These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
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  

E-print Network

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

M. Heim; A. Fritsch; A. Schuh; A. Shore; M. Thoennessen

2009-04-15

3

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

4

Shape Transitions and Jacobian Instability in Excited Krypton Isotopes  

NASA Astrophysics Data System (ADS)

Shape transitions as a function of angular momentum in even-even krypton isotopes with A = 72-84 have been investigated using the cranked Nilsson-Strutinsky method. The Jacobi shape transition from noncollective oblate to super or hyperdeformed collective prolate or triaxial shape taking place in rotating nuclei as in the case of gravitating rotating stars is studied in krypton isotopes. The cranked Nilsson-Strutinsky method with a method of tuning the angular velocity to get the fixed spins is used in the calculations. Our results show that all the krypton isotopes considered in this study are the good candidates for detecting the Jacobi shape transition. Shape evolutions as a function of spin and temperature with thermal fluctuations are studied using the Landau theory of phase transitions. The constants appearing in the Landau expression for the free energy are determined by using the free energy surfaces at ? = 0 calculated by the Strutinsky method. We show that in the presence of thermal fluctuations, the averaged shapes obtained for the considered isotopes differ from the most probable shapes. The sharp Jacobi transitions are modified due to the effect of thermal fluctuations.

Selvam, V.; Devadhason, D. R. Jayahar; Beula, J. M.

2014-12-01

5

Chromium isotopic anomalies in the Allende meteorite  

NASA Technical Reports Server (NTRS)

Abundances of the chromium isotopes in terrestrial and bulk meteorite samples are identical to 0.01 percent. However, Ca-Al-rich inclusions from the Allende meteorite show endemic isotopic anomalies in chromium which require at least three nucleosynthetic components. Large anomalies at Cr-54 in a special class of inclusions are correlated with large anomalies at Ca-48 and Ti-50 and provide strong support for a component reflecting neutron-rich nucleosynthesis at nuclear statistical equilibrium. This correlation suggests that materials from very near the core of an exploding massive star may be injected into the interstellar medium.

Papanastassiou, D. A.

1986-01-01

6

Use of a krypton isotope for rapid ion changeover at the Lawrence Berkeley Laboratory 88-inch cyclotron  

SciTech Connect

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 new technique has been proved out successfully by a recent Jet Propulsion Laboratory (JPL) test in which it was found that there was no measurable contamination from other isotopes.

Soli, G.A.; Nichols, D.K.

1989-09-01

7

Use of a krypton isotope for rapid ion changeover at the Lawrence Berkeley Laboratory 88-inch cyclotron  

NASA Technical Reports Server (NTRS)

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 new technique has been proved out successfully by a recent Jet Propulsion Laboratory (JPL) test in which it was found that there was no measurable contamination from other isotopes.

Soli, George A.; Nichols, Donald K.

1989-01-01

8

Isotopic Anomalies in CP Stars: Helium, Mercury, Platinum, and Calcium  

E-print Network

We review the classical observational results for isotopic abundance variations for several elements in CP stars. We concentrate on the "newest" anomaly, in calcium. The cosmically very rare isotope, Ca-48 can rival and even dominate the more common, alpha nuclide, Ca-40. Relevant examples are found in the hot, non-magnetic HgMn stars, and the field horizontal-branch star, Feige 86. The calcium anomaly is also present in cool, magnetic stars, including the notorious HD 101065, Przybylski's star.

Cowley, C R; Castelli, F

2007-01-01

9

Isotopic Anomalies in CP Stars: Helium, Mercury, Platinum, and Calcium  

E-print Network

We review the classical observational results for isotopic abundance variations for several elements in CP stars. We concentrate on the "newest" anomaly, in calcium. The cosmically very rare isotope, Ca-48 can rival and even dominate the more common, alpha nuclide, Ca-40. Relevant examples are found in the hot, non-magnetic HgMn stars, and the field horizontal-branch star, Feige 86. The calcium anomaly is also present in cool, magnetic stars, including the notorious HD 101065, Przybylski's star.

C. R. Cowley; S. Hubrig; F. Castelli

2007-11-15

10

Models for Interpreting Tungsten Isotope Anomalies in the Earth's Crust  

NASA Astrophysics Data System (ADS)

There have been several reports of positive tungsten isotope anomalies of about +15 ppm in rocks from Nuvvuagittuq (4.3 Ga), Isua (3.8 Ga) and Kostomuksha (2.8 Ga) that challenge models of differentiation and mantle mixing. Here, we employ constraints from experimental partitioning of W between metal and silicate, and from partial melting models, to evaluate the production and preservation of these W isotope anomalies in the Earth's earliest crust. We will also provide a revised interpretation of the Kostomuksha W isotope anomalies based on flow differentiation and metamorphism of komatiites. Two sets of models are produced. Model Set 1: Because D(metal-silicate) for W diminishes with increasing depth, the deep mantle has a higher W abundance, and a lower Hf/W ratio and consequently evolves a negative anomaly in W while the upper mantle evolves a complementary positive anomaly. Subsequent solid-state convection (4.55-2.8 Ga) mixes away the complementary W isotope anomalies to yield the modern mantle null value. This set of models predicts that the complementary negative anomalies in W should eventually be discovered in ancient magmatic rocks of deep mantle origin such as komatiites. Model Set 2: Tungsten is significantly more incompatible (like U, Th and Ba) than Hf, the latter being similar in compatibility to Sm. Our results show that extraction of low-degree partial melts (<2%) leaving a Hadean depleted mantle that can have Sm/Nd~20% higher than chondrites also creates a f(Hf/W)~2-3, sufficient to generate the anomalies observed in Archean rocks. These models increase Hf/W and Sm/Nd ratios in a correlated fashion explaining the tendency of positive W isotope anomalies to occur in rocks with positive Nd isotope anomalies. Recycling of the complementary Hadean crust would result in negative anomalies in later plume lavas, while partitioning of W into an enriched "hidden reservoir" would not. Nd isotope anomalies indicate a melting event around 35-75 Ma after solar system formation, the upper end of which is consistent with our models of Hf/W fractionation, that also yield a depleted mantle composition consistent with DMM. Production of the anomalies is accompanied by the need to preserve the anomalies. We argue that the most effective means of preserving the W isotope anomalies is by crustal storage, and we hypothesize that W is efficiently recycled back to juvenile crust during subduction zone processing. Eventually, the addition of juvenile W from the mantle will dilute the positive W isotope anomalies stored in the early crust. The amount of juvenile W required to be added is about a factor of 4 or more, and it is likely that this occurred during the late Archean crustal growth phase (2.5 Ga), so that positive W isotope anomalies are not likely to occur in much younger rocks. A secular decline in crustal W isotope anomalies is predicted.

Humayun, M.; Brandon, A. D.; Righter, K.

2012-12-01

11

Atypical Isotope Anomalies In Mid-oceanic Ridges  

NASA Astrophysics Data System (ADS)

The systematization of local Sr-Nd-Pb isotope anomalies in mid-oceanic ridges was developed basing on a degree of their spatial connection with "hot spots" and on mutual relation of abnormal MORB composition with compositions of background MORB and rocks of adjacent "hot spots". For the most part of anomalies, connected with "hot spots", compositions of background MORB, abnormal MORB and rocks of "hot spots" are characterized by uniform trend formation on isotope diagrams. It is coordinated to the common representations that these anomalies grow out as a mixture between riftogeneous magmas of MORB-type and melts, generated in adjacent "hot spots". Alongside with it, atypical anomalies were allocated. Two groups of atypical anomalies, connected to hot points, can be distinguished. The first group is represented by anomalies located in the vicinity of the Galapagoss islands "hot spots" and the Hol- lister Ridge (Pacific ocean). The character feature of this group is that volcanics of "hot spots" not continue the trend, which is formed by background and abnormal MORB of Pacific ocean, but build on the trend of MORB, which is typical for northern part of the Central Atlantic. The anomalies located in Indian ocean concern to the second group (Marion - Prince Edward, Amsterdam - St.Paul). Composition of volcanics from these "hot spots" continue the trend of background MORB of Indian ocean, however actually abnormal MORB lay far outside this trend. Two groups of the anomalies gen- erated on significant distance from "hot spots" are established also. Some anomalies, located in Indian ocean (for example, Dutoit, triple junction), are concerned to the first group. Composition of abnormal MORB in these areas form a uniform isotope series with background MORB of Indian ocean. Thus volcanics of Dutoit anomaly (West- ern Indian ridge) characterize the most "enriched" (and rocks from vicinities of triple junction - the most "depleted") final components of this series. Anomalies of other group are related with some transform faults of Atlantic (15.20'N, Oceanographer etc.). In these anomalies, alongside with basalts, which form trend with background basalts of adjacent segments of mid-oceanic ridges, rocks are found, which analogues are distributed only on significant (sometimes on tens thousand km) distance from the studied area. For example, the nearest analogues of some rocks in the Oceanographer fault (35 N) are met only in Southern Atlantic. Thus, it is not always possible to explain the local anomalies in mid-oceanic ridges by mixture between riftogeneous magmas of MORB-type and melts, generated in adjacent "hot spots". The work is supported 1 by RFBR, and federal program "the World Ocean". 2

Pustovoy, A. A.; Mironov, Yu. V.; Ryakhovsky, V. M.

12

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

2013-05-01

13

Zinc isotope anomalies. [in Allende meteorite  

NASA Technical Reports Server (NTRS)

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.

Volkening, J.; Papanastassiou, D. A.

1990-01-01

14

Zinc isotope anomalies in Allende meteorite inclusions  

NASA Technical Reports Server (NTRS)

The isotopic compositions of Zn, Cr, Ti, and Ca have been measured in a number of CAIs from the Allende meteorite. The aim was to test astrophysical models which predict large excesses of Zn-66 to accompany excesses in the neutron-rich isotopes of Ca, Ti, Cr, and Ni. Some of the CAIs show clearly resolved but small excesses for Zn-66 which are at least an order of magnitude smaller than predicted. This result may simply reflect the volatility and chemical behavior of Zn as compared to the other (more refractory) anomalous elements found in these samples. Alternatively, revision of parameters and assumptions used for the model calculations may be required.

Loss, R. D.; Lugmair, G. W.

1990-01-01

15

Isotope shift and hyperfine structure studies of the krypton ion and the thallium atom  

E-print Network

that in the high temperature plasma krypton ion source the energy spread is 1. 1 eV, snd the reduction factor is 0. 0074 for 5 KV acceleration voltage. Therel'ore, the reduced Doppler width is about 0. 44% of the unreduced Doppler width. For the A=729. 18 nm... spread is 11. 1 eV, and the reduction factor is 0. 0077 for 46 KV acceleration voltage. For the A=535. 20 nm transition between the 6p Ps~z and the 7s St~z state of Tl in a vacuum chamber, vs ? 560156300 MHz, and 6vs =3180. 5 MHz. The reduced Doppler...

Li, Yingfeng

2012-06-07

16

Neutron-rich chromium isotope anomalies in supernova nanoparticles  

E-print Network

Neutron-rich isotopes with masses near that of iron are produced in type Ia and II supernovae. 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 supernovae, 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, most likely spinels that show large enrichments in 54Cr relative to solar composition (54Cr/52Cr ratio >3.6xsolar). Such large enrichments in 54Cr can only be produced in supernovae. The mineralogy of the gr...

Dauphas, Nicolas; Chen, James; Roskosz, Mathieu; Papanastassiou, Dimitri; Stodolna, Julien; Guan, Yunbin; Ma, Chi; Eiler, John

2010-01-01

17

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

NASA Astrophysics Data System (ADS)

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 production rate data for a wide range of radioactive and stable isotopes in up to 28 target elements. In this paper, we report results for 78Kr, 80-86Kr isotopes in Rb, Sr, Y and Zr and for 124Xe, 126Xe, 128-132Xe, 134Xe, 136Xe isotopes in Ba and La. Krypton and xenon concentrations have been measured at different depths in the spheres by using conventional mass spectrometry. Based on Monte-Carlo techniques, theoretical production rates are calculated by folding depth-dependent spectra of primary and secondary protons and secondary neutrons with the excitation functions of the relevant nuclear reactions. The comparison of the model calculation results with experimental data in the thick target experiments performed at LNS and previously at CERN have allowed adjustments of the poorly known excitation functions of neutron-induced reactions. Thus, for the two experiments at SATURNE, excellent agreement is obtained between experimental and calculated production rates for most Kr and Xe isotopes in all investigated target elements. Only Xe production in Ba in the gabbro is underestimated by the calculations by about 25%. This work validates the approach of the thin-target model calculations of cosmogenic nuclide production rates in the attempt of modeling the interaction of galactic cosmic-ray protons with stony and iron meteorites in space as well as with lunar samples.

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

2002-07-01

18

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

19

More on Ru Endemic Isotope Anomalies in Meteorites  

NASA Technical Reports Server (NTRS)

We reported last year on endemic isotope anomalies for Ru in iron meteorites, pallasites, ordinary chondrites, and on a whole-rock sample of Allende. We have extended the Ru measurements to more meteorites, to refractory Ca-Al-rich inclusions (CAI) from Allende, and to a whole rock sample of Murchison (CM2). In a companion abstract we report on new measurements for the Mo isotopes, in some of the same samples. There has been a renewed interest in searching for isotope anomalies in this nuclide region, as Ru and Mo include many isotopes from r-, s-, and p-process nucleosynhesis. Furthermore, the Ru and Mo p-process isotopes show atypically high abundances, which have been hard to explain through the standard nucleosynthetic processes. Effects are possible in Ru-98 and Ru-99 from Tc-98 (with a poorly known t(sub 1/2)=4.2 to 10Ma) and from Tc-99 (t(sub 1/2)=0.21Ma). Natural Tc is now extinct on Earth due to the short half-lives, but may have been present in the early solar system. Both radiogenic and general isotope anomalies are important in understanding the processes for the formation of the early solar system. The current emphasis on Ru and Mo is also the result of the development of Negative-ion Thermal Ionization Mass Spectrometry and of Multiple-Collector, Inductively-Coupled-Mass-Spectrometry. We have also developed specific chemical siparation techniques for Ru, which eliminated mass interference effects.

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

2004-01-01

20

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

21

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

22

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

23

Evolution of deformation in the neutron-rich krypton isotopes: The {sup 96}Kr nucleus  

SciTech Connect

The energy of the first excited 2{sup +} state in {sup 96}Kr was measured as 241 keV. The nucleus was produced in the fission of {sup 238}U induced by a 954-MeV {sup 136}Xe beam and prompt {gamma} rays were observed using the clover array CLARA in coincidence with fission products identified with the PRISMA spectrometer. The evolution of the quadrupole collectivity in the Kr isotopes with N{>=}50 is discussed by comparison with that from the Rb to Mo isotones and with predictions of various theoretical calculations.

Marginean, N.; Mihai, C.; Filipescu, D.; Ghita, D.; Ionescu-Bujor, M.; Iordachescu, A.; Marginean, R.; Pascu, S.; Sava, T.; Zamfir, N. V. [Horia Hulubei National Institute of Physics and Nuclear Engineering, R-76900 Bucharest (Romania); Bucurescu, D. [Horia Hulubei National Institute of Physics and Nuclear Engineering, R-76900 Bucharest (Romania); Academy of Romanian Scientists, 54 Splaiul Independentei, R-050094 Bucharest (Romania); Ur, C. A. [Horia Hulubei National Institute of Physics and Nuclear Engineering, R-76900 Bucharest (Romania); Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Corradi, L.; Fioretto, E.; Guiot, B.; Mengoni, D.; Napoli, D. R.; Recchia, F.; Stefanini, A. M.; Silvestri, R. [INFN-Laboratori Nazionali di Legnaro, I-35020 Legnaro (Italy)] (and others)

2009-08-15

24

Structure of krypton isotopes calculated with symmetry-conserving configuration-mixing methods  

NASA Astrophysics Data System (ADS)

Shape transitions and shape coexistence in the Kr70-98 region are studied in a unified view with state-of-the-art beyond-self-consistent mean-field methods based on the Gogny D1S interaction. Beyond-mean-field effects are taken into account through the exact angular-momentum and particle-number restoration and the possibility of axial and nonaxial shape mixing. The results of the low-lying properties of these isotopes are in good agreement with the experimental data when the triaxial degree of freedom is included. Shape transitions from axial-oblate (Kr70-72) to triaxial-prolate (Kr74-78) and from spherical-triaxial (Kr86-92) to axial-oblate (Kr94-98) ground states are obtained. Additionally, low-lying 0+ excited states and quasi-? bands are found showing the richness of the collective structure in this region.

Rodríguez, Tomás R.

2014-09-01

25

Structure of Krypton isotopes calculated with symmetry conserving configuration mixing methods  

E-print Network

Shape transitions and shape coexistence in the $^{70-98}$Kr region are studied in a unified view with state-of-the-art beyond self-consistent mean field methods based on the Gogny D1S interaction. Beyond mean field effects are taken into account through the exact angular momentum and particle number restoration and the possibility of axial and non-axial shape mixing. The results of the low-lying properties of these isotopes are in good agreement with the experimental data when the triaxial degree of freedom is included. Shape transitions from axial-oblate ($^{70-72}$Kr) to triaxial-prolate ($^{74-78}$Kr) and from spherical-triaxial ($^{86-92}$Kr) to axial-oblate ($^{94-98}$Kr) ground states are obtained. Additionally, low-lying $0^{+}$ excited states and quasi-gamma bands are found showing the richness of the collective structure in this region.

Rodríguez, Tomás R

2014-01-01

26

Structure of Krypton isotopes calculated with symmetry conserving configuration mixing methods  

E-print Network

Shape transitions and shape coexistence in the $^{70-98}$Kr region are studied in a unified view with state-of-the-art beyond self-consistent mean field methods based on the Gogny D1S interaction. Beyond mean field effects are taken into account through the exact angular momentum and particle number restoration and the possibility of axial and non-axial shape mixing. The results of the low-lying properties of these isotopes are in good agreement with the experimental data when the triaxial degree of freedom is included. Shape transitions from axial-oblate ($^{70-72}$Kr) to triaxial-prolate ($^{74-78}$Kr) and from spherical-triaxial ($^{86-92}$Kr) to axial-oblate ($^{94-98}$Kr) ground states are obtained. Additionally, low-lying $0^{+}$ excited states and quasi-gamma bands are found showing the richness of the collective structure in this region.

Tomás R. Rodríguez

2014-08-21

27

Cr Isotopic Anomalies and Fractionation in Carbonaceous Chondrites  

NASA Astrophysics Data System (ADS)

Cr isotopic compositions have been measured in fraction extracted by stepwise dissolution of Crabonaceous chondrites to look if the other isotopes than 54Cr are in anomalous (non mass dependent) proportions. Only 54Cr is anomalous.

Birck, J. L.; Göpel, C.

2012-09-01

28

Calcium-48 isotopic anomalies in bulk chondrites and achondrites: Evidence for a uniform isotopic reservoir in the inner protoplanetary disk  

NASA Astrophysics Data System (ADS)

Thermal ionization mass spectrometry (TIMS) was used to measure the calcium isotopic compositions of carbonaceous, ordinary, enstatite chondrites as well as eucrites and aubrites. We find that after correction for mass-fractionation by internal normalization to a fixed 42Ca/44Ca ratio, the 43Ca/44Ca and 46Ca/44Ca ratios are indistinguishable from terrestrial ratios. In contrast, the 48Ca/44Ca ratios show significant departure from the terrestrial composition (from -2 ? in eucrites to +4 ? in CO and CV chondrites). Isotopic anomalies in ?48Ca correlate with ?50Ti: ? 48Ca=(1.09±0.11)×? 50Ti+(0.03±0.14). Further work is needed to identify the carrier phase of 48Ca-50Ti anomalies but we suggest that it could be perovskite and that the stellar site where these anomalies were created was also responsible for the nucleosynthesis of the bulk of the solar system inventory of these nuclides. The Earth has identical 48Ca isotopic composition to enstatite chondrites (EH and EL) and aubrites. This adds to a long list of elements that display nucleosynthetic anomalies at a bulk planetary scale but show identical or very similar isotopic compositions between enstatite chondrites, aubrites, and Earth. This suggests that the inner protoplanetary disk was characterized by a uniform isotopic composition (IDUR for Inner Disk Uniform Reservoir), sampled by enstatite chondrites and aubrites, from which the Earth drew most of its constituents. The terrestrial isotopic composition for 17O, 48Ca, 50Ti, 62Ni, and 92Mo is well reproduced by a mixture of 91% enstatite, 7% ordinary, and 2% carbonaceous chondrites. The Earth was not simply made of enstatite chondrites but it formed from the same original material that was later modified by nebular and disk processes. The Moon-forming impactor probably came from the same region as the other embryos that made the Earth, explaining the strong isotopic similarity between lunar and terrestrial rocks.

Dauphas, Nicolas; Chen, James H.; Zhang, Junjun; Papanastassiou, Dimitri A.; Davis, Andrew M.; Travaglio, Claudia

2014-12-01

29

Nitrogen Isotopic Anomalies in a Hydrous Interplanetary Dust Particle  

NASA Technical Reports Server (NTRS)

Interplanetary dust particles (IDPs) collected in the stratosphere are the fine-grained end member (5 - 50 microns in size) of the meteoritic material available for investigation in the laboratory. IDPs are derived from either cometary or asteroidal sources. Some IDPs contain cosmically primitive materials with isotopic signatures reflecting presolar origins. Recent detailed studies using the NanoSIMS have shown there is a wide variation of isotopic signatures within individual IDPs; grains with a presolar signature have been observed surrounded by material with a solar isotopic composition. The majority of IDPs studied have been anhydrous. We report here results from integrated NanoSIMS/FIB/TEM/Synchrotron IR studies of a hydrous IDP, focused on understanding the correlations between the isotopic, mineralogical and chemical compositions of IDPs.

Smith, J. B.; Dai, Z. R.; Weber, P. K.; Graham, G. A.; Hutcheon, I. D.; Bajt, S.; Ishii, H.; Bradley, J. P.

2005-01-01

30

Oxygen isotope anomalies of the Sun and the original environment of the Solar system  

E-print Network

We present results from a model of oxygen isotopic anomaly production through selective photodissociation of CO within the collapsing proto-Solar cloud. Our model produces a proto-Sun with a wide range of Delta_17O values depending on the intensity of the ultraviolet radiation field. Dramatically different results from two recent Solar wind oxygen isotope measurements indicate that a variety of compositions remain possible for the solar oxygen isotope composition. However, constrained by other measurements from comets and meteorites, our models imply the birth of the Sun in a stellar cluster with an enhanced radiation field and are therefore consistent with a supernova source for 60Fe in meteorites.

Jeong-Eun Lee; Edwin A. Bergin; James R. Lyons

2008-03-05

31

Isotopic Anomalies in Organic Nanoglobules from Comet 81P/Wild 2: Comparison to Murchison Nanoglobules and Isotopic Anomalies Induced in Terrestrial Organics by Electron Irradiation  

SciTech Connect

Nanoglobules are a form of organic matter found in interplanetary dust particles and primitive meteorites and are commonly associated with {sup 15}N 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 {sup 15}N anomaly ({delta}{sup 15}N = 1120{per_thousand}). Associated, non-globular, organic matter from this track is less enriched in {sup 15}N 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 ({single_bond}C{triple_bond}N) and carboxyl ({single_bond}COOH) functional groups. It is significantly enriched in D ({delta}D = 1000{per_thousand}) but has a terrestrial {sup 15}N/{sup 14}N ratio. Experiments indicate that similar D enrichments, unaccompanied by {sup 15}N 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 {sup 15}N enrichment and highly aromatic chemistry analogous to the Track 80 globule and the other only moderately enriched in {sup 15}N 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 {sup 15}N, may be explained in part by exposure to ionizing electron radiation.

De Gregorio, B.; Stroud, R; Nittler, L; Alexander, C; Kilcoyne, A; Zega, T

2010-01-01

32

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

Microsoft Academic Search

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

S. Escrig; F. Capmas; B. Dupré; C. J. Allègre

2004-01-01

33

Nucleosynthetic W isotope anomalies and the Hf-W chronometry of Ca-Al-rich inclusions  

NASA Astrophysics Data System (ADS)

Ca-Al-rich inclusions (CAI) are the oldest dated objects formed in the solar system and are pivotal reference points in early solar system chronology. Knowledge of their initial 182Hf/180Hf and 182W/184W is essential, not only for obtaining precise Hf-W ages relative to the start of the solar system, but also to assess the distribution of short-lived radionuclides in the early solar nebula. However, the interpretation of Hf-W data for CAI is complicated by nucleosynthetic W isotope variations. To explore their extent and nature, and to better quantify the initial Hf and W isotope compositions of the solar system, we obtained Hf-W data for several fine- and coarse-grained CAI from three CV3 chondrites. The fine-grained CAI exhibit large and variable anomalies in ?183W (?iW equals 0.01% deviation from terrestrial values), extending to much larger anomalies than previously observed in CAI, and reflecting variable abundances of s- and r-process W isotopes. Conversely, the coarse-grained (mostly type B) inclusions show only small (if any) nucleosynthetic W isotope anomalies. The investigated CAI define a precise correlation between initial ?182W and ?183W, providing a direct empirical means to correct the ?182W of any CAI for nucleosynthetic isotope anomalies using their measured ?183W. After correction for nucleosynthetic W isotope variations, the CAI data define an initial 182Hf/180Hf of (1.018±0.043)×10-4 and an initial ?182W of -3.49±0.07. The Hf-W formation intervals of the angrites D'Orbigny and Sahara 99555 relative to this CAI initial is 4.8±0.6 Ma, in good agreement with Al-Mg ages of these two angrites. This renders a grossly heterogeneous distribution of 26Al in the inner solar system unlikely, at least in the region were CAI and angrites formed.

Kruijer, Thomas S.; Kleine, Thorsten; Fischer-Gödde, Mario; Burkhardt, Christoph; Wieler, Rainer

2014-10-01

34

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

PubMed Central

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 (82°30?N), where there is downward transport of stratospheric air to the polar troposphere, and were analyzed for ?17O and ?18O 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 ?17O = 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 ?17O 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 ?17O 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 17Oexcess 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.

2013-01-01

35

Carbon stars and isotopic BA anomalies in meteoritic SiC grains  

NASA Astrophysics Data System (ADS)

New calculations of s-processing in TP-AGB stars of low mass based on an updated compilation of neutron capture cross sections are presented. It is shown how the reproduction of solar abundances for the s-isotopes of Ba requires a special choice of neutron capture cross sections of Ba-136 and Ba-138. It is further shown how agreement between the predictions of He shell nucleosynthesis and the Ba isotopic mixture of the G-component in SiC can be obtained, once C-stars with mean neutron exposures lower than that required to fit the solar main component are considered. Problems related to the interpretation of other isotope anomalies in SiC are also examined.

Gallino, R.; Raiteri, C. M.; Busso, M.

1993-06-01

36

Sulfur and Hydrogen Isotope Anomalies in Organic Compounds from the Murchison Meteorite  

NASA Technical Reports Server (NTRS)

Isotopic measurements have been made on organic sulfur and phosphorus compounds recently discovered in the Murchison meteorite. Carbon, hydrogen and sulfur measurements were performed on individual members of the organic sulfur compounds, alkyl sulfonates; and carbon and hydrogen measurements were made on bulk alkyl phosphonates. Cooper and Chang reported the first carbon isotopic measurements of Murchison organic sulfonates, providing insight into the potential synthetic mechanisms of these and, possibly, other organic species. Hydrogen isotopic measurements of the sulforiates now reveal deuterium excesses ranging from +660 to +2730 %. The deuterium enrichments indicate formation of the hydrocarbon portion of these compounds in a low temperature astrophysical environment consistent with that of dense molecular clouds. Measurements of the sulfur isotopes provide further constraints on the origin and mechanism of formation of these organic molecules. Recently, there has been growing documentation of sulfur isotopic anomalies in meteoritic material. Thiemens and Jackson have shown that some bulk ureilites possess excess S-33 and Thiemens et al. have reported excess S-33 in an oldhamite separate from the Norton County meteorite. Rees and Thode reported a large S-33 excess in an Allende acid residue, however, attempts to verify this measurements have been unsuccessful, possibly due to the heterogeneous nature of the carrier phase. With the recognition that sulfur isotopes may reflect chemistry in the protosolar nebula or the precursor molecular cloud, identification of potential carriers is of considerable interest. In the present study, the stable isotopes of sulfur were measured in methane sulfonic acid extracted from the Murchison meteorite. The isotopic composition was found to be: (delta)S-33 = 2.48 %, (delta)S-34 = 2.49 % and (delta)S-36 = 6.76 %. Based upon analysis of more than 60 meteoritic and numerous terrestrial samples, the mass fractionation lines are defined by Delta-33 = (delta)S-33 -0.50(delta)S-34 and Delta-36 = (delta)s-36 - 1.97 (delta)S-34. From these relationships Delta-33 = 1.24 % and Delta-36 = 0.89 % are observed. These anomalies, particularly the Delta-33, lie well outside the range of analytical uncertainty. They are the largest observed in any meteoritic component and the first found in an organosulfur compound. As discussed by Thiemens and Jackson, due to it's position on the periodic chart, sulfur undergoes chemically induced mass independent isotopic fractionations as does oxygen. Experiments by Mauersberger et. al. show that in such processes, the magnitude of fractionation for the different isotopically substituted species varies with mass and angular momentum; thus, anomalies are expected for both S-33 and S-36, but not necessarily of the same magnitude. Laboratory experiments have also confirmed that chemically produced, mass independent fractionations are mediated by molecular symmetry factors. A chemical source of fractionation requires that the sulfur isotopic anomaly was established in the gas phase, probably in reactions involving symmetric CS2. The discovery of an anomalous sulfur isotopic composition in a specific molecule containing excess deuterium is an important advance in the understanding of the cosmochemistry of sulfur. This evidence suggests that methanesulfonic acid was synthesized by interstellar processes. Further measurements and details of possible synthesis and fractionation mechanisms will be presented.

Cooper, G. W.; Thiemens, M. H.; Jackson, T.; Chang, Sherwood

1996-01-01

37

Nucleosynthetic osmium isotope anomalies in acid leachates of the Murchison meteorite  

E-print Network

We present osmium isotopic results obtained by sequential leaching of the Murchison meteorite, which reveal the existence of very large internal anomalies of nucleosynthetic origin. The Os isotopic anomalies are correlated, and can be explained by the variable contributions of components derived from the s, r and p-processes of nucleosynthesis. Much of the s-process rich osmium is released by relatively mild leaching, suggesting the existence of an easily leachable s-process rich presolar phase, or alternatively, of a chemically resistant r-process rich phase. The s-process composition of Os released by mild leaching diverges slightly from that released by aggressive digestion techniques, perhaps suggesting that the presolar phases attacked by these differing procedures condensed in different stellar environments. The correlation between 190Os and 188Os can be used to constrain the s-process 190Os/188Os ratio to be 1.275 pm 0.043. Such a ratio can be reproduced in a nuclear reaction network for a MACS value for 190Os of ~200 pm 22 mbarn at 30 keV. We also present evidence for extensive internal variation of 184Os abundances in the Murchison meteorite. This suggests that p process rich presolar grains (e.g., supernova condensates) may be present in meteorites in sufficient quantities to influence the Os isotopic compositions of the leachates.

L. Reisberg; N. Dauphas; A. Luguet; D. G. Pearson; R. Gallino; C. Zimmermann

2008-12-15

38

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

2013-01-01

39

Hibonite-bearing microspherules - A new type of refractory inclusions with large isotopic anomalies  

NASA Astrophysics Data System (ADS)

This paper presents petrographic description as well as results on the major- and trace-element chemistry and on Mg, Ca, and Ti isotopic compositions of three refractory inclusions, including 3413-1/31 inclusion from Lance and Murchison 7-228 and 7-753, the mineralogy of which is dominated by the oxide minerals spinel, hibonite, and perovskite. The microspherules examined seem to constitute a separate class of refractory inclusions, characterized by a distinct morphology and mineralogy; large excesses of Ca-48 and Ti-50, and Mg-26 depletions. It is suggested that this type of inclusions must have formed early, prior to the dilution of isotopic anomalies by mixing processes, and in an area characterized by excesses of Ca-48 and Ti-50, depletions of Mg-26, and a lack of Al-26.

Ireland, T. R.; Fahey, A. J.; Zinner, E. K.

1991-01-01

40

Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars.  

PubMed

The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess (17)O (0.4-3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O(3) reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

Shaheen, R; Abramian, A; Horn, J; Dominguez, G; Sullivan, R; Thiemens, Mark H

2010-11-23

41

The NO+O3 reaction: A triple oxygen isotope perspective on the reaction dynamics and atmospheric implications for the transfer of the ozone isotope anomaly  

NASA Astrophysics Data System (ADS)

Atmospheric nitrate shows a large oxygen isotope anomaly (? 17O), characterized by an excess enrichment of 17O over 18O, similar to the ozone molecule. Modeling and observations assign this specific isotopic composition mainly to the photochemical steady state that exists in the atmosphere between ozone and nitrate precursors, namely, the nitrogen oxides (NOx=NO+NO2). However, this transfer is poorly quantified and is built on unverified assumptions about which oxygen atoms of ozone are transferred to NOx, greatly weakening any interpretation of the nitrate oxygen isotopic composition in terms of chemical reaction pathways and the oxidation state of the atmosphere. With the aim to improve our understanding and quantify how nitrate inherits this unusual isotopic composition, we have carried out a triple isotope study of the reaction NO+O3. Using ozone intramolecular isotope distributions available in the literature, we have found that the central atom of the ozone is abstracted by NO with a probability of (8+/-5)%(+/-2?) at room temperature. This result is at least qualitatively supported by dynamical reaction experiments, the non-Arrhenius behavior of the kinetic rate of this reaction, and the kinetic isotope fractionation factor. Finally, we have established the transfer function of the isotope anomaly of O3 to NO2, which is described by the linear relationship ? 17O(NO2)=A×? 17O(O3)+B, with A=1.18+/-0.07(+/-1?) and B=(6.6+/-1.5)‰(+/-1?). Such a relationship can be easily incorporated into models dealing with the propagation of the ozone isotope anomaly among oxygen-bearing species in the atmosphere and should help to better interpret the oxygen isotope anomaly of atmospheric nitrate in terms of its formation reaction pathways.

Savarino, J.; Bhattacharya, S. K.; Morin, S.; Baroni, M.; Doussin, J.-F.

2008-05-01

42

Nucleosynthetic osmium isotope anomalies in acid leachates of the Murchison meteorite  

E-print Network

We present osmium isotopic results obtained by sequential leaching of the Murchison meteorite, which reveal the existence of very large internal anomalies of nucleosynthetic origin. The Os isotopic anomalies are correlated, and can be explained by the variable contributions of components derived from the s, r and p-processes of nucleosynthesis. Much of the s-process rich osmium is released by relatively mild leaching, suggesting the existence of an easily leachable s-process rich presolar phase, or alternatively, of a chemically resistant r-process rich phase. The s-process composition of Os released by mild leaching diverges slightly from that released by aggressive digestion techniques, perhaps suggesting that the presolar phases attacked by these differing procedures condensed in different stellar environments. The correlation between 190Os and 188Os can be used to constrain the s-process 190Os/188Os ratio to be 1.275 pm 0.043. Such a ratio can be reproduced in a nuclear reaction network for a MACS value f...

Reisberg, L; Luguet, A; Pearson, D G; Gallino, R; Zimmermann, C

2008-01-01

43

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

44

Analysis of krypton-85 and krypton-81 in a few liters of air.  

PubMed

Long-lived radioactive krypton isotopes, (81)Kr (t1/2 = 229,000 year) and (85)Kr (t1/2 = 10.76 year), are ideal tracers. (81)Kr is cosmogenic and can be used for dating groundwater beyond the (14)C age. (85)Kr is a fission product and can be applied in atmospheric studies, nuclear safety inspections, and dating young groundwater. It has long been a challenge to analyze radio-krypton in small samples, in which the total number of such isotopes can be as low as 1 × 10(5). This work presents a system developed to analyze (81)Kr and (85)Kr from a few liters of air samples. A separation system based on cryogenic distillation and gas chromatographic separation is used to extract krypton gas with an efficiency of over 90% from air samples of 1-50 L. (85)Kr/Kr and (81)Kr/Kr ratios in krypton gases are determined from single-atom counting using a laser-based atom trap. In order to test the performance of the system, we have analyzed various samples collected from ambient air and extracted from groundwater, with a minimum size of 1 L. The system can be applied to analyze (81)Kr and (85)Kr in environmental samples including air, groundwater, and ices. PMID:24641193

Tu, Le-Yi; Yang, Guo-Min; Cheng, Cun-Feng; Liu, Gu-Liang; Zhang, Xiang-Yang; Hu, Shui-Ming

2014-04-15

45

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; Dupré, B; Allègre, C J

2004-09-01

46

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

47

Optical isotope shift and hyperfine structure measurements in preparation of the ultra-sensitive detection of krypton atoms using stepwise laser excitation and field ionization  

E-print Network

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 25 26 Nuclear deformations in relation to their nuclear moments. . . Spectrum of all stable Kr isotopes on the Ss'[I/2]'s ? Sp'[I/2]i (1st - 2pi) transition. . . . . . . . . . . . . . . . . . . . . . . 60 67 27 28 29 30 31 32 33 34... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Pressures in the present apparatus provided by five 180 ls ' turbomolecular pumps . . 52 Isotopic abundance, nuclear spins and half lives of the most abundant natufal and artificial Kr isotopes . X Example of different notations used...

Lassen, Jens

2012-06-07

48

Delineating the effect of El-Nino Southern Oscillations using oxygen and sulfur isotope anomalies of sulfate aerosols  

NASA Astrophysics Data System (ADS)

Sulfate aerosols, unlike greenhouse gases, contribute to global cooling by acting as cloud condensation nuclei in the troposphere and by directly reflecting solar radiation in the stratosphere. To understand the long-term effect of natural and anthropogenic sulfate aerosol on the climate cycle, it is critical to obtain a clear picture of the factors controlling the transport and transformation of sulfate aerosols. We have employed both oxygen triple isotopes and sulfur quadruple isotopes on sulfates from Antarctic ice samples to define the oxidation history, long range transport dynamics, and sources of sulfate aerosols over time. The measurements are used to deconvolve the impact of natural and anthropogenic aerosols on the stratospheric sulfate aerosol composition. Sulfate aerosols were extracted from a snow pit at the South Pole (1979-2002) with a high resolution temporal (6 month) record of the winter and summer seasons covering two largest volcanic events, Pinatubo and El-chichon and three largest ENSO events of the century. All three oxygen and four sulfur isotopes were measured on the extracted sulfate (Shaheen et al., 2013). The high temperature pyrolysis (1000oC) of silver sulfate yielded O2 and SO2. The oxygen triple isotopic composition of the O2 gas was used to determine the oxidation history of sulfate aerosol and SO2 gas obtained during this reaction was utilized to measure sulfur quadruple isotopes following appropriate reaction chemistry (Farquhar et al., 2001). The data revealed that oxygen isotope anomalies in Antarctic aerosols (?17O = 0.8-3.7‰) from 1990 to 2001 are strongly linked to the variation in ozone levels in the upper stratosphere/lower stratosphere. The variations in ozone levels are reflective of the intensity of the ENSO events and changes in relative humidity in the atmosphere during this time period. Sulfate concentrations and sulfur quadruple isotopic composition and associated anomalies were used to elucidate the sources of sulfate aerosol to the stratosphere. The new results demonstrate that combined O-triple isotopes and S-quadruple isotopes may help to recognize paleo ENSO events and their impact on the oxidation history of sulfate aerosols. 1. R. Shaheen, M. A., T. Jackson, J. McCabe, J. Savarino, M. H. Thiemens. (2013) A Window to the Paleoclimate- Tales of Volcanoes and El-Ninño Southern Oscillations with the Oxygen Isotope Anomaly of Sulfate Aerosols, Proceedings of the National Academy of Sciences of the United States of America. 2. Farquhar, J., Savarino, J., Airieau, S., and Thiemens, M. H. (2001) Observation of wavelength-sensitive mass-independent sulfur isotope effects during SO2 photolysis: Implications for the early atmosphere, Journal of Geophysical Research-Planets 106, 32829-32839.

Shaheen, R.; Abaunza Quintero, M. M.; Jackson, T.; McCabe, J.; Savarino, J. P.; Thiemens, M. H.

2013-12-01

49

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

50

Developing hyperpolarized krypton-83 for nuclear magnetic resonance spectroscopy and magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

This dissertation discusses the production of highly nonequilibrium nuclear spin polarization, referred to as hyperpolarization or hp, in the nuclear spin I = 9/2 noble gas isotope krypton-83 using spin exchange optical pumping (SEOP). This nonequilibrium polarization yields nuclear magnetic resonance (NMR) signals that are enhanced three or more orders of magnitude above those of thermally polarized krypton and enables experiments that would otherwise be impossible. Krypton-83 possesses a nuclear electric quadrupole moment that dominates the longitudinal (T1) relaxation due to coupling of the quadrupole moment to fluctuating electric field gradients generated by distortions to the spherical symmetry of the electronic environment. Relaxation slows polarization buildup and limits the maximum signal intensity but makes krypton-83 a sensitive probe of its environment. The gas-phase krypton-83 longitudinal relaxation rate increases linearly with total gas density due to binary collisions. Density independent relaxation, caused by the formation of krypton-krypton van der Waals molecules and surface adsorption, also contributes to the observed rate. Buffer gases suppress van der Waals molecule mediated relaxation by breaking apart the weakly bound krypton dimers. Surface relaxation is gas composition independent and therefore more difficult to suppress. However, this relaxation mechanism makes hp krypton-83 sensitive to important surface properties including surface-to-volume ratio, surface chemistry, and surface temperature. The presence of surfaces with high krypton adsorption affinities (i.e. hydrophobic surfaces) accelerates the relaxation times and can produce T1 contrast in hp krypton-83 magnetic resonance imaging (MRI). Tobacco smoke deposited on surfaces generates strong T1 contrast allowing the observation of smoke deposition with spatial resolution. Conversely, water adsorption on surfaces significantly lengths the T1 times due competitive surface adsorption. Finally, this work demonstrates that hp krypton-83 MRI of intact, excised lungs is feasible. No attempts have been made to observe pathology specific contrast, but this work represents the first steps in developing hp krypton into a useful biomedical tool. Although the signal must be improved for biomedical applications, additional enhancements of up to 180 times greater than the currently obtained signal are possible through improved SEOP, and another order of magnitude increase can be obtained through isotopic enrichment.

Cleveland, Zackary I.

51

Isotopic Anomalies in Primitive Solar System Matter: Spin-State Dependent Fractionation of Nitrogen and Deuterium in Interstellar Clouds  

NASA Technical Reports Server (NTRS)

Organic material found in meteorites and interplanetary dust particles is enriched in D and N-15, 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 core. Theoretical models of interstellar fractionation at low temperatures predict large enrichments in both D and N-15 and can account for the largest isotop c enrichments measured in carbonaceous meteorites, However, more recent measurements have shown that, in some primitive samples, a large N-15 enrichment does not correlate with one in D, and that some D-enriched primitive material displays little, if any, N-15 enrichment. By considering the spin-state dependence in ion-molecule reactions involving the ortho and para forms of H2, we show that ammonia and related molecules can exhibit such a wide range of fractionation for both N-15 and D in dense cloud cores, We also show that while the nitriles, HCN and HNC, contain the greatest N-15 enrichment, this is not expected to correlate with extreme D emichment. These calculations therefore support the view that Solar System N-15 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.

Wirstrom, Eva S.; Charnley, Steven B.; Cordiner, Martin A.; Milan, Stefanie N.

2012-01-01

52

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

53

Isotopic Anomalies in Primitive Solar System Matter: Spin-State-Dependent Fractionation of Nitrogen and Deuterium in Interstellar Clouds  

NASA Technical Reports Server (NTRS)

Organic material found in meteorites and interplanetary dust particles is enriched in D and N-15. 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 N-15 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 N-15 enrichment does not correlate with one in D, and that some D-enriched primitive material displays little, if any, N-15 enrichment. By considering the spin-state dependence in ion-molecule reactions involving the ortho and para forms of H2, we show that ammonia and related molecules can exhibit such a wide range of fractionation for both N-15 and D in dense cloud cores. We also show that while the nitriles, HCN and HNC, contain the greatest N=15 enrichment, this is not expected to correlate with extreme D enrichment. These calculations therefore support the view that solar system N-15 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.

Wirstrom, Eva S.; Charnley, Steven B.; Cordiner, Martin A.; Milam, Stefanie N.

2012-01-01

54

Zinc isotopic composition of iron meteorites: Absence of isotopic anomalies and origin of the volatile element depletion  

NASA Astrophysics Data System (ADS)

High-precision Zn isotopic compositions measured by MC-ICP-MS are documented for 32 iron meteorites from various fractionally crystallized and silicate-bearing groups. The ?66Zn values range from -0.59‰ up to +5.61‰ with most samples being slightly enriched in the heavier isotopes compared with carbonaceous chondrites (0 < ?66Zn < 0.5). The ?66Zn versus ?68Zn plot of all samples defines a common linear fractionation line, which supports the hypothesis that Zn was derived from a single reservoir or from multiple reservoirs linked by mass-dependent fractionation processes. Our data for Redfields fall on a mass fractionation line and therefore refute a previous claim of it having an anomalous isotopic composition due to nonmixing of nucleosynthetic products. The negative correlation between ?66Zn and the Zn concentration of IAB and IIE is consistent with mass-dependent isotopic fractionation due to evaporation with preferential loss of lighter isotopes in the vapor phase. Data for the Zn concentrations and isotopic compositions of two IVA samples demonstrate that volatile depletion in the IVA parent body is not likely the result of evaporation. This is important evidence that favors the incomplete condensation origin for the volatile depletion of the IVA parent body.

Chen, Heng; Nguyen, Bach Mai; Moynier, Frédéric

2013-12-01

55

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

56

NOx cycle and the tropospheric ozone isotope anomaly: an experimental investigation  

NASA Astrophysics Data System (ADS)

The oxygen isotope composition of nitrogen oxides (NOx) in the atmosphere is a useful tool for understanding the oxidation of NOx into nitric acid / nitrate in the atmosphere. A set of experiments was conducted to examine change in isotopic composition of NOx due to NOx-O2-O3 photochemical cycling. At low NOx / O2 mixing ratios, NOx became progressively and nearly equally enriched in 17O and 18O over time until it reached a steady state with ?17O values of 39.3 ± 1.9‰ and ?18O values of 84.2 ± 4‰, relative to the isotopic composition of the initial O2 gas. As the mixing ratios were increased, the isotopic enrichments were suppressed by isotopic exchange between O atoms, O2, and NOx. A kinetic model was developed to simulate the observed data and it showed that the isotope effects occurring during O3 formation play a dominant role in controlling NOx isotopes and, in addition, secondary kinetic isotope effects or isotope exchange reactions are also important during NOx cycling. The data and model were consistent with previous studies which showed that the NO + O3 reactions occur mainly via the transfer of the terminal atoms of O3. The model predicts that under tropospheric concentrations of NOx and O3, the timescale of NOx-O3 isotopic equilibrium ranges from hours (for ppbv NOx / O2 mixing ratios) to days (for pptv mixing ratios) and yields steady state ?17O and ?18O values of 45‰ and 117‰ respectively (relative to Vienna Standard Mean Ocean Water (VSMOW)) in both cases. Under atmospheric conditions when O3 has high concentrations, the equilibrium between NOx and O3 should occur rapidly (h) but this equilibrium cannot be reached during polar winters and/or nights if the NOx conversion to HNO3 is faster. The experimentally derived rate coefficients can be used to model the major NOx-O3 isotopologue reactions at various pressures and in isotope modeling of tropospheric nitrate.

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

2014-05-01

57

CO self-shielding as the origin of oxygen isotope anomalies in the early solar nebula.  

PubMed

The abundances of oxygen isotopes in the most refractory mineral phases (calcium-aluminium-rich inclusions, CAIs) in meteorites have hitherto defied explanation. Most processes fractionate isotopes by nuclear mass; that is, 18O is twice as fractionated as 17O, relative to 16O. In CAIs 17O and 18O are nearly equally fractionated, implying a fundamentally different mechanism. The CAI data were originally interpreted as evidence for supernova input of pure 16O into the solar nebula, but the lack of a similar isotope trend in other elements argues against this explanation. A symmetry-dependent fractionation mechanism may have occurred in the inner solar nebula, but experimental evidence is lacking. Isotope-selective photodissociation of CO in the innermost solar nebula might explain the CAI data, but the high temperatures in this region would have rapidly erased the signature. Here we report time-dependent calculations of CO photodissociation in the cooler surface region of a turbulent nebula. If the surface were irradiated by a far-ultraviolet flux approximately 10(3) times that of the local interstellar medium (for example, owing to an O or B star within approximately 1 pc of the protosun), then substantial fractionation of the oxygen isotopes was possible on a timescale of approximately 10(5) years. We predict that similarly irradiated protoplanetary disks will have H2O enriched in 17O and 18O by several tens of per cent relative to CO. PMID:15902251

Lyons, J R; Young, E D

2005-05-19

58

Self-shielding in O2 - A possible explanation for oxygen isotopic anomalies in meteorites?  

NASA Technical Reports Server (NTRS)

The production of isotopic effects in oxygen due to self-shielding of photolysing radiation by the Schumann-Runge bands of (O-16)2 is investigated. The model studied is the simple case of incoming radiation falling on a gaseous medium of uniform composition. The enhancement of O-17 and O-18 production upon photodissociation of O2 is calculated for various column densities, and its dependence on temperature and the presence of other molecules is examined. The issue of whether the products of photolysis can be trapped and thus preserve a peculiar isotopic composition is discussed.

Navon, O.; Wasserburg, G. J.

1985-01-01

59

Analogue or Anomaly? Ocean Drilling Evidence From Marine Isotope Stage 11  

Microsoft Academic Search

Ocean Drilling makes it possible to recover high quality sedimentary archives from important earlier geologic intervals, such as Marine Isotope Stage 11 (MIS 11), approximately 400 ky BP. Similar orbital configurations and comparable atmospheric greenhouse gas concentrations have led to the suggestion that MIS 11 is a suitable, possibly the best, geological analogue for the natural development of Holocene and

J. F. McManus; D. W. Oppo; J. L. Cullen; P. Huybers; L. Federici

2003-01-01

60

Design documentation: Krypton encapsulation preconceptual design  

SciTech Connect

US EPA regulations limit the release of Krypton-85 to the environment from commercial facilities after January 1, 1983. In order to comply with these regulations, Krypton-85, which would be released during reprocessing of commercial nuclear fuel, must be collected and stored. Technology currently exists for separation of krypton from other inert gases, and for its storage as a compressed gas in steel cylinders. The requirements, which would be imposed for 100-year storage of Krypton-85, have led to development of processes for encapsulation of krypton within a stable solid matrix. The objective of this effort was to provide preconceptual engineering designs, technical evaluations, and life cycle costing data for comparison of two alternate candidate processes for encapsulation of Krypton-85. This report has been prepared by The Ralph M. Parsons Company for the US Department of Energy.

Knecht, D.A. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

1994-10-01

61

The astrophysical interpretation of isotope anomalies in graphite and SiC grains of chondrites  

NASA Technical Reports Server (NTRS)

The C, N, and Mg isotopic compositions in graphite and SiC grains of carbonaceous chondrites can be explained by nuclear processes in massive O,B stars of second generation passed a stage of WR star with intensive stellar wind, where grain condensation had taken place. The interstellar graphite and SiC grains with anomalous isotopic compositions of C, N, Ne, and Si and other elements of nucleosynthetic origin, found in non-equilibrated chondrites, are most suitable for determination of astro-physical objects, where nucleosynthesis had taken place. Two objects were examined: (1) massive O,B stars of second generation passed a stage of WR star with intensive stellar wind (O,B-WR model) and (2) low-mass stars (1 less than or equal to M/solar mass less than or equal to 3) during thermally pulsing asymptotic giant branch phase (TP-AGB model).

Lavrukhina, A. K.

1993-01-01

62

Tales of volcanoes and El-Ni?o southern oscillations with the oxygen isotope anomaly of sulfate aerosol  

PubMed Central

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-Niño Southern Oscillations (ENSO) Index (OEI). Higher ?17O 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 ?17O = 3.3‰, OEI = 11 and ?17O = 4.5‰) and normal oxidative pathways. Our high-resolution data indicated that ?17O 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.

2013-01-01

63

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-Niño 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

2013-10-29

64

Extreme Carbon Isotope Anomalies of the Proterozoic Eon: Fact or Fiction?  

Microsoft Academic Search

Post-Paleozoic carbon isotope variations constructed from time-series analyses of calcareous microfossils generally pale in comparison with the extreme variations recorded in Paleozoic and Proterozoic aged successions. The latter are primarily preserved in fine-grained inorganic carbonates, which due to their great antiquity and potential for diagenetic alteration have been viewed by some as imperfect recorders of seawater chemistry. In part, this

A. J. Kaufman

2008-01-01

65

Sources of the oxygen isotopic anomaly in atmospheric N2O  

Microsoft Academic Search

One-dimensional and two-dimensional models are used to investigate the isotopic composition of atmospheric N2O. The sources of N2O in the atmosphere are based on recent laboratory measurements of the N2O quantum yield in the mixture of O3\\/O2\\/N2 (Estupiñán et al., 2002). Two recently proposed pathways (Estupiñán et al., 2002; Prasad, 2005) are evaluated in the model. We find that the

Mao-Chang Liang; Yuk L. Yung

2007-01-01

66

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

67

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

68

Krypton-85 in the atmosphere  

E-print Network

Measurement results are presented on 85Kr content in the atmosphere over the European part of Russia in 1971-1995 based on the analysis of the commercial krypton, which is separated from air by industrial plants. Our results are by 15 per cent lower then 85Kr activites observed over West Europe. According our prediction by 2030 85Kr content in the atmosphere over Europe will amount to 1,5-3 Bq in m3 air. Average 85Kr release to the atmosphere from regeneration of spent nuclear fuel (SNF) is estimated, some 180 TBq per a ton SNF. It is advisable to recommence monitoring of 85Kr content within Russia.

A. T. Korsakov; E. G. Tertyshnik

2013-07-09

69

Atmospheric Krypton and Xenon Measurements from Mars Science Laboratory  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

70

Global Neoproterozoic (Sturtian) post-glacial sulfide-sulfur isotope anomaly recognised in Namibia  

NASA Astrophysics Data System (ADS)

The Neoproterozoic Earth experienced at least two, probably global, glaciations. Each glaciation was superceded by deposition of a layer of carbonate ('cap-carbonate') that has a distinctive lithology and depletion in 13C ( ?13C carbonate ˜ -5‰). The ˜700 Ma Sturtian glaciation is followed by deposition of a cap-carbonate and post-glacial succession which contain bacterially produced sulfides extremely enriched in 34S (average ?34S sulfide ˜ +30‰) with maximum values up to +60‰. This level of 34S enrichment in sulfides is unique to the Sturtian post-glacial succession and recognised in Australia, Canada, and China. In the Neoproterozoic of the Nama Basin, Namibia, the Gobabis Member is the basal unit of the Court Formation, which overlies the glacial Blaubeker Formation. ?13C carbonate analyses from the Gobabis Member range from -5.2 to -2.2‰ (average = -3.7‰; n = 10). ?34S sulfide ranges from +16.1 to +61.1‰ (average = +37.6‰; n = 8). These results are consistent with a Sturtian age for the Blaubeker Formation and overlying Gobabis Member, which have previously been interpreted as Sturtian. The sulfur isotopic results are comparable with ?34S sulfide in Sturtian post-glacial units of Australia, Canada and China. This adds to the evidence for correlation of the Blaubeker Formation with Sturtian glaciations on other continents. The cause of such elevated ?34S sulfide is enigmatic. Geochemical evidence suggests the sulfide was not formed from low sulfate waters nor in euxinic conditions, which discounts any known modern analogue. 34S enrichment in sulfides is therefore postulated to be caused by enrichment of 34S in contemporaneous seawater ( ?34S sulfate up to +60‰?). The rise in seawater ?34S sulfate is considered to be the result of intense bacterial sulfate reduction in an anoxic ocean during the Sturtian glaciation.

Gorjan, Paul; Walter, Malcolm R.; Swart, Roger

2003-02-01

71

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.

Schöbel, H.; Bartl, P.; Leidlmair, C.; Denifl, S.; Echt, O.; Märk, T. D.; Scheier, P.

2011-07-01

72

Krypton Fluoride Laser Driven Inertial Fusion Energy  

E-print Network

1 Krypton Fluoride Laser Driven Inertial Fusion Energy Presented to NAS Committee on the Prospects Fluoride (KrF) Laser? · Gas Laser--Excimer (Excited Dimer) · Fundamental wavelength is 248 nm · Energy

73

Krypton based adsorption type cryogenic refrigerator  

NASA Technical Reports Server (NTRS)

Krypton and a monolithic porous carbon such as Saran carbon are used respectively as the sorbate and sorbent of an adsorption type refrigerator to improve refrigeration efficiency and operational longevity.

Jones, Jack A. (Inventor); Schember, Helene R. (Inventor)

1989-01-01

74

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 SiO 2. 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

75

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

Microsoft Academic Search

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

Cynthia D. Holcomb; John A. Zollweg

1993-01-01

76

Potential for beneficial use of krypton-85  

SciTech Connect

Large quantities of krypton-85 (about 42 MCi) are contained in stored power-reactor fuels and about 1 MCi/year in fuels processed at each of the Savannah River and Hanford defense fuel-processing plants. This nuclear byproduct could be a significant material resource if used in specialized applications. Recently a technique for implanting krypton in a growing sputter-deposited metallic film has been developed. This yields a stable, high-concentration source of krypton-85 which may have applications for small power generators. Metal deposits containing up to 14 at. % have been prepared that would give a heat source of 0.9 W/cm/sup 3/ if fully enriched krypton-85 were implanted. Potential applications for up to 10-W batteries include power for runway lighting and other specialized military applications in remote locations, power for telephone or radiocommunications in the far North, and power for monitoring equipment for tracking animals. Krypton-85 has the advantage of being environmentally the most acceptable heat-producing radioisotope available for power production. 1 figure.

Tingey, G.L.; Jensen, G.A.; McClanahan, E.D.; Lytle, J.M.; Rising, K.R.

1983-03-01

77

Carbon isotope anomaly and other geochemical changes at the Triassic-Jurassic boundary from a marine section in Hungary  

Microsoft Academic Search

Most mass extinctions are linked with carbon isotope excursions, implying that biotic crises are coupled with changes in the global carbon cycle. The isotopic evolution during the end-Triassic extinction is far less documented than that for the other major Phanerozoic extinctions. Here we report a sharp and short-lived -3.50\\/00 excursion in carbon isotope values for carbonate (delta13Ccarb) corresponding to a

József Pálfy; Attila Demény; János Haas; Magdolna Hetényi; Michael J. Orchard; István Veto

2001-01-01

78

Seismically triggered anomalies in the isotope signatures of mantle-derived gases detected at degassing sites along two neighboring faults in NW Bohemia, central Europe  

NASA Astrophysics Data System (ADS)

Vogtland and NW Bohemia region is known for its earthquake swarms; the most intensive swarm since 1985/86 occurred in October 2008. To find further indications for the interaction of ascending mantle-derived fluids and the occurrence of earthquake swarms, detailed fortnightly studies of gas compositions (CO2, N2, Ar, He, H2, and CH4) and isotope ratios (?13C, ?15N, and 3He/4He) were carried out between October 2008 and April 2011 at four locations close to the Nový Kostel focal zone and at the Wettinquelle spring (Bad Brambach). From the start of the 2008 earthquake swarm seismically induced isotope-geochemical anomalies were recorded at locations along the Po?atky-Plesná fault zone (PPZ) and were, for the first time, also found at degassing locations on the Mariánské Lázn? fault zone (MLF). Variations were observed in both the temporal and spatial distributions of the anomalies as well in anomaly strengths, probably due to the positions of these fault zones relative to the focal zone, and to differences in fluid migration pathways. Prior to both the 2000 and 2008 swarms, 3He/4He ratios > 6 Ra were recorded at the Bublák mofette. These anomalous pre-seismic 3He/4He ratios suggest that both the 2000 and 2008 swarms may have been associated with the supply of fresh magma from a less degassed reservoir in the lithospheric mantle. The temporal ?13CCO2 pattern from detailed studies at Bublák between 2005 and 2011 indicates progressive magma degassing, as well as seismically induced variations in the ?13C, providing additional support to the interpretation derived from the 3He/4He ratios.

Bräuer, Karin; Kämpf, Horst; Strauch, Gerhard

2014-07-01

79

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

80

The Krypton and Xenon Contents of Atmospheric Air  

Microsoft Academic Search

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

E. Glueckauf; G. P. Kitt

1956-01-01

81

Limits to the sensitivity of living benthic foraminifera to pore water carbon isotope anomalies in methane vent environments  

NASA Astrophysics Data System (ADS)

13C depletions in the carbon isotopic composition of benthic foraminiferal tests preserved in the stratigraphic record have been interpreted as an active incorporation of methane-derived carbon. Understanding the extent to which these isotope excursions reflect basin-wide fluxes of methane carbon to bottom waters versus a local supply of methane carbon within the sediments in which benthic foraminifera live, or a postmortem diagenetic imprint is critical to the interpretation of ?13C paleoceanographic proxies. Here we evaluate the impact of chemical gradients measured in pore waters adjacent to active methane vents on carbon assimilation by living benthic foraminifera and show that those living near methane vents do not assimilate the distinctly 13C depleted methane-derived dissolved inorganic carbon into their tests from the pore water in which they were found. Our observations can be explained by the recently articulated physiological limits imposed on deep-sea fauna by low-oxygen and high-pCO2 environments. Understanding the importance of the different processes involved in the observed disequilibrium between the carbon isotopic composition of the benthic forams and the pore waters where they were found has important implications on the reliability of carbon isotopic composition of benthic foraminifera for paleoceanographic reconstructions. In particular, the observation on the inhospitability of these environments for benthic foraminifera at least for reproduction and growth raises the issue on the overprint either in the late adult stages of foraminifera that grew in a different neighboring environment or during early diagenesis in these geochemically active environments.

Herguera, J. C.; Paull, C. K.; Perez, E.; Ussler, W.; Peltzer, E.

2014-03-01

82

Nickel isotopes in iron meteorites nucleosynthetic anomalies in sulphides with no effects in metals and no trace of 60Fe  

NASA Astrophysics Data System (ADS)

Iron-60 decays to 60Ni with a half-life of 1.49 Myrs such that Ni isotopic studies of iron meteorites have the potential to provide powerful new constraints on the energy budgets and time-scales of planetesimal melting, differentiation and core formation. We report high-resolution MC-ICPMS Ni isotope compositions for the Fe-Ni metal phase from 33 iron meteorites as well as for 10 coexisting sulphides. The isotopic composition of every metal sample is indistinguishable from that of the standard within uncertainties, whereas several sulphides show an excess of 61Ni correlated with a deficit in 60Ni. These latter effects are not explicable by currently known analytical artefacts. Nor can they be readily explained by spallation reactions or radioactive decay. Based on our sampling they seem more prevalent in, but not exclusive to, non-magmatic iron meteorites and could reflect admixing of less than 0.4 ppm pure s-process component into "normal" Ni on meteorite parent bodies. Sulphides do not show the excess 60Ni expected from their high Fe/Ni ratios if they formed within the first few million years of the solar system. The data provide evidence that sulphides in iron meteorites crystallized more than 10 Myrs after the start of the solar system.

Quitté, Ghylaine; Meier, Matthias; Latkoczy, Christopher; Halliday, Alex N.; Günther, Detlef

2006-02-01

83

Vaginal Anomalies: Cloacal Anomalies  

MedlinePLUS

... feces following the procedure? Your child's ability to control either the flow of her urine or elimination of her stool depends on the severity of the anomaly. In milder cases, more than 90 percent of patients have good sphincter control and a nearly normal pattern eliminating stools. Between ...

84

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

85

1, 393412, 2004 Carbon isotope  

E-print Network

BGD 1, 393­412, 2004 Carbon isotope anomaly in the major plant C1 pool F. Keppler et al. Title Page Biogeosciences Discussions is the access reviewed discussion forum of Biogeosciences Carbon isotope anomaly.keppler@qub.ac.uk) 393 #12;BGD 1, 393­412, 2004 Carbon isotope anomaly in the major plant C1 pool F. Keppler et al. Title

Boyer, Edmond

86

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

87

Heterogeneous Isotopic Anomalies of Sm and Gd in the Norton County Meteorite: Evidence for Irradiation from the Active Early Sun  

NASA Astrophysics Data System (ADS)

Large and heterogeneous isotopic variations of 150Sm/149Sm and 158Gd/157Gd 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 (Mg2Si2O6), have a very large neutron fluence of 1.98 × 1017 n cm-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 × 1016 to 1.87 × 1017 n cm-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; Yoneda, Shigekazu

2012-02-01

88

Krypton and xenon in lunar fines  

NASA Technical Reports Server (NTRS)

Data from grain-size separates, stepwise-heated fractions, and bulk analyses of 20 samples of fines and breccias from five lunar sites are used to define three-isotope and ordinate intercept correlations in an attempt to resolve the lunar heavy rare gas system in a statistically valid approach. Tables of concentrations and isotope compositions are given.

Basford, J. R.; Dragon, J. C.; Pepin, R. O.; Coscio, M. R., Jr.; Murthy, V. R.

1973-01-01

89

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

90

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

91

Energy Levels of Krypton, Kr I through Kr XXXVI  

NASA Astrophysics Data System (ADS)

The energy levels of the krypton atom, in all stages of ionization for which experimental data are available, have been compiled. No data has yet been published for Kr XI through Kr XVIII. For H-like krypton very accurate calculated level values are compiled. In all, data for 29 spectra are given. Experimental g-factors are included for Kr I and Kr II. Calculated percentage compositions of levels are given for 12 ions. A value for the ionization energy of each ion, either experimental or theoretical, is included.

Sugar, Jack; Musgrove, Arlene

1991-09-01

92

Perfusion measurement with Rubidium 81 to Krypton 81m ratio  

E-print Network

PERFUSION MEASUREMENT WITH RUBIDIUM 81 TO KRYPTON BiM RATIO A Thesis by CHARLES WARD BEASLEY Submitted to the Graduate College of Texas A&M University in partial ful lfi 1 lment of the requirement for the degree: MASTER OF SCIENCE December... 1982 Major Subject: Veterinary Physiology PERFUSION MEASUREMENT WITH RUBIDIUM 81 TO KRYPTON 81M RATIO A Thesis by CHARLES WARD BEASLEY Approved as to style and content by: Chairma of ommittee pi Me er Member er Head of Department December...

Beasley, Charles Ward

2012-06-07

93

Magnetic anomalies  

NASA Astrophysics Data System (ADS)

The implications and accuracy of anomaly maps produced using Magsat data on the scalar and vector magnetic field of the earth are discussed. Comparisons have been made between the satellite maps and aeromagnetic survey maps, showing smoother data from the satellite maps and larger anomalies in the aircraft data. The maps are being applied to characterize the structure and tectonics of the underlying regions. Investigations are still needed regarding the directions of magnetization within the crust and to generate further correlations between anomaly features and large scale geological structures. Furthermore, an increased data base is recommended for the Pacific Ocean basin in order to develop a better starting model for Pacific tectonic movements. The Pacific basin was large farther backwards in time and subduction zones surround the basin, thereby causing difficulties for describing the complex break-up scenario for Gondwanaland.

Harrison, C. G. A.

1983-04-01

94

Binding energies of neon and krypton cluster ions  

NASA Astrophysics Data System (ADS)

We have measured the kinetic energy released in the metastable fragmentation of mass selected neon and krypton cluster ions, produced by electron impact ionization of a neutral cluster beam. Finite heat bath theory is applied to determine the transition state temperatures and binding energies of the metastable cluster ions.

Parajuli, R.; Matt, S.; Echt, O.; Stamatovic, A.; Scheier, P.; Märk, T. D.

2002-01-01

95

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) [ANL

2005-08-24

96

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.

97

Noble gas anomalies related to high-intensity methane gas seeps in the Black Sea  

NASA Astrophysics Data System (ADS)

Dissolved noble gases and tritium were analyzed at a series of high-intensity methane gas seeps in the Black Sea to study the transport and gas exchange induced by bubble-streams in the water column. These processes affect marine methane emissions to the atmosphere and are therefore relevant to climate warming. The seep areas investigated are located in the Dnepr paleo-delta, west of Crimea, and in the Sorokin Trough mud volcano area, south-east of Crimea. Noble gas concentration profiles at active seep sites revealed prominent anomalies compared to reference profiles that are unaffected by outgassing. Supersaturations of the light noble gases helium and neon observed relatively close to the sea floor are interpreted as effects of gas exchange between the water and the rising bubbles. Depletions of the heavy noble gases argon, krypton and xenon that were detected above an active, bubble-releasing mud volcano appear to be related to the injection of fluids depleted in noble gases that undergo vertical transport in the water column due to small density differences. In both cases, the noble gas anomalies clearly document seep-specific processes which are difficult to detect by other methods. Helium is generally enriched in the deep water of the Black Sea due to terrigenic input. Although exceptionally high helium concentrations observed in one seep area indicate a locally elevated helium flux, most of the seeps studied seem to be negligible sources of terrigenic helium. Noble gas analyses of sediment pore waters from the vicinity of a mud volcano showed large vertical gradients in helium concentrations. The helium isotope signature of the pore waters points to a crustal origin for helium, whereas the deep water of the Black Sea also contains a small mantle-type component.

Holzner, C. P.; McGinnis, D. F.; Schubert, C. J.; Kipfer, R.; Imboden, D. M.

2008-01-01

98

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

99

An efficient magneto-optical trap of metastable krypton atoms.  

PubMed

We report a magneto-optical trap of metastable krypton atoms with a trap loading rate of 3×10(11) atoms/s and a trap capture efficiency of 3×10(-5). The system starts with an atomic beam of metastable krypton produced in a liquid-nitrogen cooled, radio-frequency driven discharge. The metastable beam flux emerging from the discharge is 1.5×10(14) atoms/s/sr. The flux in the forward direction is enhanced by a factor of 156 with transverse laser cooling. The atoms are then slowed inside a Zeeman slower before captured by a magneto-optic trap. The trap efficiency can be further improved, possibly to the 10(-2) level, by gas recirculation. Such an atom trap is useful in trace analysis applications where available sample size is limited. PMID:21198013

Cheng, C-F; Jiang, W; Yang, G-M; Sun, Y-R; Pan, H; Gao, Y; Liu, A-W; Hu, S-M

2010-12-01

100

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

101

Electron beam pumped krypton fluoride lasers for fusion energy  

Microsoft Academic Search

High-energy electron beam pumped krypton fluoride (KrF) gas lasers are an attractive choice for inertial fusion energy (IFE). Their short wavelength and demonstrated high beam uniformity optimizes the laser-target physics, and their pulsed power technology scales to a large system. This paper presents the principals of this type of laser and the progress toward developing technologies that can meet the

JOHN D. SETHIAN; MATTHEW C. MYERS; ROBERT H. LEHMBERG; PAUL C. KEPPLE; S. P. Obenschain; FRANK HEGELER; M. Friedman; MATTHEW F. WOLFORD; RUSSELL V. SMILGYS; STEPHEN B. SWANEKAMP; DOUGLAS WEIDENHEIMER; DAVID GIORGI; DALE R. WELCH; DAVID V. ROSE; STUART SEARLES

2004-01-01

102

Dyonic Anomalies  

E-print Network

We consider the problem of coupling a dyonic p-brane in d = 2p+4 space-time dimensions to a prescribed (p+2)-form field strength. This is particularly subtle when p is odd. For the case p = 1, we explicitly construct a coupling functional, which is a sum of two terms: one which is linear in the prescribed field strength, and one which describes the coupling of the brane to its self-field and takes the form of a Wess-Zumino term depending only on the embedding of the brane world-volume into space-time. We then show that this functional is well-defined only modulo a certain anomaly, related to the Euler class of the normal bundle of the brane world-volume.

Mans Henningson; Erik P. G. Johansson

2005-08-15

103

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

104

Anomaly Structure of Supergravity and Anomaly Cancellation  

E-print Network

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)_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.

Daniel Butter; Mary K. Gaillard

2009-06-18

105

Anomaly Structure of Supergravity and Anomaly Cancellation  

E-print Network

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)_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

2009-01-01

106

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

107

Materials screening tests for the krypton-85 storage development program  

NASA Astrophysics Data System (ADS)

The results of a materials testing program for krypton-85 storage techniques are reported. Corrosion and stress corrosion tests were performed on a variety of materials including AISI 4130, Type 316 SS, Type 304 SS, Type 310 SS, Nitronic 50, and alloy A286. Test environments were high-purity liquid rubidium, liquid rubidium contaminated with oxygen, and rubidium hydroxide. Oxygen and water contaminations in liquid rubidium were found to greatly increase both general and localized corrosion of the materials tested. Alloy A286, Type 304 SS, and AISI 4130 were eliminated as candidate materials due to their susceptibility to general corrosion and stress corrosion cracking.

Nagata, P. K.

1981-04-01

108

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

109

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

110

Anomaly structure of supergravity and anomaly cancellation  

Microsoft Academic Search

We display the full anomaly structure of supergravity, including new contributions to the conformal anomaly. Our result has the super-Weyl and Kähler U(1), transformation properties that are required for implementation of the Green–Schwarz mechanism for anomaly cancellation.

Daniel Butter; Mary K. Gaillard

2009-01-01

111

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

112

Photoassociation spectroscopy of purely long-range krypton molecules  

NASA Astrophysics Data System (ADS)

Photoassociation spectra for purely long-range (PLR) krypton molecules are both computed and measured. The photoassociation laser is tuned just red of the 5s[3/2]2-5p[5/2]2 transition at 810.6 nm, over a frequency range in which fourteen different PLR potential wells support hundreds of vibrational bound states. In the experiment, laser light is directed into a cloud of magneto-optically trapped 84Kr atoms, and the emission of both ultraviolet photons and ions is monitored. Peaks in these signals are observed for laser frequencies within 200 MHz of the atomic resonance. Ongoing work is aimed at improving the experimental signal and understanding the degree of agreement between empirical data and computed molecular spectra.

Smith, Z.; Banister, J.; Norman, R.; Hoogeboom, K.; Walhout, M.

2009-11-01

113

Investigation of many-body forces in krypton and xenon  

SciTech Connect

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

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

1988-10-15

114

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

Microsoft Academic Search

Zusammenfassung Der radioaktive indifferente Luftbestandteil Krypton85 (in Ringer-Flüssigkeit) wird in die Arteria carotis communis injiziert und die Radioaktivität über der freigelegten Gehirnoberfläche verfolgt. Die Methode ergibt reproduzierbare quantitativecorticale Perfusionswerte und eignet sich auch für andere Gewebe.

N. A. Lassen; D. H. Ingvar

1961-01-01

115

Sheath oscillation characteristics and effect on near-wall conduction in a krypton Hall thruster  

NASA Astrophysics Data System (ADS)

Despite its affordability, the krypton Hall-effect thruster in applications always had problems in regard to performance. The reason for this degradation is studied from the perspective of the near-wall conductivity of electrons. Using the particle-in-cell method, the sheath oscillation characteristics and its effect on near-wall conduction are compared in the krypton and xenon Hall-effect thrusters both with wall material composed of BNSiO 2 . Comparing these two thrusters, the sheath in the krypton-plasma thruster will oscillate at low electron temperatures. The near-wall conduction current is only produced by collisions between electrons and wall, thereby causing a deficiency in the channel current. The sheath displays spatial oscillations only at high electron temperature; electrons are then reflected to produce the non-oscillation conduction current needed for the krypton-plasma thruster. However, it is accompanied with intensified oscillations.

Zhang, Fengkui; Kong, Lingyi; Li, Chenliang; Yang, Haiwei; Li, Wei

2014-11-01

116

Magnetic Anomalies over Iceland.  

PubMed

An aeromagnetic survey of Iceland reveals broad anomalies of large amplitude over zones of recent volcanic activity. The source of the anomalies is ascribed to large masses of basalt that have been coherently remagnetized by intrusive heating. A simple correlation of the Icelandic anomalies with those of the ocean floor therefore appears unjustified. PMID:17836657

Serson, P H; Hannaford, W; Haines, G V

1968-10-18

117

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

118

Analysis of spacecraft anomalies  

NASA Technical Reports Server (NTRS)

The anomalies from 316 spacecraft covering the entire U.S. space program were analyzed to determine if there were any experimental or technological programs which could be implemented to remove the anomalies from future space activity. Thirty specific categories of anomalies were found to cover nearly 85 percent of all observed anomalies. Thirteen experiments were defined to deal with 17 of these categories; nine additional experiments were identified to deal with other classes of observed and anticipated anomalies. Preliminary analyses indicate that all 22 experimental programs are both technically feasible and economically viable.

Bloomquist, C. E.; Graham, W. C.

1976-01-01

119

Anomaly detection using topology  

NASA Astrophysics Data System (ADS)

In this paper we present a new topology-based algorithm for anomaly detection in dimensionally large datasets. The motivating application is hyperspectral imaging where the dataset can be a collection of ~ 10 6 points in R k, representing the reflected (or radiometric) spectra of electromagnetic radiation. The algorithm begins by building a graph whose edges connect close pairs of points. The background points are the points in the largest components of this graph and all other points are designated as anomalies. The anomalies are ranked according to their distance to the background. The algorithm is termed Topological Anomaly Detection (TAD). The algorithm is tested on hyperspectral imagery collected with the HYDICE sensor which contains targets of known reflectance and spatial location. Anomaly maps are created and compared to results from the common anomaly detection algorithm RX. We show that the TAD algorithm performs better than RX by achieving greater separation of the anomalies from the background for this dataset.

Basener, Bill; Ientilucci, Emmett J.; Messinger, David W.

2007-04-01

120

Is the Accrual Anomaly a Global Anomaly?  

E-print Network

This paper investigates the subsequent return implications of accruals within a sample of large, developed, international equity markets and assesses whether similar institutional features account for the accrual anomaly ...

LaFond, Ryan

2005-09-23

121

The atmosphere of Mars near the surface - Isotope ratios and upper limits on noble gases  

NASA Technical Reports Server (NTRS)

Several analyses of the Martian atmosphere have been carried out with the mass spectrometer in the molecular-analysis experiment. The ratios of abundant isotopes of carbon and oxygen are within 10 per cent of terrestrial values, whereas nitrogen-15 is considerably enriched on Mars. Argon-38 has been detected, and new limits on abundances of krypton and xenon have been set. The limit on krypton is sufficiently low to suggest that the inventories of volatile substances on Mars and on earth may be distinctly different.

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

1976-01-01

122

First Detection of Krypton and Xenon in a White Dwarf  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

123

Modified effective range analysis of electron scattering from krypton  

NASA Astrophysics Data System (ADS)

The elastic cross sections for electron scattering on krypton from zero energy up to 10 eV have been analyzed by the modified effective range method. A simple model based on the analytical solution of the Schrödinger equation with the polarization potential using explicitly determined scattering phase shifts for the three lowest partial waves describes the elastic differential, integral and momentum transfer cross sections up to the energy threshold of the first inelastic process well. In detail, the contribution of the long-range polarization potential to the scattering phase shift is exactly expressed, while the contribution of the short-range effects is modelled by simple quadratic expressions (the effective range expansions). The effective range parameters are determined empirically by comparison with the latest experimental differential cross sections. Presently, the calculated integral and momentum transfer cross sections are validated against numerous electron scattering experiments and the most recent quantum-mechanical theories. To complete the picture, the two-term Boltzmann analysis is employed to determine the electron transport coefficients; the agreement with the electron swarm experimental data is found to be very good.

Fedus, Kamil

2014-10-01

124

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 Å2 with an exception near 70-80 eV.

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

2013-04-01

125

Krypton charge exchange cross sections for Hall effect thruster models  

SciTech Connect

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{sup +} + Kr and Kr{sup 2+} + Kr cross sections. The measurements of symmetric Kr{sup +} + Kr charge exchange are in good agreement with both the calculations including spin-orbit effects and previous measurements. For the symmetric Kr{sup 2+} + 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 Kr{sup 2+} + Kr {yields} Kr{sup +} + Kr{sup +} reaction show an onset near 12 eV, reaching cross sections near constant value of 1.6 A{sup 2} with an exception near 70-80 eV.

Hause, Michael L. [Institute for Scientific Research, Boston College, Chestnut Hill, Massachusetts 02159 (United States); Prince, Benjamin D.; Bemish, Raymond J. [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, New Mexico 87117 (United States)

2013-04-28

126

Quartz crystal microbalance studies of atomic scale friction of krypton on graphene  

NASA Astrophysics Data System (ADS)

The Quartz Crystal Microbalance (QCM) had been used to record adsorption and sliding friction data for molecularly thin krypton films, at 77K, on surfaces of single graphite layer (graphene) prepared under Ultra High Vacuum (UHV). Iron and nickel electrodes carbonized by reaction with CO at temperatures of about 375C and 400C respectively to produce graphene present varying surface quality. Adsorption isotherms of krypton were studied on graphene surfaces grown on iron, nickel and gold/nickel substrates. These have different lattice spacing. The adsorptions of krypton produce responses in the QCM mechanical properties that may be used to determine the formation of a monolayer adsorbate. At 77K, the krypton is known to adsorb on graphite surfaces forming two-dimensional phases which are in many respects, quite similar to the solid-gas phases encountered in the three-dimensional (bulk) substances. This work utilizes the static phase diagrams of such two-dimensional phases, in comparison to the dynamic phase change, to investigate the temperature rise at the sliding interface as a function of the sliding speed of the adsorbed krypton layer. The QCM data on graphene/nickel suggest that the temperature change of about IOK at the interface irrespective of the sliding velocity. Auger Electron Spectroscopy (AES) is used to determine the quality of surfaces.

Jaye, Cherno

127

Congenital Anomalies in Bulgaria  

Microsoft Academic Search

The paper presents data and analysis concerning congenital anomalies in Bulgaria. Assessment is based on statistical data\\u000a reported in the National Statistical Institute Yearbook: Health Protection and the Sofia registry of congenital anomalies\\u000a in the period 1996 – 1999. Forty subgroups of isolated congenital anomalies and congenital diseases, detectable at birth during\\u000a in the first year of life, have been

E. Terlemesian; S. Stoyanov

128

Noble gas abundance and isotope ratios in the atmosphere of Jupiter from the Galileo Probe Mass Spectrometer  

Microsoft Academic Search

The Galileo Probe Mass Spectrometer provided the first data on the noble gas mixing and isotope ratios in the Jovian atmosphere. These measurements and the comparison with solar values constrain models of Jupiter's formation. Significant refinements to the initially reported abundances of argon, krypton, and xenon have been enabled through post-encounter laboratory calibrations using a refurbished engineering unit mass spectrometer

P. R. Mahaffy; H. B. Niemann; A. Alpert; S. K. Atreya; J. Demick; T. M. Donahue; D. N. Harpold; T. C. Owen

2000-01-01

129

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

130

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

131

Self-organization in dc glow microdischarges in krypton: modelling and experiments  

NASA Astrophysics Data System (ADS)

Self-organized patterns of cathodic spots have been observed in microdischarges operated in xenon, but not in other gases. However, modelling has indicated that it is, in principle, possible to observe the patterns of spots in discharges operated in other gases provided that experimental conditions, in particular pressure, are right. In this work, self-organized patterns of cathodic spots are for the first time observed in dc glow microdischarges operated in a gas other than xenon: krypton. The experiments have been guided by the modelling. According to both the experiment and the modelling, patterns in krypton are similar to those found earlier in xenon, however occur at higher pressures.

Zhu, W.; Niraula, P.; Almeida, P. G. C.; Benilov, M. S.; Santos, D. F. N.

2014-10-01

132

Anomalies on orbifolds  

SciTech Connect

We discuss the form of the chiral anomaly on an S1/Z2 orbifold with chiral boundary conditions. We find that the 4-divergence of the higher-dimensional current evaluated at a given point in the extra dimension is proportional to the probability of finding the chiral zero mode there. Nevertheless the anomaly, appropriately defined as the five dimensional divergence of the current, lives entirely on the orbifold fixed planes and is independent of the shape of the zero mode. Therefore long distance four dimensional anomaly cancellation ensures the consistency of the higher dimensional orbifold theory.

Arkani-Hamed, Nima; Cohen, Andrew G.; Georgi, Howard

2001-03-16

133

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

134

Precision mass difference measurements in light rubidium and krypton isotopes utilizing beta-endpoints  

NASA Astrophysics Data System (ADS)

A technique for precise determination of ?- endpoints with an intrinsic germanium detector has been developed and checked with 27Si and 58Cu sources; QEC values of 5272 +/- 26, 8063 +/- 42 keV have been obtained for mass-separated samples of 77Rb, 75Rb and 77Kt, respectively. Mass surface systematics in this region have been examined and found to be consistent.

Moltz, D. M.; Toth, K. S.; Avignone, F. T.; Noma, H.; Ritchie, B. G.; Kern, B. D.

1982-06-01

135

Plasma parameters in a planar dc magnetron sputtering discharge of argon and krypton  

Microsoft Academic Search

The electron energy distribution function (EEDF) and plasma parameters in a planar dc magnetron sputtering discharge in argon and krypton were determined using a Langmuir probe. Two groups of electrons are observed in the discharge. The electron temperature of the cold electrons is roughly independent of the discharge pressure, while the electron temperature of the hot electrons decreases with increased

P. Sigurjonsson; J. T. Gudmundsson

2008-01-01

136

Quartz crystal microbalance studies of atomic scale friction of krypton on graphene  

Microsoft Academic Search

The Quartz Crystal Microbalance (QCM) had been used to record adsorption and sliding friction data for molecularly thin krypton films, at 77K, on surfaces of single graphite layer (graphene) prepared under Ultra High Vacuum (UHV). Iron and nickel electrodes carbonized by reaction with CO at temperatures of about 375C and 400C respectively to produce graphene present varying surface quality. Adsorption

Cherno Jaye

2006-01-01

137

Effective and accurate approach for modeling of commensurate-incommensurate transition in krypton monolayer on graphite  

NASA Astrophysics Data System (ADS)

Commensurate-incommensurate (C-IC) transition of krypton molecular layer on graphite received much attention in recent decades in theoretical and experimental researches. However, there still exists a possibility of generalization of the phenomenon from thermodynamic viewpoint on the basis of accurate molecular simulation. Recently, a new technique was developed for analysis of two-dimensional (2D) phase transitions in systems involving a crystalline phase, which is based on accounting for the effect of temperature and the chemical potential on the lattice constant of the 2D layer using the Gibbs-Duhem equation [E. A. Ustinov, J. Chem. Phys. 140, 074706 (2014)]. The technique has allowed for determination of phase diagrams of 2D argon layers on the uniform surface and in slit pores. This paper extends the developed methodology on systems accounting for the periodic modulation of the substrate potential. The main advantage of the developed approach is that it provides highly accurate evaluation of the chemical potential of crystalline layers, which allows reliable determination of temperature and other parameters of various 2D phase transitions. Applicability of the methodology is demonstrated on the krypton-graphite system. Analysis of phase diagram of the krypton molecular layer, thermodynamic functions of coexisting phases, and a method of prediction of adsorption isotherms is considered accounting for a compression of the graphite due to the krypton-carbon interaction. The temperature and heat of C-IC transition has been reliably determined for the gas-solid and solid-solid system.

Ustinov, E. A.

2014-10-01

138

Materials Screening Tests for the Krypton-85 Storage Development Program. Final Report.  

National Technical Information Service (NTIS)

The results of a materials testing program for krypton-85 storage techniques are reported. Corrosion and stress corrosion tests were performed on a variety of materials including AISI 4130, Type 316 SS, Type 304 SS, Type 310 SS, Nitronic 50, and alloy A28...

P. K. Nagata

1981-01-01

139

Effective and accurate approach for modeling of commensurate-incommensurate transition in krypton monolayer on graphite.  

PubMed

Commensurate-incommensurate (C-IC) transition of krypton molecular layer on graphite received much attention in recent decades in theoretical and experimental researches. However, there still exists a possibility of generalization of the phenomenon from thermodynamic viewpoint on the basis of accurate molecular simulation. Recently, a new technique was developed for analysis of two-dimensional (2D) phase transitions in systems involving a crystalline phase, which is based on accounting for the effect of temperature and the chemical potential on the lattice constant of the 2D layer using the Gibbs-Duhem equation [E. A. Ustinov, J. Chem. Phys. 140, 074706 (2014)]. The technique has allowed for determination of phase diagrams of 2D argon layers on the uniform surface and in slit pores. This paper extends the developed methodology on systems accounting for the periodic modulation of the substrate potential. The main advantage of the developed approach is that it provides highly accurate evaluation of the chemical potential of crystalline layers, which allows reliable determination of temperature and other parameters of various 2D phase transitions. Applicability of the methodology is demonstrated on the krypton-graphite system. Analysis of phase diagram of the krypton molecular layer, thermodynamic functions of coexisting phases, and a method of prediction of adsorption isotherms is considered accounting for a compression of the graphite due to the krypton-carbon interaction. The temperature and heat of C-IC transition has been reliably determined for the gas-solid and solid-solid system. PMID:25296827

Ustinov, E A

2014-10-01

140

Amorphization of -Thorium Phosphate Diphosphate (-TPD) irradiated with high energy krypton ions  

E-print Network

of nuclear wastes, the -Thorium Phosphate Diphosphate ceramic (-TPD), Th4(PO4)4P2O7, must be resistant as good candidates for nuclear waste immobilization [1-3]. Thorium Phosphate-Diphosphate (-TPD), -Th4(PO4Amorphization of -Thorium Phosphate Diphosphate (-TPD) irradiated with high energy krypton ions C

Paris-Sud XI, Université de

141

An Essential Hybrid Reasoning System: Knowledge and Symbol Level Accounts of KRYPTON  

Microsoft Academic Search

Hybrid inference systems are an important way to address the fact that intelligent systems have muiltifaceted rep- resentational and reasoning competence. KRYPTON is an experimental prototype that competently handles both terminological and assertional knowledge; these two kinds of information are tightly linked by having sentences in an assertional component be formed using structured com­ plex predicates denned in a complementary

Ronald J. Brachman; Victoria P. Gilbert; Hector J. Levesque

1985-01-01

142

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

Microsoft Academic Search

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

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

1971-01-01

143

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

Code of Federal Regulations, 2010 CFR

...tritium, krypton-85, or promethium-147 used in products primarily for frivolous purposes or in toys or adornments. [34 FR 9026, June 6, 1969, as amended at 40 FR 8785, Mar. 3, 1975; 43 FR 6921, Feb. 17, 1978; 52 FR 8241, Mar. 17, 1987;...

2010-01-01

144

An investigation into the influence of implanted oxygen on krypton behaviour in uranium dioxide during annealing  

NASA Astrophysics Data System (ADS)

It is generally agreed that fission gas release in hyperstoichiometric uranium dioxide is strongly influenced by the excess oxygen. However, the exact mechanisms have not been studied at the fundamental level. The aim of the work reported here was to obtain information on this topic by controlled experiments using an ion implantation approach rather than working with irradiated nuclear fuel. Krypton implants were used to create krypton bubbles in UO 2 samples to which oxygen was then added, again by implantation, to induce local changes in stoichiometry. The effect of the oxygen on subsequent krypton desorption was studied during annealing to high temperatures using transmission electron microscopy and thermal desorption spectroscopy. This combination of techniques on individual samples allowed bubble substructure changes to be followed and directly matched to the gas release measurements. Two clear effects of oxygen were seen. At around 1300 K, a new gas release stage was found; it appeared to be related to the 1600 K peak seen after Kr-only implants and could be attributed to the loss of near-surface krypton gas atom clusters, with accelerated migration in hyperstoichiometric UO 2. However, at higher temperatures the coarsening of bubbles in (Kr + O) regions was surprisingly suppressed with the bubbles appearing more uniform and smaller than in Kr-only areas. It is suggested that excess oxygen might form a complex bubble coating effectively pinning the bubbles to slow bubble migration.

Evans, J. H.; van Veen, A.; Westerduin, K. T.

1994-02-01

145

The QCD trace anomaly  

E-print Network

In this brief report we compare the predictions of a recent next-to-next-to-leading order hard-thermal-loop perturbation theory (HTLpt) calculation of the QCD trace anomaly to available lattice data. We focus on the trace anomaly scaled by T^2 in two cases: N_f=0 and N_f=3. When using the canonical value of mu = 2 pi T for the renormalization scale, we find that for Yang-Mills theory (N_f=0) agreement between HTLpt and lattice data for the T^2-scaled trace anomaly begins at temperatures on the order of 8 T_c while when including quarks (N_f=3) agreement begins already at temperatures above 2 T_c. In both cases we find that at very high temperatures the T^2-scaled trace anomaly increases with temperature in accordance with the predictions of HTLpt.

Jens O. Andersen; Lars E. Leganger; Michael Strickland; Nan Su

2011-06-02

146

Temperature Dependences of Kinetic Isotope Effects  

Microsoft Academic Search

Model-reaction calculations are used to investigate the expected incidence of temperature-dependence anomalies produced by the harmonic-vibrational contributions to kinetic isotope effects. These “anomalies” are defined as deviations from a smooth-monotonic log–log plot of isotopic rate-constant ratio vs temperature. Such deviations include inflections, extrema, and crossovers (inversions in direction with respect to the infinite-temperature, classical limit). The model systems studied represent

P. Christian Vogel; Marvin J. Stern

1971-01-01

147

Complex lymphatic anomalies.  

PubMed

Complex lymphatic anomalies include several diagnoses with overlapping patterns of clinical symptoms, anatomic location, imaging features, hematologic alterations, and complications. Lymphatic malformations likely arise through anomalous embryogenesis of the lymphatic system. Analysis of clinical, imaging, histologic, and hematologic features is often needed to reach a diagnosis. Aspiration of fluid collections can readily define fluid as chylous or not. The presence of chyle indicates dysfunction at the mesenteric or retroperitoneal level or above the cisterna chyli due to reflux. The imaging patterns of generalized lymphatic anomaly (GLA) and Gorham-Stout disease have been segregated with distinctive bone lesions and peri-osseous features. More aggressive histology (spindled lymphatic endothelial cells), clinical progression, hemorrhage, or moderate hematologic changes should raise suspicion for kaposiform lymphangiomatosis. Biopsy may be needed for diagnosis, though avoidance of rib biopsy is advised to prevent iatrogenic chronic pleural effusion. Lymphangiography can visualize the anatomy and function of the lymphatic system and may identify dysfunction of the thoracic duct in central conducting lymphatic anomalies. Local control and symptom relief are targeted by resection, laser therapy, and sclerotherapy. Emerging data suggest a role for medical therapies for complications of complex lymphatic anomalies. Outcomes include recurrent effusion, infection, pain, fracture, mortality, and rarely, malignancy. Complex lymphatic anomalies present significant diagnostic and therapeutic challenges. Results from a phase 2 study of sirolimus in these and other conditions are expected in 2014. Improved characterization of natural history, predictors of poor outcomes, responses to therapy, and further clinical trials are needed for complex lymphatic anomalies. PMID:25241096

Trenor, Cameron C; Chaudry, Gulraiz

2014-08-01

148

On isostatic geoid anomalies  

NASA Technical Reports Server (NTRS)

In regions of slowly varying lateral density changes, the gravity and geoid anomalies may be expressed as power series expansions in topography. Geoid anomalies in isostatically compensated regions can be directly related to the local dipole moment of the density-depth distribution. This relationship is used to obtain theoretical geoid anomalies for different models of isostatic compensation. The classical Pratt and Airy models give geoid height-elevation relationships differing in functional form but predicting geoid anomalies of comparable magnitude. The thermal cooling model explaining ocean floor subsidence away from mid-ocean ridges predicts a linear age-geoid height relationship of 0.16 m/m.y. Geos 3 altimetry profiles were examined to test these theoretical relationships. A profile over the mid-Atlantic ridge is closely matched by the geoid curve derived from the thermal cooling model. The observed geoid anomaly over the Atlantic margin of North America can be explained by Airy compensation. The relation between geoid anomaly and bathymetry across the Bermuda Swell is consistent with Pratt compensation with a 100-km depth of compensation.

Haxby, W. F.; Turcotte, D. L.

1978-01-01

149

Midface anomalies in children.  

PubMed

A variety of congenital midface anomalies occur in children. High-resolution computed tomography (CT) and magnetic resonance (MR) imaging have proved helpful in determining the nature and extent of dysplasia, thereby facilitating treatment planning. A classification system has been developed that groups these anomalies into four categories based on embryogenesis and anatomic location. These categories comprise anomalies that are related to the nasal cavity, nasofrontal region, nasolacrimal apparatus, and craniofacial syndromes. CT is the imaging modality of choice in children with possible choanal atresia, pyriform aperture stenosis, or anomalies of the nasolacrimal duct (eg, nasolacrimal duct stenosis, dacryocystoceles). MR imaging is the modality of choice in patients with congenital midface masses (eg, dermoid and epidermoid cysts, nasal gliomas, encephaloceles) and craniofacial syndromes (eg, Apert syndrome, Crouzon syndrome, Treacher Collins syndrome). In many cases, however, both CT and MR imaging are required to adequately evaluate midface anomalies. Familiarity with the characteristic imaging features of these anomalies along with knowledge of midface embryogenesis and normal developmental anatomy is essential to prevent misinterpretation of anatomic variations that may simulate disease. PMID:10903683

Lowe, L H; Booth, T N; Joglar, J M; Rollins, N K

2000-01-01

150

TUDE EXPRIMENTALE DES AILES DE LA RAIE 2 537 DU MERCURE PERTURBE PAR LE KRYPTON ET LE XNON  

E-print Network

831 �TUDE EXP�RIMENTALE DES AILES DE LA RAIE 2 537 � DU MERCURE PERTURB�E PAR LE KRYPTON ET LE mercure-krypton et vapeur de mercure-xénon sur un domaine spectral allant de 120 à 7 500 GHz de part et d mercure (6 'SO-6 3P1) perturbee par les gaz rares a deja fait l'objet de plusieurs travaux exp6rimentaux

Paris-Sud XI, Université de

151

Magnetic anomalies. [Magsat studies  

NASA Technical Reports Server (NTRS)

The implications and accuracy of anomaly maps produced using Magsat data on the scalar and vector magnetic field of the earth are discussed. Comparisons have been made between the satellite maps and aeromagnetic survey maps, showing smoother data from the satellite maps and larger anomalies in the aircraft data. The maps are being applied to characterize the structure and tectonics of the underlying regions. Investigations are still needed regarding the directions of magnetization within the crust and to generate further correlations between anomaly features and large scale geological structures. Furthermore, an increased data base is recommended for the Pacific Ocean basin in order to develop a better starting model for Pacific tectonic movements. The Pacific basin was large farther backwards in time and subduction zones surround the basin, thereby causing difficulties for describing the complex break-up scenario for Gondwanaland.

Harrison, C. G. A.

1983-01-01

152

Meteoritic Sulfur Isotopic Analysis  

NASA Astrophysics Data System (ADS)

Funds were requested to continue our program in meteoritic sulfur isotopic analysis. We have recently detected a potential nucleosynthetic sulfur isotopic anomaly. We will search for potential carriers. The documentation of bulk systematics and the possible relation to nebular chemistry and oxygen isotopes will be explored. Analytical techniques for delta33, delta34S, delta36S isotopic analysis were improved. Analysis ofmilligram samples is now possible. A possible relation between sulfur isotopes and oxygen was detected, with similar group systematics noted, particularly in the case of aubrites, ureilites and entstatite chondrites. A possible nucleosynthetic excess S-33 has been noted in bulk ureilites and an oldhamite separate from Norton County. High energy proton (approximately 1 GeV) bombardments of iron foils were done to experimentally determine S-33, S-36 spallogenic yields for quantitation of isotopic measurements in iron meteorites. Techniques for measurement of mineral separates were perfected and an analysis program initiated. The systematic behavior of bulk sulfur isotopes will continue to be explored.

Thiemens, Mark H.

1996-01-01

153

Meteoritic Sulfur Isotopic Analysis  

NASA Technical Reports Server (NTRS)

Funds were requested to continue our program in meteoritic sulfur isotopic analysis. We have recently detected a potential nucleosynthetic sulfur isotopic anomaly. We will search for potential carriers. The documentation of bulk systematics and the possible relation to nebular chemistry and oxygen isotopes will be explored. Analytical techniques for delta(sup 33), delta(sup 34)S, delta(sup 36)S isotopic analysis were improved. Analysis of sub milligram samples is now possible. A possible relation between sulfur isotopes and oxygen was detected, with similar group systematics noted, particularly in the case of aubrites, ureilites and entstatite chondrites. A possible nucleosynthetic excess S-33 has been noted in bulk ureilites and an oldhamite separate from Norton County. High energy proton (approximately 1 GeV) bombardments of iron foils were done to experimentally determine S-33, S-36 spallogenic yields for quantitation of isotopic measurements in iron meteorites. Techniques for measurement of mineral separates were perfected and an analysis program initiated. The systematic behavior of bulk sulfur isotopes will continue to be explored.

Thiemens, Mark H.

1996-01-01

154

Demonstrate the removal efficiency and capacity of MOF materials for krypton recovery  

SciTech Connect

Metal organic framework materials (MOFs) were developed and tested in support of the U.S. Department of Energy Office of Nuclear Energy, Fuel Cycle Technology Separations and Waste Forms Campaign. Specifically, materials are being developed for the removal of xenon (Xe) and krypton (Kr) from gaseous products of nuclear fuel reprocessing unit operations. Two metal organic framework structures were investigated in greater detail to demonstrate the removal efficiency and capacity of MOF materials for krypton recovery. Our two bed breakthrough measurements on NiDOBDC and FMOFCu indicate these materials can capture and separate parts per million levels of Xe and Kr from air. The removal efficiency and adsorption capacity for Kr on these two MOFs were further increased upon removal of Xe upfront.

Thallapally, Praveen K.; Liu, Jian; Strachan, Denis M.

2013-08-23

155

Krypton81m ventilation studies as a parameter for lung capacity after lobectomy  

Microsoft Academic Search

Spirometry and krypton-81m lung scans were performed in 17 patients before lobectomy was carried out for bronchogenic carcinoma to determine whether post-operative spirometric values could have been predicted from the pre-operative data. The patients were followed up at 3, 6 and 12 months post-operatively for lung function testing. It emerged from this study that good post-operative spirometric values could be

M. C. Bins; A. M. J. Wever; E. K. J. Pauwels; E. A. Velde

1984-01-01

156

High-Power Krypton Hall Thruster Technology Being Developed for Nuclear-Powered Applications  

NASA Technical Reports Server (NTRS)

The NASA Glenn Research Center has been performing research and development of moderate specific impulse, xenon-fueled, high-power Hall thrusters for potential solar electric propulsion applications. These applications include Mars missions, reusable tugs for low-Earth-orbit to geosynchronous-Earth-orbit transportation, and missions that require transportation to libration points. This research and development effort resulted in the design and fabrication of the NASA-457M Hall thruster that has been tested at input powers up to 95 kW. During project year 2003, NASA established Project Prometheus to develop technology in the areas of nuclear power and propulsion, which are enabling for deep-space science missions. One of the Project-Prometheus-sponsored Nuclear Propulsion Research tasks is to investigate alternate propellants for high-power Hall thruster electric propulsion. The motivation for alternate propellants includes the disadvantageous cost and availability of xenon propellant for extremely large scale, xenon-fueled propulsion systems and the potential system performance benefits of using alternate propellants. The alternate propellant krypton was investigated because of its low cost relative to xenon. Krypton propellant also has potential performance benefits for deep-space missions because the theoretical specific impulse for a given voltage is 20 percent higher than for xenon because of krypton's lower molecular weight. During project year 2003, the performance of the high-power NASA-457M Hall thruster was measured using krypton as the propellant at power levels ranging from 6.4 to 72.5 kW. The thrust produced ranged from 0.3 to 2.5 N at a discharge specific impulse up to 4500 sec.

Jacobson, David T.; Manzella, David H.

2004-01-01

157

The KLL dielectronic recombination processes for highly charged krypton, iodine and barium ions  

NASA Astrophysics Data System (ADS)

The KLL dielectronic recombination (DR) processes of ions from highly charged helium-like to oxygen-like krypton, iodine and barium ions are studied systematically in the relativistic distorted-wave approximation with configuration interaction. The KLL DR resonant energies, the corresponding resonant strengths and the theoretical spectra for each highly charged ion species are obtained. The results accord well with other available values. The behaviour of KLL resonant strengths for He-like ions with atomic number Z is analysed.

Yang, Jian-Hui; Zhang, Hong; Cheng, Xin-Lu

2010-06-01

158

Energy of the Quasi-free Electron in Argon and Krypton C. M. Evans1,  

E-print Network

Energy of the Quasi-free Electron in Argon and Krypton C. M. Evans1, and G. L. Findley2, 1 these data, a new local Wigner- Seitz model for the density dependent energy V0(P) of a quasi-free electron/medium polarization energy, and includes the thermal kinetic energy of the quasi-free electron. Using this model, V0(P

Findley, Gary L.

159

X-ray fluorescence and absorption analysis of krypton in irradiated nuclear fuel  

NASA Astrophysics Data System (ADS)

The analysis of krypton in irradiated uranium dioxide fuel has been successfully achieved by X-ray fluorescence and X-ray absorption. The present study focuses on the analytical challenge of sample and sub-sample production to perform the analysis with the restricted conditions dictated by the radioprotection regulations. It deals also with all potential interferences that could affect the quality of the measurement in fluorescence as well as in absorption mode. The impacts of all dissolved gases in the fuel matrix are accounted for the analytical result quantification. The krypton atomic environment is ruled by the presence of xenon. Other gases such as residual argon and traces of helium or hydrogen are negligible. The results are given in term of density for krypton (?3 nm-3) and xenon (?20 nm-3). The presence of dissolved, interstitial and nano-phases are discussed together with other analytical techniques that could be applied to gain information on fission gas behaviour in nuclear fuels.

Degueldre, Claude; Mieszczynski, Cyprian; Borca, Camelia; Grolimund, Daniel; Martin, Matthias; Bertsch, Johannes

2014-10-01

160

Chemical production of chondrule oxygen isotopic composition  

NASA Technical Reports Server (NTRS)

Defining the source of observed meteoritic O isotopic anomalies remains a fundamental challenge. The O isotopic composition of chondrules are particularly striking. There are at least three types of chemical processes that produce the isotopic compositions observed in chondrules and Ca-Al-rich inclusions (CAI's). The processes are rather general, viz, they require no specialized processes and the processes associated with chondrule production are likely to produce the observed compositions.

Thiemens, M. H.

1994-01-01

161

6, 88178870, 2006 Isotopic constraints  

E-print Network

) are ubiquitous in the atmo- sphere. Because of their high solubility and chemical stability, wet and dry with the current knowledge of isotopic anomaly transfers during chemical reactions. This failure calls quantification is difficult (Warneck, 2000). Light- ning, fossil fuel combustion, soil exhalation, biomass

Paris-Sud XI, Université de

162

The NEAR Rendezvous Burn Anomaly  

E-print Network

The NEAR Rendezvous Burn Anomaly of December 1998 Final Report of the NEAR (Near Earth Asteroid Report of the NEAR (Near Earth Asteroid Rendezvous) Anomaly Review Board November 1999 ©1999 The Johns .................................................................................................................................................... 4 Reconstructed Timeline

Rhoads, James

163

Global Climate Highlights and Anomalies  

NSDL National Science Digital Library

NOAA's Global Climate Highlights and Anomalies page offers weekly summaries of global climate highlights and anomalies (warm, cold, wet, dry). Areas experiencing climate anomalies are color-marked on a global map, followed by written summaries of each region's climate conditions. All weeks are posted for the year 2000 (to present), and a link points users to the complete 1999 archive.

1999-01-01

164

Microbeam titanium isotopic analysis by resonance ionization mass spectrometry  

SciTech Connect

The importance of isotopic anomalies in refractory inclusions in meteorites is well established. Measurements of the anomalies using conventional mass spectrometry are often rendered difficult, however, by isobarically interfering isotopes: for example, {sup 48}Ti and {sup 48}Ca. Resonance ionization mass spectrometry (RIMS) can substantially reduce isobaric interferences in a number of systems. We have employed RIMS for the in situ detection of Ti atoms sputtered from pure Ti metal and from several terrestrial oxides containing both Ti and Ca. Tunable lasers were employed to resonantly ionize neutral Ti atoms. We have chosen Ti specifically because of the importance of Ti isotopic anomalies in cosmochemistry.

Spiegel, D.R.; Davis, A.M.; Clayton, R.N. (Chicago Univ., IL (USA). Enrico Fermi Inst.); Pellin, M.J.; Calaway, W.F.; Burnett, J.W.; Coon, S.R.; Young, C.E.; Gruen, D.M. (Argonne National Lab., IL (USA))

1991-01-01

165

Mass Anomalies on Ganymede  

NASA Technical Reports Server (NTRS)

Radio Doppler data from two Ganymede encounters (G1 and G2) on the first two orbits in the Galileo mission have been analyzed previously for gravity information . For a satellite in hydrostatic equilibrium, its gravitational field can be modeled adequately by a truncated spherical harmonic series of degree two. However, a fourth degree field is required in order to fit the second Galileo flyby (G2). This need for a higher degree field strongly suggests that Ganymede s gravitational field is perturbed by a gravity anomaly near the G2 closest approach point (79.29 latitude, 123.68 west longitude). In fact, a plot of the Doppler residuals , after removal of the best-fit model for the zero degree term (GM) and the second degree moments (J2 and C22), suggests that if an anomaly exists, it is located downtrack of the closest approach point, closer to the equator.

Schubert, G.; Anderson, J. D.; Jacobson, R. A.; Lau, E. L.; Moore, W. B.; Palguta, J.

2004-01-01

166

Yearly Arctic Temperature Anomaly  

NSDL National Science Digital Library

This animation shows the yearly temperature anomaly over the Arctic region from 1981-82 through 2002-03. Years run from August 1 through July 31. Blue hues indicate cooling regions; red hues depict warming. Light regions indicate less change while darker regions indicate more. The temperature scale used ranges from -7.0 to +7.0 degrees Celsius in increments of .25 degrees. (See color bar below)

Starr, Cindy; Comiso, Josefino

2003-10-23

167

Satellite magnetic anomalies over subduction zones - The Aleutian Arc anomaly  

NASA Technical Reports Server (NTRS)

Positive magnetic anomalies seen in MAGSAT average scalar anomaly data overlying some subduction zones can be explained in terms of the magnetization contrast between the cold subducted oceanic slab and the surrounding hotter, nonmagnetic mantle. Three-dimensional modeling studies show that peak anomaly amplitude and location depend on slab length and dip. A model for the Aleutian Arc anomaly matches the general trend of the observed MAGSAT anomaly if a slab thickness of 7 km and a relatively high (induced plus viscous) magnetization contrast of 4 A/m are used. A second source body along the present day continental margin is required to match the observed anomaly in detail, and may be modeled as a relic slab from subduction prior to 60 m.y. ago.

Clark, S. C.; Frey, H.; Thomas, H. H.

1985-01-01

168

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

PubMed

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

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

2014-01-01

169

Secondary deuterium kinetic isotope effect for aquation, solvolysis, and isomerization reactions of trans-[Co(en)2(OSMe2)N3]2+, and the resolution of a mechanistic anomaly.  

PubMed

The two closely spaced NH signals in the (1)H NMR spectrum of trans-[Co(en)(2)(OSMe(2))(N(3))](2+) have been reassigned using 2D NMR and other techniques. Thus, the unusual syn to anti (to Co-N(3)) NH rearrangement on base catalyzed substitution of the selectively deuterated complex in ND(3)(l) has been reinterpreted as "normal", with inversion of the effective deprotonation site accompanying the act of substitution. The re-examination of this system required a repeat study of the secondary isotope effect for the acid hydrolysis reaction, previously used to assign syn and anti amine sites, and this has been extended to other solvents (Me(2)SO, MeCN). The relative NH proton exchange rates are also reconsidered. A systematic rate reduction for Me(2)SO substitution is observed for deuterium incorporation into the cis-NH centers, irrespective of whether these are syn or anti, and the effect is much greater in Me(2)SO than in water. The results are interpreted in terms of zero point energy effects and coupled vibrations. PMID:15074976

Jackson, W G

2004-04-19

170

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

171

Angular distribution of Auger electrons due to 3d-shell ionization of krypton  

NASA Technical Reports Server (NTRS)

Cross sections for electron impact ionization of krypton due to ejection of a 3rd shell electron have been calculated using screened hydrogenic and Hartree-Slater wave functions for target atom. While the total ionization cross sections in the two approximations are within 10% of each other, the Auger electron angular distribution, related to cross sections for specific magnetic quantum numbers of the 3rd electrons, is widely different in the two approximations. The angular distribution due to Hartree-Slater approximation is in excellent agreement with measurement. The physical reason for the discrepancies in the two approximations is explained.

Omidvar, K.

1977-01-01

172

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

E-print Network

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

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

2008-12-17

173

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

174

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

175

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.

176

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

177

Short wavelength laser calculations for electron pumping in neon-like krypton (Kr XXVII)  

NASA Technical Reports Server (NTRS)

Calculations of electron impact collision strengths and spontaneous radiative decay rates are made for neon-like krypton (Kr XXVII) for the 2s2 2p6, 2s2 2p5 3s, 2s2 2p5 3p, and 2s2 2p5 3d configurations. From these atomic data, the level populations as a function of the electron density are calculated at two temperatures, 1 x 10 to the 7th K and 3 x 10 to the 7th K. An analysis of level populations reveals that a volume of krypton in which a significant number of the ions are in the Kr XXVII degree of ionization can produce a significant gain in transition between the 2s2 2p5 3s and 2s2 2p5 3p configurations. At an electron density of 1 x 10 to the 19th/cu cm the plasma length has to be of the order of 1 m; at a density of 1 x 10 to the 21st/cu cm the length is reduced to approximately 0.5 cm; and at an electron density of 1 x 10 to the 22nd/cu cm the length of the plasma is further reduced to approximately 1 mm.

Feldman, U.; Bhatia, A. K.; Suckewer, S.

1983-01-01

178

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

179

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

180

Major coronary anomalies in childhood  

Microsoft Academic Search

Major coronary artery anomalies are extremely rare in childhood. We wanted to assess the historical and diagnostic features and the therapeutic options of three distinct types of coronary artery anomalies: abnormal origin of the left coronary artery from the pulmonary artery (ALCAPA), coronary fistula and coronary stenosis. In a retrospective study, 33 children with these types of coronary artery disease

Daniël Wolf; Tom Vercruysse; Bert Suys; Nico Blom; Dirk Matthys; Jaap Ottenkamp

2002-01-01

181

Anomaly detection in IP networks  

Microsoft Academic Search

Network anomaly detection is a vibrant research area. Researchers have approached this problem using various techniques such as artificial intelligence, machine learning, and state machine modeling. In this paper, we first review these anomaly detection methods and then describe in detail a statistical signal processing technique based on abrupt change detection. We show that this signal processing technique is effective

Marina Thottan; Chuanyi Ji

2003-01-01

182

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

183

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

184

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

E-print Network

Energy of the quasi-free electron in argon, krypton and xenon Xianbo Shi a,b , Luxi Li a,b , C. M ionization of the dopant, and (iii) the kinetic energy of the quasi-free electron. The polarization terms are determined by a standard statistical mechanical treatment. However, the kinetic energy of the quasi-free

Findley, Gary L.

185

Energy of the Quasi-free Electron in Supercritical Krypton near the Critical Point Luxi Li and C. M. Evans  

E-print Network

Energy of the Quasi-free Electron in Supercritical Krypton near the Critical Point Luxi Li and C. M by the quasi-free electron that arises from field ionization of the dopant, and the zero point kinetic energy of the free electron. The overall decrease in the shift of the dopant ionization energy near the critical

Evans, Cherice M.

186

Cosmogenic isotopes in the early solar system  

NASA Astrophysics Data System (ADS)

An analysis is presented of isotope anomalies in meteorites with reference to the role of cosmic rays in the early stages of the solar system; particular attention is given to abundances of rare-gas isotopes, especially neon isotopes. Several hypotheses as to the origin of isotope anomalies are presented, including the hypothesis of the explosion of a single supernova near the protosolar nebula, the hypothesis that the solar system was formed directly from the ejecta of a single supernova, and the nucleosynthesis model of Lavrukhina and Kuznetsova (1974). This latter hypothesis is based on the idea that shock waves that arise during the supernova explosion lead simultaneously to the acceleration of particles to relativistic energies (i.e., to the generation of cosmic rays) and to the fragmentation of atomic nuclei in supernova shells by accelerated particles.

Lavrukhina, A. K.

1981-04-01

187

Emission characteristics of pulse-periodic barrier-discharge plasma in a mixture of krypton with argon and liquid freon vapor  

NASA Astrophysics Data System (ADS)

Radiation of a nanosecond barrier discharge in a mixture of krypton, argon, and carbon-tetrachloride vapor is studied in the spectral range of 150-300 nm. The plasma radiation spectra and the dependences of the intensities of the 258 nm Cl2( D' ? A'), 222 nm KrCl( B ? X), and 175 nm ArCl( B ? X) bands on the partial pressure of liquid freon vapor, argon, and krypton, as well as on the discharge excitation conditions, are studied. The optimal compositions of gas mixtures for creating a broadband UV-VUV emitter based on the band system of argon chloride, krypton chloride, and chlorine molecule are determined.

Shuaibov, A. K.; Minya, A. I.; Gritsak, R. V.; Gomoki, Z. T.

2014-02-01

188

Chiral anomaly in soft collinear effective theory  

E-print Network

Anomalies have infrared and ultraviolet ingredients, and are often realized in effective theories in a nontrivial way. We study the chiral anomaly in soft collinear effective theory (SCET), where the anomaly equation has ...

Waalewijn, Wouter Jonathan

189

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

190

Reliability of CHAMP Anomaly Continuations  

NASA Technical Reports Server (NTRS)

CHAMP is recording state-of-the-art magnetic and gravity field observations at altitudes ranging over roughly 300 - 550 km. However, anomaly continuation is severely limited by the non-uniqueness of the process and satellite anomaly errors. Indeed, our numerical anomaly simulations from satellite to airborne altitudes show that effective downward continuations of the CHAMP data are restricted to within approximately 50 km of the observation altitudes while upward continuations can be effective over a somewhat larger altitude range. The great unreliability of downward continuation requires that the satellite geopotential observations must be analyzed at satellite altitudes if the anomaly details are to be exploited most fully. Given current anomaly error levels, joint inversion of satellite and near- surface anomalies is the best approach for implementing satellite geopotential observations for subsurface studies. We demonstrate the power of this approach using a crustal model constrained by joint inversions of near-surface and satellite magnetic and gravity observations for Maude Rise, Antarctica, in the southwestern Indian Ocean. Our modeling suggests that the dominant satellite altitude magnetic anomalies are produced by crustal thickness variations and remanent magnetization of the normal polarity Cretaceous Quiet Zone.

vonFrese, Ralph R. B.; Kim, Hyung Rae; Taylor, Patrick T.; Asgharzadeh, Mohammad F.

2003-01-01

191

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

192

Gravitational anomaly and transport phenomena.  

PubMed

Quantum anomalies give rise to new transport phenomena. In particular, a magnetic field can induce an anomalous current via the chiral magnetic effect and a vortex in the relativistic fluid can also induce a current via the chiral vortical effect. The related transport coefficients can be calculated via Kubo formulas. We evaluate the Kubo formula for the anomalous vortical conductivity at weak coupling and show that it receives contributions proportional to the gravitational anomaly coefficient. The gravitational anomaly gives rise to an anomalous vortical effect even for an uncharged fluid. PMID:21797593

Landsteiner, Karl; Megías, Eugenio; Pena-Benitez, Francisco

2011-07-01

193

Double shock front formation in cylindrical radiative blast waves produced by laser irradiation of krypton gas  

NASA Astrophysics Data System (ADS)

Radiative blast waves were created by irradiating a krypton cluster source from a supersonic jet with a high intensity femtosecond laser pulse. It was found that the radiation from the shock surface is absorbed in the optically thick upstream medium creating a radiative heat wave that travels supersonically ahead of the main shock. As the blast wave propagates into the heated medium, it slows and loses energy, and the radiative heat wave also slows down. When the radiative heat wave slows down to the transonic regime, a secondary shock in the ionization precursor is produced. This paper presents experimental data characterizing both the initial and secondary shocks and numerical simulations to analyze the double-shock dynamics.

Kim, I.; Quevedo, H. J.; Feldman, S.; Bang, W.; Serratto, K.; McCormick, M.; Aymond, F.; Dyer, G.; Bernstein, A. C.; Ditmire, T.

2013-12-01

194

Theory of Attosecond Transient Absorption Spectroscopy of Krypton for Overlapping Pump and Probe Pulses  

E-print Network

We present the first fully ab initio calculations for attosecond transient absorption spectroscopy of atomic krypton with overlapping pump and probe pulses. Within the time-dependent configuration interaction singles (TDCIS) approach, we describe the pump step (strong-field ionization using a near-infrared pulse) as well as the probe step (resonant electron excitation using an extreme- ultraviolet pulse) from first principles. We extent our TDCIS model and account for the spin-orbit splitting of the occupied orbitals. We discuss the spectral features seen in a recent attosecond transient absorption experiment [A. Wirth et al., Science 334, 195 (2011)]. Our results support the concept that the transient absorption signal can be directly related to the instantaneous hole population even during the ionizing pump pulse. Furthermore, we find strong deformations in the absorption lines when the overlap of pump and probe pulses is maximum. These deformations can be described by relative phase shifts in the oscillati...

Pabst, Stefan; Moulet, Antoine; Wirth, Adrian; Goulielmakis, Eleftherios; Santra, Robin

2012-01-01

195

Isotopic composition of waters from Ethiopia and Kenya: Insights into moisture sources for eastern Africa  

Microsoft Academic Search

Oxygen and deuterium isotopic values of meteoric waters from Ethiopia are unusually high when compared to waters from other high-elevation settings in Africa and worldwide. These high values are well documented; however, the climatic processes responsible for the isotopic anomalies in Ethiopian waters have not been thoroughly investigated. We use isotopic data from waters and remote data products to demonstrate

Naomi E. Levin; Edward J. Zipser; Thure E. Cerling

2009-01-01

196

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

197

1. Isotope Definitions and terms a) Isotopes and isotope ratios.  

E-print Network

3/24/2011 1 Outline 1. Isotope Definitions and terms a) Isotopes and isotope ratios. Isotopes fractionation c) Simple illustration with the water cycle 2. CO2 isotopes in photosynthesis a) Photosynthetic discrimination in C3 plants b) C3 vs C4 photosynthesis and the distinction in isotopes c) Measuring isotopic

Saleska, Scott

198

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

199

Isotopic composition and concentration of sulfur in carbonaceous chondrites  

NASA Technical Reports Server (NTRS)

New sulfur isotopic ratio measurements are reported for seven carbonaceous chondrites. Newly developed procedures permit measurement of delta S-33, delta S-34, and delta S-36 at precisions significantly greater than previously reported. A search for S-36 nucleosynthetic anomalies coproduced with anomalies in, for example, Ti-50 and Ca-48 was negative. The high endemic sulfur concentration probably dilutes any S-36 anomaly, and separation of individual sulfur phases may be needed to identify S-36 carrier phases. Large internal isotopic variations are observed, deriving from parent body and possibly nebular processes. Chondrule separates from Allende demonstrate isotopic compositions which vary as a function of diameter. High-temperature gas-solid exchange and a two-component mixing model may account for the observations. High-resolution isotopic data and structural information are reported for organic sulfur compounds separated by chemical extractions. The insoluble organics appear to be of either aliphatic or alicyclic structure and are dominant phases.

Gao, Xia; Thiemens, Mark H.

1993-01-01

200

Easter microplate evolution: Pb isotope evidence  

Microsoft Academic Search

We report on 53 Pb isotope analyses of basalts from 48 dredge stations occupied along the spreading boundaries of the Easter microplate and adjacent East Pacific Rise (EPR). Also included in the study are seven analyses of basalts from Easter and Sala y Gomez islands. A major anomaly is observed on the East Rift, around 27°S, where this ridge is

Barry B. Hanan; Jean-Guy Schilling

1989-01-01

201

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

202

Vacuum Pumping Performance Comparison of Non-Evaporable Getter Thin Films Deposited Using Argon and Krypton as Sputtering Gases  

Microsoft Academic Search

Owing to the outstanding vacuum performance and the low secondary electron yield, non-evaporable getter (NEG) thin film deposited onto interior walls has gained widespread acceptance and has been incorporated into many accelerator vacuum system designs. In this paper, the titanium-zirconium-vanadium NEG thin films were deposited onto interior wall of stainless pipes via DC magnetron sputtering method using argon and krypton

Xianghong Liu; M. Adam; Yun He; Yulin Li

2005-01-01

203

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

204

Astrometric Solar-System Anomalies  

E-print Network

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$^{-1}$. 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 prudent 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.

John D. Anderson; Michael Martin Nieto

2009-07-14

205

Spatio-temporal carbon isotope variation during the Ediacaran period in South China and its impact on bio-evolution  

Microsoft Academic Search

The Ediacaran period is characterized by the extremely negative carbon isotope anomalies and great biotic evolution in Earth\\u000a history. At least four negative carbon isotope anomalies have been reported from this interval in South China so far. It is\\u000a traditionally argued that the isotope variations can be used as a useful tool for global correlation of Ediacaran succession;\\u000a however, more

XinQiang Wang; XiaoYing Shi

2009-01-01

206

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

207

Measuring anomaly with algorithmic entropy  

NASA Astrophysics Data System (ADS)

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 determining whether a particular observation is anomalous. I propose a novel approach to anomaly detection using wavelet based algorithmic entropy that does not require modeling or large amounts of data. My method embodies the concept of information distance that rests on the fact that data encodes information. This distance is large when little information is shared, and small when there is greater information sharing. I compare my approach with several techniques in the literature using data obtained from testing of NASA's Space Shuttle Main Engines (SSME)

Solano, Wanda M.

208

Spacecraft environmental anomalies expert system  

NASA Technical Reports Server (NTRS)

A microcomputer-based expert system is being developed at the Aerospace Corporation Space Sciences Laboratory 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 and total radiation dose. These effects depend on the orbit of the satellite, the local environment (which is highly variable), the satellite exposure time and the hardness of the circuits and components of the satellite. The expert system is a rule-based system that uses the Texas Instruments Personal Consultant Plus expert system shell. The completed expert system knowledge base will include 150 to 200 rules, as well as a spacecraft attributes database, an historical spacecraft anomalies database, and a space environment database which is updated in near real-time. Currently, the expert system is undergoing development and testing within the Aerospace Corporation Space Sciences Laboratory.

Koons, H. C.; Gorney, D. J.

1988-01-01

209

Branchial Anomalies: Diagnosis and Management  

PubMed Central

Objective. To find out the incidence of involvement of individual arches, anatomical types of lesions, the age and sex incidence, the site and side of predilection, the common clinical features, the common investigations, treatment, and complications of the different anomalies. Setting. Academic Department of Otolaryngology, Head and Neck Surgery. Design. A 10 year retrospective study. Participants. 30 patients with clinically proven branchial anomalies including patients with bilateral disease totaling 34 lesions. Main Outcome Measures. The demographical data, clinical features, type of branchial anomalies, and the management details were recorded and analyzed. Results and Observations. The mean age of presentation was 18.67 years. Male to female sex ratio was 1.27?:?1 with a male preponderance. Of the 34 lesions, maximum incidence was of second arch anomalies (50%) followed by first arch. We had two cases each of third and fourth arch anomalies. Only 1 (3.3%) patients of the 30 presented with lesion at birth. The most common pathological type of lesions was fistula (58.82%) followed by cyst. 41.18% of the lesions occurred on the right side. All the patients underwent surgical excision. None of our patients had involvement of facial nerve in first branchial anomaly. All patients had tracts going superficial to the facial nerve. Conclusion. Confirming the extent of the tract is mandatory before any surgery as these lesions pass in relation to some of the most vital structures of the neck. Surgery should always be the treatment option. injection of dye, microscopic removal and inclusion of surrounding tissue while excising the tract leads to a decreased incidence of recurrence. PMID:24772172

Azeez, Arun; Thada, Nikhil Dinaker; Rao, Pallavi; Prasad, Kishore Chandra

2014-01-01

210

Second order transport from anomalies  

NASA Astrophysics Data System (ADS)

We study parity odd transport at second order in derivative expansion for a non-conformal charged fluid. We see that there are 27 parity odd transport coefficients, of which 12 are non-vanishing in equilibrium. We use the equilibrium partition function method to express 7 of these in terms of the anomaly, shear viscosity, charge diffusivity and thermodynamic functions. The remaining 5 are constrained by 3 relations which also involve the anomaly. We derive Kubo formulae for 2 of the transport coefficients and show these agree with that derived from the equilibrium partition function.

Bhattacharyya, Sayantani; David, Justin R.; Thakur, Somyadip

2014-01-01

211

Interplanetary Spaceflight Prehistory Flyby Anomalies in EGAs Search for Explanations Outlook Spacecraft Anomalies: An Update  

E-print Network

Interplanetary Spaceflight Prehistory Flyby Anomalies in EGAs Search for Explanations Outlook / 29 Spacecraft Anomalies: An Update #12;Interplanetary Spaceflight Prehistory Flyby Anomalies in EGAs Search for Explanations Outlook Overview 1 Interplanetary Spaceflight Swing-by Deep Space Network

Aste, Andreas

212

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

213

Hyperfine Field and Hyperfine Anomalies of Copper Impurities in Iron  

E-print Network

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 59-Cu, 69-Cu, and 71-Cu with magnetic moment values from collinear laser spectroscopy measurements on these isotopes. The resulting value, i.e., Bhf(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 59{\\Delta}69=0.15(9)% and 71{\\Delta}69=0.07(11)%.

V. V. Golovko; F. Wauters; S. Cottenier; M. Breitenfeldt; V. De Leebeeck; S. Roccia; G. Soti; M. Tandecki; E. Traykov; S. Van Gorp; D. Zákoucký; N. Severijns

2011-07-29

214

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...

215

Monitoring smartphones for anomaly detection  

Microsoft Academic Search

In this paper we demonstrate how to monitor a smartphone running Symbian OS in order to extract features that de- scribe the state of the device and can be used for anomaly detection. These features are sent to a remote server, be- cause running a complex intrusion detection system (IDS) on this kind of mobile device still is not feasible,

Aubrey-derrick Schmidt; Frank Peters; Florian Lamour; Sahin Albayrak

2008-01-01

216

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

217

2,0 superconformal anomaly.  

National Technical Information Service (NTIS)

The (2,0) supersymmetric Wess-Zumino-Polyakov, action is constructed and the (2,0) superconformal anomaly is given. The anomalous Ward-identity in the right sector is derived and the known operator product expansion of the N = 2 superstress energy tensor ...

T. Lhallabi

1992-01-01

218

Krypton atom and testing the limits of extreme-ultraviolet tunable-laser spectroscopy  

SciTech Connect

Measurements of several transitions in krypton carried out with a high-resolution extreme ultraviolet (xuv) laser source in 1987 were recently reanalyzed. This analysis, based on simulating the Doppler-broadened line shape of the iodine reference lines with new, greatly improved iodine reference data, yielded an order-of-magnitude improvement in the agreement between several {sup 86}Kr transition frequencies between 94.5 nm and 116.5 nm to {+-}5x10{sup -9}. The overall relative uncertainty is estimated to be {+-}6x10{sup -9}, which matches the best accuracies achieved in nanosecond short-wavelength experiments. The influence of frequency chirping in the pulsed dye amplifier chain was estimated to be rather low and to vary approximately between -7.1 MHz and +5.0 MHz for the three laser dyes used in this experiment. It is concluded that with an even more careful laser design the chirp-induced frequency shifts could be reduced to less than 1 MHz. Based on the analysis of the presumable chirp effects a correction for the {sup 86}Kr atlas by Kaufman and Humphries -0.055 53 cm{sup -1} is determined, which agrees with the result of a very recent two-photon experiment with frequency combs within just 0.000 46 cm{sup -1} (14 MHz), i.e., well within the combined errors of the three data sources involved in the intercomparison.

Trickl, T. [Forschungszentrum Karlsruhe, Institut fuer Meteorologie und Klimaforschung (IMK-IFU), Kreuzeckbahnstrasse 19, D-82467 Garmisch-Partenkirchen (Germany); Kung, A. H. [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei, Taiwan 10617 (China); Lee, Y. T. [Office of the President, Academia Sinica, Nankang, Taipei (China)

2007-02-15

219

Velocity selective bi-polarization spectroscopy for laser cooling of metastable Krypton atoms  

E-print Network

We report a velocity selective bi-polarization spectroscopy (VS-BPS) technique to generate a background-free, dispersion-like reference signal which is tunable over a wide range of frequency. In this technique, a pair of linearly polarized weak probe beams passing through a gas cell of metastable Krypton (Kr*) atoms, overlaps with a pair of counter-propagating circularly polarized strong pump beams derived from an independently tunable control laser. The polarization spectroscopy signals from the two probe beams, after subtraction, result in VS-BPS signal. The spectral shifting in VS-BPS signal can be achieved by tuning the frequency of the control laser. The dependence of the amplitude and slope of the VS-BPS signal on the RF power used for excitation of Kr atoms in the gas cell and on the power of pump beams has been studied. The frequency stability of a diode laser locked with VS-BPS signal has been found to be better than the frequency stability of the laser locked with a saturated absorption spectroscopy...

Kale, Y B; Singh, S; Mishra, S R; Rawat, H S

2014-01-01

220

Pulsed power considerations for electron beam pumped krypton fluoride lasers for inertial confinement fusion applications  

SciTech Connect

The Los Alamos National Laboratory inertial confinement fusion (ICF) program is developing the krypton-fluoride excimer laser for use as an ICF driver. The KrF laser has a number of inherent characteristics that make it a promising driver candidate, such as short wavelength (0.25 {mu}m), broad bandwidth to target (>100 cm{sup {minus}1}), pulse-shaping with high dynamic range, and the potential for high overall efficiency (>5%) and repetitive operation. The large KrF laser amplifiers needed for ICF drivers are electron-beam pumped. A key issue for all laser ICF drivers is cost, and a leading cost component of a KrF laser driver is associated with the pulsed power and electron diode. Therefore, the efficient generation of electron beams is a high priority. The Los Alamos ICF program is investigating pulsed-power and diode designs and technologies to further the development of affordable KrF laser ICF drivers. 12 refs., 8 figs.

Rose, E.A.; McDonald, T.E.; Rosocha, L.A.; Harris, D.B.; Sullivan, J.A. (Los Alamos National Lab., NM (USA)); Smith, I.D. (Pulse Sciences, Inc., San Leandro, CA (USA))

1991-01-01

221

A megajoule class krypton fluoride amplifier for single shot, high gain ICF application  

SciTech Connect

A design study is underway to define the optimal architecture for a KrF laser system which will deliver 10 MJ of 248-nm light to an ICF target. We present one approach which incorporates final power amplifiers in the megajoule class, achieving 10 MJ with four final amplifiers. Each double-pass laser amplifier employs two-sided electron-beam pumping of the laser gas medium. Details of the design are based on a Monte-Carlo electron-beam deposition code, a one-dimensional, time-dependent kinetics code, and pulsed power circuit modeling. Linear dimensions of the amplifier's extracted gain volume are 6.25 m in height and length and 5.12 m in width. Each amplifier handles 160 angularly multiplexed laser channels. The one-amagat, krypton-rich laser medium is e-beam pumped at 60-kW cm/sup /minus/3/ (4-MA at3.3-MV) over the 2-microsecond duration of the laser beam pulse train. 5 refs., 4 figs.

Rose, E.; Hanson, D.; Krohn, B.; McLeod, J.; Kang, M.

1988-01-01

222

Determination of regional esophageal transit in children by means of krypton-8 1m  

SciTech Connect

Radionuclide methods using Tc-99m have been developed in the last few years for the assessment of the esophageal transit. The method is physiologic, easy to perform and giving thus interesting informations concerning the severity of the disease as well as the effect of the applied treatment. In children, however, one is limited by radiation protection considerations, and the results are often of poor quality due to the low count rate. Furthermore, the risk of external contamination and the impossibility of repeating the test constitute significant disadvantages, particularly in young children. These problems are completely avoided by using Krypton-8lm diluted in a glucose solution. For each swallowing about 8 mCi of Kr-8 lm are administered. Sixty one-second frames are recorded and several parameters of regional transit can be extracted in a few minutes, using time activity curves and parametric images. The test is very sensitive in detecting minor regional transit alterations. The reproducibility of the test is good and phenomenons like intercurrent gastro-esophageal reflux or asynergic peristaltic waves can easily be detected. The test has been applied to 52 children, aged 1 week to 19 years, and provided helpful information concerning the localization and the importance of transit abnormalities in caustic and peptic esophagitis, postoperative cases (atresia or antireflux plasty) and in patients with neuromuscular disorders.

Piepsz, A.; Ham, H.R.; Georges, B.; Delaet, M.H.; Cadranel, S.

1984-01-01

223

Resonance-enhanced multiple ionization of krypton at an x-ray free-electron laser  

NASA Astrophysics Data System (ADS)

The sequential inner-shell multiple ionization of krypton was investigated at the Linac Coherent Light Source using ion time-of-flight spectroscopy at photon energies above (2 keV) and below (1.5 keV) the L edge with two x-ray pulse lengths (5 and 80 fs, nominally) and various pulse energies. At 2.5 mJ pulse energy, charge states up to Kr17+ were recorded for M-shell ionization and charge states up to Kr21+ for L-shell ionization. Comparing the experimental charge state distribution to Monte Carlo rate-equation calculations, we find a strong enhancement of higher charge states at 2 keV photon energy as compared to the theoretical predictions. This enhancement is explained with a resonant ionization pathway where multiple excitations into outer valence and Rydberg orbitals are followed by autoionization. These resonant pathways play an important role for the photoionization of ions with charge higher than Kr12+, for which direct one-photon L-shell photoionization is energetically impossible at 2 keV photon energy. Only a small pulse-length dependence of the charge state yield is observed at an x-ray pulse energy of 0.4 mJ.

Rudek, Benedikt; Rolles, Daniel; Son, Sang-Kil; Foucar, Lutz; Erk, Benjamin; Epp, Sascha; Boll, Rebecca; Anielski, Denis; Bostedt, Christoph; Schorb, Sebastian; Coffee, Ryan; Bozek, John; Trippel, Sebastian; Marchenko, Tatiana; Simon, Marc; Christensen, Lauge; De, Sankar; Wada, Shin-ichi; Ueda, Kiyoshi; Schlichting, Ilme; Santra, Robin; Ullrich, Joachim; Rudenko, Artem

2013-02-01

224

Status of the Level 0 Trigger Processor of the NA62 Liquid Krypton Electromagnetic Calorimeter  

NASA Astrophysics Data System (ADS)

The NA62 experiment at the CERN SPS aims to measure the Branching Ratio of the ultra-rare decay K^+ rightarrow ?^+?bar?, collecting about 100 events in two years of data taking with a signal to background ratio of 10:1. A hermetic photon veto system has been designed to efficiently reject the ?0 background, one of the main background sources, and the 20-ton liquid krypton calorimeter is a fundamental component of such system in the angular acceptance region 1-10 mrad. In this paper, we present the design of the Level 0 trigger processor that is able to identify electromagnetic clusters in the calorimeter providing information on time, position and energy reconstruction for each cluster. In particular, it is composed of 36 readout boards (TEL62), organized in a three layer parallel system, 108 mezzanines and 215 high-performance FPGAs. The system has been designed to sustain an instantaneous hit rate of 40 MHz, to process data with a latency of about 100 ?s, and to achieve a time resolution of 1.5 ns on the single cluster. Performance and functionality test results of a trigger slice, together with an updated status report of the whole level 0 trigger project, will be presented.

Bonaiuto, V.; de Simone, N.; Federici, L.; Sargeni, F.; Badoni, D.; Fucci, A.; Paoluzzi, G.; Salamon, A.; Salina, G.; Santovetti, E.; Checcucci, B.; Papi, A.; Piccini, M.; Bizzarri, M.; Venditti, S.

2014-06-01

225

Effect of Grain Boundaries on Krypton Segregation Behavior in Irradiated Uranium Dioxide  

NASA Astrophysics Data System (ADS)

Fission products, such as krypton (Kr), are known to be insoluble within UO2, segregating toward grain boundaries and eventually leading to a lowering in thermal conductivity and fuel swelling. Recent computational studies have identified that differences in grain boundary structure have a significant effect on the segregation behavior of fission products. However, experimental work supporting these simulations is lacking. Atom probe tomography was used to measure the Kr distribution across grain boundaries in UO2. Polycrystalline depleted UO2 samples were irradiated with 0.7 MeV and 1.8 MeV Kr-ions and annealed to 1000°C, 1300°C, and 1600°C for 1 h to produce a Kr-bubble dominated microstructure. The results of this work indicate a strong dependence of Kr concentration as a function of grain boundary structure. Temperature also influences grain boundary chemistry with greater Kr concentration evident at higher temperatures, resulting in a reduced Kr concentration in the bulk. Although Kr segregation takes place at elevated temperatures, no change in grain size or texture was observed in the irradiated UO2 samples.

Valderrama, Billy; He, Lingfeng; Henderson, Hunter B.; Pakarinen, Janne; Jaques, Brian; Gan, Jian; Butt, Darryl P.; Allen, Todd R.; Manuel, Michele V.

2014-11-01

226

Velocity selective bipolarization spectroscopy for laser cooling of metastable krypton atoms  

NASA Astrophysics Data System (ADS)

We report a velocity selective bi-polarization spectroscopy (VS-BPS) technique to generate a background-free, dispersion-like reference signal which is tunable over a wide range of frequency. In this technique, a pair of linearly polarized weak probe beams passing through a gas cell of metastable Krypton (Kr*) atoms, overlaps with a pair of counter-propagating circularly polarized strong pump beams derived from an independently tunable control laser. The polarization spectroscopy signals from the two probe beams, after subtraction, result in VS-BPS signal. The spectral shifting in VS-BPS signal can be achieved by tuning the frequency of the control laser. The dependence of the amplitude and slope of the VS-BPS signal on the RF power used for excitation of Kr atoms in the gas cell and on the power of pump beams has been studied. The frequency stability of a diode laser locked with VS-BPS signal has been found to be better than the frequency stability of the laser locked with a saturated absorption spectroscopy (SAS) signal. The VS-BPS signal is finally used for stabilization and tuning of the cooling laser frequency for a magneto-optical trap (MOT) for Kr* atoms.

Kale, Y. B.; Tiwari, V. B.; Singh, S.; Mishra, S. R.; Rawat, H. S.

2014-11-01

227

Probing the Isotopic Composition of Surface Waters Across Isotopic Extremes of Cryogenian Carbonates  

NASA Astrophysics Data System (ADS)

Neoproterozoic carbonate strata record unusually large and positive carbon isotope values (?13Ccarb from 4 to 10 per mil), and stratigraphically extensive large negative carbon isotope excursions (?13Ccarb < -5 per mil). Mechanisms that account for the magnitude, the facies distribution and the global abundance of these isotopically extreme carbonates in Neoproterozoic successions remain poorly understood. Little is also known about organisms and metabolisms that cycled carbon in these carbonate strata, because they rarely contain well-preserved organic-rich fossils. To better understand the cycling of carbon during the deposition of the 715-635 Ma Tayshir member of the Tsagaan Oloom Formation, Mongolia, we analyzed ?13Cfossil of two types of organic fossils that occur in 13C- enriched carbonates (+ 5 to 9.9 per mil) and within 13C-depleted carbonates of the Tayshir anomaly (-3 to -6 per mil). Because these organic microfossils are remarkably similar to the tests of modern planktonic, herbivorous tintinnid ciliates and benthic macroscopic red algae, respectively, they can be used as tracers of organic matter production in surface waters. Fossil tests were extracted by acid maceration, cleaned and analyzed morphologically and microscopically. Their carbon isotopic composition was measured using a nano-scaled elemental analyzer inlet (nano-EA-IRMS), with ±1 per mil analytical precision. To date, we analyzed 12 samples of 100-150 organic tests, representing 3 different fossiliferous parts of the Tayshir anomaly (?13Ccarb < -3 per mil) and 3 different strata predating the Tayshir anomaly (?13Ccarb > +5 per mil), respectively. More samples, including those of fossil algae and tests from the carbonate strata overlying the Tayshir anomaly, are currently being analyzed. Initial data reveal a rather constant isotopic composition of organic carbon in fossil tests (?13Cfossil), with values of -23 ±1 per mil both within 13C-enriched and 13C-depleted carbonates. The isotopic difference between ?13Cfossil and 13C-enriched carbonates is 28 to 30 per mil, suggesting maximal isotopic fractionation by primary producers, and little environmental (or diagenetic) processing of primary photosynthetic carbon. The carbonates of the Tayshir anomaly preserve two organic materials: matrix or bulk carbon characterized by a ?13Corg that covaries with ?13Ccarb, and a small, but morphologically diagnostic component whose ?13Cfossil values do not covary with ?13Ccarb. The stratigraphic thickness (~ 50 m) and isotopic heterogeneity of the organic matter within the Tayshir anomaly (~ 50 m) suggest a prolonged and large contribution of organic carbon remineralization.

Bosak, T.; Matys, E. D.; Bird, L. R.; Macdonald, F. A.; Freeman, K. H.

2012-12-01

228

Evidence of magnetic isotope effects during thermochemical sulfate reduction.  

PubMed

Thermochemical sulfate reduction experiments with simple amino acid and dilute concentrations of sulfate reveal significant degrees of mass-independent sulfur isotope fractionation. Enrichments of up to 13‰ for (33)S are attributed to a magnetic isotope effect (MIE) associated with the formation of thiol-disulfide, ion-radical pairs. Observed (36)S depletions in products are explained here by classical (mass-dependent) isotope effects and mixing processes. The experimental data contrasts strongly with multiple sulfur isotope trends in Archean samples, which exhibit significant (36)S anomalies. These results support an origin other than thermochemical sulfate reduction for the mass-independent signals observed for early Earth samples. PMID:21997216

Oduro, Harry; Harms, Brian; Sintim, Herman O; Kaufman, Alan J; Cody, George; Farquhar, James

2011-10-25

229

Lunar and Planetary Science XXXV: Isotopes in Meteorites  

NASA Technical Reports Server (NTRS)

The session"Isotopes in Meteorites" consisted of the following presentations:The Common Property of Isotopic Anomalies in Meteorites; Revised Production Rates for 22Na and 54Mn in Meteorites Using Cross Sections Measured for Neutron-induced Reactions; Modeling of 14C and 10Be Production Rates in Meteorites and Lunar Samples; Investigating Xenon Isotopic Fractionation During Rayleigh-type Distillation; The Mean Life Squared Relationship for Abundances of Extinct Radioactivities; and Magnesium Isotopic Fractionation of Forsterite During Evaporation from Different Crystallographic Surfaces.

2004-01-01

230

MAGSAT scalar and vector anomaly data analysis  

NASA Technical Reports Server (NTRS)

Efforts on the analysis of MAGSAT scalar anomaly data, the application of the scalar analysis results to three component vector data, and the comparison of MAGSAT data with corresponding MAGNET aeromagnetic and free air gravity anomaly data are briefly described.

1982-01-01

231

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. PMID:24014975

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

2013-01-01

232

Congenital bone anomalies associated with lipomas  

Microsoft Academic Search

Congenital bone anomalies are occasionally located adjacent to deep lipomas. These bone dysplasias may take the form of localized overgrowth or osseous malformation. Two patients with iliac anomalies and spinal dysraphism and one with a hypertrophied rib and vertebra associated with lipomas are described. As both the lipomas and osseous anomalies tend to lie in the same sensory nerve distribution,

James M. Sauer; M. B. Ozonoff

1985-01-01

233

Refining the anomaly consistency condition  

NASA Astrophysics Data System (ADS)

In the extended antifield formalism, a quantum BRST differential for anomalous gauge theories is constructed. Local BRST cohomological classes are characterized, in addition to the form degree and the ghost number, by the length of their descents and of their lifts, and this both in the standard and the extended antifield formalism. It is shown that during the BRST invariant renormalization of a local BRST cohomological class, the anomaly that can appear is constrained to be a local BRST cohomological class with a shorter descent and a longer lift than the given class. As an application of both results, a simple approach to the Adler-Bardeen theorem for the non-Abelian gauge anomaly is proposed. It applies independently of the gauge fixing, of power counting restrictions, and does not rely on the use of the Callan-Symanzik equation.

Barnich, Glenn

2000-08-01

234

Survey of Anomaly Detection Methods  

SciTech Connect

This survey defines the problem of anomaly detection and provides an overview of existing methods. The methods are categorized into two general classes: generative and discriminative. A generative approach involves building a model that represents the joint distribution of the input features and the output labels of system behavior (e.g., normal or anomalous) then applies the model to formulate a decision rule for detecting anomalies. On the other hand, a discriminative approach aims directly to find the decision rule, with the smallest error rate, that distinguishes between normal and anomalous behavior. For each approach, we will give an overview of popular techniques and provide references to state-of-the-art applications.

Ng, B

2006-10-12

235

Monitoring Smartphones for Anomaly Detection  

Microsoft Academic Search

In this paper we demonstrate how to monitor a smartphone running Symbian operating system and Windows Mobile in order to extract\\u000a features for anomaly detection. These features are sent to a remote server because running a complex intrusion detection system\\u000a on this kind of mobile device still is not feasible due to capability and hardware limitations. We give examples on

Aubrey-derrick Schmidt; Frank Peters; Florian Lamour; Christian Scheel; Seyit Ahmet Çamtepe; Sahin Albayrak

2009-01-01

236

Bart syndrome with associated anomalies.  

PubMed

Bart syndrome is an inherited condition characterized by epidermolysis bullosa and congenital absence of skin. It has been associated with other anomalies including pyloric atresia. The genetic abnormality has been linked to chromosome 3, with an autosomal dominant pattern of inheritance. We present a case of Bart syndrome that was associated with pyloric atresia. The literature is reviewed pertaining to this unusual association. Recommendations are offered regarding genetic counseling and anticipatory guidance for affected families. PMID:16215923

Bart, Bruce J; Lussky, Richard C

2005-10-01

237

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

238

Dyslexia: Anomaly or normal variation?  

Microsoft Academic Search

This paper is an interim report on a large-scale survey. The background to the authors’ research into dyslexia is briefly\\u000a outlined. Next comes an explication of the contrast between “anomaly” and “normal variation.” Some details are then provided\\u000a of a survey of 12,905 children, age ten, who were given a variety of educational and cognitive tests relevant to a diagnosis

T. R. Miles; Mary N. Haslum

1986-01-01

239

Cloacal anomaly with bladder tumor  

PubMed Central

A rare case of squamous cell carcinoma of bladder occurring in a 36-year-old female with persistent cloacal anomaly who presented with frequency, urgency, dysuria, and recurrent urinary tract infection is reported. Contrast Enhanced Computed Tomography with three dimensional reconstruction showed presence of bladder tumor and persistent cloaca. She underwent pelvic exenteration and wet colostomy. Histopathologic findings revealed locally advanced moderately differentiated squamous cell carcinoma. PMID:23956519

Seth, Amlesh; Ram, Ishwar

2013-01-01

240

Columbus Payloads Flow Rate Anomalies  

NASA Technical Reports Server (NTRS)

The Columbus Active Thermal Control System (ATCS) is the main thermal bus for the pressurized racks working inside the European laboratory. One of the ATCS goals is to provide proper water flow rate to each payload (P/L) by controlling actively the pressure drop across the common plenum distribution piping. Overall flow measurement performed by the Water Pump Assembly (WPA) is the only flow rate monitor available at system level and is not part of the feedback control system. At rack activation the flow rate provided by the system is derived on ground by computing the WPA flow increase. With this approach, several anomalies were raised during these 3 years on-orbit, with the indication of low flow rate conditions on the European racks FSL, BioLab, EDR and EPM. This paper reviews the system and P/Ls calibration approach, the anomalies occurred, the engineering evaluation on the measurement approach and the accuracy improvements proposed, the on-orbit test under evaluation with NASA and finally discusses possible short and long term solutions in case of anomaly confirmation.

Quaranta, Albino; Bufano, Gaetana; DePalo, Savino; Holt, James M.; Szigetvari, Zoltan; Palumberi, Sergio; Hinderer, S.

2011-01-01

241

Solvation of fluoroform and fluoroform-dimethylether dimer in liquid krypton: A theoretical cryospectroscopic study  

NASA Astrophysics Data System (ADS)

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-H...O 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. C...Kr distance dependence shows appreciable fluctuations and even changes in sign at R values close to the maximum of the C...Kr 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.

Kohls, Emilija; Mishev, Anastas; Pejov, Ljup?o

2013-08-01

242

Studies on the photochemical and thermal dissociation synthesis of krypton difluoride  

SciTech Connect

Like dioxygen difluoride (O{sub 2}F{sub 2}), KrF{sub 2} can be produced by thermal dissociation or photochemical synthesis from the elements; however, the yields are invariably much less than those obtained for O{sub 2}F{sub 2}. For example, while irradiation of liquid O{sub 2}/F{sub 2} mixtures at {minus}196{degrees}C through a sapphire window with an unfiltered 1,000W uv lamp provides in excess of 3g of O{sub 2}F{sub 2} per hour, the yield of KrF{sub 2} under identical circumstances is approximately 125 mg/hr. In this report, the yield of KrF{sub 2} in quartz and Pyrex{trademark} photochemical reactors has been examined as a function of irradiation wavelength, irradiation power, and Kr: F{sub 2} mole ratio. The uv-visible spectrum of KrF{sub 2} has also been recorded for comparison with earlier work, and the quantum yield for photodissociation at two wavelengths determined. The synthesis of KrF{sub 2} using large thermal gradients has also been examined using resistively heated nickel filaments to thermally dissociate the F{sub 2} in close proximity to liquid nitrogen-cooled metal surfaces. As a net result, KrF{sub 2} has been produced in yields in excess of 1.75 g/hr for extended periods in photochemical systems, and 2.3 g/hr for shorter periods in thermally dissociative reactors. This paper summarizes the results of examining parametrically several different types of reactors for efficiency of producing krypton difluoride.

Kinkead, S.A.; FitzPatrick, J.R.; Foropoulos, J. Jr.; Kissane, R.J.; Purson, J.D.

1993-08-01

243

Isotope spectroscopy  

NASA Astrophysics Data System (ADS)

The measurement of isotopic ratios provides a privileged insight both into nucleosynthesis and into the mechanisms operating in stellar envelopes, such as gravitational settling. In this article, we give a few examples of how isotopic ratios can be determined from high-resolution, high-quality stellar spectra. We consider examples of the lightest elements, H and He, for which the isotopic shifts are very large and easily measurable, and examples of heavier elements for which the determination of isotopic ratios is more difficult. The presence of 6Li in the stellar atmospheres causes a subtle extra depression in the red wing of the 7Li 670.7 nm doublet which can only be detected in spectra of the highest quality. But even with the best spectra, the derived 6Li abundance can only be as good as the synthetic spectra used for their interpretation. It is now known that 3D non-LTE modelling of the lithium spectral line profiles is necessary to account properly for the intrinsic line asymmetry, which is produced by convective flows in the atmospheres of cool stars, and can mimic the presence of 6Li. We also discuss briefly the case of the carbon isotopic ratio in metal-poor stars, and provide a new determination of the nickel isotopic ratios in the solar atmosphere.

Caffau, E.; Steffen, M.; Bonifacio, P.; Ludwig, H.-G.; Monaco, L.; Lo Curto, G.; Kamp, I.

2014-01-01

244

6d, Coulomb branch anomaly matching  

NASA Astrophysics Data System (ADS)

6d QFTs are constrained by the analog of 't Hooft anomaly matching: all anomalies for global symmetries and metric backgrounds are constants of RG flows, and for all vacua in moduli spaces. We discuss an anomaly matching mechanism for 6d theories on their Coulomb branch. It is a global symmetry analog of Green-Schwarz-West-Sagnotti anomaly cancellation, and requires the apparent anomaly mismatch to be a perfect square, . Then ? I 8 is cancelled by making X 4 an electric/magnetic source for the tensor multiplet, so background gauge field instantons yield charged strings. This requires the coefficients in X 4 to be integrally quantized. We illustrate this for theories. We also consider the SCFTs from N small E8 instantons, verifying that the recent result for its anomaly polynomial fits with the anomaly matching mechanism.

Intriligator, Kenneth

2014-10-01

245

Oxygen Isotopic Compositions of Fulgurites  

NASA Astrophysics Data System (ADS)

Two occurrences of vitreous rocks (fulgurites) that have resulted from the fusion of Etnean lavas, have been ascribed to the result of lightning striking the basalts and melting fresh volcanic rocks [1]. Rapidly quenched melts appear as tubular cavities that preserve the path of the discharge. Glass droplets (D <= 500 micrometers) are always dispersed around the fused lava tube and show several petrographic similarities with chondrules found in ordinary chondrites (presence of melilite, radiating skeletal fassaite, etc). In this process, high temperatures (T>1800 K) have probably been reached during timescales <=10 sec. Because it has been suggested that lightning discharges may have played an important role in the formation of chondrules [2], we have analyzed the oxygen isotope compositions of these fulgurites (our experimental protocol is described elsewhere [3]). The glass (free from any contamination from the unmelted basalt) is 1.5o/oo depleted in ^18O relative to its measured initial isotopic composition (delta^18O = +5.6o/oo); most of the data define a mass-dependent fractionation relationship (i.e. delta^17O = 0.52 x delta^18O). Therefore the data clearly do not reproduce the oxygen isotope anomaly defined for meteorites, which has a slope of 1 in the diagram delta^17O versus delta^18O (i.e. delta^17O = 1.0 x delta^18O). Nevertheless, it should be noted that some glass samples scatter around this canonical value of 0.52 with minor departures from a purely mass-dependent fractionation. If these results are confirmed by additional determinations (now in progress) on the separated glassy droplets, the following conclusions can be proposed: 1) lightning discharges do not yield oxygen isotope anomalies similar to those measured in chondrules and 2) an isotope exchange between hot chondrules and their parent nebular gas--presumably "anomalous" in its oxygen isotopes-- seems difficult to achieve within the duration of the rapid cooling of the melt. This last point is illustrated by the fact that no marked isotope exchange with atmospheric molecular oxygen is detectable. REFERENCES: 1] CLOCCHIATTI R. Eur. J. Mineral., 2, p. 479-494 (1990). 2] WHIPPLE F.L. Science 153, 54-56 (1966). 3] ROBERT F., REJOU-MICHEL A. & JAVOY M. Earth Planet. Sci. Lett. 108, 1-9 (1992).

Robert, F.; Javoy, M.

1992-07-01

246

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

247

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

248

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. PMID:12716706

Dastgiri, S; Gilmour, W; Stone, D

2003-01-01

249

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

2012-06-01

250

Endocrine disruptors and congenital anomalies.  

PubMed

The specialized literature was reviewed concerning the suspected increasing secular trends in the frequency of female births, male genital congenital anomalies, abnormal sperm counts, and testicular cancer. Although no risk factors could be identified yet, the observed sex ratio decline during the last decades has been considered to be an effect of certain pollutants on normal hormone activity, and human reproductive development. Reported increasing trends in the frequencies of hypospadias and cryptorchidism are very difficult to be interpreted due to the large variability in the registered frequency of these malformations due to operational as well as biological reasons. PMID:11923883

Rittler, Mônica; Castilla, Eduardo E

2002-01-01

251

Hot Flow Anomalies at Venus  

NASA Technical Reports Server (NTRS)

We present a multi-instrument study of a hot flow anomaly (HFA) observed by the Venus Express spacecraft in the Venusian foreshock, on 22 March 2008, incorporating both Venus Express Magnetometer and Analyzer of Space Plasmas and Energetic Atoms (ASPERA) plasma observations. Centered on an interplanetary magnetic field discontinuity with inward convective motional electric fields on both sides, with a decreased core field strength, ion observations consistent with a flow deflection, and bounded by compressive heated edges, the properties of this event are consistent with those of HFAs observed at other planets within the solar system.

Collinson, G. A.; Sibeck, David Gary; Boardsen, Scott A.; Moore, Tom; Barabash, S.; Masters, A.; Shane, N.; Slavin, J.A.; Coates, A.J.; Zhang, T. L.; Sarantos, M.

2012-01-01

252

Hydrodynamic anomalies in supercritical fluid.  

PubMed

Using the molecular dynamics simulations we investigate properties of velocity autocorrelation function of Lennard-Jones fluid at long and intermediate time scales in wide ranges of temperature and density. We show that the amplitudes of both the leading and the subleading time asymptotic terms of velocity autocorrelation function, a1 and a2, show essentially non-monotonic temperature and density dependence. There are two lines on temperature-density plain corresponding to maxima of a1 (a2) along isochors and isotherms situated in the supercritical fluid (hydrodynamic anomalies). These lines give insight into the stages of the fluid evolution into gas. PMID:25273453

Ryltsev, R E; Chtchelkatchev, N M

2014-09-28

253

Mercury isotope effects in the environmental chemistry and biochemistry of mercury-containing compounds  

Microsoft Academic Search

Mercury isotope effects in environmentally significant chemical and biochemical reactions are considered. The recently discovered anomaly for the 199Hg and 201Hg magnetic nuclei proves that both chemical and biochemical transformations of mercury compounds (outside and inside living organisms) follow radical spin-selective mechanisms. The regularities of isotope fractionation in natural photochemical processes and in living tissues are discussed.

Anatolii L Buchachenko

2009-01-01

254

Mercury isotope effects in the environmental chemistry and biochemistry of mercury-containing compounds  

NASA Astrophysics Data System (ADS)

Mercury isotope effects in environmentally significant chemical and biochemical reactions are considered. The recently discovered anomaly for the 199Hg and 201Hg magnetic nuclei proves that both chemical and biochemical transformations of mercury compounds (outside and inside living organisms) follow radical spin-selective mechanisms. The regularities of isotope fractionation in natural photochemical processes and in living tissues are discussed.

Buchachenko, Anatolii L.

2009-04-01

255

Brine history indicated by argon, krypton, chlorine, bromine, and iodine analyses of fluid inclusions from the Mississippi Valley type lead-fluorite-barite deposits at Hansonburg, New Mexico  

NASA Astrophysics Data System (ADS)

Argon, krypton, chlorine, bromine, and iodine were measured in a homogeneous population of high-salinity hydrothermal fluid inclusions from the Tertiary-age Mississippi Valley-type (MVT) lead-fluorite-barite deposits at Hansonburg, New Mexico to establish new types of evidence for the history of both the fluid and the major dissolved salts. Noble gases and halogens in fluid inclusions containing 10 -10-10 -9 L of brine ( Cl= 3 molal) were analyzed by laser microprobe noble-gas mass spectrometry ( LMNGMS) on neutron-irradiated samples. The concentrations of 36Ar ( 4.7 × 10 -8 molal) and 84Kr 1.8 × 10 -9 molal) in the fluid inclusions are equal to those of fresh surface waters in equilibrium with air at approximately 20 ± 5°. The mole ratios of Br/Cl ( 1.2 × 10 -4) and I/Cl ( 1-2 × 10 -6) are among the lowest measured in any natural waters, similar to those of modern brines formed by dissolution of Permian NaCl-bearing evaporites in southeast New Mexico. 40Ar/ 36Ar ratios (600) are twice that of air, and indicate that the fluid inclusions had excess radiogenic 40Ar ( 1.4 × 10 -5 molal) when trapped. The amount of excess 40Ar appears to be too large to have been acquired with Cl by congruent dissolution of halite-bearing evaporites, and possibly too small to have been acquired with Pb by congruent dissolution of granitic basement rocks with Proterozoic K sbnd Ar ages. From the LMNGMS data, combined with published Pb and S isotope data, we infer the following sequence of events in the history of the Hansonburg MVT hydrothermal brine: (1) the brine originated as relatively dilute meteoric water, and it did not gain or lose atmospheric Ar or Kr after recharge; (2) the originally dilute fluid acquired the bulk of its Cl and sulfate in the subsurface after recharge by dissolving halite-bearing Permian? marine evaporites; (3) the high salinity brine then acquired most of its Pb and excess radiogenic 40Ar from interactions with aquifer rocks other than evaporites, possibly clastic sedimentary rocks or basement rocks with Phanerozoic K sbnd Ar "ages"; and (4) the brine deposited fluorite without having boiled or degassed.

Böhlke, J. K.; Irwin, J. J.

1992-05-01

256

Brine history indicated by argon, krypton, chlorine, bromine, and iodine analyses of fluid inclusions from the Mississippi Valley type lead-fluorite-barite deposits at Hansonburg, New Mexico  

USGS Publications Warehouse

Argon, krypton, chlorine, bromine, and iodine were measured in a homogeneous population of high-salinity hydrothermal fluid inclusions from the Tertiary-age Mississippi Valley-type (MVT) lead-fluorite-barite deposits at Hansonburg, New Mexico to establish new types of evidence for the history of both the fluid and the major dissolved salts. Noble gases and halogens in fluid inclusions containing 10-10-10-9 L of brine (Cl = 3 molal) were analyzed by laser microprobe noble-gas mass spectrometry (lmngms) on neutron-irradiated samples. The concentrations of 36Ar (4.7 ?? 10-8 molal) and 84Kr 1.8 ?? 10-9 molal) in the fluid inclusions are equal to those of fresh surface waters in equilibrium with air at approximately 20 ?? 5??. The mole ratios of Br Cl (1.2 ?? 10-4) and I Cl (1-2 ?? 10-6) are among the lowest measured in any natural waters, similar to those of modern brines formed by dissolution of Permian NaCl-bearing evaporites in southeast New Mexico. 40Ar 36Ar ratios (600) are twice that of air, and indicate that the fluid inclusions had excess radiogenic 40Ar (1.4 ?? 10-5 molal) when trapped. The amount of excess 40Ar appears to be too large to have been acquired with Cl by congruent dissolution of halite-bearing evaporites, and possibly too small to have been acquired with Pb by congruent dissolution of granitic basement rocks with Proterozoic KAr ages. From the lmngms data, combined with published Pb and S isotope data, we infer the following sequence of events in the history of the Hansonburg MVT hydrothermal brine: (1) the brine originated as relatively dilute meteoric water, and it did not gain or lose atmospheric Ar or Kr after recharge; (2) the originally dilute fluid acquired the bulk of its Cl and sulfate in the subsurface after recharge by dissolving halite-bearing Permian? marine evaporites; (3) the high salinity brine then acquired most of its Pb and excess radiogenic 40Ar from interactions with aquifer rocks other than evaporites, possibly clastic sedimentary rocks or basement rocks with Phanerozoic KAr "ages"; and (4) the brine deposited fluorite without having boiled or degassed. ?? 1992.

Bohlke, J. K.; Irwin, J. J.

1992-01-01

257

[Measurement of the right ventricular ejection fraction during the acute phase of myocardial infarction using 81m krypton infusion. Comparison with the left ejection fraction].  

PubMed

The right ventricular ejection fraction is rarely measured, as conventional diagnostic methods (radiology, echocardiography) are confronted with the problem of representing the right ventricle as a simple tridimensional geometrical model. This is not necessary with the radio-isotopic techniques. However, all those used for the measurement of right ventricular ejection fraction lead to important methodological problems. We have therefore developed a technique of measuring this parameter with an infusion of 81 m Kr. This radioactive gas is pure gamma-ray emitter with a 13 second period. Dissolved and infused intravenously, it is eliminated during the first passage through the lung. The continuous separation of the generator of 81 m Kr is performed with isotonic dextrose solution which is then infused for a period of 7 minutes. During this time, the activity detected by the scintillation camera inclined in the 30 degrees RAO projection is stored, together with the electrocardiogram in a computer. The precordial radioactivity of the retrocardiac lung tissue is subtracted after injection of 74 MBq of 99 mTc microspheres. A graph of right ventricular activity can then be reconstructed and the right ventricular ejection fraction calculated. The left ventricular ejection fraction is then measured with 99 mTc--labelled RBCs. This method allows the right ventricular ejection fraction to be measured in the RAO projection, the best incidence for the separation of the right atrial from the right ventricular activity without interference from left ventricular activity because of the pulmonary elimination of the Krypton radioactivity. The measurement performed on a large number of cardiac cycles allows a continuous study of the right ventricular ejection fraction. At the end of the infusion there is no circulating radioactivity so that the measurement can be repeated. This technique was used in 17 patients with acute myocardial infarction. In the 7 patients with anterior infarcts reduction of the left ventricular ejection fraction was the predominant finding (21,6 +/- 6,8%). The right ventricular ejection fraction was 34,2 +/- 6,4%. On the other hand, patients with a postero-inferior infarction had little change in left ventricular ejection fraction (59,2 +/- 12%) but those with right ventricular extension of their infarcts had very reduced right ventricular ejection fractions (less than 23%). The measurement of right ventricular ejection fraction with 81 m Kr is a reliable atraumatic method for diagnosing right ventricular infarction by the quantification of its functional impairment. PMID:6407422

Wolf, J E; Comet, M; Dubois, F; Machecourt, J; Godart, J; Boutet, J; Croize, J; Gaudy, M; Mathieu, J P; Pellet, J; Denis, B

1983-02-01

258

The origin of the 'FUN' anomalies and the high temperature inclusions in the Allende meteorite. [Fractionation and Unknown Nuclear processes  

NASA Technical Reports Server (NTRS)

The discovery of isotopic anomalies in white inclusions of the meteorite Allende has led to fundamental questions concerning the origin of these anomalies and of the white inclusions themselves. An analysis of the 'FUN' anomalies in the inclusions C1 and EK1-4-1 demonstrates that these isotopic anomalies may be decomposed into individual nucleosynthetic components, which have been subjected to separate mass and component fractionations. There is no evidence that any freshly-synthesized material injected into the primitive solar nebula was of abnormal isotopic composition, or that the FUN anomalies were due to an injection of unusual material. Rather, they show the effects of large mass fractionations and an unusual mixture of normal nucleosynthetic material, likely to be in the form of interstellar grains whose size or chemistry served as a memory for the nucleosynthetic origins of their constituent atoms. Giant gaseous protoplanets, as described for the early solar nebula by Cameron (1978), are a potential site for achieving both mass and component fractionations, and for producing white inclusions in general.

Consolmagno, G. J.; Cameron, A. G. W.

1980-01-01

259

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

260

Surgical Treatment of Coronary Artery Anomalies  

PubMed Central

The surgical treatment of coronary artery anomalies continues to evolve. The most common coronary artery anomalies requiring surgical intervention include coronary artery fistulae, anomalous pulmonary origins of the coronary arteries, and anomalous aortic origins of the coronary arteries. The choice of surgical intervention for each type of coronary anomaly depends on several anatomic, physiologic, and patient-dependent variables. As surgical techniques have progressed, outcomes have continued to improve; however, controversy still exists about many aspects of the proper management of patients who have these coronary artery anomalies. We reviewed the surgical treatment of 178 patients who underwent surgery for the above-mentioned types of coronary artery anomalies at the Texas Heart Institute from December 1963 through June 2001. On the basis of this experience, we discuss historical aspects of the early treatment of these anomalies and describe their present-day management. (Tex Heart Inst J 2002;29:299–307) PMID:12484614

Reul, Ross M.; Cooley, Denton A.; Hallman, Grady L.; Reul, George J.

2002-01-01

261

Sea level anomalies exacerbate beach erosion  

NASA Astrophysics Data System (ADS)

level anomalies are intra-seasonal increases in water level forced by meteorological and oceanographic processes unrelated to storms. The effects of sea level anomalies on beach morphology are unknown but important to constrain because these events have been recognized over large stretches of continental margins. Here, we present beach erosion measurements along Onslow Beach, a barrier island on the U.S. East Coast, in response to a year with frequent sea level anomalies and no major storms. The anomalies enabled extensive erosion, which was similar and in most places greater than the erosion that occurred during a year with a hurricane. These results highlight the importance of sea level anomalies in facilitating coastal erosion and advocate for their inclusion in beach-erosion models and management plans. Sea level anomalies amplify the erosive effects of accelerated sea level rise and changes in storminess associated with global climate change.

Theuerkauf, Ethan J.; Rodriguez, Antonio B.; Fegley, Stephen R.; Luettich, Richard A.

2014-07-01

262

The DiGeorge anomaly.  

PubMed

The DiGeorge anomaly, originally considered a clinical paradigm for isolated thymus deficiency, has now been redefined as a member of a group of disorders that share in common a chromosome deletion resulting in monosomy 22q11 (CATCH-22 or DGA/VCFS). In addition to the thymus defect, conotruncal heart anomalies, dysmorphism, hypoparathyroidism, and cleft palate are prominent features. Despite the emphasis on thymus involvement in DGA, a clinically significant thymus defect is found only in a small percentage of these patients probably occurring in less than 5% of the cases. Maldescent of the thymus, however, is extremely common, leading to an absence of mediastinal thymic tissue in nearly all cases. The basic embryological fault in these disorders is an inadequate development of the facial neural-crest tissues, resulting in defective organogenesis of pharyngeal pouch derivatives that receive cephalic neural-crest contribution to the mesenchmyme. The causes for this maldevelopment are both genetic and extragenetic in origin and the genetic lesions act in concert with random environmental events to produce the ultimate clinical picture. The modern research approaches now available have cleared away most of the confusion clouding the clinical and theoretical aspects of DGA and related disorders, providing the clinician with useful landmarks to assess and treat these intriguing clinical challenges. PMID:11269228

Hong, R

2001-02-01

263

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

264

The Emergence of a Coherent Explanation for Anomalies Observed in D/Pd and H/Pd Systems  

NASA Astrophysics Data System (ADS)

Numerous observations have been made of apparent anomalies in carefully performed experimental studies of D/Pd and H/Pd systems. Such anomalies include: prompt emission of electrons and charged particles; unexplained heat in excess of known input sources; the residual presence of light elements (notably tritium, helium-3 and helium-4); the possible occurrence of isotope anomalies in higher mass elements (including the host metal); unusual conductance effects both stable and transient. The features which unify these apparently disparate observations are the common elements of the needed experimental stimuli, and the requirement for extended lattice coherent processes in any obvious explanation. An attempt will be made in this paper to compare and characterize the results of a range of experiments performed at SRI in terms of these two principals: the commonality of conditions and stimulus; the reasonable requirement for and expectation of coherent processes involving electrons and lattice trapped hydrogen isotopic entities.

McKubre, Michael C. H.; Tanzella, Francis L.; Tripodi, Paolo; Hagelstein, Peter

2000-03-01

265

Pancake kidney: A rare developmental anomaly  

PubMed Central

There are many developmental anomalies of the kidney. Pancake kidney is one of the rarest types of renal ectopia. We report a case of pancake kidney which was detected incidentally while treating a female patient for a urinary tract infection. Although urinary system anomalies often coexist with malformations of other organs and systems, no associated anomalies could be detected in this case. Pancake kidney is usually managed by surgery, but this case was managed conservatively without any complication. PMID:25024805

Tiwari, Alok Kumar; Choudhary, Anil Kumar; Khowal, Hemant; Chaudhary, Poras; Arora, Mohinder. P.

2014-01-01

266

The Mars Rover Spirit FLASH anomaly  

NASA Technical Reports Server (NTRS)

The Mars Exploration Rover 'Spirit' suffered a debilitating anomaly that prevented communication with Earth for several anxious days. With the eyes of the world upon us, the anomaly team used each scrap of information, our knowledge of the system, and sheer determination to analyze and fix the problem, then return the vehicle to normal operation. This paper will discuss the Spirit FLASH anomaly, including the drama of the investigation, the root cause and the lessons learned from the experience.

Reeves, Glenn E.; Neilson, Tracy C.

2005-01-01

267

Chiral and gravitational anomalies in any dimension  

SciTech Connect

Gravitational contributions to the chiral anomaly in 4N space-time dimensions as well as the purely gravitational anomaly in 4N-2 dimensions are expressed in terms of the Riemann--Christoffel tensor. Using this formula, we give a simple proof that if N > or = 4 there is no way to cancel the gravitational anomalies using fields of spin- 1/2 , - (3)/(2) , and -1.

Delbourgo, R.; Matsuki, T.

1985-06-01

268

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

269

Anomaly polynomial of general 6D SCFTs  

NASA Astrophysics Data System (ADS)

We describe a method to determine the anomaly polynomials of general 6D mathcal {N}={(2,0)} and mathcal {N}={(1,0)} superconformal field theories (SCFTs), in terms of the anomaly matching on their tensor branches. This method is almost purely field theoretical, and can be applied to all known 6D SCFTs. We demonstrate our method in many concrete examples, including mathcal {N}={(2,0)} theories of arbitrary type and the theories on M5 branes on asymptotically locally Euclidean (ALE) singularities, reproducing the N^3 behavior. We check the results against the anomaly polynomials computed M-theoretically via the anomaly inflow.

Ohmori, Kantaro; Shimizu, Hiroyuki; Tachikawa, Yuji; Yonekura, Kazuya

2014-10-01

270

The magnetic anomaly of the Ivreazone  

NASA Technical Reports Server (NTRS)

A magnetic field survey was made in the Ivreazone in 1969/70. The results were: significant anomaly of the vertical intensity is found. It follows the basic main part of the Ivrea-Verbano zone and continues to the south. The width of the anomaly is about 10 km, the maximum measures about +800 gamma. The model interpretation shows that possibly the anomaly belongs to an amphibolitic body, which in connection with the Ivrea-body was found by deep seismic sounding. Therefore, the magnetic anomaly provides further evidence for the conception that the Ivrea-body has to be regarded as a chip of earthmantle material pushed upward by tectonic processes.

Albert, G.

1979-01-01

271

Spin foam quantization and anomalies  

NASA Astrophysics Data System (ADS)

The most common spin foam models of gravity are widely believed to be discrete path integral quantizations of the Plebanski action. However, their derivation in present formulations is incomplete and lower dimensional simplex amplitudes are left open to choice. Since their large-spin behavior determines the convergence properties of the state-sum, this gap has to be closed before any reliable conclusion about finiteness can be reached. It is shown that these amplitudes are directly related to the path integral measure and can in principle be derived from it, requiring detailed knowledge of the constraint algebra and gauge fixing. In a related manner, minimal requirements of background independence provide non trivial restrictions on the form of an anomaly free measure. Many models in the literature do not satisfy these requirements. A simple model satisfying the above consistency requirements is presented which can be thought of as a spin foam quantization of the Husain-Kucha? model.

Bojowald, Martin; Perez, Alejandro

2010-04-01

272

Triangle Anomalies from Einstein Manifolds  

E-print Network

The triangle anomalies in conformal field theory, which can be used to determine the central charge a, correspond to the Chern-Simons couplings of gauge fields in AdS under the gauge/gravity correspondence. We present a simple geometrical formula for the Chern-Simons couplings in the case of type IIB supergravity compactified on a five-dimensional Einstein manifold X. When X is a circle bundle over del Pezzo surfaces or a toric Sasaki-Einstein manifold, we show that the gravity result is in perfect agreement with the corresponding quiver gauge theory. Our analysis reveals an interesting connection with the condensation of giant gravitons or dibaryon operators which effectively induces a rolling among Sasaki-Einstein vacua.

Sergio Benvenuti; Leopoldo A. Pando Zayas; Yuji Tachikawa

2006-01-10

273

Pictorial essay: Coronary artery variants and anomalies  

PubMed Central

CT coronary angiography has helped radiologists understand the variations and anomalies of the anatomy of the coronary arteries and, thus, to alert the cardiologist whenever such an anomaly is present. This can be of immense help to the clinician planning interventional procedures such as stenting, balloon dilatation, or graft surgery, particularly when there are secondary changes of calcification, plaque formation and stenosis. PMID:19774140

Rahalkar, Anand M.; Rahalkar, Mukund D.

2009-01-01

274

Thermal anomaly prediction in data centers  

Microsoft Academic Search

In recent years, the demand for data centers has seen tremendous growth. Simultaneously, power densities have increased resulting in greater chances of thermal anomalies - situations where the temperature at a location exceeds the safety threshold for equipment placed there. In this paper, we explore some techniques for predicting such thermal anomalies so that preemptive steps can be taken to

Manish Marwah; Ratnesh Sharma; Cullen Bash

2010-01-01

275

Caudal deficiency and asplenia anomalies in sibs.  

PubMed

The caudal deficiency and asplenia anomalies have been described separately in children. Two sibs with these two entities are described. Only another similar case, with caudal deficiency and polysplenia anomalies was found in the literature. It is possible that this association could be a new syndromic entity. An autosomal recessive mode of inheritance is suggested. PMID:3146294

Fullana, A; Garcia-Frias, E; Martinez-Frias, M L; Razquin, S; Quero, J

1986-01-01

276

The summer evening anomaly and conjugate effects  

Microsoft Academic Search

The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) GPS occultation data have been analyzed in this study to provide a better understanding of the Weddell Sea Anomaly (WSA) and to place it in the wider context of a general phenomenon that occurs near dusk in summer, which we are calling the summer evening anomaly to better capture its

A. G. Burns; S. C. Solomon; W. Wang; G. Jee; C. H. Lin; C. Rocken; Y. H. Kuo

2011-01-01

277

Risk Leveling of Network Traffic Anomalies  

Microsoft Academic Search

Summary The goal of intrusion detection is to identify attempted or ongoing attacks on a computer system or network. Many attacks aim to compromise computer networks in an online manner. Traffic anomalies have been an important indication of such attacks. Challenges in the detections lie in modeling of the large continuous streams of data and performing anomaly detection in an

Charlie Isaksson; Yu Meng; Margaret H. Dunham

2006-01-01

278

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

279

Ultrasound Characteristics of Thyroglossal Duct Anomalies  

Microsoft Academic Search

The purpose of this study was to determine the value of ultrasound examination in the diagnosis of thyroglossal duct anomalies. The ultrasound and palpation findings in 24 patients with a thyroglossal duct anomaly were reviewed. Cysts, tracts and ectopic thyroid tissue appeared to produce a characteristic ultrasound pattern in most cases. This study includes 5 patients with non-symptomatic lesions which

Robert J. Baatenburg de Jong; Robert J. Rongen; Johan S. Laméris; Paul Knegt; Carel D. A. Verwoerd

1993-01-01

280

Scintigraphic demonstration of a gallbladder anomaly  

SciTech Connect

Congenital anomalies of the gallbladder are uncommon. In this paper the authors report a case of double gallbladder in which intravenous cholecystokinin analog (CCK) was used to confirm the presence of two ectopic gallbladders rather than other biliary tract anomalies or dilated hepatic ducts.

Singh, A.; Holmes, R.A.; Witten, D.M.

1985-01-01

281

Stationary anomalies in stratospheric meteorological data sets  

Microsoft Academic Search

Several northern hemisphere stratospheric meteorological data sets are shown to contain stationary anomalies. We consider four possible explanations for the anomalies: 1) real stationary-wave features; 2) biases in the analysis and assimilation methods; 3) errors in data input into the analysis and assimilation systems; and 4) tidal signals that are undersampled in the daily analyses. Because the easterly flow in

Kenneth P. Bowman; Karl Hoppel; Richard Swinbank

1998-01-01

282

Proactive anomaly detection using distributed intelligent agents  

Microsoft Academic Search

Proactive network anomaly detection is crucial to provide quality of service guarantees for future networks. We characterize a set of proactively detectable anomalies in terms of the management information base variables. The time series data obtained from these variables are analyzed by an intelligent agent, which is a simple and lightweight signal processor. The agent provides real-time proactive alarms that

Marina Thottan; Chuanyi Ji

1998-01-01

283

Photodiode and photomultiplier areal sensitivity anomalies  

NASA Technical Reports Server (NTRS)

Several silicon photodiodes and photomultipliers were tested to determine signal variations as a light spot was scanned over the photosensitive surface of these detectors. Qualitative and quantitative data is presented to demonstrate the areal sensitivity anomalies. These anomalies are related back to the fabrication techniques of the manufacturers.

Youngbluth, O., Jr.

1977-01-01

284

Inkjet Mask Anomalies for Microfluidic Devices  

Microsoft Academic Search

The utilization of inkjet masks with UV light on a photoresistive material can be a cost-effective method for the generation of microfluidic devices for research and\\/or demonstration. The multicomponent combinations of various colors utilized in inks can lead to anomalies in the generation of the device. These anomalies are demonstrated for various UV exposures with a 365 nm source and

William Dieterle

2010-01-01

285

Anomaly detection in wireless sensor networks  

Microsoft Academic Search

Anomaly detection in wireless sensor networks is an important challenge for tasks such as fault diagnosis, intrusion detection, and monitoring applications. The algorithms developed for anomaly detection have to consider the inherent limitations of sensor networks in their design so that the energy consumption in sensor nodes is minimized and the lifetime of the network is maximized. In this survey

SUTHARSHAN RAJASEGARAR; CHRISTOPHER LECKIE; MARIMUTHU PALANISWAMI

2008-01-01

286

Magnetic resonance images of neuronal migration anomalies.  

PubMed

Neuronal migration anomalies are a spectrum of brain malformations caused by insults to migrating neuroblasts during the sixth week to fifth month of gestation. To study the characteristics of MRI findings in migration anomalies, MR images of 36 patients (28 children and 8 adults) with migration anomalies were evaluated. Five patients had lissencephaly, eight had pachygyria, twelve had schizencephaly, six had heterotopias of gray matter, three had hemimegalencephaly, and two had polymicrogyria. The frequency of migration anomalies was 0.51% of all cranial MRI studies and 1.21% of pediatric cranial MRI studies at our hospital. The major clinical presentations of these patients were seizure (64%), development delay (42%), motor deficits (42%) and mental retardation (25%). Twenty-five patients (69%) associated with other brain anomalies, including: other migration anomalies in 12 cases (33%), absence of the septum pellucidum in 10 cases (28%), Dandy-Walker malformation/variant in 5 cases, arachnoid cyst in 4 cases, agenesis of the corpus callosum in 3 cases, holoprosencephaly in 2 cases, mega cisterna magna in 1 case and cephalocele in 1 case. Some of them presented with multiple complicated anomalies. As MR imaging provides superb gray-white matter distinction, details of cortical anatomy and multiplanar capability, it can clearly delineate the detail morphologic changes of the brain caused by neuronal migration disorders as well as the associated anomalies. PMID:9780601

Jaw, T S; Sheu, R S; Liu, G C; Chou, M S

1998-08-01

287

Vanadium isotopic difference between the silicate Earth and meteorites  

NASA Astrophysics Data System (ADS)

It has been argued that the stable isotopic composition of the element vanadium (V) provides a potential indicator of the effects high-energy irradiation early in Solar System development. Such irradiation would produce enrichment in the minor isotope, 50V compared with the 400 times more abundant 51V (Gounelle et al., 2001; Lee et al., 1998). Here we show that the vanadium isotopic composition of the silicate Earth is enriched in 51V by ?0.8‰ compared with carbonaceous and ordinary chondrites as well as achondrites from Mars and the asteroid 4 Vesta. Although V is depleted by core formation, experiments reveal no isotopic fractionation between metal and silicate that could account for the observed difference in V isotope composition between terrestrial and extraterrestrial materials. Nucleosynthetic provenance of the terrestrial vanadium isotope offset is inconsistent with anomalies of other nucleosynthetically produced isotopes in bulk meteorites, which are more variable than vanadium (Burkhardt et al., 2011; Carlson et al., 2007; Trinquier et al., 2009). Furthermore, V isotopes are unlikely to have been affected by volatilization, parent body alteration or impact erosion of Earth's surface. Therefore, the cause of the isotopic difference is unclear. One possibility is that Earth's isotopically heavier V reflects a deficit in material irradiated during the initial stages of Solar System formation. Whatever the cause, the terrestrial deficit in 50V implies that bulk Earth cannot be entirely reconstructed by mixtures of different meteorites.

Nielsen, Sune G.; Prytulak, Julie; Wood, Bernard J.; Halliday, Alex N.

2014-03-01

288

Regional magnetic anomaly constraints on continental rifting  

NASA Technical Reports Server (NTRS)

Radially polarized MAGSAT anomalies of North and South America, Europe, Africa, India, Australia and Antarctica demonstrate remarkably detailed correlation of regional magnetic lithospheric sources across rifted margins when plotted on a reconstruction of Pangea. These major magnetic features apparently preserve their integrity until a superimposed metamorphoric event alters the magnitude and pattern of the anomalies. The longevity of continental scale magnetic anomalies contrasts markedly with that of regional gravity anomalies which tend to reflect predominantly isostatic adjustments associated with neo-tectonism. First observed as a result of NASA's magnetic satellite programs, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans. Accordingly, satellite magnetic observations provide a further tool for investigating continental drift to compliment other lines of evidence in paleoclimatology, paleontology, paleomagnetism, and studies of the radiometric ages and geometric fit of the continents.

Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

1985-01-01

289

Anomaly detection and reconstruction from random projections.  

PubMed

Compressed-sensing methodology typically employs random projections simultaneously with signal acquisition to accomplish dimensionality reduction within a sensor device. The effect of such random projections on the preservation of anomalous data is investigated. The popular RX anomaly detector is derived for the case in which global anomalies are to be identified directly in the random-projection domain, and it is determined via both random simulation, as well as empirical observation that strongly anomalous vectors are likely to be identifiable by the projection-domain RX detector even in low-dimensional projections. Finally, a reconstruction procedure for hyperspectral imagery is developed wherein projection-domain anomaly detection is employed to partition the data set, permitting anomaly and normal pixel classes to be separately reconstructed in order to improve the representation of the anomaly pixels. PMID:21690013

Fowler, James E; Du, Qian

2012-01-01

290

The local RG equation and chiral anomalies  

E-print Network

We generalize the local renormalization group (RG) equation to theories with chiral anomalies. We find that a new anomaly is required by the Wess-Zumino consistency conditions. Taking into account the new anomaly, the trace of the energy momentum tensor is expressed in terms of the covariant flavor currents, instead of the consistent ones. This result is used to show that a flavor rotation induced by the RG flow can be eliminated by a choice of scheme even in the presence of chiral anomalies. As part of a general discussion of chiral anomalies in the presence of background sources, we also derive non-renormalization theorems. Finally, we introduce the $\\theta$ parameter as a source, and derive constraints on a perturbative running of this parameter.

Boaz Keren-Zur

2014-06-03

291

Detecting Flow Anomalies in Distributed Systems  

E-print Network

Deep within the networks of distributed systems often contain anomalies that affect its efficiency and performance. These anomalies are difficult to detect because the distributed systems may not have sufficient sensors to monitor the flow of traffic within the interconnected nodes of the networks. Without early detection and making corrections, these anomalies may aggravate over time and could possibly cause disastrous outcomes in the system in the unforeseeable future. Using only coarse-grained information from the two end points of network flows, we propose a network transmission model and a localization algorithm, to detect the location of anomalies and rank them using a proposed metric within distributed systems. We evaluate our approach on passengers' records of an urbanized city's public transportation system and correlate our findings with passengers' postings on social media microblogs. Our experiments show that the metric derived using our localization algorithm gives a better ranking of anomalies a...

Chua, Freddy Chong Tat; Huberman, Bernardo A

2014-01-01

292

Global magnetic anomaly and aurora of Neptune  

NASA Technical Reports Server (NTRS)

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, Andrew F.

1990-01-01

293

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

294

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

295

The local RG equation and chiral anomalies  

NASA Astrophysics Data System (ADS)

We generalize the local renormalization group (RG) equation to theories with chiral anomalies. We find that a new anomaly is required by the Wess-Zumino consistency conditions. Taking into account the new anomaly, the trace of the energy momentum tensor is expressed in terms of the covariant flavor currents, instead of the consistent ones. This result is used to show that a flavor rotation induced by the RG flow can be eliminated by a choice of scheme even in the presence of chiral anomalies. As part of a general discussion of chiral anomalies in the presence of background sources, we also derive non-renormalization theorems. Finally, we introduce the $\\theta$ parameter as a source, and derive constraints on a perturbative running of this parameter.

Keren-Zur, Boaz

2014-09-01

296

The abundance and isotopic composition of Cd in iron meteorites  

NASA Astrophysics Data System (ADS)

Cadmium is a highly volatile element and its abundance in meteorites may help better understand volatility-controlled processes in the solar nebula and on meteorite parent bodies. The large thermal neutron capture cross section of 113Cd suggests that Cd isotopes might be well suited to quantify neutron fluences in extraterrestrial materials. The aims of this study were (1) to evaluate the range and magnitude of Cd concentrations in magmatic iron meteorites, and (2) to assess the potential of Cd isotopes as a neutron dosimeter for iron meteorites. Our new Cd concentration data determined by isotope dilution demonstrate that Cd concentrations in iron meteorites are significantly lower than in some previous studies. In contrast to large systematic variations in the concentration of moderately volatile elements like Ga and Ge, there is neither systematic variation in Cd concentration amongst troilites, nor amongst metal phases of different iron meteorite groups. Instead, Cd is strongly depleted in all iron meteorite groups, implying that the parent bodies accreted well above the condensation temperature of Cd (i.e., ?650 K) and thus incorporated only minimal amounts of highly volatile elements. No Cd isotope anomalies were found, whereas Pt and W isotope anomalies for the same iron meteorite samples indicate a significant fluence of epithermal and higher energetic neutrons. This observation demonstrates that owing to the high Fe concentrations in iron meteorites, neutron capture mainly occurs at epithermal and higher energies. The combined Cd-Pt-W isotope results from this study thus demonstrate that the relative magnitude of neutron capture-induced isotope anomalies is strongly affected by the chemical composition of the irradiated material. The resulting low fluence of thermal neutrons in iron meteorites and their very low Cd concentrations make Cd isotopes unsuitable as a neutron dosimeter for iron meteorites.

Kruijer, Thomas S.; Sprung, Peter; Kleine, Thorsten; Leya, Ingo; Wieler, Rainer

2013-12-01

297

Structure of Hot Flow Anomaly  

NASA Astrophysics Data System (ADS)

Hot Flow Anomalies (HFAs) were first discovered in 1980s. These are active processes of hot plasma bulks formation that usually occur at planetary bow shocks. Though HFA were studied for long time it is still not clear if they are reforming structures and what defines particular internal structure of HFA. Our study is based on the Interball Tail Probe data. We used 10-sec measurements of complex plasma analyzer SCA-1 and 1-second magnetic field measurements, and ELECTRON spectrometer 2-dimensional measurements with 3,75-sec temporal resolution. Five anomalies that were observed on the basis of well resolved structure for which we obtained displacement velocity along bow shock, flow velocities within HFA, and estimated the size. We checked if main criteria of HFA formation were fulfilled for each case. The following criteria were satisfied: motional electric field direction was directed toward current sheet at least at one side of it, bow shock was quasi-perpendicular at least at one side of HFA, and angle between current sheet normal and solar wind velocity was large. Convection velocities of plasma within HFA were calculated by subtracting average velocity from measured ion convection velocities along spacecraft trajectory through anomaly. These convection velocities viewed in coordinate system of shock normal and calculated IMF current sheet normal clearly show separation of HFA region in 3 parts: leading part, narrow central part, and trailing part. Ion velocity distributions confirm this triple structure of HFA. Thomsen et al. [1986] identified the region within HFA that they called "internal recovery". It looks like central region that we call narrow central part. Vaisberg et al. [1999] discussed separation of HFA into 2 distinct parts that correspond to leading and trailing parts. Judging from plasma convection pattern within HFAs we assumed that "internal recovery" region is the source of energy and momentum around interplanetary current sheet crossing. HFA formation mechanisms presume that HFA is formed when particles are reflected on bow shock, get swept by motional electric field and are injected back into the area. We tried to calculate the balance of energy in solar wind and within HFA to estimate what amount of reflected particles is needed for "internal recovery" area to be the real energy source. These estimations suggest that this energy balance is nearly fulfilled in 4 of 5 analyzed HFAs, and does not hold for one HFA. This energy balance may be in favor of quasi-stationary nature of HFA structure. References Thomsen, M. F., J. T. Gosling, S. A. Fuselier, S. J. Bame, and C. T. Russell (1986), Hot, diamagnetic cavities upstream from the Earth's bow shock, J. Geophys. Res., 91(A3), 2961-2973, doi:10.1029/JA091iA03p02961. Vaisberg, O.L., J.H.Waite, L.Avanov, V.N.Smirnov, D.Dempsey J.L.Burch and A.A.Skalsky, HFA-like signatures observed with Interball-Tail spacecraft, in: Solar Wind Nine, ed. By S.R.Habbal, R.Esser, J.V.Hollweg, and P.A.Isenberg, AIP 1-56396-865-7, 1999, pp. 551-554.

Shestakov, A.; Vaisberg, O. L.

2012-12-01

298

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. PMID:19528640

Briani, Giacomo; Gounelle, Matthieu; Marrocchi, Yves; Mostefaoui, Smail; Leroux, Hugues; Quirico, Eric; Meibom, Anders

2009-01-01

299

Associated nonurinary congenital anomalies among infants with congenital anomalies of kidney and urinary tract (CAKUT).  

PubMed

Infants with congenital anomalies of kidney and urinary tract (CAKUT) often have other associated anomalies. The purpose of this investigation was to assess the prevalence and the types of associated anomalies in CAKUT in a defined population from northeastern France. The associated anomalies in CAKUT were collected in all livebirths, stillbirths and terminations of pregnancy during 26 years in 346,831 consecutive births of known outcome in the area covered by our population based registry of congenital anomalies. Of the 1678 infants with CAKUT born during this period (prevalence at birth of 48.4 per 10,000), 563 (34%) had associated anomalies. There were 119 (7%) patients with chromosomal abnormalities including 33 trisomies 18 (2%), and 168 (10%) nonchromosomal recognized dysmorphic conditions. There were no predominant recognized dysmorphic conditions, but VA(C)TER(L) association (3%). However, other recognised dysmorphic conditions were registered including Meckel-Gruber syndrome (2%), and prune belly syndrome (1%). Two hundred seventy six (16%) of the patients had multiple congenital anomalies, non syndromic, non chromosomal (MCA). Anomalies in the musculoskeletal, the digestive, the cardiovascular and the central nervous systems were the most common other anomalies. Prenatal diagnosis was obtained in 71% of dysmorphic syndromes with CAKUT. In conclusion the overall prevalence of associated anomalies, which was one in three infants, emphasizes the need for a thorough investigation of infants with CAKUT. The most commonly associated major nonurinary anomalies involved the musculoskeletal system, followed by the digestive, the cardiovascular and the central nervous systems. A routine screening for other anomalies may be considered in infants and in fetuses with CAKUT. One should be aware that the anomalies associated with CAKUT can be classified into a recognizable anomaly syndrome or pattern in one out of six infants with CAKUT. PMID:24821302

Stoll, Claude; Dott, Beatrice; Alembik, Yves; Roth, Marie-Paule

2014-07-01

300

Isotopes in groundwater hydrology  

Microsoft Academic Search

Isotopes in groundwater hydrology give a direct insight into the movement and distribution processes within the aquifer. Groundwater in its natural state contains environmental isotopes and conclusions may be drawn from their abundance variations. The isotopes commonly employed in groundwater investigations are the heavy stable isotopes of the water molecule, deuterium and oxygen-18 and the radioactive isotopes, tritium and carbon-14.

J. L. TERWEY

301

Thermal Infrared Anomalies of Several Strong Earthquakes  

PubMed Central

In the history of earthquake thermal infrared research, it is undeniable that before and after strong earthquakes there are significant thermal infrared anomalies which have been interpreted as preseismic precursor in earthquake prediction and forecasting. In this paper, we studied the characteristics of thermal radiation observed before and after the 8 great earthquakes with magnitude up to Ms7.0 by using the satellite infrared remote sensing information. We used new types of data and method to extract the useful anomaly information. Based on the analyses of 8 earthquakes, we got the results as follows. (1) There are significant thermal radiation anomalies before and after earthquakes for all cases. The overall performance of anomalies includes two main stages: expanding first and narrowing later. We easily extracted and identified such seismic anomalies by method of “time-frequency relative power spectrum.” (2) There exist evident and different characteristic periods and magnitudes of thermal abnormal radiation for each case. (3) Thermal radiation anomalies are closely related to the geological structure. (4) Thermal radiation has obvious characteristics in abnormal duration, range, and morphology. In summary, we should be sure that earthquake thermal infrared anomalies as useful earthquake precursor can be used in earthquake prediction and forecasting. PMID:24222728

Wei, Congxin; Guo, Xiao; Qin, Manzhong

2013-01-01

302

Crustal structure interpreted from magnetic anomalies  

NASA Technical Reports Server (NTRS)

This review, discusses publications during the last quadrennium (1987-1990) that used aeromagnetic data, marine magnetic data, satellite magnetic data, and rock magnetic and petrologic data to provide information on the sources of magnetic anomalies. The publications reviewed reflect increased integration of rock magnetic property and petrologic studies with magnetic anomaly interpretation studies, particularly in deep crustal magnetization, exploration for hydrocarbons, and inversion of marine magnetic anomalies. Interpretations of aeromagnetic data featuring image display techniques and using the horizontal gradient method for locating magnetization boundaries became standard.

Phillips, Jeffrey D.; Reynolds, Richard L.; Frey, Herbert

1991-01-01

303

Cervical meningocele and associated spinal anomalies.  

PubMed

Simple meningoceles are infrequent forms of dysraphism and are often benign. They have been associated with other spinal anomalies. The uncommon cervical meningocele may have a higher propensity to be associated with other spinal anomalies. Four patients with cervical meningocele are presented with radiographic evaluation and clinical course. Multiple abnormalities were documented radiographically and operatively, including hydrocephalus, Chiari malformation, hydromyelia, lipomeningomyelocele, tethered cord, thickened filum terminale, diastematomyelia, Klippel-Feil syndrome, and thoracic hemivertebrae. Prior to the development of any late neurological abnormality from associated spinal anomalies, magnetic resonance imaging is recommended early in a child born with a simple meningocele. PMID:3652068

Delashaw, J B; Park, T S; Cail, W M; Vollmer, D G

1987-01-01

304

Regional magnetic anomaly constraints on continental breakup  

SciTech Connect

Continental lithosphere magnetic anomalies mapped by the Magsat satellite are related to tectonic features associated with regional compositional variations of the crust and upper mantle and crustal thickness and thermal perturbations. These continental-scale anomaly patterns when corrected for varying observation elevation and the global change in the direction and intensity of the geomagnetic field show remarkable correlation of regional lithospheric magnetic sources across rifted continental margins when plotted on a reconstruction of Pangea. Accordingly, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans.

von Frese, R.R.B.; Hinze, W.J.; Olivier, R.; Bentley, C.R.

1986-01-01

305

The conformal anomaly of M5-branes  

NASA Astrophysics Data System (ADS)

We show that the conformal anomaly for N M5-branes grows like N 3. The method we employ relates Coulomb branch interactions in six dimensions to interactions in four dimensions using supersymmetry. This leads to a relation between the six-dimensional conformal anomaly and the conformal anomaly of N = 4 Yang-Mills. Along the way, we determine the structure of the four derivative interactions for the toroidally compactified (2, 0) theory, while encountering interesting novelties in the structure of the six derivative interactions.

Maxfield, Travis; Sethi, Savdeep

2012-06-01

306

Considerations in the Interpretation of Cosmological Anomalies  

E-print Network

Anomalies drive scientific discovery -- they are associated with the cutting edge of the research frontier, and thus typically exploit data in the low signal-to-noise regime. In astronomy, the prevalence of systematics --- both "known unknowns" and "unknown unknowns" --- combined with increasingly large datasets, the widespread use of ad hoc estimators for anomaly detection, and the "look-elsewhere" effect, can lead to spurious false detections. In this informal note, I argue that anomaly detection leading to discoveries of new physics requires a combination of physical understanding, careful experimental design to avoid confirmation bias, and self-consistent statistical methods. These points are illustrated with several concrete examples from cosmology.

Peiris, Hiranya V

2014-01-01

307

US Aeromagnetic and Satellite Magnetic Anomaly Comparisons  

NASA Technical Reports Server (NTRS)

Scalar aeromagnetic data obtained by the U.S. Naval Oceanographic Office (NOO) Vector Magnetic Survey of the conterminous U.S. were screened for periods of intense diurnal magnetic activity and reduced to anomaly form, filtered, and continued upward. A number of correlations between the NOO, POGO and preliminary MAGSAT data are evident at satellite elevations, including a prominent transcontinental magnetic high which extends from the Anadarko Basin to the Cincinnati Arch. The transcontinental magnetic high is breached by negative anomalies located over the Rio Grande Rift and Mississippi River Aulacogen. Differentially reduced-to-pole NOO and POGO magnetic anomaly data show that the transcontinental magnetic high corresponds to a well-defined regional trend of negative free-air gravity and enhanced crustal thickness anomalies.

Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W. (principal investigators); Sexton, J. L.

1984-01-01

308

An ubiquitous mechanism for waterlike anomalies  

E-print Network

Using collision driven molecular dynamics a system of spherical particles interacting through an effective two length scales potential is studied. The potential can be tuned by means of a single parameter, $\\lambda$, from a ramp $(\\lambda=0.5)$ to a square-shoulder potential $(\\lambda=1.0)$ representing a family of two length scales potential in which the shortest interaction distance has higher potential energy than the largest interaction distance. For all the potentials, ranging between the ramp and the square-shoulder, density and structural anomalies were found, while the diffusion anomaly is found in all but in the square-shoulder potential. The presence anomalies in square-shoulder potential, not observed in previous simulations, confirm the assumption that the two length scales potential is an ubiquitous ingredient for a system to exhibit water-like anomalies

Alan Barros de Oliveira; Paulo A. Netz; Marcia C. Barbosa

2008-04-14

309

Reduction of satellite magnetic anomaly data  

NASA Technical Reports Server (NTRS)

Analysis of global magnetic anomaly maps derived from satellite data is facilitated by inversion to the equivalent magnetization in a constant thickness magnetic crust or, equivalently, by reduction to the pole. Previous inversions have proven unstable near the geomagnetic equator. The instability results from magnetic moment distributions which are admissible in the inversion solution but which make only small contribution to the computed values of anomaly field. Their admissibility in the solution could result from noisy or incomplete data or from small poorly resolved anomalies. The resulting magnetic moments are unrealistically large and oscillatory. Application of the method of principal components (e.g. eigenvalue decomposition and selective elimination of less significant eigenvectors) is proposed as a way of overcoming the instability and the method is demonstrated by applying it to the region around the Bangui anomaly in Central Africa.

Slud, E. V.; Smith, P. J.; Langel, R. A.

1984-01-01

310

Chemical Compositions and Anomalies in Stellar Coronae  

NASA Technical Reports Server (NTRS)

In summary, as the papers cited here and in earlier reports demonstrate, this award has enabled us to obtain a fairly good picture of the abundance anomalies in stellar coronae. The "inverse FIP" effect in very active stars has now been fleshed out as a more complex anomaly depending on FIP, whereas before it appeared only in terms of a general metal paucity, the recent solar abundance assessment of Asplund et a1 will, if correct, challenge some of the older interpretations of coronal abundance anomalies since they imply quite different relative abundances of CNO compared with Fe, Mg and Si. Further investigations have been in into the possibility of modeling some of the recent coronal abundance anomaly results in terms of Alfven wave-driven separation of neutrals and ions in the upper chromosphere. This work still remains in the seed stage, and future funding from a different program will be requested to pursue it further.

Drake, Jeremy; Oliversen, Ronald J. (Technical Monitor)

2005-01-01

311

Presolar graphite from the Murchison meteorite: An isotopic study  

NASA Astrophysics Data System (ADS)

We studied presolar graphite grains from four density fractions, KE3 (1.65-1.72 g/cm3), KFA1 (2.05-2.10 g/cm3), KFB1 (2.10-2.15 g/cm3), and KFC1 (2.15-2.20 g/cm3), extracted from the Murchison (CM2) meteorite, with the ion microprobe. One of the most interesting features of presolar graphite is that isotopic features depend on density. There are grains with 15N and 18O excesses, Si isotopic anomalies, high 26Al/27Al ratios (˜0.1), and Ca and Ti isotopic anomalies, including the initial presence of short-lived 41Ca and 44Ti. These isotopic features are qualitatively explained by nucleosynthesis in core collapse supernovae. We estimate that 76%, 50%, 7% and 1% of the KE3, KFA1, KFB1 and KFC1 grains, respectively, are supernova grains. We performed 3- and 4-zone supernova mixing calculations to reproduce the C, O (18O/16O) and Al isotopic ratios of the KE3 grains, using 15 M? model calculations by Rauscher et al. (2002). Isotopic ratios of grains with high 12C/13C ratios (>200) can be reproduced, whereas those of grains with ratios ?200 are hard to explain if we assume that graphite grains form in C-rich conditions.

Amari, Sachiko; Zinner, Ernst; Gallino, Roberto

2014-05-01

312

STEADY-STATE RELEASE FRACTION OF KRYPTON AND XENON FISSION PRODUCTS AT HIGH TEMPERATURES FROM (U,Th)Câ-GRAPHITE FUEL MATRIX IN OUT-OF-PILE EXPERIMENTS  

Microsoft Academic Search

Presented at American Nuclear Society Meeting, Boston, June 18-21, 1962. ; The release of krypton and xenon was measured as a function of temperature and ; half life in out-of-pile experiments under steady-state conditions. Nuclear ; fuels consisting of (U,Th)Câ in a graphite matrix were heated in a furnace ; to temperatures ranging from 900 to 2000 deg C. Using

E. E. Anderson; P. E. Gethard; L. R. Zumwalt

1962-01-01

313

Brine history indicated by argon, krypton, chlorine, bromine, and iodine analyses of fluid inclusions from the Mississippi Valley type lead-fluorite-barite deposits at Hansonburg, New Mexico  

Microsoft Academic Search

Argon, krypton, chlorine, bromine, and iodine were measured in a homogeneous population of high-salinity hydrothermal fluid inclusions from the Tertiary-age Mississippi Valley-type (MVT) lead-fluorite-barite deposits at Hansonburg, New Mexico to establish new types of evidence for the history of both the fluid and the major dissolved salts. Noble gases and halogens in fluid inclusions containing 10-10-10-9 L of brine (Cl

J. K. Böhlke; J. J. Irwin

1992-01-01

314

“Great Salinity Anomalies” in the North Atlantic  

Microsoft Academic Search

We revisited the “Great Salinity Anomaly” of the 1970s (GSA'70s; Dickson et al., 1988) and documented the newly identified “Great Salinity Anomaly” of the 1980s (hence termed GSA'80s), both propagated around the North Atlantic in a similar fashion. The advective mechanism, initially proposed to explain the observed sequence of low-salinity, low-temperature events during the GSA'70s, apparently holds also for the

Igor M. Belkin; Sydney Levitus; John Antonov; Svend-Aage Malmberg

1998-01-01

315

Inversion of marine magnetic anomalies by deconvolution  

E-print Network

large block size, it is demonstrated that the deconvolution technique can retrieve the equivalent source function when the anomaly due to each source block is clearly defined. The model profiles used were 115 samples in length, with a sample... magnetization structure. used to calculate the anomaly. 38 CHAPTER V RESOLUTION OF THE INVERSION TECHNIQUE The ability of the inversion procedure to recover short wavelength source blocks is limited by two factors; the sample interval of the magnetic...

Harry, Dennis Lee

2012-06-07

316

The Anomaly Structure of Regularized Supergravity  

E-print Network

On-shell Pauli-Villars regularization of the one-loop divergences of supergravity theories is used to study the anomaly structure of supergravity and the cancellation of field theory anomalies under a $U(1)$ gauge transformation and under the T-duality group of modular transformations in effective supergravity theories with three K\\"ahler moduli $T^i$ obtained from orbifold compactification of the weakly coupled heterotic string. This procedure requires constraints on the chiral matter representations of the gauge group that are consistent with known results from orbifold compactifications. Pauli-Villars regulator fields allow for the cancellation of all quadratic and logarithmic divergences, as well as most linear divergences. If all linear divergences were canceled, the theory would be anomaly free, with noninvariance of the action arising only from Pauli-Villars masses. However there are linear divergences associated with nonrenormalizable gravitino/gaugino interactions that cannot be canceled by PV fields. The resulting chiral anomaly forms a supermultiplet with the corresponding conformal anomaly, provided the ultraviolet cut-off has the appropriate field dependence, in which case total derivative terms, such as Gauss-Bonnet, do not drop out from the effective action. The anomalies can be partially canceled by the four-dimensional version of the Green-Schwarz mechanism, but additional counterterms, and/or a more elaborate set of Pauli-Villars fields and couplings, are needed to cancel the full anomaly, including D-term contributions to the conformal anomaly that are nonlinear in the parameters of the anomalous transformations.

Daniel Butter; Mary K. Gaillard

2014-10-22

317

Principal Component-based Anomaly Detection Scheme  

Microsoft Academic Search

In this chapter, a novel anomaly detection scheme that uses a robust principal component classifier (PCC) to handle computer\\u000a network security problems is proposed. An intrusion predictive model is constructed from the major and minor principal components\\u000a of the normal instances, where the difference of an anomaly from the normal instance is the distance in the principal component\\u000a space. The

Mei-ling Shyu; Shu-ching Chen; Kanoksri Sarinnapakorn; Liwu Chang

2006-01-01

318

Anomaly Detection Approaches for Communication Networks  

Microsoft Academic Search

\\u000a In recent years, network anomaly detection has become an important area for both commercial interests as well as academic\\u000a research. Applications of anomaly detection typically stem from the perspectives of network monitoring and network security.\\u000a In network monitoring, a service provider is often interested in capturing such network characteristics as heavy flows, flow\\u000a size distributions, and the number of distinct

Marina Thottan; Guanglei Liu; Chuanyi Ji

2010-01-01

319

Inkjet Mask Anomalies for Microfluidic Devices  

NASA Astrophysics Data System (ADS)

The utilization of inkjet masks with UV light on a photoresistive material can be a cost-effective method for the generation of microfluidic devices for research and/or demonstration. The multicomponent combinations of various colors utilized in inks can lead to anomalies in the generation of the device. These anomalies are demonstrated for various UV exposures with a 365 nm source and possible solutions are discussed.

Dieterle, William

2010-04-01

320

Satellite-altitude horizontal magnetic gradient anomalies used to define the Kursk Magnetic Anomaly  

NASA Astrophysics Data System (ADS)

The Kursk Magnetic Anomaly (KMA), Russia, is one of the world's largest magnetic anomalies. We used satellite altitude horizontal gradient magnetic anomaly data to study this feature. There are two main objectives of our research; the first, to determine if the technique of the horizontal magnetic anomaly gradient analysis can be applied to CHAMP satellite altitude data to define the outline of the source of the Kursk Magnetic Anomaly (KMA). Another objective is to use the ten years of CHAMP data to reproduce the horizontal magnetic anomaly gradient data that will be measured by the two lower orbiting ESA/Swarm mission. We will be able to evaluate the application of these newer satellite altitude data for studying large areas with significant crustal magnetization. While we have acquired sufficient CHAMP orbital data to compute a horizontal gradient anomaly map from these ten years of data; the future ESA/Swarm mission will, however, allow us to compute directly the horizontal magnetic anomaly without orbital altitude and/or magnetic secular variations; however the east-west gradient that the Swarm is measuring will minimize, but not eliminate, the difference in external fields between the two lower satellites. One will still need to use relatively quiet data (e.g., Kp < 1) for crustal field mapping. Our results, developed from interpreting the satellite horizontal magnetic anomaly data, indicate that the source of the KMA is bowl shaped body open to the northwest covering an area of approximately 190,000 km2.

Taylor, P. T.; Kis, K. I.; Wittmann, G.

2014-10-01

321

Clustering and Recurring Anomaly Identification: Recurring Anomaly Detection System (ReADS)  

NASA Technical Reports Server (NTRS)

This viewgraph presentation reviews the Recurring Anomaly Detection System (ReADS). The Recurring Anomaly Detection System is a tool to analyze text reports, such as aviation reports and maintenance records: (1) Text clustering algorithms group large quantities of reports and documents; Reduces human error and fatigue (2) Identifies interconnected reports; Automates the discovery of possible recurring anomalies; (3) Provides a visualization of the clusters and recurring anomalies We have illustrated our techniques on data from Shuttle and ISS discrepancy reports, as well as ASRS data. ReADS has been integrated with a secure online search

McIntosh, Dawn

2006-01-01

322

Anomaly Detection in Gamma-Ray Vehicle Spectra with Principal Components Analysis and Mahalanobis Distances  

SciTech Connect

The goal of primary radiation monitoring in support of routine screening and emergency response is to detect characteristics in vehicle radiation signatures that indicate the presence of potential threats. Two conceptual approaches to analyzing gamma-ray spectra for threat detection are isotope identification and anomaly detection. While isotope identification is the time-honored method, an emerging technique is anomaly detection that uses benign vehicle gamma ray signatures to define an expectation of the radiation signature for vehicles that do not pose a threat. Newly acquired spectra are then compared to this expectation using statistical criteria that reflect acceptable false alarm rates and probabilities of detection. The gamma-ray spectra analyzed here were collected at a U.S. land Port of Entry (POE) using a NaI-based radiation portal monitor (RPM). The raw data were analyzed to develop a benign vehicle expectation by decimating the original pulse-height channels to 35 energy bins, extracting composite variables via principal components analysis (PCA), and estimating statistically weighted distances from the mean vehicle spectrum with the mahalanobis distance (MD) metric. This paper reviews the methods used to establish the anomaly identification criteria and presents a systematic analysis of the response of the combined PCA and MD algorithm to modeled mono-energetic gamma-ray sources.

Tardiff, Mark F.; Runkle, Robert C.; Anderson, K. K.; Smith, L. E.

2006-01-23

323

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

324

Variations of the isotopic composition of sulfur in enstatite and ordinary chondrites  

NASA Technical Reports Server (NTRS)

High-precision sulfur isotopic analyses (delta S-33, delta S-34, and delta S-36) of bulk ordinary and enstatite chondrites demonstrate that systematic variations exist. The average delta S-34 values are -0.26 +/- 0.07, -0.02 +/- 0.06, and 0.49 +/- 0.16 percent for enstatite and ordinary and carbonaceous chondrites, respectively. Isotopic variations of different sample specimens of primitive meteorites, e.g., Qingzhen and Abee, were observed which may be attributed to heterogeneity in the early solar nebula. Sulfur isotopic fractionations in both bulk samples and mineral separates are mass-dependent, and no nuclear isotopic anomalies were detected. The sulfur isotopic compositions of both mineral and density separates were measured. The sulfur isotopic compositions of separated chondrules from Chainpur and Bjurbole are reported. Significant isotopic difference for the chondrules from the bulk meteorite are noted for both meteorites.

Gao, Xia; Thiemens, Mark H.

1993-01-01

325

Stable water isotopes in HadCM3: Isotopic signature of El Niño–Southern Oscillation and the tropical amount effect  

Microsoft Academic Search

Stable water isotopes have been added to the full hydrological cycle of the Hadley Centre Climate model (HadCM3) coupled atmosphere-ocean GCM. Simulations of ?18O in precipitation and at the ocean surface compare well with observations for the present-day climate. The model has been used to investigate the isotopic anomalies associated with ENSO; it is found that the anomalous ?18O in

J. C. Tindall; P. J. Valdes; L. C. Sime

2009-01-01

326

Stable isotope studies  

SciTech Connect

The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs.

Ishida, T.

1992-01-01

327

Easter microplate evolution: Pb isotope evidence  

NASA Astrophysics Data System (ADS)

We report on 53 Pb isotope analyses of basalts from 48 dredge stations occupied along the spreading boundaries of the Easter microplate and adjacent East Pacific Rise (EPR). Also included in the study are seven analyses of basalts from Easter and Sala y Gomez islands. A major anomaly is observed on the East Rift, around 27°S, where this ridge is shallowest and closest to Easter and Sala y Gomez islands. Basalts from the West Rift are less radiogenic. The means for the two rift populations are distinct, but their ranges overlap significantly. On the average, there is a systematic westward decrease in radiogenic Pb content with distance from Sala y Gomez. The Pb isotope anomaly is confined to the boundaries of the Microplate and the total range exceeds that of the entire EPR, both in the most and the least end of radiogenic Pb content. Radiogenic Pb content covaries with (La/Sm)N ratios with the exception of a nepheline-normative picritic basalt glass outlier. The trends are curvilinear. There is no correlation between the Pb isotope ratios and the bulk composition of the lavas. In Pb versus Pb isotope diagrams, basalts from the East and West rifts form two tight linear trends of statistically indistinguishable slope. Basalts from Easter and Sala y Gomez islands lie on the upper end of these trends. A binary mixing process between a radiogenic source similar to that present beneath Sala y Gomez and the large ion lithophile element (LILE)-depleted mid-ocean ridge basalt (MORB) source is strongly suggested. There is no trace of the Dupal anomaly beneath the microplate nor beneath Easter or Sala y Gomez Islands. If the Dupal anomaly is indeed continuous and of semi global extent, it must lie deeper in the mantle than the depths at which basaltic melts take source beneath the microplate and these two islands. There is also no correlation between the apparent dispersion of Pb isotope ratios and the rate at which the various ridge segments of the microplate spread. Tests of the plum pudding model across fracture zones, where smaller degrees of melting might have prevailed and preferential melting of the LILE-rich veins or plums may take place, were found to be inconclusive. In contrast, the overall variation in Pb isotopes, (La/Sm)N, and tectonic and kinematic evolution of the EPR, strongly support that the hotspot source-migrating ridge model may indeed be applicable to the region. Independent evidence suggests that the tectonic and geochemical anomaly associated with the Easter microplate is the result of the influence of a lateral mantle plume flow at shallow depth in the upper-mantle, connecting the Sala y Gomez plume with the westward migrating EPR. A small discontinuity in Pb isotope variation associated with the 25°S propagating East Rift, as also found across the 95.5°W propagator on the Galapagos Spreading Center, further supports the concept that the flux of the plume may pulsate; that is, the plume is discontinuous and probably rises in the form of a chain of blobs. The repeated tectonic disturbances and propagation of new rifts which characterize the evolution of the Easter microplate may coincide and be caused by the appearance of such blobs in the upper most mantle, as we have previously suggested for the Galapagos. There is a remarkable similarity in the geochemical, petrological, and tectonic configuration of the Easter microplate-Sala y Gomez hotspot system with that of the Galapagos, which suggests that very similar processes are at work in the two regions.

Hanan, Barry B.; Schilling, Jean-Guy

1989-06-01

328

Nickel and chromium isotopes in Allende inclusions  

NASA Technical Reports Server (NTRS)

High-precision nickel and chromium isotopic measurements were carried out on nine Allende inclusions. It is found that Ni-62, Ni-64, excesses are present in at least three of the samples. The results suggest that the most likely mechanism for the anomalies is a neutron-rich statistical equilibrium process. An indication of elevated Ni-60 is found in almost every inclusion measured. This effect is thought to be related to the decay of now extinct Fe-60. An upper limit of 1.6 X 10 to the -6th is calculated for the Fe-60/Fe-56 ratio at the time these Allende inclusions crystallized.

Birck, J. L.; Lugmair, G. W.

1988-01-01

329

Geological reasons for change in intensity of linear magnetic anomalies of the Kursk magnetic anomaly  

NASA Technical Reports Server (NTRS)

The geological reasons for fluctuations in the anomalous field intensity along the polar axes were examined. The Kursk magnetic anomaly is used as the basis for the study. A geological-geophysical section was constructed which used the results of the interpretation of gravimagnetic anomalies.

Zhavoronkin, I. A.; Kopayev, V. V.

1985-01-01

330

Signature of pending earthquake from electromagnetic anomalies  

NASA Astrophysics Data System (ADS)

Two electromagnetic (EM) anomalies have been detected in the VLF frequency band before the Athens earthquake (EQ) (Mw=5.9, Sept. 7, 1999) with the following characteristics: (i) The first and second anomaly lasted for 12 and 17 hours respectively with a cessation of 12 hours; (ii) The second anomaly ceased at about 9 hours before the EQ; (iii) The larger anomaly, the second one, contains approximately 80% of the total EM energy received; (iv) No EM disturbance has been recorded in the VHF frequency band unlike with other cases, e.g., the Kozani Grevena and Egion-Eratini earthquakes. The fault modeling of the Athens EQ, based on information obtained by radar interferometry, predicts two faults. The main fault segment is responsible for 80% of the total energy released, while the secondary fault segment for the remaining 20%. Moreover, a recent seismic data analysis supports the hypothesis that a two-event solution for the Athens EQ, is more likely than a single event solution. In addition, the absence of surface rupture explains the absence of EM detection in the VHF frequency band. The present analysis reveals that the properties of the preseismic electromagnetic anomalies might be considered as signatures of a pending earthquake.

Eftaxias, K.; Kapiris, P.; Polygiannakis, J.; Bogris, N.; Kopanas, J.; Antonopoulos, G.; Peratzakis, A.; Hadjicontis, V.

331

Hyperbolic Orbits and the Planetary Flylby Anomaly  

NASA Technical Reports Server (NTRS)

Space probes in the Solar System have experienced unexpected changes in velocity known as the flyby anomaly [1], as well as shifts in acceleration referred to as the Pioneer anomaly [2-4]. In the case of Earth flybys, ESA s Rosetta spacecraft experienced the flyby effect and NASA s Galileo and NEAR satellites did the same, although MESSENGER did not possibly due to a latitudinal property of gravity assists. Measurements indicate that both anomalies exist, and explanations have varied from the unconventional to suggestions that new physics in the form of dark matter might be the cause of both [5]. Although dark matter has been studied for over 30 years, there is as yet no strong experimental evidence supporting it [6]. The existence of dark matter will certainly have a significant impact upon ideas regarding the origin of the Solar System. Hence, the subject is very relevant to planetary science. We will point out here that one of the fundamental problems in science, including planetary physics, is consistency. Using the well-known virial theorem in astrophysics, it will be shown that present-day concepts of orbital mechanics and cosmology are not consistent for reasons having to do with the flyby anomaly. Therefore, the basic solution regarding the anomalies should begin with addressing the inconsistencies first before introducing new physics.

Wilson, T.L.; Blome, H.J.

2009-01-01

332

Discharges of krypton from Sellafield, 1951-1997, and the resultant doses to members of the public.  

PubMed

The radionulide 85Kr, which has a half-life of 10.72 years, is produced, almost exclusively, by reprocessing operations during which the fission product is released from irradiated nuclear fuel by chemical dissolution. Reprocessing plants at Sellafield, in Cumbria, have released the noble gas to atmosphere since operations commenced in 1952. Historically, krypton discharges were classified for security reasons, although these have been monitored and published by BNFL for each year since 1977. This paper reviews discharges of 85Kr from Sellafield, and consequent radiation doses, since its earliest operations. Over the past three years, discharges of 85Kr have increased due to the operation of the Thermal Oxide Fuel Reprocessing Plant (Thorp). Nonetheless, the associated annual committed effective dose to individuals remains low, peaking around 1.5 microSv a-1 to the identified critical groups, which compares with typical annual committed effective doses from natural sources of radiation of 2200 microSv. Maximum collective doses predicted from any single year of operations are 0.6 man Sv, 2 man Sv and 42 man Sv to the UK, Europe and the world respectively. Comparison may be made to natural background committed effective doses, which are of the order of 130,000 man Sva-1, 750,000 man Sva-1 and 13,000,000 man Sva-1 to the UK, EU and world populations respectively. PMID:9656191

Jackson, D; Zimmerman, C H; Gray, J

1998-06-01

333

Deflected Anomaly Mediation and Neutralino Dark Matter  

E-print Network

We study the phenomenology of the neutralino dark matter in the so called deflected anomaly mediation scenario. This scheme is obtained from the minimal anomaly mediated scenario by introducing a gauge mediated sector with $N_f$ messenger fields. Unlike the former scheme the latter has no tachyons. We find that the neutralino is still the LSP in a wide region of the parameter space: it is essentially a pure bino in the scenario with $N_f=1$ while it can also be a pure higgsino for $N_f>1$. This is very different from the naive anomaly mediated scenario which predicts a wino like neutralino. Moreover we do not find any tachyonic scalars in this scheme. After computing the relic density (considering all the possible coannihilations) we find that there are regions in the parameter space with values compatible with the latest WMAP results with no need to consider moduli fields that decay in the early universe.

Alessandro Cesarini; Francesco Fucito; Andrea Lionetto

2006-11-08

334

The Anomaly Structure of Regularized Supergravity  

E-print Network

On-shell Pauli-Villars regularization of the one-loop divergences of supergravity theories is used to study the anomaly structure of supergravity and the cancellation of field theory anomalies under a $U(1)$ gauge transformation and under the T-duality group of modular transformations in effective supergravity theories with three K\\"ahler moduli $T^i$ obtained from orbifold compactification of the weakly coupled heterotic string. This procedure requires constraints on the chiral matter representations of the gauge group that are consistent with known results from orbifold compactifications. Pauli-Villars regulator fields allow for the cancellation of all quadratic and logarithmic divergences, as well as most linear divergences. If all linear divergences were canceled, the theory would be anomaly free, with noninvariance of the action arising only from Pauli-Villars masses. However there are linear divergences associated with nonrenormalizable gravitino/gaugino interactions that cannot be canceled by PV fields...

Butter, Daniel

2014-01-01

335

Holographic entanglement entropy and gravitational anomalies  

NASA Astrophysics Data System (ADS)

We study entanglement entropy in two-dimensional conformal field theories with a gravitational anomaly. In theories with gravity duals, this anomaly is holographically represented by a gravitational Chern-Simons term in the bulk action. We show that the anomaly broadens the Ryu-Takayanagi minimal worldline into a ribbon, and that the anomalous contribution to the CFT entanglement entropy is given by the twist in this ribbon. The entanglement functional may also be interpreted as the worldline action for a spinning particle — that is, an anyon — in three-dimensional curved spacetime. We demonstrate that the minimization of this action results in the Mathisson-Papapetrou-Dixon equations of motion for a spinning particle in three dimensions. We work out several simple examples and demonstrate agreement with CFT calculations.

Castro, Alejandra; Detournay, Stephane; Iqbal, Nabil; Perlmutter, Eric

2014-07-01

336

Trace anomalies in chiral theories revisited  

NASA Astrophysics Data System (ADS)

Motivated by the search for possible CP violating terms in the trace of the energy-momentum tensor in theories coupled to gravity we revisit the problem of trace anomalies in chiral theories. We recalculate the latter and ascertain that in the trace of the energy-momentum tensor of theories with chiral fermions at one-loop the Pontryagin density appears with an imaginary coefficient. We argue that this may break unitarity, in which case the trace anomaly has to be used as a selective criterion for theories, analogous to the chiral anomalies in gauge theories. We analyze some remarkable consequences of this fact, that seem to have been overlooked in the literature.

Bonora, Loriano; Giaccari, Stefano; de Souza, Bruno Lima

2014-07-01

337

Multifractal characterization of global temperature anomalies  

NASA Astrophysics Data System (ADS)

The global monthly temperature anomaly time series for the period 1850-2012 has been investigated in terms of multifractal detrended fluctuation analysis (MF-DFA). Various multifractal observables, such as the generalized Hurst exponent, the multifractal exponent, and the singularity spectrum, are extracted and are fitted to a generalized binomial multifractal model consists of only two free parameters. The results of this analysis give a clear indication of the presence of long-term memory in the global temperature anomaly time series which causes multifractal pattern in the data. We investigate the possible other source(s) of multifractality in the series by random shuffling as well as by surrogating the original series and find that the probability density function also contributes to the observed multifractal pattern along with the long-memory effect. Surprisingly, the temperature anomaly time series are well described by the two-parameter multifractal binomial model.

Mali, Provash

2014-08-01

338

Coronary Artery Anomalies--Current Clinical Issues  

PubMed Central

The study of coronary artery anomalies would benefit from the clarification of various fundamental issues, including the definitions, classification, incidence, pathophysiologic mechanisms, and clinical relevance of each anomaly. The greatest challenge is to identify the abnormality and determine its clinical relevance so that appropriate treatment can be instituted. Currently, the coronary anatomy is essentially defined by the features of the (conductive) epicardial coronary tree and its dependent territory. Therefore, one must consider all the possible and observed variations in anatomic features that are used to describe the coronary arteries. We propose that the left anterior descending, circumflex, and right coronary arteries be considered the essential, elementary units of coronary anatomy. We also suggest that the coronary arteries be defined not by their origin or proximal course, but by their intermediate and distal segments or dependent microvascular bed. A strict classification system is necessary before meaningful data can be gathered about the incidence of coronary anomalies. With respect to clinical relevance, the greatest challenge is presented by anomalies that only occasionally cause critically severe clinical events and are otherwise compatible with a normal life. In such cases, it is not known whether the specific features of a given anomaly cause adverse clinical consequences, or whether additional episodic factors are required. To correlate subclassifiable anatomic and functional features with clinical events and prognoses, a large, multicenter database, relying on prospective, coordinated protocols, is urgently needed. In the absence of established official guidelines, we present practical protocols for diagnosing and treating coronary anomalies. (Tex Heart Inst J 2002;29:271–8) PMID:12484611

Angelini, Paolo

2002-01-01

339

Effects of Longwave Cloud Radiative Forcing Anomalies on the Atmospheric Response to Equatorial Pacific Sea Surface Temperature Anomalies  

NASA Technical Reports Server (NTRS)

The latest version of the National Center for Atmospheric Research community climate model (CCM2) has been used to investigate cloud radiative forcing (CRF) anomalies associated with equatorial Pacific sea surface temperature (SST) anomalies and the effects of the longwave CRF (LWCRF) anomalies on the atmospheric response to the SST anomalies. The SST anomalies cause large CRF anomalies, both longwave and shortwave, as well as latent heat anomalies at low latitudes on a global scale. The relative magnitude of the simulated longwave and shortwave CRF anomalies is consistent with the result of the Earth Radiation Budget Experiment (ERBE), implying that cloud height and cloud radiative properties such as emissivity and reflectivity are well simulated by the model. The LWCRF anomaly strongly enhances the precipitation anomaly in the whole tropical belt. The positive (negative) LWCRF anomaly warms (cools) the troposphere and destabilizes (stabilizes) the upper troposphere. The LWCRF anomaly enhances the Southern Oscillation and the related Walker circulation anomaly. The effects of the LWCRF anomaly are essential to the northern hemispheric extratropical circulation anomaly, the Pacific/North American pattern.

Chen, M.; Cess, Robert D.; Zhang, Ming-Hua

1995-01-01

340

Redshift Anomalies with Universal Free-Fall  

E-print Network

For most theories which parametrize modifications of General Relativity, including those which violate the equivalence principle, gravitational redshift tests typically offer weaker constraints on such test parameters than do precision measurements of the universality of free fall (UFF) and local Lorentz invariance (LLI). Although redshift anomalies are often linked with violations of UFF or LLI, they do not have to be. We offer a simple model in which particle masses anomalously vary with the gravitational potential. This generates gravitational redshift anomalies unconstrained by existing tests of UFF or LLI. We propose new experiments to limit such effects.

Michael A. Hohensee; Holger Mueller

2010-08-03

341

LHC Test of CDF $Wjj$ anomaly  

E-print Network

We discuss a test of the CDF dijet anomaly at the LHC. The recent observed dijet mass peak at the CDF is well fitted by a new particle with a mass of around 150 GeV, which decays into two jets. In this paper, we focus on only $Wjj$ signal to avoid model dependence, and comprehensively study the LHC discovery/exclusion reach. We found almost all the models are inconsistent with the result of the LHC, unless only valence quarks contribute the new process. We also discuss further prospects of the LHC search for this anomaly.

Keisuke Harigaya; Ryosuke Sato; Satoshi Shirai

2011-07-26

342

Preferential filtering for gravity anomaly separation  

NASA Astrophysics Data System (ADS)

We present the preferential filtering method for gravity anomaly separation based on Green equivalent-layer concept and Wiener filter. Compared to the conventional upward continuation and the preferential continuation, the preferential filtering method has the advantage of no requirement of continuation height. The method was tested both on the synthetic gravity data of a model of multiple rectangular prisms and on the real gravity data from a magnetite area in Jilin Province, China. The results show that the preferential filtering method produced better separation of gravity anomaly than both the conventional low-pass filtering and the upward continuation.

Guo, Lianghui; Meng, Xiaohong; Chen, Zhaoxi; Li, Shuling; Zheng, Yuanman

2013-02-01

343

The source of marine magnetic anomalies  

NASA Technical Reports Server (NTRS)

The Vine-Matthews hypothesis (1963) is examined. This hypothesis suggests that oceanic rocks become polarized in the direction of the magnetic field at the time of their formation, thus recording the polarity history of the earth's magnetic field. This produces the lineated magnetic anomalies on either side of the midoceanic ridge crests. The strength of these magnetic anomalies is studied to determine the strength of magnetization. Indirect determinations of the magnetization intensity of the oceanic crust and direct observations of the oceanic crust are compared. It is found that the average magnetization of a 6-km thick oceanic crust is 1.18 A/m.

Harrison, Christopher G. A.

1987-01-01

344

Radioactive anomaly discrimination from spectral ratios  

DOEpatents

A method for discriminating a radioactive anomaly from naturally occurring radioactive materials includes detecting a first number of gamma photons having energies in a first range of energy values within a predetermined period of time and detecting a second number of gamma photons having energies in a second range of energy values within the predetermined period of time. The method further includes determining, in a controller, a ratio of the first number of gamma photons having energies in the first range and the second number of gamma photons having energies in the second range, and determining that a radioactive anomaly is present when the ratio exceeds a threshold value.

Maniscalco, James; Sjoden, Glenn; Chapman, Mac Clements

2013-08-20

345

Magnetic anomalies northeast of Shatsky Plateau  

E-print Network

trending Japanese lineations to form a magnetic bight north of Shatsky Plateau. The bight is interpreted to be evidence of a ridge-ridge-ridge (RRR) triple junction which ex1sted from about 124 MYBP (anomaly MlON time) into the Cretaceous Duiet Per1od.... A r1dge-fault-fault (RFF) triple junction existed at Shatsky Plateau for about 17 MY (anomalies Mlg-MlDN t1me). The plate boun- daries were: a Pacif1c-Farallon (P-F) transform fault, a Pacific-Kula (P-K) spreading ridge, and a Kula-Farallon (K...

Risch, David Lawrence

2012-06-07

346

Photochemical mass-independent sulfur isotopes in achondritic meteorites.  

PubMed

Sulfides from four achondrite meteorite groups are enriched in 33S (up to 0.040 per mil) as compared with primitive chondrites and terrestrial standards. Stellar nucleosynthesis and cosmic ray spallation are ruled out as causes of the anomaly, but photochemical reactions in the early solar nebula could produce the isotopic composition. The large 33S excess present in oldhamite from the Norton County aubrite (0.161 per mil) suggests that refractory sulfide minerals condensed from a nebular gas with an enhanced carbon-oxygen ratio, but otherwise solar composition is the carrier. The presence of a mass-independent sulfur effect in meteorites argues for a similar process that could account for oxygen isotopic anomalies observed in refractory inclusions in primitive chondrites. PMID:16099982

Rai, Vinai K; Jackson, Teresa L; Thiemens, Mark H

2005-08-12

347

UV induced mass-independent sulfur isotope fractionation in stratospheric volcanic sulfate  

Microsoft Academic Search

Sulfuric acid aerosols produced in the stratosphere following massive volcanic eruptions possess a mass-independent sulfur isotopic signature, acquired when volcanic SO2 experiences UV photooxidation. The volcanic data are consistent with laboratory SO2 photooxidation experiments using UV light at 248 nm (maximum absorption of ozone), whereas sulfur isotopic anomalies previously observed in Archean samples are consistent with photodissociation at 190-220 nm.

J. Savarino; A. Romero; J. Cole-Dai; S. Bekki; M. H. Thiemens

2003-01-01

348

Barium isotopes in Allende meteorite - Evidence against an extinct superheavy element  

NASA Astrophysics Data System (ADS)

Carbon and chromite fractions from the Allende meteorite that contain isotopically anomalous xenon-131 to xenon-136 (carbonaceous chondrite fission or CCF xenon) at up to 5×1011 atoms per gram show no detectable isotopic anomalies in barium-130 to barium-138. This rules out the possibility that the CCF xenon was formed by in situ fission of an extinct superheavy element. Apparently the CCF xenon and its carbonaceous carrier are relics from stellar nucleosynthesis.

Lewis, R. S.; Anders, E.; Shimamura, T.; Lugmair, G. W.

1983-12-01

349

Congenital coronary artery anomalies angiographic classification revisited  

Microsoft Academic Search

Many fragmental classification of coronary artery anomalies (CAAs) exist, but a simple practical angiographic classification for angiographers has been never proposed. This study is aimed to suggest a simplified angiographic classification of congenital CAAs based on just a few univocal common angiographic patterns. The authors reviewed 5100 coronary angiographies in order to select CAAs patients and identify simple common angiographic

Rigatelli Gianluca; Docali Giorgio; Rossi Paolo; Bovolon Daniela; Rossi Daniele; Bandello Attilio; Lonardi Gabriele; Rigatelli Giorgio

2003-01-01

350

Psychoeducational Implications of Sex Chromosome Anomalies  

ERIC Educational Resources Information Center

Numerous anomalies involving the sex chromosomes (X or Y) have been documented and their impact on development, learning, and behavior studied. This article reviews three of these disorders, Turner syndrome, Klinefelter syndrome, and Lesch-Nyhan disease. Each of these three is associated with one or more selective impairments or behavioral…

Wodrich, David L.; Tarbox, Jennifer

2008-01-01

351

Table of hyperfine anomaly in atomic systems  

SciTech Connect

This table is a compilation of experimental values of magnetic hyperfine anomaly in atomic and ionic systems. The last extensive compilation was published in 1984 by Büttgenbach [S. Büttgenbach, Hyperfine Int. 20 (1984) 1] and the aim here is to make an up to date compilation. The literature search covers the period up to January 2011.

Persson, J.R., E-mail: jonas.persson@ntnu.no

2013-01-15

352

The anomaly data base of screwworm information  

NASA Technical Reports Server (NTRS)

Standard statistical processing of anomaly data in the screwworm eradication data system is possible from data compiled on magnetic tapes with the Univac 1108 computer. The format and organization of the data in the data base, which is also available on dedicated disc storage, are described.

Giddings, L. E.

1976-01-01

353

Locally covariant chiral fermions and anomalies  

E-print Network

We define chiral fermions in the presence of non-trivial gravitational and gauge background fields in the framework of locally covariant field theory. This allows to straightforwardly compute the chiral anomalies on non-compact Lorentzian space-times, without recourse to a weak field approximation.

Jochen Zahn

2014-07-08

354

Satellite Anomalies from Galactic Cosmic Rays  

Microsoft Academic Search

Anomalies in communication satellite operation have been caused by the unexpected triggering of digital circuits. Interactions with galactic cosmic rays were investigated as a mechanism for a number of these events. The mechanism assumed was the charging of the base-emitter capacitance of sensitive transistors to the turn-on voltage. The calculation of the cosmic ray event rate required the determination of

D. Binder; E. C. Smith; A. B. Holman

1975-01-01

355

Table of hyperfine anomaly in atomic systems  

NASA Astrophysics Data System (ADS)

This table is a compilation of experimental values of magnetic hyperfine anomaly in atomic and ionic systems. The last extensive compilation was published in 1984 by Büttgenbach [S. Büttgenbach, Hyperfine Int. 20 (1984) 1] and the aim here is to make an up to date compilation. The literature search covers the period up to January 2011.

Persson, J. R.

2013-01-01

356

Kohn anomaly in phonon driven superconductors  

NASA Astrophysics Data System (ADS)

Anomalies often occur in the physical world. Sometimes quite unexpectedly anomalies may give rise to new insight to an unrecognized phenomenon. In this paper we shall discuss about Kohn anomaly in a conventional phonon-driven superconductor by using a microscopic approach. Recently Aynajian et al.'s experiment showed a striking feature; the energy of phonon at a particular wave-vector is almost exactly equal to twice the energy of the superconducting gap. Although the phonon mechanism of superconductivity is well known for many conventional superconductors, as has been noted by Scalapino, the new experimental results reveal a genuine puzzle. In our recent work we have presented a detailed theoretical analysis with the help of microscopic calculations to unravel this mystery. We probe this aspect of phonon behaviour from the properties of electronic polarizability function in the superconducting phase of a Fermi liquid metal, leading to the appearance of a Kohn singularity. We show the crossover to the standard Kohn anomaly of the normal phase for temperatures above the transition temperature. Our analysis provides a nearly complete explanation of this new experimentally discovered phenomenon. This report is a shorter version of our recent work in JPCM.

Das, M. P.; Chaudhury, R.

2014-08-01

357

Anomaly Detection in Relational Data for the  

E-print Network

Anomaly Detection in Relational Data for the Discovery of Insider Threats Bill Eberle DepartmentECBHU2704309YOKOHAMASEATTLE JAPAN CSCO LING YUN HE 36 CHINA OCEAN SHPG 20601 0048774000ECBHU2709933YOKOHAMASEATTLE JAPAN CSCO LING YUN HE 36 CHINA OCEAN SHPG 20601 0048774000ECBHU2724727YOKOHAMASEATTLE JAPAN CSCO

Eberle, William

358

Anomalies, dimensional regularization, and the heat kernel  

SciTech Connect

In the context of dimensional continuation, it is shown that axial anomalies are associated with chiral noninvariance of the action (but not of the measure) and they can be extracted nonperturbatively from the heat kernel. Other techniques where the action is deemed invariant but the functional integral measure is not are shown to be equivalent.

Delbourgo, R.; Thompson, G.

1985-12-15

359

Conformal anomaly actions for dilaton interactions  

E-print Network

We discuss, in conformally invariant field theories such as QCD with massless fermions, a possible link between the perturbative signature of the conformal anomaly, in the form of anomaly poles of the 1-particle irreducible effective action, and its description in terms of Wess-Zumino actions with a dilaton. The two descriptions are expected to capture the UV and IR behaviour of the conformal anomaly, in terms of fundamental and effective degrees of freedom respectively, with the dilaton effective state appearing in a nonlinear realization. As in the chiral case, conformal anomalies seem to be related to the appearance of these effective interactions in the 1PI action in all the gauge-invariant sectors of the Standard Model. We show that, as a consequence of the underlying anomalous symmetry, the infinite hierarchy of recurrence relations involving self-interactions of the dilaton is entirely determined only by the first four of them. This relation can be generalized to any even space-time dimension.

Rose, Luigi Delle; Serino, Mirko

2014-01-01

360

Ocean response to surface heat anomalies  

NASA Technical Reports Server (NTRS)

An ocean general circulation model (OGCM) is used to study the response of ocean heat and mass transport to positive and negative heat flux anomalies at the ocean surface. As expected, tropical and low-latitude mixed layers respond rapidly (e-folding time about 50-70 years) to external forcing, while the response of the high-latitude mixed layer, especially the Southern Ocean and northern North Atlantic, is very slow (e-folding time greater than 300 yr). The overall response is faster for negative than positive heat flux anomaly at the surface. The meridional heat transport changes by 15% in the first 50 yr in the southern high latitudes. Surprisingly, for the next 400-500 yr the change is very small. The analysis shows that the meridional mass transport intensifies in response to a negative surface heat flux anomaly but weakens in response to a positive heat flux anomaly. For example, at model year 100 the North Atlantic Deep Water (NADW) is reduced from about 18 Sv to about 10 Sv for the positive heat flux experiment but increased to about 26 Sv for the negative heat flux experiment.

Jiang, Xingjian; Fung, Inez

1994-01-01

361

Ocean response to surface heat anomalies  

SciTech Connect

An ocean general circulation model (OGCM) is used to study the response of ocean heat and mass transport to positive and negative heat flux anomalies at the ocean surface. As expected, tropical and low-latitude mixed layers respond rapidly (e-folding time about 50-70 years) to external forcing, while the response of the high-latitude mixed layer, especially the Southern Ocean and northern North Atlantic, is very slow (e-folding time greater than 300 yr). The overall response is faster for negative than positive heat flux anomaly at the surface. The meridional heat transport changes by 15% in the first 50 yr in the southern high latitudes. Surprisingly, for the next 400-500 yr the change is very small. The analysis shows that the meridional mass transport intensifies in response to a negative surface heat flux anomaly but weakens in response to a positive heat flux anomaly. For example, at model year 100 the North Atlantic Deep Water (NADW) is reduced from about 18 Sv to about 10 Sv for the positive heat flux experiment but increased to about 26 Sv for the negative heat flux experiment.

Jiang, Xingjian; Fung, Inez (NASA. Goddard Inst. for Space Studies, New York, NY (United States))

1994-05-01

362

The inheritance anomaly: ten years after  

Microsoft Academic Search

The term inheritance anomaly was coined in 1993 by Matsuoka and Yonezawa [15] to refer to the problems arising by the coexistence of inheritance and concurrency in concurrent object oriented languages (COOLs). The quirks arising by such combination have been observed since the early eighties, when the first experimental COOLs were designed [3]. In the nineties COOLs turned from research

Giuseppe Milicia; Vladimiro Sassone

2004-01-01

363

Subband anomaly detection and spatial localization  

Microsoft Academic Search

The modulating source assumption allows us to specify the problem of anomaly detection as a problem in robust statistics. The demodulation property of the Teager energy operator is used to jointly expose amplitude and frequency features of audio sub-bands. Spectral decomposition is achieved using a scaled wavelet function acting as a band-pass filter which halves its bandwidth for each decomposition

John F. N. Salik

2007-01-01

364

Integrating network misuse and anomaly prevention  

Microsoft Academic Search

Network intrusion detection systems (NIDS) aim at preventing network attacks and unauthorised remote use of computers. More accurately, depending on the kind of attack it targets, NIDS can be oriented to detect misuses (by defining all possible attacks) or anomalies (by modelling legitimate behaviour to find those that do not fit into that model). Still, since their problem knowledge is

Y. K. Penva; Pablo G. Bringas

2008-01-01

365

Table of hyperfine anomaly in atomic systems  

E-print Network

This table is a compilation of experimental values of magnetic hyperfine anomaly in atomic and ionic systems. The last extensive compilation was published in 1984 by Buttgenbach (Hyperfine Interactions 20, (1984) p 1) and the aim here is to make an up to date compilation. The literature search covers the period to January 2011.

Jonas R. Persson

2011-10-27

366

Passive Identification and Analysis of TCP Anomalies  

E-print Network

and time, which is due to the closed-loop behavior of TCP, the TCP/IP client- server communication paradigmPassive Identification and Analysis of TCP Anomalies Marco Mellia, Michela Meo, Luca Muscariello on passive measurements of TCP traffic, main component of nowadays traffic. We propose a heuristic technique

367

Anomaly Transform method for initializing climate forecas.  

NASA Astrophysics Data System (ADS)

A new approach, an Anomaly Transform method (AT) using a physics based metric, is developed to initialize decadal climate hindcast within the German climate prediction MiKlip project. The method starts from balanced anomaly structures in space and time and between variables derived from control runs and applies an orthogalization to these. Two physics based metric are used to set up the eigen problem (1) the weighted total energy with its zonal, meridional kinetic and available potential energy terms having equal contributions, and (2) the weighted ocean heat content in which a disturbance is applied only to the initial temperature fields. The choice of a reference state defining the anomalies and the selected sequence of anomalies, once on a seasonal timescales and second on an interannual timescales, project a-priori only the slow modes of the ocean physical processes, such that the disturbances grow mainly in the Western Boundary Currents, in the ACC and ENSO regions. An additional set of initial conditions was designed to fit in a least square sense anomalies from the GECCO-2 ocean reanalysis. These sets of AT initial conditions and the MPIOM-ESM coupled model in T63L47/GR15 resolution were used for ensemble experiments and a retrospective forecast. The weighted total energy norm is used to monitor the amplitudes and rates of the fastest growing error modes. The results showed minor dependence of the instability growth on the selected metric but considerable change due to the rescaling coefficients magnitude on the perturbation amplitude. In contrary to similar atmospheric applications, we find an energy conversion from kinetic to available potential energy, which suggests different source of uncertainties mainly associated with changes in density fields.

Romanova, Vanya; Hense, Andreas

2014-05-01

368

ChemTeacher: Isotopes  

NSDL National Science Digital Library

ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Isotopes page includes resources for teaching students about the structure and uses of isotopes.

2011-01-01

369

Galactic Evolution of Silicon Isotopes: Application to Presolar SiC Grains From Meteorites  

E-print Network

We calculate and discuss the chemical evolution of the isotopic silicon abundances in the interstellar medium at distances and times appropriate to the birth of the solar system. This has several objectives, some of which are related to anomalous silicon isotope ratios within presolar grains extracted from meteorites; namely: (1) What is the relative importance for silicon isotopic compositions in the bulk ISM of Type II supernovae, Type Ia supernovae, and AGB stars? (2) Are $^{29}$Si and $^{30}$Si primary or secondary nucleosynthesis products? (3) In what isotopic direction in a three-isotope plot do core-collapse supernovae of different mass move the silicon isotopic composition? (4) Why do present calculations not reproduce the solar ratios for silicon isotopes, and what does that impose upon studies of anomalous Si isotopes in meteoritic silicon carbide grains? (5) Are chemical-evolution features recorded in the anomalous SiC grains? Our answers are formulated on the basis of the Woosley \\& Weaver (1995) supernova yield survey. Renormalization with the calculated interstellar medium silicon isotopic composition and solar composition is as an important and recurring concept of this paper. Possible interpretations of the silicon isotope anomalies measured in single SiC grains extracted from carbonaceous meteorites are then presented. The calculations suggest that the temporal evolution of the isotopic silicon abundances in the interstellar medium may be recorded in these grains.

F. X. Timmes; Donald D. Clayton

1996-06-27

370

Neutral pion lifetime measurements and the QCD chiral anomaly  

E-print Network

A fundamental property of QCD is the presence of the chiral anomaly, which is the dominant component of the ?[superscript 0]??? decay rate. Based on this anomaly and its small (?4.5%) chiral correction, a prediction of the ...

Bernstein, Aron M.

371

Detectability of Traffic Anomalies in Two Adjacent Augustin Soule1  

E-print Network

that transit between the two networks. We show that differences in the monitoring infrastructure, network engineering practices, and anomaly-detection parameters have a large impact on which anomaly detectability

372

Anal anomalies: an uncommon feature of velocardiofacial (Shprintzen) syndrome?  

PubMed Central

We report three cases of velocardiofacial syndrome (VCFS) with anal anomalies who have deletions of the 22q11 region and a further case where the proband has VCFS clinically and her father has an anal anomaly. It is important to consider VCFS in the differential diagnosis of children with anal anomalies and to look for other features of the syndrome, such as asymmetrical crying facies, submucous cleft of the palate, developmental delay, cardiac anomalies, and hypoparathyroidism. Images PMID:9032655

Worthington, S; Colley, A; Fagan, K; Dai, K; Lipson, A H

1997-01-01

373

i\\ai"GIIS... Apollo 15 Anomalies Investigation PAGE  

E-print Network

' ·~ i\\ai"GIIS... Apollo 15 Anomalies Investigation PAGE 1 OF /~-........Divl·lan DATE 10/11/71 The purpose of this ATM is to review and status the BxA effort with respect to the Apollo 15 Anomalies t '-· :·~· . . !· ·'··..'· ~· : #12;Apollo 15 Anomalies Investigation TABLE OF CONTENTS Anomalies 1. UHT/Subpackage #2 Interface 2

Rathbun, Julie A.

374

MONTHLY SEA-SURFACE TEMPERATURE ANOMALY GRAPHS FOR ATLANTIC COAST  

E-print Network

MONTHLY SEA-SURFACE TEMPERATURE ANOMALY GRAPHS FOR ATLANTIC COAST STATIONS by Franklin StearnsKeman, Director Monthly Sea-Surface Temperature Anomaly Graphs For Atlantic Coast Stations by Franklin Stearns. December 19^4 #12;Monthly Sea-Surface Temperature Anomaly Graphs For Atlantic Coast Stations by Franklin

375

Late-Term Abortion for Fetal Anomaly: Vietnamese Women's Experiences  

Microsoft Academic Search

Screening for fetal anomalies in the second trimester of pregnancy is increasingly becoming a part of antenatal care. As a consequence, more pregnant women are learning that the child they are expecting has an anomaly. This article derives from anthropological research in a hospital in Hanoi, Viet Nam, from 2003–2006 that investigated 30 women's experiences after a fetal anomaly was

Tine Gammeltoft

2008-01-01

376

Trajectory Boundary Modeling of Time Series for Anomaly Detection  

E-print Network

compares favorably with anomaly detection algorithms based on Euclidean distance and dynamic time warping on the Space Shuttle Marrotta fuel control valve data set. Keywords Time series anomaly detection, MachineTrajectory Boundary Modeling of Time Series for Anomaly Detection Matthew V. Mahoney and Philip K

Chan, Philip K.

377

Five-Year Average Global Temperature Anomalies 1880 - 2010  

NSDL National Science Digital Library

This color-coded map displays a progression of changing five-year average global surface temperatures anomalies from 1880 through 2010. The final frame represents global temperature anomalies averaged from 2006 to 2010. The temperature anomalies are computed relative to the base period 1951-1980.

Schmunk, Robert B.; Hansen, J.; Ruedy, R.; Sato, Mki; Lo, K.; Studio, Nasa/goddard S.

378

Congenital and developmental anomalies of the shoulder girdle.  

PubMed

An understanding of congenital and developmental anomalies of the shoulder girdle is facilitated by a knowledge of embryology, physeal appearance and closure, and phylogenetic changes. Scapular, clavicular, and proximal humeral anomalies are classified and discussed with reference to diagnosis and management. Finally anomalies of the shoulder girdle musculature are delineated. PMID:7001305

Samilson, R L

1980-04-01

379

El Nino: Sea Surface Temperature Anomaly and Sea Surface Height Anomaly from Sept. 1996 to Sept. 1997  

NSDL National Science Digital Library

Sea surface height anomaly is presented as topography and sea surface temperature anomaly as color. A similar visualization (animation 1415) presents this same data and includes a pan from the front view to a side view.

Shirah, Greg; Busalacchi, Antonio

1997-09-08

380

Isotopically controlled semiconductors  

SciTech Connect

Semiconductor bulk crystals and multilayer structures with controlled isotopic composition have attracted much scientific and technical interest in the past few years. Isotopic composition affects a large number of physical properties, including phonon energies and lifetimes, bandgaps, the thermal conductivity and expansion coefficient and spin-related effects. Isotope superlattices are ideal media for self-diffusion studies. In combination with neutron transmutation doping, isotope control offers a novel approach to metal-insulator transition studies. Spintronics, quantum computing and nanoparticle science are emerging fields using isotope control.

Haller, Eugene E.

2001-12-21

381

Pelger-Huët Anomaly in a cat.  

PubMed

A 14-year-old, spayed female Domestic Shorthair cat was referred to the Purdue University Veterinary Teaching Hospital (PUVTH) for iodine 131 treatment of hyperthyroidism. Upon arrival, a biochemistry profile and a CBC were performed. Approximately 50% of the neutrophils and all the eosinophils observed were hyposegmented with a mature, condensed chromatin pattern. Nuclei had a band to "dumbbell" shape, and rarely a round shape, suggesting a Pelger-Huët anomaly or a pseudo Pelger-Huët. Based on both a negative FeLV and FIV tests, the absence of any clinical signs to support an inflammatory process, and the persistence of this granulocytic morphology 6 months after its previous admission to the PUVTH, a diagnosis of Pelger-Huët anomaly was established in this cat. PMID:25115222

Deshuillers, Pierre; Raskin, Rose; Messick, Joanne

2014-09-01

382

Conditional Anomaly Detection with Soft Harmonic Functions  

PubMed Central

In this paper, we consider the problem of conditional anomaly detection that aims to identify data instances with an unusual response or a class label. We develop a new non-parametric approach for conditional anomaly detection based on the soft harmonic solution, with which we estimate the confidence of the label to detect anomalous mislabeling. We further regularize the solution to avoid the detection of isolated examples and examples on the boundary of the distribution support. We demonstrate the efficacy of the proposed method on several synthetic and UCI ML datasets in detecting unusual labels when compared to several baseline approaches. We also evaluate the performance of our method on a real-world electronic health record dataset where we seek to identify unusual patient-management decisions.

Valko, Michal; Kveton, Branislav; Valizadegan, Hamed; Cooper, Gregory F.; Hauskrecht, Milos

2012-01-01

383

A critical appraisal of the LSND anomaly  

E-print Network

The so-called 'LSND anomaly', a 3.8 sigma excess of anti-nu_e events interpreted as originating from anti-nu_mu -> anti-nu_e oscillation, gave rise to many theoretical speculations. The MiniBooNE Collaboration reported inconsistency of this interpretation with the findings from their search for nu_mu -> nu_e oscillations. Yet the origin of the LSND anomaly was never clarified. A critical issue is the prediction of the background anti-nu_e flux that was used in the analysis of the LSND experiment. For this, decisive input comes from pion spectra measured with the HARP large-angle spectrometer under conditions that closely resemble the LSND situation: a proton beam with 800 MeV kinetic energy hitting a water target.

I. Boyko

2008-10-08

384

Hyperactive behavior and minor physical anomalies.  

PubMed

Minor physical anomalies (MPAs) are congenital abnormalities of body structure which reflect fetal maldevelopment. They originate in the same embryonic layer that produces the central nervous system, and it is reasoned that MPAs are markers of nervous system anomalies. High MPA counts have been associated with hyperactive behavior in normal and clinical populations of boys, and with inhibited behavior in normal groups of girls. The present sample of children from a longitudinal study of a Danish birth cohort show no significant sex differences in mean number of MPAs, but the male hyperactivity-MPA relation and the female inhibition-MPA relation is supported in this non-clinical sample. MPAs are not recommended for use in clinical screening or diagnosis at this time, but the evidence of a congenital, biological component to hyperactive behavior may eventually have useful implications for prevention and/or intervention. PMID:4083059

Fogel, C A; Mednick, S A; Michelsen, N

1985-12-01

385

Thesis: Orientifolds, Anomalies and the Standard Model  

E-print Network

In this thesis, we study aspects of D-brane realizations of the Standard Model. Specifically, we study orientifold models with rotation and translation elements that break supersymmetry, provide the general consistency conditions and derive the massless spectrum for these type of orientifolds. These models contain in general anomalous U(1) gauge fields. The Green-Schwarz mechanism cancels the anomaly and provides a mass term for the anomalous gauge fields. We calculate the bare mass for supersymmetric and non-supersymmetric vacua and we show that higher dimensional anomalies can affect the masses of the anomalous U(1)s. Phenomenological aspects are also discussed. We evaluate the contribution of the extra U(1) fields to the anomalous moments and it is shown that this imposes constraints on the magnitude of the string scale.

P. Anastasopoulos

2005-03-07

386

Thesis: Orientifolds, Anomalies and the Standard Model  

NASA Astrophysics Data System (ADS)

In this thesis, we study aspects of D-brane realizations of the Standard Model. Specifically, we study orientifold models with rotation and translation elements that break supersymmetry, provide the general consistency conditions and derive the massless spectrum for these type of orientifolds. These models contain in general anomalous U(1) gauge fields. The Green-Schwarz mechanism cancels the anomaly and provides a mass term for the anomalous gauge fields. We calculate the bare mass for supersymmetric and non-supersymmetric vacua and we show that higher dimensional anomalies can affect the masses of the anomalous U(1)s. Phenomenological aspects are also discussed. We evaluate the contribution of the extra U(1) fields to the anomalous moments and it is shown that this imposes constraints on the magnitude of the string scale.

Anastasopoulos, P.

2005-03-01

387

Behavior profiling for robust anomaly detection  

Microsoft Academic Search

Internet attacks are evolving using evasion techniques such as polymorphism and stealth scanning. Conventional detection systems using signature-based and\\/or rule-based anomaly detection techniques no longer suffice. It is difficult to predict what form the next malware attack will take and these pose a great challenge to the design of a robust intrusion detection system. We focus on the anomalous behavioral

Shun-Wen Hsiao; Yeali S. Sun; Meng Chang Chen; Hui Zhang

2010-01-01

388

Scaling anomalies in Kaluza-Klein theory  

SciTech Connect

The effect of Pauli interactions on the scaling anomaly is to add F/sup 4/, (par. deltaF)/sup 2/ and m/sup 2/F/sup 2/ terms to the trace of the stress-tensor at one loop level, such terms being connected with renormalization. However, when the sum over all modes is taken, these extra contributions vanish upon zeta-function regularisation.

Delbourgo, R.; Thompson, G.; Weber, R.O.

1987-04-01

389

Heat flux boundary anomalies and thermal winds  

NASA Astrophysics Data System (ADS)

Several studies have shown strong effects of outer boundary heat flux patterns on the dynamo mechanism in planets. For example, the hemispherical field of the ancient Martian dynamo can be explained by a large scale sinusoidal anomaly of the core mantle boundary heat flux triggered by large scale mantle convection or giant impacts. The magnetic fields show typically the desired effect - though dynamo action is locally stronger where the underneath heat flux is higher. However, it remains an open question if these effects still apply for more realistic planetary parameters, such as vigor of the convection (Rayleigh number) or the rotation rate (Ekman). The sinusoidal variation of the CMB heat flux along the colatitude with larger heat flux in the southern and smaller in the northern hemisphere as used for Mars can lead to a concentration of magnetic field in the south. The shape of such a hemispherical dynamo matches the crustal magnetization pattern at the surface and seems therefore an admissible mode for the ancient Martian dynamo. As the consequence of the emerging latitudinal temperature gradients convection and induction are dominated by thermal winds. These zonal flows were found to be equatorial antisymmetric, axisymmetric, ageostrophic, of strong amplitude and have therefore a severe effect on core convection and especially the induction process. We measure the underlying thermal anomalies as a function of Rayleigh and Ekman number and show that they are responsible for the thermal winds. Our results suggest that temperature anomalies decrease clearly with the supercriticality of the convection due to faster stirring and mixing, but show no additional dependence on the Ekman number. Interestingly, the decline of the latitudinal temperature anomaly follows a recently suggested scaling law for the thickness of thermal boundary layers. Even though the convective supercriticality of planetary cores is rather large and therefore only a minor effect of thermal boundary disturbances is expected, we suggest thermal winds can still significantly contribute to the total kinetic energy in real planetary core.

Dietrich, Wieland; Wicht, Johannes

2013-04-01

390

Multifactor Explanations of Asset Pricing Anomalies  

Microsoft Academic Search

Previous work shows that average returns on common stocks are related to firm characteristics like size, earnings\\/price, cash flow\\/price, book-to-market equity, past sales growth, long-term past return, and short-term past return. Because these patterns in average returns apparently are not explained by the capital asset pricing model, (CAPM), they are called anomalies. The authors find that, except for the continuation

EUGENE F. FAMA; KENNETH R. FRENCH

1996-01-01

391

Cosmological anomalies and exotic smoothness structures  

E-print Network

It seems to be generally accepted that apparently anomalous cosmological observations, such as accelerating expansion, etc., necessarily are inconsistent with standard general relativity and standard matter sources. Following the suggestions of S{\\l}adkowski, we point out that in addition to exotic theories and exotic matter there is another possibility. We refer to exotic differential structures on ${\\mathbb R}^4$ which could be the source of the observed anomalies without changing the Einstein equations or introducing strange forms of matter.

Torsten Asselmeyer-Maluga; Carl H. Brans

2001-10-08

392

Video behavior profiling for anomaly detection.  

PubMed

This paper aims to address the problem of modelling video behaviour captured in surveillancevideos for the applications of online normal behaviour recognition and anomaly detection. A novelframework is developed for automatic behaviour profiling and online anomaly sampling/detectionwithout any manual labelling of the training dataset. The framework consists of the followingkey components: (1) A compact and effective behaviour representation method is developed basedon discrete scene event detection. The similarity between behaviour patterns are measured basedon modelling each pattern using a Dynamic Bayesian Network (DBN). (2) Natural grouping ofbehaviour patterns is discovered through a novel spectral clustering algorithm with unsupervisedmodel selection and feature selection on the eigenvectors of a normalised affinity matrix. (3) Acomposite generative behaviour model is constructed which is capable of generalising from asmall training set to accommodate variations in unseen normal behaviour patterns. (4) A run-timeaccumulative anomaly measure is introduced to detect abnormal behaviour while normal behaviourpatterns are recognised when sufficient visual evidence has become available based on an onlineLikelihood Ratio Test (LRT) method. This ensures robust and reliable anomaly detection and normalbehaviour recognition at the shortest possible time. The effectiveness and robustness of our approachis demonstrated through experiments using noisy and sparse datasets collected from both indoorand outdoor surveillance scenarios. In particular, it is shown that a behaviour model trained usingan unlabelled dataset is superior to those trained using the same but labelled dataset in detectinganomaly from an unseen video. The experiments also suggest that our online LRT based behaviourrecognition approach is advantageous over the commonly used Maximum Likelihood (ML) methodin differentiating ambiguities among different behaviour classes observed online. PMID:18369257

Xiang, Tao; Gong, Shaogang

2008-05-01

393

Fusion and normalization to enhance anomaly detection  

NASA Astrophysics Data System (ADS)

This study examines normalizing the imagery and the optimization metrics to enhance anomaly and change detection, respectively. The RX algorithm, the standard anomaly detector for hyperspectral imagery, more successfully extracts bright rather than dark man-made objects when applied to visible hyperspectral imagery. However, normalizing the imagery prior to applying the anomaly detector can help detect some of the problematic dark objects, but can also miss some bright objects. This study jointly fuses images of RX applied to normalized and unnormalized imagery and has a single decision surface. The technique was tested using imagery of commercial vehicles in urban environment gathered by a hyperspectral visible/near IR sensor mounted in an airborne platform. Combining detections first requires converting the detector output to a target probability. The observed anomaly detections were fitted with a linear combination of chi square distributions and these weights were used to help compute the target probability. Receiver Operator Characteristic (ROC) quantitatively assessed the target detection performance. The target detection performance is highly variable depending on the relative number of candidate bright and dark targets and false alarms and controlled in this study by using vegetation and street line masks. The joint Boolean OR and AND operations also generate variable performance depending on the scene. The joint SUM operation provides a reasonable compromise between OR and AND operations and has good target detection performance. In addition, new transforms based on normalizing correlation coefficient and least squares generate new transforms related to canonical correlation analysis (CCA) and a normalized image regression (NIR). Transforms based on CCA and NIR performed better than the standard approaches. Only RX detection of the unnormalized of the difference imagery in change detection provides adequate change detection performance.

Mayer, R.; Atkinson, G.; Antoniades, J.; Baumback, M.; Chester, D.; Edwards, J.; Goldstein, A.; Haas, D.; Henderson, S.; Liu, L.

2009-05-01

394

SOM-Based Anomaly Intrusion Detection System  

Microsoft Academic Search

In this paper, a SOM-based anomaly intrusion detection system is proposed, which can contract high-dimension data to lower,\\u000a meanwhile keeping the primary relationship between clustering and topology. During the experiment, the theory of SOM is used\\u000a to train three SOMs on the layers of system, process and network. Although our experiment environment is simpler than the\\u000a real one, the result

Chun-dong Wang; He-feng Yu; Huai-bin Wang; Kai Liu

2007-01-01

395

Modelling the Pioneer anomaly as modified inertia  

E-print Network

This paper proposes an explanation for the Pioneer anomaly: an unexplained Sunward acceleration of 8.74 +/- 1.33 x 10^-10 m s^-2 seen in the behaviour of the Pioneer probes. Two hypotheses are made: (1) Inertia is a reaction to Unruh radiation and (2) this reaction is weaker for low accelerations because some wavelengths in the Unruh spectrum do not fit within a limiting scale (twice the Hubble distance) and are disallowed: a process similar to the Casimir effect. When these ideas are used to model the Pioneer crafts' trajectories there is a slight reduction in their inertial mass, causing an anomalous Sunward acceleration of 6.9 +/- 3.5 x 10^-10 m s^-2 which agrees within error bars with the observed Pioneer anomaly beyond 10 AU from the Sun. This new scheme is appealingly simple and does not require adjustable parameters. However, it also predicts an anomaly within 10 AU of the Sun, which has not been observed. Various observational tests for the idea are proposed.

M. E. McCulloch

2006-12-20

396

Deflected anomaly mediation and neutralino dark matter  

SciTech Connect

This is a study of the phenomenology of the neutralino dark matter in the so called deflected anomaly mediation scenario. This scheme is obtained from the minimal anomaly-mediated scenario by introducing a gauge-mediated sector with N{sub f} messenger fields. Unlike the former scheme the latter has no tachyons. We find that the neutralino is still the LSP in a wide region of the parameter space: it is essentially a pure bino in the scenario with N{sub f}=1 while it can also be a pure Higgsino for N{sub f}>1. This is very different from the naive anomaly-mediated scenario which predicts a wino like neutralino. Moreover we do not find any tachyonic scalars in this scheme. After computing the relic density (considering all the possible coannihilations) we find that there are regions in the parameter space with values compatible with the latest WMAP results with no need to consider moduli fields that decay in the early universe.

Cesarini, Alessandro; Fucito, Francesco; Lionetto, Andrea [Dipartimento di Fisica, Universita di Roma 'Tor Vergata' I.N.F.N. Sezione di Roma II, Via della Ricerca Scientifica, 00133 Rome (Italy)

2007-01-15

397

CHAMP Magnetic Anomalies of the Antarctic Crust  

NASA Technical Reports Server (NTRS)

Regional magnetic signals of the crust are strongly masked by the core field and its secular variations components and hence difficult to isolate in the satellite measurements. In particular, the un-modeled effects of the strong auroral external fields and the complicated- behavior of the core field near the geomagnetic poles conspire to greatly reduce the crustal magnetic signal-to-noise ratio in the polar regions relative to the rest of the Earth. We can, however, use spectral correlation theory to filter the static lithospheric and core field components from the dynamic external field effects. To help isolate regional lithospheric from core field components, the correlations between CHAMP magnetic anomalies and the pseudo magnetic effects inferred from gravity-derived crustal thickness variations can also be exploited.. Employing these procedures, we processed the CHAMP magnetic observations for an improved magnetic anomaly map of the Antarctic crust. Relative to the much higher altitude Orsted and noisier Magsat observations, the CHAMP magnetic anomalies at 400 km altitude reveal new details on the effects of intracrustal magnetic features and crustal thickness variations of the Antarctic.

Kim, Hyung Rae; Gaya-Pique, Luis R.; vonFrese, Ralph R. B.; Taylor, Patrick T.; Kim, Jeong Woo

2003-01-01

398

Thermal expansion anomaly regulated by entropy.  

PubMed

Thermal expansion, defined as the temperature dependence of volume under constant pressure, is a common phenomenon in nature and originates from anharmonic lattice dynamics. However, it has been poorly understood how thermal expansion can show anomalies such as colossal positive, zero, or negative thermal expansion (CPTE, ZTE, or NTE), especially in quantitative terms. Here we show that changes in configurational entropy due to metastable micro(scopic)states can lead to quantitative prediction of these anomalies. We integrate the Maxwell relation, statistic mechanics, and first-principles calculations to demonstrate that when the entropy is increased by pressure, NTE occurs such as in Invar alloy (Fe3Pt, for example), silicon, ice, and water, and when the entropy is decreased dramatically by pressure, CPTE is expected such as in anti-Invar cerium, ice and water. Our findings provide a theoretic framework to understand and predict a broad range of anomalies in nature in addition to thermal expansion, which may include gigantic electrocaloric and electromechanical responses, anomalously reduced thermal conductivity, and spin distributions. PMID:25391631

Liu, Zi-Kui; Wang, Yi; Shang, ShunLi

2014-01-01

399

Thermal Expansion Anomaly Regulated by Entropy  

PubMed Central

Thermal expansion, defined as the temperature dependence of volume under constant pressure, is a common phenomenon in nature and originates from anharmonic lattice dynamics. However, it has been poorly understood how thermal expansion can show anomalies such as colossal positive, zero, or negative thermal expansion (CPTE, ZTE, or NTE), especially in quantitative terms. Here we show that changes in configurational entropy due to metastable micro(scopic)states can lead to quantitative prediction of these anomalies. We integrate the Maxwell relation, statistic mechanics, and first-principles calculations to demonstrate that when the entropy is increased by pressure, NTE occurs such as in Invar alloy (Fe3Pt, for example), silicon, ice, and water, and when the entropy is decreased dramatically by pressure, CPTE is expected such as in anti-Invar cerium, ice and water. Our findings provide a theoretic framework to understand and predict a broad range of anomalies in nature in addition to thermal expansion, which may include gigantic electrocaloric and electromechanical responses, anomalously reduced thermal conductivity, and spin distributions. PMID:25391631

Liu, Zi-Kui; Wang, Yi; Shang, ShunLi

2014-01-01

400

Bilateral diaphragmatic defect and associated multiple anomalies.  

PubMed

Although congenital diaphragmatic hernia is one of the most common congenital anomalies, complete bilateral agenesis of the diaphragm is a very rare congenital malformation and frequently associated with other major anomalies. We report a case of bilateral diaphragmatic agenesis associated with major congenital anomalies. A 2,240-g male infant was born at 35 weeks of gestation to a 34-year-old mother with a history of minimal prenatal care. Polyhydramnios was reported on prenatal level 1 scan. The patient experienced early respiratory distress requiring intubation. Apgar scores were 2/1/1 at 1, 5 and 20 minutes, respectively, and efforts to resuscitate him were unsuccessful. He died at 2 hours of age. Autopsy revealed bilateral diaphragmatic agenesis associated with right pulmonary hypoplasia, left pulmonary agenesis, multiple cardiac abnormalities and gallbladder agenesis. Cytogenetic studies showed normal male karyotype. Bilateral agenesis of the diaphragm is a life-threatening malformation. Survival of these infants often depends on cardiopulmonary function. Bilateral agenesis of the diaphragm associated with gallbladder and unilateral pulmonary agenesis is a rare entity, and its clinical significance needs further investigation. PMID:19299227

Karadeniz, Leyla; Guven, Sirin; Atay, Enver; Ovali, Fahri; Celayir, Aysenur

2009-03-01

401

Evaluation of anomalies in GLDAS-1996 dataset.  

PubMed

Global Land Data Assimilation System (GLDAS) data are widely used for land-surface flux simulations. Therefore, the simulation accuracy using GLDAS dataset is largely contingent upon the accuracy of the GLDAS dataset. It is found that GLDAS land-surface model simulated runoff exhibits strong anomalies for 1996. These anomalies are investigated by evaluating four GLDAS meteorological forcing data (precipitation, air temperature, downward shortwave radiation and downward longwave radiation) in six large basins across the world (Danube, Mississippi, Yangtze, Congo, Amazon and Murray-Darling basins). Precipitation data from the Global Precipitation Climatology Centre (GPCC) are also compared with GLDAS forcing precipitation data. Large errors and lack of monthly variability in GLDAS-1996 precipitation data are the main sources for the anomalies in the simulated runoff. The impact of the precipitation data on simulated runoff for 1996 is investigated with the Community Atmosphere Biosphere Land Exchange (CABLE) land-surface model in the Yangtze basin, for which area high-quality local precipitation data are obtained from the China Meteorological Administration (CMA). The CABLE model is driven by GLDAS daily precipitation data and CMA daily precipitation, respectively. The simulated daily and monthly runoffs obtained from CMA data are noticeably better than those obtained from GLDAS data, suggesting that GLDAS-1996 precipitation data are not so reliable for land-surface flux simulations. PMID:23579825

Zhou, Xinyao; Zhang, Yongqiang; Yang, Yonghui; Yang, Yanmin; Han, Shumin

2013-01-01

402

New structural anomaly induced by nanoconfinement  

E-print Network

We explore the structural properties of anomalous fluids confined in a nanopore using Molecular Dynamics simulations. The fluid is modeled by core-softened (CS) potentials that have a repulsive shoulder and an attractive well at a further distance. Changing the attractive well depth of the fluid-fluid interaction potential, we studied the behavior of the anomalies in the translational order parameter $t$ and excess entropy $s_{ex}$ for the particles near to the nanopore wall (contact layer) for systems with two or three layers of particles. When the attractive well of the CS potential is shallow, the systems present a three to two layers transition and, additionally to the usual structural anomaly, a new anomalous region in $t$ and $s_{ex}$. For attractive well deep enough, the systems change from three layers to a bulk-like profile and just one region of anomaly in $t$ and $s_{ex}$ is observed. Our results are discussed in the basis of the fluid-fluid and fluid-surface interactions.

Leandro B. Krott; José Rafael Bordin; Marcia Barbosa

2014-10-21

403

Unexpected variations in the triple oxygen isotope composition of stratospheric carbon dioxide.  

PubMed

We report observations of stratospheric CO2 that reveal surprisingly large anomalous enrichments in (17)O that vary systematically with latitude, altitude, and season. The triple isotope slopes reached 1.95 ± 0.05(1?) in the middle stratosphere and 2.22 ± 0.07 in the Arctic vortex versus 1.71 ± 0.03 from previous observations and a remarkable factor of 4 larger than the mass-dependent value of 0.52. Kinetics modeling of laboratory measurements of photochemical ozone-CO2 isotope exchange demonstrates that non-mass-dependent isotope effects in ozone formation alone quantitatively account for the (17)O anomaly in CO2 in the laboratory, resolving long-standing discrepancies between models and laboratory measurements. Model sensitivities to hypothetical mass-dependent isotope effects in reactions involving O3, O((1)D), or CO2 and to an empirically derived temperature dependence of the anomalous kinetic isotope effects in ozone formation then provide a conceptual framework for understanding the differences in the isotopic composition and the triple isotope slopes between the laboratory and the stratosphere and between different regions of the stratosphere. This understanding in turn provides a firmer foundation for the diverse biogeochemical and paleoclimate applications of (17)O anomalies in tropospheric CO2, O2, mineral sulfates, and fossil bones and teeth, which all derive from stratospheric CO2. PMID:23940331

Wiegel, Aaron A; Cole, Amanda S; Hoag, Katherine J; Atlas, Elliot L; Schauffler, Sue M; Boering, Kristie A

2013-10-29

404

Unexpected variations in the triple oxygen isotope composition of stratospheric carbon dioxide  

PubMed Central

We report observations of stratospheric CO2 that reveal surprisingly large anomalous enrichments in 17O that vary systematically with latitude, altitude, and season. The triple isotope slopes reached 1.95 ± 0.05(1?) in the middle stratosphere and 2.22 ± 0.07 in the Arctic vortex versus 1.71 ± 0.03 from previous observations and a remarkable factor of 4 larger than the mass-dependent value of 0.52. Kinetics modeling of laboratory measurements of photochemical ozone–CO2 isotope exchange demonstrates that non–mass-dependent isotope effects in ozone formation alone quantitatively account for the 17O anomaly in CO2 in the laboratory, resolving long-standing discrepancies between models and laboratory measurements. Model sensitivities to hypothetical mass-dependent isotope effects in reactions involving O3, O(1D), or CO2 and to an empirically derived temperature dependence of the anomalous kinetic isotope effects in ozone formation then provide a conceptual framework for understanding the differences in the isotopic composition and the triple isotope slopes between the laboratory and the stratosphere and between different regions of the stratosphere. This understanding in turn provides a firmer foundation for the diverse biogeochemical and paleoclimate applications of 17O anomalies in tropospheric CO2, O2, mineral sulfates, and fossil bones and teeth, which all derive from stratospheric CO2. PMID:23940331

Wiegel, Aaron A.; Cole, Amanda S.; Hoag, Katherine J.; Atlas, Elliot L.; Schauffler, Sue M.; Boering, Kristie A.

2013-01-01

405

Osmium Isotope Evidence for an S-Process Carrier in Primitive Chondrites  

NASA Technical Reports Server (NTRS)

The degree of isotopic mixing in the solar nebula and the nature of pre-solar components that have contributed to our solar system remain subjects of vigorous debate. Isotopic anomalies have been identified in Ca-Al inclusions in chondrites [1-4]. This indicates that refractory pre-solar components were not completely homogenized or processed away at the high temperatures experienced by CAIs. Pre-solar grains (SiC, C, etc.) are prevalent in primitive chondrites, and preserve isotopic heterogeneity resulting from the nucleosynthetic processes occurring in the stars from which these grains formed [2,4]. Several recent studies employing precise techniques for measuring Ru, Mo and Zr isotopes in bulk meteorites, have come up with varying conclusions on the degree of effectiveness of nebular mixing on the scale of bulk meteorite material. Some of these studies have reported isotopic anomalies in Mo and Ru [3,5-7], while others have not observed anomalies in Mo, Ru, or Zr [8-10]. Debate over the quality of the data, the normalization techniques employed, the absence or presence of isobaric interferences during the measurements on different types of instruments (e.g. TIMS versus ICP-MS), and other factors, has ensued [11,12].

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

2005-01-01

406

The Southeast Indian Ridge: Scale of Source Heterogeneity and Origin of the DUPAL Anomaly  

NASA Astrophysics Data System (ADS)

Results Pb and Hf isotope ratios from 124 basalt glasses sampled at < 10 km intervals along 2000 km of the Southeast Indian Ridge (SEIR) between 86°E and 110°E show bimodal distributions. The bimodality in both Pb and Hf isotope ratios confirms the presence of ancient compositional streaks in the Indian Ocean upper mantle [1]. The density of streaks is well described by a Poisson distribution having a characteristic thickness of ~25 km. Implications Pb isotopes in SEIR basalts all carry a DUPAL [3] isotope signature. Two possible origins for the bimodality and DUPAL signature are: (1) ancient melting that involved garnet fractionation, with subsequent pollution of the upper mantle by continental material during Gondwana breakup; (2) inherited heterogeneity from the early Earth. The later explanation is difficult to reconcile as it requires an input of a non-chondritic Pb composition. Pollution of the asthenosphere by material resulting from interaction of deep mantle hotspot/plumes (e.g. Karoo, Reunion) with the shallow continental lithosphere during the breakup of the Gondwana supercontinent and formation of the Indian Ocean basin adequately accounts for the DUPAL anomaly. [1] Graham et al. (2006) Nature 440, 199-202. [2] Mahoney et al. (2002) J. Petrology 43, 1155-1176. [3] Hart (1984) Nature 309, 753-757.; Histogram for Hf isotopes and bimodal distribution in the ?Hf versus 208*Pb/206*Pb binary projection for 197 SEIR glasses [this work; 1, 2]. The 2 populations overlap. Although the ?Hf means differ by only 1.5 ? units, a t-test shows that the probability the means are equal is infinitesimal (t=18). The statistics derived from this analysis are fully consistent with the discriminant value ?Hf = 11.8 [1].

Hanan, B. B.; Blichert-Toft, J.; Sayit, K.; Agranier, A.; Hemond, C.; Briais, A.; Maia, M. A.; Graham, D. W.; Albarede, F.

2012-12-01

407

Mineral associations and character of isotopically anomalous organic material in the Tagish Lake carbonaceous chondrite  

NASA Astrophysics Data System (ADS)

We report a coordinated analytical study of matrix material in the Tagish Lake carbonaceous chondrite in which the same small (?20 ?m) fragments were measured by secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), electron energy-loss spectroscopy (EELS), and X-ray absorption near-edge spectroscopy (XANES). SIMS analysis reveals H and N isotopic anomalies (hotspots), ranging from hundreds to thousands of nanometers in size, which are present throughout the fragments. Although the differences in spatial resolution of the SIMS techniques we have used introduce some uncertainty into the exact location of the hotspots, in general, the H and N isotopic anomalies are spatially correlated with C enrichments, suggesting an organic carrier. TEM analysis, enabled by site-specific extraction using a focused-ion-beam scanning-electron microscope, shows that the hotspots contain an amorphous component, Fe-Ni sulfides, serpentine, and mixed-cation carbonates. TEM imaging reveals that the amorphous component occurs in solid and porous forms, EDS indicates that it contains abundant C, and EELS and XANES at the C K edge reveal that it is largely aromatic. This amorphous component is probably macromolecular C, likely the carrier of the isotopic anomalies, and similar to the material extracted from bulk samples as insoluble organic matter. However, given the large sizes of some of the hotspots, the disparity in spatial resolution among the various techniques employed in our study, and the phases with which they are associated, we cannot entirely rule out that some of the isotopic anomalies are carried by inorganic material, e.g., sheet silicates. The isotopic composition of the organic matter points to an initially primitive origin, quite possibly within cold interstellar clouds or the outer reaches of the solar protoplanetary disk. The association of organic material with secondary phases, e.g., serpentine and carbonates, suggests that the organic matter was susceptible to parent-body processing, and thus, isotopic dilution.

Zega, Thomas J.; Alexander, Conel M. O.'D.; Busemann, Henner; Nittler, Larry R.; Hoppe, Peter; Stroud, Rhonda M.; Young, Andrea F.

2010-10-01

408

Isotopes of Pennies  

NSDL National Science Digital Library

This lab activity from Science Netlinks is designed to explain the weighted averages that are used in average atomic mass calculations. Students can be expected to learn that isotopes of an element have different masses; that isotopes are atoms of the same element that have different numbers of neutrons; and that atomic mass is the weighted average of the naturally occurring isotopes of an element.

Netlinks, Science; Science, American A.

409

Hybrid isotope separation scheme  

DOEpatents

A method of yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which a scavenger, radiating the gas with a wave length or frequency characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photochemical reaction between the scavenger, and collecting the specific isotope-containing chemical by using a recombination surface or by a scooping apparatus.

Maya, Jakob (Brookline, MA)

1991-01-01

410

Isotope Ratio Mass Spectrometry.  

PubMed

Isotope Ratio Mass Spectrometry (IRMS) is a specialized technique used to provide information about the geographic, chemical, and biological origins of substances. The ability to determine the source of an organic substance stems from the relative isotopic abundances of the elements which comprise the material. Because the isotope ratios of elements such as carbon, hydrogen, oxygen, sulfur, and nitrogen can become locally enriched or depleted through a variety of kinetic and thermodynamic factors, measurement of the isotope ratios can be used to differentiate between samples which otherwise share identical chemical compositions. Several sample introduction methods are now available for commercial isotope ratio mass spectrometers. Combustion is most commonly used for bulk isotopic analysis, whereas gas and liquid chromatography are predominately used for the real-time isotopic analysis of specific compounds within a mixture. Here, highlights of advances in instrumentation and applications within the last three years are provided to illustrate the impact of this rapidly growing area of research. Some prominent new applications include authenticating organic food produce, ascertaining whether or not African elephants are guilty of night-time raids on farmers' crops, and linking forensic drug and soil samples from a crime scene to a suspected point of origin. For the sake of brevity, we focus this Minireview on the isotope ratio measurements of lighter-elements common to organic sources; we do not cover the equally important field of inorganic isotope ratio mass spectrometry. PMID:19173039

Muccio, Zeland; Jackson, Glen P

2009-02-01

411

New perspective on Aptian carbon isotope stratigraphy: Data from delta13C records of terrestrial organic matter  

Microsoft Academic Search

Carbon isotope analyses were performed on detrital woody materials in Aptian (mid- Cretaceous) marine sediments of central Hokkaido, northern Japan. A positive delta13Cwood excursion (from -25.40\\/00 to -21.80\\/00) following a remarkable negative isotope shift is recognized in the early Aptian, and a small positive anomaly is also found in the latest Aptian. This delta13Cwood profile is exactly in phase with

Atsushi Ando; Takeshi Kakegawa; Reishi Takashima; Tsunemasa Saito

2002-01-01

412

Magnetic Anomalies in the Enderby Basin, the Southern Indian Ocean  

NASA Astrophysics Data System (ADS)

Magnetic anomalies in the Southern indian Ocean are vital to understanding initial breakup process of Gondwana. However, seafloor age estimated from magnetic anomalies still remain less well-defined because of the sparse observations in this area. To understand the seafloor spreading history related to the initial breakup process of Gondwana, vector magnetic anomaly data as well as total intensity magnetic anomaly data obtained by the R/V Hakuho-maru and the icebreaker Shirase in the Enderby Basin, Southern Indian Ocean, are used. The strikes of magnetic structures are deduced from the vector magnetic anomalies. Magnetic anomaly signals, most likely indicating Mesozoic magnetic anomaly sequence, are obtained almost parallel to the west of WNW-ESE trending lineaments just to the south of Conrad Rise inferred from satellite gravity anomalies. Most of the strikes of magnetic structures indicate NNE-SSW trends, and are almost perpendicular to the WNW-ESE trending lineaments. Mesozoic sequence magnetic anomalies with mostly WNW-ESE strikes are also observed along the NNE-SSW trending lineaments between the south of the Conrad Rise and Gunnerus Ridge. Magnetic anomalies originated from Cretaceous normal polarity superchron are found in these profiles, although magnetic anomaly C34 has been identified just to the north of the Conrad Rise. However Mesozoic sequence magnetic anomalies are only observed in the west side of the WNW-ESE trending lineaments just to the south of Conrad Rise and not detected to the east of Cretaceous normal superchron signals. These results show that counter part of Mesozoic sequence magnetic anomalies in the south of Conrad Rise would be found in the East Enderby Basin, off East Antarctica. NNE-SSW trending magnetic structures, which are similar to those obtained just to the south of Conrad Rise, are found off East Antarctica in the East Enderby Basin. However, some of the strikes show almost E-W orientations. These suggest complicated ridge reorganization occurred during initial breakup of Gondwana in the Enderby Basin.

Nogi, Y.; Sato, T.; Hanyu, T.

2013-12-01

413

Anomaly nucleation constrains SU(2) gauge theories.  

PubMed

We argue for the existence of additional constraints on SU(2) gauge theories in four dimensions when realized in ultraviolet completions admitting an analog of D-brane nucleation. In type II string compactifications these constraints are necessary and sufficient for the absence of cubic non-Abelian anomalies in certain nucleated SU(N>2) theories. It is argued that they appear quite broadly in the string landscape. Implications for particle physics are discussed; most realizations of the standard model in this context are inconsistent, unless extra electroweak fermions are added. PMID:24483790

Halverson, James

2013-12-27

414

Seeking a solution of the Pioneer Anomaly  

E-print Network

The 1972 and 1973 launched Pioneer 10 and 11 were the first missions to explore the outer solar system. They achieved stunning breakthroughs in deep-space exploration. But around 1980 an unmodeled force of \\sim 8 \\times 10^{-8} cm/s^2, directed approximately towards the Sun, appeared in the tracking data. It later was unambiguously verified as not being an artifact. The origin remains unknown (although radiant heat remains a likely cause). Increasing effort has gone into understanding this anomaly. We review the situation and describe programs to resolve the issue.

Michael Martin Nieto; John D. Anderson

2007-09-12

415

Failures and anomalies attributed to spacecraft charging  

NASA Technical Reports Server (NTRS)

The effects of spacecraft charging can be very detrimental to electronic systems utilized in space missions. Assuring that subsystems and systems are protected against charging is an important engineering function necessary to assure mission success. Spacecraft charging is expected to have a significant role in future space activities and programs. Objectives of this reference publication are to present a brief overview of spacecraft charging, to acquaint the reader with charging history, including illustrative cases of charging anomalies, and to introduce current spacecraft charging prevention activities of the Electromagnetics and Environments Branch, Marshall Space Flight Center (MSFC), National Aeronautics and Space Administration (NASA).

Leach, R. D.; Alexander, M. B. (editor)

1995-01-01

416

Origin of conductivity anomalies in the asthenosphere  

NASA Astrophysics Data System (ADS)

Electrical conductivity anomalies with anisotropy parallel to the plate motion have been observed beneath the oceanic lithosphere by electromagnetic studies (e.g., Evans et al., 2005; Baba et al., 2010; Naif et al., 2013). Electrical conductivity of the oceanic asthenosphere at ~100 km depth is very high, about 10-2 to 10-1 S/m. This zone is also known in seismology as the low velocity zone. Since Karato (1990) first suggested that electrical conductivity is sensitive to water content in NAMs, softening of asthenosphere has been regarded as a good indicator for constraining the distribution of water. There are two difficulties to explain the observed conductivity features in the asthenosphere. Recent publications on electrical conductivity of hydrous olivine suggested that olivine with the maximum soluble H2O content at the top of the asthenosphere has much lower conductivity less than 0.1 S/m (e.g., Yoshino et al., 2006; 2009a; Poe et al., 2010; Du Frane and Tyburczy, 2012; Yang, 2012), which is a typical value of conductivity anomaly observed in the oceanic mantle. Partial melting has been considered as an attractive agent for substantially raising the conductivity in this region (Shankland and Waff, 1977), because basaltic melt has greater electrical conductivity (> 100.5 S/m) and high wetting properties. However, dry mantle peridotite cannot reach the solidus temperature at depth 100 km. Volatile components can dramatically reduce melting temperature, even if its amount is very small. Recent studies on conductivity measurement of volatile-bearing melt suggest that conductivity of melt dramatically increases with increasing volatile components (H2O: Ni et al., 2010a, b; CO2: Gaillard et al., 2008; Yoshino et al., 2010; 2012a). Because incipient melt includes higher amount of volatile components, conductivity enhancement by the partial melt is very effective at temperatures just above that of the volatile-bearing peridotite solidus. In this study, the electrical conductivity of peridotite with trace amount of volatile phases was measured in single crystal olivine capsule to protect escape of water from the sample at 3 GPa. The conductivity values were significantly higher than those of dry peridotite, suggesting that the observed conductivity anomalies at the asthenosphere are caused by a presence of trace amount of volatile component in fluid or melt. On the other hand, conductivity of partial molten peridotite measured under shear showed that the conductivity parallel to the shear direction becomes one order of magnitude higher than that normal direction. These observations suggest that partial melting can explain softening and the observed geophysical anomalies of asthenosphere.

Yoshino, T.; Zhang, B.

2013-12-01

417

Gravity and magnetic anomaly data analysis  

NASA Technical Reports Server (NTRS)

Progress on the analysis MAGSAT data is reported. The MAGSAT data from 40 deg S to 70 deg N latitude and 30 deg W to 60 E longitude was reduced to radial polarization. In addition, gravity anomaly data from this area were processed and a variety of filtered maps were prepared for combined interpretation of the gravity and magnetic data in conjunction with structural and tectonic maps of the area. The VERSATEC listings and cross-reference maps of variable and array names for the spherical Earth analysis programs NVERTSM, SMFLD, NVERTG, and GFLD were also prepared.

Braile, L. W.; Hinze, W. J.; Vonfrese, R. R. B. (principal investigators)

1982-01-01

418

Torque anomaly in quantum field theory  

NASA Astrophysics Data System (ADS)

The expectation values of energy density and pressure of a quantum field inside a wedge-shaped region appear to violate the expected relationship between torque and total energy as a function of angle. In particular, this is true of the well-known Deutsch-Candelas stress tensor for the electromagnetic field, whose definition requires no regularization except possibly at the vertex. Unlike a similar anomaly in the pressure exerted by a reflecting boundary against a perpendicular wall, this problem cannot be dismissed as an artifact of an ad hoc regularization.

Fulling, S. A.; Mera, F. D.; Trendafilova, C. S.

2013-02-01

419

Non-Newtonian gravity or gravity anomalies?  

NASA Technical Reports Server (NTRS)

Geophysical measurements of G differ from laboratory values, indicating that gravity may be non-Newtonian. A spherical harmonic formulation is presented for the variation of (Newtonian) gravity inside the Earth. Using the GEM-10B Earth Gravitational Field Model, it is shown that long-wavelength gravity anomalies, if not corrected, may masquerade as non-Newtonian gravity by providing significant influences on experimental observation of delta g/delta r and G. An apparent contradiction in other studies is also resolved: i.e., local densities appear in equations when average densities of layers seem to be called for.

Rubincam, David P.; Chao, B. Fong; Schatten, Kenneth H.; Sager, William W.

1988-01-01

420

Mouse models for understanding human developmental anomalies  

SciTech Connect

The mouse experimental system presents an opportunity for studying the nature of the underlying mutagenic damage and the molecular pathogenesis of this class of anomalies by virtue of the accessibility of the zygote and its descendant blastomeres. Such studies could contribute to the understanding of the etiology of certain sporadic but common human malformations. The vulnerability of the zygotes to mutagens as demonstrated in the studies described in this report should be a major consideration in chemical safety evaluation. It raises questions regarding the danger to human zygotes when the mother is exposed to drugs and environmental chemicals.

Generoso, W.M.

1989-01-01

421

p-Process 180W anomalies in iron meteorites: Nucleosynthetic versus non-nucleosynthetic origins  

NASA Astrophysics Data System (ADS)

Heavy, proton-rich stable isotopes belong to the least abundant isotopes in the solar system. Their formation mechanisms and their stellar sources are most likely different from those of neutron-capture generated r- and s-process nuclei that comprise the majority of nuclides heavier than iron. Heavy p-nuclide abundances in meteorites are therefore potentially useful in deciphering distinct stellar contributions to the nascent solar system. We therefore conducted the first high-precision measurements of the heavy p-process isotope 180W, achieving a typical precision of ±0.7 ?-units for ca. 300 ng W. Measured samples comprise metals from magmatic- and non-magmatic iron meteorites, as well as metal from one H4 chondrite (NWA 926) and two reduced terrestrial basalts (from Disko Island, Greenland and the Dzheltul'ski massif from Eastern-Siberia, Russia). The analyzed iron meteorites show clearly resolvable 180W anomalies of up to +6 ?-units. Conversely, the chondritic metal and both terrestrial samples exhibit 180W abundances indistinguishable from the standard value. As cosmogenic effects during space exposure of the meteoroids may have affected the 180W budget, cosmic-ray exposure of the meteorites has to be critically evaluated. We therefore propose a method to approximate cosmogenic contributions to the 180W signatures in order to unravel nucleosynthetic 180W abundance anomalies. Our study reveals significant cosmogenic effects only for the longest exposed meteorites, shifting 180W anomalies always to lower values (average cosmic-ray correction-factors can be estimated to lie between 0.01 and 0.30 ?180W-units per 100 Myr of exposure). Cosmogenic effects for most of the analyzed meteorites therefore appear to be negligible with respect to the analytical precision achieved for iron meteorites. In addition to cosmic-ray exposure, radiogenic effects can be caused by putative decay of 184Os or by decay of 180Ta in its ground state. Whereas potential alpha decay of 184Os could shift 180W anomalies to higher values (but only up to levels that are within the analytical error of ˜0.5 ?-units for most samples), no significant production of 180W could have occurred from 180Ta decay. Notably, we identified significant and systematic abundance variations in 180W between different iron meteorite groups, indicating that these isotope anomalies are characteristic for their entire parent asteroids. Our finding of decreasing excesses in 180W from early formed magmatic iron meteorites (+3.8±1.2 ?-units) towards later formed non-magmatic iron meteorites (+0.6±0.5 ?-units), the analyzed chondrite and both terrestrial rocks (-0.3±0.7 ?-units) may thus mirror progressive homogenization of 180W in the early solar nebula. This overall trend is also supported by a co-variation between 180W and metal segregation ages for the different iron meteorite groups as well as by a co-variation between 180W deviations and the respective asteroidal accretion ages. Such an interpretation would suggest progressive homogenization of the solar nebula within about ˜2.5 to ˜6 Myr.

Schulz, Toni; Münker, Carsten; Peters, Stefan T. M.

2013-01-01

422

Discovery of the Vanadium Isotopes  

E-print Network

Twenty-four vanadium isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

A. Shore; A. Fritsch; M. Heim; A. Schuh; M. Thoennessen

2009-07-11

423

Discovery of the Tungsten Isotopes  

E-print Network

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

A. Fritsch; J. Q. Ginepro; M. Heim; A. Schuh; A. Shore; M. Thoennessen

2009-03-25

424

Discovery of the Silver Isotopes  

E-print Network

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

A. Schuh; A. Fritsch; J. Q. Ginepro; M. Heim; A. Shore; M. Thoennessen

2009-07-09

425

Discovery of the Tin Isotopes  

E-print Network

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

S. Amos; M. Thoennessen

2010-03-26

426

Discovery of the Indium Isotopes  

E-print Network

Thirty-eight indium isotopes (A = 98-135) have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

S. Amos; M. Thoennessen

2010-04-29

427

Discovery of the Einsteinium Isotopes  

E-print Network

Seventeen einsteinium isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

A. Bury; A. Fritsch; J. Q. Ginepro; M. Heim; A. Schuh; A. Shore; M. Thoennessen

2009-12-22

428

Discovery of the Mercury Isotopes  

E-print Network

Forty mercury isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

D. Meierfrankenfeld; M. Thoennessen

2009-12-01

429

Discovery of the Cobalt Isotopes  

E-print Network

Twenty-six cobalt isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

T. Szymanski; M. Thoennessen

2009-09-04

430

Discovery of the Cadmium Isotopes  

E-print Network

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

S. Amos; M. Thoennessen

2009-10-22

431

Discovery of the Calcium Isotopes  

E-print Network

Twenty four calcium isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

J. L. Gross; M. Thoennessen

2010-04-28

432

Discovery of the Titanium Isotopes  

E-print Network

Twentyfive titanium isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

D. Meierfrankenfeld; M. Thoennessen

2009-12-01

433

Discovery of the Iron Isotopes  

E-print Network

Twenty-eight iron isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

A. Schuh; A. Fritsch; M. Heim; A. Shore; M. Thoennessen

2009-09-01

434

Discovery of the Gold Isotopes  

E-print Network

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

A. Schuh; A. Fritsch; J. Q. Ginepro; M. Heim; A. Shore; M. Thoennessen

2009-03-10

435

Discovery of the Barium Isotopes  

E-print Network

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

A. Shore; A. Fritsch; J. Q. Ginepro; M. Heim; A. Schuh; M. Thoennessen

2009-08-13

436

Discovery of the Arsenic Isotopes  

E-print Network

Twenty-nine arsenic isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

Shore, A; Heim, M; Schuh, A; Thoennessen, M

2009-01-01

437

Discovery of the Arsenic Isotopes  

E-print Network

Twenty-nine arsenic isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

A. Shore; A. Fritsch; M. Heim; A. Schuh; M. Thoennessen

2009-02-25

438

Discovery of the cadmium isotopes  

SciTech Connect

Thirty-seven cadmium 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.

Amos, S. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Thoennessen, M., E-mail: thoennessen@nscl.msu.ed [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

2010-11-15

439

Discovery of the Cadmium Isotopes  

E-print Network

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

Amos, S

2009-01-01

440

Mercury stable isotope fractionation in a tropical ecosystem including human hair: New insights for an isotope balance  

NASA Astrophysics Data System (ADS)

Mercury contamination is an environmental problem in the Amazon basin still relevant today as impacts on human health are poorly studied. In Bolivia, indigenous people have elevated methylmercury concentrations (between 2719 and 23701 ng.g-1) in their hair. This highly toxic molecule is formed after methylation of inorganic Hg released by chemical and physical weathering and from human activities. The aim of our study is to propose a first isotope balance in a Bolivian Amazon ecosystem, through variations in Hg isotopic compositions. The discovery of mass-independent fracionation (MIF) of odd-isotopes in our organic samples (fish and human hair) opened a new way of research in tracing the sources and the processes involved in the cycle of Hg. Four types of samples are studied: liquid Hg0 from gold mining, sediment samples, fish coming from the Beni River basin (from the main channel and an associated floodplain lake) and hair from gold miners and fish-eating native populations. Hg isotopic compositions were analyzed on a Thermo-Finnigan Neptune MC-ICP-MS at the LMTG after sample digestion by HCl/HNO3 or by H2O2/HNO3 for fish samples, at 120°C. The ?202Hg values (relative to NIST 3133) are signicantly different with respect to the external precision on UM-Almaden#2 of 0.18 ‰ (2?, n = 42): -0.34 ± 0.02 ‰ for liquid mercury, between -1.33 and -0.81 ‰ for bottom and floodplain sediments (n=18), between -0.87 and 2.22 ‰ for miners hair (n=26), +1.29 ± 0.41 ‰ for native hair (n=13) and between -0.91 and -0.21 ‰ for fish samples (n=53). A large mass-independent isotope fractionation (MIF) was observed for odd isotope ratios in all hair samples and fish samples whereas weak anomalies were measured for sediment samples: - ?199Hg anomaly: -0.12 to -0.04 ‰ for sediment, -0.22 to +0.63 ‰ for fish samples and +0.13 to +1.63 ‰ for hair - ?201Hg anomaly: -0.12 to -0.02 ‰ for sediment, -0.21 to +0.43 ‰ for fish samples and +0.06 to +1.25 ‰ for hair. Both anomalies ?201Hg vs. ?199Hg are linearly correlated with a slope of +1.12‰ for native hair and a mass dependant fractionation (MDF) of ~+2‰ has been evidenced between native communities hair and fish species constituting their diet. For the same fish species, MIF anomalies differ with floodplain lakes and drainage basins suggesting that the methylmercury (MMHg) analysed in fish caught in floodplain lake reflects the photodemethylation process while in the Beni R. mainstream the negative anomalies confirm that this photochemical reactions are limited. Within the aquatic food chain of an hydrosystem, it appears that MIF anomalies can trace the fish ecology and the aquatic photochemical processes, while mass dependent fractionation can trace the trophic level as a result of excretion and metabolic processes involving mercury in the body.

Laffont, Laure; Sonke, Jeroen; Maurice, Laurence; Behra, Philippe

2010-05-01

441

Discrete R-symmetry anomalies in heterotic orbifold models  

SciTech Connect

Anomalies of discrete R symmetries appearing in heterotic orbifold models are studied. We find that the mixed anomalies for different gauge groups satisfy the universal Green-Schwarz condition, indicating that these anomalies are canceled by the Green-Schwarz mechanism. An exact relation between the anomaly coefficients of the discrete R symmetries and one-loop beta-function coefficients is obtained. We also find that the discrete R symmetries have a good chance to be unbroken down to the supersymmetry breaking scale. Even below this scale a Z{sub 2} subgroup is unbroken, and it may be an origin of the R parity of the minimal supersymmetric standard model. Relations between the R-symmetry anomalies and T-duality anomalies are also investigated.

Araki, Takeshi; Kubo, Jisuke [Institute for Theoretical Physics, Kanazawa University, Kanazawa 920-1192 (Japan); Choi, Kang-Sin [Physikalisches Institut, Universitaet Bonn, Nussalle 12, D-53115 Bonn (Germany); Kobayashi, Tatsuo [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Ohki, Hiroshi [Department of Physics, Kyoto University, Kyoto 606-8501 (Japan)

2007-09-15

442

Anomaly detection in noisy hyperspectral imagery  

NASA Astrophysics Data System (ADS)

Anomaly detection in hyperspectral imagery seeks to identify a small subset of pixels whose spectra differ most significantly from the background. The challenge is to characterize the background and noise well enough to recognize which observations are truly distinct and not simply noise outliers. The covariance-based RXD operator was developed to select low-probability pixel spectra and is therefore sensitive to noise. We compare the RXD operator to a Euclidean metric weighted by the inverse of the estimated spectral noise variance. We then combine the weighted Euclidean metric with RXD using a Lagrange multiplier and demonstrate that this formulation retains RXD's emphasis on small clusters while controlling the impact of noise. An optimum value of the Lagrange multiplier is determined based on the number of bands. We explore the utility of normalizing the pixel spectra as a step in anomaly detection. Results for the RXD, weighted-Euclidean, and Lagrange approach are presented using AVIRIS and HYDICE imagery. Based on these results, we conclude that the Euclidean, although robust to noise, does little more than emphasize the brightest pixels. The Lagrange dete