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1

Oriented xenon hydride molecules in the gas phase  

Microsoft Academic Search

The production of the xenon hydride molecules HXeX with X = I and Cl in the gas phase is reviewed. These molecules are generated by the photolysis of the hydrogen halide HI and HCl molecules on the surface of large xenon Xen clusters. Molecular dynamics simulations show that the flexible H atoms react with the heavy XeX moiety and form

Udo Buck; Michal Fárník

2006-01-01

2

Investigations of adsorbed organic molecules in Na-Y zeolite by xenon-129 NMR  

SciTech Connect

The adsorption of n-hexane, benzene, and trimethylbenzene in Na-Y zeolite supercages has been investigated by use of xenon-129 NMR. As shown by Fraissard and co-workers, xenon-129 is an excellent probe of its environment in zeolites and is sensitive to the number of adsorbed guest molecules. The xenon-129 chemical shift, when extrapolated to zero effective xenon pressure, is 89.7 {plus minus} 0.1 ppm for benzene, 89.0 {plus minus} 1.3 ppm for trimethylbenzene, and 107.7 {plus minus} 1.2 ppm for n-hexane at a concentration of two guest molecules per zeolite supercage compared to 58.9 {plus minus} 0.5 ppm for empty Na-Y zeolite supercages. This approach is useful for determining the number of adsorbed molecules inside zeolite supercages and given information about their arrangement within the supercages.

de Menorval, L.C.; Raftery, D.; Liu, S.B.; Takegoshi, K.; Ryoo, R.; Pines, A. (Lawrence Berkeley Lab., CA (USA))

1990-01-11

3

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

NASA Astrophysics Data System (ADS)

Self-defect clusters in bulk matrix might affect the thermodynamic behavior of fission gases in nuclear fuel such as uranium dioxide. With first-principles local spin-density approximation plus 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 trivacancy sites to incorporate xenon in hyperstoichiometric regime at high temperatures. The results show that in hypostoichiometric regime neutral trivacancy sites are the most favored position for diluted xenon gas, whereas in hyperstoichiometric 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 metastable states difficulty that frequently encountered in density functional theory plus U applications, namely, the quasiannealing procedure, is also discussed.

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

2010-09-01

4

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

5

Electronic Structures of Molecules XIV. Linear Triatomic Molecules, Especially Carbon Dioxide  

Microsoft Academic Search

Electron configurations of the triatomic linear molecules CO2, BO2—, N2O, CS2, COS, NO2+, N3—, NCO—, NCS—, BeF2, HgCl2, ClCN, ClBO, etc. are given. The electron configurations probably of all of these are formally analogous, or formally identical in the case of isoelectronic molecules, such as CO2, N2O, BeF2, etc. The BeH2 type is also touched on. The relations of the

Robert S. Mulliken

1935-01-01

6

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

7

Enhancing Solution-State NMR with Laser-Polarized Xenon  

NASA Astrophysics Data System (ADS)

We report measurements of the polarization transfer from laser-polarized ^129Xe to molecules in various solutions at room temperature. We have shownfootnote G. Navon, Y.-Q. Song, T. Rõõm, S. Appelt, R.E. Taylor, and A. Pines, Science 271, 1848(1996). that the nuclear dipolar couplings between xenon and protons in solution, modulated by their diffusional motion, are responsible for the transfer of the nuclear spin polarization from xenon to molecules when specific binding does not occur. However, when xenon does bind to molecules in solution-even temporarily-the coupling can be much stronger and the polarization transfer can be more efficient. We report measurements of the polarization transfer from xenon to several solutes, in particular, to ?-cyclodextrin whose coupling to xenon is found to be two orders of magnitude stronger than the diffusive couplings alone.

Goodson, B. M.; Song, Y.-Q.; Taylor, R. E.; Laws, D. D.; Pines, A.; Navon, G.

1997-03-01

8

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

9

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

PubMed

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

Beckman, E J

2004-09-01

10

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

11

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

12

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

13

Liquid xenon scintillation spectrometer  

NASA Astrophysics Data System (ADS)

A liquid xenon scintillation detector has been worked out. Liquid xenon fills up a volume 27 mm diameter by 12-30 mm long inside a quartz cylinder with a teflon reflector. Both ends of the cylinder are sealed with photomultipliers with quartz windows. The energy resolution of the detector was found to be of the same order of magnitude as NaI(Tl) crystals for the energy 120 KeV. However, the resolution increases for the higher energies and comes up to 15% for 662 KeV. The reasons of such deterioration of resolution with increasing energy are discussed.

Barabanov, I. R.; Gavrin, V. N.; Pshukov, A. M.

1987-02-01

14

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

15

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

16

Molecule matters  

Microsoft Academic Search

Carbon dioxide is a fascinating molecule; its gaseous, liquid, solid and even supercritical fluid states have unique properties\\u000a and applications. The linear triatomic structure of carbon dioxide molecule with two carbon-oxygen double bonds is all too\\u000a familiar. However a whole new world has been opened up by high pressure-high temperature experiments that effected the polymerization\\u000a of this small molecule into

T. P. Radhakrishnan

2006-01-01

17

WIMP Detection Using Liquid Xenon  

NASA Astrophysics Data System (ADS)

The missing mass 'Dark Matter' problem of the Universe is one of the most important questions facing the moden physics and astronomy. This thesis work developed the Liquid Xenon technology to detect the SUSY ark matter. The background rejection principle was tested and many technical problem are studied, including the purification of the liquid xenon to yield both long electron lifetime and long xenon scintillation light attenuation length, and xenon recoil scintillation efficiency measurement. The detector design and construction are studied. Finally a two phase xenon detector was realized for the future dark matter experiment. The key working principle is the use of proportional scintillation and electro-luminescence to detector the ionization components, which is different between background and recoil signals. The two phase test results shown that a detector energy threshold as low as 10keV can be achieved.

Wang, Hanguo

18

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

19

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

20

Xenon Isotope Releases from Buried Transuranic Waste  

Microsoft Academic Search

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

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

2004-01-01

21

Venus, Earth, Xenon  

NASA Astrophysics Data System (ADS)

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

Zahnle, K. J.

2013-12-01

22

A technique for administering xenon gas anesthesia during surgical procedures in mice.  

PubMed

Carrying out invasive procedures in animals requires the administration of anesthesia. Xenon gas offers advantages as an anesthetic agent compared with other agents, such as its protection of the brain and heart from hypoxia-induced damage. The high cost of xenon gas has limited its use as an anesthetic in animal experiments, however. The authors designed and constructed simple boxes for the induction and maintenance of xenon gas and isoflurane anesthesia in small rodents in order to minimize the amount of xenon gas that is wasted. While using their anesthesia delivery system to anesthetize pregnant mice undergoing caesarean sections, they measured the respiratory rates of the anesthetized mice, the survival of the pups and the percentages of oxygen and carbon dioxide within the system to confirm the system's safety. PMID:25333593

Ruder, Arne Mathias; Schmidt, Michaela; Ludiro, Alessia; Riva, Marco A; Gass, Peter

2014-10-21

23

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

24

The fate of xenon-131 from iodine-131 absorbed on the silver zeolite samplers  

NASA Astrophysics Data System (ADS)

The purpose of this study was to investigate whether xenon-131, the decay daughter of I-131, was retained in or escaped from the silver zeolite cartridge after iodine-131 had been adsorbed in the cartridge. Currently, silver zeolite cartridges are used in the nuclear power industry to adsorb the radioactive iodine gas in sampling lines because of their high retention efficiency for gaseous iodine but not for noble gases. If xenon-131 is desorbed and escapes from the silver zeolite cartridge, the surfaces originally occupied by iodine-131 in the silver zeolite cartridge may be vacant and thus available to adsorb other iodine gas molecules. The reusability of silver zeolite cartridges may reduce the sampling cost and radioactive waste volume and also preserve the silver resource. A silver zeolite cartridge containing only iodine-131 of known activity in a cartridge holder was connected with a blank charcoal cartridge in another cartridge holder. The end of each cartridge holder was sealed so the diffusion of xenon was contained in a closed system. Radioactive xenon-131 m, the daughter of iodine-131, was used as an indicator for stable xenon-131. The absence or presence of xenon-131m on the charcoal cartridge was used to determine if xenon-131 was desorbed from the silver zeolite cartridge. A NaI scintillator was used to detect iodine-131 and a HPGe detector was used to detect xenon- 131 m. The desorption fraction of xenon-133 from the silver zeolite cartridge was found to be 0.66 +/- 4.3% and the retention fraction of xenon-133 in the charcoal cartridge was found to be 0.61 +/- 7.5%. Xenon-131m was frequently present in the charcoal cartridge. This showed that xenon131 was desorbed and escaped from the initial occupied sites in the silver zeolite cartridge after iodine-131 decayed. The amount of xenon-131m escaping from the silver zeolite cartridge fluctuated from day to day. This is thought to be due to what is known as the tunnel blocking effect. This effect has been described in the literature and involves the random location of xenon-131m atoms in the microscopic infrastructure of the silver zeolite.

Wang, Wei-Hsung

2000-09-01

25

Gas-phase silicon micromachining with xenon difluoride  

NASA Astrophysics Data System (ADS)

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 observed. Initial characteriation of wafer surface temperature during the etch indicates tens of degrees of self-heating, which is known to cause substantial decrease in etch rate.

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

1995-09-01

26

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

27

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

28

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

29

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

30

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

31

Xenon ionization detector for digital radiography  

Microsoft Academic Search

Xenon gas x-ray detectors have been used successfully in CT scanners; however, they have been found to be unsuitable for digital radiography. We have designed and built a new type of xenon x-ray detector array and tested its suitability for digital radiography. The detector consists of two parallel plates separated by a 0.5-mm gap, filled with xenon gas at a

D. J. Drost; A. Fenster

1982-01-01

32

Molecular polarization and molecular chiralization: The first example of a chiralized xenon atom.  

PubMed

In this article we focus on the interaction between a chiral molecule and a single achiral molecule or an ensemble of achiral molecules. The desymmetrization of the achiral molecules resulting from this interaction is described as "chiralization." By analogy with electric polarization, we factorize chiralization into three factors, i.e., orientation, atomic, and electronic terms. Chiralization depends on the dipolar polarizability of the chiralized molecule but also on polarizabilities of higher order. The experimental part of this work is devoted to the electronic chiralization of a xenon atom and its observation by (129)Xe NMR spectroscopy. Copyright 2000 Wiley-Liss, Inc. PMID:11135407

Bartik; Luhmer; Collet; Reisse

2001-01-01

33

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

34

Xenon Gamma Detector Project Support  

SciTech Connect

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

Vanier,P.E.; Forman, L.

2008-04-01

35

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

36

The XENON100 Dark Matter Experiment  

SciTech Connect

The XENON100 experiment is searching for WIMPs, which are particles that may consist dark matter. It is located in the underground laboratory of Gran Sasso (LNGS) in Italy at a depth of {approx}3600 m.w.e.. The experiment description, its performance and the expected background based on Monte Carlo simulations and material screening along with the projected sensitivities of the experiment are presented. In addition, a brief description of the upgrade XENON100 detector is given.

Tziaferi, E. [Physics Institute, University of Zuerich, Winterthurerstr. 190, Zuerich (Switzerland)

2010-06-23

37

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

38

Anticonvulsant effect of xenon on neonatal asphyxial seizures.  

PubMed

Xenon, a monoatomic gas with very high tissue solubility, is a non-competitive inhibitor of N-methyl-D-aspartate (NMDA) glutamate receptor, has antiapoptotic effects and is neuroprotective following hypoxic ischaemic injury in animals. Xenon may be expected to have anticonvulsant effects through glutamate receptor blockade, but this has not previously been demonstrated clinically. We examined seizure activity on the real time and amplitude integrated EEG records of 14 full-term infants with perinatal asphyxial encephalopathy treated within 12 h of birth with 30% inhaled xenon for 24 h combined with 72 h of moderate systemic hypothermia. Seizures were identified on 5 of 14 infants. Seizures stopped during xenon therapy but recurred within a few minutes of withdrawing xenon and stopped again after xenon was restarted. Our data show that subanaesthetic levels of xenon may have an anticonvulsant effect. Inhaled xenon may be a valuable new therapy in this hard-to-treat population. PMID:23572341

Azzopardi, Denis; Robertson, Nicola J; Kapetanakis, Andrew; Griffiths, James; Rennie, Janet M; Mathieson, Sean R; Edwards, A David

2013-09-01

39

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

40

Reflectance of polytetrafluoroethylene for xenon scintillation light  

SciTech Connect

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

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

2010-03-15

41

Detection of small numbers of barium ions implanted in solid xenon for the EXO experiment  

NASA Astrophysics Data System (ADS)

In an effort to discover the yet-unknown absolute masses of neutrinos, the goal of the Enriched Xenon Observatory is to observe neutrinoless double beta decay of 136Xe. Identification of this very rare decay may be difficult even with the best conventional efforts to reduce and reject radioactive background, thus requiring additional background rejection via detection of the daughter 136Ba nucleus. One method of detection is laser-induced fluorescence of the barium atom in solid xenon. Spectra of very small numbers of barium atoms in solid xenon, as few as 3 atoms, are reported for the first time. Demonstration of detection of Ba atoms with large fluorescence efficiencies gives promise for detecting single atoms in the near future. Results from experiments involving implantation of Ba+ ions in solid xenon are discussed. One narrow excitation peak was discovered from ion beam deposition that was not found in neutral deposits. Five new emission lines are found with this same excitation spectrum. Bleaching, annealing, and laser dependence of these lines are studied. The identification of the new Ba species as Ba+ or as a barium molecule is discussed.

Cook, Shon

42

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

43

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

44

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

45

XENON: a 1 tonne Liquid Xenon Experiment for a Sensitive Dark Matter Search  

E-print Network

XENON is a novel liquid xenon experiment concept for a sensitive dark matter search using a 1-tonne active target, distributed in an array of ten independent time projection chambers. The design relies on the simultaneous detection of ionization and scintillation signals in liquid xenon, with the goal of extracting as much information as possible on an event-by-event basis, while maintaining most of the target active. XENON is expected to have effective and redundant background identification and discrimination power, higher than 99.5%, and to achieve a very low threshold, on the order of 4 keV visible recoil energy. Based on this expectation and the 1-tonne mass of active xenon, we project a sensitivity of 0.0001 events/kg/day, after 3 yr operation in an appropriate underground location. The XENON experiment has been recently proposed to the National Science Foundation (NSF) for an initial development phase leading to the development of the 100 kg unit module.

E. Aprile; E. A. Baltz; A. Curioni; K-L. Giboni; C. J. Hailey; L. Hui; M. Kobayashi; K. Ni; W. W. Craig; R. J. Gaitskell; U. Oberlack; T. Shutt

2002-07-31

46

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

47

Xenon fluorides show potential as fluorinating agents  

NASA Technical Reports Server (NTRS)

Xenon fluorides permit the controlled addition of fluorine across an olefinic double bond. They provide a series of fluorinating agents that permit ready separation from the product at a high purity. The reactions may be carried out in the vapor phase.

Chernick, C. L.; Shieh, T. C.; Yang, N. C.

1967-01-01

48

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

49

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.

Mong, B; 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; Krucken, 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

2014-01-01

50

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

51

The Genesis solar xenon composition and its relationship to planetary xenon signatures  

NASA Astrophysics Data System (ADS)

The fluence and isotopic composition of solar wind xenon have been determined from silicon collector targets flown on the NASA Genesis mission. A protocol was developed to extract gas quantitatively from samples of ?9-25 mm2, and xenon measured using the RELAX mass spectrometer. The fluence of implanted solar wind xenon is 1.202(87) × 106 atoms 132Xe cm-2, which equates to a flux of 5.14(21) × 106 atoms 132Xe cm-2 year-1 at the L1 point. This value is in good agreement with those reported in other studies. The isotopic composition of the solar wind is consistent with that extracted from the young lunar regolith and other Genesis collector targets. The more precise xenon isotopic data derived from the Genesis mission confirm models of relationships among planetary xenon signatures. The underlying composition of Xe-Q is mass fractionated solar wind; small, varying contributions of Xe-HL and 129Xe from 129I decay are present in reported meteorite analyses. In contrast, an s-process deficit is apparent in Xe-P3, which appears to have been mass fractionated to the same extent as Xe-Q from a precursor composition, suggesting similar trapping mechanisms. Solar wind xenon later evolved by the addition of ?1% (at 132Xe) of s-process xenon to this precursor. As an alternative model to a single source reservoir for Xe-P3, we propose that trapping of xenon onto carbonaceous carriers has been an ongoing process across galactic history, and that preparation of the residues in which Xe-P3 has been identified preferentially preserves longer lived host phases; a higher proportion of these sample xenon isotopic compositions from earlier in galactic chemical evolution, allowing the s-process deficit to become apparent. The relationships among SW-Xe, Xe-Q and Xe-P3 predict that the 124Xe/132Xe ratio for the solar wind is 0.00481(6).

Crowther, S. A.; Gilmour, J. D.

2013-12-01

52

Xenon ion propulsion for orbit transfer  

NASA Technical Reports Server (NTRS)

The status of critical ion propulsion system elements is reviewed. Electron bombardment ion thrusters for primary propulsion have evolved to operate on xenon in the 5-10 kW power range. Thruster efficiencies of 0.7 and specific impulse values of 4000 s have been documented. The baseline thruster currently under development by NASA LeRC includes ring-cusp magnetic field plasma containment and dished two-grid ion optics. Based on past experience and demonstrated simplifications, power processors for these thrusters should have approximately 500 parts, a mass of 40 kg, and an efficiency near 0.94. Thrust vector control, via individual thruster gimbals, is a mature technology. High pressure, gaseous xenon propellant storage and control schemes, using flight qualified hardware, result in propellant tankage fractions between 0.1 and 0.2. In-space and ground integration testing has demonstrated that ion propulsion systems can be successfully integrated with their host spacecraft.

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

1990-01-01

53

Versatile power supply circuit for xenon flashlamps  

NASA Astrophysics Data System (ADS)

A simple, versatile power supply designed to control xenon flashlamps is described. The circuit is configured to utilize an N-channel enhanced metal-oxide-semiconductor field effect transistor (MOSFET), taking the place of commonly used triggering devices such as a silicon controlled rectifier (SCR), or triac. Incorporation of the MOSFET permits flexible control of flash duty cycle and frequency by applying one signal to the transistor's gate. The circuit's versatility is demonstrated using an 8.3-W xenon flashlamp as an excitation source for a photodiode array based HPLC fluorescence detector. A detailed description of the power supply circuit is given, along with information on interfacing the circuit and the photodiode array.

Wegrzyn, Jeff; Patonay, Gabor; Warner, Isiah; Ford, Michael

1989-01-01

54

Prospects for Barium Tagging in Gaseous Xenon  

NASA Astrophysics Data System (ADS)

Tagging events with the coincident detection of a barium ion would greatly reduce the background for a neutrino-less double beta decay search in xenon. This paper describes progress towards realizing this goal. It outlines a source that can produce large quantities of Ba++ in gas, shows that this can be extracted to vacuum, and demonstrates a mechanism by which the Ba++ can be efficiently converted to Ba+ as required for laser identification.

Sinclair, D.; Rollin, E.; Smith, J.; Mommers, A.; Ackeran, N.; Aharmin, B.; Auger, M.; Barbeau, P. S.; Benitez-Medina, C.; Breidenbach, M.; Burenkov, A.; Cook, S.; Coppens, A.; Daniels, T.; DeVoe, R.; Dobi, A.; Dolinski, M. J.; Donato, K.; Fairbank, W., Jr.; Farine, J.; Giroux, G.; Gornea, G.; Graham, K.; Gratta, G.; Green, M.; Hagemann, C.; Hall, C.; Hall, K.; Hallman, D.; Hargrove, C.; Herrin, S.; Kaufman, L. K.; Leonard, D. S.; LePort, F.; Mackay, D.; MacLennan, R.; Mong, B.; Montero Díez, M.; Müller, A. R.; Neilson, R.; Niner, E.; Odian, A.; O'Sullivan, K.; Ouellet, C.; Piepke, A.; Pocar, A.; Prescott, C. Y.; Pushkin, K.; Rowson, P. C.; Slutsky, S.; Stekhanov, V.; Twelker, K.; Voskanian, N.; Vuilleumier, J.-L.; Wichoski, U.; Wodin, J.; Yang, L.; Yen, Y.-R.

2011-08-01

55

Xenon recirculation-purification with a heat exchanger  

Microsoft Academic Search

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

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

2011-01-01

56

Recovering Residual Xenon Propellant for an Ion Propulsion System  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

57

The Krypton and Xenon Contents of Atmospheric Air  

Microsoft Academic Search

The proportion of krypton and xenon in dry air has been measured by a method using distillation and low-temperature gas-chromatography for the isolation of krypton and xenon. The separation has been controlled by the use of radioactive 85Kr tracer. The krypton content of dry air is 1\\\\cdot 139 ± 0\\\\cdot 01 × 10-6 by volume. The xenon content of dry

E. Glueckauf; G. P. Kitt

1956-01-01

58

Xenon preconditioning reduces brain damage from neonatal asphyxia in rats  

Microsoft Academic Search

Xenon attenuates on-going neuronal injury in both in vitro and in vivo models of hypoxic–ischaemic injury when administered during and after the insult. In the present study, we sought to investigate whether the neuroprotective efficacy of xenon can be observed when administered before an insult, referred to as ‘preconditioning’. In a neuronal–glial cell coculture, preexposure to xenon for 2 h

Daqing Ma; Mahmuda Hossain; Garry K J Pettet; Yan Luo; Ta Lim; Stanislav Akimov; Robert D Sanders; Nicholas P Franks; Mervyn Maze

2006-01-01

59

Design and Performance of the XENON10 Dark Matter Experiment  

Microsoft Academic Search

XENON10 is the first two-phase xenon time projection chamber (TPC) developed\\u000awithin the XENON dark matter search program. The TPC, with an active liquid\\u000axenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground\\u000alaboratory (LNGS) in Italy, and operated for more than one year, with excellent\\u000astability and performance. Results from a dark matter search

E. Aprile; J. Angle; 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; D. Orlandi; G. Plante; R. Santorelli; J. M. F. dos Santos; P. Shagin; T. Shutt; P. Sorensen; S. Schulte; E. Tatananni; C. Winant; M. Yamashita

2010-01-01

60

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. Key words: Xenon, Condenser, Recirculation pump

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

61

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

62

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

63

Hyperpolarized xenon relaxation times in perfluorocarbon emulsion and plasma mixtures  

Microsoft Academic Search

Hyperpolarized xenon (Hyp-129Xe) has great potential in perfusion, blood flow and functional investigations of organs beyond the lungs. Injection of xenon in a dissolved carrier would be the best delivery method for this purpose. The blood substitute perfluorooctyl bromide (PFOB) emulsion is the leading candidate as a carrier. To assess the suitability of PFOB emulsion as a Hyp-129Xe carrier, spectra

Albert R. Cross; Dan McPhee; Dale Stevens; Mark McDonald; Giles E. Santyr

2000-01-01

64

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

PubMed Central

Background Four nursing mothers consented to anaesthesia for urgent surgery only on condition that their ability to breast feed would not be impaired. Methods Following induction of general anaesthesia with propofol and remifentanil, 65-69% xenon supplemented with remifentanil was used as an inhalational anaesthetic for maintenance. Results After finishing surgery the women could be extubated between 2:52 and 7:22 minutes. The women were fully alert just minutes after extubation and spent about 45 minutes in the recovery room before discharge to a regular ward. They resumed regular breast feeding some time later. The propofol concentration in the blood was measured after 0, 30, 90, and 300 minutes and in the milk after 90 and 300 minutes. Just 90 minutes after extubation, the concentration of propofol in the milk was limited (> 3 mg/l) so that pharmacological effects on the babies were excluded after oral intake. Also, no traces of xenon gas were found in the maternal milk at any time. After propofol induction and maintenance of anaesthesia with xenon in combination with a water-soluble short-acting drug like remifentanil, the concentration of propofol in maternal milk is low (> 3 mg/l 90 min after anesthesia) and harmless after oral intake. Conclusions These results, as well as the rapid elimination and absence of metabolism of xenon, are of great interest to nursing mothers. General anaesthesia with propofol for induction only, combined with remifentanil and xenon for maintenance, has not yet been described in breast feeding mothers. PMID:20167123

2010-01-01

65

Evidence of charge exchange pumping in calcium-xenon system  

NASA Technical Reports Server (NTRS)

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

Chubb, D. L.

1973-01-01

66

Etching Silicon Films With Xenon Difluoride  

NASA Technical Reports Server (NTRS)

Microscopic circuit structures prepared for probing. Xenon difluoride removes relatively large amounts of silicon from integratedcircuit or solar-cell structures while leaving SiO2, Si3N4, Al2O3, and other compounds intact. In Etching Apparatus, solid XeF2 sublimated in vacuum, then allowed to flow over sample at controlled rate and pressure. Wafer etched from back to expose SiO2 and Al layers for spectroscopic analysis of SiO2/Al interface. Using XeF2 technique, silicon wafer with oxide layer reduced in thickness from standard 300 micrometer to as little as 10 nanometer without adversely affecting oxide.

Hecht, M. H.

1986-01-01

67

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. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24771455

Jokisaari, Jukka; Zhu, Jianfeng

2014-10-01

68

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

69

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

70

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

71

Nuclear magnetic resonance parameters of atomic xenon dissolved in Gay-Berne model liquid crystal  

NASA Astrophysics Data System (ADS)

We present constant-pressure Monte Carlo simulations of nuclear magnetic resonance (NMR) spectral parameters, nuclear magnetic shielding relative to the free atom as well as nuclear quadrupole coupling, for atomic xenon dissolved in a model thermotropic liquid crystal. The solvent is described by Gay-Berne (GB) molecules with parametrization ?=4.4 , ?'=20.0 , and ?=?=1 . The reduced pressure of P?=2.0 is used. Previous simulations of a pure GB system with this parametrization have shown that upon lowering the temperature, the model exhibits isotropic, nematic, smectic- A , and smectic- B /molecular crystal phases. We introduce spherical xenon solutes and adjust the energy and length scales of the GB-Xe interaction to those of the GB-GB interaction. This is done through first principles quantum chemical calculations carried out for a dimer of model mesogens as well as the mesogen-xenon complex. We preparametrize quantum chemically the Xe nuclear shielding and quadrupole coupling tensors when interacting with the model mesogen, and use the parametrization in a pairwise additive fashion in the analysis of the simulation. We present the temperature evolution of Xe129/131 shielding and Xe131 quadrupole coupling in the different phases of the GB model. From the simulations, separate isotropic and anisotropic contributions to the experimentally available total shielding can be obtained. At the experimentally relevant concentration, the presence of the xenon atoms does not significantly affect the phase behavior as compared to the pure GB model. The simulations reproduce many of the characteristic experimental features of Xe NMR in real thermotropic LCs: Discontinuity in the value or trends of the shielding and quadrupole coupling at the nematic-isotropic and smectic- A -nematic phase transitions, nonlinear shift evolution in the nematic phase reflecting the behavior of the orientational order parameter, and decreasing shift in the smectic- A phase. The last observation is due to the preference of the xenon solutes to occupy the interlayer space where the density of the medium is reduced as compared to the layers. There are systematic deviations, however, in the magnitude of the shielding and its discontinuities, as well as the distribution of the solutes in the translationally ordered smectic- A phase, between the simulation and experiment. These deficiencies are believed to result from the lack of flexibility of the GB model.

Lintuvuori, Juho; Straka, Michal; Vaara, Juha

2007-03-01

72

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

73

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

74

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

2009-07-13

75

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

76

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

77

High-intensity xenon pulse light source for fluorescence excitation  

NASA Astrophysics Data System (ADS)

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

Miyamoto, Makoto; Ueno, Kazuo

1997-05-01

78

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

79

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

80

Single Ion Trapping for the Enriched Xenon Observatory.  

National Technical Information Service (NTIS)

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 ...

S. J. Waldman

2006-01-01

81

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

82

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

83

Fidelity of a xenon on-axis solar simulator  

NASA Technical Reports Server (NTRS)

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 demonstrates the high fidelity output of the xenon solar simulator.

Laws, Burt A.; Bachtel, Russell E.

1992-01-01

84

Factors affecting the adsorption of xenon on activated carbon  

SciTech Connect

The presence of water vapor was found to interfere strongly with the dynamic adsorption of /sup 133/Xe on coconut-base activated charcoal. The percent loss in the xenon adsorption coefficient was similar to values reported earlier for the adsorption of krypton on humidified charcoal. Attempts to increase the adsorption of xenon by (a) using a petroleum-based adsorbent with an extremely high surface area and (b) by impregnation of the adsorbent with iodine were not successful.

Underhill, D.W.; DiCello, D.C.; Scaglia, L.A.; Watson, J.A.

1986-08-01

85

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

86

Hyperpolarized xenon NMR and MRI signal amplification by gas extraction  

PubMed Central

A method is reported for enhancing the sensitivity of NMR of dissolved xenon by detecting the signal after extraction to the gas phase. We demonstrate hyperpolarized xenon signal amplification by gas extraction (Hyper-SAGE) in both NMR spectra and magnetic resonance images with time-of-flight information. Hyper-SAGE takes advantage of a change in physical phase to increase the density of polarized gas in the detection coil. At equilibrium, the concentration of gas-phase xenon is ?10 times higher than that of the dissolved-phase gas. After extraction the xenon density can be further increased by several orders of magnitude by compression and/or liquefaction. Additionally, being a remote detection technique, the Hyper-SAGE effect is further enhanced in situations where the sample of interest would occupy only a small proportion of the traditional NMR receiver. Coupled with targeted xenon biosensors, Hyper-SAGE offers another path to highly sensitive molecular imaging of specific cell markers by detection of exhaled xenon gas. PMID:19805177

Zhou, Xin; Graziani, Dominic; Pines, Alexander

2009-01-01

87

Detection at the single molecule level using an optical fiber  

NASA Astrophysics Data System (ADS)

We are developing a method for detecting single Ba+ ions in solid xenon on a fiber probe for the EXO double beta decay experiment. As a demonstration of potential capability, we have explored detection of Rhodamine 6G molecules and quantum dots in solution using the same optical setup. We report results on detection of ˜1 dye molecule on the average in the probe volume and attempts to do the same with quantum dots. Steps to fix single dye molecules or quantum dots in position and observe blinking from single molecules or dots will follow.

Topel, Thomas; Mong, Brian; Chen, Wei-Ting; Fairbank, William

2009-10-01

88

Mighty Molecules  

NSDL National Science Digital Library

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

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

1997-01-01

89

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).

Mills, Ben; Art, Global W.

90

Precision Magnetometry with Spin-Polarized Xenon  

NASA Astrophysics Data System (ADS)

Atomic magnetometer sensitivity is a limiting factor in precision measurements, medical imaging, and industrial applications. In particular, searches for permanent electric dipole moments (EDMs) require sensitive magnetometers which interact minimally with the primary samples. Techniques based on spin-polarized gases have been very successful in this capacity, but it remains difficult to perform correct spatial and temporal averages. Previous magnetometers (e.g. alkalis or ^199Hg) also suffer from material problems at the high voltages and low temperatures common in EDM experiments. We propose as a remedy real-time optical magnetometry based on spectroscopy of two-photon transitions in spin-polarized ^129Xe. Thermal, diffusive, and dielectric properties of xenon allow sensitive measurements in a wide range of electromagnetic field strengths and sample volumes, while long spin coherence times and a low neutron capture cross-section are favorable in neutron EDM experiments. We report on preliminary work validating the technique in ^171Yb and a parallel effort measuring the ^129Xe EDM, and discuss applications to contemporary neutron EDM measurements.

Degenkolb, Skyler; Leanhardt, Aaron; Chupp, Tim

2012-06-01

91

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

92

Low-Energy Sputtering Studies of Boron Nitride with Xenon Ions  

NASA Technical Reports Server (NTRS)

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

Ray, P. K.; Shutthanandan, V.

1999-01-01

93

Photoabsorption spectra of small cationic xenon clusters from time-dependent density functional theory  

E-print Network

Photoabsorption spectra of small cationic xenon clusters from time-dependent density functional experimental evidence and by theoretical calculations of the photoabsorption of cationic xenon clusters.4­7 Up

94

Hugoniot measurements of double-shocked precompressed dense xenon plasmas.  

PubMed

The current partially ionized plasmas models for xenon show substantial differences since the description of pressure and thermal ionization region becomes a formidable task, prompting the need for an improved understanding of dense xenon plasmas behavior at above 100 GPa. We performed double-shock compression experiments on dense xenon to determine accurately the Hugoniot up to 172 GPa using a time-resolved optical radiation method. The planar strong shock wave was produced using a flyer plate impactor accelerated up to ?6 km/s with a two-stage light-gas gun. The time-resolved optical radiation histories were acquired by using a multiwavelength channel optical transience radiance pyrometer. Shock velocity was measured and mass velocity was determined by the impedance-matching methods. The experimental equation of state of dense xenon plasmas are compared with the self-consistent fluid variational calculations of dense xenon in the region of partial ionization over a wide range of pressures and temperatures. PMID:23368058

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

2012-12-01

95

Development of liquid xenon imaging gamma-ray spectrophotometers  

NASA Astrophysics Data System (ADS)

The application of liquid xenon in high resolution, low background and efficient gamma-ray detectors for the observation in space of weak sources emitting in the 0.1 to 10 MeV energy region is investigated. The basic requirement of ultra-high purity liquid xenon, necessary for the successful operation of these detectors was satisfied with the development of an efficient and reliable purification system, capable of reducing and maintaining the concentration of electronegative impurities below one part in 109. The charge and energy resolution response of a liquid xenon (and liquid argon) ionization chamber has been systematically measured as a function of electric field strength, using various radioactive sources. The results of 4.5 percent FWHM and 2.6 percent FWHM at 1 MeV in liquid xenon and liquid argon, respectively are the best reported in the literature. Their deviation from theoretical estimates based on Fano factor statistics was interpreted as due to recombination straggling on low energy delta-electrons produced along the primary ionizing particle. The effect of photosensitive dopants in the liquid was also measured. Improved charge collection and energy resolution is observed for the case of alpha particles. In view of its application for event triggering in an imaging ionization chamber, the yield of the primary scintillation light abundantly emitted in liquid Xenon was measured using both electrons and alpha particles.

Novick, Robert; Aprile, Elena

1990-07-01

96

Hugoniot measurements of double-shocked precompressed dense xenon plasmas  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

97

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

98

Calibration of the XENON100 Time Projection Chamber  

NASA Astrophysics Data System (ADS)

The XENON Dark Matter Experiment aims at the direct detection of dark matter Weakly Interacting Massive Particles (WIMPs) with dual phase (liquid/gas) xenon time projection chambers. Following the successful performance of the XENON10, we have designed and built a new detector with a total Xe mass of 170 kg, and with 100 times less background. The XENON100 detector is currently undergoing commissioning at the Gran Sasso Underground Laboratory. The calibration of the detector with gamma sources and with low energy neutrons is essential to determine the response to electron and nuclear recoils, and their discrimination based on the ratio of ionization to scintillation, as well as on event positioning and scattering-multiplicity within the active liquid volume. External gamma sources used for the XENON100 calibration include Cs-137, Co-57 and Co-60. An external Am-Be source is used for irradiation by neutrons. Additionally, we have been testing mixing Kr-83m (tau=12.6 hr, 18 and 32 keV electrons and 13 keV x-rays) into the LXe target, as internal source of low energy electron recoils. We discuss how different detector performance parameters such as light yield and electron lifetime can be inferred from these calibrations and show how the spatial dependence of some other parameters (light collection efficiency for example) can be obtained. We also present comparisons of results from calibrations with Monte Carlo simulations.

Lim, Kyungeun

2009-05-01

99

Modeling Xenon Purification Systems in a Laser Inertial Fusion Engine  

NASA Astrophysics Data System (ADS)

A Laser Inertial Fusion Engine (LIFE) is a proposed method to employ fusion energy to produce electricity for consumers. However, before it can be built and used as such, each aspect of a LIFE power plant must first be meticulously planned. We are in the process of developing and perfecting models for an exhaust processing and fuel recovery system. Such a system is especially essential because it must be able to recapture and purify expensive materials involved in the reaction so they may be reused. One such material is xenon, which is to be used as an intervention gas in the target chamber. Using Aspen HYSYS, we have modeled several subsystems for exhaust processing, including a subsystem for xenon recovery and purification. After removing hydrogen isotopes using lithium bubblers, we propose to use cryogenic distillation to purify the xenon from remaining contaminants. Aspen HYSYS allows us to analyze predicted flow rates, temperatures, pressures, and compositions within almost all areas of the xenon purification system. Through use of Aspen models, we hope to establish that we can use xenon in LIFE efficiently and in a practical manner.

Hopkins, Ann; Gentile, Charles

2011-11-01

100

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

Microsoft Academic Search

Because xenon NMR is highly sensitive to the local environment, laser-polarized xenon could be a unique probe of living tissues. Realization of clinical and medical science applications beyond lung airspace imaging requires methods of efficient delivery of laser-polarized xenon to tissues, because of the short spin-lattice relaxation times and relatively low concentrations of xenon attainable in the body. Preliminary results

B. M. Goodson; Y.-Q. SONG; R. E. TAYLOR; V. D. SCHEPKIN; K. M. BRENNAN; G. C. CHINGAS; T. F. BUDINGER; G. N AVON; A. PINES

1997-01-01

101

Terrestrial and Martian weathering signatures of xenon components in shergottite mineral separates  

Microsoft Academic Search

Xenon-isotopic ratios, step-heating release patterns, and gas concentrations of mineral separates from Martian shergottites Roberts Massif (RBT) 04262, Dar al Gani (DaG) 489, Shergotty, and Elephant Moraine (EET) 79001 lithology B are reported. Concentrations of Martian atmospheric xenon are similar in mineral separates from all meteorites, but more weathered samples contain more terrestrial atmospheric xenon. The distributions of xenon from

J. A. Cartwright; K. D. Ocker; S. A. Crowther; R. Burgess; J. D. Gilmour

2010-01-01

102

Molecule nanoweaver  

SciTech Connect

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

103

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

E-print Network

] as interface to the Monte Carlo. The parameterization of the low energy electron range in the liquid xenon of liquid xenon and characteristics of the response of individual cells used as input parametersSimulation and evaluation of a new PET system based on liquid xenon as detection medium J

Paris-Sud XI, Université de

104

Respiratory depression in goats by stable xenon: implications for CT studies.  

PubMed

The pharmacology of stable xenon is of practical importance to users of the xenon CT-regional cerebral blood flow method. In a study in goats we have demonstrated that xenon has a characteristic respiratory depressant effect, unlike effects of comparable anesthetic concentrations of nitrous oxide and halothane. PMID:3571595

Winkler, S S; Nielsen, A; Mesina, J

1987-01-01

105

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 critical point. The energy of the quasi-free electron, arising from dopant field ionization, in xenon and for the critical isotherm. Key words: supercritical xenon, field ionization, quasi-free electron energy, electron

Findley, Gary L.

106

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

Microsoft Academic Search

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

Gani B. Ganapathi; Carl S. Engelbrecht

107

Time profile of the scintillation from liquid and gaseous xenon  

NASA Astrophysics Data System (ADS)

The decay time profile of vacuum ultraviolet scintillation induced by electronic recoils has been studied for liquid and gaseous xenon. The scintillation light from xenon excited by a gamma source was measured by using two vacuum ultraviolet sensitive photomultipliers, one for detecting scintillation and the other for counting photons of weak monochromatic light. The analysis results based on the time-correlated single photon counting method show that the time profile in the 176 nm scintillation decay curve for liquid xenon is consistent with a single exponential component and the decay time constant is 31.5±1.3 ns. This constant does not change significantly for pressure ranges between 90 kPa and 130 kPa. There is no emission wavelength dependence of the decay constant. The result corresponds to an average on electronic recoil energies up to 1.3 MeV.

Murayama, Ikuko; Nakamura, Shogo

2014-11-01

108

The distributed Slow Control System of the XENON100 experiment  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

109

Searching for double beta decay with the Enriched Xenon Observatory  

NASA Astrophysics Data System (ADS)

The Enriched Xenon Observatory (EXO) will search for neutrinoless double beta decay in 136Xe. The first phase of the experiment, EXO-200, uses 200 kg of liquid xenon enriched to 80% in 136Xe in an ultra-low background time projection chamber (TPC). EXO-200 is in the final stages of assembly at the WIPP site in Carlsbad, NM and will begin taking data in 2009 with two-year sensitivity to the half-life for neutrinoless double beta decay of 6.4 × 1025 years. According to nuclear matrix element calculations, this corresponds to an effective Majorana neutrino mass of 0.13 to 0.19 eV. The EXO collaboration is also performing R&D for simultaneous detection of the decay electrons and emerging Ba ion allowing essentially background free detection in a future, ton-scale detector. The status of EXO-200 and of the ion tagging technology in liquid xenon is described.

Kaufman, Lisa J.

2010-01-01

110

Application of Multiphoton Ionization of Liquid Xenon for Purity Measurements  

NASA Astrophysics Data System (ADS)

Detection of fluorescence from single Ba^+ daughter ions in liquid xenon is a potential key method of background discrimination in the Enriched Xenon Observatory (EXO) double beta decay experiment. An important requirement is to have ultrapure liquid in order to ensure Ba^+ ion survival for many seconds. To measure the purity of liquid Xenon we produce electrons using a 355 nm and 266nm Nd-YAG pulsed laser. By varying the laser energy, we have demonstrated that these are two- and three-photon ionization processes, respectively. As the electrons travel in the liquid some may be lost by attachment to impurities. By measuring the fraction of electrons that survive, we can determine the purity of the liquid. Having a focused beam allows us to select where the electrons are created.

Benitez Medina, Julio Cesar; Hall, Kendy; Fairbank, William

2009-10-01

111

Xenon stability analysis using the generalized nyquist criterion  

SciTech Connect

Xenon-induced spatial power oscillations caused by control rod movement may cause control problems in nuclear power plant operation. Many studies have been performed to assess the xenon stability analysis using the time-domain technique or the frequency-domain technique for the single-input/single-output (SISO) system. However, those methods are too complicated and thus too time consuming, or too simple to provide results according to control rod movement in a certain position. This study analyzes xenon axial stability using the modal expansion technique in the frequency domain with the generalized Nyquist criterion, which is suitable for a multi-input/multi-output (MIMO) system. To examine this model, an axial stability analysis has been performed for the pressurized water reactor core of YGN-1 in Korea. The studied design parameters are power level, control rod position, and core average burnup.

Choi, Yoocho; Park, Gooncherl; Chung, Changhyun (Seoul National Univ. (Korea)); Park, Jongkyun

1990-06-01

112

Reflectance of Polytetrafluoroethylene (PTFE) for Xenon Scintillation Light  

E-print Network

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 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. Fluoropolymers, namely ETFE, FEP and PFA were also measured.

Silva, C; Pereira, A; Chepel, V; Lopes, M I; Solovov, V

2009-01-01

113

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

114

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

115

TOPICAL REVIEW: Hyperpolarized xenon in NMR and MRI  

NASA Astrophysics Data System (ADS)

Hyperpolarized gases have found a steadily increasing range of applications in nuclear magnetic resonance (NMR) and NMR imaging (MRI). They can be regarded as a new class of MR contrast agent or as a way of greatly enhancing the temporal resolution of the measurement of processes relevant to areas as diverse as materials science and biomedicine. We concentrate on the properties and applications of hyperpolarized xenon. This review discusses the physics of producing hyperpolarization, the NMR-relevant properties of 129Xe, specific MRI methods for hyperpolarized gases, applications of xenon to biology and medicine, polarization transfer to other nuclear species and low-field imaging.

Oros, Ana-Maria; Shah, N. Jon

2004-10-01

116

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

PubMed

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

Rodrigues, M; Lépy, M-C; Cassette, P; Mougeot, X; Bé, M M

2014-05-01

117

The LUX Two-Phase-Xenon Dark Matter Search Experiment  

NASA Astrophysics Data System (ADS)

The race to be the first experiment to detect collisions between atoms and a new type of weakly interacting massive particle (WIMP) that is conjectured to explain dark matter is heating up. The Large Underground Xenon (LUX) detector is a second-generation WIMP dark matter search experiment that employs a liquid xenon target and provides background discrimination based on the ratio of ionization to scintillation produced in subatomic particle interactions. This experiment is designed to reach the heart of the favored parameter space for supersymmetric WIMPs and has a genuine chance to be the discovery experiment. The concept, design, schedule and reach of the experiment will be discussed.

Stiegler, Tyana; Camp, Charlie; Marquez, Zach; Rodinov, Andrew; White, James

2007-10-01

118

Ab initio study of the organic xenon insertion compound into ethylene and ethane  

NASA Astrophysics Data System (ADS)

This paper studies Xe-insertion ethylene and ethane compounds, i.e., HXeC2H3 and HXeC2H5. The structures, harmonic frequencies, and energetics for both molecules have been calculated at the MP2(full)/6-311++G(2d,2p) level. Our theoretical results predict the existence of HXeC2H3 and the instability of HXeC2H5. Natural bond orbital (NBO) analysis shows a strong ionic bond between the xenon atom and hydrocarbon radical. In addition, the interaction between the donor (Xe lone pair) and acceptor (the C-C antibonding orbital, i.e., ?*(C-C)) increases the stability of HXeC2H3.

Zhang, Min; Sheng, Li

2013-03-01

119

Carbon dioxide enhances fragility of ice crystals  

NASA Astrophysics Data System (ADS)

Ice caps and glaciers cover 7% of the Earth, greater than the land area of Europe and North America combined, and play an important role in global climate. The small-scale failure mechanisms of ice fracture, however, remain largely elusive. In particular, little understanding exists about how the presence and concentration of carbon dioxide molecules, a significant component in the atmosphere, affects the propensity of ice to fracture. Here we use atomic simulations with the first-principles based ReaxFF force field capable of describing the details of chemical reactions at the tip of a crack, applied to investigate the effects of the presence of carbon dioxide molecules on ice fracture. Our result shows that increasing concentrations of carbon dioxide molecules significantly decrease the fracture toughness of the ice crystal, making it more fragile. Using enhanced molecular sampling with metadynamics we reconstruct the free energy landscape in varied chemical microenvironments and find that carbon dioxide molecules affect the bonds between water molecules at the crack tip and decrease their strength by altering the dissociation energy of hydrogen bonds. In the context of glacier dynamics our findings may provide a novel viewpoint that could aid in understanding the breakdown and melting of glaciers, suggesting that the chemical composition of the atmosphere can be critical to mediate the large-scale motion of large volumes of ice.

Qin, Zhao; Buehler, Markus J.

2012-11-01

120

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

121

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

NASA Astrophysics Data System (ADS)

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.

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

122

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

123

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

124

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

125

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

126

Design and performance of Liquid Xenon detectors for PET  

Microsoft Academic Search

We have developed a concept for a micro-PET detector that takes advantage of the improved performances achieved by measuring light and charge in Liquid Xenon. One sector was built and testing is in progress. The good performance in terms of efficiency and image quality of a LXe PET compared to a crystal based system has been shown in simulations.

P. Amaudruz; D. Bryman; L. Kurchaninov; P. Lu; C. Marshall; J. P. Martin; A. Muennich; F. Retiere; A. Sher; V. Sossi

2008-01-01

127

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

128

Measurement of transient nonlinear refractive index in gases using xenon  

E-print Network

Measurement of transient nonlinear refractive index in gases using xenon supercontinuum single measurement of ultrafast high field processes using modest energy lasers, with pump and probe pulses totaling) and instrument resolution. The ultrafast nonlinear Kerr effect in glass, and in Ar, N2, and N2O gases is measured

Milchberg, Howard

129

Barium Tagging for the Enriched Xenon Observatory (EXO)  

NASA Astrophysics Data System (ADS)

The EXO experiment is designed to search for zero-neutrino double beta decay of the isotope Xe^136, in order to better understand the nature of neutrinos. Since the daughter of this decay is barium (Ba^136), detecting the presence of Ba^136 at a decay site (called ``barium tagging'') is the best way to reject backgrounds in the search for this decay. It is hopeful that barium tagging will be implemented in the next phase of EXO. One proposed barium tagging method is to trap the barium ion in a solid xenon matrix (by freezing the liquid xenon surrounding the decay), and move it to another location to do laser-induced fluorescence spectroscopy counting. Our group at CSU is researching the detection of single barium ions and atoms within a solid xenon matrix. A barium ion beam is used to implant the ions into freezing xenon, where laser spectroscopy is then performed. We demonstrate successful detection of very small numbers, and are nearing single-barium detection.

Walton, Timothy

2012-10-01

130

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

131

Radio detection of interstellar sulfur dioxide  

NASA Technical Reports Server (NTRS)

Interstellar sulfur dioxide (SO2) has been detected in emission from the direction of the Orion Nebula molecular cloud and from Sgr B2. SO2 is the heaviest interstellar molecule detected to date, and the only nonlinear triatomic molecule which does not contain hydrogen. The remarkable Orion emission profiles suggest that two components are supporting the SO2 emission: a dense circumstellar-type envelope, which may be in maser emission, and a warm galactic cloud component.

Snyder, L. E.; Hollis, J. M.; Ulich, B. L.; Lovas, F. J.; Johnson, D. R.; Buhl, D.

1975-01-01

132

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

133

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

134

Segregation of xenon to dislocations and grain boundaries in uranium dioxide  

SciTech Connect

It is well known that Xe, being insoluble in UO{sub 2}, segregates to dislocations and grain boundaries (GBs), where bubbles may form resulting in fuel swelling. Less well known is how sensitive this segregation is to the structure of the dislocation or GB. In this work we employ pair potential calculations to examine Xe segregation to dislocations (edge and screw) and several representative grain boundaries ({Sigma}5 tilt, {Sigma}5 twist, and random). Our calculations predict that the segregation trend depends significantly on the type of dislocation or GB. In particular we find that Xe prefers to segregate strongly to the random boundary as compared to the other two boundaries and to the screw dislocation rather than the edge. Furthermore, we observe that neither the volumetric strain nor the electrostatic potential of a site can be used to predict its segregation characteristics. These differences in segregation characteristics are expected to have important consequences for the retention and release of Xe in nuclear fuels. Finally, our results offer general insights into how atomic structure of extended defects influence species segregation.

Nerikar, P. V.; Casillas Trujillo, L. A.; Andersson, D. A.; Unal, C.; Uberuaga, B. P.; Stanek, C. R. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Parfitt, D. C.; Grimes, R. W. [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Sinnott, S. B. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2011-11-01

135

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 page features section on: the exhibit, activities, molecules and the New York Science homepage. Within the activities page, the site currently features three main lessons focusing on molecules, DNA and infra-red technology. The exhibit page displays pictures and additional information on the learning objectives of the display. The site features contact information for those interesting in more information on the exhibit.

2009-04-30

136

Modelling the phase equilibria and excess properties of the water?+?carbon dioxide binary mixture  

Microsoft Academic Search

The high-pressure phase diagram and excess thermodynamic properties of the binary mixture of carbon dioxide and water are examined using the statistical associating fluid theory for potentials of variable range (SAFT-VR). The carbon dioxide molecule is modelled with two tangentially bonded spherical segments, while the water molecule is modelled as spherical with four associating sites to represent the hydrogen bonding.

María Carolina dos Ramos; Felipe J. Blas; Amparo Galindo

2007-01-01

137

Desorption of carbon dioxide from small potassium niobate particles induced by the particles’ ferroelectric transition  

Microsoft Academic Search

The aim of this work is to understand surface properties of ferroelectric crystals related to gas adsorption. Various ferroelectric crystals involved in these studies readily adsorb carbon dioxide, thus our studies were centered on adsorption studies of this molecule. It has been claimed that a dipole moment is induced on carbon dioxide molecules that are near an oxide surface. Our

E. Ramos-Moore; J. A. Baier-Saip; A. L. Cabrera

2006-01-01

138

Desorption of carbon dioxide from small potassium niobate particles induced by the particles' ferroelectric transition  

Microsoft Academic Search

The aim of this work is to understand surface properties of ferroelectric crystals related to gas adsorption. Various ferroelectric crystals involved in these studies readily adsorb carbon dioxide, thus our studies were centered on adsorption studies of this molecule. It has been claimed that a dipole moment is induced on carbon dioxide molecules that are near an oxide surface. Our

E. Ramos-Moore; J. A. Baier-Saip; A. L. Cabrera

2006-01-01

139

Modeling Molecules  

NASA Technical Reports Server (NTRS)

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

2000-01-01

140

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

141

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

142

On search for nuclear Schiff moment in liquid xenon  

E-print Network

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

Isaev, T A; Petrov, A N; Titov, A V

2006-01-01

143

Xenon NMR studies of dynamics and exchange in zeolites  

SciTech Connect

We have found, despite earlier reports to the contrary, that for many microporous solids with one-dimensional channels (ZSM-12, ALPO-5, VPI-5, SSZ-24) the chemical shift has an anisotropic component. For ALPO-11, a detailed model has been developed which accounts for the loading-dependent chemical shift in terms of intraparticle exchange of statistical distributions of xenon atoms with 0, 1 or 2 nearest neighbors. A similar model can be applied to ZSM-12 up to moderate loadings. At higher loading levels 2D exchange methods show that interparticle exchange occurs as well. The same approach was used to study interparticle exchange in X and Y zeolite mixtures, exchange amongst zeolite clusters of up to 8 xenon atoms in the supercages of AgA zeolite, and main channel - side pocket exchange in mordenite. The parameters derived are directly relevant to the understanding of sorption and diffusion processes in zeolites.

Moudrakovski, I.L.; Ratcliffe, C.I.; Ripmeester, J.A. [Steacie Institute for Molecular Sciences, Ottawa, Ontario (Canada)

1996-10-01

144

Perfluorocarbon emulsions as intravenous delivery media for hyperpolarized xenon.  

PubMed

The use of perfluorooctyl bromide (PFOB) emulsions as delivery media for hyperpolarized xenon has been investigated. Emulsion droplet size was controlled by varying the content of egg yolk phospholipid (EYP), which served as an emulsifier. Hyperpolarized 129Xe nuclear magnetic resonance (NMR) spectra of the dissolved gas were obtained. The NMR spectra were found to be correlated strongly with the emulsion droplet size distribution. The NMR line width is determined by xenon exchange between the PFOB droplets and the aqueous environment. Our findings show that, in a 1.5-Tesla field, relatively narrow 129Xe NMR spectra are obtained for droplet sizes larger than 5 microm. Preliminary results on animal models show that PFOB emulsions have potential as hyperpolarized 129Xe carriers for in vivo magnetic resonance applications. PMID:10204864

Wolber, J; Rowland, I J; Leach, M O; Bifone, A

1999-03-01

145

Carbon dioxide power cycle  

Microsoft Academic Search

An improved direct fired power system generating and employing a combustion gas which includes carbon dioxide or a working fluid including a combustion chamber for burning a mixture which includes oxygen, carbonaceous fuel and recycled carbon dioxide working fluid at a first pressure of above 1100 PSI thereby providing a combustion gas which includes carbon dioxide and water at substantially

Osgerby

1985-01-01

146

Nitrogen dioxide detection  

DOEpatents

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

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

1993-01-01

147

Viscoelastiticy and shear thinning near the critical point of xenon  

NASA Astrophysics Data System (ADS)

The critical point is the exact combination of pressure and temperature at which a fluid is balanced between the states of liquid and gas. Everyday experience gives no hint of the unusual nature of the critical point because familiar fluids such as air and water are far from their critical temperatures. Understanding the critical point is essential for an understanding of fluids in general because the near-critical behavior is universal. Properly scaled, fluids as dissimilar as air and water have near-critical thermodynamic properties (e.g. heat capacity) and transport properties (e.g. viscosity) that are similar. Sufficiently close to the critical point, theory predicts the similarities to be exact. This talk will describe two measurements of the viscosity of xenon that were made very close (<1 mK) to xenon's critical point (289 K, 5.8 MPa). The first experiment measured the viscosity increase caused by near-critical conditions. It revealed that, close to the critical point, xenon is partly elastic: It can stretch as well as flow. The second experiment, planned for July 2002, will look for the shear-rate-induced viscosity decrease predicted by theory. Such "viscoelasticity" and "shear-thinning" are ordinarily seen only in much more complicated fluids such as polymer solutions. Slowly relaxing fluctuations cause both phenomena. The first experiment found that the time scale for viscoelasticity was 2.0 times slower than predicted. Preliminary results for shear thinning from the second experiment will be reported. Both experiments were designed to operate in the microgravity provided by the Space Shuttle. We required microgravity because Earth's gravity compresses any fluid near its critical point. Near its critical point, a layer of xenon as thin as 1 mm collapses under its own weight until the density at the bottom is 8% greater than at the top. The density difference distorts the data. Conducting the experiments on the Space Shuttle reduces the density difference by a factor of 100.

Berg, R.; Yao, M.; Moldover, M.; Zimmerli, G.

148

Atomic Mass and Nuclear Binding Energy for Xe-171 (Xenon)  

NASA Astrophysics Data System (ADS)

This document is part of the Supplement containing the complete sets of data of Subvolume A `Nuclei with Z = 1 - 54' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms'. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Xe-171 (Xenon, atomic number Z = 54, mass number A = 171).

Sukhoruchkin, S. I.; Soroko, Z. N.

149

Radiant flash pyrolysis of biomass using a xenon flashtube  

Microsoft Academic Search

Biomass materials, including lignin, redwood, corn cob, Calotropis Procera, Leucaena wood, Kraft paper, newsprint, cow manure, D-glucose, and D-cellobiose, were pyrolyzed in vacuum by the visible radiant flux emitted from a Xenon flashtube. The flux density exceeded 8 kW\\/cm² during the 1 ms flash. Sirup yields were low (avg 25%), while the gas yield was high (avg 32%). The gaseous

Mark Willard Hopkins; Michael Jerry Antal; Jack G. Kay

1984-01-01

150

Neonatal Pharyngeal Perforation Diagnosed by Xenon 133 Imaging  

PubMed Central

A premature male infant developed bilateral pneumothorax and generalized subcutaneous emphysema following difficult intubation. Xenon 133 imaging revealed accumulation of radionuclide in those areas of subcutaneous emphysema indicating a large air leak from the upper respiratory tract. Pharyngeal injury was confirmed at endoscopy. Imaging with 133Xe may offer a means of rapid diagnosis of airway injury. ImagesFigure 1Figure 2 PMID:3694699

Goolsby-Owens, Janis F.; Holmes, Chonita; Miller, Theodore Q.; Vasinrappee, Panukorn

1987-01-01

151

Vertebrobasilar insufficiency revealed by xenon-133 inhalation SPECT  

Microsoft Academic Search

A study of cerebral and cerebellar blood flow reactivity to acetazolamide by xenon-133-inhalation single photon emission computed tomography (¹³³Xe SPECT) was carried out in a patient with bouts of transient basilar ischemia, whose neurological examination, computed tomographic scan, and auditory evoked potentials were normal. Though the patient was symptom-free at the time of the study, ¹³³Xe SPECT demonstrated vertebrobasilar insufficiency

F. Delecluse; P. Voordecker; C. Raftopoulos

1989-01-01

152

Techniques for reduced spalling and increased operating life of xenon ion engines  

NASA Technical Reports Server (NTRS)

Erosion measurements were performed on a modified J-series 30 cm ion engine operating on xenon propellant. The data indicate that a factor of 15 reduction in erosion of the upstream baffle face can be obtained by introducing nitrogen into the xenon propellant. Minor design changes to reduce spalling coupled with the reduction in baffle erosion may increase the operating life of xenon ion engines.

Garner, Charles E.; Pless, L. C.; Torres, Esteban R.

1989-01-01

153

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

154

Allende meteorite: Isotopically anomalous xenon is accompanied by normal osmium  

PubMed Central

The 184Os/190Os ratio of six Allende meteorite samples was determined by neutron activation analysis. Four chromite concentrates gave a ratio differing from the terrestrial ratio by only -0.1 ± 0.4%, although they contained highly anomalous xenon enriched by up to 67% in 124Xe and 93% in 136Xe. In view of this result and the normal isotopic composition of carbon and oxygen in these fractions, it seems very unlikely that the xenon anomalies were produced in a supernova by the p and r processes. More probably, the xenon anomalies were established in the early solar system, by mass fractionation during trapping of noble gases in solids and by spontaneous fission of a superheavy element. Two other samples, containing osmium from the calcium,aluminum-rich inclusions, also gave an 184Os/190Os ratio within -0.1 ± 0.5% of the terrestrial value, although these inclusions show well-established anomalies in the light elements oxygen and magnesium, which appear to be due to pre-solar dust grains of distinctive nuclear history. Apparently the stellar source of the anomalous oxygen and magnesium did not synthesize heavier elements. PMID:16592365

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

1976-01-01

155

Transport of aromatic molecules in NaY zeolite powders  

SciTech Connect

This paper reports on Xenon-120 NMR that is used to probe macroscopic distributions of aromatic molecules adsorbed in a packed bed of 1-{mu}m NaY zeolite particles. Relative rates of guest transport through the intracrystalline (micro) and intercrystalline (macro) pores play a unique role in the axial distribution of sorbate molecules, such as hexamethylbenzene, in a zeolite powder. Xenon-129 NMR spectra show that a sharp HMB adsorption front advances through a bed of dehydrated NaY crystallites at 523 K. However, at 573 K or in the presence of coadsorbed water, HMB species disperse through the bed without forming a sharp boundary between adsorption zones. When guest transport is controlled by pseudosteady-state diffusion in the macropores, axial penetration of the bed by vapor-phase guest species occurs in a sharp adsorption front. A shrinking-core transport model then quantitatively estimates the intracrystalline diffusivities of HMB in dehydrated and partially hydrated NaY zeolite of 10{sup {minus}11} and 10{sup {minus}13} m{sup 2}/s, respectively, at 523 K. Xenon- 129 NMR proves to be a powerful tool for probing adsorbed guest distribution in zeolites, allowing relative time scales to be established for transport of molecular guests in NaY powders.

Chmelka, B.F.; Gillis, J.V.; Petersen, E.E.; Radke, C.J.

1990-10-01

156

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

PubMed

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

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

2010-08-20

157

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

158

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

159

Diffusion NMR methods applied to xenon gas for materials study.  

PubMed

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. PMID:12807139

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

2002-12-01

160

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

161

Reaction of silicon dioxide with water: a matrix isolation infrared and density functional theoretical study  

Microsoft Academic Search

Reactions of silicon dioxide with water molecules have been studied by matrix isolation infrared and density functional theoretical calculations. Silicon dioxides were prepared by reactions of laser ablated silicon atoms with oxygen in excess argon. When water molecules were added in the reagent gas, silicic acid H2SiO3 molecules were produced spontaneously on annealing. Isotopic substitution experiments showed that the H2SiO3

M. Zhou; L Zhang; H Lu; L Shao; M Chen

2002-01-01

162

Barium Ion Extraction and Identification from Laser Induced Fluorescence in Gas for the Enriched Xenon Observatory  

NASA Astrophysics Data System (ADS)

The scientific community is increasingly interested in neutrinoless double beta decay. A potential measurement of the decay rate would determine the neutrino mass and would be sensitive to some extensions of the Standard Model of particle physics. Unfortunately, the decay rate is very low and competes with natural and cosmogenic radioactivity. This thesis presents a technique that eliminates such background events. It is performed by observing the barium ion daughter from the double beta decay of xenon-136 using laser induced fluorescence. The technique is very complex and requires an excellent understanding of the barium ion spectroscopy and its chemistry in the vicinity of other molecules. Such a technique will become a unique advantage over other neutrinoless double beta decay experiments, especially if the neutrino mass is low. This thesis describes three main topics. The first one describes simulations of ionizing electrons in xenon to determine the size of a gas phase detector for a neutrinoless double beta decay measurement. It has been determined that a meter size detector would contain most electron tracks. Then, it describes the design of two barium ion sources, one relying on electric discharges across two electrodes and the other one using a high energy pulsed laser. From those sources, the spectroscopy of barium ions was studied. The branching ratio of the 62S1/2 -- ---6 2P1/2 transition was found to be 74 +/- 4%. By adding argon in the chamber, the lineshift of the transition due to collisions was found to be -132 MHz/torr while the broadening rate was 23 MHz/torr. Finally, the most interesting topic is the production of doubly charged barium ions using an electrospray source. From it, ions were extracted to vacuum in a mass spectrometer and charge conversion was achieved using triethylamine. The efficiency of the conversion of Ba+ to Ba ++ was almost 100%, with a cross-section between 1.69 x 10 -18 m2 and 2.21 x 10-18 m 2 without forming any molecules.

Rollin, Etienne

163

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

164

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.  

PubMed

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 (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. PMID:24588160

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

2014-02-28

165

THE JOURNAL OF CHEMICAL PHYSICS 135, 104303 (2011) The visible spectrum of zirconium dioxide, ZrO2  

E-print Network

THE JOURNAL OF CHEMICAL PHYSICS 135, 104303 (2011) The visible spectrum of zirconium dioxide, ZrO2; published online 8 September 2011) The electronic spectrum of a cold molecular beam of zirconium dioxide, Zr to difficulties of generation and detection of these ephemeral molecules. The dioxides can have one of three

Maier, John Paul

166

Moving Molecules!  

NSDL National Science Digital Library

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

Twin Cities Public Television, Inc.

2008-01-01

167

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. The validity range and the Ising nature of the crossover description are discussed in terms of a single scale

Boyer, Edmond

168

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...

169

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

Microsoft Academic Search

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

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

170

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

Microsoft Academic Search

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

D R May; M L Klein; G A Peyman

1976-01-01

171

Radio-Frequency-Preionized Xenon Z Pinch Source for Extreme Ultraviolet Lithography  

Microsoft Academic Search

Intense amplified spontaneous emission is generated in generally axial directions in a recombining uniform Z pinch. This effect allows the generation of highly efficient soft x-ray beams, including the intense xenon-band emission at 134 , of interest for extreme ultraviolet lithography. We discuss the characteristics of this source, including optimization of the xenon helium mix and measurements of source size,

Malcolm McGeoch

1998-01-01

172

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

E-print Network

democrite-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-Multiplier Tube (PSPMT) operating in the VUV range (178 nm). Key words: Positron emission tomography (PET

Paris-Sud XI, Université de

173

Electronic spectroscopy of oxygen atoms trapped in solid xenon W. G. Lawrence and V. A. Apkarian  

E-print Network

Electronic spectroscopy of oxygen atoms trapped in solid xenon W. G. Lawrence and V. A. Apkarian28 August 1992) The electronic spectroscopyof oxygen atoms trapped in solid xenon are reported and -covalent many-body surfacesare discussed. I. INTRODUCTION The electronic spectroscopyof atomic impurities

Apkarian, V. Ara

174

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

175

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

176

Observation and applications of single-electron charge signals in the XENON100 experiment  

E-print Network

The XENON100 dark matter experiment uses liquid xenon in a time projection chamber (TPC) to measure xenon nuclear recoils resulting from the scattering of dark matter Weakly Interacting Massive Particles (WIMPs). In this paper, we report the observation of single-electron charge signals which are not related to WIMP interactions. These signals, which show the excellent sensitivity of the detector to small charge signals, are explained as being due to the photoionization of impurities in the liquid xenon and of the metal components inside the TPC. They are used as a unique calibration source to characterize the detector. We explain how we can infer crucial parameters for the XENON100 experiment: the secondary-scintillation gain, the extraction yield from the liquid to the gas phase and the electron drift velocity.

E. Aprile; M. Alfonsi; K. Arisaka; F. Arneodo; C. Balan; L. Baudis; B. Bauermeister; A. Behrens; P. Beltrame; K. Bokeloh; A. Brown; E. Brown; S. Bruenner; G. Bruno; R. Budnik; J. M. R. Cardoso; W. -T. Chen; B. Choi; 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. Ghag; K. -L. Giboni; L. W. Goetzke; C. Grignon; E. Gross; W. Hampel; R. Itay; F. Kaether; G. Kessler; A. Kish; J. Lamblin; H. Landsman; R. F. Lang; M. Le Calloch; C. Levy; K. E. Lim; Q. Lin; S. Lindemann; M. Lindner; J. A. M. Lopes; K. Lung; T. Marrodan Undagoitia; F. V. Massoli; A. J. Melgarejo Fernandez; Y. Meng; M. Messina; A. Molinario; J. Naganoma; K. Ni; U. Oberlack; S. E. A. Orrigo; E. Pantic; R. Persiani; F. Piastra; G. Plante; N. Priel; A. Rizzo; S. Rosendahl; J. M. F. dos Santos; G. Sartorelli; J. Schreiner; M. Schumann; L. Scotto Lavina; M. Selvi; P. Shagin; H. Simgen; A. Teymourian; D. Thers; O. Vitells; H. Wang; M. Weber; C. Weinheimer

2013-11-05

177

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

178

Ultranarrow linewidth, magnetically switched, long pulse, xenon chloride laser  

NASA Technical Reports Server (NTRS)

A spectral linewidth of less than 70 fm and diffraction-limited beam divergence have been obtained from a long-pulse, electric-discharge xenon chloride laser with intracavity Fabry-Perot etalons. A gain duration of 100 ns provided for multipass operation of the etalons, significantly improving both contrast and finesse. The electrical-discharge circuit required to produce this long gain duration was comprised of a pulse-forming network, a saturable-inductor magnetic switch, and a tapered constant-impedance interface transmission line.

Pacala, T. J.; Mcdermid, I. S.; Laudenslager, J. B.

1984-01-01

179

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... width at half maximum. The experimentally measured res- onances are compared to convolved theoretical DR resonance strengths. The agreement with theory is excellent. PACS number(s): 34.80.Kw, 34.80.Dp A (ls 2s 2p )+e~A**(ls 2s 2p nln'1') ~ A *(ls 2s...

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

1993-01-01

180

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

181

Microdischarges of xenon sustained by microwaves: Determination of scaling laws  

SciTech Connect

The threshold conditions to maintain millimeter and submillimeter-size discharges of xenon with microwaves are experimentally determined. The threshold electric field required to sustain the plasma is reported as a function of gas pressure. The influence of the size of the dielectric cell in which the discharge is produced is also shown. The scaling laws are deduced from the threshold electric field measurements, assuming a few additional simplifying assumptions. The results are compared with data obtained with argon discharges sustained by surface waves in capillary tubes and the hypotheses assumed for the calculations are discussed.

Lacoste, A.; Maulat, O.; Latrasse, L.; Arnal, Y.; Pelletier, J. [Laboratoire Elaboration par Procedes Magnetiques (EPM), UPR CNRS 9033 ENSHMG, BP 95, 38402 Saint Martin d'Heres Cedex (France)

2005-04-04

182

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

183

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% at 1 MeV with a detection efficiency close to 20%. These figures of merit, combined with the excellent background suppression capability of the three-dimensional position sensitive LXe detector, yield sensitivity at the 3 sigma level to polarization fractions as small as a few percent for strong sources, even in a balloon flight.

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

1994-01-01

184

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.

185

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

SciTech Connect

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

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

1982-01-01

186

Performance characteristics of ring-cusp thrusters with xenon propellant  

NASA Technical Reports Server (NTRS)

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

Patterson, M. J.

1986-01-01

187

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

188

Scintillation response of liquid xenon to low energy nuclear recoils  

NASA Astrophysics Data System (ADS)

Liquid Xenon (LXe) is expected to be an excellent target and detection medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). We have measured the scintillation efficiency of nuclear recoils with kinetic energy between 10.4 and 56.5 keV relative to that of 122 keV gamma rays from C57o. The scintillation yield of 56.5 keV recoils was also measured as a function of applied electric field, and compared to that of gamma rays and alpha particles. The Xe recoils were produced by elastic scattering of 2.4 MeV neutrons in liquid xenon at a variety of scattering angles. The relative scintillation efficiency is 0.130±0.024 and 0.227±0.016 for the lowest and highest energy recoils, respectively. This is about 15% less than the value predicted by Lindhard, based on nuclear quenching. Our results are in good agreement with more recent theoretical predictions that consider the additional reduction of scintillation yield due to biexcitonic collisions in LXe.

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

2005-10-01

189

NMR study of the distribution of aromatic molecules in NaY zeolite  

SciTech Connect

Local and macroscopic distributions of adsorbed benzene, 1,3,5-trimethylbenzene, and hexamethylbenzene (HMB) molecules among the intracrystalline cavities of NaY zeolite samples have been investigated by {sup 129}Xe and multiple-quantum NMR. Xenon-129 NMR, a sensitive probe of macroscopic distributions of molecules in zeolites at room temperature, demonstrates the importance of sample heat treatment in distributing an adsorbate homogeneously throughout a collection of zeolite particles. NaY samples containing organic guests adsorbed at temperatures near the bulk species melting point produce multiple or broad xenon lines characteristic of macroscopic (i.e., interparticle) adsorbate concentration gradients. After thorough heat treatment of the samples at elevated temperatures, the xenon spectrum collapses to a single sharp line, consistent with a macroscopically uniform distribution. For HMB adsorbed in NaY, counting hydrogen clusters by multiple-quantum NMR reveals intraparticle HMB distributions consistent with one molecular per cavity at low loadings (average bulk loading {le} 1 molecule per cavity) and two molecules per cavity at higher loadings.

Chmelka, B.F.; Pearson, J.G.; Liu, S.B.; Ryoo, R.; de Menorval, L.C.; Pines, A. (Lawrence Berkeley Lab., CA (USA))

1991-01-10

190

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

191

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

192

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

NASA Astrophysics Data System (ADS)

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 follow 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.(H2O)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.; Pulver, Alexander Yu.; Peregudov, Alex; Artyuhov, Igor

2014-07-01

193

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

PubMed

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 follow 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·(H2O)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. PMID:25053322

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

2014-07-21

194

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

195

Ionization and scintillation response of high-pressure xenon gas to alpha particles  

E-print Network

High-pressure xenon gas is an attractive detection medium for a variety of applications in fundamental and applied physics. In this paper we study the ionization and scintillation detection properties of xenon gas at 10 bar pressure. For this purpose, we use a source of alpha particles in the NEXT-DEMO time projection chamber, the large scale prototype of the NEXT-100 neutrinoless double beta decay experiment, in three different drift electric field configurations. We measure the ionization electron drift velocity and longitudinal diffusion, and compare our results to expectations based on available electron scattering cross sections on pure xenon. In addition, two types of measurements addressing the connection between the ionization and scintillation yields are performed. On the one hand we observe, for the first time in xenon gas, large event-by-event correlated fluctuations between the ionization and scintillation signals, similar to that already observed in liquid xenon. On the other hand, we study the field dependence of the average scintillation and ionization yields. Both types of measurements may shed light on the mechanism of electron-ion recombination in xenon gas for highly-ionizing particles. Finally, by comparing the response of alpha particles and electrons in NEXT-DEMO, we find no evidence for quenching of the primary scintillation light produced by alpha particles in the xenon gas.

NEXT Collaboration; V. Álvarez; F. I. G. M. Borges; S. Cárcel; S. Cebrián; A. Cervera; C. A. N. Conde; T. Dafni; J. Díaz; M. Egorov; R. Esteve; P. Evtoukhovitch; L. M. P. Fernandes; P. Ferrario; A. L. Ferreira; E. D. C. Freitas; V. M. Gehman; A. Gil; A. Goldschmidt; H. Gómez; J. J. Gómez-Cadenas; D. González-Díaz; R. M. Gutiérrez; J. Hauptman; J. A. Hernando Morata; D. C. Herrera; 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; T. Miller; A. Moiseenko; F. Monrabal; C. M. B. Monteiro; F. J. Mora; L. M. Moutinho; J. Muñoz Vidal; H. Natal da Luz; G. Navarro; M. Nebot-Guinot; D. Nygren; C. A. B. Oliveira; R. Palma; J. Pérez; J. L. Pérez Aparicio; J. Renner; L. Ripoll; A. Rodríguez; J. Rodríguez; F. P. Santos; J. M. F. dos Santos; L. Segui; L. Serra; D. Shuman; A. Simón; C. Sofka; M. Sorel; J. F. Toledo; A. Tomás; J. Torrent; Z. Tsamalaidze; D. Vázquez; J. F. C. A. Veloso; R. Webb; J. T White; N. Yahlali

2012-11-19

196

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. Our baseline design of GraXe is a balloon made of graphene (possibly held together with a very thin structure made of radiopure fiber) and filled with xenon enriched in the Xe-136 isotope. The balloon is immersed in a large tank containing 20 tons of natural liquid xenon and instrumented with large photomultipliers. Liquid xenon is an excellent scintillator, reasonably transparent to its own light. Graphene is transparent over a large frequency range, an impermeable to the xenon. External backgrounds would be shielded by the buffer liquid xenon, and the inner volume has virtually zero background. Industrial graphene can be manufactured at a competitive cost to produce the inner balloon, and there is already near one ton of enriched Xenon available in the world...

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

2011-01-01

197

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

2011-10-27

198

In-situ laser tagging of barium ions in liquid xenon for the EXO experiment  

NASA Astrophysics Data System (ADS)

The goal of the Enriched Xenon Observatory (EXO) collaboration is to measure the half-life of neutrino-less double beta decay using a ton size liquid 136Xe detector with zero back-ground. Zero background detection can only be achieved if the daughter nucleus, 136Ba, can be tagged. The EXO collaboration is investigating several techniques to tag the 136Ba daughter. The goal of this thesis is to investigate the prospects of directly observing a single 136Ba+ ion in the liquid using a laser aimed at the decay site, hence in-situ laser tagging. Because the energy levels of Ba+ ions are expected to be altered from the vacuum configuration, in-situ laser tagging can only be accomplished if the spectroscopy of the Ba+ ions in liquid xenon is understood. An ultra pure liquid xenon test apparatus with a liquid xenon purity monitor has been built to study the spectroscopy of the Ba+ ions. An unexpected discovery of the nonresonant multiphoton ionization of liquid xenon using pulsed UV lasers was made while characterizing the purity monitor. The discovery was vital to the ability to accurately measure the purity of the liquid xenon. The spectroscopy of Ba+ ions in liquid xenon and the multiphoton ionization studies are the two key topics that are presented in this thesis.

Hall, Kendy

199

Terrestrial and Martian weathering signatures of xenon components in shergottite mineral separates  

NASA Astrophysics Data System (ADS)

Xenon-isotopic ratios, step-heating release patterns, and gas concentrations of mineral separates from Martian shergottites Roberts Massif (RBT) 04262, Dar al Gani (DaG) 489, Shergotty, and Elephant Moraine (EET) 79001 lithology B are reported. Concentrations of Martian atmospheric xenon are similar in mineral separates from all meteorites, but more weathered samples contain more terrestrial atmospheric xenon. The distributions of xenon from the Martian and terrestrial atmospheres among minerals in any one sample are similar, suggesting similarities in the processes by which they were acquired. However, in opaque and maskelynite fractions, Martian atmospheric xenon is released at higher temperatures than terrestrial atmospheric xenon. It is suggested that both Martian and terrestrial atmospheric xenon were initially introduced by weathering (low temperature alteration processes). However, the Martian component was redistributed by shock, accounting for its current residence in more retentive sites. The presence or absence of detectable 129Xe from the Martian atmosphere in mafic minerals may correspond to the extent of crustal contamination of the rock's parent melt. Variable contents of excess 129Xe contrast with previously reported consistent concentrations of excess 40Ar, suggesting distinct sources contributed these gases to the parent magma.

Cartwright, J. A.; Ocker, K. D.; Crowther, S. A.; Burgess, R.; Gilmour, J. D.

2010-08-01

200

Xenon target performance characteristics for laser-produced plasma EUV sources  

NASA Astrophysics Data System (ADS)

Laser-produced plasmas (LPPs) are being developed as light sources for EUV lithography. To meet the requirements for high-volume manufacturing, LPP EUV sources must generate intense EUV output in the 13.5 nm band, and minimize source-induced degradation of EUV optics allowing hundreds of hours of clean operation. Xenon has been identified as a promising target material for LPP EUV light sources, with the potential for both high-efficiency EUV generation, and low optics contamination. Several dense xenon target configurations have been tested including aerosol sprays, continuous liquid streams, condensed xenon droplets, and frozen solid xenon. Important LPP performance characteristics, such as conversion efficiency, EUV radiation distribution, EUV optics degradation by material erosion and/or deposition, and the physical interface to the EUV optical system, are strongly influenced by the xenon target design. The performance of xenon targets with measured conversion efficiencies in the 0.4 percent to 1.4 percent range is reported. Prospects for xenon targets to reach the EUV power generation and contamination goals for production lithography tools are addressed.

Shields, Harry; Fornaca, Steven W.; Petach, Michael B.; Michaelian, Mark; McGregor, R. Daniel; Moyer, Richard H.; St. Pierre, Randall J.

2002-07-01

201

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

202

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

203

Vertebrobasilar insufficiency revealed by xenon-133 inhalation SPECT  

SciTech Connect

A study of cerebral and cerebellar blood flow reactivity to acetazolamide by xenon-133-inhalation single photon emission computed tomography (/sup 133/Xe SPECT) was carried out in a patient with bouts of transient basilar ischemia, whose neurological examination, computed tomographic scan, and auditory evoked potentials were normal. Though the patient was symptom-free at the time of the study, /sup 133/Xe SPECT demonstrated vertebrobasilar insufficiency by showing an impaired vasodilatory response in both the occipital lobes and the right cerebellar hemisphere. Three weeks later, the patient suffered an extensive stroke in these same areas. We therefore suggest that this method could be of great value in the assessment of vertebrobasilar insufficiency.

Delecluse, F.; Voordecker, P.; Raftopoulos, C.

1989-07-01

204

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

205

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

206

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

207

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

208

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

209

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

210

Behavior of Xenon-iron system under core pressure  

NASA Astrophysics Data System (ADS)

We have studied the behavior of Xenon-iron system up to about 155 GPa and 3000 K using high-pressure in-situ X-ray diffraction. “Missing Xenon” is a long-standing problem. Earth’s atmosphere is highly depleted in Xe and more than 90 % of the Xe expected to exist is “missing”. Since the discovery that Xe becomes metallic solid with hcp structure above about 120 GPa [Eremets, et al., 2000], strong possibility has been suggested theoretically that Xe is trapped in the Earth’s core by forming compounds or by making solid solution with iron, because iron is also an hcp metal in the same pressure range. No experiment study, however, were reported in this pressure range and various arguments were made using the data up to about 50 GPa. We have studied this system directly at the pressures of the Earth’s core using laser-heated diamond anvil cell combined with synchrotron radiation. Pure iron foil was placed in the hole of a rhenium gasket and the hole was filled with liquid Xe using cryogenic loading system. In order to prevent the contact of iron with the diamond anvil, small NaCl pellet was placed between them, which worked as a pressure marker as well. After each increment of pressure at room temperature, Fe was heated from both sides of the sample using fiber laser. Temperature was measured by spectroscopic method. Angle-dispersive X-ray diffraction measurements were made at high pressure using the BL-10XU beam line of SPring-8, Nishiharima. Three independent runs were conducted. Two runs were made to clarify the behavior of Xe-Fe system. One additional run was made by directly sandwiching Fe foil in NaCl pellets without Xe, to accurately determine the volume of Fe based on NaCl pressure scale. First run in Xe-Fe system was made up to 79 GPa and 2500 K and we found the diffractions from hcp-Fe, hcp-Xe, and B2-NaCl, as well as small amount of fcc-Xe, in agreement with the previous report up to about 50 GPa. No additional diffractions were observed at all. The result remained unchanged in the second run up to about 155 GPa and 3000 K, although the Xe has completely transformed into hcp phase. The unit cell volumes of hcp-Fe observed up to about 160 GPa in the third run were indistinguishable from those observed in the first two runs under the existence of Xe. All these experimental results clearly suggests that neither any compounds are formed between Xe and iron nor any detectable amount of dissolution of Xe into iron occurs, even after Xe has transformed into metal at about 120 GPa. This result suggests that the high-pressure alloying of iron and xenon in the core, which was proposed based on the theoretical calculation (Lee and Steinle-Neumann, 2006), is unlikely to occur and we have to find some other mechanism to explain the “missing xenon”. [1] M. I. Eremets, et al., Phys. Rev. Lett., 85 2797 (2000). [2] K. K. M. Lee and G. Steinle-Neumann, Geophys. Res. Lett., 111 B02202 (2006)

Yagi, T.; Nishio-Hamane, D.; Sata, N.; Fujita, T.; Okada, T.

2009-12-01

211

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

212

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

213

Modelling the phase equilibria and excess properties of the water + carbon dioxide binary mixture  

Microsoft Academic Search

The high-pressure phase diagram and excess thermodynamic properties of the binary mixture of carbon dioxide and water are examined using the SAFT-VR approach. The carbon dioxide molecule is modelled with two tangentially bonded spherical segments, while the water molecule is modelled as spherical with four associating sites to represent the hydrogen bonding. Dispersion interactions are modelled using square-well potentials. The

Felipe J. Blasy

214

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

215

Acoustic Experiment to Measure the Bulk Viscosity of Near-Critical Xenon in Microgravity.  

National Technical Information Service (NTIS)

We plan a rigorous test of the theory of dynamic scaling by accurately measuring the bulk viscosity of xenon in microgravity 50 times closer to the critical temperature Tc than previous experiments. The bulk viscosity (or 'second viscosity' or 'dilational...

K. A. Gillis, I. Shinder, M. R. Moldover, G. A. Zimmerli

2002-01-01

216

Enhancement of solution NMR and MRI with laser-polarized xenon  

SciTech Connect

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 protons and dissolved xenon-129. Time-resolved magnetic resonance images of both nuclei in solution show that the proton magnetization is selectively perturbed in regions containing spin-polarized xenon-129. This effect could find use in nuclear magnetic resonance spectroscopy of surfaces and proteins and in magnetic resonance imaging. 33 refs., 5 figs.

Navon, G.; Song, Y.Q.; Room, T. [Univ. of California, Berkeley, CA (United States)] [and others

1996-03-29

217

Optimization of Dual-Energy Xenon-CT for Quantitative Assessment of Regional Pulmonary Ventilation  

PubMed Central

Objective Dual-energy X-ray computed tomography (DECT) offers visualization of the airways and quantitation of regional pulmonary ventilation using a single breath of inhaled xenon gas. In this study we seek to optimize scanning protocols for DECT xenon gas ventilation imaging of the airways and lung parenchyma and to characterize the quantitative nature of the developed protocols through a series of test-object and animal studies. Materials and Methods The Institutional Animal Care and Use Committee approved all animal studies reported here. A range of xenon-oxygen gas mixtures (0, 20, 25, 33, 50, 66, 100%; balance oxygen) were scanned in syringes and balloon test-objects to optimize the delivered gas mixture for assessment of regional ventilation while allowing for the development of improved three-material decomposition calibration parameters. Additionally, to alleviate gravitational effects on xenon gas distribution, we replaced a portion of the oxygen in the xenon/oxygen gas mixture with helium and compared gas distributions in a rapid-prototyped human central-airway test-object. Additional syringe tests were performed to determine if the introduction of helium had any effect on xenon quantitation. Xenon gas mixtures were delivered to anesthetized swine in order to assess airway and lung parenchymal opacification while evaluating various DECT scan acquisition settings. Results Attenuation curves for xenon were obtained from the syringe test objects and were used to develop improved three-material decomposition parameters (HU enhancement per percent xenon: Within the chest phantom: 2.25 at 80kVp, 1.7 at 100 kVp, and 0.76 at 140 kVp with tin filtration; In open air: 2.5 at 80kVp, 1.95 at 100 kVp, and 0.81 at 140 kVp with tin filtration). The addition of helium improved the distribution of xenon gas to the gravitationally non-dependent portion of the airway tree test-object, while not affecting quantitation of xenon in the three-material decomposition DECT. 40%Xe/40%He/20%O2 provided good signal-to-noise, greater than the Rose Criterion (SNR > 5), while avoiding gravitational effects of similar concentrations of xenon in a 60%O2 mixture. 80/140-kVp (tin-filtered) provided improved SNR compared with 100/140-kVp in a swine with an equivalent thoracic transverse density to a human subject with body mass index of 33. Airways were brighter in the 80/140 kVp scan (80/140Sn, 31.6%; 100/140Sn, 25.1%) with considerably lower noise (80/140Sn, CV of 0.140; 100/140Sn, CV of 0.216). Conclusion In order to provide a truly quantitative measure of regional lung function with xenon-DECT, the basic protocols and parameter calibrations needed to be better understood and quantified. It is critically important to understand the fundamentals of new techniques in order to allow for proper implementation and interpretation of their results prior to wide spread usage. With the use of an in house derived xenon calibration curve for three-material decomposition rather than the scanner supplied calibration and a xenon/helium/oxygen mixture we demonstrate highly accurate quantitation of xenon gas volumes and avoid gravitational effects on gas distribution. This study provides a foundation for other researchers to use and test these methods with the goal of clinical translation. PMID:23571834

Fuld, Matthew K.; Halaweish, Ahmed; Newell, John D.; Krauss, Bernhard; Hoffman, Eric A.

2013-01-01

218

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

Microsoft Academic Search

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

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

2002-01-01

219

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

NASA Astrophysics Data System (ADS)

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

Adams, M. R.; Aïd, S.; Anthony, P. L.; Baker, M. D.; Bartlett, J.; Bhatti, A. A.; Braun, H. M.; Busza, W.; Carroll, T. J.; Conrad, J. M.; Coutrakon, G.; Davisson, R.; Derado, I.; Dhawan, S. K.; Dougherty, W.; Dreyer, T.; Dziunikowska, K.; Eckardt, V.; Ecker, U.; Erdmann, M.; Eskreys, A.; Fang, G.; Figiel, J.; Gebauer, H. J.; Geesaman, D. F.; Gilman, R.; Green, M. C.; Haas, J.; Halliwell, C.; Hanlon, J.; Hantke, D.; Hughes, V. W.; Jackson, H. E.; Jaffe, D. E.; Jancso, G.; Jansen, D. M.; Kaufman, S.; Kennedy, R. D.; Kirk, T.; Kobrak, H. G. E.; Krzywdzinski, S.; Kunori, S.; Lord, J. J.; Lubatti, H. J.; McLeod, D.; Magill, S.; Malecki, P.; Manz, A.; Melanson, H.; Michael, D. G.; Mohr, W.; Montgomery, H. E.; Morfin, J. G.; Nickerson, R. B.; O'Day, S.; Olkiewicz, K.; Osborne, L.; Papavassiliou, V.; Pawlik, B.; Pipkin, F. M.; Ramberg, E. J.; Röser, A.; Ryan, J. J.; Salgado, C.; Salvarani, A.; Schellman, H.; Schmitt, M.; Schmitz, N.; Schüler, K. P.; Seyerlein, H. J.; Skuja, A.; Snow, G. A.; Söldner-Rembold, S.; Steinberg, P. H.; Stier, H. E.; Stopa, P.; Swanson, R. A.; Talaga, R.; Tentindo-Repond, S.; Trost, H.-J.; Venkataramania, H.; Vidal, M.; Wilhelm, M.; Wilkes, J.; Wilson, Richard; Wittek, W.; Wolbers, S. A.; Zhao, T.; Fermilab E665 Collaboration

1992-08-01

220

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

PubMed

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

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

2014-04-01

221

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

PubMed Central

Prolonged hypothermic storage causes ischemia-reperfusion injury (IRI) in the renal graft, which is considered to contribute to the occurrence of the delayed graft function (DGF) and chronic graft failure. Strategies are required to protect the graft and to prolong renal graft survival. We demonstrated that xenon exposure to human proximal tubular cells (HK-2) led to activation of range of protective proteins. Xenon treatment prior to or after hypothermia–hypoxia challenge stabilized the HK-2 cellular structure, diminished cytoplasmic translocation of high-mobility group box (HMGB) 1 and suppressed NF-?B activation. In the syngeneic Lewis-to-Lewis rat model of kidney transplantation, xenon exposure to donors before graft retrieval or to recipients after engraftment decreased caspase-3 expression, localized HMGB-1 within nuclei and prevented TLR-4/NF-?B activation in tubular cells; serum pro-inflammatory cytokines IL-1?, IL-6 and TNF-? were reduced and renal function was preserved. Xenon treatment of graft donors or of recipients prolonged renal graft survival following IRI in both Lewis-to-Lewis isografts and Fischer-to-Lewis allografts. Xenon induced cell survival or graft functional recovery was abolished by HIF-1? siRNA. Our data suggest that xenon treatment attenuates DGF and enhances graft survival. This approach could be translated into clinical practice leading to a considerable improvement in long-term graft survival. PMID:23710625

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

2013-01-01

222

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

223

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

Microsoft Academic Search

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

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

2006-01-01

224

Clathrate phase equilibria of binary and ternary mixtures containing carbon dioxide, phenol and p-cresol  

SciTech Connect

Clathrate compounds are crystalline molecules formed by a physical reaction between host molecules and low molecular-weight gases. The gas molecules occupy cavities in a network of host molecules composed of unit crystal structures. Experimental apparatus equipped with sapphire windows for visual observation was uniquely designed and built to measure clathrate phase equilibria. Phenolic compounds such as phenol and p-cresol were used as host molecules and carbon dioxide and methane as guest molecules. The dissociation pressures and temperatures were measured for several binary systems in order to investigate clathrate three-phase (vapor-clathrate-organic liquid equilibria). 10 refs., 4 figs., 2 tabs.

Yi-Ho Yoon; Seong-Pil Kang; Huen Lee [KAIST, Taejon (Korea, Republic of)

1996-12-31

225

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

226

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

227

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

228

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

229

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...

230

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

231

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

232

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.

Rohde, Robert A.; (from published NOAA data)

233

Bench Remarks: Carbon Dioxide.  

ERIC Educational Resources Information Center

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

Bent, Henry A.

1987-01-01

234

Carbon Dioxide Laser Guidelines  

PubMed Central

The carbon dioxide (CO2) laser is a versatile tool that has applications in ablative lasing and caters to the needs of routine dermatological practice as well as the aesthetic, cosmetic and rejuvenation segments. This article details the basics of the laser physics as applicable to the CO2 laser and offers guidelines for use in many of the above indications. PMID:20808594

Krupa Shankar, DS; Chakravarthi, M; Shilpakar, Rachana

2009-01-01

235

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.

236

Carbon Dioxide Removal  

NSDL National Science Digital Library

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

History, American M.

2008-01-01

237

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

2008-12-17

238

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

SciTech Connect

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

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

1990-08-01

239

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

240

Modeling the Removal of Xenon from Lithium Hydrate with Aspen HYSYS  

NASA Astrophysics Data System (ADS)

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

Efthimion, Phillip; Gentile, Charles

2011-11-01

241

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

242

Photolytical Generation of Carbon Dioxide  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

243

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.

244

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

245

Reflectance measurement of the VUV spectrum of solid xenon and its temperature dependence up to the triple point  

E-print Network

L-339 Reflectance measurement of the VUV spectrum of solid xenon and its temperature dependence up disparition vers 135 K. Abstract. 2014 Accurate solid xenon reflectance measurements in the energy range 6 films (reflection or transmission), and also in a closed cell with LiF or MgF2 windows (reflection

Boyer, Edmond

246

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

247

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

National Technical Information Service (NTIS)

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

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

1990-01-01

248

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

249

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

250

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

2012-08-09

251

Thermodynamics, compressibility, and phase diagram: Shock compression of supercritical fluid xenon.  

PubMed

Supercritical fluids have intriguing behaviors at extreme pressure and temperature conditions, prompting the need for thermodynamic properties of supercritical fluid xenon (SCF) under shock compression. Double-shock experimental data on SCF xenon in the 140 GPa pressure range were directly measured by means of a multi-channel pyrometer and a Doppler-pins-system. It entered the so-called warm dense region. We found that the shock compressed SCF Xe had higher dynamic compression and higher number density than that of liquid Xe at same shock pressure. The larger compressibility of SCF Xe in our experiments could be explained that the increase of electronic excitations and ionizations leaded to a large drop of thermal pressure and a softening of Hugoniot. The high pressure phase diagram of xenon was depicted with the aid of the degeneracy, coupling parameter, and current available experiments on the pressure-temperature plane. PMID:25273430

Zheng, J; Chen, Q F; Gu, Y J; Chen, Z Y; Li, C J

2014-09-28

252

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

253

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

254

Calibration of a liquid xenon detector with {sup 83}Kr{sup m}  

SciTech Connect

We report the preparation of a {sup 83}Kr{sup m} source and its use in calibrating a liquid xenon detector. {sup 83}Kr{sup m} atoms were produced through the decay of {sup 83}Rb and introduced into liquid xenon. Decaying {sup 83}Kr{sup m} nuclei were detected through liquid xenon scintillation. Conversion electrons with energies of 9.4 and 32.1 keV from the decay of {sup 83}Kr{sup m} were observed. This calibration source will allow the characterization of the response of noble liquid detectors at low energies. {sup 83}Kr{sup m} 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.

Kastens, L. W.; Cahn, S. B.; Manzur, A.; McKinsey, D. N. [Department of Physics, Yale University, Post Office Box 208120, New Haven, CT 06520 (United States)

2009-10-15

255

Double beta decay daughter ion detection in a solid xenon matrix for EXO  

NASA Astrophysics Data System (ADS)

0 ??? experiments are the possibly the most sensitive means available to measure the absolute mass of the neutrino as long as backgrounds can be sufficiently suppressed. The Enriched Xenon Observatory (EXO) experiment may be able to eliminate all backgrounds by detecting the daughter of the 0 ??? ( ^136Xe ->^136Ba +2e^- ) through optical fluorescence. We propose to grab the ion in the detector by freezing it in xenon ice on a cold probe, possibly an optical fiber, and then detecting it in the ice. We present progress in the detection of barium ions generated by an ion beam, and detected in a solid xenon matrix using CW laser excitation and efficient fluorescence detection.

Mong, Brian; Cook, Shon; Fairbank, William

2009-10-01

256

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.

257

Xenon behavior in TiN: A coupled XAS/TEM study  

NASA Astrophysics Data System (ADS)

Titanium nitride is a refractory material that is being considered as an inert matrix in future Generation IV nuclear reactors, in particular in relation to the Gas-cooled Fast Reactor. The main role of this matrix would be to act as a barrier against the release of fission products, in particular gaseous ones like xenon. This release phenomenon will be enhanced by high temperatures expected in the fuel vicinity: 1200 °C under normal conditions, and up to 1800 °C under accidental conditions. It is therefore necessary to investigate the behavior of volatile fission products in TiN under high temperature and irradiation. Indeed, these basic data are very useful to predict the volatile fission products released under these extreme conditions. Our previous work has shown that Xe introduced by ion implantation in sintered TiN tends to be released as a result of annealing, due to a transport mechanism towards the sample surface. The aim of the present work is to determine under which physical state Xe is in TiN. Xenon was first introduced using ion implantation at 800 keV in TiN samples obtained by hot pressing at several concentrations ranging from 0.4 to 8 at.%. Secondly, samples were annealed at high temperature, from 1000 °C to 1500 °C. Xe was then characterized by X-ray Absorption Spectroscopy and Transmission Electron Microscopy. The formation of intragranular xenon bubbles was demonstrated, and the xenon concentration which is sufficient to form bubbles is found to be lower than 0.4 at.% under our experimental conditions. These bubbles were found unpressurised at 15 K. Their size increases with the temperature and the local xenon concentration. For the highest xenon concentrations, a mechanism involving the formation of a Xe interconnected bubble network is proposed to explain Xe massive release observed by Rutherford Backscattering Spectrometry experiments.

Bès, R.; Gaillard, C.; Millard-Pinard, N.; Gavarini, S.; Martin, P.; Cardinal, S.; Esnouf, C.; Malchère, A.; Perrat-Mabilon, A.

2013-03-01

258

Sol-gel method for encapsulating molecules  

DOEpatents

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

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

2002-01-01

259

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

260

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

NASA Technical Reports Server (NTRS)

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

Schneider, W. E.

1974-01-01

261

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 × 108 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

262

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

NASA Astrophysics Data System (ADS)

A low pressure (˜0.5 mTorr in xenon and ˜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.; Takahashi, K.

2013-06-01

263

Initial observations of GeSe-xenon transport experiments performed on the D1 space flight  

NASA Technical Reports Server (NTRS)

GeSe-xenon experiments performed aboard the D1 mission at xenon pressures of 2 and 6 atm confirm the crystal growth pattern, sizes, and surface morphology of crystals previously grown aboard STS-7 for different pressures. Besides the deposition and growth of GeSe crystals on the ampoule wall, several large single-crystalline GeSe platelets with lateral dimensions much greater than those of crystals on the wall and obtained on the ground are found. The present results reemphasize the question concerning the nucleation phenomena in microgravity.

Wiedemeier, H.; Trivedi, S. B.

1986-01-01

264

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

265

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

2014-04-01

266

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

267

IONIZATION OF NITROGEN MOLECULES BY NITROGEN MOLECULES  

Microsoft Academic Search

The ionization cross section for Nâ molecules on impact with N\\/sub ; 2\\/ molecules was measured over the laboratory energy range from 30 to 1000 ev. ; The incident molecular beam was produced by the technique of ionization by ; electron impact, electrostatic acceleration and neutralization by charge transfer. ; The measurements were carried out in a low-pressure parallel plate

Nyle Utterback; Glenn Miller

1961-01-01

268

Modeling Carbon Dioxide Levels  

NSDL National Science Digital Library

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

2009-01-01

269

Sulfur dioxide removal process  

Microsoft Academic Search

A process is described for reducing the loss of sodium values in a system for removing sulfur dioxide from a gas by the use of an absorption-desorption cycle employing aqueous sodium sulfite as the essential absorption solution. Sodium sulfate and\\/or sodium thio-sulfate build-up in the system is avoided and the loss of sodium values reduced by subjecting sodium sulfate and\\/or

N. E. Nicholson; J. Scarlett

1978-01-01

270

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

271

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

272

Single-molecule fluorescence inside solid-state nanochannels  

NASA Astrophysics Data System (ADS)

One major limitation of single-molecule fluorescence spectroscopy is the finite residence time of diffusing molecules in the confocal detection volume. The time ranges in the order of milliseconds. This has typical size of femtoliter. Here, we present a concept of extending the residence time using nanochannels of ca. 60 nm x 60 nm cross-section to restrict the molecular motion. We use solid-state nanochannels of silicon and silicon dioxide. This work is aimed to use for dual-focus fluorescence detection combining Anti-Brownian ELectrophoretic or ABEL trap to actively trap single molecule.

Ghosh, Siddharth; Kumbhakar, Manoj; Platen, Mitja; Gregor, Ingo; Enderlein, Jörg

2014-03-01

273

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

274

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

275

Introduction Air Quality and Nitrogen Dioxide  

E-print Network

Introduction Air Quality and Nitrogen Dioxide Air pollution can be defined as "the presence worldwide" WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulphur dioxide and motor vehicles. Nitrogen Dioxide is produced in a number of combustion processes. Nitrogen dioxide can

276

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

277

Electrochemical cell for obtaining oxygen from carbon dioxide atmospheres  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

278

Background estimation of the XENON1T Dark Matter Search Experiment  

NASA Astrophysics Data System (ADS)

We will present the background estimation of the XENON1T detector, the next generation of the XENON phased Dark Matter search program. Detailed studies of both the electronic recoil and nuclear recoil background have been performed, including irreducible contamination from pp chain solar neutrinos and 2???-decay of ^136Xe.By exploiting the excellent self-shielding and 3D position resolution of a LXeTPC, by selecting existing low radioactivity detector materials and by placing the detector in a large active water shield and Cherenkov muon veto, the overall event rate within the fiducial target of 1.1 ton is estimated to be less than 0.5 1˜0-4 events/kg/day/keVee. This rate translates to less than one event per ton per year in the WIMP search region -- an unprecedented low background level for a dark matter experiment. For a ?SI˜10-45 cm^2 and 100 GeV/c^2 WIMP mass, XENON1T would detect of order 100 events in this exposure, providing statistics for placing significant constraints on the WIMP mass. In the absence of signal XENON1T would be capable of probing WIMP interaction cross-sections to ?SI˜2x10-47cm^2 within 2 years of operation.

Beltrame, Paolo

2012-03-01

279

Chemically fractionated fission-xenon in meteorites and on the earth  

Microsoft Academic Search

This is a report on the nature of isotopically anomalous xenon, which has been detected in two Ca-Al-rich inclusions of the Allende carbonaceous chondrite. It is extremely enriched in 132 Xe, 129 Xe, and to a lesser extent in 131 Xe. Similar large excesses of 132 Xe as well as of 131 Xe, 134 Xe, and 129 Xe have previously

Yuri A. Shukolyukov; Elmar K. Jessberger; Alexander P. Meshik; Dang Vu Minh; Jimmy L. Jordan

1994-01-01

280

Turbidity measurements in xenon reanalyzed using the master crossover functions Y. Garrabos and C. Lecoutre  

E-print Network

Turbidity measurements in xenon reanalyzed using the master crossover functions Y. Garrabos and C Bordeaux I, 87 Avenue du Dr. A. Schweitzer, F-33608 Pessac Cedex, France (Dated: 16 Fev 2009) The turbidity show that the turbidity data are well represented by the Ornstein-Zernike theory, within 1% precision

Boyer, Edmond

281

Electron-impact ionization of 4d-shell xenon and tin ions  

NASA Astrophysics Data System (ADS)

Electron-impact single ionization of xenon and tin ions for charge states where the 4d-subshell is the outermost has been investigated. Measured cross sections have been analyzed in detail by comparing with configuration-averaged distorted wave (CAWD) calculations. Contributions of different direct- and indirect ionization processes have thus been quantitatively revealed.

Borovik, A., Jr.; Gharaibeh, M. F.; Rausch, J.; Rudolph, J.; Hillenbrand, P. M.; Schippers, S.; Müller, A.

2014-04-01

282

Martian atmospheric xenon contents of Nakhla mineral separates: implications for the origin of elemental mass fractionation  

Microsoft Academic Search

Analyses of mineral separates from Nakhla reveal that Martian atmosphere-derived xenon is present in olivine and pyroxene in concentrations close to that of the bulk meteorite, and at elevated concentrations in mesostasis. We argue that neither aqueous alteration nor adsorption followed by shock incorporation are plausible mechanisms for incorporating this gas component into the meteorite, and suggest trapping occurred on

J. D Gilmour; J. A Whitby; G Turner

1999-01-01

283

XENON100 exclusion limit without considering Leff as a nuisance parameter  

NASA Astrophysics Data System (ADS)

In 2011, the XENON100 experiment has set unprecedented constraints on dark matter-nucleon interactions, excluding dark matter candidates with masses down to 6 GeV if the corresponding cross section is larger than 10-39cm2. The dependence of the exclusion limit in terms of the scintillation efficiency (Leff) has been debated at length. To overcome possible criticisms XENON100 performed an analysis in which Leff was considered as a nuisance parameter and its uncertainties were profiled out by using a Gaussian likelihood in which the mean value corresponds to the best fit Leff value (smoothly extrapolated to 0 below 3 keVnr). Although such a method seems fairly robust, it does not account for more extreme types of extrapolation nor does it enable us to anticipate how much the exclusion limit would vary if new data were to support a flat behavior for Leff below 3 keVnr, for example. Yet, such a question is crucial for light dark matter models which are close to the published XENON100 limit. To answer this issue, we use a maximum likelihood ratio analysis, as done by the XENON100 Collaboration, but do not consider Leff as a nuisance parameter. Instead, Leff is obtained directly from the fits to the data. This enables us to define frequentist confidence intervals by marginalizing over Leff.

Davis, Jonathan H.; Bœhm, Céline; Oppermann, Niels; Ensslin, Torsten; Lacroix, Thomas

2012-07-01

284

A Liquid Xenon Ionization Chamber in an All-fluoropolymer Vessel  

SciTech Connect

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

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

2007-02-26

285

Interferometric determination of xenon and krypton refractive indices in the ultraviolet region  

Microsoft Academic Search

We have measured by Fabry-Pérot interferometry the index of refraction of krypton and xenon between 1800 Å and 2550 Å. Our results are compared with other measurements in the spectral region and with theoretical values based on dispersion formulae.

R. Abjean; A. Méhu; A. Johannin-Gilles

1971-01-01

286

Characterisation of NEXT-DEMO using xenon K? X-rays  

NASA Astrophysics Data System (ADS)

The NEXT experiment aims to observe the neutrinoless double beta decay of 136Xe in a high-pressure xenon gas TPC using electroluminescence (EL) to amplify the signal from ionization. Understanding the response of the detector is imperative in achieving a consistent and well understood energy measurement. The abundance of xenon K-shell X-ray emission during data taking has been identified as a multitool for the characterisation of the fundamental parameters of the gas as well as the equalisation of the response of the detector. The NEXT-DEMO prototype is a ~ 1.5 kg volume TPC filled with natural xenon. It employs an array of 19 PMTs as an energy plane and of 256 SiPMs as a tracking plane with the TPC light tube and SiPM surfaces being coated with tetraphenyl butadiene (TPB) which acts as a wavelength shifter for the VUV scintillation light produced by xenon. This paper presents the measurement of the properties of the drift of electrons in the TPC, the effects of the EL production region, and the extraction of position dependent correction constants using K? X-ray deposits. These constants were used to equalise the response of the detector to deposits left by gammas from 22Na.

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

2014-10-01

287

New concepts for a gaseous Xenon detector for double beta decay  

NASA Astrophysics Data System (ADS)

Xenon gas is an attractive medium for the search for neutrinoless double beta decay because it offers the possibility of reasonable energy resolution, event topology reconstruction, very high intrinsic purity and background rejection through the identification of the daughter barium ion. This talk explores recent developments in the conceptual design of such a detector.

Sinclair, D.; Exo Collaboration

2010-01-01

288

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

Microsoft Academic Search

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

Theobald Fuchs; Marc Kachelriess; Willi A. Kalender

2000-01-01

289

Pulse-shape discrimination and energy resolution of a liquid-argon scintillator with xenon doping  

NASA Astrophysics Data System (ADS)

Liquid-argon scintillation detectors are used in fundamental physics experiments and are being considered for security applications. Previous studies have suggested that the addition of small amounts of xenon dopant improves performance in light or signal yield, energy resolution, and particle discrimination. In this study, we investigate the detector response for xenon dopant concentrations from 9 ± 5 ppm to 1100 ± 500 ppm xenon (by weight) in 6 steps. The 3.14-liter detector uses tetraphenyl butadiene (TPB) wavelength shifter with dual photomultiplier tubes and is operated in single-phase mode. Gamma-ray-interaction signal yield of 4.0 ± 0.1 photoelectrons/keV improved to 5.0 ± 0.1 photoelectrons/keV with dopant. Energy resolution at 662 keV improved from (4.4 ± 0.2)% (?) to (3.5 ± 0.2)% (?) with dopant. Pulse-shape discrimination performance degraded greatly at the first addition of dopant, slightly improved with additional additions, then rapidly improved near the end of our dopant range, with performance becoming slightly better than pure argon at the highest tested dopant concentration. Some evidence of reduced neutron scintillation efficiency with increasing dopant concentration was observed. Finally, the waveform shape outside the TPB region is discussed, suggesting that the contribution to the waveform from xenon-produced light is primarily in the last portion of the slow component.

Wahl, C. G.; Bernard, E. P.; Lippincott, W. H.; Nikkel, J. A.; Shin, Y.; McKinsey, D. N.

2014-06-01

290

Reduced xenon diffusion for quantitative lung studythe role of SF6  

E-print Network

Reduced xenon diffusion for quantitative lung studyÐthe role of SF6 Ross W. Mair,1 * Dominik Hoffmann,1 Sameer A. Sheth,1 Glenn P. Wong,1 James P. Butler,2 Samuel Patz,3 George P. Topulos4 and Ronald

Walsworth, Ronald L.

291

Digital imaging with a pressured xenon filled MWPC working at a high data rate  

Microsoft Academic Search

A MWPC based detection system for medical imaging is presented. The system consists of a pressurized Xenon filled MWPC and of a monochromatic, fluorescent, X-ray source using a conventional diagnostic tube with various target\\/filter combinations. The main performance of the system are: 10% efficiency, 30% energy resolution, 500 mum spatial resolution, +\\/-5 uniformity. The preliminary results of the application of

R. Bellazzini; A. Brez; A. del Guerra; M. M. Massai; M. R. Torquati; M. Franchi; G. Perri

1984-01-01

292

Combined Liquid Xenon and crystal CsI calorimeter of the CMD-3 detector  

NASA Astrophysics Data System (ADS)

The barrel electromagnetic calorimeter of the CMD-3 detector consists of two subsystems: the Liquid Xenon calorimeter and the calorimeter based on CsI scintillation crystals. Its structure and main characteristics are presented. The energy calibration procedures of the combined calorimeter are described.

Shebalin, V. E.; Anisenkov, A. V.; Bashtovoy, N. S.; Epifanov, D. A.; Erofeev, A. L.; Grebenuk, A. A.; Karpov, S. V.; Khazin, B. I.; Kovalenko, O. A.; Kozyrev, A. N.; Kuzmin, A. S.; Mikhailov, K. Yu; Razuvaev, G. P.; Ruban, A. A.; Shwartz, B. A.; Titov, V. M.; Talyshev, A. A.; Yudin, Yu V.

2014-10-01

293

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

E-print Network

a prompt gamma activation analysis facility with a peak neutron flux of *1.5 9 107 cm-2 s-1 and a beam at thermal and sub-thermal neutron energies, prompt gamma activation analysis is a suitable techniqueXenon diffusion studies with prompt gamma activation analysis Carlos A. Rios Perez · Justin D

Deinert, Mark

294

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

NASA Astrophysics Data System (ADS)

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

Dahl, Carl Eric

2009-06-01

295

Collateral Ventilation to Congenital Hyperlucent Lung Lesions Assessed on Xenon-Enhanced Dynamic Dual-Energy CT: an Initial Experience  

PubMed Central

Objective We wanted to evaluate the resistance to collateral ventilation in congenital hyperlucent lung lesions and to correlate that with the anatomic findings on xenon-enhanced dynamic dual-energy CT. Materials and Methods Xenon-enhanced dynamic dual-energy CT was successfully and safely performed in eight children (median age: 5.5 years, 4 boys and 4 girls) with congenital hyperlucent lung lesions. Functional assessment of the lung lesions on the xenon map was done, including performing a time-xenon value curve analysis and assessing the amplitude of xenon enhancement (A) value, the rate of xenon enhancement (K) value and the time of arrival value. Based on the A value, the lung lesions were categorized into high or low (A value > 10 Hounsfield unit [HU]) resistance to collateral ventilation. In addition, the morphologic CT findings of the lung lesions, including cyst, mucocele and an accessory or incomplete fissure, were assessed on the weighted-average CT images. The xenon-enhanced CT radiation dose was estimated. Results Five of the eight lung lesions were categorized into the high resistance group and three lesions were categorized into the low resistance group. The A and K values in the normal lung were higher than those in the low resistance group. The time of arrival values were delayed in the low resistance group. Cysts were identified in five lesions, mucocele in four, accessory fissure in three and incomplete fissure in two. Either cyst or an accessory fissure was seen in four of the five lesions showing high resistance to collateral ventilation. The xenon-enhanced CT radiation dose was 2.3 ± 0.6 mSv. Conclusion Xenon-enhanced dynamic dual-energy CT can help visualize and quantitate various degrees of collateral ventilation to congenital hyperlucent lung lesions in addition to assessing the anatomic details of the lung. PMID:21228937

Yang, Dong Hyun; Kim, Namkug; Park, Seung Il; Kim, Dong Kwan; Kim, Ellen Ai-Rhan

2011-01-01

296

21 CFR 73.575 - Titanium dioxide.  

...2) Color additive mixtures for food use made with titanium dioxide...in color additive mixtures for coloring foods, and the following: Silicon dioxide...dioxide may be safely used for coloring foods generally, subject to the...

2014-04-01

297

21 CFR 73.575 - Titanium dioxide.  

Code of Federal Regulations, 2012 CFR

...2) Color additive mixtures for food use made with titanium dioxide...in color additive mixtures for coloring foods, and the following: Silicon dioxide...dioxide may be safely used for coloring foods generally, subject to the...

2012-04-01

298

21 CFR 73.575 - Titanium dioxide.  

Code of Federal Regulations, 2013 CFR

...2) Color additive mixtures for food use made with titanium dioxide...in color additive mixtures for coloring foods, and the following: Silicon dioxide...dioxide may be safely used for coloring foods generally, subject to the...

2013-04-01

299

21 CFR 73.3126 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 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....

2010-04-01

300

21 CFR 73.1575 - Titanium dioxide.  

Code of Federal Regulations, 2012 CFR

... 2012-04-01 false Titanium dioxide. 73.1575 Section 73.1575...CERTIFICATION Drugs § 73.1575 Titanium dioxide. (a) Identity and specifications. (1) The color additive titanium dioxide shall conform in identity and...

2012-04-01

301

21 CFR 172.480 - Silicon dioxide.  

...2014-04-01 2014-04-01 false Silicon dioxide. 172.480 Section 172.480 Food and... Anticaking Agents § 172.480 Silicon dioxide. The food additive silicon dioxide may be safely used in food in accordance...

2014-04-01

302

21 CFR 172.480 - Silicon dioxide.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Silicon dioxide. 172.480 Section 172.480 Food and... Anticaking Agents § 172.480 Silicon dioxide. The food additive silicon dioxide may be safely used in food in accordance...

2011-04-01

303

21 CFR 73.2575 - Titanium dioxide.  

... 2014-04-01 false Titanium dioxide. 73.2575 Section 73.2575... Cosmetics § 73.2575 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide shall conform in identity and...

2014-04-01

304

21 CFR 73.1575 - Titanium dioxide.  

... 2014-04-01 false Titanium dioxide. 73.1575 Section 73.1575...CERTIFICATION Drugs § 73.1575 Titanium dioxide. (a) Identity and specifications. (1) The color additive titanium dioxide shall conform in identity and...

2014-04-01

305

40 CFR 180.1195 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

306

Carbon Dioxide Reduction Through Urban Forestry  

E-print Network

Carbon Dioxide Reduction Through Urban Forestry: Guidelines for Professional and Volunteer Tree; Simpson, James R. 1999. Carbon dioxide reduction through urban forestry of Agriculture; 237 p. Carbon dioxide reduction through urban forestry--Guidelines for professional and volunteer

Standiford, Richard B.

307

21 CFR 73.1575 - Titanium dioxide.  

Code of Federal Regulations, 2011 CFR

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

2011-04-01

308

21 CFR 73.2575 - Titanium dioxide.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 false Titanium dioxide. 73.2575 Section 73.2575... Cosmetics § 73.2575 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide shall conform in identity and...

2013-04-01

309

21 CFR 172.480 - Silicon dioxide.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Silicon dioxide. 172.480 Section 172.480 Food and... Anticaking Agents § 172.480 Silicon dioxide. The food additive silicon dioxide may be safely used in food in accordance...

2012-04-01

310

40 CFR 180.1195 - Titanium dioxide.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Titanium dioxide. 180.1195 Section 180.1195 Protection...Exemptions From Tolerances § 180.1195 Titanium dioxide. Titanium dioxide is exempted from the requirement of a...

2011-07-01

311

21 CFR 73.2575 - Titanium dioxide.  

Code of Federal Regulations, 2011 CFR

... 2011-04-01 false Titanium dioxide. 73.2575 Section 73.2575... Cosmetics § 73.2575 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide shall conform in identity and...

2011-04-01

312

21 CFR 73.2575 - Titanium dioxide.  

Code of Federal Regulations, 2012 CFR

... 2012-04-01 false Titanium dioxide. 73.2575 Section 73.2575... Cosmetics § 73.2575 Titanium dioxide. (a) Identity and specifications. The color additive titanium dioxide shall conform in identity and...

2012-04-01

313

21 CFR 73.1575 - Titanium dioxide.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 false Titanium dioxide. 73.1575 Section 73.1575...CERTIFICATION Drugs § 73.1575 Titanium dioxide. (a) Identity and specifications. (1) The color additive titanium dioxide shall conform in identity and...

2013-04-01

314

Carbon dioxide and climate  

NASA Astrophysics Data System (ADS)

The earth's climate is getting warmer because of a buildup of carbon dioxide in the atmosphere that will continue well into the next century, according to a report released October 20 by the National Research Council (NRC), the research arm of the National Academy of Sciences. As the result of a 2-year study commissioned by Congress, the NRC's Carbon Dioxide Assessment Committee predicts a global temperature rise of as much as 4.5°C by the year 2100, enough to shift weather patterns, raise sea levels, and eliminate agriculture in some parts of the world. What's more, the trend seems inevitable— even drastic changes in our energy use would not prevent the warmup, according to the committee's findings.CO2, the major contributor to a thermal “greenhouse effect” that traps re-radiated heat in the atmosphere, has risen from a concentration of 315 parts per million (ppm) to 340 ppm in one generation, largely as a result of the use of fossil fuels. Sometime in the third quarter of the next century, the report predicts, the concentration will probably be double the current level. The result will be a global warming of surface air of between 1.5° and 4.5°C, with temperature rises relatively greater at the poles.

315

Carbon Dioxide Capture and Disposal  

Microsoft Academic Search

Unless carbon dioxide from fossil fuel combustion is captured and disposed of safely and permanently, the concerns over climate change will eventually lead to the demise of fossil fuels. Because of their importance in today's energy market the phasing out of fossil fuels would likely precipitate a major energy crisis. Mineral sequestration and extraction of carbon dioxide from the air

K. S. Lackner

2002-01-01

316

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

317

Coral reefs and carbon dioxide  

SciTech Connect

This commentary argues the conclusion from a previous article, which investigates diurnal changes in carbon dioxide partial pressure and community metabolism on coral reefs, that coral `reefs might serve as a sink, not a source, for atmospheric carbon dioxide.` Commentaries from two groups are given along with the response by the original authors, Kayanne et al. 27 refs.

Buddemeier, R.W. [Kansas Geological Survey, Lawrence, KS (United States)

1996-03-01

318

Carbon Dioxide Capture and Disposal  

NASA Astrophysics Data System (ADS)

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

Lackner, K. S.

2002-05-01

319

Using metal nanostructures to form hydrocarbons from carbon dioxide, water and sunlight  

NASA Astrophysics Data System (ADS)

Based on experimental results, we propose a mechanism that allows the use of metal nanostructures to synthesize hydrocarbons and carbohydrates from carbon dioxide, water and sunlight. When sunlight impinges on cobalt nanostructures in a glass chamber, its intensity is greatly enhanced around the tips of the nanostructures through surface plasmon excitations focusing effect, and it then photodissociates the water and carbon dioxide molecules through enhanced photon absorptions of ions around the tips of the nanostructures. The photodissociated molecules in excited states remain on the cobalt nanostructure surfaces and various hydrocarbons and carbohydrates then will be formed around the surfaces at temperatures much lower than 100 oC.

Wang, Cong; Shen, Mengyan; Huo, Haibin; Ren, Haizhou; Johnson, Michael

2011-12-01

320

New Measurement of the Charge and Light Yield of Low Energy Nuclear and Electronic Recoils in Liquid Xenon  

NASA Astrophysics Data System (ADS)

Liquid xenon detectors are one of the leading technologies in direct dark matter searches. In order to improve the precision of their energy scales, it is important to characterize the scintillation and ionization of liquid xenon at low energies, where measurements with applied electric field are few or nonexistent. At Columbia University we have built a dual-phase detector, neriX, capable of simultaneously measuring the light and charge deposits from low-energy interactions in liquid xenon. The detector was designed to optimize event vertex reconstruction while maintaining a high light detection efficiency. Far detector coincidence techniques (Compton or neutron elastic scattering) are employed to extract the light and charge yields of liquid xenon as a function of energy for different particle types. In this talk we will discuss the detector calibration and performance, and will present some preliminary results.

Goetzke, L. W.; Aprile, E.; Budnik, R.; Contreras, H. A.; Melgarejo Fernandez, A. J.; Naganoma, J.; Plante, G.; Rizzo, A.

2013-04-01

321

Pulsed-discharge carbon dioxide lasers  

NASA Technical Reports Server (NTRS)

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

Willetts, David V.

1990-01-01

322

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

NASA Astrophysics Data System (ADS)

Although convection models do not preclude preservation of smaller mantle regions with more pristine composition throughout Earth's history, it has been widely assumed that the moon forming giant impact likely homogenizes the whole mantle following a magma ocean that extended all the way to the bottom of the mantle. Recent findings of tungsten and xenon heterogeneities in the mantle [1,2,3,4], however, imply that i) the moon forming giant impact may not have homogenized the whole mantle and ii) plate tectonics was inefficient in erasing early formed compositional differences, particularly for the xenon isotopes. Therefore, the xenon isotope composition in the present day mantle still preserves a memory of early Earth processes. However, determination of the xenon isotopic composition of the mantle source is still scarce, since the mantle composition is overprinted by post-eruptive atmospheric contamination in basalts erupted at ocean islands and mid ocean ridges. The xenon composition of the depleted upper mantle has been defined by the gas rich sample, 2?D43 (also known as "popping rock"), from the North Atlantic (13° 469`N). However, the composition of a single sample is not likely to define the composition of the upper mantle, especially since popping rock has an "enriched" trace element composition. We will present Ne, Ar and Xe isotope data on MORB glass samples with "normal" helium isotope composition (8±1 Ra) from the Southeast Indian Ridge, the South Atlantic Ridge, the Sojourn Ridge, the Juan de Fuca, the East Pacific Rise, and the Gakkel Ridge. Following the approach of [1], we correct for syn- and post-eruptive atmosphere contamination, and determine the variation of Ar and Xe isotope composition of the "normal" MORB source. We investigate the effect of atmospheric recycling in the variation of MORB mantle 40Ar/36Ar and 129Xe/130Xe ratios, and attempt to constrain the average upper mantle argon and xenon isotopic compositions. [1] Mukhopadhyay, Nature 2012; [2] Tucker et al., EPSL (in review); [3] Moreira et al., Nature 1998 [4] Touboul et al., Science 2012.

Peto, M. K.; Mukhopadhyay, S.

2012-12-01

323

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

324

Dynamics of pluotinum dioxide  

NASA Astrophysics Data System (ADS)

We report lattice and molecular dynamics studies on the vibrational and thermodynamic properties of PuO2. We have used a transferable interatomic model to understand the properties of the compound. Our computed elastic data, structure and specific heat are in good agreement with reported experimental and first principles results. We observe that plutonium dioxide exhibits fast ion conduction at around 2500 K. The mean square displacements of the oxygen atoms are an order of magnitude greater than that of Pu. The greater amplitude and smaller size of the oxygen ion facilitates its easy diffusion. This behavior is in sync with similar fast ion conduction in other nuclear oxides like UO2 and ThO2.

Goel, Prabhatasree; Mittal, R.; Chaplot, S. L.

2012-06-01

325

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

326

Nanophotonics and Single Molecules  

Microsoft Academic Search

Single emitting molecules are currently providing a new window into nanoscale systems ranging from biology to materials science.\\u000a The amount of information that can be extracted from each single molecule depends upon the specific photophysical properties\\u000a of the fluorophore and how these properties are affected by the nearby environment. For this reason, it is necessary to develop\\u000a single-molecule emitters with

W. E. Moerner; P. James Schuck; David P. Fromm; Anika Kinkhabwala; Samuel J. Lord; Stefanie Y. Nishimura; Katherine A. Willets; Arvind Sundaramurthy; Gordon Kino; Meng He; Zhikuan Lu; Robert J. Twieg

327

Improvement of xenon purification system using a combination of a pulse tube refrigerator and a coaxial heat exchanger  

E-print Network

We have developed a compact cryogenic system with a pulse tube refrigerator and a coaxial heat exchanger. This liquefaction-purification system not only saves the cooling power used to reach high gaseous recirculation rate, but also reduces the impurity level with high speed. The heat exchanger operates with an efficiency of 99%, which indicates the possibility for fast xenon gas recirculation in a highpressurized large-scale xenon storage with much less thermal losses.

Chen, Wan-Ting; Cussonneau, J -P; Donnard, J; Duval, S; Lemaire, O; Calloch, M Le; Ray, P Le; Mohamad-Hadi, A -F; Morteau, E; Oger, T; Scotto-Lavina, L; Stutzmann, J -S; Thers, D; Briend, P; Haruyama, T; Mihara, S; Tauchi, T

2012-01-01

328

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

NASA Astrophysics Data System (ADS)

The South Pole Telescope (SPT) has probed an expanded angular range of the CMB temperature power spectrum. Their recent analysis of the latest cosmological data prefers nonzero neutrino masses, with ?m? = (0.32±0.11) eV. This result, if confirmed by the upcoming Planck data, has deep implications on the discovery of the nature of neutrinos. In particular, the values of the effective neutrino mass m?? involved in neutrinoless double beta decay (??0?) are severely constrained for both the direct and inverse hierarchy, making a discovery much more likely. In this paper, we focus in xenon-based ??0? experiments, on the double grounds of their good performance and the suitability of the technology to large-mass scaling. We show that the current generation, with effective masses in the range of 100 kg and conceivable exposures in the range of 500 kg·year, could already have a sizeable opportunity to observe ??0? events, and their combined discovery potential is quite large. The next generation, with an exposure in the range of 10 ton·year, would have a much more enhanced sensitivity, in particular due to the very low specific background that all the xenon technologies (liquid xenon, high-pressure xenon and xenon dissolved in liquid scintillator) can achieve. In addition, a high-pressure xenon gas TPC also features superb energy resolution. We show that such detector can fully explore the range of allowed effective Majorana masses, thus making a discovery very likely.

Gómez-Cadenas, J. J.; Martín-Albo, J.; Muñoz Vidal, J.; Peña-Garay, C.

2013-03-01

329

CARBON DIOXIDE AND OUR OCEAN LEGACY  

E-print Network

of carbon dioxide from the atmosphere, or nearly half of the fossil fuel carbon emissions over this periodCARBON DIOXIDE AND OUR OCEAN LEGACY G Carbon Dioxide: Our Role The United States is the single. Every day the average American adds about 118 pounds of carbon dioxide to the atmos- phere, due largely

330

Fast electrons from multi-electron dynamics in xenon clusters induced by inner-shell ionization  

NASA Astrophysics Data System (ADS)

Fast electrons emitted from xenon clusters in strong femtosecond 90 eV pulses have been measured at the Free-electron Laser in Hamburg (FLASH). Energy absorption occurs mainly through atomic inner-shell photo-ionization. Photo-electrons are trapped in the strong Coulomb potential of the cluster ions and form a non-equilibrium plasma with supra-atomic density. Its equilibration through multiple energy-exchanging collisions within the entire cluster volume produces electrons with energies well beyond the dominant emission line of atomic xenon. Here, in contrast to traditional low-frequency laser plasma heating, the plasma gains energy from electrons delivered through massive single-photon excitation from bound states. Electron emission induced by thermalization of a non-equilibrium plasma is expected to be a general phenomenon occurring for strong atomic x-ray absorption in extended systems.

Bostedt, Christoph; Thomas, Heiko; Hoener, Matthias; Möller, Thomas; Saalmann, Ulf; Georgescu, Ionu?; Gnodtke, Christian; Rost, Jan-Michael

2010-08-01

331

UTA versus line emission for EUVL: studies on xenon emission at the NIST EBIT  

NASA Astrophysics Data System (ADS)

Spectra from xenon ions have been recorded at the NIST electron beam ion trap (EBIT) and the emission into a 2% bandwidth at 13.5 nm arising from 4d ? 5p transitions compared with those from 4d ? 4f and 4p ? 4d transitions in Xe XI and also with that obtained from the unresolved transition array (UTA) observed to peak just below 11 nm. It was found that an improvement of a factor of 5 could be gained in photon yield using the UTA rather than the 4d ? 5p emission. The results are compared with atomic structure calculations and imply that a significant gain in efficiency should be obtained using tin, in which the emission at 13.5 nm comes from a similar UTA, rather than xenon, as an EUVL source material.

Fahy, K.; Dunne, P.; McKinney, L.; O'Sullivan, G.; Sokell, E.; White, J.; Aguilar, A.; Pomeroy, J. M.; Tan, J. N.; Blagojevic, B.; LeBigot, E.-O.; Gillaspy, J. D.

2004-12-01

332

Time-Dependent Multiphoton Ionization of Xenon in the Soft-X-Ray Regime  

NASA Astrophysics Data System (ADS)

The time-dependent multiphoton ionization of xenon atoms is studied with femtosecond pulses in the excitation range of the 4d giant resonance at the photon energy of 93 eV. Benefiting from a new operation mode of the free electron laser FLASH, the measurements are performed with varying pulse durations. A strong dependence of the ion charge distribution on the pulse duration allows the different multiphoton mechanisms behind the multiple photoionization of xenon to be disentangled up to a charge state of Xe10+. The results up to Xe8+ are well explained by sequences of single photon, multiphoton, and Auger processes, but higher charge state generation suggests the need for collective electron multiphoton excitations.

Gerken, N.; Klumpp, S.; Sorokin, A. A.; Tiedtke, K.; Richter, M.; Bürk, V.; Mertens, K.; Jurani?, P.; Martins, M.

2014-05-01

333

The missing modes of self-organization in cathode boundary layer discharge in xenon  

NASA Astrophysics Data System (ADS)

Self-organized pattern formation has been previously observed in cathode boundary layer discharges (CBLDs) in high-purity xenon gas at pressures ranging from about 60 Torr to atmospheric pressure. However, certain modes predicted by the COMSOL multiphysics simulation were never observed. In this paper, using the same reactor design, we managed to fine tune the discharge current into regions that were not fully explored before. Two new self-organized patterns were observed, at the verge of the extinguishing of the self-organization. One pattern was a perfect ring that was detached from the dielectric walls. The other pattern was a series elongated spots arranged along a circle. Both patterns were preferably observed at pressures ranging from 60 to 120 Torr. The observation of these patterns may open up new discussions to the self-organized pattern formation in CBLD in xenon.

Zhu, WeiDong; Niraula, Prajwal

2014-10-01

334

Interplay between scintillation and ionization in liquid xenon Dark Matter searches  

NASA Astrophysics Data System (ADS)

We provide a new way of constraining the relative scintillation efficiency L for liquid xenon. Using a simple estimate for the electronic and nuclear stopping powers together with an analysis of recombination processes we predict both the ionization and the scintillation yields. Using presently available data for the ionization yield, we can use the correlation between these two quantities to constrain L from below. Moreover, we argue that more reliable data on the ionization yield would allow to verify our assumptions on the atomic cross sections and to predict the value of L. We conclude that the relative scintillation efficiency should not decrease at low nuclear recoil energies, which has important consequences for the robustness of exclusion limits for low WIMP masses in liquid xenon Dark Matter searches.

Bezrukov, Fedor; Kahlhoefer, Felix; Lindner, Manfred

2011-10-01

335

Xenon and other volatile anesthetics change domain structure in model lipid raft membranes.  

PubMed

Inhalation anesthetics have been in clinical use for over 160 years, but the molecular mechanisms of action continue to be investigated. Direct interactions with ion channels received much attention after it was found that anesthetics do not change the structure of homogeneous model membranes. However, it was recently found that halothane, a prototypical anesthetic, changes domain structure of a binary lipid membrane. The noble gas xenon is an excellent anesthetic and provides a pivotal test of the generality of this finding, extended to ternary lipid raft mixtures. We report that xenon and conventional anesthetics change the domain equilibrium in two canonical ternary lipid raft mixtures. These findings demonstrate a membrane-mediated mechanism whereby inhalation anesthetics can affect the lipid environment of transmembrane proteins. PMID:24299622

Weinrich, Michael; Worcester, David L

2013-12-19

336

Influence of the cathode composition on the performance of high pressure short arc xenon lamps  

NASA Astrophysics Data System (ADS)

Thoriated tungsten has been widely used as a cathode material in arc lamps. The addition of thorium reduces the work function of tungsten and allows the cathode to operate at a lower temperature. However, most of the studies on thoriated cathodes were done either for welding arcs or for metal halide lamps, where reactions with the ambient gas could contribute to the cathode erosion. In the case of completely inert, high-purity xenon gas and highly collisional arc plasma, the differences in performance of thoriated and non-thoriated cathodes are mainly material-based. In this talk we will discuss how 2% ThO2 addition to tungsten cathodes changes the lifetime, ignition performance, and stability of xenon lamps.

Minayeva, Olga B.; Doughty, Douglas A.

2006-10-01

337

Wavelength and Intensity Dependence of Short Pulse Laser Xenon Double Ionization between 500 and 2300 nm  

SciTech Connect

The wavelength and intensity dependence of xenon ionization with 50 fs laser pulses has been studied using time-of-flight mass spectrometry. We compare the ion yield distribution of singly and doubly charged xenon with the Perelomov-Popov-Terent'ev (PPT) theory, Perelomov, Popov, and Terent'ev, Zh. Eksp. Teor. Fiz. 50, 1393 (1966) [Sov. Phys. JETP 23, 924 (1966)], in the regime between 500 and 2300 nm. The intensity dependence for each wavelength is measured in a range between 1x10{sup 13} and 1x10{sup 15} W/cm{sup 2}. The Xe{sup +}-ion signal is in good agreement with the PPT theory at all used wavelengths. In addition we demonstrate that ionic 5s5p{sup 6} {sup 2}S state is excited by an electron impact excitation process and contributes to the nonsequential double ionization process.

Gingras, G.; Tripathi, A.; Witzel, B. [Centre d'Optique, Photonique et Laser, Universite Laval, Pavillon d'optique-photonique Quebec (Quebec), G1V 0A6 (Canada)

2009-10-23

338

Molecules in Living Systems  

NSDL National Science Digital Library

This lesson explains the difference between molecules in living systems and inanimate objects. In living systems, atoms and molecules are organized to a much greater degree and provide the structure of the organism. Lipids, carbohydrates, proteins, and nucleic acids are also discussed.

2012-06-19

339

Discovering Interstellar Molecules  

Microsoft Academic Search

This paper describes how high resolution spectroscopy has been the key for discovering interstellar molecules and for studying the interstellar medium. The development of radioastronomy in the 1950's has led to the detection of many interstellar molecules in the 1960s and 1970s, and the construction of a new field of research, astrochemistry. The discovery of molecular ions has confirmed the

M. Gerin

2006-01-01

340

Enzymatic DNA molecules  

NASA Technical Reports Server (NTRS)

The present invention discloses deoxyribonucleic acid enzymes--catalytic or enzymatic DNA molecules--capable of cleaving nucleic acid sequences or molecules, particularly RNA, in a site-specific manner, as well as compositions including same. Methods of making and using the disclosed enzymes and compositions are also disclosed.

Joyce, Gerald F. (Inventor); Breaker, Ronald R. (Inventor)

1998-01-01

341

What is a Molecule?  

NSDL National Science Digital Library

This video/animation shows that a molecule of water is made up of oxygen and hydrogen atoms. When oxygen and hydrogen atoms exist alone, their properties are different from the properties they have when they are chemically combined to form a water molecule

Wpsu

2007-04-09

342

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 dioxide separation and sequestration because the lower cost of carbon dioxide separation from for injection of carbon dioxide into oil or gas-bearing formations. An advantage of sequestration involving

343

Radioactive 133Xenon Gas-Filled Balloon to Prevent Restenosis Dosimetry, Efficacy, and Safety Considerations  

Microsoft Academic Search

Background—Ionizing radiation administered intraluminally via catheter-based systems using solid and sources or liquid-filled balloons has shown reduction in the neointima formation after injury in the porcine model. We propose a novel system that uses a 133-Xenon (133Xe) radioactive gas-filled balloon catheter system. Methods and Results—Overstretch balloon injury was performed in the coronary arteries of 33 domestic pigs. A novel 133

Marc Apple; Ron Waksman; Rosanna C. Chan; Yoram Vodovotz; Jana Fournadjiev; Bill G. Bass

344

Aromatic fluorine derivatives. C. reactions of pentafluorophenol with vanadium, niobium, and antimony fluorides and xenon difluoride  

SciTech Connect

Pentafluorophenol reacts with vanadium fluorides (VF/sub 5/, VOF/sub 3/, VF/sub 4/) and xenon difluoride giving perfluoro-2,5-cyclohexadien-1-one and the products from dimerization of the pentafluorophenoxyl radical, i.e., perfluoro-6-phenoxy-2,4-cyclo-hexadien-1-one, perfluoro-4-phenoxy-2,5-cyclohexadien-1-one, and perfluoro-2-phenoxy-2,5-cyclohexadien-1-one. Antimony and niobium pentafluorides give stable complexes or the corresponding pentafluorophenolates with pentafluorophenol.

Auramenko, A.A.; Bardin, V.V.; Furin, G.G.; Karelin, A.I.; Krasil'nikov, V.A.; Tushin, P.P.; Yakobson, G.G.

1985-09-20

345

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 hydrogénoïde et avec les prédictions d'une approximation semi-clas- sique. Abstract 2014 The diamagnetic-l and inter-n diamagnetic mixing regimes, until they reach the zero-field 2P3/2 ionization threshold, where

Paris-Sud XI, Université de

346

Low-lying quadrupole collective states of the light and medium Xenon isotopes  

E-print Network

Collective low lying levels of light and medium Xenon isotopes are deduced from the Generalized Bohr Hamiltonian (GBH). The microscopic seven functions entering into the GBH are built from a deformed mean field of the Woods-Saxon type. Theoretical spectra are found to be close to the ones of the experimental data taking into account that the calculations are completely microscopic, that is to say, without any fitting of parameters.

B. Mohammed-Azizi; D. E. Medjadi

2012-06-18

347

Response of piezoelectric lead zirconate titanate to high-energy xenon ion beam pulse  

NASA Astrophysics Data System (ADS)

To develop a new radiation detector, the characteristics of piezoelectric lead zirconate titanate (PZT) are currently being studied using a 400 MeV/n xenon (Xe) beam. In this study, the response of the PZT element to the pulsed beam was investigated by changing the beam intensity. It was found that the time distribution of the Xe ions in the pulse duration must be taken into account to understand the formation of the output signal that appeared on the PZT element.

Takechi, Seiji; Miura, Yoshinori; Mitsuhashi, Tomoaki; Miyachi, Takashi; Kobayashi, Masanori; Okudaira, Osamu; Shibata, Hiromi; Fujii, Masayuki; Okada, Nagaya; Murakami, Takeshi; Uchihori, Yukio

2014-11-01

348

Concentrator cell efficiency measurement errors caused by unfiltered xenon flash solar simulators  

NASA Astrophysics Data System (ADS)

In this paper, we examine the effects of increased irradiance into one subcell of triple-absorber concentrator solar cells during efficiency measurements. This situation can easily occur when unfiltered xenon flash solar simulators are used for illumination. We demonstrate how excess irradiance into bottom subcells causes artificially increased fill factors, and that commonly used measurement procedures are unable to account for any excess irradiance. The effect always results in efficiency values that are too high.

Osterwald, Carl R.; Wanlass, Mark W.; Moriarty, Tom; Steiner, Myles A.; Emery, Keith A.

2014-09-01

349

Single polarity charge sensing in high pressure xenon using a coplanar anode configuration  

NASA Astrophysics Data System (ADS)

A new design of a high pressure xenon ionization chamber has been fabricated in an attempt to eliminate the problems associated with acoustical vibrations of the Frisch grid. The function of the traditional Frisch grid has been accomplished by employing a coplanar anode system capable of single polarity charge sensing by means of the Shockley-Ramo theorem. Two different detectors have been built in order to determine if the operation of a high pressure xenon detector in coplanar anode mode is possible. The first is the helical detector comprised of two anode wires wound about a central ceramic core. Through calculation, it is shown that for a cathode bias of -5 kV a potential of 363 V is necessary to collect all of the electrons on the collecting anode, however this is contradicted by the observed pulse waveforms. The results of several experiments are presented that demonstrate the helical detector should work, however in the interest in determining if a coplanar high pressure xenon detector is viable, emphasis was placed on the second detector design. The second design is a parallel plate detector, more analogous to the coplanar semiconductor devices. This detector has demonstrated that it is possible to operate a high pressure xenon detector in coplanar anode mode. However, it is shown that the performance of this detector is limited by high surface leakage current and detector capacitance. Additionally, since the leakage current increases with potential between the two anodes, it is not possible to obtain very high resolution gamma-ray spectroscopy since the required potential between the two anodes for coplanar operation is so high that the detector is already dominated by surface leakage current as this value.

Sullivan, Clair Julia

350

Xenon arc panretinal photocoagulation for central retinal vein occlusion: a randomised prospective study  

Microsoft Academic Search

Thirty-three patients with central vein occlusion were evaluated for the effects of scatter xenon arc panretinal photocoagulation. Thirty-four eyes (2 eyes of 1 patient) were randomly divided into a treatment (15 eyes) and a nontreatment group (19 eyes). The average follow-up per eye has been 29 months. The visual prognosis was not significantly better in either group. There was no

D R May; M L Klein; G A Peyman; M Raichand

1979-01-01

351

Carbon Dioxide and Ocean Acidification  

NSDL National Science Digital Library

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

Lewis, Chris

352

XENON100 implications for naturalness in the MSSM, NMSSM, and ?-supersymmetry model  

NASA Astrophysics Data System (ADS)

In a recent paper [M. Perelstein and B. Shakya, J. High Energy Phys. 10 (2011) 142.], we discuss the correlation between the elastic neutralino-nucleon scattering cross section constrained by dark matter direct-detection experiments and fine-tuning at tree level in the electroweak symmetry breaking sector of the minimal supersymmetric Standard Model (MSSM). Here, we show that the correlation persists in the next-to-minimal supersymmetric Standard Model (NMSSM), and its variant, the ?-supersymmetry (SUSY) model. Both models are strongly motivated by the recent discovery of a 125 GeV Higgs-like particle. We also discuss the implications of the recently published bound on the direct-detection cross section from 225 live days of the XENON100 experiment. In both the MSSM and the NMSSM, most of the parameter space with fine-tuning less than 10% is inconsistent with the XENON100 bound. In the ?-SUSY model, on the other hand, large regions of completely natural electroweak symmetry breaking are still allowed, primarily due to a parametric suppression of fine-tuning with large ?. The upcoming XENON1T experiment will be able to probe most of the parameter space with less than 1% fine-tuning in all three models.

Perelstein, Maxim; Shakya, Bibhushan

2013-10-01

353

The health of SUSY after the Higgs discovery and the XENON100 data  

NASA Astrophysics Data System (ADS)

We analyze the implications for the status and prospects of supersymmetry of the Higgs discovery and the last XENON data. We focus mainly, but not only, on the CMSSM and NUHM models. Using a Bayesian approach we determine the distribution of probability in the parameter space of these scenarios. This shows that, most probably, they are now beyond the LHC reach. This negative chances increase further (at more than 95% c.l.) if one includes dark matter constraints in the analysis, in particular the last XENON100 data. However, the models would be probed completely by XENON1T. The mass of the LSP neutralino gets essentially fixed around 1 TeV. We do not incorporate ad hoc measures of the fine-tuning to penalize unnatural possibilities: such penalization arises automatically from the careful Bayesian analysis itself, and allows to scan the whole parameter space. In this way, we can explain and resolve the apparent discrepancies between the previous results in the literature. Although SUSY has become hard to detect at LHC, this does not necessarily mean that is very fine-tuned. We use Bayesian techniques to show the experimental Higgs mass is at ~ 2 ? off the CMSSM or NUHM expectation. This is substantial but not dramatic. Although the CMSSM or the NUHM are unlikely to show up at the LHC, they are still interesting and plausible models after the Higgs observation; and, if they are true, the chances of discovering them in future dark matter experiments are quite high.

Cabrera, Maria Eugenia; Casas, J. Alberto; de Austri, Roberto Ruiz

2013-07-01

354

The health of SUSY after the Higgs discovery and the XENON100 data  

E-print Network

We analyze the implications for the status and prospects of supersymmetry of the Higgs discovery and the last XENON data. We focus mainly, but not only, on the CMSSM and NUHM models. Using a Bayesian approach we determine the distribution of probability in the parameter space of these scenarios. This shows that, most probably, they are now beyond the LHC reach . This negative chances increase further (at more than 95% c.l.) if one includes dark matter constraints in the analysis, in particular the last XENON100 data. However, the models would be probed completely by XENON1T. The mass of the LSP neutralino gets essentially fixed around 1 TeV. We do not incorporate ad hoc measures of the fine-tuning to penalize unnatural possibilities: such penalization arises automatically from the careful Bayesian analysis itself, and allows to scan the whole parameter space. In this way, we can explain and resolve the apparent discrepancies between the previous results in the literature. Although SUSY has become hard to detect at LHC, this does not necessarily mean that is very fine-tuned. We use Bayesian techniques to show the experimental Higgs mass is at $\\sim 2\\ \\sigma$ off the CMSSM or NUHM expectation. This is substantial but not dramatic. Although the CMSSM or the NUHM are unlikely to show up at the LHC, they are still interesting and plausible models after the Higgs observation; and, if they are true, the chances of discovering them in future dark matter experiments are quite high.

Maria Eugenia Cabrera; J. Alberto Casas; Roberto Ruiz de Austri

2012-12-19

355

Measurements of the equations of state and spectrum of nonideal xenon plasma under shock compression  

SciTech Connect

Experimental equations of state on generation of nonideal xenon plasma by intense shock wave compression was presented in the ranges of pressure of 2-16 GPa and temperature of 31-50 kK, and the xenon plasma with the nonideal coupling parameter {Gamma} range from 0.6-2.1 was generated. The shock wave was produced using the flyer plate impact and accelerated up to {approx}6 km/s with a two-stage light gas gun. Gaseous specimens were shocked from two initial pressures of 0.80 and 4.72 MPa at room temperature. Time-resolved spectral radiation histories were recorded by using a multiwavelength channel pyrometer. The transient spectra with the wavelength range of 460-700 nm were recorded by using a spectrometer to evaluate the shock temperature. Shock velocity was measured and particle velocity was determined by the impedance matching methods. The equations of state of xenon plasma and ionization degree have been discussed in terms of the self-consistent fluid variational theory.

Zheng, J.; Gu, Y. J.; Chen, Z. Y.; Chen, Q. F. [National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, P.O. Box 919-102, Mianyang, Sichuan (China)

2010-08-15

356

Measuring Neutron Response using Data and Monte Carlo Simulation in Xenon100  

NASA Astrophysics Data System (ADS)

A relative scintillation yield (Leff) above 5.5 keVr (nuclear recoil energy) is determined using data from an exposure of XENON100 to neutrons from an Americium-Beryilium (AmBe) source. The technique requires a signal in the XENON100 Time Projection Chamber (TPC) to be in coincidence with a signal in the active liquid xenon (LXe) veto such that efficiency to low energy nuclear recoils is not compromised by the requirement of a signal in 2 or more photomultiplier tubes (PMTs). The Leff is then deduced (independently of any Monte Carlo simulation) through the comparison of the scintillation and ionization signals recorded. The calculated Leff is in excellent agreement with recent direct and indirect measurements. Comparison of the detector response to AmBe neutrons with an equivalent Monte Carlo generated spectrum is also performed. With the measured detector efficiency and a global fit to all measured values of Leff, agreement between data and Monte Carlo down to a low photoelectron level is obtained.

Scovell, Paul

2012-03-01

357

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

SciTech Connect

The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg xenon dual phase time projection chamber to search for dark matter weakly interacting massive particles (WIMPs). The detector measures simultaneously the scintillation and the ionization produced by radiation in pure liquid xenon to discriminate signal from background down to 4.5 keV nuclear-recoil energy. A blind analysis of 58.6 live days of data, acquired between October 6, 2006, and February 14, 2007, and using a fiducial mass of 5.4 kg, excludes previously unexplored parameter space, setting a new 90% C.L. upper limit for the WIMP-nucleon spin-independent cross section of 8.8x10{sup -44} cm{sup 2} for a WIMP mass of 100 GeV/c{sup 2}, and 4.5x10{sup -44} cm{sup 2} for a WIMP mass of 30 GeV/c{sup 2}. This result further constrains predictions of supersymmetric models.

Angle, J.; Manalaysay, A. [Department of Physics, University of Florida, Gainesville, Florida 32611 (United States); Department of Physics, RWTH Aachen University, Aachen, 52074 (Germany); Aprile, E.; Giboni, K. L.; Monzani, M. E.; Plante, G.; Santorelli, R.; Yamashita, M. [Department of Physics, Columbia University, New York, New York 10027 (United States); Arneodo, F. [INFN-Laboratori Nazionali del Gran Sasso, Assergi, 67010 (Italy); Baudis, L.; Orboeck, J.; Schulte, S. [Department of Physics, RWTH Aachen University, Aachen, 52074 (Germany); Bernstein, A.; Madden, N.; Winant, C. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Bolozdynya, A.; Brusov, P.; Shutt, T. [Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106 (United States); Coelho, L. C. C.; Fernandes, L. M. P. [Department of Physics, University of Coimbra, R. Larga, 3004-516, Coimbra (Portugal)] (and others)

2008-01-18

358

Measurements of the equations of state and spectrum of nonideal xenon plasma under shock compression.  

PubMed

Experimental equations of state on generation of nonideal xenon plasma by intense shock wave compression was presented in the ranges of pressure of 2-16 GPa and temperature of 31-50 kK, and the xenon plasma with the nonideal coupling parameter ? range from 0.6-2.1 was generated. The shock wave was produced using the flyer plate impact and accelerated up to ?6?km/s with a two-stage light gas gun. Gaseous specimens were shocked from two initial pressures of 0.80 and 4.72 MPa at room temperature. Time-resolved spectral radiation histories were recorded by using a multiwavelength channel pyrometer. The transient spectra with the wavelength range of 460-700 nm were recorded by using a spectrometer to evaluate the shock temperature. Shock velocity was measured and particle velocity was determined by the impedance matching methods. The equations of state of xenon plasma and ionization degree have been discussed in terms of the self-consistent fluid variational theory. PMID:20866920

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

2010-08-01

359

Studies of selenium and xenon in inductively coupled plasma mass spectrometry  

SciTech Connect

Since its development, inductively coupled plasma mass spectrometry (ICP-MS) has been a widely used analytical technique. ICP-MS offers low detection limits, easy determination of isotope ratios, and simple mass spectra from analyte elements. ICP-MS has been successfully employed for many applications including geological, environmental, biological, metallurgical, food, medical, and industrial. One specific application important to many areas of study involves elemental speciation by using ICP-MS as an element specific detector interfaced to liquid chromatography. Elemental speciation information is important and cannot be obtained by atomic spectrometric methods alone which measure only the total concentration of the element present. Part 1 of this study describes the speciation of selenium in human serum by size exclusion chromatography (SEC) and detection by ICP-MS. Although ICP-MS has been widely sued, room for improvement still exists. Difficulties in ICP-MS include noise in the background, matrix effects, clogging of the sampling orifice with deposited solids, and spectral interference caused by polyatomic ions. Previous work has shown that the addition of xenon into the central channel of the ICP decreases polyatomic ion levels. In Part 2 of this work, a fundamental study involving the measurement of the excitation temperature is carried out to further understand xenon`s role in the reduction of polyatomic ions. 155 refs.

Bricker, T.

1994-07-27

360

Pulse-shape discrimination and energy resolution of a liquid-argon scintillator with xenon doping  

E-print Network

Liquid-argon scintillation detectors are used in fundamental physics experiments and are being considered for security applications. Previous studies have suggested that the addition of small amounts of xenon dopant improves performance in light or signal yield, energy resolution, and particle discrimination. In this study, we investigate the detector response for xenon dopant concentrations from 9 +/- 5 ppm to 1100 +/- 500 ppm xenon (by weight) in 6 steps. The 3.14-liter detector uses tetraphenyl butadiene (TPB) wavelength shifter with dual photomultiplier tubes and is operated in single-phase mode. Gamma-ray-interaction signal yield of 4.0 +/- 0.1 photoelectrons/keV improved to 5.0 +/- 0.1 photoelectrons/keV with dopant. Energy resolution at 662 keV improved from (4.4 +/- 0.2)% ({\\sigma}) to (3.5 +/- 0.2)% ({\\sigma}) with dopant. Pulse-shape discrimination performance degraded greatly at the first addition of dopant, slightly improved with additional additions, then rapidly improved near the end of our dopa...

Wahl, Christopher G; Lippincott, W Hugh; Nikkel, James A; Shin, Yunchang; McKinsey, Daniel N

2014-01-01

361

Characterisation of NEXT-DEMO using xenon K$_?$ X-rays  

E-print Network

The NEXT experiment aims to observe the neutrinoless double beta decay of $^{136}$Xe in a high pressure gas TPC using electroluminescence (EL) to amplify the signal from ionization. Understanding the response of the detector is imperative in achieving a consistent and well understood energy measurement. The abundance of xenon k-shell x-ray emission during data taking has been identified as a multitool for the characterisation of the fundamental parameters of the gas as well as the equalisation of the response of the detector. The NEXT-DEMO prototype is a ~1.5 kg volume TPC filled with natural xenon. It employs an array of 19 PMTs as an energy plane and of 256 SiPMs as a tracking plane with the TPC light tube and SiPM surfaces being coated with tetraphenyl butadiene (TPB) which acts as a wavelength shifter for the VUV scintillation light produced by xenon. This paper presents the measurement of the properties of the drift of electrons in the TPC, the effects of the EL production region, and the extraction of position dependent correction constants using K$_{\\alpha}$ X-ray deposits. These constants were used to equalise the response of the detector to deposits left by gammas from $^{22}$Na.

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

2014-07-15

362

Process Based Belowground Carbon Dioxide Modeling in a Desert Ecosystem  

NASA Astrophysics Data System (ADS)

We describe a study to integrate and assess biological and physical processes that govern belowground carbon dioxide levels at a semi-arid grassland near Canyonlands National Park. Carbon dioxide concentrations were measured every 30 minutes at 5 and 15 cm depth within the rooting zones of the two dominant grass species, Stipa hymenoides and Hilaria jamesii, as well as the interspace between the two. For Stipa hymenoides at 5 cm, a rain event caused belowground carbon dioxide levels to rise from 600 ppm to 2000 ppm with a response time of 8 hours, with a gradual return to quasi-steady state levels in subsequent days. A similar response was observed for H. jamesii. We developed and simulated a one-dimensional diffusion model with a production term for various types of CO2 production from the literature (either constant with increasing depth or a process based source). The process based production considered microbial and root respiration as well as the temperature dependence of soil respiration. Model inputs included volumetric soil water content, temperature and bulk density. Incorporating a process based production term led to high correlation between measured and modeled CO2 concentrations (r2 as high as 0.92). Our results indicate that carbon dioxide levels increased during rain events due to physical (not biological) processes as the soil saturated with water, and CO2 molecules diffused more slowly from the soil.

Zobitz, J. M.; Bowling, D. R.

2003-12-01

363

Amplification of Xenon NMR and MRI by remote detection  

SciTech Connect

A novel technique is proposed in which a nuclear magneticresonance (NMR) spectrum or magnetic resonance image (MRI) is encoded andstored as spin polarization and is then moved to a different physicallocation to be detected. Remote detection allows the separateoptimization of the encoding and detection steps, permitting theindependent choice of experimental conditions, and excitation anddetection methodologies. In the first experimental demonstration of thistechnique, we show that NMR signal can be amplified by taking diluted129Xe from a porous sample placed inside a large encoding coil, andconcentrating it into a smaller detection coil. In general, the study ofNMR active molecules at low concentration that have low physical fillingfactor is facilitated by remote detection. In the second experiment, MRIinformation encoded in a very low field magnet (4-7mT) is transferred toa high field magnet (4.2 T) in order to be detected under optimizedconditions. Furthermore, remote detection allows the utilization ofultra-sensitive optical or superconducting detection techniques, whichbroadens the horizon of NMR experimentation.

Moule, Adam J.; Spence, Megan M.; Han, Song-I.; Seeley, JulietteA.; Pierce, Kimberly L.; Saxena, Sunil; Pines, Alexander

2003-03-31

364

Testing for Life's Molecules  

NSDL National Science Digital Library

In this activity, learners conduct tests for proteins, glucose, and starch. At the beginning of the activity, learners choose three items to test: one known to be ânever alive," one known to be âonce was alive,â and one mystery item. In addition, each station includes a positive control. By the end of the experiment, learners should be familiar with some of the major organic molecules and should recognize that living things, and substances derived from them, are made of organic molecules. Use this activity to bring in topics surrounding nutrition, health, and digestion--since our bodies are made up of organic molecules, we need each of these molecules as nutrients in our food.

Salter, Irene

2012-09-28

365

Of Molecules and Models.  

ERIC Educational Resources Information Center

Presents an activity in which models help students visualize both the DNA process and transcription. After constructing DNA, RNA messenger, and RNA transfer molecules; students model cells, protein synthesis, codons, and RNA movement. (MDH)

Brinner, Bonnie

1992-01-01

366

Silica and titanium dioxide nanoparticles cause pregnancy complications in mice  

NASA Astrophysics Data System (ADS)

The increasing use of nanomaterials has raised concerns about their potential risks to human health. Recent studies have shown that nanoparticles can cross the placenta barrier in pregnant mice and cause neurotoxicity in their offspring, but a more detailed understanding of the effects of nanoparticles on pregnant animals remains elusive. Here, we show that silica and titanium dioxide nanoparticles with diameters of 70 nm and 35 nm, respectively, can cause pregnancy complications when injected intravenously into pregnant mice. The silica and titanium dioxide nanoparticles were found in the placenta, fetal liver and fetal brain. Mice treated with these nanoparticles had smaller uteri and smaller fetuses than untreated controls. Fullerene molecules and larger (300 and 1,000 nm) silica particles did not induce these complications. These detrimental effects are linked to structural and functional abnormalities in the placenta on the maternal side, and are abolished when the surfaces of the silica nanoparticles are modified with carboxyl and amine groups.

Yamashita, Kohei; Yoshioka, Yasuo; Higashisaka, Kazuma; Mimura, Kazuya; Morishita, Yuki; Nozaki, Masatoshi; Yoshida, Tokuyuki; Ogura, Toshinobu; Nabeshi, Hiromi; Nagano, Kazuya; Abe, Yasuhiro; Kamada, Haruhiko; Monobe, Youko; Imazawa, Takayoshi; Aoshima, Hisae; Shishido, Kiyoshi; Kawai, Yuichi; Mayumi, Tadanori; Tsunoda, Shin-Ichi; Itoh, Norio; Yoshikawa, Tomoaki; Yanagihara, Itaru; Saito, Shigeru; Tsutsumi, Yasuo

2011-05-01

367

The missing organic molecules on Mars  

PubMed Central

GC-MS on the Viking 1976 Mars missions did not detect organic molecules on the Martian surface, even those expected from meteorite bombardment. This result suggested that the Martian regolith might hold a potent oxidant that converts all organic molecules to carbon dioxide rapidly relative to the rate at which they arrive. This conclusion is influencing the design of Mars missions. We reexamine this conclusion in light of what is known about the oxidation of organic compounds generally and the nature of organics likely to come to Mars via meteorite. We conclude that nonvolatile salts of benzenecarboxylic acids, and perhaps oxalic and acetic acid, should be metastable intermediates of meteoritic organics under oxidizing conditions. Salts of these organic acids would have been largely invisible to GC-MS. Experiments show that one of these, benzenehexacarboxylic acid (mellitic acid), is generated by oxidation of organic matter known to come to Mars, is rather stable to further oxidation, and would not have been easily detected by the Viking experiments. Approximately 2 kg of meteorite-derived mellitic acid may have been generated per m2 of Martian surface over 3 billion years. How much remains depends on decomposition rates under Martian conditions. As available data do not require that the surface of Mars be very strongly oxidizing, some organic molecules might be found near the surface of Mars, perhaps in amounts sufficient to be a resource. Missions should seek these and recognize that these complicate the search for organics from entirely hypothetical Martian life. PMID:10706606

Benner, Steven A.; Devine, Kevin G.; Matveeva, Lidia N.; Powell, David H.

2000-01-01

368

Magnesite disposal of carbon dioxide  

SciTech Connect

In this paper we report our progress on developing a method for carbon dioxide disposal whose purpose it is to maintain coal energy competitive even is environmental and political pressures will require a drastic reduction in carbon dioxide emissions. In contrast to most other methods, our approach is not aiming at a partial solution of the problem, or at buying time for phasing out fossil energy. Instead, its purpose is to obtain a complete and economic solution of the problem, and thus maintain access to the vast fossil energy reservoir. A successful development of this technology would guarantee energy availability for many centuries even if world economic growth the most optimistic estimates that have been put forward. Our approach differs from all others in that we are developing an industrial process which chemically binds the carbon dioxide in an exothermic reaction into a mineral carbonate that is thermodynamically stable and environmentally benign.

Lackner, K.S.; Butt, D.P.; Wendt, C.H.

1997-08-01

369

Molecular Structure of Carbon Dioxide  

NSDL National Science Digital Library

Carbon dioxide was first described in the 17th century by Jan Baptist van Helmont, a Belgium chemist. The chemical CO2 is released into the atmosphere when carbon-containing fossil fuels like oil, natural gas, and coal are burned in air. It is also produced by various microorganisms in fermentation and is breathed out by animals. Plants absorb carbon dioxide during photosynthesis, using both the carbon and the oxygen to construct carbohydrates. Every year the amount of CO2 in the atmosphere is increasing. CO2 build-up in the atmosphere is caused by deforestation, therefore reducing the number of trees available to absorb CO2. Excess CO2 in the environment causes Global Warming and the Greenhouse Effect. It is also toxic to humans since inhalation of large amounts of CO2 can cause suffocation. Some beverages, such as beer and sparkling wine contain carbon dioxide as a result of fermentation.

2002-08-15

370

Carbon Dioxide - Our Common "Enemy"  

NASA Technical Reports Server (NTRS)

Health effects of brief and prolonged exposure to carbon dioxide continue to be a concern for those of us who manage this pollutant in closed volumes, such as in spacecraft and submarines. In both examples, considerable resources are required to scrub the atmosphere to levels that are considered totally safe for maintenance of crew health and performance. Defining safe levels is not a simple task because of many confounding factors, including: lack of a robust database on human exposures, suspected significant variations in individual susceptibility, variations in the endpoints used to assess potentially adverse effects, the added effects of stress, and the fluid shifts associated with micro-gravity (astronauts only). In 2007 the National Research Council proposed revised Continuous Exposure Guidelines (CEGLs) and Emergency Exposure Guidelines (EEGLs) to the U.S. Navy. Similarly, in 2008 the NASA Toxicology Group, in cooperation with another subcommittee of the National Research Council, revised Spacecraft Maximum Allowable Concentrations (SMACs). In addition, a 1000-day exposure limit was set for long-duration spaceflights to celestial bodies. Herein we examine the rationale for the levels proposed to the U.S. Navy and compare this rationale with the one used by NASA to set its limits. We include a critical review of previous studies on the effects of exposure to carbon dioxide and attempt to dissect out the challenges associated with setting fully-defensible limits. We also describe recent experiences with management of carbon dioxide aboard the International Space Station with 13 persons aboard. This includes the tandem operations of the Russian Vozduk and the U.S. Carbon Dioxide Removal System. A third removal system is present while the station is docked to the Shuttle spacecraft, so our experience includes the lithium hydroxide system aboard Shuttle for the removal of carbon dioxide. We discuss strategies for highly-efficient, regenerable removal of carbon dioxide that could meet the 1000-day SMAC of 0.5%, which would apply to long-duration voyages to Mars.

James, John T.; Macatangay, Ariel

2009-01-01

371

arXiv:1106.1812v1[physics.ins-det]9Jun2011 A Xenon Gas Purity Monitor for EXO  

E-print Network

words: xenon, electronegative ion, purification, tungsten oxide, argon, space charge 1. Introduction of the GPM is discussed along with the interactions of oxygen and other impurities with the GPM's tungsten locations in the EXO-200 xenon gas system, and they have proved useful during the commissioning phase

Gratta, Giorgio

372

Seventh International Carbon Dioxide Conference  

NSDL National Science Digital Library

Organized by NOAA's Climate Monitoring and Diagnostic Laboratory (CMDL), the Seventh International Carbon Dioxide Conference is planned September 25-30 in Broomfield, Colo. At this website, scientists involved in various aspects of the global carbon cycle, especially the current increases of carbon dioxide in the atmosphere, are encouraged to attend. Users can read the preliminary announcement and can learn about the themes of the conference. Researchers can learn about abstract submissions and accommodations. The Brief Conference History link offers a nice synopsis of the accomplishments of past conferences.

373

Carbon Dioxide Absorption Heat Pump  

NASA Technical Reports Server (NTRS)

A carbon dioxide absorption heat pump cycle is disclosed using a high pressure stage and a super-critical cooling stage to provide a non-toxic system. Using carbon dioxide gas as the working fluid in the system, the present invention desorbs the CO2 from an absorbent and cools the gas in the super-critical state to deliver heat thereby. The cooled CO2 gas is then expanded thereby providing cooling and is returned to an absorber for further cycling. Strategic use of heat exchangers can increase the efficiency and performance of the system.

Jones, Jack A. (Inventor)

2002-01-01

374

Erbium diffusion in silicon dioxide  

SciTech Connect

Erbium diffusion in silicon dioxide layers prepared by magnetron sputtering, chemical vapor deposition, and thermal growth has been investigated by secondary ion mass spectrometry, and diffusion coefficients have been extracted from simulations based on Fick's second law of diffusion. Erbium diffusion in magnetron sputtered silicon dioxide from buried erbium distributions has in particular been studied, and in this case a simple Arrhenius law can describe the diffusivity with an activation energy of 5.3{+-}0.1 eV. Within a factor of two, the erbium diffusion coefficients at a given temperature are identical for all investigated matrices.

Lu Yingwei; Julsgaard, B.; Petersen, M. Christian [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Jensen, R. V. Skougaard [Department of Physics and Nanotechnology, Aalborg University, DK-9220 Aalborg O (Denmark); Pedersen, T. Garm; Pedersen, K. [Department of Physics and Nanotechnology, Aalborg University, DK-9220 Aalborg O (Denmark); Interdisciplinary Nanoscience Center-iNANO, DK-8000 Aarhus C (Denmark); Larsen, A. Nylandsted [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Interdisciplinary Nanoscience Center-iNANO, DK-8000 Aarhus C (Denmark)

2010-10-04

375

Enthalpies of dissociation of clathrate hydrates of carbon dioxide, nitrogen, (carbon dioxide + nitrogen), and (carbon dioxide + nitrogen + tetrahydrofuran)  

Microsoft Academic Search

A calorimetric technique is described for measuring the enthalpy of dissociation liberated from solid hydrates. In this study, the enthalpies of dissociation were determined at T= 273.65 K andp= 0.1 MPa for simple and mixed hydrates of carbon dioxide, nitrogen, (carbon dioxide + nitrogen), and (carbon dioxide + nitrogen + tetrahydrofuran) using an isothermal microcalorimeter. The addition of tetrahydrofuran (THF)

B.-J. Ryu

2001-01-01

376

MOLECULES IN {eta} CARINAE  

SciTech Connect

We report the detection toward {eta} Carinae of six new molecules, CO, CN, HCO{sup +}, HCN, HNC, and N{sub 2}H{sup +}, and of two of their less abundant isotopic counterparts, {sup 13}CO and H{sup 13}CN. The line profiles are moderately broad ({approx}100 km s{sup -1}), indicating that the emission originates in the dense, possibly clumpy, central arcsecond of the Homunculus Nebula. Contrary to previous claims, CO and HCO{sup +} do not appear to be underabundant in {eta} Carinae. On the other hand, molecules containing nitrogen or the {sup 13}C isotope of carbon are overabundant by about one order of magnitude. This demonstrates that, together with the dust responsible for the dimming of {eta} Carinae following the Great Eruption, the molecules detected here must have formed in situ out of CNO-processed stellar material.

Loinard, Laurent; Menten, Karl M.; Guesten, Rolf [Max-Planck Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Zapata, Luis A.; Rodriguez, Luis F. [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 3-72, 58090 Morelia, Michoacan (Mexico)

2012-04-10

377

An Antibody Molecule  

NSDL National Science Digital Library

An antibody molecule. (A) Schematic drawing of a typical antibody molecule. As indicated, this protein is Y-shaped and has two identical binding sites for its antigen, one on either arm of the 3Y.2 The protein is composed of four polypeptide chains (two identical heavy chains and two identical and smaller light chains) held together by disulfide bonds. Each chain is made up of several different domains, here shaded either blue or gray. The antigen-binding site is formed where a heavy chain variable domain (VH) and a light chain variable domain (VL) come close together. These are the domains that differ most in their sequence and structure in different antibodies. (B) Ribbon drawing of a light chain showing the parts of the VL domain most closely involved in binding to the antigen in red; these contribute half of the fingerlike loops that fold around each of the antigen molecules in (A).

BEGIN:VCARD VERSION:2.1 FN:Martin Raff N:Raff;Martin REV:2005-04-15 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Julian Lewis N:Lewis;Julian REV:2005-04-15 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Alexander Johnson N:Johnson;Alexander REV:2005-04-15 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Dennis Bray N:Bray;Dennis REV:2005-04-15 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Bruce Alberts N:Alberts;Bruce REV:2005-04-15 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Keith Roberts N:Roberts;Keith REV:2005-04-15 END:VCARD

1998-07-01

378

Photochemistry of interstellar molecules  

NASA Technical Reports Server (NTRS)

The photochemistry of two diatomic and eight polyatomic molecules is discussed quantitatively. For an interstellar molecule, the lifetime against photodecomposition depends upon the absorption cross section, the quantum yield or probability of dissociation following photon absorption, and the interstellar radiation field. The constant energy density of Habing is used for the unobserved regions of interstellar radiation field, and the field in obscuring clouds is estimated by combining the constant flux with the observed interstellar extinction curve covering the visible and ultraviolet regions. Lifetimes against photodecomposition in the unobscured regions and as a function of increasing optical thickness in obscuring clouds are calculated for the ten species. The results show that, except for CO, all the molecules have comparable lifetimes of less than one hundred years. Thus they can exist only in dense clouds and can never have been exposed to the unobscured radiation. The calculations further show that the lifetimes in clouds of moderate opacity are of the order of one million years.

Stief, L. J.

1971-01-01

379

Study of the characteristics of a piezoelectric lead zirconate titanate radiation detector using a pulsed xenon source  

SciTech Connect

The detector characteristics of piezoelectric lead zirconate titanate (PZT) were studied by directly irradiating a multilayered PZT detector with 400 MeV/n xenon ions. An extracted beam was processed with a rotating slit. Thus, passed through {approx}10{sup 3} xenon ions were available for 50 to 250 {mu}s. The effect of polarization on the output signal was discussed, and the optimal electrode configuration was determined. The output signal appeared as an isolated pulse whose amplitude was qualitatively understood by the Bethe-Bloch formula. However, the calculated and the observed values differed depending on the rotation speed of the slit. A process that can explain the differences is presented here. The output signal appearing beyond the range of 400 MeV/n xenon ion beam was discussed. The sensitivity was compared with that obtained with hypervelocity collision of dust.

Miyachi, Takashi [Research Institute of Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Chiba 275-0016 (Japan); Fujii, Masayuki; Hasebe, Nobuyuki; Okudaira, Osamu [Research Institute of Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Takechi, Seiji; Kurozumi, Atsuma; Morinaga, Shinya; Uno, Takefumi [Graduate School of Engineering, Osaka-City University, Osaka 558-8585 (Japan); Shibata, Hiromi [Graduate School of Engineering, Kyoto-University, Kyoto-606-8501 (Japan); Kobayashi, Masanori [Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Chiba 275-0016 (Japan); Murakami, Takeshi; Uchihori, Yukio [National Institute of Radiological Sciences, Chiba 263-8555 (Japan); Okada, Nagaya [Honda Electronics Co. Ltd., Toyohashi, Aichi 441-3193 (Japan)

2010-05-15

380

NASA's Evolutionary Xenon Thruster (NEXT) Long-Duration Test as of 736 kg of Propellant Throughput  

NASA Technical Reports Server (NTRS)

The NASA s Evolutionary Xenon Thruster (NEXT) program is developing the next-generation solar-electric ion propulsion system with significant enhancements beyond the state-of-the-art NASA Solar Electric Propulsion Technology Application Readiness (NSTAR) ion propulsion system to provide future NASA science missions with enhanced mission capabilities. A Long-Duration Test (LDT) was initiated in June 2005 to validate the thruster service life modeling and to qualify the thruster propellant throughput capability. The thruster has set electric propulsion records for the longest operating duration, highest propellant throughput, and most total impulse demonstrated. At the time of this publication, the NEXT LDT has surpassed 42,100 h of operation, processed more than 736 kg of xenon propellant, and demonstrated greater than 28.1 MN s total impulse. Thruster performance has been steady with negligible degradation. The NEXT thruster design has mitigated several lifetime limiting mechanisms encountered in the NSTAR design, including the NSTAR first failure mode, thereby drastically improving thruster capabilities. Component erosion rates and the progression of the predicted life-limiting erosion mechanism for the thruster compare favorably to pretest predictions based upon semi-empirical ion thruster models used in the thruster service life assessment. Service life model validation has been accomplished by the NEXT LDT. Assuming full-power operation until test article failure, the models and extrapolated erosion data predict penetration of the accelerator grid grooves after more than 45,000 hours of operation while processing over 800 kg of xenon propellant. Thruster failure due to degradation of the accelerator grid structural integrity is expected after

Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Patterson, Michael J.

2012-01-01

381

NASA's Evolutionary Xenon Thruster (NEXT) Long-Duration Test as of 736 kg of Propellant Throughput  

NASA Technical Reports Server (NTRS)

The NASA s Evolutionary Xenon Thruster (NEXT) program is developing the next-generation solar-electric ion propulsion system with significant enhancements beyond the state-of-the-art NASA Solar Electric Propulsion Technology Application Readiness (NSTAR) ion propulsion system to provide future NASA science missions with enhanced mission capabilities. A Long-Duration Test (LDT) was initiated in June 2005 to validate the thruster service life modeling and to qualify the thruster propellant throughput capability. The thruster has set electric propulsion records for the longest operating duration, highest propellant throughput, and most total impulse demonstrated. At the time of this publication, the NEXT LDT has surpassed 42,100 h of operation, processed more than 736 kg of xenon propellant, and demonstrated greater than 28.1 MN s total impulse. Thruster performance has been steady with negligible degradation. The NEXT thruster design has mitigated several lifetime limiting mechanisms encountered in the NSTAR design, including the NSTAR first failure mode, thereby drastically improving thruster capabilities. Component erosion rates and the progression of the predicted life-limiting erosion mechanism for the thruster compare favorably to pretest predictions based upon semi-empirical ion thruster models used in the thruster service life assessment. Service life model validation has been accomplished by the NEXT LDT. Assuming full-power operation until test article failure, the models and extrapolated erosion data predict penetration of the accelerator grid grooves after more than 45,000 hours of operation while processing over 800 kg of xenon propellant. Thruster failure due to degradation of the accelerator grid structural integrity is expected after groove penetration.

Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Patterson, Michael J.

2012-01-01

382

Effect of endogenous sulfur dioxide in regulating cardiovascular oxidative stress.  

PubMed

In the middle of the 1980s, nitric oxide received extensive attention because of its significant effects in life science. Then, carbon monoxide and hydrogen sulfide were discovered to be gasotransmitters playing important roles in regulating cellular homeostasis. As a common air pollutant, sulfur dioxide (SO?) can cause great harm to the human body by producing free radicals, which causes oxidative damage to various organs. Recently, endogenous SO2 was found to be produced in the cardiovascular system and might be a bioactive molecule regulating the physiological activities including cardiovascular oxidative stress. PMID:24718903

Zhu, Mingzhu; Du, Junbao; Liu, Angie Dong; Holmberg, Lukas; Tang, Chaoshu; Jin, Hongfang

2014-09-01

383

21 CFR 73.2575 - Titanium dioxide.  

Code of Federal Regulations, 2010 CFR

...specifications. The color additive titanium dioxide shall...restrictions. The color additive titanium dioxide may...consistent with good manufacturing practice. (c) Labeling...requirements. The color additive and any mixtures...

2010-04-01

384

Wiring up Single Molecules  

NSDL National Science Digital Library

In recent years, circuit design has advanced to achieve extremely small feature sizes -- literally tens of millions of transistors can be integrated in a single chip. This progress has given rise to molecular electronics, the notion of creating electronic devices with single molecules as circuit elements. In this paper, the authors "discuss transistors, where electrons flow through discrete quantum states of a single molecule." Fabrication considerations are outlined, and the current-voltage responses of several such transistors that were fabricated by the authors are shown. The paper concludes by looking ahead to future possibilities of chemically-tailored transistors that could be designed with specific properties.

385

Molecules in Motion  

NSDL National Science Digital Library

In this learning assessment, students demonstrate understanding of the following concepts: solids, liquids and gases, changes of state, convection, and density. Students create a skit where the actors and actresses are molecules, and dramatize, through body motions, how the behavior of molecules results in the observable changes we see. A detailed scoring rubric is included with the resource. The investigation supports material presented in chapter 3 "What Heats the Earth's Interior?" in the textbook, Energy flow, part of Global System Science, 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.

386

Alphabetical Listing of Molecules  

NSDL National Science Digital Library

This useful, straightforward site will help students understand the structure of molecules through visualization. It was created by W. F. Coleman, Professor of Chemistry at Wellesley College. Here, you will find several common substances including caffeine, penicillin, Viagra, and vitamin A, as well as a few more exotic ones. Using the Chime software, a free chemical structure visualization plug-in for Windows and Macintosh, each molecule isn't simply a static image. It can be rotated for a complete examination, reformatted, and saved in a variety of file formats. A download link for Chime is provided.

2007-06-03

387

Alphabetical Listing of Molecules  

NSDL National Science Digital Library

This useful, straightforward site will help students understand the structure of molecules through visualization. It was created by W. F. Coleman, Professor of Chemistry at Wellesley College. Here, you will find several common substances including caffeine, penicillin, Viagra, and vitamin A, as well as a few more exotic ones. Using the Chime software, a free chemical structure visualization plug-in for Windows and Macintosh, each molecule isn't simply a static image. It can be rotated for a complete examination, reformatted, and saved in a variety of file formats. A download link for Chime is provided.

1998-01-01

388

Mighty Molecule Models  

NSDL National Science Digital Library

As part of the SMATHematics Project: The Wonder of Science, The Power of Mathematics--a collaborative partnership between Kennesaw State University and two local school districts, fifth graders had the opportunity to puzzle out chemical formulas of propane, methanol, and other important molecules. In addition, they explored properties that characterize certain molecules and then used their newly acquired knowledge of atoms' bonding requirements to help them build three-dimensional molecular models. The effort is succeeding--as you can see by the fifth-grade classroom experience described here.

Rushton, Greg; Bencomo, Marie; Brown, Tom

2008-01-01

389

Energy Levels and Observed Spectral Lines of Xenon, Xe I through Xe LIV  

NASA Astrophysics Data System (ADS)

The energy levels and observed spectral lines of the xenon atom, in all stages of ionization for which experimental data are available, have been compiled. Sufficient data were found to generate level and line tables for Xe I-Xe XI, Xe XIX, Xe XXV-Xe XXIX, Xe XLIII-Xe XLV, and Xe LI-Xe LIV. For Xe LIII and Xe LIV theoretical values are compiled for the energy levels. In 15 of the other stages a few lines are reported. Experimental g factors are included for Xe I, Xe II, and Xe III. A value, either experimental, semiempirical, or theoretical, is included for the ionization energy of each ion.

Saloman, E. B.

2004-09-01

390

Acoustic Experiment to Measure the Bulk Viscosity of Near-Critical Xenon in Microgravity  

NASA Technical Reports Server (NTRS)

We plan a rigorous test of the theory of dynamic scaling by accurately measuring the bulk viscosity of xenon in microgravity 50 times closer to the critical temperature T(sub c) than previous experiments. The bulk viscosity zeta (or "second viscosity" or "dilational viscosity") will be determined by measuring the attenuation length of sound alpha lambda and also measuring the frequency-dependence of the speed of sound. For these measurements, we developed a unique Helmholtz resonator and specialized electro-acoustic transducers. We describe the resonator, the transducers, their performance on Earth, and their expected performance in microgravity.

Gillis, K. A.; Shinder, I.; Moldover, M. R.; Zimmerli, G. A.

2002-01-01

391

Discriminant Analysis of Xenon-133 Washout Curves, An Index of Lower Extremity Vascular Impairment  

PubMed Central

To evaluate the degree of vascular impairment in muscles of the lower extremity, xenon-133 washout was studied in a group of legs with impaired circulation and in another group with normal circulation during both resting and stressed conditions. Blood flow was computed as a discrete time function based on a single compartment model with time-varying flow. Linear discriminant analysis was performed, using the flows at the discrete times as discriminators. The resulting discriminant coefficients allow any leg so studied to be represented as a point on the discriminant score axis, which thus becomes the axis of severity of impairment.

Wilson, P. David; Fallon, F. Graham; Buddemeyer, Edward U.

1977-01-01

392

Cryogenic system with GM cryocooler for krypton, xenon separation from hydrogen-helium purge gas  

NASA Astrophysics Data System (ADS)

In the thorium molten salt reactor (TMSR), fission products such as krypton, xenon and tritium will be produced continuously in the process of nuclear fission reaction. A cryogenic system with a two stage GM cryocooler was designed to separate Kr, Xe, and H2 from helium purge gas. The temperatures of two stage heat exchanger condensation tanks were maintained at about 38 K and 4.5 K, respectively. The main fluid parameters of heat transfer were confirmed, and the structural heat exchanger equipment and cold box were designed. Designed concentrations after cryogenic separation of Kr, Xe and H2 in helium recycle gas are less than 1 ppb.

Chu, X. X.; Zhang, M. M.; Zhang, D. X.; Xu, D.; Qian, Y.; Liu, W.

2014-01-01

393

Status of the Liquid Xenon calorimeter of the CMD-3 detector  

NASA Astrophysics Data System (ADS)

Since 2010 the CMD-3 detector has been collecting data at the e+e- collider VEPP-2000 at Budker Institute of Nuclear Physics. CMD-3 is a general purpose detector designed to study e+e- annihilation into hadrons in the wide energy range ?s = 0.3-2GeV. The barrel electromagnetic calorimeter of the detector has a thickness equal to 13.5X0 and consists of two subsystems: closest to the beam pipe is the Liquid Xenon calorimeter (LXe) and the outer one is based on CsI scintillation crystals (CsI). The design of the LXe calorimeter and its current performance are presented.

Anisenkov, A. V.; Aulchenko, V. M.; Barkov, L. M.; Bashtovoy, N. S.; Epshteyn, L. B.; Grebenuk, A. A.; Ignatov, F. V.; Karpov, S. V.; Khazin, B. I.; Kozyrev, A. N.; Logashenko, I. B.; Mikhailov, K. Yu; Pestov, Yu N.; Popov, A. S.; Ruban, A. A.; Shebalin, V. E.; Titov, V. M.; Talyshev, A. A.; Yudin, Yu V.

2014-08-01

394

A Hemispherical-Involute Cavity Receiver for Stirling Engine Powered by a Xenon Arc Solar Simulator  

NASA Astrophysics Data System (ADS)

We develop a solar simulator composed of multiple xenon arc lamps combined with a faceted paraboloidal dish concentrator to drive a Stirling engine in our laboratory for all-weather indoor testing. Experiments and numerical analysis are performed to determine the radiation flux and temperature distributions on the solar receiver surface. Based on the theoretical results, we present a receiver design for a solar Stirling engine with involute tubes closely conforming to the imaginary hemisphere to obtain a substantially uniform temperature field and a high solar-thermal efficiency of 67.1%.

Li, Zhi-Gang; Tang, Da-Wei; Li, Tie; Du, Jing-Long

2011-05-01

395

Wavelength dependence of double ionization of xenon in a strong laser field  

SciTech Connect

The wavelength dependence of double ionization of xenon in a 100-fs laser pulse (2-4x10{sup 13} W/cm{sup 2}) has been studied using photoelectron imaging and ion time-of-flight spectrometry. In the wavelength ranges between 1150 and 1560 nm and 792 and 803 nm a pronounced variation of the ratio of ion yields Xe{sup 2+}/Xe{sup +} is observed. We attribute this variation to the strong influence of a 5s{sup 2}5p{sup 5}{yields}5s5p{sup 6} transition on the dynamics of double ionization.

Kaminski, Patrick; Wiehle, Rolf; Kamke, Wolfgang; Helm, Hanspeter [Department of Molecular and Optical Physics, Albert-Ludwigs-Universitaet, 79104 Freiburg (Germany); Witzel, Bernd [Departement de physique, genie physique et optique, Universite Laval Pav. Alexandre-Vachon, Quebec G1K7P4 (Canada)

2006-01-15

396

Xenon detector with high energy resolution for gamma-ray line emission registration  

NASA Astrophysics Data System (ADS)

A description of the xenon detector (XD) for gamma-ray line emission registration 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.

2014-09-01

397

Quasielastic neutron scattering from adsorbed water molecules on pyrogenic silica surfaces  

NASA Astrophysics Data System (ADS)

Quasielastic neutron scattering (QNS) from hydrated samples of high dispersion (Aerosil) and of porous dioxide silicon was investigated. The broadening of the QNS peak analysis permits one to obtain the effective diffusion coefficient D of adsorbed water molecules. It was obtained that the D-value increases with silica hydration. The mean square displacement of the water molecules from equilibrium < x2> equals approximately 0.1 Å 2 and does not depend on the quantity of adsorbed water.

Tumanov, A. A.; Zarko, V. I.

1994-04-01

398

Nitrogen dioxide, sulfur dioxide, and ammonia detector for remote sensing of vehicle emissions  

E-print Network

Nitrogen dioxide, sulfur dioxide, and ammonia detector for remote sensing of vehicle emissions monoxide, carbon dioxide, and exhaust hydrocarbons in the IR and nitric oxide in the UV. The design adds the capability to measure nitrogen dioxide in the UV with one spectrometer and to measure SO2 and NH3 along

Denver, University of

399

Carbon dioxide transport over complex terrain  

USGS Publications Warehouse

The nocturnal transport of carbon dioxide over complex terrain was investigated. The high carbon dioxide under very stable conditions flows to local low-ground. The regional drainage flow dominates the carbon dioxide transport at the 6 m above the ground and carbon dioxide was transported to the regional low ground. The results show that the local drainage flow was sensitive to turbulent mixing associated with local wind shear.

Sun, J.; Burns, S. P.; Delany, A. C.; Oncley, S. P.; Turnipseed, A.; Stephens, B.; Guenther, A.; Anderson, D. E.; Monson, R.

2004-01-01

400

A liquid Xenon Positron Emission Tomograph for small animal imaging : first experimental results of a prototype cell  

E-print Network

A detector using liquid Xenon (LXe) in the scintillation mode is studied for Positron Emission Tomography (PET) of small animals. Its specific design aims at taking full advantage of the Liquid Xenon scintillation properties. This paper reports on energy, time and spatial resolution capabilities of the first LXe prototype module equipped with a Position Sensitive Photo- Multiplier tube (PSPMT) operating in the VUV range (178 nm) and at 165 K. The experimental results show that such a LXe PET configuration might be a promising solution insensitive to any parallax effect.

Gallin-Martel, M L; Grondin, Y; Rossetto, O; Collot, J; Grondin, D; Jan, S; Martin, Ph; Mayet, F; Petit, P; Vezzu, F

2008-01-01

401

Method and apparatus for producing chlorine dioxide  

Microsoft Academic Search

A continuous method and apparatus are described for the efficient production of gaseous chlorine dioxide by the reaction between gaseous sulfur dioxide and an aqueous solution of a metallic chlorate. The chlorate solution and a highly concentrated sulfur dioxide gas are introduced into a packed columnar chamber at closely adjacent locations at the bottom of the chamber so as to

P. W. Santillie; D. M. Ramras

1984-01-01

402

Electronic structure of silicon dioxide (a review)  

NASA Astrophysics Data System (ADS)

Silicon dioxide amorphous films are the key insulators in silicon integrated circuits. The physical properties of silicon dioxide are determined by the electronic structure of this material. The currently available information on the electronic structure of silicon dioxide has been systematized.

Nekrashevich, S. S.; Gritsenko, V. A.

2014-02-01

403

2, 18491865, 2005 Carbon dioxide in  

E-print Network

BGD 2, 1849­1865, 2005 Carbon dioxide in southern Poland L. Chmura et al. Title Page Abstract is licensed under a Creative Commons License. 1849 #12;BGD 2, 1849­1865, 2005 Carbon dioxide in southern urban environment with numerous local sources of carbon dioxide. Despite of relative proximity of those

Paris-Sud XI, Université de

404

SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW  

E-print Network

SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW J. E. Santos1, G. B. Savioli2, J. M. Carcione3, D´e, Argentina SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW ­ p. #12;Introduction. I Storage of CO2). SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW ­ p. #12;Introduction. II CO2 is separated from natural

Santos, Juan

405

SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW  

E-print Network

SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW J. E. Santos1 1 Department of Mathematics, Purdue University, USA Purdue University, March 1rst, 2013 SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW ­ p. #12 (North Sea). SEISMIC MONITORING OF CARBON DIOXIDE FLUID FLOW ­ p. #12;Introduction. II CO2 is separated

Santos, Juan

406

7Carbon Dioxide Increases The Keeling Curve,  

E-print Network

7Carbon Dioxide Increases The Keeling Curve, shown to the left, shows the variation in concentration of atmospheric carbon dioxide since 1958-1974. It is based on continuous measurements taken of rapidly increasing carbon dioxide levels in the atmosphere. Additional measurements by scientists working

407

21 CFR 184.1240 - Carbon dioxide.  

...2014-04-01 2014-04-01 false Carbon dioxide. 184.1240 Section 184.1240 Food and Drugs...Substances Affirmed as GRAS § 184.1240 Carbon dioxide. (a) Carbon dioxide (empirical formula CO2 , CAS Reg. No....

2014-04-01

408

Conversion of Uranium Oxide into Nitrate with Nitrogen Dioxide  

Microsoft Academic Search

In order to decrease the amount of aqueous liquid waste discharged from nuclear fuel reprocessing, the conversion of uranium dioxide into its nitrate using liquefied nitrogen dioxide was studied. Uranium dioxide powder was immersed in liquefied nitrogen dioxide at 313 K after a pretreatment by the oxidation of the uranium dioxide with nitrogen dioxide and air at 523 K. Seventy-nine

Kayo Sawada; Daisuke Hirabayashi; Youichi Enokida; Ichiro Yamamoto

2008-01-01

409

Diversity in Biological Molecules  

ERIC Educational Resources Information Center

One of the striking characteristics of fundamental biological processes, such as genetic inheritance, development and primary metabolism, is the limited amount of variation in the molecules involved. Natural selective pressures act strongly on these core processes and individuals carrying mutations and producing slightly sub-optimal versions of…

Newbury, H. John

2010-01-01

410

Atoms, Molecules, and Ions  

NSDL National Science Digital Library

General chemistry WebCT exam/quiz questions. The Atoms, Molecules, and Ions topic covers the basics of the composition of atoms, including subatomic particles, elements, allotropes, and isotopes. Periodic placement and trends, molar mass, and molecular formulas and ions are also included.

2008-02-12

411

Sugars as signaling molecules  

Microsoft Academic Search

Recent studies indicate that, in a manner similar to classical plant hormones, sugars can act as signaling molecules that control gene expression and developmental processes in plants. Crucial evidence includes uncoupling glucose signaling from its metabolism, identification of glucose sensors, and isolation and characterization of mutants and other regulatory components in plant sugar signal transduction pathways. The emerging scenario points

Jen Sheen; Li Zhou; Jyun-Chyun Jang

1999-01-01

412

Enforcing Molecules To Behave  

Microsoft Academic Search

The last two centuries have witnessed the growth of organic photochemistry from a relatively unknown to a developed discipline. During this period, photochemists have discovered new reac-tions, established mechanisms of photoreactions, laid out the ground rules for the behavior of mol-ecules in the excited state surfaces, and found applications of photochemistry in everyday life. In spite of these achievements, photochemistry

V. Ramamurthy

413

Heterocyclic small molecule peptidomimetics  

E-print Network

Polymer-supported synthesis of a close analog (i.e. A) of an early lead, a 14- membered ring peptidomimetic D3, was described. The monovalent molecule was attached to different length linkers, and they were then paired sequentially on a triazine...

Liu, Jing

2009-05-15

414

Halley's polymeric organic molecules  

NASA Astrophysics Data System (ADS)

The detection of polymeric organic compounds in the mass spectrum of Comet Halley obtained with the Positive Ion Cluster Composition analyzer on Giotto are examined. It is found that, in addition to polyoxymethylene, other polymers and complex molecules may exist in the comet. It is suggested that polymerized hydrogen cyanide may be a source for the observed CN and NH2 jets.

Huebner, W. F.; Boice, D. C.; Korth, A.

415

Algebraic theory of molecules  

NASA Technical Reports Server (NTRS)

An algebraic formulation of quantum mechanics is presented. In this formulation, operators of interest are expanded onto elements of an algebra, G. For bound state problems in nu dimensions the algebra G is taken to be U(nu + 1). Applications to the structure of molecules are presented.

Iachello, Franco

1995-01-01

416

Mighty Molecule Models  

ERIC Educational Resources Information Center

As part of the SMATHematics Project: The Wonder of Science, The Power of Mathematics--a collaborative partnership between Kennesaw State University and two local school districts, fifth graders had the opportunity to puzzle out chemical formulas of propane, methanol, and other important molecules. In addition, they explored properties that…

Brown, Tom; Rushton, Greg; Bencomo, Marie

2008-01-01

417

Financial Atoms and Molecules  

Microsoft Academic Search

Atoms and molecules are important conceptual entities we invented to understand the physical world around us. The key to their usefulness lies in the organization of nuclear and electronic degrees of freedom into a single dynamical variable whose time evolution we can better imagine. The use of such effective variables in place of the true microscopic variables is possible because

Yik Wen Goo; Tong Wei Lian; Wei Guang Ong; Wen Ting Choi; Siew-Ann Cheong

2009-01-01

418

Geological storage of carbon dioxide  

Microsoft Academic Search

Carbon dioxide is the main compound identified as affecting the stability of the Earth's climate. A significant reduction in the volume of greenhouse gas emissions to the atmosphere is a key mechanism for mitigating against climate change. Geological storage of CO 2, or the injection and stabilization of large volumes of CO 2 in the subsurface in saline aquifers, existing

S. J. Baines; RICHARD H. WORDEN

2004-01-01

419

Sulfur Dioxide and Material Damage  

ERIC Educational Resources Information Center

This study relates sulfur dioxide levels with material damage in heavily populated or polluted areas. Estimates of loss were determined from increased maintenance and replacement costs. The data indicate a decrease in losses during the past five years probably due to decline in pollution levels established by air quality standards. (MR)

Gillette, Donald G.

1975-01-01

420

SULFUR DIOXIDE SOURCES IN AK  

EPA Science Inventory

This map shows industrial plants which emit 100 tons/year or more of sulfur dioxide (SO2) in Alaska. The SO2 sources are plotted on a background map of cities and county boundaries. Data Sources: SO2 Sites: U.S. EPA AIRS System, County Outlines: 1990 Census Tiger Line Files 1:1...

421

Investigations of photodissociation iodine lasers utilizing molecules with bonds between iodine atoms and group V elements. I - Experimental investigation of \\/CF3\\/2AsI iodine laser  

Microsoft Academic Search

The paper reports results of an experimental investigation of the feasibility of producing a photodissociation iodine laser on the basis of (CF3)2AsI. Attention was given to measurements of the absorption spectrum of (CF3)2AsI molecules, the dependence of output energy on pressure in the laser tube, and the dependence of output energy on pump energy (from the xenon flashlamp). Laser action

T. L. Andreeva; G. N. Birich; V. N. Sorokin; I. I. Struk

1976-01-01

422

Quantitative chemical exchange saturation transfer with hyperpolarized nuclei (qHyper-CEST): Sensing xenon-host exchange dynamics and binding affinities by NMR.  

PubMed

The reversible binding of xenon to host molecules has found numerous applications in nuclear magnetic resonance studies. Quantitative characterization of the Xe exchange dynamics is important to understand and optimize the physico-chemical behavior of such Xe hosts, but is often challenging to achieve at low host concentrations. We have investigated a sensitive quantification technique based on chemical exchange saturation transfer with hyperpolarized nuclei, qHyper-CEST. Using simulated signals we demonstrated that qHyper-CEST yielded accurate and precise results and was robust in the presence of large amounts of noise (10%). This is of particular importance for samples with completely unknown exchange rates. Using these findings we experimentally determined the following exchange parameters for the Xe host cryptophane-A monoacid in dimethyl sulfoxide in one type of experiment: the ratio of bound and free Xe, the Xe exchange rate, the resonance frequencies of free and bound Xe, the Xe host occupancy, and the Xe binding constant. Taken together, qHyper-CEST facilitates sensitive quantification of the Xe exchange dynamics and binding to hydrophobic cavities and has the potential to analyze many different host systems or binding sites. This makes qHyper-CEST an indispensable tool for the efficient design of highly specific biosensors. PMID:25416884

Kunth, M; Witte, C; Schröder, L

2014-11-21

423

Conformational stability from variable temperature FT-IR spectra of xenon solutions and ab initio calculations of trans 3-pentenenitrile and 3-methyl-3-butene nitrile  

NASA Astrophysics Data System (ADS)

The infrared (3500-40 cm -1) spectra of gaseous, liquid and solid 3-methyl-3-butene nitrile, CH 2C(CH 3)CH 2CN, and trans 3-pentenenitrile, CH 3CHCHCH 2CN, have been recorded. Both the cis and gauche conformers have been identified for both conformers in the fluid phases but only the cis form remains in the solid. Variable temperature (-55 to -100°C) studies of the infrared spectra of the samples dissolved in liquid xenon have been carried out. From these data, the enthalpy difference has been determined to be 174±20 cm-1(2.08±0.24 kJ/mol) for 3-methyl-3-butene nitrile with the cis conformer the more stable rotamer and 187±20 cm-1(2.23±0.24 kJ/mol) for trans 3-pentenenitrile, again with the cis rotamer the more stable form. Complete equilibrium geometries have been obtained for both rotamers for both molecules by ab initio calculations employing the 6-31G(d), 6-311G(d,p), 6-311+G(d,p) and 6-311+G(2d,2p) basis sets at the levels of restricted Hartree-Fock and/or Moller-Plesset to second order. Only the MP2/6-311+G(2d,2p) calculation gives the correct conformer stability for 3-methyl-3-butene nitrile.

Guirgis, G. A.; Shen, S.; Drew, B. R.; Durig, J. R.

2001-05-01

424

Generation of plasmas in supercritical xenon inside microcapillaries for synthesis of diamondoid  

NASA Astrophysics Data System (ADS)

Diamondoids are series of sp^3 hybridized carbon nanomaterials that could be applied in various fields such as pharmacy and optoelectronics. In our previous studies, higher order diamondoids were synthesized in supercritical fluid (SCF) plasmas in a batch-type reactor using adamantane (C10H16), the smallest diamondoid, as a precursor and seed. However the yield was low and the selectivity was difficult to control. We have developed a continuous flow SCF microplasma reactor that allows discharge volume and residence time to be adjusted. The electrodes consist of a tungsten wire inserted into a fused silica capillary and a sputtered silver outside of the capillary. We dissolved adamantane in supercritical xenon near critical point, and then generated DBDs inside the capillary using a nominal constant xenon flow rate of 0˜2.3 mL min-1. Micro-Raman spectra of the synthesized products show peaks that are characteristic of hydrocarbons possessing sp^3 hybridized bonds while gas-chromatography/mass spectrometry spectra indicate the synthesis of diamantane (C14H20) and possibly isomers of diamondoids consisting of up to nine cages, nonamantane. It is suggested that this type of SCF microplasma reactor might be effective not only for synthesis of diamondoids, but also other nanomaterials.

Oshima, Fumito; Ishii, Chikako; Stauss, Sven; Terashima, Kazuo

2012-10-01

425

Problems in cerebral blood flow calculation using xenon-133 in patients with pulmonary diseases  

SciTech Connect

We used the end-tidal concentration of xenon-133 (air curve) to estimate the profile of its arterial concentration in calculating cerebral blood flow. We examined the effects of pulmonary disease and artificial ventilation on the air curve and the calculated cerebral blood flow. We studied the relation between arterial and end-tidal xenon activities in 19 subjects, of whom 15 had pulmonary dysfunction. The t 1/2 of the declining phases of the arterial and air curves were used to express their shapes. The mean +/- SD reference t 1/2 from 15 normal volunteers was 26.8 +/- 8.4 seconds. The mean +/- SD t 1/2 s of the air and arterial curves from the 15 patients with pulmonary dysfunction were 10.4 +/- 2.9 and 33.8 +/- 10.9 seconds. The degree of pulmonary dysfunction (expressed as the pulmonary shunt percentage) correlated with distortion of the air curve. Substituting the arterial for the air curve, mean calculated cerebral blood flow (as the initial slope index) increased from 40 to 61 for the 12 patients with chronic obstructive pulmonary disease. The degree of underestimation of cerebral blood flow using the air curve correlated with the pulmonary shunt percentage. Our work confirms the problems of estimating cerebral blood flow in subjects with pulmonary dysfunction.

Hansen, M.; Jakobsen, M.; Enevoldsen, E.; Egede, F. (Odense Univ. Hospital (Denmark))

1990-05-01

426

Mixing of equations of state for xenon-deuterium using density functional theory  

SciTech Connect

We report on a theoretical study of equation of state (EOS) properties of fluid and dense plasma mixtures of xenon and deuterium to explore and illustrate the basic physics of the mixing of a light element with a heavy element. Accurate EOS models are crucial to achieve high-fidelity hydrodynamics simulations of many high-energy-density phenomena, for example inertial confinement fusion and strong shock waves. While the EOS is often tabulated for separate species, the equation of state for arbitrary mixtures is generally not available, requiring properties of the mixture to be approximated by combining physical properties of the pure systems. Density functional theory (DFT) at elevated-temperature is used to assess the thermodynamics of the xenon-deuterium mixture at different mass ratios. The DFT simulations are unbiased as to elemental species and therefore provide comparable accuracy when describing total energies, pressures, and other physical properties of mixtures as they do for pure systems. The study focuses on addressing the accuracy of different mixing rules in the temperature range 1000-40 000 K for pressures between 100 and 600 GPa (1-6 Mbar), thus, including the challenging warm dense matter regime of the phase diagram. We find that a mix rule taking into account pressure equilibration between the two species performs very well over the investigated range.

Magyar, Rudolph J.; Mattsson, Thomas R. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2013-03-15

427

A novel 83mKr tracer method for characterizing xenon gas and cryogenic distillation systems  

NASA Astrophysics Data System (ADS)

The radioactive isomer 83mKr, has many properties that make it very useful for various applications. Its low energy decay products, like conversion, shake-off and Auger electrons as well as X- and ?-rays are used for calibration purposes in neutrino mass experiments and direct dark matter detection experiments. Thanks to the short half-life of 1.83 h and the decay to the ground state 83Kr, one does not risk contamination of any low-background experiment with long-lived radionuclides. In this paper, we present a new approach, using 83mKr as a radioactive tracer in noble gases. A method of doping 83mKr, into xenon gas and its detection, using special custom-made detectors, based on a photomultiplier tube, is described. Two applications of this method are presented: firstly, it can be used to characterize the particle flow inside of gas routing systems and determine the circulation speed of gas particles inside of a gas purification system for xenon. Secondly, it is used for rapid estimating of the separation performance of a distillation system.

Rosendahl, S.; Bokeloh, K.; Brown, E.; Cristescu, I.; Fieguth, A.; Huhmann, C.; Lebeda, O.; Levy, C.; Murra, M.; Schneider, S.; V'enos, D.; Weinheimer, C.

2014-10-01

428

Development and first results of the Yale PIXeY two-phase xenon detector  

NASA Astrophysics Data System (ADS)

PIXeY (Particle Identification in Xenon at Yale) is a two-phase (liquid/gas) xenon prototype time projection chamber with 3 kg active mass. PIXeY was built to optimize energy resolution and gamma/neutron discrimination, with a number of technological improvements over previous work. Parallel-wire grids, which control the drift and proportionalscintillation fields, are optimized both for light collection efficiency and field uniformity. High quantum efficiency Hamamatsu R8778 PMTs, high-reflectivity Teflon walls, and charge-light anti-correlation techniques are also incorporated. The first run of the detector has concluded, where all systems were tested both using LED calibration methods as well as using sources for calibration and spectral measurements. Ultimately our results were limited by PMT calibration issues, low light collection caused by saturation, and low drift fields constrained by high voltage hardware. The second run of the detector is currently underway with several improved components. The feedthroughs for higher voltages have improved to allow a much higher operating voltage, new PMT bases for more stable operation have been installed, and three new grids with transparencies between 92% and 97% have been added. Once the energy resolution studies have concluded, PIXeY will serve as a platform for future improvements, including multiple optical volumes and single wire readout for R&D on gamma-ray imaging.

Destefano, Nicholas E.; Bernard, Ethan; Edwards, Blair; Gai, Moshe; Horn, Markus; Larsen, Nicole; McKinsey, Daniel; Tennyson, Brian; Wahl, Christopher

2013-09-01

429

When the dust settles: stable xenon isotope constraints on the formation of nuclear fallout.  

PubMed

Nuclear weapons represent one of the most immediate threats of mass destruction. In the event that a procured or developed nuclear weapon is detonated in a populated metropolitan area, timely and accurate nuclear forensic analysis and fallout modeling would be needed to support attribution efforts and hazard assessments. Here we demonstrate that fissiogenic xenon isotopes retained in radioactive fallout generated by a nuclear explosion provide unique constraints on (1) the timescale of fallout formation, (2) chemical fractionation that occurs when fission products and nuclear fuel are incorporated into fallout, and (3) the speciation of fission products in the fireball. Our data suggest that, in near surface nuclear tests, the presence of a significant quantity of metal in a device assembly, combined with a short time allowed for mixing with the ambient atmosphere (seconds), may prevent complete oxidation of fission products prior to their incorporation into fallout. Xenon isotopes thus provide a window into the chemical composition of the fireball in the seconds that follow a nuclear explosion, thereby improving our understanding of the physical and thermo-chemical conditions under which fallout forms. PMID:25014883

Cassata, W S; Prussin, S G; Knight, K B; Hutcheon, I D; Isselhardt, B H; Renne, P R

2014-11-01

430

Electrical and kinetical aspects of homogeneous dielectric-barrier discharge in xenon for excimer lamps  

SciTech Connect

A pulsed dielectric-barrier discharge in xenon has been simulated for operating conditions typical to excimer lamps, in which the discharge is considered spatially homogeneous. The computer model developed is based on the xenon plasma chemistry, the circuit, and the Boltzmann equations. First, the validity of the physical model was checked and compared to experimental and theoretical works, and then the model is applied in the case of a sinusoidal voltage at period frequencies in the range of 50 kHz-2 MHz. The results obtained with the present description are in good agreement with experimental measurements and one-dimensional fluid prediction in terms of electrical characteristics and vacuum ultraviolet (vuv) emission. The effect of operation voltage, power source frequency, dielectric capacitance, as well as gas pressure on the discharge efficiency and the 172, 150, and 147 nm photon generation, under the typical experimental operating conditions and for the case of a sinusoidal applied voltage, have been investigated and discussed. Calculations suggest that the overall conversion efficiency from electrical energy to vuv emission in the lamp is greater than 38%, and it will be very affected at high power source frequency and high gas pressure with a significant dependence on the dielectric capacitance.

Belasri, A. [Laboratoire de Physique des Plasmas, Materiaux Conducteurs et leurs Applications, Universite des Sciences et de la Technologie d'Oran, Oran, 1505 El-mnaouer (Algeria); Harrache, Z. [Grupo de Espectroscopia de Plasmas, Edificio A. Einstein, Campus de Rabanales, Universidad de Cordoba, E-14071 Cordoba (Spain)

2010-12-15

431

Spin-polarized metastable-atom deexcitation spectroscopy study of Xenon-adsorbed iron surfaces  

NASA Astrophysics Data System (ADS)

The electron spin polarization at the interface between nonmagnetic and ferromagnetic medias is one of the essential factors that may alter the spin transport phenomena. To investigate fundamental aspects of induced spin polarization we have examined the adsorbate-covered magnetic surfaces by means of spin polarized metastable-atom deexcitation spectroscopy (SPMDS). Use of spin-polarized metastable helium atoms in triplet states moving at thermal energies gives rise to the ultimate surface sensitivity. Although Xenon can adsorb on surfaces at low temperatures by the van der Waals force, no electron exchange with surfaces, especially no spin interaction, is expected because of its closed shell structure. SPMDS spectra measured for Xenon-adsorbed iron surfaces show three prominent peaks that are the same as those previously reported for other surfaces by D. M. Oro, et al. [Phys. Rev. A 49 (1994) 4703]. Two peaks (^2P1/2, ^2P3/2) at higher kinetic energies exhibit clear spin asymmetries while the other low energy peak has no appreciable spin asymmetry. The spin asymmetries will be discussed on the basis of spin polarization and deexcitation processes of metastable atoms.

Yamauchi, Yasushi; Kurahashi, Mitsunori; Suzuki, Taku; Sun, Xia; Wang, Zhongping

2007-03-01

432

First-principles calculations of the stability and incorporation of helium, xenon and krypton in uranium  

NASA Astrophysics Data System (ADS)

While metallic fuels have a long history of reactor use, their fundamental physical and thermodynamic properties are not well understood. Many metallic nuclear fuels are body-centered cubic alloys of uranium that swell under fission conditions, creating fission product gases such as helium, xenon and krypton. In this paper, helium, xenon, and krypton point defects are investigated in the ? and ? phases of metallic uranium using first principles calculations. A density functional theory (DFT) framework is utilized with projector augmented-wave (PAW) pseudopotentials. Formation and incorporation energies of He, Xe, and Kr are calculated at various defect positions for the prediction of fission gas behavior in uranium. In most cases, defect energies follow a size effect, with helium incorporation and formation energies being the smallest. The most likely position for the larger Xe and Kr atoms in uranium is the substitutional site. Helium atoms are likely to be found in a wide variety of defect positions due to the comparable formation energies of all defect configurations analyzed. This is the first detailed study of the stability and incorporation of fission gases in uranium.

Beeler, B.; Good, B.; Rashkeev, S.; Deo, C.; Baskes, M.; Okuniewski, M.

2012-06-01

433

Design of Two-Phase Liquid-Xenon Compton-Imaging Detector  

NASA Astrophysics Data System (ADS)

Liquid xenon offers a unique set of features for gamma and neutron measurements, including high Z, fairly high density (3 g/cm^3), gamma/neutron discrimination, fast (27-ns) scintillation signals, and demonstrated 4% FWHM energy resolution at 662 keV. Improvements to an existing detector are being made to create a position-sensitive liquid-xenon detector capable of Compton imaging. The proposed design will operate in two-phase mode to record initial scintillation light (S1), then drift free electrons past sense wires and into a gas region where the electrons will produce proportional scintillation light (S2), which very accurately counts the drifting electrons. The combination of the S1 and S2 signals, which are anti-correlated in energy, is predicted to give 2.6% FWHM energy resolution at 662 keV. The crossed sense wires will have 3-mm pitch and predicted mm-scale position resolution. A preamp to read out each wire is being designed to fulfill space and noise constraints. In order to precisely know the energy from each gamma-ray interaction, the scintillation light from each interaction must be distinguished from that due to others. Simulation, including optical reflections, is used to determine the optimal optical segmentation of the active volume using thin Teflon walls.

Wahl, Christopher; Bernard, Ethan; Kachulis, Christopher; Larsen, Nicole; Tennyson, Brian; Cahn, Sidney; McKinsey, Daniel; de Silva, Manawaduge; Destefano, Nicholas; Gai, Moshe

2012-10-01

434

Spectroscopics database for warm Xenon and Iron in Astrophysics and Laboratory Astrophysics conditions  

NASA Astrophysics Data System (ADS)

The main contribution to spectral properties of astrophysics mixtures come often from Iron. On the other hand, in the so-called domain of ``Laboratory Astrophysics,'' where astrophysics phenomena are scaled down to the laboratory, Xenon (and Argon) are commonly used gases. At so called ``warm'' temperatures (T=5-50eV), L-shell Iron and M-shell Xenon present a very large number of spectral lines, originating from billions of levels. More often than not, Local Thermodynamical Equilibrium is assumed, leading to noticeable simplification of the computation. Nevertheless, complex and powerful atomic structure codes are required. We take benefit of powerful statistics and numerics, included in our atomic structure codes, STA[1] and HULLAC[2], to generate the required spectra. Recent improvements in both fields (statistics, numerics and convergence control) allow obtaining large databases (ro x T grid of > 200x200 points, and > 10000 frequencies) for temperature down to a few eV. We plan to port these improvements in the NLTE code SCROLL[3]. [1] A.Bar-Shalom, et al, Phys. Rev. A 40, 3183 (1989) [2] M.Busquet,et al, J.Phys. IV France 133, 973-975 (2006); A.Bar-Shalom, M.Klapisch, J.Oreg, J.Oreg, JQSRT 71, 169, (2001) [3] A.Bar-Shalom, et al, Phys. Rev. E 56, R70 (1997)

Busquet, Michel; Klapisch, Marcel; Bar-Shalom, Avi; Oreg, Josse

2010-11-01

435

Thermal evolution of Earth with xenon degassing: A self-consistent approach  

NASA Astrophysics Data System (ADS)

We present a coupled atmosphere-mantle evolution model to investigate a possible connection between the present-day atmospheric budget of radiogenic xenon and the evolution of subsolidus mantle convection since the Hadean. Two different types of heat-flow scaling for mantle convection are tested; whereas a conventional scaling predicts more vigorous convection in the hotter past, a recent one predicts more sluggish dynamics. Extensive degassing expected for a putative magma ocean in the very early Earth as well as considerable atmospheric loss caused by an early intensive solar wind are taken into account by using an effective closure time. The success of modeling results is measured by how closely they can reproduce the present-day abundances of 129Xe* and 136Xe* in the atmosphere. The conventional scaling demands the present-day mantle to be highly radioactive, which in turn indicates a high initial abundance of 244Pu, and because the mantle is very efficiently processed with this scaling, a large amount of plutogenic 136Xe* is predicted to have been degassed into the atmosphere. Various parameter uncertainties are explored by Monte Carlo sampling, and our modeling results suggest that the use of the conventional scaling leads to >300% overprediction of the atmospheric 136Xe* budget, whereas we can satisfy the xenon budget more easily with the recent scaling.

Padhi, Catherine M.; Korenaga, Jun; Ozima, Minoru

2012-08-01

436

Redox Reactions of Metalloporphyrins and their Role in Catalyzed Reduction of Carbon Dioxide  

SciTech Connect

Pulse radiolysis and laser photolysis are used to study redox processes of metalloporphyrins and related complexes in order to evaluate these light absorbing molecules as sensitizers and intermediates in solar energy conversion schemes. The main thrust of the current studies is to investigate the role of reduced metalloporphyrins as intermediates in the catalyzed reduction of carbon dioxide. Studies involve cobalt and iron porphyrins, phthalocyanines, corroles, and corrins as homogeneous catalysts for reduction of carbon dioxide in solution. The main aim is to understand the mechanisms of these photochemical schemes in order to facilitate their potential utilization.

Neta, P.

2002-09-01

437

Formation and reinforcement of clusters composed of C60 molecules  

PubMed Central

We carry out two experiments: (1) the formation of clusters composed of C60 molecules via self-assembly and (2) the reinforcement of the clusters. Firstly, clusters such as fibres and helices composed of C60 molecules are produced via self-assembly in supercritical carbon dioxide. However, C60 molecules are so weakly bonded to each other in the clusters that the clusters are broken by the irradiation of electron beams during scanning electron microscope observation. Secondly, UV photons are irradiated inside a chamber in which air is filled at 1 atm and the above clusters are placed, and it was found that the clusters are reinforced; that is, they are not broken by electron beams any more. C60 molecules located at the surface of the clusters are oxidised, i.e. C60On molecules, where n = 1, 2, 3 and 4, are produced according to time-of-flight mass spectroscopy. It is supposed that oxidised C60 molecules at the surface of the clusters may have an important role for the reinforcement, but the actual mechanism of the reinforcement of the clusters has not yet been clearly understood and therefore is an open question. PMID:21711582

2011-01-01

438

Formation and reinforcement of clusters composed of C60 molecules  

NASA Astrophysics Data System (ADS)

We carry out two experiments: (1) the formation of clusters composed of C60 molecules via self-assembly and (2) the reinforcement of the clusters. Firstly, clusters such as fibres and helices composed of C60 molecules are produced via self-assembly in supercritical carbon dioxide. However, C60 molecules are so weakly bonded to each other in the clusters that the clusters are broken by the irradiation of electron beams during scanning electron microscope observation. Secondly, UV photons are irradiated inside a chamber in which air is filled at 1 atm and the above clusters are placed, and it was found that the clusters are reinforced; that is, they are not broken by electron beams any more. C60 molecules located at the surface of the clusters are oxidised, i.e. C60O n molecules, where n = 1, 2, 3 and 4, are produced according to time-of-flight mass spectroscopy. It is supposed that oxidised C60 molecules at the surface of the clusters may have an important role for the reinforcement, but the actual mechanism of the reinforcement of the clusters has not yet been clearly understood and therefore is an open question.

Kurosu, Shunji; Fukuda, Takahiro; Shibuya, Yuichi; Maekawa, Toru

2011-12-01

439

Molecules in interstellar clouds  

NASA Astrophysics Data System (ADS)

The physical conditions and chemical compositions of the gas in interstellar clouds are reviewed in light of the importance of interstellar clouds for star formation and the origin of life. The Orion A region is discussed as an example of a giant molecular cloud where massive stars are being formed, and it is pointed out that conditions in the core of the cloud, with a kinetic temperature of about 75 K and a density of 100,000-1,000,000 molecules/cu cm, may support gas phase ion-molecule chemistry. The Taurus Molecular Clouds are then considered as examples of cold, dark, relatively dense interstellar clouds which may be the birthplaces of solar-type stars and which have been found to contain the heaviest interstellar molecules yet discovered. The molecular species identified in each of these regions are tabulated, including such building blocks of biological monomers as H2O, NH3, H2CO, CO, H2S, CH3CN and H2, and more complex species such as HCOOCH3 and CH3CH2CN.

Irvine, W. M.; Hjalmarson, A.; Rydbeck, O. E. H.

440

Multiplexed single molecule immunoassays.  

PubMed

We have developed a method that enables the multiplexed detection of proteins based on counting single molecules. Paramagnetic beads were labeled with fluorescent dyes to create optically distinct subpopulations of beads, and antibodies to specific proteins were then immobilized to individual subpopulations. Mixtures of subpopulations of beads were then incubated with a sample, and specific proteins were captured on their specific beads; these proteins were then labeled with enzymes via immunocomplex formation. The beads were suspended in enzyme substrate, loaded into arrays of femtoliter wells--or Single Molecule Arrays (Simoa)--that were integrated into a microfluidic device (the Simoa disc). The wells were then sealed with oil, and imaged fluorescently to determine: a) the location and subpopulation identity of individual beads in the femtoliter wells, and b) the presence or absence of a single enzyme associated with each bead. The images were analyzed to determine the average enzyme per bead (AEB) for each bead subpopulation that provide a quantitative parameter for determining the concentration of each protein. We used this approach to simultaneously detect TNF-?, IL-6, IL-1?, and IL-1? in human plasma with single molecule resolution at subfemtomolar concentrations, i.e., 200- to 1000-fold more sensitive than current multiplexed immunoassays. The simultaneous, specific, and sensitive measurement of several proteins using multiplexed digital ELISA could enable more reliable diagnoses of disease. PMID:23719780

Rissin, David M; Kan, Cheuk W; Song, Linan; Rivnak, Andrew J; Fishburn, Matthew W; Shao, Qichao; Piech, Tomasz; Ferrell, Evan P; Meyer, Raymond E; Campbell, Todd G; Fournier, David R; Duffy, David C

2013-08-01

441

Diffusion of Oxygen and Carbon Dioxide in Semicrystalline Syndiotactic Polystyrene  

NASA Astrophysics Data System (ADS)

The solid state structure of syndiotactic polystyrene (s-PS) after crystallization from the melt and the glassy state was examined by differential scanning calorimetry (DSC), density and x-ray diffraction analysis. It was possible to prepare semicrystalline s-PS containing either pure alpha or pure beta crystalline form by melt crystallizing s-PS from 280C or 330C. The measurements confirmed the low density of both crystalline forms, which in the case of alpha crystalline form was smaller and in the case of beta crystalline form was only slightly larger than the density of the glassy amorphous s-PS. Therefore the question was posed whether these two loosely packed thermally induced crystalline forms of s-PS were permeable for transport of small gas molecules. It was shown that the beta crystalline form was virtually impermeable for the transport of oxygen and carbon dioxide. In contrast, the alpha crystalline form was highly permeable for transport of oxygen and carbon dioxide. High gas permeability of the alpha crystals was attributed to the loose crystalline structure of this crystalline form containing nanochannels oriented parallel to the polymer chain direction. A model describing diffusion and permeability of gas molecules in the composite permeation medium consisting of the amorphous matrix and the dispersed crystalline phase with nanochannels was proposed.

Nazarenko, Sergei; Prodpran, Thummanoon; Shenogin, Sergei; Shenogina, Natalia

2001-03-01

442

Investigation of liquid xenon detectors for PET: Simultaneous reconstruction of light and charge signals from 511 keV photons  

Microsoft Academic Search

We investigated the detection of gamma rays in a small liquid xenon detector to assess elements of the performance for positron emission tomography. Scintillation light was detected by large area avalanche photodiodes while the ionization electrons were measured on the anode of a time projection chamber after drifting up to 3 cm. The optimum running conditions have been investigated as

P. Amaudruz; D. Bryman; L. Kurchaninov; P. Lu; C. Marshall; J. P. Martin; A. Muennich; F. Retiere; A. Sher

2007-01-01

443

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 of the dopant, and (iii) the kinetic energy of the quasi-free electron. The polarization terms are determined by a standard statistical mechanical treatment. However, the kinetic energy of the quasi-free

Findley, Gary L.

444

Dual-Thickness Gate Oxidation Technology with Halogen\\/Xenon Implantation for Embedded Dynamic Random Access Memories  

Microsoft Academic Search

We investigated the enhanced oxidation effect of using silicon (Si) implanted with fluorine (F), iodine (I), and xenon (Xe) before gate oxidation. I and Xe, which result in shallower implants because of their higher mass numbers, were expected to be less damaging to the Si substrate. The resultant increase in oxide thickness was found to be 20%, 80%, and 50%

Taro Sugizaki; Atsushi Murakoshi; Yoshio Ozawa; Toshiro Nakanishi; Kyoichi Suguro

2001-01-01

445

Oxygen and carbon dioxide sensing  

NASA Technical Reports Server (NTRS)

A high electron mobility transistor (HEMT) capable of performing as a CO.sub.2 or O.sub.2 sensor is disclosed, hi one implementation, a polymer solar cell can be connected to the HEMT for use in an infrared detection system. In a second implementation, a selective recognition layer can be provided on a gate region of the HEMT. For carbon dioxide sensing, the selective recognition layer can be, in one example, PEI/starch. For oxygen sensing, the selective recognition layer can be, in one example, indium zinc oxide (IZO). In one application, the HEMTs can be used for the detection of carbon dioxide and oxygen in exhaled breath or blood.

Ren, Fan (Inventor); Pearton, Stephen John (Inventor)

2012-01-01

446

Molecular Structure of Nitrogen dioxide  

NSDL National Science Digital Library

Nitrogen dioxide is a brown gas that readily dimerizes at lower temperatures to form the colorless gas dinitrogen trioxide. It is a byproduct of combustion that pollutes air and its gives smog its characteristic brown color. When gasoline, diesel fuel, or coal is burned at high temperatures nitric oxide (NO) is formed. Nitric oxide reacts slowly with oxygen to form nitrogen dioxide, or it can react with many organic-oxygen containing radicals (e.g., alkoxy and peroxy radicals) found in the atmosphere (also products of combustion) to more rapidly form NO2. The photolysis of NO2 by sunlight is the only known source of ozone to the troposphere (the layer of atmosphere closest to the earth); ozone is one of the most toxic components of smog and adversely affects human, animal and plant health in densely populated polluted regions.

2002-09-11

447

Negative ions of polyatomic molecules.  

PubMed Central

In this paper general concepts relating to, and recent advances in, the study of negative ions of polyatomic molecules area discussed with emphasis on halocarbons. The topics dealt with in the paper are as follows: basic electron attachment processes, modes of electron capture by molecules, short-lived transient negative ions, dissociative electron attachment to ground-state molecules and to "hot" molecules (effects of temperature on electron attachment), parent negative ions, effect of density, nature, and state of the medium on electron attachment, electron attachment to electronically excited molecules, the binding of attached electrons to molecules ("electron affinity"), and the basic and the applied significance of negative-ion studies. PMID:7428744

Christophorou, L G

1980-01-01

448

Sonochemical reduction of carbon dioxide  

Microsoft Academic Search

Sonolysis of carbon dioxide dissolved in water was performed from a standpoint of reducing this material in atmosphere. During one hour of sonication, the amount of CO2 decreased to about half at 5°C under CO2–Ar atmosphere. The decreasing rate for CO2 followed the order Ar>He>H2>N2 and it was down with increasing temperature in the range of 5–45°C. The most favorable

Hisashi Harada

1998-01-01

449

Nongovernmental valorization of carbon dioxide  

Microsoft Academic Search

Carbon dioxide (CO2) is considered the largest contributor to the greenhouse gas effect. Most attempts to manage the flow of CO2 or carbon into our environment involve reducing net emissions or sequestering the gas into long-lived sinks. Using CO2 as a chemical feedstock has a long history, but using it on scales that might impact the net emissions of CO2

Gene Petersen; Donn Viviani; Kim Magrini-Bair; Stephen Kelley; Luc Moens; Phil Shepherd; Dan DuBois

2005-01-01

450

Interpreting recent carbon dioxide data  

NSDL National Science Digital Library

Using web-accessed climate data, students will examine the latitudinal distribution of CO2 and explain how (and why) that has changed over (recent) time. They will then work in groups of two or three to download, graph, and interpret carbon dioxide concentration data from one individual location (different groups will be assigned a different site). Each student will complete a series of questions to ensure their understanding of the concepts outlined above.

Gordon, Elizabeth

451

Photoinduced reactivity of titanium dioxide  

Microsoft Academic Search

The utilization of solar irradiation to supply energy or to initiate chemical reactions is already an established idea. If a wide-band gap semiconductor like titanium dioxide (TiO2) is irradiated with light, excited electron–hole pairs result that can be applied in solar cells to generate electricity or in chemical processes to create or degrade specific compounds. Recently, a new process used

O. Carp; C. L. Huisman; A. Reller

2004-01-01

452

Carbon Dioxide Removal via Passive Thermal Approaches  

NASA Technical Reports Server (NTRS)

A paper describes a regenerable approach to separate carbon dioxide from other cabin gases by means of cooling until the carbon dioxide forms carbon dioxide ice on the walls of the physical device. Currently, NASA space vehicles remove carbon dioxide by reaction with lithium hydroxide (LiOH) or by adsorption to an amine, a zeolite, or other sorbent. Use of lithium hydroxide, though reliable and well-understood, requires significant mass for all but the shortest missions in the form of lithium hydroxide pellets, because the reaction of carbon dioxide with lithium hydroxide is essentially irreversible. This approach is regenerable, uses less power than other historical approaches, and it is almost entirely passive, so it is more economical to operate and potentially maintenance- free for long-duration missions. In carbon dioxide removal mode, this approach passes a bone-dry stream of crew cabin atmospheric gas through a metal channel in thermal contact with a radiator. The radiator is pointed to reject thermal loads only to space. Within the channel, the working stream is cooled to the sublimation temperature of carbon dioxide at the prevailing cabin pressure, leading to formation of carbon dioxide ice on the channel walls. After a prescribed time or accumulation of carbon dioxide ice, for regeneration of the device, the channel is closed off from the crew cabin and the carbon dioxide ice is sublimed and either vented to the environment or accumulated for recovery of oxygen in a fully regenerative life support system.

Lawson, Michael; Hanford, Anthony; Conger, Bruce; Anderson, Molly

2011-01-01

453

29Counting Atoms in a Molecule The complex molecule Propanal  

E-print Network

29Counting Atoms in a Molecule The complex molecule Propanal was discovered in a dense interstellar is the ratio of carbon atoms to hydrogen atoms in propanal? Problem 4 - If the mass of a hydrogen atom of a propanal molecule in AMUs? Problem 5 - What is the complete chemical formula for propanal? C3 H __ O

454

Experimental investigation of soliton molecules  

Microsoft Academic Search

Detailed experimental investigations of the recently discovered temporal soliton molecules are reported. The optical fiber length was now extended; thus stable and unstable regimes of the soliton molecule can be distinguished from another more precisely.

H. Hartwig; M. Stratmann; F. Mitschke

2006-01-01

455

Exposure to Titanium Dioxide Nanomaterials Provokes Inflammation of an in Vitro Human Immune Construct  

PubMed Central

Nanoparticle technology is undergoing significant expansion largely because of the potential of nanoparticles as biomaterials, drug delivery vehicles, cancer therapeutics, and immunopotentiators. Incorporation of nanoparticle technologies for in vivo applications increases the urgency to characterize nanomaterial immunogenicity. This study explores titanium dioxide, one of the most widely manufactured nanomaterials, synthesized into its three most common nanoarchitectures: anatase (7–10 nm), rutile (15–20 nm), and nanotube (10–15 nm diameters, 70–150 nm length). The fully human autologous MIMIC immunological construct has been utilized as a predictive, nonanimal alternative to diagnose nanoparticle immunogenicity. Cumulatively, treatment with titanium dioxide nanoparticles in the MIMIC system led to elevated levels of proinflammatory cytokines and increased maturation and expression of costimulatory molecules on dendritic cells. Additionally, these treatments effectively primed activation and proliferation of naïve CD4+ T cells in comparison to dendritic cells treated with micrometer-sized (>1 ?m) titanium dioxide, characteristic of an in vivo inflammatory response. PMID:19769402

Schanen, Brian C.; Karakoti, Ajay S.; Seal, Sudipta; Drake, Donald R.; Warren, William L.; Self, William T.

2011-01-01

456

Inorganic Molecules; A Visual Database  

NSDL National Science Digital Library

Inorganic Molecules: A Visual Data Base contains text and graphics describing 66 molecules and ions commonly used as examples in general chemistry courses. For each molecule, fifteen molecular properties are presented visually by eight or nine different molecular models created by the CAChe Scientific Molecular Modeling program.