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1

Toward molecular mechanism of xenon anesthesia: a link to studies of xenon complexes with small aromatic molecules.  

PubMed

The present study illustrates the steps toward understanding molecular mechanism of xenon anesthesia by focusing on a link to the structures and spectra of intermolecular complexes of xenon with small aromatic molecules. A primary cause of xenon anesthesia is attributed to inhibition of N-methyl-d-aspartate (NMDA) receptors by an unknown mechanism. Following the results of quantum mechanics/molecular mechanics (QM/MM) and molecular dynamics (MD) calculations we report plausible xenon action sites in the ligand binding domain of the NMDA receptor, which are due to interaction of xenon atoms with aromatic amino-acid residues. We rely in these calculations on computational protocols adjusted in combined experimental and theoretical studies of intermolecular complexes of xenon with phenol. Successful reproduction of vibrational shifts in molecular species upon complexation with xenon measured in low-temperature matrices allowed us to select a proper functional form in density functional theory (DFT) approach for use in QM subsystems, as well as to calibrate force field parameters for MD simulations. The results of molecular modeling show that xenon atoms can compete with agonists for a place in the corresponding protein cavity, thus indicating their active role in anesthetic action. PMID:25285819

Andrijchenko, Natalya N; Ermilov, Alexander Yu; Khriachtchev, Leonid; Räsänen, Markku; Nemukhin, Alexander V

2015-03-19

2

XENON  

Microsoft Academic Search

The XENON experiment aims at the direct detection of dark matter in the form of WIMPs (Weakly Interacting Massive Particles) via their elastic scattering off Xenon nuclei. With 1 ton of LXe distributed in ten identical modules, the proposed XENON1T experiment will achieve a sensitivity more than a factor of thousand beyond current limits.The detectors are time projection chambers operated

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

2007-01-01

3

Relaxation of Spin Polarisation of Sodium Vapor due to Sodium-Xenon Van Der Waals Molecules.  

NASA Astrophysics Data System (ADS)

We have studied the relaxation of ground state sodium spin polarisation in xenon gas as a function of magnetic field in the presence of nitrogen and helium as buffer gases. The dependence of the sodium spin relaxation on magnetic. field and on the pressure of helium gas shows that the relaxation. mostly takes place in loosely bound sodium-xenon van der Waals. molecules. It is observed that the spin orbit interaction is the. dominant mechanism for the relaxation of sodium spin polarisation. We report the first measurement of the average spin orbit coupling. constant (gamma) (H/2PI)('-1) = 0.9 MHz in sodium -xenon molecule. The life time(' ). of the molecules is found to be. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). in cells containing 2 torr of xenon, 10 torr of nitrogen and a helium pressure P(He) ranging from 24 to 200 torr.

Suleman, Badar

4

Interplay of defect cluster and the stability of xenon in uranium dioxide by density functional calculations  

E-print Network

Self-defect clusters in bulk matrix might affect the thermodynamic behavior of fission gases in nuclear fuel such as uranium dioxide. With first-principles LSDA+U calculations and taking xenon as a prototype, we find that the influence of oxygen defect clusters on the thermodynamics of gas atoms is prominent, which increases the solution energy of xenon by a magnitude of 0.5 eV, about 43% of the energy difference between the two lowest lying states at 700 K. Calculation also reveals a thermodynamic competition between the uranium vacancy and tri-vacancy sites to incorporate xenon in hyper-stoichiometric regime at high temperatures. The results show that in hypo-stoichiometric regime neutral tri-vacancy sites are the most favored position for diluted xenon gas, whereas in hyper-stoichiometric condition they prefer to uranium vacancies even after taking oxygen self-defect clusters into account at low temperatures, which not only confirms previous studies but also extends the conclusion to more realistic fuel operating conditions. The observation that gas atoms are ionized to a charge state of Xe+ when at a uranium vacancy site due to strong Madelung potential implies that one can control temperature to tune the preferred site of gas atoms and then the bubble growth rate. A solution to the notorious meta-stable states difficulty that frequently encountered in DFT+U applications, namely, the quasi-annealing procedure, is also discussed.

Hua Y. Geng; Ying Chen; Yasunori Kaneta; Motoyasu Kinoshita; Q. Wu

2010-08-26

5

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

SciTech Connect

The possible transition states, minimum energy paths and migration mechanisms of defect clusters and xenon-vacancy defect clusters in uranium dioxide have been investigated using the dimer and the nudged elastic-band 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, Huiqiu; Hu, Wangyu; Sun, Xin

2014-07-01

6

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

7

Ab initio potential energy surface for the carbon dioxide molecule pair and thermophysical properties of dilute carbon dioxide gas  

NASA Astrophysics Data System (ADS)

A four-dimensional intermolecular potential energy surface (PES) for two rigid carbon dioxide molecules was determined from quantum-chemical ab initio calculations. Interaction energies for 1229 CO2-CO2 configurations were computed at the CCSD(T) level of theory using basis sets up to aug-cc-pVQZ supplemented with bond functions. An analytical site-site potential function with seven sites per CO2 molecule was fitted to the interaction energies. The PES was validated by calculating the second virial coefficient as well as viscosity and thermal conductivity in the dilute-gas limit.

Hellmann, Robert

2014-10-01

8

Systematization of published spectral data on sulfur dioxide molecule and its isotopologues  

NASA Astrophysics Data System (ADS)

The paper presents a description of properties of published spectral data on spectral lines' parameters of sulfur dioxide molecule and its isotopologues. These data were acquired from more than 150 publications for a period of 50 years. Data properties as well as data sources classification according to validity and trust criteria are presented in a form of an ontological knowledge base on information resources. Data source properties values are computed during the assessment of validity and trust1. Published ro-vibrational transitions, energy levels, spectral lines' parameters, knowledge base on information resources of sulfur dioxide molecule and its isotopologues are available in the Internet accessible information system W@DIS (http://wadis.saga.iao.ru/).

Voronina, S. S.; Akhlestin, A. Yu.; Kozodoev, A. V.; Lavrentiev, N. A.; Privezentsev, A. I.; Fazliev, A. Z.; Naumenko, O. V.

2014-11-01

9

Development of a functionalized Xenon biosensor  

SciTech Connect

NMR-based biosensors that utilize laser-polarized xenon offer potential advantages beyond current sensing technologies. These advantages include the capacity to simultaneously detect multiple analytes, the applicability to in vivo spectroscopy and imaging, and the possibility of remote amplified detection. Here we present a detailed NMR characterization of the binding of a biotin-derivatized caged-xenon sensor to avidin. Binding of functionalized xenon to avidin leads to a change in the chemical shift of the encapsulated xenon in addition to a broadening of the resonance, both of which serve as NMR markers of ligand-target interaction. A control experiment in which the biotin-binding site of avidin was blocked with native biotin showed no such spectral changes, confirming that only specific binding, rather than nonspecific contact, between avidin and functionalized xenon leads to the effects on the xenon NMR spectrum. The exchange rate of xenon (between solution and cage) and the xenon spin-lattice relaxation rate were not changed significantly upon binding. We describe two methods for enhancing the signal from functionalized xenon by exploiting the laser-polarized xenon magnetization reservoir. We also show that the xenon chemical shifts are distinct for xenon encapsulated in different diastereomeric cage molecules. This demonstrates the potential for tuning the encapsulated xenon chemical shift, which is a key requirement for being able to multiplex the biosensor.

Spence, Megan M.; Ruiz, E. Janette; Rubin, Seth M.; Lowery, Thomas J.; Winssinger, Nicolas; Schultz, Peter G.; Wemmer, David E.; Pines, Alexander

2004-03-25

10

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

11

HXeOBr in a xenon matrix  

SciTech Connect

We report on a new noble-gas molecule HXeOBr prepared in a low-temperature xenon matrix from the HBr and N{sub 2}O precursors by UV photolysis and thermal annealing. This molecule is assigned with the help of deuteration experiments and ab initio calculations including anharmonic methods. The H-Xe stretching frequency of HXeOBr is observed at 1634 cm{sup -1}, which is larger by 56 cm{sup -1} than the frequency of HXeOH identified previously. The experiments show a higher thermal stability of HXeOBr molecules in a xenon matrix compared to HXeOH.

Khriachtchev, Leonid; Tapio, Salla; Domanskaya, Alexandra V.; Raesaenen, Markku [Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 (Finland); Isokoski, Karoliina [Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Lundell, Jan [Department of Chemistry, University of Jyvaeskylae, P.O. Box 35, FIN-40014 Jyvaeskylae (Finland)

2011-03-28

12

Primordial Terrestrial Xenon Revisited  

NASA Astrophysics Data System (ADS)

Xenon solar wind composition revealed by Genesis matches mathematically derived primordial terrestrial xenon with high precision, except for 136Xe and 134Xe. This can be explained by modification of fission yields in open systems.

Meshik, A. P.; Pravdivtseva, O. V.; Hohenberg, C. M.

2014-09-01

13

Accelerating electrostatic pair methods on graphical processing units to study molecules in supercritical carbon dioxide.  

PubMed

Traditionally, electrostatic interactions are modelled using Ewald techniques, which provide a good approximation, but are poorly suited to GPU architectures. We use the GPU versions of the LAMMPS MD package to implement and assess the Wolf summation method. We compute transport and structural properties of pure carbon dioxide and mixtures of carbon dioxide with either methane or difluoromethane. The diffusion of pure carbon dioxide is indistinguishable when using the Wolf summation method instead of PPPM on GPUs. The optimum value of the potential damping parameter, ?, is 0.075. We observe a decrease in accuracy when the system polarity increases, yet the method is robust for mildly polar systems. We anticipate the method can be used for a number of techniques, and applied to a variety of systems. Substitution of PPPM can yield a two-fold decrease in the wall-clock time. PMID:25340544

Baker, John A; Hirst, Jonathan D

2014-01-01

14

First Results from XENON100  

E-print Network

First Results from XENON100 For the XENON100 Collaboration Rafael F. Lang Columbia University rafael.lang@astro.columbia.edu #12;Rafael F. Lang (Columbia): First Results from XENON100 2 The XENON Università di Bologna Jiao Tong University Shanghai #12;Rafael F. Lang (Columbia): First Results from XENON

Weaver, Harold A. "Hal"

15

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

16

Fabrication and evaluation of a free molecule micro-resistojet with thick silicon dioxide insulation and suspension  

NASA Astrophysics Data System (ADS)

A silicon free molecule micro-resistojet (FMMR) with a thermally insulating suspension frame composed of silicon dioxide has been designed, fabricated and tested. The concept was developed to increase the efficiency of FMMRs, especially in silicon-based integrated systems. Fabrication of the thick insulating frame was performed through oxidation of high-aspect ratio silicon trenches. The thermal properties of the 1 cm2 thruster were evaluated using an IR camera, and it was found that when the volume inside the frame is heated more than 200 °C using integrated nickel heaters, the temperature increase in the volume outside the frame is less than 50 °C. During operation in vacuum, the thrust range was calculated to be about 13-1070 µN and the maximum specific impulse 54 s. At maximum thrust, and a power consumption of 1.6 W, the total efficiency of the thruster was 17%. Designs of more efficient and versatile systems are discussed.

Palmer, Kristoffer; Nguyen, Hugo; Thornell, Greger

2013-06-01

17

The incorporation and migration of a single xenon atom in ceria  

NASA Astrophysics Data System (ADS)

The behavior of xenon gas is crucial for the performance of nuclear fuel materials. We report molecular statics calculation results for the characteristics of a single xenon atom in cerium oxide, a non-radioactive surrogate of uranium dioxide. A variety of possible xenon incorporation sites, including the octahedral interstitial position, single-Ce-vacancy clusters, and double-Ce-vacancy clusters were considered. The binding energies and corresponding xenon incorporation energies were computed to reveal the preferred xenon positions in ceria. Different migration mechanisms of single xenon atoms were found to be involved with various incorporation sites. The energy barriers of all possible migration pathways were calculated. Only the mobility of single xenon atoms in the double-Ce-vacancy sites, which is due to the vacancy-assisted xenon migration, can account for the xenon diffusivity implied by bubble formation observed in experiments. The results also validated the role of ceria as a reliable surrogate of uranium dioxide in studies involving xenon gas.

Miao, Yinbin; Chen, Wei-Ying; Oaks, Aaron; Mo, Kun; Stubbins, James F.

2014-06-01

18

Nanoporosity of an organo-clay shown by hyperpolarized xenon and 2D NMR spectroscopy.  

PubMed

Interlayer nanoporosity of hectorite pillared by tetraethylammonium ions is explored by hyperpolarized xenon NMR and relevant gases such as carbon dioxide revealing the adsorption capacity of the open galleries. PMID:16767236

Sozzani, Piero; Bracco, Silvia; Comotti, Angiolina; Mauri, Michele; Simonutti, Roberto; Valsesia, Patrizia

2006-05-14

19

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

20

A Molecular Dynamics Study on the Confinement of Carbon Dioxide Molecules in Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

The influence of atmospheric carbon dioxide (CO2) concentration on global warming is considered as one of the primary environmental issues of the past two decades. The main source of CO2 emission is human activity, such as the use of fossil fuels in transportation and industrial plants. Following the release of Kyoto Protocol in 1997, effective ways of controlling CO2 emissions received much attention. As a result, various materials such as activated carbon, zeolites, and carbon nanotubes (CNTs) were investigated for their CO2 adsorbing properties. CNTs were reported to have CO2 adsorption capability twice that of activated carbon, hence they received the most attention. In the current study, single walled carbon nanotubes (SWNTs) were used as one dimensional nanoporous materials and their CO2 adsorption capacity was analyzed with Molecular Dynamics simulations. Results indicated that SWNTs are excellent CO2 adsorbers and their effectiveness increase at low CO2 concentrations. In addition, we showed that by varying temperature, CO2 can be removed from the SWNTs, providing a simple method to reuse SWNTs.

Lazor, Meagan; Rende, Deniz; Baysal, Nihat; Ozisik, Rahmi

2012-02-01

21

Molecular interaction between DNA molecules and nanoscale modifications of titanium dioxide with the structures of anatase and ?-TiO2  

NASA Astrophysics Data System (ADS)

The interaction of linear DNA molecules (hydrolysis products of Lambda phage DNA) with nanoscale modifications of titanium dioxide with anatase and ?-TiO2 structures is studied. The photosensitization of adsorption and degradation processes of DNA under the effects of visible light is revealed. It is established that the anatase exhibits increased activity towards DNA in a low salt buffer, while ?-TiO2 has a higher adsorption capacity in a buffer with high ionic strength. Recommendations on the practical application of nanoscale modifications of titanium dioxide with the structures of anatase and ?-TiO2 are given.

Kutsev, M. G.; Kuz'micheva, G. M.; Obolenskaya, L. N.; Savinkina, E. V.

2012-11-01

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 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

23

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

24

Antiapoptotic activity of argon and xenon.  

PubMed

Although chemically non-reactive, inert noble gases may influence multiple physiological and pathological processes via hitherto uncharacterized physical effects. Here we report a cell-based detection system for assessing the effects of pre-defined gas mixtures on the induction of apoptotic cell death. In this setting, the conventional atmosphere for cell culture was substituted with gas combinations, including the same amount of oxygen (20%) and carbon dioxide (5%) but 75% helium, neon, argon, krypton, or xenon instead of nitrogen. The replacement of nitrogen with noble gases per se had no effects on the viability of cultured human osteosarcoma cells in vitro. Conversely, argon and xenon (but not helium, neon, and krypton) significantly limited cell loss induced by the broad-spectrum tyrosine kinase inhibitor staurosporine, the DNA-damaging agent mitoxantrone and several mitochondrial toxins. Such cytoprotective effects were coupled to the maintenance of mitochondrial integrity, as demonstrated by means of a mitochondrial transmembrane potential-sensitive dye and by assessing the release of cytochrome c into the cytosol. In line with this notion, argon and xenon inhibited the apoptotic activation of caspase-3, as determined by immunofluorescence microscopy coupled to automated image analysis. The antiapoptotic activity of argon and xenon may explain their clinically relevant cytoprotective effects. PMID:23907115

Spaggiari, Sabrina; Kepp, Oliver; Rello-Varona, Santiago; Chaba, Kariman; Adjemian, Sandy; Pype, Jan; Galluzzi, Lorenzo; Lemaire, Marc; Kroemer, Guido

2013-08-15

25

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

26

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

27

Gas-phase silicon micromachining with xenon difluoride  

Microsoft Academic Search

Xenon difluoride is a gas phase, room temperature, isotropic silicon etchant with extremely high selectivity to many materials commonly used in microelectromechancial systems, including photoresists, aluminum, and silicon dioxide. Using a simple vacuum system, the effects of etch aperture and loading were explored for etches between 10 and 200 micrometers . Etch rates as high as 40 micrometers \\/minute were

Floy I. Chang; Richard Yeh; Gisela Lin; Patrick B. Chu; Eric G. Hoffman; Ezekiel J. Kruglick; Kristofer S. Pister; Michael H. Hecht

1995-01-01

28

The potential energy surfaces of the ground and excited states of carbon dioxide molecule  

NASA Astrophysics Data System (ADS)

Potential energy surfaces (PESs) of the 1Al(1?g+), 1B2 and 3B2 electronic states of CO2 have been computed as a function of the two bond distances and the bond angle. The calculations were based on the complete active space self consistent field (CASSCF) and multiconfigurational second-order perturbation theory (CASPT2) electronic structure models. From our calculations no crossing point between 1B2 and 3B2 states was found, but there is a crossing point located between 1B2 and 3A2 state on the PESs. The energy of the crossing point is lie 0.23 eV above the CO + O (3P), which is in agreement with the value of 0.27 eV on the experiment. This implies that the mechanism of the recombination of an oxygen atom with a carbon monoxide molecule: CO( X 1?+, ?) + O(3P)?3CO2*?1CO2*?CO( X 1?+, ? = 0) + O(1 D) may occur through the 3A2 state crossing the 1B2 state. The equilibrium geometries and adiabatic excitation energies of 1,3B2, 1,3A2 states of CO2 were reported and discussed in this paper, too.

Ma, Yingying; Peng, Liang; Zhang, Hao; Yu, Jian-Guo

2014-12-01

29

Thin uranium dioxide films with embedded xenon  

NASA Astrophysics Data System (ADS)

The ion beam assisted deposition (IBAD) method was applied as a means to incorporate Xe atoms into UO2 films to fabricate reference samples that are representative of an irradiated nuclear fuel without an actual reactor irradiation. The characterization of Xe content and the films microstructure was performed using Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDXS). A set of UO2 films with excellent control of Xe content ranging from ˜1.0 to 4.0 at.% was fabricated. The thin UO2 films deposited on single crystalline 4H-SiC substrates were found to be composed primarily of randomly oriented nanocrystalline grains and a small fraction of amorphous material. TEM analysis detected no Xe-filled bubbles at a scale of 2.5 nm or larger.

Usov, I. O.; Dickerson, R. M.; Dickerson, P. O.; Hawley, M. E.; Byler, D. D.; McClellan, K. J.

2013-06-01

30

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

31

Xenon in chondritic metal.  

NASA Astrophysics Data System (ADS)

The authors report xenon isotopic abundances observed in the stepwise release of noble gases in a high-purity metal separate of the Forest Vale (H4) chondrite. They identify a 244Pu-derived fission component, due to recoils into the metal, a cosmic-ray-produced spallation component and a new trapped component which is isotopically distinct from known solar system reservoirs. The authors discuss several processes which might account for observed isotopic shifts and conclude that the signature of FVM xenon may provide clues regarding the origin of chondritic metal.

Marti, K.; Kim, J. S.; Lavielle, B.; Pellas, P.; Perron, C.

1989-10-01

32

Molecules  

NSDL National Science Digital Library

The Switzerland-based society, Molecular Diversity Preservation International (MDPI) provides this free, online journal, Molecules. This journal of synthetic and natural product chemistry encourages chemists to publish their experimental detail, particularly synthetic procedures and characterization information. "Any scattered unassembled experimental data for individual compounds which is conventionally not publishable is particularly welcomed," says the site. The idea is to get information out as quickly as possible to the scientific community. To access Molecules, follow the instructions on how to request a username and password.

1995-01-01

33

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.

2013-09-26

34

NMR of laser-polarized xenon in human?blood  

PubMed Central

By means of optical pumping with laser light it is possible to enhance the nuclear spin polarization of gaseous xenon by four to five orders of magnitude. The enhanced polarization has allowed advances in nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI), including polarization transfer to molecules and imaging of lungs and other void spaces. A critical issue for such applications is the delivery of xenon to the sample while maintaining the polarization. Described herein is an efficient method for the introduction of laser-polarized xenon into systems of biological and medical interest for the purpose of obtaining highly enhanced NMR/MRI signals. Using this method, we have made the first observation of the time-resolved process of xenon penetrating the red blood cells in fresh human blood—the xenon residence time constant in the red blood cells was measured to be 20.4 ± 2 ms. The potential of certain biologically compatible solvents for delivery of laser-polarized xenon to tissues for NMR/MRI is discussed in light of their respective relaxation and partitioning properties. PMID:8917521

Bifone, A.; Song, Y.-Q.; Seydoux, R.; Taylor, R.?E.; Goodson, B.?M.; Pietrass, T.; Budinger, T.?F.; Navon, G.; Pines, A.

1996-01-01

35

The impact of carbon dioxide and helium insufflation on experimental liver metastases, macrophages, and cell adhesion molecules  

Microsoft Academic Search

Background: Laparoscopic insufflation, proposed to reduce hepatic perfusion, may enhance hepatic tumor spread. It is unknown whether intraabdominal pressure or the gas itself influences hepatic tumor growth. In contrast to carbon dioxide, the alternative gas helium is believed to reduce malignant cell growth. Methods: For this study, 36 WAG\\/Rij rats were randomized in two experimental groups. The animals were laparoscopically

C. N. Gutt; T. Gessmann; P. Schemmer; A. Mehrabi; Th. Schmandra; Z.-G. Kim

2003-01-01

36

Thermodynamics of Liquid Mixtures of Xenon with Alkanes: (Xenon + n-Butane) and (Xenon + Isobutane)  

E-print Network

The total vapor pressure of liquid mixtures of (xenon + n-butane) has been measured at 182.34 and 195.49 K, and of (xenon + isobutane) at 195.49 K. The liquid molar volumes have also been measured at 182.34 K for both systems. The mixtures follow the behavior already found for other (xenon + alkane) mixtures, i.e., E negative deviations from Raoult’s law, negative excess molar Gibbs energies (Gm) and negative excess molar

Eduardo J. M. Filipe; Luís F. G. Martins; Jorge C. G. Calado; Clare Mccabe; George Jackson

1999-01-01

37

Degeneracy in cryptophane-xenon complex formation in aqueous solution.  

PubMed

The reversible binding of xenon to cryptophane molecules is currently heavily explored for application as a reporter system in NMR. Herein, for aqueous solution, first evidence of degenerate exchange in this host-guest system is presented based on a novel approach using hyperpolarized (129)Xe. PMID:25516919

Korchak, Sergey; Kilian, Wolfgang; Mitschang, Lorenz

2015-01-31

38

ISOTOPIC COMPOSITION OF PRIMORDIAL XENON  

Microsoft Academic Search

A large excess of Xe¹²⁹ and secondary anomalous abundances for ; many of the other isotopes of xenon were previously reported for the meteorite, ; Richardton. Similar secondary anomalies in xenon are reported for the meteorite ; Murray. For every isotope other than Xe¹²⁹, the ratio of the Murray ; percent abundance to the Richardton percent abundance was the same

J. Reynolds

1960-01-01

39

Liquid xenon excimer laser  

SciTech Connect

The characteristics of the first excimer laser and the history of its creation are presented. The threshold lasing conditions and the modern theory of active media are considered, and the prospects for the development of excimer lasers operating on condensed inert gases are discussed. It is shown that in experiments on pumping liquid xenon, lasing was obtained simultaneously on excimers of several types, including excimers in liquid and gas phases. (special issue devoted to the 80th anniversary of academician n g basov's birth)

Molchanov, Alexander G [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2003-01-31

40

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

41

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

42

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

43

Creation of Defects and Interactions Between Defects and Small Molecules on Titanium DIOXIDE(110 Surfaces: Comparative Shg and XPS Studies  

NASA Astrophysics Data System (ADS)

Rutile TiO_2 surfaces, which have broad applications in photocatalysis, have been extensively studied for over two decades. Despite this research effort, large gaps exist in the basic understanding of surface structure, methods by which surface defects can be created, and interactions between small molecules and these surfaces. In this thesis, Second Harmonic Generation (SHG) is used to probe the structure of TiO_2 (110) surfaces. These experiments show that above band-gap UV photons create oxygen-vacancy defects on single -crystal surfaces, a process previously considered unlikely. This defect-creation saturates after only 360 J/cm^2 total UV fluence. Further understanding of UV defect creation is gained through parallel X-ray Photoelectron Spectroscopy (XPS) experiments. Some Ultraviolet Photoelectron Spectroscopy (UPS) studies are also presented here, but this technique is rapidly abandoned due to difficulties in interpreting the UPS spectra without ambiguity. These studies rule out contaminant-driven interactions and allow quantification of the defects produced by UV illumination. The number of defects produced by UV at saturation is consistent with oxygen vacancies at 1/6 of the total oxygen sites present on the surface. In addition, both SHG and XPS are used to examine interactions between these defects and small molecules (interactions between defects and rm O_2, H_2O, HCOOH, and N_2 O are presented here). The results of these experiments are then compared to previous studies present in the literature on other molecules. In compiling experiments done with many different molecules, it becomes clear that the observed defect-molecule interactions correlate with the electron affinity of the molecule used. If the molecule has an electron affinity it will interact with surface defects, resulting in removal of the defect signature. It is unclear however, that removal of the defect signature in this way necessarily implies that the surface has been physically healed to become stoichiometric. XPS indicates that this is the case, but detailed study of the SHG experiments suggests that it is possible that healing may sometimes occur through the formation of rm Ti^ {4+}{:}X^- complexes from a rm Ti^{3+} defect and an electronegative molecule X. Indeed it appears that rm Ti^{4+}{:}O _sp{2}{-} complexes are present on all TiO_2(110) surfaces.

Shultz, Ashley Nicholle

44

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

45

The Enriched Xenon Observatory  

SciTech Connect

The Enriched Xenon Observatory (EXO) experiment will search for neutrinoless double beta decay of {sup 136}Xe. The EXO Collaboration is actively pursuing both liquid-phase and gas-phase Xe detector technologies with scalability to the ton-scale. The search for neutrinoless double beta decay of {sup 136}Xe is especially attractive because of the possibility of tagging the resulting Ba daughter ion, eliminating all sources of background other than the two neutrino decay mode. EXO-200, the first phase of the project, is a liquid Xe time projection chamber with 200 kg of Xe enriched to 80% in {sup 136}Xe. EXO-200, which does not include Ba-tagging, will begin taking data in 2009, with two-year sensitivity to the half-life for neutrinoless double beta decay of 6.4x10{sup 25} years. This corresponds to an effective Majorana neutrino mass of 0.13 to 0.19 eV.

Dolinski, M. J. [Stanford University Physics Department, 382 Via Pueblo Mall, Stanford, CA 94305-4060 (United States)

2009-12-17

46

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

47

Solubilized xenon 133 lung scintigraphy  

SciTech Connect

Lung scanning using solubilized xenon 133 can provide important information concerning both pulmonary perfusion and ventilation. This technique proved valuable in establishing the diagnosis of congenital lobar emphysema in a 7-month-old baby.

Oates, E.; Sarno, R.C.

1988-11-01

48

High-efficiency plasma display panel based on a high xenon mole fraction  

SciTech Connect

The luminance efficiency of a plasma display panel is directly related to the vacuum-ultraviolet (VUV) light emitted from excited xenon atoms and molecules. The emission efficiency of 173 nm VUV light is measured in terms of the xenon mole fraction ({chi}) and is shown to become considerably enhanced at a high xenon mole fraction. For example, the emission efficiency at {chi}=0.35 under a pressure of 400 Torr is more than 2.5 times that at {chi}=0.1. The experimental data agree remarkably well with theoretical predictions.

Uhm, Han S. [Department of Molecular Science and Technology, Ajou University, Suwon 443-949 (Korea, Republic of); Son, Chang G.; Hong, Byung H.; Choi, Eun H. [PDP Research Center, Department of Electrophysics, Kwangwoon University, Seoul 139-701 (Korea, Republic of)

2009-09-15

49

CMD-3 Liquid Xenon Calorimeter's signals processing  

E-print Network

CMD-3 Liquid Xenon Calorimeter's signals processing for timing measurements. Leonid Epshtein Budker connected to constitute 264 «towers»; signal of each tower is processed by electronic channel. Liquid Xenon

50

Xenon forms stable compound with fluorine  

NASA Technical Reports Server (NTRS)

Experiments show that xenon and fluorine combine readily at 400 deg C to form xenon tetrafluoride, which is colorless, crystalline, chemically stable and solid at room temperature. This process can be used for the separation of xenon from mixtures with other noble gases.

Claassen, H. H.; Malm, J. G.; Selig, H. H.

1966-01-01

51

The XENON dark matter experiment , E. Aprileb  

E-print Network

The XENON dark matter experiment T. Shutta , E. Aprileb , E. Baltzb , K. Gibonib , P. Majewskib , M Laboratory, Livermore, CA 94550 We report on progress of the XENON collaboration, which is developing a liquid xenon time projection chamber technology for use in a very-large-mass dark matter experiment

McDonald, Kirk

52

Generation of dihydrogen molecule and hydrosilylation of carbon dioxide catalyzed by zinc hydride complex: theoretical understanding and prediction.  

PubMed

Generation of H2 from methanol/water and hydrosilylation of CO2 catalyzed by [tris(2-pyridylthio)methyl]zinc hydride [?(3)-Tptm]ZnH 1 were investigated with DFT and MP2 methods. The hydrosilylation of CO2 occurs via the CO2 insertion into the Zn-H bond of 1 followed by the metathesis of a Zn-(?(1)-OCOH) bond with hydrosilane to yield silyl formate and regenerate 1. The CO2 insertion easily occurs, but the metathesis is difficult because of the formation of a very stable Zn-(?(2)-O2CH) species before the metathesis. The ?G°(‡) value of the metathesis with triethoxysilane is much smaller than that with phenylsilane because electronegative methoxy groups stabilize the transition state bearing hypervalent Si center, which is consistent with the experimental result that triethoxysilane is used in the hydrosilylation of CO2. It is theoretically predicted here that hydrosilane with two electronegative OEt groups or one to three F groups can be applied to this reaction. In the generation of H2 from methanol/water by 1, the first step is the metathesis of 1 with the O-H bond of methanol/water to produce [?(3)-Tptm]Zn(OMe)/[k(3)-Tptm]Zn(OH) and dihydrogen molecule. The next step is the metathesis of the Zn-OMe/Zn-OH bond with hydrosilane to yield silyl ether and regenerate 1. The first metathesis is rate-determining but the second one occurs with very small activation energy, indicating that various hydrosilanes can be applied to this reaction. PMID:25076412

Deshmukh, Milind Madhusudan; Sakaki, Shigeyoshi

2014-08-18

53

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

54

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

55

Latest results from XENON100 data  

E-print Network

XENON100 is the current phase of the XENON dark matter program, which aims for the direct detection of WIMPs with liquid xenon time-projection chambers. We present the status of the experiment after 224.6 live days taken in 2011 and 2012 during which the detector successfully improved in terms of more calibration data, higher xenon purity, lower threshold and better background removal. The analysis has yielded no evidence for dark matter interactions. The status of the next generation XENON1T detector will be briefly described.

Luca Scotto Lavina; for the XENON100 Collaboration

2013-05-01

56

Molecular dynamics simulation of vibrational energy relaxation of highly excited molecules in fluids. III. Equilibrium simulations of vibrational energy relaxation of azulene in carbon dioxide  

NASA Astrophysics Data System (ADS)

The expressions for vibrational energy relaxation (VER) rates of polyatomic molecules in terms of equilibrium capacity time correlation functions (TCFs) derived in the first paper of this series [J. Chem. Phys. 110, 5273 (1999)] are used for the investigation of VER of azulene in carbon dioxide at low (3.2 MPa) and high (270 MPa) pressure. It is shown that for both cases the VER times evaluated on the basis of the same potential model via solute-solvent interaction capacity TCFs by means of equilibrium molecular dynamics (EMD) simulations satisfactorily agree with the nonequilibrium (NEMD) molecular dynamics [J. Chem. Phys. 110, 5286 (1999)] and experimental [J. Chem. Phys. 105, 3121 (1996)] results as well. Thus it follows that these methods can complement each other in characterizing VER from different points of view. Although more computational power and refined methods of dealing with simulated data are required for EMD simulations, they allow the use of powerful tools of equilibrium statistical mechanics for investigating the relaxation process. To this end, an analysis of VER mechanisms on the basis of normal mode and atomic representations is carried out. The influence of temperature and CO2 pressure on azulene normal mode spectra and solvent assisted intermode coupling in connection with the eigenvector structure is investigated in great detail. The normal mode capacity cross-correlation matrix reveals the significance of intermode coupling, which significantly contributes to intramolecular vibrational energy redistribution (IVR). As a new concept, partial normal mode relaxation rates are introduced. It is shown that these rates demonstrate similar properties as the energy exchange rates through particular normal modes in nonequilibrium simulations. Atomic spectra and friction coefficients are characterized by a complicated frequency dependence due to contributions from many normal modes. Atomic capacity TCFs and partial relaxation rates are analyzed and reveal a similar picture to that obtained from NEMD simulations. These results show that VER and IVR cannot be separated from each other and have to be considered as mutually connected processes.

Heidelbach, C.; Vikhrenko, V. S.; Schwarzer, D.; Fedchenia, I. I.; Schroeder, J.

1999-11-01

57

Marvelous Molecules  

NSDL National Science Digital Library

Presented by the New York Hall of Science, the Marvelous Molecules Web site accompanies its physical museum's exhibit by offering descriptions and additional online activities. The first page "About the Exhibit" shows what is available at the museum and gives interesting facts about molecules. The next page "All About Molecules" explains what a molecule is and gives eight examples (e.g., aspirin and carbon dioxide). The next page called "Marvelous Activities" contains several activities, one of which is the "How Many Molecules Are You?" interactive exercise. Here, users input their weight to see how many molecules their bodies contain and how that compares to other living things. Geared mainly towards kids, the Web site should give all people a fun way to learn.

1969-12-31

58

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

59

Xenon preconditioning: molecular mechanisms and biological effects  

PubMed Central

Xenon is one of noble gases and has been recognized as an anesthetic for more than 50?years. Xenon possesses many of the characteristics of an ideal anesthetic, but it is not widely applied in clinical practice mainly because of its high cost. In recent years, numerous studies have demonstrated that xenon as an anesthetic can exert neuroprotective and cardioprotective effects in different models. Moreover, xenon has been applied in the preconditioning, and the neuroprotective and cardioprotective effects of xenon preconditioning have been investigated in a lot of studies in which some mechanisms related to these protections are proposed. In this review, we summarized these mechanisms and the biological effects of xenon preconditioning. PMID:23305274

2013-01-01

60

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

61

Xenon and Krypton in the Bruderheim Meteorite  

Microsoft Academic Search

In a series of heating experiments, xenon, radiogenic XeR, and krypton con- tents, and the xenon and krypton isotopic composition of the Bruderheim meteorite were studied for the separated minerals feldspar, pyroxene, olivine, and trollire and for numerous chondrule fractions. Important differences among the individual minerals and between min- erals and chondrules were observed, and the following conclusions were reached:

Craig Merrihue

1966-01-01

62

Reactions of xenon with iridium- and Osmiumhexafluoride.  

PubMed

Xenon and Iridiumhexafluoride react at temperatures above room temperature forming XeF+IrF6-. In presence of SbF5 FXe+IrSbF11- is formed. Xenon and Osmiumhexafluoride form in solution a blue charge transfer complex that cannot be isolated as a solid. PMID:24169702

Tamadon, Farhad; Seidel, Stefan; Seppelt, Konrad

2013-01-01

63

Results from the XENON1T Demonstrator  

NASA Astrophysics Data System (ADS)

The current stage of the XENON Dark Matter Search project, XENON100, constitutes one of the best performing dark matter experiments in the world, setting the best upper limit on the cross section for spin independent WIMP-nucleus scattering. The next generation detector within the program, XENON1T, is at the end of its design phase and construction will start in the present year. XENON1T is a liquid xenon dual-phase time projection chamber with a 1 Ton fiducial mass, and it will improve the present XENON100 limit by 2 orders of magnitude. However, the increase in mass in the new detector presents several technological challenges. In order to address the required improvements, a fully operational prototype of the detector, the XENON1T Demonstrator, has been built at Columbia University. In this talk we will present the main results of the XENON1T Demonstrator R&D program, comprising high-speed recirculation on a full-scale cryogenic system, the observation of electron drift over 30 cm, and the operation of the detector with a cathode high voltage exceeding 30kV and preliminary results of the new 60 and 100 cm setups.

Contreras, Hugo; Aprile, Elena; Budnik, Ranny; Goetzke, Luke; Plante, Guillaume; Messina, Marcello; Rizzo, Alfio; Melgarejo, Antonio; Naganoma, Junji; Chaguine, Petr

2013-04-01

64

Optical and electron spin resonance studies of xenon-nitrogen-helium condensates containing nitrogen and oxygen atoms.  

PubMed

We present the first observations of excimer XeO* molecules in molecular nitrogen films surrounding xenon cores of nanoclusters. Multishell nanoclusters form upon the fast cooling of a helium jet containing small admixtures of nitrogen and xenon by cold helium vapor (T = 1.5 K). Such nanoclusters injected into superfluid helium aggregate into porous impurity-helium condensates. Passage of helium gas with admixtures through a radio frequency discharge allows the storage of high densities of radicals stabilized in impurity-helium condensates. Intense recombination of the radicals occurs during destruction of such condensates and generates excited species observable because of optical emission. Rich spectra of xenon-oxygen complexes have been detected upon destruction of xenon-nitrogen-helium condensates. A xenon environment quenches metastable N((2)D) atoms but has a much weaker effect on the luminescence of N((2)P) atoms. Electron spin resonance spectra of N((4)S) atoms trapped in xenon-nitrogen-helium condensates have been studied. High local concentrations of nitrogen atoms (up to 10(21) cm(-3)) stabilized in xenon-nitrogen nanoclusters have been revealed. PMID:25353614

Boltnev, Roman E; Bykhalo, Igor B; Krushinskaya, Irina N; Pelmenev, Alexander A; Khmelenko, Vladimir V; Mao, Shun; Meraki, Adil; Wilde, Scott C; McColgan, Patrick T; Lee, David M

2015-03-19

65

Xenon geochronology of Schwarzwald pitchblendes  

Microsoft Academic Search

The uranium- \\/fission-xenon systems in eleven samples selected from three occurrences in the Schwarz- wald were investigated\\u000a (Menzenschwand, Wittichen, M?llenbach). Relationships between mineralogical properties, Xe release profiles and Xe-Xe age\\u000a spectra provide criteria for sample suitability for U-Xe and Xe-Xe dating and interpretation of the Xe-Xe age spectra. U leaching\\u000a from pitchblendes was demonstrated for three of the Wittichen samples,

A. P. Meshik; H. J. Lippolt; Yu. M. Dymkov

2000-01-01

66

Energy transfer studies in krypton-xenon mixtures excited in a cooled DC discharge  

Microsoft Academic Search

The VUV spectrum of gaseous mixtures of krypton with a small amount of xenon added was investigated in the range 115–200 nm.\\u000a The mixtures were excited in a capillary DC discharge where the capillary could be cooled by using liquid nitrogen. The mixed\\u000a molecule band around the Xe I resonance line at ? = 147 nm and the mixed molecule

B. Krylov; G. Gerasimov; A. Morozov; A. Arnesen; R. Hallin; F. Heijkenskjold

2000-01-01

67

Focused electron-beam-induced etching of silicon dioxide  

Microsoft Academic Search

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

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

2005-01-01

68

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

69

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

70

Pure xenon hexafluoride prepared for thermal properties studies  

NASA Technical Reports Server (NTRS)

Preparation of a xenon hexafluoride and sodium fluoride salt yields a sample of the highest possible purity for use in thermal measurements. The desired hexafluoride can easily be freed from the common contaminants, xenon tetra-fluoride, xenon difluoride, and xenon oxide tetrafluoride, because none of these compounds reacts with sodium fluoride.

Malm, J. G.; Osborne, D. W.; Schreiner, F.

1967-01-01

71

The atmosphere of Mars - Detection of krypton and xenon  

NASA Technical Reports Server (NTRS)

Krypton and xenon have been discovered in the Martian atmosphere with the mass spectrometer on the second Viking lander. Krypton is more abundant than xenon. The relative abundances of the krypton isotopes appear normal, but the ratio of xenon-129 to xenon-132 is enhanced on Mars relative to the terrestrial value for this ratio. Some possible implications of these findings are discussed.

Owen, T.; Biemann, K.; Biller, J. E.; Lafleur, A. L.; Rushneck, D. R.; Howarth, D. W.

1976-01-01

72

Hyperpolarized Xenon for NMR and MRI Applications  

PubMed Central

Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) suffer from intrinsic low sensitivity because even strong external magnetic fields of ~10 T generate only a small detectable net-magnetization of the sample at room temperature 1. Hence, most NMR and MRI applications rely on the detection of molecules at relative high concentration (e.g., water for imaging of biological tissue) or require excessive acquisition times. This limits our ability to exploit the very useful molecular specificity of NMR signals for many biochemical and medical applications. However, novel approaches have emerged in the past few years: Manipulation of the detected spin species prior to detection inside the NMR/MRI magnet can dramatically increase the magnetization and therefore allows detection of molecules at much lower concentration 2. Here, we present a method for polarization of a xenon gas mixture (2-5% Xe, 10% N2, He balance) in a compact setup with a ca. 16000-fold signal enhancement. Modern line-narrowed diode lasers allow efficient polarization 7 and immediate use of gas mixture even if the noble gas is not separated from the other components. The SEOP apparatus is explained and determination of the achieved spin polarization is demonstrated for performance control of the method. The hyperpolarized gas can be used for void space imaging, including gas flow imaging or diffusion studies at the interfaces with other materials 8,9. Moreover, the Xe NMR signal is extremely sensitive to its molecular environment 6. This enables the option to use it as an NMR/MRI contrast agent when dissolved in aqueous solution with functionalized molecular hosts that temporarily trap the gas 10,11. Direct detection and high-sensitivity indirect detection of such constructs is demonstrated in both spectroscopic and imaging mode. PMID:22986346

Witte, Christopher; Kunth, Martin; Döpfert, Jörg; Rossella, Federica; Schröder, Leif

2012-01-01

73

Extreme confinement of xenon by cryptophane-111 in the solid state.  

PubMed

Solids that sorb, capture and/or store the heavier noble gases are of interest because of their potential for transformative rare gas separation/production, storage, or recovery technologies. Herein, we report the isolation, crystal structures, and thermal stabilities of a series of xenon and krypton clathrates of (±)-cryptophane-111 (111). One trigonal crystal form, Xe@111?y(solvent), is exceptionally stable, retaining xenon at temperatures of up to about 300?°C. The high kinetic stability is attributable not only to the high xenon affinity and cage-like nature of the host, but also to the crystal packing of the clathrate, wherein each window of the molecular container is blocked by the bridges of adjacent containers, effectively imprisoning the noble gas in the solid state. The results highlight the potential of discrete molecule materials exhibiting intrinsic microcavities or zero-dimensional pores. PMID:25504739

Joseph, Akil I; Lapidus, Saul H; Kane, Christopher M; Holman, K Travis

2015-01-26

74

Nitrogen Dioxide  

MedlinePLUS

... here: EPA Home Air & Radiation Six Common Pollutants Nitrogen Dioxide Announcements October 5, 2012 - EPA proposes revisions to NO 2 monitoring requirements Learn More Nitrogen dioxide (NO 2 ) is one of a group ...

75

Results from the XENON100 Dark Matter Search Experiment  

E-print Network

XENON100 is a liquid xenon time projection chamber built to search for rare collisions of hypothetical, weakly interacting massive particles (WIMPs), which are candidates for the dark matter in our universe, with xenon atoms. Operated in a low-background shield at the Gran Sasso Underground Laboratory in Italy, XENON100 has reached the unprecedented background level of XENON1T detector in Hall B of the Gran Sasso Laboratory will start in late 2012.

Laura Baudis; for the XENON Collaboration

2012-03-07

76

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

77

Measurement of radon and xenon binding to a cryptophane molecular host  

PubMed Central

Xenon and radon have many similar properties, a difference being that all 35 isotopes of radon (195Rn–229Rn) are radioactive. Radon is a pervasive indoor air pollutant believed to cause significant incidence of lung cancer in many geographic regions, yet radon affinity for a discrete molecular species has never been determined. By comparison, the chemistry of xenon has been widely studied and applied in science and technology. Here, both noble gases were found to bind with exceptional affinity to tris-(triazole ethylamine) cryptophane, a previously unsynthesized water-soluble organic host molecule. The cryptophane–xenon association constant, Ka = 42,000 ± 2,000 M-1 at 293 K, was determined by isothermal titration calorimetry. This value represents the highest measured xenon affinity for a host molecule. The partitioning of radon between air and aqueous cryptophane solutions of varying concentration was determined radiometrically to give the cryptophane–radon association constant Ka = 49,000 ± 12,000 M-1 at 293 K. PMID:21690357

Jacobson, David R.; Khan, Najat S.; Collé, Ronald; Fitzgerald, Ryan; Laureano-Pérez, Lizbeth; Bai, Yubin; Dmochowski, Ivan J.

2011-01-01

78

PIERS ONLINE, VOL. 5, NO. 7, 2009 637 Ventilation Efficiency and Carbon Dioxide (CO2) Concentration  

E-print Network

PIERS ONLINE, VOL. 5, NO. 7, 2009 637 Ventilation Efficiency and Carbon Dioxide (CO2) Concentration complex organic molecules being broken down to simpler molecules, such as carbon dioxide and water. Carbon dioxide waste is removed from the body through respiration. Carbon dioxide content in fresh air

Halgamuge, Malka N.

79

XENON dark matter searches: Results and the future  

SciTech Connect

XENON100 is a dark matter search experiment looking for elastic WIMP scattering using a 62 kg liquid target. WIMP search data from XENON100 published in 2012 has set the world's strongest limits on WIMP-nucleus spinindependent, elastic scattering. It has also set the strongest limits on WIMP-nucleus spin-dependent scattering considering neutron scattering only, and competitive limits considering proton scattering only. The successor experiment to XENON100, XENON1T, is currently under construction, with commissioning scheduled to begin in 2014. XENON1T's design goal is a 100 fold increase in sensitivity for elastic WIMP searches over XENON100.

Brown, Andrew [Physics Department, Purdue University - 525 Northwestern Ave., West Lafayette, IN 47907 (United States); Collaboration: XENON Collaboration

2014-06-24

80

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

81

Xenon lighting adjusted to plant requirements  

NASA Technical Reports Server (NTRS)

Xenon lamps are available as low and high power lamps with relatively high efficiency and a relatively long lifetime up to several thousand hours. Different construction types of short-arc and long-arc lamps permit a good adaptation to various applications in projection and illumination techniques without substantial changes of the spectral quality. Hence, the xenon lamp was the best choice for professional technical purposes where high power at simultaneously good spectral quality of the light was required. However, technical development does not stand still. Between the luminous efficacy of xenon lamps of 25-50 lm/W and the theoretical limit for 'white light' of 250 lm/W is still much room for improvement. The present development mainly favors other lamp types, like metal halide lamps and fluorescent lamps for commercial lighting purposes. The enclosed sections deal with some of the properties of xenon lamps relevant to plant illumination; particularly the spectral aspects, the temporal characteristics of the emission, and finally the economy of xenon lamps will be addressed. Due to radiation exceeding the natural global radiation in both the ultraviolet (UV) and the infrared (IR) regions, filter techniques have to be included into the discussion referring to the requirements of plant illumination. Most of the presented results were obtained by investigations in the GSF phytotron or in the closed Phytocell chambers of the University of Erlangen. As our experiences are restricted to area plant illumination rather than spot lights our discussion will concentrate on low pressure long-arc xenon lamps which are commonly used for such plant illuminations. As the spectral properties of short-arc lamps do not differ much from those of long-arc lamps most of our conclusions will be valid for high pressure xenon lamps too. These lamps often serve as light sources for small sun simulators and for monochromators which are used for action spectroscopy of plant responses.

Koefferlein, M.; Doehring, T.; Payer, Hans D.; Seidlitz, H. K.

1994-01-01

82

Separation of rare gases and chiral molecules by selective binding in porous organic cages  

SciTech Connect

Abstract: The rare gases krypton, xenon, and radon pose both an economic opportunity and a potential environmental hazard. Xenon is used in commercial lighting, medical imaging, and anesthesia, and can sell for $5,000 per kilogram. Radon, by contrast, Is naturally radioactive and the second largest cause of lung cancer, and radioactive xenon, 133Xe, was a major pollutant released In the Fukushima Daiichi Nuclear Power Plant disaster. We describe an organic cage molecule that can capture xenon and radon with unprecedented selectivity, suggesting new technologies for environmental monitoring, removal of pollutants, or the recovery of rare, valuable elements from air.

Chen, Linjiang; Reiss, Paul S.; Chong, Samantha Y.; Holden, Daniel; Jelfs, Kim E.; Hasell, Tom; Little, Marc A.; Kewley, Adam; Briggs, Michael E.; Stephenson, Andrew; Thomas, K. M.; Armstrong, Jayne A.; Bell, Jon; Busto, Jose; Noel, Raymond; Liu, Jian; Strachan, Denis M.; Thallapally, Praveen K.; Cooper, Andrew I.

2014-10-31

83

Xenon Isotope Releases from Buried Transuranic Waste  

NASA Astrophysics Data System (ADS)

Xenon is an inert rare gas produced as a fission product in nuclear reactors and through spontaneous fission of some transuranic isotopes. Thus, xenon will be released from buried transuranic waste. Two complementary methods are used to measure xenon isotopes: radiometric analysis for short-lived radioxenon isotopes and mass spectrometry for detection of stable xenon isotopes. Initial measurements near disposal facilities at the U.S. Department of Energy's Hanford Site show radioxenon and stable xenon isotopic signatures that are indicative of transuranic waste. Radioxenon analysis has greater sensitivity due to the lower background concentrations and indicates spontaneous fission due to the short half life of the isotopes. Stable isotope ratios may be used to distinguish irradiated fuel sources from pure spontaneous fission sources and are not as dependent on rapid release from the waste form. The release rate is dependent on the type of waste and container integrity and is the greatest unknown in application of this technique. Numerical multi-phase transport modeling of burial grounds at the Idaho National Engineering and Environmental Laboratory indicates that, under generalized conditions, the radioxenon isotopes will diffuse away from the waste and be found in the soil cap and adjacent to the burial ground at levels many orders of magnitude above the detection limit.

Dresel, P. E.; Waichler, S. R.; Kennedy, B. M.; Hayes, J. C.; McIntyre, J. I.; Giles, J. R.; Sondrup, A. J.

2004-12-01

84

Direct Dark Matter Search with XENON100  

E-print Network

The XENON100 experiment is the second phase of the XENON program for the direct detection of the dark matter in the universe. The XENON100 detector is a two-phase Time Projection Chamber filled with 161 kg of ultra pure liquid xenon. The results from 224.6 live days of dark matter search with XENON100 are presented. No evidence for dark matter in the form of WIMPs is found, excluding spin-independent WIMP-nucleon scattering cross sections above 2 $\\times$ 10$^{-45}$ cm$^2$ for a 55 GeV/c$^2$ WIMP at 90% confidence level (C.L.). The most stringent limit is established on the spin-dependent WIMP-neutron interaction for WIMP masses above 6 GeV/c$^2$, with a minimum cross section of 3.5 $\\times$ 10$^{-40}$ cm$^2$ (90% C.L.) for a 45 GeV/c$^2$ WIMP. The same dataset is used to search for axions and axion-like-particles. The best limits to date are set on the axion-electron coupling constant for solar axions, $g_{Ae}$ < 7.7 $\\times$ 10$^{-12}$ (90% C.L.), and for axion-like-particles, $g_{Ae}$ < 1 $\\times$ 10$^{-12}$ (90% C.L.) for masses between 5 and 10 keV/c$^2$.

S. E. A. Orrigo; for the XENON Collaboration

2015-01-14

85

Direct Dark Matter Search with XENON100  

E-print Network

The XENON100 experiment is the second phase of the XENON program for the direct detection of the dark matter in the universe. The XENON100 detector is a two-phase Time Projection Chamber filled with 161 kg of ultra pure liquid xenon. The results from 224.6 live days of dark matter search with XENON100 are presented. No evidence for dark matter in the form of WIMPs is found, excluding spin-independent WIMP-nucleon scattering cross sections above 2 $\\times$ 10$^{-45}$ cm$^2$ for a 55 GeV/c$^2$ WIMP at 90% confidence level (C.L.). The most stringent limit is established on the spin-dependent WIMP-neutron interaction for WIMP masses above 6 GeV/c$^2$, with a minimum cross section of 3.5 $\\times$ 10$^{-40}$ cm$^2$ (90% C.L.) for a 45 GeV/c$^2$ WIMP. The same dataset is used to search for axions and axion-like-particles. The best limits to date are set on the axion-electron coupling constant for solar axions, $g_{Ae}$ < 7.7 $\\times$ 10$^{-12}$ (90% C.L.), and for axion-like-particles, $g_{Ae}$ < 1 $\\times$ 10...

Orrigo, S E A

2015-01-01

86

Xenon NMR measurements of permeability and tortuosity in reservoir rocks  

E-print Network

Xenon NMR measurements of permeability and tortuosity in reservoir rocks Ruopeng Wanga,b , Tina of laser-polarized xenon into the rock core. Tortuosity is determined from measurements of the time-dependent diffusion coefficient using thermal xenon in sealed samples. The initial results from a limited number

Walsworth, Ronald L.

87

SINGLE ION TRAPPING FOR THE ENRICHED XENON OBSERVATORY  

E-print Network

SINGLE ION TRAPPING FOR THE ENRICHED XENON OBSERVATORY A DISSERTATION SUBMITTED TO THE DEPARTMENT. 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

Gratta, Giorgio

88

Emission Cross Sections for Neutral Xenon Impacted by Xe+  

E-print Network

Emission Cross Sections for Neutral Xenon Impacted by Xe+ and Xe2+ by Jason D. Sommerville A Thesis Emission cross sections for Neutral Xenon Impacted by Xe+ and Xe2+ by Jason D. Sommerville is hereby for eleven transitions from the 5p5 6p configuration to the 5p5 6s configuration of neutral xenon occur- ring

King, Lyon B.

89

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

90

Heat capacity measurements of xenon on graphite  

NASA Astrophysics Data System (ADS)

Experimental results are reported on the measurement of the heat capacity of xenon absorbed on a graphitized carbon black (Graphon) in the range 60-120 K. At low temperatures (˜60 K) the heat capacity tends to the one calculated by lattice dynamics, but a pronounced maximum centered at 109 K was observed at higher temperatures, with a width at mid-height of approximately 10 K. Comparison of these results with vapor pressure isotherms of Thomy and Duval shows this maximum to be probably due to a melting transition in the adsorbed xenon layer.

de Rouffignac, Eric; Wade, William H.

1981-03-01

91

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 ?-, ß/?-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; Östman, Conny; Colmsjö, Anders

2011-04-01

92

Preparation of Neutron-activated Xenon for Liquid Xenon Detector Calibration  

E-print Network

We report the preparation of neutron-activated xenon for the calibration of liquid xenon (LXe) detectors. Gamma rays from the decay of xenon metastable states, produced by fast neutron activation, were detected and their activities measured in a LXe scintillation detector. Following a five-day activation of natural xenon gas with a Cf-252 (4 x 10^5 n/s) source, the activities of two gamma ray lines at 164 keV and 236 keV, from Xe-131m and Xe-129m metastable states, were measured at about 95 and 130 Bq/kg, respectively. We also observed three additional lines at 35 keV, 100 keV and 275 keV, which decay away within a few days. No long-lifetime activity was observed after the neutron activation.

K. Ni; R. Hasty; T. M. Wongjirad; L. Kastens; A. Manzur; D. N. McKinsey

2007-09-27

93

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

94

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

95

Diffusion of xenon (1); tridecane (2)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) xenon; (2) tridecane

Winkelmann, J.

96

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

97

Thermal Infrared Radiation and Carbon Dioxide in the Atmosphere  

E-print Network

Thermal Infrared Radiation and Carbon Dioxide in the Atmosphere Bill Satzer 3M Company #12;Outline,840 · Oxygen (O2) 209,460 · Argon (Ar) 9340 · Carbon dioxide (CO2) 394 · Methane (CH4) 1.79 · Ozone (O3) 0 wavelength of interest is about 400 times the size of a carbon dioxide molecule. Interaction is via

Olver, Peter

98

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 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

99

Site blocking in silver-exchanged zeolite Y by carbon monoxide and ethene using xenon adsorption and 129Xe NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The adsorption isotherms and 129Xe NMR chemical shifts of xenon in the zeolites NaY, AgY, and in AgY preloaded with ? 1 molecule/supercage ethene and carbon monoxide were measured at 25°C. The experimental data reveal the blocking of the silver-cation sites for xenon by the preadsorbed molecules. Ethene and CO are found to block the previously postulated two types of silver-cation species in the supercages of AgY in a different way.

Boddenberg, B.; Watermann, J.

1993-03-01

100

Spectroscopy of Ba and Ba+ deposits in solid xenon for barium tagging in nEXO  

NASA Astrophysics Data System (ADS)

Progress on a method of barium tagging for the nEXO double beta decay experiment is reported. Absorption and emission spectra for deposits of barium atoms and ions in solid xenon matrices are presented. Excitation spectra for prominent emission lines, temperature dependence, and bleaching of the fluorescence reveal the existence of different matrix sites. A regular series of sharp lines observed in Ba+ deposits is identified with some type of barium hydride molecule. Lower limits for the fluorescence quantum efficiency of the principal Ba emission transition are reported. Under current conditions, an image of fewer than or equal to 104 Ba atoms can be obtained. Prospects for imaging single Ba atoms in solid xenon are discussed.

Mong, B.; Cook, S.; Walton, T.; Chambers, C.; Craycraft, A.; Benitez-Medina, C.; Hall, K.; Fairbank, W.; Albert, J. B.; Auty, D. J.; Barbeau, P. S.; Basque, V.; Beck, D.; Breidenbach, M.; Brunner, T.; Cao, G. F.; Cleveland, B.; Coon, M.; Daniels, T.; Daugherty, S. J.; DeVoe, R.; Didberidze, T.; Dilling, J.; Dolinski, M. J.; Dunford, M.; Fabris, L.; Farine, J.; Feldmeier, W.; Fierlinger, P.; Fudenberg, D.; Giroux, G.; Gornea, R.; Graham, K.; Gratta, G.; Heffner, M.; Hughes, M.; Jiang, X. S.; Johnson, T. N.; Johnston, S.; Karelin, A.; Kaufman, L. J.; Killick, R.; Koffas, T.; Kravitz, S.; Krücken, R.; Kuchenkov, A.; Kumar, K. S.; Leonard, D. S.; Licciardi, C.; Lin, Y. H.; Ling, J.; MacLellan, R.; Marino, M. G.; Moore, D.; Odian, A.; Ostrovskiy, I.; Piepke, A.; Pocar, A.; Retiere, F.; Rowson, P. C.; Rozo, M. P.; Schubert, A.; Sinclair, D.; Smith, E.; Stekhanov, V.; Tarka, M.; Tolba, T.; Twelker, K.; Vuilleumier, J.-L.; Walton, J.; Weber, M.; Wen, L. J.; Wichoski, U.; Yang, L.; Yen, Y.-R.; Zhao, Y. B.; nEXO Collaboration

2015-02-01

101

Spectroscopy of Ba and Ba$^+$ deposits in solid xenon for barium tagging in nEXO  

E-print Network

Progress on a method of barium tagging for the nEXO double beta decay experiment is reported. Absorption and emission spectra for deposits of barium atoms and ions in solid xenon matrices are presented. Excitation spectra for prominent emission lines, temperature dependence and bleaching of the fluorescence reveal the existence of different matrix sites. A regular series of sharp lines observed in Ba$^+$ deposits is identified with some type of barium hydride molecule. Lower limits for the fluorescence quantum efficiency of the principal Ba emission transition are reported. Under current conditions, an image of $\\le10^4$ Ba atoms can be obtained. Prospects for imaging single Ba atoms in solid xenon are discussed.

B. Mong; S. Cook; T. Walton; C. Chambers; A. Craycraft; C. Benitez-Medina; K. Hall; W. Fairbank Jr.; J. B. Albert; D. J. Auty; P. S. Barbeau; V. Basque; D. Beck; M. Breidenbach; T. Brunner; G. F. Cao; B. Cleveland; M. Coon; T. Daniels; S. J. Daugherty; R. DeVoe; T. Didberidze; J. Dilling; M. J. Dolinski; M. Dunford; L. Fabris; J. Farine; W. Feldmeier; P. Fierlinger; D. Fudenberg; G. Giroux; R. Gornea; K. Graham; G. Gratta; M. Heffner; M. Hughes; X. S. Jiang; T. N. Johnson; S. Johnston; A. Karelin; L. J. Kaufman; R. Killick; T. Koffas; S. Kravitz; R. Krucken; A. Kuchenkov; K. S. Kumar; D. S. Leonard; C. Licciardi; Y. H. Lin; J. Ling; R. MacLellan; M. G. Marino; D. Moore; A. Odian; I. Ostrovskiy; A. Piepke; A. Pocar; F. Retiere; P. C. Rowson; M. P. Rozo; A. Schubert; D. Sinclair; E. Smith; V. Stekhanov; M. Tarka; T. Tolba; K. Twelker; J. -L. Vuilleumier; J. Walton; M. Weber; L. J. Wen; U. Wichoski; L. Yang; Y. -R. Yen; Y. B. Zhao

2014-10-09

102

Energy of the quasi-free electron in xenon Xianbo Shi a  

E-print Network

Energy of the quasi-free electron in xenon Xianbo Shi a , Luxi Li a , C.M. Evans a,, G.L. Findley b of trimethylamine and of N,N-dimethylaniline doped into xenon is presented as a function of xenon number density up. These data exhibit a decrease in the xenon induced shift of the dopant ionization energy near the xenon

Findley, Gary L.

103

The Significance of the Bond Angle in Sulfur Dioxide.  

ERIC Educational Resources Information Center

Examined are the illustrations and descriptions of the molecular structure of sulfur dioxide found in selected chemistry textbooks. Inconsistencies and incorrect information are indicated. It is suggested that molecules other than sulfur dioxide be used as examples of molecules for which resonance is important. (CW)

Purser, Gordon H.

1989-01-01

104

Roughening transition in adsorbed xenon multilayers  

NASA Astrophysics Data System (ADS)

Experimental evidence for a roughening transition in adsorbed xenon multilayers on palladium is presented. The clearly layer-distinctive Xe 5p photoemission is used to measure adsorption isotherms as well as the relative equilibrium population of individual Xe layers. Below a transition temperature TR xenon is adsorbed layer by layer—each layer being completed before any substantial population of the next layer occurs—with sharp first order phase transition steps for the second and third layer. Above TR the adsorption proceeds in a continuous manner, with rounded steps in the isotherms and simultaneous population of different layers. Layer population and critical temperature analysis suggests that the transition temperature is indeed the roughening temperature of the Xe film.

Miranda, R.; Albano, E. V.; Daiser, S.; Wandelt, K.; Ertl, G.

1984-03-01

105

The Large Underground Xenon (LUX) Experiment  

E-print Network

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 $2\\times 10^{-46}$ cm$^{2}$, equivalent to $\\sim$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.

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

2012-11-21

106

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

107

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

108

A cryogenic distillation column for the XENON1T experiment  

NASA Astrophysics Data System (ADS)

The XENON collaboration aims for the direct detection of cold dark matter in form of weakly interacting massive particles (WIMPs). A dual phase time projection chamber filled with liquid xenon is used to detect the WIMP-nucleon interaction. For the next generation experiment XENON1T with an active target mass of 1 ton of xenon, a new distillation column to remove krypton out of xenon to a concentration of < 5 × 10?13 (0.5 ppt) natural krypton in xenon is designed and tested at the Institut für Kernphysik, Universitat Munster. The experimental setup together with two diagnostic tools is presented, as well as one stability test of a 11 hour distillation run at the designed flowrate of 3 kg per hour.

Rosendahl, S.; Brown, E.; Cristescu, I.; Fieguth, A.; Huhmann, C.; Murra, M.; Weinheimer, C.

2014-11-01

109

Controlled pulse-etching with xenon difluoride  

Microsoft Academic Search

A gas-phase, room-temperature, plasmaless isotropic etching system has been used for bulk and thin film silicon etching. A computer controlled multi-chambered etcher is used to provide precisely metered pulses of xenon difluoride (XeF2) gas to the etch chamber. Etch rates as high as 15 microns per minute have been observed. The etch appears to have infinite selectivity to many common

Patrick B. Chu; Jeffrey T. Chen; Richard Yeht; Gisela Lin; Jeff C. P. Huang; B. A. Warneke; S. J. Pister

1997-01-01

110

Cerebral blood flow tomography with xenon-133  

Microsoft Academic Search

Cerebral blood flow (CBF) can be measured tomographically by inhalation of Xenon-¹³³. The calculation is based on taking a sequence of tomograms during the wash-in and wash-out phase of the tracer. Due to the dynamic nature of the process, a highly sensitive and fast moving single photon emission computed tomograph (SPECT) is required. Two brain-dedicated SPECT systems designed for this

N LASSEN

1985-01-01

111

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

112

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

113

Detection of krypton in xenon for dark matter applications  

E-print Network

We extend our technique for observing very small concentrations of impurities in xenon gas to the problem of krypton detection. We use a conventional mass spectrometer to identify the krypton content of the xenon, but we improve the sensitivity of the device by about five orders of magnitude with a liquid nitrogen cold trap. We find that the absolute krypton concentration of the xenon can be inferred from the mass spectrometry measurements, and we identify krypton signals at concentrations as low as 0.5x10^{-12} mol/mol (Kr/Xe). This technique simplifies the monitoring of krypton backgrounds for WIMP dark matter searches in liquid xenon.

Dobi, Attila; Hall, Carter; Langford, Thomas; Slutsky, Simon; Yen, Yung-Ruey

2011-01-01

114

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

115

Liquid Xenon Detectors for Particle Physics and Astrophysics  

E-print Network

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. We begin with a summary of the fundamental properties of liquid xenon as radiation detection medium, in light of the most current theoretical and experimental information. After a brief introduction of the different type of liquid xenon detectors, we continue with 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. We will introduce each application with a brief 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 experiments like MEG, currently the largest liquid xenon scintillation detector in operation, dedicated to the rare mu -> e + gamma decay, to the future XMASS which also exploits only liquid xenon scintillation to address an ambitious program of rare event searches, to the class of time projection chambers like XENON and EXO which exploit both scintillation and ionization of liquid xenon for dark matter and neutrinoless double beta decay, respectively, we anticipate unrivaled performance and important contributions to physics in the next few years.

E. Aprile; T. Doke

2009-10-26

116

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

Hébrard; Marty, B.

2012-12-01

117

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

118

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

119

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

120

Positive column contraction in mercury-xenon fluorescent lamps  

Microsoft Academic Search

Summary form only given. In general, ultra-violet radiation of mercury is used to excite phosphors of fluorescent lamps. Xenon vacuum ultra-violet radiation is also used for excitation of phosphor, for example, of plasma display panels. We have been developing fluorescent lamps using both mercury and xenon radiation. But when discharge current is increased, positive column of the discharge tube filled

H. Motomura; Y. Tachi; M. Aono

2002-01-01

121

Experimental Evidence of a Roughening Transition in Adsorbed Xenon Multilayers  

NASA Astrophysics Data System (ADS)

In this Letter evidence is provided for a roughening transition in adsorbed xenon multilayers on palladium. The layer-distinctive Xe 5p photoemission is used to measure adsorption isotherms as well as the relative equilibrium population of individual Xe layers. Below the roughening temperature TR xenon adsorbs layer by layer. Above TR simultaneous population of different layers takes place.

Miranda, R.; Albano, E. V.; Daiser, S.; Ertl, G.; Wandelt, K.

1983-08-01

122

Absorption and resonance Raman spectra of Pb2, Pb3, and Pb4 in xenon matrices  

NASA Technical Reports Server (NTRS)

Matrix isolation techniques are used to investigate the spectra of lead molecules and, in particular, to obtain resonance Raman spectra of lead vapors isolated in solid xenon matrices. The presence of Pb2 is confirmed by the visible adsorption, and Raman spectra yield a vibrational frequency for the ground state of 108 per cm and a dissociation energy of 8200 per cm. A second resonance Raman progression indicates a Pb3 species of D3h symmetry. Finally, two additional Raman features at approximately 111 per cm spacing are evidence for a third species, tentatively identified as Pb4.

Stranz, D. D.; Khanna, R. K.

1981-01-01

123

Effect of pH and counterions on the encapsulation properties of xenon in water-soluble cryptophanes.  

PubMed

In the (129)Xe?NMR-based biosensing approach in which the hyperpolarized noble gas is transported to biological receptors for a sensitive molecular imaging, cryptophanes are excellent xenon host systems. However to avoid formation of self-organized systems, these hydrophobic cage molecules can be rendered water soluble by introduction of ionic groups. We show that the sensitivity of xenon to its local environment and the presence of these ionic functions can lead to interesting properties. For a first water-soluble cryptophane derivative, we show that a precise monitoring of the local pH can be performed. For a second cryptophane, the presence of ionic groups close to the cryptophane cavity modifies the xenon binding constant and in-out exchange rate. The latter allows the tuning of physical properties of xenon-cryptophane interactions without resorting to a change of the cavity size. These results open new perspectives on the influence of chemical modifications of cryptophanes for optimizing the biosensor properties. PMID:20886471

Berthault, Patrick; Desvaux, Hervé; Wendlinger, Thierry; Gyejacquot, Marina; Stopin, Antoine; Brotin, Thierry; Dutasta, Jean-Pierre; Boulard, Yves

2010-11-15

124

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

125

Environmental application of stable xenon and radioxenonmonitoring  

SciTech Connect

Characterization of transuranic waste is needed to makedecisions about waste site remediation. Soil-gas sampling for xenonisotopes can be used to define the locations of spent fuel andtransuranic wastes. Radioxenon in the subsurface is characteristic oftransuranic waste and can be measured with extreme sensitivity usinglarge-volume soilgas samples. Measurements at the Hanford Site showed133Xe and 135Xe levels indicative of 240Pu spontaneous fission. Stablexenon isotopic ratios from fission are distinct from atmospheric xenonbackground. Neutron capture by 135Xe produces an excess of 136Xe inreactor-produced xenon providing a means of distinguishing spent fuelfrom separated transuranic materials.

Dresel, P. Evan; Olsen, Khris B.; Hayes, James C.; McIntyre,Justin I.; Waichler, Scott R.; Milbrath, Brian D.; Cooper, Matt; Kennedy,B. Mack

2006-09-05

126

Reentrant Layering: The xenon on graphite system  

NASA Astrophysics Data System (ADS)

The physical adsorption of multilayers of xenon on graphite is the best system so far to resolve the differences in the interpretation of experiments and computations. Recent high resolution adsorption isotherms, heat capacity, and diffraction experiments show remarkable detail in the growth of microscopically thin films. By direct observation of equilibrium structures, our study shows these transitions are driven by substrate induced stress. The derivative of the adsorption isotherm is proportional to the isothermal compressibility of the film. The simulations compute compressibilities in agreement with the experimental data.

Phillips, James M.

1997-03-01

127

Ab initio calculation of shocked xenon reflectivity  

NASA Astrophysics Data System (ADS)

Reflectivity of shocked compressed xenon plasma is calculated within the framework of the density functional theory approach. Dependencies on the frequency of incident radiation and on the plasma density are analyzed. The Fresnel formula for the reflectivity is used. The longitudinal expression in the long-wavelength limit is applied for the calculation of the imaginary part of the dielectric function. The real part of the dielectric function is calculated by means of the Kramers-Kronig transformation. The results are compared with experimental data. The approach for the calculation of plasma frequency is developed.

Norman, G.; Saitov, I.; Stegailov, V.; Zhilyaev, P.

2015-02-01

128

Xenon NMR of phase biaxiality in liquid crystals.  

PubMed

Biaxial thermotropic nematic liquid crystals would be of great importance in liquid crystal display technology. Less than a decade ago, such liquid crystals were suggested. The biaxiality of the phases was confirmed using (2)H NMR spectroscopy of deuterated probe molecules. The spectra were collected from a sample rotating around an axis perpendicular to the external magnetic field, resulting in a two-dimensional powder pattern. We have proposed an alternate technique that is based on the second order quadrupole shift detectable in (131)Xe NMR spectra of dissolved xenon. The method has many advantages, such as the NMR spectra are taken from a static sample and the (131)Xe quadrupole coupling tensor is extremely sensitive to the symmetry of the phase. In the present study, we report results obtained on a 600-MHz NMR spectrometer. Together with the data of our earlier study, they confirm that the asymmetry parameter of the (131)Xe quadrupole coupling tensor in the nematic phase of a ferroelectric liquid crystal is 0.85 and in the smectic A phase ca 0.62, indicating significant phase biaxiality. PMID:24771455

Jokisaari, Jukka; Zhu, Jianfeng

2014-10-01

129

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

130

Magnetic resonance imaging of convection in laser-polarized xenon R. W. Mair,1  

E-print Network

Magnetic resonance imaging of convection in laser-polarized xenon R. W. Mair,1 C.-H. Tseng,1,2 G. P and diffusion of laser-polarized xenon (129 Xe) gas undergoing convection above evaporating laser-polarized liquid xenon. The large xenon NMR signal provided by the laser-polarization technique allows more rapid

Walsworth, Ronald L.

131

Interstellar Molecules 161 as of March 2010  

E-print Network

nitrosyl hydride CN cyanide radical HF hydrogen fluoride hydrogen ion* carbon monoxide ion sulfur monoxide hydrogen molecule CO carbon monoxide water* hydrogen sulfide* CP HCN hydrogen cyanide HNC hydrogen isocyanide CS NO nitric oxide carbon dioxide* sulfur dioxide NS SO sulfur monoxide magnesium cyanide hydrogen

Dickel, Hélène R.

132

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

133

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.

2014-08-27

134

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

135

Environmental Applications of Stable Xenon and Radioxenon Monitoring  

SciTech Connect

Improved detection capabilities are needed at several Department of Energy sites to make remedial decisions about facilities and landfill cleanup. For facility monitoring air samples can be collected from within a facility and analyzed for short lived radioxenons to estimate inventories of residual plutonium holdup within the facility. For landfill cleanup activities soil gas sampling for xenon isotopes can be used to define the locations of spent fuel and transuranic wastes. Short-lived radioxenon isotopes are continuously produced by spontaneous fission of plutonium-240 in transuranic wastes. Large volume soil-gas samples provide extremely sensitive measurement of radioxenon in the subsurface; a characteristic of transuranic waste. The analysis employs a modified Automated Radioxenon Sampling and Analysis (ARSA) system. Proof of principle measurements at a Hanford Site liquid waste disposal site showed xenon-133 at levels in soil gas are approximately 16,000 times the detection limit and lower levels of xenon-135 from the spontaneous fission of plutonium-240 were also measured. Stable xenon isotopes are also produced by spontaneous fission but are subject to background concentrations in ambient air samples (facilities) but less so in soil gas where free exchange with ambient air is restricted. Rare gas mass spectrometry is used for highly precise stable xenon isotopic measurements. Stable xenon isotopic ratios from fission are distinct from natural xenon background ratios. Neutron capture on xenon-135 produces an excess of xenon-136 above fission ratios and thus provides a means of distinguishing reactor sources (e.g. spent fuel) from separated transuranic materials (plutonium).

Dresel, P. Evan; Olsen, Khris B.; Hayes, James C.; McIntyre, Justin I.; Waichler, Scott R.; Kennedy, B. M.

2008-06-01

136

Ionization and scintillation of nuclear recoils in gaseous xenon  

E-print Network

Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope $\\alpha$-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

Renner, J; Goldschmidt, A; Matis, H S; Miller, T; Nakajima, Y; Nygren, D; Oliveira, C A B; Shuman, D; Álvarez, V; Borges, F I G; Cárcel, S; Castel, J; Cebrián, S; Cervera, A; Conde, C A N; Dafni, T; Dias, T H V T; Díaz, J; Esteve, R; Evtoukhovitch, P; Fernandes, L M P; Ferrario, P; Ferreira, A L; Freitas, E D C; Gil, A; Gómez, H; Gómez-Cadenas, J J; González-Díaz, D; Gutiérrez, R M; Hauptman, J; Morata, J A Hernando; Herrera, D C; Iguaz, F J; Irastorza, I G; Jinete, M A; Labarga, L; Laing, A; Liubarsky, I; Lopes, J A M; Lorca, D; Losada, M; Luzón, G; Marí, A; Martín-Albo, J; Martínez, A; Moiseenko, A; Monrabal, F; Monserrate, M; Monteiro, C M B; Mora, F J; Moutinho, L M; Vidal, J Muñoz; da Luz, H Natal; Navarro, G; Nebot-Guinot, M; Palma, R; Pérez, J; Aparicio, J L Pérez; Ripoll, L; Rodríguez, A; Rodríguez, J; Santos, F P; Santos, J M F dos; Seguí, L; Serra, L; Simón, A; Sofka, C; Sorel, M; Toledo, J F; Tomás, A; Torrent, J; Tsamalaidze, Z; Veloso, J F C A; Villar, J A; Webb, R C; White, J; Yahlali, N

2014-01-01

137

Ionization and scintillation of nuclear recoils in gaseous xenon  

E-print Network

Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope $\\alpha$-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

J. Renner; V. M. Gehman; A. Goldschmidt; H. S. Matis; T. Miller; Y. Nakajima; D. Nygren; C. A. B. Oliveira; D. Shuman; V. Álvarez; F. I. G. Borges; S. Cárcel; J. Castel; S. Cebrián; A. Cervera; C. A. N. Conde; T. Dafni; T. H. V. T. Dias; J. Díaz; R. Esteve; P. Evtoukhovitch; L. M. P. Fernandes; P. Ferrario; A. L. Ferreira; E. D. C. Freitas; A. Gil; H. Gómez; J. J. Gómez-Cadenas; D. González-Díaz; R. M. Gutiérrez; J. Hauptman; J. A. Hernando Morata; D. C. Herrera; F. J. Iguaz; I. G. Irastorza; M. A. Jinete; L. Labarga; A. Laing; I. Liubarsky; J. A. M. Lopes; D. Lorca; M. Losada; G. Luzón; A. Marí; J. Martín-Albo; A. Martínez; A. Moiseenko; F. Monrabal; M. Monserrate; C. M. B. Monteiro; F. J. Mora; L. M. Moutinho; J. Muñoz Vidal; H. Natal da Luz; G. Navarro; M. Nebot-Guinot; R. Palma; J. Pérez; J. L. Pérez Aparicio; L. Ripoll; A. Rodríguez; J. Rodríguez; F. P. Santos; J. M. F. dos Santos; L. Seguí; L. Serra; A. Simón; C. Sofka; M. Sorel; J. F. Toledo; A. Tomás; J. Torrent; Z. Tsamalaidze; J. F. C. A. Veloso; J. A. Villar; R. C. Webb; J. White; N. Yahlali

2014-09-09

138

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

139

A Xenon Condenser with a Remote Liquid Storage Vessel  

E-print Network

We describe the design and operation of a system for xenon liquefaction in which the condenser is separated from the liquid storage vessel. The condenser is cooled by a pulse tube cryocooler, while the vessel is cooled only by the liquid xenon itself. This arrangement facilitates liquid particle detector research by allowing easy access to the upper and lower flanges of the vessel. We find that an external xenon gas pump is useful for increasing the rate at which cooling power is delivered to the vessel, and we present measurements of the power and efficiency of the apparatus.

S. Slutsky; Y. -R. Yen; H. Breuer; A. Dobi; C. Hall; T. Langford; D. S. Leonard; L. J. Kaufman; V. Strickland; N. Voskanian

2009-07-25

140

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

141

Pulse Shape in 2-Phase Xenon Detectors  

NASA Astrophysics Data System (ADS)

Understanding the shape and size of the primary (S1) and secondary (S2) scintillation pulses in noble elements is crucial for discriminating between different particle interactions. Monte Carlo results from NEST (the Noble Element Simulation Technique) will be presented which match the available data from liquid xenon on the dependence of the recombination time, which is a critical piece of the S1 pulse timing structure, on dE/dx, interaction type, and electric field magnitude. In addition, a model for the S2 pulse shape and the dependence of its width on the depth of an interaction in a detector will be presented which takes into account drift speed, the single/triplet time constants, diffusion, thermal electron trapping at a liquid-gas interface, and other effects.

Mock, Jeremy

2013-04-01

142

Effect of relativity on the ionization spectra of the xenon fluorides XeFn (n=2, 4, 6).  

PubMed

Noble gas compounds exhibit special chemical bonding situations and have been investigated by various spectroscopic and theoretical techniques. In this work we calculate the ionization spectra of the xenon fluorides (XeF2,XeF4, and XeF6) in the valence and subvalence (down to Xe 4d) areas by application of the recently developed Dirac-Hartree-Fock one-particle propagator technique. In this technique, the relativistic (four-component) and electron correlation effects are computed simultaneously. The xenon compounds show considerable spin-orbit splitting strongly influencing the photoelectron spectrum not reproducible in prior calculations. Comparison to one-component methods is made and the occurring satellite structures are interpreted. The satellite structures can be attributed either to the breakdown of the one-particle picture or to a reflection of intra-atomic and interatomic Auger decay processes within the molecule. PMID:15974733

Pernpointner, Markus; Cederbaum, Lorenz S

2005-06-01

143

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

144

The unbearable lightness of being: CDMS versus XENON  

E-print Network

The CDMS-II collaboration has reported 3 events in a Si detector, which are consistent with being nuclear recoils due to scattering of Galactic dark matter particles with a mass of about 8.6 GeV and a cross-section on neutrons of about 2 x 10^-41 cm^2. While a previous result from the XENON10 experiment has supposedly ruled out such particles as dark matter, we find by reanalysing the XENON10 data that this is not the case. Some tension remains however with the upper limit placed by the XENON100 experiment, independently of astrophysical uncertainties concerning the Galactic dark matter distribution. We explore possible ways of ameliorating this tension by altering the properties of dark matter interactions. Nevertheless, even with standard couplings, light dark matter is consistent with both CDMS and XENON10/100.

Frandsen, Mads T; McCabe, Christopher; Sarkar, Subir; Schmidt-Hoberg, Kai

2013-01-01

145

The unbearable lightness of being: CDMS versus XENON  

E-print Network

The CDMS-II collaboration has reported 3 events in a Si detector, which are consistent with being nuclear recoils due to scattering of Galactic dark matter particles with a mass of about 8.6 GeV and a cross-section on neutrons of about 2 x 10^-41 cm^2. While a previous result from the XENON10 experiment has supposedly ruled out such particles as dark matter, we find by reanalysing the XENON10 data that this is not the case. Some tension remains however with the upper limit placed by the XENON100 experiment, independently of astrophysical uncertainties concerning the Galactic dark matter distribution. We explore possible ways of ameliorating this tension by altering the properties of dark matter interactions. Nevertheless, even with standard couplings, light dark matter is consistent with both CDMS and XENON10/100.

Mads T. Frandsen; Felix Kahlhoefer; Christopher McCabe; Subir Sarkar; Kai Schmidt-Hoberg

2013-07-01

146

The unbearable lightness of being: CDMS versus XENON  

NASA Astrophysics Data System (ADS)

The CDMS-II collaboration has reported 3 events in a Si detector, which are consistent with being nuclear recoils due to scattering of Galactic dark matter particles with a mass of ~ 8.6 GeV and a cross-section on neutrons of ~ 2 × 10-41 cm2. While a previous result from the XENON10 experiment has supposedly ruled out such particles as dark matter, we find by reanalysing the XENON10 data that this is not the case. Some tension remains however with the upper limit placed by the XENON100 experiment, independently of astrophysical uncertainties concerning the Galactic dark matter distribution. We explore possible ways of ameliorating this tension by altering the properties of dark matter interactions. Nevertheless, even with standard couplings, light dark matter is consistent with both CDMS and XENON10/100.

Frandsen, Mads T.; Kahlhoefer, Felix; McCabe, Christopher; Sarkar, Subir; Schmidt-Hoberg, Kai

2013-07-01

147

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

148

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

149

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

150

The unbearable lightness of being: CDMS versus XENON  

SciTech Connect

The CDMS-II collaboration has reported 3 events in a Si detector, which are consistent with being nuclear recoils due to scattering of Galactic dark matter particles with a mass of ? 8.6 GeV and a cross-section on neutrons of ? 2 × 10{sup ?41} cm{sup 2}. While a previous result from the XENON10 experiment has supposedly ruled out such particles as dark matter, we find by reanalysing the XENON10 data that this is not the case. Some tension remains however with the upper limit placed by the XENON100 experiment, independently of astrophysical uncertainties concerning the Galactic dark matter distribution. We explore possible ways of ameliorating this tension by altering the properties of dark matter interactions. Nevertheless, even with standard couplings, light dark matter is consistent with both CDMS and XENON10/100.

Frandsen, Mads T. [CP3-Origins and the Danish Institute for Advanced Study, University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark); Kahlhoefer, Felix; Sarkar, Subir [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom); McCabe, Christopher [Institute for Particle Physics Phenomenology, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Schmidt-Hoberg, Kai, E-mail: frandsen@cp3-origins.net, E-mail: felix.kahlhoefer@physics.ox.ac.uk, E-mail: christopher.mccabe@durham.ac.uk, E-mail: s.sarkar@physics.ox.ac.uk, E-mail: kai.schmidt-hoberg@cern.ch [Theory Division, CERN, 1211 Geneva 23 (Switzerland)

2013-07-01

151

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)

1988-01-01

152

Utilizing a Water-Soluble Cryptophane with Fast Xenon Exchange Rates for Picomolar Sensitivity NMR Measurements  

PubMed Central

Hyperpolarized 129Xe chemical exchange saturation transfer (129Xe Hyper-CEST) NMR is a powerful technique for the ultrasensitive, indirect detection of Xe host molecules (e.g., cryptophane-A). Irradiation at the appropriate Xe-cryptophane resonant radio frequency results in relaxation of the bound hyperpolarized 129Xe and rapid accumulation of depolarized 129Xe in bulk solution. The cryptophane effectively ‘catalyzes’ this process by providing a unique molecular environment for spin depolarization to occur, while allowing xenon exchange with the bulk solution during the hyperpolarized lifetime (T1 ? 1 min). Following this scheme, a triacetic acid cryptophane-A derivative (TAAC) was indirectly detected at 1.4 picomolar concentration at 320 K in aqueous solution, which is the record for a single-unit xenon host. To investigate this sensitivity enhancement, the xenon binding kinetics of TAAC in water was studied by NMR exchange lifetime measurement. At 297 K, kon ? 1.5 × 106 M?1s?1 and koff = 45 s?1, which represent the fastest Xe association and dissociation rates measured for a high-affinity, water-soluble xenon host molecule near rt. NMR linewidth measurements provided similar exchange rates at rt, which we assign to solvent-Xe exchange in TAAC. At 320 K, koff was estimated to be 1.1 × 103 s?1. In Hyper-CEST NMR experiments, the rate of 129Xe depolarization achieved by 14 pM TAAC in the presence of RF pulses was calculated to be 0.17 µM·s?1. On a per cryptophane basis, this equates to 1.2 × 104 129Xe atoms s?1 (or 4.6 × 104 Xe atoms s?1, all Xe isotopes), which is more than an order of magnitude faster than koff, the directly measurable Xe-TAAC exchange rate. This compels us to consider multiple Xe exchange processes for cryptophane-mediated bulk 129Xe depolarization, which provide at least 107-fold sensitivity enhancements over directly detected hyperpolarized 129Xe NMR signals. PMID:23106513

Bai, Yubin; Hill, P. Aru; Dmochowski, Ivan J.

2012-01-01

153

A Solid Xenon Catcher for Rare Isotope Laser Spectroscopy  

Microsoft Academic Search

Solid xenon layers are proposed as an alternative to graphite catchers for collecting samples at on-line separators. The formation\\u000a of solid xenon layers is described. Sample atoms of bismuth have been held for up to a day in such layers before being released\\u000a as cold free atoms for laser spectroscopy measurement. An application to studying daughter nuclei produced by ?-decay

A. E. Ezwam; J. Billowes

154

A Solid Xenon Catcher for Rare Isotope Laser Spectroscopy  

Microsoft Academic Search

Solid xenon layers are proposed as an alternative to graphite catchers for collecting samples at on-line separators. The formation\\u000a of solid xenon layers is described. Sample atoms of bismuth have been held for up to a day in such layers before being released\\u000a as cold free atoms for laser spectroscopy measurement. An application to studying daughter nuclei produced by ?$$\\\\alpha$$-decay

A. E. Ezwam; J. Billowes

2005-01-01

155

Development of liquid xenon detectors for gamma ray astronomy  

Microsoft Academic Search

The application of liquid xenon in high-resolution detectors for gamma-ray astronomy is being investigated. Initial results from a pulse-shape analysis of ionization signals in a liquid-xenon gridded chamber indicate that it is possible to achieve the necessary liquid purity for the transport of free electrons with simple techniques. The energy resolution has been measured as a function of applied electric

Elena Aprile; Masayo Suzuki

1989-01-01

156

Neuroprotective and neurotoxic properties of the 'inert' gas, xenon  

Microsoft Academic Search

Background. Antagonists of the N-methyl-D-aspartate (NMDA) subtype of glutamate recep- tors have been shown not only to have neuroprotective effects but also to exhibit neurotoxic properties. In this study, we used c-Fos, a protein product of an immediate early gene, as a marker of neuronal injury to compare the neuroprotective effects of xenon and the neurotoxic properties of xenon, nitrous

D. Ma; S. Wilhelm; M. Maze; N. P. Franks

2002-01-01

157

Gallery of Greenhouse Gas Molecules  

NSDL National Science Digital Library

This static visualization from Global Warming Art depicts the chemical characteristics of eight greenhouse gas molecules - carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), water (H2O), ozone (O3), sulfur hexafluoride (SF6), dichlorodifluoromethane (CFC-12), and trichlorofluoromethane (CFC-11).

Ben Mills

158

Modeling the selectivity of activated carbons for efficient separation of hydrogen and carbon dioxide  

E-print Network

the separation of hydrogen and carbon dioxide via adsorption in activated carbons. In the simulations, both hydrogen and carbon dioxide molecules are modeled as Lennard-Jones spheres, and the activated carbons essentially no preference over the two gases and the selectivity of carbon dioxide relative to hydrogen falls

Wu, Jianzhong

159

A coherent understanding of low-energy nuclear recoils in liquid xenon  

E-print Network

Liquid xenon detectors such as XENON10 and XENON100 obtain a significant fraction of their sensitivity to light (xenon for nuclear recoils also bears heavily on detector sensitivity, yet numerous measurements have not succeeded in obtaining concordant results. In this article we show that the ratio of detected ionization to scintillation can be leveraged to constrain the scintillation yield. We also present a rigorous treatment of liquid xenon detector threshold and energy resolution. Notably, the effective energy resolution differs significantly from a simple Poisson distribution. We conclude with a calculation of dark matter exclusion limits, and show that existing data from liquid xenon detectors strongly constrain recent interpretations of light dark matter.

Peter Sorensen

2010-09-07

160

Cold Ion-Molecule Chemistry with a Stark Decelerator Beamline  

NASA Astrophysics Data System (ADS)

We describe an experimental method for studying ion-molecule reactive collisions at very low energies. Building on our previous work using an electrostatic quadrupole guide as a source of cold neutral molecules, we discuss a proof of principle study of the charge-exchange reaction between cold xenon ions and Stark decelerated ammonia molecules. Ammonia molecules from a pulsed supersonic expansion are produced at low velocities using the Stark deceleration technique of Meijer and co-workers. The decelerated molecules are focussed using pulsed electrostatic hexapoles into the centre of a radiofrequency ion trap where they collide with cold xenon ions. A fast-opening vacuum-compatible mechanical shutter installed in the beamline is used to prevent transmission of the undecelerated molecules and carrier gas into the ion trap chamber. To prepare the target ions, the ion trap is loaded with calcium ions, which are Doppler laser cooled to form a low-temperature ordered ``Coulomb crystal'' phase. Xenon ions formed by resonant multiphoton ionisation are subsequently loaded and sympathetically cooled through their Coulomb interaction with the laser-cooled ions. The spatial distribution of fluorescence emitted by the laser-cooled ions in the multicomponent crystal is imaged; reactive collisions of Xe^+ with ND_3 are observed and quantified through changes in this distribution. By varying the high voltage switching sequence applied to the decelerator, the velocity of the ammonia molecules can be tuned from around 250 m/s to 35 m/s. For collisions with trapped xenon ions, this corresponds to collision energies (expressed in temperature units) from 65 K down to close to 1 K.

Oldham, James M.; Bell, Martin T.; Harper, Lee D.; Softley, Timothy P.

2012-06-01

161

Low-energy positron interactions with xenon  

NASA Astrophysics Data System (ADS)

Low-energy interactions of positrons with xenon have been studied both experimentally and theoretically. The experimental measurements were carried out using a trap-based positron beam with an energy resolution of ˜80 meV, while the theoretical calculations were carried out using the convergent close-coupling method and the relativistic optical potential approach. Absolute values of the grand total, positronium formation and grand total minus positronium formation cross sections are presented over the energy range of 1-60 eV. Elastic differential cross sections (DCS), for selected energies, are also presented both below and above the positronium formation threshold. Fine energy-step measurements of the positronium formation cross section over the energy range of 4.4-8.4 eV, and measurements of the elastic DCS at the energies of 5.33 and 6.64 eV, have been carried out to investigate the ionization threshold regions corresponding to the 2P3/2 and 2P1/2 states of the Xe+ ion. The present results are compared with both experimental and theoretical values from the literature where available.

Machacek, J. R.; Makochekanwa, C.; Jones, A. C. L.; Caradonna, P.; Slaughter, D. S.; McEachran, R. P.; Sullivan, J. P.; Buckman, S. J.; Bellm, S.; Lohmann, B.; Fursa, D. V.; Bray, I.; Mueller, D. W.; Stauffer, A. D.

2011-12-01

162

Positron scattering measurements from Krypton and Xenon  

NASA Astrophysics Data System (ADS)

As a part of a comprehensive program of low energy positron scattering, measurements have been made for a variety of scattering processes from the heavier rare gases, krypton and xenon. In the case of positron scattering, there have been large disagreements between different experiments, and experimental and theoretical determinations of scattering cross sections for these targets. A wide range of low energy positron scattering measurements is now possible, thanks to the development of the Surko trap and beam system, which provides a high energy resolution source of positrons [1-3]. The resulting positron beam is magnetised, and techniques developed for measuring cross sections in the magnetic fields mean that a wide range of scattering processes are now able to be investigated with high accuracy. This presentation will present measurements of total scattering, positronium formation and elastic differential scattering for both of these targets. The strongly forward peaked nature of the differential cross sections will be highlighted, especially as it relates to previous disagreements between different experimental measurements of the grand total cross section. In the case of positronium formation, the difference between present measurements and previous studies will also be discussed. [1] T. Murphy and C. M. Surko, Phys. Rev. A 46, 5696 (1992) [2] S. J. Gilbert et al., Appl. Phys. Lett. 70, 1944 (1997) [3] J. P. Sullivan et al. Phys. Rev. A 66, 042708 (2002)

Sullivan, James; Machacek, Joshua; Makochekanwa, Casten; Jones, Adric; Caradonna, Peter; Slaughter, Daniel; Buckman, Stephen; Mueller, Dennis

2012-06-01

163

Cerebral blood flow tomography with xenon-133  

SciTech Connect

Cerebral blood flow (CBF) can be measured tomographically by inhalation of Xenon-/sup 133/. The calculation is based on taking a sequence of tomograms during the wash-in and wash-out phase of the tracer. Due to the dynamic nature of the process, a highly sensitive and fast moving single photon emission computed tomograph (SPECT) is required. Two brain-dedicated SPECT systems designed for this purpose are mentioned, and the method is described with special reference to the limitations inherent in the soft energy of the 133Xe primary photons. CBF tomography can be used for a multitude of clinical and investigative purposes. This article discusses in particular its use for the selection of patients with carotid occlusion for extracranial/intracranial bypass surgery, for detection of severe arterial spasm after aneurysm bleeding, and for detection of low flow areas during severe migraine attacks. The use of other tracers for CBF tomography using SPECT is summarized with emphasis on the /sup 99m/Tc chelates that freely pass the intact blood-brain barrier. The highly sensitive brain-dedicated SPECT systems described are a prerequisite for achieving high resolution tomograms with such tracers.

Lassen, N.A.

1985-10-01

164

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.

Carlyn Little

1997-01-01

165

Xenon-enhanced CT imaging of local pulmonary ventilation  

NASA Astrophysics Data System (ADS)

We are using the unique features of electron beam CT (EBCT) in conjunction with respiratory and cardiac gating to explore the use of non-radioactive xenon gas as a pulmonary ventilation contrast agent. The goal is to construct accurate and quantitative high-resolution maps of local pulmonary ventilation in humans. We are evaluating xenon-enhanced computed tomography in the pig model with dynamic tracer washout/dilution and single breath inhalation imaging protocols. Scanning is done via an EBCT scanner which offers 50 msec scan aperture speeds. CT attenuation coefficients (image gray scale value) show a linear increase with xenon concentration (r equals 0.99). We measure a 1.55 Hounsfield Unit (HU) enhancement (kV equals 130, mA equals 623) per percentage increase in xenon gas concentration giving an approximately 155 HU enhancement with 100% xenon gas concentration as measured in a plexiglass super-syringe. Early results indicate that a single breath (from functional residual capacity to total lung capacity) of 100% xenon gas provides an average 32 +/- 1.85 (SE) HU enhancement in the lung parenchyma (maximum 50 HU) and should not encounter unwanted xenon side effects. However, changes in lung density occurring during even short breath holds (as short as 10 seconds) may limit using a single breath technique to synchronous volumetric scanning, currently possible only with EBCT. Preliminary results indicate close agreement between measured regional xenon concentration-time curves and theoretical predictions for the same sample. More than 10 breaths with inspirations to as high as 25 cmH2O airway pressure were needed to clear tracer from all lung regions and some regions had nearly linear rather than mono-exponential clearance curves. When regional parenchymal xenon concentration-time curves were analyzed, vertical gradients in ventilation and redistribution of ventilation at higher inspiratory flow rates were consistent with known pulmonary physiology. We present here a works in progress, showing results from two pigs illustrating the high resolution and detailed regional information obtainable with careful attention to cardiac and respiratory gating during a multi-breath washout period.

Tajik, Jehangir K.; Tran, Binh Q.; Hoffman, Eric A.

1996-04-01

166

Luminescence evidence for bulk and surface excitons in free xenon clusters  

SciTech Connect

The cathodoluminescence spectra of free xenon clusters produced by condensation of xenon-argon gas mixtures in supersonic jets expanding into vacuum were studied. By varying the initial experimental parameters, including the xenon concentration, we could obtain clusters with a xenon core (300-3500 atoms) covered by an argon outer shell as well as shell-free xenon clusters ({approx_equal}1500 atoms). The cluster size and temperature ({approx_equal}40 K for both cases) were measured electronographically. Luminescence bands evidencing the existence of bulk and surface excitons were detected for shell-free xenon clusters. The emission from bulk excitons in small clusters is supposed to be due to processes of their multiple elastic reflections from the xenon-vacuum interface. The presence of an argon shell causes extinction of the excitonic bands. In addition, some bands were found which have no analogs for bulk xenon cryosamples.

Danylchenko, O. G.; Doronin, Yu. S.; Kovalenko, S. I.; Libin, M. Yu.; Samovarov, V. N.; Vakula, V. L. [B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Lenin Avenue, Kharkiv, 61103 (Ukraine)

2007-10-15

167

Xenon low-n Rydberg states in supercritical argon near the critical point  

E-print Network

Xenon low-n Rydberg states in supercritical argon near the critical point Luxi Li a,b , Xianbo Shi simulation of the 6s and 6s Rydberg states (including the blue satellite bands) of xenon doped into argon

Findley, Gary L.

168

Converging xenon shock waves driven by megagauss magnetic fields  

SciTech Connect

We attempted to implode a conducting metal linear at high velocity, and our failure to do so led to switching, or rapidly transferring the field from pushing an aluminum conductor to snow-plowing a half-atmosphere of xenon gas. We successfully initiated convergent xenon gas shocks with the use of a magnetohydrodynamic switch and coaxial high-explosive, flux-compression generators. Principal diagnostics used to study the imploding xenon gas were /sup 133/Xe radioactive tracers, continuous x-ray absorption, and neutron output. We compressed the xenon gas about five to sixfold at a velocity of 10 cm/..mu..s at a radius of 4 cm. The snowplow efficiency was good; going from 13- to 4-cm radius, we lost only about 20% of the mass. The temperature of the imploded sheath was determined by mixing deuterium with the xenon and measuring the neutron output. Using reasonable assumptions about the amount, density, and uniformity of the compressed gas, we estimate that we reached temperatures as high as 155 eV. Energy-loss mechanisms that we encountered included wall ablation and Taylor instabilities of the back surface.

Shearer, J.W.; Steinberg, D.J.

1986-07-01

169

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.; Gärtner, K.; Hlatshwayo, T. T.; van der Berg, N. G.; Thabethe, T. T.

2014-08-01

170

Screen for Carbon Dioxide.  

ERIC Educational Resources Information Center

Presents a set of laboratory experiments that can assist students in the detection of carbon dioxide. Offers a variation of the supported drop method of carbon dioxide detection that provides readily visible positive results. Includes background information on carbon dioxide. (ML)

Foster, John; And Others

1986-01-01

171

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

172

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

173

High-field NMR of adsorbed xenon polarized by laser pumping  

Microsoft Academic Search

Optical pumping has been used to enhance the pulsed NMR signal of 129Xe, allowing the detecting of low-pressure xenon gas and of xenon adsorbed on powdered solids. We observe an increase in sensitivity of more than 2 orders of magnitude over conventional NMR, the current limitation being the laser power. Adsorbed xenon is observed at 298 K on graphitized carbon

D. Raftery; H. Long; T. Meersmann; P. J. Grandinetti; L. Reven; A. Pines

1991-01-01

174

A xenon gas purity monitor for EXO , C. Hall a,n  

E-print Network

A xenon gas purity monitor for EXO A. Dobi a , C. Hall a,n , S. Herrin b , A. Odian b , C September 2011 Available online 19 September 2011 Keywords: Xenon Electronegative ion Purification Tungsten versions of a xenon gas purity monitor (GPM) developed for the EXO double beta decay program. The devices

Gratta, Giorgio

175

Magnetic resonance imaging of laser polarized liquid xenon C. H. Tseng,1,2  

E-print Network

Magnetic resonance imaging of laser polarized liquid xenon C. H. Tseng,1,2 R. W. Mair,1 G. P. Wong liquid xenon, and image exchange between the liquid and vapor phases. The exceptionally large averaging. Applications may include imaging of density equilibration and convective flow near xenon's liquid

Walsworth, Ronald L.

176

Xenon diffusion studies with prompt gamma activation analysis Carlos A. Rios Perez Justin D. Lowrey  

E-print Network

Xenon diffusion studies with prompt gamma activation analysis Carlos A. Rios Perez · Justin D 2011 Abstract Developing a better understanding of xenon transport through porous systems is critical rates of xenon and argon gases through a porous medium. The University of Texas at Austin maintains

Deinert, Mark

177

Experimental data analysis on xenon above the critical temperature from nonlinear renormalization group  

E-print Network

L-127 Experimental data analysis on xenon above the critical temperature from nonlinear and specific heat data on xenon using the recent non- linear renormalization group calculations obtained shown to be necessary in the analysis of experimental data on xenon [1] at equilibrium along its

Paris-Sud XI, Université de

178

Mass transfer of helium, neon, argon, and xenon through a steady-state upper mantle  

Microsoft Academic Search

We have examined the steady-state upper mantle model for helium, neon, argon, and xenon following the mass transfer approach presented by Kellogg and Wasserburg (1990) for helium and Porcelli and Wasserburg (1995a) for xenon. The model explains the available observational data of mantle helium, neon, argon, and xenon isotope compositions and provides specific predictions regarding the rare gas isotopic compositions

D. Porcelli; G. J. Wasserburg

1995-01-01

179

EUV Radiation of Xenon Plasma Streams Generated by Magnetoplasma I.E. Garkusha1  

E-print Network

EUV Radiation of Xenon Plasma Streams Generated by Magnetoplasma Compressor I.E. Garkusha1 , V generation lithography. In both approaches xenon has advantage to be used as working gas due to considerably. This paper presents the investigations xenon plasma streams generated by magnetoplasma compressor (MPC

Harilal, S. S.

180

Scattering of xenon from Ni,,111...: Collision-induced corrugation and energy transfer dynamics  

E-print Network

Scattering of xenon from Ni,,111...: Collision-induced corrugation and energy transfer dynamics in which a beam of xenon atoms collides with a clean Ni 111 surface, and the speed and angular is independent of initial and final scattering angles. This result is attributed to multiple xenon

Zare, Richard N.

181

DISCOVERY OF THE TWO-NEUTRINO DOUBLE-BETA DECAY OF XENON-136 WITH EXO-200  

E-print Network

DISCOVERY OF THE TWO-NEUTRINO DOUBLE-BETA DECAY OF XENON-136 WITH EXO-200 A DISSERTATION SUBMITTED Enriched Xenon Observatory (EXO-200) detector is currently taking data to search for the neutrinoless enriched liquid xenon. The analysis presented here describes the recent observation with EXO-200 of the two

Gratta, Giorgio

182

Exploring Surfaces and Cavities in Lipoxygenase and Other Proteins by Hyperpolarized Xenon-129 NMR  

E-print Network

Exploring Surfaces and Cavities in Lipoxygenase and Other Proteins by Hyperpolarized Xenon-129 NMR: This paper presents an exploratory study of the binding interactions of xenon with the surface of several studies of Xe bound to the surface of materials,3,4 medical imaging of xenon in lungs5 and blood,6

Ronquist, Fredrik

183

Simulation and evaluation of a new PET system based on liquid xenon as detection medium  

E-print Network

Simulation and evaluation of a new PET system based on liquid xenon as detection medium J ionization potential, liquid xenon is an excellent medium for the tracking and the accurate energy measurement of -rays in the MeV energy domain. The use of liquid xenon associated to a micro gap structure

Paris-Sud XI, Université de

184

Sublimative desorption of xenon from Ru(100) Gabriel Kerner, Ori Stein, Yigal Lilach, and Micha Asscher*  

E-print Network

Sublimative desorption of xenon from Ru(100) Gabriel Kerner, Ori Stein, Yigal Lilach, and Micha , George and co-workers have investigated the submonolayer xenon diffusion on a stepped Pt 11,11,9 surface addressed the 2D melting and diffusion of multilayer xenon on surfaces. In addition to its basic importance

Asscher, Micha

185

Diamagnetic behaviour of xenon Rydberg states studied by the R.F. optogalvanic method  

E-print Network

249 Diamagnetic behaviour of xenon Rydberg states studied by the R.F. optogalvanic method J. P behaviour of xenon nf Rydberg states is studied using single-mode dye laser excita- tion and an R xenon can offer interesting opportunities for studies of this type. We want furthermore to emphasize

Paris-Sud XI, Université de

186

Angle-resolved photoemission of xenon adsorbed on Pt(111) : commensurate and incommensurate monolayers  

E-print Network

1753 Angle-resolved photoemission of xenon adsorbed on Pt(111) : commensurate and incommensurate The dispersion curves of the commensurate (~3 x ~3) R30° and the hexagonal compact incommensurate rotated xenon and particularly xenon layers form a hexagonal (or nearly hexagonal) compact structure on most single crystals [1

Paris-Sud XI, Université de

187

Xenon purity analysis for EXO-200 via mass spectrometry , C. Hall a,n  

E-print Network

Xenon purity analysis for EXO-200 via mass spectrometry A. Dobi a , C. Hall a,n , S. Slutsky a , Y 2012 Available online 7 February 2012 Keywords: Xenon Double beta decay Purity Mass spectrometry a b s t r a c t We describe purity measurements of the natural and enriched xenon stockpiles used by the EXO

Gratta, Giorgio

188

Characteristic parameters of xenon near its liquid-gas critical point Yves Garrabos and Carole Lecoutre  

E-print Network

Characteristic parameters of xenon near its liquid-gas critical point Yves Garrabos and Carole the singular behaviors of the isothermal compressibility of xenon along the critical isochore in the homogeneous domain and the vapor-liquid coexisting densities of xenon in the nonhomogenous domain

Boyer, Edmond

189

Methoden zur optischen Qualitatskontrolle Anwendung in der Produktion von Xenon-Lampen  

E-print Network

Methoden zur optischen Qualit¨atskontrolle Anwendung in der Produktion von Xenon Arbeit werden Methoden zur optischen Qualit¨atskontrolle von Xenon- Lampen evaluiert. Die automatische-Nearest-Neighbor eingeteilt werden. Die besten Ergebnisse bei der Klassifikation von geschwei�ten und ungeschwei�ten Xenon

190

RELAXATION PROCESSES OF Xe*(3P2) METASTABLE ATOMS IN ARGON-XENON MIXTURES  

E-print Network

L- 105 RELAXATION PROCESSES OF Xe*(3P2) METASTABLE ATOMS IN ARGON-XENON MIXTURES M. CHENEVIER, N*(3P2) by two-body collisions with argon k3, and by three-body collisions with an argon and a xenon Abstracts 34.50H - 82.20 Introduction. - Recently several types of xenon halide excimer laser have been

Paris-Sud XI, Université de

191

Mechanistic Insights into Xenon Inhibition of NMDA Receptors from MD Simulations Lu Tian Liu,  

E-print Network

Mechanistic Insights into Xenon Inhibition of NMDA Receptors from MD Simulations Lu Tian Liu, Yan) receptors has been viewed as a primary cause of xenon anesthesia, yet the mechanism is unclear. Here, we investigated interactions between xenon and the ligand-binding domain (LBD) of a NMDA receptor and examined

Xu, Yan

192

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

193

Background simulations of the XENON100 dark matter detector  

NASA Astrophysics Data System (ADS)

The XENON100 detector is a dual-phase xenon time projection chamber (XeTPC) used to search for dark matter in the form of weakly interacting massive particles (WIMPs) by measuring simultaneously the scintillation and ionization signals produced by nuclear recoils. The 65 kg XeTPC is instrumented by 178 PMTs and is surrounded by a 85 kg LXe active veto with 64 PMTs. All materials and components used to build the detector (PMTs, PMT bases, stainless steel, PTFE, copper, etc) have been screened with high purity germanium detectors operating at the Gran Sasso underground laboratory. Special attention has been paid to the choice of construction materials. Using the measured radioactivity as input to the Monte Carlo, we have simulated the response of the XENON100 detector to obtain the expected gamma and neutron backgrounds, which largely determine the sensivity reach of the experiment.

Plante, Guillaume

2008-04-01

194

Calibration of a Liquid Xenon Detector with Kr-83m  

E-print Network

We report the preparation of a Kr-83m source and its subsequent use in calibrating a liquid xenon detector. Kr-83m atoms were produced through the decay of Rb-83 atoms trapped in zeolite molecular sieve and were then introduced into liquid xenon. Decaying Kr-83m nuclei were detected through liquid xenon scintillation. Conversion electrons with energies of 9.4 keV and 32.1 keV from the decay of Kr-83m were both observed. This calibration source will allow the characterization of the scintillation and ionization response of noble liquid detectors at low energies, highly valuable for the search for WIMP dark matter. Kr-83m may also be useful for measuring fluid flow dynamics, both to understand purification in noble liquid-based particle detectors, as well as for studies of classical and quantum turbulence in superfluid helium.

L. W. Kastens; S. B. Cahn; A. Manzur; D. N. McKinsey

2009-12-11

195

Bronchial imaging in humans using xenon K-edge dichromography  

NASA Astrophysics Data System (ADS)

This report describes the initial use of K-edge xenon dichromography for imaging the bronchial tree in humans. The subjects inhale an anatomic dead-space volume of a mixture of 80% xenon and 20% oxygen, following which a dichromographic line-scan image is recorded using two monochromatic synchrotron radiation beams closely bracketing the k-edge of xenon (34.56 keV). Images of airways, from main-stem bronchi to fourth-order branches, are recorded with a pixel resolution of 0.5×0.5 mm. The scanning rate is 12 cm/s, the line exposure time is 4 ms, the skin dose to the exposed area (125 mm × 150 mm) is <0.35 rad.

Giacomini, J. C.; Gordon, H.; O'Neil, R.; Van Kessel, A.; Cason, B.; Chapman, D.; Lavendar, W.; Gmur, N.; Menk, R.; Thomlinson, W.; Zhong, Z.; Rubenstein, E.

1998-02-01

196

Direct Dark Matter Searches with CDMS and XENON  

E-print Network

The Cryogenic Dark Matter Search (CDMS) and XENON experiments aim to directly detect dark matter in the form of weakly interacting massive particles (WIMPs) via their elastic scattering on the target nuclei. The experiments use different techniques to suppress background event rates to the minimum, and at the same time, to achieve a high WIMP detection rate. The operation of cryogenic Ge and Si crystals of the CDMS-II experiment in the Soudan mine yielded the most stringent spin-independent WIMP-nucleon cross-section (~10^{-43} cm^2) at a WIMP mass of 60 GeV/c^2. The two-phase xenon detector of the XENON10 experiment is currently taking data in the Gran Sasso underground lab and promising preliminary results were recently reported. Both experiments are expected to increase their WIMP sensitivity by a one order of magnitude in the scheduled science runs for 2007.

Kaixuan Ni; Laura Baudis

2006-11-09

197

SUSY Dark Matter In Light Of CDMS/XENON Limits  

E-print Network

In this talk we briefly review the current CDMS/XENON constraints on the neutralino dark matter in three popular supersymmetric models: the minimal (MSSM), the next-to-minimal (NMSSM) and the nearly minimal (nMSSM). The constraints from the dark matter relic density and various collider experiments are also taken into account. The conclusion is that for each model the current CDMS/XENON limits can readily exclude a large part of the parameter space allowed by other constraints and the future SuperCDMS or XENON100 can cover most of the allowed parameter space. The implication for the Higgs search at the LHC is also discussed. It is found that in the currently allowed parameter space the MSSM charged Higgs boson is quite unlikely to be discovered at the LHC while the neutral Higgs bosons $H$ and $A$ may be accessible at the LHC in the parameter space with a large $\\mu$ parameter.

Jin Min Yang

2011-02-24

198

Xenon Recirculation-Purification with a Heat Exchanger  

E-print Network

Liquid-xenon based particle detectors have been dramatically growing in size during the last years, and are now exceeding the one-ton scale. The required high xenon purity is usually achieved by continuous recirculation of xenon gas through a high-temperature getter. This challenges the traditional way of cooling these large detectors, since in a thermally well insulated detector, most of the cooling power is spent to compensate losses from recirculation. The phase change during recondensing requires five times more cooling power than cooling the gas from ambient temperature to -100C (173 K). Thus, to reduce the cooling power requirements for large detectors, we propose to use the heat from the purified incoming gas to evaporate the outgoing xenon gas, by means of a heat exchanger. Generally, a heat exchanger would appear to be only of very limited use, since evaporation and liquefaction occur at zero temperature difference. However, the use of a recirculation pump reduces the pressure of the extracted liquid, forces it to evaporate, and thus cools it down. We show that this temperature difference can be used for an efficient heat exchange process. We investigate the use of a commercial parallel plate heat exchanger with a small liquid xenon detector. Although we expected to be limited by the available cooling power to flow rates of about 2 SLPM, rates in excess of 12 SLPM can easily be sustained, limited only by the pump speed and the impedance of the flow loop. The heat exchanger operates with an efficiency of (96.8 +/- 0.5)%. This opens the possibility for fast xenon gas recirculation in large-scale experiments, while minimizing thermal losses.

K. L. Giboni; E. Aprile; B. Choi; T. Haruyama; R. F. Lang; K. E. Lim; A. J. Melgarejo; G. Plante

2011-03-04

199

Adsorption Studies of Xenon on Carbon Nano Horns  

NASA Astrophysics Data System (ADS)

Adsorption isotherm measurements on recently discovered nano-aggregates of single walled graphitic nano horns (SWNH) were performed to identify the various adsorption sites present in these materials, using Xenon. The energy of the highest binding energy site was determined from the isosteric heat of adsorption for nine (190 K 305 K) different temperatures at low coverages. It is found that the energy value for this site on SWNH is 48that of graphite and 15carbon nanotubes (SWNT) for the same adsorbate. We will also present results on the monolayer capacity of Xenon on SWNH.

Zambano, A. J.; McMillin, W.; Takahashi, K.; Kokaki, F.; Yudasaka, M.; Iijima, S.; Talapatra, S.; Migone, A. D.

2001-03-01

200

Xenon purity analysis for EXO-200 via mass spectrometry  

E-print Network

We describe purity measurements of the natural and enriched xenon stockpiles used by the EXO-200 double beta decay experiment based on a mass spectrometry technique. The sensitivity of the spectrometer is enhanced by several orders of magnitude by the presence of a liquid nitrogen cold trap, and many impurity species of interest can be detected at the level of one part-per-billion or better. We have used the technique to screen the EXO-200 xenon before, during, and after its use in our detector, and these measurements have proven useful. This is the first application of the cold trap mass spectrometry technique to an operating physics experiment.

A. Dobi; C. Hall; S. Slutsky; Y. -R. Yen; B. Aharmin; M. Auger; P. S. Barbeau; C. Benitez-Medina; M. Breidenbach; B. Cleveland; R. Conley; J. Cook; S. Cook; I. Counts; W. Craddock; T. Daniels; C. G. Davis; J. Davis; R. deVoe; M. Dixit; M. J. Dolinski; K. Donato; W. Fairbank Jr.; J. Farine; P. Fierlinger; D. Franco; G. Giroux; R. Gornea; K. Graham; G. Gratta; C. Green; C. Hagemann; K. Hall; D. Hallman; C. Hargrove; S. Herrin; M. Hughes; J. Hodgson; F. Juget; A. Karelin; L. J. Kaufman; A. Kuchenkov; K. Kumar; D. S. Leonard; G. Lutter; D. Mackay; R. MacLellan; M. Marino; B. Mong; M. Montero Díez; P. Morgan; A. R. Müller; R. Neilson; A. Odian; K. O'Sullivan; A. Piepke; A. Pocar; C. Y. Prescott; K. Pushkin; A. Rivas; E. Rollin; P. C. Rowson; A. Sabourov; D. Sinclair; K. Skarpaas; V. Stekhanov; V. Strickland; M. Swift; K. Twelker; J. -L. Vuilleumier; J. -M. Vuilleumier; M. Weber; U. Wichoski; J. Wodin; J. D. Wright; L. Yang

2011-09-06

201

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

202

Coating Glass Cells with OTS The glass cells we use to polarize xenon or to store polarized  

E-print Network

Coating Glass Cells with OTS The glass cells we use to polarize xenon or to store polarized xenon need to be coated. This is because without coating wall collisions of the xenon can bring the xenon. The OTS (octadecyltrichlorosilane) we use consists of a long hydrocarbon chain

Walsworth, Ronald L.

203

Separation of rare gases and chiral molecules by selective binding in porous organic cages.  

PubMed

The separation of molecules with similar size and shape is an important technological challenge. For example, rare gases can pose either an economic opportunity or an environmental hazard and there is a need to separate these spherical molecules selectively at low concentrations in air. Likewise, chiral molecules are important building blocks for pharmaceuticals, but chiral enantiomers, by definition, have identical size and shape, and their separation can be challenging. Here we show that a porous organic cage molecule has unprecedented performance in the solid state for the separation of rare gases, such as krypton and xenon. The selectivity arises from a precise size match between the rare gas and the organic cage cavity, as predicted by molecular simulations. Breakthrough experiments demonstrate real practical potential for the separation of krypton, xenon and radon from air at concentrations of only a few parts per million. We also demonstrate selective binding of chiral organic molecules such as 1-phenylethanol, suggesting applications in enantioselective separation. PMID:25038731

Chen, Linjiang; Reiss, Paul S; Chong, Samantha Y; Holden, Daniel; Jelfs, Kim E; Hasell, Tom; Little, Marc A; Kewley, Adam; Briggs, Michael E; Stephenson, Andrew; Thomas, K Mark; Armstrong, Jayne A; Bell, Jon; Busto, Jose; Noel, Raymond; Liu, Jian; Strachan, Denis M; Thallapally, Praveen K; Cooper, Andrew I

2014-10-01

204

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

PubMed Central

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

2013-01-01

205

Sound Absorption and Dispersion along the Critical Isochore in Xenon  

Microsoft Academic Search

Ultrasonic and Brillouin absorption and velocity data along the critical isochore in xenon are reinterpreted in terms of modified theoretical expressions derived within the framework of the Fixman-Mistura theory. The new expressions mainly arise from avoiding the unjustified assumption of small dispersion near a liquid-gas critical point. Numerical analysis of the data shows quite satisfactory agreement between theory and experiment

Don Eden; Carl W. Garland; Jan Thoen

1972-01-01

206

Genetically encoded reporters for hyperpolarized xenon magnetic resonance imaging  

E-print Network

Genetically encoded reporters for hyperpolarized xenon magnetic resonance imaging Mikhail G Pines5,6, David V. Schaffer2,7 and Vikram S. Bajaj5,6 * Magnetic resonance imaging (MRI) enables high , such that its magnetic resonance signal in a saturated aqueous solution at millimolar concentrations

Schaffer, David V.

207

Pulse processing for the PET liquid xenon multiwire ionisation chamber  

Microsoft Academic Search

The readout and data acquisition systems designed for a first prototype of liquid xenon position sensitive gamma ray detector for Positron Emission Tomography is described, The problem of measurement of the gamma ray energy in the gridless multiwire ionisation chamber is considered. A previously suggested drift time based correction algorithm, allowing correction of the amplitude spectra for the contribution of

P. Crespo; J. van der Marel; V. Chepel; M. I. Lopes; D. Santos; L. Janeiro; V. Solovov; R. F. Marques; A. J. P. L. Policarpo

1998-01-01

208

Pulse processing for the PET liquid xenon multiwire ionisation chamber  

Microsoft Academic Search

The readout and data acquisition systems designed for a first prototype of liquid xenon position sensitive gamma ray detector for Positron Emission Tomography is described. The problem of measurement of the gamma ray energy in the gridless multiwire ionisation chamber is considered. A previously suggested drift time based correction algorithm, allowing correction of the amplitude spectra for the contribution of

P. Crespo; J. van der Marel; V. Chepel; M. I. Lopes; D. Santos; L. Janeiro; V. Solovov; R. F. Marques; A. J. P. L. Policarpo

2000-01-01

209

Two-dimensional readout in a liquid xenon ionisation chamber  

Microsoft Academic Search

A two-dimensional readout with metal strips deposited on both sides of a glass plate is investigated aiming to assess the possibility of its use in a liquid xenon ionisation chamber for positron emission tomography. Here, we present results obtained with an ?-source. It is shown that position resolution of ?1mm, fwhm, can be achieved for free charge depositions equivalent to

V. Solovov; V. Chepel; A. Pereira; M. I. Lopes; R. Ferreira Marques; A. J. P. L. Policarpo

2002-01-01

210

Xenon-filled ionization counters utilizing a virtual Frisch grid  

Microsoft Academic Search

A new design for a compact and rugged high- pressure xenon-fill ionization detector is being explored at Constellation Technology Corporation (Constellation). The basic design approach is to use a detector geometry that eliminates the effect of the induced charge from uncollected ions without using any shielding mesh. This approach is called a virtual grid ionization chamber and can be employed

R. A. Austin

2007-01-01

211

Construction of a high power xenon ion laser  

Microsoft Academic Search

Construction of a pulsed xenon ion laser, which has a combined peak power on all visible lines of over 80 kW is described. Design of the laser and the pulsing circuit is detailed, and the light pulse shape, peak power and electrical effieciency of the laser are discussed.

Clinton D. Harper; Martin Gundersen

1974-01-01

212

Xe-129 NMR of xenon dissolved in biological media.  

NASA Astrophysics Data System (ADS)

The high solubility and large chemical shift of ^129Xe in various tissues makes it an ideal, non-invasive probe for pathological conditions such as cancer or atherosclerosis. To this end, we report NMR measurements of lineshapes, chemical shifts, and relaxation times of ^129Xe dissolved in the following biological tissues in vitro: heart, muscle, sinew, stomach(R.K. Mazitov, K. M. Enikeev, et al., Dokl. Akad. Nauk) 365, 396 (1999)., and the white and yolk of egg. NMR measurements of xenon dissolved in olive and sunflower oils are also reported. Tissues weighing 160--250 mg, not exposed to freezing, were studied in a 11.75 T field at the ^129Xe resonance frequency of 138.4 MHz; the pressure of xenon in the sealed-sample ampoules was ~20 bar. The influence of drugs and water content on tissues was studied. No xenon-water clathrates(J.A. Ripmeester and D.W. Davidson, J. Mol. Struct. ) 75, 67 (1981). were observed in the tissues, even at the high pressures used. The aim of this study is to establish possible correlations between the NMR parameters of dissolved xenon and the state of the tissue.

Mazitov, R. K.; Kuzma, N. N.; Happer, W.; Driehuys, B.; Merrill, G. F.

2002-03-01

213

Ultraviolet Absorption of Solid Argon, Krypton, and Xenon  

Microsoft Academic Search

The absorption spectra of thin films of argon, krypton, and xenon have been measured between 20 and 50°K in the region from 1600 to 900 Å (8 to 14 eV). The spectra show: (a) strong doublets corresponding to the atomic resonance doublets, (b) lines apparently of nonatomic nature, and (c) absorption continua. The experimental results are discussed in terms of

Giancarlo Baldini

1962-01-01

214

The effect of nitrogen on xenon ion engine erosion  

NASA Technical Reports Server (NTRS)

Erosion studies were performed on a 30-cm diameter J-series ion engine modified for operation on xenon propellant. The erosion rates of molybdenum and tantalum badges placed at different locations within the discharge chamber were measured as a function of the percentage of nitrogen (by mass) added to the xenon propellant. Reductions in the erosion rates of these badges of a factor of 8 to 50 were observed at nitrogen addition fractions between 0.5 to 2.0 percent. Reductions in cathode-side baffle erosion were achieved by adding nitrogen to the xenon propellant or by increasing the cathode orifice diameter. Analyses show that no significant degradation in ion engine performance should be expected at these nitrogen mass fractions. XRD, XPS and Auger analyses indicate the existence of nitrogen and nitrides in the surface of some but not all of the badges used in the tests where nitrogen was added to the xenon. Difficulty in identifying surface nitrides in the samples may be due to the existence of surface oxides and contaminants, or to the small thicknesses of the nitride layers.

Garner, Charles E.; Brophy, John R.; Pless, L. C.; Barnett, John W.

1990-01-01

215

Fidelity of a xenon on-axis solar simulator  

Microsoft Academic Search

Xenon on-axis solar simulators are currently used in the thermal vacuum test chambers at NASA Johnson Space Center. These simulators provide a controllable system to closely match the radiation conditions in space. Through a series of alignment procedures, the uniformity, controllability, and spectral distribution of the simulators are certified in order to provide good correlation with theoretical analysis. This certification

Burt A. Laws; Russell E. Bachtel

1992-01-01

216

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

E-print Network

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 discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

Kathawa, J; Thoennessen, M

2012-01-01

217

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

E-print Network

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 discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

J. Kathawa; C. Fry; M. Thoennessen

2012-01-20

218

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

219

Photoionization detector for the detection of xenon light  

SciTech Connect

A photionization detector is described with a high quantum efficiency at wavelengths shorter than about 2000 A. This instrument, coupled to a xenon gas scintillation proportional counter has an energy resolution of 9.5% FWHM at 6 keV. The vapor pressure and absorption coefficient of TMAE are measured and the prospects of an imaging gas scintillation proportional counter are discussed.

Anderson, D.F.

1980-01-01

220

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

221

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

Frédéric Hourdin; J.-P. Issartel

2000-01-01

222

CORTICOSTEROID-INDUCED VASOCONSTRICTION STUDIED BY XENON 133 CLEARANCE  

Microsoft Academic Search

Cutaneous blood flow in corticosteroid-blanched skin was measured by xenon 133 clearance. Flow rates through symmetrical sites of the forearm in normal subjects revealed no significant differences. A comparison of control sites and those treated with flurandrenolide revealed a significant vasoconstriction at the test site. The results suggest that vasoconstriction activity of topical corticosteroids may be quantitated utilizing isotope clearance

Terrence P. Greeson; Norman E. Levan; Robert I. Freedman; Woon H. Wong

1973-01-01

223

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

224

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

225

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

226

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.

227

Interstellar molecules  

NASA Technical Reports Server (NTRS)

Progress in the discovery and study of interstellar molecules is summarized. The 36 molecular species thus far identified in interstellar space are listed in several groups which include simple hydrides, oxides, and sulfides, various derivatives of ammonia, molecules involving linear carbon chains, cyanides, and molecules related in structure to formaldehyde, alcohols, or ethers. Several free radicals are described, the discovery of molecules in external galaxies is discussed, and possible mechanisms for molecular formation are noted. Methods for examining relative isotopic abundances by measuring molecules in interstellar clouds are outlined, mechanisms for the excitation of interstellar molecules are reviewed, and values are presented for the C-12/C-13 abundance ratio in a number of interstellar clouds. The detection of interstellar masers is discussed along with pumping mechanisms and masing transitions in H2CO, CH, OH, and SiO. The nature of dense interstellar clouds is examined in terms of several simple and complex cloud models, with emphasis on multiple condensation models.

Townes, C. H.

1976-01-01

228

Carbon dioxide detection by boron nitride nanotubes  

NASA Astrophysics Data System (ADS)

The effect of gas molecule adsorption is investigated on the density of states of (9,0) zigzag boron nitride nanotube within a random tight-binding Hamiltonian model. The Green function approach and coherent potential approximation have been implemented. The results show that the adsorption of carbon dioxide gas molecules by boron atoms only leads to a donor type semiconductor while the adsorption by nitrogen atoms only leads to an acceptor. Since the gas molecules are adsorbed by both boron and nitrogen atoms, a reduction of the band gap is found. In all cases, increasing the gas concentration causes an increase in the height of the peaks in the band gap. This is due to an increasing charge carrier concentration induced by adsorbed gas molecules.

Mousavi, Hamze; Kurdestany, Jamshid Moradi; Bagheri, Mehran

2012-08-01

229

a Study of Reactive Quenching of Xenon by Chlorides Using Two-Photon Laser Excitation  

NASA Astrophysics Data System (ADS)

State-selective two-photon laser excitation is utilized to study inelastic energy transfer in rare gas halide reactions. These studies have helped to understand the energy pathways and reaction processes important to the physics of the excimer laser. Moreover, they have lead to a better fundamental understanding of electronic energy transfer. In particular, reactions of Xe (5p ^5np, np^' n = 6,7) with chlorine molecules are studied. The observed quench rates were surprisingly large; experimental cross sections extended from 400A^2 to 1000A^2. Previous models for the excimer laser used only reaction cross sections of 200A ^2 for the lowest excited states of xenon (5p^56s); they neglected all more highly excited states. Nevertheless, it was shown that the large reactions rates are consistent with current theory; the reaction Rg^{*} + Cl_2 is vibronically coupled onto the Rg^{+} + Cl _sp{2}{-} ionic surface by means of the Cl_2 molecular vibrations. In addition, the neutral termolecular reactive collisions, Rg^{*} + Cl _2 + Rg to RgCl^{*} + Cl + Rg, were observed. The large rates (~10 ^{-28}cm^6 /sec) were understood by means of an orbiting collision complex model; the role of the third body (Rg) was not to take up excess thermal energy as had been assumed in previous calculations, but to enhance the probability for charge transfer between the two neutral species (Rg ^{*} and Cl_2) by altering the effective ionization limit. This process could be important in any high density neutral reaction that proceeds through an ionic intermediary. These results have shown that termolecular reactions are universal to many forms of energy transfer reactions; furthermore, we can no longer hope to understand chemistry at high pressures by a study of binary reactions at low pressures. Also, quenching measurements in pure rare gases were studied. Bimolecular reaction rates were determined for Xe (5p^5np, np^ ' n = 6,7) in xenon and argon buffer gases. In general, the quenching rates in argon were about a factor of two small than in xenon buffers. This effect was understood in terms of an orbiting collision model whereby the nature of the long range dispersion forces determined the orbiting rates. For Xe 6p(1/2) _0 a multicomponent decay was observed in argon, the mixed state was attributed to Xe 5d(1/2) _1 by studying the collisionally induced VUV fluorescence. This study has also unambiguously identified the product channels involved in curve crossings observed in earlier optical collision studies. References. N. Bowering, T. D. Raymond, and J. W. Keto, Phys. Rev. Lett 52, 1880 (1984).

Bruce, Michael Richard

1990-01-01

230

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

231

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.

232

Production of Carbon Dioxide  

NSDL National Science Digital Library

In this chemistry activity, learners use common chemicals to produce carbon dioxide and observe its properties. This resource includes brief questions for learners to answer after the experiment. Use this activity to introduce learners to carbon dioxide and its use as a fire extinguisher. Note: this activity involves an open flame.

The Science House

2014-01-28

233

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.

234

First axion results from the XENON100 experiment  

NASA Astrophysics Data System (ADS)

We present the first results of searches for axions and axionlike particles with the XENON100 experiment. The axion-electron coupling constant, gAe, has been probed by exploiting the axioelectric effect in liquid xenon. A profile likelihood analysis of 224.6 live days × 34-kg exposure has shown no evidence for a signal. By rejecting gAe larger than 7.7×10-12 (90% C.L.) in the solar axion search, we set the best limit to date on this coupling. In the frame of the DFSZ and KSVZ models, we exclude QCD axions heavier than 0.3 and 80 eV /c2, respectively. For axionlike particles, under the assumption that they constitute the whole abundance of dark matter in our galaxy, we constrain gAe to be lower than 1×10-12 (90% C.L.) for masses between 5 and 10 keV /c2.

Aprile, E.; Agostini, F.; Alfonsi, M.; Arisaka, K.; Arneodo, F.; Auger, M.; Balan, C.; Barrow, P.; Baudis, L.; Bauermeister, B.; Behrens, A.; Beltrame, P.; Bokeloh, K.; Brown, A.; Brown, E.; Bruenner, S.; Bruno, G.; Budnik, R.; Cardoso, J. M. R.; Colijn, A. P.; Contreras, H.; Cussonneau, J. P.; Decowski, M. P.; Duchovni, E.; Fattori, S.; Ferella, A. D.; Fulgione, W.; Gao, F.; Garbini, M.; Geis, C.; Goetzke, L. W.; Grignon, C.; Gross, E.; Hampel, W.; Itay, R.; Kaether, F.; Kessler, G.; Kish, A.; Landsman, H.; Lang, R. F.; Le Calloch, M.; Lellouch, D.; Levy, C.; Lindemann, S.; Lindner, M.; Lopes, J. A. M.; Lung, K.; Lyashenko, A.; Macmullin, S.; Marrodán Undagoitia, T.; Masbou, J.; Massoli, F. V.; Mayani Paras, D.; Melgarejo Fernandez, A. J.; Meng, Y.; Messina, M.; Miguez, B.; Molinario, A.; Murra, M.; Naganoma, J.; Ni, K.; Oberlack, U.; Orrigo, S. E. A.; Pantic, E.; Persiani, R.; Piastra, F.; Pienaar, J.; Plante, G.; Priel, N.; Reichard, S.; Reuter, C.; Rizzo, A.; Rosendahl, S.; Dos Santos, J. M. F.; Sartorelli, G.; Schindler, S.; Schreiner, J.; Schumann, M.; Scotto Lavina, L.; Selvi, M.; Shagin, P.; Simgen, H.; Teymourian, A.; Thers, D.; Tiseni, A.; Trinchero, G.; Vitells, O.; Wang, H.; Weber, M.; Weinheimer, C.; Xenon100 Collaboration

2014-09-01

235

Xenon Isotopes in Irradiated and Unirradiated Samples of ALH84001  

NASA Astrophysics Data System (ADS)

Interior samples .110, .111, .112, altered sample .127 and fusion crust sample .136 from the SNC meteorite ALH 84001 [1] have been studied. Approximately 3mg of each sample was degassed stepwise in five minute heating steps on a filament. Temperature was monitored with an optical pyrometer while the chamber pressure was measured with a capacitance manometer. An aliquot (~1% ) of the evolved gas was characterised using a quadrupole mass spectrometer, the remainder was gettered and admitted to the RELAX mass spectrometer [2] for xenon isotopic analysis. The data obtained from 5 unirradiated samples is shown in figure 1. These data are consistent with a mixing among terrestrial (air) xenon, SPB-xenon [3] and Chassigny-like xenon [4], with a maximum 129Xe/132Xe of 1.92 and a minimum 136Xe/132Xe of 0.313. There is no evidence of the excess (i.e. exceeding that required to be on the SPB-Chassigny mixing line) 129Xe previously attributed to a heterogeneously distributed 129Xe-rich component [5]. This absence could be explained by the mixture of air xenon into even the most 129Xe rich of our extractions or by our smaller samples (3-4mg vs 142mg) having failed to sample this phase. Samples of .127, .111 and .112 were irradiated with a thermal neutron fluence of 7.22x10^18 n cm^-2. Each showed a marked peak release of excesses of 129Xe and reactor-derived isotopes (128Xe, 131Xe, 136Xe) at high temperature (1500-1800 degrees C), while the 129Xe/128Xe showed an increase with temperature and was consistent in the largest releases from each sample. (Excesses are calculated assuming 130Xe was derived from a Chassigny component.) Excess 128Xe always accompanied excess 129Xe and the high temperature points (containing 50% of the excess 129Xe evolved) from the 3 samples define a mixing line with Chassigny. However, more data is needed to establish a true correlation. The fission isotope ratios in the irradiated samples are consistent with neutron-induced fission of 235U, and indicate an abundance of around 20ppb (total U). Assuming xenon has a 4 billion year closure age as argon does [6], the 238U spontaneous fission contribution to a typical high-temperature, SPB xenon-rich extraction is ~1%. The major release of active gases in each sample (unirradiated and irradiated) was between 600 and 800 deg C and was composed of CO2 and CO. Evolved gas pressures were converted to equivalent masses of carbonate assuming published Mg - Ca - Fe abundances for this phase [1]; altered sample .127 contained 5 times as much carbonate as the mean of the other samples (0.4% vs 0.08%). The inferred xenon content of the carbonate was significantly above blank in only one unirradiated sample and yielded a carbonate 130Xe content of 6x10^-10 cc STP/g and 129Xe/132Xe=1.03+/-0.03, 136Xe/132Xe=0.33+/-0.02, indicating that carbonate is not the major carrier of SPB-Xe in these samples. Significant excesses of 128Xe and 131Xe were associated with the CO/CO2 release in the irradiated sample of .127. References: [1] Mittlefehldt D. W. (1994) Meteoritics, 29, 214-221. [2] Gilmour J. D. et al. (1994) Rev. Sci. Instrum., 65, 617-625. [3] Swindle T. D. et al. (1986) GCA, 52, 1001-1015. [4] Ott U. (1988) GCA, 52, 1937-1948. [5] Swindle T. D. et al. (1995) GCA, 59, 793-801. [6] Ash R. D. et al., this volume.

Gilmour, J. D.; Whitby, J. A.; Ash, R. D.; Turner, G.

1995-09-01

236

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

237

Theoretical study of xenon adsorption in UO2 nanoporous matrices  

NASA Astrophysics Data System (ADS)

We present a theoretical study of xenon incorporation in UO2 nanocavities, by means of Grand Canonical Monte Carlo calculations based on semi-empirical potentials. We first characterize the reconstruction of the matrix around an empty cavity which leads to a stoechiometry change from UO2 to UO in this region. Then, we determine xenon adsorption isotherms which exhibit an abrupt transition from a dilute phase to a dense one and an increase in the density of the latter phase as a function of temperature. This last result is attributed to a vibrational entropy effect by means of a mean field analysis. Finally, the pressure calculation inside the bubble proves the limitations of the usual mesoscopic models based on gas state behaviour.

Colbert, Mehdi; Tréglia, Guy; Ribeiro, Fabienne

2014-12-01

238

Theoretical study of xenon adsorption in UO2 nanoporous matrices.  

PubMed

We present a theoretical study of xenon incorporation in UO2 nanocavities, by means of Grand Canonical Monte Carlo calculations based on semi-empirical potentials. We first characterize the reconstruction of the matrix around an empty cavity which leads to a stoechiometry change from UO2 to UO in this region. Then, we determine xenon adsorption isotherms which exhibit an abrupt transition from a dilute phase to a dense one and an increase in the density of the latter phase as a function of temperature. This last result is attributed to a vibrational entropy effect by means of a mean field analysis. Finally, the pressure calculation inside the bubble proves the limitations of the usual mesoscopic models based on gas state behaviour. PMID:25388362

Colbert, Mehdi; Tréglia, Guy; Ribeiro, Fabienne

2014-12-01

239

Development of liquid xenon detectors for gamma ray astronomy  

NASA Technical Reports Server (NTRS)

The application of liquid xenon in high-resolution detectors for gamma-ray astronomy is being investigated. Initial results from a pulse-shape analysis of ionization signals in a liquid-xenon gridded chamber indicate that it is possible to achieve the necessary liquid purity for the transport of free electrons with simple techniques. The energy resolution has been measured as a function of applied electric field, using electrons and gamma-rays from a 207Bi source. At a field of 12 kV/cm the noise-substracted energy resolution of the dominant 569-keV gamma-ray line is 34 keV FWHM (full width at half maximum). This value is mostly determined by recombination of electron-ion pairs on delta-electron tracks.

Aprile, Elena; Suzuki, Masayo

1989-01-01

240

Gamma Ray Spectroscopy with Scintillation Light in Liquid Xenon  

E-print Network

Scintillation light from gamma ray irradiation in liquid xenon is detected by two Hamamatsu R9288 photomultiplier tubes (PMTs) immersed in the liquid. UV light reflector material, PTFE, is used to optimize the light collection efficiency. The detector gives a high light yield of 6 photoelectron per keV (pe/keV), which allows efficient detection of the 122 keV gamma-ray line from Co-57, with a measured energy resolution of (8.8+/-0.6)% (sigma). The best achievable energy resolution, by removing the instrumental fluctuations, from liquid xenon scintillation light is estimated to be around 6-8% (sigma) for gamma-ray with energy between 662 keV and 122 keV.

K. Ni; E. Aprile; K. L. Giboni; P. Majewski; M. Yamashita

2006-08-04

241

High Pressure XENON Gamma-Ray Spectrometers for Field Use  

SciTech Connect

This project explored a new concept for high-pressure xenon ionization chambers by replacing the Frisch grid with coplanar grid electrodes similar to those used in wide bandgap semiconductor gamma-ray spectrometers. This work is the first attempt to apply the coplanar grid anode design in a gas ionization chamber in order to achieve to improved energy resolution. Three prototype detectors, two cylindrical and one parallel plate configurations, were built and tested. While the detectors did not demonstrate energy resolutions as good as other high pressure xenon gamma-ray spectrometers, the results demonstrated that the concept of single polarity charge sending using coplanar grid electrodes will work in a gas detector.

David K. Wehe; Zong He; Glenn K. Knoll

2004-02-16

242

A coherent understanding of low-energy nuclear recoils in liquid xenon  

SciTech Connect

Liquid xenon detectors such as XENON10 and XENON100 obtain a significant fraction of their sensitivity to light (?<10 GeV) particle dark matter by looking for nuclear recoils of only a few keV, just above the detector threshold. Yet in this energy regime a correct treatment of the detector threshold and resolution remains unclear. The energy dependence of the scintillation yield of liquid xenon for nuclear recoils also bears heavily on detector sensitivity, yet numerous measurements have not succeeded in obtaining concordant results. In this article we show that the ratio of detected ionization to scintillation can be leveraged to constrain the scintillation yield. We also present a rigorous treatment of liquid xenon detector threshold and energy resolution. Notably, the effective energy resolution differs significantly from a simple Poisson distribution. We conclude with a calculation of dark matter exclusion limits, and show that existing data from liquid xenon detectors strongly constrain recent interpretations of light dark matter.

Sorensen, Peter, E-mail: pfs@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States)

2010-09-01

243

Investigations of Wafer Scale Etching with Xenon Difluoride  

Microsoft Academic Search

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

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

2006-01-01

244

Cryogenic Technology Development For The MEG Liquid Xenon Calorimeter  

SciTech Connect

Cryogenic key technologies have been developed for the muon rare decay experiment (MEG) at the Paul Scherrer Institute, Switzerland. These technologies are the high power pulse tube cryocooler for precise temperature and pressure control of liquid xenon in the calorimeter, a purification system with a cryogenic liquid pump and a cryogenic dewar with 1000 L storage capacity. The paper describes the general concepts and the first test results of each technology. All the results imply a promising performance for the coming MEG experiment.

Haruyama, Tomiyoshi [KEK, High Energy Accelerator Research Organization 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2008-02-21

245

Flight qualification of an 18-mN xenon thruster  

NASA Astrophysics Data System (ADS)

In this paper, we describe an 18-mN xenon ion propulsion subsystem (XIPS) and our plans to flight-qualify the critical component of this system. The XIPS consists of a 13-cm-diam thruster, a power supply, and a xenon storage and control unit. The thruster produces 17.8 mN of thrust at a specific impulse of 2585 s, with an input power of about 439 W. The power supply contains only about 400 parts in its 7 individual power modules: screen, accel, discharge, two keepers, and two beaters. The power supply is designed to operate from a 29- to 34-V or a 49- to 53-V power bus and achieves an overall efficiency of 88 to 90 percent over these ranges. Xenon propellant is stored at an initial pressure of 7.6 MPa (1100 psia) to give a tankage fraction of only about 12 percent. Control of the xenon flow rates is accomplished using a pressure regulator to reduce the storage pressure to 68.9 kPA (10 psia) on the upstream side of flow restrictors located in the lines leading to the discharge chamber and the discharge and neutralizer cathodes. We describe our plans to qualify the XIPS thruster by subjecting two flight units to qualification testing, including performance, thermal-vacuum, and vibration tests. In addition, we describe our plans to subject the qualification thrusters to a cyclic life test, in which we intend to accumulate at least 12,000 h and over 6,000 ON/OFF cycles. We also describe our plans to subject two XIPS cathodes to a continuous-operation life test of unspecified duration; we plan to test these cathodes until failure.

Beattie, J. R.; Williams, J. D.; Robson, R. R.

1993-02-01

246

Quench gases for xenon- (and krypton-) filled proportional counters  

NASA Technical Reports Server (NTRS)

Xenon-filled proportional counters are used extensively in astronomy, particularly in the hard X-ray region. The choice of quench gas can have a significant effect on the operating characteristics of the instrument although the data necessary to make the choice are not easily obtainable. Results which detail the performance obtained from both cylindrical and parallel field geometries for a wide variety of readily available, ultrahigh or research grade purity, quench gases are presented.

Ramsey, B. D.; Agrawal, P. C.

1988-01-01

247

Shear thinning near the critical point of xenon  

NASA Astrophysics Data System (ADS)

We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids, near the critical point of xenon. The data span a wide range of reduced shear rate: 10-3xenon at amplitudes 3?m??? , C? depends also on both x0 and ? . The data were compared with numerical calculations based on the Carreau-Yasuda relation for complex fluids: ?(??)/?(0)=[1+A?|???|]-x?/(3+x?) , where x?=0.069 is the critical exponent for viscosity and mode-coupling theory predicts A?=0.121 . For xenon we find A?=0.137±0.029 , in agreement with the mode coupling value. Remarkably, the xenon data close to the critical temperature Tc were independent of the cooling rate (both above and below Tc ) and these data were symmetric about Tc to within a temperature scale factor. The scale factors for the magnitude of the oscillator’s response differed from those for the oscillator’s phase; this suggests that the surface tension of the two-phase domains affected the drag on the screen below Tc .

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

2008-04-01

248

Microwave power absorption coefficient of an ECR xenon ion thruster  

Microsoft Academic Search

A 20-cm diameter xenon ion thruster with electron cyclotron resonance (ECR) discharge generates 30 mN of thrust at a total electric power consumption of 1 kW for spacecraft propulsion by ejecting 1.1 keV ion beam. By optimizing the discharge chamber length, magnetic field and propellant flow injection, ion beam currents of 500 mA at a microwave power of 100 W had been obtained at a

Kazutaka Nishiyama; Hitoshi Kuninaka

2008-01-01

249

Xenon and hypothermia combine to provide neuroprotection from neonatal asphyxia  

Microsoft Academic Search

Perinatal asphyxia can result in neuronal injury with long-term neurological and behavioral consequences. Although hypothermia may provide some modest benefit, the intervention itself can produce adverse consequences. We have investigated whether xenon, an antagonist of the N-methyl-D-aspartate subtype of the glutamate receptor, can enhance the neuroprotection provided by mild hypothermia. Cultured neurons injured by oxygen-glucose deprivation were pro- tected by

Daqing Ma; Mahmuda Hossain; Andre Chow; Mubarik Arshad; Renee M. Battson; Robert D. Sanders; Huseyin Mehmet; A. David Edwards; Nicholas P. Franks; Mervyn Maze

2005-01-01

250

Regional Cerebral Blood Flow Estimated by 133 Xenon Inhalation  

Microsoft Academic Search

Regional Cerebral Blood Flow Estimated by ™Xenon Inhalation • A method is described for estimating the clearance rate and fractional blood flow of the fast (gray matter) compartment of the brain from the first ten minutes of 133Xe clearance curves, following a one-minute inhalation. Computer-simulated data were used to test the adequacy of the two-compartmental model employed, and to evaluate

WALTER D. OBRIST; HOWARD K. THOMPSON; SHAN WANG; WILLIAM E. WILKINSON

1975-01-01

251

NMR investigations of surfaces and interfaces using spin-polarized xenon  

SciTech Connect

{sup 129}Xe NMR is potentially useful for the investigation of material surfaces, but has been limited to high surface area samples in which sufficient xenon can be loaded to achieve acceptable signal to noise ratios. In Chapter 2 conventional {sup 129}Xe NMR is used to study a high surface area polymer, a catalyst, and a confined liquid crystal to determine the topology of these systems. Further information about the spatial proximity of different sites of the catalyst and liquid crystal systems is determined through two dimensional exchange NMR in Chapter 3. Lower surface area systems may be investigated with spin-polarized xenon, which may be achieved through optical pumping and spin exchange. Optically polarized xenon can be up to 10{sup 5} times more sensitive than thermally polarized xenon. In Chapter 4 highly polarized xenon is used to examine the surface of poly(acrylonitrile) and the formation of xenon clathrate hydrates. An attractive use of polarized xenon is as a magnetization source in cross polarization experiments. Cross polarization from adsorbed polarized xenon may allow detection of surface nuclei with drastic enhancements. A non-selective low field thermal mixing technique is used to enhance the {sup 13}C signal of CO{sub 2} of xenon occluded in solid CO{sub 2} by a factor of 200. High-field cross polarization from xenon to proton on the surface of high surface area polymers has enabled signal enhancements of {approximately}1,000. These studies, together with investigations of the efficiency of the cross polarization process from polarized xenon, are discussed in Chapter 5. Another use of polarized xenon is as an imaging contrast agent in systems that are not compatible with traditional contrast agents. The resolution attainable with this method is determined through images of structured phantoms in Chapter 6.

Gaede, H.C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States). Materials Science Div.

1995-07-01

252

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

Microsoft Academic Search

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

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

2008-01-01

253

EUV emission from xenon in the 1080 nm wavelength range using a compact ECR ion source  

E-print Network

EUV emission from xenon in the 10­80 nm wavelength range using a compact ECR ion source H. Merabet is assignment of numerous new optical transitions for xenon in the 10­80 nm range to create a database. PACS: 32.30.�r; 32.30.Jc; 32.70.�n; 32.70.Fw Keywords: EUV emission; Xenon atomic spectra; 13.4 nm

Godunov, Alexander L.

254

Micromegas operation in high pressure xenon: charge and scintillation readout  

E-print Network

The operational characteristics of a Micromegas operating in pure xenon at the pressure range of 1 to 10 bar are investigated. The maximum charge gain achieved in each pressure is approximately constant, around 4x10^2, for xenon pressures up to 5 bar and decreasing slowly above this pressure down to values somewhat above 10^2 at 10 bar. The MM presents the highest gains for xenon pressures above 4 bar, when compared to other micropattern gaseous multipliers. The lowest energy resolution obtained for X-rays of 22.1 keV exhibits a steady increase with pressure, from 12% at 1bar to about 32% at 10 bar. The effective scintillation yield, defined as the number of photons exiting through the MM mesh holes per primary electron produced in the conversion region was calculated. This yield is about 2x10^2 photons per primary electron at 1 bar, increasing to about 6x10^2 at 5 bar and, then, decreasing again to 2x10^2 at 10 bar. The readout of this scintillation by a suitable photosensor will result in higher gains but with increased statistical fluctuations.

C. Balan; E. D. C. Freitas; T. Papaevangelou; I. Giomataris; H. Natal da Luz; C. M. B. Monteiro; J. M. F. dos Santos

2010-09-15

255

A Comprehensive Study of the Large Underground Xenon Detector  

NASA Astrophysics Data System (ADS)

The Large Underground Xenon (LUX) dark matter search experiment operates a time projection chamber constructed of 370 kg of xenon, currently installed in the Homestake gold mine. The goal of the experiment is to detect Weakly Interacting Massive Particles (WIMPs). Novel calibration methods for this uniquely large detector are discussed. Background events due to standard model physics processes including cosmogenically activated xenon, alpha emission, and neutron production are shown to be negligible in recent 85 day WIMP search data. The LUX Monte Carlo simulation includes a new physical model, the Nobel Element Simulation Technique (NEST), for scintillation and ionization. NEST describes energy-, particle-, field- and medium-dependent behavior of a charge recombination model. A simulated data acquisition chain that bridges the gap between simulation and data has been developed to permit full testing of the analysis tools employed by LUX. Signal generation by cumulative photon responses are described algorithmically. Computational optimization has been performed to decrease processing time by a factor of fifty. A new technique for event depth estimation using machine learning and image analysis is introduced. Variable length waveforms are converted to fixed dimension field maps for use in machine learning. A support vector machine trained against pulse shapes with known depth successfully regressed depth without direct measurement of highly variable pulse widths. The world's most stringent limits on spin-independent WIMP-nucleon scattering cross section are presented.

Woods, Michael Austin

256

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

257

Light-induced, site-selective isomerization of glyoxylic acid in solid xenon  

NASA Astrophysics Data System (ADS)

The isomerization of glyoxylic acid (GA) and its water complex was studied in a low temperature xenon matrix. The aim of these studies was to understand how xenon environment affects the cis-trans GA interconversion upon near infrared irradiation. In solid xenon, the GA conformers are embedded in two different matrix sites. These show up as different vibrational bands of GA that exhibit different kinetic rates of isomerization. Upon complexation with water, the isomerization process slows down. Xenon matrix appears not to affect energy relaxation process via intramolecular or intermolecular hydrogen bond as compared with previous experiments in an argon.

Olbert-Majkut, Adriana; Wierzejewska, Maria; Lundell, Jan

2014-11-01

258

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

259

Interstellar Molecules  

ERIC Educational Resources Information Center

Radioastronomy reveals that clouds between the stars, once believed to consist of simple atoms, contain molecules as complex as seven atoms and may be the most massive objects in our Galaxy. (Author/DF)

Solomon, Philip M.

1973-01-01

260

Preparation of Inclusion Complex of Piroxicam with Cyclodextrin by Using Supercritical Carbon Dioxide  

E-print Network

carbon dioxide 1. Introduction Novel pharmaceutical molecules often exhibit a limited solubility in water or the temperature. Moreover, additional advantages lie in the use of carbon dioxide (CO2) which properties of non1 Preparation of Inclusion Complex of Piroxicam with Cyclodextrin by Using Supercritical Carbon

Boyer, Edmond

261

Diffusion NMR methods applied to xenon gas for materials study  

NASA Technical Reports Server (NTRS)

We report initial NMR studies of (i) xenon gas diffusion in model heterogeneous porous media and (ii) continuous flow laser-polarized xenon gas. Both areas utilize the pulsed gradient spin-echo (PGSE) techniques in the gas phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients--a brief overview of this area is provided in the Introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t) (an indicator of mean squared displacement), to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. We find that D(t) of imbibed xenon gas at short diffusion times is similar for the mixed bead pack and a pack of the smaller sized beads alone, hence reflecting the pore surface area to volume ratio of the smaller bead sample. The approach of D(t) to the long-time limit follows that of a pack of the larger sized beads alone, although the limiting D(t) for the mixed bead pack is lower, reflecting the lower porosity of the sample compared to that of a pack of mono-sized glass beads. The Pade approximation is used to interpolate D(t) data between the short- and long-time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20-200 mm s-1). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm s-1 owing to the high diffusivity of gases compared with liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data, namely flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack. c2002 John Wiley & Sons, Ltd.

Mair, R. W.; Rosen, M. S.; Wang, R.; Cory, D. G.; Walsworth, R. L.

2002-01-01

262

Gold cluster/titanium dioxide heterojunction photovoltaic cell  

NASA Astrophysics Data System (ADS)

Metal clusters have recently been applied as photosensitizers to wet-type photovoltaic cells. However, there are some practical issues including instability of the clusters in a liquid phase and leakage of electrolyte. To address these issues, we fabricated a heterojunction photovoltaic cell with solid-state layers of glutathione-protected Au25 clusters and titanium dioxide (TiO2). The ITO/TiO2/Au25/Au cell responded to visible and near infrared light even at 900 nm. Short-circuit photocurrent was ˜14 ?A cm-2 and open-circuit photovoltage was 0.53 V under a xenon lamp (>480 nm, 75 mW cm-2).

Nakamura, Eiji; Kogo, Atsushi; Sakai, Nobuyuki; Tatsuma, Tetsu

2014-08-01

263

Carbon dioxide removal process  

DOEpatents

A process and apparatus for separating carbon dioxide from gas, especially natural gas, that also contains C.sub.3+ hydrocarbons. The invention uses two or three membrane separation steps, optionally in conjunction with cooling/condensation under pressure, to yield a lighter, sweeter product natural gas stream, and/or a carbon dioxide stream of reinjection quality and/or a natural gas liquids (NGL) stream.

Baker, Richard W.; Da Costa, Andre R.; Lokhandwala, Kaaeid A.

2003-11-18

264

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

265

Environmental perturbations on foreign atoms and molecules in solid argon, krypton and xenon  

Microsoft Academic Search

Perturbations which are responsible for the shifts of electronic and vibrational spectra of species trapped in a solid are considered in terms of the intermolecular potential which describes interactions between these species and neighbouring atoms. It is shown that in certain instances London's theory can give an adequate approximation to the dispersion energy between an electronically excited species and a

Maclyn McCarty Jr.; G. Wilse Robinson

1959-01-01

266

51A Simple Model for Atmospheric Carbon Dioxide The graph to the left shows the 'Keeling Curve' which plots the increase in  

E-print Network

51A Simple Model for Atmospheric Carbon Dioxide The graph to the left shows the 'Keeling Curve' which plots the increase in atmospheric carbon dioxide between 1958-2005. The average net annual rate of the element carbon on Earth. Note that, for every 44 gigatons of the carbon dioxide molecule, there are 12

267

Observing and preventing rubidium runaway in a direct-infusion xenon-spin hyperpolarizer optimized for high-resolution hyper-CEST (chemical exchange saturation transfer using hyperpolarized nuclei) NMR  

SciTech Connect

Xenon is well known to undergo host-guest interactions with proteins and synthetic molecules. As xenon can also be hyperpolarized by spin exchange optical pumping, allowing the investigation of highly dilute systems, it makes an ideal nuclear magnetic resonance probe for such host molecules. The utility of xenon as a probe can be further improved using Chemical Exchange Saturation Transfer using hyperpolarized nuclei (Hyper-CEST), but for highly accurate experiments requires a polarizer and xenon infusion system optimized for such measurements. We present the design of a hyperpolarizer and xenon infusion system specifically designed to meet the requirements of Hyper-CEST measurements. One key element of this design is preventing rubidium runaway, a chain reaction induced by laser heating that prevents efficient utilization of high photon densities. Using thermocouples positioned along the pumping cell we identify the sources of heating and conditions for rubidium runaway to occur. We then demonstrate the effectiveness of actively cooling the optical cell to prevent rubidium runaway in a compact setup. This results in a 2–3-fold higher polarization than without cooling, allowing us to achieve a polarization of 25% at continuous flow rates of 9 ml/min of {sup 129}Xe. The simplicity of this design also allows it to be retrofitted to many existing polarizers. Combined with a direction infusion system that reduces shot-to-shot noise down to 0.56% we have captured Hyper-CEST spectra in unprecedented detail, allowing us to completely resolve peaks separated by just 1.62 ppm. Due to its high polarization and excellent stability, our design allows the comparison of underlying theories of host-guest systems with experiment at low concentrations, something extremely difficult with previous polarizers.

Witte, C.; Kunth, M.; Rossella, F.; Schröder, L., E-mail: lschroeder@fmp-berlin.de [ERC Project BiosensorImaging, Leibniz-Institut für Molekulare Pharmakologie, Berlin (Germany)

2014-02-28

268

Observing and preventing rubidium runaway in a direct-infusion xenon-spin hyperpolarizer optimized for high-resolution hyper-CEST (chemical exchange saturation transfer using hyperpolarized nuclei) NMR  

NASA Astrophysics Data System (ADS)

Xenon is well known to undergo host-guest interactions with proteins and synthetic molecules. As xenon can also be hyperpolarized by spin exchange optical pumping, allowing the investigation of highly dilute systems, it makes an ideal nuclear magnetic resonance probe for such host molecules. The utility of xenon as a probe can be further improved using Chemical Exchange Saturation Transfer using hyperpolarized nuclei (Hyper-CEST), but for highly accurate experiments requires a polarizer and xenon infusion system optimized for such measurements. We present the design of a hyperpolarizer and xenon infusion system specifically designed to meet the requirements of Hyper-CEST measurements. One key element of this design is preventing rubidium runaway, a chain reaction induced by laser heating that prevents efficient utilization of high photon densities. Using thermocouples positioned along the pumping cell we identify the sources of heating and conditions for rubidium runaway to occur. We then demonstrate the effectiveness of actively cooling the optical cell to prevent rubidium runaway in a compact setup. This results in a 2-3-fold higher polarization than without cooling, allowing us to achieve a polarization of 25% at continuous flow rates of 9 ml/min of 129Xe. The simplicity of this design also allows it to be retrofitted to many existing polarizers. Combined with a direction infusion system that reduces shot-to-shot noise down to 0.56% we have captured Hyper-CEST spectra in unprecedented detail, allowing us to completely resolve peaks separated by just 1.62 ppm. Due to its high polarization and excellent stability, our design allows the comparison of underlying theories of host-guest systems with experiment at low concentrations, something extremely difficult with previous polarizers.

Witte, C.; Kunth, M.; Rossella, F.; Schröder, L.

2014-02-01

269

Volume 191, number 5 CHEMICAL PHYSICS LETTERS 10April 1992 Oriented geminate recombination of Cl2 in solid xenon  

E-print Network

in solid xenon at high pressure G.J. Hoffman, E. Sekreta and V.A. Apkarian ' Department of Chemistry emission in CIZ-doped solid xenon under high pressure, in a diamond anvil cell (DAC). The motivation behind

Apkarian, V. Ara

270

Modeling total reduced sulfur and sulfur dioxide emissions from a kraft recovery boiler using an artificial neural network, and, Investigating volatile organic compounds in an urban intermountain valley using a TD/GC/MS methodology and intrinsic tracer molecules  

NASA Astrophysics Data System (ADS)

Back-propagation neural networks were trained to predict total reduced sulfur (TRS) and SO2 emissions from kraft recovery boiler operational data. A 0.721 coefficient of correlation was achieved between actual and predicted sulfur emissions on test data withheld from network training. The artificial neural network (ANN) models found an inverse, linear relationship between TRS/SO2 emissions and percent opacity. A number of relationships among operating parameters and sulfur emissions were identified by the ANN models. These relationships were used to formulate strategies for reducing sulfur emissions. Disagreement between ANN model predictions on a subsequent data set revealed an additional scenario for sulfur release not present in the training data. ANN modeling was demonstrated to be an effective tool for analyzing process variables when balancing productivity and environmental concerns. Five receptor sites distributed in the Missoula Valley, Montana, were employed to investigate possible VOC (benzene, 2,3,4-trimethylpentane, toluene, ethylbenzene, m-/p-xylene, o-xylene, naphthalene, acetone, chloroform, ?-pinene, ?-pinene, p-cymene and limonene) sources. The most dominant source of VOCs was found to be vehicle emissions. Furthermore, anthropogenic sources of terpenoids overwhelmed biogenic emissions, on a local scale. Difficulties correlating wind direction and pollutant levels could be explained by wind direction variability, low wind speed and seasonally dependent meteorological factors. Significant evidence was compiled to support the use of p-cymene as a tracer molecule for pulp mill VOC emissions. Apportionment techniques using o-xylene and p-cymene as tracers for automobile and pulp mill emissions, respectively, were employed to estimate each source's VOC contribution. Motor vehicles were estimated to contribute between 56 and 100 percent of the aromatic pollutants in the Missoula Valley airshed, depending upon the sampling location. Pulp mill emissions were estimated to account from 1 to 34 percent of the aromatic chemicals in the airshed. Measured ambient chloroform levels were attributable to the pulp mill (12-70%) and non-point source urban emissions (7.5-30%).

Wrobel, Christopher Louis

2000-11-01

271

Q4 Consider a model for n identical xenon atoms of mass m that are trapped on the surface of a solid. A xenon atom can be tightly bound to  

E-print Network

Q4 Consider a model for n identical xenon atoms of mass m that are trapped on the surface of a solid. A xenon atom can be tightly bound to one of N adsorption sites with binding energy Ea (a positive it is free to move along the surface, the xenon atom has both kinetic energy mv2 /2 and constant potential

Ha, Taekjip

272

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

SciTech Connect

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 Ni-Fe-S center called the C-cluster to reduce carbon dioxide to carbon monoxide and uses a second Ni-Fe-S 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 A long) to allow for intermolecular CO transport. Here, we report a 2.5 A 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, T.I.; Blasiak, L.C.; Seravalli, J.; Ragsdale, S.W.; Drennan, C.L.; /MIT /SLAC, SSRL /Nebraska U.

2009-05-11

273

'Escentric' molecules.  

PubMed

Can a fragrance be revolutionary? In this commentary, the creation of two unusual, extravagant fine fragrances, 'escentric01' and 'molecule01', is described. In response to the fantasy components found in release notes of many recent perfume launches, both center around a single real fragrance raw material, the transparent woody aroma chemical 'Iso E Super' (1+2). The perfume 'escentric01' contains 65% of it, accompanied by Trisamber (3), red pepper, lime oil, incense and musks, while 'molecule01' consists exclusively of 'Iso E Super' (1+2). The elegant woody note lives here its own eccentric life--the revolution starts. PMID:18618401

Schön, Geza

2008-06-01

274

One-dimensional fluid simulations of a helium - xenon filled ac colour plasma flat panel display pixel  

Microsoft Academic Search

One-dimensional (1D) fluid simulations are used to model a helium-xenon filled ac plasma display pixel. The model includes four levels for helium atomic states, seven levels for xenon atomic states and a xenon dimer state. The model also includes VUV emission including photon trapping due to collisional broadening from the resonant atomic xenon at wavelengths of 129 nm and 147

Ramana Veerasingam; Robert B. Campbell; Robert T. McGrath

1997-01-01

275

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

276

American Institute of Aeronautics and Astronautics An Optical Diagnostic for Xenon Hall Thrusters Including Metastable  

E-print Network

spectroscopy. The emissions are compared to a collisional-radiative model which incorporates emission applications. Nearly all modern HETs use xenon as their propellant. While work has been done utilizing other propellants such as bismuth,1 it is likely that xenon will remain the propellant of choice for many years

King, Lyon B.

277

XENON-133 IN CALIFORNIA, NEVADA, AND UTAH FROM THE CHERNOBYL ACCIDENT (JOURNAL VERSION)  

EPA Science Inventory

The accident at the Chernobyl nuclear reactor in the USSR introduced numerous radioactive nuclides into the atmosphere, including the noble gas xenon-133. EPA's Environmental Monitoring Systems Laboratory, Las Vegas, NV, detected xenon-133 from the Chernobyl accident in air sampl...

278

democrite-00024907,version2-23Nov2005 Experimental study of a liquid Xenon PET  

E-print Network

of the leading techniques of nu- clear medicine to access to metabolic and functional information. PET is useddemocrite-00024907,version2-23Nov2005 Experimental study of a liquid Xenon PET prototype module M (PET). The specific design aims at taking full advantage of the liquid Xenon properties. It does

Paris-Sud XI, Université de

279

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; Górny, K; Wojcieszyk, D; Dendzik, Z; Gburski, Z

2014-08-14

280

Helium, neon, argon, krypton and xenon in gas emanations from Yellowstone and Lassen volcanic National Parks  

Microsoft Academic Search

The abundance of helium, neon, argon, krypton and xenon were measured in gas emanations from thermal springs in Yellowstone National Park, Wyoming and Lassen National Park, California. The determinations were made using an isotope dilution procedure. The isotopic composition of argon and the relative abundances of argon, neon, krypton and xenon indicate that these gases originated from the atmosphere through

E. Mazor; G. J. Wasserburg

1965-01-01

281

Efficiency Analysis of a Hall Thruster Operating with Krypton and Xenon  

Microsoft Academic Search

Krypton has recently become the focus of attention in the Hall thruster community because of its relatively large specific impulse as compared to xenon and its potential to operate with comparable efficiencies. However, before krypton can be considered a viable propellant choice for missions, the performance gap between xenon and krypton must be reduced. A series of diagnostic measurements are

Jesse A. Linnell; Alec D. Gallimore

2006-01-01

282

Theoretical studies of vibrational relaxation of iodine in low density liquid xenon  

E-print Network

1787 Theoretical studies of vibrational relaxation of iodine in low density liquid xenon J. K for vibrational relaxation of iodine in low density liquid xenon are presented. Simple generalized Langevin relaxation data. This is explained, at least in part, by noting that the iodine vibrational motion perturbs

Paris-Sud XI, Université de

283

In vivo Mapping of Local Cerebral Blood Flow by Xenon-Enhanced Computed Tomography  

Microsoft Academic Search

A noninvasive technique has been developed to measure and display local cerebral blood flow (LCBF) in vivo. In this procedure, nonradioactive xenon gas is inhaled and the temporal changes in radiographic enhancement produced by the inhalation are measured by sequential computerized tomography. The time-dependent xenon concentrations in various anatomical units in the brain are used to derive both the local

David Gur; Walter F. Good; Sidney K. Wolfson; Howard Yonas; Leonard Shabason

1982-01-01

284

Rapid curing of bonding composite with a xenon plasma arc light  

Microsoft Academic Search

The use of light-cured orthodontic adhesives is an increasingly popular method for the bonding of orthodontic brackets. However, one of the disadvantages of light-cured adhesives is their long curing times. The xenon plasma arc curing light is purported to dramatically reduce the required curing time. The purpose of this study was to test the efficiency of a xenon plasma arc

Larry J. Oesterle; Sheldon M. Newman; W. Craig Shellhart

2001-01-01

285

An improved interatomic potential for xenon in UO2: a combined density functional theory/genetic algorithm approach.  

PubMed

We have created an improved xenon interatomic potential for use with existing UO2 potentials. This potential was fit to density functional theory calculations with the Hubbard U correction (DFT + U) using a genetic algorithm approach called iterative potential refinement (IPR). We examine the defect energetics of the IPR-fitted xenon interatomic potential as well as other, previously published xenon potentials. We compare these potentials to DFT + U derived energetics for a series of xenon defects in a variety of incorporation sites (large, intermediate, and small vacant sites). We find the existing xenon potentials overestimate the energy needed to add a xenon atom to a wide set of defect sites representing a range of incorporation sites, including failing to correctly rank the energetics of the small incorporation site defects (xenon in an interstitial and xenon in a uranium site neighboring uranium in an interstitial). These failures are due to problematic descriptions of Xe-O and/or Xe-U interactions of the previous xenon potentials. These failures are corrected by our newly created xenon potential: our IPR-generated potential gives good agreement with DFT + U calculations to which it was not fitted, such as xenon in an interstitial (small incorporation site) and xenon in a double Schottky defect cluster (large incorporation site). Finally, we note that IPR is very flexible and can be applied to a wide variety of potential forms and materials systems, including metals and EAM potentials. PMID:24553248

Thompson, Alexander E; Meredig, Bryce; Wolverton, C

2014-03-12

286

X-ray diffraction of krypton and xenon mixtures adsorbed on graphite T. Ceva, M. Goldmann (*) and C. Marti  

E-print Network

1527 X- ray diffraction of krypton and xenon mixtures adsorbed on graphite T. Ceva, M. Goldmann 1986) Résumé. 2014 En étudiant, par diffraction des rayons X, les mélanges xenon-krypton absorbés sur. Abstract 2014 Mixtures of xenon and krypton adsorbed on graphite at 45 K are studied by X ray diffraction

Boyer, Edmond

287

Energy of the quasi-free electron in argon, krypton and xenon Xianbo Shi a,b  

E-print Network

Energy of the quasi-free electron in argon, krypton and xenon Xianbo Shi a,b , Luxi Li a,b , C. M ionization measurements of various high-n molecular Rydberg states doped into argon, krypton and xenon, krypton and xenon from the dilute gas up to the density of the triple point liquid, on both critical

Findley, Gary L.

288

The effects of He addition on the performance of the fission-fragment excited Ar/Xe atomic xenon laser  

E-print Network

The effects of He addition on the performance of the fission-fragment excited Ar/Xe atomic xenon September 1990; accepted for publication 8 November 1990) The intrinsic power efficiency of the atomic xenon of a fission-fragment excited atomic xenon laser. Adding He increases the heat capacity without appreciably

Kushner, Mark

289

"Liquid Xenon R&D for Future Large-Scale Dark-Matter Detectors" , D B Cline1  

E-print Network

1 "Liquid Xenon R&D for Future Large-Scale Dark-Matter Detectors" M Atac1 , D B Cline1 , K T Mc in the direct observation of nuclear recoils. The ZEPLIN-II detector (with 35-kg of liquid xenon medium), which. These tests will include: 1. photon amplification in liquid and gas xenon using a CsI internal photo

McDonald, Kirk

290

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

291

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.

Paul Anderson

2013-03-12

292

Mobility and fluorescence of barium ions in xenon gas for the exo experiment  

NASA Astrophysics Data System (ADS)

The Enriched Xenon Observatory (EXO) is an experiment which aims to observe the neutrinoless double beta decay of 136Xe. The measurement of this decay would give information about the absolute neutrino mass and whether or not the neutrino is its own antiparticle. Since this is a very rare decay, the ability to reject background events by detecting the barium ion daughter from the double beta decay would be a major advantage. EXO is currently operating a detector with 200 kg of enriched liquid xenon, and there are plans to build a ton scale xenon detector. Measurements of the purity of liquid xenon in our liquid xenon test cell are reported. These results are relevant to the research on detection of single barium ions by our research group at Colorado State University. Details of the operation of the purity monitor are described. The effects of using a purifier, recirculation and laser ablation on the purity of liquid xenon are discussed. Mobility measurements of barium in xenon gas are reported for the first time. The variation of mobility with xenon gas pressure suggests that a significant fraction of molecular ions are formed when barium ions interact with xenon gas at high pressures. The measured mobility of Ba+ in Xe gas at different pressures is compared with the predicted theoretical value, and deviations are explained by a model that describes the fraction of molecular ions in Xe gas as a function of pressure. The results are useful for the analysis of experiments of fluorescence of Ba+ in xenon gas. It is also important to know the mobility of the ions in order to calculate the time they interact with an excitation laser in fluorescence experiments and in proposed 136 Ba+ daughter detection schemes. This thesis presents results of detection of laser induced fluorescence of Ba+ ions in Xe gas. Measurements of the pressure broadening of the excitation spectra of Ba+ in xenon gas are presented. Nonradiative decays due to gas collisions and optical pumping affect the number of fluorescence counts detected. A model that treats the barium ion as a three level system is used to predict the total number of fluorescence counts and correct for optical pumping. A pressure broadening coefficient for Ba+ in xenon gas is extracted and limits for p-d and d-s nonradiative decay rates are extracted. Although fluorescence is reduced significantly at 5-10 atm xenon pressure, the measurements in this thesis indicate that it is still feasible to detect 136Ba+ ions directly in high pressure xenon gas, e.g. in a double beta decay detector.

Benitez Medina, Julio Cesar

293

Collisional energy transfer from excited nitrogen dioxide  

NASA Astrophysics Data System (ADS)

The radiative lifetimes of gaseous nitrogen dioxide excited by pulsed, tunable dye laser radiation are determined for excitation wavelengths ranging from 400 to 750 nm. When the data are expressed in the form of zero-pressure radiative rate constants (k(sub 0)/s exp -1), they fit a linear equation with respect to excitation energy. This fit predicts a radiative lifetime of 64 microseconds for 400 nm excitation and 102 microseconds at 750 nm. The effects of pressure, observation delay time, and wavelength range of the fluorescence detection apparatus are determined for both radiative lifetime and quenching constant. Dispersed fluorescence spectra from excited nitrogen dioxide are analyzed into three-parameter functions that approximate the corresponding excited state population distributions. Energy transfer from nitrogen dioxide excited at 532 nm and colliding with thirteen buffer gases is studied by this population deconvolution method. The energy removal rate constants increase in the order Ne, Ar, Kr, Xe, He, CO, N2, O2, NO, NO2, CO2, SF6, SO2. The energy transfer rate constant is strongly correlated with the number of degrees of freedom of the buffer molecule and with low vibrational frequencies of the buffer molecule. Population deconvolution from excited nitrogen dioxide fluorescence spectra is again employed to find energy removal rate constants for the NO2*-NO2 collisions, excited by dye laser at 475.34, 435.04, and 400.00 nm. The energy transfer rate constant increases with decreasing excitation wavelength. The energy removal rate constant between 400 and 532 nm excitation increases as the (3.6 +/- 0.4) power of the excitation photon energy.

Patten, K. O.

1991-05-01

294

The polarization sensitivity of the liquid xenon imaging telescope  

NASA Technical Reports Server (NTRS)

The properties and the expected performance of a liquid xenon (LXe) gamma ray imaging telescope, optimized for the MeV energy region, are presented. The unique potential of this telescope as a Compton polarimeter is particularly emphasized. Based on Monte Carlo simulations we show that the modulation factor is as high as 40 percent at 1 MeV with a detection efficiency close to 20 percent. These figures of merit combined with the excellent background suppression capability of the three dimensional position sensitive LXe detector yield sensitivity at the three sigma level to polarization fractions as small as a few percent for strong sources, even in a balloon flight.

Aprile, Elena; Bolotnikov, A.; Chen, D.; Mukherjee, R.

1993-01-01

295

Low energy positron scattering from krypton and xenon  

NASA Astrophysics Data System (ADS)

Absolute grand total, positronium formation, and grand total minus positronium formation cross sections for positron scattering from krypton and xenon have been measured with an energy resolution of ~60 meV over the energy range 0.5-60 eV. Experimental results for elastic differential cross sections measured using the same apparatus, for selected energies both below and above the Ps threshold, are also presented. Theoretical estimations of these cross sections are also performed using the convergent close coupling method (CCC) and the relativistic optical potential (ROP) approach.

Makochekanwa, C.; Machacek, J. R.; Jones, A. C. L.; Caradonna, P.; Slaughter, D. S.; McEachran, R. P.; Sullivan, J. P.; Buckman, S. J.; Fursa, D.; Bray, I.; Stauffer, A. D.

2012-11-01

296

Krypton and xenon in the atmosphere of Venus  

NASA Technical Reports Server (NTRS)

The paper reports a determination by the Pioneer Venus large probe neutral mass spectrometer of upper limits to the concentration of krypton and xenon along with most of their isotopes in the atmosphere of Venus. The upper limit to the krypton mixing ratio is estimated at 47 ppb, with a very conservative estimate at 69 ppb. The probable upper limit to the sum of the mixing ratios of the isotopes Xe-128, Xe-129, Xe-130, Xe-131, and Xe-132 is 40 ppb by volume, with a very conservative upper limit three times this large.

Donahue, T. M.; Hoffman, J. H.; Hodges, R. R., Jr.

1981-01-01

297

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

298

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.

299

Xenon adsorption on defected single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) simulation is used to compute the adsorption isotherms of xenon (Xe) gas on defected open ended single-walled nanotubes (o-SWNT). We perform a simulation based on a many-body interatomic Brenner potential with a two-body interatomic Lennard-Jones (LJ) potential. Adsorption isotherms of Xe on (10, 10) o-SWNT for several temperatures, between 95 and 130 K, are measured. Adsorption coverage, isosteric heat, and binding energy were calculated at various temperatures and pressures and compared with the same properties for the perfect (10, 10) o-SWNT. It is shown that adsorption occurs both inside and outside of an o-SWNTs.

Jalili, S.; Vaez, A.

2007-04-01

300

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

301

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

302

Dielectronic Recombination Cross-Sections of Fluorinelike Xenon  

E-print Network

PHYSICAL REVIEW A VOLUME 47, NUMBER 3 MARCH 1993 Dielectronic recombination cross sections of Snorinelike xenon D. R. DeWitt, D. Schneider, M. H. Chen, and M. B. Schneider Laturence Li uermore National Laboratory, Uniuersity of California.... E. Marrs, M. A. Levine, C. L. Bennett, M. H. Chen, J. R. Henderson, M. B. Schneider, and J. H. Scofield, Phys. Rev. Lett. 62, 2104 (1989). [4] R. Ali, C. P. Bhalla, C. L. Cocke, M. Schulz, and M. Stockli, Phys. Rev. A 44, 223 (1991);R. Ali, C. P...

Dewitt, D. R.; Schneider, D.; Chen, M. H.; Schneider, M. B.; Church, David A.; Weinberg, G.; Sakurai, M.

1993-01-01

303

Shear Thinning Near the Critical Point of Xenon  

NASA Technical Reports Server (NTRS)

We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids, near the critical point of xenon. The data span a wide range of reduced shear rate: 10(exp -3) < gamma-dot tau < 700, where gamma-dot tau is the shear rate scaled by the relaxation time tau of critical fluctuations. The measurements had a temperature resolution of 0.01 mK and were conducted in microgravity aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity. The viscometer measured the drag on a delicate nickel screen as it oscillated in the xenon at amplitudes 3 mu,m < chi (sub 0) >430 mu, and frequencies 1 Hz < omega/2 pi < 5 Hz. To separate shear thinning from other nonlinearities, we computed the ratio of the viscous force on the screen at gamma-dot tau to the force at gamma-dot tau approximates 0: C(sub gamma) is identical with F(chi(sub 0), omega tau, gamma-dot tau )/F)(chi(sub 0, omega tau, 0). At low frequencies, (omega tau)(exp 2) < gamma-dot tau, C(sub gamma) depends only on gamma-dot tau, as predicted by dynamic critical scaling. At high frequencies, (omega tau)(exp 2) > gamma-dot tau, C(sub gamma) depends also on both x(sub 0) and omega. The data were compared with numerical calculations based on the Carreau-Yasuda relation for complex fluids: eta(gamma-dot)/eta(0)=[1+A(sub gamma)|gamma-dot tau|](exp - chi(sub eta)/3+chi(sub eta)), where chi(sub eta) =0.069 is the critical exponent for viscosity and mode-coupling theory predicts A(sub gamma) =0.121. For xenon we find A(sub gamma) =0.137 +/- 0.029, in agreement with the mode coupling value. Remarkably, the xenon data close to the critical temperature T(sub c) were independent of the cooling rate (both above and below T(sub c) and these data were symmetric about T(sub c) to within a temperature scale factor. The scale factors for the magnitude of the oscillator s response differed from those for the oscillator's phase; this suggests that the surface tension of the two-phase domains affected the drag on the screen below T(sub c).

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

2008-01-01

304

Xenon gamma-ray detector for ecological applications  

NASA Astrophysics Data System (ADS)

A description of the xenon detector (XD) for ecological applications is presented. The detector provides high energy resolution and is able to operate under extreme environmental conditions (wide temperature range and unfavorable acoustic action). Resistance to acoustic noise as well as improvement in energy resolution has been achieved by means of real-time digital pulse processing. Another important XD feature is the ionization chamber's thin wall with composite housing, which significantly decreases the mass of the device and expands its energy range, especially at low energies.

Novikov, Alexander S.; Ulin, Sergey E.; Chernysheva, Irina V.; Dmitrenko, Valery V.; Grachev, Victor M.; Petrenko, Denis V.; Shustov, Alexander E.; Uteshev, Ziyaetdin M.; Vlasik, Konstantin F.

2015-01-01

305

Xenon excimer emission from multicapillary discharges in direct current mode  

SciTech Connect

Microdischarges in xenon have been generated in a pressure range of 400-1013 mbar with a fixed flow rate of 100 sccm. These microdischarges are obtained from three metallic capillary tubes in series for excimer emission. Total discharge voltage is thrice as large as that of a single capillary discharge tube at current levels of up to 12 mA. Total spectral irradiance of vacuum ultraviolet (VUV) emission also increases significantly compared to that of the single capillary discharge. Further, the irradiance of the VUV emission is strongly dependent on pressure as well as the discharge current.

Lee, Byung-Joon; Rahaman, Hasibur; Nam, Sang Hoon [Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of); Giapis, Konstantinos P. [Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States); Iberler, Marcus; Jacoby, Joachim [Institute of Applied Physics, Goethe University, Max-von-Laue-St. 1, 60438 Frankfurt am Main (Germany); Frank, Klaus [Physics Department I, F.A., University of Erlangen-Nuremberg, D-91058 Erlangen (Germany)

2011-08-15

306

The adsorption of argon, krypton and xenon on activated charcoal  

SciTech Connect

Charcoal adsorption beds are commonly used to remove radioactive noble gases from contaminated gas streams. The design of such beds requires the adsorption coefficient for the noble gas. Here an extension of the Dubinin-Radushkevich theory of adsorption is developed to correlate the effects of temperature, pressure, concentration, and carrier gas on the adsorption coefficients of krypton, xenon, and argon on activated carbon. This model is validated with previously published adsorption measurements. It accurately predicts the equilibrium adsorption coefficient at any temperature and pressure if the potential energies of adsorption, the micropore volume, and the van der Waals constants of the gases are known. 18 refs., 4 figs.

Underhill, D.W. [Univ. of South Carolina, Columbia, SC (United States)

1996-08-01

307

Irreversible xenon insertion into a small-pore zeolite at moderate pressures and temperatures.  

PubMed

Pressure drastically alters the chemical and physical properties of materials and allows structural phase transitions and chemical reactions to occur that defy much of our understanding gained under ambient conditions. Particularly exciting is the high-pressure chemistry of xenon, which is known to react with hydrogen and ice at high pressures and form stable compounds. Here, we show that Ag16Al16Si24O8·16H2O (Ag-natrolite) irreversibly inserts xenon into its micropores at 1.7?GPa and 250?°C, while Ag(+) is reduced to metallic Ag and possibly oxidized to Ag(2+). In contrast to krypton, xenon is retained within the pores of this zeolite after pressure release and requires heat to desorb. This irreversible insertion and trapping of xenon in Ag-natrolite under moderate conditions sheds new light on chemical reactions that could account for the xenon deficiency relative to argon observed in terrestrial and Martian atmospheres. PMID:25143221

Seoung, Donghoon; Lee, Yongmoon; Cynn, Hyunchae; Park, Changyong; Choi, Kwang-Yong; Blom, Douglas A; Evans, William J; Kao, Chi-Chang; Vogt, Thomas; Lee, Yongjae

2014-09-01

308

Irreversible xenon insertion into a small-pore zeolite at moderate pressures and temperatures  

NASA Astrophysics Data System (ADS)

Pressure drastically alters the chemical and physical properties of materials and allows structural phase transitions and chemical reactions to occur that defy much of our understanding gained under ambient conditions. Particularly exciting is the high-pressure chemistry of xenon, which is known to react with hydrogen and ice at high pressures and form stable compounds. Here, we show that Ag16Al16Si24O8·16H2O (Ag-natrolite) irreversibly inserts xenon into its micropores at 1.7?GPa and 250?°C, while Ag+ is reduced to metallic Ag and possibly oxidized to Ag2+. In contrast to krypton, xenon is retained within the pores of this zeolite after pressure release and requires heat to desorb. This irreversible insertion and trapping of xenon in Ag-natrolite under moderate conditions sheds new light on chemical reactions that could account for the xenon deficiency relative to argon observed in terrestrial and Martian atmospheres.

Seoung, Donghoon; Lee, Yongmoon; Cynn, Hyunchae; Park, Changyong; Choi, Kwang-Yong; Blom, Douglas A.; Evans, William J.; Kao, Chi-Chang; Vogt, Thomas; Lee, Yongjae

2014-09-01

309

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.

Randy Richardson

310

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.

2014-06-24

311

First Axion Results from the XENON100 Experiment  

E-print Network

We present the first results of searches for axions and axion-like-particles with the XENON100 experiment. The axion-electron coupling constant, $g_{Ae}$, has been tested by exploiting the axio-electric effect in liquid xenon. A profile likelihood analysis of 224.6 live days $\\times$ 34 kg exposure has shown no evidence for a signal. By rejecting $g_{Ae}$, larger than $7.7 \\times 10^{-12}$ (90% CL) in the solar axion search, we set the best limit to date on this coupling. In the frame of the DFSZ and KSVZ models, we exclude QCD axions heavier than 0.3 eV/c$^2$ and 80 eV/c$^2$, respectively. For axion-like-particles, under the assumption that they constitute the whole abundance of dark matter in our galaxy, we constrain $g_{Ae}$, to be lower than $1 \\times 10^{-12}$ (90% CL) for masses between 5 and 10 keV/c$^2$.

The XENON100 Collaboration; E. Aprile; F. Agostini; M. Alfonsi; K. Arisaka; F. Arneodo; M. Auger; C. Balan; P. Barrow; L. Baudis; B. Bauermeister; A. Behrens; P. Beltrame; K. Bokeloh; A. Brown; E. Brown; S. Bruenner; G. Bruno; R. Budnik; J. M. R. Cardoso; A. P. Colijn; H. Contreras; J. P. Cussonneau; M. P. Decowski; E. Duchovni; S. Fattori; A. D. Ferella; W. Fulgione; F. Gao; M. Garbini; C. Geis; L. W. Goetzke; C. Grignon; E. Gross; W. Hampel; R. Itay; F. Kaether; G. Kessler; A. Kish; H. Landsman; R. F. Lang; M. Le Calloch; D. Lellouch; C. Levy; S. Lindemann; M. Lindner; J. A. M. Lopes; K. Lung; A. Lyashenko; S. Macmullin; T. Marrodan Undagoitia; J. Masbou; F. V. Massoli; D. Mayani Paras; A. J. Melgarejo Fernandez; Y. Meng; M. Messina; B. Miguez; A. Molinario; M. Murra; J. Naganoma; U. Oberlack; S. E. A. Orrigo; E. Pantic; R. Persiani; F. Piastra; J. Pienaar; G. Plante; N. Priel; S. Reichard; C. Reuter; A. Rizzo; S. Rosendahl; J. M. F. dos Santos; G. Sartorelli; S. Schindler; J. Schreiner; M. Schumann; L. Scotto Lavina; M. Selvi; P. Shagin; H. Simgen; A. Teymourian; D. Thers; A. Tiseni; G. Trinchero; O. Vitells; H. Wang; M. Weber; C. Weinheimer

2014-08-27

312

Genetically encoded reporters for hyperpolarized xenon magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) enables high-resolution non-invasive observation of the anatomy and function of intact organisms. However, previous MRI reporters of key biological processes tied to gene expression have been limited by the inherently low molecular sensitivity of conventional 1H MRI. This limitation could be overcome through the use of hyperpolarized nuclei, such as in the noble gas xenon, but previous reporters acting on such nuclei have been synthetic. Here, we introduce the first genetically encoded reporters for hyperpolarized 129Xe MRI. These expressible reporters are based on gas vesicles (GVs), gas-binding protein nanostructures expressed by certain buoyant microorganisms. We show that GVs are capable of chemical exchange saturation transfer interactions with xenon, which enables chemically amplified GV detection at picomolar concentrations (a 100- to 10,000-fold improvement over comparable constructs for 1H MRI). We demonstrate the use of GVs as heterologously expressed indicators of gene expression and chemically targeted exogenous labels in MRI experiments performed on living cells.

Shapiro, Mikhail G.; Ramirez, R. Matthew; Sperling, Lindsay J.; Sun, George; Sun, Jinny; Pines, Alexander; Schaffer, David V.; Bajaj, Vikram S.

2014-07-01

313

PERSONAL MONITOR FOR NITROGEN DIOXIDE  

EPA Science Inventory

An attempt was made to develop a personal monitor to measure nitrogen dioxide. Sampling of nitrogen dioxide is accomplished by permeation through a silicone membrane into a alkaline thymol blue solution. The nitrogen dioxide is converted to nitrite and is then quantitated by colo...

314

Arnold Schwarzenegger THE CARBON DIOXIDE  

E-print Network

i Arnold Schwarzenegger Governor THE CARBON DIOXIDE ABATEMENT POTENTIAL OF CALIFORNIA'S MID, Afzal Siddiqui, and Judy Lai. 2011. The Carbon Dioxide Abatement Potential of California's Mid/Agricultural/Water EndUse Energy Efficiency · Renewable Energy Technologies · Transportation The Carbon Dioxide

315

8, 73157337, 2008 Carbon dioxide  

E-print Network

ACPD 8, 7315­7337, 2008 Carbon dioxide distributions over Europe C. Gurk et al. Title Page Abstract distributions of carbon dioxide over Europe C. Gurk1 , H. Fischer1 , P. Hoor1 , M.G. Lawrence1 , J. Lelieveld1 Publications on behalf of the European Geosciences Union. 7315 #12;ACPD 8, 7315­7337, 2008 Carbon dioxide

Paris-Sud XI, Université de

316

Can xenon in water inhibit ice growth? Molecular dynamics of phase transitions in water$-$Xe system  

E-print Network

Motivated by recent experiments showing the promise of noble gases as cryoprotectants, we perform molecular dynamics modeling of phase transitions in water with xenon under cooling. We study the structure and dynamics of xenon water solution as a function of temperature. Homogeneous nucleation of clathrate hydrate phase is observed and characterized. As the temperature is further reduced we observe hints of dissociation of clathrate due to stronger hydrophobic hydration, pointing towards a possible instability of clathrate at cryogenic temperatures and conversion to an amorphous phase comprised of "xenon + hydration shell" Xe$\\cdot$(H$_{2}$O)$_{21.5}$ clusters. Simulations of ice$-$xenon solution interface in equilibrium and during ice growth reveal the effects of xenon on the ice$-$liquid interface, where adsorbed xenon causes roughening of ice surface but does not preferentially form clathrate. These results provide evidence against the ice-blocker mechanism of xenon cryoprotection.

Artyukhov, Vasilii I; Peregudov, Alex; Artyuhov, Igor

2014-01-01

317

Can xenon in water inhibit ice growth? Molecular dynamics of phase transitions in water$-$Xe system  

E-print Network

Motivated by recent experiments showing the promise of noble gases as cryoprotectants, we perform molecular dynamics modeling of phase transitions in water with xenon under cooling. We study the structure and dynamics of xenon water solution as a function of temperature. Homogeneous nucleation of clathrate hydrate phase is observed and characterized. As the temperature is further reduced we observe hints of dissociation of clathrate due to stronger hydrophobic hydration, pointing towards a possible instability of clathrate at cryogenic temperatures and conversion to an amorphous phase comprised of "xenon + hydration shell" Xe$\\cdot$(H$_{2}$O)$_{21.5}$ clusters. Simulations of ice$-$xenon solution interface in equilibrium and during ice growth reveal the effects of xenon on the ice$-$liquid interface, where adsorbed xenon causes roughening of ice surface but does not preferentially form clathrate. These results provide evidence against the ice-blocker mechanism of xenon cryoprotection.

Vasilii I. Artyukhov; Alexander Yu. Pulver; Alex Peregudov; Igor Artyuhov

2014-07-11

318

Chlorine Dioxide (Gas)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Chlorine dioxide (ClO2) gas is registered by the U.S. Environmental Protection Agency (EPA) as a sterilant for use in manufacturing, laboratory equipment, medical devices, environmental surfaces, tools and clean rooms. Aqueous ClO2 is registered by the EPA as a surface disinfectant and sanitizer fo...

319

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.)

320

Carbon dioxide recycling  

EPA Science Inventory

The recycling of carbon dioxide to methanol and dimethyl ether is seen to offer a substantial route to renewable and environmentally carbon neutral fuels. One of the authors has championed the ?Methanol Economy" in articles and a book. By recycling ambient CO2, the authors argue ...

321

Atmospheric Carbon Dioxide  

NSDL National Science Digital Library

This figure, the famous Keeling Curve, shows the history of atmospheric carbon dioxide concentrations as directly measured at Mauna Loa, Hawaii. This curve is an essential piece of evidence that shows the increased greenhouse gases that cause recent increases in global temperatures.

Robert A. Rohde

322

Carbon dioxide sensor  

SciTech Connect

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

323

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.

324

Sulfur Dioxide Pollution Monitor.  

ERIC Educational Resources Information Center

The sulfur dioxide pollution monitor described in this document is a government-owed invention that is available for licensing. The background of the invention is outlined, and drawings of the monitor together with a detailed description of its function are provided. A sample stream of air, smokestack gas or the like is flowed through a…

National Bureau of Standards (DOC), Washington, DC.

325

Measurement of the reflectivity to 178nm light of the PTFE used in the Xenon100  

NASA Astrophysics Data System (ADS)

The XENON100 time projection chamber (TPC) uses polytetrafluoroethylene (PTFE) both as insulator and as VUV-light reflector. The reflectivity of PTFE, however, is not well established, especially considering that it significantly depends on the surface finish. Furthermore, the PTFE in XENON100 is in contact with the liquid xenon at about -100^oC, which can also affect the reflecting property. A set-up consisting of a monochromator and a vacuum chamber was developed within the XENON100 collaboration and operated at the Columbia University Nevis Laboratory to measure the reflectivity of PTFE and other material samples, relevant for future XENON detectors. The chamber is equipped with an Iwatani PDC08 pulse tube refrigerator (PTR) to be able to cool down the samples to liquid xenon temperature. The same set-up has also been used to measure, for the first time, the quantum efficiency (QE) of the Hamamatsu R8520-06-AL XENON100 photomultipliers at low temperature.

Choi, Bin

2011-04-01

326

GraXe, graphene and xenon for neutrinoless double beta decay searches  

E-print Network

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-coated titanium mesh and filled with liquid xenon (LXe) enriched in the Xe-136 isotope is immersed in a large volume of natural LXe instrumented with photodetectors. Liquid xenon is an excellent scintillator, reasonably transparent to its own light. Graphene is transparent over a large frequency range, and impermeable to the xenon. Event position could be deduced from the light pattern detected in the photosensors. External backgrounds would be shielded by the buffer of natural LXe, leaving the ultra-radiopure internal volume virtually free of background. Industrial graphene can be manufactured at a competitive cost to produce the sphere. Enriching xenon in the isotope Xe-136 is easy and relatively cheap, and there is already near one ton of enriched xenon available in the world (currently being used by the EXO, KamLAND-Zen and NEXT experiments). All the cryogenic know-how is readily available from the numerous experiments using liquid xenon. An experiment using the GraXe concept appears realistic and affordable in a short time scale, and its physics potential is enormous.

J. J. Gomez-Cadenas; F. Guinea; M. M. Fogler; M. I. Katsnelson; J. Martin-Albo; F. Monrabal; J. Muñoz-Vidal

2012-02-23

327

The breakthrough curve combination for xenon sampling dynamics in a carbon molecular sieve column.  

PubMed

In the research of xenon sampling and xenon measurements, the xenon breakthrough curve plays a significant role in the xenon concentrating dynamics. In order to improve the theoretical comprehension of the xenon concentrating procedure from the atmosphere, the method of the breakthrough curve combination for sampling techniques should be developed and investigated under pulse injection conditions. In this paper, we describe a xenon breakthrough curve in a carbon molecular sieve column, the combination curve method for five conditions is shown and debated in detail; the fitting curves and the prediction equations are derived in theory and verified by the designed experiments. As a consequence, the curves of the derived equations are in good agreement with the fitting curves by tested. The retention times of the xenon in the column are 61.2, 42.2 and 23.5 at the flow rate of 1200, 1600 and 2000 mL min(-1), respectively, but the breakthrough times are 51.4, 38.6 and 35.1 min. PMID:25423488

Shu-jiang, Liu; Zhan-ying, Chen; Yin-zhong, Chang; Shi-lian, Wang; Qi, Li; Yuan-qing, Fan; Huai-mao, Jia; Xin-jun, Zhang; Yun-gang, Zhao

2015-01-21

328

GraXe, graphene and xenon for neutrinoless double beta decay searches  

SciTech Connect

We propose a new detector concept, GraXe (to be pronounced as grace), to search for neutrinoless double beta decay in {sup 136}XE. 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 {sup 136}XE isotope is immersed in a large volume of natural LXe instrumented with photodetectors. Liquid xenon is an excellent scintillator, reasonably transparent to its own light. Graphene is transparent over a large frequency range, and impermeable to the xenon. Event position could be deduced from the light pattern detected in the photosensors. External backgrounds would be shielded by the buffer of natural LXe, leaving the ultra-radiopure internal volume virtually free of background. Industrial graphene can be manufactured at a competitive cost to produce the sphere. Enriching xenon in the isotope {sup 136}XE is easy and relatively cheap, and there is already near one ton of enriched xenon available in the world (currently being used by the EXO, KamLAND-Zen and NEXT experiments). All the cryogenic know-how is readily available from the numerous experiments using liquid xenon. An experiment using the GraXe concept appears realistic and affordable in a short time scale, and its physics potential is enormous.

Gómez-Cadenas, J.J.; Martín-Albo, J.; Monrabal, F.; Vidal, J. Muñoz [Instituto de Física Corpuscular (IFIC), CSIC and Universitat de Valencia, Calle Catedrático José Beltrán, 2, 46980 Valencia (Spain); Guinea, F. [Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Calle Sor Juana Inés de la Cruz, 3, 28049 Madrid (Spain); Fogler, M.M. [Department of Physics, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093 (United States); Katsnelson, M.I., E-mail: gomez@mail.cern.ch, E-mail: paco.guinea@icmm.csic.es, E-mail: mfogler@ucsd.edu, E-mail: katsnel@sci.kun.nl, E-mail: justo.martin-albo@ific.uv.es, E-mail: francesc.monrabal@ific.uv.es, E-mail: jmunoz@ific.uv.es [Institute for Molecules and Materials, Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen (Netherlands)

2012-02-01

329

Revisiting XENON100's constraints (and signals?) for low-mass dark matter  

SciTech Connect

Although observations made with the CoGeNT and CDMS experiments have been interpreted as possible signals of low-mass ( ? 7–10 GeV) dark matter particles, constraints from the XENON100 collaboration appear to be incompatible with this hypothesis, at least at face value. In this paper, we revisit XENON100's constraint on dark matter in this mass range, and consider how various uncertainties and assumptions made might alter this conclusion. We also note that while XENON100's two nuclear recoil candidates each exhibit very low ratios of ionization-to-scintillation signals, making them difficult to attribute to known electronic or neutron backgrounds, they are consistent with originating from dark matter particles in the mass range favored by CoGeNT and CDMS. We argue that with lower, but not implausible, values for the relative scintillation efficiency of liquid xenon (L{sub eff}), and the suppression of the scintillation signal in liquid xenon at XENON100's electric field (S{sub nr}), these two events could consistently arise from dark matter particles with a mass and cross section in the range favored by CoGeNT and CDMS. If this interpretation is correct, we predict that the LUX experiment, with a significantly higher light yield than XENON100, should observe dark matter induced events at an observable rate of ? 3–24 per month.

Hooper, Dan, E-mail: dhooper@fnal.gov [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States)

2013-09-01

330

Single molecule spectroscopy of tetrahedral oligophenylenevinylene molecules  

E-print Network

Single molecule spectroscopy of tetrahedral oligophenylenevinylene molecules Melissa A. Summers form 17 July 2002 Abstract We probe the fluorescence from single molecules of a new class of tetrahedral oligo(phenylenevinylene) (OPV) molecules. Our results show that the tetrahedral molecules contain

Buratto, Steve

331

Modeling the infrared and raman spectra of silicon dioxide clusters absorbing water  

Microsoft Academic Search

The effect of absorbed water on the dielectric properties of silicon dioxide nanoparticles is studied by the molecular dynamic method. It is demonstrated using the model of flexible molecules that increasing the number of water molecules in the (SiO2)50 cluster to 40 results in an enhancement of absorption of infrared radiation over the frequency range 0 cm-1 <= omega <=

A. E. Galashev; O. R. Rakhmanova; L. A. Zemnukhova

2011-01-01

332

Building Molecules  

NSDL National Science Digital Library

This online interactive has three activities in the NanoLab (press the upper right button): Build, Zoom, and Transform. In Build, learners build increasingly complex molecules out of carbon, oxygen, and hydrogen, and is useful for connecting subscripts and the number of atoms, and for introducing 3D molecular structures which are automatically built. Zoom is a "powers of 10" zoom-in ranging from 10,000 kilometers to 1 nanometer. Transform is a simulation of water changing phase from solid to liquid to gas. Through exploration of the site learners form a better understanding of the composition of matter.

Rensselaer Polytechnic Institute

2005-01-01

333

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

334

Pretreatment for cellulose hydrolysis by carbon dioxide explosion  

SciTech Connect

Cellulosic materials were treated with supercritical carbon dioxide to increase the reactivity of cellulose, thereby to enhance the rate and the extent of cellulose hydrolysis. In this pretreatment process, the cellulosic materials such as Avicel, recycled paper mix, sugarcane bagasse and the repulping waste of recycled paper are placed in a reactor under pressurized carbon dioxide at 35 C for a controlled time period. Upon an explosive release of the carbon dioxide pressure, the disruption of the cellulosic structure increases the accessible surface area of the cellulosic substrate to enzymatic hydrolysis. Results indicate that supercritical carbon dioxide is effective for pretreatment of cellulose. An increase in pressure facilitates the faster penetration of carbon dioxide molecules into the crystalline structures, thus more glucose is produced from cellulosic materials after the explosion as compared to those without the pretreatment. This explosion pretreatment enhances the rate of cellulosic material hydrolysis as well as increases glucose yield by as much as 50%. Results from the simultaneous saccharification and fermentation tests also show the increase in the available carbon source from the cellulosic materials for fermentation to produce ethanol. As an alternative method, this supercritical carbon dioxide explosion has a possibility to reduce expense compared with ammonia explosion, and since it is operated at the low temperature, it will not cause degradation of sugars such as those treated with steam explosion due to the high-temperature involved.

Zheng, Y.; Lin, H.M.; Tsao, G.T. [Purdue Univ., West Lafayette, IN (United States). Lab of Renewable Resources Engineering] [Purdue Univ., West Lafayette, IN (United States). Lab of Renewable Resources Engineering

1998-11-01

335

Using carbon dioxide as a building block in organic synthesis.  

PubMed

Carbon dioxide exits in the atmosphere and is produced by the combustion of fossil fuels, the fermentation of sugars and the respiration of all living organisms. An active goal in organic synthesis is to take this carbon--trapped in a waste product--and re-use it to build useful chemicals. Recent advances in organometallic chemistry and catalysis provide effective means for the chemical transformation of CO? and its incorporation into synthetic organic molecules under mild conditions. Such a use of carbon dioxide as a renewable one-carbon (C1) building block in organic synthesis could contribute to a more sustainable use of resources. PMID:25600683

Liu, Qiang; Wu, Lipeng; Jackstell, Ralf; Beller, Matthias

2015-01-01

336

Photodissociation Dynamics of Atmospherically Important Molecules: Carbon Dioxide and Ozone.  

NASA Astrophysics Data System (ADS)

The photodissociation dynamics of CO_2 following excitation at 157 nm have been studied by probing the internal and translational energy distributions of the CO product via vacuum-ultraviolet laser-induced fluorescence. The rotational distributions for CO in upsilon = 0 and upsilon = 1 were measured and found to be nonBoltzmann with both rotational distributions being highly structured. The relative vibrational population (upsilon = 0/upsilon = 1) was determined to be 3.7 +/- 1.2. CO Doppler profiles were found to have widths in accord with the available translational energy, display a v | J correlation and be best described by an isotropic angular distribution (beta = 0.0 +/- 0.4). The ultraviolet photodissociation of O _3, which results in the products, O( ^1D) + O_2(a ^1 Delta_{rm g}) and O( ^3 P) + O_2(X ^3Sigma_{rm g}^ -), has been investigated by probing selected fragments via resonance-enhanced multiphoton ionization (REMPI) coupled with time-of-flight ion imaging. Images of the 2D projection of the nascent 3D velocity distribution of O(^3P) from the 226 nm dissociation of O_3 were obtained and show that the fragment is produced with a bimodal velocity distribution. Laser-induced fluorescence experiments determined that the slower O(^3P ) fragments are co-produced with O_2(X ^3Sigma_{rm g}^ -, upsilon >= 26), a species recent kinetic experiments have suggested can react rapidly with O_2 to form O _3 + O. The possibility of the autocatalytic mechanism for odd oxygen production, O_3 + hupsilon to O _2(X ^3Sigma_{rm g}^-, upsilon >= 26) + O; O_2(X ^3Sigma_ {rm g}^-, upsilon >= 26) + O_2 to O _3 + O, and its implication for the "ozone deficit" problem are discussed. Preliminary imaging results suggest that the O(^3P) velocity distribution is bimodal for O_3 dissociation at 252 through 193 nm and that the population ratio of the slow to fast O(^3P) fragments varies significantly with photolysis wavelength. Images of O_2[ a ^1 Delta_{rm g} (upsilon, J)] from the 248 nm dissociation of O_3 were also obtained and show strong evidence of v-J correlation. The images were accurately simulated using a Monte Carlo forward convolution program that accounts for the dependence of the detection efficiency on angular momentum polarization and assumes an impulsive dissociation from the ground-state geometry (beta = 1.18). Preliminary imaging results for O(^1D) from the 205.47 nm dissociation of O_3 were also obtained. These images appear to show some type of orbital alignment for the O(^1D) product and might support the formation of O( ^1D) in coincidence with both O_2(a ^1Delta_{rm g}) and O_2(b ^1Sigma _{rm g}^+)..

Miller, Robin Lynn

1995-01-01

337

Scintillation efficiency for low energy nuclear recoils in liquid xenon dark matter detectors  

NASA Astrophysics Data System (ADS)

We perform a theoretical study of the scintillation efficiency of the low energy region crucial for liquid xenon dark matter detectors. We develop a computer program to simulate the cascading process of the recoiling xenon nucleus in liquid xenon and calculate the nuclear quenching effect due to atomic collisions. We use the electronic stopping power extrapolated from experimental data to the low energy region, and take into account the effects of electron escape from electron-ion pair recombination using the generalized Thomas-Imel model fitted to scintillation data. Our result agrees well with the experiments from neutron scattering and vanishes rapidly as the recoil energy drops below 3 keV.

Mu, Wei; Xiong, Xiaonu; Ji, Xiangdong

2015-02-01

338

XENON10/100 dark matter constraints: examining the Leff dependence  

E-print Network

The determination of dark matter constraints from liquid xenon direct detection experiments depends upon the amount of scintillation light produced by nuclear recoils in the detector, a quantity that is characterized by the scintillation efficiency factor Leff. We examine how uncertainties in the measurements of Leff and the extrapolated behavior of Leff at low recoil energies (where measurements do not exist) affect the constraints from experiments such as XENON10 and XENON100, particularly in the light WIMP regions of interest for the DAMA and CoGeNT experimental results.

Christopher Savage

2010-12-17

339

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

340

A New Approach to the Origin of Xenon-HL  

NASA Astrophysics Data System (ADS)

Xenon-HL carried by interstellar diamonds in primitive meteorites [1] resembles xenon produced in the p- and r-processes of nucleosynthesis (thought to occur in supernovae) in that it is enriched in the light (hence 'L'), p-only, isotopes 124,126Xe and the heavy (hence 'H'), r-only, isotopes 134,136Xe. Detailed comparison reveals different levels of enhancement in Xe-H, however, of 134Xe and 136Xe. As a result, ad-hoc scenarios have been suggested, like a mini-r-process, intermediate between s-and r-process, for producing Xe-H [2]. However, inventing a special process in order to account for a significant fraction of one element (several percent of the Xe in primitive meteorites is Xenon-HL) without evidence for such a process to have contributed significantly to anything else, is not a very attractive solution. Here we propose to consider instead that Xe-H is basically 'normal' r-process Xe that a chemical fractionation effect has turned into Xe-H. In doing so we compare r-process Xe with 'pure 'Xe-HL (i.e. Xe-HL extrapolated to 130Xe degrees 0, where 'real' HL-Xe is the product of mixing with ~ normal Xe). The r-process acts on a rapid (~1 sec) timescale (e.g. [3]), producing neutron-rich nuclides far from stability, that subsequently decay via a series of beta-decays into stable endproducts. As the precursors of the different Xe isotopes have different lifetimes, the isotopic composition of the Xe in supernova ejecta will be time-dependent on that time-scale. From the figure, where the development of the ratio 134Xe/136Xe is shown, it is obvious that after approx. 2 hours this ratio is equal to that of 'pure' Xe-H. If, at that time, a chemical separation can be achieved between the Te and I precursors on one hand and Xe on the other, we are left with Xe for which this ratio is identical to that in Xe-H. At this time little 129,131,132Xe will have been produced, because their precursors have much longer half-lives. In order to account for the small, but non-zero abundances in pure Xe-H of these isotopes, on the order of 5% of fully developed r-process Xe may have to be admixed, an observation supported by the fact that in 'pure' Xe-H these isotopes occur in ratios relative to each other that are consistent with r-process Xe proper. Also, because in the p-process 126Xe is in part originally produced as 126Ba with a half-life of 97 min., a separation of Ba from Xe on a similar time-scale may account for the fact that (126Xe/124Xe)L < (126Xe/124Xe)p. Condensation comes to mind as an obvious means to achieve a separation between xenon and the other elements, but timescales usually associated with the formation of supernova condensates are years rather than hours. We note, however, that for certain assumptions about the cooling process of supernovae, the first condensates may form in the ejecta after about 10^3-10^4sec. already [4]. Taken at face value, the existence of Xe-HL may serve to support such a fast cooling scenario. References: [1] Lewis R. S. et al. (1987) Nature, 326, 160-162. [2] Clayton D. D. (1989) Astrophys. J., 340, 613-619. [3] Kratz K.-L. et al. (1993) Astrophys. J., 403, 216-238. [4] Lattimer J. M. et al. (1978) Astrophys. J., 219, 230-249.

Ott, U.

1995-09-01

341

Scintillation Response of Liquid Xenon to Low Energy Nuclear Recoils  

E-print Network

Liquid Xenon (LXe) is expected to be an excellent target and detector medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). Knowledge of LXe ionization and scintillation response to low energy nuclear recoils expected from the scattering of WIMPs by Xe nuclei is important for determining the sensitivity of LXe direct detection experiments. Here we report on new measurements of the scintillation yield of Xe recoils with kinetic energy as low as 10 keV. The dependence of the scintillation yield on applied electric field was also measured in the range of 0 to 4 kV/cm. Results are in good agreement with recent theoretical predictions that take into account the effect of biexcitonic collisions in addition to the nuclear quenching effect.

E. Aprile; K. L. Giboni; P. Majewski; K. Ni; M. Yamashita; R. Hasty; A. Manzur; D. N. McKinsey

2005-03-29

342

Position Reconstruction in a Dual Phase Xenon Scintillation Detector  

NASA Astrophysics Data System (ADS)

We studied the application of statistical reconstruction algorithms, namely maximum likelihood and least squares methods, to the problem of event reconstruction in a dual phase liquid xenon detector. An iterative method was developed for in-situ reconstruction of the PMT light response functions from calibration data taken with an uncollimated gamma-ray source. Using the techniques described, the performance of the ZEPLIN-III dark matter detector was studied for 122 keV gamma-rays. For the inner part of the detector (R<100 mm), spatial resolutions of 13 mm and 1.6 mm FWHM were measured in the horizontal plane for primary and secondary scintillation, respectively. An energy resolution of 8.1% FWHM was achieved at that energy. The possibility of using this technique for improving performance and reducing cost of scintillation cameras for medical applications is currently under study.

Solovov, V. N.; Belov, V. A.; Akimov, D. Yu.; Araujo, H. M.; Barnes, E. J.; Burenkov, A. A.; Chepel, V.; Currie, A.; DeViveiros, L.; Edwards, B.; Ghag, C.; Hollingsworth, A.; Horn, M.; Kalmus, G. E.; Kobyakin, A. S.; Kovalenko, A. G.; Lebedenko, V. N.; Lindote, A.; Lopes, M. I.; Luscher, R.; Majewski, P.; Murphy, A. S. J.; Neves, F.; Paling, S. M.; Pinto da Cunha, J.; Preece, R.; Quenby, J. J.; Reichhart, L.; Scovell, P. R.; Silva, C.; Smith, N. J. T.; Smith, P. F.; Stekhanov, V. N.; Sumner, T. J.; Thorne, C.; Walker, R. J.

2012-12-01

343

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

344

Multiple-ionization of xenon atoms by positron impact  

NASA Technical Reports Server (NTRS)

Previously the cross sections were measured for positronium formation and single ionization by positron impact for He and H2. With the same apparatus, slightly modified, the single and multiple ionization of xenon is now investigated. The principle of the method is the detection of ion and positron in time correlation which allows the discrimination of positronium formation (whereby the positron vanishes) and the destinction of single, double and triple impact ionization (which lead to different ion flight times from the gas target to the ion detector). By using secondary electrons from the positron moderator, similar measurements were performed on electron impact ionization. By comparing with literature values for electron multiple ionization cross sections, the detection-probability ratios were determined for the differently charged ions.

Kruse, Georg; Quermann, Andreas; Raith, Wilhelm; Sinapius, Guenther

1990-01-01

345

Circular and linear magnetic birefringences in xenon at ? = 1064 nm.  

PubMed

The circular and linear magnetic birefringences corresponding to the Faraday and the Cotton-Mouton effects, respectively, have been measured in xenon at ? = 1064?nm. The experimental setup is based on time dependent magnetic fields and a high finesse Fabry-Pérot cavity. Our value of the Faraday effect is the first measurement at this wavelength. It is compared to theoretical predictions. Our uncertainty of a few percent yields an agreement at better than 1? with the computational estimate when relativistic effects are taken into account. Concerning the Cotton-Mouton effect, our measurement, the second ever published at ? = 1064?nm, agrees at better than 1? with theoretical predictions. We also compare our error budget with that established for other experimental published values. PMID:25833585

Cadène, Agathe; Fouché, Mathilde; Rivère, Alice; Battesti, Rémy; Coriani, Sonia; Rizzo, Antonio; Rizzo, Carlo

2015-03-28

346

Reactivity of Xenon with Ice at Planetary Conditions  

NASA Astrophysics Data System (ADS)

We report results from high pressure and temperature experiments that provide evidence for the reactivity of xenon with water ice at pressures above 50 GPa and a temperature of 1500 K—conditions that are found in the interiors of Uranus and Neptune. The x-ray data are sufficient to determine a hexagonal lattice with four Xe atoms per unit cell and several possible distributions of O atoms. The measurements are supplemented with ab initio calculations, on the basis of which a crystallographic structure with a Xe4O12H12 primitive cell is proposed. The newly discovered compound is formed in the stability fields of superionic ice and ?-O2, and has the same oxygen subnetwork as the latter. Furthermore, it has a weakly metallic character and likely undergoes sublattice melting of the H subsystem. Our findings indicate that Xe is expected to be depleted in the atmospheres of the giant planets as a result of sequestration at depth.

Sanloup, Chrystèle; Bonev, Stanimir A.; Hochlaf, Majdi; Maynard-Casely, Helen E.

2013-06-01

347

Neon and Xenon adsorption on opened carbon nanohorns  

NASA Astrophysics Data System (ADS)

Adsorption isotherms were measured for neon adsorbed on opened (oxidized) carbon nanohorn aggregates. The isotherms were performed at eleven different temperatures between 19 to 40 K. Two distinct substeps are present in logarithmic plots of the adsorption data. The two substeps correspond to high and low binding energy sites present in the nanohorn aggregates. The values of the isosteric heat as a function of substrate loading was calculated; it shows features corresponding to the two adsorption isotherm substeps. The results for neon will be compared to those from ongoing measurements for xenon adsorbed on the same sample of open carbon nanohorn aggregates as well as to a previous study of neon on closed carbon nanohorns.

Ziegler, Carl; Krungleviciute, Vaiva; Migone, Aldo; Yudasaka, Masako; Iijima, Sumio

2013-03-01

348

Investigation of many-body forces in krypton and xenon  

SciTech Connect

The simplicity of the state dependence at relatively high temperatures ofthe many-body potential contribution to the pressure and energy has been pointed out previously (J. Ram and P. A. Egelstaff, J. Phys. Chem. Liq. 14, 29 (1984); A. Teitsima and P. A. Egelstaff, Phys. Rev. A 21, 367 (1980)). In this paper, we investigate how far these many-body potential terms may be represented by simple models in the case of krypton on the 423-, 273-, 190-, and 150-K isotherms, and xenon on the 170-, 210-, and 270-K isotherms. At the higher temperatures the best agreement is found for the mean-field type of theory, and some consequences are pointed out. On the lower isotherms a state point is found where the many-body energy vanishes, and large departures from mean-field behavior are observed. This is attributed to the influence of short-ranged many-body forces.

Salacuse, J.J.; Egelstaff, P.A.

1988-10-15

349

Dual-phase liquid xenon detectors for dark matter searches  

NASA Astrophysics Data System (ADS)

Dual-phase time projection chambers (TPCs) filled with the liquid noble gas xenon (LXe) are currently the most sensitive detectors searching for interactions of WIMP dark matter in a laboratory-based experiment. This is achieved by combining a large, monolithic dark matter target of a very low background with the capability to localize the interaction vertex in three dimensions, allowing for target fiducialization and multiple-scatter rejection. The background in dual-phase LXe TPCs is further reduced by the simultaneous measurement of the scintillation and ionization signal from a particle interaction, which is used to distinguish signal from background signatures. This article reviews the principle of dual-phase LXe TPCs, and provides an overview about running as well as future experimental efforts.

Schumann, Marc

2014-08-01

350

Increasing the Life of a Xenon-Ion Spacecraft Thruster  

NASA Technical Reports Server (NTRS)

A short document summarizes the redesign of a xenon-ion spacecraft thruster to increase its operational lifetime beyond a limit heretofore imposed by nonuniform ion-impact erosion of an accelerator electrode grid. A peak in the ion current density on the centerline of the thruster causes increased erosion in the center of the grid. The ion-current density in the NSTAR thruster that was the subject of this investigation was characterized by peak-to-average ratio of 2:1 and a peak-to-edge ratio of greater than 10:1. The redesign was directed toward distributing the same beam current more evenly over the entire grid andinvolved several modifications of the magnetic- field topography in the thruster to obtain more nearly uniform ionization. The net result of the redesign was to reduce the peak ion current density by nearly a factor of two, thereby halving the peak erosion rate and doubling the life of the thruster.

Goebel, Dan; Polk, James; Sengupta, Anita; Wirz, Richard

2007-01-01

351

Deep Space Mission Applications for NEXT: NASA's Evolutionary Xenon Thruster  

NASA Technical Reports Server (NTRS)

NASA's Evolutionary Xenon Thruster (NEXT) is designed to address a need for advanced ion propulsion systems on certain future NASA deep space missions. This paper surveys seven potential missions that have been identified as being able to take advantage of the unique capabilities of NEXT. Two conceptual missions to Titan and Neptune are analyzed, and it is shown that ion thrusters could decrease launch mass and shorten trip time, to Titan compared to chemical propulsion. A potential Mars Sample return mission is described, and compassion made between a chemical mission and a NEXT based mission. Four possible near term applications to New Frontiers and Discovery class missions are described, and comparisons are made to chemical systems or existing NSTAR ion propulsion system performance. The results show that NEXT has potential performance and cost benefits for missions in the Discovery, New Frontiers, and larger mission classes.

Oh, David; Benson, Scott; Witzberger, Kevin; Cupples, Michael

2004-01-01

352

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

353

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

354

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

355

Multiphoton ionization and third-harmonic generation in atoms and molecules  

SciTech Connect

We will discuss recent experiments on multiphoton ionization and third-harmonic generation in rare gases and small molecules using focused laser power densities of 10/sup 9/ to 10/sup 11/ W/cm/sup 2/. Also, some elementary experiments using vacuum ultraviolet light generated by frequency tripling in xenon and krypton will be described. These experiments include absorption and ionization studies using vacuum ultraviolet radiation as well as two-photon ionization using one vacuum ultraviolet photon and one laser photon.

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

1982-01-01

356

Carbon Dioxide Landscape  

NASA Technical Reports Server (NTRS)

23 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a view of some of the widely-varied terrain of the martian south polar residual cap. The landforms here are composed mainly of frozen carbon dioxide. Each year since MGS arrived in 1997, the scarps that bound each butte and mesa, or line the edges of each pit, in the south polar region, have changed a little bit as carbon dioxide is sublimed away. The scarps retreat at a rate of about 3 meters (3 yards) per martian year. Most of the change occurs during each southern summer.

Location near: 86.7oS, 9.8oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

2005-01-01

357

CARBON DIOXIDE FIXATION.  

SciTech Connect

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} conversion. Recent achievements in the efficiency of solar energy conversion and in catalysis suggest that this approach holds a great deal of promise for contributing to future needs for fuels and chemicals.

FUJITA,E.

2000-01-12

358

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

359

Large scale xenon purification using cryogenic distillation for dark matter detectors  

NASA Astrophysics Data System (ADS)

A high efficiency cryogenic distillation system for removal of radioactive krypton-85 (85Kr) from commercially available xenon (Xe) has been designed, developed and assessed to meet the requirements of high sensitivity, low background dark matter detection experiments. The concentration of krypton (Kr) in a commercial xenon product can be decreased from 10?9 to 10?12 mol/mol based on the theoretical design and simulation. The experimental measurements showed that the concentration of krypton was decreased to 10?11 mol/mol with 99% xenon collection efficiency at maximum flow rate of 5 kg/h. Over 500 kg of xenon has been purified using this system, which has been used as the detection medium in project Panda X, the first dark matter detector developed in China.

Wang, Z.; Bao, L.; Hao, X. H.; Ju, Y. L.; Pushkin, K.; He, M.

2014-11-01

360

Ionization and equation of state of dense xenon at high pressures and high temperatures.  

PubMed

The ionization degree and equation of state of dense xenon plasma were calculated by using self-consistent fluid variational theory for temperature of 4-30kK and density of 0.01-8.5gcm;{3} . The dense fluid xenon will be ionized at high pressures and temperatures. The ionization energy of xenon will be lowered due to the interactions among all particles of Xe, Xe+ , Xe2+ , and e . The ionization degree is obtained from nonideal ionization equilibrium, taking into account the correlative contributions to the chemical potential which is determined self-consistently by the free energy function. The composition of xenon has been calculated with given densities and temperatures in the region of partial ionization. The calculated results show a pressure softening regime at the onset of ionization. Comparison is performed with available shock-wave experiments and other theoretical calculations. PMID:19257150

Chen, Q F; Cai, L C; Gu, Y J; Gu, Y

2009-01-01

361

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

362

Detection of brown adipose tissue and thermogenic activity in mice by hyperpolarized xenon MRI.  

PubMed

The study of brown adipose tissue (BAT) in human weight regulation has been constrained by the lack of a noninvasive tool for measuring this tissue and its function in vivo. Existing imaging modalities are nonspecific and intrinsically insensitive to the less active, lipid-rich BAT of obese subjects, the target population for BAT studies. We demonstrate noninvasive imaging of BAT in mice by hyperpolarized xenon gas MRI. We detect a greater than 15-fold increase in xenon uptake by BAT during stimulation of BAT thermogenesis, which enables us to acquire background-free maps of the tissue in both lean and obese mouse phenotypes. We also demonstrate in vivo MR thermometry of BAT by hyperpolarized xenon gas. Finally, we use the linear temperature dependence of the chemical shift of xenon dissolved in adipose tissue to directly measure BAT temperature and to track thermogenic activity in vivo. PMID:25453088

Branca, Rosa Tamara; He, Ting; Zhang, Le; Floyd, Carlos S; Freeman, Matthew; White, Christian; Burant, Alex

2014-12-16

363

Nonlinear dynamical behavior of Xenon atoms along dislocation lines in UO2+x nuclear fuel  

NASA Astrophysics Data System (ADS)

Experimental results showed that there are a few Xenon atom bubbles connected by the dislocation line in the UO2+x nuclear fuel, and the largest radius of bubbles is about 45 nm. This phenomenon is in contrast to traditional bubble formation mechanism. This phenomenon is very important in understanding the properties of nuclear fuel. In this work, we apply a time-dependent microscopic atom transport equation and take into account stress coherent potential in the boundary of the dislocation. Using the equation, we numerically solved the stress coherence effect and studied the transfer properties of Xenon atoms along the dislocation line. Our numerical results show that the transport of the Xenon atoms along the dislocation changes nonlinearly with the external driving energy, and reaches at the saturation values. It explains the growth limit of Xenon atom bubbles that is in agreement with the experiment results.

Sui, PengFei; Dai, ZhenHong

2015-01-01

364

Index of refraction, Rayleigh scattering length, and Sellmeier coefficients in solid and liquid argon and xenon  

E-print Network

Like all the noble elements, argon and xenon are scintillators, \\emph{i.e.} they produce light when exposed to radiation. Large liquid argon detectors have become widely used in low background experiments, including dark matter and neutrino research. However, the index of refraction of liquid argon at the scintillation wavelength has not been measured and current Rayleigh scattering length calculations disagree with measurements. Furthermore, the Rayleigh scattering length and index of refraction of solid argon and solid xenon at their scintillation wavelengths have not been previously measured or calculated. We introduce a new calculation using previously measured data in liquid and solid argon and xenon to extrapolate the optical properties at the scintillation wavelengths using the Sellmeier dispersion relationship. As a point of validation, we compare our extrapolated index of refraction for liquid xenon against the measured value and find agreement within the uncertainties. This method results in a Rayle...

Grace, Emily

2015-01-01

365

Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment  

E-print Network

The low-background, VUV-sensitive 3-inch diameter photomultiplier tube R11410 has been developed by Hamamatsu for dark matter direct detection experiments using liquid xenon as the target material. We present the results from the joint effort between the XENON collaboration and the Hamamatsu company to produce a highly radio-pure photosensor (version R11410-21) for the XENON1T dark matter experiment. After introducing the photosensor and its components, we show the methods and results of the radioactive contamination measurements of the individual materials employed in the photomultiplier production. We then discuss the adopted strategies to reduce the radioactivity of the various PMT versions. Finally, we detail the results from screening 216 tubes with ultra-low background germanium detectors, as well as their implications for the expected electronic and nuclear recoil background of the XENON1T experiment.

Aprile, E; Alfonsi, M; Arazi, L; Arisaka, K; Arneodo, F; Auger, M; Balan, C; Barrow, P; Baudis, L; Bauermeister, B; Behrens, A; Beltrame, P; Brown, A; Brown, E; Bruenner, S; Bruno, G; Budnik, R; Buetikofer, L; Cardoso, J M R; Coderre, D; Colijn, A P; Contreras, H; Cussonneau, J P; Decowksi, M P; Di Giovanni, A; Duchovni, E; Fattori, S; Ferella, A D; Fieguth, A; Fulgione, W; Garbini, M; Geis, C; Goetzke, L W; Grignon, C; Gross, E; Hampel, W; Itay, R; Kaether, F; Kessler, G; Kish, A; Landsman, H; Lang, R F; Calloch, M Le; Lellouch, D; Levinson, L; Levy, C; Lindemann, S; Lindner, M; Lopes, J A M; Lyashenko, A; Macmullin, S; Undagoitia, T Marrodan; Masbou, J; Massoli, F V; Mayani, D; Fernandez, A J Melgarejo; Meng, Y; Messina, M; Miguez, B; Molinario, A; Morana, G; Murra, M; Naganoma, J; Oberlack, U; Orrigo, S E A; Pakarha, P; Pantic, E; Persiani, R; Piastra, F; Pienaar, J; Plante, G; Priel, N; Rauch, L; Reichard, S; Reuter, C; Rizzo, A; Rosendahl, S; Santos, J M F dos; Sartorelli, G; Schindler, S; Schreiner, J; Schumann, M; Lavina, L Scotto; Selvi, M; Shagin, P; Simgen, H; Teymourian, A; Thers, D; Tiseni, A; Trinchero, G; Tunnell, C; Vitells, O; Wall, R; Wang, H; Weber, M; Weinheimer, C; Laubenstein, M

2015-01-01

366

Frozen Carbon Dioxide  

NASA Technical Reports Server (NTRS)

1 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a south polar residual cap landscape, formed in frozen carbon dioxide. There is no place on Earth that one can go to visit a landscape covering thousands of square kilometers with frozen carbon dioxide, so mesas, pits, and other landforms of the martian south polar region are as alien as they are beautiful. The scarps of the south polar region are known from thousands of other MGS MOC images to retreat at a rate of about 3 meters (3 yards) per martian year, indiating that slowly, over the course of the MGS mission, the amount of carbon dioxide in the martian atmosphere has probably been increasing.

Location near: 86.9oS, 25.5oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

2005-01-01

367

Carbon Dioxide Landforms  

NASA Technical Reports Server (NTRS)

19 March 2004 The martian south polar residual ice cap is mostly made of frozen carbon dioxide. There is no place on Earth that a person can go to see the landforms that would be produced by erosion and sublimation of hundreds or thousands of cubic kilometers of carbon dioxide. Thus, the south polar cap of Mars is as alien as alien can get. This image, acquired in February 2004 by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC), shows how the cap appears in summer as carbon dioxide is subliming away, creating a wild pattern of pits, mesas, and buttes. Darker surfaces may be areas where the ice contains impurities, such as dust, or where the surface has been roughened by the removal of ice. This image is located near 86.3oS, 0.8oW. This picture covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the top/upper left.

2004-01-01

368

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

369

Measurement of the Cotton-Mouton effect in nitrogen, oxygen, carbon dioxide, argon, and krypton with the Q & A apparatus  

E-print Network

Experiments for vacuum birefringence and vacuum dichroism have been set up with high-finesse high magnetic experimental apparatuses, which seem to be ideal for small gaseous Cotton-Mouton effect (CME) measurements. PVLAS Collaboration has measured CMEs in krypton, xenon and neon at the wavelength of 1064 nm. In this Letter, we report on our measurement of CMEs in nitrogen, oxygen, carbon dioxide, argon, and krypton at the same wavelength in a magnetic field B = 2.3 T at pressure P = 0.5-300 Torr and temperature T = 295-298 K. Our results agree with the PVLAS results in the common cases.

Hsien-Hao Mei; Wei-Tou Ni; Sheng-Jui Chen; Sheau-shi Pan

2009-02-11

370

Measurement of the Cotton-Mouton effect in nitrogen, oxygen, carbon dioxide, argon, and krypton with the Q & A apparatus  

E-print Network

Experiments for vacuum birefringence and vacuum dichroism have set up high-finesse high magnetic experimental apparatuses which are ideal for gaseous Cotton-Mouton effect measurements. PVLAS Collaboration has recently measured Cotton-Mouton effects in krypton, xenon and neon at the wavelength of 1064 nm. In this Letter, we report on our measurement of Cotton-Mouton effects in nitrogen, oxygen, carbon dioxide, argon, and krypton at pressure P = 0.5-300 Torr, temperature T = 295-298 K, and laser wavelength of 1064 nm in a magnetic field B = 2.3 T, using our Q & A experimental setup, which are in agreement with the PVLAS results.

Mei, Hsien-Hao; Chen, Sheng-Jui; Pan, Sheau-shi

2008-01-01

371

[Different effects of illumination with xenon and sulfur lamp on growth and development of cotton plants].  

PubMed

Experiments were carried out with cotton (Gossgpium hirsutum cv. Xuzhou 142) plants to study the effects of illumination with xenon and sulfur lamp on development of cotton plants. The results showed that, compared with xenon lamp, illumination with sulfur lamp inhibited excessive elongation of hypocotyl via promotion of longitudinal elongation of epidermis and cortex cells, increased the numbers of branches, buds and bolls significantly. It suggested that illumination with sulfur lamp rendered cotton photomorphogenesis more favorable to yield formation. PMID:15599051

Gao, Jin-Peng; Yu, Xin-Jian; Chen, Qi-Lin; Lin, Zhi-Ping; Chen, Jin-Xing; Xu, Chun-He

2004-04-01

372

VUV RADIATION SOURCES: High-power short-pulse xenon dimer spontaneous radiation source  

NASA Astrophysics Data System (ADS)

A high-power VUV radiation source based on a self-sustained nanosecond volume discharge in an inhomogeneous electric field is developed. It is shown that the volume discharge can be formed at high xenon and helium pressures without using a preionisation source. The 8-ns (FWHM), 172-nm, 1-MW radiation pulses emitted into a total solid angle are obtained in xenon at a pressure of 12 atm.

Lomaev, Mikhail I.; Mesyats, Gennadii A.; Rybka, D. V.; Tarasenko, Viktor F.; Baksht, E. Kh

2007-06-01

373

Analysis of Discharge Parameters in Xenon-Filled Coaxial DBD Tube  

Microsoft Academic Search

In this paper, a xenon-filled coaxial dielectric barrier discharge (DBD) has been studied to understand the high-pressure nonequilibrium nonthermal plasma discharge. A quartz coaxial DBD tube (ID: 6 mm, OD: 12 mm) at 400-mbar xenon-filled pressure has been used in the experiment. A unipolar pulselike voltage up to a ?6-kV peak working at 30 kHz has been applied to the

Udit Narayan Pal; Pooja Gulati; Niraj Kumar; Mahesh Kumar; M. S. Tyagi; B. L. Meena; A. K. Sharma; Ram Prakash

2011-01-01

374

A measurement of the relativistic rise in xenon-filled ionisation chambers for cosmic ray iron  

NASA Technical Reports Server (NTRS)

The relativistic rise of ionization in a pair of xenon-filled pulse ion chambers was measured for primary iron nuclei during a recent balloon flight. Energy calibration over the range 21.5-60 GeV/n was made with a Freon-12 gas Cerenkov detector. This allowed a comparison with recent calculations of the relativistic rise in xenon counters and an estimate of the ion chamber resolution above 21.5 GeV/n to be made.

Gregory, J. C.; Parnell, T. A.

1980-01-01

375

Suitability of high-pressure xenon as scintillator for gamma ray spectroscopy  

E-print Network

In this paper we report the experimental study of high-pressure xenon used as a scintillator, in the context of developing a gamma ray detector. We measure a light yield near 2 photoelectrons per keV for xenon at 40 bar. Together with the light yield, we also measured an energy resolution of ~9% (FWHM) at 662 keV, dominated by the statistical fluctuations in the number of photoelectrons.

F. Resnati; U. Gendotti; R. Chandra; A. Curioni; G. Davatz; H. Frederich; A. Gendotti; L. Goeltl; R. Jebali; D. Murer; A. Rubbia

2012-12-17

376

Xenon and krypton isotopes in extraterrestrial regolith soils and in the solar wind  

Microsoft Academic Search

Isotopic distributions of pure solar-wind xenon and krypton are derived from an extensive data base of xenon and krypton compositions evolved from lunar and meteoritic regolith samples by acid-etching or combustion-pyrolysis experiments in several different laboratories. Regolith Xe and Kr are nonuniform mixtures of primary solar-wind components with others arising in situ from cosmic-ray spallation, neutron-capture in iodine and bromine,

R. O. Pepin; R. H. Becker; P. E. Rider

1995-01-01

377

High density self-broadening of the first xenon and krypton resonance line (*)  

E-print Network

9 High density self-broadening of the first xenon and krypton resonance line (*) P. Laporte and H,96 nm du xénon et 123,58 nm du krypton est étudié dans le domaine de densité 1-100 amagat (2,7 x 1019 xenon line and 123.58 nm krypton line is studied in the density range 1-100 amagat (2.7 x 1019 2014 2

Paris-Sud XI, Université de

378

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

379

Can pulsed xenon ultraviolet light systems disinfect aerobic bacteria in the absence of manual disinfection?  

PubMed

Whereas pulsed xenon-based ultraviolet light no-touch disinfection systems are being increasingly used for room disinfection after patient discharge with manual cleaning, their effectiveness in the absence of manual disinfection has not been previously evaluated. Our study indicates that pulsed xenon-based ultraviolet light systems effectively reduce aerobic bacteria in the absence of manual disinfection. These data are important for hospitals planning to adopt this technology as adjunct to routine manual disinfection. PMID:25681301

Jinadatha, Chetan; Villamaria, Frank C; Ganachari-Mallappa, Nagaraja; Brown, Donna S; Liao, I-Chia; Stock, Eileen M; Copeland, Laurel A; Zeber, John E

2015-04-01

380

Imaging local cerebral blood flow by Xenon-enhanced computed tomography — Technical optimization procedures  

Microsoft Academic Search

Methods are described for non-invasive, computer-assisted serial scanning throghout the human brain during eight minutes of inhalation of 27%–30% Xenon gas in order to measure local cerebral blood flow (LCBF). Optimized Xenonenhanced computed tomography (XeCT) was achieved by 5-second scanning at one-minute intervals utilizing a state-of-the-art CT scanner and rapid delivery of Xenon gas via a face mask. Values for

J. S. Meyer; T. Shinohara; A. Imai; M. Kobari; F. Sakai; T. Hata; W. T. Oravez; G. M. Timpe; T. Deville; E. Solomon

1988-01-01

381

Enhancement of Solution NMR and MRI with Laser-Polarized Xenon  

Microsoft Academic Search

Optical pumping with laser light can be used to polarize the nuclear spins of gaseous xenon-129. When hyperpolarized xenon-129 is dissolved in liquids, a time-dependent departure of the proton spin polarization from its thermal equilibrium is observed. The variation of the magnetization is an unexpected manifestation of the nuclear Overhauser effect, a consequence of cross-relaxation between the spins of solution

G. Navon; Y.-Q. Song; S. Appelt; R. E. Taylor; A. Pines

1996-01-01

382

SAUNA—a system for automatic sampling, processing, and analysis of radioactive xenon  

Microsoft Academic Search

A system for automatic sampling, processing, and analysis of atmospheric radioxenon has been developed. From an air sample of about 7m3 collected during 12h, 0.5cm3 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

A. Ringbom; T. Larson; A. Axelsson; K. Elmgren; C. Johansson

2003-01-01

383

Ultrafast measurements of chlorine dioxide photochemistry  

SciTech Connect

Time-resolved mass spectrometry and time-resolved photoelectron spectroscopy are used to study the ultrafast photodissociation dynamics of chlorine dioxide, an important constituent in stratospheric ozone depletion. Chapter 1 introduces these pump/probe techniques, in which a femtosecond pump pulse excites a molecule to a dissociative state. At a later time, a second femtosecond probe pulse ionizes the molecule. The resulting mass and photoelectron spectra are acquired as a function of the delay between the pump and probe pulses, which follows the evolution of the molecule on the excited state. A comparison to other techniques used to study reaction dynamics is discussed. Chapter 2 includes a detailed description of the design and construction of the experimental apparatus, which consists of a femtosecond laser system, a molecular beam time-of-flight spectrometer, and a data acquisition system. The time-of-flight spectrometer is specifically designed to have a short flight distance to maximize the photoelectron collection efficiency without degrading the resolution, which is limited by the bandwidth of the femtosecond laser system. Typical performance of the apparatus is demonstrated in a study of the time-resolved photoelectron spectroscopy of nitric oxide. The results of the time-resolved mass spectrometry experiments of chlorine dioxide are presented in Chapter 3. Upon excitation to the A {sup 2}A{sub 2} state near 3.2 eV, the molecule dissociates through an indirect two-step mechanism. The direct dissociation channel has been predicted to be open, but is not observed. A quantum beat is observed in the OClO{sup +} species, which is described as a vibrational coherence of the optically prepared A {sup 2}A{sub 2} state. Chapter 4 presents the results of the time-resolved photoelectron experiments of chlorine dioxide. At short delay time, the quantum beat of the OClO{sup +} species is observed in the X {sup 1}A{sub 1} state of the ion. At infinite delay, the signal is dominated by the ClO{sup +} ion, observed in a variety of electronic states. The photoelectron data is shown to support the indirect two-step dissociation mechanism derived from the mass results. Conclusions of the mass and photoelectron results are discussed in context of the stratospheric ozone depletion problem.

Ludowise, P.D.

1997-08-01

384

Abatement of Xenon and Iodine Emissions from Medical Isotope Production Facilities  

SciTech Connect

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.

Doll, Charles G.; Sorensen, Christina M.; Bowyer, Ted W.; Friese, Judah I.; Hayes, James C.; Hoffman, Emma L.; Kephart, Rosara F.

2014-04-01

385

Mind Molecules  

PubMed Central

Scientific styles vary tremendously. For me, research is largely about the unfettered pursuit of novel ideas and experiments that can test multiple ideas in a day, not a year, an approach that I learned from my mentor Julius “Julie” Axelrod. This focus on creative conceptualizations has been my métier since working in the summers during medical school at the National Institutes of Health, during my two years in the Axelrod laboratory, and throughout my forty-five years at Johns Hopkins University School of Medicine. Equally important has been the “high” that emerges from brainstorming with my students. Nothing can compare with the eureka moments when, together, we sense new insights and, better yet, when high-risk, high-payoff experiments succeed. Although I have studied many different questions over the years, a common theme emerges: simple biochemical approaches to understanding molecular messengers, usually small molecules. Equally important has been identifying, purifying, and cloning the messengers' relevant biosynthetic, degradative, or target proteins, at all times seeking potential therapeutic relevance in the form of drugs. In the interests of brevity, this Reflections article is highly selective, and, with a few exceptions, literature citations are only of findings of our laboratory that illustrate notable themes. PMID:21543333

Snyder, Solomon H.

2011-01-01

386

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

387

Carbon dioxide affects global ecology  

Microsoft Academic Search

Man's activities are changing the carbon dioxide and oxygen content of the entire atmosphere. These changes may, in turn, affect worldwide weather and the growth of plants. Under normal conditions, the amounts of carbon dioxide and oxygen in the atmosphere remain approximately in equilibrium on a year-to-year basis. The atmosphere today contains about 21% oxygen and about 0.032% carbon dioxide

Eugene K. Peterson

1969-01-01

388

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

389

The nature of the heterogeneity of the isotopic composition of xenon in meteorites, terrestrial and lunar rocks  

Microsoft Academic Search

This paper discusses protogenic or solar xenon, the unique component of the primary gas cloud. Changes in the isotopic composition of primitive xenon are caused by the fission process of U-238 and Pu-244, and Cm-248, and by the B-decay of I-129 as well as by the formation of spalogenic xenon during the interaction of cosmic rays with barium and other

Gerling

1985-01-01

390

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

E-print Network

We have developed a new method to measure krypton traces in xenon at so far unprecedented low concentrations. This is a mandatory task for many near-future low-background particle physics detectors. Our system is based on a cryogenic gas chromatographic krypton/xenon separation and a subsequent mass spectroscopic krypton quantification. We prove this system to reach a detection limit of 8 ppq (parts per quadrillion) and present results of distilled xenon with krypton concentrations below 1 ppt.

Lindemann, Sebastian

2014-01-01

391

Tunable V.U.V. radiation generated by non-resonant phase matched odd harmonic generation in xenon gas  

E-print Network

in xenon gas Tran ba' Chu (1,*), A. Bouvier (1), A. J. Bouvier (1) and R. Fischer (2) (1) Laboratoire de.U.V. radiation has been generated by non-resonant fifth-harmonic generation in xenon in the domain 1135-1170 Ã?) of the xenon gas is of the order of 10-47 e.s.u. J. Phys. France 49 (1988) 1725-1729 OCTOBRE 1988

Boyer, Edmond

392

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

393

21 CFR 73.575 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

...Titanium dioxide. (a) Identity. (1) The color additive titanium dioxide is synthetically prepared TiO2...subject to the following restrictions: (1) The quantity of titanium dioxide does not exceed 1 percent by weight of the food....

2010-04-01

394

21 CFR 184.1240 - Carbon dioxide.  

Code of Federal Regulations, 2010 CFR

...Drugs 3 2010-04-01 2009-04-01 true Carbon dioxide. 184.1240 Section 184.1240 Food...Specific Substances Affirmed as GRAS § 184.1240 Carbon dioxide. (a) Carbon dioxide (empirical formula CO2 , CAS...

2010-04-01

395

21 CFR 73.3126 - Titanium dioxide.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Titanium dioxide. 73.3126 Section 73... Medical Devices § 73.3126 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide (CAS Reg. No....

2011-04-01

396

21 CFR 73.1575 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

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

2010-04-01

397

21 CFR 73.1575 - Titanium dioxide.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Titanium dioxide. 73.1575 Section...CERTIFICATION Drugs § 73.1575 Titanium dioxide. (a) Identity and specifications. (1) The color additive titanium dioxide shall conform in...

2011-04-01

398

21 CFR 73.3126 - Titanium dioxide.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Titanium dioxide. 73.3126 Section 73... Medical Devices § 73.3126 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide (CAS Reg. No....

2014-04-01

399

21 CFR 73.3126 - Titanium dioxide.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Titanium dioxide. 73.3126 Section 73... Medical Devices § 73.3126 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide (CAS Reg. No....

2012-04-01

400

21 CFR 73.3126 - Titanium dioxide.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Titanium dioxide. 73.3126 Section 73... Medical Devices § 73.3126 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide (CAS Reg. No....

2013-04-01

401

Thermodynamics and phase equilibria of carbon dioxide\\/polymer systems  

Microsoft Academic Search

A theoretical approach, the SAFT (Statistical Associating Fluid Theory) equation of state, is adapted and extended to understand the thermodynamics and phase equilibria of systems containing carbon dioxide (CO 2), CO2-philic and CO2-phobic compounds, including both small molecules (such as n-alkanes and n-perfluoroalkanes) and macromolecules (homopolymers, polymer blends and copolymers), to provide rapid reliable predictions for a wide range of

Coray Mariu Colina

2004-01-01

402

Fast oscillatory behavior of the excited xenon density in the discharge cells of a plasma display panel  

SciTech Connect

Fast oscillation of the excited xenon density occurs universally after an electrical discharge in the cells of a plasma display panel. A theoretical model based on ion plasma oscillation simulates this oscillatory behavior of the excited xenon density reasonably well. The magnitude and lifetime of the excited xenon density in a metastable state depend highly on the electrode configuration. Particularly, T-type electrodes provide better generation and confinement of excited xenon atoms for an abundant emission of 173 nm ultraviolet light at a high level of efficiency.

Uhm, Han S. [Department of Molecular Science and Technology, Ajou University, Suwon 443-749 (Korea, Republic of); Choi, Eun H. [Department of Electrophysics, PDP Research Center, Kwangwoon University, Seoul 139-701 (Korea, Republic of)

2009-03-15

403

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. PMID:7151750

Stevens, A A

1982-01-01

404

Carbon dioxide and terrestrial ecosystems  

Microsoft Academic Search

This book is a summary of the current research which addresses the effects of elevated carbon dioxide on terrestrial ecosystems and an identification of significant unresolved issues. Chapters address the carbon dioxide effects on trees and forests, unmanaged herbaceous ecosystems, and crops. Included are experimental studies, conceptual models, general mathematical models, dynamic simulation models.

G. W. Koch; H. A. Mooney

1996-01-01

405

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

406

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

407

Human Regional Pulmonary Gas Exchange with Xenon Polarization Transfer (XTC)  

NASA Astrophysics Data System (ADS)

Xenon Transfer Contrast (XTC) is an existing imaging method (Ruppert et al, Magn Reson Med, 51:676-687, 2004) that measures the fraction F of ^129Xe magnetization that diffuses from alveolar gas spaces to septal parenchymal tissue in lungs in a specified exchange time. As previously implemented, XTC is a 2-breath method and has been demonstrated in anesthetized animals. To use XTC in humans and to avoid issues associated with obtaining identical gas volumes on subsequent breath-hold experiments as well as precise image registration in post-processing, a single breath XTC method was developed that acquires three consecutive gradient echo images in an 8s acquisition. We report here initial measurements of the mean and variance of F for 5 normal healthy subjects as well as 7 asymptomatic smokers. The experiments were performed at two lung volumes (˜45 and 65% of TLC). We found that both the mean and variance of F increased with smoking history. In comparison, standard pulmonary function tests such as DLCO FEV1 showed no correlation with smoking history.

Muradian, Iga; Butler, James; Hrovat, Mirko; Topulos, George; Hersman, Elizabeth; Ruset, Iulian; Covrig, Silviu; Frederick, Eric; Ketel, Stephen; Hersman, F. W.; Patz, Samuel

2007-03-01

408

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

409

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

410

FIRST DETECTION OF KRYPTON AND XENON IN A WHITE DWARF  

SciTech Connect

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 [Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University Tuebingen, Sand 1, 72076 Tuebingen (Germany); Kruk, Jeffrey W. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-07-01

411

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

412

s-process studies - Xenon and krypton isotopic abundances  

NASA Technical Reports Server (NTRS)

We propose an analysis of the s-process contributions to the isotopes of xenon and krypton. The object is to aid studies of the possibility that meteorites may contain gas that was carried in presolar grains that were grown in stellar ejecta and that were not degassed prior to incorporation into parent bodies. That model suggests routine interstellar fractionation of s-isotopes from r-isotopes owing to differential incorporation into dust. We show that a deficiency of s-process nuclei cannot yield details of Xe-X, but the gross similarities are strong enough to lead one to think that such a deficiency may play a role in a more complicated explanation. We predict the existence of an s-rich complement somewhere if fractional separation of this type has played a role in Xe-X. We show that the analogous decomposition of krypton is more uncertain, and we call for measurements of neutron-capture cross sections to alleviate these uncertainties.

Clayton, D. D.; Ward, R. A.

1978-01-01

413

Collectivity in the light Xenon isotopes: A shell model study  

E-print Network

The lightest Xenon isotopes are studied in the framework of the Interacting Shell Model (ISM). The valence space comprises all the orbits lying between the magic closures N=Z=50 and N=Z=82. The calculations produce collective deformed structures of triaxial nature that encompass nicely the known experimental data. Predictions are made for the (still unknown) N=Z nucleus 108-Xe. The results are interpreted in terms of the competition between the quadrupole correlations enhanced by the pseudo-SU(3) structure of the positive parity orbits and the pairing correlations brought in by the 0h11/2 orbit. We have studied as well the effect of the excitations from the 100-Sn core on our predictions. We show that the backbending in this region is due to the alignment of two particles in the 0h11/2 orbit. In the N=Z case, one neutron and one proton align to J=11 and T=0. In 110-Xe and 112-Xe the alignment begins in the J=10 T=1 channel and it is dominantly of neutron neutron type. Approaching the band termination the alignment of a neutron and a proton to J=11 and T=0 takes over. In a more academic mood, we have explored the role of the isovector and isoscalar pairing correlations on the structure on the yrast bands of 108-Xe and 110-Xe and examined the role of the isovector and isoscalar pairing condensates in these N~Z nuclei.

E. Caurier; F. Nowacki; A. Poves; K. Sieja

2010-09-20

414

Adsorption of Xenon on Hipco Single Walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

We have measured the adsorption of Xenon on purified HiPco SWCNTs for coverages in the first layer. We wanted to compare the results on this substrate to those we had obtained on lower purity arc-discharge produced nanotubes. In order to obtain an estimate for the binding energy. We measured six low-coverage isotherms for temperatures between 220K and 260K. We determined a value of 272 meV for the binding energy; this value is lower, by about 4% than the value we had reported on arc discharge nanotubes^1. It is 1.67 times greater than the value for this quantity on planar graphite. We have measured five full isotherms at 150K, 155K, 160K, 165K, and 175K and have used these data to obtain the coverage dependence of the isosteric heat. The experimental values will be compared with computer simulation results for this quantity that have been conducted using different models for bundles^2. 1 A. J. Zambano, S. Talapatra, and A. D. Migone Physics Review B, 64, 2001. 2 Wei Shi, and J. Karl Johnson Physical Review Letters 91, 2003. * The present study was supported by the National Science Foundation through Grant # DMR-0089713

Rawat, Dinesh

2005-03-01

415

Reactivity of xenon with ice at planetary conditions.  

PubMed

We report results from high pressure and temperature experiments that provide evidence for the reactivity of xenon with water ice at pressures above 50 GPa and a temperature of 1500 K-conditions that are found in the interiors of Uranus and Neptune. The x-ray data are sufficient to determine a hexagonal lattice with four Xe atoms per unit cell and several possible distributions of O atoms. The measurements are supplemented with ab initio calculations, on the basis of which a crystallographic structure with a Xe4O12H12 primitive cell is proposed. The newly discovered compound is formed in the stability fields of superionic ice and ?-O2, and has the same oxygen subnetwork as the latter. Furthermore, it has a weakly metallic character and likely undergoes sublattice melting of the H subsystem. Our findings indicate that Xe is expected to be depleted in the atmospheres of the giant planets as a result of sequestration at depth. PMID:23848893

Sanloup, Chrystèle; Bonev, Stanimir A; Hochlaf, Majdi; Maynard-Casely, Helen E

2013-06-28

416

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

417

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

418

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. [CSIR–CEERI Pilani, Rajasthan 333031 (India)] [CSIR–CEERI 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

419

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

420

Carbon dioxide pellet blasting augmented xenon flashlamp coatings removal design and prototype demonstration project; Pram project. Final report  

SciTech Connect

Air Force aircraft exterior coatings are removed every 4 to 8 years to facilitate various maintenance functions. One of the largest generators of hazardous waste in the Air Force has typically been the paint removal operations. Historically, the Air Force has used extremely harsh chemicals to remove the advanced coatings used on modern aircraft. Large volumes of hazardous waste (e.g., approximately 10,000 gallons for the F-15 aircraft) are produced with each aircraft that is stripped. In addition, the chemicals are not compatible with composite substrates.

NONE

1993-03-30

421

Why Do Some Molecules Absorb Infrared Energy?  

NSDL National Science Digital Library

In this demonstration activity, students make structural models of gas molecules using pipe cleaners and polystyrene balls and test their molecules for their resonant frequency. Students shake the models, count vibrations, and compare the resonance frequencies of different gases. Students learn that photons of infrared energy vibrate at the right frequency to transfer their energy to carbon dioxide and methane, which in turn causes those molecules to vibrate, which is experienced in the real world as heat. The teacher's guide includes illustrative videos for this resource. This activity is supported by a textbook chapter, What's So Special about CO²?, 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.

2012-09-28

422

PHYSICAL REVIE% 8 VOLUME 37, NUMBER 2 15 JANUARY 1988-I Dynamics of xenon, krypton, and methane monolayers in registry with graphite  

E-print Network

PHYSICAL REVIE% 8 VOLUME 37, NUMBER 2 15 JANUARY 1988-I Dynamics of xenon, krypton, and methane of monolayers of xenon, krypton, and methane adsorbed on graphite. Only the ~3Xv 3 sohd phase is considered

Glyde, Henry R.

423

Internal plasma potential measurements of a Hall thruster using xenon and krypton propellant  

SciTech Connect

For krypton to become a realistic option for Hall thruster operation, it is necessary to understand the performance gap between xenon and krypton and what can be done to reduce it. A floating emissive probe is used with the Plasmadynamics and Electric Propulsion Laboratory's High-speed Axial Reciprocating Probe system to map the internal plasma potential structure of the NASA-173Mv1 Hall thruster [R. R. Hofer, R. S. Jankovsky, and A. D. Gallimore, J. Propulsion Power 22, 721 (2006); and ibid.22, 732 (2006)] using xenon and krypton propellant. Measurements are taken for both propellants at discharge voltages of 500 and 600 V. Electron temperatures and electric fields are also reported. The acceleration zone and equipotential lines are found to be strongly linked to the magnetic-field lines. The electrostatic plasma lens of the NASA-173Mv1 Hall thruster strongly focuses the xenon ions toward the center of the discharge channel, whereas the krypton ions are defocused. Krypton is also found to have a longer acceleration zone than the xenon cases. These results explain the large beam divergence observed with krypton operation. Krypton and xenon have similar maximum electron temperatures and similar lengths of the high electron temperature zone, although the high electron temperature zone is located farther downstream in the krypton case.

Linnell, Jesse A.; Gallimore, Alec D. [Plasmadynamics and Electric Propulsion Laboratory, Department of Aerospace Engineering, University of Michigan, 1919 Green Road B107, Ann Arbor, Michigan 48109 (United States)

2006-09-15

424

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

425

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

426

Enhanced carbon dioxide adsorption through carbon nanoscrolls.  

PubMed

Over the last few years, significant efforts have been devoted to exploring the capabilities of carbon based structures for gas separation and filtration. In the present study the layering behavior of carbon dioxide transported through carbon nanoscrolls is examined through molecular dynamics simulations. The layering arrangements are investigated for carbon nanoscrolls with intralayer distances spanning from 4.2 to 8.3 Å at temperature of 300 K and pressures ranging from 5 to 20 bars. Characteristic layering structures are developed around the internal and external surfaces of the nanoscroll for all the examined cases. It is shown that the number of layers, their relative strength, and the starting point of bifurcation phenomena vary as a function of the nanoscrolls' intralayer distance, scroll's core radius, CO2 density, and gas structure interactions. It is also shown that the number of carbon dioxide molecules adsorbed per scroll's carbon particles is a function of the scroll's surface-to-volume ratio and is maximized under certain structural configurations. PMID:22304187

Mantzalis, Dimitrios; Asproulis, Nikolaos; Drikakis, Dimitris

2011-12-01

427

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

428

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.

2012-09-28

429

Carbon Dioxide Landscape  

NASA Technical Reports Server (NTRS)

7 July 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a mid-summer view of the south polar residual cap at full MOC resolution, 1.5 m (5 ft) per pixel. During each of the three summers since the start of the MGS mapping mission in March 1999, the scarps that form mesas and pits in the 'Swiss cheese'-like south polar terrain have retreated an average of about 3 meters (1 yard). The material is frozen carbon dioxide; another 3 meters or so of each scarp is expected to be removed during the next summer, in late 2005. This image is located near 86.0oS, 350.8oW, and covers an area about 1.5 km (0.9 mi) wide. Sunlight illuminates the scene from the top/upper left.

2004-01-01

430

A liquid xenon PET camera -Simulation and position sensitive PMT tests S.Jan, J.Collot, E Tournefier  

E-print Network

A liquid xenon PET camera - Simulation and position sensitive PMT tests S.Jan, J.Collot, E a Positron Emission Tomograph (PET) based on the use of liquid xenon (LXe) as an active medium. This PET (½½ ) PET camera dedicated to hadrontherapy is also considered. This development is proposed by three

Paris-Sud XI, Université de

431

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

432

Study of emission of a volume nanosecond discharge plasma in xenon, krypton and argon at high pressures  

Microsoft Academic Search

The emission properties of a volume nanosecond discharge plasma produced in xenon, krypton and argon at high pressures in a discharge gap with a cathode having a small radius of curvature are studied. Spectra in the range 120–850 nm and amplitude—time characteristics of xenon emission at different regimes and excitation techniques are recorded and analysed. It is shown that upon

E Kh Baksht; Mikhail I Lomaev; D V Rybka; Viktor F Tarasenko

2006-01-01

433

Stability of xenon oxides at high pressures *, Daniel Y. Jung2, Artem R. Oganov1,3  

E-print Network

Stability of xenon oxides at high pressures Qiang Zhu1 *, Daniel Y. Jung2, Artem R. Oganov1 conditions, may become reactive under pressure. The possibility of the formation of stable xenon oxides at high pressures (XeO, XeO2 and XeO3 become stable at pressures above 83, 102 and 114 GPa, respectively

Oganov, Artem R.

434

PHYSICAL REVIEW A 89, 023408 (2014) High-spectral-resolution attosecond absorption spectroscopy of autoionization in xenon  

E-print Network

of autoionization in xenon Birgitta Bernhardt,1,2,* Annelise R. Beck,1,2 Xuan Li,1 Erika R. Warrick,1,2 M. Justine; published 10 February 2014) The decay of highly excited states of xenon after absorption of extreme

Neumark, Daniel M.

435

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

436

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

437

Collectivity in the light xenon isotopes: A shell model study  

SciTech Connect

The lightest xenon isotopes are studied in the shell model framework, within a valence space that comprises all the orbits lying between the magic closures N=Z=50 and N=Z=82. The calculations produce collective deformed structures of triaxial nature that encompass nicely the known experimental data. Predictions are made for the (still unknown) N=Z nucleus {sup 108}Xe. The results are interpreted in terms of the competition between the quadrupole correlations enhanced by the pseudo-SU(3) structure of the positive parity orbits and the pairing correlations brought in by the 0h{sub 11/2} orbit. We also have studied the effect of the excitations from the {sup 100}Sn core on our predictions. We show that the backbending in this region is due to the alignment of two particles in the 0h{sub 11/2} orbit. In the N=Z case, one neutron and one proton align to J=11 and T=0. In {sup 110,112}Xe the alignment begins in the J=10, T=1 channel and it is dominantly of neutron-neutron type. Approaching the band termination the alignment of a neutron-proton pair to J=11 and T=0 takes over. In a more academic mood, we have studied the role of the isovector and isoscalar pairing correlations on the structure on the yrast bands of {sup 108,110}Xe and examined the possible existence of isovector and isoscalar pairing condensates in these N{approx}{approx}Z nuclei.

Caurier, E.; Nowacki, F.; Sieja, K. [IPHC, IN2P3-CNRS et Universite Louis Pasteur, F-67037 Strasbourg (France); Poves, A. [Departamento de Fisica Teorica e IFT-UAM/CSIC, Universidad Autonoma de Madrid, E-28049 Madrid (Spain)

2010-12-15

438

Momentum Transfer in a Spinning Fuel Tank Filled with Xenon  

NASA Technical Reports Server (NTRS)

Transient spin-up and spin-down flows inside of spacecraft fuel tanks need to be analyzed in order to properly design spacecraft control systems. Knowledge of the characteristics of angular momentum transfer to and from the fuel is used to size the de-spin mechanism that places the spacecraft in a controllable in-orbit state. In previous studies, several analytical models of the spin-up process were developed. However, none have accurately predicted all of the flow dynamics. Several studies have also been conducted using Navier-Stokes based methods. These approaches have been much more successful at simulating the dynamic processes in a cylindrical container, but have not addressed the issue of momentum transfer. In the current study, the spin-up and spin-down of a fuel tank filled with gaseous xenon has been investigated using a three-dimensional unsteady Navier-Stokes code. Primary interests have been concentrated on the spin-up/spin-down time constants and the initial torque imparted on the system. Additional focus was given to the relationship between the dominant flow dynamics and the trends in momentum transfer. Through the simulation of both a cylindrical and a spherical tank, it was revealed that the transfer of angular momentum is nonlinear at early times and tends toward a linear pattern at later times. Further investigation suggests that the nonlinear spin up is controlled by the turbulent transport of momentum, while the linear phase is controlled by a Coriolis driven (Ekman) flow along the outer wall. These results indicate that the spinup and spin-down processes occur more quickly in tanks with curved surfaces than those with defined top, bottom, and side walls. The results also provide insights for the design of spacecraft de-spin mechanisms.

Peugeot, John W.; Dorney, Daniel J.

2006-01-01

439

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

440

Evaluation of Xenon Gas Detection as a Means for Identifying Buried Transuranic Waste at the Radioactive Waste Management Complex, Idaho National Environmental and Engineering Laboratory  

Microsoft Academic Search

Xenon is produced as a fission product in nuclear reactors and through spontaneous fission of some transuranic (TRU) isotopes. Xenon gas is nearly inert and will be released from buried TRU waste. This document describes and evaluates the potential for analyzing xenon isotopes in soil gas to detect TRU waste in the subsurface at the Idaho National Environmental and Engineering

P Evan Dresel; Scott R. Waichler

2004-01-01

441

Strong nondipole effects in low-energy photoionization of the 5s and 5p subshells of xenon W. R. Johnson  

E-print Network

Strong nondipole effects in low-energy photoionization of the 5s and 5p subshells of xenon W. R from the 5s and 5p subshells of xenon for photon energies below 200 eV. The nondipole parameter 5s of photoionization of the outer 5s and 5p subshells of xenon. Partial cross sections n ( ), angular

Johnson, Walter R.

442

Scintillation response of liquid xenon to low energy nuclear recoils E. Aprile,* K. L. Giboni, P. Majewski, K. Ni, and M. Yamashita  

E-print Network

Scintillation response of liquid xenon to low energy nuclear recoils E. Aprile,* K. L. Giboni, P 2005) Liquid Xenon (LXe) is expected to be an excellent target and detection medium to search for dark by elastic scattering of 2.4 MeV neutrons in liquid xenon at a variety of scattering angles. The relative

443

Liquid xenon time projection chamber for gamma rays in the MeV region: Development status  

NASA Technical Reports Server (NTRS)

The feasibility of a large volume Liquid Xenon Time Projection Chamber (LXe-TPC) for three dimensional imaging and spectroscopy of cosmic gamma ray sources, was tested with a 3.5 liter prototype. The observation of induction signals produced by MeV gamma rays in liquid xenon is reported, with a good signal-to-noise ratio. The results represent the first experimental demonstration with a liquid xenon ionization chamber of a nondestructive readout of the electron image produced by point-like charges, using a sense wire configuration of the type originally proposed in 1970 by Gatti et al. An energy resolution as good as that previously measured by the millimeter size chambers, was achieved with the large prototype of 4.4 cm drift gap.

Aprile, E.; Bolotnikov, A.; Chen, D.; Mukherjee, R.

1992-01-01

444

Laser-induced fluorescence study of a xenon Hall thruster  

Microsoft Academic Search

2  \\u000a 0?6p[3\\/2]2(3P2-1D2) transition at 823.2 nm and the xenon-ion 5d[3]7\\/2?6p[2]5\\/2\\u000a 0(4D7\\/2-4P5\\/2) transition is used to measure plasma parameters in the plume of a laboratory-model xenon Hall thruster. The Hall discharge\\u000a operates nominally at 62 V, 4.2 A, and 3.2 mg?s-1 xenon flow, with an overall thruster power of 320 W. A tunable semiconductor diode laser and an Ar+-pumped dye laser are used to probe the respective excited-state

R. J. Cedolin; W. A. Hargus Jr.; P. V. Storm; R. K. Hanson; M. A. Cappelli

1997-01-01

445

Opening of single-walled carbon nanotubes: evidence given by krypton and xenon adsorption  

NASA Astrophysics Data System (ADS)

Adsorption isotherms of krypton between 77 and 93 K and xenon between 110 and 120 K on mechanically-opened single-walled carbon nanotubes (SWNTs) have been measured. The comparison of the results with those obtained under the same conditions on closed nanotubes is discussed. Evidence of adsorption inside the tubes is given through the appearance of an additional adsorbed amount at very low relative pressure on the isotherms. Different orderings are predicted for xenon and krypton, based on their respective adsorbed amounts inside the nanotubes, and on geometrical considerations. Finally, the fraction of opened nanotubes accessible to xenon and krypton was estimated, as well as the impurity content originating from the cutting process.

Babaa, M. R.; Stepanek, I.; Masenelli-Varlot, K.; Dupont-Pavlovsky, N.; McRae, E.; Bernier, P.

2003-05-01

446

Performance of a cryogenic system prototype for the XENON1T Detector  

E-print Network

We have developed an efficient cryogenic system with heat exchange and associated gas purification system, as a prototype for the XENON1T experiment. The XENON1T detector will use about 3 ton of liquid xenon (LXe) at a temperature of 175K as target and detection medium for a dark matter search. In this paper we report results on the cryogenic system performance focusing on the dynamics of the gas circulation-purification through a heated getter, at flow rates above 50 Standard Liter per Minute (SLPM). A maximum flow of 114 SLPM has been achieved, and using two heat exchangers in parallel, a heat exchange efficiency better than 96% has been measured.

Elena Aprile; Ran Budnik; Bin Choi; Hugo Contreras; Karl Giboni; Luke Goetzke; Rafael Lang; Kyungeun Lim; Antonio melgarejo; Petr Shagin

2012-08-29

447

Dark Matter Results from 100 Live Days of XENON100 Data  

E-print Network

We present results from the direct search for dark matter with the XENON100 detector, installed underground at the Laboratori Nazionali del Gran Sasso of INFN, Italy. XENON100 is a two-phase time projection chamber with a 62 kg liquid xenon target. Interaction vertex reconstruction in three dimensions with millimeter precision allows to select only the innermost 48 kg as ultra-low background fiducial target. In 100.9 live days of data, acquired between January and June 2010, no evidence for dark matter is found. Three candidate events were observed in a pre-defined signal region with an expected background of 1.8 +/- 0.6 events. This leads to the most stringent limit on dark matter interactions today, excluding spin-independent elastic WIMP-nucleon scattering cross-sections above 7.0x10^-45 cm^2 for a WIMP mass of 50 GeV/c^2 at 90% confidence level.

XENON100 Collaboration; E. Aprile; K. Arisaka; F. Arneodo; A. Askin; L. Baudis; A. Behrens; K. Bokeloh; E. Brown; T. Bruch; G. Bruno; J. M. R. Cardoso; W. -T. Chen; B. Choi; D. Cline; E. Duchovni; S. Fattori; A. D. Ferella; F. Gao; K. -L. Giboni; E. Gross; A. Kish; C. W. Lam; J. Lamblin; R. F. Lang; C. Levy; K. E. Lim; Q. Lin; S. Lindemann; M. Lindner; J. A. M. Lopes; K. Lung; T. Marrodan Undagoitia; Y. Mei; A. J. Melgarejo Fernandez; K. Ni; U. Oberlack; S. E. A. Orrigo; E. Pantic; R. Persiani; G. Plante; A. C. C. Ribeiro; R. Santorelli; J. M. F. dos Santos; G. Sartorelli; M. Schumann; M. Selvi; P. Shagin; H. Simgen; A. Teymourian; D. Thers; O. Vitells; H. Wang; M. Weber; C. Weinheimer

2011-09-07

448

Study of light detection and sensitivity for a ton-scale liquid xenon dark matter detector  

E-print Network

Ton-scale liquid xenon detectors operated in two-phase mode are proposed and being constructed recently to explore the favored parameter space for the Weakly Interacting Massive Particles (WIMPs) dark matter. To achieve a better light collection eff ciency while limiting the number of electronics channels compared to the previous generation detectors, large-size photomultiplier tubes (PMTs) such as the 3-inch-diameter R11410 from Hamamatsu are suggested to replace the 1-inch-square R8520 PMTs. In a two-phase xenon dark matter detector, two PMT arrays on the top and bottom are usually used. In this study, we compare the performance of two different ton-scale liquid xenon detector conf gurations with the same number of either R11410 (conf g.1) or R8520 (conf g.2) for the top PMT array, while both using R11410 PMTs for the bottom array.

Y Wei; Q Lin; X Xiao; K Ni

2014-05-11

449

Carbon Dioxide Sequestration Industrial-scale processes are available for separating carbon dioxide from the post-  

E-print Network

Carbon Dioxide Sequestration Industrial-scale processes are available for separating carbon dioxide of a coal gasification power plant. The separated carbon dioxide can be compressed and transported dioxide separation and sequestration because the lower cost of carbon dioxide separation from

450

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

451

The relative transfer rates for sodium and xenon from gut lumen to plasma in man.  

PubMed

1. A whole-gut perfusion technique has been used to compare the rates of intestinal absorption of sodium and xenon. 2. The calculated transit-time spectra for sodium and xenon across the gut mucosa do not differ significantly either in mean transit time or, for the first 15 min, in shape. 3. These results support the hypothesis that the rate of transfer of sodium from the small intestinal lumen to plasma is limited by blood flow. 4. It is suggested that some features of cholera can be explained by the hypothesis. PMID:844255

Love, A H; Chen, L C; Reeve, J; Veall, N

1977-03-01

452

Near-infrared scintillation of xenon by 63Ni beta decay  

NASA Astrophysics Data System (ADS)

The near-infrared scintillation of xenon gas by the ? decay of 37MBq of Ni63 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 2×105photons/s at 20kPa and 1×105photons/s at 100kPa. Spectral data show three dominant peaks at 823, 828, and 882nm as well as the formation of metastable states.

Yoshimizu, Norimasa; Lal, Amit; Pollock, Clifford R.

2006-07-01

453

Boltzmann expansion in a radiofrequency conical helicon thruster operating in xenon and argon  

SciTech Connect

A low pressure ({approx}0.5 mTorr in xenon and {approx}1 mTorr in argon) Boltzmann expansion is experimentally observed on axis within a magnetized (60 to 180 G) radiofrequency (13.56 MHz) conical helicon thruster for input powers up to 900 W using plasma parameters measured with a Langmuir probe. The axial forces, respectively, resulting from the electron and magnetic field pressures are directly measured using a thrust balance for constant maximum plasma pressure and show a higher fuel efficiency for argon compared to xenon.

Charles, C.; Boswell, R. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia)] [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Takahashi, K. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia) [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Department of Electrical Engineering, Tohoku University, Sendai 980-9579 (Japan)

2013-06-03

454

Saturated absorption at nanowatt power levels using metastable xenon in a high-finesse optical cavity.  

PubMed

Strong saturated absorption at nanowatt power levels has been demonstrated using metastable xenon in a high finesse optical cavity. The use of metastable xenon allows a high quality factor of Q = 2 × 10(8) to be achieved at relatively high atomic densities without any contamination or damage to the optical surfaces, which is often a problem when using high-density rubidium or other alkali atoms. This technique provides a relatively straightforward way to produce nonlinearities at the single-photon level with possible applications in quantum communications and computing. PMID:25321758

Hickman, G T; Pittman, T B; Franson, J D

2014-09-22

455

Differential Sputtering Behavior of Pyrolytic Graphite and Carbon-Carbon Composite Under Xenon Bombardment  

NASA Technical Reports Server (NTRS)

A differential sputter yield measurement technique is described, which consists of a quartz crystal monitor that is swept at constant radial distance from a small target region where a high current density xenon ion beam is aimed. This apparatus has been used to characterize the sputtering behavior of various forms of carbon including polycrystalline graphite, pyrolytic graphite, and PVD-infiltrated and pyrolized carbon-carbon composites. Sputter yield data are presented for pyrolytic graphite and carbon-carbon composite over a range of xenon ion energies from 200 eV to 1 keV and angles of incidence from 0 deg (normal incidence) to 60 deg .

Williams, John D.; Johnson, Mark L.; Williams, Desiree D.

2003-01-01

456

Test Chamber for Optimizing a High Pressure Xenon Neutrinoless Double Beta Decay Detector  

NASA Astrophysics Data System (ADS)

The NEXT experiment is designed to search for neutrinoless double beta decay in high pressure xenon gas; the gas is enriched with ^136Xe which is a double beta decay candidate emitter. It is currently in the research and development phase and is scheduled to be operating in Canfranc Underground Laboratory in Huesca Spain within the next 5 years. High pressure xenon gas is chosen because of its excellent energy resolution and the ability to observe tracks. Observation of the track end points will provide excellent background rejection. The design and principle of a test chamber used to optimize the detector design will be discussed.

Robert, Paul

2009-10-01

457

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

SciTech Connect

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.

Shutt, Tom (Case Western Reserve) [Case Western Reserve

2007-06-13

458

Scintillation Pulse Shape Discrimination in a Two-Phase Xenon Time Projection Chamber  

E-print Network

The energy and electric field dependence of pulse shape discrimination in liquid xenon have been measured in a 10 gm two-phase xenon time projection chamber. We have demonstrated the use of the pulse shape and charge-to-light ratio simultaneously to obtain a leakage below that achievable by either discriminant alone. A Monte Carlo is used to show that the dominant fluctuation in the pulse shape quantity is statistical in nature, and project the performance of these techniques in larger detectors. Although the performance is generally weak at low energies relevant to elastic WIMP recoil searches, the pulse shape can be used in probing for higher energy inelastic WIMP recoils.

J. Kwong; P. Brusov; T. Shutt; C. E. Dahl; A. I. Bolozdynya; A. Bradley

2009-08-06

459

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

E-print Network

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 {\\it 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.

Peter Sorensen; Carl Eric Dahl

2011-01-31

460

Stability analysis of the commensurate monolayer solid of xenon/graphite  

NASA Astrophysics Data System (ADS)

A stability analysis based on model calculations of the grand potential finds that the transition from hexagonal incommensurate to commensurate monolayer solid of xenon/graphite is continuous with increasing pressure, in agreement with experimental observations. An atomic-scale interaction model gives an internally consistent account of the thermal expansion of the solid at the two-dimensional sublimation curve and of the chemical potential increase for isothermal compression from monolayer condensation to the commensurate solid. An estimate is given for the corrugation energy of xenon/graphite.

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

2008-03-01

461

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

462

Diagnosing on plasma plume from xenon Hall thruster with collisional-radiative model  

SciTech Connect

The collisional-radiative model for xenon is used to calculate the electron density and temperature, and the atom population distribution in the plasma plume from a xenon Hall thruster. In the calculation, 173 levels of atom population are considered; only the processes of electron induced excitation and deexcitation, and spontaneous decay are simulated. The plasma plume is assumed to be optically thin. Consequently, the reasonable parameters of plasma plume along the outside center line of the thruster channel are obtained by making the calculated emission spectrum corresponding to measured ones and based on the atomic data available on site and by codes.

Yang Juan [College of Astronautics, Northwestern Polytechnic University, Xi'an 710072 (China); Yokota, Shigeru; Kaneko, Ryotaro; Komurasaki, Kimiya [Department of Aeronautics and Astronautics, University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-8656 (Japan)

2010-10-15

463

Saturated absorption at nanowatt power levels using metastable xenon in a high-finesse optical cavity  

E-print Network

Strong saturated absorption at nanowatt power levels has been demonstrated using metastable xenon in a high-finesse optical cavity. The use of metastable xenon allows a high quality factor of Q=2*10^8 to be achieved at relatively high atomic densities without any contamination or damage to the optical surfaces, which is often a problem when using high-density rubidium or other alkali atoms. This technique provides a relatively straightforward way to produce nonlinearities at the single-photon level with possible applications in quantum communications and computing.

G. T. Hickman; T. B. Pittman; J. D. Franson

2014-09-19

464

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

465

Effect of nonlocal electron kinetics on the characteristics of a dielectric barrier discharge in xenon  

SciTech Connect

The established dynamics of a dielectric barrier discharge in xenon at a pressure of 400 Torr is simulated in the framework of a one-dimensional fluid model in the local and nonlocal field approximations. It is shown that taking into account the nonlocal character of the electric field does not qualitatively change physical processes in a dielectric barrier discharge, but significantly affects its quantitative characteristics. In particular, the sheath thickness decreases, plasma ionization intensifies, the spatiotemporal distribution of the mean electron energy changes, and the discharge radiation efficiency increases. Electron kinetics in a dielectric barrier discharge in xenon is analyzed using the nonlocal field approximation.

Avtaeva, S. V.; Skornyakov, A. V. [Kyrgyz-Russian Slavic University (Kyrgyzstan)

2009-07-15

466

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.

2012-08-03

467

Reducing carbon dioxide to products  

DOEpatents

A method reducing carbon dioxide to one or more products may include steps (A) to (C). Step (A) may bubble said carbon dioxide into a solution of an electrolyte and a catalyst in a divided electrochemical cell. The divided electrochemical cell may include an anode in a first cell compartment and a cathode in a second cell compartment. The cathode may reduce said carbon dioxide into said products. Step (B) may adjust one or more of (a) a cathode material, (b) a surface morphology of said cathode, (c) said electrolyte, (d) a manner in which said carbon dioxide is bubbled, (e), a pH level of said solution, and (f) an electrical potential of said divided electrochemical cell, to vary at least one of (i) which of said products is produced and (ii) a faradaic yield of said products. Step (C) may separate said products from said solution.

Cole, Emily Barton; Sivasankar, Narayanappa; Parajuli, Rishi; Keets, Kate A

2014-09-30

468

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.

Chris Lewis

469

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 ...

Sill - Earth Systems Science

2010-11-16

470

Analysis of Substrate Access to Active Sites in Bacterial Multicomponent Monooxygenase Hydroxylases: X-ray Crystal Structure of Xenon-Pressurized Phenol Hydroxylase from Pseudomonas sp. OX1†,‡  

PubMed Central

In all structurally characterized bacterial multicomponent monooxygenase (BMM) hydroxylase proteins, a series of hydrophobic cavities in the ?-subunit trace a conserved path from the protein exterior to the carboxylate-bridged diiron active site. The present study examines these cavities as a potential route for dioxygen transport to the active site by crystallographic characterization of a xenon-pressurized sample of the hydroxylase component of phenol hydroxylase from Pseudomonas sp. OX1. Computational analyses of the hydrophobic cavities in the hydroxylase ?-subunits of phenol hydroxylase (PHH), toluene/o-xylene monooxygenase (ToMOH), and soluble methane monooxygenase (sMMOH) are also presented. The results, together with previous findings from crystallographic studies of xenon-pressurized sMMO hydroxylase, clearly identify the propensity for these cavities to bind hydrophobic gas molecules in the protein interior. This proposed functional role is supported by recent stopped flow kinetic studies of ToMOH variants (Song, et al., 2011). In addition to information about the Xe sites, the structure determination revealed significantly reduced regulatory protein binding to the hydroxylase in comparison to the previously reported structure of PHH, as well as the presence of a newly identified metal binding site in the ?-subunit that adopts a linear coordination environment consistent with Cu(I), and a glycerol molecule bound to Fe1 in a fashion that is unique among hydrocarbon-diiron site adducts reported to date in BMM hydroxylase structures. Finally, a comparative analysis of the ?-subunit structures of MMOH, ToMOH, and PHH details proposed routes for the other three BMM substrates, the hydrocarbon, electrons, and protons, comprising cavities, channels, hydrogen-bonding networks, and pores in the structures of their ?-subunits. PMID:22136180

McCormick, Michael S.; Lippard, Stephen J.

2011-01-01

471

Recuperative supercritical carbon dioxide cycle  

DOEpatents

A power plant includes a closed loop, supercritical carbon dioxide system (CLS-CO.sub.2 system). The CLS-CO.sub.2 system includes a turbine-generator and a high temperature recuperator (HTR) that is arranged to receive expanded carbon dioxide from the turbine-generator. The HTR includes a plurality of heat exchangers that define respective heat exchange areas. At least two of the heat exchangers have different heat exchange areas.

Sonwane, Chandrashekhar; Sprouse, Kenneth M; Subbaraman, Ganesan; O'Connor, George M; Johnson, Gregory A

2014-11-18

472

System for reducing sulfur dioxide  

SciTech Connect

A system for reducing sulfur dioxide in which a vessel is provided with an inlet for receiving coal and a plurality of gas distribution nozzles for receiving the sulfur dioxide and discharging same downwardly in the lower portion of the vessel for flowing upwardly in a counterflow relation to the coal. The coal flows through a distribution device located in the hopper section of the vessel for insuring an even distribution of coal through the vessel.

Bischoff, W.F.; Steiner, P.

1980-06-10

473

Chemistry of titanium dioxide nanoparticles  

NASA Astrophysics Data System (ADS)

With increasing energy costs, government regulations, and an expanding population, alternative low-cost methods for the treatment of waste air and water have shown renewed interest. The utilization of solar energy to promote catalytic reactions, including photodegradation of pollutants, is an attractive and well-established field of research. Titanium dioxide nanoparticles are the most widely employed catalyst material in photocatalytic studies. Owing to its high surface area and electronic structure, the anatase phase of TiO 2 is an excellent photocatalyst. However, a detailed understanding of the physical, chemical, and electronic properties of TiO2 that influence the photocatalytic reaction rate does not exist. One goal of this work is the determination of how the degradation rate over TiO2 nanoparticle is influenced by the particle size. To meet this goal, detailed analysis of the particles was carried out using standard catalytic techniques combined with infrared spectroscopy to probe the decomposition of an organic probe molecule, formic acid. It was shown using infrared spectroscopy that the size of the particle does influence the rate of photodegradation. However for particles as small as five nanometers, the increased rate could be described by accounting for the increased surface area of the particles. Novel synthesis conditions for the synthesis of high purity particles is required to develop a better understanding of how the size can influence the particle's catalytic properties. Combustion synthesis serves as an attractive method for the synthesis of high purity TiO2 nanoparticles. The high temperatures present in a combustion flame promotes the decomposition of organometallic precursors and subsequent synthesis of metal oxide nanoparticles. Numerous synthesis conditions can influence the product powder. This research investigated some of these conditions for the synthesis of TiO2 nanoparticles. Additionally the thermal properties of TiO2 nanoparticles was investigated. It is known that the more active phase for photocatalysis, anatase, is metastable at extremely small particle sizes (< 15 nm). A premixed ethylene combustion flame was employed in conjunction with a novel rapid-insertion sampler. This allowed for the extraction of high purity anatase particles before sintering and phase transformation to the less photoactive rutile phase could occur. The thermal properties of these particles were then investigated as part of an effort to investigate the catalytic properties of the flame synthesized particles. Results show that high-purity phase-pure anatase particles in the nanometer size range could be synthesized in a combustion flame. These particles were shown to be thermally stable to 773 K before sintering and phase transformation to rutile occurred.

McCormick, John

474

Nitrogen dioxide fluorescence from N2O5 photolysis  

NASA Astrophysics Data System (ADS)

The products of ultraviolet photolysis of N2O5 are NO3 and a wavelength dependent mixture of NO2, NO*2, and NO+O, where NO*2 represents one or more excited electronic states of nitrogen dioxide. This NO*2 emits the visible fluorescence spectrum of nitrogen dioxide (photolysis induced fluorescence, PIF), and this spectrum was compared with monochromatically excited NO2 fluorescence spectra (laser induced fluorescence, LIF). In a series of experiments, dispersed PIF and LIF spectra were measured where reactant pressure was 200 mTorr, delay time was 30 ns, and observation time was 600 ns. According to results obtained by Sugimoto and co-workers, under these conditions the continuous spectrum, which reflects the overall internal energy of NO*2, had been little modified by collision, although there was degradation of fine structure. The continuous LIF spectra were fit to an empirical function, and the PIF spectra were shown to be well represented by a linear combination of these mono-energetic excitation spectra. The coefficients of this linear combination plus other considerations were interpreted to give the almost nascent internal energy distribution of the electronically excited nitrogen dioxide molecules produced by N2O5 photolysis. This non-Boltzmann internal energy distribution indicates that electronically excited nitrogen dioxide is produced in the 2B1 state when N2O5 is photolyzed.

Oh, Daniel; Sisk, Wade; Young, Anthony; Johnston, Harold

1986-12-01

475

Molecule of the Month  

NSDL National Science Digital Library

From the University of Bristol's School of Chemistry, this site features a new molecule each month. For example, the molecule for April is Melatonin. Each molecule comes with a link to a Webpage from a university or commercial site containing further information. (Links may require Chime, VRML, or Java.) Contributors may submit molecule pages to be considered in future months. Monthly molecules date back to January 1996.

476

Modeling the infrared and raman spectra of silicon dioxide clusters absorbing water  

Microsoft Academic Search

The effect of absorbed water on the dielectric properties of silicon dioxide nanoparticles is studied by the molecular dynamic\\u000a method. It is demonstrated using the model of flexible molecules that increasing the number of water molecules in the (SiO2)50 cluster to 40 results in an enhancement of absorption of infrared radiation over the frequency range 0 cm?1 ? ? ?

A. E. Galashev; O. R. Rakhmanova; L. A. Zemnukhova

2011-01-01

477

Exploring surfaces and cavities in lipoxygenase and other proteins by hyperpolarized xenon-129 NMR.  

PubMed

This paper presents an exploratory study of the binding interactions of xenon with the surface of several different proteins in the solution and solid states using both conventional and hyperpolarized (129)Xe NMR. The generation of hyperpolarized (129)Xe by spin exchange optical pumping affords an enhancement by 3-4 orders of magnitude of its NMR signal. As a result, it is possible to observe Xe directly bound to the surface of micromolar quantities of lyophilized protein. The highly sensitive nature of the (129)Xe line shape and chemical shift are used as indicators for the conditions most likely to yield maximal dipolar contact between (129)Xe nuclei and nuclear spins situated on the protein. This is an intermediate step toward achieving the ultimate goal of NMR enhancement of the binding-site nuclei by polarization transfer from hyperpolarized (129)Xe. The hyperpolarized (129)Xe spectra resulting from exposure of four different proteins in the lyophilized, powdered form have been examined for evidence of binding. Each of the proteins, namely, metmyoglobin, methemoglobin, hen egg white lysozyme, and soybean lipoxygenase, yielded a distinctly different NMR line shape. With the exception of lysozyme, the proteins all possess a paramagnetic iron center which can be expected to rapidly relax the (129)Xe and produce a net shift in its resonance position if the noble gas atom occupies specific binding sites near the iron. At temperatures from 223 to 183 K, NMR signals were observed in the 0-40 ppm chemical shift range, relative to Xe in the gas phase. The signals broadened and shifted downfield as the temperature was reduced, indicating that Xe is exchanging between the gas phase and internal or external binding sites of the proteins. Additionally, conventional (129)Xe NMR studies of metmyoglobin and lipoxygenase in the solution state are presented. The temperature dependence of the chemical shift and line shape indicate exchange of Xe between adsorption sites on lipoxygenase and Xe in the solvent on the slow to intermediate exchange time scale. The NMR results are compared with N(2), Xe, and CH(4) gas adsorption isotherms. It is found that lipoxygenase is unique among the proteins studied in possessing a relatively high affinity for gas molecules, and in addition, demonstrating the most clearly resolved adsorbed (129)Xe NMR peak in the lyophilized state. PMID:16429610

Bowers, C R; Storhaug, V; Webster, C E; Bharatam, J; Cottone, A; Gianna, R; Betsey, K; Gaffney, B J

1999-10-13

478

Exploring Surfaces and Cavities in Lipoxygenase and Other Proteins by Hyperpolarized Xenon-129 NMR  

PubMed Central

This paper presents an exploratory study of the binding interactions of xenon with the surface of several different proteins in the solution and solid states using both conventional and hyperpolarized 129Xe NMR. The generation of hyperpolarized 129Xe by spin exchange optical pumping affords an enhancement by 3–4 orders of magnitude of its NMR signal. As a result, it is possible to observe Xe directly bound to the surface of micromolar quantities of lyophilized protein. The highly sensitive nature of the 129Xe line shape and chemical shift are used as indicators for the conditions most likely to yield maximal dipolar contact between 129Xe nuclei and nuclear spins situated on the protein. This is an intermediate step toward achieving the ultimate goal of NMR enhancement of the binding-site nuclei by polarization transfer from hyperpolarized 129Xe. The hyperpolarized 129Xe spectra resulting from exposure of four different proteins in the lyophilized, powdered form have been examined for evidence of binding. Each of the proteins, namely, metmyoglobin, methemoglobin, hen egg white lysozyme, and soybean lipoxygenase, yielded a distinctly different NMR line shape. With the exception of lysozyme, the proteins all possess a paramagnetic iron center which can be expected to rapidly relax the 129Xe and produce a net shift in its resonance position if the noble gas atom occupies specific binding sites near the iron. At temperatures from 223 to 183 K, NMR signals were observed in the 0–40 ppm chemical shift range, relative to Xe in the gas phase. The signals broadened and shifted downfield as the temperature was reduced, indicating that Xe is exchanging between the gas phase and internal or external binding sites of the proteins. Additionally, conventional 129Xe NMR studies of metmyoglobin and lipoxygenase in the solution state are presented. The temperature dependence of the chemical shift and line shape indicate exchange of Xe between adsorption sites on lipoxygenase and Xe in the solvent on the slow to intermediate exchange time scale. The NMR results are compared with N2, Xe, and CH4 gas adsorption isotherms. It is found that lipoxygenase is unique among the proteins studied in possessing a relatively high affinity for gas molecules, and in addition, demonstrating the most clearly resolved adsorbed 129Xe NMR peak in the lyophilized state. PMID:16429610

Storhaug, V.; Webster, C. E.; Bharatam, J.; Cottone, A.; Gianna, R.; Betsey, K.; Gaffney, B. J.

2005-01-01

479

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

480

Novel nuclear magnetic resonance techniques for studying biological molecules  

SciTech Connect

Over the fifty-five year history of Nuclear Magnetic Resonance (NMR), considerable progress has been made in the development of techniques for studying the structure, function, and dynamics of biological molecules. The majority of this research has involved the development of multi-dimensional NMR experiments for studying molecules in solution, although in recent years a number of groups have begun to explore NMR methods for studying biological systems in the solid-state. Despite this new effort, a need still exists for the development of techniques that improve sensitivity, maximize information, and take advantage of all the NMR interactions available in biological molecules. In this dissertation, a variety of novel NMR techniques for studying biomolecules are discussed. A method for determining backbone ({phi}/{psi}) dihedral angles by comparing experimentally determined {sup 13}C{sub a}, chemical-shift anisotropies with theoretical calculations is presented, along with a brief description of the theory behind chemical-shift computation in proteins and peptides. The utility of the Spin-Polarization Induced Nuclear Overhauser Effect (SPINOE) to selectively enhance NMR signals in solution is examined in a variety of systems, as are methods for extracting structural information from cross-relaxation rates that can be measured in SPINOE experiments. Techniques for the production of supercritical and liquid laser-polarized xenon are discussed, as well as the prospects for using optically pumped xenon as a polarizing solvent. In addition, a detailed study of the structure of PrP 89-143 is presented. PrP 89-143 is a 54 residue fragment of the prion proteins which, upon mutation and aggregation, can induce prion diseases in transgenic mice. Whereas the structure of the wild-type PrP 89-143 is a generally unstructured mixture of {alpha}-helical and {beta}-sheet conformers in the solid state, the aggregates formed from the PrP 89-143 mutants appear to be mostly {beta}-sheet.

Laws, David D.

2000-06-01