (by a factor of 20!) from the atmospheres of Earth and Mars. So far, the host silica was assumed to be quartz, which is in contradiction with theory. The xenon-fibrous silica molecule is computed to be stable well beyond room temperature. The calculated Raman spectra of the species agree well with the main features of the experiments by Sanloup et al. The results predict computationally the existence of a new family of noble-gas containing materials. The fibrous silica species are finite molecules, their laboratory preparation should be feasible, and potential applications are possible. PMID:24807740

Kalinowski, Jaroslaw; Rsnen, Markku; Gerber, R Benny

2014-05-21

13

A periodic orbit bifurcation analysis of vibrationally excited isotopologues of sulfur dioxide and water molecules: symmetry breaking substitutions.  

PubMed

Theoretical predictions and assignment of highly excited vibrational states and their organization is one of the most important challenges in molecular spectroscopy. A systematic procedure to investigate such problems is locating the principal families of periodic orbits that emanate from the stationary points of the molecule and then following their evolution with the total energy. This results in constructing continuation/bifurcation diagrams that assist in locating the critical bifurcation energies and to discover new types of vibrational modes. Another parameter that may influence the dynamics of a molecule is isotopic mass substitution. In this article, we investigate the effect of symmetry breaking by isotopic mass substitution of triatomic molecules with C(2v) symmetry in classical and quantum dynamics. Sulfur dioxide and water molecules in their ground electronic state are studied by employing accurate potential energy surfaces. Continuation/bifurcation diagrams of periodic orbits are constructed by varying the energy and the mass of one oxygen atom of sulfur dioxide and one hydrogen atom of a water molecule. The transition from normal-to-local mode vibrations is studied in terms of a pitchfork to a center-saddle elementary bifurcation of periodic orbits. The results presented in this article aim to help the assignment of experimentally obtained spectra. PMID:20825241

Mauguiere, Frederic; Rey, Michael; Tyuterev, Vladimir; Suarez, Jaime; Farantos, Stavros C

2010-09-16

14

Condensed xenon scintillators  

Microsoft Academic Search

Liquid and solid xenon were investigated as scintillator media for the detection of charged particles. The LET dependence of the integral light output was studied over a wide range of ionization densities using alpha and beta particles and heavy ions of 1.4 MeV\\/amu. For solid xenon, scintillation decay times were measured by the delayed single-photon method. For liquid xenon, a

W. Baum; S. Gotz; H. Heckwolf; P. Heeg; M. Mutterer; J. P. Theobald

1988-01-01

15

Strange xenon in Jupiter  

Microsoft Academic Search

Jupiter's helium-rich atmosphere contains xenon with excess136Xe and the ratio of r-products more closely resembles strange xenon (Xe-X, alias Xe-HL) seen in carbonaceous chondrites\\u000a than xenon seen in the solar wind (SW-Xe). The linkage of primordial helium with Xe-X, as seen on a microscopic scale in meteorites,\\u000a apparently extended across planetary distances in the solar nebula, This is expected if

O. Manuel; K. Windler; A. Nolte; L. Johannes; J. Zirbel; D. Ragland

1998-01-01

16

Magnetism-tunable oligoacene dioxide diradicals: promising magnetic oligoacene-like molecules.  

PubMed

Graphene oxide has attracted intense research interest recently because the graphene oxide synthesis route, as a promising alternative for cost-effective mass production of graphene, has been explored. To further study the oxidation process and possible mechanism and to explore applicability of the oxidized products, we have performed a computational study on three series of oligoacene dioxides, focusing on their structures and electronic properties. Taking 1,5-dioxidized naphthalene as a starting point, three series of oligoacene dioxides are considered as follows: 1) middle insertion by 1-2 benzene rings; 2) single-side expansion using 1-2 benzene rings; 3) double-side expansion using two benzene rings. On the basis of density functional theory and complete active space self-consistent field (CASSCF) calculations, we reveal that oligoacene dioxides in the middle insertion series have a triplet ground state, whereas those in the single-side expansion series and the double-side expansion series have open-shell broken-symmetry singlet diradical ground states except for their common origin naphthalene-1,5-dioxide whose ground state is triplet and which is also viewed as the origin of the middle insertion series. Magnetic coupling interactions of these oligoacene dioxides are also determined. This work should help people toward an atomistic understanding of the electronic structures and properties of possible intermediates or products and even the oxidation mechanism of graphene sheets, and provides a reasonable strategy of designing novel graphene-oxide-based magnetic materials. PMID:23139198

Yang, Hongfang; Han, Li; Zhao, Jing; Song, Xinyu; Song, Qisheng; Bu, Yuxiang

2012-12-21

17

Is xenon eldest?  

NASA Technical Reports Server (NTRS)

It is well known that the solubility of noble gases in magmas decreases with increasing atomic weight. Xenon, the weightiest of the stable noble gases, is the least soluble atmospheric gas in magma. It is not unreasonable to suppose that the noble gases should have degassed from (or equilibrated with) a bubbling mantle in order of increasing solubility, such that xenon was the most rapidly degassed and helium the least. The apparent relative ages of the famous radiogenic noble gas isotopes agrees, at least qualitatively, with this premise. When atmospheric loss processes are assigned their proper place, several long-standing xenonological puzzles become added evidence for xenon's relative antiquity. Xenon being the afore-mentioned sense the oldest atmospheric gas, will have been most greatly subject to escape, be it impact-driven or EUV-driven. Nonradiogenic xenon's pronounced isotopic fractionation has already been attributed to escape; why it should be more fractionated than krypton would be assigned to xenon's greater atmospheric age. The small atmospheric inventory of xenon relative to the other nonradiogenic noblegases, known as the 'missing xenon' problem, could easily be explained by differential escape. The relatively tiny atmospheric inventories of the radiogenic daughter products of 129 Iodine and 244 Plutonium, both much smaller than would be expected from the inferred abundances of the parents in meteorites, offer a third and fourth data to support the hypothesis that Earth has lost most of its xenon.

Zahnle, K.

1994-01-01

18

Xenon\\/computed tomography cerebral blood flow measurements. Methods and accuracy  

Microsoft Academic Search

We performed a series of five baboon experiments to compare cerebral blood flow measured with an improved stable xenon\\/CT method and the radiolabelled microsphere technique at a PaCO of 40 mm Hg. The xenon\\/CT method was implemented by fitting the arterial xenon uptake with a double exponential function, by measuring the oxygen and carbon dioxide concentrations continuously during each breath

PANOS P. FATOUROS; ABUND O. WIST; P. R. S. KISHORE; DOUGLAS S. DEWITT; JAMES A. HALL; RICHARD L. KEENAN; LAURAINE M. STEWART; ANTHONY MARMAROU; SUNG C. CHOI; HERMES A. KONTOS

1987-01-01

19

A challenge for green chemistry: designing molecules that readily dissolve in carbon dioxide.  

PubMed

Carbon dioxide is a green yet feeble solvent whose full potential won't be realized until we develop a more thorough understanding of its solvent behavior at the molecular level. Fortunately, advances in molecular modeling coupled with experiments are rapidly improving our understanding of CO(2)'s behavior, permitting design of new, more sustainable "CO(2)-philes". PMID:15340588

Beckman, E J

2004-09-01

20

Critical Viscosity of Xenon  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Because xenon near the critical point will collapse under its own weight, experiments on Earth (green line) are limited as they get closer (toward the left) to the critical point. CVX in the microgravity of space (red line) moved into unmeasured territory that scientists had not been able to reach.

2001-01-01

21

Critical Viscosity of Xenon  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The sample cell at the heart of CVX-2 will sit inside a thermostat providing three layers of insulation. The cell itself comprises a copper body that conducts heat efficiently and smoothes out thermal variations that that would destroy the xenon's uniformity. Inside the cell, the oscillating screen viscometer element is supported between two pairs of electrodes that deflect the screen and then measure screen motion.

2001-01-01

22

Critical Viscosity of Xenon  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of liquid xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Resembling a tiny bit of window screen, the oscillator at the heart of CVX-2 will vibrate between two pairs of paddle-like electrodes. The slight bend in the shape of the mesh has no effect on the data. What counts are the mesh's displacement in the xenon fluid and the rate at which the displacement dampens. The unit shown here is encased in a small test cell and capped with a sapphire windown to contain the xenon at high pressure.

2001-01-01

23

Xenon Feed System Progress.  

National Technical Information Service (NTIS)

This paper reports on Moog's efforts to support the design, development, assembly and test of an electric propulsion xenon feed system for a flight technology demonstration program. Major accomplishments include: (1) Utilization of the Moog Proportional F...

J. K. Barbaritis P. T. King

2006-01-01

24

Critical Viscosity of Xenon  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Shear thirning will cause a normally viscous fluid -- such as pie filling or whipped cream -- to deform and flow more readily under high shear conditions. In shear thinning, a pocket of fluid will deform and move one edge forward, as depicted here.

2001-01-01

25

Xenon Tetrafluoride: Reaction with Aqueous Solutions  

Microsoft Academic Search

Xenon tetrafluoride reacts with water to yield xenon, oxygen, hydrofluoric acid, and a very soluble species containing xenon. Evaporation of the solution yields a white, crystalline substance which has been identified as xenon (VI) oxide, XeO3.

Stanley M. Williamson; Charles W. Koch

1963-01-01

26

XENON TETRAFLUORIDE: REACTION WITH AQUEOUS SOLUTIONS  

Microsoft Academic Search

Xenon tetrafluoride reacts with water to yield xenon, oxygen, ; hydrofluoric acid, and a very soluble species containing xenon. Evaporation of ; the solution yields a white, crystalline substance which was identified as xenon ; (VI) oxide, XeO. (auth);

S. M. Williamson; C. W. Koch

1963-01-01

27

Aggregation of amphiphilic molecules in supercritical carbon dioxide: A small angle X-ray scattering study  

SciTech Connect

Highly soluble amphiphilic materials are shown to form aggregates in supercritical CO{sub 2}. The strategy for synthesis of these amphiphilic molecules involves incorporating CO{sub 2}-philic segments that, for this study, are perfluorinated alkyl chains. These CO{sub 2} -philic regions function like the hydrocarbon tails of conventional surfactant molecules used in liquid organic solvents. Synthesis and characterization of three different CO{sub 2} amphiphiles are reported. Subsequent small angle X-ray scattering (SAXS) measurements were used to characterize the aggregation of these materials in supercritical CO{sub 2}. Each of the three amphiphiles studied showed a different type of aggregation behavior. A graft copolymer consisting of a CO{sub 2}-philic backbone and CO{sub 2}-phobic grafts associated into a micellar structure in the presence of water to promote hydrogen bonding. These aggregates contain approximately 600 grafts in the core. The commercially available surfactant perfluoroalkylpoly( ethylene oxide), or F(CF{sub 2}){sub 6-10}CH{sub 2} CH{sub 2}O(CH{sub 2}CH{sub 2}O){sub 3-8}H, forms classic reverse micelle structures having radii of about 84 A under the conditions of high pressure required to solubilize the material. A third amphiphile, the semifluorinated alkane diblock molecule F(CF{sub 2}){sub 10}(CH{sub 2}){sub 10}H, may form small aggregates of at most 4 unimers per aggregate. 41 refs., 10 figs., 1 tab.

Fulton, J.L.; Pfund, D.M. [Pacific Northwest Lab., Richland, WA (United States); McClain, J.B.; Romack, T.J.; Maury, E.E.; Combes, J.R.; Samulski, E.T.; DeSimone, J.M. [Univ. of Noth Carolina, Chapel Hill, NC (United States); Capel, M. [Brookhaven National Lab., Upton, NY (United States)

1995-11-01

28

Critical Viscosity of Xenon  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2001 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The thermostat for CVX sits inside the white cylinder on a support structure that is placed inside a pressure canister. A similar canister holds the electronics and control systems. The CVX-2 arrangement is identical. The principal investigator is Dr. Robert F. Berg (not shown) of the National Institutes of Standards and Technology, Gaithersburg, MD. This is a detail view of MSFC 0100143.

2001-01-01

29

Requirements for Xenon International  

SciTech Connect

This document defines the requirements for the new Xenon International radioxenon system. The output of this project will be a Pacific Northwest National Laboratory (PNNL) developed prototype and a manufacturer-developed production prototype. The two prototypes are intended to be as close to matching as possible; this will be facilitated by overlapping development cycles and open communication between PNNL and the manufacturer.

Hayes, James C.; Ely, James H.; Haas, Derek A.; Harper, Warren W.; Heimbigner, Tom R.; Hubbard, Charles W.; Humble, Paul H.; Madison, Jill C.; Morris, Scott J.; Panisko, Mark E.; Ripplinger, Mike D.; Stewart, Timothy L.

2013-09-26

30

Titantium Dioxide Nanoparticles Assembled by DNA Molecules Hybridization and Loading of DNA Interacting Proteins  

PubMed Central

This work demonstrates the assembly of TiO2 nanoparticles with attached DNA oligonucleotides into a 3D mesh structure by allowing base pairing between oligonucleotides. A change of the ratio of DNA oligonucleotide molecules and TiO2 nanoparticles regulates the size of the mesh as characterized by UV-visible light spectra, transmission electron microscopy and atomic force microscopy images. This type of 3D mesh, based on TiO2-DNA oligonucleotide nanoconjugates, can be used for studies of nanoparticle assemblies in material science, energy science related to dye-sensitized solar cells, environmental science as well as characterization of DNA interacting proteins in the field of molecular biology. As an example of one such assembly, proliferating cell nuclear antigen protein (PCNA) was cloned, its activity verified, and the protein was purified, loaded onto double strand DNA oligonucleotide-TiO2 nanoconjugates, and imaged by atomic force microscopy. This type of approach may be used to sample and perhaps quantify and/or extract specific cellular proteins from complex cellular protein mixtures affinity based on their affinity for chosen DNA segments assembled into the 3D matrix.

WU, Aiguo; Paunesku, Tatjana; Brown, Eric M. B.; Babbo, Angela; Cruz, Cecille; Aslam, Mohamed; Dravid, Vinayak; Woloschak, Gayle E

2009-01-01

31

Electrochemical Reduction of Carbon Dioxide on Pyrite as a Pathway for Abiogenic Formation of Organic Molecules  

NASA Astrophysics Data System (ADS)

A wide spectrum of electrode potentials of minerals that compose sulfide ores enables the latter, when in contact with hydrothermal solutions, to form galvanic pairs with cathode potentials sufficient for electrochemical reduction of CO2. The experiments performed demonstrated the increase of cathode current on the rotating pyrite disc electrode in a range of potentials more negative than -800 mV in presence of CO2. In high-pressure experiments performed in a specially designed electrochemical cell equipped with a pyrite cathode and placed into autoclave, accumulation of formate was demonstrated after 24 hr passing of CO2 (50 atm, room temperature) through electrolyte solution. The formation of this product started on increasing the cathode potential to -800 mV (with respect to saturated silver chloride electrode). The yield grew exponentially upon cathode potential increase up to -1200 mV. The maximum current efficiency (0.12%) was registered at cathode potentials of about -1000 mV. No formate production was registered under normal atmospheric pressure and in the absence of imposed cathode potential. Neither in experiments, nor in control was formaldehyde found. It is proposed that the electrochemical reduction of CO2 takes part in the formation of organic molecules in hydrothermal solutions accompanying sulfide ore deposits and in `black smokers' on the ocean floor.

Vladimirov, M. G.; Ryzhkov, Y. F.; Alekseev, V. A.; Bogdanovskaya, V. A.; Otroshchenko, V. A.; Kritsky, M. S.

2004-08-01

32

Hyperpolarized xenon-129 production and applications  

NASA Astrophysics Data System (ADS)

Hyperpolarized 3He and 129Xe were initially developed and used in the nuclear physics community. Lately they are primarily used in Medical Resonance Imaging (MRI). Although first MRI polarized gas images were acquired using 129Xe, the research community has focused mostly on 3He, due to the well-known polarizing methods and higher polarization numbers achieved. The main purpose of this thesis is to present a novel design of a large-scale SEOP polarizer for producing large quantities of highly polarized 129Xe. High Rb-Xe spin-exchange rates through long-lived van de Waals molecules at low total pressure, implemented in a novel counterflow polarizer design, resulted in xenon polarization as high as 50% for 1.2 liters/hour, with a maximum of 64% for 0.3 l/h. We characterized and improved the polarization process by finding the optimum operating parameters of the polarizer. Two new methods to efficiently use high-power diode lasers are described: a new optical arrangement for a better beam shaping of fiber coupled lasers and the first external-cavity spectrum narrowing of a stack of laser diode arrays. A new accumulation technique for the hyperpolarized xenon was developed and full recovery of polarization after a freeze-thaw cycle was demonstrated for the first time. Two approaches for xenon delivery, frozen and gas states, were developed. Hyperpolarized xenon transportation to Brigham and Women's Hospital was successfully accomplished for collaborative research. First MRI images using hyperpolarized xenon acquired at BWH are presented. Final chapter is focused on describing a low field human MRI scanner using hyperpolarized 3He. We built a human scale imager with open access for orientational studies of the lung functionality. Horizontal and vertical human lung images were acquired as a first stage of this project.

Ruset, Iulian C.

33

Vibrational Relaxation of Ground-State Oxygen Molecules With Atomic Oxygen and Carbon Dioxide  

NASA Astrophysics Data System (ADS)

Vertical water vapor profiles are key to understanding the composition and energy budget in the mesosphere and lower thermosphere (MLT). The SABER instrument onboard NASA's TIMED satellite measures such profiles by detecting H2O(?2) emission in the 6.8 ?m region. Collisional deactivation of vibrationally excited O2, O2(X3?-g, ? = 1) + H2O ? O2(X3?-g, ? = 0) + H2O(?2), is an important source of H2O(?2). A recent study has identified two other processes involving excited O2 that control H2O(?2) population in the MLT: (1) the vibrational-translational (V-T) relaxation of O2(X3?-g, ? = 1) level by atomic oxygen and (2) the V-V exchange between CO2 and excited O2 molecules [1]. Over the past few years SRI researchers have measured the atomic oxygen removal process mentioned above at room temperature [2] and 240 K [3]. These measurements have been incorporated into the models for H2O(?2) emission [1]. Here we report laboratory studies of the collisional removal of O2(X3?-g, ? = 1) by O(3P) at room temperature and below, reaching temperatures relevant to mesopause and polar summer MLT (~150 K). Instead of directly detecting the O2(X3?-g, ? = 1) population, a technically simpler approach is used in which the ? = 1 level of the O2(a1?g) state is monitored. A two-laser method is employed, in which the pulsed output of the first laser near 285 nm photodissociates ozone to produce atomic oxygen and O2(a1?g, ? = 1), and the pulsed output of the second laser detects O2(a1?g, ? = 1) via resonance-enhanced multiphoton ionization. With ground-state O2 present, owing to the rapid equilibration of the O2(X3?-g, ? = 1) and O2(a1?g, ? = 1) populations via the processes O2(a1?g, ? = 1) + O2(X3?-g, ? = 0) ? O2(a1?g, ? = 0) + O2(X3?-g, ? = 1), the information on the O2(X3?-g, ? = 1) kinetics is extracted from the O2(a1?g, ? = 1) temporal evolution. In addition, measurements of the removal of O2(X3?-g, ? = 1) by CO2 at room temperature will also be presented. This work is supported by the Johns Hopkins University, Applied Physics Laboratory, under grant 939991 (under NASA grant NAG5-13002). [1] Feofilov, A., Kutepov, A. A., Garca-Comas, M., Lpez-Puertas, M., Marshall, B. T., Gordley, L. L., Manuilova, R. O., Yankovsky, V. A., Pesnell, W. D., Goldberg, R. A., Petelina, S. V., and Russell III., J. M. 'SABER/TIMED Observations of Water Vapor in the Mesosphere: Retrieval Methodology and First Results'. Submitted to J. of Atmos. and Terrest. Phys., (2008). [2] Kalogerakis, K. S., Copeland, R. A., and Slanger, T. G., J. of Chem. Phys., 123, 194303, (2005). [3] Pejakovic, D. A., Campbell, Z., Kalogerakis, K. S., Copeland, R. A., and Slanger, T. G., Eos. Trans. AGU 85(47), Fall Meet. Suppl., Abstract SA41A-1032, (2004).

Saran, D. V.; Pejakovic, D. A.; Copeland, R. A.

2008-12-01

34

Xenon/computed tomography cerebral blood flow measurements. Methods and accuracy.  

PubMed

We performed a series of five baboon experiments to compare cerebral blood flow measured with an improved stable xenon/CT method and the radiolabelled microsphere technique at a PaCO2 of 40 mm Hg. The xenon/CT method was implemented by fitting the arterial xenon uptake with a double exponential function, by measuring the oxygen and carbon dioxide concentrations continuously during each breath and by taking into account the lung-to-brain transit time of xenon. The time of xenon inhalation was extended to 30 minutes to obtain more reliable estimates of CBF in white matter regions. The results indicate an overall correlation coefficient of 0.92 between the two methods and good numeric agreement. PMID:3679761

Fatouros, P P; Wist, A O; Kishore, P R; DeWitt, D S; Hall, J A; Keenan, R L; Stewart, L M; Marmarou, A; Choi, S C; Kontos, H A

1987-09-01

35

Nuclear excited xenon flashlamp  

SciTech Connect

The optical emissions of nuclear excited Xenon plasmas were investigated to determine basic parameters important to photolytic pumping of lasers. Gas mixtures of Helium-3 and Xenon were irradiated in the steady state mode in the University of Florida Training Reactor at neutron flux levels of about 10/sup 12//cm/sup 2/.s, generating a power density in the gas of approximately 3 milliwatts/cm/sup 3/. Optical emissions from the gas were primarily due to Xe/sub 2/* band emission at 172 nm with a few Xell lines in the visible and ir. Energy transfer from the /sup 3/He(n,p)T reaction to the Xe/sub 2/* 172 nm band was 67.0% +- 10%. High pressure gas mixtures (4 atm.) of Helium-3 and Xenon were irradiated in the pulse mode (250 ..mu..s FWHM) at the fast burst reactor at the Aberdeen Pulsed Radiation Facility at thermal neutron flux levels of about 10/sup 17//cm/sup 2/.s, generating a power density in the gas of about 1 kilowatt/cm/sup 3/. Optical emissions from the gas extended from the vacuum ultraviolet through the visible to the infrared, resembling a discharge excited lamp with a current density of about 1500 amp./cm/sup 2/. Such a lamp could pump a Neodymium YAG or liquid laser.

Cox, J.D.

1982-01-01

36

Shear Thinning in Xenon  

NASA Technical Reports Server (NTRS)

We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids such as molten plastics or ketchup, near the critical point of xenon. The data span a wide range of dimensionless shear rate: the product of the shear rate and the relaxation time of critical fluctuations was greater than 0.001 and was less than 700. As predicted by theory, shear thinning occurred when this product was greater than 1. The measurements were conducted aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity.

Bergm Robert F.; Moldover, Michael R.; Yao, Minwu; Zimmerli, Gregory A.

2009-01-01

37

Bonding of xenon hydrides.  

PubMed

We have computed the structure and stability of the xenon hydrides HXeY (with Y = F, Cl, Br, I, CCH, CN, NC) using relativistic density functional theory (DFT) at ZORA-BP86/TZ2P level. All model systems HXeY studied here are bound equilibrium structures, but they are also significantly destabilized with respect to Xe and HY. We have analyzed the bonding in HXeY in order to arrive at a simple picture that explains the main trends in stability. PMID:19658392

Prez-Peralta, Nancy; Jurez, Rosalba; Cerpa, Erick; Bickelhaupt, F Matthias; Merino, Gabriel

2009-09-01

38

Bonding of Xenon Hydrides  

NASA Astrophysics Data System (ADS)

We have computed the structure and stability of the xenon hydrides HXeY (with Y = F, Cl, Br, I, CCH, CN, NC) using relativistic density functional theory (DFT) at ZORA-BP86/TZ2P level. All model systems HXeY studied here are bound equilibrium structures, but they are also significantly destabilized with respect to Xe and HY. We have analyzed the bonding in HXeY in order to arrive at a simple picture that explains the main trends in stability.

Prez-Peralta, Nancy; Jurez, Rosalba; Cerpa, Erick; Bickelhaupt, F. Matthias; Merino, Gabriel

2009-08-01

39

Optical pumping and xenon NMR  

SciTech Connect

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping [sup 129]Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the [sup 131]Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

Raftery, M.D.

1991-11-01

40

Optical pumping and xenon NMR  

SciTech Connect

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping {sup 129}Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the {sup 131}Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

Raftery, M.D.

1991-11-01

41

Environmental Considerations for Xenon Electric Propulsion  

Microsoft Academic Search

In the present study, the focus is on potential environmental effects associated with electric thrusters that use xenon propellant. The study is broad in scope, providing background on electric propulsion systems, structure of the atmosphere, xenon production and applications, xenon chemistry, etc. Few measurement data exist concerning the atmospheric distribution of xenon, therefore this distribution has been calculated. Although the

Mark W. Crofton; Toby D. Hain

42

Venus, Earth, Xenon  

NASA Astrophysics Data System (ADS)

Xenon has been regarded as an important goal of many proposed missions to Venus. This talk is intended to explain why. Despite its being the heaviest gas found in natural planetary atmospheres, there is more evidence that Xe escaped from Earth than for any element apart from helium: (i) Atmospheric Xe is very strongly mass fractionated (at about 4% per amu) from any known solar system source. This suggests fractionating escape that preferentially left the heavy Xe isotopes behind. (ii) Xe is underabundant compared to Kr, a lighter noble gas that is not strongly mass fractionated in air. (iii) Radiogenic Xe is strongly depleted by factors of several to ~100 compared to the quantities expected from radioactive decay of primordial solar system materials. In these respects Xe on Mars is similar to Xe on Earth, but with one key difference: Xe on Mars is readily explained by a simple process like hydrodynamic escape that acts on an initially solar or meteoritic Xe. This is not so for Earth. Earth's Xe cannot be derived by an uncontrived mass fractionating process acting on any known type of Solar System Xe. Earth is a stranger, made from different stuff than any known meteorite or Mars or even the Sun. Who else is in Earth's family? Comets? We know nothing. Father Zeus? Data from Jupiter are good enough to show that jovian Xe is not strongly mass-fractionated but not good enough to determine whether Jupiter resembles the Earth or the Sun. Sister Venus? Noble gas data from Venus are incomplete, with Kr uncertain and Xe unmeasured. Krypton was measured by several instruments on several spacecraft. The reported Kr abundances are discrepant and were once highly controversial. These discrepancies appear to have been not so much resolved as forgotten. Xenon was not detected on Venus. Upper limits were reported for the two most abundant xenon isotopes 129Xe and 132Xe. From the limited data it is not possible to tell whether Venus's affinities lie with the solar wind, or with the chondrites, with Earth, or with none of the above. Modern spacecraft mass spectrometers are at least 100-fold more sensitive to noble gases. Sending such an instrument to Venus may be the last best hope for decrypting what Earth's noble gases have been trying to tell us.

Zahnle, K. J.

2013-12-01

43

Critical Viscosity of Xenon investigators  

NASA Technical Reports Server (NTRS)

Dr. Dr. Robert F. Berg (right), principal investigator and Dr. Micheal R. Moldover (left), co-investigator, for the Critical Viscosity of Xenon (CVX/CVX-2) experiment. They are with the National Institutes of Standards and Technology, Gaithersburg, MD. The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Although it does not easily combine with other chemicals, its viscosity at the critical point can be used as a model for a range of chemicals.

2001-01-01

44

Dendritic solidification of xenon  

NASA Astrophysics Data System (ADS)

Experiments on xenon dendrites growing in a three-dimensional volume of pure, supercooled melt have been performed. The shapes of the dendrites have been determined with high lateral resolution. The dendrites grow in a stable mode and do not show oscillations in the growth velocity nor in the curvature of the dendrite tip. The dendrites do not have the shape of a paraboloid of revolution. Surface anisotropies determine the shape of the dendrites. Four fins grow along a dendrite. The contour of these fins can be described by a power law z | x| ? with ? ? 1.67. These experimental results are in agreement with the analytical work of E. Brener [Phys. Rev. Lett. 71 (1993) 3653]. Both experiments and analytical work are compatible with the assumption that thermal fluctuations initiate side branching. Tip oscillations can be excluded.

Bisang, U.; Bilgram, J. H.

1996-09-01

45

A Decade of Xenon Chemistry  

ERIC Educational Resources Information Center

Presents reactions for the formation of xenon compounds and compounds of the other inert gases. Provides bonding and structure theories for noble gas compounds and speculates on possible applications. (GS)

Moody, G. J.

1974-01-01

46

The local microenvironment surrounding dansyl molecules attached to controlled pore glass in pure and alcohol-modified supercritical carbon dioxide.  

PubMed

We report on the local microenvironment surrounding a free dansyl probe, dansyl attached to controlled pore glass (D-CPG), and dansyl molecules attached to trimethylsilyl-capped CPG (capped D-CPG) in pure and alcohol-modified supercritical CO2. These systems were selected to provide insights into the local microenvironment surrounding a reactive agent immobilized at a silica surface in contact with pure and cosolvent-modified supercritical CO2. Local surface-bound dansyl molecule solvation on the CPG surface depends on the dansyl molecule surface loading, the surface chemistry (uncapped versus capped), the bulk fluid density, and the alcohol gas phase absolute acidity. At high dansyl loadings, the surface-bound dansyl molecules are largely "solvated" by other dansyl molecules and these molecules are not affected significantly by the fluid phase. When the dansyl surface loading decreases, dansyl molecules can be accessed/solvated/wetted by the fluid phase. However, at the lowest dansyl loadings studied, the dansyl molecules are in a fluid inaccessible/restrictive environment and do not sense the fluid phase to any significant degree. In uncapped D-CPG, one can poise the system such that the local concentration of an environmentally less responsible cosolvent (alcohol) in the immediate vicinity of surface-immobilized dansyl molecules can approach 100% even though the bulk solution contains orders of magnitude less of this less environmentally responsible cosolvent. In capped C-CPG, the surface excess is attenuated in comparison to that of uncapped D-CPG. The extent of this cosolvent surface excess is discussed in terms of the dansyl surface loading, the local density fluctuations, the cosolvent and surface silanol gas phase acidities, and the silica surface chemistry. These results also have implications for cleanings, extractions, heterogeneous reactions, separations, and nanomaterial fabrication using supercritical fluids. PMID:18537278

Page, Phillip M; McCarty, Taylor A; Munson, Chase A; Bright, Frank V

2008-06-01

47

Vibrationally state selected ion molecule experimental and computational studies of both reactant charge states of [nitrogen dioxide + ethyne]+ and HOD+ with nitrogen dioxide  

NASA Astrophysics Data System (ADS)

Ion molecule studies have not only determined reactivity of systems that would have otherwise been unavailable, but also provide a perspective that improves the understanding of the mechanisms that drive reaction. Presented here are studies of three ion molecule systems one of which is accompanied by an extensive set of direct dynamics trajectory calculations. In the first system presented, NO2+ in six different vibrational states was reacted with C2H2 over the center-of-mass energy range from 0.03 to 3.3 eV. The effects of the symmetric bend overtone (0200) excitation are particularly strong (factor of 4) while the delta overtone (0220) effects are much weaker. A large set of quasi-classical trajectories were calculated at the PBE1PBE/6-311G** level of theory, in an attempt to understand the mechanistic origins of this observation. The trajectories reproduce experiment where comparable. Analysis of these trajectories resolves the mechanistic origins of this vibrational effect. Similar experimental measurements were made for the first excited electronic state of this system where the charge is localized on the acetylene. The C 2H2+ reactant was prepared in four distinct modes. Because both reactants have one unpaired electron, collisions can occur with either singlet or triplet coupling of these unpaired electrons, and the contributions the three channels (charge, O-, and O transfer) are separated based on distinct recoil dynamics. The effects of C2H 2+ vibration are modest, but mode specific. Integral cross sections and product recoil velocity distributions were also measured for reaction of HOD+ with NO2, in which the HOD+ reactant was prepared in its ground state, and with mode-selective excitation in the 001 (OH stretch), 100 (OD stretch) and bend (010) modes. In addition, we measured the 300 K thermal kinetics in a selected ion flow tube reactor and report product branching ratios different from previous measurements. Reaction is found to occur on both the singlet and triplet surfaces with near unit efficiency. Origins of discrepancies in the thermal versus beam experiments are discussed. Nine mechanisms contribute to four product channels (proton, deuteron, charge, and O- transfer) with the contributions from each resolved. Vibrational effects allow determination of energy partitioning in proton and deuteron transfer reactions near the product ion dissociation threshold.

Boyle, Jason M.

48

Xenon filled silicon germanium thermoelectric generators  

NASA Technical Reports Server (NTRS)

An analysis is presented that shows the desirability and feasibility of using a xenon fill in the initial stages of operation of a silicon-germanium radioisotope thermoelectric generator to be used in outer-planetary exploration. The xenon cover gas offers protection against oxidation and against material sublimation, and allows the generator to deliver required power throughout the prelaunch and launch phases. The protective mechanisms afforded by the xenon cover gas and the mechanization of a xenon supply system are also discussed.

Dewinter, F.

1972-01-01

49

Critical Viscosity of Xenon team  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The thermostat for CVX sits inside the white cylinder on a support structure (at left) that is placed inside a pressure canister. A similar canister (right) holds the electronics and control systems. The CVX-2 arrangement is identical. The principal investigator is Dr. Robert F. Berg (not shown) of the National Institutes of Standards and Technology, Gaithersburg, MD.

2001-01-01

50

Critical Viscosity of Xenon team  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The thermostat for CVX sits inside the white cylinder on a support structure (at left) that is placed inside a pressure canister. A similar canister (right) holds the electronics and control systems. The CVX-2 arrangement is identical. The principal investigator is Dr. Robert F. Berg (left) of the National Institutes of Standards and Technology, Gaithersburg, MD.

2001-01-01

51

Atmospheric xenon radioactive isotope monitoring.  

PubMed

The Comprehensive Nuclear Test Ban Treaty (CTBT) organisation is implementing a world-wide monitoring network in order to check that the State Signatories comply with the treaty. One of the monitoring facilities consists of an atmospheric noble gas monitoring equipment. According to the requirements annexed in the treaty, the French Atomic Energy Commission (CEA) developed a device, called SPALAX, which automatically extracts xenon from ambient air and makes in situ measurements of the activities of four xenon radioisotopes (131mXe, 133mXe, 133Xe, 135Xe). The originality of this device is noticeable essentially in the gas sample processing method: thanks to the coupling of a gas permeator and of a noble gas specific adsorbent, it can selectively extract and concentrate xenon to more than 3 x 10 E6. This process is carried out continuously without cryogenic cooling, without any regeneration time. The detection of the xenon radioactive isotopes is done automatically by high spectral resolution gamma spectrometry, a robust technology well-suited for on-field instrumentation. In the year 2000, a prototype was involved in an international evaluation exercise directed by the CTBT organisation (CTBTO). This exercise demonstrated that the SPALAX equipment perfectly met the requirements of the CTBTO for such systems. On the basis of the continuous 24-h resolution record of the atmospheric xenon radioactive isotopes concentrations, the SPALAX system also demonstrated that ambient levels of 133Xe can fluctuate quickly from less than the detection limit to over 40 x 10(-3) Bq m(-3). In order to build an industrial version of this equipment, the CEA entered into a partnership with a French engineering company (S.F.I., Marseille, France), which is now able to produce an industrial version of SPALAX, i.e. more compact and more efficient than the prototypes. The 133Xe minimum detectable concentration is 0.15 x 10(-3) Bq m(-3) air per 24 h sampling cycle. PMID:15162864

Fontaine, J P; Pointurier, F; Blanchard, X; Taffary, T

2004-01-01

52

Substituent Effects on Xenon Binding Affinity and Solution Behavior of Water-Soluble Cryptophanes  

PubMed Central

A water-soluble triacetic acid cryptophane-A derivative (TAAC) was synthesized and determined by isothermal titration calorimetry (ITC) and fluorescence quenching assay to have a xenon association constant of 33,000 M?1 at 293 K, which is the largest value measured for any host molecule to date. Fluorescence lifetime measurements of TAAC in the presence of varying amounts of xenon indicated static quenching by the encapsulated xenon and the presence of a second non-xenon-binding conformer in solution. Acid-base titrations and aqueous NMR spectroscopy of TAAC and a previously synthesized tri-(triazole propionic acid) cryptophane-A derivative (TTPC) showed how solvation of the carboxylate anions can affect the aqueous behavior of the large, nonpolar cryptophane. Specifically, whereas only the crown-crown (CC) conformer of TTPC was observed, a crown-saddle (CS) conformer of TAAC was also detected in aqueous solution.

Hill, P. Aru; Wei, Qian; Troxler, Thomas; Dmochowski, Ivan J.

2009-01-01

53

Xenon emission accompanying fracture of xenon-implanted cubic zirconia  

SciTech Connect

The emission of xenon following the fracture of xenon-implanted cubic zirconia has been studied using mass spectrometry. All samples showed intense Xe bursts at failure. Order of magnitude estimates of the amount of Xe released suggest that micrometer-scale regions of the tensile surface on either side of the fracture surface of these samples do not show sufficient damage to account for this emission. However, SEM micrographs of the fracture surface show evidence for extensive microcracking immediately adjacent to the tensile surface. It is believed that these microcracks are formed when the advancing crack encounters the tensile stresses immediately below the Xe-implanted surface layer and disrupts the Xe inclusions produced by implantation. Some samples also show Xe bursts prior to failure; SEM observations of these samples show shallow conchoidal cracks on the tensile surface, which apparently form during loading and would account for the release of Xe prior to failure.

Norton, M.G.; Jiang, Wenbiao (Washington State Univ., Pullman, WA (United States). Dept. of Mechanical and Materials Engineering); Dickinson, J.T.; Jensen, L.C.; Langford, S.C. (Washington State Univ., Pullman, WA (United States). Dept. of Physics); Fleischer, E.L.; Mayer, J.W. (Cornell Univ., Ithaca, NY (United States). Dept. of Materials Science and Engineering)

1993-08-01

54

Viscosity of Xenon Examined in Microgravity  

NASA Technical Reports Server (NTRS)

Why does water flow faster than honey? The short answer, that honey has a greater viscosity, merely rephrases the question. The fundamental answer is that viscosity originates in the interactions between a fluid s molecules. These interactions are so complicated that, except for low-density gases, the viscosity of a fluid cannot be accurately predicted. Progress in understanding viscosity has been made by studying moderately dense gases and, more recently, fluids near the critical point. Modern theories predict a universal behavior for all pure fluids near the liquid-vapor critical point, and they relate the increase in viscosity to spontaneous fluctuations in density near this point. The Critical Viscosity of Xenon (CVX) experiment tested these theories with unprecedented precision when it flew aboard the Space Shuttle Discovery (STS-85) in August 1997. Near the critical point, xenon is a billion times more compressible than water, yet it has about the same density. Because the fluid is so "soft," it collapses under its own weight when exposed to the force of Earth s gravity - much like a very soft spring. Because the CVX experiment is conducted in microgravity, it achieves a very uniform fluid density even very close to the critical point. At the heart of the CVX experiment is a novel viscometer built around a small nickel screen. An oscillating electric field forces the screen to oscillate between pairs of electrodes. Viscosity, which dampens the oscillations, can be calculated by measuring the screen motion and the force applied to the screen. So that the fluid s delicate state near the critical point will not be disrupted, the screen oscillations are set to be both slow and small.

Zimmerli, Gregory A.; Berg, Robert F.; Moldover, Michael R.

1999-01-01

55

Single molecule magnets with protective ligand shells on gold and titanium dioxide surfaces: In situ electrospray deposition and x-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Two single molecule magnets based on the dodecamanganese (III, IV) cluster with either benzoate or terphenyl-4-carboxylate ligands, have been studied on the Au(111) and rutile TiO2(110) surfaces. We have used in situ electrospray deposition to produce a series of surface coverages from a fraction of a monolayer to multilayer films in both cases. X-ray absorption spectroscopy measured at the Mn L-edge (Mn 2p) has been used to study the effect of adsorption on the oxidation states of the manganese atoms in the core. In the case of the benzoate-functionalised complex reduction of the manganese metal centres is observed due to the interaction of the manganese core with the underlying surface. In the case of terphenyl-4-carboxylate, the presence of this much larger ligand prevents the magnetic core from interacting with either the gold or the titanium dioxide surfaces and the characteristic Mn3+ and Mn4+ oxidation states necessary for magnetic behaviour are preserved.

Handrup, Karsten; Richards, Victoria J.; Weston, Matthew; Champness, Neil R.; O'Shea, James N.

2013-10-01

56

Stability of xenon oxides at high pressures.  

PubMed

Xenon, which is quite inert under ambient conditions, may become reactive under pressure. The possibility of the formation of stable xenon oxides and silicates in the interior of the Earth could explain the atmospheric missing xenon paradox. Using an ab initio evolutionary algorithm, we predict the existence of thermodynamically stable Xe-O compounds at high pressures (XeO, XeO(2) and XeO(3) become stable at pressures above 83, 102 and 114GPa, respectively). Our calculations indicate large charge transfer in these oxides, suggesting that large electronegativity difference and high pressure are the key factors favouring the formation of xenon compounds. However, xenon compounds cannot exist in the Earth's mantle: xenon oxides are unstable in equilibrium with the metallic iron occurring in the lower mantle, and xenon silicates are predicted to decompose spontaneously at all mantle pressures (<136GPa). However, it is possible that xenon atoms may be retained at defects in mantle silicates and oxides. PMID:23247179

Zhu, Qiang; Jung, Daniel Y; Oganov, Artem R; Glass, Colin W; Gatti, Carlo; Lyakhov, Andriy O

2013-01-01

57

Xenon fluoride solutions effective as fluorinating agents  

NASA Technical Reports Server (NTRS)

Solutions of xenon fluorides in anhydrous hydrogen fluoride have few disruptive effects and leave a residue consisting of gaseous xenon, which can be recovered and refluorinated. This mild agent can be used with materials which normally must be fluorinated with fluorine alone at high temperatures.

Hyman, H. H.; Quarterman, L. A.; Sheft, I.

1967-01-01

58

High pressure xenon ionization detector  

DOEpatents

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

Markey, John K. (New Haven, CT)

1989-01-01

59

High pressure xenon ionization detector  

DOEpatents

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

Markey, J.K.

1989-11-14

60

Xenon Gamma Detector Project Support  

SciTech Connect

This project provided funding of $48,500 for part of one year to support the development of compressed xenon spectrometers at BNL. This report describes upgrades that were made to the existing detector system electronics during that period, as well as subsequent testing with check sources and Special Nuclear Materials. Previous testing of the equipment extended only up to the energy of 1.3 MeV, and did not include a spectrum of Pu-239. The new electronics allowed one-button activation of the high voltage ramp that was previously controlled by manual adjustments. Mechanical relays of the charging circuit were replaced by a tera-ohm resistor chain and an optical switch. The preamplifier and shaping amplifier were replaced by more modern custom designs. We found that the xenon purity had not been degraded since the chamber was filled 10 years earlier. The resulting spectra showed significantly better resolution than sodium iodide spectra, and could be analyzed quite effectively by methods using peak area templates.

Vanier,P.E.; Forman, L.

2008-04-01

61

Optical absorption and fluorescence studies in high pressure cesium-xenon mixtures  

Microsoft Academic Search

The pressure and temperature dependent absorption and fluorescence spectra of the cesium-xenon (CsXe) molecule have been examined. In contrast to previous investigations of the alkali-rare gas molecules, cesium atomic states that have weakly allowed optical transitions have been studied and have been shown to form excimer levels that are attractive for application as potential dissociation lasers. In particular, the (Cs[7^{2}S]Xe)*

J. G. Eden; B. E. Cherrington; J. T. Verdeyen

1976-01-01

62

The MEG Liquid Xenon calorimeter  

NASA Astrophysics Data System (ADS)

The MEG experiment at PSI is searching for the lepton-flavour violating decay of the muon into an electron-gamma pair. It is expected to take physics data during the years 2008-2011. From the first three months of data at the end of 2008, we got an upper limit BR(?+ ? e+ + ?) ? 3.0 10-11 (90% C.L.). The core of the MEG experiment is an innovative gamma-ray detector, this is a large acceptance and large mass (roughly 2.2 Tons) liquid xenon volume read by photo-multiplier tubes, which is used to measure the photon energy and the position and time of its first conversion. The operation of the detector during the 2008 run will be presented together with several calibration techniques developed to monitor its stability and behaviour during experimental data taking.

Gallucci, G.

2010-04-01

63

Liquid xenon gamma ray imager  

US Patent & Trademark Office Database

A gamma ray imager includes a chamber containing a scintillation liquid such as xenon and several mutually optically isolated interaction modules immersed in the scintillation liquid within the chamber. Multiple photodetectors optically coupled to the modules separately detect scintillation light resulting from gamma ray interactions in the modules. Charge readout devices coupled to the modules provide time projection chamber-class detection of ionization charges produced by gamma ray interactions within the modules. A signal processor connected to the multiple photodetectors and charge readout devices analyzes signals produced by gamma ray interactions within the modules and calculates from the signals gamma ray energy and gamma ray angle. The calculations use Compton scattering formula inversion and also use anti-correlation of prompt scintillation light signals from gamma ray interactions and charge signals from gamma ray interactions.

2013-07-02

64

NMR Study of Dilute Molecular Hydrogen in Liquid Xenon  

NASA Astrophysics Data System (ADS)

Pulsed NMR measurements have been made at 20.00 MHz of the diffusion coefficient D, the spin-lattice relaxation time T(,1), and the spin-spin relaxation time T(,2) of ortho-hydrogen as a dilute impurity (< 1%) in liquid xenon. The measurements were obtained as a function of temperature (T) near the saturated vapor pressure curve from the triple point to the critical point, and represent the behavior of an isolated hydrogen molecule in the otherwise pure liquid. Samples were prepared by condensing xenon gas into a liquid near the triple point and circulating gaseous hydrogen through the sample with a closed cycle pump until the desired concentration was attained. Diffusion coefficients were determined using the spin-echo technique in a calibrated field gradient. Near the triple point they are found to have an activated temperature dependence similar to that of self-diffusion in liquid xenon but deviate upward at higher temperatures. The principle of corresponding states is used to compare D to similar data taken by Conradi for ortho-hydrogen in other rare gas liquids. This comparison is found to successful when the xenon potential parameters along with the reduced mass an H(,2)-Xe gas pair are used. Self-diffusion in liquid xenon is well described using the empirical expression (rho)D = cT('(beta)) with (beta) = 2.87 and (rho) the density. This expression is also found to describe the temperature dependence of D near the triple point. A hard sphere molecular dynamics calculation for the ratio of impurity to self-diffusion is found to describe qualitatively the behavior of the experimental ratio. T(,1) is found to be larger than the corresponding times in the other rare gas liquids. Consequently (tau)(,1), the molecular relaxation time, is smaller, but still in the weak collision limit, and therefore Bloom-Oppenheim theory is still appropriate. (T(,1))(,liquid) < (T(,1))(,gas) below 230K, and Deutch and Oppenheim's extension of Bloom -Oppenheim theory to multiple particle collisions is used to explain this fact. Above 230K (T(,1))(,liquid) (DBLTURN) (T(,1))(,gas) which is interpreted to mean that binary collisions are primarily responsible for relaxation.

Edwards, Carl Monroe

65

Xenon-Sensitized Radiolysis of Propane.  

National Technical Information Service (NTIS)

The xenon-sensitized radiolysis of propane was investigated in the presence and absence of small amounts of ion and free radical interceptors. From an analysis of mixtures of deuterated propanes and a knowledge of radical disproportionation yields in the ...

L. I. Bone L. W. Sieck J. H. Futrell

1965-01-01

66

Spectra of Pulsed and Continuous Xenon Discharges.  

National Technical Information Service (NTIS)

Spectral distributions over the range 0.35 to 1.1 micron were measured for representative pulsed and continuous-burning xenon arc lamps. Optical conversion efficiencies were computed for several spectral regions. Measurements were taken at different curre...

J. H. Goncz

1965-01-01

67

Cryogenic xenon droplets for advanced lithography  

SciTech Connect

A cryogenic xenon droplet production system for use in anadvanced laser plasma source for x-ray lithography has been designed, fabricated, and tested at ORNL. The droplet generator is based on proven (ink jet printer) drop-on-demand.

Gouge, M.J.; Fisher, P.W.

1996-04-01

68

Transportable Xenon Laboratory (TXL-1) Operations Manual  

SciTech Connect

The Transportable Xenon Laboratory Operations Manual is a guide to set up and shut down TXL, a fully contained laboratory made up of instruments to identify and measure concentrations of the radioactive isotopes of xenon by taking air samples and analyzing them. The TXL is housed in a standard-sized shipping container. TXL can be shipped to and function in any country in the world.

Thompson, Robert C.; Stewart, Timothy L.; Willett, Jesse A.; Woods, Vincent T.

2011-03-07

69

Measurements of Ambient RadioXenon Levels Using the Automated RadioXenon Sampler/Analyzer.  

SciTech Connect

The Pacific Northwest National Laboratory has developed an Automated Radio-Xenon Sampler/Analyzer for the CTBT to measure radio-xenon isotopes. This system uses a beta-gamma coincidence counting detector to produce two-dimensional plots of gamma energy versus beta energy.

McIntyre, Justin I.; Abel, Keith H.; Hayes, James C.; Heimbigner, Tom R.; Panisko, Mark E.; Reeder, Paul L.; Thompson, Robert C.

2001-06-01

70

Stirring Up an Elastic Fluid: Critical Viscosity of Xenon-2 (CVX-2)  

NASA Technical Reports Server (NTRS)

Whipped cream stays in place even when turned upside down. Yet it readily flows through the nozzle of a spray can to reach the dessert plate. This demonstrates the phenomenon of shear thinning that is important to many industrial and physical processes. Paints, film emulsions, and other complex solutions that are highly viscous under normal conditions but become thin and flow easily under shear forces. A simple fluid, such as water, does not exhibit shear thinning under normal conditions. Very close to the liquid-vapor critical point, where the distinction between liquid and vapor disappears, the fluid becomes more complex and is predicted to display shear thinning. At the critical point, xenon atoms interact over long distances in a classical model of cooperative phenomena. Physicists rely on this system to learn how long-range order arises. The Critical Viscosity of Xenon Experiment (CVX-2) will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Although it does not easily combine with other chemicals, its viscosity at the critical point can be used as a model for a range of fluids. Viscosity originates from the interactions of individual molecules. It is so complicated that, except for the simplest gas, it cannot be calculated accurately from theory. Tests with critical fluids can provide key data, but are limited on Earth because critical fluids are highly compressed by gravity. CVX-2 employs a tiny metal screen vibrating between two electrodes in a bath of critical xenon. The vibrations and how they dampen are used to measure viscosity. CVX flew on STS-85 (1997), where it revealed that, close to the critical point, the xenon is partly elastic: it can 'stretch' as well as flow. For STS-107, the hardware has been enhanced to determine if critical xenon is a shear-thinning fluid.

Berg, Robert F.; Moldover, Michael R.; Zimmerli, Gregory A.; Motil, Susan M. (Technical Monitor)

2002-01-01

71

[To the effective concentration of xenon].  

PubMed

The present literature discusses what effective concentration of xenon may be used to induce adequate anesthesia. To examine the analgesic properties of the substance, 38 patients undergone laparoscopic operations for calculous cholecystitis under informational saturation EEG (INEEG) monitoring were included into this study. All the patients were divided into 3 groups in accordance to the mode of anesthesia maintenance and INEEG monitoring. In Groups 1 and 2, the concentration of xenon was maintained at 70%; INEEG monitoring was made in the of-line mode. In Group 3, the concentration of xenon was gradually decreased from 70% to the minimum value at which the level of INEEG was 40-50%, which corresponds to the adequate depth of anesthesia. The use of 70% xenon concentration and the standard doses offentanyl (3.1 +/- 1.6 microg/kg/h) resulted in excessively deep anesthesia (38 +/- 4% INEEG). Reduction of the dose of fentanyl on an average to 1.5 +/- 0.8 microg/kg/h permitted more adequate anesthesia; however, an excessively deep anesthesia is encountered in 40% of cases, as evidenced by INEEG. The active use of INEEG monitoring in Group 3 makes it possible to perform an adequate anesthesia (46 +/- 4% INEEG) and to determine the xenon concentration necessary for this, which is equivalent to 42 +/- 11% with the dose of fentanyl of 0.9 +/- 0.8 microg/kg/h. PMID:15938090

Kazakov, E A; Subbotin, V V; Likhvantsev, V V; Sitnikov, A V

2005-01-01

72

Xenon migration behaviour in titanium nitride  

NASA Astrophysics Data System (ADS)

Titanium nitride is one of the inert matrixes proposed to surround the fuel in gas cooled fast reactor (GFR) systems. These reactors operate at high temperature and necessitate refractory materials presenting a high chemical stability and good mechanical properties. A total retention of the most volatile fission products, such as Xe, I or Cs, by the inert matrix is needed during the in pile process. The thermal migration of xenon in TiN was studied by implanting 800 keV Xe ++ ions in sintered samples at an ion fluence of 5 10 15 cm -2. Annealing was performed at temperatures ranging from 1673 to 1923 K for 1 and 3 h. Xenon concentration profiles were studied by Rutherford backscattering spectrometry (RBS) using 2.5 MeV ?-particles. The migration behaviour of xenon corresponds to a gas migration model. It is dominated by a surface directed transport with a slight diffusion component. The mean activation energy corresponding to the diffusion component was found to be 2.2 0.3 eV and corresponds to the Brownian motion of xenon bubbles. The directed Xe migration can be interpreted in term of bubble transport using Evans model. This last process is mostly responsible for xenon release from TiN.

Gavarini, S.; Toulhoat, N.; Peaucelle, C.; Martin, P.; Mende, J.; Pipon, Y.; Jaffrezic, H.

2007-05-01

73

Bisphosphine dioxides  

DOEpatents

A process is described for the production of organic bisphosphine dioxides from organic bisphosphonates. The organic bisphosphonate is reacted with a Grignard reagent to give relatively high yields of the organic bisphosphine dioxide.

Moloy, K.G.

1990-02-20

74

Bisphosphine dioxides  

DOEpatents

A process for the production of organic bisphosphine dioxides from organic bisphosphonates. The organic bisphosphonate is reacted with a Grignard reagent to give relatively high yields of the organic bisphosphine dioxide.

Moloy, Kenneth G. (Charleston, WV)

1990-01-01

75

Reflectance of polytetrafluoroethylene for xenon scintillation light  

SciTech Connect

Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet (VUV) wavelength region ({lambda}{approx_equal}175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work, we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived, and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Other fluoropolymers, namely, ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and perfluoro-alkoxyalkane (PFA) were also measured.

Silva, C.; Pinto da Cunha, J.; Pereira, A.; Chepel, V.; Lopes, M. I.; Solovov, V.; Neves, F. [Department of Physics, LIP-Coimbra, University of Coimbra, P-3004 516 Coimbra (Portugal)

2010-03-15

76

Pressurised xenon as scintillator for gamma spectroscopy  

NASA Astrophysics Data System (ADS)

Detectors based on liquid or gas xenon have been used and are in use for a number of applications, in particular for the detection of gamma rays. Xenon is a well-suited medium for gamma spectroscopy thanks to its high atomic number and, consequently, large cross-section for photo-electric absorption. This paper presents experimental studies of high pressure xenon as a scintillator, with the aim of developing a gamma ray detector for the detection of Special Nuclear Materials (SNM). The first goal was to study the dependence of the light yield and of the energy resolution on the thermodynamic conditions. We present preliminary results from an optimised version of the detector.

Resnati, F.

2013-09-01

77

Reflectance of polytetrafluoroethylene for xenon scintillation light  

NASA Astrophysics Data System (ADS)

Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet (VUV) wavelength region (?~=175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work, we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived, and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Other fluoropolymers, namely, ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and perfluoro-alkoxyalkane (PFA) were also measured.

Silva, C.; Pinto da Cunha, J.; Pereira, A.; Chepel, V.; Lopes, M. I.; Solovov, V.; Neves, F.

2010-03-01

78

Quenching of vacuum ultraviolet fluorescence emission from electron beam excited quasi-molecular xenon  

Microsoft Academic Search

A pressure dependent quenching of the VUV broad-band fluorescence (bandwidth 15 nm centred at lambda 173 nm) from high pressure xenon has been measured for pressures from 25 to 215 p.s.i. The experimental results can be explained by collisional de-excitation of the excited Xe2 molecules by Xe atoms. A quenching cross section of ~ 10-17 cm2, and molecular radiative lifetime

D. J. Bradley; M. H. R. Hutchinson; H. Koetser

1973-01-01

79

Photolabile xenon hydrides: A case study of HXeSH and HXeH  

NASA Astrophysics Data System (ADS)

The photo-induced transformations of HXeSH and HXeH under the action of IR and visible light have been studied using FTIR spectroscopy. The xenon hydrides were produced by the X-ray induced decomposition of H2S and its isotopomers in a solid xenon matrix at 7.5 K followed by thermal annealing at the temperatures up to 45 K. Selective IR-induced photodissociation of HXeSH at 3500-2500 cm-1 was attributed to vibrational excitation of the 3?H-Xe mode. The IR-photodecomposed HXeSH molecules can be almost quantitative recovered below 22 K with very small effective activation energy (~20 meV) indicating local character of this process. Analysis of the photoactivity of xenon hydrides in the visible region revealed previously unknown absorptions for HXeSH (in the region of 400-700 nm) and HXeH (above 700 nm). The decomposition of HXeH occurs due to both direct photolysis and reactions of ``hot'' H atoms produced from the photodissociation of HXeSH. The efficiency of thermal recovery for both xenon hydrides after photolysis with visible light was found to be dependent on the excitation wavelength, which was explained by the effect of photon energy on spatial distribution of the dissociation fragments.

Ryazantsev, Sergey V.; Kobzarenko, Alexey V.; Feldman, Vladimir I.

2013-09-01

80

Ion-Molecule Association Reactions Involving NO(+) and H2S, SO2, OCS, SF6, N2O, CO, OR Xe.  

National Technical Information Service (NTIS)

Quantitative measurements have been made of the three-body association rate coefficients for the clustering of hydrogen sulfide, sulfur dioxide, carbonyl sulfide, sulfur hexafluoride, nitrous oxide, carbon monoxide, and xenon to the positive nitric oxide ...

J. A. Vanderhoff M. S. Miller J. M. Heimerl

1976-01-01

81

DFT-MD simulations of shocked Xenon  

NASA Astrophysics Data System (ADS)

Xenon is not only a technologically important element used in laser technologies, jet propulsion and dental anesthesia, but it is also arguably the simplest material in which to study the metal-insulator transition at high pressure. Because of its closed shell electronic configuration, Xenon is often assumed to be chemically inert, interacting almost entirely through the van der Waals interaction, and at liquid density, is typically modeled well using Leonard-Jones potentials. However, such modeling has a limited range of validity as Xenon is known to form compounds at normal conditions and likely exhibits considerably more chemistry at higher densities when hybridization of occupied orbitals becomes significant. In this talk, we present DFT-MD simulations of shocked liquid Xenon with the goal of developing an improved equation of state. The relative importance of the van der Waals interaction compared to other Coulomb interactions is considered, and estimates of the relative accuracy of various density functionals are quantified. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Magyar, Rudolph J.; Mattsson, Thomas R.

2009-03-01

82

Atomistic study of stability of xenon nanoclusters in uranium oxide  

SciTech Connect

Density-functional theory calculations of the xenon incorporation energies in point defects in urania have been done in order to fit empirical potentials. With this set of parameters, we have considered the incorporation of xenon in small and extended defects such as planar interstitials, grain boundaries, faceted, and spherical voids. The results show that xenon atoms are more likely to aggregate than to be homogeneously distributed in the urania grains. SIGMA5 grain boundary and spherical shape voids are the most favorable defects of xenon atom incorporation. The presence of xenon atoms in nanovoids affects their shape. The energy gain to aggregate xenon atoms into clusters saturates for cluster sizes of about 15-20 Schottky defects. This demonstrates that medium size defects are just as favorable as big size defects for xenon incorporation.

Chartier, A.; Van Brutzel, L. [DEN, Service de Chimie Physique, CEA, F-91191 Gif-sur-Yvette (France); Freyss, M. [DEN, Service d'Etudes et de Simulation du Comportement des Combustibles, CEA, F-13108 Saint-Paul lez Durance (France)

2010-05-01

83

Anticipatory control of xenon in a pressurized water reactor  

SciTech Connect

A method is described for automatically dampening xenon-135 spatial transients in the core of a pressurized water reactor having control rods which regulate reactor power level, comprising the steps of: measuring the neutron flu in the reactor core at a plurality of axially spaced locations on a real-time, on-line basis; repetitively generating from the neutron flux measurements, on a point-by-point basis, signals representative of the current axial distribution of xenon-135, and signals representative of the current rate of change of the axial distribution of xenon-135; generating from the xenon-135 distribution signals and the rate of change of xenon distribution signals, control signals for reducing the xenon transients; and positioning the control rods as a function of the control signals to dampen the xenon-135 spatial transients.

Impink, A.J. Jr.

1987-02-10

84

An automated multidimensional preparative gas chromatographic system for isolation and enrichment of trace amounts of xenon from ambient air.  

PubMed

The monitoring of radioactive xenon isotopes is one of the principal methods for the detection of nuclear explosions in order to identify clandestine nuclear testing. In this work, a miniaturized, multiple-oven, six-column, preparative gas chromatograph was constructed in order to isolate trace quantities of radioactive xenon isotopes from ambient air, utilizing nitrogen as the carrier gas. The multidimensional chromatograph comprised preparative stainless steel columns packed with molecular sieves, activated carbon, and synthetic carbon adsorbents (e.g., Anasorb-747 and Carbosphere). A combination of purification techniques--ambient adsorption, thermal desorption, back-flushing, thermal focusing, and heart cutting--was selectively optimized to produce a well-defined xenon peak that facilitated reproducible heart cutting and accurate quantification. The chromatographic purification of a sample requires approximately 4 h and provides complete separation of xenon from potentially interfering components (such as water vapor, methane, carbon dioxide, and radon) with recovery and accuracy close to 100%. The preparative enrichment process isolates and concentrates a highly purified xenon gas fraction that is suitable for subsequent ultra-low-level ?-, /?-spectroscopic or high-resolution mass spectrometric measurement (e.g., to monitor the gaseous fission products of nuclear explosions at remote locations). The Xenon Processing Unit is a free-standing, relatively lightweight, and transportable system that can be interfaced to a variety of sampling and detection systems. It has a relatively inexpensive, rugged, and compact modular (19-inch rack) design that provides easy access to all parts for maintenance and has a low power requirement. PMID:21347675

Larson, Tuula; stman, Conny; Colmsj, Anders

2011-04-01

85

Preliminary Measurements of the Xenon Triple Point  

NASA Astrophysics Data System (ADS)

Ever since the construction and definition of the highly successful International Temperature Scale of 1990 (ITS-90), one severe deficiency of the scale has been recognized, without a reliable remedy. The problem is the fact that the only then available high-quality fixed point between the argon triple point and the water triple point was the mercury triple point, which unfortunately is situated rather closely to the water triple point, thus having an extremely strong influence on the interpolation function of SPRTs in the Ar{-}H2O range. Already before 1990, measurements on possible fixed points better placed in this temperature range have been investigated, such as the triple points of krypton and xenon. However, results have been rather elusive, mainly regarding the rather large melting range of their transition. A turning point was the 2005 paper from the National Research Council (NRC, Canada), where it was established that the relatively high content of krypton was the culprit for the large melting range of the xenon transitions published previously. Indeed, measurements on a xenon sample with very low krypton content produced a very high-quality plateau, of the same level as other ITS-90 fixed points. However, no follow-up measurements have been reported, and thus neither have comparison measurements been reported. Shortly, after the appearance of the NRC paper, Istituto Nazionale di Ricerca Metrologica (INRIM, Italy) acquired a batch of the same high-purity xenon as used by NRC with the aim of preparing a few sealed cells with it and trying to reproduce the NRC results. However, with the start of the Neon Project (Euromet Project 770), the realization of these intentions had to be postponed until now. Last December, three cells of different design have been filled with this high-quality xenon and preliminary results of the measurements on the triple point are reported.

Steur, P. P. M.; Giraudi, D.

2014-04-01

86

Soil meso- and microporosity studied by 129Xe nmr spectroscopy of adsorbed xenon  

NASA Astrophysics Data System (ADS)

The pore structure of soil significantly affects its density and the transport of water, air, nutrients and pollutants through the soil. Micropores (< 2 nm) play a special role in sorption processes, since most of the soil surface area is located in such pores. Meso- and macropores (2 - 50 nm and >50 nm, respectively) act as a transport system, the former pores provide an access to micropores. Despite of significant progress in evaluating soil porosity by the use of electron microscopy, mercury intrusion porosimetry and standard adsorption methods, many aspects still need further examination. In the present contribution, 129Xe NMR spectroscopy of adsorbed xenon was applied for the first time for the characterisation of soil meso- and microporosity. Soils with different texture were studied. The impact of organic matter on the porosity of the mineral phase was analysed. Also, we examined the influence of paramagnetic soil constituents on the 129Xe resonance parameters. The study of the model system, Ca-montmorillonite, demonstrated that quantitative information about pore sizes in soil related materials can be provided, if the impact of paramagnetic species is avoided. In natural soils, the pores within the mineral phase can be analysed for relatively large particles (>20-50 m), where the 129Xe resonance parameters are not affected by xenon exchange between intra- and interparticle void spaces. In contrast, for the clay-sized fractions the combined internal - external pore system is probed. The presence of micropores (< 2 nm) can always be inferred from the observed 129Xe downfield shifts increasing with xenon pressure. In contrast, spectral lines close to the xenon gas line position suggest adsorption in large interparticle pores. In the studied soils (Luvisol, Gleysol and Podzol) no micropores within the mineral phase available for xenon adsorption were found. The possible reason is that such pores are occupied by small molecules of the soil organic matter. When xenon exchange between different adsorption zones (e.g., pores of differing size) was slow on an NMR time scale, separate signals were distinguished, each characterising xenon behaviour in the respective adsorption zone. Variable extent of accessibility of mesopores within the mineral phase of the various soils has been revealed. In Podzol it was shown to be higher than in other soils studied. A model for the possible mutual location of organic matter and iron species in natural soils is suggested. Complementary studies using standard adsorption methods were performed and they showed a good coincidence with the 129Xe NMR results.

Filimonova, S.; Knicker, H.; Husler, W.; Kgel-Knabner, I.

2003-04-01

87

BRIEF COMMUNICATIONS: Investigation of the gain and emission spectrum of a TE laser utilizing a mixture of isotopically substituted carbon dioxide molecules  

Microsoft Academic Search

The results are presented of theoretical and experimental investigations of the gain and emission spectrum of a TE laser utilizing a mixture of isotopically substituted 12CO2 and 13CO2 molecules. It was found that, in a wide range of active-medium pressures (p = 100-3500 Torr) and excitation levels (T3 = 1200-2400 K), a gas mixture such the concentration of 13CO2 (x13)

V. O. Petukhov; N. N. Sazhina; V. S. Starovoitov; S. A. Trushin; N. V. Cheburkin; S. K. Chekin; V. V. Churakov

1985-01-01

88

The breast feeding mother and xenon anaesthesia: four case reports. Breast feeding and xenon anaesthesia  

PubMed Central

Background Four nursing mothers consented to anaesthesia for urgent surgery only on condition that their ability to breast feed would not be impaired. Methods Following induction of general anaesthesia with propofol and remifentanil, 65-69% xenon supplemented with remifentanil was used as an inhalational anaesthetic for maintenance. Results After finishing surgery the women could be extubated between 2:52 and 7:22 minutes. The women were fully alert just minutes after extubation and spent about 45 minutes in the recovery room before discharge to a regular ward. They resumed regular breast feeding some time later. The propofol concentration in the blood was measured after 0, 30, 90, and 300 minutes and in the milk after 90 and 300 minutes. Just 90 minutes after extubation, the concentration of propofol in the milk was limited (> 3 mg/l) so that pharmacological effects on the babies were excluded after oral intake. Also, no traces of xenon gas were found in the maternal milk at any time. After propofol induction and maintenance of anaesthesia with xenon in combination with a water-soluble short-acting drug like remifentanil, the concentration of propofol in maternal milk is low (> 3 mg/l 90 min after anesthesia) and harmless after oral intake. Conclusions These results, as well as the rapid elimination and absence of metabolism of xenon, are of great interest to nursing mothers. General anaesthesia with propofol for induction only, combined with remifentanil and xenon for maintenance, has not yet been described in breast feeding mothers.

2010-01-01

89

The Large Underground Xenon (LUX) experiment  

NASA Astrophysics Data System (ADS)

The Large Underground Xenon (LUX) collaboration has designed and constructed a dual-phase xenon detector, in order to conduct a search for Weakly Interacting Massive Particles (WIMPs), a leading dark matter candidate. The goal of the LUX detector is to clearly detect (or exclude) WIMPS with a spin independent cross-section per nucleon of 210-46 cm2, equivalent to 1 event/100 kg/month in the inner 100-kg fiducial volume (FV) of the 370-kg detector. The overall background goals are set to have <1 background events characterized as possible WIMPs in the FV in 300 days of running. This paper describes the design and construction of the LUX detector.

Akerib, D. S.; Bai, X.; Bedikian, S.; Bernard, E.; Bernstein, A.; Bolozdynya, A.; Bradley, A.; Byram, D.; Cahn, S. B.; Camp, C.; Carmona-Benitez, M. C.; Carr, D.; Chapman, J. J.; Chiller, A.; Chiller, C.; Clark, K.; Classen, T.; Coffey, T.; Curioni, A.; Dahl, E.; Dazeley, S.; de Viveiros, L.; Dobi, A.; Dragowsky, E.; Druszkiewicz, E.; Edwards, B.; Faham, C. H.; Fiorucci, S.; Gaitskell, R. J.; Gibson, K. R.; Gilchriese, M.; Hall, C.; Hanhardt, M.; Holbrook, B.; Ihm, M.; Jacobsen, R. G.; Kastens, L.; Kazkaz, K.; Knoche, R.; Kyre, S.; Kwong, J.; Lander, R.; Larsen, N. A.; Lee, C.; Leonard, D. S.; Lesko, K. T.; Lindote, A.; Lopes, M. I.; Lyashenko, A.; Malling, D. C.; Mannino, R.; Marquez, Z.; McKinsey, D. N.; Mei, D.-M.; Mock, J.; Moongweluwan, M.; Morii, M.; Nelson, H.; Neves, F.; Nikkel, J. A.; Pangilinan, M.; Parker, P. D.; Pease, E. K.; Pech, K.; Phelps, P.; Rodionov, A.; Roberts, P.; Shei, A.; Shutt, T.; Silva, C.; Skulski, W.; Solovov, V. N.; Sofka, C. J.; Sorensen, P.; Spaans, J.; Stiegler, T.; Stolp, D.; Svoboda, R.; Sweany, M.; Szydagis, M.; Taylor, D.; Thomson, J.; Tripathi, M.; Uvarov, S.; Verbus, J. R.; Walsh, N.; Webb, R.; White, D.; White, J. T.; Whitis, T. J.; Wlasenko, M.; Wolfs, F. L. H.; Woods, M.; Zhang, C.

2013-03-01

90

A liquid xenon development and test system  

NASA Astrophysics Data System (ADS)

Large liquid xenon detectors became rather popular in the last years, especially for Dark Matter searches. However, each new experiment or application presents its own specifications and requirements which first have to be explored with a small set up. Although much cheaper and easier to operate, a small liquid xenon system is nearly as complex as a large one. A small test set up is described as platform for such preliminary tests. The set up was thoroughly tested during the last two years of operation, and there are four identical systems running in different labs. The design is intended to be versatile and can be used as basis for similar instruments, whereas a complete new design would still cost several months of design, acquisition of parts, construction, assembly, and testing.

Giboni, K. L.; Ji, X.; Lin, H.; Tan, A.; Ye, T.; Zhang, Y.; Zhao, L.

2014-04-01

91

Port and harbor patrol car loaded Xenon search light  

NASA Astrophysics Data System (ADS)

The container ship yard is brighten by the lighting, but after Sunset of the sea side is dark during a crescent. On the sea side lighting, we propose to use to patrol car loaded Xenon search light. Generally, the Pacific Ocean of a surface of the sea swimming fishes such as Samma (Mackerel pike) likes strong visible light as a Xenon search light beam. In the feeling of the human eyes and brains with a strong visible light beam such as Xenon search light, the reaction is divided two kind of types, to avoid reaction's humans have a feeling that bad conscience, and no reaction's humans tend to have a feeling of good mind. For the black painted unmanned objects of visible watching is needed as possible as strong visible light beam of the Xenon search light. The optical system of the Xenon search light consists of a Xenon lamp, a parabolic mirror and the filters.

Amoh, Hiroshi; Takenami, Takashi

2005-05-01

92

Optimization of Xenon Biosensors for Detection of ProteinInteractions  

SciTech Connect

Hyperpolarized 129Xe NMR can detect the presence of specific low-concentration biomolecular analytes by means of the xenon biosensor, which consists of a water-soluble, targeted cryptophane-A cage that encapsulates xenon. In this work we use the prototypical biotinylated xenon biosensor to determine the relationship between the molecular composition of the xenon biosensor and the characteristics of protein-bound resonances. The effects of diastereomer overlap, dipole-dipole coupling, chemical shift anisotropy, xenon exchange, and biosensor conformational exchange on protein-bound biosensor signal were assessed. It was found that optimal protein-bound biosensor signal can be obtained by minimizing the number of biosensor diastereomers and using a flexible linker of appropriate length. Both the linewidth and sensitivity of chemical shift to protein binding of the xenon biosensor were found to be inversely proportional to linker length.

Lowery, Thomas J.; Garcia, Sandra; Chavez, Lana; Ruiz, E.Janette; Wu, Tom; Brotin, Thierry; Dutasta, Jean-Pierre; King, David S.; Schultz, Peter G.; Pines, Alex; Wemmer, David E..

2005-08-03

93

Two-color multiphoton ionization of xenon  

SciTech Connect

Two independently tunable, linearly polarized dye lasers have been used to study multiphoton ionization of gaseous xenon. One laser is tuned near three-photon resonance with the allowed 6s(3/2)/sup degree//sub J/ = 1 resonance, which is not observed with one laser at these pressures because of the destructive interference between the three-photon-excitation and third-harmonic-excitation pathways to the 6s(3/2)/sup degree//sub J/ = 1 state. The second laser is tuned to resonance with higher allowed np and np' sstates of xenon. The missing ionization signal is seen to be dramatically restored by the addition of the second laser beam; however, the signal again disappears as the pressure is increased. These results are discussed in relation to recent experimental and theoretical studies of cancellation effects between three-photon excitation and third-harmonic generation. Spectroscopic information obtained from tuning each dye laser, together with data on the angular distributions resulting from rotating the plane of polarization of one laser relative to that of the second laser, clearly shows that two different ionization mechanisms are operative. In addition, these experiments unambiguously illustrate the importancce of dissociative ionization of quasi-dimers of xenon over a rather broad frequency range.

Compton, R.N.; Miller, J.C.

1985-02-01

94

High-power atomic xenon laser  

NASA Astrophysics Data System (ADS)

The high pressure atomic xenon laser is becoming the most promising light source in the wavelength region of a few microns. The merits are high efficiency (so far up to 8 percent), high output energies (15 J/liter at 9 bar), high continuous output power (more than 200 W/liter), no gas dissociation and thermal heating of the lower laser level. Compared with the well-known low pressure xenon laser the power performance is now roughly a factor thousand higher. The operation of the system, based on three-body-collisions, uses the metastable state of the xenon atom as the ground state so that in the recirculation of energy a high quantum efficiency is obtained. Furthermore the homogeneous line broadening caused by the high collision frequency has also a strong beneficial effect on the efficiency. However, the required intense homogeneous excitation of the gas medium at high density is from a technical point of view a great challenge. From our experimental and theoretical work we found that at optimum performance the input power must be 1 to 2.5 [KW cm-3 atm-2]. We describe our results obtained with e-beam sustained and x-ray preionized systems delivering pulsed energies in the range of joules per liter. Furthermore we describe our recent results on continuous RF excited wave guide systems of about 37 cm length with output powers in the range of watts.

Witteman, Wilhelmus J.; Peters, Peter J.; Botma, Hako; Tskhai, S. N.; Udalov, Yu. B.; Mei, Qi-Chu; Ochkin, V. N.

1995-03-01

95

Formation of clusters composed of C60 molecules via self-assembly in critical fluids  

NASA Astrophysics Data System (ADS)

Fullerenes are promising candidates for intelligent, functional nanomaterials because of their unique mechanical, electronic and chemical properties. However, it is necessary to invent some efficient but relatively simple methods of producing structures composed of fullerenes for the development of nanomechatronic, nanoelectronic and biochemical devices and sensors. In this paper, we show that various structures such as straight fibres, networks formed by fibres, wide sheets and helical structures, which are composed of C60 molecules, are created by placing C60-crystals in critical ethane, carbon dioxide and xenon even though C60 molecules do not dissolve or disperse in the above fluids. It is supposed, judging by the intermolecular potentials between C60 and C60, between C60 and ethane, and between ethane and ethane, that C60-clusters grow with the assistance of solvent molecules, which are trapped between C60 molecules under critical conditions. This room-temperature self-assembly cluster growth process in critical fluids may open up a new methodology of forming structures built up with fullerenes without the need for any ultra-fine processing technologies.

Fukuda, Takahiro; Ishii, Koji; Kurosu, Shunji; Whitby, Raymond; Maekawa, Toru

2007-04-01

96

Recovering Residual Xenon Propellant for an Ion Propulsion System  

NASA Technical Reports Server (NTRS)

Future nuclear-powered Ion-Propulsion- System-propelled spacecraft such as Jupiter Icy Moon Orbiter (JIMO) will carry more than 10,000 kg of xenon propellant. Typically, a small percentage of this propellant cannot be used towards the end of the mission because of the pressure drop requirements for maintaining flow. For large missions such as JIMO, this could easily translate to over 250 kg of unusable xenon. A proposed system, the Xenon Recovery System (XRS), for recovering almost all of the xenon remaining in the tank, would include a cryopump in the form of a condenser/evaporator that would be alternatively cooled by a radiator, then heated electrically. When the pressure of the xenon in the tank falls below 0.7 MPa (100 psia), the previously isolated XRS will be brought online and the gas from the tank would enter the cryopump that is initially cooled to a temperature below saturation temperature of xenon. This causes xenon liquefaction and further cryopumping from the tank till the cryopump is full of liquid xenon. At this point, the cryopump is heated electrically by small heaters (70 to 80 W) to evaporate the liquid that is collected as high-pressure gas (<7 MPa; 1,000 psia) in an intermediate accumulator. Check valves between the tank and the XRS prevent the reverse flow of xenon during the heating cycle. The accumulator serves as the high-pressure source of xenon gas to the Xenon Feed System (XFS) downstream of the XRS. This cycle is repeated till almost all the xenon is recovered. Currently, this system is being baselined for JIMO.

Ganapathi, Gani; Skakkottai, P.; wu, Jiunn Jeng

2006-01-01

97

Liquid xenon detectors for particle physics and astrophysics  

NASA Astrophysics Data System (ADS)

This article reviews the progress made over the last 20years in the development and applications of liquid xenon detectors in particle physics, astrophysics, and medical imaging experiments. A summary of the fundamental properties of liquid xenon as radiation detection medium, in light of the most current theoretical and experimental information is first provided. After an introduction of the different type of liquid xenon detectors, a review of past, current, and future experiments using liquid xenon to search for rare processes and to image radiation in space and in medicine is given. Each application is introduced with a survey of the underlying scientific motivation and experimental requirements before reviewing the basic characteristics and expected performance of each experiment. Within this decade it appears likely that large volume liquid xenon detectors operated in different modes will contribute to answering some of the most fundamental questions in particle physics, astrophysics, and cosmology, fulfilling the most demanding detection challenges. From detectors based solely on liquid xenon (LXe) scintillation, such as in the MEG experiment for the search of the rare ??e? decay, currently the largest liquid xenon detector in operation, and in the XMASS experiment for dark matter detection, to the class of time projection chambers which exploit both scintillation and ionization of LXe, such as in the XENON dark matter search experiment and in the Enriched Xenon Observatory for neutrinoless double beta decay, unrivaled performance and important contributions to physics in the next few years are anticipated.

Aprile, E.; Doke, T.

2010-07-01

98

Liquid xenon detectors for particle physics and astrophysics  

SciTech Connect

This article reviews the progress made over the last 20 years in the development and applications of liquid xenon detectors in particle physics, astrophysics, and medical imaging experiments. A summary of the fundamental properties of liquid xenon as radiation detection medium, in light of the most current theoretical and experimental information is first provided. After an introduction of the different type of liquid xenon detectors, a review of past, current, and future experiments using liquid xenon to search for rare processes and to image radiation in space and in medicine is given. Each application is introduced with a survey of the underlying scientific motivation and experimental requirements before reviewing the basic characteristics and expected performance of each experiment. Within this decade it appears likely that large volume liquid xenon detectors operated in different modes will contribute to answering some of the most fundamental questions in particle physics, astrophysics, and cosmology, fulfilling the most demanding detection challenges. From detectors based solely on liquid xenon (LXe) scintillation, such as in the MEG experiment for the search of the rare ''{mu}{yields}e{gamma}'' decay, currently the largest liquid xenon detector in operation, and in the XMASS experiment for dark matter detection, to the class of time projection chambers which exploit both scintillation and ionization of LXe, such as in the XENON dark matter search experiment and in the Enriched Xenon Observatory for neutrinoless double beta decay, unrivaled performance and important contributions to physics in the next few years are anticipated.

Aprile, E.; Doke, T. [Department of Physics, Columbia University, New York, New York 10027 (United States); Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan)

2010-07-15

99

Magnetic resonance imaging of convection in laser-polarized xenon  

NASA Technical Reports Server (NTRS)

We demonstrate nuclear magnetic resonance (NMR) imaging of the flow and diffusion of laser-polarized xenon (129Xe) gas undergoing convection above evaporating laser-polarized liquid xenon. The large xenon NMR signal provided by the laser-polarization technique allows more rapid imaging than one can achieve with thermally polarized gas-liquid systems, permitting shorter time-scale events such as rapid gas flow and gas-liquid dynamics to be observed. Two-dimensional velocity-encoded imaging shows convective gas flow above the evaporating liquid xenon, and also permits the measurement of enhanced gas diffusion near regions of large velocity variation.

Mair, R. W.; Tseng, C. H.; Wong, G. P.; Cory, D. G.; Walsworth, R. L.

2000-01-01

100

High-Rydberg Xenon Submillimeter-Wave Detector  

NASA Technical Reports Server (NTRS)

Proposed detector for infrared and submillimeter-wavelength radiation uses excited xenon atoms as Rydberg sensors instead of customary beams of sodium, potassium, or cesium. Chemically inert xenon easily stored in pressurized containers, whereas beams of dangerously reactive alkali metals must be generated in cumbersome, unreliable ovens. Xenon-based detector potential for infrared astronomy and for Earth-orbiter detection of terrestrial radiation sources. Xenon atoms excited to high energy states in two stages. Doubly excited atoms sensitive to photons in submillimeter wavelength range, further excited by these photons, then ionized and counted.

Chutjian, Ara

1987-01-01

101

A photochemical answer to the 'xenon paradox'  

NASA Astrophysics Data System (ADS)

Xenon is depleted by one order of magnitude relative to other volatile elements when normalized to the chondritic composition. Furthermore, atmospheric xenon is far more enriched in the heavy isotopes relatively to chondritic and solar compositions (3-4%.amu-1) than atmospheric krypton (< 1%.amu-1). This discrepancy, known as the 'xenon paradox', has led to sophisticated models of atmospheric evolution coupled with mantle geodynamics (Pepin, 1991; Tolstikhin and Marty, 1998) and cometary contributions (Dauphas, 2003; Owen et al., 1992) that could explain terrestrial noble gas patterns under ad hoc conditions during the building stages of the Earth, no more than ~200 Ma following the beginning of solar system formation. Yet, xenon having an isotopic composition intermediate between the atmospheric and the chondritic ones has been recently documented in Archean (?3 Ga-old) sedimentary rocks (Pujol et al., 2011), suggesting that isotopic fractionation of Xe occurred over a much longer period of time than previously thought, during the Hadean and the Archean eons. In that case, assuming a Rayleigh type isotope evolution for atmospheric Xe requires an enrichment fractionation factor of 1.3% in heavy isotopes for Xe remaining in the atmosphere. This is clearly within the range of values observed in laboratory experiments aimed at trapping and fractionating Xe isotopes in solids, which is only effective upon ionization (Marrocchi et al., 2011; Kuga et al., 2012). We report here a possibility for explaining the 'xenon paradox' through interaction of the Hadean/Archean atmosphere with EUV light from the young Sun. By using a new photochemical model, we have found out that atmospheric Xe depletion and enrichment in heavy Xe isotopes could be achieved by EUV photoionization deep enough in the atmosphere to allow the preferential implantation of the heavier Xe isotopes in organic aerosols, the formation of which is itself triggered by UV photochemistry. Most of the ionized Xe would have escaped from the atmosphere into space by hydrodynamic escape (Zahnle, 2011). We have established that this mechanism specifically affected Xe and was particularly effective during the Hadean/Archean times, since the irradiation flux was expected to be orders of magnitude higher than today (Ribas et al., 2010). Dauphas (2003), Icarus 165, 326-339. Kuga et al. (2012), #2347 Goldschmidt 2012 Marrocchi et al. (2011), GCA 75, 6255-6266. Owen et al. (1992), Nature 358, 43-46. Pepin (1991), Icarus 92, 1-79. Pujol et al. (2011), Earth Planet. Sci. Lett. 308, 298-306. Ribas et al. (2010), Astrophys. J. 714, 384-395. Srinivasan, (1976), Earth Planet. Sci. Lett. 31, 129-141. Tolstikhin and Marty (1998), Chem. Geol. 147, 27-52. Zahnle (2011), #2241 Goldschmidt 2011

Hbrard; Marty, B.

2012-12-01

102

Method for the simultaneous preparation of Radon-211, Xenon-125, Xenon-123, Astatine-211, Iodine-125 and Iodine-123  

DOEpatents

A method for simultaneously preparing Radon-211, Astatine-211, Xenon-125, Xenon-123, Iodine-125 and Iodine-123 in a process that includes irradiating a fertile metal material then using a one-step chemical procedure to collect a first mixture of about equal amounts of Radon-211 and Xenon-125, and a separate second mixture of about equal amounts of Iodine-123 and Astatine-211.

Mirzadeh, Saed (East Setauket, NY); Lambrecht, Richard M. (Quogue, NY)

1987-01-01

103

Evidence of charge exchange pumping in calcium-xenon system  

NASA Technical Reports Server (NTRS)

Presented evidence shows that charge exchanges between xenon ions and calcium atoms may produce an inversion between 5s or 4d and 4p energy levels of calcium ions. The dependence of measured intensity ratios on power input to the xenon plasma indicates that charge exchange pumping of the 5s and 4d levels predominates over electron collisional pumping of these levels.

Chubb, D. L.

1973-01-01

104

Parameters in a dynamically compressed xenon plasma laser  

Microsoft Academic Search

Laser action from triply ionized xenon has been found to occur during the dynamical contraction of the xenon plasma column. Laser lines between the near ultraviolet and the orange portion of the spectrum have been detected. Their peak powers, time of occurrence, duration, wavelength, and coherence length have been measured. Optimum currents and pressures have been found and compared with

A. Papayoanou; R. G. Buser; I. M. Gumeiner

1973-01-01

105

Distillation purification and radon assay of liquid xenon  

SciTech Connect

We succeeded to reduce the Kr contamination in liquid xenon by a factor of 1/1000 with a distillation system in Kamioka mine. Then, the remaining radioactivities (Radon and Kr) in purified liquid xenon were measured with the XMASS prototype detector. In this talk, the distillation system and the remaining internal radioactivity levels are reported.

Takeuchi, Yasuo [Kamioka Observatory, ICRR, Univ. of Tokyo, Kamioka-cho, Hida-shi, Gifu 506-1205 (Japan)

2005-09-08

106

Xenon-Ion Drilling of Tungsten Films  

NASA Technical Reports Server (NTRS)

High-velocity xenon ions used to drill holes of controlled size and distribution through tungsten layer that sheaths surface of controlled-porosity dispenser cathode of traveling wave-tube electron emitter. Controlled-porosity dispenser cathode employs barium/calcium/ aluminum oxide mixture that migrates through pores in cathode surface, thus coating it and reducing its work function. Rapid, precise drilling technique applied to films of other metals and used in other applications where micron-scale holes required. Method requires only few hours, as opposed to tens of hours by prior methods.

Garner, C. E.

1986-01-01

107

Evidence of charge exchange pumping in calcium-xenon system  

NASA Technical Reports Server (NTRS)

Charge exchange between xenon ions and calcium atoms may produce an inversion between the 5s or 4d and 4p energy levels of the calcium ions. A low power flowing xenon plasma seeded with calcium was utilized to determine if charge exchange or electron collisions populate the 5s and 4d levels Ca(+). Line intensity ratios proportional to the density ratios n5s/n4p and n4d/n4p were measured. From the dependence of these intensity ratios on power input to the xenon plasma it was concluded that charge exchange pumping of the 5s and 4d levels predominates over electron collisional pumping of these levels. Also, by comparing intensity ratios obtained using argon and krypton in place of xenon with those obtained in xenon the same conclusion was made.

Chubb, D. L.

1973-01-01

108

Xenon ion propulsion for orbit transfer  

NASA Technical Reports Server (NTRS)

For more than 30 years, NASA has conducted an ion propulsion program which has resulted in several experimental space flight demonstrations and the development of many supporting technologies. Technologies appropriate for geosynchronous stationkeeping, earth-orbit transfer missions, and interplanetary missions are defined and evaluated. The status of critical ion propulsion system elements is reviewed. Electron bombardment ion thrusters for primary propulsion have evolved to operate on xenon in the 5 to 10 kW power range. Thruster efficiencies of 0.7 and specific impulse values of 4000 s were documented. The baseline thruster currently under development by NASA LeRC includes ring-cusp magnetic field plasma containment and dished two-grid ion optics. Based on past experience and demonstrated simplifications, power processors for these thrusters should have approximately 500 parts, a mass of 40 kg, and an efficiency near 0.94. Thrust vector control, via individual thruster gimbals, is a mature technology. High pressure, gaseous xenon propellant storage and control schemes, using flight qualified hardware, result in propellant tankage fractions between 0.1 and 0.2. In-space and ground integration testing has demonstrated that ion propulsion systems can be successfully integrated with their host spacecraft. Ion propulsion system technologies are mature and can significantly enhance and/or enable a variety of missions in the nation's space propulsion program.

Rawlin, V. K.; Patterson, M. J.; Gruber, R. P.

1990-01-01

109

METEORITIC KRYPTON AND BARIUM VERSUS THE GENERAL ISOTOPIC ANOMALIES IN METEORITIC XENON  

Microsoft Academic Search

General isotopic anomalies in meteoritic xenon are described in detail. ; Where superior isotopic analyses exist, the xenon anomalies appear to be the same ; for all meteorites. In other cases there is fair evidence that the xenon ; examined is a mixture of meteoritic and contaminating atmospheric xenon. Two ; superior krypton analyses for carbonaceous chondrites show no anomalies

D. Krummenacher; C. M. Merrihue; R. O. Pepin; J. H. Reynolds

1962-01-01

110

Improvement of optical diagnostic methods for a xenon operating thruster plasma  

Microsoft Academic Search

Improvement of contemporary plasma optical diagnostic technique for xenon Hall effect based thrusters is considered. This improvement has become possible after critical revision of collisional radiative model for the thruster plasma. In particular, three important processes have been included into the collisional radiative model: excitation of the xenon emissions in collisions between xenon ions and atoms; step-wise excitation of xenon

Georgy Karabadzhak

2004-01-01

111

PIXeY - Liquid Xenon R&D at Yale  

NASA Astrophysics Data System (ADS)

In recent years xenon has risen as a medium for particle detection, exhibiting a number of desirable qualities that make it well-suited for applications such as medical imaging, imaging of nuclear materials, and fundamental physics research. Xenon is a bright scintillator, with a fast (45 ns) response time, a large charge yield and high electron mobility. The high density (3 g/mL) and high atomic number (Z = 54) of liquid xenon make it ideal for detecting gamma rays with high efficiency over large energy ranges. PIXeY (Particle Identification in Xenon at Yale) is a compact, liquid-xenon-based TPC that operates in either single or two-phase (liquid/gas) mode and detects both charge and light signals produced by particle interactions within the detector. The initial goal of the experiment is to study xenon physics with implications for the operation and design for future large scale experiments (for dark matter or double beta decay), including energy resolution and event discrimination. This presentation will provide an overview of the experiment and discuss the xenon physics studies planned, the results so far and a brief overview of future plans.

Edwards, Blair; Bernard, Ethan; Cahn, Sidney; Larsen, Nicole; Lyashenko, Alexey; McKinsey, Daniel; Nikkel, James; Shin, Yunchang; Tennyson, Brian; Wahl, Christopher; Destefano, Nicholas; Gai, Moshe

2013-04-01

112

The XENON1T Dark Matter Search Experiment  

NASA Astrophysics Data System (ADS)

The worldwide race towards direct dark matter detection in the form of WIMPs has been dramatically accelerated by the remarkable progress and evolution of liquid xenon time projection chambers (LXeTPCs). With a realistic discovery potential, XENON100 has already reached a sensitivity of 7E-45 cm^2, and continues to accrue data at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy towards its ultimate sensitivity reach at the 2E-45 cm^2 level for the spin-independent WIMP-nucleon cross-section. To fully explore the favored parameter space for WIMP dark matter in search of a first robust and statistically significant discovery, or to confirm any hint of a signal from XENON100, the next phase of the XENON program will be a detector at the ton scale - XENON1T. The XENON1T detector, based on 2.2 ton of LXe viewed by low radioactivity photomultiplier tubes and housed in a water Cherenkov muon veto at LNGS, is presented. The detector design is advancing and construction of major systems will begin in 2012, with data taking beginning in 2015. Capable of probing WIMP interaction cross-sections to 2E-47cm^2 within 2 years of operation, XENON1T will provide the sensitivity to probe a particularly favorable region of electroweak physics.

Ghag, Chamkaur

2012-03-01

113

Thermal Conductivity Measurement of Xe-Implanted Uranium Dioxide Thick Films using Multilayer Laser Flash Analysis  

SciTech Connect

The Fuel Cycle Research and Development program's Advanced Fuels campaign is currently pursuing use of ion beam assisted deposition to produce uranium dioxide thick films containing xenon in various morphologies. To date, this technique has provided materials of interest for validation of predictive fuel performance codes and to provide insight into the behavior of xenon and other fission gasses under extreme conditions. In addition to the structural data provided by such thick films, it may be possible to couple these materials with multilayer laser flash analysis in order to measure the impact of xenon on thermal transport in uranium dioxide. A number of substrate materials (single crystal silicon carbide, molybdenum, and quartz) containing uranium dioxide films ranging from one to eight microns in thickness were evaluated using multilayer laser flash analysis in order to provide recommendations on the most promising substrates and geometries for further investigation. In general, the uranium dioxide films grown to date using ion beam assisted deposition were all found too thin for accurate measurement. Of the substrates tested, molybdenum performed the best and looks to be the best candidate for further development. Results obtained within this study suggest that the technique does possess the necessary resolution for measurement of uranium dioxide thick films, provided the films are grown in excess of fifty microns. This requirement is congruent with the material needs when viewed from a fundamental standpoint, as this length scale of material is required to adequately sample grain boundaries and possible second phases present in ceramic nuclear fuel.

Nelson, Andrew T. [Los Alamos National Laboratory

2012-08-30

114

Carbon dioxide  

NSDL National Science Digital Library

Bubbles are an indicator of a chemical reaction. An indicator is an object, material, or organism that tells you if a specific substance is present. In the sugar test, carbon dioxide gas release is an indicator that yeast is using sugar to grow. The more gas produced, the more sugar a specific substance contains.

Arie Melamed-Katz (None;)

2007-06-19

115

Cryopumping system for tests of xenon ion thrusters  

SciTech Connect

A cryopumping system suitable for testing xenon ion thrusters was designed and tested. The aimed temperature of a CP (cryopanel) was below 50 K, since the vapor pressure of xenon was low enough at the temperature. The system-alone-tests showed the attained temperature of the CP was below 50 K and the CP could evacuate xenon with a pumping speed of over 600,000 l/s. But while an ion thruster was operating, the speed fell to 40,000 l/s and a continuous operational time was restricted to about 90 minutes.

Hayakawa, Y.; Kitamura, S.; Nakamura, Y.; Miyazaki, K.; Obama, T.

1987-01-01

116

Analysis of the XENON100 dark matter search data  

NASA Astrophysics Data System (ADS)

The XENON100 experiment, situated in the Laboratori Nazionali del Gran Sasso, aims at the direct detection of dark matter in the form of weakly interacting massive particles (WIMPs), based on their interactions with xenon nuclei in an ultra low background dual-phase time projection chamber. This paper describes the general methods developed for the analysis of the XENON100 data. These methods have been used in the 100.9 and 224.6 live days science runs from which results on spin-independent elastic, spin-dependent elastic and inelastic WIMP-nucleon cross-sections have already been reported.

Aprile, E.; Alfonsi, M.; Arisaka, K.; Arneodo, F.; Balan, C.; Baudis, L.; Behrens, A.; Beltrame, P.; Bokeloh, K.; Brown, E.; Bruno, G.; Budnik, R.; Cardoso, J. M. R.; Chen, W.-T.; Choi, B.; Cline, D. B.; Contreras, H.; Cussonneau, J. P.; Decowski, M. P.; Duchovni, E.; Fattori, S.; Ferella, A. D.; Fulgione, W.; Gao, F.; Garbini, M.; Giboni, K.-L.; Goetzke, L. W.; Grignon, C.; Gross, E.; Hampel, W.; Kish, A.; Lamblin, J.; Landsman, H.; Lang, R. F.; Le Calloch, M.; Levy, C.; Lim, K. E.; Lin, Q.; Lindemann, S.; Lindner, M.; Lopes, J. A. M.; Lung, K.; Marrodn Undagoitia, T.; Massoli, F. V.; Mei, Y.; Melgarejo Fernandez, A. J.; Meng, Y.; Molinario, A.; Nativ, E.; Ni, K.; Oberlack, U.; Orrigo, S. E. A.; Pantic, E.; Persiani, R.; Plante, G.; Priel, N.; Rizzo, A.; Rosendahl, S.; dos Santos, J. M. F.; Sartorelli, G.; Schreiner, J.; Schumann, M.; Scotto Lavina, L.; Scovell, P. R.; Selvi, M.; Shagin, P.; Simgen, H.; Teymourian, A.; Thers, D.; Vitells, O.; Wang, H.; Weber, M.; Weinheimer, C.

2014-02-01

117

High fidelity equation of state for xenon : integrating experiments and first principles simulations in developing a wide-range equation of state model for a fifth-row element.  

SciTech Connect

The noble gas xenon is a particularly interesting element. At standard pressure xenon is an fcc solid which melts at 161 K and then boils at 165 K, thus displaying a rather narrow liquid range on the phase diagram. On the other hand, under pressure the melting point is significantly higher: 3000 K at 30 GPa. Under shock compression, electronic excitations become important at 40 GPa. Finally, xenon forms stable molecules with fluorine (XeF{sub 2}) suggesting that the electronic structure is significantly more complex than expected for a noble gas. With these reasons in mind, we studied the xenon Hugoniot using DFT/QMD and validated the simulations with multi-Mbar shock compression experiments. The results show that existing equation of state models lack fidelity and so we developed a wide-range free-energy based equation of state using experimental data and results from first-principles simulations.

Flicker, Dawn G.; Root, Seth; Mattsson, Thomas Kjell Rene; Magyar, Rudolph J.; Carpenter, John H.

2010-05-01

118

Penile blood flow by xenon-133 washout  

SciTech Connect

Penile erectile failure is often attributed to abnormalities of vascular supply or drainage, but few direct measurements of penile blood flow have been made. We describe the xenon washout method for measurement of penile blood flow, and present the results obtained in a group of normal and impotent subjects. The procedure was performed with standard nuclear imaging equipment. Flaccid-state penile blood flow in the impotent patients studied was not significantly different from the normal group, suggesting that flaccid-state measurements may not be helpful in evaluation of erectile failure. However, this method can be used to measure penile venous outflow with stimulated or induced erection, and may provide a method for detecting abnormal venous leakage.

Haden, H.T.; Katz, P.G.; Mulligan, T.; Zasler, N.D.

1989-06-01

119

Modeling pulse characteristics in Xenon with NEST  

NASA Astrophysics Data System (ADS)

A comprehensive model for describing the characteristics of pulsed signals, generated by particle interactions in xenon detectors, is presented. An emphasis is laid on two-phase time projection chambers, but the models presented are also applicable to single phase detectors. In order to simulate the pulse shape due to primary scintillation light, the effects of the ratio of singlet and triplet dimer state populations, as well as their corresponding decay times, and the recombination time are incorporated into the model. In a two phase time projection chamber, when simulating the pulse caused by electroluminescence light, the ionization electron mean free path in gas, the drift velocity, singlet and triplet decay times, diffusion constants, and the electron trapping time, have been implemented. This modeling has been incorporated into a complete software package, which realistically simulates the expected pulse shapes for these types of detectors.

Mock, J.; Barry, N.; Kazkaz, K.; Stolp, D.; Szydagis, M.; Tripathi, M.; Uvarov, S.; Woods, M.; Walsh, N.

2014-04-01

120

Viscoelasticity of Xenon near the Critical Point  

NASA Technical Reports Server (NTRS)

Using a novel, overdamped, oscillator flown aboard the Space Shuttle, we measured the viscosity of xenon near the liquid-vapor critical point in the frequency range 2 Hz less than or equal to f less than or equal to 12 Hz. The measured viscosity divergence is characterized by the exponent z(sub eta) = 0.0690 +/- 0.0006, in agreement with the value z(sub eta) = 0.067 +/- 0.002 calculated from a two-loop perturbation expansion. Viscoelastic behavior was evident when t = (T - T(sub c))/T(sub c) less than 10(exp -5) and dominant when t less than 10(exp -6), further from T(sub c) than predicted. Viscoelastic behavior scales as Af(tau) where tau is the fluctuation decay time. The measured value of A is 2.0 +/- 0.3 times the result of a one-loop calculation. (Uncertainties stated are one standard uncertainty.)

Berg, Robert F.; Moldover, Michael R.; Zimmerli, Gregory A.

1999-01-01

121

A study of nitrogen and carbon dioxide chemisorption on platinum black  

Microsoft Academic Search

The relationship between sites responsible for nitrogen chemisorption and sites responsible for stronger adsorption of carbon dioxide on platinum black is reported. A 2 to 1 ratio has been found between molecules of more strongly adsorbed carbon dioxide and molecules of nitrogen chemisorbed on individual samples. This relationship has allowed us to deduce the structure of chemisorbed carbon dioxide. Carbon

E. F. Rissmann; J. M. Parry

1992-01-01

122

Determination of time-course change rate for arterial xenon using the time course of tissue xenon concentration in xenon-enhanced computed tomography  

SciTech Connect

In calculating tissue blood flow (TBF) according to the Fick principle, time-course information on arterial tracer concentration is indispensable and has a considerable influence on the accuracy of calculated TBF. In TBF measurement by xenon-enhanced computed tomography (Xe-CT), nonradioactive xenon gas is administered by inhalation as a tracer, and end-tidal xenon is used as a substitute for arterial xenon. There has been the assumption that the time-course change rate for end-tidal xenon concentration (Ke) and that for arterial xenon concentration (Ka) are substantially equal. Respiratory gas sampling is noninvasive to the patient and Ke can be easily measured by exponential curve fitting to end-tidal xenon concentrations. However, it is pointed out that there would be a large difference between Ke and Ka in many cases. The purpose of this work was to develop a method of determining the Ka value using the time course of tissue xenon concentration in Xe-CT. The authors incorporated Ka into the Kety autoradiographic equation as a parameter to be solved, and developed a method of least-squares to obtain the solution for Ka from the time-course changes in xenon concentration in the tissue. The authors applied this method of least-squares to the data from Xe-CT abdominal studies performed on 17 patients; the solution for Ka was found pixel by pixel in the spleen, and its Ka map was created for each patient. On the one hand, the authors obtained the average value of the Ka map of the spleen as the calculated Ka (Ka{sub calc}) for each patient. On the other hand, the authors measured Ka (Ka{sub meas}) using the time-course changes in CT enhancement in the abdominal aorta for each patient. There was a good correlation between Ka{sub calc} and Ka{sub meas} (r=0.966, P<0.0001), and these two Ka values were close to each other (Ka{sub calc}=0.935xKa{sub meas}+0.089). This demonstrates that Ka{sub calc} would be close to the true Ka value. Accuracy of TBF by Xe-CT can be improved with use of the average value of the Ka map of an organ like the spleen that has a single blood supply (only arterial inflow)

Sase, Shigeru; Takahashi, Hideaki; Ikeda, Hiroki; Kobayashi, Minoru; Matsumoto, Nobuyuki; Suzuki, Michihiro [Anzai Medical Co., Ltd., 3-9-15 Nishi-Shinagawa, Shinagawa-ku, Tokyo 141-0033 (Japan); Department of Internal Medicine, Division of Gastroenterology and Hepatology, School of Medicine, St. Marianna University, 2-16-1 Miyamae-ku, Sugao, Kawasaki 216-5811 (Japan)

2008-06-15

123

High-intensity xenon pulse light source for fluorescence excitation  

NASA Astrophysics Data System (ADS)

A newly developed 60W xenon flash lamp, L6604 and L6605, achieves the goals of longer operating life, higher output, and improved light stability. It operates at 2 Joules per flash input energy with approximately a 4 microsecond flash duration. The stability achieved is 2-3 percent peak-to-peak during a lifetime of 5 X 10e7 flashes, which is almost double that of conventional xenon flash lamps. This newly developed xenon flashlamp should serve as an excellent light source for analytical cytology and other fluorescence instruments. It can function as a high output, stable excitation light source for conventional fluorescence or delayed luminescence with a CCD. Besides providing powerful and stable illumination for absorption analysis of cells on slides, this lamp eliminates the optical artifacts associated with vibration of the stage which often limit throughput. This paper will describe in detail performance improvements obtained from this newly developed xenon flash lamp.

Miyamoto, Makoto; Ueno, Kazuo

1997-05-01

124

Fission xenon from extinct Pu-244 in 14,301.  

NASA Technical Reports Server (NTRS)

Xenon extracted in step-wise heating of lunar breccia 14,301 contains a fission-like component in excess of that attributable to uranium decay during the age of the solar system. There seems to be no adequate source for this component other than Pu-244. Verification that this component is in fact due to the spontaneous fission of extinct Pu-244 comes from the derived spectrum which is similar to that observed from artificially produced Pu-244. It thus appears that Pu-244 was extant at the time lunar crustal material cooled sufficiently to arrest the thermal diffusion of xenon. Subsequent history has apparently maintained the isotopic integrity of plutonium fission xenon. Of major importance are details of the storage itself. Either the fission component is the result of in situ fission of Pu-244 and subsequent storage in 14,301 material, or the fission xenon was stored in an intermediate reservoir before incorporation into 14,301.

Drozd, R.; Hohenberg, C. M.; Ragan, D.

1972-01-01

125

Fluorination of amorphous thin-film materials with xenon fluoride  

DOEpatents

A method is disclosed for producing fluorine-containing amorphous semiconductor material, preferably comprising amorphous silicon. The method includes depositing amorphous thin-film material onto a substrate while introducing xenon fluoride during the film deposition process.

Weil, R.B.

1987-05-01

126

Time-resolved xenon flash-lamp opacity measurements.  

PubMed

A laser-aided technique has been used for measuring time-resolved optical transmissions of xenon flash lamps at numerous visible and infrared wavelengths, flash-lamp current densities, lamp diameters, pulse durations, and xenon pressures. Long-pulse ( 600-s) and short-pulse ( 10-s) cases specific for optically pumping solid-state, dye, and atomic iodine lasers were studied. Opacity measurements were made for flash-lamp current densities up to 30 kA/cm(2) . Flash lamps having fused silica envelope diameters between 0.8 and 4.5 cm and xenon pressures between 2 and 450 Torr were investigated in these experiments. Xenon temperatures between 6000 and 25,000 K were estimated from the frequencies of observed arc-acoustic oscillations. Important applications for increasing the pumping efficiencies of large Nd:glass and photolytic iodine laser amplifiers are discussed. PMID:20963067

Linford, G J

1994-12-20

127

Stark Widths Of Ionized Xenon UV Lines Of Low Intensity  

SciTech Connect

Stark width measurements of several low intensity Xe II spectral lines (5d - 4f transitions) in UV region, are presented here for the first time. These measurements were obtained from helium - xenon pulsed arc plasma.

Cirisan, M.; Djurovic, S. [Faculty of Sciences, Department of Physics, Trg Dositeja Obradovica 4, 21000 Novi Sad (Serbia); Pelaez, R. J.; Aparicio, J. A.; Mar, S. [Departamento de Fisica Teorica Atomica y Optica, Facultad de Ciencias, Universidad de Valladolid, P. Prado de la Magdalena s/n, 47071 Valladolid (Spain)

2007-04-23

128

NASA's Evolutionary Xenon Thruster (NEXT) Ion Propulsion System Information Summary.  

National Technical Information Service (NTIS)

This document is a guide to New Frontier's mission proposal teams. The document describes the development and status of the NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system (IPS) technology, its application to planetary missions, and the pr...

E. S. Pencil S. W. Benson

2008-01-01

129

Purging means and method for Xenon arc lamps  

NASA Technical Reports Server (NTRS)

High pressure Xenon short-arc lamp with two reservoirs which are selectively connectable to the lamp's envelope is described. One reservoir contains an absorbent which will absorb both Xenon and contaminant gases such as CO2 and O2. The absorbent temperature is controlled to evacuate the envelope of both the Xenon and the contaminant gases. The temperature of the absorbent is then raised to desorb only clean Xenon while retaining the contaminant gases, thereby clearing the envelope of the contaminant gases. The second reservoir contains a gas whose specific purpose is, to remove the objectional metal film which deposits gradually on the interior surface of the lamp envelope during normal arc operation. The origin of the film is metal transferred from the cathode of the arc lamp by sputtering or other gas transfer processes.

Miller, C. G. (inventor)

1973-01-01

130

Radon removal from gaseous xenon with activated charcoal  

NASA Astrophysics Data System (ADS)

Many low background experiments using xenon need to remove radioactive radon to improve their sensitivities. However, no method of continually removing radon from xenon has been described in the literature. We studied a method to remove radon from xenon gas through an activated charcoal trap. From our measurements we infer a linear relationship between the mean propagation velocity vRn of radon and vXe of xenon in the trap with vRn/vXe=(0.960.10)10-3 at -85 C. As the mechanism for radon removal in this charcoal trap is its decay, knowledge of this parameter allows us to design an efficient radon removal system for the XMASS experiment. The verification of this system found that it reduces radon by a factor of 0.07, which is in line with its expected average retention time of 14.8 days for radon.

Abe, K.; Hieda, K.; Hiraide, K.; Hirano, S.; Kishimoto, Y.; Kobayashi, K.; Koshio, Y.; Liu, J.; Martens, K.; Moriyama, S.; Nakahata, M.; Nishiie, H.; Ogawa, H.; Sekiya, H.; Shinozaki, A.; Suzuki, Y.; Takachio, O.; Takeda, A.; Ueshima, K.; Umemoto, D.; Yamashita, M.; Hosokawa, K.; Murata, A.; Otsuka, K.; Takeuchi, Y.; Kusaba, F.; Motoki, D.; Nishijima, K.; Tasaka, S.; Fujii, K.; Murayama, I.; Nakamura, S.; Fukuda, Y.; Itow, Y.; Masuda, K.; Nishitani, Y.; Takiya, H.; Uchida, H.; Kim, Y. D.; Kim, Y. H.; Lee, K. B.; Lee, M. K.; Lee, J. S.; Xmass Collaboration

131

Fluorination of amorphous thin-film materials with xenon fluoride  

DOEpatents

A method is disclosed for producing fluorine-containing amorphous semiconductor material, preferably comprising amorphous silicon. The method includes depositing amorphous thin-film material onto a substrate while introducing xenon fluoride during the film deposition process.

Weil, Raoul B. (Haifa, IL) [Haifa, IL

1988-01-01

132

Laser-induced fluorescence diagnostics of xenon plasmas  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence of excited-state neutral- and ionic-xenon transitions has been used as a diagnostic tool in xenon plasmas. Spectroscopic models based on Voigt-broadened line shapes were developed from hyperfine-splitting information for the resonance- broadened neutral-xenon 6s[3/2]1o/to 6p[1/2]0 transition at 828 nm, the predominantly Doppler-broadened 6s[3/2]2o/to 6p[3/2]2 transition at 823nm, and the xenon-ion 5d[3]7/2/to 6p[2]5/2o/ (4D7/2/to[4]P5/2) transition at 605 nm. Tunable narrow-linewidth semiconductor diode lasers were used to probe the neutral-xenon transitions, and an Ar+-pumped dye laser was used for the xenon-ion transition. The models of the neutral-xenon transitions were used to make measurements of the kinetic temperature from line-shape analyses in a low-pressure dc glow discharge with an uncertainty of 10%. The broadening of the 828-nm transition by the resonant interaction of its lower level with ground-state xenon was also developed into a number density diagnostic. The spectral broadening of this transition was investigated in the dc glow discharge for densities of 41021 to 21024 atoms m-3. The 828-nm broadening constant at low densities and at 311 K was found to be 6.04/ ([/pm]0.66)10-21 MHzm3 atom-1, in agreement with the impact theory for resonance broadening. At densities above 61023 atoms m-3 the recorded line shapes of this transition exhibited an asymmetry, providing clear evidence of the breakdown of the impact approximation. The measured Lorentzian broadening for the 823-nm transition was 8.3/ ([/pm]1.8)10-22 MHzm3 atom-1 at 311K. LIF measurements of xenon plasma parameters in the plume of a laboratory- model Hall thruster using the neutral-xenon 823-nm transition and the xenon-ion 605-nm transition demonstrated the application of the diagnostics. Axial neutral velocities from 100 m s-1 to 400 m s- 1 and ion velocities as high as 12 km s-1 were measured, indicating that the charge-exchange phenomenon was not significant. The spectral-line shapes of the ion suggested a spread in ion energies through a non- Maxwellian distribution of axial velocities. Neutral kinetic temperatures of 500 (200)K were observed under standard thruster operating conditions.

Cedolin, Renato James

1997-12-01

133

Xenon diffusion studies with prompt gamma activation analysis  

Microsoft Academic Search

Developing a better understanding of xenon transport through porous systems is critical to predicting how this gas will enter\\u000a the atmosphere after a below ground nuclear weapons test. Radioxenon monitoring is a vital part of the Comprehensive Nuclear-Test-Ban\\u000a Treaty (CTBT) International Monitoring System. This work details the development of prompt gamma activation analysis for measuring\\u000a the diffusion rates of xenon

Carlos A. Rios Perez; Justin D. Lowrey; Steven Biegalski; Mark R. Deinert

134

Breakdown characteristics of xenon HID Lamps  

NASA Astrophysics Data System (ADS)

The breakdown characteristics of mercury free xenon high intensity discharge (HID) lamps exhibit a large statistical time lag often having a large scatter in breakdown voltages. In this paper, we report on results from a computational investigation of the processes which determine the ignition voltages for positive and negative pulses in commercial HID lamps having fill pressures of up to 20 atm. Steep voltage rise results in higher avalanche electron densities and earlier breakdown times. Circuit characteristics also play a role. Large ballast resistors may limit current to the degree that breakdown is quenched. The breakdown voltage critically depends on cathode charge injection by electric field emission (or other mechanisms) which in large part controls the statistical time lag for breakdown. For symmetric lamps, ionization waves (IWs) simultaneously develop from the bottom and top electrodes. Breakdown typically occurs when the top and bottom IWs converge. Condensed salt layers having small conductivities on the inner walls of HID lamps and on the electrodes can influence the ignition behavior. With these layers, IWs tend to propagate along the inner wall and exhibit a different structure depending on the polarity.

Babaeva, Natalia; Sato, Ayumu; Brates, Nanu; Noro, Koji; Kushner, Mark

2009-10-01

135

Optimization of Xenon Difluoride Vapor Delivery  

SciTech Connect

Xenon difluoride (XeF{sub 2}) has been shown to provide many process benefits when used as a daily maintenance recipe for ion implant. Regularly flowing XeF{sub 2} into the ion source cleans the deposits generated by ion source operation. As a result, significant increases in productivity have been demonstrated. However, XeF{sub 2} is a toxic oxidizer that must be handled appropriately. Furthermore, it is a low vapor pressure solid under standard conditions ({approx}4.5 torr at 25 deg. C). These aspects present unique challenges for designing a package for delivering the chemistry to an ion implanter. To address these challenges, ATMI designed a high-performance, re-usable cylinder for dispensing XeF{sub 2} in an efficient and reliable manner. Data are presented showing specific attributes of the cylinder, such as the importance of internal heat transfer media and the cylinder valve size. The impact of mass flow controller (MFC) selection and ion source tube design on the flow rate of XeF{sub 2} are also discussed. Finally, cylinder release rate data are provided.

Sweeney, Joseph; Marganski, Paul; Kaim, Robert; Wodjenski, Mike; Gregg, John; Yedave, Sharad; Sergi, Steve; Bishop, Steve; Eldridge, David; Zou Peng [ATMI, Inc., Danbury, Connecticut 06810 (United States)

2008-11-03

136

Let's Make Molecules  

NSDL National Science Digital Library

In this activity, learners use gumdrops and toothpicks to model the composition and molecular structure of three greenhouse gases: carbon dioxide (CO2), water vapor (H2O) and methane (CH4). Learners explore how greenhouse gases are released into the atmosphere as well as how these gases contribute to global climate change. This activity guide includes an extension activity in which learners move their bodies to model the arrangement of atoms in a methane molecule.

Sciencenter

2010-01-01

137

Positron Scattering from Molecules  

NASA Astrophysics Data System (ADS)

We review recent total cross section results from the University of Trento for positron scattering from the molecules carbon dioxide, tetrahydrofuran, 3-hydroxy-tetrahydrofuran, formic acid and methanol and ethanol. Where possible comparison is made to other experimental data and with results from state of the art scattering calculations. These comparisons indicate that at low positron energies the scattering process is dominated by the dipole polarisability and, if applicable, the permanent dipole moment of the species in question.

Brunger, M. J.; Zecca, A.

2009-07-01

138

Spectrally Resolved Magnetic Resonance Imaging of the XenonBiosensor  

SciTech Connect

Due to its ability to non-invasively record images, as well as elucidate molecular structure, nuclear magnetic resonance is the method of choice for applications as widespread as chemical analysis and medical diagnostics. Its detection threshold is, however, limited by the small polarization of nuclear spins in even the highest available magnetic fields. This limitation can, under certain circumstances, be alleviated by using hyper-polarized substances. Xenon biosensors make use of the sensitivity gain of hyperpolarized xenon to provide magnetic resonance detection capability for a specific low-concentration target. They consist of a cryptophane cage, which binds one xenon atom, and which has been connected via a linker to a targeting moiety such as a ligand or antibody. Recent work has shown the possibility of using the xenon biosensor to detect small amounts of a substance in a heterogeneous environment by NMR. Here, we demonstrate that magnetic resonance (MR) provides the capability to obtain spectrally and spatially resolved images of the distribution of immobilized biosensor, opening the possibility for using the xenon biosensor for targeted imaging.

Hilty, Christian; Lowery, Thomas; Wemmer, David; Pines, Alexander

2005-07-15

139

Influence of radiation damage on xenon diffusion in silicon carbide  

NASA Astrophysics Data System (ADS)

Diffusion of xenon in poly and single crystalline silicon carbide and the possible influence of radiation damage on it are investigated. For this purpose 360 keV xenon ions were implanted in commercial 6H-SiC and CVD-SiC wafers at room temperature, 350 C and 600 C. Width broadening of the implantation profiles and xenon retention during isochronal and isothermal annealing up to temperatures of 1500 C was determined by RBS-analysis, whilst in the case of 6H-SiC damage profiles were simultaneously obtained by ?-particle channelling. No diffusion or xenon loss was detected in the initially amorphized and eventually recrystallized surface layer of cold implanted 6H-SiC during annealing up to 1200 C. Above that temperature serious erosion of the implanted surface occurred, which made any analysis impossible. No diffusion or xenon loss is detected in the hot implanted 6H-SiC samples during annealing up to 1400 C. Radiation damage dependent grain boundary diffusion is observed at 1300 C in CVD-SiC.

Friedland, E.; Grtner, K.; Hlatshwayo, T. T.; van der Berg, N. G.; Thabethe, T. T.

2014-08-01

140

Hugoniot measurements of double-shocked precompressed dense xenon plasmas  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

141

Low-Energy Sputtering Studies of Boron Nitride with Xenon Ions  

NASA Technical Reports Server (NTRS)

Sputtering of boron nitride with xenon ions was investigated using secondary ion (SIMS) and secondary neutral (SNMS) mass spectrometry. The ions generated from the ion gun were incident on the target at an angle of 50' with respect to the surface'normal. The energy of ions ranged from 100 eV to 3 keV. A flood electron gun was used to neutralize the positive charge build-up on the target surface. The intensities of sputtered neutral and charged particles, including single atoms, molecules, and clusters, were measured as a function of ion energy. Positive SIMS spectra were dominated by the two boron isotopes whereas BN- and B- were the two major constituents of the negative SIMS spectra. Nitrogen could be detected only in the SNMS spectra. The intensity-energy curves of the sputtered particles were similar in shape. The knees in P-SIMS and SNMS intensity-energy curves appear at around I keV which is significantly higher that 100 to 200 eV energy range at which knees appear in the sputtering of medium and heavy elements by ions of argon and xenon. This difference in the position of the sputter yield knee between boron nitride and heavier targets is due to the reduced ion energy differences. The isotopic composition of secondary ions of boron were measured by bombarding boron nitride with xenon ions at energies ranging from 100 eV to 1.5 keV using a quadrupole mass spectrometer. An ion gun was used to generate the ion beam. A flood electron gun was used to neutralize the positive charge buildup on the target surface. The secondary ion flux was found to be enriched in heavy isotopes at lower incident ion energies. The heavy isotope enrichment was observed to decrease with increasing primary ion energy. Beyond 350 eV, light isotopes were sputtered preferentially with the enrichment increasing to an asymptotic value of 1.27 at 1.5 keV. The trend is similar to that of the isotopic enrichment observed earlier when copper was sputtered with xenon ions in the same energy range.

Ray, P. K.; Shutthanandan, V.

1999-01-01

142

Hypersatellite and satellite transitions in xenon atoms  

NASA Astrophysics Data System (ADS)

Decay of double-K-shell-vacancy states in xenon atoms, created in the decay of 131Cs, was investigated. The measurements were performed with a pair of germanium detectors, a fast-slow coincidence system, and a three-parameter pulse-height analyzer. In the analysis of the two-dimensional E1-E2 spectrum, improved least-squares routines were applied. The following results were derived: the probability of creation of a double K-shell vacancy per 131Cs decay, PKK=(1.48+/-0.35)10-5 the hypersatellite energy shifts ?h(K?)=(653+/-20) eV, ?h(K?1)=(834+/-39) eV, and ?h(K?2)=(903+/-81) eV; the average values of the satellite energy shifts due to the presence of an L3- or L2-shell spectator vacancy ?s(K?L-1)=(80+/-15) eV, ?s(K?1L-1)=(169+/-34) eV, and ?s(K?2L-1)=(261+/-81) eV; the intensity ratios of the hypersatellite transitions, I(K?h2)/I(K?h1)=0.94+/-0.18, I(K?h1)/I(K?h1)=0.36+/-0.06, and I(K?h2)/ I(K?h1)=0.09+/-0.04 the intensity ratios of the satellite transitions I(K?2L-1)/I(K?1L-1)=0.44+/-0.10 and 0.44+/-0.09 for an L3 and L2 spectator vacancy, respectively; and the intensity ratios of some other satellite transitions.

Ilakovac, K.; Veskovi?, M.; Horvat, V.; Kaui?, S.

1990-10-01

143

Development of a xenon detector for treaty verification. Final report  

SciTech Connect

The project objective was to determine the feasibility of the gas proportional scintillator detector (GPSD) technology to sensitively and selectively detect the decay products of the metastable xenon isotopes as a means of treaty verification for the CTBT. During the course of the project, the investigation involved both computer simulations and laboratory measurements with a GPSD. During the fourth quarter the authors have further investigated the dedicated GPSD response to x-rays and conversion electrons from {sup 109}Cd and {sup 57}Co radioactive sources, comparing simulated and experimental results. The response of a customized high pressure GPSC was also simulated to the higher energy conversion electrons from xenon radioisotopes. An alternative hybrid detector system is proposed showing excellent prospects for xenon radioisotope detection.

NONE

1998-07-21

144

Performance of a refrigerated charcoal trap for xenon-133.  

PubMed

The impulse response function of a charcoal trap to a bolus of xenon-133 was determined as a function of the total number of hours run both at room temperature and at 25 degrees C. The peak of the response function for a new trap at room temperature reached a value of 360 MPC at 11 h. After 150 h of operation, the impulse response function was determined at -25 degrees C reaching a value of only 35 MPC at 25 h. The exhaust concentration of a trap in a busy nuclear medicine department using 150 mCi of xenon per week was measured and found to be 1600 MPC. The trap was placed in the freezer and kept there while it continued in use. Over a period of 3 weeks, the concentration of xenon in the exhaust of the trap dropped to a value of 13 MPC, or less than 1% of its value at room temperature. PMID:7322086

Powell, M; Grando, R; Robeson, W

1981-01-01

145

Single Ion Trapping for the Enriched Xenon Observatory  

SciTech Connect

In the last decade, a variety of neutrino oscillation experiments have established that there is a mass difference between neutrino flavors, without determining the absolute neutrino mass scale. The Enriched Xenon Observatory for neutrinoless double beta decay (EXO) will search for the rare decays of xenon to determine the absolute value of the neutrino mass. The experiment uses a novel technique to minimize backgrounds, identifying the decay daughter product in real time using single ion spectroscopy. Here, we describe single ion trapping and spectroscopy compatible with the EXO detector. We extend the technique of single ion trapping in ultrahigh vacuum to trapping in xenon gas. With this technique, EXO will achieve a neutrino mass sensitivity of {approx_equal} .010 eV.

Waldman, Samuel J.; /Stanford U., Phys. Dept. /SLAC

2006-03-28

146

Study of the electromagnetic background in the XENON100 experiment  

SciTech Connect

The XENON100 experiment, located at the Laboratori Nazionali del Gran Sasso, aims to directly detect dark matter in the form of weakly interacting massive particles via their elastic scattering off xenon nuclei. We present a comprehensive study of the predicted electronic recoil background coming from radioactive decays inside the detector and shield materials and intrinsic radioactivity in the liquid xenon. Based on GEANT4 Monte Carlo simulations using a detailed geometry together with the measured radioactivity of all detector components, we predict an electronic recoil background in the energy region of interest and 30 kg fiducial mass of less than 10{sup -2} events{center_dot}kg{sup -1{center_dot}}day{sup -1{center_dot}}keV{sup -1}, consistent with the experiment's design goal. The predicted background spectrum is in very good agreement with the data taken during the commissioning of the detector in Fall 2009.

Aprile, E.; Choi, B.; Giboni, K.-L.; Lang, R. F.; Lim, K. E.; Melgarejo Fernandez, A. J.; Plante, G. [Physics Department, Columbia University, New York, New York 10027 (United States); Arisaka, K.; Cline, D.; Lam, C. W.; Lung, K.; Pantic, E.; Teymourian, A.; Wang, H. [Physics and Astronomy Department, University of California, Los Angeles (United States); Arneodo, F. [INFN, Laboratori Nazionali del Gran Sasso, Assergi, 67100 (Italy); Askin, A.; Baudis, L.; Behrens, A.; Ferella, A. D.; Kish, A. [Physics Institute, University of Zuerich, Winterthurerstrasse 190, CH-8057, Zuerich (Switzerland)

2011-04-15

147

Modeling the Energy Resolution of Xenon with NEST  

NASA Astrophysics Data System (ADS)

In addition to explaining the mean yields, NEST (the Noble Element Simulation Technique) can also address the energy resolution degrading effects in noble elements, for both electron and nuclear recoils (ER and NR). Liquid and gaseous xenon will be presented as examples. A non-binomial recombination fluctuation model will be discussed which well describes the intrinsic, supra-Poissonian resolution observed in xenon. It is combined with electric field effects, the Fano factor, and detector efforts, such as finite light collection efficiency and PMT quantum efficiency. In matters of conflicting dark matter search results observed by experiments such as XENON100 and CoGeNT, a stochastic, non-analytic, partially non-Gaussian understanding of the energy resolution for low-energy, WIMP-like nuclear recoils may be part of the solution. ER-NR discrimination can be predicted well with such an understanding.

Uvarov, Sergey

2013-04-01

148

The distributed Slow Control System of the XENON100 experiment  

NASA Astrophysics Data System (ADS)

The XENON100 experiment, in operation at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy, was designed to search for evidence of dark matter interactions inside a volume of liquid xenon using a dual-phase time projection chamber. This paper describes the Slow Control System (SCS) of the experiment with emphasis on the distributed architecture as well as on its modular and expandable nature. The system software was designed according to the rules of Object-Oriented Programming and coded in Java, thus promoting code reusability and maximum flexibility during commissioning of the experiment. The SCS has been continuously monitoring the XENON100 detector since mid 2008, remotely recording hundreds of parameters on a few dozen instruments in real time, and setting emergency alarms for the most important variables.

Aprile, E.; Alfonsi, M.; Arisaka, K.; Arneodo, F.; Balan, C.; Baudis, L.; Behrens, A.; Beltrame, P.; Bokeloh, K.; Brown, E.; Bruno, G. M.; Budnik, R.; Le Calloch, M.; Cardoso, J. M.; Chen, W.-T.; Choi, B.; Contreras, H.; Cussonneau, J.-P.; Decowski, M. P.; Duchovni, E.; Fattori, S.; Ferella, A. D.; Fulgione, W.; Gao, F.; Garbini, M.; Giboni, K.-L.; Goetzke, L. W.; Grignon, C.; Gross, E.; Hampel, W.; McKinsey, D. N.; Kish, A.; Lamblin, J.; Lang, R. F.; Levy, C.; Lim, K. E.; Lin, Q.; Lindemann, S.; Lindner, M.; Lopes, J. A. M.; Lung, K.; Manzur, A.; Marrodn Undagoitia, T.; Massoli, F. V.; Mei, Y.; Melgarejo Fernandez, A. J.; Meng, Y.; Molinario, A.; Nativ, E.; Ni, K.; Oberlack, U.; Orrigo, S. E. A.; Pantic, E.; Patricio, J. V.; Persiani, R.; Plante, G.; Priel, N.; Ribeiro, A. C. C.; Rizzo, A.; Rosendahl, S.; dos Santos, J. M. F.; Sartorelli, G.; Schreiner, J.; Schumann, M.; Scotto Lavina, L.; Scovell, P. R.; Selvi, M.; Shagin, P.; Simgen, H.; Teymourian, A.; Thers, D.; Vitells, O.; Wang, H.; Weber, M.; Weinheimer, C.

2012-12-01

149

Post-Launch Performance Characterization of the Xenon Feed System on Deep Space One  

Microsoft Academic Search

Propulsion for the Deep Space One @SI) spacecraft is provided by a xenon ion engine. Xenon is stored in a supercritical state and is delivered as a low pressure gas to the thruster and two cathodes (called the main cathode and neutralizer) by a Xenon Feed System (XFS). This mission requires tight constraints on thruster performance, which in turn requires

Gani B. Ganapathi; Carl S. Engelbrecht

150

A Study of Radon Background in the XENON100 Experiment  

NASA Astrophysics Data System (ADS)

The XENON100 Dark Matter experiment has recently published first results from an analysis of 11.2 live days of data, setting an upper limit on the spin-independent WIMP-nucleon elastic scattering cross section of 3.410-44 cm2 at 55 GeV/c2 and 90% confidence level. This article focuses on one specific background component of the XENON100 detector by presenting two independent methods of measuring the 222Rn concentration during operation phase. A first estimate of radon activity is derived for the 11.2 days analysis, proving the feasibility of on-line radon monitoring. Remaining systematic uncertainties are discussed.

Weber, Marc

2011-04-01

151

Standardization of xenon-127 and measurement of photon emission intensities.  

PubMed

Xenon-127 was standardized by internal gas counting using three proportional counters in a differential arrangement to eliminate edge effects. The detection efficiency of the proportional counters was calculated by considering the cascade of events following the electron capture and associated gamma transitions. Activity per unit volume was measured with 0.7% relative standard uncertainty. Gamma-ray spectrometry was performed and absolute photon emission intensities were derived. This study shows that (127)Xe could be a surrogate for (133)Xe for the calibration of remote radio-xenon monitoring stations. PMID:24360861

Rodrigues, M; Lpy, M-C; Cassette, P; Mougeot, X; B, M M

2014-05-01

152

Computer simulations of the Adsorption of Xenon onto a C60 monolayer on Ag (111)  

NASA Astrophysics Data System (ADS)

We performed Grand Canonical Monte Carlo simulations to study the adsorption of Xenon on a substrate composed of C60 molecules placed on top of a Ag(111) surface. The C60 molecules form a commensurate structure at a distance of 0.227 nm above the Ag surface. The interaction potential between the Xe atoms and the substrate has two contributions: from the C60 molecules and from the Ag atoms. In the simulations, the interaction with the Ag surface was computed using an ab initio van der Waals potential, varying as 1/d^3. The interaction between the Xe atoms and each C60 molecule was computed using a potential previously developed by Hernandez et.al. (E. S. Hernandez, M. W. Cole and M. Boninsegni, ``Wetting of spherical surfaces by quantum fluids'', J. Low Temp. Phys. 134, 309-314 (2004)), who integrated the Lennard Jones interaction over the surface of a spherical buckyball. The total potential has especially attractive 3-fold sites, positioned 0.4 nm above the point between each three buckyballs. The low coverage uptake populates those sites, and then continues forming a monolayer. The adsorption isotherms show several steps, typical of substrates that have distinct adsorption sites. We compare the results with the experimental data.

Gatica, Silvina; Cole, Milton; Diehl, Renee

2007-03-01

153

Investigations of Buffer-Gases Role in Xenon and Halogen Excimer Mixtures  

NASA Astrophysics Data System (ADS)

Excimer- is an acronym in use for the excited dimmer, molecule which does not exist in the ground state but only in an excited state. This paper presents the role of the buffer-gas atoms (Ar, Ne, He), in the (Cl2/I2 Xe) excimer radiation emission mechanisms. The same buffer-gas produced a different effect on the excimer emission intensity: the neon and argon addition to xenon/chlorine/iodine had a negative effect while the helium and neon addition had a positive effect. The Penning reactions play an important role in the excimer radiation generation in connection with the gas-buffer addition and the halogen ionization potential value. The measurements are performed using a dielectric barrier discharge (DBD) at moderate pressure in a panel, respectively classic coaxial geometry.

Ciobotaru, L. C.; Porosnicu, C.

2010-10-01

154

Application of Xenon in Gas Mixture for Drift Proportional Chambers.  

National Technical Information Service (NTIS)

A method for increasing the gas amplification coefficient in drift proportional chambers at the expense of using a gas mixtures with xenon additions is considered. One of such mixtures comprises 86% Ar + 7% CO sub 2 + 7% Xe. The main Advantages of such mi...

V. K. Gorbunov V. A. Krasnov A. B. Kurepin V. I. Razin A. I. Reshetin

1979-01-01

155

Density Functional Theory (dft) Simulations of Shocked Liquid Xenon  

NASA Astrophysics Data System (ADS)

Xenon is not only a technologically important element used in laser technologies and jet propulsion, but it is also one of the most accessible materials in which to study the metal-insulator transition with increasing pressure. Because of its closed shell electronic configuration, xenon is often assumed to be chemically inert, interacting almost entirely through the van der Waals interaction, and at liquid density, is typically modeled well using Leonard-Jones potentials. However, such modeling has a limited range of validity as xenon is known to form compounds under normal conditions and likely exhibits considerably more chemistry at higher densities when hybridization of occupied orbitals becomes significant. We present DFT-MD simulations of shocked liquid xenon with the goal of developing an improved equation of state. The calculated Hugoniot to 2 MPa compares well with available experimental shock data. Sandia is a mul-tiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Mattsson, Thomas R.; Magyar, Rudolph J.

2009-12-01

156

THE SEPARATION OF XENON AND DEUTERIUM BY THERMAL DIFFUSION  

Microsoft Academic Search

A nuclear reactor of the suspension type is characterized by the fact ; that the fission products will continuously escape from the nuclear fuel and ; travel through the ensemble of fuel and moderator. Among these products, xenon ; isotopes are relatively important, and the separation of these isotopes from ; deuterium is one of the engineering problems connected with

Heymann

1959-01-01

157

Discovery of palladium, antimony, tellurium, iodine, and xenon isotopes  

SciTech Connect

Currently, thirty-eight palladium, thirty-eight antimony, thirty-nine tellurium, thirty-eight iodine, and forty xenon isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

Kathawa, J.; Fry, C.; Thoennessen, M., E-mail: thoennessen@nscl.msu.edu

2013-01-15

158

Pulsed xenon flashlamp device for the treatment of psoriasis  

NASA Astrophysics Data System (ADS)

We present our research into a pulsed xenon lamp source for the treatment of psoriasis and other skin disorders. Various filtering techniques, lamp configurations, power supply configurations and delivery systems are discussed. Comparisons are made to existing treatment modalities. Cryogen cooling of the treatment site is discussed.

Baumgardner, Jonathan M.; Hennings, David R.; Johnston, Thomas F., Jr.; Taylor, Eric

2003-06-01

159

Subsurface nuclear tests monitoring through the CTBT xenon network  

Microsoft Academic Search

We present the first evaluation of the atmospheric xenon network to be installed as part of the International Monitoring System (IMS) in the frame of the Comprehensive Test Ban Treaty (CTBT). We show that this network should, by itself, provide a significant contribution to the total efficiency of the IMS. For this evaluation, we introduce an inverse approach based upon

Frdric Hourdin; J.-P. Issartel

2000-01-01

160

Xenon hydrate dissociation measurements with model protein systems.  

PubMed

Effective long-term storage remains a significant challenge to the use and development of protein pharmaceuticals. We have investigated the interactions between clathrate hydrates and model protein solutions to determine the effects on hydrate formation. Here, the dissociation curve and equilibrium conditions for xenon clathrate hydrate with model lysozyme and lactate dehydrogenase (LDH) protein solutions have been studied using calorimetry measurements at pressures ranging from 3 to 20 bar. Sucrose in solution was shown to exhibit small inhibition effects on xenon hydrate formation, shifting the dissociation curve and decreasing the conversion of water to hydrate by 15-26%. The addition of l-histidine buffer and lysozyme at low concentrations did not substantially inhibit hydrate formation. However, small shifts in the dissociation curve were demonstrated for solutions containing LDH. The presence of lysozyme and LDH in solution did not significantly alter the conversion of water to hydrate, indicating that these and similar proteins do not substantially affect the extent of xenon gas hydrate formation. Preliminary experiments were performed for LDH solutions to assess the impact of xenon hydrate formation and dissociation on enzymatic activity, with samples stored in hydrate systems showing small decreases in activity. PMID:21790193

Booker, Ryan D; Koh, Carolyn A; Sloan, E Dendy; Sum, Amadeu K; Shalaev, Evgenyi; Singh, Satish K

2011-09-01

161

Development of the Cryopanel for Tests of Xenon Ion Thrusters.  

National Technical Information Service (NTIS)

A cryopanel suitable for testing zenon ion thrusters was designed and tested. The target temperature of the cryopanel was below 50 K, since the vapor pressure of xenon was low enough at that temperature. This high-temperature-cryopanel has a cylindrical s...

T. Obama K. Kajiwara Y. Hayakawa K. Miyazaki S. Kitamura

1988-01-01

162

Improved xenon lamp for solar simulators: A concept  

NASA Technical Reports Server (NTRS)

Short-arc xenon lamp proposes to produce more uniform solar output. With this lamp, both axes of sensors can be tested with same setup. Lamp includes cathode with conical tip and annular anode. Annulus is supported by angled projection to avoid interference with passage of light generated by arc.

Schmidt, L. F.

1974-01-01

163

Mobility of atomic hydrogen in solid krypton and xenon  

Microsoft Academic Search

Atomic hydrogen is produced in xenon and krypton matrix by in situ x-ray induced photolysis of the dopants water, butane, acetone, or methane and trapped interstitially forming the caged hydrogen with characteristic VUV absorption bands. Their thermal bleaching as investigated between 8 K and 45 K cannot be described by a first-order process. A random walk model is introduced considering

J. Eberlein; Martin Creuzburg

1997-01-01

164

NASA's Evolutionary Xenon Thruster (NEXT) Ion Propulsion System Information Summary  

NASA Technical Reports Server (NTRS)

This document is a guide to New Frontiers mission proposal teams. The document describes the development and status of the NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system (IPS) technology, its application to planetary missions, and the process anticipated to transition NEXT to the first flight mission.

Pencil, Eirc S.; Benson, Scott W.

2008-01-01

165

Distribution of Unionized Propellant Xenon in a Hall Thruster Plume  

Microsoft Academic Search

Laser absorption spectroscopy was applied to a magnetic layer type hall thruster plume in the different ambient pressure to evaluate the influence of the ambient pressure on the number density measurement. As a result, up to 76 % of the measured meta- stable number density by an 823.16 nm line was found the background xenon at the acceleration channel exit.

Shigeru Yokota; Daichi Sakoh; Kimiya Komurasaki; Yoshihiro Arakawa

2007-01-01

166

In vivo NMR and MRI using injection delivery of laser-polarized xenon  

PubMed Central

Because xenon NMR is highly sensitive to the local environment, laser-polarized xenon could be a unique probe of living tissues. Realization of clinical and medical science applications beyond lung airspace imaging requires methods of efficient delivery of laser-polarized xenon to tissues, because of the short spin-lattice relaxation times and relatively low concentrations of xenon attainable in the body. Preliminary results from the application of a polarized xenon injection technique for in vivo 129Xe NMR/MRI are extrapolated along with a simple model of xenon transit to show that the peak local concentration of polarized xenon delivered to tissues by injection may exceed that delivered by respiration by severalfold.

Goodson, B. M.; Song, Y.-Q.; Taylor, R. E.; Schepkin, V. D.; Brennan, K. M.; Chingas, G. C.; Budinger, T. F.; Navon, G.; Pines, A.

1997-01-01

167

[Electroencephalogram, informational saturation of electroencephalogram, and bispectral index during xenon anesthesia for laparoscopic operations].  

PubMed

The depth of xenon anesthesia was never evaluated by modern methods of EEG monitoring, and hence, we studied changes in EEG, INEEG, and BIS during different stages of xenon narcosis and evaluated the possibility of using these values as criteria of xenon anesthesia adequacy. The study was carried out in 60 patients during laparoscopic operations on abdominal organs. The patients were divided into 2 groups receiving different gas anesthetics (xenon or nitric oxide). The results indicate that xenon monoanesthesia caused dose-dependent changes in the native and treated EEG; xenon is a good inhalation anesthetic providing adequate anesthesia for little traumatic operations even in case of mononarcosis; INEEG and BIS monitoring during xenon anesthesia allows an objective evaluation of its depth. PMID:12221874

Likhvantsev, V V; Volovik, A G; Petrov, O V; Sitnikov, A V; Subbotin, V V

2002-01-01

168

Applications of highly spin-polarized xenon in NMR  

SciTech Connect

The main goal of the work presented in this thesis is produce highly spin-polarized xenon to create much greater signal intensities (up to 54,000 times greater) so as to allow studies to be made on systems with low surface area and long spin-lattice relaxation times. The spin-exchange optical pumping technique used to create high nuclear spin polarization is described in detail in chapter two. This technique is initially applied to some multiple-pulse optically detected NMR experiments in low magnetic field (50G) that allow the study of quadrupoler interactions with a surface of only a few square centimeters. In chapter three the apparatus used to allow high field {sup 129}Xe NMR studies to be performed with extremely high sensitivity is described and applied to experiments on diamagnetic susceptibility effects in thin ({approximately}2000 layers) films of frozen xenon. Preliminary surface investigations of laser polarized {sup 129}Xe adsorbed an a variety of materials (salts, molecular crystals, amorphous carbon, graphite) are then discussed. A full detailed study of the surface of a particular polymer, poly(acrylic acid), is presented in chapter four which shows the kind of detailed information that can be obtained from this technique. Along with preliminary results for several similar polymers, a summary is given of xenon studies of a novel ultra-high surface area polymer, poly(triarylcarbinol). Finally in chapter five the exciting possibility of transferring the high spin order of the laser polarized xenon has been used to transfer nuclear spin order to {sup 13}CO{sub 2} in a xenon matrix and to protons on poly(triarylcarbinol).

Long, H.W. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States)

1993-09-01

169

Molecule Shapes  

NSDL National Science Digital Library

Explore molecule shapes by building molecules in 3D! How does molecule shape change with different numbers of bonds and electron pairs? Find out by adding single, double or triple bonds and lone pairs to the central atom. Then, compare the model to real molecules!

Simulations, Phet I.; Moore, Emily; Olson, Jonathan; Lancaster, Kelly; Chamberlain, Julia; Perkins, Kathy

2011-10-10

170

Mighty Molecules  

NSDL National Science Digital Library

In this activity, learners use marshmallows and gum drops to construct seven models of molecules. Learners classify (solid, liquid or gas) and draw diagrams of the molecules. Learners can also create a table showing the chemical formula for each molecule and identify a common use for each chemical. Use this activity to introduce learners to molecules, compounds, and bonds.

Little, Carlyn; Lahart, David; Meyers, Ted; Weisblat, Brooks

1997-01-01

171

High Precision Xenon Measurements Reveal the Presence of Solar Xenon in the Mantle Source of Mid Ocean Ridge Basalts  

NASA Astrophysics Data System (ADS)

Xenon isotopes provide unique insights into the sources of volatile material for planet Earth, the degassing of the mantle, and the chemical evolution of the mantle. Whether the Earth's mantle has solar or planetary heavy noble gases has remained a fundamental and outstanding question. Resolving this issue is crucial for planet accretion models and understanding how volatiles were incorporated into the solid Earth. Here we report the detection of solar, or possibly chondritic (Q), xenon in a gas-rich basalt glass. The sample was collected from the Hotu Matua seamount chain, located south of the Sojourn Ridge, during the 2001 Cook16MV expedition. Xenon was extracted by step crushing fresh basalt glass in vacuum, and xenon isotopes were measured using the Nu multicollector noble gas mass spectrometer at Harvard. Based on reproducibility of standards run over a period of 3 days, which were similar in size (3.5 x 10^{-14}cc of ^{130}Xe) to the sample, external precision for ^{124,126}Xe/^{130}Xe ratios are better than 2%, for ^{128}Xe/^{130}Xe is 7, and for ^{129}Xe/^{130}Xe and ^{136}Xe/^{130}Xe ratios are 4. These uncertainties are only marginally larger than predicted from counting statistics. A clear excess in ^{124,126,128}Xe was observed. The anomalies in non-radiogenic isotopes of xenon cannot result from instrumental mass fractionation or other experimental artifacts since excesses in ^{128}Xe are correlated with excesses in ^{129}Xe. In addition, the ^{129}Xe/^{130}Xe and ^{136}Xe/^{130}Xe ratios fall on the MORB line. Thus, we conclude that the anomalies in the non-radiogenic isotopes of xenon are a real feature of the mantle source of MORBs. Excesses in ^{124,126,128}Xe/^{130}Xe ratios plot on the air solar mixing line and indicate the presence of a solar xenon component in the MORB source. Since the non-radiogenic isotopic composition of solar and Q xenon are similar, a chondritic xenon component cannot be ruled out. Krypton isotopes can potentially distinguish between a solar and a Q component and additional high-precision Kr isotopic measurements are currently underway. The correlation between ^{128}Xe and ^{129}Xe excesses in our sample defines a steeper trajectory than the correlation seen in CO2 well gases, although given the small number of data points such a conclusion is tentative. Nevertheless, a steeper trend implies a significantly larger solar component than previously determined values of 20% (e.g., Holland and Ballentine, 2006). While we are in the process of making additional Xe measurements, a major implication of the current data is that subduction zones must form a significant barrier to the transport of atmospheric Xe into the mantle in order to preserve the solar signature. Alternatively, mantle domains that have been largely isolated from the convective mantle must exist. Leakage of xenon from such a reservoir would then provide the excess ^{129}Xe associated with the solar signature seen in the MORB source. [Ref:Holland and Ballentine, Nature 441, 186, 2006].

Mukhopadhyay, S.; Langmuir, C. H.

2006-12-01

172

The Light Response of the XENON100 Time Projection Chamber and the Measurements of the Optical Parameters with the Xenon Scintillation Light  

NASA Astrophysics Data System (ADS)

The XENON program is a phased project using liquid xenon as a sensitive detector medium in search for weakly interacting massive particles (WIMPs). These particles are the leading candidates to explain the non-baryonic, cold dark matter in our Universe. XENON100, the successor experiment of XENON10, has increased the target liquid xenon mass to 61 kg with a 100 times reduction in background rate enabling a large increase in sensitivity to WIMP-nucleon interaction cross-section. To-date, the most stringent limit on this cross-section over a wide range of WIMP masses have been obtained with XENON100. XENON100 is a detector responding to the scintillation of xenon and the work of this thesis will mainly focus on the light response of the detector. Chapter 1 describes the evidences for dark matter and some of the detection methods, roughly divided by the indirect and the direct detection. In the section 1.2.2 for direct detection, a treatment of interaction rate of WIMPs is introduced. Chapter 2 is a description of the XENON100 detector, some of the main characteristics of liquid xenon, followed by the detector design. In Chapter 3, the light response of the XENON100 time projection chamber (TPC) is explained, including the Monte Carlo simulation work that was carried out prior to the main data taking. The Monte Carlo provided the basic idea of understanding the detector in the early stage of design and calibration, but the actual corrections of the light signals were determined later with the real data. Several optical parameters are critical in explaining the light response, such as the quantum efficiency (QE) of the photomultipliers (PMTs) used in the detector and the reflectivity of the teflon (Polytetrafluoroethylene, PTFE) material that surrounds the liquid xenon target volume and defines the TPC. Since the few existing measurements of reflectivity of PTFE in liquid xenon were performed in different conditions and thus could not be applied, the XENON collaboration put some effort in setting up a reliable and an independent measurement for these parameters. The QE of the Hamamatsu R8520 PMTs at liquid xenon temperature was measured at the Columbia Nevis Laboratory, as described in Chapter 4. A similar but a revised setup was built later at the University of Muenster in Germany for measuring the reflectivity of the PTFE (Chapter 5). These measurements are important for a deeper understanding of XENON100 and the next phase of the program with a XENON1T as well as for other liquid xenon experiments. Chapter 6 explains the details of the energy scale derived from the measurement of the light signals in XENON100 and the cuts used for the analysis, which has led to the most recent scientific results from this experiments. In 2012, the XENON100 dark matter results from 225 live days set the most stringent limit on the spin-independent elastic WIMP- nucleon interaction cross section for WIMP masses above 8 GeV/c2, with a minimum of 2 x 10-45 cm2 at 55 GeV/c2 and 90% confidence level. With this result XENON100 continues to be the leading experiment in the direct search for dark matter.

Choi, Bin

173

Future Sulfur Dioxide Emissions  

Microsoft Academic Search

The importance of sulfur dioxide emissions for climate change is now established, although substantial uncertainties remain. This paper presents projections for future sulfur dioxide emissions using the MiniCAM integrated assessment model. A new income-based parameterization for future sulfur dioxide emissions controls is developed based on purchasing power parity (PPP) income estimates and historical trends related to the implementation of sulfur

Steven J. Smith; Hugh M. Pitcher; Tom M. Wigley

2005-01-01

174

Nitrogen dioxide detection  

DOEpatents

Method and apparatus for detecting the presence of gaseous nitrogen dioxide and determining the amount of gas which is present. Though polystyrene is normally an insulator, it becomes electrically conductive in the presence of nitrogen dioxide. Conductance or resistance of a polystyrene sensing element is related to the concentration of nitrogen dioxide at the sensing element.

Sinha, Dipen N. (Los Alamos, NM); Agnew, Stephen F. (Los Alamos, NM); Christensen, William H. (Buena Park, CA)

1993-01-01

175

Mesoscale Backtracking by Means of Atmospheric Transport Modeling of Xenon Plumes Measured by Radionuclide Gas Stations  

NASA Astrophysics Data System (ADS)

The monitoring of atmospheric radioactive xenon concentration is performed for nuclear safety regulatory requirements. It is also planned to be used for the detection of hypothetical nuclear tests in the framework of the Comprehensive nuclear-Test-Ban Treaty (CTBT). In this context, the French Atomic Energy Commission designed a high sensitive and automated fieldable station, named SPALAX, to measure the activity concentrations of xenon isotopes in the atmosphere. SPALAX stations were set up in Western Europe and have been operated quite continuously for three years or more, detecting principally xenon-133 and more scarcely xenon-135, xenon-133m and xenon-131m. There are around 150 nuclear power plants in the European Union, research reactors, reprocessing plants, medical production and application facilities releasing radioactive xenon in normal or incidental operations. A numerical study was carried out aiming to explain the SPALAX measurements. The mesoscale Atmospheric Transport Modelling involves the MM5 suite (PSU- NCAR) to predict the wind fields on nested domains, and FLEXPART, a 3D Lagrangian particle dispersion code, used to simulate the backward transport of xenon plumes detected by the SPALAX. For every event of detection, at least one potential xenon source has a significant efficiency of emission. The identified likely sources are located quite close to the SPALAX stations (some tens of kilometres), or situated farther (a few hundreds of kilometres). A base line of some mBq per cubic meter in xenon-133 is generated by the nuclear power plants. Peaks of xenon-133 ranging from tens to hundreds of mBq per cubic meter originate from a radioisotope production facility. The calculated xenon source terms required to obtain the SPALAX measurements are discussed and seem consistent with realistic emissions from the xenon sources in Western Europe.

Armand, P. P.; Achim, P.; Taffary, T.

2006-12-01

176

Searching for Double Beta Decay with the Enriched Xenon Observatory  

SciTech Connect

The Enriched Xenon Observatory (EXO) Collaboration is building a series of experiments to search for the neutrinoless double beta decay of {sup 136}Xe. The first experiment, known as EXO-200, will utilize 200 kg of xenon enriched to 80% in the isotope of interest, making it the largest double beta decay experiment to date by one order of magnitude. This experiment is rapidly being constructed, and will begin data taking in 2007. The EXO collaboration is also developing a technique to identify on an event-by-event basis the daughter barium ion of the double beta decay. If successful, this method would eliminate all conventional radioactive backgrounds to the decay, resulting in an ideal experiment. We summarize here the current status of EXO-200 construction and the barium tag R&D program.

Hall, C.; /SLAC

2007-03-16

177

The uses of helium and xenon in current clinical practice.  

PubMed

The noble gases have always been an enigma. Discovered late in the history of chemistry and in seemingly small quantities in our atmosphere, they are some of the most unreactive elements known. However, despite being extremely inert, the noble gases (helium, neon, argon, krypton, xenon and radon) have found diverse and ever expanding applications in medicine. Of all of them, the gases that have found the greatest number of uses in the field of anaesthesia and related specialties are helium and xenon. This review focuses on the history of the discovery of both gases, their unique physicochemical properties and describes their uses in clinical practice with particular emphasis on those applicable to anaesthesia. PMID:18289236

Harris, P D; Barnes, R

2008-03-01

178

First Dark Matter Results from the XENON100 Experiment  

SciTech Connect

The XENON100 experiment, in operation at the Laboratori Nazionali del Gran Sasso in Italy, is designed to search for dark matter weakly interacting massive particles (WIMPs) scattering off 62 kg of liquid xenon in an ultralow background dual-phase time projection chamber. In this Letter, we present first dark matter results from the analysis of 11.17 live days of nonblind data, acquired in October and November 2009. In the selected fiducial target of 40 kg, and within the predefined signal region, we observe no events and hence exclude spin-independent WIMP-nucleon elastic scattering cross sections above 3.4x10{sup -44} cm{sup 2} for 55 GeV/c{sup 2} WIMPs at 90% confidence level. Below 20 GeV/c{sup 2}, this result constrains the interpretation of the CoGeNT and DAMA signals as being due to spin-independent, elastic, light mass WIMP interactions.

Aprile, E.; Choi, B.; Giboni, K.-L.; Lang, R. F.; Lim, K. E.; Melgarejo Fernandez, A. J.; Plante, G. [Physics Department, Columbia University, New York, New York 10027 (United States); Arisaka, K.; Brown, E.; Cline, D. B.; Lam, C. W.; Pantic, E.; Teymourian, A.; Wang, H. [Physics and Astronomy Department, University of California, Los Angeles (United States); Arneodo, F.; Fattori, S. [INFN Laboratori Nazionali del Gran Sasso, Assergi, 67100 (Italy); Askin, A.; Baudis, L.; Behrens, A.; Ferella, A. D. [Physics Institute, University of Zuerich, Winterthurerstr. 190, CH-8057 (Switzerland)

2010-09-24

179

A Study of Radon Background in the XENON100 Experiment  

SciTech Connect

The XENON100 Dark Matter experiment has recently published first results from an analysis of 11.2 live days of data, setting an upper limit on the spin-independent WIMP-nucleon elastic scattering cross section of 3.4x10{sup -44} cm{sup 2} at 55 GeV/c{sup 2} and 90% confidence level. This article focuses on one specific background component of the XENON100 detector by presenting two independent methods of measuring the {sup 222}Rn concentration during operation phase. A first estimate of radon activity is derived for the 11.2 days analysis, proving the feasibility of on-line radon monitoring. Remaining systematic uncertainties are discussed.

Weber, Marc [Max-Planck-Institut fuer Kernphysik, Postfach 103980, D-69029 Heidelberg (Germany)

2011-04-27

180

Experimental investigations of argon and xenon ion sources  

NASA Technical Reports Server (NTRS)

The multipole thruster was used to investigate the use of argon and xenon propellants as possible alternatives to the electric thruster propellants of mercury and cesium. The multipole approach was used because of its general high performance level. The design employed, using flat and cylindrical rolled sections of sheet metal, was selected for ease of fabrication, design, assembly, and modification. All testing was conducted in a vacuum facility and the pumping was accomplished by a 0.8 m diffusion pump together with liquid nitrogen cooled liner. Minimum discharge losses were in the 200-250 ev. ion range for both argon and xenon. Flatness parameters were typically in the 0.70-0.75 range.

Kaufman, H. R.

1975-01-01

181

Search for the nuclear Schiff moment in liquid xenon  

SciTech Connect

A parameter of the P,T-odd Hamiltonian characterizing interaction of the nuclear Schiff moment with the gradient of electronic density on the Xe nucleus is calculated for an isolated Xe atom and for liquid xenon. We use a more realistic model of liquid medium than the spherical cell model used by Ravaine and Derevianko [Phys. Rev. A 69, 050101(R) (2004)]. Qualitatively different results for enhancement of the P,T-odd effect in liquid xenon are obtained when polarization of the medium is taken into account. Thus, proper choice of the liquid phase model is crucially important even for calculation of the properties dependent mostly on the electronic density near a nucleus.

Isaev, T. A.; Petrov, A. N.; Mosyagin, N. S.; Titov, A. V. [Petersburg Nuclear Physics Institute, Gatchina, 188300 (Russian Federation); St.-Petersburg State University, Chemistry Department, St.-Petersburg 198504 (Russian Federation)

2007-03-15

182

Two Photon Spectroscopy of the 6p Manifold of Xenon.  

NASA Astrophysics Data System (ADS)

A computer-controlled, frequency-doubled, tunable pulsed dye laser was used to excite members of the 6p manifold of xenon at pressures from less than one Torr to ten thousand Torr. A sensitive detection scheme, linear over a broad dynamic range, was used to measure the fluorescence from the laser excited and collisionally excited states. The two photon absorption profiles for the three dipole-dipole allowed transitions from the ground state have been recorded. These spectra have been analyzed using the impact approximation, the quasistatic approximation, and the Anderson-Talman theory to extract the interaction potentials of these states with ground state xenon atoms for internuclear separations greater than 3.75 Angstroms.

Raymond, Thomas Daniel

183

Two photon spectroscopy of the 6p manifold of xenon  

SciTech Connect

A computer-controlled, frequency-doubled, tunable pulsed dye laser was used to excite members of the 6p manifold of xenon at pressures from less than one Torr to ten thousand Torr. A sensitive detection scheme, linear over a broad dynamic range, was used to measure the fluorescene from the laser excited and collisionally excited states. The two photon absorption profiles for the three dipole-dipole allowed transitions from the ground state have been recorded. These spectra have been analyzed using the impact approximation, the quasistatic approximation, and the Anderson-Talman theory to extract the interaction potentials of these states with ground state xenon atoms for internuclear separations greater than 3.75 Angstroems.

Raymond, T.D.

1983-01-01

184

Experimental determination of the xenon isotopic fractionation during adsorption  

NASA Astrophysics Data System (ADS)

Adsorption of noble gases into solids is often posited to account for their abundance patterns in meteorites, terrestrial rocks, and planetary atmospheres. Since these elements present isotope variations among geochemical reservoirs, we have experimentally tested the possibility that adsorption of neutral noble gases could result in isotopic fractionation. Our experiment consists of a cycle of adsorption/desorption processes in which xenon is progressively lost from a reservoir by equilibrium adsorption on kerogen and on montmorillonite. Any isotopic fractionation would then be amplified by the Rayleigh-like distillation experiment. The fractionation factors ? are extrapolated to be -0.18 0.08 per u and -0.22 0.07 per u (both at the 2? level) for kerogen and montmorillonite, respectively. Thus, adsorption of neutral noble gases alone cannot account for the specific isotopic composition of noble gases trapped in meteorites, nor for the isotopic composition of xenon in the terrestrial and martian atmospheres.

Marrocchi, Yves; Marty, Bernard

2013-08-01

185

Near-threshold photoionization of xenon metastable atoms  

NASA Technical Reports Server (NTRS)

Photoionization from metastable levels of atomic xenon has been studied in the wavelength range from the threshold at 4622 A to 2700 A. Structure in the photoionization signal, due to autoionization, is analyzed to provide term values, lifetimes, and line-shape parameters of the autoionizing states. These parameters, together with the estimated absolute cross sections, are used to derive discrete and continuum oscillator strengths.

Rundel, R. D.; Dunning, F. B.; Goldwire, H. C., Jr.; Stebbings, R. F.

1975-01-01

186

Gamma-ray spectrometer utilizing xenon at high pressure  

Microsoft Academic Search

A prototype gamma-ray spectrometer utilizing xenon gas near the critical point (166C, 58 atm) is under development. The spectrometer will function as a room-temperature ionization chamber detecting gamma rays in the energy range 100 keV2 MeV, with an energy resolution intermediate between semiconductor (Ge) and scintillation (NaI) spectrometers. The energy resolution is superior to that of a NaI scintillation spectrometer

G. C. Smith; G. J. Mahler; B. Yu; W. R. Kane; J. K. Markey

1994-01-01

187

Supercritical xenon-filled hollow-core photonic bandgap fiber.  

PubMed

We demonstrate that filling a hollow-core photonic-bandgap fiber with supercritical xenon creates a medium with a controllable density up to several hundred times that at STP, while working at room temperature. The high compressibility of the supercritical fluid allows rapid tuning of the spectral guidance window by making small changes of gas pressure near the critical point. We discuss potential applications of this system in linear and nonlinear optics. PMID:23736625

Lynch-Klarup, K E; Mondloch, E D; Raymer, M G; Arrestier, D; Gerome, F; Benabid, F

2013-06-01

188

Molecule nanoweaver  

DOEpatents

A method, apparatus, and system for constructing uniform macroscopic films with tailored geometric assemblies of molecules on the nanometer scale. The method, apparatus, and system include providing starting molecules of selected character, applying one or more force fields to the molecules to cause them to order and condense with NMR spectra and images being used to monitor progress in creating the desired geometrical assembly and functionality of molecules that comprise the films.

Gerald, II; Rex E. (Brookfield, IL); Klingler, Robert J. (Glenview, IL); Rathke, Jerome W. (Homer Glen, IL); Diaz, Rocio (Chicago, IL); Vukovic, Lela (Westchester, IL)

2009-03-10

189

XENON in medical area: emphasis on neuroprotection in hypoxia and anesthesia.  

PubMed

Xenon is a medical gas capable of establishing neuroprotection, inducing anesthesia as well as serving in modern laser technology and nuclear medicine as a contrast agent. In spite of its high cost, its lack of side effects, safe cardiovascular and organoprotective profile and effective neuroprotective role after hypoxic-ischemic injury (HI) favor its applications in clinics. Xenon performs its anesthetic and neuroprotective functions through binding to glycine site of glutamatergic N-methyl-D-aspartate (NMDA) receptor competitively and blocking it. This blockage inhibits the overstimulation of NMDA receptors, thus preventing their following downstream calcium accumulating cascades. Xenon is also used in combination therapies together with hypothermia or sevoflurane. The neuroprotective effects of xenon and hypothermia cooperate synergistically whether they are applied synchronously or asynchronously. Distinguishing properties of Xenon promise for innovations in medical gas field once further studies are fulfilled and Xenon's high cost is overcome. PMID:23369273

Esencan, Ecem; Yuksel, Simge; Tosun, Yusuf Berk; Robinot, Alexander; Solaroglu, Ihsan; Zhang, John H

2013-01-01

190

Constraints on Nucleosynthesis from Xenon Isotopes in Presolar Material  

NASA Astrophysics Data System (ADS)

By applying theoretical constraints to three-dimensional fits of xenon isotope data from presolar grains, we show that they strongly suggest a nucleosynthesis process that produces ``r-process'' isotopes without producing s-process isotopes (128Xe, 130Xe) and without producing the conventional r-process isotope 136Xe. It is one of three distinct nucleosynthetic sources that are necessary and sufficient to explain the gross variation in xenon isotopic data across all presolar material. The other source contributing r-process isotopes is responsible for the heavy isotope signature identified in nanodiamonds, which is also present in presolar SiC, and is associated with light isotope enrichment. The relative enrichments of heavy and light isotopes in this component in nanodiamonds and SiC grains are different, implying that the parent nucleosynthetic processes are not inextricably linked. Because minor variations in the isotopic compositions of xenon trapped in nanodiamonds show that two distinct sites contributed nanodiamonds to the early solar system within the average grain lifetime, it is suggested that Type IIa supernovae (SNe IIa) are not the source of the nanodiamonds. The s-process signature derived is consistent with that derived from mixing lines between grain subpopulations for isotopes on the s-process path. This implies that a pure end-member is present in the grains (although not approached in analyses). Our approach is more general and provides a less restrictive set of numerical constraints to be satisfied by proposed theoretical treatments of nucleosynthesis.

Gilmour, J. D.; Turner, G.

2007-03-01

191

Allende meteorite: Isotopically anomalous xenon is accompanied by normal osmium  

PubMed Central

The 184Os/190Os ratio of six Allende meteorite samples was determined by neutron activation analysis. Four chromite concentrates gave a ratio differing from the terrestrial ratio by only -0.1 0.4%, although they contained highly anomalous xenon enriched by up to 67% in 124Xe and 93% in 136Xe. In view of this result and the normal isotopic composition of carbon and oxygen in these fractions, it seems very unlikely that the xenon anomalies were produced in a supernova by the p and r processes. More probably, the xenon anomalies were established in the early solar system, by mass fractionation during trapping of noble gases in solids and by spontaneous fission of a superheavy element. Two other samples, containing osmium from the calcium,aluminum-rich inclusions, also gave an 184Os/190Os ratio within -0.1 0.5% of the terrestrial value, although these inclusions show well-established anomalies in the light elements oxygen and magnesium, which appear to be due to pre-solar dust grains of distinctive nuclear history. Apparently the stellar source of the anomalous oxygen and magnesium did not synthesize heavier elements.

Takahashi, H.; Higuchi, H.; Gros, Jacques; Morgan, John W.; Anders, Edward

1976-01-01

192

High-pressure xenon detector development at Constellation Technology Corporation  

NASA Astrophysics Data System (ADS)

Xenon-filled ionization detectors, due to their high atomic number fill gas ( Z=54), moderate densities (0.3-0.5 g/cm 3) and good energy resolution (2-4% at 662 keV), fill an important niche between more familiar technologies such as NaI(Tl) scintillators and germanium detectors. Until recently, difficulties with obtaining sufficient xenon purity, reducing microphonic sensitivity, and developing low-noise electronics compatible with small ionization signals have hampered the development of this nuclear detection field. Constellation Technology Corporation, whose experience with xenon detectors goes back to the mid 1990s, has made significant progress in these areas and has developed a commercial line of detectors with active volumes ranging from small (35 g Xe) to large (1400 g Xe). Current applications for Constellation's detectors are principally in the area of defense (Unmanned Aerial Vehicles and Advanced Spectroscopic Portals), but as awareness of this technology grows, it will surely find applications in a much expanded range of fields.

Austin, Robert A.

2007-08-01

193

Isotopic signature of atmospheric xenon released from light water reactors.  

PubMed

A global monitoring system for atmospheric xenon radioactivity is being established as part of the International Monitoring System to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The isotopic activity ratios of (135)Xe, (133m)Xe, (133)Xe and (131m)Xe are of interest for distinguishing nuclear explosion sources from civilian releases. Simulations of light water reactor (LWR) fuel burn-up through three operational reactor power cycles are conducted to explore the possible xenon isotopic signature of nuclear reactor releases under different operational conditions. It is studied how ratio changes are related to various parameters including the neutron flux, uranium enrichment and fuel burn-up. Further, the impact of diffusion and mixing on the isotopic activity ratio variability are explored. The simulations are validated with reported reactor emissions. In addition, activity ratios are calculated for xenon isotopes released from nuclear explosions and these are compared to the reactor ratios in order to determine whether the discrimination of explosion releases from reactor effluents is possible based on isotopic activity ratios. PMID:16650919

Kalinowski, Martin B; Pistner, Christoph

2006-01-01

194

Krypton assay in xenon at the ppq level using a gas chromatographic system and mass spectrometer  

NASA Astrophysics Data System (ADS)

We have developed a new method to measure krypton traces in xenon at unprecedented low concentrations. This is a mandatory task for many near-future low-background particle physics detectors. Our system separates krypton from xenon using cryogenic gas chromatography. The amount of krypton is then quantified using a mass spectrometer. We demonstrate that the system has achieved a detection limit of 8 ppq (parts per quadrillion) and present results of distilled xenon with krypton concentrations below 1 ppt.

Lindemann, Sebastian; Simgen, Hardy

2014-02-01

195

Gamma detectors based on high-pressure xenon: their development and application  

NASA Astrophysics Data System (ADS)

Various modifications of xenon detectors and their parameters in comparison with gamma-detectors of other types are considered. Prospects of xenon detectors' applicatins in gamma-spectroscopy based on experimental results are discussed including detection and control of radioactive and fissile materials displacement, definition of uranium enrichment rate, and measurements of nuclear reactor radioactive gas waste concentration. Possibilities for xenon detector use for environmental control and measurement of cosmic gamma radiation on orbital stations are considered.

Ulin, Sergey E.; Dmitrenko, Valery V.; Grachev, V. M.; Uteshev, Z. M.; Vlasik, K. F.; Chernysheva, I. V.; Dukhvalov, A. G.; Kotler, F. G.; Pushkin, K. N.

2004-10-01

196

Gamma detectors based on high pressure xenon: their development and application  

NASA Astrophysics Data System (ADS)

Various modifications of xenon detectors and their parameters in comparison with gamma-detectors of other types are considered. Prospects of xenon detectors' applications in gamma-spectroscopy based on experimental results are discussed including detection and control of radioactive and fissile materials displacement, definition of uranium enrichment rate, and measurements of nuclear reactor radioactive gas waste concentration. Possibilities for xenon detector use for environmental control and measurement of cosmic gamma radiation on orbital stations are considered.

Ulin, Sergey E.; Dmitrenko, Valery V.; Grachev, V. M.; Uteshev, Z. M.; Vlasic, K. F.; Chernysheva, I. V.; Duhvalov, A. G.; Kotler, F. G.; Pushkin, K. N.

2004-01-01

197

Early outgassing of Mars supported by differential water solubility of iodine and xenon  

NASA Technical Reports Server (NTRS)

The Martian atmosphere has a high X-129/Xe-132 ratio compared to the Martian mantle. As Xe-129 is the daughter product of the extinct nuclide I-129, a means of fractionating iodine from xenon early in Martian history appears necessary to account for the X-129/Xe-132 ratios of its known reservoirs. A model is presented here to account for the Marian xenon data which relies on the very different solubilities of xenon and iodine in water to fractionate them after outgassing. Atmospheric xenon is lost by impact erosion during heavy bombardment, followed by release of Xe-129 produced from I-129 decay in the crust.

Musselwhite, Donald S.; Drake, Michael J.; Swindle, Timothy D.

1991-01-01

198

Shock compression of a fifth period element: liquid xenon to 840 GPa.  

PubMed

Current equation of state (EOS) models for xenon show substantial differences in the Hugoniot above 100 GPa, prompting the need for an improved understanding of xenon's behavior at extreme conditions. We performed shock compression experiments on liquid xenon to determine the Hugoniot up to 840 GPa, using these results to validate density functional theory (DFT) simulations. Despite the nearly fivefold compression, we find that the limiting Thomas-Fermi theory, exact in the high density limit, does not accurately describe the system. Combining the experimental data and DFT calculations, we developed a free-energy-based, multiphase EOS capable of describing xenon over a wide range of pressures and temperatures. PMID:20868109

Root, Seth; Magyar, Rudolph J; Carpenter, John H; Hanson, David L; Mattsson, Thomas R

2010-08-20

199

The carbon dioxide cycle  

USGS Publications Warehouse

The seasonal CO2 cycle on Mars refers to the exchange of carbon dioxide between dry ice in the seasonal polar caps and gaseous carbon dioxide in the atmosphere. This review focuses on breakthroughs in understanding the process involving seasonal carbon dioxide phase changes that have occurred as a result of observations by Mars Global Surveyor. ?? 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

James, P. B.; Hansen, G. B.; Titus, T. N.

2005-01-01

200

Temperature VS Carbon Dioxide  

NSDL National Science Digital Library

In this activity, students examine the relationship between carbon dioxide levels and global temperature change by studying a graph of these two variables. They will discover that by using data from ice cores, scientists can determine temperature and carbon dioxide levels in the air as far back as a hundred thousand years in the past. The students try to predict which variable is the independent one and then make a graph of temperature change and carbon dioxide levels. After making their graph, students describe the relationship between temperature and carbon dioxide levels in the atmosphere to determine if their predictions were correct.

201

Neutral compounds with xenon-germanium bonds: a theoretical investigation on FXeGeF and FXeGeF?.  

PubMed

The structure and stability of FXeGeF and FXeGeF3 were investigated by MP2, CCSD(T), and B3LYP calculations, and their bonding situation was examined by NBO and AIM analysis. These molecules are thermochemically stable with respect to dissociation into F + Xe + GeF(n) (n = 1, 3), and kinetically stable with respect to dissociation into Xe + GeF(n+1), thus suggesting their conceivable existence as metastable species. FXeGeF and FXeGeF3 are best described by the resonance structures F(-)(Xe-GeF(+)) and F(-)(Xe-GeF3(+)), and feature essentially ionic xenon-fluorine interactions. The xenon-germanium bonds have instead a significant contribution of covalency. The comparison with XeGeF(+) and XeGeF3(+) suggests that the stability of FXeGeF and FXeGeF3 arises from the F(-)-induced stabilization of these ionic moieties. This structural motif resembles that encountered in other noble-gas neutral and ionic species. PMID:24720441

Borocci, Stefano; Giordani, Maria; Grandinetti, Felice

2014-05-01

202

Xenon Sputter Yield Measurements for Ion Thruster Materials  

NASA Technical Reports Server (NTRS)

In this paper, we describe a technique that was used to measure total and differential sputter yields of materials important to high specific impulse ion thrusters. The heart of the technique is 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. Differential sputtering yields were generally measured over a full 180 deg arc in a plane that included the beam centerline and the normal vector to the target surface. Sputter yield results are presented for a xenon ion energy range from 0.5 to 10 keV and an angle of incidence range from 0 deg to 70 deg from the target surface normal direction for targets consisting of molybdenum, titanium, solid (Poco) graphite, and flexible graphite (grafoil). Total sputter yields are calculated using a simple integration procedure and comparisons are made to sputter yields obtained from the literature. In general, the agreement between the available data is good. As expected for heavy xenon ions, the differential and total sputter yields are found to be strong functions of angle of incidence. Significant under- and over-cosine behavior is observed at low- and high-ion energies, respectively. In addition, strong differences in differential yield behavior are observed between low-Z targets (C and Ti) and high-Z targets (Mo). Curve fits to the differential sputter yield data are provided. They should prove useful to analysts interested in predicting the erosion profiles of ion thruster components and determining where the erosion products re-deposit.

Williams, John D.; Gardner, Michael M.; Johnson, Mark L.; Wilbur, Paul J.

2003-01-01

203

A 650 J e-beam-pumped atomic xenon laser  

SciTech Connect

The atomic xenon laser has been scaled from the 80 J per pulse output energy level reported to 650 J, using a large two-sided {ital e}-beam-pumped device. The extraction volume dimensions were 0.5 m {center dot} 0.65 m {center dot} 3 m. The gas was pumped at a temporally and spatially averaged rate of 70 kW/cm{sup 3}, and the spatially averaged specific input energy was 115 J/L. An aluminum rear reflector and an uncoated, fused silica output coupler were aligned to form a plane-parallel optical resonator. Output energy measurements were made with a full-aperture calorimeter, and the temporal pulse shape of the 1.7 {mu}m laser radiation was recorded with a spectrally filtered germanium photodiode. The device was operated with argon-xenon gas mixtures at pressures ranging from 20 to 40 psia at a temperature of 23{degrees} C, and the xenon mole fraction was empirically optimized. The maximum output energy of 650 J was obtained at an intrinsic efficiency (output energy divided by energy deposited in gas) of 0.57%. A higher efficiency of 0.85% was achieved by using a shorter {ital e}-beam pulse, at a reduced laser output energy of 495 J. Laser output which began shortly after the start of the {ital e}-beam pulse continued well beyond the termination of that pulse, decaying at an exponential rate with an {ital e}-fold time of 1.8 {mu}s. A possible explanation for the observed laser pulse shape is discussed.

Litzenberger, L.N.; Trainor, D.W.; McGeoch, M.W. (Avco-Everett Research Lab., Everett, MA (USA))

1990-09-01

204

Bulk viscosity of stirred xenon near the critical point.  

PubMed

We deduce the thermophysical properties of near-critical xenon from measurements of the frequencies and half-widths of the acoustic resonances of xenon maintained at its critical density in centimeter-sized cavities. In the reduced temperature range 1 x 10-3<(T-Tc)/Tc<7 x 10 (-6), we measured the resonance frequency and quality factor (Q) for each of six modes spanning a factor of 27 in frequency. As Tc was approached, the frequencies decreased by a factor of 2.2 and the Q's decreased by as much as a factor of 140. Remarkably, these results are predicted (within +/-2% of the frequency and within a factor of 1.4 of Q) by a model for the resonator and a model for the frequency-dependent bulk viscosity zeta(omega) that uses no empirically determined parameters. The resonator model is based on a theory of acoustics in near-critical fluids developed by Gillis, Shinder, and Moldover [Phys. Rev. E 70, 021201 (2004)]. In addition to describing the present low-frequency data (from 120 Hz to 7.5 kHz), the model for zeta(omega) is consistent with ultrasonic (0.4--7 MHz) velocity and attenuation data from the literature. However, the model predicts a peak in the temperature dependence of the dissipation in the boundary layer that we did not detect. This suggests that the model overestimates the effect of the bulk viscosity on the thermal boundary layer. In this work, the acoustic cavities were heated from below to stir the xenon, thereby reducing the density stratification resulting from Earth's gravity. The stirring reduced the apparent equilibration time from several hours to a few minutes, and it reduced the effective temperature resolution from 60 mK to approximately 2 mK, which corresponds to (T-Tc)/Tc approximately =7 x 10(-6). PMID:16383593

Gillis, K A; Shinder, I I; Moldover, M R

2005-11-01

205

Formation of copper clusters on the surface of a xenon buffer layer  

NASA Astrophysics Data System (ADS)

We applied the molecular dynamics technique to the study of the formation of three-dimensional nanoclusters on a xenon surface. The main physical mechanisms were established of the processes of formation of their structure. Equilibrium configurations of copper clusters on the solid xenon layer were determined and the energies of their formation were calculated.

Marchenko, I. G.; Marchenko, I. I.

2014-05-01

206

INTEGRAL AND SPECTRAL CHARACTERISTICS OF ATON STATIONARY PLASMA THRUSTER OPERATING ON KRYPTON AND XENON  

Microsoft Academic Search

The integral characteristics of an ATON (1) stationary plasma thruster operating on xenon and krypton are investigated. It is shown that, with krypton, the thrust at the same mass flow rate of the working gas is greater and the efficiency is somewhat lower than those with xenon. An efficiency of ~60% was achieved with krypton for the specific impulse attaining

A. I. Bugrova; A. I. Morozov; A. S. Lipatov; A. M. Bishaev; V. K. Kharchevnikov; M. V. Kozintseva

207

Slope Method for Prediction of Cirus Critical Heights During Xenon Transients.  

National Technical Information Service (NTIS)

The prediction of critical heavy water heights in Cirus during xenon transients after the reactor shut-down depends upon the operating history of the reactor. The classical approach for the calculation of iodine and xenon concentrations on the reactor pow...

N. Mahendra

1976-01-01

208

High pressure equation of state for solid xenon from interatomic potentials  

Microsoft Academic Search

The interatomic pair potential for xenon recently derived by Aziz and Slaman (AS) is used to calculate pressure as function of volume for solid xenon, and the results are compared with experimental data and with those calculated using the earlier potential of Barker, Klein and Bobetic (BKB). If the Axilrod-Teller (AT) interaction is included agreement with experiment is good up

J. A. Barker

1987-01-01

209

Early treatment with xenon protects against the cold ischemia associated with chronic allograft nephropathy in rats.  

PubMed

Chronic allograft nephropathy (CAN) is a common finding in kidney grafts with functional impairment. Prolonged hypothermic storage-induced ischemia-reperfusion injury is associated with the early onset of CAN. As the noble gas xenon is clinically used as an anesthetic and has renoprotective properties in a rodent model of ischemia-reperfusion injury, we studied whether early treatment with xenon could attenuate CAN associated with prolonged hypothermic storage. Exposure to xenon enhanced the expression of insulin growth factor-1 (IGF-1) and its receptor in human proximal tubular (HK-2) cells, which, in turn, increased cell proliferation. Xenon treatment before or after hypothermia-hypoxia decreased cell apoptosis and cell inflammation after reoxygenation. The xenon-induced HK-2 cell proliferation was abolished by blocking the IGF-1 receptor, mTOR, and HIF-1? individually. In the Fischer-to-Lewis rat allogeneic renal transplantation model, xenon exposure of donors before graft retrieval or recipients after engraftment enhanced tubular cell proliferation and decreased tubular cell death and cell inflammation associated with ischemia-reperfusion injury. Compared with control allografts, xenon treatment significantly suppressed T-cell infiltration and fibrosis, prevented the development of CAN, and improved renal function. Thus, xenon treatment promoted recovery from ischemia-reperfusion injury and reduced susceptibility to the subsequent development of CAN in allografts. PMID:24025645

Zhao, Hailin; Luo, Xianghong; Zhou, Zhaowei; Liu, Juying; Tralau-Stewart, Catherine; George, Andrew J T; Ma, Daqing

2014-01-01

210

Evaluation of pulmonary perfusion in lung regions showing isolated xenon-133 ventilation washout defects  

Microsoft Academic Search

Xenon-133 washout phase imaging is often used to help determine whether the etiology of a perfusion defect is embolic or due to pulmonary parenchymal pathology, such as chronic obstructive pulmonary disease. This study was designed to evaluate the pulmonary blood flow patterns associated with isolated defects on xenon washout images. Scintigraphic lung studies were reviewed until 100 cases with abnormal

DAVID L. BUSHNELL; KUL B. SOOD; PARVEZ SHIRAZI; INDRA PAL

1990-01-01

211

Collision-induced light scattering in a thin xenon layer between graphite slabs - MD study  

NASA Astrophysics Data System (ADS)

The collision-induced light scattering many-body correlation functions and their spectra in thin xenon layer located between two parallel graphite slabs have been investigated by molecular dynamics computer simulations. The results have been obtained at three different distances (densities) between graphite slabs. Our simulations show the increased intensity of the interaction-induced light scattering spectra at low frequencies for xenon atoms in confined space, in comparison to the bulk xenon sample. Moreover, we show substantial dependence of the interaction-induced light scattering correlation functions of xenon on the distances between graphite slabs. The dynamics of xenon atoms in a confined space was also investigated by calculating the mean square displacement functions and related diffusion coefficients. The structural property of confined xenon layer was studied by calculating the density profile, perpendicular to the graphite slabs. Building of a fluid phase of xenon in the innermost part of the slot was observed. The nonlinear dependence of xenon diffusion coefficient on the separation distance between graphite slabs has been found.

Dawid, A.; Grny, K.; Wojcieszyk, D.; Dendzik, Z.; Gburski, Z.

2014-08-01

212

Response of XENON10 to Neutrons: Comparison of Monte Carlo and data  

Microsoft Academic Search

The XENON experiment uses liquid xenon (LXe) as the target medium for detecting Cold Dark Matter in the form of Weakly Interacting Massive Particles (WIMPs). Event by event discrimination is achieved by simultaneously measuring the ionization and scintillation signal produced by nuclear recoil events. The discrimination power is calibrated based on neutron and gamma calibrations done using external AmBe and

Angel Manzur

2007-01-01

213

A prospective study of xenon arc photocoagulation for central retinal vein occlusion  

Microsoft Academic Search

Twenty patients with central retinal vein occlusion were randomly divided into two groups in a prospective study to evaluate the effects of xenon are photocoagulation in central retinal vein occlusion. The patients in one group were treated with 360 degrees scatter xenon photocoagulation and the others received no treatment. The average follow-up was 18 months. There were no cases of

D R May; M L Klein; G A Peyman

1976-01-01

214

Collision-induced light scattering in a thin xenon layer between graphite slabs - MD study.  

PubMed

The collision-induced light scattering many-body correlation functions and their spectra in thin xenon layer located between two parallel graphite slabs have been investigated by molecular dynamics computer simulations. The results have been obtained at three different distances (densities) between graphite slabs. Our simulations show the increased intensity of the interaction-induced light scattering spectra at low frequencies for xenon atoms in confined space, in comparison to the bulk xenon sample. Moreover, we show substantial dependence of the interaction-induced light scattering correlation functions of xenon on the distances between graphite slabs. The dynamics of xenon atoms in a confined space was also investigated by calculating the mean square displacement functions and related diffusion coefficients. The structural property of confined xenon layer was studied by calculating the density profile, perpendicular to the graphite slabs. Building of a fluid phase of xenon in the innermost part of the slot was observed. The nonlinear dependence of xenon diffusion coefficient on the separation distance between graphite slabs has been found. PMID:24755364

Dawid, A; Grny, K; Wojcieszyk, D; Dendzik, Z; Gburski, Z

2014-08-14

215

Single Molecules  

NSDL National Science Digital Library

A new molecular science journal, Single Molecules, from Wiley Interscience, "will provide researchers with a broad overview of current methods and techniques, recent applications and shortcomings of present techniques in the field of single molecules." With temporary free access, the journal's latest issue contains a few full-text articles, with more articles being regularly added. This journal is currently calling for papers.

216

Spontaneous mode locking in long-cavity xenon lasers  

SciTech Connect

Spontaneous mode locking in Fabry--Perot xenon lasers has been experimentally investigated for cavity lengths up to 66 m. Our results show dependence of the number of pulses per round-trip time on the cavity length and the excitation current. Other dynamical effects such as the ringing and modulation of the mode-locked pulses have been observed. A semiclassical model for the self-locking of an inhomogeneously broadened laser is also presented. Numerical results based on this model describe many dynamical features observed in our experiments.

Tarroja, M. F. H.; Sharafi, M.; Casperson, L. W.

1989-08-01

217

Low Energy Solar Neutrino Detection by using Liquid Xenon  

NASA Astrophysics Data System (ADS)

Possibility to use ultra pure liquid Xenon as a low energy solar neutrino detector by means of ?+e scattering is evaluated. A possible detector with 10 tons of fiducial volume will give ~14 events for pp-neutrinos and ~6 events for 7Be neutrinos with the energy threshold at 50 keV. The detector can be built with known and established technologies. High density of the liquid- Xe would provide self-shields against the incoming backgrounds originating from the container and outer environments.

Suzuki, Y.

2001-01-01

218

Frequency-Dependent Viscosity of Xenon Near the Critical Point  

NASA Technical Reports Server (NTRS)

We used a novel, overdamped oscillator aboard the Space Shuttle to measure the viscosity eta of xenon near its critical density rho(sub c), and temperature T(sub c). In microgravity, useful data were obtained within 0.1 mK of T(sub c), corresponding to a reduced temperature t = (T -T(sub c))/T(sub c) = 3 x 10(exp -7). The data extend two decades closer to T(sub c) than the best ground measurements, and they directly reveal the expected power-law behavior eta proportional to t(sup -(nu)z(sub eta)). Here nu is the correlation length exponent, and our result for the small viscosity exponent is z(sub eta) = 0.0690 +/- 0.0006. (All uncertainties are one standard uncertainty.) Our value for z(sub eta) depends only weakly on the form of the viscosity crossover function, and it agrees with the value 0.067 +/- 0.002 obtained from a recent two-loop perturbation expansion. The measurements spanned the frequency range 2 Hz less than or equal to f less than or equal to 12 Hz and revealed viscoelasticity when t less than or equal to 10(exp -1), further from T(sub c) than predicted. The viscoelasticity scales as Af(tau), where tau is the fluctuation-decay time. The fitted value of the viscoelastic time-scale parameter A is 2.0 +/- 0.3 times the result of a one-loop perturbation calculation. Near T(sub c), the xenon's calculated time constant for thermal diffusion exceeded days. Nevertheless, the viscosity results were independent of the xenon's temperature history, indicating that the density was kept near rho(sub c), by judicious choices of the temperature vs. time program. Deliberately bad choices led to large density inhomogeneities. At t greater than 10(exp -5), the xenon approached equilibrium much faster than expected, suggesting that convection driven by microgravity and by electric fields slowly stirred the sample.

Berg, Robert F.; Moldover, Michael R.; Zimmerli, Gregory A.

1999-01-01

219

Mission Advantages of NEXT: NASA's Evolutionary Xenon Thruster  

NASA Technical Reports Server (NTRS)

With the demonstration of the NSTAR propulsion system on the Deep Space One mission, the range of the Discovery class of NASA missions can now be expanded. NSTAR lacks, however, sufficient performance for many of the more challenging Office of Space Science (OSS) missions. Recent studies have shown that NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system is the best choice for many exciting potential OSS missions including outer planet exploration and inner solar system sample returns. The NEXT system provides the higher power, higher specific impulse, and higher throughput required by these science missions.

Oleson, Steven; Gefert, Leon; Benson, Scott; Patterson, Michael; Noca, Muriel; Sims, Jon

2002-01-01

220

A 5-kW xenon ion thruster lifetest  

NASA Technical Reports Server (NTRS)

The results of the first life test of a high power ring-cusp ion thruster are presented. A 30-cm laboratory model thruster was operated steady-state at a nominal beam power of 5 kW on xenon propellant for approximately 900 hours. This test was conducted to identify life-timing erosion modifications, and to demonstrate operation using simplified power processing. The results from this test are described including the conclusions derived from extensive post-test analyses of the thruster. Modifications to the thruster and ground support equipment, which were incorporated to solve problems identified by the lifetest, are also described.

Patterson, Michael J.; Verhey, Timothy R.

1990-01-01

221

A liquid xenon TPC for a medical imaging Compton telescope  

NASA Astrophysics Data System (ADS)

A new technique for medical imaging, "3? imaging", is studied by our group at SUBATECH for few years. A small liquid xenon time projection chamber prototype has been built in order to demonstrate the feasibility of this technique. With an ultra-low-noise front-end electronics, the energy deposit and resolution of 511 keV ?-ray as a function of drift electric field (E) is measured with high precision. 500 ?m of z resolution is estimated by measuring the charge carriers drift velocity and time resolution.

Oger, T.; Chen, W.-T.; Cussonneau, J.-P.; Donnard, J.; Duval, S.; Lamblin, J.; Lemaire, O.; Mohamad Hadi, A. F.; Leray, P.; Morteau, E.; Scotto Lavina, L.; Stutzmann, J.-S.; Thers, D.

2012-12-01

222

Synthesis of Diamondoids by Supercritical Xenon Discharge Plasma  

NASA Astrophysics Data System (ADS)

Diamondoids were synthesized by dielectric barrier discharges in supercritical xenon containing dissolved adamantane, which served as a precursor. The synthesis of diamantane was confirmed by gas chromatography mass spectrometry measurements, in addition to energy-dispersive X-ray spectroscopy and micro-Raman spectroscopy measurements. Moreover, the possible synthesis of two higher-order diamondoids, pentamantane and decamantane, with molecular weights of 330 and 456, respectively, is indicated from the selective ion monitoring mode. The largest production yield was obtained in the vicinity of the critical point.

Shizuno, Tomoki; Miyazoe, Hiroyuki; Saito, Koya; Stauss, Sven; Suzuki, Minoru; Sasaki, Takehiko; Terashima, Kazuo

2011-03-01

223

Experimental evidence on interaction between xenon and bovine serum albumin  

NASA Astrophysics Data System (ADS)

Xenon gas interacts with bovine serum albumin (BSA) dissolved in a physiological buffer solution. The fluorescence quenching related to the Trp emission is reversible and depends linearly on the time of saturation by Xe. The most probable site of this interaction is Trp212. The common emission of all BSA fluorophores is also influenced by Xe but this quenching is more complex and suggests: (i) at least two sites occupied by Xe and related to the Tyr and Trp residues; (ii) structural variations of BSA induced by the Xe guest atoms.

Wo?oszyn, ?ukasz; Ilczyszyn, Marek; Ilczyszyn, Maria M.

224

Evaluation of carrier agents for hyperpolarized xenon MRI  

NASA Technical Reports Server (NTRS)

Several biocompatible carrier agents, in which xenon is highly soluble and has a long T(1), were tested, and injected in living rats. These included saline, Intralipid suspension, perfluorocarbon emulsion and (129)Xe gas-filled liposomes. The T(1) of (129)Xe in these compounds ranged from 47 to 116 s. Vascular injection of these carrier agents was tolerated well, encouraging their use for further experiments in live animals. In vivo spectra, obtained from gas-filled liposomes and perfluorocarbon solutions, suggest that these carrier agents have potential for use in angiography and perfusion imaging. Copyright 2000 John Wiley & Sons, Ltd.

Venkatesh, A. K.; Zhao, L.; Balamore, D.; Jolesz, F. A.; Albert, M. S.

2000-01-01

225

Xenon in and at the End of the Tunnel of Bifunctional Carbon Monoxide Dehydrogenase/Acetyl-CoA Synthase,  

PubMed Central

A fascinating feature of some bifunctional enzymes is the presence of an internal channel or tunnel to connect the multiple active sites. A channel can allow for a reaction intermediate generated at one active site to be used as a substrate at a second active site, without the need for the intermediate to leave the safety of the protein matrix. One such bifunctional enzyme is carbon monoxide dehydrogenase/acetyl-CoA synthase from Moorella thermoacetica (mtCODH/ACS). A key player in the global carbon cycle, CODH/ACS uses a NiFeS center called the C-cluster to reduce carbon dioxide to carbon monoxide and uses a second NiFeS center, called the A-cluster, to assemble acetyl-CoA from a methyl group, coenzyme A, and C-cluster-generated CO. mtCODH/ACS has been proposed to contain one of the longest enzyme channels (138 long) to allow for intermolecular CO transport. Here, we report a 2.5 resolution structure of xenon-pressurized mtCODH/ACS and examine the nature of gaseous cavities within this enzyme. We find that the cavity calculation program CAVENV accurately predicts the channels connecting the C- and A-clusters, with 17 of 19 xenon binding sites within the predicted regions. Using this X-ray data, we analyze the amino acid composition surrounding the 19 Xe sites and consider how the protein fold is utilized to carve out such an impressive interior passageway. Finally, structural comparisons of Xe-pressurized mtCODH/ACS with related enzyme structures allow us to study channel design principles, as well as consider the conformational flexibility of an enzyme that contains a cavity through its center.

Doukov, Tzanko I.; Blasiak, Leah C.; Seravalli, Javier; Ragsdale, Stephen W.; Drennan, Catherine L.

2011-01-01

226

Carbon Dioxide Emission Estimates  

NSDL National Science Digital Library

The Carbon Dioxide Information Analysis Center of the Oak Ridge National Laboratory provides this new data on carbon dioxide emissions from fossil fuel burning, hydraulic cement production, and gas flaring in 1995. Data for one degree grid cells can be downloaded from the site in addition to code for analysis of the data.

227

Carbon Dioxide Fountain  

ERIC Educational Resources Information Center

This article presents the development of a carbon dioxide fountain. The advantages of the carbon dioxide fountain are that it is odorless and uses consumer chemicals. This experiment also is a nice visual experiment that allows students to see evidence of a gaseous reagent being consumed when a pressure sensor is available. (Contains 3 figures.)

Kang, Seong-Joo; Ryu, Eun-Hee

2007-01-01

228

Carbon Dioxide and Climate.  

ERIC Educational Resources Information Center

The amount of carbon dioxide in the atmosphere is increasing at a rate that could cause significant warming of the Earth's climate in the not too distant future. Oceanographers are studying the role of the ocean as a source of carbon dioxide and as a sink for the gas. (Author/BB)

Brewer, Peter G.

1978-01-01

229

Stratospheric nitrogen dioxide in the vicinity of Soufriere, St. Vincent  

NASA Technical Reports Server (NTRS)

In April 1979, measurements of nitrogen dioxide in the upper atmosphere were made near Soufriere Volcano by twilight optical-absorption techniques. The derived value of 5 x 10 to the 15th molecules per square centimeter column implies an enhancement of 25 percent over earlier abundances measured in the same latitudinal regions. This enhancement may represent the normal stratospheric variability of nitrogen dioxide in the equatorial region, but in any case may be considered an upper limit to the volcano's effect on the total nitrogen dioxide abundance.

Romick, G. J.; Murcray, D. G.; Williams, W. J.

1982-01-01

230

Scintillation response of liquid xenon to low energy nuclear recoils  

SciTech Connect

Liquid Xenon (LXe) is expected to be an excellent target and detection medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). We have measured the scintillation efficiency of nuclear recoils with kinetic energy between 10.4 and 56.5 keV relative to that of 122 keV gamma rays from {sup 57}Co. The scintillation yield of 56.5 keV recoils was also measured as a function of applied electric field, and compared to that of gamma rays and alpha particles. The Xe recoils were produced by elastic scattering of 2.4 MeV neutrons in liquid xenon at a variety of scattering angles. The relative scintillation efficiency is 0.130{+-}0.024 and 0.227{+-}0.016 for the lowest and highest energy recoils, respectively. This is about 15% less than the value predicted by Lindhard, based on nuclear quenching. Our results are in good agreement with more recent theoretical predictions that consider the additional reduction of scintillation yield due to biexcitonic collisions in LXe.

Aprile, E.; Giboni, K.L.; Majewski, P.; Ni, K.; Yamashita, M.; Hasty, R.; Manzur, A.; McKinsey, D.N. [Physics Department and Astrophysics Laboratory, Columbia University, New York, New York 10027 (United States); Department of Physics, Yale University, P.O. Box 208120, New Haven, Connecticut 06520 (United States)

2005-10-01

231

Lifetime Modeling of Xenon Hollow Cathodes Used in Electric Propulsion  

NASA Astrophysics Data System (ADS)

Xenon hollow cathodes with barium calcium aluminate impregnated tungsten inserts are widely used in electric propulsion. These high current, low power cathodes are employed in ion thrusters, Hall thrusters, and on the International Space Station in plasma contactors. The entitlement lifetime of a thermionic emission cathode impregnated with barium-containing compounds is determined by the evolution and transport of barium away from the emitter surface. A model is being developed to study the process of barium transport and loss from the emitter insert in hollow cathodes. A thermodynamic model of the chemical process of barium evolution has been adapted from that of Lipeles and Kan^1. The model accounts for the diffusion of barium and barium oxide gas through the xenon expellant and loss of barium-containing gases through the cathode orifice as well as loss by condensation. Axial barium density profiles are presented and cathode lifetimes are estimated. Results of the model are compared with experimental results from the extensive hollow cathode life test database at the NASA Glenn Research Center. 1. Lipeles, R.A., Kan, H.K.A., Appl. Surf. Sci. 16, 189(1983).

Kovaleski, Scott

2001-10-01

232

Two-photon laser spectroscopy of xenon collision pairs  

NASA Astrophysics Data System (ADS)

A computer-controlled, frequency-doubled, pulsed dye laser has been used in conjunction with a sensitive and linear photodetection scheme to measure the two-photon absorption profiles of the ground to 6p[ 12]0, 6p[ 32]2, and 6p[ 52 ]2 two-photon transitions in xenon over a pressure range of a few Torr to 10 000 Torr. Absolute two-photon coefficients are reported. Line-shape measurements of the shift and width of the Lorentzian core allow the deduction of the long-range dispersion terms of the Xe-Xe* interaction potentials. An analysis of the line wings under the quasistatic approximation has permitted the extraction of the difference potentials for 3.75<=R<=8.0 . These short-and long-range difference potentials have been combined and used in an Anderson-Talman phase-shift calculation to reconstruct the absorption profiles. Measurements of the fluorescence following selective laser excitation have been taken and branching fractions for collisional excitation to other members of the 6p manifold at a xenon pressure of 100 Torr are reported.

Raymond, T. D.; Bwering, N.; Kuo, Chien-Yu; Keto, J. W.

1984-02-01

233

Stepwise Ionization of Xenon in RF Plasma Display Panels  

NASA Astrophysics Data System (ADS)

The efficiency for conversion of electrical energy to visible photons in typical Plasma Display Panels(PDP's)conditions (3-10%Xe in Ne, 100's of kHz, 500 torr, 100 microns) is low (about 1 lumen/watt). The main factor limiting the efficiency is the energy lost in heating ions in the sheaths. RF excitation (10's of MHz) would therefore be more efficient, and investigations of RF PDP's are underway. We present here a study of the role electron-impact ionization of the xenon metastable atoms on the ionization balance in RF PDP's. In this study, rate equations for the resonance, R, and metastable, M, atoms are coupled to our fluid model of PDP's. Cascading from and excitation to the higher excited states are included via one parameter. Uncertainties in the excitation transfer rates and branching ratios for cascading to R and M preclude a more precise treatment. For 3%Xe in Ne, 400 torr, and 40 MHz, direct ionization dominates the ionization balance. Stepwise ionization is important for low discharge powers and high xenon concentrations.

Punset, C.; Pitchford, L. C.; Boeuf, J.-P.

2001-10-01

234

Performance characteristics of ring-cusp thrusters with xenon propellant  

NASA Technical Reports Server (NTRS)

The performance characteristics and operating envelope of several 30-cm ring-cusp ion thrusters with xenon propellant were investigated. Results indicate a strong performance dependence on the discharge chamber boundary magnetic fields and resultant distribution of electron currents. Significant improvements in discharge performance over J-series divergent-field thrusters were achieved for large throttling ranges, which translate into reduced cathode emission currents and reduced power dissipation which should be of significant benefit for operation at thruster power levels in excess of 10 kW. Mass spectrometry of the ion beam was documented for both the ring-cusp and J-series thrusters with xenon propellant for determination of overall thruster efficiency, and lifetime. Based on the lower centerline values of doubly charged ions in the ion beam and the lower operating discharge voltage, the screen grid erosion rate of the ring-cusp thruster is expected to be lower than the divergent-field J-series thruster by a factor of 2.

Patterson, M. J.

1986-01-01

235

Interstellar molecules  

NASA Astrophysics Data System (ADS)

Some 70 different molecular species have so far been detected variously in diffuse interstellar clouds, dense interstellar clouds, and circumstellar shells. Only simple (diatomic and triatomic) species exist in diffuse clouds because of the penetration of destructive UV radiations, whereas more complex (polyatomic) molecules survive in dense clouds as a result of the shielding against this UV radiation provided by dust grains. A current list of interstellar molecules is given together with a few other molecular species that have so far been detected only in circumstellar shells. Also listed are those interstellar species that contain rare isotopes of several elements. The gas phase ion chemistry is outlined via which the observed molecules are synthesized, and the process by which enrichment of the rare isotopes occurs in some interstellar molecules is described.

Smith, D.

1987-09-01

236

Mobius Molecules  

ERIC Educational Resources Information Center

Discusses formation of chemical molecules via Mobius strip intermediates, and concludes that many special physics-chemical properties of the fully closed circular form (1) of polyoma DNA are explainable by this topological feature. (CC)

Eckert, J. M.

1973-01-01

237

Modeling Molecules  

NASA Technical Reports Server (NTRS)

The molecule modeling method known as Multibody Order (N) Dynamics, or MBO(N)D, was developed by Moldyn, Inc. at Goddard Space Flight Center through funding provided by the SBIR program. The software can model the dynamics of molecules through technology which stimulates low-frequency molecular motions and properties, such as movements among a molecule's constituent parts. With MBO(N)D, a molecule is substructured into a set of interconnected rigid and flexible bodies. These bodies replace the computation burden of mapping individual atoms. Moldyn's technology cuts computation time while increasing accuracy. The MBO(N)D technology is available as Insight II 97.0 from Molecular Simulations, Inc. Currently the technology is used to account for forces on spacecraft parts and to perform molecular analyses for pharmaceutical purposes. It permits the solution of molecular dynamics problems on a moderate workstation, as opposed to on a supercomputer.

2000-01-01

238

Gas-Phase and Surface Reactions in Xenon Lamp-Assisted Organometallic Vapor-Phase Epitaxy of ZnSe  

NASA Astrophysics Data System (ADS)

In this paper, the influence of xenon lamp irradiation on gas-phase and surface reactions in organometallic vapor-phase epitaxy of ZnSe on GaAs is investigated. The irradiation only to the gas phase scarcely influences the growth rate, while irradiation to the growth surface is essential for growth rate enhancement. Numbers of incident photons and those of adhered molecules are found to be of the same order, i.e., most photons irradiated onto the substrate are associated with the epitaxial growth. The above experimental results strongly suggest that incident photons enhance some surface reactions, resulting in higher growth rates and lower growth temperatures compared with those reactions occuring under no irradiation.

Fujita, Shizuo; Takeuchi, Fumiyo Y.; Fujita, Shigeo

1988-11-01

239

Ultraviolet gas-discharge lamp on iodine molecules  

NASA Astrophysics Data System (ADS)

The emission characteristics of a pulsed-periodic UV radiation source are reported. The source excited by a pulsed-periodic capacitive discharge initiated in helium-iodine vapor, neon-iodine vapor, or krypton-iodine vapor mixtures radiates in the spectral range 200-450 nm. It is shown that most of the plasma radiation power concentrates in the integral line of the iodine atom (206.2 nm) and in the D'- A' band of the iodine molecule with a maximum at 342 nm. The radiation intensity of the lamp is optimized in accordance with the partial pressure of the inert gases. The discharge plasma parameters that are of interest for simulating the process kinetics and the output characteristics of an UV source based on molecular iodine, atomic iodine, and xenon iodide are calculated in helium-iodine vapor and xenon-iodine vapor mixtures.

Shuaibov, A. K.; Minya, A. I.; Gomoki, Z. T.; Kalyuzhnaya, A. G.; Shchedrin, A. I.

2010-08-01

240

Response of liquid xenon to low-energy ionizing radiation and its use in the XENON10 dark matter search  

NASA Astrophysics Data System (ADS)

This dissertation focuses on developments aimed at improving the effectiveness and understanding of liquid xenon particle detectors in their use in the field of dark matter direct detection. Chapter 3 covers the XENON10 experiment, which searches for evidence of direct interactions between Weakly Interacting Massive Particles (WIMPs) and Xe nuclei. The 3-D position sensitive liquid xenon time projection chamber acquired 58.6 live days of WIMP search data from October, 2006 through February, 2007. The results of these data set new limits on both spin-independent and spin-dependent interactions. The spin-independent WIMP-nucleon cross section is constrained to be less than 4.5 x 10-44 cm2 for WIMPs of mass 30 GeV/ c2 and less than 8.8 x 10-44 cm2 for WIMPs of mass 100 GeV/c2 at the 90% confidence level. The spin-dependent WIMP-neutron and WIMP-proton cross sections are constrained to be less than 10-39 cm 2 and 10-36 cm2, respectively. Finally, the mass of the heavy Majorana neutrino, in the context of a dark matter candidate, is excluded for masses in the range 10 GeV/c2 to 2.2TeV/c2. Chapter 4 discusses the study of the relative scintillation efficiency of nuclear recoils in liquid xenon. The two existing measurements of the relative scintillation efficiency of nuclear recoils below 20 keV lead to inconsistent extrapolations at lower energies. This results in a different energy scale and thus sensitivity reach of liquid xenon dark matter detectors. A new measurement of the relative scintillation efficiency below 10 keV, performed with a liquid xenon scintillation detector and optimized for maximum light collection is discussed. Greater than 95% of the interior surface of this detector was instrumented with photomultiplier tubes, giving a scintillation yield of 19.6 photoelectrons/keV electron equivalent for 122 keV gamma rays. The relative scintillation efficiency for nuclear recoils of 5 keV is found to be 0.14, staying constant around this value up to 10 keV. For higher energy recoils we measure a value of 0.21, consistent with previously reported data. In light of this new measurement, the XENON10 experiment's upper limits on spin-independent WIMP-nucleon cross section, which were calculated assuming a constant 0.19 relative scintillation efficiency, change from 8.8 x 10-44 cm2 to 9.9 x 10-44 cm2 for WIMPs of mass 100 GeV/c2, and from 4.5 x 10-44 cm2 to 5.6 x 10-44 cm2 for WIMPs of mass 30 GeV/ c2. In Chapter 6, I highlight the fact that a difficult task with many particle detectors focusing on interactions below 100 keV is to perform a calibration in the appropriate energy range that adequately probes all regions of the detector. Because detector response can vary greatly in various locations within the device, a spatially uniform calibration is important. A new method for calibration of liquid xenon (LXe) detectors is presented, using the short-lived 83mKr. This source has transitions at 9.4 and 32.1 keV, and as a noble gas like Xe, it disperses uniformly in all regions of the detector. Even for low source activities, the existence of the two transitions provides a method of identifying the decays that is free of background. At decreasing energies, the LXe light yield increases, while the amount of electric field quenching is diminished. Additionally, if any long-lived radioactive backgrounds are introduced by this method, it is shown that they will present less than 67x10 -6 events kg-1 day-1 keV-1 of background in the next generation of LXe dark matter direct detection searches. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

Manalaysay, Aaron Gosta

241

Xenon treatment attenuates early renal allograft injury associated with prolonged hypothermic storage in rats.  

PubMed

Prolonged hypothermic storage elicits severe ischemia-reperfusion injury (IRI) to renal grafts, contributing to delayed graft function (DGF) and episodes of acute immune rejection and shortened graft survival. Organoprotective strategies are therefore needed for improving long-term transplant outcome. The aim of this study is to investigate the renoprotective effect of xenon on early allograft injury associated with prolonged hypothermic storage. Xenon exposure enhanced the expression of heat-shock protein 70 (HSP-70) and heme oxygenase 1 (HO-1) and promoted cell survival after hypothermia-hypoxia insult in human proximal tubular (HK-2) cells, which was abolished by HSP-70 or HO-1 siRNA. In the brown Norway to Lewis rat renal transplantation, xenon administered to donor or recipient decreased the renal tubular cell death, inflammation, and MHC II expression, while delayed graft function (DGF) was therefore reduced. Pathological changes associated with acute rejection, including T-cell, macrophage, and fibroblast infiltration, were also decreased with xenon treatment. Donors or recipients treated with xenon in combination with cyclosporin A had prolonged renal allograft survival. Xenon protects allografts against delayed graft function, attenuates acute immune rejection, and enhances graft survival after prolonged hypothermic storage. Furthermore, xenon works additively with cyclosporin A to preserve post-transplant renal function. PMID:23759444

Zhao, Hailin; Yoshida, Akira; Xiao, Wei; Ologunde, Rele; O'Dea, Kieran P; Takata, Masao; Tralau-Stewart, Catherine; George, Andrew J T; Ma, Daqing

2013-10-01

242

Carbon dioxide concentrator  

NASA Technical Reports Server (NTRS)

Passed exhaled air through electrochemical cell containing alkali metal carbonate aqueous solution, and utilizes platinized electrodes causing reaction of oxygen at cathode with water in electrolyte, producing hydroxyl ions which react with carbon dioxide to form carbonate ions.

Williams, C. F.; Huebscher, R. G.

1972-01-01

243

Carbon Dioxide Monitoring.  

National Technical Information Service (NTIS)

The collection of luminescent microorganisms are maintained under cultivation to provide suitable biosensors for the testing program for carbon dioxide. The basic bioluminescent agar medium is currently being used for growth of the cultures. Tests of lumi...

P. S. Biernacki J. J. Kalvinskas

1973-01-01

244

Carbon dioxide (reduction).  

National Technical Information Service (NTIS)

The twin problems of global warming, caused by an increase in atmospheric carbon dioxide (CO2) concentrations, and limited fossil fuel resources have stimulated research in the utilization of CO2. These problems would be partially alleviated by the develo...

A. Fujita

2000-01-01

245

Heterogeneous Nuclear Reactor Models for Optimal Xenon Control.  

NASA Astrophysics Data System (ADS)

Nuclear reactors are generally modeled as homogeneous mixtures of fuel, control, and other materials while in reality they are heterogeneous-homogeneous configurations comprised of fuel and control rods along with other materials. Similarly, for space-time studies of a nuclear reactor, homogeneous, usually one-group diffusion theory, models are used, and the system equations are solved by either nodal or modal expansion approximations. Study of xenon-induced problems has also been carried out using similar models and with the help of dynamic programming or classical calculus of variations or the minimum principle. In this study a thermal nuclear reactor is modeled as a two-dimensional lattice of fuel and control rods placed in an infinite-moderator in plane geometry. The two-group diffusion theory approximation is used for neutron transport. Space -time neutron balance equations are written for two groups and reduced to one space-time algebraic equation by using the two-dimensional Fourier transform. This equation is written at all fuel and control rod locations. Iodine -xenon and promethium-samarium dynamic equations are also written at fuel rod locations only. These equations are then linearized about an equilibrium point which is determined from the steady-state form of the original nonlinear system equations. After studying poisonless criticality, with and without control, and the stability of the open-loop system and after checking its controllability, a performance criterion is defined for the xenon-induced spatial flux oscillation problem in the form of a functional to be minimized. Linear -quadratic optimal control theory is then applied to solve the problem. To perform a variety of different additional useful studies, this formulation has potential for various extensions and variations; for example, different geometry of the problem, with possible extension to three dimensions, heterogeneous -homogeneous formulation to include, for example, homogeneously -distributed burnable poisons, inclusion of additional terms, for example, fast fission and resonance absorption, different fuel and control rod diameters, different distances between rods, different fuel enrichment in different fuel rods, different control concentration in different control rods, and different forms of the performance index, to name a few.

Gondal, Ishtiaq Ahmad

246

Predicted properties of microhollow cathode discharges in xenon  

NASA Astrophysics Data System (ADS)

A fluid model has been developed and used to help clarify the physical mechanisms occurring in microhollow cathode discharges (MHCD). Calculated current-voltage (I-V) characteristics and gas temperatures in xenon at 100 Torr are presented. Consistent with previous experimental results in similar conditions, we find a voltage maximum in the I-V characteristic. We show that this structure reflects a transition between a low-current, abnormal discharge localized inside the cylindrical hollow cathode to a higher-current, normal glow discharge sustained by electron emission from the outer surface of the cathode. This transition, due to the geometry of the device, is a factor contributing to the well-known stability of MHCDs.

Boeuf, J. P.; Pitchford, L. C.; Schoenbach, K. H.

2005-02-01

247

A New Electrostatically-focused UV HPD for Liquid Xenon  

SciTech Connect

Appropriate photodetectors are a major challenge for liquid xenon technology as proposed by the next generation of double beta decay, solar neutrino, and dark matter searches. The primary photon signal is tiny and in the hard ultraviolet, the installation is cryogenic, and the sensors themselves must not introduce background. Hybrid photodiodes (HPDs) provide an easy substitute for a conventional PMT with the added advantages of low radioactivity, better area coverage, and single photoelectron counting. A computer-controlled test setup capable of characterizing optical properties of ultraviolet photodetectors was installed. It was used to compare photomultiplier tubes, silicon photomultipliers, avalanche photodiodes, and a novel-design custom HPD developed by the DEP company under this proposal.

Cushman, Priscilla Brooks [University of Minnesota

2013-07-10

248

Investigations of Wafer Scale Etching with Xenon Difluoride  

NASA Astrophysics Data System (ADS)

A good and uniform bulk silicon wafer etching method can be applied to the wafer thinning process in MEMS and 3D applications. In this study, the use of a Xenon Difluoride (XeF2) gas-phase etching system, operating at room temperature, has been investigated for bulk silicon wafer thinning. We investigated the Si-wafer surface morphology and profile following each XeF2 etching process cycle. Theoretical results are used to compare with the experimental results as well. A clean wafer surface by proper surface treatments is significant to achieve a uniform surface profile and morphology for XeF2 etching. A proper design of etching cycle with nitrogen ambient during etching is necessary to achieve the fastest and uniform silicon etching rate. The silicon etching rate is reported as a function of etching pressure, nitrogen pressure, and etching duration.

Chen, K. N.; Hoivik, N.; Lin, C. Y.; Young, A.; Ieong, M.; Shahidi, G.

2006-03-01

249

Performance of 10-kW class xenon ion thrusters  

NASA Technical Reports Server (NTRS)

Presented are performance data for laboratory and engineering model 30 cm-diameter ion thrusters operated with xenon propellant over a range of input power levels from approximately 2 to 20 kW. Also presented are preliminary performance results obtained from laboratory model 50 cm-diameter cusp- and divergent-field ion thrusters operating with both 30 cm- amd 50 cm-diameter ion optics up to a 20 kW input power. These data include values of discharge chamber propellant and power efficiencies, as well as values of specific impulse, thruster efficiency, thrust and power. The operation of the 30 cm- and 50 cm-diameter ion optics are also discussed.

Patterson, Michael J.; Rawlin, Vincent K.

1988-01-01

250

Investigation of a pulsed xenon discharge at medium pressure  

NASA Astrophysics Data System (ADS)

The pulsed discharge in xenon at pressures between 10 and 50 Torr and a peak current of 130 mA has been analysed by means of a time-dependent, spatially one-dimensional fluid model. Main features of the model of the radially inhomogeneous discharge plasma in a discharge tube with an inner diameter of 6.5 mm are given. The comparison of results of model calculations with experimental data shows good agreement for the axial electric field, and the qualitative behaviour of measured axis densities of low-lying excited states is reproduced well by the model. The analysis of the spatiotemporal variation of the pulsed discharge shows the formation of a constricted column plasma at increasing pressure. In particular, a pronouncedly nonlocal behaviour of the electron component is found, and the densities of the metastable and resonance atoms are predicted to have a radial profile with a maximum out of the axis during the discharge phase.

Gnybida, M.; Uhrlandt, D.; Loffhagen, D.

2012-05-01

251

Power Processing Unit of Xenon Ion Propulsion System  

NASA Astrophysics Data System (ADS)

The structure and optimizing of designing, selecting of parameter was described in this paper, according to the character and desiring of 20cm Xenon ion propulsion system. The Impulse Specific of 20cm XIPS is 3000s,and its thrust is 40mN.The power processing unit (PPU) consists in some modules, they are main hollow cathode heating supply, its igniting one, the contact one, the neutralize heating supply, its igniting one, the contact one, the screen supply, the accelerating supply, and anode supply. Also, the power supply of Xenon storage and feed unit and digital interface and control unit were introduced here. The power supply works with technique of pulse width modulating (PWM) controlled by voltage or current, according to the desiring of the thruster, their stability of output is about 3%. The protecting measure was used as overvoltage, overcurrent and fold back current limiting. For the screen supply, which is higher voltage output, three transformers and three bridges were used to ensure its reliability. The parameter of these modules, showes as following, the igniting supplies outputs1500V/100mA,with protecting of fold back current limiting. The hollow cathode heating supply outputs 0~6V,which is alternate, voltage programmable output and the frequency is 20KHz.The screen is 1000V/0.79A,with stabililizing voltage and protecting of over current output. The anode is 5~7.5A stabililizing current output. The accelerator is -200V/10mA with protecting of over current output. The total power consumptions of PPU are 1100W,and efficient of transfer is more than 80%.

Tiemin, C.

2002-01-01

252

Atmospheric Krypton and Xenon Measurements from Mars Science Laboratory  

NASA Astrophysics Data System (ADS)

The heavy noble gases krypton and xenon are important tracers of planetary processes from accretion to differentiation and to atmospheric escape. Their abundance and stable isotopic ratios are also indicative of sources as well. The Sample Analysis at Mars (SAM) investigation on the Curiosity rover has measured the Martian atmosphere and reported on the volume mixing ratio of its major constituents (Mahaffy et al., 2013). Here we report the abundance and isotopic ratios of Kr and Xe in the atmosphere of Mars as obtained by semi-static operation of the SAM quadrupole mass spectrometer. Viking provided the first in situ detection of these gases (Owen et al, 1977), suggesting upper limits of 300 ppb for Kr and 80 ppb for Xe, based upon calibration gases with terrestrial isotopic abundances. The abundances of individual isotopes as well as their ratios to one another have been derived from martian meteorite samples by many investigators (e.g., Becker & Pepin, 1984; Bogard & Garrison, 1998). The SAM heavy noble gas data complement the argon isotopic data reported in Mahaffy et al., 2013. Becker, R. H., & Pepin, R. O. (1984). The case for a Martian origin of the shergottites: Nitrogen and noble gases in EETA 79001. Earth and Planetary Science Letters, 69(2), 225-242. Bogard, D. D., & Garrison, D. H. (1998). Relative abundances of argon, krypton, and xenon in the Martian atmosphere as measured in Martian meteorites. Geochimica et cosmochimica acta, 62(10), 1829-1835. Mahaffy, et al., (2013) Abundance and isotopic composition of gases in the martian atmosphere from the Curiosity rover. Science 341, 263-266 Owen, T. et al.,(1977). The composition of the atmosphere at the surface of Mars. Journal of Geophysical research, 82(28), 4635-4639.

Conrad, P. G.; Malespin, C. A.; Franz, H.; Manning, H. L.; Trainer, M. G.; Wong, M. H.; Brunner, A.; Atreya, S. K.; Pepin, R. O.; Jones, J. H.; Owen, T. C.; Mahaffy, P. R.

2013-12-01

253

An ultra-low background PMT for liquid xenon detectors  

NASA Astrophysics Data System (ADS)

Results are presented from radioactivity screening of two models of photomultiplier tubes designed for use in current and future liquid xenon experiments. The Hamamatsu 5.6 cm diameter R8778 PMT, used in the LUX dark matter experiment, has yielded a positive detection of four common radioactive isotopes: 238U, 232Th, 40K, and 60Co. Screening of LUX materials has rendered backgrounds from other detector materials subdominant to the R8778 contribution. A prototype Hamamatsu 7.6 cm diameter R11410 MOD PMT has also been screened, with benchmark isotope counts measured at <0.4238U/<0.3232Th/<8.340K/2.00.2 60Co mBq/PMT. This represents a large reduction, equal to a change of {1}/{24}238U/{1}/{9}232Th/{1}/{8}40K per PMT, between R8778 and R11410 MOD, concurrent with a doubling of the photocathode surface area (4.5-6.4 cm diameter). 60Co measurements are comparable between the PMTs, but can be significantly reduced in future R11410 MOD units through further material selection. Assuming PMT activity equal to the measured 90% upper limits, Monte Carlo estimates indicate that replacement of R8778 PMTs with R11410 MOD PMTs will change LUX PMT electron recoil background contributions by a factor of {1}/{25} after further material selection for 60Co reduction, and nuclear recoil backgrounds by a factor of {1}/{36}. The strong reduction in backgrounds below the measured R8778 levels makes the R11410 MOD a very competitive technology for use in large-scale liquid xenon detectors.

Akerib, D. S.; Bai, X.; Bernard, E.; Bernstein, A.; Bradley, A.; Byram, D.; Cahn, S. B.; Carmona-Benitez, M. C.; Carr, D.; Chapman, J. J.; Clark, K.; Coffey, T.; Edwards, B.; de Viveiros, L.; Dragowsky, M.; Druszkiewicz, E.; Faham, C. H.; Fiorucci, S.; Gaitskell, R. J.; Gibson, K. R.; Hall, C.; Hanhardt, M.; Holbrook, B.; Ihm, M.; Jacobsen, R. G.; Kastens, L.; Kazkaz, K.; Larsen, N.; Lee, C.; Lindote, A.; Lopes, M. I.; Lyashenko, A.; Malling, D. C.; Mannino, R.; McKinsey, D. N.; Mei, D.-M.; Mock, J.; Morii, M.; Nelson, H.; Neves, F.; Nikkel, J. A.; Pangilinan, M.; Phelps, P.; Shutt, T.; Silva, C.; Skulski, W.; Solovov, V. N.; Sorensen, P.; Spaans, J.; Stiegler, T.; Sweany, M.; Szydagis, M.; Taylor, D.; Thomson, J.; Tripathi, M.; Uvarov, S.; Verbus, J. R.; Walsh, N.; Webb, R.; White, J. T.; Wlasenko, M.; Wolfs, F. L. H.; Woods, M.; Zhang, C.

2013-03-01

254

Cerebral blood flow response to changes in arterial carbon dioxide tension during hypothermic cardiopulmonary bypass in children  

SciTech Connect

We examined the relationship of changes in partial pressure of carbon dioxide on cerebral blood flow responsiveness in 20 pediatric patients undergoing hypothermic cardiopulmonary bypass. Cerebral blood flow was measured during steady-state hypothermic cardiopulmonary bypass with the use of xenon 133 clearance methodology at two different arterial carbon dioxide tensions. During these measurements there was no significant change in mean arterial pressure, nasopharyngeal temperature, pump flow rate, or hematocrit value. Cerebral blood flow was found to be significantly greater at higher arterial carbon dioxide tensions (p less than 0.01), so that for every millimeter of mercury rise in arterial carbon dioxide tension there was a 1.2 ml.100 gm-1.min-1 increase in cerebral blood flow. Two factors, deep hypothermia (18 degrees to 22 degrees C) and reduced age (less than 1 year), diminished the effect carbon dioxide had on cerebral blood flow responsiveness but did not eliminate it. We conclude that cerebral blood flow remains responsive to changes in arterial carbon dioxide tension during hypothermic cardiopulmonary bypass in infants and children; that is, increasing arterial carbon dioxide tension will independently increase cerebral blood flow.

Kern, F.H.; Ungerleider, R.M.; Quill, T.J.; Baldwin, B.; White, W.D.; Reves, J.G.; Greeley, W.J. (Duke Univ. Medical Center, Durham, NC (USA))

1991-04-01

255

Biological Molecules  

NSDL National Science Digital Library

Paul Anderson describes the four major biological molecules found in living things. He begins with a brief discussion of polymerization. Dehydration synthesis is used to connect monomers into polymers and hydrolysis breaks them down again. The major characteristics of nucleic acids are described as well as there directionality from 3' to 5' end.

Anderson, Paul

2013-03-12

256

Progress on Acoustic Measurements of the Bulk Viscosity of Near-Critical Xenon (BVX)  

NASA Technical Reports Server (NTRS)

We plan to determine the bulk viscosity of xenon 10 times closer [in reduced temperature tau = (T-Tc)/Tc] to its liquid-vapor critical point than ever before. (Tc is the critical temperature.) To do so, we must measure the dispersion and attenuation of sound at frequencies 1/100 of those used previously. In general, sound attenuation has contributions from the bulk viscosity acting throughout the volume of the xenon as well as contributions from the thermal conductivity and the shear viscosity acting within thin thermoacoustic boundary layers at the interface between the xenon and the solid walls of the resonator. Thus, we can determine the bulk viscosity only when the boundary layer attenuation is small and well understood. We present a comparison of calculations and measurements of sound attenuation in the acoustic boundary layer of xenon near its liquid-vapor critical point.

Gillis, Keith A.; Shinder, Iosif I.; Moldover, Michael R.; Zimmerli, Gregory A.

2004-01-01

257

NASA's Evolutionary Xenon Thruster (NEXT) Power Processing Unit (PPU) Capacitor Failure Root Cause Analysis.  

National Technical Information Service (NTIS)

The NASA's Evolutionary Xenon Thruster (NEXT) project is developing an advanced ion propulsion system for future NASA missions for solar system exploration. A critical element of the propulsion system is the Power Processing Unit (PPU) which supplies regu...

A. J. Birchenough J. F. Soeder J. W. Dunning L. R. Pinero R. J. Scheidegger

2012-01-01

258

Experimental studies of a zeeman-tuned xenon laser differential absorption apparatus.  

PubMed

A Zeeman-tuned cw xenon laser differential absorption device is described. The xenon laser was tuned by axial magnetic fields up to 5500 G generated by an unusually large water-cooled dc solenoid. Xenon laser lines at 3.37 micro, 3.51 micro, and 3.99 micro were tuned over ranges of 6 A, 6 A, and 11 A, respectively. To date, this apparatus has been used principally to study the details of formaldehyde absorption lines lying near the 3 .508-micro xenon laser transition. These experiments revealed that the observed absorption spectrum of formaldehyde exhibits a sufficiently unique spectral structure that the present technique may readily be used to measure relative concentrations of formaldehyde in samples of polluted air. PMID:20125492

Linford, G J

1973-06-01

259

A study of xenon isotopes in a martian meteorite using the RELAX ultrasensitive mass spectrometer  

SciTech Connect

The Refrigerator Enhanced Analyser for Xenon (RELAX), an ultrasensitive resonance ionization time-of-flight mass spectrometer, has been used with a laser microprobe to investigate the isotopic composition of xenon trapped in the martian meteorite ALH84001. The laser microprobe has a spatial resolution of the order of 100{mu}m thus allowing the in situ analysis of individual mineral grains in a polished section when combined with ultrasensitive, low blank sample analysis. We present results showing that the mineral orthopyroxene in ALH84001 contains a trapped xenon component consistent with a martian origin. Additionally, a cosmic ray exposure age of 15Ma for ALH84001 is obtained from spallation derived xenon trapped within an apatite grain.

Whitby, J A; Gilmour, J D; Turner, G [Department of Earth Sciences, Manchester University, Oxford Road, Manchester M13 9PL (United Kingdom)

1997-01-15

260

Light output and collected charge in xenon-doped liquid argon  

NASA Astrophysics Data System (ADS)

The light output and the collected charge in xenon-doped liquid argon under 207Bi conversion electron excitation have been studied as a function of an applied electric field with the xenon concentration [Xe] less than 1.9%. With increasing [Xe], the light output was increased and was maximized at [Xe] = 1.9%, having about as twice as much intensity with respect to that in pure argon. The amount of collected charge in xenon-doped liquid argon was nearly equal to that in pure argon up to 2500 ppm of [Xe], above which a slight increase was observed. The increase in light output can be explained by the difference in the conversion efficiency of the POPOP wavelength shifter for 130 nm scintillation photons in liquid argon and for 175 nm scintillation photons in xenon-doped liquid argon.

Suzuki, M.; Hishida, M.; Ruan(Gen), J.; Kubota, S.

1993-03-01

261

Shadowing in the muon-xenon inelastic scattering cross section at 490 GeV  

Microsoft Academic Search

Inelastic scattering of 490 GeV mu+ from deuterium and xenon nuclei has been studied for xBj>s.001. The ratio of the xenon\\/deuterium cross section per nucleon is observed to vary with xBj, with a depletion in the kinematic range 0.001 < xBj < 0.025 which exhibits no significant Q2 dependence. An electromagnetic calorimeter was used to verify the radiative corrections.

M. R. Adams; S. Ad; P. L. Anthony; M. D. Baker; J. Bartlett; A. A. Bhatti; H. M. Braun; W. Busza; T. J. Carroll; J. M. Conrad; G. Coutrakon; R. Davisson; I. Derado; S. K. Dhawan; W. Dougherty; T. Dreyer; K. Dziunikowska; V. Eckardt; U. Ecker; M. Erdmann; A. Eskreys; G. Fang; J. Figiel; H. J. Gebauer; D. F. Geesaman; R. Gilman; M. C. Green; J. Haas; C. Halliwell; J. Hanlon; D. Hantke; V. W. Hughes; H. E. Jackson; D. E. Jaffe; G. Jancso; D. M. Jansen; S. Kaufman; R. D. Kennedy; T. Kirk; H. G. E. Kobrak; S. Krzywdzinski; S. Kunori; J. J. Lord; H. J. Lubatti; D. McLeod; S. Magill; P. Malecki; A. Manz; H. Melanson; D. G. Michael; W. Mohr; H. E. Montgomery; J. G. Morfin; R. B. Nickerson; S. O'Day; K. Olkiewicz; L. Osborne; V. Papavassiliou; B. Pawlik; F. M. Pipkin; E. J. Ramberg; A. Rser; J. J. Ryan; C. Salgado; A. Salvarani; H. Schellman; M. Schmitt; N. Schmitz; K. P. Schler; H. J. Seyerlein; A. Skuja; G. A. Snow; S. Sldner-Rembold; P. H. Steinberg; H. E. Stier; P. Stopa; R. A. Swanson; R. Talaga; S. Tentindo-Repond; H.-J. Trost; H. Venkataramania; M. Vidal; M. Wilhelm; J. Wilkes; Richard Wilson; W. Wittek; S. A. Wolbers; T. Zhao

1992-01-01

262

12-cm magneto-electrostatic containment argon/xenon ion source development  

NASA Technical Reports Server (NTRS)

The original 12 cm hexagonal magneto-electrostatic containment (MESC) discharge chamber described by Moore in 1969 has been optimized for argon and xenon operation. Argon mass utilization efficiencies of 65 to 77 percent were achieved at keeper-plus-main discharge energy consumptions of 244 to 422 eV/ion respectively. Xenon performance of 85 to 96 percent mass utilization were realized at 203 to 350 eV/ion. The paper discusses the optimization process and test results.

Ramsey, W. D.

1978-01-01

263

Study of large area avalanche photodiode for detecting liquid xenon scintillation  

Microsoft Academic Search

A large area avalanche photodiode (LAAPD) has been investigated as a possible photosensor for detecting liquid xenon scintillation. The LAAPD proved to be operational at the temperature of liquid xenon (down to -105C) with the dark current significantly reduced with respect to that at room temperature (less than 1 pA versus 30 nA at 20C). The bias voltage needed to

V. N. Solovov; V. Chepel; M. I. Lopes; R. F. Marques; A. J. P. L. Policarpo

1999-01-01

264

A xenon gas proportional scintillation counter with a UV-sensitive large-area avalanche photodiode  

Microsoft Academic Search

The performance characteristics of a xenon gas proportional scintillation counter comprising a large-area avalanche photodiode with enhanced ultraviolet sensitivity were evaluated. By integrating the photodiode within the xenon gas envelope of the scintillator, the intervening quartz window was eliminated. Energy resolutions of 7.8% and 4.4% were measured for 5.9- and 22.1-keV X-rays, respectively. The results demonstrate that large-area avalanche photodiodes

J. A. M. Lopes; J. M. F. dos Santos; R. E. Morgado; C. A. N. Conde

2001-01-01

265

Global characteristics of an ATON stationary plasma thruster operating with krypton and xenon  

Microsoft Academic Search

The global characteristics of an ATON stationary plasma thruster operating on xenon and krypton are investigated. It is shown\\u000a that, with krypton, the thrust at the same mass flow rate of the working gas is greater and the efficiency is somewhat lower\\u000a than those with xenon. An efficiency of ?60% was achieved with krypton for the specific impulse attaining 3000

A. I. Bugrova; A. S. Lipatov; A. I. Morozov; L. V. Solomatina

2002-01-01

266

Xenon Pretreatment May Prevent Early Memory Decline after Isoflurane Anesthesia and Surgery in Mice  

PubMed Central

Postoperative cognitive decline (POCD) is a common complication following surgery, but its aetiology remains unclear. We hypothesized that xenon pretreatment prevents POCD by suppressing the systemic inflammatory response or through an associated protective signaling pathway involving heat shock protein 72 (Hsp72) and PI3-kinase. Twenty-four hours after establishing long-term memory using fear conditioning training, C57BL/6 adult male mice (n?=?12/group) received one of the following treatments: 1) no treatment group (control); 2) 1.8% isoflurane anesthesia; 3) 70% xenon anesthesia; 4) 1.8% isoflurane anesthesia with surgery of the right hind leg tibia that was pinned and fractured; or 5) pretreatment with 70% xenon for 20 minutes followed immediately by 1.8% isoflurane anesthesia with the surgery described above. Assessments of hippocampal-dependent memory were performed on days 1 and 7 after treatment. Hsp72 and PI3-kinase in hippocampus, and plasma IL-1?, were measured using western blotting and ELISA respectively, from different cohorts on day 1 after surgery. Isoflurane induced memory deficit after surgery was attenuated by xenon pretreatment. Xenon pretreatment prevented the memory deficit typically seen on day 1 (P?=?0.04) but not on day 7 (P?=?0.69) after surgery under isoflurane anesthesia, when compared with animals that underwent surgery without pretreatment. Xenon pretreatment modulated the expression of Hsp72 (P?=?0.054) but had no significant effect on PI3-kinase (P?=?0.54), when compared to control. Xenon pretreatment also reduced the plasma level increase of IL-1? induced by surgery (P?=?0.028). Our data indicated that surgery and/or Isoflurane induced memory deficit was attenuated by xenon pretreatment. This was associated with a reduction in the plasma level of IL-1? and an upregulation of Hsp72 in the hippocampus.

Vizcaychipi, Marcela P.; Lloyd, Dafydd G.; Wan, Yanjie; Palazzo, Mark G.; Maze, Mervyn; Ma, Daqing

2011-01-01

267

GraXe, graphene and xenon for neutrinoless double beta decay searches  

Microsoft Academic Search

We propose a new detector concept, GraXe (to be pronounced as grace), to search for neutrinoless double beta decay in 136XE. GraXe combines a popular detection medium in rare-event searches, liquid xenon, with a new, background-free material, graphene.In our baseline design of GraXe, a sphere made of graphene-coated titanium mesh and filled with liquid xenon (LXe) enriched in the 136XE

J. J. Gmez-Cadenas; F. Guinea; M. M. Fogler; M. I. Katsnelson; J. Martn-Albo; F. Monrabal; J. Muoz Vidal

2012-01-01

268

Iodine129\\/Xenon129 Age of Magnetite from the Orgueil Meteorite  

Microsoft Academic Search

Magnetite from the Orgueil C1 chondrite is only 2.0 2.4 million years older by the iodine-xenon method than the next oldest meteorite, the Karoonda C4 chondrite. This age ties the primitive C1 chondrites to the extensive iodine-xenon chronology of normal chrondrites. If Karoonda and Orgueil magnetite formed from similar material, then the age difference is an upper limit to

Gregory F. Herzog; Edward Anders; E. C. Alexander Jr.; P. K. Davis; R. S. Lewis

1973-01-01

269

EUV spectroscopy of xenon ions created using an electron beam ion trap  

Microsoft Academic Search

Laser-produced plasma source development for Extreme Ultra Violet (EUV) lithography has concentrated on xenon, since XeXI emits at 13.5 nm, the wavelength at which the reflectivity of MoSi mirrors is centred. However it is not obvious that the required conversion efficiencies can be achieved using xenon, and tin has been identified as a strong emitter at this wavelength. The transitions

K. Fahy; E. Sokell; G. O'Sullivan; A. Cummings; A. Aguilar; J. D. Gillaspy; J. M. Pomeroy; J. N. Tan

2005-01-01

270

Moving Molecules!  

NSDL National Science Digital Library

In this activity about molecular diffusion (located on page 2 of the PDF), learners will make predictions and move molecules of iodine through a seemingly solid plastic sandwich bag. The process of diffusion will be visually indicated by a color change when the iodine reacts with starch inside the bag. Information in the resource explains how this activity relates to nanoparticles and research. Related to linked video, DragonflyTV Nano: Nanosilver.

Twin Cities Public Television, Inc.

2008-01-01

271

Abatement of xenon and iodine emissions from medical isotope production facilities.  

PubMed

The capability of the International Monitoring System (IMS) to detect xenon from underground nuclear explosions is dependent on the radioactive xenon background. Adding to the background, medical isotope production (MIP) by fission releases several important xenon isotopes including xenon-133 and iodine-133 that decays to xenon-133. The amount of xenon released from these facilities may be equivalent to or exceed that released from an underground nuclear explosion. Thus the release of gaseous fission products within days of irradiation makes it difficult to distinguish MIP emissions from a nuclear explosion. In addition, recent shortages in molybdenum-99 have created interest and investment opportunities to design and build new MIP facilities in the United States and throughout the world. Due to the potential increase in the number of MIP facilities, a discussion of abatement technologies provides insight into how the problem of emission control from MIP facilities can be tackled. A review of practices is provided to delineate methods useful for abatement of medical isotopes. PMID:24418952

Doll, Charles G; Sorensen, Christina M; Bowyer, Theodore W; Friese, Judah I; Hayes, James C; Hoffmann, Emmy; Kephart, Rosara

2014-04-01

272

Control of spatial xenon oscillations in pressurized water reactors via the Kalman filter  

SciTech Connect

A direct control method is developed to control the spatial xenon oscillations in pressurized water reactors. The xenon and iodine concentration difference between the top and bottom halves of the core is estimated by using the extended Kalman filter (EKF), which is a closed-loop estimation method. The measurement equation used in the observer is the axial offset measurement equation, which reflects the xenon unbalanced effect on the axial offset. Meanwhile, some of the coefficients of the observer are estimated on-line to reduce estimation error resulting from model error, i.e., simplified xenon and iodine dynamics. Therefore, the estimation can be guaranteed to be accurate, and the success of the estimation does not greatly depend on the accuracy of the observer model. The predicted one-step ahead xenon concentration, by using the EKF, was used to calculate the possible axial offset variation, and then the control rod motion was calculated to compensate for it. The simulation results show that the proposed method successfully controls the xenon oscillations.

Lin, C.; Lin, Y.J. (National Tsing Hua Univ., Hsinchu (Taiwan, Province of China). Dept. of Nuclear Engineering)

1994-12-01

273

Xenon Treatment Protects Against Cold Ischemia Associated Delayed Graft Function and Prolongs Graft Survival in Rats  

PubMed Central

Prolonged hypothermic storage causes ischemia-reperfusion injury (IRI) in the renal graft, which is considered to contribute to the occurrence of the delayed graft function (DGF) and chronic graft failure. Strategies are required to protect the graft and to prolong renal graft survival. We demonstrated that xenon exposure to human proximal tubular cells (HK-2) led to activation of range of protective proteins. Xenon treatment prior to or after hypothermiahypoxia challenge stabilized the HK-2 cellular structure, diminished cytoplasmic translocation of high-mobility group box (HMGB) 1 and suppressed NF-?B activation. In the syngeneic Lewis-to-Lewis rat model of kidney transplantation, xenon exposure to donors before graft retrieval or to recipients after engraftment decreased caspase-3 expression, localized HMGB-1 within nuclei and prevented TLR-4/NF-?B activation in tubular cells; serum pro-inflammatory cytokines IL-1?, IL-6 and TNF-? were reduced and renal function was preserved. Xenon treatment of graft donors or of recipients prolonged renal graft survival following IRI in both Lewis-to-Lewis isografts and Fischer-to-Lewis allografts. Xenon induced cell survival or graft functional recovery was abolished by HIF-1? siRNA. Our data suggest that xenon treatment attenuates DGF and enhances graft survival. This approach could be translated into clinical practice leading to a considerable improvement in long-term graft survival.

Zhao, H; Watts, H R; Chong, M; Huang, H; Tralau-Stewart, C; Maxwell, P H; Maze, M; George, A J T; Ma, D

2013-01-01

274

Design and construction of a cryogenic distillation device for removal of krypton for liquid xenon dark matter detectors.  

PubMed

Liquid xenon (Xe) is one of the commendable detecting media for the dark matter detections. However, the small content of radioactive krypton-85 ((85)Kr) always exists in the commercial xenon products. An efficient cryogenic distillation system to remove this krypton (Kr) from commercial xenon products has been specifically designed, developed, and constructed in order to meet the requirements of the dark matter experiments with high- sensitivity and low-background. The content of krypton in regular commercial xenon products can be reduced from 10(-9) to 10(-12), with 99% xenon collection efficiency at maximum flow rate of 5 kg/h (15SLPM). The purified xenon gases produced by this distillation system can be used as the detecting media in the project of Panda X, which is the first dark matter detector developed in China. PMID:24517821

Wang, Zhou; Bao, Lei; Hao, Xihuan; Ju, Yonglin

2014-01-01

275

Carbon Dioxide Exercise  

NSDL National Science Digital Library

In this activity, students work in groups, plotting carbon dioxide concentrations over time on overheads and estimating the rate of change over five years. Stacked together, the overheads for the whole class show an increase on carbon dioxide over five years and annual variation driven by photosynthesis. This exercise enables students to practice basic quantitative skills and understand how important sampling intervals can be when studying changes over time. A goal is to see how small sample size may give incomplete picture of data.

Richardson, Randy; Collection, Serc -.

276

Reversible sorption of nitrogen and xenon gas by the guest-free zeolite tris( o-phenylenedioxy)cyclotriphosphazene (TPP)  

Microsoft Academic Search

The sorption of nitrogen at 77K and xenon at 298K by the guest-free zeolite tris(o-phenylenedioxy)cyclotriphosphazene (TPP) was investigated. Xenon atoms show a remarkable affinity to the trigonal cavity of TPP by occupying about 90% of these sites at the pressure of about 100kPa. Efficient sorption originates from a van der Waals type complex of xenon in the ?-electron-rich environment given

G. Couderc; T. Hertzsch; N.-R. Behrnd; K. Krmer; J. Hulliger

2006-01-01

277

Investigating Nitrogen Dioxide  

NSDL National Science Digital Library

Students will investigate Nitrogen Dioxide levels in the atmosphere during a one year time span using data sets from MyNASAData website. They will draw conclusions about what factors around the world effect NO2 levels (season, population, industry, etc.)

278

Carbon dioxide fixation.  

National Technical Information Service (NTIS)

Solar carbon dioxide fixation offers the possibility of a renewable source of chemicals and fuels in the future. Its realization rests on future advances in the efficiency of solar energy collection and development of suitable catalysts for CO(sub 2) conv...

E. Fujita

2000-01-01

279

Sulfur Dioxide Detector.  

National Technical Information Service (NTIS)

A composition is provided for detecting the presence of sulfur dioxide by changing color. One type of composition is prepared by mixing a small amount of finely ground potassium permanganate with finely powdered activated silica gel to produce a lilac col...

J. A. Amy H. C. Huber

1980-01-01

280

Bench Remarks: Carbon Dioxide.  

ERIC Educational Resources Information Center

Discusses the properties of carbon dioxide in its solid "dry ice" stage. Suggests several demonstrations and experiments that use dry ice to illustrate Avogadro's Law, Boyle's Law, Kinetic-Molecular Theory, and the effects of dry ice in basic solution, in limewater, and in acetone. (TW)

Bent, Henry A.

1987-01-01

281

Carbon Dioxide Increases  

NSDL National Science Digital Library

In this problem set, learners will analyze the Keeling Curve showing carbon dioxide concentration in the atmosphere since 1985 to answer a series of questions. Answer key is provided. This is part of Earth Math: A Brief Mathematical Guide to Earth Science and Climate Change.

282

Carbon dioxide sensor  

DOEpatents

The present invention generally relates to carbon dioxide (CO.sub.2) sensors. In one embodiment, the present invention relates to a carbon dioxide (CO.sub.2) sensor that incorporates lithium phosphate (Li.sub.3PO.sub.4) as an electrolyte and sensing electrode comprising a combination of lithium carbonate (Li.sub.2CO.sub.3) and barium carbonate (BaCO.sub.3). In another embodiment, the present invention relates to a carbon dioxide (CO.sub.2) sensor has a reduced sensitivity to humidity due to a sensing electrode with a layered structure of lithium carbonate and barium carbonate. In still another embodiment, the present invention relates to a method of producing carbon dioxide (CO.sub.2) sensors having lithium phosphate (Li.sub.3PO.sub.4) as an electrolyte and sensing electrode comprising a combination of lithium carbonate (Li.sub.2CO.sub.3) and barium carbonate (BaCO.sub.3).

Dutta, Prabir K. (Worthington, OH); Lee, Inhee (Columbus, OH); Akbar, Sheikh A. (Hilliard, OH)

2011-11-15

283

Capturing Carbon Dioxide  

NSDL National Science Digital Library

In this activity, learners investigate carbon sequestration by creating a carbonated beverage out of apple juice and dry ice. This experiment illustrates how carbon dioxide can be stored in a substance. Learners compare and contrast the results to determine if liquid carbonation is an effective method for carbon sequestration. Safety note: this activity involves dry ice; please follow recommended guidelines.

Saltz, Austen

2010-01-01

284

Carbon Dioxide Removal  

NSDL National Science Digital Library

In this experiment using sprigs of Elodea, learners will observe a natural process that removes carbon dioxide (CO2) from Earth's atmosphere. This process is a part of the carbon cycle and results in temperature suitable for life. Note: this experiment requires that learners make observations an hour or the next day after they set up the materials.

History, American M.

2008-01-01

285

Performance capabilities of the 12-centimeter Xenon ion thruster  

NASA Technical Reports Server (NTRS)

The 8- and 12-cm mercury ion thruster systems were developed primarily to provide N-S station keeping of satellites with masses up to about 1800 to 3600 kg respectively. The on-orbit propulsion requirements of recently proposed Large Space Systems (LSS) are beyond the thrust capabilities of the baseline 8- and 12-cm thruster systems. This paper presents a characterization of the performance capabilities of the 12-cm Xenon ion thruster to enable an evaluation of its application to LSS auxiliary propulsion requirements. With minor thruster modifications and simplifications the thrust was increased to 64 mN, a factor of six over the baseline 12-cm mercury thruster performance. The thruster was operated over a range of specific impulse of about 2000 to 4000 seconds and at total efficiencies up to 68.0 percent. The operating levels reached in this study were found to be close to the operating limits of the thruster design in terms of perveance, grid breakdown voltage and thruster component temperatures such as those of the magnets and cathode baffle.

Mantenieks, M.; Schatz, M.

1984-01-01

286

First Detection of Krypton and Xenon in a White Dwarf  

NASA Astrophysics Data System (ADS)

We report on the first detection of the noble gases krypton (Z = 36) and xenon (54) in a white dwarf. About 20 Kr VI- VII and Xe VI- VII lines were discovered in the ultraviolet spectrum of the hot DO-type white dwarf RE 0503-289. The observations, performed with the Far Ultraviolet Spectroscopic Explorer, also reveal highly ionized photospheric lines from other trans-iron group elements, namely Ga (31), Ge (32), As (33), Se (34), Mo (42), Sn (50), Te (52), and I (53), from which gallium and molybdenum are new discoveries in white dwarfs, too. For Kr and Xe, we performed an NLTE analysis and derived mass fractions of log Kr = -4.3 0.5 and log Xe = -4.2 0.6, corresponding to an enrichment by factors of 450 and 3800, respectively, relative to the Sun. The origin of the large overabundances is unclear. We discuss the roles of neutron-capture nucleosynthesis in the precursor star and radiation-driven diffusion. It is possible that diffusion is insignificant and that the observed metal abundances constrain the evolutionary history of the star. Its hydrogen deficiency may be the consequence of a late helium-shell flash or a binary white dwarf merger.

Werner, Klaus; Rauch, Thomas; Ringat, Ellen; Kruk, Jeffrey W.

2012-07-01

287

Extended testing of xenon ion thruster hollow cathodes  

NASA Technical Reports Server (NTRS)

A hollow cathode wear-test of 508 hours was successfully completed at an emission current of 23.0 A and a xenon flow rate of 10 Pa-L/s. This test was the continuation of a hollow cathode contamination investigation. Discharge voltage was stable at 16.7 V. The cathode temperature averaged 1050 C with a 7 percent drop during the wear-test. Discharge ignition voltage was found to be approximately 20 V and was repeatable over four starts. Post-test analyses of the hollow cathode found a much improved internal cathode condition with respect to earlier wear-test cathodes. Negligible tungsten movement occurred and no formation of mono-barium tungstate was observed. These results correlated with an order-of-magnitude reduction in propellant feed-system leakage rate. Ba2CaWO6 and extensive calcium crystal formation occurred on the upstream end of the insert. Ba-Ca compound depositions were found on the Mo insert collar, on the Re electrical leads, and in the gap between the insert and cathode wall. This wear-test cathode was found to be in the best internal condition and had the most stable operating performance of any hollow cathode tested during this contamination investigation.

Sarver-Verhey, Timothy R.

1992-01-01

288

Excimer emission from pulsed microhollow cathode discharges in xenon  

SciTech Connect

Direct current (dc) microhollow cathode discharge (MHCD) is an intense source for excimer radiation in vacuum ultraviolet at a wavelength of 172 nm in a high pressure xenon (Xe) gas. The concentration of precursors for the excimer formation, i.e., excited and ionized gas atoms, increases significantly by applying high voltage pulse onto the dc MHCD over the pulse duration range from 20 to 100 ns. The intensity of the excimer emission for the voltage pulse of 20 ns duration exceeds that of the emission intensity obtained from the same MHCD operated only in the dc mode, by one order of magnitude. In addition, the emission intensity increases by one order of magnitude over the pulse duration range from 20 to 100 ns. It can be assumed that the emission intensity of the MHCD source increases as long as the duration of the high voltage pulse is shorter than the electron relaxation time. For the high voltage pulse of 100 ns duration, the emission intensity has been found to be further enhanced by a factor of three when the gas pressure is increased from 200 to 800 mbar.

Lee, B.-J.; Nam, S. H. [Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of)] [Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of); Rahaman, H. [CSIRCEERI Pilani, Rajasthan 333031 (India)] [CSIRCEERI Pilani, Rajasthan 333031 (India); Iberler, M.; Jacoby, J. [Institute of Applied Physics, Goethe University, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany)] [Institute of Applied Physics, Goethe University, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany); Frank, K. [Physics Department 1, University of Erlangen Nuremberg, 91058 Erlangen (Germany)] [Physics Department 1, University of Erlangen Nuremberg, 91058 Erlangen (Germany)

2013-12-15

289

First Detection of Krypton and Xenon in a White Dwarf  

NASA Technical Reports Server (NTRS)

We report on the first detection of the noble gases krypton (Z = 36) and xenon (54) in a white dwarf. About 20 KrVI-VII and Xe VI-VII lines were discovered in the ultraviolet spectrum of the hot DO-type white dwarf RE 0503-289. The observations, performed with the Far Ultraviolet Spectroscopic Explorer, also reveal highly ionized photospheric lines from other trans-iron group elements, namely Ga (31), Ge (32), As (33), Se (34), Mo (42), Sn (50), Te (52), and I (53), from which gallium and molybdenum are new discoveries in white dwarfs, too. For Kr and Xe, we performed an NLTE analysis and derived mass fractions of log Kr = -4.3 plus or minus 0.5 and log Xe = -4.2 plus or minus 0.6, corresponding to an enrichment by factors of 450 and 3800, respectively, relative to the Sun. The origin of the large overabundances is unclear. We discuss the roles of neutron-capture nucleosynthesis in the-precursor star and radiation-driven diffusion. It is possible that diffusion is insignificant and thaI the observed metal abundances constrain the evolutionary history of the star. Its hydrogen deficiency may be the consequence of a late helium-shell nash or a binary white dwarf merger.

Werner, Klaus; Rauch, Thomas; Ringat, Ellen; Kruk, Jeffrey W.

2012-01-01

290

Extended-testing of xenon ion thruster hollow cathodes  

NASA Technical Reports Server (NTRS)

A hollow cathode wear-test of 508 hours was successfully completed at an emission current of 23.0 A and a xenon flow rate of 10 Pa-L/s. This test was the continuation of a hollow cathode contamination investigation. Discharge voltage was stable at 16.7 V. The cathode temperature averaged 1050 C with a 7 percent drop during the wear-test. Discharge ignition voltage was found to be approximately 20 V and was repeatable over four starts. Post-test analyses of the hollow cathode found a much improved internal cathode condition with respect to earlier wear-test cathodes. Negligible tungsten movement occurred and no formation of mono-barium tungsten was observed. These results correlated with an order-of-magnitude reduction in propellant feed-system leakage rate. Ba2CaWO6 and extensive calcium crystal formation occurred on the upstream end of the insert. Ba-Ca compound depositions were found on the Mo insert collar, on the Re electrical leads, and in the gap between the insert and cathode wall. This wear-test cathode was found to be in the best internal condition and had the most stable operating performance of any hollow cathode tested during this contamination investigation.

Sarver-Verhey, Timothy R.

1992-01-01

291

Thrust Stand Characterization of the NASA Evolutionary Xenon Thruster (NEXT)  

NASA Technical Reports Server (NTRS)

Direct thrust measurements have been made on the NASA Evolutionary Xenon Thruster (NEXT) ion engine using a standard pendulum style thrust stand constructed specifically for this application. Values have been obtained for the full 40-level throttle table, as well as for a few off-nominal operating conditions. Measurements differ from the nominal NASA throttle table 10 (TT10) values by 3.1 percent at most, while at 30 throttle levels (TLs) the difference is less than 2.0 percent. When measurements are compared to TT10 values that have been corrected using ion beam current density and charge state data obtained at The Aerospace Corporation, they differ by 1.2 percent at most, and by 1.0 percent or less at 37 TLs. Thrust correction factors calculated from direct thrust measurements and from The Aerospace Corporation s plume data agree to within measurement error for all but one TL. Thrust due to cold flow and "discharge only" operation has been measured, and analytical expressions are presented which accurately predict thrust based on thermal thrust generation mechanisms.

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

2010-01-01

292

Conceptual Design of the Nuclear Electronic Xenon Ion System (NEXIS)  

NASA Technical Reports Server (NTRS)

In support of the NEXIS program, Aerojet-Redmond Operations, with review and input from the JPL and Boeing, has completed the design for a development model (DM) discharge chamber assembly and main discharge cathode assembly. These efforts along with the work by JPL to develop the carbon-carbon-composite ion optics assembly have resulted in a complete ion engine design. The goal of the NEXIS program is to significantly advance the current state of the art by developing an ion engine capable of operating at an input power of 20kW, an Isp of 7500 sec and have a total xenon through put capability of 2000 kg. In this paper we will describe the methodology used to design the discharge chamber and cathode assemblies and describe the resulting final design. Specifics will include the concepts used for the mounting of the ion optics along with the concepts used for the gimbal mounts. In addition, we will present results of a vibrational analysis showing how the engine will respond to a typical Delta IV heavy vibration spectrum.

Monheiser, Jeff; Polk, Jay; Randolph, Tom

2004-01-01

293

Noble Gas Xenon Is a Novel Adenosine Triphosphate-sensitive Potassium Channel Opener  

PubMed Central

Background Adenosine triphosphate-sensitive potassium (KATP) channels in brain are involved in neuroprotective mechanisms. Pharmacologic activation of these channels is seen as beneficial, but clinical exploitation by using classic K+ channel openers is hampered by their inability to cross the bloodbrain barrier. This is different with the inhalational anesthetic xenon, which recently has been suggested to activate KATP channels; it partitions freely into the brain. Methods To evaluate the type and mechanism of interaction of xenon with neuronal-type KATP channels, these channels, consisting of Kir6.2 pore-forming subunits and sulfonylurea receptor-1 regulatory subunits, were expressed in HEK293 cells and whole cell, and excised patch-clamp recordings were performed. Results Xenon, in contrast to classic KATP channel openers, acted directly on the Kir6.2 subunit of the channel. It had no effect on the closely related, adenosine triphosphate (ATP)-regulated Kir1.1 channel and failed to activate an ATP-insensitive mutant version of Kir6.2. Furthermore, concentrationinhibition curves for ATP obtained from inside-out patches in the absence or presence of 80% xenon revealed that xenon reduced the sensitivity of the KATP channel to ATP. This was reflected in an approximately fourfold shift of the concentration causing half-maximal inhibition (IC50) from 26 4 to 96 6 ?m. Conclusions Xenon represents a novel KATP channel opener that increases KATP currents independently of the sulfonylurea receptor-1 subunit by reducing ATP inhibition of the channel. Through this action and by its ability to readily partition across the bloodbrain barrier, xenon has considerable potential in clinical settings of neuronal injury, including stroke.

Bantel, Carsten; Maze, Mervyn; Trapp, Stefan

2010-01-01

294

Carbon dioxide dangers demonstration model  

USGS Publications Warehouse

Carbon dioxide is a dangerous volcanic gas. When carbon dioxide seeps from the ground, it normally mixes with the air and dissipates rapidly. However, because carbon dioxide gas is heavier than air, it can collect in snowbanks, depressions, and poorly ventilated enclosures posing a potential danger to people and other living things. In this experiment we show how carbon dioxide gas displaces oxygen as it collects in low-lying areas. When carbon dioxide, created by mixing vinegar and baking soda, is added to a bowl with candles of different heights, the flames are extinguished as if by magic.

Venezky, Dina; Wessells, Stephen

2010-01-01

295

Method for the simultaneous preparation of radon-211, xenon-125, xenon-123, astatine-211, iodine-125 and iodine-123  

DOEpatents

The invention relates to a practical method for commercially producing radiopharmaceutical activities and, more particularly, relates to a method for the preparation of about equal amount of Radon-211 (/sup 211/Rn) and Xenon-125 (/sup 125/Xe) including a one-step chemical procedure following an irradiation procedure in which a selected target of Thorium (/sup 232/Th) or Uranium (/sup 238/U) is irradiated. The disclosed method is also effective for the preparation in a one-step chemical procedure of substantially equal amounts of high purity /sup 123/I and /sup 211/At. In one preferred arrangement of the invention almost equal quantities of /sup 211/Rn and /sup 125/Xe are prepared using a onestep chemical procedure in which a suitably irradiated fertile target material, such as thorium-232 or uranium-238, is treated to extract those radionuclides from it. In the same one-step chemical procedure about equal quantities of /sup 211/At and /sup 123/I are prepared and stored for subsequent use. In a modified arrangement of the method of the invention, it is practiced to separate and store about equal amounts of only /sup 211/Rn and /sup 125/Xe, while preventing the extraction or storage of the radionuclides /sup 211/At and /sup 123/I.

Mirzadeh, S.; Lambrecht, R.M.

1985-07-01

296

Photolytical Generation of Carbon Dioxide  

NASA Astrophysics Data System (ADS)

Carbon dioxide has been found by Cassini VIMS throughout the Saturnian system in locations such as Iapetus' equator where the temperature is too high for it to remain as free ice for more than a few hundred years. We suggest that the 4.26 micron absorption feature found on Iapetus and Hyperion (that has been attributed to complexed CO2) is the result of either UV photolysis or ion bombardment driving chemistry between the carbon rich layer and the water ice regolith. We conducted experiments to simulate the generation of CO2 by UV radiation under conditions similar to those on the surface of Iapetus. A simulated icy regolith was created in an argon atmosphere using flash-frozen, degassed water crushed into sub-millimeter sized particles. Isotopically labeled amorphous carbon (13C), which was ground into a fine dust, was mixed into the regolith allowing for extensive grain contact. This sample was placed in a vacuum chamber and cooled to temperatures as low at 60K. The sample was irradiated with UV light, and the products were measured using both a mass spectrometer to identify free molecules and an IR spectrometer for molecules that remained trapped on and in the simulated regolith. We report on the production and reaction rates of CO2 and CO, as well as the generation of free hydrogen and oxygen as detected by a SRS-100 mass spectrometer. We also identify residual products that either freeze on the surface or become entrained by or adsorbed onto the ice grains. We attempt to match the CO2 absorption feature found on Iapetus with that seen in our simulation, perhaps identifying a possible source of CO2 in the Saturnian system. Finally, we estimate the time required for these reactions to occur on Iapetus to see if UV photolysis would be effective.

Palmer, E. E.; Brown, R. H.

2008-12-01

297

First Results from the XENON10 Dark Matter Experiment the Gran Sasso Underground Lab  

NASA Astrophysics Data System (ADS)

We report the first results from a search for Weakly Interacting Massive Particles (WIMPs) with the XENON10 experiment operating underground at the Gran Sasso Laboratory. XENON10 is the first dual phase xenon time projection chamber (XeTPC) module realized within the XENON program. The 3D-postion sensitive detector has an active mass of 15 kg of liquid xenon, viewed by two arrays of compact photomultipliers, to measure simultaneously the scintillation and the ionization, via proportional scintillation in the gas. Background rejection on an event-by-event basis is achieved through this measurement and 3D event localization. The detector was deployed underground in Spring 2006 and mounted in its shield in Summer 2006. The experiment has been operating continuously for the past five months, with a high degree of stability and very good performance. The energy threshold is <10 keV and the background rate is <1evt/kg/keV/day. In-situ gamma and neutron calibrations have been carried out to define event selection and energy threshold for nuclear recoil candidates. Data taking continues as of this writing. A blind analysis on the latest months of data is currently being performed using only calibration data. WIMP search results are expected by early Spring 2007.

Aprile, Elena

2007-04-01

298

Modeling Double Hole Dynamics in Intense Laser Produced Xenon Cluster Plasmas  

NASA Astrophysics Data System (ADS)

When femtosecond laser pulses with intensities greater than 10^19W/cm^2 interact with a cluster of xenon atoms, the atoms are stripped of their N-shell electrons in less than a femtosecond and a Coulomb explosion ensues with ions initially in the ground state of Ni-like xenon. X-ray lasing at 2.86 has been observed in such cluster explosions [1] and gain coefficients were measured. Gains comparable to those measured have been obtained in the single hole states of Co-like xenon in an initial non-equilibrium theoretical analysis of these experiments [2]. Alternatively, x-ray amplification has also been attributed to the generation of population inversions between double and single hole states in the M-shell ions of xenon [3]. In order to investigate the viability of this possibility, we have added double hole states to the Fe-like ionization stage of our detailed ionization dynamic model of Ni-, Co-, and Fe-like xenon [2]. Results from our model calculations will be presented in this talk. [0pt] [1] A. B. Borisov, et. al., J. Phys. B: At. Mol. Opt. Phys. 40 (2007) F307. [2] Tz. B. Petrova, et. al., J. Phys. B: At. Mol. Opt. Phys. 43 (2010) 025601. [3] W. Andreas Schroeder, et. al., J. Phys. B: At. Mol. Opt. Phys. 34 (2001) 297.

Petrova, Tzvetelina; Whitney, Kenneth; Davis, Jack; Petrov, George

2010-11-01

299

Measurement of xenon plasma properties in an ion thruster using laser Thomson scattering technique  

SciTech Connect

This paper reports on the development of a method for measuring xenon plasma properties using the laser Thomson scattering technique, for application to ion engine system design. The thresholds of photo-ionization of xenon plasma were investigated and the number density of metastable atoms, which are photo-ionized by a probe laser, was measured using laser absorption spectroscopy, for several conditions. The measured threshold energy of the probe laser using a plano-convex lens with a focal length of 200 mm was 150 mJ for a xenon mass flow rate of 20 {mu}g/s and incident microwave power of 6 W; the probe laser energy was therefore set as 80 mJ. Electron number density was found to be (6.2 {+-} 0.4) Multiplication-Sign 10{sup 17} m{sup -3} and electron temperature was found to be 2.2 {+-} 0.4 eV at a xenon mass flow rate of 20 {mu}g/s and incident microwave power of 6 W. The threshold of the probe laser intensity against photo-ionization in a miniature xenon ion thruster is almost constant for various mass flow rates, since the ratio of population of the metastable atoms to the electron number density is little changed.

Yamamoto, N.; Tomita, K.; Sugita, K.; Kurita, T.; Nakashima, H.; Uchino, K. [Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka 816-8580 (Japan)

2012-07-15

300

Modeling the Removal of Xenon from Lithium Hydrate with Aspen HYSYS  

NASA Astrophysics Data System (ADS)

The Laser Inertial Fusion Engine (LIFE) project mission is to provide a long-term, carbon-free source of sustainable energy, in the form of electricity. A conceptual xenon removal system has been modeled with the aid of Aspen HYSYS, a chemical process simulator. Aspen HYSYS provides excellent capability to model chemical flow processes, which generates outputs which includes specific variables such as temperature, pressure, and molar flow. The system is designed to strip out hydrogen isotopes deuterium and tritium. The base design bubbles plasma exhaust laden with x filled with liquid helium. The system separates the xenon from the hydrogen, deuterium, and tritium with a lithium hydrate and a lithium bubbler. After the removal of the hydrogen and its isotopes, the xenon is then purified by way of the process of cryogenic distillation. The pure hydrogen, deuterium, and tritium are then sent to the isotope separation system (ISS). The removal of xenon is an integral part of the laser inertial fusion engine and Aspen HYSYS is an excellent tool to calculate how to create pure xenon.

Efthimion, Phillip; Gentile, Charles

2011-11-01

301

Evaluation of pulmonary perfusion in lung regions showing isolated xenon-133 ventilation washout defects  

SciTech Connect

Xenon-133 washout phase imaging is often used to help determine whether the etiology of a perfusion defect is embolic or due to pulmonary parenchymal pathology, such as chronic obstructive pulmonary disease. This study was designed to evaluate the pulmonary blood flow patterns associated with isolated defects on xenon washout images. Scintigraphic lung studies were reviewed until 100 cases with abnormal ventilation results were obtained. Ventilation abnormalities were compared with the corresponding perfusion scan results at the same anatomic site. Of the 208 individual lung regions with xenon abnormalities, 111 showed isolated washout defects (that is, with normal washin). Ninety-four of these 111 sites showed either normal perfusion or a small, nonsegmental corresponding perfusion defect. Three segmental perfusion defects were noted in association with isolated xenon retention. In each of these cases, however, the patient was felt actually to have pulmonary embolism. Thus, it is recommended that, for interpretation of scintigraphic images in the assessment of pulmonary embolism, lung pathology associated with isolated xenon retention not be considered a potential cause for large or segmental perfusion defects.

Bushnell, D.L.; Sood, K.B.; Shirazi, P.; Pal, I. (VA Hines Hospital, IL (USA))

1990-08-01

302

Modeling Carbon Dioxide Levels  

NSDL National Science Digital Library

In this activity students will explore levels of Carbon Dioxide ( C02) in the atmosphere over time. There is concern that levels of C02 are rising; and finding a good mathematical model for CO2 levels is an important part of determining if this is attributable to human technology. Students draw a scatter plot, choose two points to create a linear model for the data, then use the model to make predictions.

2009-01-01

303

Sulfur dioxide disposal system  

Microsoft Academic Search

There is disclosed a multi-stage process for reducing sulfur dioxide to sulfur or to hydrogen sulfide whereby a hydrogen-containing gas from a high temperature gasifier is used. In the first stage of the process, the gasifier exit gas is contacted at a minimum temperature of about 1800° F. With recycle gas containing SO2, H2S, COS, mercaptans, and CS2 in order

Kamody

1981-01-01

304

Titanium dioxide photocatalysis  

Microsoft Academic Search

Scientific studies on photocatalysis started about two and a half decades ago. Titanium dioxide (TiO2), which is one of the most basic materials in our daily life, has emerged as an excellent photocatalyst material for environmental purification. In this review, current progress in the area of TiO2 photocatalysis, mainly photocatalytic air purification, sterilization and cancer therapy are discussed together with

Akira Fujishima; Tata N. Rao; Donald A. Tryk

2000-01-01

305

A New Wide-Range Equation of State for Xenon  

NASA Astrophysics Data System (ADS)

We describe the development of a new wide-range equation of state (EOS) for xenon. Three different prior EOS models predicted significant variations in behavior along the high pressure Hugoniot from an initial liquid state at 163.5 K and 2.97 g/cm^3, which is near the triple point. Experimental measurements on Sandia's Z machine as well as density functional theory based molecular dynamics calculations both invalidate the prior EOS models in the pressure range from 200 to 840 GPa [1]. The reason behind these EOS model disagreements is found to lie in the contribution from the thermal electronic models. A new EOS [2], based upon the standard separation of the Helmholtz free energy into ionic and electronic components, is constructed by combining the successful parts of prior models with a semi-empirical electronic model. Both the fluid and fcc solid phases are combined in a wide-range, multi-phase table. The new EOS is tabulated on a fine temperature and density grid, to preserve phase boundary information, and is available as table number 5191 in the LANL SESAME database [3]. Improvements over prior EOS models are found not only along the Hugoniot, but also along the melting curve and in the region of the liquid-vapor critical point. [4pt] *Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.[4pt] [1] S. Root et. al., Physical Review Letters 105, 085501 (2010).[2] J. H. Carpenter et. al., EPJ Web of Conferences 10, 00018 (2010).[3] http://t1web.lanl.gov/

Carpenter, John H.

2011-06-01

306

NASA's Evolutionary Xenon Thruster (NEXT) Component Verification Testing  

NASA Technical Reports Server (NTRS)

Component testing is a critical facet of the comprehensive thruster life validation strategy devised by the NASA s Evolutionary Xenon Thruster (NEXT) program. Component testing to-date has consisted of long-duration high voltage propellant isolator and high-cycle heater life validation testing. The high voltage propellant isolator, a heritage design, will be operated under different environmental condition in the NEXT ion thruster requiring verification testing. The life test of two NEXT isolators was initiated with comparable voltage and pressure conditions with a higher temperature than measured for the NEXT prototype-model thruster. To date the NEXT isolators have accumulated 18,300 h of operation. Measurements indicate a negligible increase in leakage current over the testing duration to date. NEXT 1/2 in. heaters, whose manufacturing and control processes have heritage, were selected for verification testing based upon the change in physical dimensions resulting in a higher operating voltage as well as potential differences in thermal environment. The heater fabrication processes, developed for the International Space Station (ISS) plasma contactor hollow cathode assembly, were utilized with modification of heater dimensions to accommodate a larger cathode. Cyclic testing of five 1/22 in. diameter heaters was initiated to validate these modified fabrication processes while retaining high reliability heaters. To date two of the heaters have been cycled to 10,000 cycles and suspended to preserve hardware. Three of the heaters have been cycled to failure giving a B10 life of 12,615 cycles, approximately 6,000 more cycles than the established qualification B10 life of the ISS plasma contactor heaters.

Herman, Daniel A.; Pinero, Luis R.; Sovey, James S.

2009-01-01

307

Chlorine dioxide and hemodialysis  

SciTech Connect

Because it has little or no tendency to generate carcinogenic trihalomethanes such as chloroform, chlorine dioxide is an attractive alternative to chlorine for drinking water disinfection. There are, however, concerns about its acute toxicity, and the toxic effects of its by-products, chlorite and chlorate. The human experience with chlorine dioxide in both controlled, prospective studies and in actual use situations in community water supplies have as yet failed to reveal adverse health effects. The EPA has recommended standards of 0.06 mg/L for chlorine dioxide and standards of 0.007 mg/L for chlorite and chlorate in drinking water. Among groups who may be at special risk from oxychlorines in drinking water are patients who must undergro chronic extracorporeal hemodialysis. Although even units for home hemodialysis are supposed to be equipped with devices which effectively remove oxychlorines, there is a always a possibility of operator error or equipment failure. When the equipment is adequately maintained, it is likely that dialysis patients will have more intensive exposures from drinking water than from dialysis fluids despite the much larger volumes of water that are involved in dialysis. This paper discusses a hemodialysis and the standards and effects of oxychlorines. 90 refs., 2 tabs.

Smith, R.P. (Dartmouth Coll., Hanover, NH (USA). Dept. of Pharmacology and Toxicology)

1989-05-01

308

Xenon adsorbed in zeolite NaY: A systematic molecular dynamics study with a flexible framework approach  

Microsoft Academic Search

Molecular dynamics simulations are performed in order to study systematically the behaviour of xenon in zeolite Na-Y over a wide range of temperatures and loadings. For these investigations a full flexible framework approach is used and the polarizability of xenon is taken into account. The good agreement between the results of the simulations and available experimental data indicates that the

G. Schrimpf; J. Brickmann

1995-01-01

309

Facile xenon capture and release at room temperature using a metal-organic framework: a comparison with activated charcoal  

SciTech Connect

Two well known Metal organic frameworks (MOF-5, NiDOBDC) were synthesized and studied for facile xenon capture and separation. Our results indicate the NiDOBDC adsorbs significantly more xenon than MOF-5, releases it more readily than activated carbon, and is more selective for Xe over Kr than activated carbon.

Thallapally, Praveen K.; Grate, Jay W.; Motkuri, Radha K.

2012-01-11

310

Subpicosecond-pulse development in a colliding-pulse mode-locking dye laser pumped by a pulsed xenon laser  

SciTech Connect

We obtain 0.34-psec optical pulses by using a long-pulse xenon-ion laser as a pump source in a colliding-pulse mode-locking (CPM) configuration. The pump shape is an important parameter affecting the development of short pulses. Some characteristics of xenon- and argon-laser-pumped CPM systems are compared.

Ansari, H.; Dienes, A.; Whinnery, J.R.

1985-01-01

311

Using Point Reactor Models and Genetic Algorithms for On-Line Global Xenon Estimation in Nuclear Reactors  

Microsoft Academic Search

Estimation of xenon concentration at a given time instant is usually a difficult problem since the initial conditions are often unknown as well as a number of the model parameters. The feasibility of obtaining the model parameters of a point reactor xenon evolution model with genetic algorithms (GAs) has been investigated earlier using data obtained from a point reactor model

Tunc Aldemir; Giancarlo Torri; Marzio Marseguerra; Enrico Zio; Jeffrey A. Borkowski

2003-01-01

312

Radioactive Plume from the Three Mile Island Accident: Xenon133 in Air at a Distance of 375 Kilometers  

Microsoft Academic Search

The transit of an air mass containing radioactive gas released from the Three Mile Island reactor was recorded in Albany, New York, by measuring xenon-133. These measurements provide an evaluation of Three Mile Island effluents to distances greater than 100 kilometers. Two independent techniques identified xenon-133 in ambient air at concentrations as high as 3900 picocuries per cubic meter. The

Martin Wahlen; Charles O. Kunz; John M. Matuszek; William E. Mahoney; Roger C. Thompson

1980-01-01

313

Direct measurement for the decay probabilities of 4dj hole states in xenon by means of photoelectron-ion coincidences  

Microsoft Academic Search

The decay probabilities of the 4dj hole states in xenon into the differently charged ion states, i.e. fluorescence decay, normal Auger together with discrete double Auger decay and continuous double Auger decay, are measured directly by means of coincidences between 4dj photoelectrons and xenon ions. Special emphasis is given to the strength of continuous double Auger transitions which is a

B. Kammerling; B. Krassig; V. Schmidt

1992-01-01

314

Progress on the Characterization of the Yale ``PIXeY'' Two-Phase Xenon Detector  

NASA Astrophysics Data System (ADS)

PIXeY (Particle Identification in Xenon at Yale) is a two-phase (liquid/gas) xenon prototype detector with 3-kg active mass. The two-phase xenon technology has many applications that include gamma-ray imaging, neutrinoless double beta decay searches, and dark matter searches. PIXeY was built to optimize energy resolution and gamma/neutron discrimination, with a number of technological improvements over previous work. Parallel-wire grids, which control the drift and proportional-scintillation fields, are optimized both for light collection efficiency and field uniformity. High quantum efficiency Hamamatsu R8778 PMTs, high-reflectivity Teflon walls, and charge-light anti-correlation techniques are also incorporated. PIXeY will serve as a platform for future improvements, including multiple optical volumes and single wire readout for R&D on gamma-ray imaging and track-imaging studies. The latest progress on the detector will be presented.

Destefano, Nicholas; Gai, Moshe; McKinsey, Daniel; Bernard, Ethan; Cahn, Sidney; Curioni, Alessandro; Edwards, Blair; Kachulis, Christopher; Larsen, Nicole; Lyashenko, Alexey; Nikkel, James; Skin, Yunchang; Wahl, Christopher; Young, Alexander

2012-10-01

315

A study of the scintillation light induced in liquid xenon by electrons and alpha particles  

SciTech Connect

The authors have measured the time dependence and the intensity of the primary scintillation light in liquid xenon excited by {sup 241}Am alpha particles and {sup 207}Bi internal conversion electrons, at different electric field strengths. High purity liquid xenon was used to fill a parallel plate ionization chamber equipped with a CaF{sub 2} window coupled to a UV sensitive photomultiplier tube. The effect of the specific ionization density on the scintillation light as well as the time correlation between the light signal and the charge signal is reported. The authors demonstrate that the fast scintillation signal produced in liquid xenon by an ionizing particle provides an ideal trigger in a detector aiming at a complete three-dimensional even reconstruction with an excellent background rejection capability.

Aprile, E.; Mukherjee, R.; Suzuki, M. (Columbia Univ., New York, NY (USA). Dept. of Physics)

1990-04-01

316

First Results from the XENON10 Dark Matter Experiment at the Gran Sasso National Laboratory  

NASA Astrophysics Data System (ADS)

The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg xenon dual phase time projection chamber to search for dark matter weakly interacting massive particles (WIMPs). The detector measures simultaneously the scintillation and the ionization produced by radiation in pure liquid xenon to discriminate signal from background down to 4.5 keV nuclear-recoil energy. A blind analysis of 58.6 live days of data, acquired between October 6, 2006, and February 14, 2007, and using a fiducial mass of 5.4 kg, excludes previously unexplored parameter space, setting a new 90% C.L. upper limit for the WIMP-nucleon spin-independent cross section of 8.810-44cm2 for a WIMP mass of 100GeV/c2, and 4.510-44cm2 for a WIMP mass of 30GeV/c2. This result further constrains predictions of supersymmetric models.

Angle, J.; Aprile, E.; Arneodo, F.; Baudis, L.; Bernstein, A.; Bolozdynya, A.; Brusov, P.; Coelho, L. C. C.; Dahl, C. E.; Deviveiros, L.; Ferella, A. D.; Fernandes, L. M. P.; Fiorucci, S.; Gaitskell, R. J.; Giboni, K. L.; Gomez, R.; Hasty, R.; Kastens, L.; Kwong, J.; Lopes, J. A. M.; Madden, N.; Manalaysay, A.; Manzur, A.; McKinsey, D. N.; Monzani, M. E.; Ni, K.; Oberlack, U.; Orboeck, J.; Plante, G.; Santorelli, R.; Dos Santos, J. M. F.; Shagin, P.; Shutt, T.; Sorensen, P.; Schulte, S.; Winant, C.; Yamashita, M.

2008-01-01

317

Nanoemulsion contrast agents with sub-picomolar sensitivity for xenon NMR.  

PubMed

A new type of contrast agent for Xe NMR based on surfactant-stabilized perfluorocarbon-in-water nanoemulsions has been produced. The contrast agent uses dissolved hyperpolarized xenon gas as a nonperturbing reporting medium, as xenon freely exchanges between aqueous solution and the perfluorocarbon interior of the droplets, which are spectroscopically distinguishable and allow for chemical exchange saturation transfer (CEST) detection of the agent. Nanoemulsions with droplet diameters between 160 and 310 nm were produced and characterized using hyperpolarized (129)Xe combined with CEST detection. Saturation parameters were varied and data were modeled numerically to determine the xenon exchange dynamics of the system. Nanoemulsion droplets were detected at concentrations as low as 100 fM, corresponding to <1 ?L of perfluorocarbon per liter of solution. The straightforward, inexpensive production of these agents will facilitate future development toward molecular imaging and chemical sensing applications. PMID:23742228

Stevens, Todd K; Ramirez, R Matthew; Pines, Alexander

2013-07-01

318

A Search for Nonstandard Neutron Spin Interactions using Dual Species Xenon Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

NMR measurements using polarized noble gases can constrain possible exotic spin-dependent interactions involving nucleons. A differential measurement insensitive to magnetic field fluctuations can be performed using a mixture of two polarized species with different ratios of nucleon spin to magnetic moment. We used the NMR cell test station at Northrop Grumman Corporation (NGC) (developed to evaluate dual species xenon vapor cells for the Nuclear Magnetic Resonance Gyroscope) to search for NMR frequency shifts of xenon-129 and xenon-131 when a non-magnetic zirconia rod is modulated near the NMR cell. We simultaneously excited both Xe isotopes and detected free-induction-decay transients. In combination with theoretical calculations of the neutron spin contribution to the nuclear angular momentum, the measurements put a new upper bound on possible monopole-dipole interactions of the neutron for ranges around 1mm. This work is supported by the NGC Internal Research and Development (IRAD) funding, the Department of Energy, and the NSF.

Bulatowicz, Michael; Larsen, Michael; Mirijanian, James; Fu, Changbo; Yan, Haiyang; Smith, Erick; Snow, Mike; Walker, Thad

2012-06-01

319

Thermal excitation in a spatially modulated monolayer solid: Incommensurate xenon/graphite  

NASA Astrophysics Data System (ADS)

Calculations of the properties of monolayer xenon/graphite for temperatures up to its triple point at 100 K are reported. The average lattice constant and orientational epitaxy angle for the monolayer solid are evaluated along its (two-dimensional) sublimation curve. The incommensurate rotated lattice approaches the incommensurate aligned configuration as the melting temperature is approached, as in experiments. The calculated temperature, latent heat of melting, and solid-liquid density difference at the triple point agree with experiment. The methods include molecular dynamics simulations for large submonolayer patches of xenon and both self-consistent-phonon and perturbation-variation approximations. An overall quantitative agreement between the simulations, calculations, and experimental data is achieved with an interaction model that includes the spatially periodic xenon-graphite corrugation energy.

Novaco, A. D.; Bruch, L. W.

2014-03-01

320

Measurement of Xenon Viscosity as a Function of Low Temperature and Pressure  

NASA Technical Reports Server (NTRS)

The measurement of xenon gas viscosity at low temperatures (175-298 K) and low pressures (350 torr-760 torr) has been performed in support of Hall Thruster testing at NASA Lewis Research Center. The measurements were taken using the capillary flow technique. Viscosity measurements were repeatable to within 3%. The results in this paper are in agreement with data from Hanley and Childs and suggest that the data from Clarke and Smith is approximately 2% low. There are no noticeable pressure effects on xenon absolute viscosity for the pressure range from 350 torr to 760 torr.

Grisnik, Stanley P.

1998-01-01

321

Development of a xenon/computed tomography cerebral blood flow quality assurance phantom  

SciTech Connect

A simple, easy to use, quality assurance and performance test phantom was developed for the xenon/computed tomography (CT) cerebral blood flow method. The phantom combines an inhalation system which allows for the simulation of xenon buildup or washout in the arterial blood as well as a multisection translatable cylinder in which several sections can be scanned during a preselected protocol to simulate the CT enhancement in brain tissue during a study. The phantom and scanning protocol are described and their use is demonstrated. The results compare favorably to the theoretically expected fast, intermediate, and slow flow values designed into the phantom.

Good, W.F.; Gur, D.; Herron, J.M.; Kennedy, W.H.

1987-09-01

322

Nuclear recoil energy scale in liquid xenon with application to the direct detection of dark matter  

SciTech Connect

We show for the first time that the quenching of electronic excitation from nuclear recoils in liquid xenon is well-described by Lindhard theory, if the nuclear recoil energy is reconstructed using the combined (scintillation and ionization) energy scale proposed by Shutt et al.. We argue for the adoption of this perspective in favor of the existing preference for reconstructing nuclear recoil energy solely from primary scintillation. We show that signal partitioning into scintillation and ionization is well-described by the Thomas-Imel box model. We discuss the implications for liquid xenon detectors aimed at the direct detection of dark matter.

Sorensen, P; Dahl, C E

2011-02-14

323

Iodine-129/xenon-129 age of magnetite from the orgueil meteorite.  

PubMed

Magnetite from the Orgueil C1 chondrite is only 2.0 +/- 2.4 million years older by the iodine-xenon method than the next oldest meteorite, the Karoonda C4 chondrite. This age ties the primitive C1 chondrites to the extensive iodine-xenon chronology of normal chrondrites. If Karoonda and Orgueil magnetite formed from similar material, then the age difference is an upper limit to the formation time of these meteorites-and by customary extension, the solar system. Condensation, chondrule formation, accretion, and metamorphism of the Karoonda parent body all seem to have been completed within a few million years. PMID:17817809

Herzog, G F; Anders, E; Alexander, E C; Davis, P K; Lewis, R S

1973-05-01

324

Long term spectral irradiance measurements of a 1000-watt xenon arc lamp  

NASA Technical Reports Server (NTRS)

Spectral irradiance measurements over the range of 200 to 1060 nm were made on a 1000-watt xenon arc lamp over a period of 1500 hours. Four sets of measurements were made after periods of 70, 525, 1000, and 1500 hours of operation. The lamp (Hanovia Compact Xenon Arc Lamp) was mounted in the NASA Solar Irradiation System. When used in the System, the lamp is used as the radiating source for six test stations. Measurements were made of both the longterm stability (or variation of spectral irradiance as a function of time) and the actual spectral irradiance incident on the test specimen.

Schneider, W. E.

1974-01-01

325

Angular correlations in the sequential two-photon double ionisation of atomic xenon  

NASA Astrophysics Data System (ADS)

The sequential two-photon double ionization has been analyzed for the 4d electrons of atomic xenon in the region of the giant resonance and beyond (70-200 eV), for which intense FEL radiation is available at the free electron laser FLASH. The 4d vacancies in xenon couple strongly to the autoionization continuum with lifetimes of only a few fs, and their Auger decay thus competes with the subsequent (second-and higher-step) photoionization in typical FEL pulses.

Fritzsche, S.; Grum-Grzhimailo, A. N.; Gryzlova, E. V.; Kabachnik, N. M.

2012-11-01

326

Spectra of highly ionized xenon (630nm) excited in W7AS plasmas  

Microsoft Academic Search

. The xenon spectrum, excited in ECR- and NBI-heated plasmas with central electron densities of around 1020m-3, and central electron temperatures from 0.7 to 2.5keV, has been studied photoelectrically with a multi-channel grazing-incidence\\u000a spectrometer. Besides numerous well-known lines of Zn- and Cu-like Xenon, more than 50 additional lines which have not yet\\u000a been published in the literature have been found

H. H. Hacker; R. Burhenn; K. Kondo; M. Anton; D. Assmus; S. Baeumel; C. Beidler; T. Bindemann; R. Brakel; G. Cattanei; A. Dinklage; A. Dodhy; D. Dorst; H. Ehmler; A. Elsner; M. Endler; K. Engelhardt; V. Erckmann; Y. Feng; C. Fuchs; F. Gadelmeier; J. Geiger; L. Giannone; P. Grigull; G. Gruenwald; O. Grulke; E. Harmeyer; H. J. Hartfuss; F. Herrnegger; M. Hirsch; J. Hofner; F. Hollmann; E. Holzhauer; Y. Igitkhanov; R. Jaenicke; F. Karger; M. Kick; J. Kisslinger; S. Klose; J. Knauer; H. Kroiss; G. Khner; A. Kus; H. Laqua; R. Liu; H. Maassberg; N. Marushchenko; K. McCormick; G. Michel; F. Noke; W. Ott; M. Otte; M. G. Pacco-Duechs; F. P. Penningsfeld; E. Polunovsky; F. Probst; F. Purps; N. Ruhs; N. Rust; N. J. Saffert; A. Salat; J. Sallander; F. Sardei; F. Schneider; M. Schubert; I. Sidorenko; E. Speth; R. Suess; H. Thomsen; F. Volpe; F. Wagner; A. Weller; C. Wendland; A. Werner; H. Wobig; E. Wuersching; D. Zimmermann

2001-01-01

327

Results from the XENON10 and the Race to Detect Dark Matter with Noble Liquids  

ScienceCinema

Detectors based on liquid noble gases have the potential to revolutionize the direct search for WIMP dark matter. The XENON10 experiment, of which I am a member, has recently announced the results from it's first data run and is now the leading WIMP search experiment. This and other experiments using xenon, argon and neon have the potential to rapidly move from the current kg-scale target mass to the ton scale and well beyond. This should allow a (nearly) definitive test or discovery of dark matter if it is in the form of weakly interacting massive particles.

328

Hyperpolarized Xenon-129 Magnetic Resonance Imaging of Functional Lung Microstructure  

NASA Astrophysics Data System (ADS)

Hyperpolarized 129Xe (HXe) is a non-invasive contrast agent for lung magnetic resonance imaging (MRI), which upon inhalation follows the functional pathway of oxygen in the lung by dissolving into lung tissue structures and entering the blood stream. HXe MRI therefore provides unique opportunities for functional lung imaging of gas exchange which occurs from alveolar air spaces across the air-blood boundary into parenchymal tissue. However challenges in acquisition speed and signal-to-noise ratio have limited the development of a HXe imaging biomarker to diagnose lung disease. This thesis addresses these challenges by introducing parallel imaging to HXe MRI. Parallel imaging requires dedicated hardware. This work describes design, implementation, and characterization of a 32-channel phased-array chest receive coil with an integrated asymmetric birdcage transmit coil tuned to the HXe resonance on a 3 Tesla MRI system. Using the newly developed human chest coil, a functional HXe imaging method, multiple exchange time xenon magnetization transfer contrast (MXTC) is implemented. MXTC dynamically encodes HXe gas exchange into the image contrast. This permits two parameters to be derived regionally which are related to gas-exchange functionality by characterizing tissue-to-alveolar-volume ratio and alveolar wall thickness in the lung parenchyma. Initial results in healthy subjects demonstrate the sensitivity of MXTC by quantifying the subtle changes in lung microstructure in response to orientation and lung inflation. Our results in subjects with lung disease show that the MXTC-derived functional tissue density parameter exhibits excellent agreement with established imaging techniques. The newly developed dynamic parameter, which characterizes the alveolar wall, was elevated in subjects with lung disease, most likely indicating parenchymal inflammation. In light of these observations we believe that MXTC has potential as a biomarker for the regional quantification of 1) emphysematous tissue destruction in chronic obstructive pulmonary disease (using the tissue density parameter) and 2) parenchymal inflammation or thickening (using the wall thickness parameter). By simultaneously quantifying two lung function parameters, MXTC provides a more comprehensive picture of lung microstructure than existing lung imaging techniques and could become an important non-invasive and quantitative tool to characterize pulmonary disease.

Dregely, Isabel

329

Water and Carbon Dioxide Adsorption at Olivine Surfaces  

SciTech Connect

Plane-wave density functional theory (DFT) calculations were performed to simulate water and carbon dioxide adsorption at the (010) surface of five olivine minerals, namely, forsterite (Mg2SiO4), calcio-olivine (Ca2SiO4), tephroite (Mn2SiO4), fayalite (Fe2SiO4), and Co-olivine (Co2SiO4). Adsorption energies per water molecule obtained from energy minimizations varied from -78 kJ mol-1 for fayalite to -128 kJ mol-1 for calcio-olivine at sub-monolayer coverage and became less exothermic as coverage increased. In contrast, carbon dioxide adsorption energies at sub-monolayer coverage ranged from -20 kJ mol-1 for fayalite to -59 kJ mol-1 for calcio-olivine. Therefore, the DFT calculations show a strong driving force for carbon dioxide displacement by water at the surface of all olivine minerals in a competitive adsorption scenario. Additionally, adsorption energies for both water and carbon dioxide were found to be more exothermic for the alkaline-earth (AE) olivines than for the transition-metal (TM) olivines and to not correlate with the solvation enthalpies of the corresponding divalent cations. However, a correlation was obtained with the charge of the surface divalent cation indicating that the more ionic character of the AE cations in the olivine structure relative to the TM cations leads to greater interactions with adsorbed water and carbon dioxide molecules at the surface and thus more exothermic adsorption energies for the AE olivines. For calcio-olivine, which exhibits the highest divalent cation charge of the five olivines, ab initio molecular dynamics simulations showed that this effect leads both water and carbon dioxide to react with the surface and form hydroxyl groups and a carbonate-like species, respectively.

Kerisit, Sebastien N.; Bylaska, Eric J.; Felmy, Andrew R.

2013-11-14

330

Carbon dioxide sequestration by carbon nanotubes: Application of graph theoretical approach  

Microsoft Academic Search

A graph theoretical approach is applied to analyze the dynamic evolution of retention of carbon dioxide (CO2) molecules in single-walled carbon nanotubes (SWNTs). The trajectories of the molecules were obtained from the Molecular Dynamics (MD) simulations performed at constant temperature, T=300K, with a duration of 10ns. The simulation box contains four single-walled carbon nanotubes and 408 CO2 molecules with a

Deniz Rende; Nihat Baysal; Rahmi Ozisik

2010-01-01

331

Nitrogen dioxide detection  

SciTech Connect

An apparatus is described for detection of nitrogen dioxide in a gas comprised of: (a) sensing element consisting of polystyrene having at least one pair of opposing surfaces, where the conductance and resistance of said sensing element do not vary in response to the presence in said gas of varying amounts of water vapor; (b) a first electrode having at least one surface in contact with a first of said sensing element opposing surfaces; (c) a second electrode having at least one surface in contact with a second of said sensing clement opposing and (d) means for measuring the conductance or resistance of said sensing element between said electrodes.

Sinha, D.N.; Agnew, S.F.; Christensen, W.H.

1993-06-29

332

Process for sequestering carbon dioxide and sulfur dioxide  

DOEpatents

A process for sequestering carbon dioxide, which includes reacting a silicate based material with an acid to form a suspension, and combining the suspension with carbon dioxide to create active carbonation of the silicate-based material, and thereafter producing a metal salt, silica and regenerating the acid in the liquid phase of the suspension.

Maroto-Valer, M. Mercedes (State College, PA); Zhang, Yinzhi (State College, PA); Kuchta, Matthew E. (State College, PA); Andresen, John M. (State College, PA); Fauth, Dan J. (Pittsburgh, PA)

2009-10-20

333

Microwave spectra and conformational studies of ethylamine from temperature dependent Raman spectra of xenon solutions and ab initio calculations  

NASA Astrophysics Data System (ADS)

FT-microwave spectroscopy was carried out where the trans conformer was identified to be the most stable conformer. Variable temperature (-60 to -100 C) studies of the Raman spectra (4000-50 cm-1) of ethylamine, CH3CH2NH2 dissolved in liquefied xenon have been carried out. From these data both conformers have been identified and their relative stabilities obtained. The enthalpy difference has been determined to be 62 6 cm-1 (0.746 0.072 kJ mol-1) with the trans conformer the more stable form. The percentage of the gauche conformer is estimated to be 60% at ambient temperature. The conformational stabilities have been predicted from ab initio calculations with the Mller-Plesset perturbation method to the second order (MP2(full)) and the fourth order (MP4(SDTQ)) as well as with density functional theory by the B3LYP method by utilizing a variety of basis sets. Vibrational assignments have been made for the observed bands which have been predicted by MP2(full)/6-31G(d) ab initio calculations which includes harmonic force fields, frequencies, infrared intensities, Raman activities and depolarization ratios for both conformers. The results are discussed and compared to the corresponding properties of some similar molecule.

Darkhalil, Ikhlas D.; Nagels, Nick; Herrebout, Wouter A.; van der Veken, Benjamin J.; Gurusinghe, Ranil M.; Tubergen, Michael J.; Durig, James R.

2014-06-01

334

Polarization and hyperfine transitions of metastable xenon-129 in discharge cells and pressure shift of cesium in neon  

NASA Astrophysics Data System (ADS)

This thesis summarizes the results of two experimental studies of spin polarized atoms. In the first experiments, I studied optically pumped metastable Xe atoms that were produced in glass cells with weak electrical discharges in low-pressure Xe gas. The polarization and relaxation rates of metastable 129Xe atoms are measured with magnetic resonance spectroscopy, at both microwave frequencies, where DeltaF = 1 transitions are induced between the sublevels, and at radiofrequencies, corresponding to DeltaF = 0 transitions. The nuclear spin polarization of the optically pumped velocity group is measured to be 22 +/- 2%. The relaxation of metastable xenon atoms is dominated by depolarizing collisions with ground state atoms. We also present a model to simulate the density matrix with optical pumping and the magnetic resonances, and to use the resulting density matrix to simulate the attenuation of the optical pumping light, which provides the primary data for my studies. The second experiments were aimed at detecting any non-linearities in the pressure shift of the hyperfine frequency of Cs atoms in Ne buffer gas. Such nonlinear shifts can be produced by the formation and breakup of CsNe Van der Waals molecules. Nonlinear shifts have been observed in the heavier buffer gases, Ar, Kr and Xe. My work shows the nonlinear part of the pressure shift from Ne is too small to be detectable with my apparatus, the most sensitive available today.

Xia, Tian

335

21 CFR 73.2575 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Titanium dioxide. 73.2575 Section 73... Cosmetics § 73.2575 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide shall conform in identity...

2010-04-01

336

21 CFR 73.1575 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Titanium dioxide. 73.1575 Section 73...CERTIFICATION Drugs § 73.1575 Titanium dioxide. (a) Identity and specifications... (1) The color additive titanium dioxide shall conform in identity...

2010-04-01

337

40 CFR 180.1195 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 2010-07-01 false Titanium dioxide. 180.1195 Section 180.1195 Protection... Exemptions From Tolerances § 180.1195 Titanium dioxide. Titanium dioxide is exempted from the requirement of a...

2010-07-01

338

21 CFR 73.2575 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Titanium dioxide. 73.2575 Section 73... Cosmetics § 73.2575 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide shall conform in identity...

2009-04-01

339

40 CFR 180.1195 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

... 2009-07-01 2009-07-01 false Titanium dioxide. 180.1195 Section 180.1195 Protection... Exemptions From Tolerances § 180.1195 Titanium dioxide. Titanium dioxide is exempted from the requirement of a...

2009-07-01

340

21 CFR 73.1575 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Titanium dioxide. 73.1575 Section 73...CERTIFICATION Drugs § 73.1575 Titanium dioxide. (a) Identity and specifications... (1) The color additive titanium dioxide shall conform in identity...

2009-04-01

341

21 CFR 172.480 - Silicon dioxide.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 2013-04-01 false Silicon dioxide. 172.480 Section 172.480 ...CONSUMPTION Anticaking Agents § 172.480 Silicon dioxide. The food additive silicon dioxide may be safely used in food in...

2013-04-01

342

Electrochemical cell for obtaining oxygen from carbon dioxide atmospheres  

NASA Technical Reports Server (NTRS)

For manned missions to Mars to become a reality, an efficient and reliable means of obtaining oxygen from the carbon dioxide-rich atmosphere will be required. Otherwise, the high cost of transporting the oxygen needed to sustain the astronauts will severely restrict the expedition to the martian surface. Recently, the use of electrochemical devices has been explored as a means of obtaining oxygen from the carbon dioxide-rich atmosphere. In these devices, oxygen ions diffuse through solid oxide membranes, thus, separating oxygen from the other gases presented. This phenomenon has only recently been explored as a means of obtaining large quantities of oxygen from toxic atmospheres, although first observed by Walter nernst in 1899. Nernst observed that stabilized zirconia will conduct oxygen ions when an electrical potential is applied across metallic electrodes applied to the ceramic membrane. Diatomic oxygen molecules are dissociated at the positive electrode/electrolyte interface. The oxygen ions enter the ceramic body due to the ion density gradient which is produced by the electrical potential across the electrolytic membrane. Once the ions have diffused through the membrane, they reform diatomic oxygen molecules at the anode. The separation of oxygen from carbon dioxide is achieved by the combination of thermal and electrochemical processes. The thermal decomposition of carbon dioxide (at 1000 C) results in the production of carbon monoxide and oxygen by the reaction.

Hooker, M. W.; Rast, H. E.; Rogers, D. K.

1989-01-01

343

Carbon dioxide adsorbent study  

NASA Technical Reports Server (NTRS)

A study was initiated on the feasibility of using the alkali metal carbonate - bi-carbonate solid-gas reaction to remove carbon dioxide from the atmosphere of an EVA life support system. The program successfully demonstrates that carbon dioxide concentrations could be maintained below 0.1 mole per cent using this chemistry. Further a practical method for distributing the carbonates in a coherent sheet form capable of repeated regeneration (50 cycles) at modest temperatures (423 K), without loss in activity was also demonstrated. Sufficiently high reaction rates were shown to be possible with the carbonate - bi-carbonate system such that EVA hardware could be readily designed. Experimental and design data were presented on the basis of which two practical units were designed. In addition to conventional thermally regenerative systems very compact units using ambient temperature cyclic vacuum regeneration may also be feasible. For a one man - 8 hour EVA unit regenerated thermally at the base ship a system volume of 14 liters is estimated.

Onischak, M.; Baker, B. S.

1973-01-01

344

Carbon dioxide and climate  

SciTech Connect

Scientific and public interest in greenhouse gases, climate warming, and global change virtually exploded in 1988. The Department's focused research on atmospheric CO{sub 2} contributed sound and timely scientific information to the many questions produced by the groundswell of interest and concern. Research projects summarized in this document provided the data base that made timely responses possible, and the contributions from participating scientists are genuinely appreciated. In the past year, the core CO{sub 2} research has continued to improve the scientific knowledge needed to project future atmospheric CO{sub 2} concentrations, to estimate climate sensitivity, and to assess the responses of vegetation to rising concentrations of CO{sub 2} and to climate change. The Carbon Dioxide Research Program's goal is to develop sound scientific information for policy formulation and governmental action in response to changes of atmospheric CO{sub 2}. The Program Summary describes projects funded by the Carbon Dioxide Research Program during FY 1990 and gives a brief overview of objectives, organization, and accomplishments.

Not Available

1990-10-01

345

Sulfur dioxide removal process  

SciTech Connect

A process is described for removing sulfur dioxide from a gas stream with a buffered, aqueous thiosulfate/polythionate solution which comprises: (a) introducing sulfur dioxide-containing gas, recovered hydrogen sulfide, and a buffered, aqueous, lean thiosulfate/polythionate solution to an SO/sub 2/-gas/liquid contacting zone; (b) recovering cleaned gas and a buffered, aqueous, enriched thiosulfate/polythionate solution from the SO/sub 2/-gas/liquid contacting zone; (c) introducing the recovered, enriched solution to a regeneration zone; (d) introducing externally supplied hydrogen sulfide to the regeneration zone to react a portion of the recovered, enriched solution therein to form a slurry of elemental sulfur in a buffered, aqueous, lean thiosulfate/polythionate solution; (e) recovering unreacted excess hydrogen sulfide from the regeneration zone for use in step (a); and (f) withdrawing the slurry from the regeneration zone, separating elemental sulfur from the slurry, and recovering the buffered, aqueous, lean thiosulfate/polythionate solution for use in step (a).

Sliger, A.G.; O'Donnell, J.J.; Northup, A.H. Jr.

1987-01-06

346

Penile xenon (/sup 133/Xe) washout: a rapid method of screening for vasculogenic impotence  

SciTech Connect

The radioactive inert gas xenon (/sup 133/Xe) is a well-established isotopic indicator used to assess vascular status in many organ systems. Xenon-133 was used to evaluate male impotence. Xenon-133 was injected subcutaneously at the level of the coronal sulcus in the detumescent state. Using the gamma camera, sequential images were obtained and computer-generated curves calculated. The clearance time for 50 per cent washout of the injected /sup 133/Xe (T1/2) was then calculated for each patient, as well as a control group. Preliminary findings indicate a correlation with such established techniques of evaluating erectile impotence as history, physical examination, penile pulse Doppler tracings, and brachial-penile blood pressure index. The xenon-133 washout study was a rapid, minimally invasive, reproducible, and cost-effective method of screening those impotent patients for vasculogenic etiology of their erectile impotence. We recommend the addition of this method to the surgeon engaged in the care of impotent males.

Nseyo, U.O.; Wilbur, H.J.; Kang, S.A.; Flesh, L.; Bennett, A.H.

1984-01-01

347

A Liquid Xenon Ionization Chamber in an All-fluoropolymer Vessel  

SciTech Connect

A novel technique has been developed to build vessels for liquid xenon ionization detectors entirely out of ultra-clean fluoropolymer. We describe the advantages in terms of low radioactivity contamination, provide some details of the construction techniques, and show the energy resolution achieved with a prototype all-fluoropolymer ionization detector.

LePort, F.; Pocar, A.; Bartoszek, L.; DeVoe, R.; Fierlinger, P.; Flatt, B.; Gratta, G.; Green, M.; Montero Diez, M.; Neilson, R.; O'Sullivan, K.; Wodin, J.; Woisard, D.; Baussan, E.; Breidenbach, M.; Conley, R.; Fairbank, W., Jr.; Farine, J.; Hall, K.; Hallman, D.; Hargrove, C.; /Stanford U., Phys. Dept. /Applied Plastics Technology, Bristol /Neuchatel U. /SLAC /Colorado State U. /Laurentian U. /Carleton U. /Alabama U. /Moscow, ITEP

2007-02-26

348

Photoionization Study of Diatomic-Ion Formation in Argon, Krypton, and Xenon  

Microsoft Academic Search

Ionization current at wavelengths of discrete absorption lines of five resonance series of argon, krypton, and xenon has been observed in the vacuum ultraviolet. This ionization is due to a collision process between electronically excited and ground-state atoms resulting in formation of a diatomic ion and an electron. Using the helium and argon continuum light sources, it was possible to

Robert E. Huffman; Daniel H. Katayama

1966-01-01

349

Searching for neutrinoless double beta decay with gas-xenon TPCs: R&D for next  

NASA Astrophysics Data System (ADS)

The search for neutrinoless double beta (??0?) decay is fundamental to probe the character of neutrinos and to determine the their mass. Several experiments in this field are using different techniques in order to achieve good energy resolution (<= 1%), very low background contamination (~ 10-4 counts/(keV.kg. y)) and large target mass (> 100 kg), that are required for that research. Natural xenon consists almost 9% of 136Xe, a possible ??0? emitter and can be easily enriched. A xenon TPC can provide the excellent energy resolution moreover, in a gaseous phase, the signature of the decay given by the two electrons can be detected reducing considerable the background. The NEXT collaboration aims to build a pressurized gaseous detector of about 100 kg of enriched xenon to be operated at the Canfranc Underground Laboratory in Spain. An extensive R&D has been carried out by the collaboration in the last two years with several prototypes, investigating both energy resolution and tracking capabilities in xenon gas.

Santorelli, Roberto; NEXT Collaboration

2012-04-01

350

Free-Free Transitions Following Six-Photon Ionization of Xenon Atoms  

Microsoft Academic Search

The energy spectrum of electrons produced by multiphoton ionization of xenon atoms has been analyzed with a retarding potential technique. We have shown that the discrete absorption of photons above the six-photon ionization threshold was observable under specified conditions. A simple model based upon inverse bremsstrahlung gives a resonable agreement with the experiments.

P. Agostini; F. Fabre; G. Mainfray; G. Petite; N. K. Rahman

1979-01-01

351

Measurement of 248-nm, subpicosecond pulse durations by two-photon fluorescence of xenon excimers.  

PubMed

A technique for measuring the duration of single ultrashort pulses at KrF(*) wavelengths has been developed that employs fluorescence from xenon excimers excited by two-photon absorption of atom pairs. Pulses of ~350-fsec duration have been measured at 248 nm. PMID:19738806

Hutchinson, M H; McIntyre, I A; Gibson, G N; Rhodes, C K

1987-02-01

352

A Redetermination of the Relative Abundances of the Isotopes of Neon, Krypton, Rubidium, Xenon, and Mercury  

Microsoft Academic Search

A careful redetermination of isotopic abundance ratios in neon, krypton, rubidium, xenon, and mercury has been made. The mass spectrometer employed was calibrated for mass discriminative effects with a synthetic argon isotope mixture made from essentially pure samples of A36 and A40. The present results together with those obtained from an earlier study on carbon, nitrogen, oxygen, argon, and potassium

Alfred O. Nier

1950-01-01

353

Mass Spectrometric Observation of Ions Formed During Shock Wave Heating of Gaseous Krypton and Xenon.  

National Technical Information Service (NTIS)

Mass spectrometric observation of ions sampled directly from shock waves in krypton and xenon at 3600 to 7800 K shows that the principal ion is usually Kr+ or Xe+. Appreciable quantities of impurity ions have also been identified, and it is shown that the...

R. A. Creswell M. A. DiValentin J. E. Dove

1966-01-01

354

Spectral characteristics of a high-current pulsed discharge in xenon  

NASA Astrophysics Data System (ADS)

The radiation characteristics of a pulsed discharge xenon lamp are experimentally and theoretically studied. The data on radiation spectra are obtained for various compositions and pressures of working medium, energies and time profiles of excitation pulse, discharge gap configurations, etc. Electron temperature and mean spectroscopic symbol of emitting ions are estimated. It is demonstrated that cw radiation (continuum) results from the photorecombination transitions.

Baksht, E. Kh.; Boichenko, A. M.; Galakhov, I. V.; Zolotovskii, V. I.; Lomaev, M. I.; Osin, V. A.; Rybka, D. V.; Tarasenko, V. F.; Tkachev, A. N.; Yakovlenko, S. I.

2007-06-01

355

Characteristics of the 2.65 (mu)m atomic xenon laser.  

National Technical Information Service (NTIS)

The laser characteristics of the 2.65 (mu)m xenon laser transition are reviewed. Measured and extrapolated laser efficiency in nuclear pumped and electron beam pumped system is reported. Previous research has indicated that the reported power efficiency i...

G. A. Hebner

1995-01-01

356

Glioblastoma blood flow measured with stable xenon CT indicates tumor necrosis, vascularity, and brain invasion  

PubMed Central

Tumor vasculature is a promising therapeutic target in glioblastoma. Imaging tumor blood flow may help assess the efficacy of anti-angiogenic treatments. We determined the clinical usefulness of stable xenon CT performed preoperatively in patients with glioblastoma. This is a prospective cohort study. We determined absolute tumor blood flow before surgery in 38 patients with glioblastoma using stable xenon CT. We also histologically examined tumor specimens obtained from surgery and quantified their vascularity (by CD31 and CD105 immunostain), necrosis (by hematoxylin and eosin stain), and the presence of neuronal processes (by neurofilament immunostain). According to the xenon CT blood flow map, there are 3 types of glioblastoma. Type I glioblastomas have unimodal high blood flow histograms; histologically there is little necrosis and vascular proliferation. Type II glioblastomas have unimodal low blood flow histograms; histologically there is prominent necrosis and vascular proliferation. We propose that in type II glioblastoma, the abnormal vessels induced by hypoxia are inefficient at promoting blood flow. Type III glioblastomas have multimodal blood flow histograms. Histologically there is significant neuronal tissue within the tumor. Patients with type III glioblastomas were more likely to develop a post-surgical deficit, consistent with the inclusion of normal tissue within the tumor. Preoperative measurement of absolute blood flow with stable xenon CT in patients with glioblastoma predicts key biological features of the tumor and may aid surgical planning.

Crocker, Matthew; Saadoun, Samira; Jury, Alexa; Jones, Chris; Zacharoulis, Stergios; Thomas, Samiwel; Zwiggelaar, Reyer; Bridges, Leslie R.; Bell, B. Anthony; Papadopoulos, Marios C.

2012-01-01

357

Radio-controlled xenon flashers for atmospheric monitoring at the HiRes cosmic ray observatory  

Microsoft Academic Search

Stable, robust ultraviolet light sources for atmospheric monitoring and calibration pose a challenge for experiments that measure air fluorescence from cosmic ray air showers. One type of light source in use at the High Resolution Fly's Eye (HiRes) cosmic ray observatory features a xenon flashbulb at the focal point of a spherical mirror to produce a 1 ?s pulse of

L. R. Wiencke; T. Abu-Zayyad; M. Al-Seady; K. Belov; D. J. Bird; J. Boyer; G. F. Chen; R. W. Clay; H. Y. Dai; B. R. Dawson; P. Denholm; J. Gloyn; D. He; Y. Ho; M. A. Huang; C. C. H. Jui; M. J. Kidd; D. B. Kieda; B. Knapp; S. Ko; K. Larson; E. C. Loh; E. J. Mannel; J. N. Matthews; J. R. Meyer; A. Salman; K. M. Simpson; J. D. Smith; P. Sokolsky; D. Steenblik; J. K. K. Tang; S. Taylor; S. B. Thomas; C. R. Wilkinson

1999-01-01

358

Low-Energy Sputtering Studies of Boron Nitride with Xenon Ions.  

National Technical Information Service (NTIS)

Sputtering of boron nitride with xenon ions was investigated using secondary ion (SIMS) and secondary neutral (SNMS) mass spectrometry. The ions generated from the ion gun were incident on the target at an angle of 50' with respect to the surface'normal. ...

P. K. Ray V. Shutthanandan

1999-01-01

359

Transient Xenon Effect on Plant Control in MSRs - Validation of Simulation Model -  

Microsoft Academic Search

Molten Salt Reactors (MSRs) are fluid fuel-type thermal reactors moderated by graphite. MSRs have been expected as the generation IV nuclear power plants for many advantages such as high potential in safety and so on. On the other hand, as the MSRs are thermal reactors the poison behavior of xenon during operation can't be ignored due to large thermal neutron

Suzuki Katsumi; Shimazu Yoichiro

2004-01-01

360

Monte Carlo simulation of electron trajectories in high pressure xenon gas  

Microsoft Academic Search

A Monte Carlo calculation was developed to simulate electron trajectories in high pressure gas. In this report we discuss the calculation and some of the results relevant for the design of a high pressure xenon gas time projection chamber suitable for double beta decay experiment. Our calculation is quite general and can be extended towards a larger range of gas

M. Z. Iqbal; B. M. G. O'Callaghan; H. T. Wong

1987-01-01

361

Direct comparison of a Xenon and a solid state CT detector system: Measurements under working conditions  

Microsoft Academic Search

Measurements of various image quality parameters were carried out with two different detector systems in an otherwise unchanged medical computed tomography (CT) scanner. As all other components of the scanner and the image reconstruction system remained identical, the authors were able to quantify the difference in performance between a xenon gas ionization detector and a new solid-state scintillation detector in

Theobald Fuchs; Marc Kachelriess; Willi A. Kalender

2000-01-01

362

Evaluation of hemodynamic effects of xenon in dogs undergoing hemorrhagic shock  

PubMed Central

OBJECTIVES: The anesthetic gas xenon is reported to preserve hemodynamic stability during general anesthesia. However, the effects of the gas during shock are unclear. The objective of this study was to evaluate the effect of Xe on hemodynamic stability and tissue perfusion in a canine model of hemorrhagic shock. METHOD: Twenty-six dogs, mechanically ventilated with a fraction of inspired oxygen of 21% and anesthetized with etomidate and vecuronium, were randomized into Xenon (Xe; n?=?13) or Control (C; n?=?13) groups. Following hemodynamic monitoring, a pressure-driven shock was induced to reach an arterial pressure of 40 mmHg. Hemodynamic data and blood samples were collected prior to bleeding, immediately after bleeding and 5, 20 and 40 minutes following shock. The Xe group was treated with 79% Xe diluted in ambient air, inhaled for 20 minutes after shock. RESULT: The mean bleeding volume was 44 mL.kg?1 in the C group and 40 mL.kg?1 in the Xe group. Hemorrhage promoted a decrease in both the cardiac index (p<0.001) and mean arterial pressure (p<0.001). These changes were associated with an increase in lactate levels and worsening of oxygen transport variables in both groups (p<0.05). Inhalation of xenon did not cause further worsening of hemodynamics or tissue perfusion markers. CONCLUSIONS: Xenon did not alter hemodynamic stability or tissue perfusion in an experimentally controlled hemorrhagic shock model. However, further studies are necessary to validate this drug in other contexts.

Franceschi, Ruben C.; Malbouisson, Luiz; Yoshinaga, Eduardo; Auler, Jose Otavio Costa; de Figueiredo (in memoriam), Luiz Francisco Poli; Carmona, Maria Jose C.

2013-01-01

363

A note on the biological activity of the noble gas compound xenon trioxide.  

NASA Technical Reports Server (NTRS)

Comparison of xenon trioxide for toxicity in the few common oxidants using three bioassays. On a molar basis XeO3 and HOCl were similar, but XeO3 was less active than expected when comparisons were based on normality.

Siegel, S. M.; Smith, C. W.

1972-01-01

364

NEW COMPOUNDS OF NOBLE GASES: THE FLUORIDES OF XENON AND RADON  

Microsoft Academic Search

Synthesis of xenon di-, tetra-, and hexafluoride and radon difluoride is ; described and properties of the compounds are discussed. Radon difiuoride was ; prepared by heating a radon--fluorine mixture to 400 deg for 30 min. It is much ; less volatiie than its Xe analog, and has resistance to reduction by H, which ; occurs only above 200 deg

Bartlett

1963-01-01

365

Forward Hadron Production in Muon Deep Inelastic Scattering at 490 GEV from Deuterium and Xenon  

Microsoft Academic Search

This thesis presents measurements of the energy fraction z and transverse momentum of the final state charged hadrons in muon deep inelastic scattering at 490 GeV from deuterium and xenon targets. The measurements were made as part of Experiment 665 at Fermilab. The ratio of the forward hadron multiplicity between the two nuclei shows that at large transfer energy, upsilon

Alexandro F. Salvarani

1991-01-01

366

Isotopically anomalous xenon in meteorites - A new clue to its origin  

NASA Astrophysics Data System (ADS)

The CCF xenon component in primitive meteorites, which has been attributed either to fission of a superheavy element or to nucleosynthesis in a supernova, does not show the large enrichment in Xe-129 (from decay of 16 Myr I-129) expected for supernova ejecta. Although this problem can be circumvented by ad hoc assumptions, a fission origin of CCFXe seems more likely.

Lewis, R. S.; Anders, E.

1981-08-01

367

A Theoretical Investigation of Isotopic Anomalies of Xenon in Terrestrial and Extra-Terrestrial Samples.  

National Technical Information Service (NTIS)

The abundance and isotopic composition of noble gases in meteorites is discussed in relation to the composition of the early solar system. Carbonaceous chondrites contain a unique Xenon-X, which is rich in heavy and light isotopes. Variations in the occur...

D. D. Sabu

1977-01-01

368

Purification of krypton-xenon mixture from fluorine-containing gases  

NASA Astrophysics Data System (ADS)

Active alumina was used to purify krypton-xenon mixtures from fluorine-containing gases (tetrafluoromethane and sulfur hexafluoride). At 580C, the admixtures are converted into aluminum trifluoride, with their content in the test gas mixture reducing from hundreds of ppm to 0.1 ppm or even below.

Adamov, V. S.; Yatkin, V. A.

2007-06-01

369

30 cm Diameter Xenon Ion Thruster: Design and Initial Test Results.  

National Technical Information Service (NTIS)

The design and initial test results of a 30 cm diameter xenon cusp type ion thruster are described. The designed thrust and specific impulse of the laboratory model are 150 mN and 3500 sec, respectively, at the exhaust beam energy of 1.0 keV. With the lab...

Y. Yamagiwa Y. Takeshita H. Kawauchi H. Yoshida D. Miyazaki

1988-01-01

370

Intercomparison Experiments of Systems for the Measurement of Xenon Radionuclides in the Atmosphere  

SciTech Connect

Radioactive xenon monitoring is one of the main technologies used for detection of underground nuclear explosions. Precise and reliable measurements of 131mXe, 133gXe, 133mXe, and 135gXe are required as part of the International Monitoring System (IMS) for compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT).

Auer, M.; Axelssson, A.; Blanchard, X.; Bowyer, Ted W.; Brachet, G.; Bulowski, I.; Dubasov, Y.; Elmgren, K.; Fontaine, J. P.; Harms , W.; Hayes, James C.; Heimbigner, Tom R.; McIntyre, Justin I.; Panisko, Mark E.; Popov, Y.; Ringbom, Anders; Sartorius, H.; Schmid, S.; Schulze, J.; Schlosser, Clemens; Taffary, T.; Weiss, W.; Wernsperger, B.

2004-06-01

371

Pressure-induced bonding and compound formation in xenon?hydrogen solids  

SciTech Connect

Closed electron shell systems, such as hydrogen, nitrogen or group 18 elements, can form weakly bound stoichiometric compounds at high pressures. An understanding of the stability of these van der Waals compounds is lacking, as is information on the nature of their interatomic interactions. We describe the formation of a stable compound in the Xe-H{sub 2} binary system, revealed by a suite of X-ray diffraction and optical spectroscopy measurements. At 4.8 GPa, a unique hydrogen-rich structure forms that can be viewed as a tripled solid hydrogen lattice modulated by layers of xenon, consisting of xenon dimers. Varying the applied pressure tunes the Xe-Xe distances in the solid over a broad range from that of an expanded xenon lattice to the distances observed in metallic xenon at megabar pressures. Infrared and Raman spectra indicate a weakening of the intramolecular covalent bond as well as persistence of semiconducting behaviour in the compound to at least 255 GPa.

Somayazulu, Maddury; Dera, Przemyslaw; Goncharov, Alexander F.; Gramsch, Stephen A.; Liermann, Peter; Yang, Wenge; Liu, Zhenxian; Mao, Ho-kwang; Hemley, Russell J. (CIW); (UC)

2010-11-03

372

The physics of background discrimination in liquid xenon, and first results from Xenon10 in the hunt for WIMP dark matter  

NASA Astrophysics Data System (ADS)

The WIMP limit set by the Xenon10 experiment in 2007 signals a new era in direct detection of dark matter, with several large-scale liquid target detectors now under construction. A major challenge in these detectors will be to understand backgrounds at the level necessary to claim a positive WIMP signal. In liquid xenon, these backgrounds are dominated by electron recoils, which may be distinguished from the WIMP signal (nuclear recoils) by their higher charge-to-light ratio. During the construction and operation of Xenon10, the prototype detector Xed probed the physics of this discrimination. Particle interactions in liquid xenon both ionize and excite xenon atoms, giving charge and scintillation signals, respectively. Some fraction of ions recombine, reducing the charge signal and creating additional scintillation. The charge-to-light ratio, determined by the initial exciton-ion ratio and the ion recombination fraction, provides the basis for discrimination between electron and nuclear recoils. Intrinsic fluctuations in the recombination fraction limit discrimination. Changes in recombination induce an exact anti-correlation between charge and light, and when calibrated this anti-correlation distinguishes recombination fluctuations from uncorrelated fluctuations in the measured signals. We determine the mean recombination and recombination fluctuations as a function of energy and applied field for electron and nuclear recoils, finding that recombination fluctuations are already the limiting factor for discrimination above ~12 keVr (nuclear recoil energy). Below 12 keVr statistical fluctuations in the number of scintillation photons counted dominate, and we project a x6 improvement in background rejection with a x2 increase in light collection efficiency. We also build a simple recombination model that successfully reproduces the mean recombination in electron and nuclear recoils, including the surprising reversal of the expected trend for recombination with ionization density in low energy electron recoils. The model also reproduces the measured recombination fluctuations to within a factor of two at high energies. Surprisingly, the model suggests that recombination at low energies is independent of ionization density, and our observed discrimination is due not to the different stopping powers of electrons and nuclei as was thought, but rather to a different initial exciton-ion ratio. We suggest two possible physical models for this new result.

Dahl, Carl Eric

2009-06-01

373

Aspects of carbon dioxide utilization  

Microsoft Academic Search

Carbon dioxide reacts with hydrogen, alcohols, acetals, epoxides, amines, carboncarbon unsaturated compounds, etc. in supercritical carbon dioxide or in other solvents in the presence of metal compounds as catalysts. The products of these reactions are formic acid, formic acid esters, formamides, methanol, dimethyl carbonate, alkylene carbonates, carbamic acid esters, lactones, carboxylic acids, polycarbonate (bisphenol-based engineering polymer), aliphatic polycarbonates, etc. Especially,

Iwao Omae

2006-01-01

374

Reaction products of chlorine dioxide.  

PubMed Central

Inspection of the available literature reveals that a detailed investigation of the aqueous organic chemistry of chlorine dioxide and systematic identification of products formed during water disinfection has not been considered. This must be done before an informed assessment can be made of the relative safety of using chlorine dioxide as a disinfectant alternative to chlorine. Although trihalomethanes are generally not formed by the action of chlorine dioxide, the products of chlorine dioxide treatment of organic materials are oxidized species, some of which also contain chlorine. The relative amounts of species types may depend on the amount of chlorine dioxide residual maintained and the concentration and nature of the organic material present in the source water. The trend toward lower concentrations of chlorinated by-products with increasing ClO2 concentration, which was observed with phenols, has not been observed with natural humic materials as measured by the organic halogen parameter. Organic halogen concentrations have been shown to increase with increasing chlorine dioxide dose, but are much lower than those observed when chlorine is applied. Aldehydes have been detected as apparent by-products of chlorine dioxide oxidation reactions in a surface water that is a drinking water source. Some other nonchlorinated products of chlorine dioxide treatment may be quinones and epoxides. The extent of formation of these moieties within the macromolecular humic structure is also still unknown.

Stevens, A A

1982-01-01

375

Analysis on the dyeing of polypropylene fibers in supercritical carbon dioxide  

Microsoft Academic Search

Polypropylene fibers were dyed in supercritical carbon dioxide system and the results were compared with those of fiber dyed\\u000a in water system. Dye uptake value calculated by a UV spectrum indicated that polypropylene fiber dyeing was much better in\\u000a carbon dioxide than in water. Optical microscopical analysis showed that dye molecules had diffused thoroughly into fiber\\u000a in CO2 because of

S. K. Liao; P. S. Chang; Y. C. Lin

2000-01-01

376

Inference and analysis of xenon outflow curves under multi-pulse injection in two-dimensional chromatography.  

PubMed

Multidimensional gas chromatography is widely applied to atmospheric xenon monitoring for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). To improve the capability for xenon sampling from the atmosphere, sampling techniques have been investigated in detail. The sampling techniques are designed by xenon outflow curves which are influenced by many factors, and the injecting condition is one of the key factors that could influence the xenon outflow curves. In this paper, the xenon outflow curves of single-pulse injection in two-dimensional gas chromatography has been tested and fitted as a function of exponential modified Gaussian distribution. An inference formula of the xenon outflow curve for six-pulse injection is derived, and the inference formula is also tested to compare with its fitting formula of the xenon outflow curve. As a result, the curves of both the one-pulse and six-pulse injections obey the exponential modified Gaussian distribution when the temperature of the activated carbon column's temperature is 26C and the flow rate of the carrier gas is 35.6mLmin(-1). The retention time of the xenon peak for one-pulse injection is 215min, and the peak width is 138min. For the six-pulse injection, however, the retention time is delayed to 255min, and the peak width broadens to 222min. According to the inferred formula of the xenon outflow curve for the six-pulse injection, the inferred retention time is 243min, the relative deviation of the retention time is 4.7%, and the inferred peak width is 225min, with a relative deviation of 1.3%. PMID:24007686

Shu-Jiang, Liu; Zhan-Ying, Chen; Yin-Zhong, Chang; Shi-Lian, Wang; Qi, Li; Yuan-Qing, Fan

2013-10-11

377

Carbon Dioxide Capture and Disposal  

NASA Astrophysics Data System (ADS)

Unless carbon dioxide from fossil fuel combustion is captured and disposed of safely and permanently, the concerns over climate change will eventually lead to the demise of fossil fuels. Because of their importance in today's energy market the phasing out of fossil fuels would likely precipitate a major energy crisis. Mineral sequestration and extraction of carbon dioxide from the air are two advanced technologies for carbon sequestration that aim at maintaining access to the vast fossil energy resources for centuries to come. While it is straightforward to dispose of carbon dioxide in limited amounts and for a limited time, permanent disposal of trillions of tons of carbon poses serious challenges. The formation of solid mineral carbonates from readily available minerals would provide safe and permanent storage. Capture of carbon dioxide from air makes it possible to sequester carbon dioxide emissions from sources other than power plants. This is important considering that even the relatively minor reductions suggested by the Kyoto Accord would have required the US to eliminate carbon dioxide emissions comparable to those of the entire 1990 coal fired power plant fleet. Capture of carbon dioxide from the air, would make it possible to close the carbon cycle in the transportation sector without phasing out liquid hydrocarbon fuels. It eliminates the need for long distance transport of carbon dioxide and allows the continued use of the existing energy infrastructure. Mineral sequestration at remote sites combined with on site carbon dioxide capture from air, would allow for long term stabilization of atmospheric carbon dioxide levels. I will outline the current state of the technology and point to advances required before these approaches are ready for large-scale implementation.

Lackner, K. S.

2002-05-01

378

Phase behavior of mixed submonolayer films of krypton and xenon on graphite.  

PubMed

Using the results of extensive Monte Carlo simulations in the canonical and grand canonical ensembles, we discuss the phase behavior of mixed submonolayer films of krypton and xenon adsorbed on the graphite basal plane. The calculations have been performed using two- and three-dimensional models of the systems studied. It has been demonstrated that out-of-plane motion does not affect the properties of the films as long as the total density is well below the monolayer completion and at moderate temperatures. For the total densities close to the monolayer completion, the promotion of particles to the second layer considerably affects the film properties. Our results are in a reasonable agreement with the available experimental data. The melting point of submonolayer films has been shown to exhibit non-monotonous changes with the film composition, and reaches minimum for the xenon concentration of about 50%. At the temperatures below the melting point, the structure of solid phases depends upon the film composition and the temperature; one can also distinguish commensurate and incommensurate phases. Two-dimensional calculations have demonstrated that for the xenon concentration between about 15% and 65% the adsorbed film exhibits the formation of a superstructure, in which each Xe atom is surrounded by six Kr atoms. This superstructure is stable only at very low temperatures and transforms into the mixed commensurate (?3?3)R30 phase upon the increase of temperature. Such a superstructure does not appear when a three-dimensional model is used. Grand canonical ensemble calculations allowed us to show that for the xenon concentration of about 3% the phase diagram topology of monolayer films changes from the krypton-like (with incipient triple point) to the xenon-like (with ordinary triple point). PMID:22502538

Patrykiejew, A; Soko?owski, S

2012-04-14

379

Production of Krypton and Xenon Isotopes by Galactic Protons  

NASA Astrophysics Data System (ADS)

The production of krypton from target elements Rb (Rb(sub)2SO(sub)4), Sr (SrF(sub)2), Y, Zr, and of xenon in Ba (Ba glass), La (LaF(sub)3) is studied in a simulation experiment of the galactic cosmic-ray proton bombardment of stony meteoroids in space [1,2]. This investigation is part of the experiment LNS 172 by which a 50-cm-diameter artificial meteoroid (gabbro) was isotropically irradiated at Saturne with 1.6 GeV protons. Measurements of krypton production vs. depth are now complete in the four investigated target elements. In the ^81Kr-^83Kr dating method, the production ratio P(sub)81/P(sub)83 can be evaluated from the cosmogenic spectrum of krypton in the meteorite according to the formula: P(sub)81/P(sub)83=0.95[(^80Kr/^83Kr)(sub)c+(^82Kr/^83Kr)(sub)c]/2 [3] where (^80Kr/^83Kr)(sub)c and (^82Kr/^83Kr)c represent the measured cosmogenic ratios assuming no contribution from (n,gamma) nuclear reactions on Br. Applying this formula to this experiment, a good agreement with the measured production ratio is obtained for Zr and Y targets. On the other hand, this formula overestimates the measured production ratio by 6% for Sr and 15% for Rb. Taking a mean composition of ordinary chondrites [4], the production ratio ^81Kr/^83Kr decreases from the surface to the center by 4% but the value calculated with the formula still exceeds the measured ratio by 7%. The ratio ^78Kr/^83Kr also shows a decrease by 10% from the surface to the center. Variation by 20% of the concentration of target elements can change this ratio by 10%, but, for the same variation, dependence on the target chemistry is less than 4% for ^81Kr/^83Kr. For Xe, depth profiles of production in Ba and La are reported. Production of ^126Xe shows a steep increase from the surface to center by a factor of 1.5 for Ba and of 2 for La. All the production ratios also increase from the surface to the center except ^124Xe/^126Xe, which is decreasing and ^136Xe/^126Xe, which is almost constant. This work was partially supported by C.N.R.S., by IN2P3, and by INSU (Programme National de Planetologie). References: [1] Michel R. et al (1991) Meteoritics, 26, 372a. [2] Gilabert et al. (1992) Meteoritics, 27, 223. [3] Marti K. (1967) Phys. Rev. Lett., 18, 264-266. [4] Wasson J. T. and Kallemeyn G. W. (1988) Phil. Trans. R. Soc., A325, 535-544.

Gilabert, E.; Lavielle, B.; Simonoff, G. N.; Rosel, R.; Herpers, U.; Schnatz-Buttgen, M.; Lupke, M.; Michel, R.

1993-07-01

380

New Observations of Interstellar Organic Molecules. (Abstract Only).  

National Technical Information Service (NTIS)

Discussed here are new observations of 3-carbon-containing interstellar molecules which play an important role in the chemistry of dense molecular clouds: protonated carbon dioxide, formic acid, and propynal. In 1984 a new oxide of carbon, C3O, was discov...

W. M. Irvine P. Friberg H. E. Matthews Y. C. Minh L. M. Ziurys

1990-01-01

381

Ion-Molecule Reactions in Gas Phase Radiation Chemistry.  

ERIC Educational Resources Information Center

Discusses some aspects of the radiation chemistry of gases, focusing on the ion-molecule and charge neutralization reactions which set study of the gas phase apart. Uses three examples that illustrate radiolysis, describing the radiolysis of (1) oxygen, (2) carbon dioxide, and (3) acetylene. (CS)

Willis, Clive

1981-01-01

382

Simultaneous Measurement of Ionization and Scintillation from Nuclear Recoils in Liquid Xenon for a Dark Matter Experiment  

SciTech Connect

We report the first measurements of the absolute ionization yield of nuclear recoils in liquid xenon, as a function of energy and electric field. Independent experiments were carried out with two dual-phase time-projection chamber prototypes, developed for the XENON dark matter project. We find that the charge yield increases with decreasing recoil energy, and exhibits only a weak field dependence. These results are the first unambiguous demonstration of the capability of dual-phase xenon detectors to discriminate between electron and nuclear recoils down to 20 keV, a key requirement for a sensitive dark matter search.

Aprile, E.; Giboni, K. L.; Majewski, P.; Ni, K.; Yamashita, M. [Physics Department and Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027 (United States); Dahl, C. E.; Kwong, J. [Department of Physics, Princeton University, Princeton, New Jersey 08540 (United States); Viveiros, L. de; Gaitskell, R. J. [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States); Shutt, T. [Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106 (United States)

2006-08-25

383

Sampling Carbon Dioxide  

NSDL National Science Digital Library

In this lab activity, student teams hypothesize which source has a greater becomes CO² concentration: their breath, auto exhaust, or air in the classroom. They test gas samples from each of these sources, plot data, and hypothesize about the respective role engine exhaust and animal respiration play in contemporary climate change. The lab procedures require Bromthymol Blue indicator solution (BTB), household ammonia, vinegar, and balloons. Links to videos supporting the investigations are provided. This activity is supported by a textbook chapter, "How is Carbon Dioxide Measured?," part of the unit, Climate Change, in Global Systems Science (GSS), an interdisciplinary course for high school students that emphasizes how scientists from a wide variety of fields work together to understand significant problems of global impact.

384

Uranium dioxide electrolysis  

DOEpatents

This is a single stage process for treating spent nuclear fuel from light water reactors. The spent nuclear fuel, uranium oxide, UO.sub.2, is added to a solution of UCl.sub.4 dissolved in molten LiCl. A carbon anode and a metallic cathode is positioned in the molten salt bath. A power source is connected to the electrodes and a voltage greater than or equal to 1.3 volts is applied to the bath. At the anode, the carbon is oxidized to form carbon dioxide and uranium chloride. At the cathode, uranium is electroplated. The uranium chloride at the cathode reacts with more uranium oxide to continue the reaction. The process may also be used with other transuranic oxides and rare earth metal oxides.

Willit, James L. (Batavia, IL); Ackerman, John P. (Prescott, AZ); Williamson, Mark A. (Naperville, IL)

2009-12-29

385

Carbon dioxide: atmospheric overload  

SciTech Connect

The level of carbon dioxide in the atmosphere is increasing and may double within the next century. The result of this phenomenon, climatic alterations, will adversely affect crop production, water supplies, and global temperatures. Sources of CO2 include the combustion of fossil fuels, photosynthesis, and the decay of organic matter in soils. The most serious effect of possible climatic changes could occur along the boundaries of arid and semiarid regions. Shifts is precipitation patterns could accelerate the processes of desertification. An increase of 5..cap alpha..C in the average temperature of the top 1000 m of ocean water would raise sea level by 2 m. CO2 releases to the atmosphere can be reduced by controlling emissions from fossil fuel-fired facilities and by careful harvesting of forest regions. (3 photos, 5 references)

Not Available

1980-04-01

386

Focused electron-beam-induced etching of silicon dioxide  

NASA Astrophysics Data System (ADS)

Focused electron-beam (FEB)-induced etching of silicon dioxide with xenon difluoride has been investigated as a selective nanoscale etching technique. In order to gain an understanding of the parameters that control etch rate and etch efficiency, the effects of beam current, beam energy, and scan rate conditions on the FEB process were examined. High etch rates were obtained for low beam energy, high beam current, and high scan rates. Experimental results also indicated that the FEB etch process is governed by the electron-stimulated desorption of oxygen from the SiO2 matrix, and subsequently rate limited by XeF2 availability. Based on experimental evidence and existing literature, a simple, two-step model was introduced to qualitatively describe the etch mechanism. The model involves a cyclical process, which is initiated by the reduction of a surface layer of SiO2 to elemental silicon. The exposed silicon surface is then removed by a chemical-mediated etch reaction.

Randolph, S. J.; Fowlkes, J. D.; Rack, P. D.

2005-08-01

387

Focused electron-beam-induced etching of silicon dioxide  

SciTech Connect

Focused electron-beam (FEB)-induced etching of silicon dioxide with xenon difluoride has been investigated as a selective nanoscale etching technique. In order to gain an understanding of the parameters that control etch rate and etch efficiency, the effects of beam current, beam energy, and scan rate conditions on the FEB process were examined. High etch rates were obtained for low beam energy, high beam current, and high scan rates. Experimental results also indicated that the FEB etch process is governed by the electron-stimulated desorption of oxygen from the SiO{sub 2} matrix, and subsequently rate limited by XeF{sub 2} availability. Based on experimental evidence and existing literature, a simple, two-step model was introduced to qualitatively describe the etch mechanism. The model involves a cyclical process, which is initiated by the reduction of a surface layer of SiO{sub 2} to elemental silicon. The exposed silicon surface is then removed by a chemical-mediated etch reaction.

Randolph, S.J.; Fowlkes, J.D.; Rack, P.D. [University of Tennessee, Department of Materials Science and Engineering, 434 Dougherty Engineering Building, Knoxville, Tennessee 37996-2200 (United States)

2005-08-01

388

The photodetachment cross-section and threshold energy of negative ions in carbon dioxide  

NASA Technical Reports Server (NTRS)

Threshold energy and sunlight photodetachment measurements on negative carbon dioxide ions, using a 2.5 kw light pressure xenon lamp, show that: (1) Electron affinity of CO3(+) is larger than 2.7 e.V. and that an isomeric form of CO3(+) is likely an error; (2) The photodetachment cross section of CO3(-) will roughly be like a step function across the range of 4250 to 2500A, having its threshold energy at 4250A; (3) Sunlight photodetachment rate for CO3(-) is probably much smaller than elsewhere reported; and (4) The probability of having photodetached electrons re-attach to form negative ions is less than 1%. Mass identifying drift tube tests confirm that the slower ion is CO3(-), formed through the O(-) + 2CO2 yields CO3(-) + CO2 reaction.

Helmy, E. M.; Woo, S. B.

1974-01-01

389

Pulsed-discharge carbon dioxide lasers  

NASA Technical Reports Server (NTRS)

The purpose is to attempt a general introduction to pulsed carbon dioxide lasers of the kind used or proposed for laser radar applications. Laser physics is an excellent example of a cross-disciplinary topic, and the molecular spectroscopy, energy transfer, and plasma kinetics of the devices are explored. The concept of stimulated emission and population inversions is introduced, leading on to the molecular spectroscopy of the CO2 molecule. This is followed by a consideration of electron-impact pumping, and the pertinent energy transfer and relaxation processes which go on. Since the devices are plasma pumped, it is necessary to introduce a complex subject, but this is restricted to appropriate physics of glow discharges. Examples of representative devices are shown. The implications of the foregoing to plasma chemistry and gas life are discussed.

Willetts, David V.

1990-01-01

390

Studies of K-Ar dating and xenon from extinct radioactivities in breccia 14318; implications for early lunar history  

NASA Technical Reports Server (NTRS)

The lunar breccia 14318 is one of three Apollo-14 breccias containing substantial amounts of parentless xenon from the spontaneous fission of extinct Pu-244. The argon and xenon contained in this breccia were studied by stepwise heating of pristine and neutron-irradiated samples. The isotopic composition of xenon from fission, determined by an improved method, is shown to be from Pu-244. Concentrations of this fissiogenic xenon are in substantial excess (15-fold) of what could be produced by spontaneous fission of U-238. The breccia is found to contain abundant trapped argon with an Ar-40/Ar-36 ratio of roughly 14. Otherwise, the argon is radiogenic and gives a convincing K-Ar age of 3.69 plus or minus 0.09 b.y. by the stepwise Ar-40/Ar-39 method, nearly in agreement with ages for other Apollo-14 breccias.

Reynolds, J. H.; Alexander, E. C., Jr.; Davis, P. K.; Srinivasan, B.

1974-01-01

391

Xenon isotopic composition of the Mid Ocean Ridge Basalt (MORB) source  

NASA Astrophysics Data System (ADS)

Although convection models do not preclude preservation of smaller mantle regions with more pristine composition throughout Earth's history, it has been widely assumed that the moon forming giant impact likely homogenizes the whole mantle following a magma ocean that extended all the way to the bottom of the mantle. Recent findings of tungsten and xenon heterogeneities in the mantle [1,2,3,4], however, imply that i) the moon forming giant impact may not have homogenized the whole mantle and ii) plate tectonics was inefficient in erasing early formed compositional differences, particularly for the xenon isotopes. Therefore, the xenon isotope composition in the present day mantle still preserves a memory of early Earth processes. However, determination of the xenon isotopic composition of the mantle source is still scarce, since the mantle composition is overprinted by post-eruptive atmospheric contamination in basalts erupted at ocean islands and mid ocean ridges. The xenon composition of the depleted upper mantle has been defined by the gas rich sample, 2?D43 (also known as "popping rock"), from the North Atlantic (13 469`N). However, the composition of a single sample is not likely to define the composition of the upper mantle, especially since popping rock has an "enriched" trace element composition. We will present Ne, Ar and Xe isotope data on MORB glass samples with "normal" helium isotope composition (81 Ra) from the Southeast Indian Ridge, the South Atlantic Ridge, the Sojourn Ridge, the Juan de Fuca, the East Pacific Rise, and the Gakkel Ridge. Following the approach of [1], we correct for syn- and post-eruptive atmosphere contamination, and determine the variation of Ar and Xe isotope composition of the "normal" MORB source. We investigate the effect of atmospheric recycling in the variation of MORB mantle 40Ar/36Ar and 129Xe/130Xe ratios, and attempt to constrain the average upper mantle argon and xenon isotopic compositions. [1] Mukhopadhyay, Nature 2012; [2] Tucker et al., EPSL (in review); [3] Moreira et al., Nature 1998 [4] Touboul et al., Science 2012.

Peto, M. K.; Mukhopadhyay, S.

2012-12-01

392

The Development of the improved equipment for the measurement radionuclides of xenon in atmospheric air  

NASA Astrophysics Data System (ADS)

The Radium Khlopin Institute have developed the mobile (vehicle based) equipment attended for the providing of the monitoring of radioactive xenon isotopes in atmospheric air on territories, neighboring with NPP. This equipment comprises the improved sampling installation with sample-processing unit and specialized spectrometer of ?-?-coincidences. The principal specificity of sampling installation is the using of the gas-cooling machine attended for the reaching of the cryogenic temperatures, which works without helium, using for cooling the processed air itself. The capacity of sampling reaches 20 cubic meters per hour with the xenon extraction factor of 75%. The duration of the sampling cycle forms 3 - 7 hours depending of the xenon volume requirements. The sample-processing unit is designed on preparative gas chromatograph scheme. Duration of sample-processing procedure does not exceed one and half hour. The volume of the prepared sample is around half liter, it contains 3 - 7 cubic centimeters of the xenon, depending of sampling cycle time. For measurements of xenon radioisotopes containing in obtained sample, was developed a ?-?-coincidences spectrometer on the base of the "ORTEC" HP Ge detector equipped with scintillation ?-detector designed as Marinelli chamber of 700 cm3 volume. This spectrometer allows to reduce the ambient background more than in 20 times, with ?-channel efficiency reduction not more than in 1.5 times. The minimum detectable activity of 133?? (MDA), evaluated by Currie formula for probability 95 % is 0.05 Bq at the exposition of 20 hours. Spectrometer is also intended for determination of the stable krypton and xenon concentrations in ?-chamber by X-ray-fluorescent method. Therefore, in a shield of the spectrometer collimating pinhole is made and 241Am source is installed. To improve the sensitivity of the analysis beryllium window is made in ?-chamber wall, adjoining to the HPGe detector. X-ray-fluorescent analysis allows to surely define Xe volumetric concentration of 0.05% in ?-cell, that is equivalent less then 0,5 cm3 of Xe. The first approbation of described equipment was fulfilled in St. Petersburg at autumn of 2007 year and have shown that the spectrometer allows to measure 133Xe concentration at the level of 2 mBq/m3, and this value is in a good agreement with the results of other measurements. Described equipment was practically approbated in field conditions on 2008 year during the expeditionary work carryout in Sosnovyi Bor, Udomlya and Polyarnie Zori - the cities of North-West of Russia, which are located in close neighboring with acting NPP.

Pakhomov, S. A.; Dubasov, Y. V.

2009-04-01

393

Sol-gel method for encapsulating molecules  

DOEpatents

A method for encapsulating organic molecules, and in particular, biomolecules using sol-gel chemistry. A silica sol is prepared from an aqueous alkali metal silicate solution, such as a mixture of silicon dioxide and sodium or potassium oxide in water. The pH is adjusted to a suitably low value to stabilize the sol by minimizing the rate of siloxane condensation, thereby allowing storage stability of the sol prior to gelation. The organic molecules, generally in solution, is then added with the organic molecules being encapsulated in the sol matrix. After aging, either a thin film can be prepared or a gel can be formed with the encapsulated molecules. Depending upon the acid used, pH, and other processing conditions, the gelation time can be from one minute up to several days. In the method of the present invention, no alcohols are generated as by-products during the sol-gel and encapsulation steps. The organic molecules can be added at any desired pH value, where the pH value is generally chosen to achieve the desired reactivity of the organic molecules. The method of the present invention thereby presents a sufficiently mild encapsulation method to retain a significant portion of the activity of the biomolecules, compared with the activity of the biomolecules in free solution.

Brinker, C. Jeffrey (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Bhatia, Rimple (Albuquerque, NM); Singh, Anup K. (San Francisco, CA)

2002-01-01

394

Fitting formula for the injection volume of a gas chromatograph for radio-xenon sampling in the lower troposphere.  

PubMed

GC is usually used for xenon concentration and radon removal in the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty. In a gas chromatograph, the injection volume is defined to calculate the column capacity. In this paper, the injection volume was investigated and a fitting formula for the injection volume was derived and discussed subsequently. As a consequence, the xenon injection volume exponentially decreased with the column temperature increased, but exponentially increased as the flow rate increased. PMID:24659471

Shu-Jiang, Liu; Zhan-Ying, Chen; Shi-Lian, Wang; Yin-Zhong, Chang; Qi, Li; Yuan-Qing, Fan; Yun-Gang, Zhao; Huai-Mao, Jia; Xin-Jun, Zhang; Jun, Wang

2014-06-01

395

Radioactive plume from the Three Mile Island accident: xenon-133 in air at a distance of 375 kilometers  

Microsoft Academic Search

As a result of the Three Mile Island nuclear reactor accident in March 1979, the passage of radioactive xenon-133 through Albany, N.Y., was monitored from March 29-April 2, 1979. Monitoring techniques are described. Ambient air Xenon-133 concentrations as high as 3900 pico Ci\\/cu m were recorded. The local gamma ray whole body dose from the passing radioactivity amounted to 0.004

M. Wahlen; C. O. Kunz; J. M. Matuszek; W. E. Mahoney; R. C. Thompson

1980-01-01

396

Xenon isotopic signature study of the primary coolant of CANDU nuclear power plant to enhance CTBT verification  

Microsoft Academic Search

To support interpretation of observed atmospheric 135Xe, 133Xe, 133mXe and 131mXe, a database of xenon radioisotope in the primary coolant of CANDU reactors has been established. This database is comprised\\u000a of 40000 records of high-quality xenon radioisotope analyses. Records from the database were retrieved by a specifically designed\\u000a data-mining module and subjected to further analysis. Results from the analysis were

W. Zhang; K. Ungar; I. Hoffman; R. Lawrie

2009-01-01

397

Water Molecule Residence Times  

NSDL National Science Digital Library

How long will a molecule of Water stay in a particular reservoir? What is the average time a molecule of Water will stay in an ocean? What is the average time a molecule of water will stay in a river? A lake? As groundwater? A glacier? How long will a water vapor molecule stay suspended in the atmosphere? Why is the residence ...

Science, Sill -.

2010-11-16

398

Physics of Molecules  

NASA Astrophysics Data System (ADS)

Many varieties of molecule have been detected in the Milky Way and in other galaxies. The processes by which these molecules are formed and destroyed are now broadly understood (see INTERSTELLAR CHEMISTRY). These molecules are important components of galaxies in two ways. Firstly, radiation emitted by molecules enables us to trace the presence of diffuse gas, to infer its physical properties and ...

Williams, D.; Murdin, P.

2000-11-01

399

Cage Reactions of T-Butoxy Radicals. Effects of Viscosity and of Intervening Molecules.  

National Technical Information Service (NTIS)

The effects of changes in viscosity on amounts of cage DPB (t-BuOO-t-Bu) produced from DBPO (t-BuOOCOCOOO-t-Bu), from DBH (t-BuON-NO-t-Bu), and from DBP itself are reported. The presence of a nitrogen molecule or two carbon dioxide molecules in the cage c...

H. Kiefer T. G. Traylor

1968-01-01

400

Voltammetric Membrane Chlorine Dioxide Electrode.  

National Technical Information Service (NTIS)

A voltammetric membrane electrode system has been modified and applied to the in situ measurement of chlorine dioxide. The electrode system consisted of a gold cathode, a silver/silver chloride reference electrode, and a gold counter electrode. Different ...

R. Dormond-Herrera K. H. Mancy

1980-01-01

401

Carbon Dioxide and Ocean Acidification  

NSDL National Science Digital Library

Demonstrates the affect of increased dissolved carbon dioxide on water pH using a cheap, non-toxic acid/base indicator. Students bubble breath through a straw into red cabbage juice and note the color change.

Lewis, Chris

402

NASA Satellite Sees Carbon Dioxide  

NSDL National Science Digital Library

In this problem set, learners will analyze a map of atmospheric carbon dioxide derived from satellite data. Answer key is provided. This is part of Earth Math: A Brief Mathematical Guide to Earth Science and Climate Change.

403

Xenon migration in UO2 under irradiation studied by SIMS profilometry  

NASA Astrophysics Data System (ADS)

During Pressurized Water Reactor operation, around 25% of the created Fission Products (FP) are Xenon and Krypton. They have a low solubility in the nuclear fuel and can either (i) agglomerate into bubbles which induce mechanical stress in the fuel pellets or (ii) be released from the pellets, increasing the pressure within the cladding and decreasing the thermal conductivity of the gap between pellets and cladding. After fifty years of studies on the nuclear fuel, all mechanisms of Fission Gas Release (FGR) are still not fully understood. This paper aims at studying the FGR mechanisms by decoupling thermal and irradiation effects and by assessing the Xenon behavior for the first time by profilometry. Samples are first implanted with 136Xe at 800 keV corresponding to a projected range of 140 nm. They are then either annealed in the temperature range 1400-1600 C, or irradiated with heavy energy ions (182 MeV Iodine) at Room Temperature (RT), 600 C or 1000 C. Depth profiles of implanted Xenon in UO2 are determined by Secondary Ion Mass Spectrometry (SIMS). It is shown that Xenon is mobile during irradiation at 1000 C. In contrast, thermal treatments do not induce any Xenon migration process: these results are correlated to the formation of Xenon bubbles observed by Transmission Electron Microscopy. At depths lower than about 40 nm (zone 1), no bubbles are observed, At depths in between 40 nm and 110 nm (zone 2), a large number of small bubbles (around 2 nm in diameter) can be observed. By comparing with the SRIM profile, it appears that this area corresponds to the maximum of the defect profile, The third zone displays two bubble populations. The first population has the same size than the bubbles present in zone 2. The bubble size of the second population is significantly larger (up to around 10 nm). A STEM micrograph is presented in Fig. 4. It highlights the Xenon bubbles more clearly. It appears that the largest bubbles are located mainly near dislocations which are predominantly in zone 3. TEM micrographs obtained on the samples annealed at 1400 C (not shown here) show only small sized bubbles (around 2 nm). The presence of these bubbles could explain that no Xenon migration occurs even after annealing at 1600 C during 16 h. Moreover, concerning Xe thermal resolution, this can only occur if the bubble is overpressurized [21]. It was shown by Martin et al. [22] that at high temperature (over 1400 C) non pressurized aggregates are observed. So in our experiments, Xe thermal resolution is unlikely.The bubble sizes measured after 1400 C and 1600 C annealing are in agreement with literature data, in particular, with those of Michel et al. [23] obtained in Xenon implanted UO2 samples. Indeed they observed 1 nm sized bubbles at 600 C, which could reach 3 nm at 1400 C. Either conditions of the Neumann type for which the surface is impermeable which means that the Xenon flux is equal to zero and can be expressed by Eq. (2). {dC}/{dx}|surface=0 Or conditions of the Dirichlet type with a constant Xenon concentration at the surface expressed by Eq. (3). C(0,t)=constant We chose Neumann conditions since we observed a slight increase of Xenon concentration at the surface for the profiles of the samples irradiated at 600 C and at 1000 C. In order to simulate the evolution of the Xenon concentration profiles, as-implanted profiles were first fitted with Gaussian shaped curves. The evolution of these curves was then simulated by using the one dimensional finite difference method. Therefore, the total depth profile was discretized into 1.5 nm slices. D, v, k parameters were thus deduced from successive iterations until the final profile is correctly fitted. It is important to keep in mind that each migration mechanism induces a particular modification of the profile shape: a broadening is characteristic of a diffusion process, a profile shift is significant of a transport process and an area decrease means a release mechanism. Consequently, only one set of parameters can allow a correct fit of the final profile

Marchand, B.; Moncoffre, N.; Pipon, Y.; Brerd, N.; Garnier, C.; Raimbault, L.; Sainsot, P.; Epicier, T.; Delafoy, C.; Fraczkiewicz, M.; Gaillard, C.; Toulhoat, N.; Perrat-Mabilon, A.; Peaucelle, C.

2013-09-01

404

Tunable pulsed carbon dioxide laser  

NASA Technical Reports Server (NTRS)

Transverse electrically-excited-atmosphere (TEA) laser is continuously tunable over several hundred megahertz about centers of spectral lines of carbon dioxide. It is operated in single longitudinal mode (SLM) by injection of beam from continuous-wave, tunable-waveguide carbon dioxide laser, which serves as master frequency-control oscillator. Device measures absorption line of ozone; with adjustments, it is applicable to monitoring of atmospheric trace species.

Megie, G. J.; Menzies, R. T.

1981-01-01

405

Cervical thorium dioxide granuloma ('thorotrastoma').  

PubMed

An elderly woman had an expanding cervical mass that entrapped and compressed the adjacent cranial nerves, blood vessels, and muscles. The mass was dense on radiographs, extended from the skull base to low neck in the prevertebral and parapharyngeal tissues, and showed mixed intensity on MR. A previous direct carotid arteriogram with thorium dioxide as the contrast agent suggested the histologically proved diagnosis of a cervical thorium dioxide granuloma ("thorotrastoma"). PMID:7502983

Nguyen, B T; Yousem, D M; Hayden, R E; Montone, K T

1995-09-01

406

Discovery potential of xenon-based neutrinoless double beta decay experiments in light of small angular scale CMB observations  

NASA Astrophysics Data System (ADS)

The South Pole Telescope (SPT) has probed an expanded angular range of the CMB temperature power spectrum. Their recent analysis of the latest cosmological data prefers nonzero neutrino masses, with ?m? = (0.320.11) eV. This result, if confirmed by the upcoming Planck data, has deep implications on the discovery of the nature of neutrinos. In particular, the values of the effective neutrino mass m?? involved in neutrinoless double beta decay (??0?) are severely constrained for both the direct and inverse hierarchy, making a discovery much more likely. In this paper, we focus in xenon-based ??0? experiments, on the double grounds of their good performance and the suitability of the technology to large-mass scaling. We show that the current generation, with effective masses in the range of 100 kg and conceivable exposures in the range of 500 kgyear, could already have a sizeable opportunity to observe ??0? events, and their combined discovery potential is quite large. The next generation, with an exposure in the range of 10 tonyear, would have a much more enhanced sensitivity, in particular due to the very low specific background that all the xenon technologies (liquid xenon, high-pressure xenon and xenon dissolved in liquid scintillator) can achieve. In addition, a high-pressure xenon gas TPC also features superb energy resolution. We show that such detector can fully explore the range of allowed effective Majorana masses, thus making a discovery very likely.

Gmez-Cadenas, J. J.; Martn-Albo, J.; Muoz Vidal, J.; Pea-Garay, C.

2013-03-01

407

Development of a double-phase Xenon cell using micromegas charge readout for applications in dark matter physics  

NASA Astrophysics Data System (ADS)

A Micromegas micro pattern charge readout device has been operated at room temperature in Argon and Xenon from 1 to 3.5 atm and also within the saturated vapour phase of a double-phase Xenon target. The dependence of the gain on the amplification field, the pressure and the proportion of quencher has been evaluated. From a fit to the Townsend relation ?=APexp(-BP/E) the gas parameters A and B were derived and compared with existing data. For the first time Micromegas was operated in double-phase Xenon charge produced within the liquid extracted across the phase boundary prior to amplification in the gas. A 2% concentration of Methane, selected as a quencher to suppress UV photon feedback effects in the gas phase whilst allowing scintillation within the liquid, was blended with Xenon. A maximum gain of 529 was inferred from the measurement of the charge collected at the anode in saturated vapour at 1450 Torr. Operation in double phase however was limited to periods up to 30 min due to condensation of Xenon within the Micromegas and the corresponding collapse of the amplification field. This situation was partially alleviated by heating the anode. Possible improvements to the readout configuration are discussed in the context of operation in double-phase Xenon-based dark matter detectors as a replacement for photomultiplier optical readout.

Lightfoot, P. K.; Hollingworth, R.; Spooner, N. J. C.; Tovey, D.

2005-12-01

408

Conformational flexibility, UV-induced decarbonylation, and FTIR spectra of 1-phenyl-1,2 propanedione in solid xenon and in the low temperature amorphous phase.  

PubMed

1-Phenyl-1,2-propanedione has been isolated in low-temperature xenon matrixes and studied by FTIR spectroscopy, supported by DFT(B3LYP)/6-311++G(d,p) calculations. In good agreement with previous electron diffraction data [Shen, Q.; Hagen, K. J. Phys. Chem. 1993, 97, 985], the calculations predicted the existence of only one stable conformation for the compound, in which the O=C-C=O dihedral angle is 135.6 degrees. On the other hand, the experimental data clearly reveals that, in the as-deposited xenon matrixes (T = 20 K), there is a distribution of molecules with different O=C-C=O dihedral angles around the equilibrium value. This distribution results from the efficient trapping of the conformational distribution existing in the gas phase, prior to deposition, which is determined by the low frequency, large amplitude torsional vibration around the C-C central bond. Upon annealing to higher temperatures (T approximately 45 K), the initially trapped conformational distribution can be modified in a certain degree, favoring more polar structures (corresponding to smaller O=C-C=O dihedral angles), as a result of the interactions with the matrix media. Irradiation of the matrix with UV light (lambda > 235 nm) led to decarbonylation of the compound, with generation of acetophenone and carbon monoxide, with an almost complete consumption of the reagent after 1100 min of irradiation (k = 2.8 x 10(-2) min.(-1)). Aggregation of the compound resulting from the matrix warming was also investigated, providing useful information for interpretation of the spectroscopic data obtained for the low-temperature amorphous state of the neat compound. PMID:16833887

Lopes, Susy; Gmez-Zavaglia, Andrea; Lapinski, Leszek; Fausto, Rui

2005-06-30

409

RF Noise Generation in High-Pressure Short-Arc DC Xenon Lamps  

NASA Astrophysics Data System (ADS)

Continuous direct current xenon arcs will generate RF noise under certain circumstance, which can lead to excessive electro- magnetic interference in systems that use these arcs as light sources. Phenomenological observations are presented for xenon arcs having arc gaps 1 mm, cold fill pressures of 2.5 MPa, and currents up to 30 amps. Using a loop antenna in the vicinity of an operating lamp, it is observed that as the current to the arc is lowered there is a reproducible threshold at which the RF noise generation begins. This threshold is accompanied by a small abrupt drop in voltage (0.2 volts). The RF emission appears in pulses 150 nsec wide separated by 300 nec - the pulse interval decreases with decreasing current. The properties of the RF emission as a function of arc parameters (such as pressure, arc gap, electrode design) will be discussed and a semi-quantitative model presented.

Minayeva, Olga; Doughty, Douglas

2007-10-01

410

Near-infrared scintillation of xenon by {sup 63}Ni beta decay  

SciTech Connect

The near-infrared scintillation of xenon gas by the {beta} decay of 37 MBq of {sup 63}Ni was studied, in the interest of its use in integrated devices for applications such as optical beacons and wavelength calibration. The emission was imaged and analyzed using Spencer's theory of electron penetration using xenon scattering cross sections derived from Thomas-Fermi theory. The total emission was approximately 2x10{sup 5} photons/s at 20 kPa and 1x10{sup 5} photons/s at 100 kPa. Spectral data show three dominant peaks at 823, 828, and 882 nm as well as the formation of metastable states.

Yoshimizu, Norimasa; Lal, Amit; Pollock, Clifford R. [SonicMEMS Laboratory, Department of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853 (United States)

2006-07-10

411

Nonlinear optical processes in xenon and krypton studied by two-color multiphoton ionization  

SciTech Connect

Multiphoton ionization (MPI) and third-harmonic generation (THG) in xenon and krypton have been studied via three-photon resonance with the xenon 6s'(1/2)/sub 1//sup 0/ and krypton 5s((3/2)/sub 1//sup 0/ states. A second, tunable dye laser is used to couple these states to higher-lying even-parity states. Observations are reported regarding the third-harmonic related cancellation of the intermediate s-state population and the mechanisms of population of the final states. Effects of the four-photon resonance on THG are detailed. Changes induced by the second laser reduce THG in normally favorable regions and enable it in otherwise forbidden regions. Striking effects in the MPI spectra due to the changes induced in THG are reported.

Blazewicz, P.R.; Miller, J.C.

1988-09-15

412

Characterization of the Xenon-10 Dark Matter Detector with regard to electric field and light response  

NASA Astrophysics Data System (ADS)

Electrostatic and Monte Carlo Simulations of the Xenon-10 Dark Matter Detector were carried out. Electrostatic simulations led to optimization of the charge sensitive region through proper determination of resistor chain values for the field shaping wires and through maximization of the charge sensitive region by reducing areas of charge loss. These simulations also led to identification of problem regions which would otherwise hindered detector calibration and data analysis. Monte Carlo simulations of the light response for both primary and secondary scintillation light were instrumental in position reconstruction in the gas phase of the detector and in the identification of events occurring inside the problem regions found in the electrostatic simulations. Data comparison with Activated Xenon ( 131 Xe) with its gamma ray feature at 164 keV and isotropic event distribution showed good agreement with simulated data.

Gomez, Roman G.

413

SAUNAa system for automatic sampling, processing, and analysis of radioactive xenon  

NASA Astrophysics Data System (ADS)

A system for automatic sampling, processing, and analysis of atmospheric radioxenon has been developed. From an air sample of about 7 m3 collected during 12 h, 0.5 cm3 of xenon is extracted, and the atmospheric activities from the four xenon isotopes 133Xe, 135Xe, 131mXe, and 133mXe are determined with a beta-gamma coincidence technique. The collection is performed using activated charcoal and molecular sieves at ambient temperature. The sample preparation and quantification are performed using preparative gas chromatography. The system was tested under routine conditions for a 5-month period, with average minimum detectable concentrations below 1 mBq/ m3 for all four isotopes.

Ringbom, A.; Larson, T.; Axelsson, A.; Elmgren, K.; Johansson, C.

2003-08-01

414

Effect of Cesium and Xenon Seeding in Negative Hydrogen Ion Sources  

SciTech Connect

It is well known that cesium seeding in volume hydrogen negative ion sources leads to a large reduction of the extracted electron current and in some cases to the enhancement of the negative ion current. The cooling of the electrons due to the addition of this heavy impurity was proposed as a possible cause of the mentioned observations. In order to verify this assumption, the authors seeded the hydrogen plasma with xenon, which has an atomic weight almost equal to that of cesium. The plasma properties were studied in the extraction region of the negative ion source Camembert III using a cylindrical electrostatic probe while the negative ion relative density was studied using laser photodetachment. It is shown that the xenon mixing does not enhance the negative ion density and leads to the increase of the electron density, while the cesium seeding reduces the electron density.

Bacal, M.; Brunteau, A.M.; Deniset, C.; Elizarov, L.I.; Sube, F.; Tontegode, A.Y.; Whealton, J.H.

1999-09-06

415

Development of a High-Power Coaxial Pulse Tube Refrigerator for a Liquid Xenon Calorimeter  

NASA Astrophysics Data System (ADS)

A high-power coaxial pulse tube refrigerator has been designed, fabricated and tested to meet the requirements of liquefaction and re-condensation of xenon gas for a large liquid xenon calorimeter. A feature of this pulse tube refrigerator is that a cylindrical regenerator placed inside of the pulse tube for space saving and easy fabrication. It provides a cooling power of 70 W at 165 K by using a 2.2 kW GM-type compressor. The cooling power performance up to 120 W using a much larger compressor was also tested. The outer cylinder is a stainless steel pipe of 60 mm diameter, 180 mm in length and 0.5 mm in thickness. The regenerator consists of about 900 disk sheets of #300 stainless steel mesh packed in a Bakelite tube.

Haruyama, T.; Kasami, K.; Inoue, H.; Mihara, S.; Matsubara, Y.

2004-06-01

416

A liquid xenon imaging telescope for 1-30 MeV gamma-ray astrophysics  

NASA Technical Reports Server (NTRS)

A study of the primary scintillation light in liquid xenon excited by 241 Am alpha particles and 207 Bi internal conversion electrons are discussed. The time dependence and the intensity of the light at different field strengths have been measured with a specifically designed chamber, equipped with a CaF sub 2 light transmitting window coupled to a UV sensitive PMT. The time correlation between the fast light signal and the charge signal shows that the scintillation signals produced in liquid xenon by ionizing particles provides an ideal trigger in a Time Projection type LXe detector aiming at full imaging of complex gamma-ray events. Researchers also started Monte Carlo calculations to establish the performance of a LXe imaging telescope for high energy gamma-rays.

Aprile, Elena; Mukherjee, Reshmi; Suzuki, Masayo

1989-01-01

417

Time-Dependent Multiphoton Ionization of Xenon in the Soft-X-Ray Regime  

NASA Astrophysics Data System (ADS)

The time-dependent multiphoton ionization of xenon atoms is studied with femtosecond pulses in the excitation range of the 4d giant resonance at the photon energy of 93 eV. Benefiting from a new operation mode of the free electron laser FLASH, the measurements are performed with varying pulse durations. A strong dependence of the ion charge distribution on the pulse duration allows the different multiphoton mechanisms behind the multiple photoionization of xenon to be disentangled up to a charge state of Xe10+. The results up to Xe8+ are well explained by sequences of single photon, multiphoton, and Auger processes, but higher charge state generation suggests the need for collective electron multiphoton excitations.

Gerken, N.; Klumpp, S.; Sorokin, A. A.; Tiedtke, K.; Richter, M.; Brk, V.; Mertens, K.; Jurani?, P.; Martins, M.

2014-05-01

418

Development of a High-Power Coaxial Pulse Tube Refrigerator for a Liquid Xenon Calorimeter  

SciTech Connect

A high-power coaxial pulse tube refrigerator has been designed, fabricated and tested to meet the requirements of liquefaction and re-condensation of xenon gas for a large liquid xenon calorimeter. A feature of this pulse tube refrigerator is that a cylindrical regenerator placed inside of the pulse tube for space saving and easy fabrication. It provides a cooling power of 70 W at 165 K by using a 2.2 kW GM-type compressor. The cooling power performance up to 120 W using a much larger compressor was also tested. The outer cylinder is a stainless steel pipe of 60 mm diameter, 180 mm in length and 0.5 mm in thickness. The regenerator consists of about 900 disk sheets of no. 300 stainless steel mesh packed in a Bakelite tube.

Haruyama, T.; Kasami, K.; Inoue, H. [KEK, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Mihara, S. [ICEPP, International Center for Elementary Particle Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Matsubara, Y. [Nihon University, 7-24-1 Narashinodai, Funabashi, Chiba 274-8501 (Japan)

2004-06-23

419

Calculated characteristics of radio-frequency plasma display panel cells including the influence of xenon metastables  

NASA Astrophysics Data System (ADS)

Although alternating-current plasma display panels (ac PDPs) are now produced by several companies, improvements are still necessary. In particular, the overall efficiency of the discharge in the standard configuration is low, on the order of 1 lm/W i.e., about 0.5% of the power dissipated in the discharge is transformed into useful visible photons. One way to substantially improve the efficiency of PDPs is to use radio-frequency (rf) excitation because, when compared to ac PDPs, less of the electrical energy input is dissipated by ions in the sheath and relatively more power is deposited in excitation of the xenon, which produces the ultraviolet photons used to excite the phosphors. In this article, we show calculated discharge characteristics for typical rf PDP conditions and pay particular attention to the role of the xenon metastable atoms in the ionization balance. Our discussion is limited to the sustaining regime, the ``on-state,'' of a PDP cell.

Pitchford, L. C.; Kang, J.; Punset, C.; Boeuf, J. P.

2002-12-01

420

Wavelength and Intensity Dependence of Short Pulse Laser Xenon Double Ionization between 500 and 2300 nm  

SciTech Connect

The wavelength and intensity dependence of xenon ionization with 50 fs laser pulses has been studied using time-of-flight mass spectrometry. We compare the ion yield distribution of singly and doubly charged xenon with the Perelomov-Popov-Terent'ev (PPT) theory, Perelomov, Popov, and Terent'ev, Zh. Eksp. Teor. Fiz. 50, 1393 (1966) [Sov. Phys. JETP 23, 924 (1966)], in the regime between 500 and 2300 nm. The intensity dependence for each wavelength is measured in a range between 1x10{sup 13} and 1x10{sup 15} W/cm{sup 2}. The Xe{sup +}-ion signal is in good agreement with the PPT theory at all used wavelengths. In addition we demonstrate that ionic 5s5p{sup 6} {sup 2}S state is excited by an electron impact excitation process and contributes to the nonsequential double ionization process.

Gingras, G.; Tripathi, A.; Witzel, B. [Centre d'Optique, Photonique et Laser, Universite Laval, Pavillon d'optique-photonique Quebec (Quebec), G1V 0A6 (Canada)

2009-10-23

421

Effect of cesium and xenon seeding in negative hydrogen ion sources  

NASA Astrophysics Data System (ADS)

It is well known that cesium seeding in volume hydrogen negative ion sources leads to a large reduction of the extracted electron current and in some cases to the enhancement of the negative ion current. The cooling of the electrons due to the addition of this heavy impurity was proposed as a possible cause of the mentioned observations. In order to verify this assumption, we seeded the hydrogen plasma with xenon, which has an atomic weight almost equal to that of cesium. The plasma properties were studied in the extraction region of the negative ion source Camembert III using a cylindrical electrostatic probe while the negative ion relative density was studied using laser photodetachment. It is shown that the xenon mixing does not enhance the negative ion density and leads to the increase of the electron density, while the cesium seeding reduces the electron density.

Bacal, M.; Bruneteau, A. M.; Deniset, C.; Elizarov, L. I.; Sube, F.; Tontegode, A. Y.; Whealton, J. H.

2000-02-01

422

Radiogenic Xenon-129 in Silicate Inclusions in the Campo Del Cielo Iron Meteorite  

NASA Technical Reports Server (NTRS)

Iron meteorites present a challenge for the I-Xe dating technique because it is usually the inclusions, not metal, that contain radiogenic xenon and iodine. Silicate inclusions are frequent in only types IAB and IIE, and earlier studies of irons have demonstrated that I-Xe system can survive intact in these inclusions preserving valuable age information. Our previous studies of the I-Xe record in pyroxene grains from Toluca iron suggested an intriguing relationship between apparent I-Xe ages and (Mg+Fe)/Fe ratios. The I-Xe system in K-feldspar inclusions from Colomera (IIE) had the fingerprint of slow cooling, with an indicated cooling rate of 2-4 C/Ma. Here we present studies of the iodine-xenon system in a silicate-graphite-metal (SiGrMet) inclusion of the IA Campo del Cielo iron meteorite from the collection of the Museum of Natural History in Vienna.

Meshik, A.; Kurat, G.; Pravdivtseva, O.; Hohenberg, C. M.

2004-01-01

423

Intercomparison experiments of systems for the measurement of xenon radionuclides in the atmosphere  

Microsoft Academic Search

Radioactive xenon monitoring is one of the main technologies used for the detection of underground nuclear explosions. Precise and reliable measurements of 131mXe, 133gXe, 133mXe, and 135gXe are required as part of the International Monitoring System for compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). For the first time, simultaneous testing of four highly sensitive and automated fieldable radioxenon measurement systems

M. Auer; A. Axelssson; X. Blanchard; Ted W. Bowyer; G. Brachet; I. Bulowski; Y. Dubasov; K. Elmgren; J. P. Fontaine; W. Harms; James C. Hayes; Tom R. Heimbigner; Justin I. McIntyre; Mark E. Panisko; Y. Popov; Anders Ringbom; H. Sartorius; S. Schmid; J. Schulze; Clemens Schlosser; T. Taffary; W. Weiss; B. Wernsperger

2004-01-01

424

Electron-impact excitation cross sections from the xenon J=2 metastable level  

Microsoft Academic Search

Cross sections for electron-impact excitation from the 5p⁵6s J=2 metastable level of xenon to the lowest six levels of the 5p⁵6p configuration have been measured. The cross sections generally have very large magnitudes (10⁻¹⁵ cm²) and scale with the corresponding optical oscillator strengths. The substantial variations observed in the energy dependence of the cross sections for the six levels can

R. O. Jung; John B. Boffard; L. W. Anderson; Chun C. Lin

2005-01-01

425

Electron-impact excitation cross sections from the xenon J=2 metastable level  

Microsoft Academic Search

Cross sections for electron-impact excitation from the 5p65s J=2 metastable level of xenon to the lowest six levels of the 5p65p configuration have been measured. The cross sections generally have very large magnitudes (10-15cm2) and scale with the corresponding optical oscillator strengths. The substantial variations observed in the energy dependence of the cross sections for the six levels can also

R. O. Jung; John B. Boffard; L. W. Anderson; Chun C. Lin

2005-01-01

426

Production of charged hadrons by positive muons on deuterium and xenon at 490 GeV  

Microsoft Academic Search

Results on the production of charged hadrons in muon-deuteron and muon-xenon interactions are presented. The data were taken with the E665 spectrometer, which was exposed to the 490 GeV muon beam of the Tevatron at Fermilab. The use of a streamer chamber as vertex detector provides nearly 4p acceptance for charged particles. The D data are compared with the Xe

M. Aderholz; S. Ad; P. L. Anthony; M. D. Baker; J. Bartlett; A. A. Bhatti; H. M. Braun; W. Busza; T. J. Caroll; J. M. Conrad; G. Coutrakon; R. Davisson; I. Derado; S. K. Dhawan; W. Dougherty; T. Dreyer; K. Dziunikowska; V. Eckardt; U. Ecker; M. Erdmann; A. Eskreys; J. Figiel; H. J. Gebauer; D. F. Geesaman; R. Gilman; M. C. Green; J. Haas; C. Halliwell; J. Hanlon; D. Hantke; V. W. Hughes; H. E. Jackson; D. E. Jaffe; G. Jancso; D. M. Jansen; S. Kaufman; R. D. Kennedy; T. Kirk; H. G. E. Kobrak; S. Krzywdzinski; S. Kunori; J. J. Lord; H. J. Lubatti; D. McLeod; S. Magill; P. Malecki; A. Manz; H. Melanson; D. G. Michael; W. Mohr; H. E. Montgomery; J. G. Morfin; R. B. Nickerson; S. O'Day; K. Olkiewicz; L. Osborne; V. Papavassiliou; B. Pawlik; F. M. Pipkin; E. J. Ramberg; A. Rser; J. J. Ryan; C. W. Salgado; A. Salvarani; H. Schellman; M. Schmitt; N. Schmitz; K. P. Schler; H. J. Seyerlein; A. Skuja; G. A. Snow; S. Sldner-Rembold; P. H. Steinberg; H. E. Stier; P. Stopa; R. A. Swanson; R. Talaga; S. Tentindo-Repond; H.-J. Trost; H. Venkataramania; M. Wilhelm; J. Wilkes; R. Wilson; W. Wittek; S. A. Wolbers; T. Zhao

1994-01-01

427

Repeated Least Squares Analysis of Simulated Xenon Computed Tomographic Measurements of Regional Cerebral Blood Flow  

Microsoft Academic Search

Summary: Computer simulations were done as a feasibility study of xenon computed tomographic measurements of regional cerebral blood flow. Accu-raey of initial least Squares estimates of gray matter and white matter rate constants from a two-compartment model depended very little on the number and timing of scans, but did depend significantly on the enhancement-to-noise ratio as well as on the

H. T. Thaler; J. A. Baglivo; H. C. Lu; D. A. Rottenberg; Thaler

1982-01-01

428

Neon and xenon isotopes in MORB: implications for the earth-atmosphere evolution  

Microsoft Academic Search

The isotopic composition of neon and xenon measured in MORB glasses confirm significant deviations from atmospheric values. These are (1) 21Ne excesses which are attributed to nucleogenic reactions in the mantle: (2) 20Ne\\/22Ne ratios higher than the air ratio interpreted as an evidence for the occurrence of solar-type Ne at depth: (3) 129Xe and 131-136Xe excesses, attributed to both extinct

Bernard Marty

1989-01-01

429

New measurement of the relative scintillation efficiency of xenon nuclear recoils below 10 keV  

SciTech Connect

Liquid xenon is an important detection medium in direct dark matter experiments, which search for low-energy nuclear recoils produced by the elastic scattering of WIMPs with quarks. The two existing measurements of the relative scintillation efficiency of nuclear recoils below 20 keV lead to inconsistent extrapolations at lower energies. This results in a different energy scale and thus sensitivity reach of liquid xenon dark matter detectors. We report a new measurement of the relative scintillation efficiency below 10 keV performed with a liquid xenon scintillation detector, optimized for maximum light collection. Greater than 95% of the interior surface of this detector was instrumented with photomultiplier tubes, giving a scintillation yield of 19.6 photoelectrons/keV electron equivalent for 122-keV {gamma} rays. We find that the relative scintillation efficiency for nuclear recoils of 5 keV is 0.14, staying constant around this value up to 10 keV. For higher energy recoils we measure a value of 0.21, consistent with previously reported data. In light of this new measurement, the XENON10 experiment's upper limits on spin-independent WIMP-nucleon cross section, which were calculated assuming a constant 0.19 relative scintillation efficiency, change from 8.8x10{sup -44} cm{sup 2} to 9.9x10{sup -44} cm{sup 2} for WIMPs of mass 100 GeV/c{sup 2}, and from 4.5x10{sup -44} cm{sup 2} to 5.6x10{sup -44} cm{sup 2} for WIMPs of mass 30 GeV/c{sup 2}.

Aprile, E.; Choi, B.; Giboni, K. L.; Lim, K.; Monzani, M. E.; Plante, G.; Santorelli, R.; Yamashita, M. [Department of Physics, Columbia University, New York, New York 10027 (United States); Baudis, L. [Physik-Institut, Universitaet Zuerich, CH-8057 Zuerich (Switzerland); Manalaysay, A. [Physik-Institut, Universitaet Zuerich, CH-8057 Zuerich (Switzerland); Department of Physics, University of Florida, Gainesville, Florida 32611 (United States)

2009-04-15

430

Absolute number of scintillation photons in liquid xenon by alpha-particles  

SciTech Connect

This paper reports on the absolute scintillation yield obtained to be 3.26 [times] 10[sup 5] for alpha-particles of 5.303 MeV in liquid xenon. This result followed from fitting the absolute photo-electron yields measured with a VUV sensitive photomultiplier, which was used as a photo-diode, to the results of Monte-Carlo simulation.

Miyajima, M.; Sasaki, S.; Tawara, H. (National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)); Shibamura, E. (Saitama College of Health, Kamiokubo 519, Urawa, Saitama 338 (Japan))

1992-08-01

431

A field-deployable gamma-ray spectrometer utilizing xenon at high pressure  

Microsoft Academic Search

Prototype gamma-ray spectrometers utilizing xenon gas at high pressure, suitable for applications in the nuclear safeguards, arms control, and nonproliferation communities, have been developed at Brookhaven National Laboratory (BNL). These spectrometers function as ambient-temperature ionization chambers detecting gamma rays with good efficiency in the energy range 50 keV - 2 MeV, with an energy resolution intermediate between semiconductor (Ge) and

G. C. Smith; G. J. Mahler; B. Yu; C. Salwen; W. R. Kane; J. R. Lemley

1996-01-01

432

High-pressure equations of state of krypton and xenon by a statistical mechanical theory  

Microsoft Academic Search

We present statistical mechanical calculations for krypton and xenon, employing accurate pair potentials with and without condensed-phase modifications. A unique feature of the present work is that solid- and fluid-phase thermodynamic properties are both computed within a single framework, using our recently developed hard-sphere perturbation theory. Results are applied to analyze experimental fluid, solid, and fluidsolid transition data, ranging up

Jae Hyun Kim; Taikyue Ree; Francis H. Ree

1989-01-01

433

High-pressure equations of state of krypton and xenon by a statistical mechanical theory  

Microsoft Academic Search

We present statistical mechanical calculations for krypton and xenon, employing accurate pair potentials with and without condensed-phase modifications. A unique feature of the present work is that solid- and fluid-phase thermodynamic properties are \\/ital both\\/ computed within a \\/ital single\\/ framework, using our recently developed hard-sphere perturbation theory. Results are applied to analyze experimental fluid, solid, and fluid--solid transition data,

Jae Hyun Kim; Taikyue Ree; Francis H. Ree

1989-01-01

434

Numerical model of an ac plasma display panel cell in neon-xenon mixtures  

Microsoft Academic Search

We present a self-consistent 1D model of the discharge initiated in an ac plasma display panel cell. The model is based on a two-moments fluid description of electron and ion transport, coupled with Poissons equation, and with a set of kinetic equations characterizing the evolution of the population of excited states leading to UV emission in neon-xenon mixtures. Results are

J. Meunier; Ph. Belenguer; J. P. Boeuf

1995-01-01

435

GraXe, graphene and xenon for neutrinoless double beta decay searches  

Microsoft Academic Search

We propose a new detector concept, GraXe (to be pronounced as grace), to search for neutrinoless double beta decay in Xe-136. GraXe combines a popular detection medium in rare-event searches, liquid xenon, with a new, background-free material, graphene. In our baseline design of GraXe, a sphere made of graphene --- possibly held together with a very light synthetic woven ---

J. J. Gomez-Cadenas; F. Guinea; M. M. Fogler; M. I. Katsnelson; J. Martin-Albo; F. Monrabal; J. Muoz-Vidal

2011-01-01

436

Krypton and Xenon Losses in Low-Pressure Air Separation Rectification Units  

Microsoft Academic Search

There are over 40 types of Russian air-separation plant (ASP) [1]. From the viewpoint of the economics of extracting krypton Kr and xenon Xe, the main interest attaches to ASP producing gaseous oxygen at a level of not less than 3000 m 3 \\/h, which may be termed high-production plant. Such plant uses a low-pressure cycle with an air expansion

A. M. Arkharov; M. Yu. Savinov; V. L. Bondarenko; A. S. Bronshtein

2003-01-01

437

Structure of strong shock waves in xenon. I: Electron temperature measurements  

Microsoft Academic Search

Time-resolved electron temperature measurements were taken behind incident normal shock waves in an arc-driven shock tube using xenon as the test gas at an initial driven tube pressure of 0.1 Torr. At shock wave velocities from 6 to 10 km\\/sec, the two-line intensity ratio technique involving the spectral lines of XeII was used to determine the electron temperature. The data

Robert A. Golobic; Robert M. Nerem

1973-01-01

438

Fluctuations during freezing and melting at the solid-liquid interface of xenon  

Microsoft Academic Search

Dynamic light-scattering experiments have been performed to study the dynamical processes at the solid-liquid interface during freezing and melting on a mesoscopic length scale. Xenon has been used as a model substance because it forms a simple liquid, and van der Waals forces are the only interactions between the atoms. A solid-liquid interface is formed by melting a sphere with

S. di Nardo; J. H. Bilgram

1995-01-01

439

Excitation of the 5p57p levels of xenon by electron impact  

NASA Astrophysics Data System (ADS)

We have used our relativistic distorted-wave method to calculate cross sections for the electron-impact excitation of the ground state of xenon to all the 5 p 57 p fine-structure levels. The results are compared with the recent experimental measurements of Jung et al. [Phys. Rev. A 80, 062708 (2009)]. Analytic fits to our cross sections are also provided for use in plasma modeling studies.

Sharma, L.; Srivastava, R.; Stauffer, A. D.

2011-05-01

440

Evaluation of electrical conductivity in high-pressure plasmas formed in xenon with sodium as additive  

Microsoft Academic Search

Results of a numerical evaluation of the electrical conductivity in high-pressure plasmas of intermediate degrees of ionization formed in xenon with, respectively, 1% and 10% of sodium are presented, for temperatures between 2000 K and 20 000 K, and for pressures ranging from the normal atmospheric value Patm = 0.1 MPa up to 2.5 MPa. The equilibrium plasma composition, necessary

N V Novakovi?; S M Stojilkovi?; B S Mili?

1990-01-01

441

Aromatic fluorine derivatives. C. reactions of pentafluorophenol with vanadium, niobium, and antimony fluorides and xenon difluoride  

SciTech Connect

Pentafluorophenol reacts with vanadium fluorides (VF/sub 5/, VOF/sub 3/, VF/sub 4/) and xenon difluoride giving perfluoro-2,5-cyclohexadien-1-one and the products from dimerization of the pentafluorophenoxyl radical, i.e., perfluoro-6-phenoxy-2,4-cyclo-hexadien-1-one, perfluoro-4-phenoxy-2,5-cyclohexadien-1-one, and perfluoro-2-phenoxy-2,5-cyclohexadien-1-one. Antimony and niobium pentafluorides give stable complexes or the corresponding pentafluorophenolates with pentafluorophenol.

Auramenko, A.A.; Bardin, V.V.; Furin, G.G.; Karelin, A.I.; Krasil'nikov, V.A.; Tushin, P.P.; Yakobson, G.G.

1985-09-20

442

Third-harmonic generation in a pulsed supersonic jet of xenon  

Microsoft Academic Search

Third-harmonic generation to 1182 A is reported in a pulsed supersonic jet of xenon. Using a valve equipped with a 1-mm-diameter nozzle and for an incident power of 18 MW at 3547 A, a peak power of 260 W in a 2.9-nsec pulse, corresponding to 4.7 x 10 to the 11th photons per pulse and an average power of 7.5

A. H. Kung

1983-01-01

443

Effect of Exhaust Magnetic Field in a Helicon Double-Layer Thruster Operating in Xenon  

Microsoft Academic Search

A xenon ion beam is spatially characterized by using a retarding-field energy analyzer positioned 7 cm downstream of a helicon double-layer thruster (HDLT) operating at 500-W radio-frequency power, 0.07-mtorr (9.33 times 10-3Pa) gas pressure, and with an exhaust magnetic field diverging from a maximum of about 142 G (0.0142 T) inside the thruster to about 26 G (0.026 T) at

Christine Charles; Rod W. Boswell

2008-01-01

444

Bubble dynamics and sonoluminescence from helium or xenon in mercury and water  

NASA Astrophysics Data System (ADS)

Numerical simulations of bubble pulsation and sonoluminescence (SL) have been performed for helium or xenon bubbles in mercury and water under the experimental conditions of Futakawa [M. Futakawa, T. Naoe, and M. Kawai, in Nonlinear AcousticsFundamentals and Applications: 18th International Symposium on Nonlinear Acoustics (ISNA 18), AIP Conf. Proc. No. 1022, edited by B. O. Enflo, C. M. Hedberg, and L. Kari (AIP, New York, 2008), p. 197]. The results of the numerical simulations have revealed that the bubble expansion is much larger in water than in mercury mainly because the density of water is one order of magnitude smaller than that of mercury. The SL intensity is higher in water than that in mercury although the maximum bubble temperature is lower. This is caused by the much larger amount of vapor inside a bubble as the saturated vapor pressure of water is four orders of magnitude larger than that of mercury at room temperature. The SL intensity from xenon is much larger than that from helium due both to lower ionization potential and higher bubble temperature due to lower thermal conductivity. The instantaneous SL power may be as large as 200 W from xenon in water. The maximum temperature inside a xenon bubble in mercury may be as high as about 80 000 K. It is suggested that the maximum pressure in mercury due to shock waves emitted from bubbles increases as the SL intensity increases, although they are not simply correlated in water because the amount of water vapor trapped inside a bubble influences the SL intensity in a complex way.

Yasui, Kyuichi; Kato, Kazumi

2012-09-01

445

Xenon arc panretinal photocoagulation for central retinal vein occlusion: a randomised prospective study  

Microsoft Academic Search

Thirty-three patients with central vein occlusion were evaluated for the effects of scatter xenon arc panretinal photocoagulation. Thirty-four eyes (2 eyes of 1 patient) were randomly divided into a treatment (15 eyes) and a nontreatment group (19 eyes). The average follow-up per eye has been 29 months. The visual prognosis was not significantly better in either group. There was no

D R May; M L Klein; G A Peyman; M Raichand

1979-01-01

446

Physiological response of rats to delivery of helium and xenon: implications for hyperpolarized noble gas imaging  

NASA Technical Reports Server (NTRS)

The physiological effects of various hyperpolarized helium and xenon MRI-compatible breathing protocols were investigated in 17 Sprague-Dawley rats, by continuous monitoring of blood oxygen saturation, heart rate, EKG, temperature and endotracheal pressure. The protocols included alternating breaths of pure noble gas and oxygen, continuous breaths of pure noble gas, breath-holds of pure noble gas for varying durations, and helium breath-holds preceded by two helium rinses. Alternate-breath protocols up to 128 breaths caused a decrease in oxygen saturation level of less than 5% for either helium or xenon, whereas 16 continuous-breaths caused a 31.5% +/- 2.3% decrease in oxygen saturation for helium and a 30.7% +/- 1. 3% decrease for xenon. Breath-hold protocols up to 25 s did not cause the oxygen saturation to fall below 90% for either of the noble gases. Oxygen saturation values below 90% are considered pathological. At 30 s of breath-hold, the blood oxygen saturation dropped precipitously to 82% +/- 0.6% for helium, and to 76.5% +/- 7. 4% for xenon. Breath-holds longer than 10 s preceded by pre-rinses caused oxygen saturation to drop below 90%. These findings demonstrate the need for standardized noble gas inhalation procedures that have been carefully tested, and for continuous physiological monitoring to ensure the safety of the subject. We find short breath-hold and alternate-breath protocols to be safe procedures for use in hyperpolarized noble gas MRI experiments. Copyright 2000 John Wiley & Sons, Ltd.

Ramirez, M. P.; Sigaloff, K. C.; Kubatina, L. V.; Donahue, M. A.; Venkatesh, A. K.; Albert, M. S.; ALbert, M. S. (Principal Investigator)

2000-01-01

447

Experimental determination of tetrafluoromethane and hexafluoroethane accumulation in khrom-3 kryptonxenon mixture producing equipment  

Microsoft Academic Search

Experimental data are provided on perfluorocarbon accumulation from atmospheric air in an industrial facility in Ukraine in\\u000a the process of air treatment in a modern air-fractionating plant with production of kryptonxenon mixture. Comparison of the\\u000a obtained data with the calculated values supports the proposition put forward by these authors regarding the crucial contribution\\u000a of adsorption processes to the final outcome

V. L. Bondarenko; N. P. Losyakov; V. B. Vorotyntsev; V. A. Mamrenko; Ya. V. Dzyuzyura; A. A. Vinnik

2010-01-01

448

Bubble dynamics and sonoluminescence from helium or xenon in mercury and water.  

PubMed

Numerical simulations of bubble pulsation and sonoluminescence (SL) have been performed for helium or xenon bubbles in mercury and water under the experimental conditions of Futakawa et al. [M. Futakawa, T. Naoe, and M. Kawai, in Nonlinear Acoustics-Fundamentals and Applications: 18th International Symposium on Nonlinear Acoustics (ISNA 18), AIP Conf. Proc. No. 1022, edited by B. O. Enflo, C. M. Hedberg, and L. Kari (AIP, New York, 2008), p. 197]. The results of the numerical simulations have revealed that the bubble expansion is much larger in water than in mercury mainly because the density of water is one order of magnitude smaller than that of mercury. The SL intensity is higher in water than that in mercury although the maximum bubble temperature is lower. This is caused by the much larger amount of vapor inside a bubble as the saturated vapor pressure of water is four orders of magnitude larger than that of mercury at room temperature. The SL intensity from xenon is much larger than that from helium due both to lower ionization potential and higher bubble temperature due to lower thermal conductivity. The instantaneous SL power may be as large as 200 W from xenon in water. The maximum temperature inside a xenon bubble in mercury may be as high as about 80?000K. It is suggested that the maximum pressure in mercury due to shock waves emitted from bubbles increases as the SL intensity increases, although they are not simply correlated in water because the amount of water vapor trapped inside a bubble influences the SL intensity in a complex way. PMID:23031026

Yasui, Kyuichi; Kato, Kazumi

2012-09-01

449

Xenon Purification Research and Development for the LZ Dark Matter Experiment  

NASA Astrophysics Data System (ADS)

The LZ Experiment is a next generation dark matter detector based on the current LUX detector design, with a 7-ton active volume. Although many research and development breakthroughs were achieved for the 350 kg LUX detector, the large volume scaling required for LZ presents a new set of design challenges that need to be overcome. Because the search for WIMP-like dark matter requires ultra low background experiments, the xenon target material in the LZ detector must meet purity specifications beyond what is commercially available. This challenge is two-fold. The xenon must contain extremely low amounts of electronegative impurities such as oxygen, which attenuate the charge signal. Additionally, it must also have very little of the inert isotope Kr-85, a beta-emitter that can obscure the dark matter signal in the detector volume. The purity requirements for the LUX experiment have been achieved, but the factor of 20 scaling in volume for LZ and increased demands for sensitivity mean that new research and development work must be done to increase our xenon purification capabilities. This talk will focus on the efforts being done at Case Western Reserve University to meet these strict purity requirements for the LZ Experiment.

Pech, Katherin

2013-04-01

450

First results from the XENON10 dark matter experiment at the Gran Sasso National Laboratory.  

PubMed

The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg xenon dual phase time projection chamber to search for dark matter weakly interacting massive particles (WIMPs). The detector measures simultaneously the scintillation and the ionization produced by radiation in pure liquid xenon to discriminate signal from background down to 4.5 keV nuclear-recoil energy. A blind analysis of 58.6 live days of data, acquired between October 6, 2006, and February 14, 2007, and using a fiducial mass of 5.4 kg, excludes previously unexplored parameter space, setting a new 90% C.L. upper limit for the WIMP-nucleon spin-independent cross section of 8.8x10(-44) cm2 for a WIMP m