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1

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

2

Discovery of the krypton isotopes  

SciTech Connect

Thirty-two krypton isotopes have been observed so far and the discovery of these isotopes is discussed here. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

Heim, M.; Fritsch, A.; Schuh, A.; Shore, A. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Thoennessen, M. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)], E-mail: thoennessen@nscl.msu.edu

2010-07-15

3

Xenon and krypton isotopic anomalies in a natural nuclear reactor and at the epicenter of a nuclear explosion  

Microsoft Academic Search

The purpose of this work was to investigate the possibility of the appearance of Xe and Kr isotopic anomalies in a natural reactor owing to migration processes. Four objects of study were used. The first was a soil sample from the crater formed by the first atomic bomb in Alamagordo, New Mexico, in 1945. The second sample consisted of standard

Yu. A. Shukolyukov; A. P. Meshik; O. V. Pravdivtseva; A. B. Verkhovskii

1988-01-01

4

Atom trap trace analysis of krypton isotopes  

Microsoft Academic Search

A new method of ultrasensitive isotope trace analysis has been developed. This method, based on the technique of laser manipulation of neutral atoms, has been used to count individual ⁸⁵Kr and ⁸¹Kr atoms present in a natural krypton gas sample with isotopic abundances in the range of 10⁻¹¹ and 10⁻¹³, respectively. This method is free of contamination from other isotopes

K. Bailey; C. Y. Chen; X. Du; Y. M. Li; Z.-T. Lu; T. P. OConnor; L. Young

1999-01-01

5

Shape Coexistence In Light Krypton Isotopes  

Microsoft Academic Search

Shape coexistence in the light krypton isotopes was studied in a series of experiments at GANIL using various experimental techniques. A new low-lying 0+ state, a so-called shape isomer, was found in delayed conversion-electron spectroscopy after fragmentation reactions. The systematics of such low-lying 0+ states suggests that the ground states of the isotopes 78Kr and 76Kr have prolate deformation, while

E. Clment; E. Bouchez; A. Chatillon; W. Korten; Y. Le Coz; Ch. Theisen; C. Andreoiu; F. Becker; B. Blank; A. Buerger; P. Butler; J. M. Casandjian; W. N. Catford; T. Czosnyka; A. Emsallem; G. de France; G. Georgiev; J. Gerl; F. Hannachi; K. Hauschild; R.-D. Herzberg; F. Johnston-Theasby; J. Iwanicki; D. Jenkins; P. Napiorkowski; F. de Oliveira Santos; G. Sletten; I. Matea; R. Wadsworth; F. de Oliviera Santos; D. Pantelica; J. Pinston; P. Rahkila; M. Rejmund; M. Stanoiu; C. Timis; J. N. Wilson; M. Zielinska

2005-01-01

6

Atom trap trace analysis of krypton isotopes  

SciTech Connect

A new method of ultrasensitive isotope trace analysis has been developed. This method, based on the technique of laser manipulation of neutral atoms, has been used to count individual {sup 85}Kr and {sup 81}Kr atoms present in a natural krypton gas sample with isotopic abundances in the range of 10{sup {minus}11} and 10{sup {minus}13}, respectively. This method is free of contamination from other isotopes and elements and can be applied to several different isotope tracers for a wide range of applications. The demonstrated detection efficiency is 1 x 10{sup {minus}7}. System improvements could increase the efficiency by many orders of magnitude.

Bailey, K.; Chen, C. Y.; Du, X.; Li, Y. M.; Lu, Z.-T.; O'Connor, T. P.; Young, L.

1999-11-17

7

Shape Coexistence In Light Krypton Isotopes  

SciTech Connect

Shape coexistence in the light krypton isotopes was studied in a series of experiments at GANIL using various experimental techniques. A new low-lying 0+ state, a so-called shape isomer, was found in delayed conversion-electron spectroscopy after fragmentation reactions. The systematics of such low-lying 0+ states suggests that the ground states of the isotopes 78Kr and 76Kr have prolate deformation, while states with prolate and oblate shape are practically degenerate and strongly mixed in 74Kr, and that the oblate configuration becomes the ground state in 72Kr. This scenario was tested in experiments performing low-energy Coulomb excitation of radioactive 76Kr and 74Kr beams from the SPIRAL facility. Both transitional and diagonal electromagnetic matrix elements were extracted from the observed {gamma}-ray yields. The results find the prolate shape for the ground-state bands in 76Kr and 74Kr and an oblate deformation for the excited 2{sub 2}{sup +} state in 74Kr, confirming the proposed scenario of shape coexistence.

Clement, E.; Goergen, A.; Bouchez, E.; Chatillon, A.; Korten, W.; Le Coz, Y.; Theisen, Ch.; Huerstel, A.; Lucas, R.; Wilson, J.N. [DAPNIA/SPhN, CEA Saclay, F-91191 Gif-sur-Yvette (France); Andreoiu, C.; Butler, P.; Herzberg, R.-D.; Iwanicki, J.; Jenkins, D.; Jones, G. [Dept. of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Becker, F.; Gerl, J. [Gesellschaft fuer Schwerionenforschwg, D-64291 Darmstadt (Germany); Blank, B.; Hannachi, F. [CEN Bordeaux-Gradignan, IN2P3-CNRS, F-33175 Gradignan Cedex (France)] [and others

2005-04-05

8

Shape coexistence in neutron-deficient krypton isotopes  

Microsoft Academic Search

Shape coexistence in the light krypton isotopes was studied in two low-energy Coulomb excitation experiments using radioactive Kr74 and Kr76 beams from the SPIRAL facility at GANIL. The ground-state bands in both isotopes were populated up to the 8+ state via multi-step Coulomb excitation, and several non-yrast states were observed. Large sets of matrix elements were extracted for both nuclei

E. Clment; A. Grgen; W. Korten; E. Bouchez; A. Chatillon; J.-P. Delaroche; M. Girod; H. Goutte; A. Hrstel; Y. Le Coz; A. Obertelli; S. Pru; Ch. Theisen; J. N. Wilson; M. Zielinska; C. Andreoiu; F. Becker; P. A. Butler; J. M. Casandjian; W. N. Catford; T. Czosnyka; G. De France; J. Gerl; R.-D. Herzberg; J. Iwanicki; D. G. Jenkins; G. D. Jones; P. J. Napiorkowski; G. Sletten; C. N. Timis

2007-01-01

9

Shape coexistence in neutron-deficient krypton isotopes  

Microsoft Academic Search

Shape coexistence in the light krypton isotopes was studied in two low-energy Coulomb excitation experiments using radioactive Kr and Kr beams from the SPIRAL facility at GANIL. The ground-state bands in both isotopes were populated up to the 8{sup +} state via multi-step Coulomb excitation, and several non-yrast states were observed. Large sets of matrix elements were extracted for both

E. Clement; A. Goergen; W. Korten; E. Bouchez; A. Chatillon; A. Huerstel; Y. Le Coz; A. Obertelli; Ch. Theisen; J. N. Wilson; J.-P. Delaroche; M. Girod; H. Goutte; S. Peru; M. Zielinska; C. Andreoiu; P. A. Butler; R.-D. Herzberg; D. G. Jenkins; G. D. Jones

2007-01-01

10

Krypton isotope analysis using near-resonant stimulated Raman spectroscopy  

SciTech Connect

A method for measuring low relative abundances of {sup 85}Kr in one liter or less samples of air has been under development here at Pacific Northwest Laboratory. The goal of the Krypton Isotope Laser Analysis (KILA) method is to measure ratios of 10{sup {minus}10} or less of {sup 85}Kr to more abundant stable krypton. Mass spectrometry and beta counting are the main competing technologies used in rare-gas trace analysis and are limited in application by such factors as sample size, counting times, and selectivity. The use of high-resolution lasers to probe hyperfine levels to determine isotopic abundance has received much attention recently. In this study, we report our progress on identifying and implementing techniques for trace {sup 85}Kr analysis on small gas samples in a static cell as well as limitations on sensitivity and selectivity for the technique. High-resolution pulsed and cw lasers are employed in a laser-induced fluorescence technique that preserves the original sample. This technique, is based on resonant isotopic depletion spectroscopy (RIDS) in which one isotope is optically depleted while preserving the population of a less abundant isotope. The KILA method consists of three steps. In the first step, the 1s{sub 5} metastable level of krypton is populated via radiative cascade following two-photon excitation of the 2p{sub 6} energy level. Next, using RBDS, the stable krypton isotopes are optically depleted to the ground state through the 1s{sub 4} level with the bulk of the {sup 85}Kr population being preserved. Finally, the remaining metastable population is probed to determine {sup 85}Kr concentration. The experimental requirements for each of these steps are outlined below.

Whitehead, C.A.; Cannon, B.D.; Wacker, J.F.

1994-12-01

11

On the Production of Krypton Isotopes by Galactic Protons  

Microsoft Academic Search

The production of krypton isotopes from target elements Rb (Rb2SO4), Sr (SrF2), Y, Zr and of xenon in Ba (Ba glass), La (LaF2) have been studied in a simulation experiment. This investigation is part of the experiment LNS 172 by which a 50-cm- diameter artificial meteoroid (gabro) was isotropically irradiated at SATURNE with 1.6-GeV protons to simulate the galactic cosmic

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

1992-01-01

12

Isotope shifts and nuclear charge radii of krypton isotopes across the N=50 shell closure  

Microsoft Academic Search

Optical isotope shifts have been measured in the 5s[3\\/2]02-5p[3\\/2]2 transition in atomic krypton (lambda=760 nm) using collinear-fast-beam laser spectroscopy. Isotope shifts were determined for the short-lived neutron-rich isotopes 88Kr and 90Kr, as well as for all the stable isotopes between A=78 and 86, thus extending the data in this element, for the first time, beyond the N=50 shell closure. The

H. A. Schuessler; A. Alousi; R. M. Evans; M. Brieger; F. Buchinger; Y. F. Li

1990-01-01

13

Shape Coexistence in Light Krypton Isotopes  

Microsoft Academic Search

Coexisting states of prolate and oblate shapes were studied via Coulomb excitation of radioactive 74Kr and 76Kr beams at safe energies at GANIL. The results for the transitional E2 matrix elements for several yrast transitions in both isotopes are in contradiction with the B(E2) values extracted from the lifetimes that are found in the literature. This motivated a new lifetime

A. Grgen; E. Clment; E. Bouchez; A. Chatillon; W. Korten; Y. Le Coz; Ch. Theisen; J. N. Wilson; C. Andreoiu; F. Becker; J. M. Casandjian; A. Dewald; G. de France; J. Gerl; J. Iwanicki; N. Marginean; B. Melon; R. Menegazzo; O. Mller; G. Sletten; C. Timis; D. Tonev; C. A. Ur; K. O. Zell; M. Zielinska

2005-01-01

14

Isotopes of tellurium, xenon and krypton in Allende meteorite retain record of nucleosynthesis  

Microsoft Academic Search

Various mixtures of r-, p- and s-nucleosynthesis products have been observed in the isotopes of tellurium, xenon and krypton extracted from mineral separates of the Allende meteorite. The presence of several isotopically distinct components in these high Z elements and the close association of isotopically normal low Z elements with particular isotopes of the high Z elements suggest that our

R. V. Ballad; L. L. Oliver; R. G. Downing; O. K. Manuel

1979-01-01

15

Estimation of neutron-induced spallation yields of krypton isotopes  

NASA Astrophysics Data System (ADS)

A procedure is outlined for estimating cross sections for neutron-induced spallation products relative to those for proton-induced reactions. When combined with known proton spallation systematics, it is demonstrated that cumulative yields for cosmogenically-important stable 84Kr and 86Kr isotopes are ~1.4 and ~2.8 times greater, respectively, for incident neutrons compared to protons at 0.2<=E<=3.0 GeV for nearby medium mass targets. Yields for lighter kryptons are relatively insensitive to the identity of the incident nucleon. NUCLEAR REACTIONS (n, spallation), 0.2<=En<=3.0 GeV, stable Kr product yield estimates from proton spallation systematics.

Karol, Paul J.; Tobin, Michael J.; Shibata, Seiichi

1983-10-01

16

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

Microsoft Academic Search

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

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

1995-01-01

17

Isotope shifts and nuclear charge radii of krypton isotopes across the N =50 shell closure  

SciTech Connect

Optical isotope shifts have been measured in the 5{ital s}(3/2){sub 2}{sup 0}--5{ital p}(3/2){sub 2} transition in atomic krypton ({lambda}=760 nm) using collinear-fast-beam laser spectroscopy. Isotope shifts were determined for the short-lived neutron-rich isotopes {sup 88}Kr and {sup 90}Kr, as well as for all the stable isotopes between {ital A}=78 and 86, thus extending the data in this element, for the first time, beyond the {ital N}=50 shell closure. The deduced changes in the nuclear charge radii show a decrease of the charge radius with increasing neutron number below {ital N}=50, and a much more rapid increase above it. A preliminary interpretation of the results is given in terms of the droplet model.

Schuessler, H.A.; Alousi, A.; Evans, R.M.; Brieger, M.; Buchinger, F.; Li, Y.F. (Department of Physics, Texas A M University, College Station, TX (USA) Foster Radiation Laboratory, McGill University, Montreal, Quebec (Canada))

1990-09-10

18

Production of Krypton and Xenon Isotopes by Galactic Protons  

Microsoft Academic Search

The production of krypton from target elements Rb (Rb(sub)2SO(sub)4), Sr (SrF(sub)2), Y, Zr, and of xenon in Ba (Ba glass), La (LaF(sub)3) is studied in a simulation experiment of the galactic cosmic-ray proton bombardment of stony meteoroids in space [1,2]. This investigation is part of the experiment LNS 172 by which a 50-cm-diameter artificial meteoroid (gabbro) was isotropically irradiated at

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

1993-01-01

19

Solubility of krypton, xenon and radon in polycarbonates. Application for measurement of their radioactive isotopes  

Microsoft Academic Search

Bisphenol-A polycarbonates have a high absorption ability for noble gases that can be employed for sampling and measurement of radioactive isotopes of these gases. In this report the solubility of krypton, xenon and radon in the specified polycarbonates is determined by measurement of 85Kr, 133Xe and 222Rn absorbed in polycarbonate specimens. The found solubility is used to develop a general

D. Pressyanov; K. Mitev; I. Dimitrova; S. Georgiev

2011-01-01

20

Isotopic analyses of krypton and xenon in fourteen stone meteorites  

Microsoft Academic Search

The concentrations and isotopic compositions of Kr and Xe in twelve chondrites and two achondrites have been determined. In addition to the trapped component, Kr and Xe produced by spallation and (n, v.\\/) reactions as well as fission and radiogenic Xe have been found. Because of the chemical uniformity of the ordinary chondrites the concentrations of spallation-produced Kr and Xe

O. Eugster; P. Eberhardt; J. Geiss

1969-01-01

21

Development of an improved detector for krypton-81 and other noble-gas isotopes  

SciTech Connect

Phase 1 studies focused on the annealing (transient melting) of silicon and germanium targets with a krypton-fluoride (KrF) excimer laser. A suitable target of a semiconducting material--as a means of storing noble gas atoms--is a key component of a device called the RISTRON for counting isotopes of a noble gas. A means for isotopic selective counting of atoms such as 39Ar for ocean water circulation studies and 81Kr for groundwater and ice-cap dating would be of considerable interest to earth scientists. In the RISTRON, ions are created by resonance ionization of neutral krypton atoms released from one of the targets by pulsed laser melting, and these ions are implanted in a second target after isotopic enrichment. The studies evaluated the space charge or plasma effects created as an undesirable by-product of the annealing of a semiconductor with a pulsed excimer laser. The studies showed that the space charge produced when either silicon or germanium is annealed with a KrF laser can be removed with modest electric fields in less than one microsecond.

Hurst, G.S.

1988-08-25

22

Krypton and argon isotope analysis by collinear fast beam diode laser spectroscopy  

SciTech Connect

Argon and Krypton ions are accelerated and focused through a Cs-vapour charge exchange cell. Neutral atoms in the emerging beam are optically excited from the metastable 1s5 state to the 2pg state by tunable cw diode lasers at 811.5nm. At 10keV beam energy the spectra of Ar and Kr are separated by {approx}0.5nm with counterpropagating beams and by less than 0.1 nm with copropagating beams. The absorption lines of the individual isotopes cover a spectral range of {approx}10GHz for each element. Linewidths of less than 100 MHz were observed.

Lehmann, Bernhard; Ludin, Andrea; Tschannen, Thomas [Physics Institute, University of Bern, Sidlerstr.5, CH-3012 Bern (Switzerland)

1995-04-01

23

Use of a Krypton Isotope for Rapid Ion Changeover at the Lawrence Berkeley Laboratory 88-Inch Cyclotron.  

National Technical Information Service (NTIS)

An isotope of krypton, Kr86, has been combined with a mix of Ar, Ne, and N ions at the electron cyclotron resonance (ECR) source, at the Lawrence Berkeley Laboratory cyclotron, to provide rapid ion changeover in Single Event Phenomena (SEP) testing. The n...

G. A. Soli D. K. Nichols

1989-01-01

24

Neutron Capture Cross Sections of the Krypton Isotopes and the S-Process Branching at sup 79 Se.  

National Technical Information Service (NTIS)

The input data for an analysis of the s-process branching at sup 79 Se have been significantly improved. The neutron capture cross sections for the stable krypton isotopes (except sup 86 Kr) were measured between 3 and 240 keV neutron energy. In addition,...

G. Walter B. Leugers F. Kaeppeler Z. Y. Bao D. Erbe

1984-01-01

25

The Measurement of the Partition Coefficient of Krypton between Brain Cortex and Blood by a Double Isotope Method  

Microsoft Academic Search

The brain cortex-blood partition coefficient for krypton has been estimated in dogs using a double isotope method. Allowance has been made for the blood content of the brain tissue. The average value of 091 6% for a blood haematocrit of 50% was obtained. This value compares favourably with the figure of 092 obtained by other workers using an autoradiographic technique

H. I. Glass; A. M. Harper

1962-01-01

26

Independent Yields of Krypton and Xenon Isotopes in Thermal-Neutron Fission of 235U. Observation of an Odd-Even Effect in the Element Yield Distribution  

Microsoft Academic Search

The fractional and independent fission yields of krypton isotopes (masses 87 to 94) and xenon isotopes (masses 137-143) produced in thermal-neutron fission of 235U were measured using a mass separator operating in an on-line mode with a fission source exposed to time-controlled neutron fluxes. The noble-gas isotopes were collected simultaneously at given times and each mass was measured separately. The

B. Ehrenberg; S. Amiel

1972-01-01

27

Long-term sedimentary recycling of rare sulphur isotope anomalies.  

PubMed

The accumulation of substantial quantities of O2 in the atmosphere has come to control the chemistry and ecological structure of Earth's surface. Non-mass-dependent (NMD) sulphur isotope anomalies in the rock record are the central tool used to reconstruct the redox history of the early atmosphere. The generation and initial delivery of these anomalies to marine sediments requires low partial pressures of atmospheric O2 (p(O2); refs 2, 3), and the disappearance of NMD anomalies from the rock record 2.32 billion years ago is thought to have signalled a departure from persistently low atmospheric oxygen levels (less than about 10(-5) times the present atmospheric level) during approximately the first two billion years of Earth's history. Here we present a model study designed to describe the long-term surface recycling of crustal NMD anomalies, and show that the record of this geochemical signal is likely to display a 'crustal memory effect' following increases in atmospheric p(O2) above this threshold. Once NMD anomalies have been buried in the upper crust they are extremely resistant to removal, and can be erased only through successive cycles of weathering, dilution and burial on an oxygenated Earth surface. This recycling results in the residual incorporation of NMD anomalies into the sedimentary record long after synchronous atmospheric generation of the isotopic signal has ceased, with dynamic and measurable signals probably surviving for as long as 10-100 million years subsequent to an increase in atmospheric p(O2) to more than 10(-5) times the present atmospheric level. Our results can reconcile geochemical evidence for oxygen production and transient accumulation with the maintenance of NMD anomalies on the early Earth, and suggest that future work should investigate the notion that temporally continuous generation of new NMD sulphur isotope anomalies in the atmosphere was likely to have ceased long before their ultimate disappearance from the rock record. PMID:23615613

Reinhard, Christopher T; Planavsky, Noah J; Lyons, Timothy W

2013-04-24

28

The longevity of the South Pacific isotopic and thermal anomaly  

USGS Publications Warehouse

The South Pacific is anomalous in terms of the Sr, Nd, and Pb isotope ratios of its hot spot basalts, a thermally enhanced lithosphere, and possibly a hotter mantle. We have studied the Sr, Nd, and Pb isotope characteristics of 12 Cretaceous seamounts in the Magellans, Marshall and Wake seamount groups (western Pacific Ocean) that originated in this South Pacific Isotopic and Thermal Anomaly (SOPITA). The range and values of isotope ratios of the Cretaceous seamount data are similar to those of the island chains of Samoa, Tahiti, Marquesas and Cook/Austral in the SOPITA. These define two major mantle components suggesting that isotopically extreme lavas have been produced at SOPITA for at least 120 Ma. Shallow bathymetry, and weakened lithosphere beneath some of the seamounts studied suggests that at least some of the thermal effects prevailed during the Cretaceous as well. These data, in the context of published data, suggest: 1. (1)|SOPITA is a long-lived feature, and enhanced heat transfer into the lithosphere and isotopically anomalous mantle appear to be an intrinsic characteristic of the anomaly. 2. (2)|The less pronounced depth anomaly during northwesterly plate motion suggests that some of the expressions of SOPITA may be controlled by the direction of plate motion. Motion parallel to the alignment of SOPITA hot spots focusses the heat (and chemical input into the lithosphere) on a smaller cross section than oblique motion. 3. (3)|The lithosphere in the eastern and central SOPITA appears to have lost its original depleted mantle characteristics, probably due to enhanced plume/lithosphere interaction, and it is dominated by isotopic compositions derived from plume materials. 4. (4)|We speculate (following D.L. Anderson) that the origin of the SOPITA, and possibly the DUPAL anomaly is largely due to focussed subduction through long periods of the geological history of the earth, creating a heterogeneous distribution of recycled components in the lower mantle. ?? 1991.

Staudigel, H.; Park, K. -H.; Pringle, M.; Rubenstone, J. L.; Smith, W. H. F.; Zindler, A.

1991-01-01

29

Zinc isotope anomalies. [In Allende meteorite  

SciTech Connect

The Zn isotope composition in refractory-element-rich inclusions of the Allende meteorite are determined. Typical inclusions contain normal Zn. A unique inclusion of the Allende meteorite shows an excess for Zn-66 of 16.7 + or - 3.7 eu (1 eu = 0.01 percent) and a deficit for Zn-70 of 21 + or - 13 eu. These results indicate the preservation of exotic components even for volatile elements in this inclusion. The observed excess Zn-66 correlates with excesses for the neutron-rich isotopes of Ca-48, Ti-50, Cr-54, and Fe-58 in the same inclusion. 32 refs.

Volkening, J.; Papanastassiou, D.A. (California Institute of Technology, Pasadena (USA))

1990-07-01

30

Krypton and argon isotope analysis by collinear fast beam diode laser spectroscopy  

Microsoft Academic Search

Argon and Krypton ions are accelerated and focused through a Cs-vapour charge exchange cell. Neutral atoms in the emerging beam are optically excited from the metastable 1s5 state to the 2pg state by tunable cw diode lasers at 811.5nm. At 10keV beam energy the spectra of Ar and Kr are separated by ?0.5nm with counterpropagating beams and by less than

Bernhard Lehmann; Andrea Ludin; Thomas Tschannen

1995-01-01

31

Isotopic anomalies in high Z elements: Uranium  

SciTech Connect

Uranium in terrestrial volcanic ejecta from mantle-related sources has been analyzed mass spectrometrically. The objective was to seek supporting evidence for or refutation isotopic variations reported by Fried et al. (1985) for some such samples. The possibility that terrestrial U is not of constant isotopic composition is extraordinary. If true, mechanisms for creating the variation must be sought and the lack of homogenization within the earth addressed. Samples of 100 grams or more were processed in order to minimize reagent and environmental (laboratory) blank interference and to permit isolation of large amounts (several to tens of ..mu..g) of U for the mass spectrometer (MS) measurements, which utilizes aliquots of /approximately/1 ..mu..g. Aliquants from four volcanic samples gave data which indicate enrichments of /sub 235/U ranging from 0.2% to 5.9% in the 235/238 ratio relative normal uranium ratios. These relative enrichments are consistent with, and in some cases, higher than the 0.18% enrichment reported by Fried et al. (1985) for two volcanic lava samples. However, we were not able to reproduce their results on the Kilauea lava for which they report 0.18% /sup 235/U enrichment. The relative error in our MS ratios is 0.05% -- 0.07%. 1 tab.

Jovanovic, S.; Reed, G.W. Jr.; Essling, A.M.; Rauh, E.G.; Graczyk, D.G.

1989-03-01

32

Iron isotope anomalies. [In carbonaceous meteorites  

SciTech Connect

Precise determinations of the Fe isotope abundances yield identical results for a terrestrial standard and for samples of carbonaceous meteorites. Fe-54/Fe-56 = 0.062669; Fe-57/Fe-56 = 0.023261 + or - 0.000002; and Fe-58/Fe-56 = 0.0031132 + or - 0.0000011 are found. Refractory element-rich inclusions from the Allende carbonaceous meteorite yield hints of deficits in Fe-57/Fe-56 of up to -3.9 + or - 2.6 parts in 10,000 and a hint of excess in Fe-58/Fe-56 of up to 27 + or - 11 parts in 10,000. One special (FUN) inclusion shows a large excess of 2.9 percent, uniquely attributable to Fe-58. This excess correlates with large excesses in the same inclusion in the neutron-rich isotopes Ca-48, Ti-50 and Cr-54. These results strengthen the evidence for an exotic nucleosynthetic component produced by neutron-rich, statistical equilibrium burning, and injected into the interstellar medium. 29 refs.

Voelkening, J.; Papanastassiou, D.A. (California Institute of Technology, Pasadena (USA))

1989-12-01

33

Neutron-rich Chromium Isotope Anomalies in Supernova Nanoparticles  

NASA Astrophysics Data System (ADS)

Neutron-rich isotopes with masses near that of iron are produced in Type Ia and II supernovae (SNeIa and SNeII). Traces of such nucleosynthesis are found in primitive meteorites in the form of variations in the isotopic abundance of 54Cr, the most neutron-rich stable isotope of chromium. The hosts of these isotopic anomalies must be presolar grains that condensed in the outflows of SNe, offering the opportunity to study the nucleosynthesis of iron-peak nuclei in ways that complement spectroscopic observations and can inform models of stellar evolution. However, despite almost two decades of extensive search, the carrier of 54Cr anomalies is still unknown, presumably because it is fine grained and is chemically labile. Here, we identify in the primitive meteorite Orgueil the carrier of 54Cr anomalies as nanoparticles (<100 nm), most likely spinels that show large enrichments in 54Cr relative to solar composition (54Cr/52Cr ratio >3.6 solar). Such large enrichments in 54Cr can only be produced in SNe. The mineralogy of the grains supports condensation in the O/Ne-O/C zones of an SNII, although a Type Ia origin cannot be excluded. We suggest that planetary materials incorporated different amounts of these nanoparticles, possibly due to late injection by a nearby SN that also delivered 26Al and 60Fe to the solar system. This idea explains why the relative abundance of 54Cr and other neutron-rich isotopes vary between planets and meteorites. We anticipate that future isotopic studies of the grains identified here will shed new light on the birth of the solar system and the conditions in SNe.

Dauphas, N.; Remusat, L.; Chen, J. H.; Roskosz, M.; Papanastassiou, D. A.; Stodolna, J.; Guan, Y.; Ma, C.; Eiler, J. M.

2010-09-01

34

NEUTRON-RICH CHROMIUM ISOTOPE ANOMALIES IN SUPERNOVA NANOPARTICLES  

SciTech Connect

Neutron-rich isotopes with masses near that of iron are produced in Type Ia and II supernovae (SNeIa and SNeII). Traces of such nucleosynthesis are found in primitive meteorites in the form of variations in the isotopic abundance of {sup 54}Cr, the most neutron-rich stable isotope of chromium. The hosts of these isotopic anomalies must be presolar grains that condensed in the outflows of SNe, offering the opportunity to study the nucleosynthesis of iron-peak nuclei in ways that complement spectroscopic observations and can inform models of stellar evolution. However, despite almost two decades of extensive search, the carrier of {sup 54}Cr anomalies is still unknown, presumably because it is fine grained and is chemically labile. Here, we identify in the primitive meteorite Orgueil the carrier of {sup 54}Cr anomalies as nanoparticles (<100 nm), most likely spinels that show large enrichments in {sup 54}Cr relative to solar composition ({sup 54}Cr/{sup 52}Cr ratio >3.6 x solar). Such large enrichments in {sup 54}Cr can only be produced in SNe. The mineralogy of the grains supports condensation in the O/Ne-O/C zones of an SNII, although a Type Ia origin cannot be excluded. We suggest that planetary materials incorporated different amounts of these nanoparticles, possibly due to late injection by a nearby SN that also delivered {sup 26}Al and {sup 60}Fe to the solar system. This idea explains why the relative abundance of {sup 54}Cr and other neutron-rich isotopes vary between planets and meteorites. We anticipate that future isotopic studies of the grains identified here will shed new light on the birth of the solar system and the conditions in SNe.

Dauphas, N. [Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States); Remusat, L.; Papanastassiou, D. A.; Guan, Y.; Ma, C.; Eiler, J. M. [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Chen, J. H. [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Roskosz, M.; Stodolna, J., E-mail: dauphas@uchicago.ed [Unite Materiaux et Transformations, Universite de Lille 1, CNRS UMR 8207, 59655 Villeneuve d'Ascq (France)

2010-09-10

35

Neutron-poor Nickel Isotope Anomalies in Meteorites  

NASA Astrophysics Data System (ADS)

We present new, mass-independent, Ni isotope data for a range of bulk chondritic meteorites. The data are reported as ?60Ni58/61, ?62Ni58/61, and ?64Ni58/61, or the parts per ten thousand deviations from a terrestrial reference, the NIST SRM 986 standard, of the 58Ni/61Ni internally normalized 60Ni/61Ni, 62Ni/61Ni, and 64Ni/61Ni ratios. The chondrites show a range of 0.15, 0.29, and 0.84 in ?60Ni58/61, ?62Ni58/61, and ?64Ni58/61 relative to a typical sample precision of 0.03, 0.05, and 0.08 (2 s.e.), respectively. The carbonaceous chondrites show the largest positive anomalies, enstatite chondrites have approximately terrestrial ratios, though only EH match Earth's composition within uncertainty, and ordinary chondrites show negative anomalies. The meteorite data show a strong positive correlation between ?62Ni58/61 and ?64Ni58/61, an extrapolation of which is within the error of the average of previous measurements of calcium-, aluminium-rich inclusions. Moreover, the slope of this bulk meteorite array is 3.003 0.166 which is within the error of that expected for an anomaly solely on 58Ni. We also determined to high precision (~10 ppm per AMU) the mass-dependent fractionation of two meteorite samples which span the range of ?62Ni58/61 and ?64Ni58/61. These analyses show that "absolute" ratios of 58Ni/61Ni vary between these two samples whereas those of 62Ni/61Ni and 64Ni/61Ni do not. Thus, Ni isotopic differences seem most likely explained by variability in the neutron-poor 58Ni, and not correlated anomalies in the neutron-rich isotopes, 62Ni and 64Ni. This contrasts with previous inferences from mass-independent measurements of Ni and other transition elements which invoked variable contributions of a neutron-rich component. We have examined different nucleosynthetic environments to determine the possible source of the anomalous material responsible for the isotopic variations observed in Ni and other transition elements within bulk samples. We find that the Ni isotopic variability of the solar system cannot be explained by mixing with a component of bulk stellar ejecta from either SN II, Wolf-Rayet or, an asymptotic giant branch source and is unlikely to result from bulk mixing of material from an SN Ia. However, variable admixture of material from the Si/S zone of an SN II can create all the characteristics of Ni isotope variations in solar system materials. Moreover, these characteristics can also be provided by an SN II with a range of masses from 15 to 40 M ?, showing that input from SN II is a robust source for Ni isotope variations in the solar system. Correlations of Ni isotope anomalies with O, Cr, and Ti isotope ratios and Pb/Yb in bulk meteorites suggest that the heterogeneous distribution of isotopic anomalies in the early solar system likely resulted from nebular sorting of chemically or physically different materials bearing different amounts of isotopes synthesized proximally to the collapse of the protosolar nebula.

Steele, Robert C. J.; Coath, Christopher D.; Regelous, Marcel; Russell, Sara; Elliott, Tim

2012-10-01

36

NEUTRON-POOR NICKEL ISOTOPE ANOMALIES IN METEORITES  

SciTech Connect

We present new, mass-independent, Ni isotope data for a range of bulk chondritic meteorites. The data are reported as {epsilon}{sup 60}Ni{sub 58/61}, {epsilon}{sup 62}Ni{sub 58/61}, and {epsilon}{sup 64}Ni{sub 58/61}, or the parts per ten thousand deviations from a terrestrial reference, the NIST SRM 986 standard, of the {sup 58}Ni/{sup 61}Ni internally normalized {sup 60}Ni/{sup 61}Ni, {sup 62}Ni/{sup 61}Ni, and {sup 64}Ni/{sup 61}Ni ratios. The chondrites show a range of 0.15, 0.29, and 0.84 in {epsilon}{sup 60}Ni{sub 58/61}, {epsilon}{sup 62}Ni{sub 58/61}, and {epsilon}{sup 64}Ni{sub 58/61} relative to a typical sample precision of 0.03, 0.05, and 0.08 (2 s.e.), respectively. The carbonaceous chondrites show the largest positive anomalies, enstatite chondrites have approximately terrestrial ratios, though only EH match Earth's composition within uncertainty, and ordinary chondrites show negative anomalies. The meteorite data show a strong positive correlation between {epsilon}{sup 62}Ni{sub 58/61} and {epsilon}{sup 64}Ni{sub 58/61}, an extrapolation of which is within the error of the average of previous measurements of calcium-, aluminium-rich inclusions. Moreover, the slope of this bulk meteorite array is 3.003 {+-} 0.166 which is within the error of that expected for an anomaly solely on {sup 58}Ni. We also determined to high precision ({approx}10 ppm per AMU) the mass-dependent fractionation of two meteorite samples which span the range of {epsilon}{sup 62}Ni{sub 58/61} and {epsilon}{sup 64}Ni{sub 58/61}. These analyses show that 'absolute' ratios of {sup 58}Ni/{sup 61}Ni vary between these two samples whereas those of {sup 62}Ni/{sup 61}Ni and {sup 64}Ni/{sup 61}Ni do not. Thus, Ni isotopic differences seem most likely explained by variability in the neutron-poor {sup 58}Ni, and not correlated anomalies in the neutron-rich isotopes, {sup 62}Ni and {sup 64}Ni. This contrasts with previous inferences from mass-independent measurements of Ni and other transition elements which invoked variable contributions of a neutron-rich component. We have examined different nucleosynthetic environments to determine the possible source of the anomalous material responsible for the isotopic variations observed in Ni and other transition elements within bulk samples. We find that the Ni isotopic variability of the solar system cannot be explained by mixing with a component of bulk stellar ejecta from either SN II, Wolf-Rayet or, an asymptotic giant branch source and is unlikely to result from bulk mixing of material from an SN Ia. However, variable admixture of material from the Si/S zone of an SN II can create all the characteristics of Ni isotope variations in solar system materials. Moreover, these characteristics can also be provided by an SN II with a range of masses from 15 to 40 M{sub Sun }, showing that input from SN II is a robust source for Ni isotope variations in the solar system. Correlations of Ni isotope anomalies with O, Cr, and Ti isotope ratios and Pb/Yb in bulk meteorites suggest that the heterogeneous distribution of isotopic anomalies in the early solar system likely resulted from nebular sorting of chemically or physically different materials bearing different amounts of isotopes synthesized proximally to the collapse of the protosolar nebula.

Steele, Robert C. J.; Coath, Christopher D.; Regelous, Marcel; Elliott, Tim [Bristol Isotope Group, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ (United Kingdom); Russell, Sara, E-mail: r.steele@uclmail.net [Meteoritics and Cosmic mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD (United Kingdom)

2012-10-10

37

Wolf-Rayet Stars and the Isotopic Anomaly Connection  

NASA Astrophysics Data System (ADS)

Isotopic anomalies are now known to be carried by high-temperature inclusions of primitive meteorites that formed from solar reservoirs out of equilibrium with the rest of the solar nebula, as well as by various types of grains (diamond, graphite, SiC) that are considered to be of circumstellar origin, and have survived the process of incorporation into the solar system (see e.g. [1] for a recent review). Such anomalies provide new clues to many important astrophysical problems, and raise the question of their nucleosynthetic origin. In fact, they offer the exciting perspective of confronting abundance observations with nucleosynthesis models for a very limited number of events, even possibly a single one. This situation is in marked contrast with the one encountered when trying to understand the bulk solar system composition. Up to now, Red Giant stars, massive mass loosing objects (of the Wolf-Rayet type), novae or supernovae have been proposed as possible contributors to the observed anomalies. In this paper, we revisit the role that could possibly be played in that respect by Wolf-Rayet (WR) stars. Wolf-Rayet stars are appealing isotopic anomaly contributors for many reasons. In particular (1) they are observed to loose mass at very large rates that can exceed 10^-5M solar masses yr^-l, the ejected material being contaminated with the products of hydrogen and helium burning, and (2) certain WR stars are known to make dust episodically in their winds [e.g., 2]. In addition, the role of WR stars would be well in line with the "bing-bang" model for the isotopic anomalies promoted by Reeves [3]. The aim of this contribution is to extent and update previous calculations [4,5] of the isotopic anomalies that could be carried by the wind of WR stars of various masses and initial compositions during different phases of their evolution, those anomalies possibly loading circumstellar WR grains. The calculation of the WR wind composition is performed on grounds of detailed stellar evolutionary models that incorporate extended nuclear reaction networks, as well as recent improvements in our knowledge of various basic physical ingredients, like mass loss rates, opacities, or nuclear reaction rates. Results will be presented for various radionuclides with lifetimes in excess of ~10^5 yr, which are considered to be responsible for certain observed anomalies, or which could lead to anomalies that remain unobserved at present. Isotopic patterns for the elements ranging from carbon to lead will also be presented. Those predictions will be confronted with existing data, or will help unravel cases of potential interest for further laboratory quest. References: [1] Harper C. L. Jr. (1992) In Nuclei in the Cosmos II (F. Kappeler and K. Wisshak, eds.), 113-126, IOP Publ. Co. [2] Williams P. M. et al. (1992) Mon. Not. R. Astron. Soc., 258, 461-475. [3] Reeves H. (1978) In Protostars and Planets (T. Gehrels, ed.), 339-426, Univ. of Arizona. [4] Arnould M. and Prantzos N. (1986) In Nucleosynthesis and Its Implications on Nuclear and Particle Physics, (J. Audouze and N. Mathieu, eds.), 363-372, Reidel. [5] Meynet G. and Arnould M. (1993) In Origin and Evolution of the Elements (N. Prantzos et al., eds.), Cambridge, in press.

Arnould, M.; Paulus, G.; Meynet, G.

1993-07-01

38

MULTIPLE ORIGINS OF NITROGEN ISOTOPIC ANOMALIES IN METEORITES AND COMETS  

SciTech Connect

Isotopic fractionation and mixing calculations compared with coupled hydrogen and nitrogen isotopic composition of organic molecules from primitive chondrites, interplanetary dust particles (IDPs), and comets C/1995 O1 (Hale-Bopp) and 81P/Wild2 reveal that meteoritic and cometary organic matter contains three different isotopic components of different origins. (1) A major component of carbonaceous chondrites, IDPs, and comets Hale-Bopp and Wild2 shows correlated H and N isotopic compositions attributable to isotope exchange between an organic matter of solar composition and a reservoir formed by ion-molecule reactions at T < 25 K under conditions where competing reactions are strongly inhibited, possibly in the final evolutionary stages of the presolar cloud core, or more likely in the coldest outer regions of the solar protoplanetary disk. (2) In carbonaceous chondrites, IDPs, and comet Wild2, this component is mixed with a {sup 15}N-rich component having identical {sup 15}N and D enrichments relative to the protosolar gas. Temperatures > 100 K deduced from the low D/H ratio and an anti-correlation between the abundance of this component and meteoritic age indicate a late origin in the solar protoplanetary disk. N{sub 2} self-shielding and the non-thermal nucleosynthesis of {sup 15}N upon irradiation are possible but unlikely sources of this component, and a chemical origin is preferred. (3) An interstellar component with highly fractionated hydrogen isotopes and unfractionated nitrogen isotopes is present in ordinary chondrites. A dominantly solar origin of D and {sup 15}N excesses in primitive solar system bodies shows that isotopic anomalies do not necessarily fingerprint an interstellar origin and implies that only a very small fraction of volatile interstellar matter survived the events of solar system formation.

Aleon, Jerome, E-mail: Jerome.Aleon@csnsm.in2p3.f [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CSNSM-CNRS-IN2 P3, Bat 104, Orsay Campus 91405 (France)

2010-10-20

39

The calcium isotopic anomaly in magnetic CP stars  

NASA Astrophysics Data System (ADS)

Chemically peculiar stars in the magnetic sequence can show the same isotopic anomaly in calcium previously discovered for mercury-manganese stars in the non-magnetic sequence. In extreme cases, the dominant isotope is the exotic 48Ca. Measurements of Ca II lines arising from 3d-4p transitions reveal the anomaly by showing shifts up to 0.2 for the extreme cases - too large to be measurement errors. We report measurements of miscellaneous objects, including two metal-poor stars, two apparently normal F-stars, an Am-star, and the N-star U Ant. Demonstrable anomalies are apparent only for the Ap stars. The largest shifts are found in rapidly oscillating Ap stars and in one weakly magnetic Ap star, HD 133792. We note the possible relevance of these shifts for the GAIA mission. Based on observations obtained at the European Southern Observatory, La Silla and Paranal, Chile (ESO programme Nos. 65.L-0316, 68.D-0254 and 266.D-5655).

Cowley, C. R.; Hubrig, S.

2005-03-01

40

Nucleosynthetic Nd isotope anomalies in primitive enstatite chondrites  

NASA Astrophysics Data System (ADS)

We carried out stepwise dissolutions of four primitive enstatite chondrites (EC) belonging to the EH subgroup. Large Nd isotope anomalies are found in the most refractory phases, dissolved using strong acids. Residues are characterized by excesses in 142Nd and deficits in 145Nd, 148Nd and 150Nd isotopes. The Nd anomalies measured in the ALHA77295 residue are even greater than those measured in the Murchison carbonaceous chondrite (CC) using a similar analytical technique (Qin et al., 2011). Once corrected for a common Sm/Nd evolution, the 142Nd excess in the ALHA77295 residue is equal to 700 ppm relative to the terrestrial standard value. The Nd isotope patterns measured in EC and CC residues can be adjusted to coincide by adding a small amount of an s-process-rich carrier phase such as SiC and 0.075% is required to fit the ALHA7795 residue. Small isotope differences still persist between these residues even if they can be considered similar within error. In enstatite chondrites, residues have a deficit in 150Nd similar to or smaller than that measured in 148Nd, whereas in SiC extracted from carbonaceous chondrites or in whole rock, the deficit in 150Nd is always greater than that in 148Nd. Moreover in a binary 142Nd-148Nd diagram, the best-fit lines obtained for leachates and residues from carbonaceous chondrites and enstatite chondrites have slightly different slopes. For the same 148Nd/144Nd ratio, the anomalous component in an enstatite chondrite has a higher 142Nd/144Nd ratio compared to carbonaceous chondrites, a feature already observed at the whole rock scale. Our results suggest that different chondrite groups sample different reservoirs of presolar grains formed in different environments. Assuming that the carrier of this anomalous component measured in residues of enstatite chondrites are SiC, our results may suggest that different meteorite parent bodies sample reservoirs of presolar SiC formed in different stellar environments. This could explain why ALHA77295, the sample which is the most enriched in presolar grains, has a bulk 142Nd isotope composition similar to the terrestrial value. Further investigation of enstatite chondrites is needed to test whether the isotope composition of the most refractory phases is similar to that measured in carbonaceous chondrites and in particular the 144Sm that is a p-process isotope only. Finally this study highlights the difficulty of interpreting the 142Nd excess in terrestrial samples relative to chondrites since incomplete mixing of nucleosynthetic material in the solar nebula creates significant 142Nd variation, as shown by ALHA77295.

Boyet, M.; Gannoun, A.

2013-11-01

41

ABSOLUTE YIELDS OF THE ISOTOPES OF XENON AND KRYPTON IN THE NEUTRON FISSION OF Pu239  

Microsoft Academic Search

Using isotope dilution techniques and mass spectrometry, absolute yields ; of the Xe and Kr isotopes in the neutron-induced fission of Pu²³⁹ were ; determined. Nine of these yields lead to cumulative yields of the respective ; mass chains 131, 132, 134, 136, 83, 84, 85, 86, and two give absolute independent ; yields of the shielded precursors in their

K. Fritze; C. C. McMullen; H. G. Thode

1959-01-01

42

ENDF/B-V Neutron Cross Section Evaluation for the Krypton Isotopes.  

National Technical Information Service (NTIS)

The evaluation of the neutron cross-section data for the six stable isotopes of Kr from 10 exp -5 eV to 20 MeV is described. These evaluations incorporate all the new data on these isotopes, including those on the resonance parameters, level schemes of th...

A. Prince

1979-01-01

43

Beyond relativistic mean-field studies of low-lying states in neutron-deficient krypton isotopes  

NASA Astrophysics Data System (ADS)

Background: Neutron-deficient krypton isotopes are of particular interest due to the coexistence of oblate and prolate shapes in low-lying states and the transition of the ground state from one dominate shape to another as a function of neutron number. Moreover, the onset of large E2 transition strength around 76Kr indicates the erosion of the N=40 subshell gap.Purpose: A detailed interpretation of these phenomena in neutron-deficient Kr isotopes requires the use of a method going beyond a mean-field approach that permits the determination of spectra and transition probabilities. The aim of this work is to provide a systematic calculation of low-lying states in the even-even 6886Kr isotopes and to understand the shape coexistence phenomenon and the onset of large collectivity around N=40 from beyond relativistic mean-field studies.Method: The starting point of our method is a set of relativistic mean-field plus BCS wave functions generated with a constraint on triaxial deformations (?,?). The excitation energies and electric multipole transition strengths of low-lying states are calculated by solving a five-dimensional collective Hamiltonian (5DCH) with parameters determined by the mean-field wave functions. To examine the role of triaxiality, a configuration mixing of both particle-number- and angular-momentum-projected axially deformed states is also carried out within the exact generator coordinate method based on the same energy density functional.Results: The energy surfaces, the excitation energies of 02+, 21+, and 22+ states, as well as the E0 and E2 transition strengths are compared with the results of similar 5DCH calculations but with parameters determined by the nonrelativistic mean-field wave functions, as well as with the available data. The results show a picture of oblate-triaxial-prolate shape transition. Coexistence of low-lying excited 0+ states is found to be a common feature in the neutron-deficient Kr isotopes. The underlying mechanism responsible for the shape coexistence is discussed.Conclusions: The main features of the low-spin spectra and the systematics of excitation energies and transition strengths in the neutron-deficient Kr isotopes are reproduced very well. The effects of dynamic correlations and triaxiality turn out to have important influences on the balance between the competing oblate and prolate states. An exact treatment of configuration mixing of particle-number- and angular-momentum-projected triaxial states is highly demanded to pin down these effects.

Fu, Y.; Mei, H.; Xiang, J.; Li, Z. P.; Yao, J. M.; Meng, J.

2013-05-01

44

Development of Resonant Photoionization Mass Spectrometer for Determination of Isotopic Compositions of Krypton  

NASA Astrophysics Data System (ADS)

An ultra sensitive resonance photoionization mass-spectrometer analysis of isotopic compositions of Kr is being developed. Nonlinear four-wave mixing is used to generate a VUV light for the first transition of three-color Kr ionization scheme.

Strashnov, I.; Blagburn, D. J.; Gilmour, J. D.

2008-03-01

45

Description of even-even Krypton isotopes by the Interacting Boson Approximation  

Microsoft Academic Search

Energy spectra andB(E2) values of the even-even Kr isotopes7482Kr have been analyzed in terms of the IBA-2 model of Otsuka, Arima and Iachello [6, 7]. We can reproduce the variation of collectivity along the isotope chain by means of a consistent set of 5 parameters, essentially only one of them has been varied with neutron number. The low lying 02+

U. Kaup; A. Gelberg

1979-01-01

46

Krypton hygrometer  

SciTech Connect

An improved spectroscopic hygrometer includes a krypton-filled source tube that produces emissions at 123.58 nm for selective absorption by water vapor in a gaseous sample. The method for measuring water vapor density requires generation of ultraviolet radiation from a krypton source, receipt of the radiation by a detector, and passage of a gaseous sample through the radiation that is directed to the detector. The krypton radiation has been found to be an effective source for hygrometry purposes, and a practical improvement over prior hydrogen sources.

Campbell, G. S.; Gauthier, R. V.; Tanner, B. D.

1985-07-02

47

Resonant Photoionization Mass Spectrometer for Determination of Isotopic Compositions of Krypton in Extraterrestrial Samples  

NASA Astrophysics Data System (ADS)

An ultra sensitive MS for determination of Kr has been developed. A four wave mixing in Xe is used for generation of vuv light necessary for the first resonant step of three color ionization scheme. Kr isotopic ratios of air samples and Stannern meteorite determined.

Strashnov, I.; Blagburn, D. J.; Gilmour, J. D.

2009-03-01

48

Capture cross section measurements of krypton and xenon isotopes and the fundamental parameters of the s-process  

SciTech Connect

The capture cross sections of Kr and Xe isotopes have been determined by a fast cyclic activation technique. The data were used to perform s-process calculations with phenomenological models. The weak and the main s-process component were studied. Astrophysical parameters were determined in the frame of the model, i.e., iron seed abundance, the neutron exposure, average number of neutrons captured by the iron seed, the temperature dependence of the neutron exposure, neutron density, temperature, and electron density. The solar abundances of Kr and Xe were determined. From the Kr-85 branching the pulse width of a pulsed s-process was estimated. The isotopic anomaly Xe-S, s-process Xe, was investigated. 51 refs.

Beer, H. (Kernforschungszentrum Karlsruhe GmbH (Federal Republic of Germany))

1991-07-01

49

Xenon and Krypton in the Bruderheim Meteorite  

Microsoft Academic Search

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

Craig Merrihue

1966-01-01

50

Strategy Analysis for Krypton-85 Waste Management.  

National Technical Information Service (NTIS)

Krypton-85 is a chemically inert, radioactive gas produced by fission of uranium or plutonium isotopes. Depending on the fuel cycle, krypton-85 production in nuclear reactors may range from approx. 200 to approx. 600 kCi/GW/sub e/-year. However, the EPA h...

D. A. Knecht R. A. Brown

1979-01-01

51

The isotopic homogeneity in the early solar system: Revisiting the CAI oxygen isotopic anomaly  

NASA Astrophysics Data System (ADS)

Since the first discovery of the mass-independently fractionated oxygen isotopes in anhydrous, high temperature Ca-Al rich inclusion minerals in carbonaceous meteorites (CAIs) by Clayton et al. (1), their common occurrence in primitive meteorites has generally been regarded to reflect some fundamental process prevalent in the early solar nebula. The CAI oxygen isotopic composition is uniquely characterized by (i) large mass independent isotopic fractionation and (ii) their isotopic data in an oxygen three isotope plot (?17O - ?18O (?17O ? {(17O/16O)/(17O/16O)SMOW - 1} 1000) yield nearly a straight line with a slope 1.0. In establishing these characteristics, ion microprobe analyses has played a central role, especially an isotopic mapping technique (isotopography) was crucial (e.g., 2). The extraordinary oxygen isotopic ratio in CAIs is widely attributed to the self-shielding absorption of UV radiation in CO, one of the dominant chemical compounds in the early solar nebula (3). However, the self-shielding scenario necessarily leads to the unusual prediction that a mean solar oxygen isotopic composition differs from most of planetary bodies including Earth, Moon, and Mars. If the self-shielding process were indeed responsible to the CAI oxygen isotopic anomaly, this would require a fundamental revision of the current theory of the origin of the solar system, which generally assumes the initial total vaporization of nebula material to give rise to isotopic homogenization. The GENESIS mission launched in 2001(4), which collected oxygen in the solar wind was hoped to resolve the isotopic composition of the Sun. However, because of difficulties in correcting for instrumental and more importantly for intrinsic isotopic fractionation between the SW and the Sun, a final answer is yet to be seen (5). Here, we show on the basis of the oxygen isotopic fractionation systematics that the self shielding hypothesis cannot explain the key characteristics of the CAI oxygen isotopic fractionation, that is, a slope = 1.0 linear array in an oxygen three isotope plot ?17O - ?18O. Therefore, the prediction of the self-shielding hypothesis that the solar oxygen isotopic composition must be different from planetary objects is not supported by the CAI oxygen isotopic data, and we think that the general homogeneity of isotopic composition in the early solar nebula is still a valid assumption. References [1] Clayton R.N. et al, Science, 182, 485-88, 1973. [2] Yurimoto H. et al. Applied Surface Science, 793, 203-204, 2003. [3] Clayton R., Nature 415, 317, 2002. [4] Burnett D.S. et al., Space Science Review, 105, 509-543, 2003. [5] McKeegan K. et al. 2009. Abstract #2494. 40th LPSC, 2009. [5] Wieler R. Meteoritics & Planetary Science, 44, A218, 2009. [|#22#|

Ozima, M.; Yamada, A.

2009-12-01

52

Molybdenum isotope anomalies in meteorites: Constraints on solar nebula evolution and origin of the Earth  

NASA Astrophysics Data System (ADS)

The early evolution of the solar nebula involved substantial transport of mass, resulting in mixing and homogenization of isotopically diverse materials that were contributed to the solar system from multiple stellar nucleosynthetic sources. The efficiency of this mixing, as well as its timescale can be quantified by determining nucleosynthetic isotope variations among meteorites and terrestrial planets. Here we present Mo isotopic data for a wide range of samples, including Ca-Al-rich inclusions, chondrites and differentiated meteorites, as well as martian and terrestrial samples. Most meteorites are depleted in s-process Mo relative to the Earth, and only the IAB-IIICD irons, angrites and martian meteorites have terrestrial Mo isotopic compositions. In contrast, most Ca-Al-rich inclusions are enriched in r-process Mo, but one inclusion is characterized by a large s-process deficit. Molybdenum isotopic anomalies in the bulk meteorites correlate with those in Ru exactly as predicted from nucleosynthetic theory, but no obvious correlation is apparent between Mo and Ni anomalies. Therefore, s-process Mo and Ru seem to be hosted in the same carrier, which must be distinct from the carrier responsible for isotopic anomalies in the Fe-group elements (Ni, Cr, Ti). Furthermore, the isotopic heterogeneity in Mo (and other elements) contrasts with the isotopic homogeneity for Hf and Os, indicating that different s-process carriers once existed in the early solar nebula and that only some of these were heterogeneously distributed. The Mo isotopic anomalies of meteorites and their components decrease over time and with increasing size of the parent bodies, providing evidence for a progressive homogenization of the solar nebula. However, the carbonaceous chondrites exhibit larger Mo anomalies than expected for their age, indicating that they received a greater portion of material from the outer solar system (where homogenization was slow) than other meteorite parent bodies and terrestrial planets.Compared to the meteorites, Earth is enriched in s-process Mo and must have accreted from material distinct from the meteorites. Combined Mo and O isotopic data show that the composition of the Earth cannot be reconstructed by any known combination of meteorites, implying that meteorites may be inappropriate proxies for the isotopic composition of the bulk Earth. This is exemplified by the covariation of 92Mo and 142Nd anomalies in chondrites, showing that the 142Nd deficit of chondrites compared to the accessible Earth may not unequivocally be interpreted as a signature of an early differentiation of the Earth. However, further high precision isotopic data are needed to evaluate the role of chondrites in defining the isotopic composition of the Earth.

Burkhardt, Christoph; Kleine, Thorsten; Oberli, Felix; Pack, Andreas; Bourdon, Bernard; Wieler, Rainer

2011-12-01

53

Model Calculations of Continuous-Wave Laser Ionization of Krypton.  

National Technical Information Service (NTIS)

This report describes modeling of a scheme that uses continuous-wave (CW) lasers to ionize selected isotopes of krypton with high isotopic selectivity. The models predict that combining this ionization scheme with mass spectrometric measurement of the res...

B. D. Cannon

1999-01-01

54

The chemistry of krypton  

Microsoft Academic Search

Krypton is the only noble gas other than xenon to give rise to isolable compounds in macroscopic amounts, although the chemistry of krypton is presently limited to the +2 oxidation state. The strong oxidant-fluorinator properties and thermal instabilities of krypton(II) compounds have posed considerable challenges to determining the extent to which the chemistries of krypton(II) and xenon(II) are analogous. Krypton(II)

John F. Lehmann; Hlne P. A. Mercier; Gary J. Schrobilgen

2002-01-01

55

NOx cycle and tropospheric ozone isotope anomaly: an experimental investigation  

NASA Astrophysics Data System (ADS)

The oxygen isotope composition of nitrogen oxides (NOx) in the atmosphere may be a useful tool for understanding the oxidation of NOx into nitric acid/nitrate in the atmosphere. A set of experiments were conducted to examine changes in isotopic composition of NOx due to O3-NOx photochemical cycling. At low NO2/O2 mixing ratios, NO2 becomes progressively and nearly equally enriched in 17O and 18O over time until it reaches a steady state with ?17O values of 40.6 1.9 and ?18O values of 84.2 4, relative to the isotopic composition of the O2 gas. As the mixing ratio increases, isotopic exchange between O atoms and O2 and NOx suppresses the isotopic enrichments. A kinetic model simulating the observed data shows that the isotope effects during ozone formation play a more dominant role compared to kinetic isotope effects during NO oxidation or exchange of NO2. The model results are consistent with the data when the NO + O3 reaction occurs mainly via the transfer of the terminal atom of O3. The model predicts that under tropospheric concentrations of the three reactants, the timescale of NOx isotopic equilibrium ranges from hours (ppbv mixing ratios) to days/weeks (pptv) and yields steady state ?17O and ?18O values of 46 and 115 respectively with respect to Vienna Standard Mean Ocean Water. Interpretation of tropospheric nitrate isotope data can now be done with the derived rate coefficients of the major isotopologue reactions at various pressures.

Michalski, G.; Bhattacharya, S. K.; Girsch, G.

2013-04-01

56

Anomalies  

SciTech Connect

Anomalies have a diverse impact on many aspects of physical phenomena. The role of anomalies in determining physical structure from the amplitude for decay to the foundations of superstring theory will be reviewed. 36 refs.

Bardeen, W.A.

1985-08-01

57

A search for nickel isotopic anomalies in iron meteorites and chondrites  

NASA Astrophysics Data System (ADS)

We report Ni isotopic data, for 58,60-62Ni, on (1) FeNi metal and sulfides in different groups of iron meteorites, (2) sulfides and a whole rock sample of the St. Sverin chondrite, and (3) chondrules from the Chainpur chondrite. We have developed improved, Multiple-Collector, Positive ion Thermal Ionization Mass Spectrometric (MC-PTIMS) techniques, with Ni + ionization efficiency at 1, and chemical separation techniques for Ni which reduce mass interferences to the 1 ppm level, so that no mass interference corrections need be applied, except for 64Ni (from 64Zn, at the 0.1 level), for which we do not report results. We normalize the data to 62Ni/ 58Ni to correct for mass dependent isotope fractionation. No evidence was found for resolved radiogenic or general Ni isotope anomalies at the resolution levels of 0.2 and 0.5 ?u (?u = 0.01%) for 60Ni/ 58Ni and 61Ni/ 58Ni, respectively. From the 56Fe/ 58Ni ratios and ?( 60Ni/ 58Ni) values, we calculate upper limits for the initial value of ( 60Fe/ 56Fe) 0 of (a) <2.7 10 -7 for Chainpur chondrules, (b) <10 -8 for the St. Sverin sulfide, and (c) <4 10 -9 for sulfides from iron meteorites. We measured some of the same meteorites measured by other workers, who reported isotopic anomalies in Ni, using Multiple-Collector, Inductively-Coupled Mass Spectrometry. Our results do not support the previous reports of Ni isotopic anomalies in sulfide samples from Mundrabilla by Cook et al. [Cook D. L., Clayton R. N., Wadhwa M., Janney P. E., and Davis A. M. (2008). Nickel isotopic anomalies in troilite from iron meteorites. Geophy. Res. Lett. 35, L01203] and in sulfides from Toluca and Odessa by Quitt et al. [Quitt G., Meier M., Latkoczy C., Halliday A. N., and Gunther D., (2006). Nickel isotopes in iron meteorites-nucleosynthetic anomalies in sulfides with no effects in metals and no trace of 60Fe. Earth Planet. Sci. Lett. 242, 16-25]. Hence, we find no need for specialized physical-chemical planetary processes for the preservation of different Ni isotope compositions, between FeNi metal and sulfides in the same iron meteorites, as proposed by the above reports nor for complex astrophysical scenarios to provide the very peculiar Ni isotope anomalies reported by these workers for sulfides.

Chen, J. H.; Papanastassiou, D. A.; Wasserburg, G. J.

2009-03-01

58

Anomalies.  

ERIC Educational Resources Information Center

|This theme issue on anomalies includes Web sites, CD-ROMs and software, videos, books, and additional resources for elementary and junior high school students. Pertinent activities are suggested, and sidebars discuss UFOs, animal anomalies, and anomalies from nature; and resources covering unexplained phenonmenas like crop circles, Easter Island,

Online-Offline, 1999

1999-01-01

59

Isotopic anomalies in organic nanoglobules from Comet 81P/Wild 2: Comparison to Murchison nanoglobules and isotopic anomalies induced in terrestrial organics by electron irradiation  

NASA Astrophysics Data System (ADS)

Nanoglobules are a form of organic matter found in interplanetary dust particles and primitive meteorites and are commonly associated with 15N and D isotopic anomalies that are suggestive of interstellar processes. We report the discovery of two isotopically-anomalous organic globules from the Stardust collection of particles from Comet 81P/Wild 2 and compare them with nanoglobules from the Murchison CM2 meteorite. One globule from Stardust Cometary Track 80 contains highly aromatic organic matter and a large 15N anomaly (? 15N = 1120). Associated, non-globular, organic matter from this track is less enriched in 15N and contains a mixture of aromatic and oxidized carbon similar to bulk insoluble organic material (IOM) from primitive meteorites. The second globule, from Cometary Track 2, contains non-aromatic organic matter with abundant nitrile ( sbnd C tbnd N) and carboxyl ( sbnd COOH) functional groups. It is significantly enriched in D (?D = 1000) but has a terrestrial 15N/ 14N ratio. Experiments indicate that similar D enrichments, unaccompanied by 15N fractionation, can be reproduced in the laboratory by electron irradiation of epoxy or cyanoacrylate. Thus, a terrestrial origin for this globule cannot be ruled out, and, conversely, exposure to high-energy electron irradiation in space may be an important factor in producing D anomalies in organic materials. For comparison, we report two Murchison globules: one with a large 15N enrichment and highly aromatic chemistry analogous to the Track 80 globule and the other only moderately enriched in 15N with IOM-like chemistry. The observation of organic globules in Comet 81P/Wild 2 indicates that comets likely sampled the same reservoirs of organic matter as did the chondrite parent bodies. The observed isotopic anomalies in the globules are most likely preserved signatures of low temperature (<10 K) chemistry in the interstellar medium or perhaps the outer regions of the solar nebula. In other extraterrestrial samples, D isotopic anomalies, but not those of 15N, may be explained in part by exposure to ionizing electron radiation.

De Gregorio, Bradley T.; Stroud, Rhonda M.; Nittler, Larry R.; Alexander, Conel M. O.'D.; Kilcoyne, A. L. David; Zega, Thomas J.

2010-08-01

60

Nickel isotopic anomalies in troilite from iron meteorites  

NASA Astrophysics Data System (ADS)

We measured nickel isotopes, via multicollector inductively coupled plasma mass spectrometry (MC-ICPMS), in troilite (FeS) from ten iron meteorites from both non-magmatic (IAB) and magmatic (IIAB, IIIAB, IVA) groups. These are the first reported measurements of 64Ni (the least abundant Ni isotope) in meteoritic sulfides. No excesses of 60Ni from the decay of the short-lived radionuclide 60Fe (t1/2 = 1.49 My) were found in any of the samples. Resolvable deficits in 60Ni were observed in five samples. These deficits are inconsistent with the effects from 60Fe decay, given the Fe/Ni ratios in these troilites. Also, variations were found in 61Ni and 64Ni in several samples. The variations in Ni isotopic compositions of these samples may be due to the preservation of a component within the troilite that is characterized by the nucleosynthetic signature expected for Ni produced either by a type II supernova or by an AGB star.

Cook, David L.; Clayton, Robert N.; Wadhwa, Meenakshi; Janney, Philip E.; Davis, Andrew M.

2008-01-01

61

Striking nitrogen isotope anomaly in the Bencubbin and Weatherford meteorites  

SciTech Connect

The stony-iron meteorites Bencubbin and Weatherford contain nitrogen with a ratio of nitrogen-15 to nitrogen-14 larger than normal by as much as a factor of 2. The excess nitrogen-15 may be due either to a nucleosynthetic origin or to extreme isotopic fractionation. In the former case, it may reflect failure to homogenize nitrogen-15 produced in nova explosions. In the latter case, it may reflect chemical processing at temperatures below 40 K in a presolar molecular cloud. 34 references.

Prombo, C.A.; Clayton, R.N.

1985-11-01

62

Oxygen isotope anomaly observed in water vapor from Alert, Canada and the implication for the stratosphere.  

PubMed

To identify the possible anomalous oxygen isotope signature in stratospheric water predicted by model studies, 25 water vapor samples were collected in 2003-2005 at Alert station, Canada (8230'N), where there is downward transport of stratospheric air to the polar troposphere, and were analyzed for ?(17)O and ?(18)O relative to Chicago local precipitation (CLP). The latter was chosen as a reference because the relatively large evaporative moisture source should erase any possible oxygen isotope anomaly from the stratosphere. A mass-dependent fractionation coefficient for meteoric waters, ?MDF(H2O) = 0.529 0.003 [2? standard error (SE)], was determined from 27 CLP samples collected in 2003-2005. An oxygen isotopic anomaly of ?(17)O = 76 16 ppm (2? SE) was found in water vapor samples from Alert relative to CLP. We propose that the positive oxygen isotope anomalies observed at Alert originated from stratospheric ozone, were transferred to water in the stratosphere, and subsequently mixed with tropospheric water at high latitudes as the stratospheric air descended into the troposphere. On the basis of this ground signal, the average ?(17)O in stratospheric water vapor predicted by a steady-state box model is ?40. Seven ice core samples (1930-1991) from Dasuopu glacier (Himalayas, China) and Standard Light Antarctic Precipitation did not show an obvious oxygen isotope anomaly, and Vienna Standard Mean Ocean Water exhibited a negative ?(17)O relative to CLP. Six Alert snow samples collected in March 2011 and measured at Laboratoire des Sciences du Climat et de l'Environnement, Gif sur Yvette, France, had (17)Oexcess of 45 5 ppm (2? SE) relative to Vienna Standard Mean Ocean Water. PMID:24009339

Lin, Ying; Clayton, Robert N; Huang, Lin; Nakamura, Noboru; Lyons, James R

2013-09-05

63

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

Microsoft Academic Search

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

E. Mazor; G. J. Wasserburg

1965-01-01

64

Model Calculations of Continuous-Wave Laser Ionization of Krypton  

SciTech Connect

This report describes modeling of a scheme that uses continuous-wave (CW) lasers to ionize selected isotopes of krypton with high isotopic selectivity. The models predict that combining this ionization scheme with mass spectrometric measurement of the resulting ions can be the basis for ultra-sensitive methods to measure {sup 85}Kr in the presence of a 10{sup 11} excess of the stable krypton isotopes. Two experimental setups are considered in this model: the first setup is for krypton as a static gas, the second is for krypton in an atomic beam. In the static gas experiment, for a total krypton press of 10{sup {minus}4} torr and 10 W of power in the cavity, the model predicts a total krypton ion current of 4.6 x 10{sup 8} s{sup {minus}1} and for a {sup 85}Kr/Kr of 10{sup {minus}11} a {sup 85}Kr ion current of 3.5 s{sup {minus}1} or about 10,000 per hour. The atomic beam setup allowed higher isotopic selectivity; the model predicts a {sup 85}Kr ion current of 18 s{sup {minus}1} or 65,000 per hour.

Bret D. Cannon

1999-07-27

65

Heavy Element Abundances and Isotope Anomalies in HR7775 and Chi LUPI  

NASA Astrophysics Data System (ADS)

Over the past few years a GTO team project hasobtained extensive GHRS echelle data of UV transitionsof heavy elements in the Hg-Mn stars chi Lupi andKappa Cancri. Isotopic anomalies, in which only theheaviest isotope of Hg, Pt and Tl is present, havebeen observed in chi Lupi, but are apparently absentin Kappa Cancri. Kappa Cancri is distinguished fromchi Lupi by both its higher effective temperature andits larger Mn abundance. To help constraintheoretical interpretations of the abundance andisotope anomalies, this program will observe the Hg-Mnstar HR7775, which has the same effective temperatureas chi-Lupi, but also has substantially higher Mn andBi abundances. Observations of HR 7775 will includelines of B III, S I, Au II and III, Pt I, II, and III,Hg II and III, Ru II, Zr III, Ge I, As I, Cd II, Gd III,Ta II, Sb II and N I. Additional observations ofchi Lupi will also be obtained including observationsof Bi III, Tl III, Cu II and Ir II.

Brandt, John

1995-07-01

66

Osmium isotopic constraints on the nature of the DUPAL anomaly from Indian mid-ocean-ridge basalts.  

PubMed

The isotopic compositions of mid-ocean-ridge basalts (MORB) from the Indian Ocean have led to the identification of a large-scale isotopic anomaly relative to Pacific and Atlantic ocean MORB. Constraining the origin of this so-called DUPAL anomaly may lead to a better understanding of the genesis of upper-mantle heterogeneity. Previous isotopic studies have proposed recycling of ancient subcontinental lithospheric mantle or sediments with oceanic crust to be responsible for the DUPAL signature. Here we report Os, Pb, Sr and Nd isotopic compositions of Indian MORB from the Central Indian ridge, the Rodriguez triple junction and the South West Indian ridge. All measured samples have higher (187)Os/(188)Os ratios than the depleted upper-mantle value and Pb, Sr and Nd isotopic compositions that imply the involvement of at least two distinct enriched components in the Indian upper-mantle. Using isotopic and geodynamical arguments, we reject both subcontinental lithospheric mantle and recycled sediments with oceanic crust as the cause of the DUPAL anomaly. Instead, we argue that delamination of lower continental crust may explain the DUPAL isotopic signature of Indian MORB. PMID:15343331

Escrig, S; Capmas, F; Dupr, B; Allgre, C J

2004-09-01

67

Simulation of the diurnal variations of the oxygen isotope anomaly (?17O) of reactive atmospheric species  

NASA Astrophysics Data System (ADS)

The isotope anomaly (?17O) of secondary atmospheric species such as nitrate (NO3-) or hydrogen peroxide (H2O2) has potential to provide useful constrains on their formation pathways. Indeed, the ?17O of their precursors (NOx, HOx etc.) differs and depends on their interactions with ozone, which is the main source of non-zero ?17O in the atmosphere. Interpreting variations of ?17O in secondary species requires an in-depth understanding of the ?17O of their precursors taking into account non-linear chemical regimes operating under various environmental settings. This article reviews and illustrates a series of basic concepts relevant to the propagation of the ?17O of ozone to other reactive or secondary atmospheric species within a photochemical box model. We present results from numerical simulations carried out using the atmospheric chemistry box model CAABA/MECCA to explicitly compute the diurnal variations of the isotope anomaly of short-lived species such as NOx and HOx. Using a simplified but realistic tropospheric gas-phase chemistry mechanism, ?17O was propagated from ozone to other species (NO, NO2, OH, HO2, RO2, NO3, N2O5, HONO, HNO3, HNO4, H2O2) according to the mass-balance equations, through the implementation of various sets of hypotheses pertaining to the transfer of ?17O during chemical reactions. The model results confirm that diurnal variations in ?17O of NOx predicted by the photochemical steady-state relationship during the day match those from the explicit treatment, but not at night. Indeed, the ?17O of NOx is "frozen" at night as soon as the photolytical lifetime of NOx drops below ca. 10 min. We introduce and quantify the diurnally-integrated isotopic signature (DIIS) of sources of atmospheric nitrate and H2O2, which is of particular relevance to larger-scale simulations of ?17O where high computational costs cannot be afforded.

Morin, S.; Sander, R.; Savarino, J.

2011-04-01

68

Update and improvement of the global krypton-85 emission inventory.  

PubMed

Krypton-85 is mainly produced in nuclear reactors by fission of uranium and plutonium and released during chopping and dissolution of spent fuel rods in nuclear reprocessing facilities. As noble gas it is suited as a passive tracer for evaluation of atmospheric transport models. Furthermore, research is ongoing to assess its quality as an indicator for clandestine reprocessing activities. This paper continues previous efforts to compile a comprehensive historic emission inventory for krypton-85. Reprocessing facilities are the by far largest emitters of krypton-85. Information on sources and calculations used to derive the annual krypton-85 emission is provided for all known reprocessing facilities in the world. In addition, the emission characteristics of two plants, Tokai (Japan) and La Hague (France), are analysed in detail using emission data with high temporal resolution. Other types of krypton-85 sources are power reactors, naval reactors and isotope production facilities. These sources contribute only little or negligible amounts of krypton-85 compared to the large reprocessing facilities. Taking the decay of krypton-85 into account, the global atmospheric inventory is estimated to about 5500 PBq at the end of 2009. The correctness if the inventory has been proven by meteorological simulations and its error is assumed to be in the range of a few percent. PMID:22858641

Ahlswede, Jochen; Hebel, Simon; Ross, J Ole; Schoetter, Robert; Kalinowski, Martin B

2012-08-02

69

THE SPONTANEOUS FISSION OF CALIFORNIUM254 IN TYPE I SUPERNOVAE AND ANOMALY IN THE ABUNDANCE OF THE ISOTOPES OF Te, Xe, AND Sm  

Microsoft Academic Search

The laws governlng the relative abundunce of isotopes and the anomaly in ; the abundance of the isotopes of tellurium and xenon are considered. An ; hypothesis is advanced explaining the anomalously great abundance of Te-128, Te-; 130, Xe-128, and Xe-131 by the addition of decay products of nuclei that arise ; due to the spontaneous fission of transuranium isotopes.

Selinov

1959-01-01

70

Ca ISOTOPE EFFECTS IN ORGUEIL LEACHATES AND THE IMPLICATIONS FOR THE CARRIER PHASES OF {sup 54}Cr ANOMALIES  

SciTech Connect

Primitive meteorites contain small {sup 40}Ca excesses, in addition to rare anomalies in {sup 48}Ca. Refractory inclusions from Vigarano and Allende have larger {sup 40}Ca and resolvable {sup 48}Ca anomalies. These results imply that Ca isotopic heterogeneities were still present in the early solar system at both the mineral and whole-rock scale. The absence of correlated Ca isotope anomalies in leachates from the CI1 chondrite Orgueil containing large {sup 54}Cr anomalies has implications on the origin of the Cr anomalies. {sup 54}Cr has to be produced either in massive stars during s-process nucleosynthesis without accompanying {sup 48}Ca or in particular zones in the rare Type Ia supernovae. In the latter case, {sup 54}Cr has been produced in a zone predominantly enriched in Cr and {sup 54}Cr and not mixed with other zones, or {sup 54}Cr has been produced together with other neutron-rich nuclides and there has been subsequent decoupling of this material in the star, in the solar system, or in the laboratory.

Moynier, Frederic; Podosek, Frank A.; Brannon, Joyce [Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St Louis, One Brookings Drive, St Louis, MO 63130 (United States); Simon, Justin I.; DePaolo, Donald J. [Center for Isotope Geochemistry, Department of Earth and Planetary Science, University of California, Berkeley, CA 94720 (United States); Meyer, Bradley S., E-mail: moynier@levee.wustl.ed, E-mail: fap@levee.wustl.ed, E-mail: jcbontravel@yahoo.co, E-mail: Justin.I.Simon@NASA.go, E-mail: depaolo@eps.berkeley.ed, E-mail: mbradle@clemson.ed [Department of Physics and Astronomy, Clemson University, 118 Kinard Laboratory, Clemson, SC 29634-0978 (United States)

2010-07-20

71

Investigating atmospheric transport processes using cosmogenic 35S and oxygen isotopic anomaly (?17O) in sulfate  

NASA Astrophysics Data System (ADS)

Sulfate aerosols have been recognized to possess hazardous impact on both climate and human health. Improved understanding of the SO2 residence time and sulfate aerosol transport is needed for assessing its influences on climate. Cosmogenically produced 35S (half-life~87 days)1 measurements have been used to understand the atmospheric transport process, boundary layer dynamics and its effect on the tropospheric SO2 oxidation rate constant. Our method involves determining 35S in gaseous SO2 and aerosol sulfate samples collected twice a week at Scripps Institute of Oceanography Pier (La Jolla, CA) for a year along with the determination of oxygen isotopes in both coarse and fine particle samples. The oxygen isotopes measurement in sulfate and 35S measurements were done by isotope ratio mass spectrometry and low-noise liquid scintillation spectroscopy2, respectively. The data show that 35S activity is significantly different for coarse and fine particles, with the latter possessing higher activity as it is mainly produced from the gas phase oxidation of SO2 at higher altitude. The fluctuation in 35S activity in fine particles indicates mixing of air masses from higher altitude. The coarse particles show nearly constant 35S activity which is either due to the constant uptake rate of SO2 by sea salt aerosol or the coagulation of fine particles together. The normalized activity 35S/S is about 5 times higher in both coarse and fine particles during Santa Ana wind event. Santa Ana wind is characterized by low humidity (<20%) and relatively high temperature and may have an impact on SO2 oxidation. We are investigating the sulfate oxygen isotope signature and the correlation between oxygen anomaly and 35S activity in sulfate. 1. Lal D., P. K. Malhotra, and B. Peters, On the production of radioisotopes in the atmosphere by cosmic radiation and their application in meteorology, J. Atmos. AndTerrest. Phys. 12, 306, 1958 2. Brother, L.A., G. Dominguez, A. Abramian, A. Corbin, Ben Bluen, and M. H. Thiemens, Otimized low-level liquid scintillation spectroscopy of 35S for atmospheric and biogeochemical chemistry applications, Proceedings National Acad. Sci. 107, 5311, 2010

Hill-Falkenthal, J. C.; Pandey, A.; Coupal, E.; Kim, S. D.; Dominguez, G.; Thiemens, M. H.

2010-12-01

72

Erosion during accretion: Consequences for planetary iron-silicate ratios and tungsten isotope anomalies  

NASA Astrophysics Data System (ADS)

The late stages of planetary accretion involve stochastic, large collisions [1]. Although such collisions are usually assumed to result in perfect mergers, many of the collisions may instead result in hit-and-run events [2, 3] or erosion of existing bodies' mantles [4]. Impact-related erosion can have profound consequences for the rate and style of accretion [5] and the bulk chemistries of terrestrial planets [6]. Here we present some preliminary investigations into the occurrence of erosional collisions during late-stage accretion and consequences for the bulk chemistry and isotopic characteristics of the resulting planets. We have performed a preliminary investigation into the nature of late-stage accretion using an N-body simulation in which the different possible collision outcomes are treated in a more realistic manner than hitherto. The simulation starts with 155 planetesimals of roughly lunar mass; at the end, four bodies remain with masses of 0.83, 0.62, 0.33, and 0.02 Mearth. Collisional efficiency is parametrized based on the results of [7]. The results of the collisions, especially highly disruptive collisions, are idealized in order to be computationally tractable; in particular, bodies smaller than a minimum mass are not permitted. To track the bulk compositional evolution of the bodies, we assume all are initially chondritic. We alter the bulk chemistry after an impact according to a scheme which is based on the assumption that mantle material is much more likely to be eroded than core material. We track the tungsten isotopic evolution of each body using the method of [8] and treat the extent of core-mantle equilibration as a free parameter. The stochastic nature of planetary accretion means that even with perfect mergers, the tungsten isotope anomaly (eW) of the final bodies will vary, due to variations in the timing of the impacts which create the final bodies. Irrespective of accretion style, the extent of core re-equilibration affects eW. Including the effects of impact erosion results in a larger spread in eW and an increase in the average eW. A range in values of silicate mass fraction is produced, supporting the idea that erosional accretion can cause changes in bulk chemistry [6]. Compared with simulations assuming perfect mergers, we find that the time required to complete terrestrial planet formation is longer (190 Myr). Due to the long formation time and the observed existence of tungsten isotopic anomalies preserved in terrestrial and meteoric samples, core-mantle equilibration was likely minor. Future work will include a more realistic model for fragment size distribution and a greater number of simulation runs. [1] O'Brien et al. (2006) Icarus 184, 39-58. [2] Asphaug et al. (2006) Nature 439, 155-160. [3] Kokubo & Genda (2010) ApJ 714, L21-L25. [4] Benz et al. (2007) Space Sci Rev 132, 189-202. [5] Chambers (2008) Icarus 198, 256-273. [6] O'Neill & Palme (2008) Phil Trans R Soc A 366, 4205-4238. [7] Asphaug (2009) Ann Rev Earth Planet Sci 37, 413-448. [8] Nimmo & Agnor (2006) EPSL 243, 26-43. [9] Agnor & Asphaug (2004) ApJ 613, L157-L160. [10] Kleine et al. (2009) GCA 75, 5150-5188.

Dwyer, C. A.; Nimmo, F.; Asphaug, E. I.; O'Brien, D. P.; Chambers, J.

2011-12-01

73

Improvement of the resonance ionization mass spectrometer performance for precise isotope analysis of krypton and xenon at the ppt level in argon  

Microsoft Academic Search

Resonance ionization mass spectrometry (RIMS) is an effective method for the isotope analysis of trace elements in terms of its insensitivity to isobaric interferences. In view of this advantage, RIMS has been proposed for application to the failed fuel detection and location (FFDL) system of the fast reactor. The principle of the FFDL technique using RIMS involves the isotope analysis

Yoshihiro Iwata; Chikara Ito; Hideki Harano; Takafumi Aoyama

2010-01-01

74

Measurements and kinetics modeling of the O2/CO2 dependence of the oxygen-17 isotope anomaly in carbon dioxide  

NASA Astrophysics Data System (ADS)

Ozone formed in the atmosphere and the laboratory is not only unusually enriched in the heavy rare isotopes of oxygen for the small difference in masses for 17O and 18O relative to 16O, but the enrichments are also non-mass-dependent, with a 17O anomaly of ?17O ? 40 per mil (where ?17O = ln17O - 0.52 x ln18O). Unusual kinetic isotope effects in the three-body ozone formation reaction were determined to be the source of the anomalous oxygen isotopic composition (Janssen et al., 1999, Mauersberger et al.,1999). Theoretical work has suggested that the observed non-mass-dependent enrichments emerge from dynamically driven, non-statistical effects resulting from the short lifetime of the rovibrationally excited O3* complex or its collisional stabilization to stable O3, particularly for the symmetric over the asymmetric isotopologues (e.g., Gao and Marcus 2001). Stratospheric CO2 also has an anomalous oxygen isotopic composition that is thought to be transferred from ozone by photolysis to form O(1D) followed by the O(1D)+CO2 isotope exchange reaction, although some have postulated that an additional anomalous isotope effect must also exist in at least one of the other reactions for this system (e.g., Shaheen et al. 2007). To further investigate the anomalous isotopic compositions ofCO2, we have conducted additional photochemical experiments measuring the enrichments of 17O and 18O in CO2 relative to O2 in irradiated mixtures of O2 and CO2. We then compared these and previous results from other laboratories with a photochemical kinetics model using both measured and derived kinetic isotope effects in ozone formation. Our model can quantitatively predict the enrichments and 17O anomaly in both ozone and CO2 without additional non-mass-dependent isotope effects for pressures and O2/CO2 mixing ratios relevant to the stratosphere. However, the model cannot predict the relative enrichments or isotope anomaly in CO2 for our or previous experiments at low O2/CO2 ratios, so a number of additional hypothetical mechanisms that have isotope effects with possible O2/CO2dependences were introduced into the model. While including some of these mechanisms does result in a decrease in the relative enrichments in CO2 as the O2/CO2 ratio decreases, none of the mechanisms in the model can predict the large change observed experimentally. While the underlying mechanism(s) of the O2/CO2 dependence thus remains an open question, the model results also point to additional measurements of the pressure and bath gas dependence of isotope effects in both ozone formation and other reactions in this system that could help to resolve the model-measurement discrepancies at higher pressures and at low O2/CO2 ratios.

Wiegel, A. A.; Boering, K. A.

2012-04-01

75

ISOTOPIC ANOMALIES IN PRIMITIVE SOLAR SYSTEM MATTER: SPIN-STATE-DEPENDENT FRACTIONATION OF NITROGEN AND DEUTERIUM IN INTERSTELLAR CLOUDS  

SciTech Connect

Organic material found in meteorites and interplanetary dust particles is enriched in D and {sup 15}N. This is consistent with the idea that the functional groups carrying these isotopic anomalies, nitriles and amines, were formed by ion-molecule chemistry in the protosolar nebula. Theoretical models of interstellar fractionation at low temperatures predict large enrichments in both D and {sup 15}N and can account for the largest isotopic enrichments measured in carbonaceous meteorites. However, more recent measurements have shown that, in some primitive samples, a large {sup 15}N enrichment does not correlate with one in D, and that some D-enriched primitive material displays little, if any, {sup 15}N enrichment. By considering the spin-state dependence in ion-molecule reactions involving the ortho and para forms of H{sub 2}, we show that ammonia and related molecules can exhibit such a wide range of fractionation for both {sup 15}N and D in dense cloud cores. We also show that while the nitriles, HCN and HNC, contain the greatest {sup 15}N enrichment, this is not expected to correlate with extreme D enrichment. These calculations therefore support the view that solar system {sup 15}N and D isotopic anomalies have an interstellar heritage. We also compare our results to existing astronomical observations and briefly discuss future tests of this model.

Wirstroem, Eva S.; Cordiner, Martin A.; Charnley, Steven B.; Milam, Stefanie N., E-mail: ewirstrom@gmail.com [Astrochemistry Laboratory and Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Greenbelt, MD 20770 (United States)

2012-09-20

76

Cross sections for the proton-induced production of krypton isotopes from Rb, Sr, Y, and Zr for energies up to 1600 MeV  

Microsoft Academic Search

The production by proton-induced reactions of stable and long-lived Kr-isotopes from Rb, Sr, Y, and Zr was investigated by using isotope dilution mass spectrometry of targets irradiated at PSI\\/CH, TSL\\/S and LNS\\/F. Cumulative cross sections were determined for energies between 81 and 1600 MeV, between 15.4 and 1600 MeV, and between 70 and 1600 MeV for the target element Rb,

E. Gilabert; B. Lavielle; S. Neumann; M. Gloris; R. Michel; Th. Schiekel; F. Sudbrock; U. Herpers

1998-01-01

77

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

National Technical Information Service (NTIS)

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

D. D. Sabu

1977-01-01

78

Mass-Independent Isotope Fractionation of Molybdenum and Ruthenium and the Origin of Isotopic Anomalies in Murchison  

Microsoft Academic Search

Dauphas et al.'s model for the nucleosynthetic origin of Mo and Ru anomalies in meteorites leaves the case of Murchison (CM2) unexplained. We explore the possibility that such a discrepancy is due to mass-independent effects controlled by nuclear field shift with, in particular, ``staggering'' between odd and even masses. We first demonstrate the existence of such mass-independent fractionation of Mo

Toshiyuki Fujii; Frdric Moynier; Philippe Telouk; Francis Albarde

2006-01-01

79

Hyperfine anomaly in Be isotopes in the cluster model and the neutron spatial distribution  

SciTech Connect

The study of the hyperfine anomaly of neutron rich nuclei, in particular, neutron halo nuclei, can give a very specific and unique way to measure their neutron distribution and confirm a halo structure. The hyperfine structure anomaly in Be{sup +} ions is calculated with a realistic electronic wave function, obtained as a solution of the Dirac equation. In the calculations, the Coulomb potential modified by the charge distribution of the clustered nucleus and three electrons in the 1s{sup 2}2s configuration is used. The nuclear wave function is obtained in the core+nucleon model of {sup 9,11}Be. The aim of this study is to test whether the hyperfine structure anomaly reflects a halo structure in {sup 11}Be.

Parfenova, Y.; Leclercq-Willain, Ch. [Physique Nucleaire Theorique et Physique Mathematique, CP229, Universite Libre de Bruxelles, B-1050 Brussels (Belgium)

2005-08-01

80

Oxygen Isotopic Anomaly in Terrestrial Atmospheric Carbonates and its Implications to Understand the Role of Water on Mars  

NASA Astrophysics Data System (ADS)

Mineral aerosols produced from wind-blown soils are an important component of the earth system and comprise about 1000-3000 Tg.yr-1 compared to 400 Tg.yr-1 of secondary aerosols (e.g. carbonaceous substances, organics, sulfate and nitrates). Aerosols have important consequences for health, visibility and the hydrological cycle as they provide reactive surfaces for heterogeneous chemical transformation that may influence gas phase chemistry in the atmosphere. Tropospheric ozone produced in a cascade of chemical reactions involving NOx and VOCs, can interact with aerosol surfaces to produce new compounds. Oxygen triple isotopic compositions of atmospheric carbonates have been used for the first time to track heterogeneous chemistry at the aerosol surfaces and to resolve a chemical mechanism that only occurs on particle surfaces. Fine and coarse aerosol samples were collected on filter papers in La Jolla, CA for one week. Aerosol samples were digested with phosphoric acid and released CO2 was purified chromatographically and analyzed for O isotopes after fluorination. Data indicated oxygen isotopic anomaly (?17O = ?17O - 0.524 ?18O) ranging from 0.9 to 3.9 per mill. Laboratory experiments revealed that adsorbed water on particle surfaces facilitates the interaction of the gaseous CO2 and O3 with formation of anomalous hydrogen peroxide and carbonates. This newly identified chemical reaction scenario provides a new explanation for production of the isotopically anomalous carbonates found in the SNC Martian meteorites and terrestrial atmospheric carbonates and it also amplifies understanding of water related processes on the surface of Mars. The formation of peroxide via this heterogeneous reaction on aerosols surface suggests a new oxidative process of utility in understanding ozone and oxygen chemistry both at Mars and Earth.

Thiemens, M. H.; Shaheen, R.

2010-12-01

81

A burial diagenesis origin for the Ediacaran Shuram-Wonoka carbon isotope anomaly  

NASA Astrophysics Data System (ADS)

Marked negative ? 13C excursions in Ediacaran-age carbonate sediments have been identified in several sections globally, but are not recognized in all sections of similar age. The presence of ? 13C carb values as low as -12 has been interpreted as recording fundamentally different processes in the global carbon cycle than those recognized today. The ? 13C carb anomalies are strongly correlated with ? 18O carb values but are not represented in ? 13C org records. While no primary depositional processes have been identified that can produce the correlated ? 18O-? 13C arrays, simulations show that fluid-rock interaction with high- pCO 2 fluids is capable of producing such arrays at geologically reasonable pCO 2 and water-rock ratios. Variations in the Mg/Ca ratio and sulfate concentration of the altering fluid determine the extent of dolomite vs. calcite and anhydrite in the resulting mineral assemblage. Incorporation of an initially aragonitic mineralogy demonstrates that high Sr, low Mn/Sr and modest alteration of 87Sr/ 86Sr in ancient carbonates are all compatible with a burial diagenesis mechanism for generation of the ? 13C anomalies, and do not necessarily imply preservation of primary values. The profound Ediacaran negative ? 13C anomalies can be adequately explained by well-understood diagenetic processes, conflated with the difficulty of correlating Precambrian sections independently of chemostratigraphy. They are not a record of primary seawater variations and need not have independent stratigraphic significance.

Derry, Louis A.

2010-05-01

82

Tales of volcanoes and El-Nino southern oscillations with the oxygen isotope anomaly of sulfate aerosol.  

PubMed

The ability of sulfate aerosols to reflect solar radiation and simultaneously act as cloud condensation nuclei renders them central players in the global climate system. The oxidation of S(IV) compounds and their transport as stable S(VI) in the Earth's system are intricately linked to planetary scale processes, and precise characterization of the overall process requires a detailed understanding of the linkage between climate dynamics and the chemistry leading to the product sulfate. This paper reports a high-resolution, 22-y (1980-2002) record of the oxygen-triple isotopic composition of sulfate (SO4) aerosols retrieved from a snow pit at the South Pole. Observed variation in the O-isotopic anomaly of SO4 aerosol is linked to the ozone variation in the tropical upper troposphere/lower stratosphere via the Ozone El-Nio Southern Oscillations (ENSO) Index (OEI). Higher (17)O values (3.3, 4.5, and 4.2) were observed during the three largest ENSO events of the past 2 decades. Volcanic events inject significant quantities of SO4 aerosol into the stratosphere, which are known to affect ENSO strength by modulating stratospheric ozone levels (OEI = 6 and (17)O = 3.3, OEI = 11 and (17)O = 4.5) and normal oxidative pathways. Our high-resolution data indicated that (17)O of sulfate aerosols can record extreme phases of naturally occurring climate cycles, such as ENSOs, which couple variations in the ozone levels in the atmosphere and the hydrosphere via temperature driven changes in relative humidity levels. A longer term, higher resolution oxygen-triple isotope analysis of sulfate aerosols from ice cores, encompassing more ENSO periods, is required to reconstruct paleo-ENSO events and paleotropical ozone variations. PMID:23447567

Shaheen, Robina; Abauanza, Mariana; Jackson, Teresa L; McCabe, Justin; Savarino, Joel; Thiemens, Mark H

2013-02-27

83

Excitation rate and background measurements during LIF studies on krypton  

SciTech Connect

The Krypton Isotope Laser Analysis (KILA) method is being developed at the Pacific Northwest Laboratory (PNL) to measure [sup 85]Kr concentrations in small air samples. The technique uses high-resolution lasers to excite individual isotopes of krypton specifically to induce [sup 85]Kr to fluorescence for detection by optical means. Production of krypton metastables via two-photon excitation to the 2p[sub 6] state has been shown to be 0.15% efficient in 0.13 mTorr of krypton--sufficiently high to demonstrate overall feasibility of the KILA method. Since this goal was met, focus has been directed toward development of a working vacuum ultraviolet (VUV) fluorescence detection system and toward understanding the VUV background. This report describes the progress made in these two areas. The second step of the KILA process is to optically pump all except the [sup 85]Kr isotopes from the metastable state back to the ground state using laser-induced fluorescence (LIF). The rate of this process and the VUV background afterward will determine the sensitivity and selectivity of the KILA approach. De-excitation of the metastable population was accomplished via one-photon absorption of a continuous-wave (c-w) laser to the 2p[sub 8] energy level. Non-isotopically selective de-excitation rates as high as 5 [times] 10[sup 5] sec[sup [minus]1] have been measured, yielding a signal-to-background ratio of >10[sup 6]. The lifetime of the metastables is 1.2 msec in 200 mTorr of neon--much longer than the time required to de-excite krypton metastables and to detect fluorescence produced by [sup 85]Kr. After attaining these high de-excitation rates, a gated VUV detection system was built with a dynamic range large enough to measure a small background following de-excitation of large metastable populations. Future experiments will focus on reducing the background level by another 2--3 orders of magnitude and perfecting the isotopically selective de-excitation technique with known samples.

Whitehead, C.A.; Cannon, B.D.; Wacker, J.F.

1993-04-01

84

Experimental Investigation of Continuous-Wave Laser Ionization of Krypton  

SciTech Connect

This report describes experimental investigations of a method that uses continuous-wave (CW) lasers to ionize selected isotopes of krypton with high isotopic selectivity. The experiments show that the ionization rate is at least a factor of 100 lower than calculated with our model that has been described in a previous report. This discrepancy may be due to a much smaller excitation cross section that expected based on previous work and/or the aberrations in the ultraviolet beam used for the first step in the excitation. Additional problems with damage to mirrors, alignment instabilities, and manufacturers halting production of key products make this approach not worth further development at this time

Cannon, Bret D.; Shannon, Robert F.

2001-10-30

85

Hf-Nd isotope and trace element constraints on subduction inputs at island arcs: limitations of Hf anomalies as sediment input indicators  

NASA Astrophysics Data System (ADS)

New Nd-Hf isotope and trace element data for Javanese volcanoes are combined with recently published data to place constraints on subduction inputs at the Sunda arc in Indonesia and assess the value of Hf anomalies (expressed as Hf/Hf* and Sm/Hf ratios) as tracers of such inputs. Hf anomaly does not correlate with Hf isotope ratio in Javanese lavas however, Hf/Hf* and Sm/Hf ratios do correlate with SiO2. Contrary to previous work, we show that Hf anomaly variation may be controlled by fractionation of clinopyroxene and/or amphibole during magmatic differentiation and does not represent the magnitude or type of subduction input in some arcs. Correlation of Sm/Hf with indices of differentiation for other arcs (e.g. Vanuatu, New Britain, Mariana) suggests that differentiation control on Sm/Hf ratios of volcanic rocks may be a relatively common phenomenon. This study corroborates the use of Nd-Hf isotope co-variations in arc volcanic rocks to ascertain subduction input characteristics. The trajectories of regional volcano groups (East, Central and West Java) in Nd-Hf isotope space reveal heterogeneity in the subducted sediment input along Java, which reflects present-day spatial variations in sediment compositions on the down-going plate in the Java Trench.

Handley, H. K.; Turner, S.; MacPherson, C.; Davidson, J. P.; Gertisser, R.

2010-12-01

86

Silver isotopic anomalies in iron meteorites: cosmic-ray production and other possible sources  

SciTech Connect

The sources of excess /sup 107/Ag observed in iron meteorites by Kaiser, Kelly, and Wasserburg (1980) are examined, with emphasis on the reactions of cosmic-ray particles with palladium. The cross sections for the production of the silver isotopes from palladium by energetic cosmic-ray particles are evaluated or estimated and used to calculate spallogenic production rates relative to that of /sup 53/Mn from iron. The upper limit for the production rate of excess /sup 107/Ag by galactic-cosmic-ray particles is 400 atoms/min/kg(Pd) which, over an exposure age of 10/sup 9/ years, would make only 1% of the observed excesses of /sup 107/Ag. Neutron-capture reactions with Pd isotopes produce mainly /sup 109/Ag. Binary fission of a siderophilic superheavy element would be expected to yield more /sup 109/Ag than /sup 107/Ag. An intense proton irradiation in the early solar system probably would produce a lower ratio of (/sup 107/Pd//sup 108/Pd) to (/sup 26/Al//sup 27/Al) than observed in meteorites. Therefore the presence of excess /sup 107/Ag in iron meteorites with large Pd/Ag ratios very likely is due to the incorporation of 6.5 x 10/sup 6/-year /sup 107/Pd of nucleosynthetic origin in these meteorites.

Reedy, R.C.

1980-04-18

87

Evolution, Abundance and Biocalcification of Calcareous Nannoplankton During the Aptian (Early Cretaceous): Causes and Consequences for C Isotopic Anomalies, Climate Changes and the Carbon Cycle.  

NASA Astrophysics Data System (ADS)

The mid Cretaceous is marked by extreme greenhouse conditions, coeval with emplacement of large igneous provinces, C isotopic anomalies, major changes in structure and composition of the oceans, and accelerated rates in the evolutionary history of calcareous plankton. The Aptian is a crucial interval to decipher links between biotic evolution and environmental pressure: it is appealing for understanding nannofloral biocalcification and feedbacks in the carbonate system and in the global carbon cycle. Ontong Java, Manihiki and Kerguelen Plateaus formed in the Aptian affecting the ocean-atmosphere system with excess CO2, changes in Ca2+ and Mg2+ concentrations, and varying nutrient cycling. Two large C isotopic anomalies are associated with episodes of prolonged high primary productivity, changes in alkality, global warming and cooling, anoxia, speciations and extinctions in planktonic communities. Nannofossil diversity, abundance and biocalcification are quantified in continuous, complete, pelagic sections to derive biosphere-geosphere interactions at short and long time scales. The early Aptian C isotopic anomaly interrupts a speciation episode in calcareous nannoplankton paralleled by a drastic reduction in nannofossil paleofluxes culminating in the nannoconid crisis preceding the Oceanic Anoxic Event 1a and the negative C isotopic spike linked to clathrate melting presumably triggered by the thermal maximum at the onset of the mid Cretaceous greenhouse climate. No extinctions are recorded. In the early late Aptian resumption of nannoconid production and appearance of several taxa are coeval with a return to normal C isotopic values. The occurrence of calpionellids and diversified planktonic foraminifers indicate successful biocalcification and restoration of the thermocline. In the late Aptian a drop in nannofossil abundance and accelerated extinction rates are associated with another C isotopic excursion under cool conditions possibly due to a prolonged volcanic winter or reversed greenhouse conditions resulting from a draw-down of carbon dioxide after accelerated weathering and massive burial of organic carbon-rich sediments in the oceans.

Erba, E.

2005-12-01

88

Detection of residual krypton in xenon gas for WIMP dark matter searches  

NASA Astrophysics Data System (ADS)

The next generation of WIMP dark matter searches using liquid xenon as a target medium will require unprecedented rejection of residual krypton contamination. Krypton contains the beta emitting isotope ^85Kr, with a relative abundance of about 10-11 (^85Kr/^natKr), and this beta decay can be an important source of background for these experiments. Krypton is typically present in commercially produced xenon at the level of tens of parts-per-billion, about four orders of magnitude too large for present day dark matter experiments such as XENON, LUX, and XMASS. Additional processing via gas chromatography and distillation are used to separate krypton from xenon, but measuring the remaining krypton level at the part-per-trillion (ppt) level is challenging. Recently we have developed a highly sensitive and simple technique to measure residual krypton contamination in xenon gas using an RGA mass spectrometer and a liquid nitrogen cold trap. We describe here the results of our calibration experiments to determine the ultimate limit of detection of the method, and we discuss the implications for the next generation of WIMP dark matter experiments.

Dobi, Attila

2011-04-01

89

Spin relaxation in hyperpolarized krypton-83 and xenon-129  

NASA Astrophysics Data System (ADS)

The potential medical application of hyperpolarized (hp) krypton-83 (spin S = 9/2) [1] make a better insight into the NMR relaxation behavior of this isotope desirable, in particular since the relaxation limits the observed signal intensity but also provides a source for MRI contrast. The quadrupolar relaxation of krypton-83 is shown to be highly dependent on temperature, optical pumping gas mixture, the nature of surrounding surfaces and the applied magnetic field strength [2, 3]. The relaxation is mainly caused by quadrupolar interactions during brief surface adsorption periods of the krypton atoms onto the surrounding container walls. In contrast to xenon-129, interactions with paramagnetic impurities in the surface or with gas phase oxygen are not significant. 1) Pavlovskaya, et al. Proc. Natl. Acad. Sci. U.S.A.,2005. 102: 18275-18279; 2) Cleveland, Z.I., et al. J. Chem. Phys., 2006. 124(4) 044311; 3) Stupic, K.F et al. Solid State Nucl. Magn. Reson., 2006. 29: 79-84.

Meersmann, Thomas; Cleveland, Zackary; Stupic, Karl; Pavlovskaya, Galina

2007-03-01

90

Carbon isotope curve and iridium anomaly in the Albian-Cenomanian paleoceanic deposits of the Eastern Kamchatka  

NASA Astrophysics Data System (ADS)

We studied Albian-Cenomanian paleoceanic carbonate-siliceous deposits of the Kamchatsky Mys Peninsula (Eastern Kamchatka, Russia). They are deposited in association with pillow-basalts and hyaloclastites. The thickness of the studied section is about 10 m. The deposits are represented mainly by rhythmical intercalation of red-brown radiolarian jaspers, pink nannoplankton limestones as well as siliceous limestones. In the middle and upper parts of the section there are two beds enriched by organic carbon. The largest organic matter contents in this beds amount to 68%. The calculated values of the hydrogen and oxygen indexes indicate that the carbonaceous beds consist of marine organic matter. The accumulation of the carbonaceous beds reflects oxygen depletion in intermediate oceanic waters (ocean anoxic events, OAE). The structure of the studied section emphasizes its similarity to the contemporary deposits recovered by ODP and DSDP sites on Hess and Shatsky Rises. Two orders of rhythmicity were observed in the section. The rhythmicity of the first order (average thickness of a rhythm is 5-7 cm) is an alternation of reddish brown radiolarian jaspers and pink nannofossil limestones. The rhythmicity of the second order is characterized by an increase in thickness of the jasper or limy layer in every 4th-5th rhythm of the first order and marked by an elevation of the silica content in calcareous layers. The rhythmicity formation can be attributed to fluctuation of astronomical parameters (Milankovitch cycles) with periods of 21 and 100 kyr. The character of atmospheric circulation and ocean currents served as transmission link. The section was sampled layerwise and more than 100 samples were taken. The radiolarians were extracted from the samples of jaspers and siliceous limestones lying between carbonaceous beds. The educed radiolarian complexes allowed us to define the age of the deposits as Cenomanian. For more detailed dating of members of the section we have determined contents of carbon and oxygen stable isotopes in limestones and have compared the received results to isotope curves of other regions. In studied section the curve of d13C is characterized by a clearly expressed positive shift at the level of the lower carbonaceous bed. Below it and in the overlapping stratum of siliceous limestone (1 cm thickness) d13C has the values of 1.9-2.1 pro mille and above it d13C increases up to 2.5-3 pro mille. The precise d13C maximum after a sharp shift is correlatable with the form of a d13C curve of the Middle Cenomanian Tethyan sections. Accordingly, it is possible to assert, that the lower carbonaceous bed was formed during the mid-Cenomanian anoxic event (MCE). Gradual increase of d13C in the upper part of our section is similar to change of d13C in Upper Cenomanian fragments of Tethyan sections, i.e. the lower carbonaceous bed corresponds to anoxic event at the Cenomanian/Turonian boundary (OAE2). Neutron activation analysis indicates increased up to 9 ppb concentration of Ir at the bottom of the lower carbonaceous bed (inorganic part of the sample was analyzed comprising 46% of the bulk rock). This anomaly correlates in the studied section with a positive shift of d13C. Taking into account radiolarian age data this allows to correlate the anomaly with the MCE. A source of iridium and other elements of the platinum group could be basalts and hyaloclastites from the eruptions during the sedimentation period. Anoxic conditions promoted deposit enrichment in ore elements. This work was supported by the RFBR (No. 10-05-00065).

Savelyev, D. P.; Savelyeva, O. L.; Palechek, T. N.; Pokrovsky, B. G.

2012-04-01

91

The triple point of krypton  

NASA Astrophysics Data System (ADS)

Phase transitions of pure substances provide the key reference temperatures, otherwise known as "defining fixed points", of the International Temperature Scale. At temperatures below the triple point of mercury (234.3156 K), the substances involved are gases at room temperature and include the triple points of hydrogen (13.8033 K), neon (24.5561 K), oxygen (54.3584 K) and argon (83.8058 K). The Consultative Committee for Thermometry also provides a list of "secondary reference points" whose quality approaches (or is equivalent to) that of the defining fixed points of the ITS Here, we report direct measurements of the triple point of krypton on the ITS-90, review the historical measurements that CCT WG2 relied upon for its 1996 assessment, and demonstrate that the triple point of krypton is a "first quality" secondary reference point. Based on our measurements, the temperature of the triple point of krypton is 115.7755 K +/- 0.3 mK (k=1).

Hill, K. D.

2013-09-01

92

Hf-Nd isotope and trace element constraints on subduction inputs at island arcs: Limitations of Hf anomalies as sediment input indicators  

NASA Astrophysics Data System (ADS)

New Nd-Hf isotope and trace element data for Javanese volcanoes are combined with recently published data to place constraints on subduction inputs at the Sunda arc in Indonesia and assess the value of Hf anomalies (expressed as Hf/Hf* and Sm/Hf ratios) as tracers of such inputs. Hf anomaly does not correlate with Hf isotope ratio in Javanese lavas, however, Hf/Hf* and Sm/Hf ratios do correlate with SiO2. Contrary to previous work, we show that Hf anomaly variation may be controlled by fractionation of clinopyroxene and/or amphibole during magmatic differentiation and does not represent the magnitude or type of subduction input in some arcs. Correlation of Sm/Hf with indices of differentiation for other arcs (e.g., Vanuatu, New Britain, and Mariana) suggests that differentiation control on Sm/Hf ratios in volcanic arc rocks may be a relatively common phenomenon. This study corroborates the use of Nd-Hf isotope co-variations in arc volcanic rocks to ascertain subduction input characteristics. The trajectories of regional volcano groups (East, Central and West Java) in Nd-Hf isotope space reveal heterogeneity in the subducted sediment input along Java, which reflects present-day spatial variations in sediment compositions on the down-going plate in the Java Trench. The high Sm/Hf ratio required in the sediment end-member for some Javanese basalts suggests that partial melting of subducted sediment occurs in the presence of residual zircon, and is inconsistent with residual monazite or allanite.

Handley, Heather K.; Turner, Simon; MacPherson, Colin G.; Gertisser, Ralf; Davidson, Jon P.

2011-04-01

93

Geophysical problems of krypton-85 in the atmosphere  

SciTech Connect

The properties of krypton-85 as a radionuclide are examined with emphasis on its interaction with surrounding objects that influence geophysical processes occurring in the atmosphere. The discussion covers the principal physical and chemical characteristics of krypton-85, measurement of the krypton-85 concentration in the atmosphere; krypton-85 sources and sinks in the atmosphere, and the circulation and spread of krypton-85 in the atmosphere. Attention is also given to the possible influence of the additional ionization caused by krypton-85 on the geophysical processes in the atmosphere and the influence of krypton-85 on the earth's biological world. 190 refs.

Styra, B.I.; Butkus, D.; (AN LSSR, Institut Fiziki, Vilnius, Lithuanian SSR)

1991-01-01

94

High-resolution mass spectrometric study of pure helium droplets, and droplets doped with krypton  

NASA Astrophysics Data System (ADS)

Mass spectra of doped and undoped helium droplets are presented. The high resolution of the time-of-flight spectrometer ( m/ ?m ? 5000) makes it possible to fully resolve small helium cluster ions from impurities and to unambiguously identify abundance anomalies in the size distribution of He n +. The yield of He4 + shows the well-known enhancement relative to other small cluster ions when the expansion changes from sub- to supercritical, provided the electron energy exceeds a value of 40 1 eV, the threshold for formation of electronically excited ions. Upon doping with krypton, pure Kr n + cluster ions containing up to 41 Kr atoms are observed. The spectra exhibit abundance anomalies at 13, 16, 19, 22 & 23, 26 and 29, in agreement with spectra obtained by ionization of bare krypton clusters that are formed in neat supersonic beams. Mixed clusters He m Kr+ indicate closure of a solvation shell at m = 12.

Schbel, H.; Bartl, P.; Leidlmair, C.; Denifl, S.; Echt, O.; Mrk, T. D.; Scheier, P.

2011-07-01

95

Physical Properties and Heat Transfer Characteristics of Materials for Krypton-85 Storage.  

National Technical Information Service (NTIS)

Krypton-85 decay results in heat generation, and the subsequent temperature increase in the krypton-85 storage media must be evaluated. This report compiles the physical properties of krypton and of potential krypton-85 storage materials which are require...

A. B. Christensen

1977-01-01

96

Diffusion of Krypton85 in Dense Gases  

Microsoft Academic Search

With two high-pressure quasi-stationary diffusion cells, one depending upon ionization current measurement and the other scintillation detection of radioactive tracer activity, Fick's law diffusivities were determined for the diffusion of tracer amounts of krypton-85 in dense gases of krypton, argon, nitrogen, helium, carbon dioxide, and ethylene for isotherms about room temperature and densities to 15 mole\\/liter. In order to obtain

Leo Durbin; Riki Kobayashi

1962-01-01

97

Krypton  

Microsoft Academic Search

From the chemical composition of Galactic interstellar dust to the metallicity of QSO absorption line systems, solar system (photospheric and\\/or meteoritic) elemental abundances have served as the standard against which such measures have been compared and interpreted. However, recent analysis of the interstellar abundance of oxygen (Meyer et al. 1994), particularly in low density sight lines, has suggested that solar

J. A. Cardelli; D. M. Meyer

1995-01-01

98

Preferential site occupancy observed in coexpanded argon-krypton clusters  

SciTech Connect

Free heterogeneous argon-krypton clusters have been produced by coexpansion and investigated by means of x-ray photoelectron spectroscopy. By examining cluster surface and bulk binding energy shifts, relative intensities, and peak widths, we show that in the mixed argon-krypton clusters the krypton atoms favor the bulk and argon atoms are pushed to the surface. Furthermore, we show that krypton atoms in the surface layer occupy high-coordination sites and that heterogeneous argon-krypton clusters produced by coexpansion show the same surface structure as argon host clusters doped with krypton. These observations are supported by site-dependent calculations of chemical shifts.

Lundwall, M.; Bergersen, H.; Lindblad, A.; Oehrwall, G.; Svensson, S.; Bjoerneholm, O. [Department of Physics, Uppsala University, Box 530, SE-751 21 Uppsala (Sweden); Tchaplyguine, M. [MAX-lab, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden)

2006-10-15

99

Theoretical investigation of isotopic anomalies of xenon in terrestrial and extra-terrestrial samples. Final technical report, 1972--1977  

Microsoft Academic Search

The abundance and isotopic composition of noble gases in meteorites is discussed in relation to the composition of the early solar system. Carbonaceous chondrites contain a unique Xenon-X, which is rich in heavy and light isotopes. Variations in the occurrence of type-X and type-Y (the normal component) noble gases are of such magnitude that neither the injection of material from

Sabu

1977-01-01

100

SST Anomalies + Wind Anomalies  

NSDL National Science Digital Library

Sea surface temperature (SST) anomalies and sea surface wind anomalies show the development of the 2002-2003 El Nino based on data from NASAs Aqua and QuikSCAT spacecraft. The wind data has been processed using the Variational Analysis Method (VAM).

Shirah, Greg; Allen, Jesse; Adamec, David

2003-02-03

101

Measurements of isotope shift in visible lines of KrI by saturated-absorption techniques  

Microsoft Academic Search

The isotope shifts have been measured for all even isotopes of neutral krypton A=78 to 86 for the two visible lines lambda =557 and 556 nm by a Doppler-free saturated-absorption experiment. There is evidence for a non-regular position of the different isotopes which can be related to the variations of several nuclear properties along the series of krypton isotopes.

C. Brechignac

1977-01-01

102

Determination of Oxygen Self-Diffusion in Akermanite, Anorthite, Diopside, and Spinel: Implications for Oxygen Isotopic Anomalies and the Thermal Histories of Ca-Al-rich Inclusions  

NASA Astrophysics Data System (ADS)

Oxygen self-diffusion coefficients have been measured for three natural clinopyroxenes (diopside end member), a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic akermanite over oxygen fugacities ranging from the NNO to IW buffers. The experiments employed a gas-solid isotopic exchange technique utilizing 99% ^18O-enriched COCO2 gas mixtures to control both the oxygen fugacity and the isotopic composition of the exchange reservoir. Diffusion profiles of the ^18O tracer were obtained by in-depth analysis with an ion microprobe. The experimental results yield Arrhenius relations that appear here in the hard copy. At a given temperature, oxygen diffuses about 100 times more slowly in diopside than indicated by previous bulk-exchange experiments [1]. Our data for anorthite, spinel, and akermanite agree well with prior results obtained by gas-solid isotopic exchange and depth profiling methods [2-4]. Since these other experiments were conducted at different oxygen fugacities, this agreement indicates that diffusion of oxygen in these nominally iron-free minerals is not greatly affected by fO2 in the range between pure oxygen and the iron-wustite buffer. The oxygen diffusion data are used to evaluate the effects of three different types of therrnal histories upon the oxygen isotopic compositions of minerals found in Type B calciumaluminum-rich inclusions (CAIBs): (1) gas-solid exchange during isothermal heating, (2) gassolid exchange due to instantaneous heating followed by cooling at different rates, and (3) isotopic exchange with a gaseous reservoir during partial melting and recrystallization. With the assumptions that the mineral compositions within a CAIB were uniformly enriched in ^16O prior to any thermal processing, that effective diffusion dimensions may be estimated from observed grain sizes, and that diffusion in diopside is similar to that in fassaite, all the above scenarios fail to reproduce either the relative oxygen isotopic anomalies observed in CAIBs and/or yield improbably long or unrealistically intense thermal histories relative to both current theoretical models of nebular evolution and inferences from other isotopic systems. The failure of these simple models, coupled with recent observations of "disturbed" Mg isotopic abundances and petrographic features in anorthite and melilite indicative of alteration and recrystallization [5,6], suggests that the oxygen isotopic compositions of these phases may have also been modified by alteration and recrystallization during multiple melting events. Because the modal abundance of spinel remains relatively constant for plausible melting scenarios and its relatively sluggish diffusion kinetics prevent substantial equilibration, Mg-Al spinel is a reliable indicator of the oxygen isotopic composition of precursor material that formed CAIBs. References: [1] Connolly C. and Muehlenbachs K. (1988) GCA, 52, 1585-1592. [2] Elphick S. C. et al. (1988) Contrib. Mineral. Petrol., 100, 490-495. [3] Reddy K. P. and Cooper A. R. (1981) J. Am. Ceram. Soc., 64, 368-371. [4] Yunmoto H. et al. (1989) GCA, 53, 2387-2394. [5] Podosek F. A. et al. (1991) GCA, 55, 1083-1110. [6] MacPherson G. J. and Davis A. M. (1993) GCA, 57, 231-243.

Ryerson, F. J.; McKeegan, K. D.

1993-07-01

103

Theoretical Investigation of Isotopic Anomaly of Xenon in Carbonaceous Chondrites and Other Terrestrial and Extra-Terrestrial Samples.  

National Technical Information Service (NTIS)

The composition of Xe released from carbonaceous chondrites between 600 and 1000 C, particularly its isotopic trapped forms, is analyzed. Data show trapped Xe to have the following forms: Xe-124, 126, 130, 131, 132, 134, and 136. Attempts were also made t...

D. D. Sabu

1974-01-01

104

Hot subdwarf stars in close-up view. IV. Helium abundances and the 3He isotopic anomaly of subdwarf B stars  

NASA Astrophysics Data System (ADS)

Atmospheric parameters and helium abundances of 44 bright subdwarf B stars have been determined. More than half of our sample consists of newly discovered stars from the Edinburgh Cape survey. We showed that effective temperatures and surface gravities can be derived from high resolution echelle spectra with sufficient accuracy. Systematic uncertainties have been determined by comparing the parameters derived from the high resolution data with the ones derived from medium resolution spectra. Helium abundances have been measured with high accuracy. Besides the known correlation of helium abundance with temperature, two distinct sequences in helium abundance have been confirmed. Significant isotopic shifts of helium lines due to an enrichment in 3He have been found in the spectra of 8 subluminous B stars (sdBs). Most of these stars cluster in a small temperature range between 27 000 K and 31 000 K very similar to the known 3He-rich main sequence B stars, which also cluster in such a small strip, but at different temperatures. Both the helium sequences and the isotopic anomaly are discussed. Tables 1 and 2 and Appendix A are available in electronic form at http://www.aanda.org

Geier, S.; Heber, U.; Edelmann, H.; Morales-Rueda, L.; Kilkenny, D.; O'Donoghue, D.; Marsh, T. R.; Copperwheat, C.

2013-09-01

105

Solubilities of small molecules in liquid krypton  

SciTech Connect

Solubilities of MoF/sub 6/, CO/sub 2/, CH/sub 2/O, HN/sub 3/, and CH/sub 3/OH in liquid krypton have been measured over temperature intervals between 118 and 165 K. The solubilities at 140 K vary from approx. = 0.1 mol/L for CO/sub 2/ to approx. = 2 x 10/sup -4/ mol/L for HN/sub 3/. Relative solubilities of CCl/sub 4/ and SO/sub 2/ in liquid krypton have also been determined. The solubilities are compared with the Hildebrand-Preston-Prausnitz formalism of regular solution theory. Methanol is found to dissolve in liquid krypton as dimers or higher aggregates. Integrated cross sections have been measured for a few absorption features of the dissolved compounds.

Beattie, W.H.; Maier, W.B. II.; Freund, S.M.; Holland, R.F.

1982-01-01

106

Causes for negative carbon isotope anomalies in Mesozoic marine sediments : Constraints from modern and ancient anoxic settings  

Microsoft Academic Search

Oceanic Anoxic Events (OAEs) were short periods in Earth history (0.5-1 Ma) characterized by atypically high burial rates of organic carbon in marine sediments worldwide. OAEs reflect increased marine primary production and\\/or enhanced organic matter preservation under anoxic water column conditions, and caused the global atmospheric and marine carbon reservoirs to become enriched in 13C. Isotopic enrichments are typically recorded

Y. van Breugel

2006-01-01

107

Mineralogical characterization of a unique material having heavy oxygen isotope anomaly in matrix of the primitive carbonaceous chondrite Acfer 094  

NASA Astrophysics Data System (ADS)

We report the mineral compositions and micro-texture of the isotopically anomalous (? 17,18O SMOW +180) Fe-S-Ni-O material recently discovered in matrix of the primitive carbonaceous chondrite Acfer 094 [Sakamoto N., Seto Y., Itoh S., Kuramoto K., Fujino K., Nagashima K., Krot A. N. and Yurimoto H. (2007) Oxygen isotope evidence for remnants of the early solar system primordial water. Science317, 231-233]. Synchrotron radiation X-ray diffraction and transmission electron microscopy studies indicate that this material consists of the symplectitically intergrown magnetite (Fe 3O 4) and pentlandite (Fe 5.7Ni 3.3S 8) with magnetite/pentlandite volume ratio of 2.3. Magnetite forms column-shaped grains (10-30 nm in diameter and 100-200 nm in length); pentlandite occurs as worm-shaped grains or aggregates of grains 100-300 nm in size between magnetite crystals. Although both the X-ray diffraction and electron energy loss spectra support identification of iron oxide as magnetite, the electron diffraction patterns show that magnetite has a weak 3-fold superstructure, possibly due to ordering of vacancies. We infer that the isotopically anomalous symplectite formed by sulfurization and oxidization of metal grains either in the solar nebula or on an icy planetesimal. The intersite cation distribution of pentlandite suggests that timescale of oxidation was no longer than 1000 years.

Seto, Yusuke; Sakamoto, Naoya; Fujino, Kiyoshi; Kaito, Takashi; Oikawa, Tetsuo; Yurimoto, Hisayoshi

2008-06-01

108

Determination of oxygen self-diffusion in kermanite, anorthite, diopside, and spinel: Implications for oxygen isotopic anomalies and the thermal histories of Ca-Al-rich inclusions  

NASA Astrophysics Data System (ADS)

Oxygen self-diffusion coefficients have been measured for three natural diopsidic clinopyroxenes, a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic kermanite for oxygen fugacities ranging from the NNO to IW buffers. The experiments employed a gas-solid isotopic exchange technique utilizing 99% 18O-enriched CO-CO2 gas mixtures to control both the oxygen fugacity and the isotopic composition of the exchange reservoir. Diffusion profiles of the 18O tracer were obtained by in-depth analysis with an ion microprobe. The experimental results, fit to the Arrhenius relation D = D0e(-QRT), yield the following: Do (m2 s-1)Q (kJ mol-1)diopside4.3- 3.8+32.6 10 - 4457 26kermanite4.7- 4.4+83.5 10 - 7457 26278 33spinel2.2- 1.8+8.7 10 - 7404 21anorthite8.4- 8.0+174 10 - 13162 36At a given temperature, oxygen diffuses about 100 times more slowly in diopside than indicated by previous bulk-exchange experiments (CONNOLLY and MUEHLENBACHS, 1988). Our data for anorthite, spinel, and kermanite agree well with prior results obtained by gas-solid exchange and depth profiling methods (ELPHICK et al., 1988; REDDY and COOPER, 1981; YURIMOTO et al., 1989, respectively). Since these other experiments were conducted at different oxygen fugacities, this agreement indicates that diffusion of oxygen in these nominally Fe-free minerals is not greatly affected by fO2 in the range between pure oxygen and the iron-wstite buffer. However, our diffusion coefficients for anorthite, melilite, and spinel are also uniformly lower than those obtained by bulk analysis of crushed powders at similar temperatures (MUEHLENBACHS and KUSHIRO, 1974; HAYASHI and MUEHLENBACHS, 1986; ANDO and OISHI, 1974).The oxygen diffusion data are used to evaluate the effects of three different types of thermal histories upon the oxygen isotopic compositions of minerals found in Type B Ca-Al-rich inclusions (CAIBs) in carbonaceous chondrites: (1) gas-solid exchange during isothermal heating,(2) gas-solid exchange as a function of cooling rate subsequent to instantaneous heating, and(3) isotopic exchange with a gaseous reservoir during partial melting and recrystallization. With the assumptions that the mineral compositions within a CAIB were uniformly enriched in 16O prior to any thermal processing, that effective diffusion dimensions may be estimated from observed grain sizes, and that diffusion in diopside is similar to that in fassaitic clinopyroxene, none of the above scenarios can reproduce the relative oxygen isotopic anomalies observed in CAIBs without improbably long or unrealistically intense thermal histories relative to current theoretical models of nebular evolution. The failure of these simple models, coupled with recent observations of disturbed magnesium isotopic abundances and correlated petrographic features in anorthite and melilite indicative of alteration and recrystallization, suggests that the oxygen isotopic compositions of these phases may have also been modified by alteration and recrystallization possibly interspersed with multiple melting events. Because the modal abundance of spinel remains relatively constant for plausible melting scenarios, and its relatively sluggish diffusion kinetics prevent substantial equilibration, Mg-Al spinel is the most reliable indicator of the oxygen isotopic composition of precursor material which formed Type B CAIs.

Ryerson, F. J.; McKeegan, Kevin D.

1994-09-01

109

Chromium isotope anomaly in an impactite sample from the El'gygytgyn structure, Russia: Evidence for a ureilite projectile?  

NASA Astrophysics Data System (ADS)

The 3.6 Ma, 18-km-diameter El'gygytgyn impact structure (Arctic Russia) is unique among the currently known terrestrial impact craters in that it is the only one that was formed in acid volcanic rocks. Previous analyses of impactites from El'gygytgyn showed minor enrichments of the siderophile elements, including Ir, which, together with distinct Cr enrichments, gave rise to speculation that an achondritic projectile was involved. We studied the major and trace element composition in samples from the new ICDP drill core obtained near the center of the structure, as well as the chromium isotopic composition of an impact glass sample collected on the surface. Several suevitic breccias from the upper part of the suevite sequence in the drill core show higher Cr and Ni contents compared with felsic volcanic rocks in the lower part of the core and from surface samples. However, it is difficult to unambiguously establish a meteoritic component from trace element data, as input from (rare) mafic target rocks is a possibility. In contrast, the Cr isotopic composition of the impact glass sample yielded a nonterrestrial ?54Cr value of -0.72 0.31 (2 std. err.). This negative ?54Cr is different from known carbonaceous chondrite values (?54Cr of +0.95 to +1.65), but is nearly identical to reported values for ureilites (approximately -0.77). The value is, however, also within analytical error of eucrites (approximately -0.38) and ordinary chondrites (approximately -0.42). Given the chemical signatures found in previous analyses of El'gytgytgyn impactites and the similarity of our Cr isotopic data to ureilites, we suggest that the impacting asteroid could have been an F-type asteroid of mixed composition, similar to the recent Almahata Sitta fall in Sudan.

Foriel, Julien; Moynier, Frederic; Schulz, Toni; Koeberl, Christian

2013-07-01

110

Hyperpolarized krypton-83 as a contrast agent for magnetic resonance imaging.  

PubMed

For the first time, magnetic resonance imaging (MRI) with hyperpolarized (hp) krypton-83 (83Kr) has become available. The relaxation of the nuclear spin of 83Kr atoms (I = 9/2) is driven by quadrupolar interactions during brief adsorption periods on surrounding material interfaces. Experiments in model systems reveal that the longitudinal relaxation of hp 83Kr gas strongly depends on the chemical composition of the materials. The relaxation-weighted contrast in hp 83Kr MRI allows for the distinction between hydrophobic and hydrophilic surfaces. The feasibility of hp 83Kr MRI of airways is tested in canine lung tissue by using krypton gas with natural abundance isotopic distribution. Additionally, the influence of magnetic field strength and the presence of a breathable concentration of molecular oxygen on longitudinal relaxation are investigated. PMID:16344474

Pavlovskaya, Galina E; Cleveland, Zackary I; Stupic, Karl F; Basaraba, Randall J; Meersmann, Thomas

2005-12-12

111

10 CFR 30.19 - Self-luminous products containing tritium, krypton-85, or promethium-147.  

Code of Federal Regulations, 2010 CFR

...Self-luminous products containing tritium, krypton-85, or promethium-147. 30.19...Self-luminous products containing tritium, krypton-85, or promethium-147. (a...self-luminous products containing tritium, krypton-85, or promethium-147,...

2009-01-01

112

10 CFR 30.19 - Self-luminous products containing tritium, krypton-85, or promethium-147.  

Code of Federal Regulations, 2010 CFR

...Self-luminous products containing tritium, krypton-85, or promethium-147. 30.19...Self-luminous products containing tritium, krypton-85, or promethium-147. (a...self-luminous products containing tritium, krypton-85, or promethium-147,...

2010-01-01

113

HETEROGENEOUS ISOTOPIC ANOMALIES OF SM AND GD IN THE NORTON COUNTY METEORITE: EVIDENCE FOR IRRADIATION FROM THE ACTIVE EARLY SUN  

SciTech Connect

Large and heterogeneous isotopic variations of {sup 150}Sm/{sup 149}Sm and {sup 158}Gd/{sup 157}Gd due to neutron capture reactions caused by cosmic-ray irradiation were found in chemical and mineral separates from the Norton County meteorite. The light-colored separates, consisting mainly of enstatite (Mg{sub 2}Si{sub 2}O{sub 6}), have a very large neutron fluence of 1.98 Multiplication-Sign 10{sup 17} n cm{sup -2}, which is 10 times higher than that of the whole rock. Furthermore, four chemical separates showed a large variation in neutron fluences, ranging from 1.82 Multiplication-Sign 10{sup 16} to 1.87 Multiplication-Sign 10{sup 17} n cm{sup -2}. The variable amounts of neutron fluences from a small single fragment of the Norton County meteorite cannot be simply explained by single-stage cosmic-ray irradiation in space. Rare earth element (REE) analyses revealed that the fractions with high neutron fluences have similar chemical properties to those in the early condensates in the solar system, showing depletions of Eu and Yb in their REE abundance patterns. The data provide evidence for an activity of the early Sun (T Tauri), suggesting the migration of early and intense irradiation materials into the Norton County meteorite's parent body.

Hidaka, Hiroshi; Kondo, Tomoyo [Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Yoneda, Shigekazu, E-mail: hidaka@hiroshima-u.ac.jp [Department of Science and Engineering, National Museum of Nature and Science, Tokyo 169-0073 (Japan)

2012-02-20

114

Stable Isotope Anomalies and Low Chloride Concentrations in Pore Water of CH4-Rich Sediments at the Tanegashima Mud Volcano, Japan  

NASA Astrophysics Data System (ADS)

Pore water from sediments collected at a Tanegashima mud volcano was analyzed for ? 13C (PDB) of dissolved CH4 together with other chemical components, Cl- and SO42-, and the ? 18O and ? D (SMOW). The Tanegashima mud volcanoes are located at the water depths from 1400 m to 1800 m, off Tanegashima island between Ryukyu trench and Ryukyu arc of Japan. It is situated at the end of south-western convergent plate boundary on Nankai-trough, which forms a part of Philippine Sea plate subducting under Eurasian plate. This cruise was conducted as a part of the JNOC (Japan National Oil Corporation) geochemical survey by R/V Hakurei-maru II. The concentrations of CH4 were generally higher than 100 micro-mol/kg. Its highest concentration (715 micro-mol/kg) was found in the crest core of a mud volcano. The ? 13C values ranged from -32 to -50 . C2H6 was detected only in the pore waters collected from the vicinity of the crest of the mud volcano. The highest ? 13C (around -22 ) and low C1/C2 concentration ratios (less than 100) were measured at the crest site, supporting the thermogenical production of methane. Other geochemical anomalies were also observed in the crest pore water. The concentrations of Cl- in the pore water at this site were extremely depleted to a minimum of 350 mmol/kg. The Cl- anomaly has not been previously reported for pore water from mud volcanoes around Japan. An endmember of isotopic composition of the fluid is estimated to be +12 for ? 18O and -40 for ? D. From these results we conclude that the most likely process to reduce pore water salinity is primarily the mixing of clay mineral dehydration water with seawater. The thermogenic methane found in the crest pore waters of the Tanegashima mud volcano may be brought from the depths of sediments due to the migration of fluid evolved by mineral the dehydration process.

Nakayama, N.; Tsunogai, U.; Ashi, J.; Gamo, T.

2004-12-01

115

The argon and krypton interatomic potentials revisited  

Microsoft Academic Search

Accurate interatomic potentials are constructed which represent subtle but significant improvements for the argon and krypton interactions. The potentials are of the HFD-B form with definite advantages over the HFD-C form. These new potentials incorporate recent determinations of the C6 dispersion coefficient and accurately predict the best available spectroscopy, scattering and bulk data, some of which data were published after

Ronald A. Aziz; M. J. Slaman

1986-01-01

116

Continuously Recording Field Monitor for Krypton85  

Microsoft Academic Search

Krypton-85 from nuclear power generation is released to the atmosphere mainly during fuel reprocessing. The monitor described here is designed for use in the vicinity of these facilities. It is battery operated, resistant to weather exposure, and portable. Sensitivity has been verified in the field as 10-20 pCi\\/liter. The detector array uses two pairs of betasensitive dual window pancake GM

Robert T. Graveson; Harold Beck; Donald C. Freeswick

1975-01-01

117

Gravitational anomalies  

Microsoft Academic Search

The effective action for fermions moving in external gravitational and gauge fields is analyzed in terms of the corresponding external field propagator. The central object in our approach is the covariant energy-momentum tensor which is extracted from the regular part of the propagator at short distances. It is shown that the Lorentz anomaly, the conformal anomaly and the gauge anomaly

H. Leutwyler; S. Mallik

1986-01-01

118

The radioactivity of atmospheric krypton in 1949--1950  

Microsoft Academic Search

The chemical element, krypton, whose principal source is the atmosphere, had a long-lived radioactive content, in the mid 1940s, of less than 5 dis. per min. per liter of krypton. In the late 1940s this had risen to values in the range of a hundred dis. per min. per liter. It is now some hundred times higher than the late

A. Turkevich; L. Winsberg; H. Flotow; R. M. Adams

1997-01-01

119

Hyperpolarized Krypton-83 as a MRI Contrast Agent  

NASA Astrophysics Data System (ADS)

Hyperpolarized krypton-83 (I = 9/2) yields NMR signal enhancements [1] of 1200 to 4500 times that of thermal equilibrium value depending on the composition of the optical pumping gas mixture. The quadrupolar relaxation of krypton-83 provides surface sensitive contrast in MRI [2] and yields information about surface hydrophobicity [3], surface-to-volume ratio, surface temperature, and surface hydration. These characteristics make hp krypton-83 MRI a promising technique for materials science applications and medical diagnosis. Experimental hp krypton-83 results in model systems with biomedically relevant coatings (e.g. lung surfactant and cigarette tar) are presented. Additionally, preliminary results from hp krypton-83 in excised rodent lungs are discussed. (1) ZI Cleveland, et al., Chem. Phys., 2006. 124(4) 044311. (2) GE Pavlovskaya, et al., Proc. Natl. Acad. Sci. U.S.A.,2005. 102: 18275-18279. (3) KF Stupic, et al., Solid State Nucl. Magn. Reson., 2006. 29: 79-84.

Cleveland, Zackary; Pavlovskaya, Galina; Stupic, Karl; Repine, John; Meersmann, Thomas

2007-03-01

120

Precision electromagnetic calorimetry with liquid krypton  

SciTech Connect

Test beam results of a liquid krypton electromagnetic calorimeter with projective accordion electrode are presented. The electrode design includes a fine segmentation section to enhance the {pi}{sup 0} rejection and pointing. The test was carried out at the H4 beam line at the CERN SPS with electron beams of energy from 20 to 200 GeV. Preliminary results of energy resolution, linearity, {mu} response are presented. The author also presents the dependence of the energy resolution on the amount of inactive material in front of the calorimeter.

Takai, H.

1995-02-01

121

Solubilities of krypton and xenon in dichlorodifluoromethane  

SciTech Connect

The solubility behavior of krypton and xenon in dichlorodifluoromethane was investigated for the Consolidated Fuel Reprocessing Program (CFRP) in support of the fluorocarbon absorption process. The solubility data derived from solute radioisotopes had uncertainties of approx. 0.1%. Values for Henry's law constants were initially determined under equilibrium conditions at infinite solute dilution. Based on these results, the study was extended to finite solute concentrations. Nonidealities in the two binary systems were expressed as gas phase fugacity coefficients for each solute at 10/sup 0/ intervals over the range -30 to +50/sup 0/C. 22 references, 4 figures, 2 tables.

Shaffer, J.H.; Shockley, W.E.; Greene, C.W.

1984-07-01

122

CAMPing by the sea: Evidence for synchrony of volcanism and the end-Triassic extinction and carbon isotope anomaly from a marine Triassic-Jurassic boundary section  

NASA Astrophysics Data System (ADS)

The end-Triassic extinction (ETE) is one of the five largest Phanerozoic mass extinctions, associated with and likely triggered by rapid and severe environmental change. Volcanism in the Central Atlantic Magmatic Province (CAMP) has been proposed as the main trigger, but direct evidence for this linkage is scarce. To help constrain scenarios for the Triassic-Jurassic boundary (TJB) events, we obtained a temporally highly resolved, multidisciplinary dataset from the Kendlbachgraben section in the Northern Calcareous Alps in Austria. The section belongs to the same paleogeographic unit (Eiberg Basin) and share similar stratigraphies with the newly selected base Jurassic GSSP at Kuhjoch. The topmost beds of the Rhaetian Kssen Formation yielded an REE pattern that differs from all other levels in an enrichment of heavy REEs, hinting at some minor contribution from mantle-derived magmatic material to the sedimentary basin. Micromineralogy of the same bed revealed pseudomorphs of altered, euhedral pyroxene and amphibole crystals. Their well-faceted morphology excludes any terrestrial weathering and transport, but is consistent with their origin from air-fallen distal mafic volcanic ash. Peculiar spherical or rounded grains, altered to illite/aluminoceladonite were also observed, likely representing altered volcanic glass. The dominant clay mineral of this bed is low- to medium-charged smectite, accompanied by vermiculite, both typical alteration products of mafic rocks. These features from a bed deposited very near to the TJB are interpreted as direct evidence of CAMP volcanism, immediately preceding the main extinction event and the initial negative carbon isotope anomaly. Clay mineralogy of the Rhaetian-Hettangian Kendlbach Formation (overlying the Kssen Formation) reveals a kaolinite-dominated interval at the base of the formation, followed by an illite-dominated interval. Thus a hot and humid period may have characterized the TJB, in agreement with a previously suggested super-greenhouse episode, which was likely connected to degassing during CAMP volcanism. On the other hand, our study of pyrite, and the stratigraphic distribution of abundance of Ce and other redox sensitive elements provide little support for widespread anoxia, which was also cited previously as a possible cause for the marine TJB extinction.

Plfy, J.; Zajzon, N.

2012-04-01

123

?-decay study of neutron-rich bromine and krypton isotopes  

NASA Astrophysics Data System (ADS)

Short-lived neutron-rich nuclei including 93Br, 93Kr, and 94Kr were produced in proton-induced fission of 238U at the Holifield Radioactive Ion Beam Facility in Oak Ridge. Their ? decay was studied by means of a high-resolution online mass separator and ?-? spectroscopy methods. The half-life of T1/2 = 152(8) ms and ?-delayed branching ratio of Pn = 53-8+11% measured for 93Br differs from the previously reported values of T1/2 = 102(10) ms and Pn = 68(7)%. At the same time the half-life of 94Kr T1/2 = 227(14) ms and both the half-life of T1/2 = 1.298(54) s and ?-delayed branching ratio of Pn = 1.9-0.2+0.6% of 93Kr are in very good agreement with literature values. The decay properties of 93Br include previously unreported ? transitions following ?-delayed neutron emission.

Miernik, K.; Rykaczewski, K. P.; Grzywacz, R.; Gross, C. J.; Stracener, D. W.; Batchelder, J. C.; Brewer, N. T.; Cartegni, L.; Fija?kowska, A.; Hamilton, J. H.; Hwang, J. K.; Ilyushkin, S. V.; Jost, C.; Karny, M.; Korgul, A.; Krlas, W.; Liu, S. H.; Madurga, M.; Mazzocchi, C.; Mendez, A. J., II; Miller, D.; Padgett, S. W.; Paulauskas, S. V.; Ramayya, A. V.; Surman, R.; Winger, J. A.; Woli?ska-Cichocka, M.; Zganjar, E. F.

2013-07-01

124

Shell Structure and Shape Changes in Neutron Rich Krypton Isotopes  

SciTech Connect

B(E2;2{sub 1}{sup +}{yields}0{sub 1}{sup +}) values have been measured for the unstable nuclei {sup 88}Kr (N = 52) and {sup 92}Kr (N = 56) using projectile Coulomb excitation at ISOLDE, CERN. With this experiment the local maximum in E(2{sub 1}{sup +}) in {sup 92}Kr and the role of the N = 56 subshell closure can be studied.

Muecher, D.; Jolie, J.; Blazhev, A.; Eberth, J.; Fransen, C.; Scherillo, A.; Warr, N.; Weisshaar, D. [Institut fuer Kernphysik, Universitaet zu Koeln, D-50937 Koeln (Germany); Iwanicki, J.; Czosnyka, T.; Kownacki, J.; Napiorkowski, P.; Zielinska, M. [Heavy Ion Laboratory, Warsaw University, 02-093 Warsaw (Poland); Stefanescu, I.; Walle, J. van de; Huyse, M.; Duppen, P. van [KU Leuven, Instituut voor Kern-en Stralingsfysica, B-3001 Leuven (Belgium); Becker, F.; Gerl, J.; Mandal, S. [Gesellschaft fuer Schwerionenforschung, 64291 Darmstadt (Germany)] (and others)

2009-01-28

125

Iatrogenic choroidal neovascularization after krypton red laser photocoagulation.  

PubMed

A major cause for failure of krypton red laser photocoagulation in patients with exudative age-related macular degeneration has been the development of recurrent choroidal neovascularization adjacent to the previously treated areas. After reviewing the possible causes of recurrences, it is apparent that a certain number are iatrogenic, ie, induced by krypton red laser causing disruption and damage to the pigment epithelium-Bruch's membrane-choroidal complex. We describe three separate episodes in two patients of iatrogenic recurrent choroidal neovascularization after krypton red laser photocoagulation. PMID:2471948

Orth, D H; Flood, T P; Packo, K H

1989-04-01

126

The Radioactive Isotopes of Bromine: Isomeric Forms of Bromine 80  

Microsoft Academic Search

A study of the radioactive isotopes of bromine has been carried out by cross checking a number of nuclear reactions induced by bombarding the elements arsenic, selenium, bromine, krypton and rubidium with neutrons, deuterons, and electrically accelerated alpha-particles. The results indicate that the active isotope bromine 80 exists in two isomeric forms, from which it decays with the respective periods

Arthur H. Snell

1937-01-01

127

10 CFR 32.22 - Self-luminous products containing tritium, krypton-85 or promethium-147: Requirements for license...  

Code of Federal Regulations, 2010 CFR

...Self-luminous products containing tritium, krypton-85 or promethium-147: Requirements...Self-luminous products containing tritium, krypton-85 or promethium-147: Requirements...self-luminous products containing tritium, krypton-85, or promethium-147, or to...

2010-01-01

128

10 CFR 32.22 - Self-luminous products containing tritium, krypton-85 or promethium-147: Requirements for license...  

Code of Federal Regulations, 2010 CFR

...Self-luminous products containing tritium, krypton-85 or promethium-147: Requirements...Self-luminous products containing tritium, krypton-85 or promethium-147: Requirements...self-luminous products containing tritium, krypton-85, or promethium-147, or to...

2009-01-01

129

Theory of attosecond absorption spectroscopy in krypton  

NASA Astrophysics Data System (ADS)

A theory for time-domain attosecond pump-attosecond probe photoabsorption spectroscopy is formulated and related to the atomic response. The theory is illustrated through a study of attosecond absorption spectroscopy in krypton. The atomic parameters entering the formulation such as energies and Auger widths, as well as wave functions and dipole coupling matrix elements, are determined by accurate many-body structure calculations. We create a hole in a valence shell by an attosecond pump, couple an inner-shell electron to the hole by an attosecond probe, and then monitor the formation of the hole in this manner. In a second example, a hole is created in an inner shell by the first pulse, and the second probe pulse couples an even more tightly bound state to that hole. The hole decays in this example by Auger electron emission, and the absorption spectroscopy follows the decay of the hole and the associated coherences in real time.

Baggesen, J. C.; Lindroth, E.; Madsen, L. B.

2012-01-01

130

Low-energy positron interactions with krypton  

SciTech Connect

Cross sections for positron scattering from krypton have been measured with an energy resolution of {approx}60 meV over the energy range 0.5-60 eV. Absolute values of the grand total ({sigma}{sub GT}), positronium formation ({sigma}{sub Ps}), and grand total minus positronium formation ({sigma}{sub GT}-{sigma}{sub Ps},) cross sections are presented. Theoretical estimations of {sigma}{sub GT} and {sigma}{sub GT}-{sigma}{sub Ps} are also performed for this target using the convergent close-coupling method and the relativistic optical potential approach. We also provide experimental and theoretical results for elastic differential cross sections, for selected energies both below and above the Ps threshold. Where available, the present results are compared to both experimental and theoretical values from the literature.

Makochekanwa, C.; Machacek, J. R.; Jones, A. C. L.; Caradonna, P.; Slaughter, D. S.; McEachran, R. P.; Sullivan, J. P.; Buckman, S. J.; Bellm, S.; Lohmann, B.; Fursa, D. V.; Bray, I.; Mueller, D.W.; Stauffer, A. D.; Hoshino, M. [ARC Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); ARC Centre for Antimatter-Matter Studies, The University of Adelaide, Adelaide, South Australia (Australia); ARC Centre for Antimatter-Matter Studies, Curtin University of Technology, GPO Box U1987, Perth, Western Australia 6845 (Australia); Physics Department, University of North Texas, Denton, Texas 76201 (United States); Department of Physics and Astronomy, York University, Toronto (Canada); Department of Physics, Sophia University, Chiyoda-ku, Tokyo (Japan)

2011-03-15

131

TheD-100 Performance and Plume Characterization on Krypton  

Microsoft Academic Search

The performance of a D-100 thruster with anode layer, designed to operate on xenon at a nominal operating power of 4.5 kW, was investigated during operation on krypton. This evaluation was preliminary to a more thorough investigation of D-100 operation on alternative propellants, such as mixtures of krypton and xenon. Several operating regimes were evaluated ranging in power from 0.9

Colleen M. Marrese; James M. Haas; Matthew T. Domonkost; Alec D. Gallimore

132

The Radioactivity of Atmospheric Krypton in 1949-1950  

Microsoft Academic Search

The chemical element krypton, whose principal source is the atmosphere, had a long-lived radioactive content, in the mid-1940s, of less than 5 dpm per liter of krypton. In the late 1940s, this content had risen to values in the range of 100 dpm per liter. It is now some hundred times higher than the late 1940 values. This radioactivity is

Anthony Turkevich; Lester Winsberg; Howard Flotow; Richard M. Adams

1997-01-01

133

Spectra of heliumlike krypton from tokamak fusion test reactor plasmas  

SciTech Connect

Krypton has been injected into ohmically-heated TFTR plasmas with peak electron temperatures of 6 key to study the effects of krypton on the plasma performance and to investigate the emitted krypton line radiation, which is of interest for future-generation tokamaks such as ITER, both as a diagnostic of the central ion temperature and for the control of energy release from the plasma by radiative cooling. The emitted radiation was monitored with a bolometer array, an X-ray pulse height analysis system, and a high-resolution Johann-type crystal spectrometer; and it was found to depend very sensitively on the electron temperature profile. Satellite spectra of heliumlike krypton, KrXXXV, near 0.95 {Angstrom} including lithiumlike, berylliumlike and boronlike features were recorded in second order Bragg reflection. Radiative cooling and reduced particle recycling at the plasma edge region were observed as a result of the krypton injection for all investigated discharges. The observations are in reasonable agreement with modeling calculations of the krypton ion charge state distribution including radial transport.

Bitter, M.; Hsuan, H.; Bush, C.; Cohen, S.; Cummings, C.J.; Grek, B.; Hill, K.W.; Schivell, J.; Zarnstorff, M. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Beiersdorfer, P.; Osterheld, A. [Lawrence Livermore National Lab., CA (United States); Smith, A. [Lock Haven Univ., Lock Haven, PA (United States); Fraenkel, B. [Hebrew Univ., Jerusalem (Israel)

1993-04-01

134

Spectra of heliumlike krypton from tokamak fusion test reactor plasmas  

SciTech Connect

Krypton has been injected into ohmically-heated TFTR plasmas with peak electron temperatures of 6 key to study the effects of krypton on the plasma performance and to investigate the emitted krypton line radiation, which is of interest for future-generation tokamaks such as ITER, both as a diagnostic of the central ion temperature and for the control of energy release from the plasma by radiative cooling. The emitted radiation was monitored with a bolometer array, an X-ray pulse height analysis system, and a high-resolution Johann-type crystal spectrometer; and it was found to depend very sensitively on the electron temperature profile. Satellite spectra of heliumlike krypton, KrXXXV, near 0.95 [Angstrom] including lithiumlike, berylliumlike and boronlike features were recorded in second order Bragg reflection. Radiative cooling and reduced particle recycling at the plasma edge region were observed as a result of the krypton injection for all investigated discharges. The observations are in reasonable agreement with modeling calculations of the krypton ion charge state distribution including radial transport.

Bitter, M.; Hsuan, H.; Bush, C.; Cohen, S.; Cummings, C.J.; Grek, B.; Hill, K.W.; Schivell, J.; Zarnstorff, M. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Beiersdorfer, P.; Osterheld, A. (Lawrence Livermore National Lab., CA (United States)); Smith, A. (Lock Haven Univ., Lock Haven, PA (United States)); Fraenkel, B. (Hebrew Univ., Jerusalem (Israel))

1993-04-01

135

Gravitational anomalies  

Microsoft Academic Search

It is shown that in certain parity-violating theories in 4k+2 dimensions, general covariance is spoiled by anomalies at the one-loop level. This occurs when Weyl fermions of spin-1\\/2 or -3\\/2 or self-dual antisymmetric tensor fields are coupled to gravity. (For Dirac fermions there is no trouble.) The conditions for anomaly cancellation between fields of different spin is investigated. In six

Luis Alvarez-Gaum; Edward Witten

1984-01-01

136

Global corresponding states representation of the interfacial tension and capillary constant for the binary mixtures argon + krypton, methane + krypton, and krypton + ethane  

SciTech Connect

Corresponding states theories for surface tension and capillary constant have been evaluated using constant liquid mole fraction and constant [open quotes]fugacity fraction[close quotes] reference fluids for three binary systems. Experimental vapor-liquid equilibria, capillary constant, and surface tension data for argon + krypton, methane + krypton, and krypton + ethane systems were measured from 125 K to the critical line. These results form a database for phase behavior of varying complexity between simple compounds. The database has been used to compare the [open quotes]fugacity fraction[close quotes] corresponding states theory for capillary constant and surface tension with the traditional corresponding states theory which uses as a reference fluid a liquid with constant mole fraction. The database was also used to test the Moldover and Rainwater prediction for the surface tension coefficient in the fugacity fraction corresponding states theory. 33 refs., 11 figs., 10 tabs.

Holcomb, C.D.; Zollweg, J.A. (Cornell Univ., Ithaca, NY (United States))

1993-05-06

137

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

138

Efficiency Analysis of a Hall Thruster Operating with Krypton and Xenon  

Microsoft Academic Search

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

Jesse A. Linnell; Alec D. Gallimore

2006-01-01

139

The krypton and xenon markets up to the year 2000  

NASA Astrophysics Data System (ADS)

Krypton and xenon are rare gases which are found in air in concentrations of about 1.14 and 0.087 ppm, respectively. They are produced in specially equipped, very large air separation units by adding a special raw gas extraction unit. Then this raw gas is purified and the krypton and xenon are separated by cryogenic methods. These rare gases are used in the lamp industry, for medical applications and in laser and research applications. The market for krypton and xenon is growing. The production capacity for these gases is limited and this results in a cyclic behavior of availability and market price. In the next few years, 10-20 million liters of krypton and one to two million liters of xenon will become available on the market due to new investments in the USA, South Africa and the AGA AB joint venture in the USSR. The total world production capacity of krypton and xenon will increase to 60-80 million liters. To influence the availability of these gases it is important to have close partnership between user and producer, which will realize bright and unorthodox ideas for the supply and use of these rare gases. Marketing Manager of AGA AB

Hammarlund, Nils

1992-05-01

140

The Liquid Krypton Hugoniot at Megabar Pressures  

NASA Astrophysics Data System (ADS)

Krypton is an ideal candidate to study multi-Mbar pressure effects on elements with filled-shell electron configurations. Few experimental data on Kr at high pressures exist, however, with prior Hugoniot data limited to below 1 Mbar. Similar to liquid xenon [1], the current Kr equation of state (EOS) models agree with the data and each other below 1 Mbar, but diverge with increasing pressure. We examine the liquid Kr Hugoniot up to 8 Mbar by using density functional theory (DFT) methods and by performing shock compression experiments on the Sandia Z -- accelerator. Our initial DFT Kr Hugoniot calculations indicated the standard PAW potential is inadequate at the high pressures and temperatures occurring under strong shock compression. A new Kr PAW potential was constructed giving improved scattering properties of the atom at high energies. The Z Hugoniot measurements above 1 Mbar validated the DFT results and the pseudo-potential. The DFT and Z results suggest that the current EOS models require some modifications. [1] S. Root et al., PRL, 105, 085501 (2010). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U. S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Root, Seth; Magyar, Rudy J.; Mattsson, Ann E.; Hanson, David L.; Mattsson, Thomas R.

2011-06-01

141

Kinetic modelling of krypton fluoride laser systems  

SciTech Connect

A kinetic model has been developed for the KrF* rare gas halide laser system, specifically for electron-beam pumped mixtures of krypton, fluorine, and either helium or argon. The excitation produced in the laser gas by the e-beam was calculated numerically using an algorithm checked by comparing the predicted ionization yields in the pure rare gases with their experimental values. The excitation of the laser media by multi-kilovolt x-rays was also modeled and shown to be similar to that produced by high energy electrons. A system of equations describing the transfer of the initial gas excitation into the laser upper level was assembled using reaction rate constants from both experiment and theory. A one-dimensional treatment of the interaction of the laser radiation with the gas was formulated which considered spontaneous and stimulated emission and absorption. The predictions of this model were in good agreement with the fluorescence signals and gain and absorption measured experimentally.

Jancaitis, K.S.

1983-11-01

142

DOWN'S ANOMALY.  

ERIC Educational Resources Information Center

BOTH CLINICAL AND PATHOLOGICAL ASPECTS AND MATHEMATICAL ELABORATIONS OF DOWN'S ANOMALY, KNOWN ALSO AS MONGOLISM, ARE PRESENTED IN THIS REFERENCE MANUAL FOR PROFESSIONAL PERSONNEL. INFORMATION PROVIDED CONCERNS (1) HISTORICAL STUDIES, (2) PHYSICAL SIGNS, (3) BONES AND MUSCLES, (4) MENTAL DEVELOPMENT, (5) DERMATOGLYPHS, (6) HEMATOLOGY, (7)

PENROSE, L.S.; SMITH, G.F.

143

Technical Note: Calibration instrument for the krypton hygrometer KH20  

NASA Astrophysics Data System (ADS)

A calibration instrument for krypton hygrometers (KH20, Campbell Sci.) with variable path length is presented. This unit allows for in-situ calibrations of the krypton hygrometer, which is typically not very stable over time, during measuring campaigns. It was constructed mainly for application at high altitudes and low temperatures, where further improvements are needed to the IR-hygrometers which are normally used. The changing path length requires that a changing concentration of the absorber be simulated. Because oxygen absorbs more strongly than water vapour, the calibration is made against oxygen and transferred to water vapour. The design of the calibration instrument is made as one unit containing a stepper motor system, PC and humidity sensor. For the calibration, it is necessary to install the krypton hygrometer on this unit.

Foken, T.; Falke, H.

2012-02-01

144

Technical Note: Calibration device for the krypton hygrometer KH20  

NASA Astrophysics Data System (ADS)

A calibration device for krypton hygrometers (KH20, Campbell Scientific, Inc.) with variable path length is presented. This unit allows for in-situ calibrations of the krypton hygrometer, which is typically not very stable over time, during measuring campaigns. It was constructed mainly for application at high altitudes and low temperatures, where further improvements are needed to the IR-hygrometers which are normally used. The changing path length requires that a changing concentration of the absorber be simulated. Because oxygen absorbs more strongly than water vapour, the calibration is made against oxygen and transferred to water vapour. The design of the calibration instrument is made as one unit containing a stepper motor system, PC and humidity sensor. For the calibration, it is necessary to install the krypton hygrometer on this unit.

Foken, T.; Falke, H.

2012-08-01

145

Krypton red laser photocoagulation of the ocular fundus. 1982.  

PubMed

The theoretical rationale, the histopathologic evidence, and the preliminary clinical studies related to krypton red laser (KRL) photocoagulation of the ocular fundus are reviewed. The authors report on their experience with currently available laser systems using this wavelength (647.1 nm) for photocoagulation of retinal vascular proliferative diseases and chorioretinal diseases associated with exudative manifestations. A histopathologic and clinical comparison of argon blue-green laser (ABGL), the pure argon green laser (AGL), and the krypton yellow laser (KYL), with reference to photocoagulation treatment of the ocular fundus is also discussed. PMID:22451947

Yannuzzi, Lawrence A; Shakin, Jeffrey L

2012-02-01

146

Optogalvanic Measurement of Even Parity Rydberg Levels in Krypton Gas.  

National Technical Information Service (NTIS)

An optogalvanic detection scheme, in conjunction with a single-step pulsed laser excitation has been used to measure the energy of even parity Rydberg levels in krypton. The excitation scheme starts from the 5s(3/2)2 and 5s'(1/2)0 metastable states, which...

M. S. Kandola

1984-01-01

147

Photocoagulation of disciform macular lesions with krypton laser  

Microsoft Academic Search

Ten vascular disciform mucular lesions were treated by krypton laser photocoagulation. In 8 the lesion resolved after therapy, and in 7 the retina remained flat for 6 months. On those patients treated successfully 6 had a visual acuity of 6\\/12 or better. The morphology of the laser lesion differed from that of the argon lesion in that there is no

A C Bird; R H Grey

1979-01-01

148

Ultraviolet Absorption of Solid Argon, Krypton, and Xenon  

Microsoft Academic Search

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

Giancarlo Baldini

1962-01-01

149

Thermophysical properties of neon, argon, krypton, and xenon  

Microsoft Academic Search

Addressing the thermophysical properties of the rare gas elements - neon, argon, krypton, and xenon - this thorough work offers new research and uniform data. Tables cover properties in these elements crystalline, liquid, and gaseous states, spanning a temperature range of 0-1300 K, and for pressures up to 100 MPa. This volume contains thermodynamic properties in the solid phase and

V. A. Rabinovich; A. A. Vasserman; V. I. Nedostup; L. S. Veksler

1987-01-01

150

Exploring Interstellar Krypton Abundance Variations at Kiloparsec Scales  

Microsoft Academic Search

We propose to obtain high-resolution STIS echelle observations of the interstellar Kr I 1236 absorption toward eight stars situated in the Galactic disk beyond the Carina\\/Sagittarius or Perseus Arms. The measurement of interstellar krypton abundances is a relatively simple way to investigate elemental abundance variations in the Galaxy, since its dominant form is neutral and it is undepleted in the

Stefan Cartledge

2003-01-01

151

Laboratory Tests of Production Krypton-Filled Marine Signal Lamps.  

National Technical Information Service (NTIS)

This report compares detailed measurements of the performance of krypton-filled and argon-filled 6.2-volt marine signal lamps of the 0.46-ampere and 0.70-ampere sizes. Measurements included: current drain, luminous intensity, and color temperature as func...

P. O. Chapman

1965-01-01

152

Atom Trap, Krypton-81, and Saharan Water  

ScienceCinema

Since radiocarbon dating was first demonstrated in 1949, the field of trace analyses of long-lived cosmogenic isotopes has seen steady growth in both analytical methods and applicable isotopes. The impact of such analyses has reached a wide range of scientific and technological areas. A new method, named Atom Trap Trace Analysis (ATTA), was developed by our group and used to analyze {sup 81}Kr (t{sub 1/2} = 2.3 x 10{sup 5} years, isotopic abundance {approx} 1 x 10{sup -12}) in environmental samples. In this method, individual {sup 81}Kr atoms are selectively captured and detected with a laser-based atom trap. {sup 81}Kr is produced by cosmic rays in the upper atmosphere. It is the ideal tracer for dating ice and groundwater in the age range of 10{sup 4}-10{sup 6} years. As the first real-world application of ATTA, we have determined the mean residence time of the old groundwater in the Nubian Aquifer located underneath the Sahara Desert. Moreover, this method of capturing and probing atoms of rare isotopes is also applied to experiments that study exotic nuclear structure and test fundamental symmetries.

153

Atom Trap, Krypton-81, and Saharan Water  

SciTech Connect

Since radiocarbon dating was first demonstrated in 1949, the field of trace analyses of long-lived cosmogenic isotopes has seen steady growth in both analytical methods and applicable isotopes. The impact of such analyses has reached a wide range of scientific and technological areas. A new method, named Atom Trap Trace Analysis (ATTA), was developed by our group and used to analyze {sup 81}Kr (t{sub 1/2} = 2.3 x 10{sup 5} years, isotopic abundance {approx} 1 x 10{sup -12}) in environmental samples. In this method, individual {sup 81}Kr atoms are selectively captured and detected with a laser-based atom trap. {sup 81}Kr is produced by cosmic rays in the upper atmosphere. It is the ideal tracer for dating ice and groundwater in the age range of 10{sup 4}-10{sup 6} years. As the first real-world application of ATTA, we have determined the mean residence time of the old groundwater in the Nubian Aquifer located underneath the Sahara Desert. Moreover, this method of capturing and probing atoms of rare isotopes is also applied to experiments that study exotic nuclear structure and test fundamental symmetries.

Lu, Zheng-Tian (ANL)

2005-08-24

154

Congenital anomalies  

PubMed Central

Over the past decade, amniotic fluid-derived stem cells have emerged as a novel, experimental approach for the treatment of a wide variety of congenital anomalies diagnosed either in utero or postnatally. There are a number of unique properties of amniotic fluid stem cells that have allowed it to become a major research focus. These include the relative ease of accessing amniotic fluid cells in a minimally invasive fashion by amniocentesis as well as the relatively rich population of progenitor cells obtained from a small aliquot of fluid. Mesenchymal stem cells, c-kit positive stem cells, as well as induced pluripotent stem cells have all been derived from human amniotic fluid in recent years. This article gives a pediatric surgeons perspective on amniotic fluid stem cell therapy for the management of congenital anomalies. The current status in the use of amniotic fluid-derived stem cells, particularly as they relate as substrates in tissue engineering-based applications, is described in various animal models. A roadmap for further study and eventual clinical application is also proposed.

Kunisaki, Shaun M.

2012-01-01

155

Detection of very rare isotopes by laser collinear resonant ionization of fast atoms  

NASA Astrophysics Data System (ADS)

Results are presented of the work on the development of a method for detecting ultra rare isotopes, based on the collinear isotope-selective laser ionization of atoms in a fast bearn. The rare isotope3He was detected at a selectivity of 109 and isotope-selective ionization of krypton atoms was demonstrated. A scheme is suggested for detecting the rare radioactive isotopes85Kr and81Kr. The technique has been exploited for the measurement of hyperfine structures and isotope shifts of unstable Yb isotopes.

Kudryavtsev, Yu. A.

1992-10-01

156

On the interference of Kr during carbon isotope analysis of methane using continuous-flow combustion-isotope ratio mass spectrometry  

NASA Astrophysics Data System (ADS)

Stable carbon isotope analysis of methane (?13C of CH4) on atmospheric samples is one key method to constrain the current and past atmospheric CH4 budget. A frequently applied measurement technique is gas chromatography (GC) isotope ratio mass spectrometry (IRMS) coupled to a combustion-preconcentration unit. This report shows that the atmospheric trace gas krypton (Kr) can severely interfere during the mass spectrometric measurement, leading to significant biases in ?13C of CH4, if krypton is not sufficiently separated during the analysis. According to our experiments, the krypton interference is likely composed of two individual effects, with the lateral tailing of the doubly charged 86Kr peak affecting the neighbouring m/z 44 and partially the m/z 45 Faraday cups. Additionally, a broad signal affecting m/z 45 and especially m/z 46 is assumed to result from scattered ions of singly charged krypton. The introduced bias in the measured isotope ratios is dependent on the chromatographic separation, the krypton-to-CH4 mixing ratio in the sample, the focusing of the mass spectrometer as well as the detector configuration and can amount to up to several per mil in ?13C. Apart from technical solutions to avoid this interference, we present correction routines to a posteriori remove the bias.

Schmitt, J.; Seth, B.; Bock, M.; van der Veen, C.; Mller, L.; Sapart, C. J.; Prokopiou, M.; Sowers, T.; Rckmann, T.; Fischer, H.

2013-05-01

157

Determination of low levels of krypton in helium by gas chromatography  

SciTech Connect

Krypton-helium mixture was used as an adsorbate for surface area measurement--. The surface area measurements depend on the accuracy with which the krypton concentration is known. Generally gas tanks supplied by Union Carbide provide a nominal value of 0.1% krypton in helium. The surface area measurements require, however, that the krypton concentraion be known to +- 0.001% or better. A standard plot of krypton volume in microliters vs the area under the curve as measured by a planimeter using the helium detector and Molecular Sieve 5A column was obtained. Results with a thermal conductivity detector using Molecular Sieve 5A and Carbon Molecular Sieve are also given. Low levels of krypton in helium can be measured with precision using either a helium or a thermal conductivity detector with Molecular Sieve 5A or Carbon Molecular Sieve columns. 2 figures, 1 table. (DP)

Evans, D.L.; Mukherji, A.K.

1980-03-01

158

Condensation of Solids in Space. Isotope Fractionation in the Model System C-O.  

National Technical Information Service (NTIS)

The reported chemical fractionation of a single isotope O-16 under simulated space conditions provides the first experimental proof for the hypothesis that the oxygen isotopic anomaly (and other similar anomalies) seen in meteorites is a product of chemic...

G. Arrhenius

1983-01-01

159

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

160

Off-gas treatment and krypton disposal in HTGR-fuel element reprocessing  

Microsoft Academic Search

Krypton, tritium and iodine are separated from burner off-gas by CO-liquification and rectification at room tempearture. Krypton is concentrated in the lower boiling fraction, while tritium and iodine are concentrated in the higher boiling fraction (AKUT-process). The dissolver off-gas is decontaminated by a cryogenic process. Based on safety and economy, the disposal of compressed krypton confined in steel cylinders by

M. Laser; H. Beaujean; J. Bohnenstingl; P. Filss; M. Heidendael; S. Mastera; E. Merz; H. Vygen

1972-01-01

161

Structure of liquid krypton under atmospheric pressure: An EXAFS and reverse Monte Carlo study  

SciTech Connect

The local atomic structure of liquid krypton under atmospheric pressure has been studied with the technique of x-ray absorption fine structure (XAFS). For measuring the XAFS of liquid krypton at low temperature, a special sample holding method is applied. The x-ray absorption spectra of gaseous and solid krypton are also measured for the comparison and data analysis. Based on the reverse Monte Carlo simulation and the constructed configurations, the radial distribution function as well as the coordination number and bond-angle distribution of liquid krypton is given.

Wang Qiang; Li Chenxi; Niu Xiaojuan; Shen Rong; Lu Kunquan; Wei Shiqiang; Wu Zhonghua; Liu Tao; Xie Yaning; Hu Tiandou [Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China)

2005-09-01

162

ANOMALY STRUCTURE OF SUPERGRAVITY AND ANOMALY CANCELLATION  

SciTech Connect

We display the full anomaly structure of supergravity, including new D-term contributions to the conformal anomaly. This expression has the super-Weyl and chiral U(1){sub K} transformation properties that are required for implementation of the Green-Schwarz mechanism for anomaly cancellation. We outline the procedure for full anomaly cancellation. Our results have implications for effective supergravity theories from the weakly coupled heterotic string theory.

Butter, Daniel; Gaillard, Mary K.

2009-06-10

163

Rotational spectrum and internal dynamics of tetrahydrofuran-krypton.  

PubMed

The rotational spectrum of the tetrahydrofuran-krypton van der Waals complex has been investigated by pulsed-jet Fourier transform microwave spectroscopy. The spectra of the (84)Kr and (86)Kr isotopologues have been assigned and the krypton atom is located nearly over the oxygen atom, almost perpendicular to the COC plane. Each rotational transition is split into two component lines due to, according to the observed Coriolis coupling term between the tunneling states, the residual pseudorotational effects of the ring in the complex. The splitting between the two vibrational sublevels is 87.462(2) and 87.062(2) MHz for the (84)Kr and (86)Kr isotopologues, respectively. These splittings have been used to determine the barrier to inversion, B(2) = 67 cm(-1). The dissociation energy has been estimated to be 3.7 kJ ?mol(-1) from centrifugal distortion effects. PMID:22109993

Gou, Qian; Feng, Gang; Evangelisti, Luca; Maris, Assimo; Marchini, Marianna; Velino, Biagio; Caminati, Walther

2011-11-23

164

Mobility of electrons in supercritical krypton: Role of density fluctuations  

SciTech Connect

Excess electrons were generated in supercritical krypton by means of pulsed x-ray irradiation, and the electron transport phenomena were studied. Electron signals immediately after a 30 ps pulse showed a distinctive feature characteristic of the presence of the Ramsauer-Townsend minimum in the momentum transfer cross section. The dependence of the drift velocity v{sub D} on field strength was found to be concave upward in the low field region and then to go through a maximum with increasing field strength, which is also typical of the presence of a minimum in the scattering cross section at an intermediate field strength. A minimum in the electron mobility was observed at about one-half the critical density. The acoustical phonon scattering model, which successfully explained the mobility change in this density region in supercritical xenon, was again found to account for the mobility in supercritical krypton.

Nishikawa, Masaru; Holroyd, Richard A.; Preses, Jack M. [Faculty of Engineering, Kanagawa Institute of Technology, 1030 Shimo-Ogino, Astugi 243-0292 (Japan); Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2007-07-07

165

Vapour-liquid equilibrium in the krypton-xenon system  

NASA Astrophysics Data System (ADS)

Isothermal vapour-liquid data were measured for the krypton-xenon system at ten temperatures between 165 and 270 K and pressures to 6.7 MPa, using a vapour recirculating technique. The mixture critical line has been located in (P, T, x) space. Barker's method of data reduction has been used to test the thermodynamic consistency of isotherms below the critical temperature of krypton (209.4 K) and the excess Gibbs energy was evaluated, at the same temperatures, as a function of composition. The results of the experiments have been compared with predictions of the Peng-Robinson equation of state. With interaction parameter calculated by fitting the isotherm of 200.64 K, this equation predicts the liquid and vapour phase compositions to within about a few mole per cent over most of the experimental range.

Calado, Jorge C. G.; Chang, Elaine; Streett, William B.

1983-01-01

166

X-Ray Fluorescence With a Krypton Gas Proportional Counter  

NASA Astrophysics Data System (ADS)

X-Ray fluorescence analysis of potential meteorites can provide evidence of the typical iron and nickel content of certain classes of meteorites. The resolution of a Krypton-Carbon Dioxide filled proportional counter is sufficient to resolve the K X-rays of these low Z elements. The detector operates at room temperature, and the associated electronic circuit is simple and can be assembled quickly.

Peterson, David

2007-11-01

167

Auger decay of 3p-ionized krypton  

SciTech Connect

A theoretical study of Auger cascades during the decay of 3p{sub 1/2} and 3p{sub 3/2} vacancies in krypton has been performed by level-by-level calculations using a wide configuration interaction basis. Auger spectra for all steps of the cascades are presented and are compared with the existing experimental data. Good agreement of our results with the branching ratios of ions measured by a coincidence technique is obtained.

Jonauskas, V.; Kucas, S.; Karazija, R. [Institute of Theoretical Physics and Astronomy, Vilnius University, A. Gostauto 12, Vilnius LT-01108 (Lithuania)

2011-11-15

168

Krypton spectroscopy diagnosis of high temperature implosions. Final technical report  

SciTech Connect

The research work addressed the topics of observation of K-shell krypton lines, determindation of temperature by continuous slope and by line-intensity ratio, mixing diagnosis based on high-opacity Kr lines, a method for measuring the escape factor f, diagnosis of density using low-opacity lines, and diagnosis of {rho}R using high-opacity lines. A major program to demonstrate feasibility of direct-drive laser fusion is underway at LLE.

NONE

1995-12-31

169

Decay of Excited Species in a Pulsed Discharge in Krypton  

Microsoft Academic Search

The emission in the afterglow of a pulsed discharge in krypton has been investigated. Measurements of the decay times of the resonance radiation at lambda1236 and a diffuse molecular radiation at lambda1250 and longer wavelengths have been made as functions of pressure at 295 and 196K. The measurements have been interpreted on the assumption of a simple two-time-constant

R. Turner

1967-01-01

170

Resonance strength for KLL dielectronic recombination of hydrogenlike krypton  

NASA Astrophysics Data System (ADS)

We report KLL dielectronic recombination (DR) resonance strength for hydrogenlike krypton Kr35+ measured with an electron-beam ion trap. X rays emitted from both DR and radiative recombination (RR) are observed as a function of electron-beam energy over the KLL resonances. The DR resonance strength is obtained by normalizing the DR x-ray counts to theoretical RR cross sections. The experimental strength is shown to agree with theoretical strength calculated using the flexible atomic code.

Hu, Zhimin; Li, Yueming; Nakamura, Nobuyuki

2013-05-01

171

The cosmic molybdenum-ruthenium isotope correlation  

Microsoft Academic Search

Dauphas et al. (Astrophys. J. 565 (2002) 640-644) reported molybdenum isotopic anomalies in differentiated and bulk primitive meteorites. It is shown here that these isotopic anomalies correlate with one another in exactly the way expected from nucleosynthesis theory if different regions of the nebula received different contributions of s-process matter synthesized in low- mass AGB stars. Furthermore, when bulk measurements

Nicolas Dauphasa; Andrew M. Davisa; Bernard Martyd; Laurie Reisbergd

172

Global gravitational anomalies  

Microsoft Academic Search

A general formula for global gauge and gravitational anomalies is derived. It is used to show that the anomaly free supergravity and superstring theories in ten dimensions are all free of global anomalies that might have ruined their consistency. However, it is shown that global anomalies lead to some restrictions on allowed compactifications of these theories. For example, in the

Edward Witten

1985-01-01

173

Analysis of mechanisms which lead to electrical breakdown in a krypton-filled tube using the time delay method  

Microsoft Academic Search

Contributions of krypton ions and krypton metastables, as well as contributions of gamma-radiation and cosmic rays to the electrical breakdown in a krypton-filled tube have been analysed by use of the time delay method. The experimental results have shown that each of these contributions strictly depends on the afterglow period. The time delay method has enabled the determination of both

Momcilo M. Pejovic; Goran S. Ristic

2000-01-01

174

Chiral anomalies and differential geometry  

SciTech Connect

Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references. (WHK)

Zumino, B.

1983-10-01

175

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

176

A comparative histopathological study of argon and krypton laser irradiations of the human retina  

Microsoft Academic Search

A series of comparative exposures to both argon and krypton lasers have been made at 3 locations in a human retina--the fovea, the macula, and intraretinal vessels. In the fovea argon irradiations resulted in damage to both the inner and outer retinal layers as a result of absorption within the pigment epithelium and the macular pigment, while krypton exposures damaged

J Marshall; A C Bird

1979-01-01

177

Relativistic Multichannel Treatment of Krypton Spectra across the First Ionization Threshold  

Microsoft Academic Search

The relativistic multichannel theory has been extended to calculate both the eigen quantum defects mualpha, transformation matrix Uialpha, and the eigen dipole matrix elements Dalpha of krypton. The Rydberg and autoionization spectra of krypton across the first ionization threshold are calculated within the framework of multichannel quantum defect theory. Our calculated spectra are in agreement with the absolute measurement data.

Yi-Zhi Qu; Yong-Lun Peng

2005-01-01

178

Calculated phase boundary including corrugation effects for krypton layers physisorbed onto spherical substrates  

Microsoft Academic Search

A molecular-dynamics technique is utilized to calculate the melting curve of submonolayer and complete layers of krypton atoms physisorbed onto a spherical substrate. Two models of the substrate are used. In the first model the substrate is treated as a spherical continuum whose differential elements interact with krypton atoms via Lennard-Jones (LJ) potential. Hysteresis is present in the melting transition

M. K. Balasubramanya; M. W. Roth

2001-01-01

179

[Effect of krypton-containing gas mixture on Japanese quail embryo development].  

PubMed

Investigated were effects of gas mixture with up to 3.0 kgs/cm2 of krypton on the embryonic development of domesticated Japanese quail (Coturnix coturnix japonica dom.). Results demonstrated absence of a serious krypton effect on Japanese quail embryos. Development of embryos proceeded in due course; morphometrically the experimental embryos were essentially similar to controls. It should be noted that despite exposure to acute hypoxic hypoxia during the initial 12 hours of development in the krypton-containing gas mixture, viability of quail embryos was high enough which can be ascribed to the krypton protective action. Besides, an additional experiment showed that krypton partial pressure of 5-5.5 kgs/cm2 produces the narcotic effect on adult Japanese quails. PMID:18564569

Kussmaul', A R; Gur'eva, T S; Dadasheva, O A; Pavlov, N B; Pavlov, B N

180

Investigation of the thermal and photochemical reactions of ozone with styrene in argon and krypton matrices  

NASA Astrophysics Data System (ADS)

The matrix isolation technique, combined with infrared spectroscopy and twin jet codeposition, has been used to characterize intermediates formed during the ozonolysis of styrene. Absorptions assigned to early intermediates grew in after warming the matrix from 19 K to 68 K in the twin jet krypton matrix experiments. A number of these absorptions have been assigned to the primary ozonide, formaldehyde-O-oxide Criegee intermediate, and secondary ozonide of styrene, transient species not previously observed for this system. In contrast, the room temperature reaction of ozone with styrene led to the observation of "late," stable products of this ozonolysis reaction. These product absorptions were observed after merged jet deposition, followed by cryogenic trapping in solid argon. Irradiation with ? ? 220 nm of merged and twin jet argon matrices involving ozone led to O atom production and subsequent reaction with styrene. Identification of intermediates formed during the ozonolysis of styrene was further supported by 18O isotopic labeling experiments as well as theoretical density functional calculations at the B3LYP/6-311G++(d,2p) level.

Coleman, Bridgett E.; Ault, Bruce S.

2012-09-01

181

Krypton gas cylinders as a source of radiation.  

PubMed

A standard 40 foot shipping container with a cargo of pressurized krypton gas in 159 steel cylinders, which had triggered a radiation alarm, was investigated to address radiation safety and illicit nuclear trafficking concerns. The investigation included contamination and dose rate measurements as well as in situ high resolution gamma spectroscopy. The dose rate measurements gave a maximum value of 0.07 microSv h(-1) above background (0.08 to 0.11 microSv h(-1)) on the cylinder surface and no detectable increase above background at distances of 1 m and higher. Contamination monitor readings showed a similar relative increase (plus 8 cpm) above background (about 12 cpm) to the dose rate readings. Quantitative gamma spectroscopy revealed a contamination of the gas with 85Kr at a level of 3.5 x 10(5) Bq kg(-1). This value was found to be consistent with analytical and numerical estimates based on current data for atmospheric 85Kr, which is captured from ambient air together with stable krypton during the production process. This incident demonstrates an apparent lack of radiation-related knowledge by those who handle krypton gas, as well as by border control personnel and emergency responders. We therefore propose to improve labeling and documentation standards for such shipments. This effort may be facilitated by introducing the new category of "technically enhanced artificial radioactive material," or "TEARM" (similar to the existing "naturally occurring radioactive material" or "NORM" and "technically enhanced naturally occurring radioactive material" or "TENORM" categories). PMID:20539125

Fischer, Helmut W; Bielefeld, Tom; Hettwig, Bernd

2010-07-01

182

Krypton-81m ventilation scanning: acute respiratory disease  

SciTech Connect

From experience with 700 patients undergoing ventilation and perfusion lung scanning with krypton-81m/technetium-99m technique, 34 patients suffering from nonembolic acute respiratory disease were selected for review. In 16 patients with pneumonia, all had defects of ventilation corresponding to, or larger than, the radiologic consolidation. In 13 patients there was some preservation of perfusion in the consolidated region. In two of the three patients with matched defects, the pneumonia was of long standing. In seven patients with collapse or atelectasis and in 11 patients with acute reversible bronchial obstruction and normal volume lungs, a similar pattern or ventillation and perfusion was observed.

Lavender, J.P. (Royal Postgraduate Medical School, London, England); Irving, H.; Armstrong, J.D. II

1981-02-01

183

Performance of an accordion electromagnetic calorimeter with liquid krypton  

SciTech Connect

Beam test results of the liquid krypton electromagnetic calorimeter with a projective accordion type electrode structure are presented. The electrode had a fine segmentation in the front to enhance {pi}{sup 0} rejection and pointing. The test was carried out at the H4 line at the CERN SPS with e{sup {minus}} beams between 20 and 200 GeV. Preliminary results of energy resolution, linearity, {mu} response and the dependence of the energy resolution on the amount of inactive material in front of the calorimeter are presented.

Lissuaer, D.

1994-12-31

184

A new capability in isotope geochemistry  

NASA Astrophysics Data System (ADS)

International Workshop on Tracer Applications of Noble Gas Radionuclides; Argonne, Illinois, 21-22 June 2012 The noble gas radionuclides krypton-81 (81Kr; 229,000-year half-life), krypton-85 (85Kr; 10.8-year half-life), and argon-39 (39Ar; 269-year half-life) have ideal properties for tracing fluid transport in Earth systems. Their principal applications include determination of groundwater residence times (81Kr, 85Kr, and 39Ar) and seawater ventilation ages (39Ar). In practice, however, few studies have employed noble gas radionuclides because of the large sample sizes required and the complex analytical systems required for measuring their extremely low isotopic abundances (10-16 to 10-11). Most published studies have used low-level radioactive decay counting for 39Ar and 85Kr, but the low activity of 81Kr has necessitated the development of various atom-counting methods over the past 4 decades.

Sturchio, Neil C.; Lu, Zheng-Tian; Schlosser, Peter

2012-10-01

185

SST Anomalies + Wind Anomalies (with dates)  

NSDL National Science Digital Library

Sea surface temperature (SST) anomalies and sea surface wind anomalies show the development of the 2002-2003 El Nino based on data from NASAs Aqua and QuikSCAT spacecraft. The wind data has been processed using the Variational Analysis Method (VAM).

Shirah, Greg; Allen, Jesse; Adamec, David

2003-02-03

186

ISOTOPIC COMPOSITION OF PRIMORDIAL XENON  

Microsoft Academic Search

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

J. Reynolds

1960-01-01

187

Ejection ages from krypton-81krypton83 dating and pre-atmospheric sizes of martian meteorites  

Microsoft Academic Search

Cosmic-ray exposure (CRE) ages and Mars ejection times were calculated from the radionuclide 81Kr and stable Kr isotopes for seven martian meteorites. The following 81Kr-Kr CRE ages were obtained: Los Angeles = 3.35 +\\/- 0.70 Ma; Queen Alexandra Range 94201 = 2.22 +\\/- 0.35 Ma; Shergotty = 3.05 +\\/- 0.50 Ma; Zagami = 2.98 +\\/- 0.30 Ma; Nakhla = 10.8

O. Eugster; H. Busemann; S. Lorenzetti; D. Terribilini

2002-01-01

188

Anomalies in the Heavy Hg Isotopes.  

National Technical Information Service (NTIS)

The (p,t) reaction has been performed on natural Hg and separated sup 204 Hg, sup 202 Hg, sup 200 Hg, sup 198 Hg, sup 196 Hg targets, using a 25 MeV proton beam from the Orsay MP tandem accelerator and a split pole spectrometer. New excited 0 exp + levels...

M. Vergnes G. Berrier-Ronsin G. Rotbard

1983-01-01

189

The Elliptic Anomaly.  

National Technical Information Service (NTIS)

An independent variable different from the time for elliptic orbit integration is used. Such a time transformation provides an analytical step-size regulation along the orbit. An intermediate anomaly (an anomaly intermediate between the eccentric and the ...

G. Janin V. R. Bond

1980-01-01

190

Rotation of methyl radicals in a solid krypton matrix  

NASA Astrophysics Data System (ADS)

Electron spin resonance (ESR) measurements were carried out to study the rotation of methyl radicals (CH3) in a solid krypton matrix at 17-31 K temperature range. The radicals were produced by dissociating methane by plasma bursts generated by a focused 193 nm excimer laser radiation during the krypton gas condensation on the substrate. The ESR spectrum exhibits only isotropic features at the temperature range examined, and the intensity ratio between the symmetric (A) and antisymmetric (E) spin state lines exhibits weaker temperature dependence than in a solid argon matrix. However, the general appearance of the methyl radical spectrum depends strongly on temperature due to the pronounced temperature dependency of the E state linewidths. The rotational energy level populations are analyzed based on the static crystal field model, pseudorotating cage model, and quantum chemical calculations for an axially symmetric, planar rotor. Crystal field strength parameter values of -140 cm-1 in Ar and -240 cm-1 in Kr match most closely the experimentally observed rotational energy level shifts from the gas phase value. In the alternative model, considering the lattice atom movement in a pseudorotating cage, the effective lowering of the rotational constants B and C to 80%-90% leads to similar effects.

Kiljunen, Toni; Popov, Evgeny; Kunttu, Henrik; Eloranta, Jussi

2009-04-01

191

Krypton-85 hydrofracture engineering feasibility and safety evaluation  

SciTech Connect

Engineering studies have been made to determine the hazards associated with the disposal of /sup 85/Kr using the hydrofracture process. To assess the hazards, an effort has been made to identify the equipment required to entrain and dissolve the noble gas into the grout stream at hydrofracture pressure (up to 350 bar). Off-the-shelf or slightly modified equipment has been identified for safe and effective compression and gas-grout mixing. Each monthly injection disposes of 1.6 x 10/sup 6/ Ci of /sup 85/Kr. By connecting only one gas cylinder to the injection system at a time, the maximum amount of krypton likely to be released as a result of equipment failure is limited to 128,000 Ci. An evaluation by Los Alamos Technical Associates shows that releasing this amount of gas in less than one hour under worst-case meteorological conditions through a 30-m stack would result in a whole-body dose of 170 millirem at a distance of 1 km from the facility. A krypton collection and recovery system can further reduce this dose to 17 millirem; increasing the distance to the site boundary to 3 km can also reduce the dose by a factor of ten. Lung and skin dose estimates are 1.6 and 120 times the whole-body dose, respectively. These are all worst-case values; releases under more typical conditions would result in a significantly lower dose. No insurmountable safety or engineering problems have been identified.

Peretz, F.J.; Muller, M.E.; Pan, P.Y.

1981-07-01

192

Familial Poland anomaly  

Microsoft Academic Search

The Poland anomaly is usually a non-genetic malformation syndrome. This paper reports two second cousins who both had a typical left sided Poland anomaly, and this constitutes the first recorded case of this condition affecting more than one member of a family. Despite this, for the purposes of genetic counselling, the Poland anomaly can be regarded as a sporadic condition

T J David

1982-01-01

193

Peters' Anomaly - Anaesthetic Management  

PubMed Central

Summary Peters' anomaly occurs as an isolated ocular abnormality, in association with other systemic abnormality or one component of a number of well-defined syndromes. We review our experience of anaesthetic management and systemic association of peters' anomaly. To the best of our knowledge there are no reports in the literature of Peters' anomaly with relevant to anaesthesia.

M, Senthilkumar; V, Darlong; Punj, Jyotsna; Pandey, Ravinder

2009-01-01

194

Beam of metastable krypton atoms extracted from a rf-driven discharge  

SciTech Connect

A rf-driven discharge is used to produce a beam of metastable krypton atoms at the 5s(3/2){sub 2} level with an angular flux density of 4x10{sup 14}s{sup -1}sr{sup -1} and most probable velocity of 290 m/s, while consuming 7x10{sup 16} krypton atoms/s. When operated in a gas-recirculation mode, the source consumes 2x10{sup 15} krypton atoms/s with the same atomic-beam output.

Chen, C. Y.; Bailey, K.; Li, Y. M.; O'Connor, T. P.; Lu, Z.-T.; Du, X.; Young, L.; Winkler, G.

2001-01-01

195

The blood flow of the cerebral cortex determined by radioactive krypton 85  

Microsoft Academic Search

Zusammenfassung Der radioaktive indifferente Luftbestandteil Krypton85 (in Ringer-Flssigkeit) wird in die Arteria carotis communis injiziert und die Radioaktivitt ber der freigelegten Gehirnoberflche verfolgt. Die Methode ergibt reproduzierbare quantitativecorticale Perfusionswerte und eignet sich auch fr andere Gewebe.

N. A. Lassen; D. H. Ingvar

1961-01-01

196

The wash-out of intraarterially injected Krypton 85 from the intestine of the cat  

Microsoft Academic Search

Zusammenfassung Der zeitliche Verlauf der Elimination von intraarteriell injiziertem Krypton aus den Geweben des Katzendarmes wurde untersucht. Die gefundene Eliminationskurve konnte in vier Teilkurven aufgelst und die anatomische Lokalisierung und funktionelle Bedeutung dieser Komponenten kurz diskutiert werden.

O. Lundgren; M. Kampp

1966-01-01

197

Structures of small mixed krypton-xenon clusters.  

PubMed

Structures of small mixed krypton-xenon clusters of different compositions with an average size of 30-37 atoms are investigated. The Kr 3d(5/2) and Xe 4d(5/2) surface core level shifts and photoelectron intensities originating from corner, edge, and face/bulk sites are analyzed by using soft x-ray photoelectron spectroscopy. Structural models are derived from these experiments, which are confirmed by theoretical simulation taking induced dipole interactions into account. It is found that one or two small Xe cores are partly embedded in the surface of the Kr clusters. These may grow and merge leading to a phase separation between the two rare gas moieties in mixed clusters with increasing the Xe content. PMID:22779598

Nagasaka, Masanari; Kosugi, Nobuhiro; Rhl, Eckart

2012-06-21

198

The evaluation of right ventricular performance using krypton-81m  

SciTech Connect

The availability of krypton-81m suitable for intravenous injection provides an easy means for assessing right ventricular function. The superimposition of the other heart chambers does not constitute a problem. The activity in the left heart is negligible and the study can be performed in the right anterior oblique position to obtain optimal separation between the right atrium and the right ventricle. Lung activity is quite high and should be corrected before computing the right ventricular ejection fraction. This correction can be accomplished by performing Tc-99m MAA perfusion scintigraphy. The measurement of the right ventricular ejection fraction appears to be reproducible with very small inter-and intraobserver variability. Good quality phase and amplitude images can be obtained with such high count rates.

Ham, H.R.; Piepsz, A.; Vandevivere, J.; Guillaume, M.; Goethals, P.; Lenaers, A.

1983-06-01

199

Performance of an electromagnetic liquid krypton calorimeter based on a ribbon electrode tower structure  

Microsoft Academic Search

The NA48 collaboration is preparing a new experiment at CERN aiming to study CP violation in the K0-K0 system with an accuracy of 2 10?4 in the parameter Re(??\\/?). Decays in two ?0's will be recorded by a quasi-homogeneous liquid krypton calorimeter. A liquid krypton calorimeter has been chosen to combine good energy, position and time resolution with precise

G. D. Barr; C. Bruschini; C. Bocquet; P. Buchholz; D. Cundy; N. Doble; W. Funk; L. Gatignon; A. Gonidec; B. Hallgren; G. Kesseler; A. Lacourt; G. Laverrire; G. Linser; M. Martini; A. Norton; D. Schinzel; W. Seidl; M. S. Sozzi; H. Taureg; O. Vossnack; H. Wahl; P. Wertelaers; J. Weterings; M. Ziolkowski; A. Kalinin; V. Kekelidze; Yu. Kozhevnikov; L. Bertolotto; V. Carassiti; J. Duclos; A. Gianoli; P. L. Frabetti; M. Savri; O. Zeitnitz; M. Calvetti; P. Lubrano; M. Pepe; P. Calafiura; C. Cerri; F. Costantini; R. Fantechi; B. Gorini; I. Mannelli; V. Marzulli; D. Bdrde; P. Debu; A. Givernaud; L. Gosset; J. Heitzmann; E. Mazzucato; B. Peyaud; R. Turlay; C. Biino; A. Ceccucci; P. Maas; S. Palestini

1996-01-01

200

[Heredity of orthodontic anomalies].  

PubMed

The survey of most common orthodontic anomalies is given in this article. Authors, utilizing literature data, their own research as well as their therapeutic experience, try to elucidate the role of genetics in determination of dental anomalies and malocclusion. They emphasise the fact that genetically determined orthodontic anomalies are not easy to treat. Retention of treatment result could also be a problem. Occurrence of an anomaly in one member of the family should lead to the examination of other members, especially the young ones. PMID:24041019

Svbov, Miroslava; Racek, Jaroslav; Markov, Marie

2013-01-01

201

Pathway to cryogen free production of hyperpolarized Krypton-83 and Xenon-129.  

PubMed

Hyperpolarized (hp) (129)Xe and hp (83)Kr for magnetic resonance imaging (MRI) are typically obtained through spin-exchange optical pumping (SEOP) in gas mixtures with dilute concentrations of the respective noble gas. The usage of dilute noble gases mixtures requires cryogenic gas separation after SEOP, a step that makes clinical and preclinical applications of hp (129)Xe MRI cumbersome. For hp (83)Kr MRI, cryogenic concentration is not practical due to depolarization that is caused by quadrupolar relaxation in the condensed phase. In this work, the concept of stopped flow SEOP with concentrated noble gas mixtures at low pressures was explored using a laser with 23.3 W of output power and 0.25 nm linewidth. For (129)Xe SEOP without cryogenic separation, the highest obtained MR signal intensity from the hp xenon-nitrogen gas mixture was equivalent to that arising from 15.51.9% spin polarized (129)Xe in pure xenon gas. The production rate of the hp gas mixture, measured at 298 K, was 1.8 cm(3)/min. For hp (83)Kr, the equivalent of 4.40.5% spin polarization in pure krypton at a production rate of 2 cm(3)/min was produced. The general dependency of spin polarization upon gas pressure obtained in stopped flow SEOP is reported for various noble gas concentrations. Aspects of SEOP specific to the two noble gas isotopes are discussed and compared with current theoretical opinions. A non-linear pressure broadening of the Rb D(1) transition was observed and taken into account for the qualitative description of the SEOP process. PMID:23209620

Six, Joseph S; Hughes-Riley, Theodore; Stupic, Karl F; Pavlovskaya, Galina E; Meersmann, Thomas

2012-11-27

202

The cosmic molybdenumruthenium isotope correlation  

Microsoft Academic Search

Dauphas et al. [Astrophys. J. 565 (2002) 640644] reported molybdenum isotopic anomalies in differentiated and bulk primitive meteorites. It is shown here that these isotopic anomalies correlate with one another in exactly the way expected from nucleosynthesis theory if different regions of the nebula received different contributions of s-process matter synthesized in low-mass AGB stars. Furthermore, when bulk measurements are

Nicolas Dauphas; Andrew M. Davis; Bernard Marty; Laurie Reisberg

2004-01-01

203

Anomalies in Political Economy  

Microsoft Academic Search

Results in cognitive psychology and experimental economics indicate that under identifiable conditions individuals do not act in an economically rational way. These results are important for Political Economy. Anomalies appear in the behaviour of voters, politicans and administrators. Economic markets do not fully eliminate anomalies in the aggregation process. It is shown that political aggregation by democracy, bargaining or bureaucracy

Bruno S. Frey; Reiner Eichenberger

1991-01-01

204

Large area electron beam pumped krypton fluoride laser amplifier  

SciTech Connect

Nike is a recently completed multi-kilojoule krypton fluoride (KrF) laser that has been built to study the physics of direct drive inertial confinement fusion. This paper describes in detail both the pulsed power and optical performance of the largest amplifier in the Nike laser, the 60 cm amplifier. This is a double pass, double sided, electron beam-pumped system that amplifies the laser beam from an input of 50 J to an output of up to 5 kJ. It has an optical aperture of 60 cm {times} 60 cm and a gain length of 200 cm. The two electron beams are 60 cm high {times} 200 cm wide, have a voltage of 640 kV, a current of 540 kA, and a flat top power pulse duration of 250 ns. A 2 kG magnetic field is used to guide the beams and prevent self-pinching. Each electron beam is produced by its own Marx/pulse forming line system. The amplifier has been fully integrated into the Nike system and is used on a daily basis for laser-target experiments. {copyright} {ital 1997 American Institute of Physics.}

Sethian, J.D.; Obenschain, S.P.; Gerber, K.A.; Pawley, C.J.; Serlin, V.; Sullivan, C.A. [Plasma Physics Division, Naval Research Laboratory, Washington DC 20375 (United States); Webster, W. [Research Support Instruments, 4325-B Forbes Boulevard, Lanham, Maryland 20706 (United States); Deniz, A.V.; Lehecka, T. [Science Applications International Corporation, 1710 Goodridge Drive, McLean, Virginia 22102 (United States); McGeoch, M.W. [PLEX Corporation, 21 Addington Road, Brookline, Massachusetts 02146 (United States); Altes, R.A.; Corcoran, P.A.; Smith, I.D. [Pulse Sciences, Incorporated, 600 McCormick Street, San Leandro, California 94577 (United States); Barr, O.C. [Pharos Technical Enterprises, 1603 Barcelona Street, Livermore, California 94550 (United States)

1997-06-01

205

FIRST DETECTION OF KRYPTON AND XENON IN A WHITE DWARF  

SciTech Connect

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

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

2012-07-01

206

Detection of tobacco smoke deposition by hyperpolarized krypton-83 MRI.  

PubMed

Despite the importance of the tobacco smoke particulate matter in the lungs to the etiology of pulmonary disease in cigarette smokers, little is currently known about the spatial distribution of particle deposition or the persistence of the resulting deposits in humans, and no satisfactory technique currently exists to directly observe tobacco smoke condensate in airways. In this proof-of-principle work, hyperpolarized (hp) 83Kr MRI and NMR spectroscopy are introduced as probes for tobacco smoke deposition in porous media. A reduction in the hp-83Kr longitudinal (T1) relaxation of up to 95% under near-ambient humidity, pressure and temperature conditions was observed when the krypton gas was brought into contact with surfaces that had been exposed to cigarette smoke. This smoke-induced acceleration of the 83Kr self-relaxation was observed for model glass surfaces that, in some experiments, were coated with bovine lung surfactant extract. However, a similar effect was not observed with hp-(129)Xe indicating that the 83Kr sensitivity to smoke deposition was not caused by paramagnetic species but rather by quadrupolar relaxation due to high adsorption affinity for the smoke deposits. The 83Kr T1 differences between smoke-treated and untreated surfaces were sufficient to produce a strong contrast in variable flip angle FLASH hp-83Kr MRI, suggesting that hp-83Kr may be a promising contrast agent for in vivo pulmonary MRI. PMID:17826938

Cleveland, Zackary I; Pavlovskaya, Galina E; Stupic, Karl F; Wooten, Jan B; Repine, John E; Meersmann, Thomas

2007-09-10

207

First Detection of Krypton and Xenon in a White Dwarf  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

208

Inertial Fusion Target Physics Advantages with the Krypton Fluoride Laser  

NASA Astrophysics Data System (ADS)

The krypton fluoride (KrF) laser's short wavelength, broad bandwidth and capability to provide extremely uniform target illumination are advantages towards obtaining high gain direct drive implosions. The short wavelength helps suppress deleterious laser-plasma instabilities, and allows one to employ higher ablation pressures. In addition, the KrF architecture allows one to zoom down the focal diameter to follow the size of the imploding pellet, thereby improving the coupling efficiency. The NRL researchers have been conducting theoretical and experimental studies to quantify the beneficial effects of utilizing KrF light. Experiments using the Nike facility have confirmed that KrF light significantly increases the threshold for laser-plasma instability. This presentation will discuss the observed target physics with KrF light and its effects towards facilitating the high gains needed for power production with inertial fusion. Simulations indicate that shock ignited designs can achieve gains above 200 with KrF energies as low a 1 megajoule. For fusion energy a laser driver must be capable of high repetition rates (5-10 Hz) along with adequate efficiency and durability. The Electra KrF 30-cm aperture electron-beam-pumped amplifier has demonstrated long duration continuous operation at high-repetition rates. This and other advances show that the KrF laser should be able to meet the requirements.

Obenschain, Stephen

2010-11-01

209

Thermal beam of metastable krypton atoms produced by optical excitation  

SciTech Connect

A room-temperature beam of krypton atoms in the metastable 5s[3/2]{sub 2} level is demonstrated via an optical excitation method. A Kr-discharge lamp is used to produce vacuum ultraviolet photons at 124 nm for the first-step excitation from the ground level 4p{sup 6} {sup 1}S{sub 0} to the 5s[3/2]{sub 1} level. An 819 nm Ti:sapphire laser is used for the second-step excitation from 5s[3/2]{sub 1} to 5s[3/2]{sub 2} followed by a spontaneous decay to the 5s[3/2]{sub 2} metastable level. A metastable atomic beam with an angular flux density of 3x10{sup 14} s{sup -1} sr{sup -1} is achieved at the total gas flow rate of 0.01 cm{sup 3}/s at STP (or 3x10{sup 17} at./s). The dependences of the flux on the gas flow rate, laser power, and lamp parameters are investigated.

Ding, Y.; Hu, S.-M.; Bailey, K.; Davis, A. M.; Dunford, R. W.; Lu, Z.-T.; O'Connor, T. P.; Young, L. [Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 (United States); Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026 (China); Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637 (United States); Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60639 (United States); Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)

2007-02-15

210

Krypton charge exchange cross sections for Hall effect thruster models  

NASA Astrophysics Data System (ADS)

Following discharge from a Hall effect thruster, charge exchange occurs between ions and un-ionized propellant atoms. The low-energy cations produced can disturb operation of onboard instrumentation or the thruster itself. Charge-exchange cross sections for both singly and doubly charged propellant atoms are required to model these interactions. While xenon is the most common propellant currently used in Hall effect thrusters, other propellants are being considered, in particular, krypton. We present here guided-ion beam measurements and comparisons to semiclassical calculations for Kr+ + Kr and Kr2+ + Kr cross sections. The measurements of symmetric Kr+ + Kr charge exchange are in good agreement with both the calculations including spin-orbit effects and previous measurements. For the symmetric Kr2+ + Kr reaction, we present cross section measurements for center-of-mass energies between 1 eV and 300 eV, which spans energies not previously examined experimentally. These cross section measurements compare well with a simple one-electron transfer model. Finally, cross sections for the asymmetric Kr2+ + Kr --> Kr+ + Kr+ reaction show an onset near 12 eV, reaching cross sections near constant value of 1.6 A?2 with an exception near 70-80 eV.

Hause, Michael L.; Prince, Benjamin D.; Bemish, Raymond J.

2013-04-01

211

Hydrodynamics with Triangle Anomalies  

SciTech Connect

We consider the hydrodynamic regime of theories with quantum anomalies for global currents. We show that a hitherto discarded term in the conserved current is not only allowed by symmetries, but is in fact required by triangle anomalies and the second law of thermodynamics. This term leads to a number of new effects, one of which is chiral separation in a rotating fluid at nonzero chemical potential. The new kinetic coefficients can be expressed, in a unique fashion, through the anomaly coefficients and the equation of state. We briefly discuss the relevance of this new hydrodynamic term for physical situations, including heavy-ion collisions.

Son, Dam T. [Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1550 (United States); Surowka, Piotr [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States); Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)

2009-11-06

212

Vascular anomalies in children.  

PubMed

Vascular anomalies are divided in two major categories: tumours (such as infantile hemangiomas) and malformations. Hemangiomas are common benign neoplasms that undergo a proliferative phase followed by stabilization and eventual spontaneous involution, whereas vascular malformations are rare structural anomalies representing morphogenetic errors of developing blood vessels and lymphatics. It is important to properly diagnose vascular anomalies early in childhood because of their distinct differences in morbidity, prognosis and need for a multidisciplinary management. We discuss a number of characteristic clinical features as clues for early diagnosis and identification of associated syndromes. PMID:22090176

Weibel, L

2011-11-01

213

Breaking through the Glass Ceiling: The Correlation Between the Self-Diffusivity in and Krypton Permeation through Deeply Supercooled Liquid Nanoscale Methanol Films  

SciTech Connect

Molecular beam techniques, temperature-programmed desorption (TPD), and reflection absorption infrared spectroscopy (RAIRS) are used to explore the relationship between krypton permeation through and the self-diffusivity of supercooled liquid methanol at temperatures near (100-115 K) the glass transition temperature, Tg (103 K). Layered films, consisting of CH3OH and CD3OH, are deposited ontop of a monolayer of Kr on a graphene covered Pt(111) substrate at 25 K. Concurrent Kr TPD and RAIRS spectra are acquired during the heating of the composite film to temperatures above Tg. The CO vibrational stretch is sensitive to the local molecular environment and is used to determine the supercooled liquid diffusivity from the intermixing of the isotopic layers. We find that the Kr permeation and the diffusivity of the supercooled liquid are directly and quantitatively correlated. These results validate the rare gas permeation technique as a tool for probing the diffusivity of supercooled liquids.

Smith, R. Scott; Matthiesen, Jesper; Kay, Bruce D.

2010-03-28

214

Breaking through the glass ceiling: The correlation between the self-diffusivity in and krypton permeation through deeply supercooled liquid nanoscale methanol films  

NASA Astrophysics Data System (ADS)

Molecular beam techniques, temperature-programmed desorption (TPD), and reflection absorption infrared spectroscopy (RAIRS) are used to explore the relationship between krypton permeation through and the self-diffusivity of supercooled liquid methanol at temperatures (100-115 K) near the glass transition temperature, Tg (103 K). Layered films, consisting of CH3OH and CD3OH, are deposited on top of a monolayer of Kr on a graphene covered Pt(111) substrate at 25 K. Concurrent Kr TPD and RAIRS spectra are acquired during the heating of the composite film to temperatures above Tg. The CO vibrational stretch is sensitive to the local molecular environment and is used to determine the supercooled liquid diffusivity from the intermixing of the isotopic layers. We find that the Kr permeation and the diffusivity of the supercooled liquid are directly and quantitatively correlated. These results validate the rare-gas permeation technique as a tool for probing the diffusivity of supercooled liquids.

Smith, R. Scott; Matthiesen, Jesper; Kay, Bruce D.

2010-03-01

215

Skyrmions and Anomalies.  

National Technical Information Service (NTIS)

The author summarizes the works presented at the meeting on Skyrmions and anomalies. He divides the principal issues of this workshop into five categories: QCD effective Lagrangians, chiral bags and the Cheshire cat principle, strangeness problem, phenome...

M. Rho

1987-01-01

216

Recurrent chest wall anomalies.  

PubMed

Chest wall anomalies are a heterogeneous group of malformations requiring repair. Recurrence and the need for secondary repair may occur. Congenital anomalies, including bifid sternum, pentalogy of Cantrell, Jeunes's syndrome and Poland's anomaly, rarely recur. Pectus carinatum may recur in the original surgical area or an adjacent area and most often recurs in patients who undergo repair before completion of teenage growth. Pectus excavatum may recur in approximately 5% of patients. Simple recurrence, floating sternum, or Acquired Jeune's syndrome may result. All of these would require reoperation. Each chest wall anomaly recurrence requires an individualized approach to timing and type of repair. Overall excellent results should be obtained for operative repair of recurrences. PMID:12728394

Colombani, Paul M

2003-05-01

217

Anomalies and gravity  

Microsoft Academic Search

Anomalies in Yang-Mills type gauge theories of gravity are reviewed. Particular attention is paid to the relation between the Dirac spin, the axial current j5 and the non-covariant gauge spin C. Using diagrammatic techniques, we show that only generalizations of the U(1)- Pontrjagin four-form F ? F = dC arise in the chiral anomaly, even when coupled to gravity. Implications

Eckehard W. Mielke; Eckehard W

2006-01-01

218

Elastic electron scattering in krypton in the energy range from 5 to 10 eV  

SciTech Connect

Differential cross sections for elastic electron scattering in krypton have been measured at the energies of 5,7.5, and 10 eV over the scattering angle range from 30 deg. to 180 deg. The measurements for backward scattering employed the magnetic angle-changing technique. These differential cross sections have been integrated to yield the elastic integral and momentum transfer cross sections at the above energies. These new results are compared with the most recent measurements and calculations of the respective cross sections in krypton. The dependence of the differential cross sections on atomic polarizability of the heavier rare gas atoms argon, krypton, and xenon has also been investigated over the electron energy range 5-30 eV and for forward, backward, and intermediate scattering angles.

Linert, Ireneusz; Mielewska, Brygida; Zubek, Mariusz [Department of Physics of Electronic Phenomena, Gdansk University of Technology, 80-233 Gdansk (Poland); King, George C. [School of Physics and Astronomy, Manchester University, Manchester M13 9 PL (United Kingdom)

2010-01-15

219

Half-lives of some Radioactive Isotopes  

Microsoft Academic Search

IN the course of investigations with radioactive isotopes in this Department, anomalous rates of decay have been observed with some isotopes in particular chemical forms. The escape of iodine-131 from evaporated samples of sodium iodide has already been reported by one of us1, and Hevesy2 has reported the escape of carbon-14 from exposed samples of barium carbonate. Anomalies have also

W. K. Sinclair; A. F. Holloway

1951-01-01

220

Emission in argon and krypton at 147 nm excited by runaway-electron-induced diffusion discharge  

SciTech Connect

Plasma emission of a pulsed diffuse discharge produced at increased pressures due to the preionisation of the gap by runaway electrons is studied in argon, krypton, and xenon. Nanosecond voltage pulses with the amplitude {approx}220 kV were applied to the discharge gap. It is shown that the presence of xenon ({approx}0.01%) in argon and krypton leads to the emergence of high-power narrowband radiation at awavelength of 147 nm. It is assumed that this radiation belongs to the bands of heteronuclear molecules Xe*Ar and Xe*Kr.

Gerasimov, Gennadii N; Krylov, B E [Research Center 'Vavilov State Optical Institute', St.Petersburg (Russian Federation); Lomaev, Mikhail I; Rybka, D V; Tarasenko, Viktor F [Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation)

2010-05-26

221

Determination of L Binding Energies of Krypton by the Photoelectron Method  

Microsoft Academic Search

Energies of the photoelectrons Kr LI,II,III(Mo Lalpha), Kr LI,II(Mo Lbeta1), Kr LI(Ag Lalpha), Kr LI(Ti Kalpha), and Kr LI(Cr Kalpha) were measured with a 90 electrostatic analyzer. Krypton was irradiated in the gaseous phase. The following values of the binding energies of krypton L electrons were obtained: LI=1921.2+\\/-0.8 eV; LII=1727.2+\\/-0.6 eV; LIII=1674.8+\\/-0.6 eV. These values are compared in modified Moseley

Manfred O. Krause

1965-01-01

222

Beam of metastable krypton atoms extracted from a microwave-driven discharge  

SciTech Connect

A microwave-driven discharge is used to produce a thermal beam of metastable krypton atoms at the 5s[3/2]{sub 2} level with an angular flux density of 7x10{sup 14} s{sup -1} sr{sup -1}, while consuming 1x10{sup 17} krypton atoms/s. This source of atomic beam uses commercially available microwave parts, and has achieved comparable beam flux and excitation efficiency with a previously described source that employs a rf-driven discharge [C. Y. Chen et al., Rev. Sci. Instrum. 72, 271 (2001)].

Ding, Y.; Bailey, K.; Davis, A. M.; Hu, S.-M.; Lu, Z.-T.; O'Connor, T. P. [Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 and Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) and Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) and Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 and Department of Geophysical Sciences, University of Chicago, Chicago, Illinois 60637 (United States) and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026 (China) and Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637; Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) and Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States); Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2006-12-15

223

A beam of metastable krypton atoms extracted from a microwave-driven discharge.  

SciTech Connect

A microwave-driven discharge is used to produce a thermal beam of metastable krypton atoms at the 5s[3/2]{sub 2} level with an angular flux density of 7 x 10{sup 14} s{sup -1} sr{sup -1}, while consuming 1 x 10{sup 17} krypton atoms/s. This source of atomic beam uses commercially available microwave parts, and has achieved comparable beam flux and excitation efficiency with a previously described source that employs a rf-driven discharge [C. Y. Chen et al., Rev. Sci. Instrum. 72, 271 (2001)].

Ding, Y.; Bailey, K.; Davis, A. M.; Hu, S.-M.; Lu, Z.-T.; O'Connor, T. P.; Physics; Univ. of Chicago; Unvi. of Science and Technology of China

2006-01-01

224

Purely-long-range krypton molecules in singly and doubly excited binding potentials  

SciTech Connect

Diatomic potentials for krypton are computed and also probed experimentally. For a probe-laser wavelength near 811 nm, several strong dipole-dipole interactions produce purely-long-range potential wells in the singly excited manifold of (s+p) potentials and in the doubly excited manifold of (p+p) and (s+d) potentials. Evidence of resonant photoassociation into bound states of these potential wells is observed in the emission of ions and ultraviolet photons from a magneto-optically trapped krypton cloud.

Smith, Z. S.; Harmon, A.; Banister, J.; Norman, R.; Hoogeboom-Pot, K.; Walhout, M. [Department of Physics and Astronomy, Calvin College, Grand Rapids, Michigan 49546 (United States)

2010-01-15

225

Raman and Laser-Induced Fluorescence Signatures of Isotopically Primitive and Normal IDPs  

NASA Astrophysics Data System (ADS)

Isotopically primitive IDPs have lower laser-induced fluorescence and wider Raman D bands than normal IDPs. Combined Raman/SIMS study suggests that there may be multiple carbonaceous carriers for the N-isotopic anomalies in primitive IDPs.

Wopenka, B.; Floss, C.

2012-03-01

226

Beta-decay study of neutron rich isotopes of Bromine and Krypton  

SciTech Connect

Short lived neutron rich nuclei including 93 Br, 93 Kr and 94 Kr were produced in proton induced fission of 238 U at the HRIBF in Oak Ridge. Their beta decay was studied by means of a high resolution on line mass separator and beta gamma spectroscopy methods. The half life of 93Br T1/2 = 152(8) ms and delayed branching ratio of Pn = 53-8+11 may be compared to the previously reported values of T1/2 = 102(10) ms and Pn = 68(7)%. At the same time the half life of 94Kr T1/2 = 227(14) ms and B delayed branching ratio of Pn = 1.9+0.6 0.2 % of 93Kr are in very good agreement with literature values. The decay properties of 93Br include four new gamma transitions following beta delayed neutron emission.

Miernik, Krzysztof A [ORNL; Gross, Carl J [ORNL; Grzywacz, Robert Kazimierz [ORNL; Madurga, M [University of Tennessee, Knoxville (UTK); Mendez, II, Anthony J [ORNL; Miller, D. [University of Tennessee, Knoxville (UTK); Padgett, S [University of Tennessee, Knoxville (UTK); Paulauskas, Stanley V [ORNL; Rykaczewski, Krzysztof Piotr [ORNL; Stracener, Daniel W [ORNL; Wolinska-Cichocka, Marzena [ORNL; Zganjar, E. F. [Louisiana State University; Batchelder, J. C. [Oak Ridge Associated Universities (ORAU); Brewer, N.T. [Vanderbilt University; Cartegni, L. [University of Tennessee, Knoxville (UTK); Fijalkowska, Aleksandra G [ORNL; Hamilton, J. H. [Vanderbilt University; Hwang, J. K. [Vanderbilt University; Ilyushkin, S. [Mississippi State University (MSU); Jost, Carola U [ORNL; Karny, M. [University of Warsaw; Korgul, A. [University of Warsaw; Krolas, W. [Oak Ridge Associated Universities (ORAU); Liu, S.H. [UNIRIB/ORAU and Vanderbilt University, Nashville, Tennessee; Mazzocchi, C. [University of Warsaw; Ramayya, A. V. [Vanderbilt University; Surman, Rebecca [Union College; Winger, J. A. [Mississippi State University (MSU); Wolinska-Cichocka, M [Oak Ridge Associated Universities (ORAU)

2013-01-01

227

A multi-isotopic and trace element investigation of the CretaceousTertiary boundary layer at Stevns Klint, Denmark inferences for the origin and nature of siderophile and lithophile element geochemical anomalies  

Microsoft Academic Search

Os, Sr, Nd and Pb isotope data were collected from a profile across the CretaceousTertiary (KT) boundary layer at Stevns Klint, Denmark. ?Nd [T=65 Ma] values from within the boundary layer (Fish Clay) are lower by ?1 ? unit than those of the underlying Maastrichtian limestone and the overlying Danian chalk sequences. Systematic profile-upward changes of Pb, Sr and Os

Robert Frei; Karin M. Frei

2002-01-01

228

Deactivation of krypton atoms in the metastable 5s({sup 3}P{sub 2}) state in collisions with krypton and argon atoms  

SciTech Connect

The collision deactivation of the metastable 5s[3/2]{sub 2}{sup o}({sup 3}P{sub 2}) state of krypton atoms is studied by the absorption probe method in electron-beam-excited high-pressure Ar-Kr mixtures with a low krypton content. The rate constants of plasma-chemical reactions Kr* + Kr + Ar {yields} Kr{sub 2}* + Ar [(4.1{+-}0.4)x10{sup -33} cm{sup 6} s{sup -1}] and Kr* + 2Ar {yields} ArKr* + Ar (less than 10{sup -35} cm{sup 6} s{sup -1}) are measured for the first time and the rate constant of the reaction Kr* + Ar {yields} products + Ar [(3.8{+-}0.4)x10{sup -15} cm{sup 3} s{sup -1}] is refined. (active media)

Zayarnyi, D A; L'dov, A Yu; Kholin, I V [P N Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2009-09-30

229

Astrometric solar system anomalies  

SciTech Connect

There are at least four unexplained anomalies connected with astrometric data. perhaps the most disturbing is the fact that when a spacecraft on a flyby trajectory approaches the Earth within 2000 km or less, it often experiences a change in total orbital energy per unit mass. next, a secular change in the astronomical unit AU is definitely a concern. It is increasing by about 15 cm yr{sup -1}. The other two anomalies are perhaps less disturbing because of known sources of nongravitational acceleration. The first is an apparent slowing of the two Pioneer spacecraft as they exit the solar system in opposite directions. Some astronomers and physicists are convinced this effect is of concern, but many others are convinced it is produced by a nearly identical thermal emission from both spacecraft, in a direction away from the Sun, thereby producing acceleration toward the Sun. The fourth anomaly is a measured increase in the eccentricity of the Moon's orbit. Here again, an increase is expected from tidal friction in both the Earth and Moon. However, there is a reported unexplained increase that is significant at the three-sigma level. It is produent to suspect that all four anomalies have mundane explanations, or that one or more anomalies are a result of systematic error. Yet they might eventually be explained by new physics. For example, a slightly modified theory of gravitation is not ruled out, perhaps analogous to Einstein's 1916 explanation for the excess precession of Mercury's perihelion.

Nieto, Michael Martin [Los Alamos National Laboratory; Anderson, John D [PROPULSION LABORATORY

2009-01-01

230

Gravity anomalies on Venus  

NASA Astrophysics Data System (ADS)

Doppler radio tracking of the Pioneer Venus orbiter has provided gravity measures over a significant portion of Venus. Feature resolution is approximately 300-1000 km within an area extending from 10 deg S to 40 deg N latitude and from 70 deg W to 130 deg E longitude (approximately equal to 200 deg). Many anomalies were detected, and there is considerable correlation with radar altimetry topography (Pettengill et al., 1980). The amplitudes of the anomalies are relatively mild and similar to those on earth at this resolution. Calculations for isostatic adjustment reveal that significant compensation has occurred.

Sjogren, W. L.; Phillips, R. J.; Birkeland, P. W.; Wimberly, R. N.

1980-12-01

231

Common Congenital Anomalies  

PubMed Central

Congenital anomalies account for a substantial proportion of childhood morbidity and mortality. They have become proportionately larger because of the decline of such other categories as infections or birth trauma. Approximately 3% of newborns have a serious handicapping or potentially lethal condition; in longterm studies the frequency is much higher. There is no good evidence to suggest that the rates of congenital anomalies are increasing, although this is a common perception. This article discusses diagnosis and management (especially genetic implications) of heart defects, neural tube defects, orofacial clefting, dislocated hip, clubfoot, and hypospadias.

Lowry, R. B.

1985-01-01

232

The isotope hydrology of Quaternary climate change.  

PubMed

Understanding the links between climate change and human migration and culture is an important theme in Quaternary archaeology. While oxygen and hydrogen stable isotopes in high-latitude ice cores provide the ultimate detailed record of palaeoclimate extending back to the Middle Pleistocene, groundwater can act as a climate archive for areas at lower latitudes, permitting a degree of calibration for proxy records such as lake sediments, bones, and organic matter. Not only can oxygen and hydrogen stable isotopes be measured on waters, but the temperature of recharge can be calculated from the amount of the atmospheric noble gases neon, argon, krypton, and xenon in solution, while residence time can be estimated from the decay of the radioisotopes carbon-14, chlorine-36, and krypton-81 over timescales comparable to the ice core record. The Pleistocene-Holocene transition is well characterised in aquifers worldwide, and it is apparent that isotope-temperature relationships of the present day are not necessarily transferable to past climatic regimes, with important implications for the interpretation of proxy isotope data. Groundwaters dating back to one million years, i.e., to beyond the Middle Pleistocene, are only found in major aquifer basins and information is relatively sparse and of low resolution. Speleothem fluid inclusions offer a way of considerably increasing this resolution, but both speleothem formation and large-scale groundwater recharge requires humid conditions, which may be relatively infrequent for areas currently experiencing arid climates. Both types of record therefore require caution in their interpretation when considering a particular archaeological context. PMID:21051074

Darling, W G

2010-11-03

233

Preliminary safety evaluation of a commercial-scale krypton-85 encapsulation facility  

SciTech Connect

This report demonstrates that a commercial-scale facility for encapsulating krypton-85 in zeolite-5A or glass at a 2000 MTHM per year nuclear fuel reprocessing plant can be designed to contain fragments and the 340 to 850 kCi krypton-85 inventory from an assumed catastrophic failure of the high pressure vessel. The vessel failure was assumed as a worst case and was not based on a detailed design evaluation or operating experience. The process design is based on existing commercial hot isostatic pressing technology operated at up to 40 times the scale required for krypton encapsulation. From the calculated process gas inventory in the pressure vessel and vessel design, the explosive energy of 8.4 kg TNT and vessel plug and fragment velocities were calculated. The facility Containment Cell housing the high pressure vessel was designed to contain the gases, fragments, and the shock wave energy calculated for vessel failure. The Access Cell located directly above the Containment Cell was designed to be a tertiary confinement of krypton-85, should the access hatch be breached.

Christensen, A.B.; Tanner, J.E.; Knecht, D.A.

1980-09-01

234

Preliminary safety evaluation of a commercial-scale krypton-85 encapsulation facility  

SciTech Connect

This paper demonstrates that a commercial-scale facility for encapsulating krypton-85 in zeolite-5A or glass at a 2000 MTHM per year nuclear fuel reprocessing plant can be designed to contain fragments and the 340 to 850 kCi krypton-85 inventory from an assumed catastrophic failure of the high pressure vessel. The vessel failure was assumed as a worst case and was not based on a detailed design evaluation or operating experience. The process design is based on existing commercial hot isostatic pressing technology operated at up to 40 times the scale required for krypton encapsulation. From the calculated process gas inventory in the pressure vessel and vessel design, the maximum explosive energy of 8.4 kg TNT and resulting vessel plug and fragment velocities were calculated. The facility Containment Cell housing the high pressure vessel was designed to contain the gases, fragments, and the shock wave energy calculated for a hypothetical vessel failure. The Access Cell located directly above the Containment Cell was designed to be a tertiary confinement of krypton-85, should the access hatch be breached. 3 figures, 2 tables.

Christensen, A.B.; Tanner, J.E.; Knecht, D.A.

1980-01-01

235

Survey of methods for separating and immobilizing krypton-85 arising from a nuclear fuel reprocessing plant.  

National Technical Information Service (NTIS)

This report reviews the literature on methods to separate and immobilize krypton-85 arising from dissolution or prior treatment of nuclear fuel in a reprocessing plant. It was prepared as part of a broader review of fuel reprocessing waste management meth...

P. Taylor

1990-01-01

236

Identification of Krypton Kr XVIII to Kr XXIX Spectra Excited in TFR Tokamak Plasmas  

Microsoft Academic Search

The emission spectrum of krypton (injected into TFR tokamak plasmas) has been recorded photographically in the 15-300 spectral range by means of a 2 m grazing incidence spectrograph. Preliminary identification work, based on isoelectronic regularities from known spectra of other ions and ionization equilibrium calculations, has allowed 48 lines (belonging to the O I, F I, Na I, Mg

J. F. Wyart

1985-01-01

237

Adsorption measurements of argon, neon, krypton, nitrogen, and methane on activated carbon up to 650 MPa  

Microsoft Academic Search

The physisorption of argon, krypton, neon, nitrogen, and methane on GAC activated carbon has been measured in the above critical region by a dielectric method. The measurements were done at room temperature and at pressures up to 650 MPa corresponding to reduced densities of up to 3.25. With the exception of nitrogen, all the measured excess adsorption isotherms show a

P. Malbrunot; D. Vidal; J. Vermesse; R. Chahine; T. K. Bose

1992-01-01

238

Treatment of retinal detachment with congenital optic pit by krypton laser photocoagulation  

Microsoft Academic Search

Five patients with a congenital pit of the optic nerve and serous detachment of the macular retina were treated with krypton laser photocoagulation to the juxtapapillary region in an attempt to induce resolution of the retinal detachment. The subretinal fluid resolved after laser therapy in four of the patients. In the fifth, the retinal detachment was successfully treated with pars

W. Annesley; G. Brown; J. Bolling; R. Goldberg; D. Fischer

1987-01-01

239

On the use of multiple photon processes in krypton for laser guiding of electron beams  

SciTech Connect

Neutral krypton atoms were excited from the ground state 4p/sup 6/ /sup 1/S/sub 0/ to the 4p/sup 5/ 6p(3/2)/sub 2/ state by a resonant two-photon absorption from a line-narrowed ArF excimer laser operating at 193.41 nm. A third photon, absorbed while the atom is in the excited state, ionizes it. Excited state and ion densities were theoretically computed using a standard rate-equation analysis. The irradiance levels used (1 - 5 x 10/sup 8/ W/cm/sup 2/) were too low for significant ground and excited state ac Stark and Rabi effects. The photon detection system was calibrated with a standard tungsten lamp. Ion signals were measured with known electrical components. The resonance results were compared with predictions of non-resonant ionization based on a standard formulation. The ion and excited state densities have been used with a modified electron beam propagation code (IPROP) to model such propagation in a low pressure laser-excited krypton channel. The modifications included the effects to field ionization of the excited krypton atoms. Implications for guiding of e-beams using ArF excited krypton are discussed. 12 refs., 1 tab.

Radziemski, L.J.; Khambatta, N.M.; Oertel, J.A.; Silk, R.; Mack, J.M.; Mitrovich, D.

1989-01-01

240

A new approach to decipher the origin of the carbonaceous chondrite fission krypton and xenon  

Microsoft Academic Search

It is suggested that the carbonaceous chondrite fission krypton and xenon, as measured in the primitive meteorites, may have been produced by nuclear fission induced by CNO flare particles in the few-MeV\\/nucleon energy range on very heavy target elements such as Au, Hg, Tl, Pb, and Bi. It is speculatively proposed that the locale of this process has been the

H. W. Mueller; O. A. Schaeffer

1978-01-01

241

Statistical analysis of the electrical breakdown time delay distributions in krypton  

Microsoft Academic Search

The statistical analysis of the experimentally observed electrical breakdown time delay distributions in the krypton-filled diode tube at 2.6 mbar is presented. The experimental distributions are obtained on the basis of 1000 successive and independent measurements. The theoretical electrical breakdown time delay distribution is evaluated as the convolution of the statistical time delay with exponential, and discharge formative time with

Jugoslav P. Karamarkovic; Miodrag K. Radovic

2006-01-01

242

Ionization EM calorimetry with accordion electrodes and liquid krypton or argon  

SciTech Connect

The results of a study and tests of a liquid krypton/argon electromagnetic calorimeter with accordion electrode structure are briefly summarized. This includes the calorimeter response to electrons and muons, energy, pointing and timing resolution, and a measurement by multiple sampling. The electrode layout with fine segmentation is illustrated.

Radeka, V.

1993-11-01

243

Understanding Layer Promotion and Its Relationship to Melting in Krypton on Graphite Using Artificial Constraints  

Microsoft Academic Search

Constant particle number, density and temperature (N, ?, T) Molecular-Dynamics simulations are used to study second layer promotion and melting in a complete monolayer of krypton deposited onto a graphite substrate. In order to study the vertical behavior of the system and its relationship to melting, artificial horizontal constraints are introduced and their effects are systematically monitored. We find that

E. J. Chamberlin; M. W. Roth

244

Absorption Spectra of Krypton and Xenon in Their Regions of Autoionization.  

National Technical Information Service (NTIS)

The absorption cross section spectra of krypton and xenon, obtained at narrow spectral bandwidths are reported. Both gases were studied in their regions of autoionization, 840 to 880 A and 918 to 990 A for Kr and Xe, respectively. In Kr over the entire wa...

R. D. Hudson V. L. Carter

1973-01-01

245

[Effects of xenon and krypton-containing breathing mixtures on clinical and biochemical blood indices in animals].  

PubMed

Effects of 24-hr breathing air mixtures containing xenon (XBM) and krypton (KBM) were compared in terms of hormonal status, and blood biochemical indices and morphology in laboratory animals. Some changes observed in blood and hormone indices could be a nonspecific adaptive response. Hence, we should elicit whether these effects are quickly reversible or long. For several indices krypton was a more favorable factor than xenon. However, some of its effects invite to delve into effects of different krypton concentrations on organism. PMID:17682508

Kussmaul', A R; Bogacheva, M A; Shkurat, T P; Pavlov, B N

246

Rhenium-osmium isotopes and platinum-group elements in the Rum Layered Suite, Scotland: Implications for Cr-spinel seam formation and the composition of the Iceland mantle anomaly  

NASA Astrophysics Data System (ADS)

The Rum Layered Suite is a layered mafic-ultramafic body that was emplaced during Palaeogene North Atlantic margin rifting. It is a classic open-system magma chamber, constructed of 16 repeated coupled peridotite-troctolite units, some of which have laterally extensive ~ 2 mm-thick platinum-group element (PGE) enriched (~ 2 g g- 1) Cr-spinel seams at their bases. In order to investigate Cr-spinel seam petrogenesis and enrichment of the PGE, abundances of these elements and Re-Os isotopes have been determined at three stratigraphic levels of the Rum Layered Suite that represent major magma replenishment events. Individual units preserve a range of initial 187Os/188Os ratios, demonstrating heterogeneity in the composition of replenishing magmas. Data for both the Cr-spinel seams and overlying silicates reveal that the processes that formed the Cr-spinel also concentrated the PGE, following magma replenishment. There is no evidence for structurally-bound PGE in Cr-spinel. Instead, the PGE budget of the Rum Layered Suite is linked to base metal sulphides, especially pentlandite, and to PGE alloys contained within the Cr-spinel seams, but which exist as separate phases at Cr-spinel grain boundaries. The range in initial Os isotope compositions (?Os = 3.4 to 36) in the Rum Layered Suite can be successfully modelled by 5-8% assimilation of Lewisian gneiss coupled with changing PGE contents in the replenishing magmas associated with sulphide removal. Initial 187Os/188Os ratios for Rum rocks range from 0.1305 to 0.1349 and are atypical of the convecting upper mantle, but are within the range for recently erupted picrites and basalts from Iceland and Palaeogene picrites and basalts from Baffin Island, Greenland and Scotland. Thus, the Os isotope data suggest that the North Atlantic Igneous Province magmas were collectively produced from a mantle source with components that remained relatively unchanged in Os isotopic composition over the past 60 Ma, and that likely contain a recycled lithospheric component.

O'Driscoll, Brian; Day, James M. D.; Daly, J. Stephen; Walker, Richard J.; McDonough, William F.

2009-08-01

247

Gravity anomalies on Venus  

Microsoft Academic Search

Doppler radio tracking of the Pioneer Venus orbiter has provided gravity measures over a significant portion of Venus. Feature resolution is approximately 300-1000 km within an area extending from 10 deg S to 40 deg N latitude and from 70 deg W to 130 deg E longitude (approximately equal to 200 deg). Many anomalies were detected, and there is considerable

W. L. Sjogren; R. J. Phillips; P. W. Birkeland; R. N. Wimberly

1980-01-01

248

Superstrings, anomalies and unification  

SciTech Connect

This volume contains the lectures covering the main lines of developments in the presently most active field of particle physics: string field theory, anomalies, unification and physics beyond the Planck length. The lectures are generally pedagogical in style, designed at the postdoctoral level, but at the same time they introduce one to the most recent results in the field.

Martinis, M.; Andric, I.

1987-01-01

249

The Pioneer Anomaly  

NASA Astrophysics Data System (ADS)

Radio-metric Doppler tracking data received from the Pioneer 10 and 11 spacecraft from heliocentric distances of 20-70 AU has consistently indicated the presence of a small, anomalous, blue-shifted frequency drift uniformly changing with a rate of 6 10^{-9} Hz/s. Ultimately, the drift was interpreted as a constant sunward deceleration of each particular spacecraft at the level of a_P = (8.74 1.33) 10^{-10} m/s^2. This apparent violation of the Newton's gravitational inverse square law has become known as the Pioneer anomaly; the nature of this anomaly remains unexplained. In this review, we summarize the current knowledge of the physical properties of the anomaly and the conditions that led to its detection and characterization. We review various mechanisms proposed to explain the anomaly and discuss the current state of efforts to determine its nature. A comprehensive new investigation of the anomalous behavior of the two Pioneers has begun recently. The new efforts rely on the much-extended set of radio-metric Doppler data for both spacecraft in conjunction with the newly available complete record of their telemetry files and a large archive of original project documentation. As the new study is yet to report its findings, this review provides the necessary background for the new results to appear in the near future. In particular, we provide a significant amount of information on the design, operations and behavior of the two Pioneers during their entire missions, including descriptions of various data formats and techniques used for their navigation and radio-science data analysis. As most of this information was recovered relatively recently, it was not used in the previous studies of the Pioneer anomaly, but it is critical for the new investigation.

Turyshev, Slava G.; Toth, Viktor T.

2010-09-01

250

Spacecraft Environmental Anomalies Expert System.  

National Technical Information Service (NTIS)

A microcomputer based expert system is being developed to assist in the diagnosis of satellite anomalies caused by the space environment. The expert system is designed to address anomalies caused by surface charging, bulk charging, single event effects, a...

H. C. Koons D. J. Gorney

1988-01-01

251

Ferret Workflow Anomaly Detection System.  

National Technical Information Service (NTIS)

The Ferret workflow anomaly detection system project 2003-2004 has provided validation and anomaly detection in accredited workflows in secure knowledge management systems through the use of continuous, automated audits. A workflow, process, or procedure,...

T. J. Smith S. Bryant

2005-01-01

252

Hepatic exstrophy complicating Poland's anomaly.  

PubMed

Poland's anomaly is comprised of a constellation of anomalies. To be included in the syndrome, a child must have a deficiency of the pectoralis major and minor muscles and an associated anomaly of either the ipsilateral breast or hand. Associated defects may include syndactyly osseous and cartilagenous costal aplasia and adactyly. A case of hepatic exstrophy through a full-thickness chest wall defect in an infant with Poland's anomaly is reported. PMID:12149703

Puder, Mark; Greene, Arin; Mooney, David

2002-08-01

253

Hepatic exstrophy complicating Poland's anomaly  

Microsoft Academic Search

Poland's anomaly is comprised of a constellation of anomalies. To be included in the syndrome, a child must have a deficiency of the pectoralis major and minor muscles and an associated anomaly of either the ipsilateral breast or hand. Associated defects may include syndactyly osseous and cartilagenous costal aplasia and adactyly. A case of hepatic exstrophy through a full-thickness chest

Mark Puder; Arin Greene; David Mooney

2002-01-01

254

Neutron-Rich Equilibrium Nucleosynthesis and Meteoritic Abundance Anomalies  

NASA Astrophysics Data System (ADS)

Experimental data on correlated 48Ca, 50Ti, and 54Cr abundance anomalies in meteoritic inclusions lend support to the idea that the natural synthesis of these rare isotopes occurs within neutron-rich stellar zones that have achieved nuclear statistical equilibrium (NSE). The author has studied matter in the neutron-rich environment near the mass-cut of a proto neutron star that is shock heated to NSE and subsequently ejected in the supernova event. The correlated abundance anomalies can be explained if a typical supernova event contributes only a small amount of such neutron-rich matter.

Hartman, D.

255

Comparison in the analytical performance between krypton and argon glow discharge plasmas as the excitation source for atomic emission spectrometry  

Microsoft Academic Search

The emission characteristics of ionic lines of nickel, cobalt, and vanadium were investigated when argon or krypton was employed\\u000a as the plasma gas in glow discharge optical emission spectrometry. A dc Grimm-style lamp was employed as the excitation source.\\u000a Detection limits of the ionic lines in each iron-matrix alloy sample were compared between the krypton and the argon plasmas.\\u000a Particular

Kazuaki Wagatsuma

2009-01-01

256

Performance of a continuous-wave forsterite laser with krypton ion, Ti:sapphire, and Nd:YAG pump lasers  

Microsoft Academic Search

The authors characterize continuous-wave operation of a chromium-doped forsterite (Cr4+:Mg2SiO4) laser using krypton ion, Ti:sapphire, and Nd:YAG lasers as pump sources. Measurements were made pumping at 647 nm and 676 nm with the krypton ion laser, between 690 and 1010 nm with the Ti:sapphire laser, and at 1.06 ?m with the Nd:YAG laser. Threshold pump powers and slope efficiencies are

Timothy J. Carrig; Clifford R. Pollock

1993-01-01

257

Holographic gravitational anomalies  

Microsoft Academic Search

In the AdS\\/CFT correspondence one encounters theories that are not invariant under diffeomorphisms. In the boundary theory this is a gravitational anomaly, and can arise in 4k+2 dimensions. In the bulk, there can be gravitational Chern-Simons terms which vary by a total derivative. We work out the holographic stress tensor for such theories, and demonstrate agreement between the bulk and

Per Kraus; Finn Larsen

2006-01-01

258

Mixed states from anomalies  

NASA Astrophysics Data System (ADS)

There are several instances where quantum anomalies of continuous and discrete classical symmetries play an important role in fundamental physics. Examples come from chiral anomalies in the Standard Model of fundamental interactions and gravitational anomalies in string theories. Their generic origin is the fact that classical symmetries may not preserve the domains of quantum operators like the Hamiltonian. In this work, we show by simple examples that anomalous symmetries can often be implemented at the expense of working with mixed states having nonzero entropies. In particular there is the result on color breaking by non-abelian magnetic monopoles. This anomaly can be rectified by using impure states. We also argue that non-abelian groups of twisted bundles are always anomalous for pure states sharpening an earlier argument of Sorkin and Balachandran [A. P. Balachandran, G. Marmo, B. S. Skagerstam, and A. Stern, Classical Topology and Quantum States (World Scientific, Singapore, 1991).]. This is the case of mapping class groups of geons [A. P. Balachandran, G. Marmo, B. S. Skagerstam, and A. Stern, Classical Topology and Quantum States (World Scientific, Singapore, 1991).] indicating that large diffeos are anomalous for pure states in the presence of geons. Nevertheless diffeo invariance may be restored by using impure states. This work concludes with examples of these ideas drawn from molecular physics. The above approach using impure states is entirely equivalent to restricting all states to the algebra of observables invariant under the anomalous symmetries. For anomalous gauge groups such as color, this would mean that we work with observables singlet under global gauge transformations. For color, this will mean that we work with color singlets, a reasonable constraint.

Balachandran, A. P.; de Queiroz, Amilcar R.

2012-01-01

259

Complex vascular anomalies.  

PubMed

The classification system for vascular anomalies now used by experts worldwide comprises two distinct disease entities that differ in their biologic and pathologic features: vascular tumors and vascular malformations. Vascular tumors include infantile and congenital hemangiomas, tufted angiomas, and kaposiform hemangioendotheliomas. Infantile hemangiomas, the most common vascular anomaly, generally have a predetermined life cycle (proliferation and subsequent involution). GLUT-1, a glucose transporter, is a marker for these specific lesions during all phases of development. Vascular malformations are classified according to their vascular tissue of origin and include capillary, venous, arteriovenous, lymphatic, and mixed malformations. Complex lymphatic malformations and complex mixed malformations, which may have most vascular components, are the most difficult vascular malformations to successfully treat. These lesions are present at birth and often expand or grow in response to trauma, infection, or hormonal changes. Imaging advancements have enabled more accurate assessments and improved management of vascular anomalies. In addition, many lesions are now being managed with targeted pharmacologic therapy. Propranolol and steroids are used for complex or disfiguring tumors, and new anti-angiogenesis inhibitors such as sirolimus are selectively used to treat lymphatic and venous lymphatic malformations that are poorly responsive to sclerotherapy, embolization, and surgical excision. Multimodal therapies are often essential for complex lesions and require the combined expertise of an interdisciplinary team. PMID:23989523

Azizkhan, Richard G

2013-10-01

260

Space Weather and Satellite Anomalies  

NASA Astrophysics Data System (ADS)

Results of the Satellite Anomaly Project, which aims to improve the methods of safeguarding satellites in the Earth's magnetosphere from the negative effects of the space environment, are presented. Anomaly data from the "Kosmos" series satellites in the period 1971-1999 are com-bined in one database, together with similar information on other spacecrafts. This database contains, beyond the anomaly information, various characteristics of the space weather: geo-magnetic activity indices (Ap, AE and Dst), fluxes and fluencies of electrons and protons at different energies, high energy cosmic ray variations and other solar, interplanetary and solar wind data. A comparative analysis of the distribution of each of these parameters relative to satellite anomalies was carried out for the total number of anomalies (about 6000 events), and separately for high ( 5000 events) and low (about 800 events) altitude orbit satellites. No relation was found between low and high altitude satellite anomalies. Daily numbers of satel-lite anomalies, averaged by a superposed epoch method around sudden storm commencements and proton event onsets for high (?1500 km) and low (1500 km) altitude orbits revealed a big difference in a behavior. Satellites were divided on several groups according to the orbital char-acteristics (altitude and inclination). The relation of satellite anomalies to the environmental parameters was found to be different for various orbits that should be taken into account under developing of the anomaly frequency models. The preliminary anomaly frequency models are presented. Keywords: Space weather; Satellite anomalies; Energetic particles; Magnetic storms

Dorman, Lev; Iucci, N.; Levitin, A. E.; Belov, A. V.; Eroshenko, E. A.; Ptitsyna, N. G.; Villoresi, G.; Chizhenkov, G. V.; Gromova, L. I.; Parisi, M.; Tyasto, M. I.; Yanke, V. G.

261

Geologic interpretation of gravity anomalies  

SciTech Connect

This Russian textbook provides a sufficiently complete and systematic illumination of physico-geologic and mathematical aspect of complex problem of interpretation of gravity anomalies. The rational methods of localization of anomalies are examined in detail. All methods of interpreting gravity anomalies are described which have found successful application in practice. Also given are ideas of some new methods of the interpretation of gravity anomalies, the prospects for further development and industrial testing. Numerous practical examples to interpretation are given. Partial Contents: Bases of gravitational field theory; Physico-geologic bases of gravitational prospecting; Principles of geologic interpretation of gravity anomalies; Conversions and calculations of anomalies; Interpretation of gravity anomalies for bodies of correct geometric form and for bodies of arbitrary form; Geologic interpretation of the results of regional gravitational photographing; Searches and prospecting of oil- and gas-bearing structures and of deposits of ore and nonmetalliferous useful minerals.

Andreyev, B.A.; Klushin, I.G.

1990-04-19

262

Anomaly General Circulation Models.  

NASA Astrophysics Data System (ADS)

The feasibility of the anomaly model is assessed using barotropic and baroclinic models. In the barotropic case, both a stationary and a time-dependent model has been formulated and constructed, whereas only the stationary, linear case is considered in the baroclinic case. Results from the barotropic model indicate that a relation between the stationary solution and the time-averaged non-linear solution exists. The stationary linear baroclinic solution can therefore be considered with some confidence. The linear baroclinic anomaly model poses a formidable mathematical problem because it is necessary to solve a gigantic linear system to obtain the solution. A new method to find solution of large linear system, based on a projection on the Krylov subspace is shown to be successful when applied to the linearized baroclinic anomaly model. The scheme consists of projecting the original linear system on the Krylov subspace, thereby reducing the dimensionality of the matrix to be inverted to obtain the solution. With an appropriate setting of the damping parameters, the iterative Krylov method reaches a solution even using a Krylov subspace ten times smaller than the original space of the problem. This generality allows the treatment of the important problem of linear waves in the atmosphere. A larger class (nonzonally symmetric) of basic states can now be treated for the baroclinic primitive equations. These problem leads to large unsymmetrical linear systems of order 10000 and more which can now be successfully tackled by the Krylov method. The (R7) linear anomaly model is used to investigate extensively the linear response to equatorial and mid-latitude prescribed heating. The results indicate that the solution is deeply affected by the presence of the stationary waves in the basic state. The instability of the asymmetric flows, first pointed out by Simmons et al. (1983), is active also in the baroclinic case. However, the presence of baroclinic processes modifies the dominant response. The most sensitive areas are identified; they correspond to north Japan, the Pole and Greenland regions. A limited set of higher resolution (R15) experiments indicate that this situation is still present and enhanced at higher resolution. The linear anomaly model is also applied to a realistic case. (Abstract shortened with permission of author.).

Navarra, Antonio

263

Transpupillary CW YAG laser coagulation. A comparison with argon green and krypton red lasers.  

PubMed

The authors have developed a CW YAG laser for transpupillary coagulation. The effects of CW YAG coagulation on the retina, retinal vessels, and fovea were compared with those produced by the krypton red and argon green lasers. To produce threshold coagulative lesions in monkeys and rabbits, we needed five to ten times more energy with the CW YAG than with the krypton red or argon green lasers. Nerve fiber damage was observed only when coagulating retinal vessels with the argon green laser. At the parameters used, none of the lasers damaged the sensory retina of the fovea. The CW YAG may be used as a new mode of laser coagulation in the treatment of retinal diseases. PMID:6688868

Peyman, G A; Conway, M D; House, B

1983-08-01

264

AA stacking, tribological and electronic properties of double-layer graphene with krypton spacer.  

PubMed

Structural, energetic, and tribological characteristics of double-layer graphene with commensurate and incommensurate krypton spacers of nearly monolayer coverage are studied within the van der Waals-corrected density functional theory. It is shown that when the spacer is in the commensurate phase, the graphene layers have the AA stacking. For this phase, the barriers to relative in-plane translational and rotational motion and the shear mode frequency of the graphene layers are calculated. For the incommensurate phase, both of the barriers are found to be negligibly small. A considerable change of tunneling conductance between the graphene layers separated by the commensurate krypton spacer at their relative subangstrom displacement is revealed by the use of the Bardeen method. The possibility of nanoelectromechanical systems based on the studied tribological and electronic properties of the considered heterostructures is discussed. PMID:24160531

Popov, Andrey M; Lebedeva, Irina V; Knizhnik, Andrey A; Lozovik, Yurii E; Potapkin, Boris V; Poklonski, Nikolai A; Siahlo, Andrei I; Vyrko, Sergey A

2013-10-21

265

AA stacking, tribological and electronic properties of double-layer graphene with krypton spacer  

NASA Astrophysics Data System (ADS)

Structural, energetic, and tribological characteristics of double-layer graphene with commensurate and incommensurate krypton spacers of nearly monolayer coverage are studied within the van der Waals-corrected density functional theory. It is shown that when the spacer is in the commensurate phase, the graphene layers have the AA stacking. For this phase, the barriers to relative in-plane translational and rotational motion and the shear mode frequency of the graphene layers are calculated. For the incommensurate phase, both of the barriers are found to be negligibly small. A considerable change of tunneling conductance between the graphene layers separated by the commensurate krypton spacer at their relative subangstrom displacement is revealed by the use of the Bardeen method. The possibility of nanoelectromechanical systems based on the studied tribological and electronic properties of the considered heterostructures is discussed.

Popov, Andrey M.; Lebedeva, Irina V.; Knizhnik, Andrey A.; Lozovik, Yurii E.; Potapkin, Boris V.; Poklonski, Nikolai A.; Siahlo, Andrei I.; Vyrko, Sergey A.

2013-10-01

266

High-accuracy mass measurements of neutron-rich Kr isotopes  

SciTech Connect

The atomic masses of the neutron-rich krypton isotopes {sup 84,86-95}Kr have been determined with the tandem Penning trap mass spectrometer ISOLTRAP with uncertainties ranging from 20 to 220 ppb. The masses of the short-lived isotopes {sup 94}Kr and {sup 95}Kr were measured for the first time. The masses of the radioactive nuclides {sup 89}Kr and {sup 91}Kr disagree by 4 and 6 standard deviations, respectively, from the present Atomic-Mass Evaluation database. The resulting modification of the mass surface with respect to the two-neutron separation energies as well as implications for mass models and stellar nucleosynthesis are discussed.

Delahaye, P.; Kellerbauer, A. [ISOLDE, CERN, Physics Department, CH-1211 Geneva 23 (Switzerland); Audi, G.; Lunney, D. [CSNSM-CNRS-IN2P3, F-91405 Orsay (France); Blaum, K.; George, S. [Johannes Gutenberg-Universitaet, Institut fuer Physik, D-55099 Mainz (Germany); Gesellschaft fuer Schwerionenforschung GSI, D-64291 Darmstadt (Germany); Carrel, F.; Herfurth, F.; Yazidjian, C. [Gesellschaft fuer Schwerionenforschung GSI, D-64291 Darmstadt (Germany); Herlert, A.; Schweikhard, L. [Ernst-Moritz-Arndt-Universitaet, Institut fuer Physik, D-17487 Greifswald (Germany); Kluge, H.-J. [Gesellschaft fuer Schwerionenforschung GSI, D-64291 Darmstadt (Germany); Ruprecht-Karls-Universitaet Heidelberg, Physikalisches Institut, D-69120 Heidelberg (Germany)

2006-09-15

267

Carbon dioxide-krypton separation and radon removal from nuclear-fuel-reprocessing off-gas streams  

SciTech Connect

General Atomic Company (GA) is conducting pilot-plant-scale tests that simulate the treatment of radioactive and other noxious volatile and gaseous constituents of off-gas streams from nuclear reprocessing plants. This paper reports the results of engineering-scale tests performed on the CO/sub 2//krypton separation and radon holdup/decay subsystems of the GA integrated off-gas treatment system. Separation of CO/sub 2/ from krypton-containing gas streams is necessary to facilitate subsequent waste processing and krypton storage. Molecular sieve 5A achieved this separation in dissolver off-gas streams containing relatively low krypton and CO/sub 2/ concentrations and in krypton-rich product streams from processes such as the krypton absorption in liquid carbon dioxide (KALC) process. The CO/sub 2//krypton separation unit is a 30.5-cm-diameter x 1.8-m-long column containing molecular sieve 5A. The loading capacity for CO/sub 2/ was determined for gas mixtures containing 250 ppM to 2.2% CO/sub 2/ and 170 to 750 ppM krypton in either N/sub 2/ or air. Gas streams rich in CO/sub 2/ were diluted with N/sub 2/ to reduce the temperature rise from the heat of adsorption, which would otherwise affect loading capacity. The effluent CO/sub 2/ concentration prior to breakthrough was less than 10 ppM, and the adsorption capacity for krypton was negligible. Krypton was monitored on-line with a time-of-flight mass spectrometer and its concentration determined quantitatively by a method of continuous analysis, i.e., selected-ion monitoring. Radon-220 was treated by holdup and decay on a column of synthetic H-mordenite. The Rn-220 concentration was monitored on-line with flow-through diffused-junction alpha detectors. Single-channel analyzers were utilized to isolate the 6.287-MeV alpha energy band characteristic of Rn-220 decay from energy bands due to daughter products.

Hirsch, P.M.; Higuchi, K.Y.; Abraham, L.

1982-07-01

268

Modification of a krypton ion pumped dye laser for selected multimode operation.  

PubMed

We describe a method for tailoring the output spectrum of a cw krypton-ion-pumped dye laser to suit a particular multimode application. The method uses both theoretical calculations and simple experimental measurements to allow component selection for the required spectra. While a specific laser system is discussed, the method is generally applicable to other systems. Results of the described modifications are given. PMID:20556180

Connally, W J; Morton, R G

1990-02-20

269

Identification of Krypton Kr XVIII to Kr XXIX Spectra Excited in TFR Tokamak Plasmas  

NASA Astrophysics Data System (ADS)

The emission spectrum of krypton (injected into TFR tokamak plasmas) has been recorded photographically in the 15-300 spectral range by means of a 2 m grazing incidence spectrograph. Preliminary identification work, based on isoelectronic regularities from known spectra of other ions and ionization equilibrium calculations, has allowed 48 lines (belonging to the O I, F I, Na I, Mg I, Al I, Ar I and K I sequences) to be identified.

Wyart, J. F.; TFR Group

1985-06-01

270

Thermodynamic and molecular properties of gas hydrates from mixtures containing methane, argon, and krypton  

Microsoft Academic Search

Because hydrate formation in pipelines, processing operations, and reservoirs is generally undesirable, studies of gas-hydrate thermodynamics, particularly examinations of conditions where a second hydrate phase or a hydrocarbon-rich phase exists in addition to the water, hydrate, and gas phases, are important to the natural gas industry. In this study, analysts used experimental methane-krypton and methane-argon hydrate data to generate chemical-potential,

G. D. Holder; G. Corbin; K. D. Papadopoulos

1980-01-01

271

Renormalization-group treatment of a Potts lattice gas for krypton adsorbed onto graphite  

Microsoft Academic Search

Krypton atoms adsorbed in submonolayer quantities onto the basal graphite surface may be represented by a triangular lattice gas with nearest-neighbor exclusion and further-neighbor attraction decreasing with separation. We view this as a three-state Potts model with thermodynamic vacancies which are controlled by a chemical potential. A position-space renormalization-group treatment is performed by adapting Migdal's approximate recursion to the triangular

A. N. Berker; S. Ostlund; F. A. Putnam

1978-01-01

272

Tomography of regional ventilation and perfusion using krypton 81m in normal subjects and asthmatic patients  

Microsoft Academic Search

Single photon emission computed tomography, a rotating gamma camera, and continuous inhalation or infusion of krypton 81m (half life 13 seconds) were used to measure regional ventilation (V), perfusion (Q), and ventilation-perfusion (V\\/Q) ratios in five normal subjects in supine, prone, and lateral decubitus postures and in three asthmatic patients (supine posture only) before and after inhalation of 2.5 mg

D Orphanidou; J M Hughes; M J Myers; A R Al-Suhali; B Henderson

1986-01-01

273

Solar-wind krypton and solid\\/gas fractionation in the early solar nebula  

Microsoft Academic Search

Krypton is the best candidate for determining limits on solid\\/gas fractionation in the early sun because of the smoothness of the odd-mass abundance curve in its mass region, which permits relatively precise interpolations of its abundance assuming no fractionation. Here the authors calculate the solar-system Kr abundance from solar-wind noble-gas ratios, determined previously by low-temperature oxidations of lunar ilmenite grains,

Roger C. Wiens; D. S. Burnett; M. Neugebauer; R. O. Pepin

1991-01-01

274

TOTAL NEUTRON CROSS SECTIONS OF HELIUM, NEON, ARGON, KRYPTON, AND XENON  

Microsoft Academic Search

The total neutron cross sections of the noble gases helium, neon, argon, ; krypton, and xenon were measured for neutron energies from 120 kev to 6.2 Mev and ; from 12.1 Mev to 19.8 Mev by a transmission experiment. The neutrons were ; produced using the Li⁷(p,n)Be⁷, the T(p,n)He³, the D(d,n)He\\/sup ; 3\\/, and the T(d,n)He⁴ reactions in the appropriate

F. J. Vaughn; W. L. Imhof; R. G. Johnson; M. Walt

1960-01-01

275

Measurement of the K?2/K?1 ratio in heliumlike krypton  

SciTech Connect

We report the measurement of the K{beta}{sub 2}/K{beta}{sub 1} ratio of He-like krypton using the SuperEBIT electron beam ion trap at the Lawrence Livermore National Laboratory. The energy of these lines are about 15 keV, which is twice as high as the energy of such lines measured before. A comparison with theoretical predictions shows poor agreement, concerning the trend uncovered earlier where the measured result is considerably larger than predicted.

Beiersdorfer, P; Gu, M F; Brown, G V; Chen, H; Kelley, R; Kilbourne, C A; Porter, F S; Smith, A J; Thorn, D B

2008-08-25

276

Soft X-Ray Images of Krypton Gas-Puff Z-Pinches  

Microsoft Academic Search

A series of experiments has been carried out on Qiang-guang I generator to study the dynamics of krypton gas-puff Z-pinches. The generator was operated at a peak current of 1.5 MA with a rise-time of 80 ns. The specific linear mass of gas liner was about 20 mug\\/cm in these experiments. In the diagnostic system, a four-frame x-ray framing camera

Meng-tong Qiu; Bin Kuai; Zheng-zhong Zeng; Min Lu; Kui-lu Wang; Ai-ci Qiu; Mei Zhang; Jian-hui Luo

2002-01-01

277

The Application of Convolution-Based Statistical Model on the Breakdown Time Delay Distributions in Krypton  

Microsoft Academic Search

Summary form only given. The convolution-based model of the electrical breakdown time delay distribution is applied for the statistical analysis of experimental results in krypton-filled diode tube at 2.6 mbar. The electrical breakdown time delay distribution is obtained as the convolution of two random variables (statistical time delay with exponential and discharge formative time with Gaussian distribution). The distribution parameters

C. A. Maluckov; J. P. Karamarkovic; M. K. Radovic; M. M. Pejovic

2005-01-01

278

Electron-impact excitation from the (4p55s) metastable states of krypton  

Microsoft Academic Search

Theoretical results from multistate semirelativistic Breit-Pauli R-matrix calculations and two first-order distorted-wave calculations are presented for electron-impact excitation of krypton from the (4p55s) J=0,2 metastable states to the (4p55s) and (4p55p) manifolds. Except for a few cases, in which the method to account for relativistic effects becomes surprisingly critical, fair overall agreement between the predictions from the various theoretical models

A. Dasgupta; K. Bartschat; D. Vaid; A. N. Grum-Grzhimailo; D. H. Madison; M. Blaha; J. L. Giuliani

2002-01-01

279

Familial Poland anomaly revisited.  

PubMed

Poland anomaly (PA) is a pectoral muscle hypoplasia/aplasia variably associated with ipsilateral thoracic (TA) and/or upper limb anomalies (ULA). PA is usually sporadic and sometimes familial, making recurrence risk an issue in genetic counseling. Multidisciplinary evaluation of 240 PA patients was carried out, including physical examination of patients and their parents in 190 PA (subjects of the study). Familial conditions were classified into three groups. Group1: true familial PA (F-PA): pectoral muscle defects with familial recurrence: 8(4.2%). Group2: familial Poland-like anomaly families (F-PLA): PA index case and ?1 relative(s) showing normal pectoral muscles but ULA and/or TA common in PA: 16(8.4%). Group3: sporadic PA (S-PA): 166(87.4%). F-PA indicated a stronger male (87.5%) and left side (62.5%) prevalence, but fewer ULA (37.5%) compared to the other two groups. Maternal transmission (6/8) was more common in F-PA. Statistical significance was not reached due to the small number of F-PA and F-PLA. Karyotyping and array-comparative genomic hybridization were performed in 13 families. Three maternally inherited copy number variants were identified in three patients: 1p31.1 deletion, Xp11.22 duplication, and 16q23.1 duplication. Interestingly, the proband's mother carrying the 16q23.1 duplication displayed moderate breast and areola asymmetry, but normal pectoral muscles on ultrasound. Though there is no recent review discussing recurrence of PA, we reviewed 31 published PA families. On the basis of our study and previous reports, familial PA is not uncommon. Nonetheless, no information can be derived either regarding a molecular basis or clinical tools with which to identify cases with recurrence risk. PMID:22110015

Baban, Anwar; Torre, Michele; Costanzo, Sara; Gimelli, Stefania; Bianca, Sebastiano; Divizia, Maria Teresa; Sns, Filippo Maria; Garavelli, Livia; Rivieri, Francesca; Lerone, Margherita; Valle, Maura; Ravazzolo, Roberto; Calevo, Maria Grazia

2011-11-22

280

The cosmic molybdenum-ruthenium isotope correlation  

NASA Astrophysics Data System (ADS)

Dauphas et al. [Astrophys. J. 565 (2002) 640-644] reported molybdenum isotopic anomalies in differentiated and bulk primitive meteorites. It is shown here that these isotopic anomalies correlate with one another in exactly the way expected from nucleosynthesis theory if different regions of the nebula received different contributions of s-process matter synthesized in low-mass AGB stars. Furthermore, when bulk measurements are grouped by meteorite class, the molybdenum isotopic anomalies correlate with the ruthenium isotopic anomalies recently reported by Chen et al. [Lunar Planet. Sci. XXXIV (2003) #1789], again indicating a heterogeneous distribution of s-process matter. As molybdenum is only moderately siderophile, most of the molybdenum presently in the mantle was delivered before the completion of core formation. In contrast, because ruthenium is highly siderophile, nearly all of the mantle ruthenium was delivered by a late veneer, after the end of core formation. Thus, the fact the silicate Earth lies on the Mo-Ru cosmic correlation supports the idea that the Earth accreted homogeneously. Stated otherwise, the feeding zone of the Earth did not change drastically with time, as both the bulk of the Earth and the late veneer accreted from material from the same Mo-Ru isotopic reservoir.

Dauphas, Nicolas; Davis, Andrew M.; Marty, Bernard; Reisberg, Laurie

2004-10-01

281

54Cr Anomalies in the Orgueil Carbonaceous Chondrite  

Microsoft Academic Search

Cr in CI meteorites displays isotopic anomalies in a unique pattern [1-3]. Etching of bulk Orgueil in relatively mild reactants (CH3COOH and dilute HNO3) dissolves most (>80%) of the Cr along with most of other major cations (Mg, Ca, Fe, Ni, Al). The Cr thus dissolved is deficient in 54Cr by about 6 epsilon-units (using 50Cr\\/52Cr normalization). Much of the

F. A. Podosek; U. Ott; J. C. Brannon; T. J. Bernatowicz; C. R. Neal

1995-01-01

282

Isotopic distributions.  

PubMed

Isotopic information determined by mass spectrometry can be used in a wide variety of applications. Broadly speaking these could be classified as "passive" applications, meaning that they use naturally occurring isotopic information, and "active" applications, meaning that the isotopic distributions are manipulated in some way. The classic passive application is the determination of chemical composition by comparing observed isotopic patterns of molecules to theoretically calculated isotopic patterns. Active applications include isotope exchange experiments of a variety of types, as well as isotope labeling in tracing studies and to provide references for quantitation. Regardless of the type of application considered, the problem of theoretical calculation of isotopic patterns almost invariably arises. This paper reviews a number of application examples and computational approaches for isotopic studies in mass spectrometry. PMID:23666722

Rockwood, Alan L; Palmblad, Magnus

2013-01-01

283

Water: Thermodynamic and Dynamic Anomalies  

SciTech Connect

While the majority of fluids contract upon cooling, water expands when cooled below T = 4 deg. C at atmospheric pressure. This effect is called density anomaly. Besides the density anomaly, there are more than 60 other anomalies known for water. Diffusivity is one of them. For normal liquids the diffusion coefficient decreases under compression. However, experimental results have shown that for water at temperatures below approximately 10 deg. C, the diffusion coefficient increases under compression and has a maximum. The temperature of maximum density line, inside which the density anomaly occurs, and the line of maximum in diffusivity are located in the same region of the pressure-temperature phase diagram of water. We show how simulations for water also show thermodynamic and dynamic anomalies. These anomalies are then demonstrated to be related to two length scales effective potential.

Barbosa, Marcia C. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil)

2009-04-19

284

Automated anomaly detection processor  

NASA Astrophysics Data System (ADS)

Robust exploitation of tracking and surveillance data will provide an early warning and cueing capability for military and civilian Law Enforcement Agency operations. This will improve dynamic tasking of limited resources and hence operational efficiency. The challenge is to rapidly identify threat activity within a huge background of noncombatant traffic. We discuss development of an Automated Anomaly Detection Processor (AADP) that exploits multi-INT, multi-sensor tracking and surveillance data to rapidly identify and characterize events and/or objects of military interest, without requiring operators to specify threat behaviors or templates. The AADP has successfully detected an anomaly in traffic patterns in Los Angeles, analyzed ship track data collected during a Fleet Battle Experiment to detect simulated mine laying behavior amongst maritime noncombatants, and is currently under development for surface vessel tracking within the Coast Guard's Vessel Traffic Service to support port security, ship inspection, and harbor traffic control missions, and to monitor medical surveillance databases for early alert of a bioterrorist attack. The AADP can also be integrated into combat simulations to enhance model fidelity of multi-sensor fusion effects in military operations.

Kraiman, James B.; Arouh, Scott L.; Webb, Michael L.

2002-07-01

285

Thermodynamics, gravitational anomalies and cones  

NASA Astrophysics Data System (ADS)

By studying the Euclidean partition function on a cone, we argue that pure and mixed gravitational anomalies generate a "Casimir momentum" which manifests itself as parity violating coefficients in the hydrodynamic stress tensor and charge current. The coefficients generated by these anomalies enter at a lower order in the hydrodynamic gradient expansion than would be naively expected. In 1 + 1 dimensions, the gravitational anomaly affects coefficients at zeroth order in the gradient expansion. The mixed anomaly in 3 + 1 dimensions controls the value of coefficients at first order in the gradient expansion.

Jensen, Kristan; Loganayagam, R.; Yarom, Amos

2013-02-01

286

Elemental and isotopic composition of the galactic cosmic rays  

Microsoft Academic Search

It is now established that there are important differences in elemental and isotopic abundance between the source matter of galactic cosmic rays and the solar system matter. These large differences (more than a factor of 2 in some cases, in contrast to less than or equal to1% for isotopic anomalies in solar system matter) may become essential clues to the

J A Simpson

1983-01-01

287

AKUT: a process for separating aerosols, krypton, and tritium from the combustion waste gases in the reprocessing of high temperature fuel elements  

Microsoft Academic Search

In the AKUT method the aerosols are separated by electric and absolute filters. The waste gas is then burned with measured quantities of oxygen before it is liquified at 65-70 atm. This liquefied waste gas is fed into a rectification column, and a krypton-rich fraction containing 10- 20% by volume of krypton is drawn off at the top of the

M. Laser; H. Beaujean; H. Vygen

1973-01-01

288

Mesure directe de gaz a l'aide des radio lments metteurs beta ou alpha: adsorption de krypton-85 sur des solides de faible surface  

Microsoft Academic Search

A cell is described suitable for studying the physical adsorption of krypton labelled with krypton-85. The aim was the measurement of the beta rays from the adsorbate. Inside the cell a semiconductor detector is set on the metallic sample container. In order to achieve a good temperature equilibrium of the sample with the cryogenic bath, the walls of the cell,

G. Beurton; P. Bussiere

1970-01-01

289

External Genital Anomalies in Newborn Babies  

Microsoft Academic Search

Objective: External genital anomalies are common congenital anomalies, especially in male newborns. It seems that the incidence of these anomalies is increasing. Although the etiology of these anomalies is obscure in most cases, genetic and environmental factors have important roles. This study aimed to determine the types and frequency of these anomalies in newborn babies and to compare the results

Siamak Shiva; Pediatric Endocrinologist; Mohammad-Hosein Hoseinian

2008-01-01

290

Segregation of isotopes of heavy metals due to light-induced drift: results and problems  

Microsoft Academic Search

Atutov and Shalagin (1988) proposed light-induced drift (LID) as a physically well understandable mechanism to explain the formation of isotopic anomalies observed in CP stars. We have generalized the theory of LID and applied it to diffusion of heavy elements and their isotopes in quiescent atmospheres of CP stars. Diffusional segregation of isotopes of chemical elements is described by the

A. Sapar; A. Aret; R. Poolame; L. Sapar

2008-01-01

291

Ti, Si and Mg Isotope Systematics of FUN CAI CMS-1  

NASA Astrophysics Data System (ADS)

FUN CAIs preserve large isotopic anomalies in several neutron-rich isotopes including 50Ti, as well as extreme mass-dependent fractionations in Mg and Si. We report on the Ti, Si and Mg isotopic compositions of a new Allende FUN CAI designated CMS-1.

Williams, C. D.; Wadhwa, M.; Janney, P. E.; Hines, R. R.; Bullock, E. S.; MacPherson, G. J.

2012-09-01

292

The earnings-price anomaly  

Microsoft Academic Search

This review explores systematic explanations for the anomalous evidence in the relation between accounting earnings and stock prices. The anomaly is that estimated future abnormal returns are predicted by public information about future earnings, contained in (1) current earnings and (2) current financial statement ratios. The current-earnings anomaly appears due to either market inefficiency or substantial costs of investors acquiring

Ray Ball

1992-01-01

293

Measuring anomaly with algorithmic entropy  

Microsoft Academic Search

Anomaly detection refers to the identification of observations that are considered outside of normal. Since they are unknown to the system prior to training and rare, the anomaly detection problem is particularly challenging. Model based techniques require large quantities of existing data are to build the model. Statistically based techniques result in the use of statistical metrics or thresholds for

Wanda M. Solano

2007-01-01

294

Power Coefficient Anomaly in JOYO.  

National Technical Information Service (NTIS)

Power Coefficient Anomaly appeared in JOYO, which occurred in 75MW Power Ascension Test, Summer 1979. The substance of this anomaly was the non-reproducible power coefficient during the initial power-up from 50MWt to 75MWt and the permanent reactivity los...

M. Ishikawa Y. Yamashita Y. Nara H. Yamamoto

1981-01-01

295

Gravity Anomalies over Ocean Ridges  

Microsoft Academic Search

Summary The presence of positive free-air gravity anomalies over ocean ridges is supported by both the global solutions derived essentially from satellite observations and by surface measurements. The anomalies over the ridges observed by the satellite solutions are described by the harmonics of degree 8 or 9 and higher and they can be supported statically if maximum shear stresses in

Kurt Lambeck

1972-01-01

296

Anomalies in the Solar System  

Microsoft Academic Search

Several observations show unexplained phenomena in our solar system. These observations are e.g. the Pioneer Anomaly, an unexplained constant acceleration of the Pioneer 10 and 11 spacecraft, the Flyby Anomaly, an unexplained increase of the velocity of a series of spacecraft after Earth gravity assists, the recently reported increase of the Astronomical Unit defined by the distance of the planets

Hansjoerg Dittus

2008-01-01

297

Congenital cardiac anomalies in calves  

Microsoft Academic Search

Seven cases of congenital cardiac anomalies in calves were reviewed from the files of the Ohio Veterinary Diagnostic Laboratory. The collection of material occurred during a six-month period from June 1977 to January 1978. The major clinical signs were dyspnoea, failure to gain weight and sudden death in young animals. The cardiac defects included two patent ductus arteriosus, two anomalies

GE Sandusky; CW Smith

1981-01-01

298

Anomaly equations and intersection theory  

NASA Astrophysics Data System (ADS)

Six-dimensional supergravity theories with mathcal{N} = (1, 0) supersymmetry must satisfy anomaly equations. These equations come from demanding the cancellation of gravitational, gauge and mixed anomalies. The anomaly equations have implications for the geometrical data of Calabi-Yau threefolds, since F-theory compactified on an elliptically fibered Calabi-Yau threefold with a section generates a consistent six-dimensional mathcal{N} = (1, 0) supergravity theory. In this paper, we show that the anomaly equations can be summarized by three intersection theory identities. In the process we also identify the geometric counterpart of the anomaly coefficients in particular, those of the abelian gauge groups that govern the low-energy dynamics of the theory. We discuss the results in the context of investigating string universality in six dimensions.

Park, Daniel S.

2012-01-01

299

Isotopic Compositions of Cometary Matter Returned by Stardust  

Microsoft Academic Search

Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P\\/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single 17O-enriched circumstellar stardust grain, silicate

McKeegan Kevin D; Alon Jerome; Bradley John; Brownlee Donald; Busemann Henner; Butterworth Anna; Chaussidon Marc; Fallon Stewart; Floss Christine; Gilmour Jamie; Gounelle Matthieu; Graham Giles; Guan Yunbin; Heck Philipp R; Hoppe Peter; Hutcheon Ian D; Huth Joachim; Ishii Hope; Ito Motoo; Jacobsen Stein B; Kearsley Anton; Leshin Laurie A; Liu Ming-Chang; Lyon Ian; Marhas Kuljeet; Marty Bernard; Matrajt Graciela; Meibom Anders; Messenger Scott; Mostefaoui Smail; Mukhopadhyay Sujoy; Nakamura-Messenger Keiko; Nittler Larry; Palma Russ; Pepin Robert O; Papanastassiou Dimitri A; Robert Franois; Schlutter Dennis; Snead Christopher J; Stadermann Frank J; Stroud Rhonda; Tsou Peter; Westphal Andrew; Young Edward D; Ziegler Karen; Zimmermann Laurent; Ernst Zinner

2006-01-01

300

Breaking through the glass ceiling: the correlation between the self-diffusivity in and krypton permeation through deeply supercooled liquid nanoscale methanol films.  

PubMed

Molecular beam techniques, temperature-programmed desorption (TPD), and reflection absorption infrared spectroscopy (RAIRS) are used to explore the relationship between krypton permeation through and the self-diffusivity of supercooled liquid methanol at temperatures (100-115 K) near the glass transition temperature, T(g) (103 K). Layered films, consisting of CH(3)OH and CD(3)OH, are deposited on top of a monolayer of Kr on a graphene covered Pt(111) substrate at 25 K. Concurrent Kr TPD and RAIRS spectra are acquired during the heating of the composite film to temperatures above T(g). The CO vibrational stretch is sensitive to the local molecular environment and is used to determine the supercooled liquid diffusivity from the intermixing of the isotopic layers. We find that the Kr permeation and the diffusivity of the supercooled liquid are directly and quantitatively correlated. These results validate the rare-gas permeation technique as a tool for probing the diffusivity of supercooled liquids. PMID:20370128

Smith, R Scott; Matthiesen, Jesper; Kay, Bruce D

2010-03-28

301

Anomaly mediation from unbroken supergravity  

NASA Astrophysics Data System (ADS)

When supergravity (SUGRA) is spontaneously broken, it is well known that anomaly mediation generates sparticle soft masses proportional to the gravitino mass. Recently, we showed that one-loop anomaly-mediated gaugino masses should be associated with unbroken supersymmetry (SUSY). This counterintuitive result arises because the underlying symmetry structure of (broken) SUGRA in flat space is in fact (unbroken) SUSY in anti-de Sitter (AdS) space. When quantum corrections are regulated in a way that preserves SUGRA, the underlying AdS curvature (proportional to the gravitino mass) necessarily appears in the regulated action, yielding soft masses without corresponding goldstino couplings. In this paper, we extend our analysis of anomaly mediation to sfermion soft masses. Already at tree-level we encounter a number of surprises, including the fact that zero soft masses correspond to broken (AdS) SUSY. At one-loop, we explain how anomaly mediation appears when regulating SUGRA in a way that preserves super-Weyl invariance. We find that recent claims in the literature about the non-existence of anomaly mediation were based on a Wilsonian effective action with residual gauge dependence, and the gauge-invariant 1PI effective action contains the expected anomaly-mediated spectrum. Finally, we calculate the sfermion spectrum to all orders, and use supertrace relations to derive the familiar two-loop soft masses from minimal anomaly mediation, as well as unfamiliar tree-level and one-loop goldstino couplings consistent with renormalization group invariance.

D'Eramo, Francesco; Thaler, Jesse; Thomas, Zachary

2013-09-01

302

Krypton laser photocoagulation induces retinal vascular remodeling rather than choroidal neovascularization.  

PubMed

The purpose of this study is to analyze the retina and choroid response following krypton laser photocoagulation. Ninety-two C57BL6/Sev129 and 32 C57BL/6J, 5-6-week-old mice received one single krypton (630 nm) laser lesion: 50 microm, 0.05 s, 400 mW. On the following day, every day thereafter for 1 week and every 2-3 days for the following 3 weeks, serial sections throughout the lesion were systematically collected and studied. Immunohistology using specific markers or antibodies for glial fibrillary acidic protein (GFAP) (astrocytes, glia and Muller's cells), von Willebrand (vW) (vascular endothelial cells), TUNEL (cells undergoing caspase dependent apoptosis), PCNA (proliferating cell nuclear antigen) p36, CD4 and F4/80 (infiltrating inflammatory and T cells), DAPI (cell nuclei) and routine histology were carried out. Laser confocal microscopy was also performed on flat mounts. Temporal and spatial observations of the created photocoagulation lesions demonstrate that, after a few hours, activated glial cells within the retinal path of the laser beam express GFAP. After 48 h, GFAP-positive staining was also detected within the choroid lesion center. "Movement" of this GFAP-positive expression towards the lasered choroid was preceded by a well-demarcated and localized apoptosis of the retina outer nuclear layer cells within the laser beam path. Later, death of retinal outer nuclear cells and layer thinning at this site was followed by evagination of the inner nuclear retinal layer. Funneling of the entire inner nuclear and the thinned outer nuclear layers into the choroid lesion center was accompanied by "dragging" of the retinal capillaries. Thus, from days 10 to 14 after krypton laser photocoagulation onward, well-formed blood capillaries (of retinal origin) were observed within the lesion. Only a few of the vW-positive capillary endothelial cells stained also for PCNA p36. In the choroid, dilatation of the vascular bed occurred at the vicinity of the photocoagulation site and around it. Confocal microscopy demonstrates that the vessels throughout the path lesion are located within the neuroretina while in the choroid (after separation of the neural retina) only GFAP-positive but no lectin-positive cells can be seen. The involvement of infiltrating inflammatory cells in these remodeling and healing processes remained minimal throughout the study period. During the 4 weeks following krypton laser photocoagulation in the mouse eye, processes of wound healing and remodeling appear to be driven by cells (and vessels) originating from the retina. PMID:16564044

Behar-Cohen, F; Benezra, D; Soubrane, G; Jonet, L; Jeanny, J C

2006-03-24

303

Total Neutron Cross Sections of Helium, Neon, Argon, Krypton, and Xenon  

Microsoft Academic Search

The total neutron cross sections of the noble gases helium, neon, argon, krypton, and xenon have been measured for neutron energies from 120 kev to 6.2 Mev and from 12.1 Mev to 19.8 Mev by a transmission experiment. The neutrons were produced using the Li7(p, n)Be7, the T(p, n)He3, the D(d, n)He3, and the T(d, n)He4 reactions in the appropriate

F. J. Vaughn; W. L. Imhof; R. G. Johnson; M. Walt

1960-01-01

304

Relativistic effects on the 4p-5s excitations of krypton  

Microsoft Academic Search

Generalized oscillator strengths of krypton for 4p6(1S0)-->4p5(2P3\\/2,1\\/2)5s are calculated in the first Born approximation at a self-consistent-field level with Dirac-Fock, Dirac-Slater, Hartree-Fock, and Hartree-Slater wave functions. Strong relativistic effects are noticed. The estimate of relaxation on a single-electron matrix element suggests the necessity of a Dirac-Fock multiconfiguration calculation for the excitations.

Qi-Cun Shi; Ke-Zun Xu; Zhang-Jin Chen; Hyuck Cho; Jia-Ming Li

1998-01-01

305

Reactor antineutrino anomaly  

SciTech Connect

Recently, new reactor antineutrino spectra have been provided for {sup 235}U, {sup 239}Pu, {sup 241}Pu, and {sup 238}U, increasing the mean flux by about 3%. To a good approximation, this reevaluation applies to all reactor neutrino experiments. The synthesis of published experiments at reactor-detector distances <100 m leads to a ratio of observed event rate to predicted rate of 0.976{+-}0.024. With our new flux evaluation, this ratio shifts to 0.943{+-}0.023, leading to a deviation from unity at 98.6% C.L. which we call the reactor antineutrino anomaly. The compatibility of our results with the existence of a fourth nonstandard neutrino state driving neutrino oscillations at short distances is discussed. The combined analysis of reactor data, gallium solar neutrino calibration experiments, and MiniBooNE-{nu} data disfavors the no-oscillation hypothesis at 99.8% C.L. The oscillation parameters are such that |{Delta}m{sub new}{sup 2}|>1.5 eV{sup 2} (95%) and sin{sup 2}(2{theta}{sub new})=0.14{+-}0.08 (95%). Constraints on the {theta}{sub 13} neutrino mixing angle are revised.

Mention, G.; Fechner, M. [CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette (France); Lasserre, Th.; Cribier, M. [CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette (France); Astroparticule et Cosmologie APC, 10 rue Alice Domon et Leonie Duquet, 75205 Paris cedex 13 (France); Mueller, Th. A.; Lhuillier, D.; Letourneau, A. [CEA, Irfu, SPhN, Centre de Saclay, F-91191 Gif-sur-Yvette (France)

2011-04-01

306

Anomalies and graded coisotropic branes  

NASA Astrophysics Data System (ADS)

We compute the anomaly of the axial U(1) current in the A-model on a Calabi-Yau manifold, in the presence of coisotropic branes discovered by Kapustin and Orlov. Our results relate the anomaly-free condition to a recently proposed definition of graded coisotropic branes in Calabi-Yau manifolds. More specifically, we find that a coisotropic brane is anomaly-free if and only if it is gradable. We also comment on a different grading for coisotropic submanifolds introduced recently by Oh.

Li, Yi

2006-03-01

307

A SEARCH FOR {sup 70}Zn ANOMALIES IN METEORITES  

SciTech Connect

No {sup 70}Zn isotopic anomalies have been detected in primitive meteorites to a level of precision of less than 40 parts per million (2{sigma}). Any pre-existing nucleosynthetic anomaly on {sup 70}Zn was averaged out by mixing in the solar nebula before planetary accretion in the solar system. Because neutron-rich nuclides {sup 70}Zn and {sup 60}Fe are produced by similar nucleosynthetic processes in core-collapse supernovae, the homogeneity of {sup 70}Zn in meteorites limits the possible heterogeneity of extinct {sup 60}Fe radioactivity in the early solar system. Assuming that Fe and Zn have not been decoupled during incorporation into the solar system, the homogeneity of the {sup 70}Zn/{sup 64}Zn ratio measured here implies that the {sup 60}Fe/{sup 56}Fe ratio was homogenized to less than 15% dispersion before the formation of planetary bodies. The lack (Zn, Ni, Fe) or presence (Ti, Cr) of neutron-rich isotopic anomalies in the iron mass region may be controlled by the volatility of presolar carriers in the nebula.

Moynier, Frederic; Podosek, Frank A. [Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130 (United States); Dauphas, Nicolas [Origins Laboratory, Department of Geophysical Sciences and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637 (United States)], E-mail: moynier@levee.wustl.edu, E-mail: fap@levee.wustl.edu, E-mail: dauphas@uchicago.edu

2009-08-01

308

Pacific Temperature Anomalies with Graph  

NSDL National Science Digital Library

This animation shows the El Nino-La Nina Sea Surface Temperature Anomaly from January 1997 through July 1999. A graph inset shows the global average sea surface temperature fluctuation during this time period.

Shirah, Greg; Bridgman, Tom; Starr, Cindy; Busalacchi, Antonio; Schultz, Peter

2003-08-30

309

Axial Anomaly in Nonrenormalizable Theories.  

National Technical Information Service (NTIS)

The anomaly for the axial current in nonrenormalizable theories with electromagnetic coupling is considered. The spinor electrodynamics with Pauli term is examined in detail using the Feynman graph technique and the point-splitting method. The same finite...

S. Marculescu L. Mezincescu

1978-01-01

310

Four-body interaction energy for compressed solid krypton from quantum theory.  

PubMed

The importance of the four-body contribution in compressed solid krypton was first evaluated using the many-body expansion method and the coupled cluster theory with full single and double excitations plus perturbative treatment of triples. All different four-atom clusters existing in the first- and second-nearest neighbor shells of face-centered cubic krypton were considered, and both self-consistent-field Hartree-Fock and correlation parts of the four-body interaction were accurately determined from the ambient conditions up to eightfold volume compression. We find that the four-body interaction energy is negative at compression ratio lower than 2, where the dispersive forces play a dominant role. With increasing the compression, the four-body contribution becomes repulsive and significantly cancels the over-softening effects of the three-body potential. The obtained equation of state (EOS) was compared with the experiments and the density-functional theory calculations. It shows that combination of the four-body effects with two- and three-body interactions leads to an excellent agreement with EOS measurements throughout the whole experimental range 0-130 GPa, and extends the prediction to 300 GPa. PMID:22852598

Tian, Chunling; Wu, Na; Liu, Fusheng; Saxena, Surendra K; Zheng, Xingrong

2012-07-28

311

Photon W value for krypton in the M-shell transition region.  

PubMed

Absolute W values for krypton have been measured for incident X rays with energies in the range of 85 to 1000 eV, using monochromatic synchrotron radiation and a multiple-electrode ion chamber technique that yields the absolute intensity of the X-ray beam and the photoabsorption cross section. To improve the purity of the incident X rays, the electron storage ring was operated at an energy lower than the normal mode, and thin filters were used. The W values are derived from the measured photon intensity and photoabsorption cross section, using the mean charges of the residual ions obtained in previous work. A considerable oscillation of the W values with the photon energy was found in the region near the krypton 3d electron ionization edge. The results are discussed and compared with data in the literature for low-energy electrons and with the calculations from a model that includes multiple photoionization effects related to inner-shell ionization. PMID:11500141

Saito, N; Suzuki, I H

2001-09-01

312

Diagnosis of high-temperature implosions using low- and high-opacity Krypton lines  

SciTech Connect

High-temperature laser target implosions can be achieved by using relatively thin-shell targets, and they can be. diagnosed by doping the fuel with krypton and measuring K-shell and L-shell lines. Electron temperatures of up to 5 keV at modest compressed densities ({approximately}1-5g/cm{sup 3}) are predicted for such experiments, with ion temperatures peaking above 10 keV at the center. It is found that the profiles of low-opacity (optically thin) lines in the expected density range are dominated by the Doppler broadening and can provide a measurement of the ion temperature if spectrometers of spectral resolution {Delta}{lambda}/{lambda} {ge} 1000 are used. For high-opacity lines, obtained with a higher krypton fill pressure, the measurement of the escape factor can yield the {rho}R of the compressed fuel. At higher densities, Stark broadening of low-opacity lines becomes important and can provide a density measurement, whereas lines of higher opacity can be used to estimate the extent of mixing.

Yaakobi, B.; Epstein, R. [Univ. of Rochester, NY (United States). Lab. for Laser Energetics; Hooper, C.F. Jr.; Haynes, D.A. Jr. [Univ. of Florida, Gainesville, FL (United States)] [and others

1996-04-01

313

Argon-krypton ion laser as light source for medical photocoagulation applications  

NASA Astrophysics Data System (ADS)

Photocoagulators are one of the most popular laser devices in medicine. Due to different kind of interaction of particular wavelength range of laser light with live tissues, sources of laser radiation which can cover as much as possible of visible spectrum are still very wanted (see [1,2]). In last years it also can be observed the intensive developing works on new photocoagulation technique called "micropulse coagulation" [3,4]. The most critical feature of lasers for micropulse coagulation is the possibility of fast switching between two selected laser power values. It seems that the good proposal for these applications can be ion laser filled with argon-krypton mixture. Authors previously have indicated the possibility of improvement of generation conditions in this type of laser in presence of buffer gases [5,6] and with use developed by authors pulse supply regime [7,8]. These improvements allow to obtain output power values of most important argon and krypton laser lines in laser filled with mixture of both gases, similar to values available in laser filled with pure gases. Presented in this paper the following researches are concerned on verification of possibilities of use of the developed laser system in photocoagulation with possibility of use of the laser system in micropulse coagulation technique.

Kami?ski, Wojciech; Warda, Piotr; Kasprzak, Jan; Kesik, Jerzy

2013-01-01

314

Evaluation of target power supplies for krypton storage in sputter-deposited metals  

SciTech Connect

Implantation of /sup 85/Kr in a growing sputtered metal deposit has been studied for the containment of /sup 85/Kr recovered from the reprocessing of spent nuclear fuel. PNL, as part of DOE's research program for /sup 85/Kr storage, has developed krypton trapping storage devices (KTSDs) in a range of sizes for ''cold'' and radioactive testing. The KTSD is a stainless steel canister that contains a sputtering target for depositing an amorphous rare-earth transition metal on the inner wall and simultaneously implanting low-energy krypton ions in the growing deposit. This report covers the design requirements for the target power supply and the description, testing and evaluation of three basic designs. The designs chosen for evaluation were: (1) a standard commercial power supply with an external PNL-designed current interrupter, (2) a commercially manufactured power supply with an integral series-type interrupter, and (3) a commercially manufactured power supply with an integral shunt-type interrupter. The units were compared on the basis of performance, reliability, and life-cycle cost. 8 refs., 9 figs., 2 tabs.

Greenwell, E.N.; McClanahan, E.D.; Moss, R.W.

1986-04-01

315

Diffusion coefficient of krypton atoms in helium gas at low and moderate temperatures  

NASA Astrophysics Data System (ADS)

In the present work, using the Chapman-Enskog method for dilute gases, the diffusion coefficients of ground krypton atoms in a very weakly ionized helium buffer gas are revisited. The calculations are carried out quantum mechanically in the range of low and moderate temperatures. The 1 ?+ potential-energy curve via which Kr approaches He is constructed from the most recent ab initio energy points. The reliable data points used in the construction are smoothly connected to adequate long- and short-range forms. The calculations of the classical second virial coefficients and the Boyle temperature of the helium-krypton mixture are also discussed. These coefficients and their variations in terms of temperature are analysed by adopting the constructed HeKr potential and the Lennard-Jones form that fits it. The diffusion and elastic cross sections are also explored and the resonance features they exhibit are closely examined. The variation law of the diffusion coefficients with temperature is determined for typical values of density and pressure. The coefficients show excellent agreement with the available experimental data; the discrepancies do not exceed 5%.

Bouazza, M. T.; Bouledroua, M.

316

Isotope-shift calculations for atoms with one valence electron  

SciTech Connect

This work presents a method for the ab initio calculation of isotope shift in atoms and ions with one valence electron above closed shells. As a zero approximation, we use relativistic Hartree-Fock and then calculate correlation corrections. The main motivation for developing the method comes from the need to analyze whether different isotope abundances in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine-structure constant {alpha} was smaller at early epoch. We test the isotope-shift method by comparing the calculated and experimental isotope shift for the alkali-metal and alkali-metal-like atoms Na, Mg II, K, Ca II and Ba II. The agreement is found to be good. We then calculate the isotope shift for some astronomically relevant transitions in Si II and Si IV, Mg II, Zn II, and Ge II.

Berengut, J. C.; Dzuba, V. A.; Flambaum, V. V. [School of Physics, University of New South Wales, Sydney 2052, (Australia)

2003-08-01

317

Hydration of krypton and consideration of clathrate models of hydrophobic effects from the perspective of quasi-chemical theory  

Microsoft Academic Search

Ab initio molecular dynamics (AIMD) results on a kryptonwater liquid solution are presented and compared to recent XAFS results for the radial hydration structure for a Kr atom in liquid water solution. Though these AIMD calculations have important limitations of scale, the comparisons with the liquid solution results are satisfactory and significantly different from the radial distributions extracted from the

Henry S. Ashbaugh; D. Asthagiri; Lawrence R. Pratt; Susan B. Rempe

2003-01-01

318

Soft X-ray Emission Optimization Studies with Krypton and Xenon Gases in Plasma Focus Using Lee Model  

NASA Astrophysics Data System (ADS)

The X-ray emission properties of krypton and xenon plasmas are numerically investigated using corona plasma equilibrium model. Numerical experiments have been investigated on various low energy plasma focus devices with Kr and Xe filling gases using Lee model. The Lee model was applied to characterize and to find the optimum combination of soft X-ray yields (Ysxr) for krypton (~4 ) and xenon (~3 ) plasma focus. These combinations give Ysxr = 0.018 J for krypton, and Ysxr = 0.5 J for xenon. Scaling laws on Kr and Xe soft X-ray yields, in terms of storage energies E0, peak discharge current Ipeak and focus pinch current Ipinch were found over the range from 2.8 to 900 kJ. Soft X-ray yields scaling laws in terms of storage energies were found to be as and for Kr and Xe, respectively, (E0 in kJ and Ysxr in J) with the scaling showing gradual deterioration as E0 rises over the range. The maximum soft X-ray yields are found to be about 0.5 and 27 J from krypton and xenon, respectively, for storage energy of 900 kJ. The optimum efficiencies for soft X-ray yields (0.0002 % for Kr) and (0.0047 % for Xe) are with capacitor bank energies of 67.5 and 225 kJ, respectively.

Akel, Mohamad

2013-10-01

319

Neutron and Charged-Particle Induced Cross Sections for Radiochemistry in the Region of Bromine and Krypton  

SciTech Connect

We have developed a set of modeled nuclear reaction cross sections for use in radiochemical diagnostics. Systematics for the input parameters required by the Hauser-Feshbach statistical model were developed and used to calculate neutron and proton induced nuclear reaction cross sections in the mass region of bromine and krypton (34 {le} Z {le} 37, 40 {le} N {le} 47).

Hoffman, R; Dietrich, F; Bauer, R; Kelley, K; Mustafa, M

2004-07-23

320

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

Microsoft Academic Search

The emission properties of a volume nanosecond discharge plasma produced in xenon, krypton and argon at high pressures in a discharge gap with a cathode having a small radius of curvature are studied. Spectra in the range 120850 nm and amplitudetime characteristics of xenon emission at different regimes and excitation techniques are recorded and analysed. It is shown that upon

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

2006-01-01

321

The Viscosity and Thermal Conductivity Coefficients for Dense Gaseous and Liquid Argon, Krypton, Xenon, Nitrogen, and Oxygen  

Microsoft Academic Search

Data for the viscosity and thermal conductivity coefficients of argon, nitrogen, and oxygen have been critically evaluated. A functional form to represent the data has been proposed. The function is basically the same for both coefficients. The critical point enhancement in the thermal conductivity coefficient is included. Transport properties of krypton and xenon are calculated by means of the principle

H. J. M. Hanley; R. D. McCarty; W. M. Haynes

1974-01-01

322

Transport of atmospheric trace gases to the water table: Implications for groundwater dating with chlorofluorocarbons and krypton 85  

Microsoft Academic Search

Chlorofluorocarbons and krypton 85 are trace gases whose atmospheric concentrations have been increasing over the past few decades. As they are soluble in water, they have been used as groundwater age indicators over timescales ranging from a few years to a few decades. In this paper we show that the time lag for transport of these atmospheric trace gases through

P. G. Cook; D. K. Solomon

1995-01-01

323

A comparative study of argon laser and krypton laser in the treatment of diabetic optic disc neovascularisation  

Microsoft Academic Search

A comparative study of the relative efficacy of the krypton and argon lasers in the treatment of disc new vessels in diabetic retinopathy was made. Resolution of the disc new vessels was achieved in both instances. There were clinical differences in the use and effects of the 2 lasers.

W E Schulenburg; A M Hamilton; R K Blach

1979-01-01

324

Hydraulic Mass-Exchange Characteristics of a Rectification Column with Spiral-Prismatic Packing in Krypton and Xenon Purification Processes  

Microsoft Academic Search

The technology of krypton and xenon purification in modern installations making high-purity products is based on low-temperature rectification of multicomponent mixtures (MCMs). The economic efficiency of the purification processes is determined to a considerable extent by the sophistication of the rectification column design. Years of experience from the production of inert gases show that the best results in this regard

A. M. Arkharov; M. Yu. Savinov; V. L. Bondarenko; A. S. Bronshtein

2003-01-01

325

Shape evolution in yttrium and niobium neutron-rich isotopes  

SciTech Connect

The isotopic evolution of the ground-state nuclear shapes and the systematics of one-quasiproton configurations are studied in neutron-rich odd-A yttrium and niobium isotopes. We use a self-consistent Hartree-Fock-Bogoliubov formalism based on the Gogny energy density functional with two parametrizations, D1S and D1M. The equal-filling approximation is used to describe odd-A nuclei preserving both axial and time-reversal symmetries. Shape-transition signatures are identified in the N=60 isotopes in both the charge radii and spin parities of the ground states. These signatures are a common characteristic for nuclei in the whole mass region. The nuclear deformation and shape coexistence inherent to this mass region are shown to play a relevant role in the understanding of the spectroscopic features of the ground and low-lying one-quasiproton states. Finally, a global picture of the neutron-rich A{approx}100 mass region from krypton up to molybdenum isotopes is illustrated with the systematics of the nuclear charge radii isotopic shifts.

Rodriguez-Guzman, R.; Sarriguren, P. [Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, Serrano 123, E-28006 Madrid (Spain); Robledo, L. M. [Departamento de Fisica Teorica, Modulo 15, Universidad Autonoma de Madrid, E-28049 Madrid (Spain)

2011-04-15

326

Shape evolution in yttrium and niobium neutron-rich isotopes  

NASA Astrophysics Data System (ADS)

The isotopic evolution of the ground-state nuclear shapes and the systematics of one-quasiproton configurations are studied in neutron-rich odd-A yttrium and niobium isotopes. We use a self-consistent Hartree-Fock-Bogoliubov formalism based on the Gogny energy density functional with two parametrizations, D1S and D1M. The equal-filling approximation is used to describe odd-A nuclei preserving both axial and time-reversal symmetries. Shape-transition signatures are identified in the N=60 isotopes in both the charge radii and spin parities of the ground states. These signatures are a common characteristic for nuclei in the whole mass region. The nuclear deformation and shape coexistence inherent to this mass region are shown to play a relevant role in the understanding of the spectroscopic features of the ground and low-lying one-quasiproton states. Finally, a global picture of the neutron-rich A~100 mass region from krypton up to molybdenum isotopes is illustrated with the systematics of the nuclear charge radii isotopic shifts.

Rodriguez-Guzman, R.; Sarriguren, P.; Robledo, L. M.

2011-04-01

327

Absolute and Mass-Dependent Titanium Isotope Compositions of Solar System Materials  

NASA Astrophysics Data System (ADS)

Mass dependent Ti isotope data for various solar system material will be presented. This data has been obtained via double spike technique using ^47 Ti and ^49Ti as spikes. Absolute nucleosynthetic anomalie data for Ti will be presented also.

Williams, N. H.; Fehr, M. A.; Akram, W. M.; Parkinson, I. J.; Schnbchler, M.

2013-09-01

328

Mass-independent Isotope Fractionation of Molybdenum and Ruthenium in Murchison  

Microsoft Academic Search

We propose that isotopic anomalies of Mo and Ru found in Murchison (CM2) may be due to the nuclear field shift effect. This shift results from a mass-independent character via the nuclear charge distribution.

T. Fujii; F. Moynier; P. Telouk; F. Albarde

2006-01-01

329

Mass-independent fractionation of mercury isotopes in the environment  

NASA Astrophysics Data System (ADS)

The toxicity of mercury's methylated species and its biomagnification in aquatic food chains and global dispersion by the atmosphere are the cause of worldwide health problems. Recent reports have observed natural mass-dependent fractionation in mercury isotopes, and recent theoretical work has demonstrated that isotopic separation in mercury is due primarily to nuclear field shifts (nuclear volume effect), and the magnetic spin effect gives rise to mass-independent fractionation (MIF) of odd neutron number isotopes. Now we present analytical evidence of mass-independent isotopic variations in mercury produced by both nuclear volume and magnetic isotope processes. Even mass number isotopes exhibit a pattern indistinguishable from that produced by mass-dependent fractionation, with both positive and negative 199Hg and 201Hg anomalies. MIF is easier to reliably determine in Hg isotopes than mass-dependent fractionation alone, and thus it provides a potentially important key in constraining models of mercury sources and pathways in the environment.

Ghosh, Sanghamitra; Xu, Yingfeng; Humayun, Munir; Odom, Leroy

2008-03-01

330

Graph anomalies in cyber communications  

SciTech Connect

Enterprises monitor cyber traffic for viruses, intruders and stolen information. Detection methods look for known signatures of malicious traffic or search for anomalies with respect to a nominal reference model. Traditional anomaly detection focuses on aggregate traffic at central nodes or on user-level monitoring. More recently, however, traffic is being viewed more holistically as a dynamic communication graph. Attention to the graph nature of the traffic has expanded the types of anomalies that are being sought. We give an overview of several cyber data streams collected at Los Alamos National Laboratory and discuss current work in modeling the graph dynamics of traffic over the network. We consider global properties and local properties within the communication graph. A method for monitoring relative entropy on multiple correlated properties is discussed in detail.

Vander Wiel, Scott A [Los Alamos National Laboratory; Storlie, Curtis B [Los Alamos National Laboratory; Sandine, Gary [Los Alamos National Laboratory; Hagberg, Aric A [Los Alamos National Laboratory; Fisk, Michael [Los Alamos National Laboratory

2011-01-11

331

Hyperfine field and hyperfine anomalies of copper impurities in iron  

SciTech Connect

A new value for the hyperfine magnetic field of copper impurities in iron is obtained by combining resonance frequencies from experiments involving {beta}-NMR on oriented nuclei on {sup 59}Cu, {sup 69}Cu, and {sup 71}Cu with magnetic moment values from collinear laser spectroscopy measurements on these isotopes. The resulting value, i.e., B{sub hf}(CuFe) = -21.794(10) T, is in agreement with the value adopted until now but is an order of magnitude more precise. It is consistent with predictions from ab initio calculations. Comparing the hyperfine field values obtained for the individual isotopes, the hyperfine anomalies in Fe were determined to be {sup 59{Delta}69}=0.15(9)% and {sup 71{Delta}69}=0.07(11)%.

Golovko, V. V.; Wauters, F.; Breitenfeldt, M.; De Leebeeck, V.; Roccia, S.; Soti, G.; Tandecki, M.; Traykov, E.; Van Gorp, S.; Severijns, N. [Instituut voor Kern- en Stralingsfysica, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Cottenier, S. [Center for Molecular Modeling, Ghent University, Technologiepark 903, B-9052 Zwijnaarde (Belgium); Zakoucky, D. [Nuclear Physics Institute, ASCR, CZ-250 68 Rez (Czech Republic)

2011-07-15

332

A primitive plume neon component in MORB: The Shona ridge-anomaly, South Atlantic (5152S)  

Microsoft Academic Search

We report on He and Ne isotopes in basaltic glasses from eight dredge stations occupied over the Shona gravity and topographic anomaly high on the Mid-Atlantic Ridge around 5152S. The results indicate the presence of a primitive, little degassed, 3He-rich mantle component. 3He4He ratios correlate positively with the bathymetric and gravity anomaly, with values ranging from 12.5 to 6.4 times

Manuel Moreira; Thomas Staudacher; Philippe Sarda; Jean-Guy Schilling; Claude Jean Allgre

1995-01-01

333

[Vascular anomaly of the iris].  

PubMed

A 48-year-old man presented with a vascular anomaly of the iris in the left eye. Slit-lamp microscopy revealed dilated and tortuous vessels of the iris between 12 and 4 o'clock. Fluorescein angiography confirmed a diagnosis of arteriovenous (AV) malformation of the iris. The vessel originated at the iris base, passed to the pupillary margin and returned to the base. Such AV-malformations of the iris are very rare, benign vascular anomalies that have to be distinguished from other, potentially malignant pathologies of the iris (e. g. tortuous vessels in iris melanoma). PMID:22526009

Ponto, K A; Mirshahi, A

2012-07-01

334

Congenital cardiac anomalies in calves.  

PubMed

Seven cases of congenital cardiac anomalies in calves were reviewed from the files of the Ohio Veterinary Diagnostic Laboratory. The collection of material occurred during a six-month period from June 1977 to January 1978. The major clinical signs were dyspnoea, failure to gain weight and sudden death in young animals. The cardiac defects included two patent ductus arteriosus, two anomalies of the coronary vessels, one persistent truncus arteriosus, one transposition of the aorta and pulmonary artery and one ventricular septal defect. PMID:7210447

Sandusky, G E; Smith, C W

1981-02-21

335

High resolution krypton M/sub 4,5/ x-ray emission spectra  

SciTech Connect

High resolution M/sub 4,5/ (3d ..-->.. 4p) x-ray emission spectra from a krypton plasma were measured using a recently developed grazing-incidence reflection-grating monochromator/spectrometer with very high flux rates at extreme ultraviolet and soft x-ray wave lengths. The nominal resolving power of the instrument, E/..delta..E, is about 300 in this energy range (approx.80 eV). Three dipole-allowed 3d ..-->.. 4p emission lines were observed at 80.98 eV, 80.35 eV and 79.73 eV. A broad peak at about 82.3 eV is tentatively assigned to transitions resulting from Kr/sup 2 +/, and effects of excitation energy on M/sub 4,5/ x-ray emission were observed. 9 refs., 3 figs., 1 tab.

Perera, R.C.C.; Hettrick, M.C.; Lindle, D.W.

1987-10-01

336

Generalized oscillator strengths for 5s, 5s{sup '}, and 5p excitations of krypton  

SciTech Connect

The absolute generalized oscillator strengths (GOSs) for 5s, 5s{sup '}, 5p [5/2]{sub 3,2}, 5p [3/2]{sub 1,2}, and 5p [1/2]{sub 0} transitions of krypton have been determined in a large K{sup 2} region at a high electron-impact energy of 2500 eV. The positions of the minima and maxima of these GOSs have been determined. The present results show that the angular resolution and pressure effect have great influence on the position and the amplitude of the minimum for the GOS of 5s+5s{sup '} transitions. When these effects are considered, the measured minimum position for the GOS of 5s+5s{sup '} transitions is in excellent agreement with the calculation of Chen and Msezane [J. Phys. B 33, 5397 (2000)].

Li Wenbin; Zhu Linfan; Yuan Zhensheng; Sun Jianmin; Cheng Huadong; Xu Kezun [Laboratory of Bond-Selective Chemistry, Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui, 230027 (China); Zhong Zhiping [Department of Physics, the Graduate School of the Chinese Academy of Sciences, P.O. Box 3908, Beijing 100039 (China); Liu Xiaojing

2003-06-01

337

Computation of thermodynamic and transport properties to predict thermophoretic effects in an argon-krypton mixture.  

PubMed

Thermophoresis is the movement of molecules caused by a temperature gradient. Here we report the results of a study of thermophoresis using non-equilibrium molecular dynamics simulations of a confined argon-krypton fluid subject to two different temperatures at thermostated walls. The resulting temperature profile between the walls is used along with the Soret coefficient to predict the concentration profile that develops across the channel. We obtain the Soret coefficient by calculating the mutual diffusion and thermal diffusion coefficients. We report an appropriate method for calculating the transport coefficients for binary systems, using the Green-Kubo integrals and radial distribution functions obtained from equilibrium molecular dynamics simulations of the bulk fluid. Our method has the unique advantage of separating the mutual diffusion and thermal diffusion coefficients, and calculating the sign and magnitude of their individual contributions to thermophoresis in binary mixtures. PMID:24116632

Miller, Nicholas A T; Daivis, Peter J; Snook, Ian K; Todd, B D

2013-10-14

338

Solar-wind krypton and solid/gas fractionation in the early solar nebula  

SciTech Connect

Krypton is the best candidate for determining limits on solid/gas fractionation in the early sun because of the smoothness of the odd-mass abundance curve in its mass region, which permits relatively precise interpolations of its abundance assuming no fractionation. Here the authors calculate the solar-system Kr abundance from solar-wind noble-gas ratios, determined previously by low-temperature oxidations of lunar ilmenite grains, normalized to Si by spacecraft solar-wind measurements. The estimated {sup 83}Kr abundance of 4.1 {plus minus} 1.5 per 10{sup 6} Si atoms is within uncertainty of estimates assuming no fractionation, determined from DI-chondrite abundances of surrounding elements. This is significant because it is the first such constraint on solid/gas fractionation, though the large uncertainty only confines it to somewhat less than a factor of two.

Wiens, R.C.; Burnett, D.S.; Neugebauer, M. (California Inst. of Tech., Pasadena (USA)); Pepin, R.O. (Univ. of Minnesota, Minneapolis (USA))

1991-02-01

339

Statistical analysis of the electrical breakdown time delay distributions in krypton  

SciTech Connect

The statistical analysis of the experimentally observed electrical breakdown time delay distributions in the krypton-filled diode tube at 2.6 mbar is presented. The experimental distributions are obtained on the basis of 1000 successive and independent measurements. The theoretical electrical breakdown time delay distribution is evaluated as the convolution of the statistical time delay with exponential, and discharge formative time with Gaussian distribution. The distribution parameters are estimated by the stochastic modelling of the time delay distributions, and by comparing them with the experimental distributions for different relaxation times, voltages, and intensities of UV radiation. The transition of distribution shapes, from Gaussian-type to the exponential-like, is investigated by calculating the corresponding skewness and excess kurtosis parameters. It is shown that the mathematical model based on the convolution of two random variable distributions describes experimentally obtained time delay distributions and the separation of the total breakdown time delay to the statistical and formative time delay.

Maluckov, Cedomir A.; Karamarkovic, Jugoslav P.; Radovic, Miodrag K.; Pejovic, Momcilo M. [Technical Faculty in Bor, University of Belgrade, Vojske Jugoslavije 24, 19210 Bor (Serbia and Montenegro); Faculty of Civil Engineering and Architecture, University of Nis, Beogradska 14, 18000 Nis (Serbia and Montenegro); Faculty of Sciences and Mathematics, University of Nis, P.O. Box 224, 18001 Nis (Serbia and Montenegro); Faculty of Electronic Engineering, University of Nis, P.O. Box 73, 18001 Nis (Serbia and Montenegro)

2006-08-15

340

Computation of thermodynamic and transport properties to predict thermophoretic effects in an argon-krypton mixture  

NASA Astrophysics Data System (ADS)

Thermophoresis is the movement of molecules caused by a temperature gradient. Here we report the results of a study of thermophoresis using non-equilibrium molecular dynamics simulations of a confined argon-krypton fluid subject to two different temperatures at thermostated walls. The resulting temperature profile between the walls is used along with the Soret coefficient to predict the concentration profile that develops across the channel. We obtain the Soret coefficient by calculating the mutual diffusion and thermal diffusion coefficients. We report an appropriate method for calculating the transport coefficients for binary systems, using the Green-Kubo integrals and radial distribution functions obtained from equilibrium molecular dynamics simulations of the bulk fluid. Our method has the unique advantage of separating the mutual diffusion and thermal diffusion coefficients, and calculating the sign and magnitude of their individual contributions to thermophoresis in binary mixtures.

Miller, Nicholas A. T.; Daivis, Peter J.; Snook, Ian K.; Todd, B. D.

2013-10-01

341

Single and double ionization of neon, krypton and xenon by positron impact  

NASA Astrophysics Data System (ADS)

Measurements of the single 0953-4075/30/17/019/img1 and the ratio of double to single 0953-4075/30/17/019/img2 ionization cross sections for positron impact on neon, krypton and xenon are presented from near threshold to 1000 eV. By multiplying the 0953-4075/30/17/019/img3 values of each target by the appropriate 0953-4075/30/17/019/img4, new data for the corresponding double 0953-4075/30/17/019/img5 ionization cross sections have also been obtained. The ratio between positron and electron 0953-4075/30/17/019/img4 maxima is generally seen to be lower for higher target atomic number, as expected from the static interaction between the projectile and undistorted target. Comparison with available data suggests that Ps formation accompanied by the production of singly or doubly charged ions is a significant channel in positron - atom scattering.

Kara, V.; Paludan, K.; Moxom, J.; Ashley, P.; Laricchia, G.

1997-09-01

342

Charge-Changing Cross Sections from the Fragmentation of Relativistic Krypton and Silver Nuclei.  

NASA Astrophysics Data System (ADS)

The fragmentation of ultraheavy nuclei is of great interest in cosmic ray and nuclear physics. The charge -changing cross sections are measured for the fragmentation of krypton and silver nuclei on targets of hydrogen, polyethylene, lithium, carbon, aluminum, copper, tin, and lead at energies from 450 to 1500 MeV/nucleon. The detector system used in these measurements and the method used in determining the charge-changing cross sections are described. New energy independent and dependent models of the total charge-changing cross sections are introduced. The need to introduce electron measured nuclear radius to describe the interactions over the large range of beams and targets is demonstrated. Using the measured nuclear radii eliminates the need to use an effective hydrogen mass or radii. A simple hard sphere model with a constant overlap term is adequate, when using the measured nuclear radii, to describe the beam and target dependence of the total charge-changing cross sections. A new form of the partial charge-changing cross sections on heavy targets is introduced. The new krypton and silver partial cross sections are compared to earlier models and new parameters values are found when appropriate. No evidence is found at these energies for limiting fragmentation or factorization of the partial cross sections. The charge -changing cross sections on targets heavier than hydrogen follow a power law unlike the hydrogen containing targets. A study of the charge-pickup cross sections is made and the beam dependence is found to be dependent on the neutron excess rather than just the mass number.

Nilsen, Bjorn Steven

1994-01-01

343

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

PubMed

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

Patrykiejew, A; Soko?owski, S

2012-04-14

344

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

NASA Astrophysics Data System (ADS)

Using the results of extensive Monte Carlo simulations in the canonical and grand canonical ensembles, we discuss the phase behavior of mixed submonolayer films of krypton and xenon adsorbed on the graphite basal plane. The calculations have been performed using two- and three-dimensional models of the systems studied. It has been demonstrated that out-of-plane motion does not affect the properties of the films as long as the total density is well below the monolayer completion and at moderate temperatures. For the total densities close to the monolayer completion, the promotion of particles to the second layer considerably affects the film properties. Our results are in a reasonable agreement with the available experimental data. The melting point of submonolayer films has been shown to exhibit non-monotonous changes with the film composition, and reaches minimum for the xenon concentration of about 50%. At the temperatures below the melting point, the structure of solid phases depends upon the film composition and the temperature; one can also distinguish commensurate and incommensurate phases. Two-dimensional calculations have demonstrated that for the xenon concentration between about 15% and 65% the adsorbed film exhibits the formation of a superstructure, in which each Xe atom is surrounded by six Kr atoms. This superstructure is stable only at very low temperatures and transforms into the mixed commensurate (33)R30 phase upon the increase of temperature. Such a superstructure does not appear when a three-dimensional model is used. Grand canonical ensemble calculations allowed us to show that for the xenon concentration of about 3% the phase diagram topology of monolayer films changes from the krypton-like (with incipient triple point) to the xenon-like (with ordinary triple point).

Patrykiejew, A.; Soko?owski, S.

2012-04-01

345

Ce isotope abundance in chondritic and HED meteorites  

NASA Astrophysics Data System (ADS)

138La, 136Ce and 138Ce are p-process nuclides, and their isotopic abundances are generally low due to their modes of nucleosynthesis compared with other isotopes of La and Ce (139La, 140Ce and 142Ce). Tanimizu et al. (2004) mentioned that, using the 140Ce/142Ce ratio as the normalizing value, 136Ce isotope abundance could be acted as an indicator of p-process nuclide anomaly for extra-terrestrial materials to understand the nucleosynthetic origins of solar system matter. Then, meteoritic primordial composition of Ce isotope provides useful information related with 138La decay system. Especially, combined Ce/Nd isotope data in geological and cosmological materials enable us the modeling of the light REE profiles of the source material. We measured Ce isotope ratio for fifteen meteorites, using 140Ce/142Ce=7.941 as the normalizing value, in order to compare Ce isotope abundance between chondritic and HED meteorites. Of them, Ce isotope abundances from two chondritic meteorites were deviated from the average abundances of other 13 meteorites. In this report, we will discuss cosmochemical significance of Ce isotope anomaly.

Lee, S.; Asahara, Y.; Tanaka, T.; Lee, S. R.

2011-12-01

346

Anomalous nitrogen isotope ratio in comets.  

PubMed

High-resolution spectra of the CN B2 summation operator +-X2 summation operator + (0,0) band at 390 nanometers yield isotopic ratios for comets C/1995 O1 (Hale-Bopp) and C/2000 WM1 (LINEAR) as follows: 165 +/- 40 and 115 +/- 20 for 12C/13C, 140 +/- 35 and 140 +/- 30 for 14N/15N. Our N isotopic measurements are lower than the terrestrial 14N/15N = 272 and the ratio for Hale-Bopp from measurements of HCN, the presumed parent species of CN. This isotopic anomaly suggests the existence of other parent(s) of CN, with an even lower N isotopic ratio. Organic compounds like those found in interplanetary dust particles are good candidates. PMID:12970562

Arpigny, Claude; Jehin, Emmanul; Manfroid, Jean; Hutsemkers, Damien; Schulz, Rita; Stwe, J A; Zucconi, Jean-Marc; Ilyin, Ilya

2003-09-12

347

Production of krypton and xenon isotopes in thick stony and iron targets isotropically irradiated with 1600 MeV protons  

Microsoft Academic Search

Two spherical targets made of gabbro with a radius of 25 cm and of steel with a radius of 10 cm were irradiated isotropically with 1.6 GeV protons at the SATURNE synchrotron at Laboratoire National Saturne (LNS)\\/CEN Saclay, in order to simulate the production of nuclides in meteorites induced by galactic cosmic-ray protons in space. These experiments supply depth dependent

E. Gilabert; B. Lavielle; R. Michel; I. Leya; S. Neumann; U. Herpers

2002-01-01

348

Quantum tunneling and trace anomaly  

Microsoft Academic Search

We compute the corrections, using the tunneling formalism based on a quantum WKB approach, to the Hawking temperature and BekensteinHawking entropy for the Schwarzschild black hole. The results are related to the trace anomaly and are shown to be equivalent to findings inferred from Hawking's original calculation based on path integrals using zeta function regularization. Finally, exploiting the corrected temperature

Rabin Banerjee; Bibhas Ranjan Majhi

2009-01-01

349

Mbius Syndrome with Poland's Anomaly  

Microsoft Academic Search

A five-year-old boy with Mbius syndrome, Poland's anomaly, and dextrocardia is described. These malformations have not been previously reported. The propositus had ipsilateral absence of the sternal portion of the pectoralis major muscle associated with acromicria, syndactyly, brachydactyly of the index, middle, ring, and fifth finger, as well as radiological evidence of hypoplasia of the index middle and ring fingers,

Gerald I. Sugarman; Herbert H. Stark

1973-01-01

350

Coral can have growth anomalies  

EPA Science Inventory

Coral growth anomalies (GAs) are changes in the coral cells that deposit the calcium carbonate skeleton. They usually appear as raised areas of the skeleton and tissue that are different from the surrounding normal areas on the same colony. The features include abnormal shape a...

351

Lunar rocks and thermal anomalies  

Microsoft Academic Search

Recent microwave and infrared spectral observations of several of the large bright-rayed craters on the moon suggest that the thermal anomalies in these craters are produced by large rocks, boulders, and exposed rock strata. The data for the crater Tycho can be simulated by a surface consisting of 16% loose rocks of I-meter size and 4% exposed rock strata. A

David Buhl

1971-01-01

352

Building envelope thermal anomaly analysis  

Microsoft Academic Search

A detailed study has been made of building energy thermal anomalies (BETA's) in a large modern office building using computer simulation, on-site inspections, and infrared thermography. The goal was to better understand the heat and moisture flow through these ''bridges,'' develop the beginnings of a classification scheme, and establish techniques for assessing the potential for retrofit or initial design modifications.

B. S. Melton; P. Mulroney; T. Scott; K. W. Childs

1987-01-01

353

Anomaly detection from hyperspectral imagery  

Microsoft Academic Search

We develop anomaly detectors, i.e., detectors that do not presuppose a signature model of one or more dimensions, for three clutter models: the local normal model, the global normal mixture model, and the global linear mixture model. The local normal model treats the neighborhood of a pixel as having a normal probability distribution. The normal mixture model considers the observation

D. W. J. Stein; S. G. Beaven; L. E. Hoff; E. M. Winter; A. P. Schaum; A. D. Stocker

2002-01-01

354

Anomaly-specified virtual dimensionality  

NASA Astrophysics Data System (ADS)

Virtual dimensionality (VD) has received considerable interest where VD is used to estimate the number of spectral distinct signatures, denoted by p. Unfortunately, no specific definition is provided by VD for what a spectrally distinct signature is. As a result, various types of spectral distinct signatures determine different values of VD. There is no one value-fit-all for VD. In order to address this issue this paper presents a new concept, referred to as anomaly-specified VD (AS-VD) which determines the number of anomalies of interest present in the data. Specifically, two types of anomaly detection algorithms are of particular interest, sample covariance matrix K-based anomaly detector developed by Reed and Yu, referred to as K-RXD and sample correlation matrix R-based RXD, referred to as R-RXD. Since K-RXD is only determined by 2nd order statistics compared to R-RXD which is specified by statistics of the first two orders including sample mean as the first order statistics, the values determined by K-RXD and R-RXD will be different. Experiments are conducted in comparison with widely used eigen-based approaches.

Chen, Shih-Yu; Paylor, Drew; Chang, Chein-I.

2013-09-01

355

Archaeological Anomalies in the Bahamas  

Microsoft Academic Search

Controversial claims have been made for the presence of anom- alous underwater archaeological sites in the Bahamas by a number of in- vestigators. The proponents emphasize extraordinary explanations for the anomalies and tend to bypass the scientific journals in favor of popular presentations with little scientific rigor. The skeptics debunk selected claims for some of the sites, do not adequately

DOUGLAS G. RICHARDS

1988-01-01

356

Registries of congenital anomalies: EUROCAT.  

PubMed

Congenital anomalies are one of the potential adverse effects of the environment on reproductive health. Registries of congenital anomalies are useful to detect abnormal frequencies, clusters, and trends. Such registries should meet a number of conditions, including an appropriate population denominator, an efficient system for collecting information, standardized diagnostic procedures, postmortem examinations of still-births, and linkage of records. The EUROCAT (European Registration of Congenital Anomalies and Twins) program is a Concerted Action of the Commission of the European Communities initiated in 1979. One of its objectives is the surveillance of congenital anomalies as related to environmental hazards. This surveillance system covers at present 350,000 births per year in 15 countries. A number of problems encountered in the development of EUROCAT and in the course of ongoing activities are reviewed: populations coverage, classification of malformations, coding, definition and coverage of late fetal death, registration of induced abortion, validation of diagnostic information, registration of late diagnosed cases, and maintenance of motivation in data collection. The issue of confidentiality and the need for strict safeguards for the protection of individual privacy are emphasized. PMID:8243386

Lechat, M F; Dolk, H

1993-07-01

357

Pregnancy outcome and Ebstein's anomaly.  

PubMed Central

BACKGROUND--Ebstein's anomaly is an uncommon congenital cardiac abnormality that may be associated with cyanosis and arrhythmias. For those female patients with the anomaly who survive to adult life there is little information available about pregnancy, maternal complications, and fetal outcome. This study was designed to address this issue so that these patients can receive appropriate advice and management. METHODS AND RESULTS--Forty two pregnancies in 12 women with Ebstein's anomaly were studied. The mothers' cardiac lesions were assessed on the basis of symptoms, the presence of cyanosis or arrhythmia, and by echocardiographic grading of severity. In the absence of important maternal cyanosis or arrhythmia, pregnancy was well tolerated. Neonatal outcome was good though there was an increased risk of prematurity and dysmaturity in the babies born to mothers with cyanosis. CONCLUSIONS--This study indicates that women with Ebstein's anomaly who reach child-bearing age can be advised that pregnancy is likely to be well tolerated with good fetal outcome. Maternal arrhythmia or cyanosis are indications for closer maternal and fetal observation.

Donnelly, J E; Brown, J M; Radford, D J

1991-01-01

358

Anomalies: Ultimatums, Dictators and Manners  

Microsoft Academic Search

Economics can be distinguished from other social sciences by the belief that most (all?) behavior can be explained by assuming that agents have stable, well-defined preferences and make rational choices consistent with those pref- erences in markets that (eventually) clear. An empirical result qualifies as an anomaly if it is difficult to \\

Colin Camerer; Richard H. Thaler

359

Accounting Anomalies and Information Uncertainty  

Microsoft Academic Search

We examine whether rational investor responses to information uncertainty explain properties of and returns to accounting-based trading anomalies. We proxy for information uncertainty with two measures of earnings quality: the standard deviation of the residuals from a Dechow and Dichev (2002) model relating accruals to cash flows, and the absolute value of performance-adjusted abnormal accruals from a modified Jones (1991)

Jennifer Francis; Ryan LaFond; Per Olsson; Katherine Schipper

2003-01-01

360

Stable platinum isotope measurements in presolar nanodiamonds by TEAMS.  

PubMed

Nanodiamonds are stardust grains commonly found in primitive meteorites. They survived the formation of the solar system and kept their own individuality. Measurements of trace-element isotopic signatures in these grains will help understanding heavy element nucleosynthesis in massive stars and dust formation from their ejecta. We have continued previous attempts to search for stable Pt isotope anomalies in nanodiamonds via trace element accelerator mass spectrometry (TEAMS). The installation of a new injector beam line at the VERA facility allowed studying low traces of stable elements in different materials. Moreover, recent experiments showed that VERA provides the required measurement precision together with a low Pt machine background. Here, we observed for the first time an indication for enhancements of (198)Pt/(195)Pt isotope ratios in two diamond residues prepared by different chemical separation techniques from the Allende meteorite. Variations in other isotopic ratios were within analytical uncertainty, and no anomaly was identified in a third diamond fraction. PMID:23565017

Wallner, A; Melber, K; Merchel, S; Ott, U; Forstner, O; Golser, R; Kutschera, W; Priller, A; Steier, P

2013-01-01

361

Threshold anomaly in doublet nd-scattering.  

National Technical Information Service (NTIS)

The doublet nd-scattering amplitude behaviour near the three-particle threshold is studied analytically and numerically. The scattering amplitude possesses an anomaly caused by the small energy of singlet deuteron virtual level. The anomaly manifests itse...

D. V. Shapoval I. V. Simenog

1988-01-01

362

ANOMALIES OF THE FLEXOR DIGITORUM SUPERFICIALIS MUSCLE  

Microsoft Academic Search

Three anomalies of the human flexor digitorum superficialis are presented. The normal development of this muscle from the amphibian to the human is discussed and the described anomalies of the muscle in humans classified.

D ELLIOT; A. R KHANDWALA; M KULKARNI

1999-01-01

363

In utero sonography of genitourinary anomalies  

Microsoft Academic Search

Congenital anomalies of the genitourinary system represent the commonest fetal anomaly. The sonographic findings in hydronephrosis,\\u000a multicystic kidney (dysplastic kidney) polycystic kidney, and renal agenesis are reviewed.

R. C. Sanders

1992-01-01

364

Gated right ventricular studies using krypton-81m: comparison with first-pass studies using gold-195m  

SciTech Connect

Krypton-81m, given by continuous i.v. infusion, has been successfully used for the equilibrium ECG-gated assessment of right ventricular function. We compared gated studies with 81mKr (half-life 13 sec) with first-pass studies using 195mAu (half-life 30.5 sec). Krypton studies analyzed using variable regions of interest (ROIs) led to a significantly higher calculated right ventricular ejection fraction (RVEF) than with a fixed ROI, both with and without background correction. The differences between first-pass studies and gated studies without background correction were significant (p less than 0.01), whereas they were not with background correction. These data suggest that large systematic errors exist in the calculation of RVEF depending on the analysis method and that background correction is important when different techniques are compared.

Caplin, J.L.; Flatman, W.D.; Dymond, D.S.

1986-05-01

365

The aetiology of sigma model anomalies  

NASA Astrophysics Data System (ADS)

Certain nonlinear sigma models with fermions are ill-defined due to an anomaly which exhibits characteristics of both the nonabelian gauge theory anomaly and the SU(2) anomaly. The simplest way to diagnose the anomaly involves consideration of the global topology of the theory. We review the mathematical methods needed for this analysis and apply them to several supersymmetric sigma models. Some of these are found to be anomalous.

Moore, Gregory; Nelson, Philip

1985-03-01

366

Magnetic anomalies, layered intrusions and Mars  

Microsoft Academic Search

Studies of remanence-controlled magnetic anomalies on Earth provide possibilities to interpret the nature of crustal rocks that cause the large remanent anomalies on Mars. What types of conditions on Earth can create large remanent magnetic anomalies? Such an anomaly, extending for 20 km centered over a norite layer in the Bjerkreim-Sokndal (BKS) Intrusion, shows a minimum ?13000 nT below background

S. A. McEnroe; J. R. Skilbrei; P. Robinson; F. Heidelbach; F. Langenhorst; L. L. Brown

2004-01-01

367

Determination and analysis of plasma parameters for simulations of radiative blast waves launched in clusters of xenon and krypton  

NASA Astrophysics Data System (ADS)

In this work several relevant parameters and properties for krypton and xenon plasmas are analyzed, such as, for example, the average ionization, the plasma thermodynamic regimes, the radiative power losses and the mean opacities. This analysis is performed in a range of density and temperature typically found in laboratory experiments to generate radiative blast waves in laser-heated clustered plasmas. A polynomial fit of those parameters is also presented. Finally an analysis of the thermal cooling instability is performed.

Rodriguez, R.; Gil, J. M.; Espinosa, G.; Florido, R.; Rubiano, J. G.; Mendoza, M. A.; Martel, P.; Minguez, E.; Symes, D. R.; Hohenberger, M.; Smith, R. A.

2012-04-01

368

Monitoring of kratom or Krypton intake in urine using GC-MS in clinical and forensic toxicology  

Microsoft Academic Search

The Thai medicinal plant Mitragyna speciosa (kratom) is misused as a herbal drug. Besides this, a new herbal blend has appeared on the drugs of abuse market, named Krypton,\\u000a a mixture of O-demethyltramadol (ODT) and kratom. Therefore, urine drug screenings should include ODT and focus on the metabolites of the kratom alkaloids mitragynine (MG), paynantheine (PAY), speciogynine (SG), and speciociliatine

Anika A. Philipp; Markus R. Meyer; Dirk K. Wissenbach; Armin A. Weber; Siegfried W. Zoerntlein; Peter G. M. Zweipfenning; Hans H. Maurer

2011-01-01

369

On the spectra of highly-ionized krypton, strontium, zirconium and rhodium excited in the plasma of the TFR tokamak  

NASA Astrophysics Data System (ADS)

Storntium, zirconium and rhodium have been injected into TFR tokamak plasmas by using the laser blow-off technique, and their spectra recorded either photographically (Zr, 10-92 ) or photoelectrically (all three elements, 10-330 ). Line identifications for several isoelectronic sequences from sodium-like to gallium-like are reported. Additionally, isoelectronic regularities observed for these three elements have allowed to identify a few krypton lines left unidentified in our previous work [1].

TFR Group; Wyart, J. F.

1988-01-01

370

Conclusions on plutonium separation from atmospheric krypton-85 measured at various distances from the Karlsruhe reprocessing plant  

Microsoft Academic Search

For wide-area atmospheric monitoring, krypton-85 is the best indicator for clandestine plutonium separations. The detection and false alarm rates were determined from weekly samples at five different distances from the Karlsruhe reprocessing plant between 1985 and 1988. The detection rate for the separation of 4 kg of plutonium per week was found to be as high as 8090% at a

Martin B. Kalinowski; Hartmut Sartorius; Stefan Uhl; Wolfgang Weiss

2004-01-01

371

Photoionization of the outer shells of neon, argon, krypton, and xenon using the relativistic random-phase approximation  

Microsoft Academic Search

Multichannel photoionization calculations using the relativistic random-phase approximation for the outer shells in the rare gases, neon, argon, krypton, and xenon, are presented. Total cross sections and partial cross sections for ns subshells are determined and compared with experiment and with alternative calculations at low energies. Branching ratios of ²P:²P cross sections which are sensitive to relativistic and correlation effects

W. R. Johnson; K. T. Cheng

1979-01-01

372

Photoionization of the outer shells of neon, argon, krypton, and xenon using the relativistic random-phase approximation  

Microsoft Academic Search

Multichannel photoionization calculations using the relativistic random-phase approximation for the outer shells in the rare gases, neon, argon, krypton, and xenon, are presented. Total cross sections and partial cross sections for ns subshells are determined and compared with experiment and with alternative calculations at low energies. Branching ratios of 2P32:2P12 cross sections which are sensitive to relativistic and correlation effects

W. R. Johnson; K. T. Cheng

1979-01-01

373

Investigation of the combined adsorption of krypton, xenon, and water vapor of the off-gas of atomic power stations  

Microsoft Academic Search

A radiochromatogra phic system of purifying the off-gas from the short-lived krypton, xenon, and iodine nuclides is presently used in Russian atomic power stations and in foreign atomic power stations equipped with the aid of the USSR. The basic elements of the system are filter-adsorbers filled with activated carbon and a drying unit [1-3]. Dynamic adsorption and radioactive decay in

I. E. Nakhutin; D. V. Ochkin; S. A. Tret'yak

1980-01-01

374

On the spectra of highly-ionized krypton, strontium, zirconium and rhodium excited in the plasma of the TFR tokamak  

Microsoft Academic Search

Storntium, zirconium and rhodium have been injected into TFR tokamak plasmas by using the laser blow-off technique, and their spectra recorded either photographically (Zr, 10-92 ) or photoelectrically (all three elements, 10-330 ). Line identifications for several isoelectronic sequences from sodium-like to gallium-like are reported. Additionally, isoelectronic regularities observed for these three elements have allowed to identify a few krypton

J. F. Wyart

1988-01-01

375

Monitoring of kratom or Krypton intake in urine using GC-MS in clinical and forensic toxicology.  

PubMed

The Thai medicinal plant Mitragyna speciosa (kratom) is misused as a herbal drug. Besides this, a new herbal blend has appeared on the drugs of abuse market, named Krypton, a mixture of O-demethyltramadol (ODT) and kratom. Therefore, urine drug screenings should include ODT and focus on the metabolites of the kratom alkaloids mitragynine (MG), paynantheine (PAY), speciogynine (SG), and speciociliatine (SC). The aim of this study was to develop a full-scan gas chromatography-mass spectrometry procedure for monitoring kratom or Krypton intake in urine after enzymatic cleavage of conjugates, solid-phase extraction, and trimethylsilylation. With use of reconstructed mass chromatography with the ions m/z 271, 286, 329, 344, 470, 526, 528, and 586, the presence of MG, 16-carboxy-MG, 9-O-demethyl-MG, and/or 9-O-demethyl-16-carboxy-MG could be indicated, and in case of Krypton, with m/z 58, 84, 116, 142, 303, 361, 393, and 451, the additional presence of ODT and its nor metabolite could be indicated. Compounds were identified by comparison with their respective reference spectra. Depending on the plant type, dose, administration route, and/or sampling time, further metabolites of MG, PAY, SG, and SC could be detected. The limits of detection (signal-to-noise ratio of 3) were 100 ng/ml for the parent alkaloids and 50 ng/ml for ODT. As mainly metabolites of the kratom alkaloids were detected in urine, the detectability of kratom was tested successfully using rat urine after administration of a common user's dose of MG. As the metabolism in humans was similar, this procedure should be suitable to prove an intake of kratom or Krypton. PMID:21153588

Philipp, Anika A; Meyer, Markus R; Wissenbach, Dirk K; Weber, Armin A; Zoerntlein, Siegfried W; Zweipfenning, Peter G M; Maurer, Hans H

2010-12-12

376

Oxide and oxide fluorides of xenon(IV) and new developments in xenon(II), and krypton(II) chemistry  

Microsoft Academic Search

This Thesis extends the fundamental chemistry of the noble-gas elements, namely, xenon and krypton. More specifically, the chemistry of Xe(IV) has been extended by the synthesis and characterization of Xe(IV) oxide and oxide fluoride derivatives. The syntheses of XeOF2, F2OXeN?CCH 3, and XeOF2 ˙nHF and their structural characterizations are described. All three compounds are endothermic and explosive at temperatures approaching

David S Brock

2011-01-01

377

Atomic data for neutron-capture elements. II. Photoionization and recombination properties of low-charge krypton ions  

Microsoft Academic Search

We present multi-configuration Breit-Pauli distorted-wave photoionization (PI) cross sections and radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for the first six krypton ions. These were calculated with the AUTOSTRUCTURE code, using semi-relativistic radial wavefunctions in intermediate coupling. Kr has been detected in several planetary nebulae (PNe) and H II regions, and is a useful tracer of neutron-capture nucleosynthesis.

N. C. Sterling

2011-01-01

378

Rotational excitations of a symmetric top in cubic orientational potentials: CH3D matrix-isolated in argon and krypton  

Microsoft Academic Search

Measurements with inelastic neutron scattering of the rotational spectra of the symmetric top molecule CH3D as substitutional impurities in crystalline argon and krypton are presented. The energy of the J=1 doublet is shifted by 33% and 27% respectively, compared to the completely free rotor. Spin-rotational wave functions for the free CH3D rotor are constructed and used for the calculation of

B. Asmussen; D. Balszunat; M. Prager; C. J. Carlile; H. Bttner

1995-01-01

379

Safeguarding SCADA Systems with Anomaly Detection  

Microsoft Academic Search

This paper will show how the accuracy and security of SCADA systems can be improved by using anomaly detection to identify bad values caused by attacks and faults. The performance of invariant induction and n- gram anomaly-detectors will be compared and this paper will also outline plans for taking this work further by integrating the output from several anomaly- detecting

John Bigham; David Gamez; Ning Lu

2003-01-01

380

A signal analysis of network traffic anomalies  

Microsoft Academic Search

Identifying anomalies rapidly and accurately is critical to the efficient operation of large computer networks. Accurately characterizing important classes of anomalies greatly facilitates their identification; however, the subtleties and complexities of anomalous traffic can easily confound this process. In this paper we report results of signal analysis of four classes of network traffic anomalies: outages, flash crowds, attacks and measurement

Paul Barford; Jeffery Kline; David Plonka; Amos Ron

2002-01-01

381

Debendox does not cause the Poland anomaly  

Microsoft Academic Search

The suggestion that Debendox may cause the Poland anomaly is refuted by a study of the antenatal drug exposure in 46 cases of the Poland anomaly and 32 cases of isolated absence of the pectoralis major. Debendox had been prescribed in one case of the Poland anomaly and in one case of isolated pectoralis absence, but in neither was the

T J David

1982-01-01

382

Poland anomaly in mother and daughter.  

PubMed

We report on Poland anomaly in a mother and her daughter. Further family history was negative for abnormalities of the hands or the pectoralis major muscle. A review of published cases of familial Poland anomaly is presented. Implications concerning the possible etiology of familial cases of Poland anomaly are given. PMID:2556920

Cobben, J M; Robinson, P H; van Essen, A J; van der Wiel, H L; ten Kate, L P

1989-08-01

383

Limb Body Wall Complex: A Rare Anomaly  

PubMed Central

We present autopsy findings of a case of limb body wall complex (LBWC). The fetus had encephalocele, genitourinary agenesis, skeletal anomalies and body wall defects. The rare finding in our case is the occurrence of both cranial and urogenital anomalies. The presence of complex anomalies in this fetus, supports embryonal dysplasia theory of pathogenesis for LBWC.

Chikkannaiah, Panduranga; Dhumale, Hema; Kangle, Ranjit; Shekar, Rosini

2013-01-01

384

Conclusions on plutonium separation from atmospheric krypton-85 measured at various distances from the Karlsruhe reprocessing plant.  

PubMed

For wide-area atmospheric monitoring, krypton-85 is the best indicator for clandestine plutonium separations. The detection and false alarm rates were determined from weekly samples at five different distances from the Karlsruhe reprocessing plant between 1985 and 1988. The detection rate for the separation of 4 kg of plutonium per week was found to be as high as 80-90% at a distance of less than 1 km, 70% at 5 km, 40% at 39 km, and 15% at 130 km. At distances up to 40 km, the false alarm rate is less than 3.5%. On average, the fuel released 28 TBq krypton-85 per kg plutonium. For weapons-grade plutonium, the krypton signal would be lower by a factor of 2. Hence, the given percentages correspond to the detection probabilities for the separation of a significant quantity (8 kg) of plutonium per weekly sample under the specific meteorological conditions of the WAK. The minimum separation rates that could have been detected are 2 gram of weapons-grade plutonium per week at a distance of less than 1 km, 40 g/week at 5 km, 200 g/week at 39 km, and 1000 g/week at 130 km. PMID:15023448

Kalinowski, Martin B; Sartorius, Hartmut; Uhl, Stefan; Weiss, Wolfgang

2004-01-01

385

Using Krypton K-shell Emission as a Diagnostic of Fuel Conditions in Implosions of SIO2 Shells  

NASA Astrophysics Data System (ADS)

To study how hi-Z impurities in imploding capsules affect the equilibration of ion, electron, and radiation temperatures, the D3He fill gas of SIO2 shells have been doped with various amounts of krypton and xenon. If xenon is used as the main adjustable impurity affecting this equilibration, the amount of krypton placed in the D3He fill gas can be kept at a level that minimizes the optical depth of the krypton K-shell emission lines. With the small optical depths, these emission lines can provide important time-resolved information on the electron temperature in the imploding fuel through the analysis of the relative intensities of the lines. With sufficient spectral resolution, these lines can even provide time-resolved information on the electron density of the imploding fuel by analyzing the widths of the emission lines. Used in conjunction with the emitted proton spectrum from which time-resolved ion temperature and rhoR can be inferred, we can directly study the effect of hi-Z impurities on temperature equilibration and yield.

Gunderson, Mark; Wilson, Douglas; Kyrala, George; Benage, John

2006-10-01

386

Isotopic homogeneity of iron in the early solar nebula.  

PubMed

The chemical and isotopic homogeneity of the early solar nebula, and the processes producing fractionation during its evolution, are central issues of cosmochemistry. Studies of the relative abundance variations of three or more isotopes of an element can in principle determine if the initial reservoir of material was a homogeneous mixture or if it contained several distinct sources of precursor material. For example, widespread anomalies observed in the oxygen isotopes of meteorites have been interpreted as resulting from the mixing of a solid phase that was enriched in 16O with a gas phase in which 16O was depleted, or as an isotopic 'memory' of Galactic evolution. In either case, these anomalies are regarded as strong evidence that the early solar nebula was not initially homogeneous. Here we present measurements of the relative abundances of three iron isotopes in meteoritic and terrestrial samples. We show that significant variations of iron isotopes exist in both terrestrial and extraterrestrial materials. But when plotted in a three-isotope diagram, all of the data for these Solar System materials fall on a single mass-fractionation line, showing that homogenization of iron isotopes occurred in the solar nebula before both planetesimal accretion and chondrule formation. PMID:11460156

Zhu, X K; Guo, Y; O'Nions, R K; Young, E D; Ash, R D

2001-07-19

387

Anomalies and Discrete Chiral Symmetries  

SciTech Connect

The quantum anomaly that breaks the U(1) axial symmetry of massless multi-flavored QCD leaves behind a discrete flavor-singlet chiral invariance. With massive quarks, this residual symmetry has a close connection with the strong CP-violating parameter theta. One result is that if the lightest quarks are degenerate, then a first order transition will occur when theta passes through pi. The resulting framework helps clarify when the rooting prescription for extrapolating in the number of flavors is valid.

Creutz, M.

2009-09-07

388

Astrometric Solar-System Anomalies  

NASA Astrophysics Data System (ADS)

There are four unexplained anomalies connected with astrometric data. Perhaps the most disturbing is the fact that when a spacecraft on a flyby trajectory approaches the Earth within 2000 km or less, it experiences a gain in total orbital energy per unit mass (Anderson et al., Phys. Rev. Lett. 100, 091102). This amounts to a net velocity increase of 13.5 mm/s for the NEAR spacecraft at a closest approach of 539 km, 3.9 mm/s for the Galileo spacecraft at 960 km, and 1.8 mm/s for the Rosetta spacecraft at 1956 km. Next, I suggest the change in the astronomical unit AU is definitely a concern. It is increasing by about 15 cm/yr (Krasinsky and Brumberg, Celes. Mech. & Dynam. Astron. 90, 267). The other two anomalies are perhaps less disturbing because of known sources of nongravitational acceleration. The first is an apparent slowing of the two Pioneer spacecraft as they exit the solar system in opposite directions (Anderson et al., Phys. Rev. D 65, 082004). Some, including me, are convinced this effect is of concern, but many are convinced it is produced by a nearly identical thermal emission from both spacecraft, in a direction away from the Sun, thereby producing acceleration toward the Sun. The fourth anomaly is a measured increase in the eccentricity of the Moon's orbit. Here again, an increase is expected from tidal friction in both the Earth and Moon. However, there is a reported increase that is about three times larger than expected (J. G. Williams, DDA/AAS Brouwer Award Lecture, Halifax, Nova Scotia 2006). We suspect that all four anomalies have mundane explanations. However, the possibility that they will be explained by a new theory of gravitation is not ruled out, perhaps analogous to Einstein's 1916 explanation of the excess precession of Mercury's perihelion.

Anderson, John D.

2009-05-01

389

Population-wide Anomaly Detection  

Microsoft Academic Search

Early detection of disease outbreaks, particularly an outbreak due to an act of bioterrorism, is a critically important problem due to the potential to reduce both morbidity and mortality. One of the most lethal bioterrorism scenarios is a large-scale release of inhalational anthrax. The Population-wide Anomaly Detection and Assessment (PANDA) algorithm (1) is specifically designed to monitor health-care data for

Weng-Keen Wong; Gregory F. Cooper; Denver H. Dash; John D. Levander; John N. Dowling; William R. Hogan; Michael M. Wagner

390

Surgical treatment of cloacal anomalies  

Microsoft Academic Search

From 19891998 14 patients were treated with cloacal anomalies: 5 typical cloacas (PC), 5 posterior cloacas, and 4 cloacal\\u000a exstrophies (CE); 12 underwent surgery. Four typical cloacas were resolved with posterior sagittal anorectovagino-urethroplasty\\u000a (PSARVUP), whereas in the 5th total urogenital mobilization (TUM) was used. Three PCs were managed with transanorectal TUM\\u000a and 2 with anterior TUM without opening the anal

Z. D. Krstic; M. Lukac; R. Lukac; Z. Smoljanic; V. Vukadinovic; D. Varinac

2001-01-01

391

[An obscure anomaly: regional odontodysplasia].  

PubMed

In a 3-year-old child, acute dental abscesses in combination with clinical and radiographic impressions of a number of deciduous teeth indicated regional odontodysplasia as probable diagnosis. Histological examination of the removed deciduous teeth confirmed the diagnosis. Early determination of this regional developmental anomaly in the odontogenesis is of great importance for optimal guidance of the dental care of a patient with regional odontodysplasia. PMID:20446549

Hoff, M; van der Haring, I S; van der Wal, J E; Vissink, A

2010-04-01

392

Lunar thermal anomalies: infrared observations.  

PubMed

The lunar craters Tycho, Copernicus, and Aristarchus have been observed during lunar night at wavelengths between 3 and 14 microns. After an initial fast decrease to a color temperature of 220 degrees K, the temperature remains nearly constant through the lunar night. The data suggest that these thermal anomalies (craters) contain hot and cold regions with the hot portions constituting 2 to 10 percent of the area and probably thermally connected to a subsurface temperatuer of about 200 degrees K. PMID:17800369

Allen, D A; Ney, E P

1969-04-25

393

Semiconductor isotope engineering  

SciTech Connect

Isotopic control of semiconductor crystals offers a wide range of scientific and technical opportunities. We review neutron transmutation doping of natural and isotopically controlled semiconductor structures, special properties of isotope superlattices, the effect of host isotopes on local vibrational modes of low mass impurities, and intrinsic properties which depend on isotope mass and isotopic composition of single crystals.

Haller, E.E.

1993-05-01

394

Energy Anomaly and Polarizability of Carbon Nanotubes  

SciTech Connect

The energy of Fermi sea perturbed by an external potential is analyzed with the help of an energy anomaly. Using an example of massive Dirac fermions on a circle, we illustrate how the anomaly accounts for the contribution of the deep-lying states. The energy anomaly is a universal function of the applied field and is related to known field-theoretic anomalies. Applied to the transverse polarizability of carbon nanotubes, the anomaly reveals universality and scale invariance of the response dominated by {pi} electrons. The electron band transformation in a strong field-effect regime is predicted.

Novikov, D.S. [Department of Electrical Engineering and Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Levitov, L.S. [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2006-01-27

395

Anomaly detection and diagnosis in Grid environments.  

SciTech Connect

Identifying and diagnosing anomalies in application behavior is critical to delivering reliable application-level performance. In this paper we introduce a strategy to detect anomalies and diagnose the possible reasons behind them. Our approach extends the traditional window-based strategy by using signal-processing techniques to filter out recurring, background fluctuations in resource behavior. In addition, we have developed a diagnosis technique that uses standard monitoring data to determine which related changes in behavior may cause anomalies. We evaluate our anomaly detection and diagnosis technique by applying it in three contexts when we insert anomalies into the system at random intervals. The experimental results show that our strategy detects up to 96% of anomalies while reducing the false positive rate by up to 90% compared to the traditional window average strategy. In addition, our strategy can diagnose the reason for the anomaly approximately 75% of the time.

Yang, L.; Liu, C.; Schopf, J. M.; Foster, I.; Mathematics and Computer Science; Univ. of Chicago; Microsoft Corp.

2007-01-01

396

Microwave Excitation of Argon Ion and Helium-Krypton Ion Lasers  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Pulsed microwave excitation of noble gas ion lasers at frequencies between 3 and 17 GHz is investigated. The advantages of using microwaves instead of conventional DC sources to pump a laser are explained. These include the lower electrode and discharge tube wear due to the oscillating nature of a microwave electric field. The propagation of microwave radiation in an ionised gas is examined. At the frequencies used, the skin depth of an Argon ion laser discharge is shown to be approximately 1 mm, indicating good microwave power absorption. The dependence of the microwave power absorption on the frequency is shown to be weak. Microwave transmission at a dielectric/gas -discharge boundary, similar to those in the laser coupling structures used, is found to be around 1% of the incident power. It is suggested that for maximum laser efficiency, microwave power should be introduced directly into the gas discharge. Two microwave coupling structure designs for supplying microwave power to the laser discharges are described. The first of these, a waveguide coupler device based on the 3dB branch guide coupler, produces a transverse electric field across the laser tube. The procedure used to design a branch guide coupler using a Chebyshev impedance taper and T-junction discontinuity corrections is outlined, and a description of the entire laser coupling structure is given. The second design comprises a helix wrapped round the laser tube and produces an axial electric field. The electric field distribution around a helix is calculated as a function of helix parameters and the effects of surrounding objects are considered. The best helix dimensions are found for optimum laser operation. The characteristics of conventional Argon ion and Helium-Krypton ion lasers are given. No significant differences between conventional noble gas ion lasers and the microwave excited lasers reported here are observed. At the input powers used (~100 kW peak, 1 uS pulses, 1000 pps), 100 mW, 1 uS and 30 mW, 5 uS laser pulses are observed from Argon and Helium-Krypton gas mixtures, respectively. The transverse and axially excited lasers perform equally well.

Dobie, Paul J.

397

Osmium isotope evidence for an s-process carrier in primitive chondrites.  

PubMed

Osmium extracted from unequilibrated bulk chondrites has isotope anomalies consistent with an insoluble s-process carrier, termed Os(i) here. Osmium from metamorphosed bulk chondrites does not have isotope anomalies, implying that the Os(i) carrier was destroyed by metamorphism. The isotopic homogeneity of metamorphosed bulk chondrites is consistent with extremely effective mixing of presolar grains from varied sources in the nebula. Osmium in the Os(i) carrier is likely from nucleosynthetic sites with a neutron density about two to four times as high as that of the average solar s-process Os. PMID:16109878

Brandon, A D; Humayun, M; Puchtel, I S; Leya, I; Zolensky, M

2005-08-19

398

Segregation of isotopes of heavy metals due to light-induced drift: results and problems  

Microsoft Academic Search

Atutov and Shalagin (1988) proposed light-induced drift (LID) as a physically\\u000awell understandable mechanism to explain the formation of isotopic anomalies\\u000aobserved in CP stars. We generalized the theory of LID and applied it to\\u000adiffusion of heavy elements and their isotopes in quiescent atmospheres of CP\\u000astars. Diffusional segregation of isotopes of chemical elements is described by\\u000athe equations

A. Sapar; A. Aret; R. Poolamae

2007-01-01

399

Multielectron coincidence study of the double Auger decay of 3d-ionized krypton  

SciTech Connect

Multielectron coincidence data for triple ionization of krypton have been recorded above the 3d ionization threshold at two photon energies (140 and 150 eV). Three principal transition pathways have been observed, two involving double Auger transitions from Kr{sup +}, and one involving single Auger transitions from Kr{sup 2+} created by direct single-photon double ionization. The decay of the 3d{sup 9} {sup 2}D{sub 5/2,3/2} states in Kr{sup +} has been analyzed in some detail and is found to be strongly dominated by cascade processes where two electrons with well-defined energies are emitted. The decay paths leading to the 4s{sup 2}4p{sup 3} {sup 4}S, {sup 2}D, and {sup 2}P states of Kr{sup 3+} are analyzed and energies of seven intermediate states in Kr{sup 2+} are given. A preliminary investigation of the decay paths from Kr{sup +} 3d{sup 9}4p{sup 5}nl shake-up states has also been carried out.

Andersson, E.; Hedin, L.; Rubensson, J.-E.; Karlsson, L.; Feifel, R. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden); Fritzsche, S. [Department of Physics, P.O. Box 3000, Fin-90014 University of Oulu (Finland); GSI Helmholtzzentrum fuer Schwerionenforschung, D-64291 Darmstadt (Germany); Linusson, P. [Department of Physics, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm (Sweden); Eland, J. H. D. [Department of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ (United Kingdom)

2010-10-15

400

Two-photon (vacuum ultraviolet + visible) spectroscopy of argon, krypton, xenon, and molecular hydrogen  

SciTech Connect

Two-photon transitions have been examined in argon, krypton, xenon, and molecular hydrogen using a coherent vacuum ultraviolet (VUV) photon at a fixed wavelength of 118 nm and a tunable photon from a dye laser. The 118 nm VUV photon is produced by third harmonic generation in xenon using UV light at 355 nm from a frequency tripled Nd:YAG laser. Though the VUV intensity is very weak, (approx.100 nJ per pulse) it was utilized very efficiently since most of VUV photons in the ionization region were absorbed. Spectra were obtained in the region of 12.5 to 13.5 eV and the corresponding two-photon rate constants were calculated. This is the first time that coherent VUV light has been employed with tunable visible light for the production of two-photon spectra and the measurement of two-photon rates. The two-photon ionization rate of xenon was measured using photons at fixed wavelengths of 118 and 355 nm. A new parameter is proposed for direct comparison of the data from various two-photon experiments.

McCann, M.P.; Chen, C.H.; Payne, M.G.

1988-11-01

401

Effects of pulmonary inhalation on hyperpolarized krypton-83 magnetic resonance T1 relaxation.  

PubMed

The (83)Kr magnetic resonance (MR) relaxation time T(1) of krypton gas in contact with model surfaces was previously found to be highly sensitive to surface composition, surface-to-volume ratio, and surface temperature. The work presented here explored aspects of pulmonary (83)Kr T(1) relaxation measurements in excised lungs from healthy rats using hyperpolarized (hp) (83)Kr with approximately 4.4% spin polarization. MR spectroscopy without spatial resolution was applied to the ex vivo lungs that actively inhale hp (83)Kr through a custom designed ventilation system. Various inhalation schemes were devised to study the influence of anatomical dead space upon the measured (83)Kr T(1) relaxation times. The longitudinal (83)Kr relaxation times in the distal airways and the respiratory zones were independent of the lung inhalation volume, with T(1) = 1.3 s and T(1) = 1.0 s, depending only on the applied inhalation scheme. The obtained data were highly reproducible between different specimens. Further, the (83)Kr T(1) relaxation times in excised lungs were unaffected by the presence of up to 40% oxygen in the hp gas mixture. The results support the possible importance of (83)Kr as a biomarker for evaluating lung function. PMID:21628780

Stupic, K F; Elkins, N D; Pavlovskaya, G E; Repine, J E; Meersmann, T

2011-05-31

402

Radiation damage induced by krypton ions in sintered alpha-Al2O3.  

PubMed

Alpha-alumina is a useful thermoluminescence (TL) dosemeter. The knowledge of its behaviour under irradiation is thus of primary importance. The purpose of this paper is to characterise the radiation damage produced by swift krypton ions using various experimental methods, namely TL, optical absorption, fluorescence and electron paramagnetic resonance (EPR). After ion irradiation, the TL intensity is shown to decrease, whereas the optical absorption rises in the whole studied wavelength range. These two phenomena seem to be related to one another. Furthermore, optical absorption measurements highlight the appearance of new absorption bands probably owing to oxygen vacancies. Induced defects are also observed in the EPR spectra of irradiated pellets. They are likely related to electronic holes trapped on oxygen ions. The concentration of these defects increases with ion fluence and fluorescence measurements indicate that some pre-existing defects such as F2(2+) centres follow the same trend up to approximately 4.1 x 10(13) ions cm(-2). PMID:16644989

Dalmasso, C; Iacconi, P; Beauvy, M; Lapraz, D; Balan, E; Calas, G

2006-04-27

403

Spin-orbit effect on strong-field ionization of krypton  

SciTech Connect

A recent pump-probe experiment employing tunable, linearly polarized x rays demonstrated that Kr{sup +} ions produced via strong-field ionization in a linearly polarized laser field are aligned, but that the degree of alignment is greatly overestimated by nonrelativistic strong-field ionization models. An effective one-electron model of strong-field ionization is presented that includes the effect of spin-orbit interaction. The method makes use of a flexible finite-element basis set and determines ionization rates in this square-integrable basis using a complex absorbing potential. It is found that even at the electric-field strength corresponding to the saturation intensity for the ionization of Kr, there is very little mixing between the 4p{sub 3/2} and 4p{sub 1/2} outer-valence orbitals. This shows that the uncoupled m{sub l},m{sub s} projection quantum numbers are inappropriate to describe the Kr{sup +} states that are populated by strong-field ionization of krypton. For the x-ray probe step, a description is developed, within a density-matrix formalism. It is demonstrated that the inclusion of spin-orbit interaction in the ionization process provides satisfactory agreement with the experimental observation. Possibilities for time-resolved studies utilizing fs and sub-fs laser pulses are indicated.

Santra, Robin; Dunford, Robert W.; Young, Linda [Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2006-10-15

404

Mixture fraction and its Dissipation in a turbulent flame by using Krypton PLIF  

NASA Astrophysics Data System (ADS)

Simultaneous conserved scalar and temperature imaging was performed in turbulent non-premixed jet flames (TNF DLR-A and -B) by using two-photon PLIF of Krypton and planar Rayleigh scattering, respectively. The motivation is to study the scalar and thermal dissipation characteristics of the flames. The experiments were performed at axial distances of 10 and 20 tube diameters (D) from the jet exit. The mixture fraction (f) field was calculated from the Kr LIF and the temperature images using a combination of the state relationship and an iterative technique. The mean and RMS of the f and T compared very well with those of the point measurements made by previous researchers. The mixture fraction and thermal dissipation field appeared very similar away from the flame and less similar close to the flame. Mixture fraction diffusion and thermal diffusion conditioned on f and T reveal a linear trend, whose slope is very similar to the time scale estimated by the ratio of the respective dissipation to the variance.

Narayanaswamy, Venkat; Hsu, Andrea; Clemens, Noel; Frank, Jonathan

2010-11-01

405

Effects of Pulmonary Inhalation on Hyperpolarized Krypton-83 Magnetic Resonance T1 Relaxation  

PubMed Central

The 83Kr magnetic resonance (MR) relaxation time T1 of krypton gas in contact with model surfaces was previously found to be highly sensitive to surface composition, surface to volume ratio, and surface temperature. The current work explored aspects of pulmonary 83Kr T1 relaxation measurements in excised lungs from healthy rats using hyperpolarized (hp) 83Kr with approximately 4.4 % spin polarization. MR spectroscopy without spatial resolution was applied to the ex vivo lungs that actively inhale hp 83Kr through a custom designed ventilation system. Various inhalation schemes were devised to explore the influence of anatomical dead space upon the measured 83Kr T1 relaxation times. The longitudinal 83Kr relaxation times in the distal airways and the respiratory zones were independent of the lung inhalation volume, with T1 = 1.3 s and T1 = 1.0 s, depending only on the applied inhalation scheme. The obtained data was highly reproducible between different specimens. Further, the 83Kr T1 relaxation times in excised lungs were unaffected by the presence of up to 40% oxygen in the hp gas mixture. The results support the possible importance of 83Kr as a biomarker for evaluating lung function.

Stupic, K.F.; Elkins, N.D.; Pavlovskaya, G.E.; Repine, J.E.; Meersmann, T.

2011-01-01

406

A thermal beam of metastable krypton atoms produced by optical excitation.  

SciTech Connect

A room-temperature beam of krypton atoms in the metastable 5s[3/2]{sub 2} level is demonstrated via an optical excitation method. A Kr-discharge lamp is used to produce vacuum ultraviolet photons at 124 nm for the first-step excitation from the ground level 4p{sup 6} {sup 1}S{sub 0} to the 5s[3/2]{sub 1} level. An 819 nm Ti:sapphire laser is used for the second-step excitation from 5s[3/2]{sub 1} to 5s[3/2]{sub 2} followed by a spontaneous decay to the 5s[3/2]{sub 2} metastable level. A metastable atomic beam with an angular flux density of 3 x 10{sup 14} s{sup -1} sr{sup -1} is achieved at the total gas flow rate of 0.01 cm{sup 3}/s at STP (or 3 x 10{sup 17} at./s). The dependences of the flux on the gas flow rate, laser power, and lamp parameters are investigated.

Ding, Y.; Hu, S.-M.; Bailey, K.; Davis, A. M.; Dunford, R. W.; Lu, Z.-T.; O'Connor, T. P.; Young, L.; Univ. of Chicago; Univ. of Science and Technology of China

2007-02-08

407

Survival of children born with congenital anomalies  

PubMed Central

Aim: To describe the survival to age 5 years of children born with congenital anomalies. Methods: Between 1980 and 1997, 6153 live born cases of congenital anomaly were diagnosed and registered by the population based Glasgow Register of Congenital Anomalies. They were retrospectively followed to assess their survival status from birth up to the age of 5 years. Results: The proportions of all live born infants with congenital anomalies surviving to the end of the first week, and first and fifth year were 94%, 89%, and 88%, respectively. Survival to age 5, the end point of follow up, was significantly poorer for infants with chromosomal anomalies (48%) compared to neural tube defects (72%), respiratory system anomalies (74%), congenital heart disease (75%), nervous system anomalies (77%), and Down's syndrome (84%). Conclusion: Although almost 90% of all live born infants with congenital anomalies survive to 5 years, there are notable variations in survival between anomaly types. Our findings should be useful for both clinicians and geneticists to assess the prognosis of congenital anomalies. This information is also important for affected families and for the planning of health care needs for this high risk population.

Dastgiri, S; Gilmour, W; Stone, D

2003-01-01

408

Prenatal Sonographic Diagnosis of Focal Musculoskeletal Anomalies  

PubMed Central

Focal musculoskeletal anomalies vary, and can manifest as part of a syndrome or be accompanied by numerous other conditions such as genetic disorders, karyotype abnormalities, central nervous system anomalies and other skeletal anomalies. Isolated focal musculoskeletal anomaly does, however, also occur; its early prenatal diagnosis is important in deciding prenatal care, and also helps in counseling parents about the postnatal effects of numerous possible associated anomalies. We have encountered 50 cases involving focal musculoskeletal anomalies, including focal limb dysplasia [radial ray abnormality (n=3), mesomelic dysplasia (n=1)]; anomalies of the hand [polydactyly (n=8), syndactyly (n=3), ectrodactyly (n=1), clinodactyly (n=6), clenched hand (n=5)]; anomalies of the foot [clubfoot (n=10), rockerbottom foot (n=5), sandal gap deformity (n=1), curly toe (n=2)]; amniotic band syndrome (n=3); and anomalies of the focal spine [block vertebra (n=1), hemivertebra (n=1)]. Among these 50 cases, five [polydactyly (n=1), syndactyly (n=2) and curly toe (n=2)] were confirmed by postnatal physical evaluation, two (focal spine anomalies) were diagnosed after postnatal radiologic examination, and the remaining 43 were proven at autopsy. For each condition, we describe the prenatal sonographic findings, and include a brief review.

Ryu, Jung Kyu; Choi, Jong Sun

2003-01-01

409

Strictly anomaly mediated supersymmetry breaking  

NASA Astrophysics Data System (ADS)

We consider an extension of the minimal supersymmetric Standard Model with anomaly mediation as the only source of supersymmetry breaking, and the tachyonic slepton problem solved by a gauged U(1) symmetry. The extra gauge symmetry is broken at high energies in a manner preserving supersymmetry, while also introducing both the seesaw mechanism for neutrino masses, and the Higgs ?-term. We call the model strictly anomaly mediated supersymmetry breaking. We present typical spectra for the model and compare them with those from so-called minimal anomaly mediated supersymmetry breaking. We find a Standard Model-like Higgs of mass 125 GeV with a gravitino mass of 140 TeV and tan??=16. However, the muon anomalous magnetic moment is 3? away from the experimental value. The model naturally produces a period of hybrid inflation, which can exit to a false vacuum characterized by large Higgs vacuum expectation values, reaching the true ground state after a period of thermal inflation. The scalar spectral index is reduced to approximately 0.975, and the correct abundance of neutralino dark matter can be produced by decays of thermally produced gravitinos, provided the gravitino mass (and hence the Higgs mass) is high. Naturally light cosmic strings are produced, satisfying bounds from the cosmic microwave background. The complementary pulsar timing and cosmic ray bounds require that strings decay primarily via loops into gravitational waves. Unless the loops are extremely small, the next generation pulsar timing array will rule out or detect the string-derived gravitational radiation background in this model.

Hindmarsh, Mark; Jones, D. R. Timothy

2013-04-01

410

Iridium anomaly in the Upper Devonian of the Canning Basin, Western Australia  

NASA Astrophysics Data System (ADS)

A moderate iridium anomaly, about 20 times the local background, has been found in Upper Devonian rocks in the Canning Basin. It occurs at or near the Frasnian-Famennian boundary, which is known to be associated with a major mass-extinction event of global extent. The anomaly occurs in an extremely condensed limestone sequence laid down under quiet deepwater conditions. Its occurrence suggests a causal link with some form of meteoroid impact. Moreover, carbon isotope data indicate that a large reduction in biomass could have occurred at this level. However, the anomaly coincides with a stromatolite bed containing the fossil cyanobacterium Frutexites; iridium, platinum, iron, manganese, cobalt, arsenic, antinomy, and cerium are preferentially concentrated in filaments of this organism, with concentations ranging from two to five times that of the matrix. It is possible that Frutexites extracted these elements directly from seawater, without the need for their derivation from an extraterrestrial source.

Playford, P. E.; McLaren, D. J.; Orth, C. J.; Gilmore, J. S.; Goodfellow, W. D.

1984-10-01

411

Anomaly detection for internet surveillance  

NASA Astrophysics Data System (ADS)

Many threats in the real world can be related to activity of persons on the internet. Internet surveillance aims to predict and prevent attacks and to assist in finding suspects based on information from the web. However, the amount of data on the internet rapidly increases and it is time consuming to monitor many websites. In this paper, we present a novel method to automatically monitor trends and find anomalies on the internet. The system was tested on Twitter data. The results showed that it can successfully recognize abnormal changes in activity or emotion.

Bouma, Henri; Raaijmakers, Stephan; Halma, Arvid; Wedemeijer, Harry

2012-05-01

412

A new anomaly matching condition?  

NASA Astrophysics Data System (ADS)

We formulate ``Witten'' matching conditions for confining gauge theories. The conditions are analogous to 't Hooft's, but involve Witten's global SU(2) anomaly. Using a group theoretic result of Geng, Marshak, Zhao and Okubo, we show that if the fourth homotopy group of the flavor group H is trivial (?4(H)=0) then realizations of massless composite fermions that satisfy the't Hooft conditions also satisfy the Witten conditions. If ?4(H) is nontrivial, the new matching conditioms can yield additional information about the low energy spectrum of the theory. We give a simple physical proof of Geng et al.'s result. Junior Fellow, Harvard Society of Fellows.

Bhansali, Vineer; Hsu, Stephen D. H.

1993-03-01

413

Mass Independent Fractionation of Mercury Isotopes in the Environment  

NASA Astrophysics Data System (ADS)

The toxicity of mercury's methylated species, biomagnification in aquatic food chains and global dispersion by the atmosphere makes it a worldwide health problem. Recent reports have observed natural mass dependent fractionation in mercury isotopes, and recent theoretical work has emphasized that isotopic separation in mercury is due primarily to nuclear field shifts (nuclear volume effect) or a magnetic isotope effect. Both effects produce mass-independent fractionation (MIF). Separation factors are closely proportional to mass number for even neutron number isotopes. Odd mass number mercury isotopes depart from this relationship, giving rise to a component of mass-independent fractionation. During equilibrium exchange reactions, the nuclear volume effect is a function of the oxidation state of the Hg chemical species: Hg0, and methylmercury, exhibit positive deviations, and oxidized species (e.g., Hg+2) exhibit negative deviations. We present analytical evidence of mass independent isotopic variations in mercury produced by both nuclear volume and magnetic isotope effects in a wide variety of natural environmental samples - peat, sediment, soil and moss. Even mass number isotopes exhibit a pattern indistinguishable from that produced by mass-dependent fractionation, with both positive and negative 199Hg and 201Hg anomalies. For majority of the samples analyzed, magnetic isotope effect seems to be more significant than nuclear volume effect. MIF is more accurately determined in Hg isotopes than mass dependent fractionation alone, and thus it provides a potentially important key in constraining models of mercury sources and pathways in the environment.

Ghosh, S.; Xu, Y.; Humayun, M.; Odom, A. L.

2007-12-01

414

Giant Hyperfine Anomaly between Bound Negative Muon and Rh Nucleus in Pd Metal  

Microsoft Academic Search

The Knight shift of negative muon (mu-Pd) in Pd metal has been determined to be - (9.0 +\\/- 0.7)% at T=11 K, revealing an unusually large hyperfine anomaly between mu-Pd and its equivalent isotope RhPd; Hhf(mu-Pd)Hhf(RhPd)=0.64+\\/-0.05, or ?mu-?N=-(36+\\/-5)%. Its implication is discussed in terms of the spatial distribution of the electron spin density in transition metals.

T. Yamazaki; R. S. Hayano; Y. Kuno; J. Imazato; K. Nagamine; S. E. Kohn; C. Y. Huang

1979-01-01

415

How double volcanic chains sample geochemical anomalies from the lowermost mantle  

NASA Astrophysics Data System (ADS)

The distinct isotopic compositions of basalts from the two parallel tracks of Hawaiian volcanoes suggest a bilateral zonation of the underlying mantle plume, with an enriched southern side. Such zonation is not unique to Hawaii, but may well be a common feature of other Pacific hotspots. This remarkable isotopic pattern, revealed by double volcanic chains, appears to be related to the so-called DUPAL isotopic anomaly in the Pacific mantle, which correlates with the seismically imaged 'Large Low-Shear-Velocity Province'. Here we show how a large-scale isotopic gradient, exemplified by the radiogenic isotope ratio Pb?208/Pb?206, maps from the deep mantle into the Hawaiian plume conduit, and how it ultimately surfaces as Pb?208/Pb?206 variations in double-chain volcanoes. Our numerical simulations reveal a novel 'lobate' conduit structure which generates an overall bilateral isotopic zonation within the Hawaiian melting zone. Comparison between our model predictions and Pb?208/Pb?206 of several Hawaiian volcanoes shows that a deep-seated, north-south, isotopic gradient can explain the enriched southern (Loa) chain as well as the Pb?208/Pb?206 decline from shield to post-shield lavas, observed in several of the volcanoes. The results provide a mechanism for directly linking geochemical maps of ocean island basalts to the structure and composition of the lowermost mantle inferred by seismic tomography.

Farnetani, Cinzia G.; Hofmann, Albrecht W.; Class, Cornelia

2012-12-01

416

The DiGeorge anomaly.  

PubMed

The DiGeorge anomaly, DGA (formerly termed DiGeorge syndrome), is now known to be a developmental field defect in which pharyngeal pouch derivatives do not arise, usually because of inadequate neural crest contributions. The conditions in which this occurs include exposure to teratogens, cytogenetic abnormalities, and Mendelian disorders. As a result, the facies and cardiovascular defects which occur are very characteristic. Two rare conotruncal anomalies, type B interrupted aortic arch and truncus arteriosus account for over half of the cardiac lesions seen in DGA. Failure of descent of the thymus is extremely common in DGA, but immunodeficiency which requires correction occurs only in approximately 25% of the cases. The term, complete DGA, should be reserved for those patients in need of reconstitution of the immune system. One can identify those patients requiring treatment of the thymic defect by T cell enumeration and in vitro proliferation assays. Two alternatives for therapy are thymus transplantation and bone marrow transplantation from a HLA matched sibling. PMID:1931005

Hong, R

1991-01-01

417

Pristine extraterrestrial material with unprecedented nitrogen isotopic variation  

PubMed Central

Pristine meteoritic materials carry light element isotopic fractionations that constrain physiochemical conditions during solar system formation. Here we report the discovery of a unique xenolith in the metal-rich chondrite Isheyevo. Its fine-grained, highly pristine mineralogy has similarity with interplanetary dust particles (IDPs), but the volume of the xenolith is more than 30,000 times that of a typical IDP. Furthermore, an extreme continuum of N isotopic variation is present in this xenolith: from very light N isotopic composition (?15NAIR = ?310 20), similar to that inferred for the solar nebula, to the heaviest ratios measured in any solar system material (?15NAIR = 4,900 300). At the same time, its hydrogen and carbon isotopic compositions exhibit very little variation. This object poses serious challenges for existing models for the origin of light element isotopic anomalies.

Briani, Giacomo; Gounelle, Matthieu; Marrocchi, Yves; Mostefaoui, Smail; Leroux, Hugues; Quirico, Eric; Meibom, Anders

2009-01-01

418

Pristine extraterrestrial material with unprecedented nitrogen isotopic variation.  

PubMed

Pristine meteoritic materials carry light element isotopic fractionations that constrain physiochemical conditions during solar system formation. Here we report the discovery of a unique xenolith in the metal-rich chondrite Isheyevo. Its fine-grained, highly pristine mineralogy has similarity with interplanetary dust particles (IDPs), but the volume of the xenolith is more than 30,000 times that of a typical IDP. Furthermore, an extreme continuum of N isotopic variation is present in this xenolith: from very light N isotopic composition (delta(15)N(AIR) = -310 +/- 20 per thousand), similar to that inferred for the solar nebula, to the heaviest ratios measured in any solar system material (delta(15)N(AIR) = 4,900 +/- 300 per thousand). At the same time, its hydrogen and carbon isotopic compositions exhibit very little variation. This object poses serious challenges for existing models for the origin of light element isotopic anomalies. PMID:19528640

Briani, Giacomo; Gounelle, Matthieu; Marrocchi, Yves; Mostefaoui, Smail; Leroux, Hugues; Quirico, Eric; Meibom, Anders

2009-06-15

419

Anomaly-free sets of fermions  

SciTech Connect

We present new techniques for finding anomaly-free sets of fermions. Although the anomaly cancellation conditions typically include cubic equations with integer variables that cannot be solved in general, we prove by construction that any chiral set of fermions can be embedded in a larger set of fermions which is chiral and anomaly-free. Applying these techniques to extensions of the Standard Model, we find anomaly-free models that have arbitrary quark and lepton charges under an additional U(1) gauge group.

Batra, Puneet; /Argonne; Dobrescu, Bogdan A.; /Fermilab; Spivak, David; /UC, Berkeley, Math. Dept.

2005-10-01

420

Anomaly-free sets of fermions  

SciTech Connect

We present new techniques for finding anomaly-free sets of fermions. Although the anomaly cancellation conditions typically include cubic equations with integer variables that cannot be solved in general, we prove by construction that any chiral set of fermions can be embedded in a larger set of fermions which is chiral and anomaly-free. Applying these techniques to extensions of the standard model, we find anomaly-free models that have arbitrary quark and lepton charges under an additional U(1) gauge group.

Batra, Puneet; Dobrescu, Bogdan A.; Spivak, David [High Energy Physics Division, Argonne National Lab, Argonne, Illinois 60439 (United States); Theoretical Physics Department, Fermilab, Batavia, Illinois 60510 (United States); Mathematics Department, University of California, Berkeley, California 94720 (United States)

2006-08-15

421

Correlated Nitrogen and Carbon Anomalies in an Anhydrous Interplanetary Dust Particle - Implications for Extraterrestrial Organic Matter Accreted by the Prebiotic Earth  

SciTech Connect

Given the ubiquitous presence of H and N isotopic anomalies in interplanetary dust particles (IDPs) and their probable association with carbonaceous material, the lack of similar isotopic anomalies in C has been a major conundrum. We report here the first observation of correlated N and C isotopic anomalies in organic matter within an anhydrous IDP. The {sup 15}N composition of the anomalous region is the highest seen to date in an IDP and is accompanied by a moderate depletion in {sup 13}C. Our observations establish the presence of hetero-atomic organic compounds of presolar origin among the constant flux of carbonaceous material accreting to the terrestrial planets within IDPs. Theoretical models suggest that low temperature formation of organic compounds in cold interstellar molecular clouds does produce C and N fractionations, but it remains to be seen if these models can reproduce the specific effects we observe here.

Floss, C; Stadermann, F J; Bradley, J P; Dai, Z; Bajt, S; Graham, G

2003-12-17

422

Localized versus delocalized excitations just above the 3d threshold in krypton clusters studied by Auger electron spectroscopy.  

PubMed

We present Auger spectroscopy studies of large krypton clusters excited by soft x-ray photons with energies on and just above the 3d(52) ionization threshold. The deexcitation spectra contain new features as compared to the spectra measured both below and far above threshold. Possible origins of these extra features, which stay at constant kinetic energies, are discussed: (1) normal Auger process with a postcollision interaction induced energy shift, (2) recapture of photoelectrons into high Rydberg orbitals after Auger decay, and (3) excitation into the conduction band (or "internal" ionization) followed by Auger decay. The first two schemes are ruled out, hence internal ionization remains the most probable explanation. PMID:17902910

Tchaplyguine, M; Kivimki, A; Peredkov, S; Sorensen, S L; Ohrwall, G; Schulz, J; Lundwall, M; Rander, T; Lindblad, A; Rosso, A; Svensson, S; Mrtensson, N; Bjrneholm, O

2007-09-28

423

Direct measurement of the transfer rates of muons from ?p muonic atoms to argon, krypton and xenon atoms  

Microsoft Academic Search

SummaryWe have measured the rates of the muon transfer reaction ?p+\\u000a z\\u000a Y??\\u000a z\\u000a Y+p in a target of ultra-pure gaseous hydrogen at 10 atmospheres contaminated by a small proportion of the\\u000a z\\u000a Y element (\\u000a z\\u000a Y stands here for argon, krypton and xenon). The results are compared with preceding experimental data and discussed in connection\\u000a with those obtained

A. Placci; E. Zavattini; A. Bertin; A. Vitale

1969-01-01

424

Solvation of fluoroform and fluoroform-dimethylether dimer in liquid krypton: a theoretical cryospectroscopic study.  

PubMed

A hybrid, sequential statistical physics-quantum mechanical electronic-quantum mechanical nuclei approach has been applied to study the C-H stretching frequencies of bare fluoroform dissolved in liquid krypton under cryogenic conditions (at ~130 K), as well as upon blue shifting hydrogen bonding interactions with dimethylether in the same solvent. The structure of the liquid at 130 K was generated by Monte Carlo simulations of cryogenic Kr solutions containing either fluoroform or fluoroform and dimethylether molecules. Statistically uncorrelated configurations were appropriately chosen from the equilibrated MC runs and supermolecular clusters containing solute and solvent molecules (either standalone or embedded in the "bulk" part of the solvent treated as a polarizable continuum) were subjected to quantum mechanical electronic (QMel) and subsequent quantum mechanical nuclei (QMnuc) calculations. QMel calculations were implemented to generate the in-liquid 1D intramolecular C-H stretching vibrational potential of the fluoroform moiety and subsequently in the QMnuc phase the corresponding anharmonic C-H stretching frequency was computed by diagonalization techniques. Finally, the constructed vibrational density of states histograms were compared to the experimental Raman bands. The calculated anharmonic vibrational frequency shifts of the fluoroform C-H stretching mode upon interaction with dimethylether in liquid Kr are in very good agreement with the experimental data (20.3 at MP2 level vs. 16.6 cm(-1) experimentally). Most of this relatively large frequency blue shift is governed by configurations characterized by a direct C-HO contact between monomers. The second population detected during MC simulations, characterized by reversed orientation of the monomers, has a minor contribution to the spectral appearance. The experimentally observed trend in the corresponding bandwidths is also correctly reproduced by our theoretical approach. Solvation of the fluoroform monomer, according to experiment, results in small C-H stretching frequency red shift (~-2 cm(-1)), while our approach predicts a blue shift of about 10 cm(-1). By a detailed analysis of the anharmonic C-H stretching frequency dependence on the position of the nearest solvent krypton atom and also by analyzing the vibrational Stark effect induced by the local fluctuating field component parallel to the C-H axis, we have derived several conclusions related to these observations. The frequency vs. CKr distance dependence shows appreciable fluctuations and even changes in sign at R values close to the maximum of the CKr radial distribution function, so that most of the first-shell Kr atoms are located at positions at which the CH frequency shifts acquire either small negative or small positive values. It so happens, therefore, that even the actual sign of the frequency shift is strongly dependent on the correct description of the first solvation shell around CF3H by the Monte Carlo method, much more than the other in-liquid properties calculated by similar approaches. PMID:23927267

Kohls, Emilija; Mishev, Anastas; Pejov, Ljup?o

2013-08-01

425

Analysis of neutral active particle loss in afterglow in krypton at 2.6 mbar pressure  

SciTech Connect

This paper presents the analysis of the surface recombination and/or de-excitation of neutral active particles in two different volume krypton-filled tubes at pressure of 2.6 mbar with 1 ppm oxygen impurities. The analysis was performed on the basis of secondary electron emission from the cathode induced by positive ions and neutral active particles using the experimental data of electrical breakdown time delay mean value t{sub d} as a function of afterglow period {tau} ('memory curve'). It was shown that the main channel of neutral active particles' loss in afterglow is their recombination and/or de-excitation on the bulb walls. The loss rate increases with the increase of available wall surface per unit of gas volume. It was also shown that in early afterglow (15 ms for the tube with smaller bulb volume and 30 ms for the tube with bigger bulb volume) positive ions are formed in the mutual collisions of neutral active particles, and these ions dominantly influence the secondary electron emission from the cathode. In late afterglow (to 30 s for the tube with smaller bulb volume and to 150 s for the tube with bigger bulb volume) neutral active particles have dominant role in secondary electron emission from the cathode. The probability for this process decreases with the increase of afterglow period as a consequence of the decrease of the concentration of neutral active particles in gas, and this probability is smaller for the tube with smaller bulb volume. The influence of additional electron yield in the electrode gap caused by gamma radiation on breakdown initiation is also analyzed. It is shown that the influence of the neutral active particles in the process of secondary electron emission in the case of gamma radiation is also significant in both early and late afterglow.

Pejovic, Momcilo M.; Karamarkovic, Jugoslav P.; Ristic, Goran S.; Pejovic, Milic M. [Faculty of Electronic Engineering, University of Nis, P.O. Box 73, 18001 Nis (Serbia); Faculty of Civil Engineering and Architecture, University of Nis, A. Medvedeva 14, 18001 Nis (Serbia); Faculty of Electronic Engineering, University of Nis, P.O. Box 73, 18001 Nis (Serbia)

2008-01-15

426

Tomography of regional ventilation and perfusion using krypton 81m in normal subjects and asthmatic patients.  

PubMed Central

Single photon emission computed tomography, a rotating gamma camera, and continuous inhalation or infusion of krypton 81m (half life 13 seconds) were used to measure regional ventilation (V), perfusion (Q), and ventilation-perfusion (V/Q) ratios in five normal subjects in supine, prone, and lateral decubitus postures and in three asthmatic patients (supine posture only) before and after inhalation of 2.5 mg nebulised salbutamol. Vertical and horizontal gradients of V, Q, and V/Q were examined at three levels in each lung in regions of 1.9 cm3 size. In normal subjects V and Q increased along the axis of gravity in all postures and at all levels in the lung except for V in the prone position. Smaller horizontal gradients were found with an increase in V and Q from caudal to cranial--again except in the prone posture, where the gradient was slightly reversed. Constraint to outward motion of the ventral chest and abdominal wall is the most likely explanation for the different behaviour in the prone posture. In chronic asthma the vertical gradients of V and V/Q were the reverse of normal, but the Q gradient was normal. Bronchodilator treatment did not affect the vertical or horizontal gradients significantly, but analysis of individual regions showed that, relatively, V/Q worsened in 42% of them; this was associated in two thirds with an increase in fractional Q. After inhalation of beta agonist local vasodilatation may influence V/Q ratios in some units more than bronchodilatation. Images

Orphanidou, D; Hughes, J M; Myers, M J; Al-Suhali, A R; Henderson, B

1986-01-01

427

Analysis of neutral active particle loss in afterglow in krypton at 2.6 mbar pressure  

NASA Astrophysics Data System (ADS)

This paper presents the analysis of the surface recombination and/or de-excitation of neutral active particles in two different volume krypton-filled tubes at pressure of 2.6 mbar with 1 ppm oxygen impurities. The analysis was performed on the basis of secondary electron emission from the cathode induced by positive ions and neutral active particles using the experimental data of electrical breakdown time delay mean value td as a function of afterglow period ? (``memory curve''). It was shown that the main channel of neutral active particles' loss in afterglow is their recombination and/or de-excitation on the bulb walls. The loss rate increases with the increase of available wall surface per unit of gas volume. It was also shown that in early afterglow (15 ms for the tube with smaller bulb volume and 30 ms for the tube with bigger bulb volume) positive ions are formed in the mutual collisions of neutral active particles, and these ions dominantly influence the secondary electron emission from the cathode. In late afterglow (to 30 s for the tube with smaller bulb volume and to 150 s for the tube with bigger bulb volume) neutral active particles have dominant role in secondary electron emission from the cathode. The probability for this process decreases with the increase of afterglow period as a consequence of the decrease of the concentration of neutral active particles in gas, and this probability is smaller for the tube with smaller bulb volume. The influence of additional electron yield in the electrode gap caused by gamma radiation on breakdown initiation is also analyzed. It is shown that the influence of the neutral active particles in the process of secondary electron emission in the case of gamma radiation is also significant in both early and late afterglow.

Pejovic, Momcilo M.; Karamarkovic, Jugoslav P.; Ristic, Goran S.; Pejovic, Milic M.

2008-01-01

428

Hot Flow Anomalies at Venus  

NASA Astrophysics Data System (ADS)

We present a multi-instrument study of a Hot Flow Anomaly (HFA) observed by the Venus Express spacecraft in the Venutian foreshock, expanding on an initial study by Slavin et al [2009] that employed magnetometer observations of an HFA-like event during the flyby of NASA's Messenger spacecraft. Whilst the Messenger events were indicative of an HFA, they were unable to demonstrate the unambiguous signatures of plasma heating or deflection due to the paucity of data. We examine the complex internal structure of a Venutian HFA on the 22nd of March 2008, incorporating both Venus Express magnetometer and ASPERA plasma observations to demonstrate the presence of plasma heating within one such event. Centered on an interplanetary discontinuity and bounded by shock, the properties of this event are consistent with those of HFA's observed at other planets within the Solar System. Finally, we present a discussion of the implications of an HFA on the planet Venus.

Collinson, G. A.; Sibeck, D. G.; Masters, A.; Shane, N.; Slavin, J. A.; Coates, A. J.; Zhang, T.; Boardsen, S. A.; Moore, T. E.; Barabash, S.

2011-12-01

429

Oculoauriculovertebral spectrum and cerebral anomalies.  

PubMed Central

We report on three Dutch children with a clinical diagnosis of oculoauriculovertebral spectrum (OAVS) and hydrocephalus. The clinical features are compared to 15 published cases of OAVS and hydrocephalus. Several other cerebral abnormalities were present in the whole group. About half of the cases had cleft lip/palate, anophthalmia/microphthalmia, or a cardiac defect. Mental retardation was found in five of the surviving 11 patients and early death occurred in one-third. We compared the cases with OAVS and hydrocephalus with published reports of OAVS and other cerebral anomalies and found no significant clinical differences. However, the clinical characteristics were clearly more severely expressed than generally found in patients with OAVS. Children with OAVS and more severe clinical features, especially anophthalmia/microphthalmia and cleft lip/palate, seem to be at an increased risk for cerebral malformations and for mental retardation. Images

Schrander-Stumpel, C T; de Die-Smulders, C E; Hennekam, R C; Fryns, J P; Bouckaert, P X; Brouwer, O F; da Costa, J J; Lommen, E J; Maaswinkel-Mooy, P D

1992-01-01

430

Barbados Corals as Recorders of Amazon River Salinity Anomalies  

NASA Astrophysics Data System (ADS)

Low salinity plumes of Amazon and Orinoco sourced water have previously been detected around the island of Barbados. Barbados corals may therefore have the potential to record salinity anomalies governed by natural, climate-related, and anthropogenic changes in the Amazon and Orinoco Basin watersheds beyond the recent historic record. In order to determine whether Barbados corals record salinity variations associated with local or Amazon/Orinoco sourced signals, multiple specimens of Montastraea sp. and Siderastrea sp. coral skeletons were analyzed for stable C and O isotope and Sr/Ca variations. Corals were collected from the northwest, central-west, and southwest regions of the island to determine degree of salinity signal heterogeneity over a 5-6 year period at approximately monthly resolution. Four separate published paleotemperature equations were used to assess the importance of temperature on stable oxygen isotope composition. In situ temperature measurements obtained from NOAA show an annual sea surface temperature (SST) cycle of approximately 4 degrees Celsius off Barbados. If governed solely by SST, stable isotope data from all 8 corals in this study indicate a significantly greater annual temperature range of approximately 6 degrees Celsius. This suggests that salinity related fluctuations in oxygen isotopic composition of water are an important influence on the geochemistry of Barbados corals. Some regional differences in geochemical composition of corals were apparent. Corals from the southwest of Barbados showed the clearest sub-annual isotope signal, better correlations with mean annual SST measurements, and lowest mean salinity of the regions. Corals from the central-west and northwest showed distinctly higher mean, but more variable, salinity than corals from the south. Stable carbon isotope data from southwest corals also best potentially reflect the Suess Effect. Montastraea sp. corals generally show a higher paleotemperature offset from in situ values, suggesting that the ability to extract salinity data from Barbados corals may be species-specific. These results may have implications for understanding local eddy patterns as Amazon-sourced water encounters Barbados. It is possible that the central and northern lee coasts may be less impacted by Amazon water and more subject to local restriction from open marine conditions and/or increased evaporative effects.

Greer, L.; Telfeyan, K.; Arienzo, M. M.; Rosenberg, A. D.; Waite, A. J.; Swart, P. K.

2010-12-01

431

Magnetic Anomalies in the Red Sea  

Microsoft Academic Search

Marine magnetic profiles over the Red Sea between 18 degrees N and 25 degrees N latitudes confirm previous hypotheses that strongly magnetic rocks underlie the axial trough. The symmetrical nature of the anomalies and their close correspondence to seafloor spreading magnetic models support a rifting origin for the trough. The dominant magnetic anomaly trends strike about N 35 degrees W

J. D. Phillips

1970-01-01

432

IONOSPHERIC EQUATORIAL ANOMALY STUDIES DURING SOLAR STORMS  

Microsoft Academic Search

The ionosphere is the major error source in GNSS receivers. Models for single frequency time delay correction do not work at low geomagnetic latitude regions (20), where the ionosphere has a peculiar behavior, known as the Ionospheric Equatorial Anomaly. In order to study the global behavior of the Ionospheric Equatorial Anomaly, dynamic maps based on IONEX data have been generated.

Alexandre B. V. Oliveira; F. Walter

433

Stochastic perturbative derivation of the axial anomaly  

NASA Astrophysics Data System (ADS)

The axial anomaly is calculated as the infinite Langevin time limit of stochastic triangle diagrams. Their regularization is insured with the help of an analytic stochastic regulator. The usual axial anomaly is recovered only when the Langevin equations used to generate the perturbative expansion are gauge covariant.

Ader, J. P.; Wallet, J. C.

1986-12-01

434

Anomaly detection and classification for hyperspectral imagery  

Microsoft Academic Search

Anomaly detection becomes increasingly important in hyperspectral image analysis, since hyperspectral imagers can now uncover many material substances which were previously unresolved by multispectral sensors. Two types of anomaly detection are of interest and considered in this paper. One was previously developed by Reed and Yu to detect targets whose signatures are distinct from their surroundings. Another was designed to

Chein-I. Chang; Shao-Shan Chiang

2002-01-01

435

Junction magnetic anomaly north of Waikato River  

Microsoft Academic Search

A linear magnetic anomaly is traced northwards from Waikato through North Auckland and Northland until it meets the Tasman Sea west of Kaitaia. The anomaly, which has amplitudes up to 700 gammas and half-widths of 515 km, is believed to be due to serpentinite and probably represents the extension of the ultramafic belt which separates the principal facies of the

Trevor Hatherton; R. H. Sibson

1970-01-01

436

A Classification Framework for Anomaly Detection  

Microsoft Academic Search

One way to describe anomalies is by saying that anomalies are not concentrated. This leads to the problem of finding level sets for the data generating density. We interpret this learning problem as a binary classification problem and compare the corresponding classification risk with the standard performance measure for the density level problem. In particular it turns out that the

Ingo Steinwart; Don R. Hush; Clint Scovel

2005-01-01

437

Cor triatriatum dexter with imperforate Ebstein's anomaly.  

PubMed Central

A case of cor triatriatum dexter is described in which the anomalous right atrial partition is identified as the right venous valve; there is an associated anomaly of the right atrioventricular valve which combines features of Ebstein's anomaly, and an atypical, imperforate, tricuspid atresia. Images

Gerlis, L M; Anderson, R H

1976-01-01

438

The biological basis of expected utility anomalies  

Microsoft Academic Search

We assess the biological basis of expected utility anomalies through an experiment of the Allais paradox. A questionnaire study of 120 subjects replicates the anomalies and further gathers information about the respondents bio-characteristics, such as gender, age, parenthood, handedness, second to fourth digit ratio, current emotional state, past negative experiences, and religiousness. We find that some of those bio-characteristics matter

Raul Matsushita; Dinor Baldo; Bruna Martin; Sergio Da Silva

2007-01-01

439

Minor physical anomalies in Tourette syndrome  

Microsoft Academic Search

Background and Objectives: The prevalence of minor physical anomalies (prenatal errors of morphogenesis) was evaluated in patients with Tourette syndrome to get indirect data on the possible role of aberrant neurodevelopment in the aetiology of Tourette syndrome. No published study is known on the minor physical anomaly preva- lence in this recently intensively investigated disorder, and connecting to current opinions

Gyrgyi Csbi; Jlia Gdoros; Sra Jeges; Eszter Gyenge; Mtys Trixler; Tams Tnyi

2008-01-01

440

Detecting and analyzing relationships among anomalies  

Microsoft Academic Search

The HRL anomaly analysis tool was developed as part of the IEEE VAST Challenge 2009. One of the tasks involved processing badge and network traffic in order to detect and identify a fictitious embassy employee suspected of leaking information. The tool is designed to assist an analyst in detecting, analyzing, and visualizing anomalies and their relationships. Two key visualizations in

David Allen; Tsai-Ching Lu; Dave Huber

2009-01-01

441

Anomalies of Nuclear Criticality, Revision 6  

SciTech Connect

This report is revision 6 of the Anomalies of Nuclear Criticality. This report is required reading for the training of criticality professionals in many organizations both nationally and internationally. This report describes many different classes of nuclear criticality anomalies that are different than expected.

Clayton, E. D.; Prichard, Andrew W.; Durst, Bonita E.; Erickson, David; Puigh, Raymond J.

2010-02-19

442

A New, Principled Approach to Anomaly Detection  

SciTech Connect

Intrusion detection is often described as having two main approaches: signature-based and anomaly-based. We argue that only unsupervised methods are suitable for detecting anomalies. However, there has been a tendency in the literature to conflate the notion of an anomaly with the notion of a malicious event. As a result, the methods used to discover anomalies have typically been ad hoc, making it nearly impossible to systematically compare between models or regulate the number of alerts. We propose a new, principled approach to anomaly detection that addresses the main shortcomings of ad hoc approaches. We provide both theoretical and cyber-specific examples to demonstrate the benefits of our more principled approach.

Ferragut, Erik M [ORNL; Laska, Jason A [ORNL; Bridges, Robert A [ORNL

2012-01-01

443

Global magnetic anomaly and aurora of Neptune  

SciTech Connect

The large offset and tilt of Neptune's dipole magnetic field combine to create a global magnetic anomaly, analogous to but much more important than Earth's South Atlantic Anomaly. Energetic particle precipitation loss within the Neptune anomaly creates atmospheric drift shadows within which particle fluxes are greatly reduced. The energetic particle dropout observed by Voyager near closest approach occurred near the predicted times when Voyager passed within the atmospheric drift shadow. Extremely soft, structured bursts of ions and electrons within the drift shadow may result from plasma wave-induced pitch angle scattering of trapped particles confined near the magnetic equator. The dropout does not necessarily imply that Voyager passed through an Earth-like discrete auroral zone, as earlier reported. The ion and electron fluxes observed within the dropout period correspond to particles that must precipitate to Neptune's atmosphere within the anomaly region. This anomaly precipitation can account for a major portion of the ultraviolet emissions previously identified as Neptune aurora.

Cheng, A.F. (Johns Hopkins Univ., Laurel, MD (USA))

1990-09-01

444

Atmospheric anomalies observed during earthquake occurrences  

NASA Astrophysics Data System (ADS)

Appearance of anomalies in the atmosphere before earthquakes (EQs) has been verified, through observation of anomalous transmission of VHF electromagnetic (EM) waves beyond line-of-sight. Anomalous increase of the received intensity for a few minutes - several hours on a day was identified by the previous 15-day running median and its inter-quartile range. The cross-correlation between the EQ occurrences and the anomalies shows that the appearance of anomalies was significantly enhanced within 5 days before M >= 4.8 EQs. The one-day average number of the anomaly appearance within 5 days was found 2.4 times larger than that of other days. Through the polarization measurement of the received EM waves, the anomalies were found to occur in the atmosphere.

Fujiwara, H.; Kamogawa, M.; Ikeda, M.; Liu, J. Y.; Sakata, H.; Chen, Y. I.; Ofuruton, H.; Muramatsu, S.; Chuo, Y. J.; Ohtsuki, Y. H.

2004-09-01

445

Upward continuation of surface gravity anomalies  

NASA Astrophysics Data System (ADS)

Investigations on the upward continuation of gravity anomalies given on the surface of the Earth's visible topography are reported. Results are compared for three upward continuation procedures: first, the direct Poisson integration of the original terrain-uncorrected surface anomalies; second, the direct Poisson integration of terrain-corrected (i.e., Faye) surface anomalies; and third, the so-called indirect method. In the indirect method the original anomaly field is basically split into three frequency ranges that are then modeled separately: the low frequencies are modeled by spherical harmonics; the medium frequencies are modeled by Poisson integration of residual surface anomalies with long-wavelength terrain correction applied; and the high frequencies are modeled by prism integration of the gravitational effects of certain shallow topographic masses of assumed constant density.

Cruz, J. Y.; Laskowski, P.

1984-12-01

446

An impactor origin for lunar magnetic anomalies.  

PubMed

The Moon possesses strong magnetic anomalies that are enigmatic given the weak magnetism of lunar rocks. We show that the most prominent grouping of anomalies can be explained by highly magnetic extralunar materials from the projectile that formed the largest and oldest impact crater on the Moon: the South Pole-Aitken basin. The distribution of projectile materials from a model oblique impact coincides with the distribution of magnetic anomalies surrounding this basin, and the magnetic properties of these materials can account for the intensity of the observed anomalies if they were magnetized in a core dynamo field. Distal ejecta from this event can explain the origin of isolated magnetic anomalies far from this basin. PMID:22403388

Wieczorek, Mark A; Weiss, Benjamin P; Stewart, Sarah T

2012-03-01

447

Anomalies of water and simple liquids  

NASA Astrophysics Data System (ADS)

This thesis applies statistical physics approaches and computer simulations to investigate quantitatively the relationship between the structure and the dynamic and thermodynamic anomalies observed in water and some other simple liquids. In Chapter 1, we give a general introduction to the properties of water. In Chapter 2 we address the question of whether spherically-symmetric potentials are also able to reproduce the structural anomalies found in systems with local tetrahedral order. We find that water-like structural order anomalies exist for the two-scale "ramp potential". Our findings suggest that the water-like relationship between structural order and anomalies is related to the presence of two different length scales in the potential. In Chapter 3, we use the ratio of characteristic length scales of the two-scale ramp potential as a control parameter to investigate the evolution of dynamic, thermodynamic and structural anomalies. In this manner we show that the family of tunable spherically-symmetric potentials so generated evolves continuously between water-like and hard sphere behavior. These findings suggest that strong orientational interactions in the first shell of water are not necessary for a liquid to show thermodynamic, dynamic and structural anomalies, and highlight the importance of the second shell of water. In Chapter 4, we investigate how much orientation-dependent first-shell interaction and the second-shell environment each contribute to water's anomalies. We show that the changes in the second shell of water are the structural bases for the anomalies. In Chapter 5, we study the quantitative connection between our idealized ramp potential and water's pair potential, as well as the relation between the regions of anomalies in their respective phase diagrams. Finally in Chapter 6 we show that the "two-body excess entropy" is a useful quantity for predicting the regions of thermodynamic, dynamic and structural anomalies of water.

Yan, Zhenyu

448

Light element isotopic compositions of cometary matter returned by the STARDUST mission  

SciTech Connect

Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild2 particle fragments, however extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Non-terrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is {sup 16}O-enriched like refractory inclusions in meteorites, suggesting formation in the hot inner solar nebula and large-scale radial transport prior to comet accretion in the outer solar system.

McKeegan, K D; Aleon, J; Bradley, J; Brownlee, D; Busemann, H; Butterworth, A; Chaussidon, M; Fallon, S; Floss, C; Gilmour, J; Gounelle, M; Graham, G; Guan, Y; Heck, P R; Hoppe, P; Hutcheon, I D; Huth, J; Ishii, H; Ito, M; Jacobsen, S B; Kearsley, A; Leshin, L A; Liu, M; Lyon, I; Marhas, K; Marty, B; Matrajt, G; Meibom, A; Messenger, S; Mostefaoui, S; Nakamura-Messenger, K; Nittler, L; Palma, R; Pepin, R O; Papanastassiou, D A; Robert, F; Schlutter, D; Snead, C J; Stadermann, F J; Stroud, R; Tsou, P; Westphal, A; Young, E D; Ziegler, K; Zimmermann, L; Zinner, E

2006-10-10

449

The 129Xe Anomaly in MORB: Gone with the Wind?  

NASA Astrophysics Data System (ADS)

I have performed replicate crushing experiments on two glass MORB (East Pacific Rise and Mid Atlantic Ridge) in which previous whole-rock melting experiments showed ^40Ar/^36Ar ratios ranging up to ~15,000, indicating efficient trapping of gases from the mantle [1,2]. I loaded nearly a gram of mm-sized pieces and crushed varying portions of them under vacuum, transferring the released gases directly into the mass spectrometer and obtaining more than 20 separate aliquots. Though the Xe/Ar ratio was higher than atmospheric in all aliquots, indicating the presence of mantle xenon, none of the data show any excess ^129Xe from the decay of ^129I early in earth history. It is clear that some terrestrial xenon contains the anomaly [3], but it is not at all clear that the MORB source region does, though some models of mantle and atmospheric evolution rely heavily on this result [4]. I have gone through the literature, and find a diversity of results. Four papers, all from the same laboratory, present clear evidence of the anomaly [4-7], five others do not [8-12], and one straddles the fence [1]. The situation is complicatedby the ubiquitous presence in MORB of a component withatmospheric-like rare gas isotopic ratios. I shall discuss the attempts of various workers to separate these components, and the probability that a true anomaly exists in all or in some MORB source regions, by comparing Xe isotopic data obtained through stepwise heating, total fusion, or crushing experiments, with other pertinent ratios. "I have forgot much, Cynara, gone with the wind; Have flung roses, roses riotously with the throng." References: [1] Fisher D. E. (1986) GCA, 50, 2531-2541. [2] Fisher D. E. (1985) JGR, 90, B2, 1801-1807. [3] Boulos M. S. and Manuel O. K. (1971) Science, 174, 837-840. [4] Allegre C. J. (1983) Nature, 303, 762-766. [5] Staudacher T. and Allegre C. J. (1982) EPSL, 60, 389-406. [6] Staudacher T. (1989) EPSL, 96, 119- 133. [7] Marty B. (1989) EPSL, 94, 45-56. [8] Fisher D. E., EPSL, for publ. [9] Hiyagon H. (1992) GCA, 56, 1301-1316. [10] Ozima M. and Zashu S. (1983) EPSL, 62, 24-40. [11] Takaoka N. and Nagao K. (1978) Nature, 276, 491-492. [12] Kirsten T. and Richter H. (1981) Meteoritics, 16, 341.

Fisher, D. E.

1993-07-01

450

Systematic study of sulfur isotopic composition in iron meteorites and the occurrence of excess S-33 and S-36  

Microsoft Academic Search

The paper concentrates on isotopic measurements of sulfur in different sulfur-carrier phases: troilite inclusions, Fe-Ni alloy, and schreibersite (possibly including daubreelite). Variations in S-34 isotope ratio are observed in some troilite inclusions, and no evidence of nucleosynthetic sulfur isotopic anomalies are found in the troilite inclusions. Excesses of S-33 and S-36 are observed in both FeNi alloy and schreibersite of

Xia Gao; Mark H. Thiemens

1991-01-01

451

Effect of pressure of helium, argon, krypton, and xenon on the porosity, microstructure, and mechanical properties of commercially pure titanium castings  

Microsoft Academic Search

Statement of problem. Porosity is a frequently observed casting defect in dental titanium alloys. Purpose. This study evaluated the effect of pressure of helium, argon, krypton, and xenon on the porosity, microstructure, and mechanical properties of commercially pure titanium (cp Ti) castings. Material and methods. Eight groups (A-H) of 16 rectangular wax patterns each (30 mm in length, 3 mm

Spiros Zinelis

2000-01-01

452

Method for separating isotopes  

DOEpatents

Isotopes are separated by contacting a feed solution containing the isotopes with a cyclic polyether wherein a complex of one isotope is formed with the cyclic polyether, the cyclic polyether complex is extracted from the feed solution, and the isotope is thereafter separated from the cyclic polyether.

Jepson, B.E.

1975-10-21

453

ATTA - A New Method of Ultrasensitive Trace-Isotope Analysis  

NASA Astrophysics Data System (ADS)

We have developed a new method of ultrasensitive trace-isotope analysis based upon the technique of laser manipulation of neutral atoms [1]. This new method allows us to count individual 85Kr and 81Kr atoms present in a natural krypton sample with isotopic abundances in the range of 10-11 and 10-13, respectively. Isotope analysis of 81Kr can be used to date polar ice, and 85Kr is a tracer used in monitoring nuclear wastes. In this experiment metastable Kr atoms were produced in a discharge, decelerated via the Zeeman slowing technique, and captured by a Magneto-Optical Trap where the atoms were counted by measuring their