bluuebunny/crossref_metadata_2025 huggingface dataset:
Primitive xenon in diogenites and plutonium‐244‐fission xenon ages of a diogenite, a howardite, and eucrites
Authors: Michel Th. , Eugster O.
Published: June 2012

Abstract The 244Pu‐fission‐136Xe retention ages of howardites, eucrites, and diogenites (HEDs) show that these meteorites have retained Xe since they were formed about 4500 Ma ago. For the Garland diogenite and the Millbillillie eucrite, we obtain fission Xe ages of 4525 ± 40 Ma and 4486 ± 40 Ma, respectively. If Xe isotope data reported by other workers are also considered, we conclude that the monomict equilibrated eucrites Camel Donga, Juvinas, and Millbillillie formed about 40 Ma later than Pasamonte, a polymict unequilibrated eucrite. Stannern, a monomict equilibrated brecciated eucrite, yields a 244Pu‐136Xe age of 4442 Ma. The 40K‐40Ar retention ages fall, for most HEDs, into the 1000–4000 Ma age range, indicating that 40Ar is generally not well retained. The good retentivity for Xe of HEDs allows us to study primordial trapped Xe in these meteorites. Except for Shalka, in which other authors found Kr and Xe from terrestrial atmospheric contamination only, we present for the first time Kr and Xe isotopic data for diogenites. We studied Ellemeet, Garland, Ibbenbühren, Shalka, and Tatahouine. We show that Tatahouine contains two types of trapped Xe: a terrestrial contamination acquired by an irreversible adsorption process and released at pyrolysis temperatures up to 800 °C, and indigenous primordial Xe released primarily between 800 °C and 1200 °C. The isotopic composition of this primordial Xe is identical to that proposed earlier to be present in primitive achondrites and termed U‐Xe or “primitive” Xe, but it has not been directly observed in achondrites until now. This type of primitive Xe is important for understanding the evolution of other Xe reservoirs in the Solar System. Terrestrial atmospheric Xe (corrected for fission Xe and radiogenic Xe from outgassing of the Earth) is related to it by a mass dependent fractionation favoring the heavier Xe isotopes. This primitive Xe is isotopically very similar to solar Xe except for 134Xe and 136Xe. Solar Xe appears to contain an enrichment of unknown origin for these isotopes relative to the primitive Xe.
ALH 82102: An Antarctic meteorite embedded partly in ice
Authors: Kråhenbühl Urs , Langenauer Marcel
Published: June 2012

Abstract We measured the concentrations of F, Cl, Br and I in two different aliquots of the meteorite ALH 82102. This H5 chondrite was recovered at the Allan Hills region, while it was partially embedded in the ice. One aliquot was taken from that part of the surface of the meteorite that was still in the ice, and the other one was taken from the side, which was poking out of the ice. Both aliquots are highly, and nearly to the same degree, contaminated with halogens. The observed enrichments occurred mainly during the time the meteorite was lying on the surface of the ice by deposition and/or adsorption of aerosols, salts, and gaseous components. A contamination during the time it was covered by the ice is unlikely. We conclude, therefore, that this meteorite was not always buried in the ice during its “residence time” on Earth. In order to accumulate the observed contamination, it had to be on the surface of the ice part of the time between its fall onto the Earth and its collection. The age of the ice surrounding the meteorite cannot be equal to the measured terrestrial age of ALH 82102.
A new titanium‐bearing calcium aluminosilicate phase: I. Meteoritic occurrences and formation in synthetic systems
Authors: Paque Julie M. , Beckett John R. , Barber David J. , Stolper Edward M.
Published: June 2012

Abstract A new titanium‐bearing calcium aluminosilicate mineral has been identified in coarse‐grained calcium‐aluminum‐rich inclusions (CAIs) from carbonaceous chondrites. The formula for this phase, which we have temporarily termed “UNK,” is Ca3Ti(Al, Ti)2(Si, Al)3O14, and it is present in at least 8 of the 20 coarse‐grained CAIs from the Allende CV3 chondrite examined as part of this project. The phase occurs in Types A and B1 inclusions as small tabular crystals oriented along two mutually perpendicular planes in melilite.

UNK crystallizes from melts in dynamic crystallization experiments conducted in air from four bulk compositions modeled after Types A, B1, B2 and C inclusions. Cooling rates resulting in crystallization of UNK ranged from 0.5 to 200 °C/h from maximum (initial) temperatures of 1375 to 1580 °C. Only below 1190 °C does UNK itself begin to crystallize. To first order, the presence or absence of UNK from individual experiments can be understood in terms of the compositions of residual melts and nucleation probabilities.

Compositions of synthetic and meteoritic UNK are very similar in terms of major oxides, differing only in the small amounts of trivalent Ti (7–13% of total Ti) in meteoritic samples. UNK crystallized from the Type A analog is similar texturally to that found in CAIs, although glass, which is typically associated with synthetic UNK, is not observed in meteoritic occurrences. A low Ti end‐member of UNK (“Si‐UNK”) with a composition near that of Ca3Al2Si4O14 was produced in a few samples from the Type B1 analog. This phase has not been found in the meteoritic inclusions.
A new titanium‐bearing calcium aluminosilicate phase: II. Crystallography and crystal chemistry of grains formed in slowly cooled melts with bulk compositions of calcium‐ aluminum‐rich inclusions
Authors: Barber David J. , Beckett John R. , Paque Julie M. , Stolper Edward
Published: June 2012

Abstract The crystallography and crystal chemistry of a new calcium‐titanium‐aluminosilicate mineral (UNK) observed in synthetic analogs to calcium‐aluminum‐rich inclusions (CAIs) from carbonaceous chondrites was studied by electron diffraction techniques. The unit cell is primitive hexagonal or trigonal, with a = 0.790 ± 0.002 nm and c = 0.492 ± 0.002 nm, similar to the lattice parameters of melilite and consistent with cell dimensions for crystals in a mixer furnace slag described by Barber and Agrell (1994). The phase frequently displays an epitactic relationship in which melilite acts as the host, with (0001)UNK | (001)mel and <10T0>UNK | <100>mel. If one of the two space groups determined by Barber and Agrell (1994) for their sample of UNK is applicable (P3ml or P31m), then the structure is probably characterized by puckered sheets of octahedra and tetrahedra perpendicular to the c‐axis with successive sheets coordinated by planar arrays of Ca. In this likely structure, each unit cell contains three Ca sites located in mirror planes, one octahedrally coordinated cation located along a three‐fold axis and five tetrahedrally coordinated cations, three in mirrors and two along triads. The octahedron contains Ti but, because there are 1.3–1.9 cations of Ti/formula unit, some of the Ti must also be in tetrahedral coordination, an unusual but not unprecedented situation for a silicate. Tetrahedral sites in mirror planes would contain mostly Si, with lesser amounts of Al while those along the triads correspondingly contain mostly Al with subordinate Ti. The structural formula, therefore, can be expressed as

with Si + Ti = 4. Compositions of meteoritic and synthetic Ti‐bearing samples of the phase can be described in terms of a binary solid solution between the end‐members Ca3TiAl2Si3O14 and Ca3Ti(AlTi)(AlSi2)O14. A Ti‐free analog with a formula of Ca3Al2Si4O14 synthesized by Paque et al. (1994) is thought to be related structurally but with the octahedral site being occupied by Al, that is
Igneous petrology of the new ureilites Nova 001 and Nullarbor 010
Authors: Treiman Allan H. , Berkley John L.
Published: June 2012

Abstract— The Nova 001 [= Nuevo Mercurio (b)] and Nullarbor 010 meteorites are ureilites, both of which contain euhedral graphite crystals. The bulk of the meteorites are olivine (Fo79) and pyroxenes (Wo9En73Fs18, Wo3En77Fs20), with a few percent graphite and minor amounts of troilite, Ni‐Fe metal, and possibly diamond. The rims of olivine grains are reduced (to Fo91) and contain abundant blebs of Fe metal. Silicate mineral grains are equant, anhedral, up to 2 mm across, and lack obvious preferred orientations. Euhedral graphite crystals (to 1 mm x 0.3 mm) are present at silicate grain boundaries, along boundaries and protruding into the silicates, and entirely within silicate mineral grains. Graphite euhedra are also present as radiating clusters and groups of parallel plates grains embedded in olivine; no other ureilite has comparable graphite textures. Minute lumps within graphite grains are possibly diamond, inferred to be a result of shock. Other shock effects are limited to undulatory extinction and fracturing. Both ureilites have been weathered significantly. Considering their similar mineralogies, identical mineral compositions, and identical unusual textures, Nova 001 and Nullarbor 010 are probably paired. Based on olivine compositions, Nova 001 and Nullarbor 010 are in Group 1 (FeO‐rich) of Berkley et al. (1980). Silicate mineral compositions are consistent with those of other known ureilites. The presence of euhedral graphite crystals within the silicate minerals is consistent with an igneous origin, and suggests that large proportions of silicate magma were present locally and crystallized in situ.
Neodymium, strontium and chromium isotopic studies of the LEW86010 and Angra dos Reis meteorites and the chronology of the angrite parent body
Authors: Nyquist L. E. , Bansal B. , Wiesmann H. , Shih C.‐Y.
Published: June 2012

Abstract— Neodymium, strontium, and chromium isotopic studies of the LEW86010 angrite established its absolute age and the formation interval between its crystallization and condensation of Allende CAIs from the solar nebula. Pyroxene and phosphate were found to contain ∼98% of its Sm and Nd inventory. A conventional 147Sm‐143Nd isochron yielded an age of 4.53 ± 0.04 Ga (2 σ) and ∍143 Nd = 0.45 ± 1.1. An 146Sm‐142Nd isochron gives initial 146Sm/144Sm = 0.0076 ± 0.0009 and ∍143 Nd = −2.5 ± 0.4. The Rb‐Sr analyses give initial 87Sr/86Sr (I87Sr) = 0.698972 ± 8 and 0.698970 ± 18 for LEW and ADOR, respectively, relative to 87Sr/86Sr = 0.71025 for NBS987. The difference, ΔI87Sr, between I87Sr for the angrites and literature values for Allende CAIs, corresponds to ∼9 Ma of growth in a solar nebula with a CI chondrite value of 87Rb/86Sr = 0.91, or ∼5 Ma in a nebula with solar photospheric 87Rb/86Sr = 1.51. Excess 53Cr from extinct 53Mn (t1/2 = 3.7 Ma) in LEW86010 corresponds to initial 53Mn/55Mn = 1.44 ± 0.07 × 10−6 and closure to Cr isotopic homogenization 18.2 ± 1.7 Ma after formation of Allende inclusions, assuming initial 53Mn/55Mn = 4.4 ± 1.0 × 10−5 for the inclusions as previously reported by the Paris group (Birck and Allegre, 1988). The 146Sm/144Sm value found for LEW86010 corresponds to solar system initial (146Sm/144Sm)o = 0.0080 ± 0.0009 for crystallization 8 Ma after Allende, the difference between Pb‐Pb ages of angrites and Allende, or 0.0086 ± 0.0009 for crystallization 18 Ma after Allende, using the Mn‐Cr formation interval. The isotopic data are discussed in the context of a model in which an undifferentiated “chondritic” parent body formed from the solar nebula ∼2 Ma after Allende CAIs and subsequently underwent differentiation accompanied by loss of volatiles. Parent bodies with Rb/Sr similar to that of CI, CM, or CO chondrites could satisfy the Cr and Sr isotopic systematics. If the angrite parent body had Rb/Sr similar to that of CV meteorites, it would have to form slightly later, ∼2.6 Ma after the CAIs, to satisfy the Sr and Cr isotopic systematics.
Metamorphism and aqueous alteration in low petrographic type ordinary chondrites
Authors: Sears Derek W. G. , Morse Andrew D. , Hutchison Robert , Guimon R. Kyle , Jie Lu , Alexander C. M. O'D. , Benoit Paul H. , Wright Ian , Pillinger Colin , Xie Tian , Lipschutz Michael E.
Published: June 2012

Abstract— In order to investigate the relative importance of dry metamorphism and aqueous alteration in the history of chondrules, chondrules were hand‐picked from the Semarkona (petrographic type 3.0), Bishunpur (3.1), Chainpur (3.4), Dhajala (3.8) and Allegan (5) chondrites, and matrix samples were extracted from the first three ordinary chondrites. The thermoluminescence (TL) properties of all the samples were measured, and appropriate subsets of the samples were analyzed by electron‐microprobe and radiochemical neutron activation and the water and H‐isotopic composition determined.

The TL data for chondrules from Semarkona and Bishunpur scatter widely showing no unambiguous trends, although group B1 chondrules tend to have lower sensitivities and lower peak temperatures compared with group A5 chondrules. It is argued that these data reflect the variety of processes accompanying chondrule formation. The chondrules show remarkably uniform contents of the highly labile elements, indicating mineralogical control on abundance and volatile loss from silicates and loss and recondensation of mobile chalcophiles and siderophiles in some cases. Very high D/H values (up to ∼8000‰ SMOW) are observed in certain Semarkona chondrules, a confirmation of earlier work.

With increasing petrographic type, mean TL sensitivities of the chondrules increase, the spread of values within an individual meteorite decreases, and peak temperatures and peak widths show trends indicating that the TL is mainly produced by feldspar and that dry, thermal metamorphism is the dominant secondary process experienced by the chondrules. The TL sensitivities of matrix samples also increase with petrographic type. Chainpur matrix samples show the same spread of peak temperatures and peak widths as Chainpur chondrules, indicating metamorphism‐related changes in the feldspar are responsible for the TL of the matrix. The TL data for the Semarkona and Bishunpur matrix samples provide, at best, only weak evidence for aqueous alteration, but the matrix contains H with approximately terrestrial D/H values, even though it contains much water. Secondary processes (probably aqueous alteration) presumably lowered the D/H of the matrix and certain chondrules. While chondrule properties appear to be governed primarily by formation processes and subsequent metamorphism, the matrix of Semarkona has a more complex history involving aqueous alteration as a meteorite‐wide process.
Isotopic composition of carbonates in the SNC meteorites Allan Hills 84001 and Nakhla
Authors: Jull A. J. T. , Eastoe C. J. , Xue S. , Herzog G. F.
Published: June 2012

Abstract— We have measured the 13C/12C and 14C/12C ratios in CO2 released by acid etching of the carbonate‐bearing SNC meteorites Allan Hills 84001 and Nakhla. Most of the C released is strongly enriched in 13C. In 10 out of 12 samples, 15‰ <δ13C < 55‰. Terrestrial values of carbonateδ13C from weathering products are generally between −10 and +10‰. Two leachate samples especially rich in 13C, ALH 84001,27 and Nakhla 25, have elemental Si/Mg ratios much lower than those of the bulk meteorites and 14C activities that are much lower than the values expected for terrestrial carbonates. The former observation indicates that these leachates consist primarily of carbonates and, less likely, phosphates. The latter observation implies that heavy C was introduced not by terrestrial weathering but by extraterrestrial processes. For ALH 84001,121 (sample 27) and Nakhla (BM 1913,26) δ13C = +41‰ and +35‰, respectively. The measured 18O/16O ratios in the leaches are similar: δ18O ∼ 15 ± 5‰, contrasting with 4.2‰ in the bulk silicates. We infer that the C in the carbonates retains an extraterrestrial isotopic signature, but probably not O, due to its ease of isotopic exchange (Cole and Ohmoto, 1986).
Chemistry and mineralogy of oxidation products on the surface of the Hoba nickel‐iron meteorite
Authors: Golden D. C. , Ming D. W. , Zolensky M. E.
Published: June 2012

Abstract— An oxide layer adjacent to the surface of the Hoba Ni‐Fe meteorite was analyzed chemically and mineralogically. Maghemite, magnetite, goethite and lepidocrocite were the main Fe minerals found in the oxide layer surrounding Hoba. Most of the Ni from the unweathered original meteorite was distributed among the above minerals with spinel‐type oxides (maghemite and magnetite) having the largest Ni fraction. Some Ni migrated to the limestone in which the meteorite is embedded. No evidence for zaratite or akaganeite was found in the oxide layer. Sulfate derived from the oxidation of troilite precipitated as gypsum. Phosphate accumulation in limestone in contact with the meteorite is probably due to phosphate adsorbed on Fe‐oxides. Maghemite with some magnetite was the oxidation product immediately next to the meteorite metal surface, which accommodated most of the Ni and Fe from the meteorite into its structure. Upon oxidation, some of the Ni, which was incorporated into calcite, was released. Cobalt associated with the oxides stayed within the oxide structure regardless of the oxidation state and did not migrate to the limestone. This suggests that Co may be a good tracer for oxides of meteoritic origin.
Phase diagrams describing solid‐gas equilibria in the system Fe‐Mg‐Si‐O‐C‐H, and its bearing on redox states of chondrites
Authors: Tsuchiyama Akira , Kitamura Masao
Published: June 2012

Abstract— Phase diagrams describing solid‐gas equilibria in the system Fe‐Mg‐Si‐O‐C‐H under H‐rich conditions (∼700–2000 K and 10−2–10−20 atm of Ph2), including solar nebula conditions, were constructed based on thermochemical calculations. Boundaries of vaporous phases, which are the first phases to condense from a gas, can be obtained without calculating condensation temperatures of individual gas compositions because the numbers of major gaseous species are the same as those of components in the concerned systems. Fractionations by condensation and/or evaporation can be discussed easily in such phase diagrams. A thermal divide, which is a barrier that vapors cannot cross by a single cooling process, was recognized in the phase diagrams. This is present on the Fe‐MgO‐SiO2‐CO‐H plane at high temperatures (≥500–700 K) and plays an important role in fractionations.

Oxidizing states of ordinary chondrites and carbonaceous chondrites before aqueous alteration are located at the O‐rich side of the thermal divide. Such oxidizing states can be formed from the solar gas by fractionation in the primordial solar nebula because the solar composition is located on the O‐rich side. On the other hand, the reducing states of enstatite chondrites, located at the O‐poor side, cannot be formed as long as the thermal divide is present. The reducing states can be obtained by CO to CH4 molecular reaction at low temperatures (≤500–700 K), where the high‐temperature thermal divide is absent. Addition of H2O‐rich and CH4‐rich ice can explain establishment of the redox states of ordinary and enstatite chondrites, respectively.
Nitrogen isotopic composition of CK chondrites
Authors: Sugiura Naoji , Zashu Shigeo
Published: June 2012

Abstract— Nitrogen abundances and isotopic compositions of four CK chondrites (ALH85002, EET92002, Yamato6903 and Karoonda) were measured by a stepped‐combustion method. Neon and Ar were also measured for the same samples. Two types of isotopically light N were observed. One of them is labile N released at low temperatures (∼300 °C). This N is observed only in ALH85002. The other N is extracted at high temperatures (900−1200 °C) from all CK chondrites; although, the isotopic compositions are somewhat variable. There is a fair correlation between the excess 15N values and the abundance of trapped 36Ar for the high‐temperature component, suggesting presolar origin of these species. The light N (δ15N = −106.8‰) observed in Karoonda is one of the lightest N components ever reported for bulk chondrites.
Search for extractable fullerenes in the Allende meteorite
Authors: Heymann D.
Published: June 2012

Abstract— In an effort to confirm earlier observations of fullerenes in the Allende meteorite by Becker et al. (1994), we have treated nine separate whole‐rock chips of this meteorite with toluene to search for extractable C60 and C70 fullerenes. The analysis was done with high performance liquid chromatography. Less than 1 ppb C60 and C70 were detected in a total of 131.82 g of this meteorite. Becker et al. (1994) have estimated a content of 100 ppm in one Allende sample. Either they have grossly overestimated the C60 content of their sample, or Allende is very inhomogeneous concerning fullerenes.
Geophysical studies of the Montagnais impact crater, Canada
Authors: Pilkington M. , Jansa L. F. , Grieve R. A. F.
Published: June 2012

Abstract— The 45‐km diameter Montagnais impact structure, Nova Scotia, Canada, is characterized by a positive, circular 8 mGal gravity anomaly associated with its central uplift. The negative gravity anomaly, which is expected for a complex crater of this size, is not observed within the structure, and magnetic data lack any well‐defined, crater‐related signature. The absence of a negative gravity anomaly implies that no low‐density zone generally related to fracturing and brecciation exists. Since Montagnais appears well preserved, this zone has not been removed by erosion. Its formation may have been impeded due to the lack of competency in the target rocks. The crater was formed in a shallow marine environment where the lack of strength in the unconsolidated sediments may have prevented the preservation of voids and fractures that cause a negative gravity anomaly as observed over other impact craters. Additionally, the efficient absorption of impact energy by unconsolidated target material may have inhibited fracture/void development. Although the gravity signature of impact craters formed on land is well known, structures occurring in unconsolidated target material, such as continental shelf environments, constitute another signature that should also be recognized.
The Bawku LL5 Chondrite
Authors: Reed S. J. B. , Chinner G. A.
Published: June 2012

Abstract— A meteorite fall was observed on 1989 December 29 in the vicinity of Bawku, North Ghana (11°05′N, 0°11′W). Two fragments (59 and 1498 g) of a stony meteorite were subsequently recovered. This is classified as an LL5 monomict breccia of shock category S2. The olivine and pyroxene compositions are Fa26.8 and Fs22.6 respectively.
Weathering in Antarctic H and CR chondrites: Quantitative analysis through Mössbauer spectroscopy
Authors: Burns Roger G. , Burbine Thomas H. , Fisher Duncan S. , Binzel Richard P.
Published: June 2012

Abstract— Mössbauer spectroscopy is a very useful tool for identifying ferric iron weathering products in meteorites because of the capability to quantify the relative amounts of ferric iron in them. Mössbauer measurements were made of 33 Antarctic H chondrites (predominately H5) and two paired Antarctic CR chondrites. The primary goals of this study are to determine if Mössbauer spectroscopy can be used to determine which phases are weathering in Antarctic meteorites and if the relative amounts of ferric iron correlate with terrestrial age. Determining which minerals are weathering in ordinary chondrites appears very difficult due to variations in composition for different ordinary chondrites of the same meteorite class and possible problems in preparing homogeneous samples. The analysis of the two paired CR chondrites appears to indicate that metallic iron is predominately weathering to produce ferric iron for this class of meteorite. No correlation is seen between the relative amounts of ferric iron and terrestrial age for ordinary chondrites. One Antarctic H5 chondrite (ALHA77294) with a short 14C age of 135 ± 200 years from the dating of interior carbonate weathering products does have a relatively low amount of ferric iron, which is consistent with this meteorite being exposed on the surface for a relatively short time.
No iridium anomaly after the 1908 Tunguska impact: Evidence from a Greenland ice core
Authors: Rasmussen Kaare L. , Clausen Henrk B. , Kallemeyn Gregory W.
Published: June 2012

Abstract— We have determined the abundances of Ir and other elements by neutron activation analysis on annual dust samples from an ice core from Site B in the Crête region in central Greenland covering the years 1905–1914. Iridium was detected in all samples, but we found no excess Ir above the background in the years following the Tunguska event. The lack of an Ir anomaly in the years after the Tunguska impact combined with the knowledge of the energy released during the impact and our present knowledge about stratospheric transport implies either a very low Ir content of the impactor or an exceptionally high geocentric velocity for the impactor.
Cosmogenic nitrogen isotopic disequilibrium observed in meteorites
Authors: Sugiura N. , Hashizume K. , Miura Y. , Kiyota K. , Zashu S.
Published: June 2012

Abstract— The isotopic disequilibrium of N molecules in meteorites was examined. For a large data‐set, consisting of mass compositions of N molecules extracted at 1200 °C by stepped combustion of chondrites and eucrites, we find that a cosmogenic‐N‐enriched component and a normal air‐like N component are isotopically disequilibrated with each other. The isotopic composition of the cosmogenic‐N‐enriched component seems to be variable, although the cause for the variation is not clear. The abundance of indigenous atomic N in silicate minerals seems to be small. Indigenous N in meteoritic silicates, if present, may be present in the form of N molecules.
The origin of circumstellar silicon carbide grains found in meteorites
Authors: Lodders K. , Fegley B.
Published: June 2012

Abstract— Condensation calculations for C‐rich circumstellar envelopes are used to model the condensation sequence of C, TiC, and SiC, and trace‐element patterns observed in circumstellar SiC grains. Some properties of carbon star envelopes are briefly discussed, and condensation temperatures for major and trace elements are computed for a wide array of total pressure, C/O‐ratios, and s‐process elemental abundances. The comparison of calculated patterns for trace‐element solid solutions in SiC with the different observed patterns measured by Amari et al. (1995) yields an association of the grains to at least three different groups of carbon stars.
Cristobalite‐ and tridymite‐bearing clasts in Parnallee (LL3) and Farmington (L5)
Authors: Bridges J. C. , Franchi I. A. , Hutchison R. , Morse A. D. , Long J. V. P. , Pillinger C. T.
Published: June 2012

Abstract— A set of cristobalite‐ and tridymite‐rich igneous clasts (CB1 to CB8) have been found in Parnallee (LL3.6). They consist of clinoenstatite, minor feldspathic mesostasis and cristobalite veined by endiopsideaugite. The largest clast, CB8, is 1.6 cm in diameter and contains veined tridymite and cristobalite, clinoenstatite (zoned to ferroaugite and pyroxferroite Fs75.6Wo20.0) and plagioclase. Compared to bulk ordinary chondrites (OC), the bulk clasts are depleted in Al (0.02–0.8× OC), Na and K and enriched in Si (1.6–2.0× OC) and Ca (1.3–4.5× OC). Bulk CB8 has LREE > HREE (La/Lu = 1.6) with a positive Eu anomaly (Eu/Eu* = 2.4). Textural observations suggest that the clasts cooled rapidly (24–420 °C/h) above 1200 °C. Clasts CB1—CB8 contain the isotopically heaviest O yet found in ordinary chondrites (up to δ17O = +8.7%o, δ18O = +11.6%o). Enrichment in the heavy isotopes of O is dependent on the proportion of cristobalite (or tridymite) in the clasts. A regression line CRIL (Cristobalite Line), with slope 0.77, is defined by the isotopic compositions of CB1—CB8, the Farmington clast and ordinary chondrite chondrules. An 16O‐poor gas reservoir, whose composition must lie at some point along the extension of CRIL, has undergone varying degrees of isotopic exchange with most ordinary chondrite material. Silica polymorphs have undergone the greatest degree of exchange because of their open, framework structures. Silicon in CB1—CB8 has normal isotopic ratios. A model is proposed that involves differentiation of H‐group material through extraction of volatile elements in a vapour phase, loss of an Fe‐Ni‐S melt and metastable crystallisation (60–70%) of olivine. The calculated residual liquid is silica‐oversaturated and its subsequent predicted crystallisation sequence resembles that preserved in CB1—CB8. This model may require two stages of heating, the second one prior to cristobalite crystallisation (if the silica polymorph crystallises within its predicted stability field of > 1500 °C). Isotopic exchange took place either when CB1—CB8 were ejected from their parent body due to impact or near the surface of the parent body, perhaps in an ejecta blanket setting. The latter option is preferred because it is more consistent with our igneous model.
Beryllium‐10 and aluminum‐26 in individual cosmic spherules from Antarctica
Authors: Nishiizumi K. , Arnold J. R. , Brownlee D. E. , Caffee M. W. , Finkel R. C. , Harvey R. P.
Published: June 2012

Abstract— We present data for the cosmogenic nuclides 10Be and 26Al in a suite of 24 extraterrestrial spherules, collected from Antarctic moraines and deep sea sediments. All of the 10 large spherules collected in glacial till at Lewis Cliff are extraterrestrial. As in earlier work, the great majority of particles show prominent solar cosmic‐ray (SCR) production of 26Al, indicating bombardment ages on the order of 106 years or even longer. These long ages are in direct contradiction to model ages for small particles in the inner Solar System and may require reconsideration of models of small particle lifetimes. A small fraction of the particles so far measured (6/42) possess cosmogenic radionuclide patterns consistent with predictions for meteoroid spall droplets. We believe that most of the spherules were bombarded in space primarily as bodies not much larger than their present size.

The content of in situ produced 10Be and 26Al in quartz pebbles in the same moraine suggests that these spherules may have on average a significant terrestrial age.
The Roosevelt County 079–090 meteorites
Authors: Benedix G. K. , Kinsey L. K. , McCoy T. J. , Keil K. , Wieler R.
Published: June 2012

Abstract— We have classified 12 new, moderately to severely weathered meteorites from Roosevelt County, New Mexico (RC 079–090) that were recovered between 1969 and 1993. They include nine H chondrites and three L chondrites of petrologic types 4 to 6 and shock classification S1 to S4. Among these are a flight‐oriented specimen of an H5 chondrite, an L4 chondrite with a porphyritic impact‐melt rock clast, an H5 fragmental breccia with an unusual weathering assemblage (probably a Ca sulfate), and an H4 chondrite with unequilibrated pyroxenes.
The Meteoritical Bulletin, No. 78, 1995 November*
Authors: Wlotzka Frank
Published: June 2012

Abstract— This Meteoritical Bulletin lists 53 meteorites, of which 16 are from the Nullarbor, Australia, and 12 from Roosevelt County, New Mexico. Besides ordinary chondrites, there are five irons and one howardite (Mundrabilla 018). Four of the meteorites are falls (Baszkówka, Campos Salos, Neagari, and New Halfa).
Constraints on formation processes of two coarse‐grained calcium‐ aluminum‐rich inclusions: A study of mantles, islands and cores
Authors: Meeker Gregory P.
Published: June 2012

Abstract— Many coarse‐grained calcium‐ aluminum‐rich inclusions (CAIs) contain features that are inconsistent with equilibrium liquid crystallization models of origin. Spinel‐free islands (SFIs) in spinel‐rich cores of Type B CAIs are examples of such features. One model previously proposed for the origin of Allende 5241, a Type B1 CAI containing SFIs, involves the capture and assimilation of xenoliths by a liquid droplet in the solar nebula (El Goresy et al., 1985; MacPherson et al., 1989). This study reports new textural and chemical zoning data from 5241 and identifies previously unrecognized chemical zoning patterns in the melilite mantle and in a SFI. These zoning patterns are identified by large‐scale elemental mapping techniques. The compositional zoning is completely independent of, and cross‐cuts individual melilite crystals in the mantle, a relation that suggests the mantle was deposited or accreted onto a preexisting core of the inclusion. Lack of correlation with individual mantle crystals also suggests that the mantle totally recrystallized at subsolidus temperatures. Sodium distribution maps demonstrate that most of the Na in 5241 was introduced during the secondary alteration process. Major‐ and trace‐element data from the SFI boundary in a second type B1 CAI, Allende 3529Z, were obtained. The boundary bisects a large fassaite crystal. If the SFI is a relict xenolith, then chemical differences are likely to be present across the boundary. Electron microprobe analysis of the fassaite crystal reveals concentric zoning of Ti, which is unrelated to the SFI boundary, as well as distinct zones enriched in Al and depleted in Ti+3. Ion microprobe analyses at the SFI boundary show no significant variation in Ba, Sc, V, Cr, Sr, Zr, Nb and REE in fassaite. There is no evidence that requires the capture of a xenolith in 3529Z. Based on chemical zoning and textural arguments, it is suggested that both of these CAIs formed by a process of partial melting of precursors, which contained either vesicles or spinel‐free grains. Allende 5241 shows evidence for vapor condensation and accretion and/or introduction of a second liquid to form the melilite mantle. Chemical zoning patterns in the mantles of the inclusions indicate that 3529Z experienced a higher degree of partial melting than 5241, but it was not high enough to melt spinel or completely melt and homogenize relict fassaite components.
Nullarbor 018: A new L6 chondrite from Australia
Authors: Ruzicka Alex
Published: June 2012

Abstract— A new meteorite find from the Nullarbor Plain in Australia was studied using optical, SEM, and electron microprobe techniques. The meteorite, Nullarbor 018, is an orthodox L6 chondrite that experienced minor‐to‐moderate alteration of metal during terrestrial weathering (grade A–B to B). During weathering, troilite was preferentially altered, and roughly 20% of the original complement of S in the meteorite was removed. Shock metamorphic effects corresponding to shock stage S4 (or shock facies d) are found, including the presence of some diaplectic feldspar (maskelynite). The meteorite is not obviously paired with other finds from the Nullarbor region, but the possibility that it is paired cannot be excluded.
Cobalt‐rich, nickel‐poor metal (wairauite) in the Ningqiang carbonaceous chondrite
Authors: Hua Xin , Eisenhour Don D. , Buseck Peter R.
Published: June 2012

Abstract— A structurally ordered cubic metal grain containing ∼39 wt% Co, 61 wt% Fe, and <0.6 wt% Ni (∼Fe3Co2) was found associated with troilite and pentlandite in the matrix of the Ningqiang carbonaceous chondrite. This mineral is similar to terrestrial wairauite. Experimental data in the Fe‐Co system indicate that this CsCl‐type Co‐rich metal is stable below 700 °C. Phase relations in the Fe‐Co‐Ni system show that Co cannot fractionate from Ni above 500 °C. The dominant opaque minerals of awaruite, magnetite, and pentlandite in Ningqiang suggest relatively oxidizing conditions.
Adenylate Cyclases of
Trypanosoma brucei
Inhibit the Innate Immune Response of the Host
Authors: Salmon Didier , Vanwalleghem Gilles , Morias Yannick , Denoeud Julie , Krumbholz Carsten , Lhommé Frédéric , Bachmaier Sabine , Kador Markus , Gossmann Jasmin , Dias Fernando Braga Stehling , De Muylder Géraldine , Uzureau Pierrick , Magez Stefan , Moser Muriel , De Baetselier Patrick , Van Den Abbeele Jan , Beschin Alain , Boshart Michael , Pays Etienne
Published: June 2012

Tricky Tryps

African trypanosomes, responsible for human sleeping sickness, are known for their powerful strategies of immune evasion, in particular antigenic variation. Adding another facet to this adaptive potential,

Salmon
et al.

(p.
463
, published online 14 June; see the cover) now show that early after infection, these parasites subvert the first line of innate host defense by inhibiting tumor necrosis factor-α synthesis in myeloid cells. This occurs through the stress-induced synthesis and release of cyclic adenosine monophosphate by phagocytosed parasites. The findings provide a long-sought function for the abundant and diverse adenylate cyclases in salivarian trypanosomes. Furthermore, this altruistic host colonization strategy, in which a proportion of parasites are sacrificed so that others can thrive, also highlights the selective advantage of population behavior in infection.
Aerobic neuromuscular electrical stimulation—an emerging technology to improve haemoglobin A1c in type 2 diabetes mellitus: results of a pilot study
Authors: Crowe Louis , Caulfield Brian
Published: June 2012

Objectives

A new generation of neuromuscular electrical stimulation (NMES) devices can exercise aerobically at equivalent rates to voluntary exercise. Many with type 2 diabetes cannot or will not exercise sufficiently. The objective of this pilot investigation was to see (1) if it was an acceptable training modality for men with type 2 diabetes mellitus and (2) to assess effects on haemoglobin A1c levels.

Design, setting, participants and intervention

A case series of eight men with type 2 diabetes mellitus (aged 53±8; body mass index 32±5 5 kg/m2) trained with the NMES system for 1 h 6 times weekly for 8 weeks, unsupervised, at home. There were no other medication or lifestyle interventions. The aerobic NMES exercise system delivers a repeating set of four complex staggered pulses at high intensities (typically 100 mA+) through an array of eight thigh electrodes.

Outcome measures

The primary outcome measures were changes in haemoglobin A1c and the responses in a questionnaire on participants' perceptions of the system. Body mass and composition were also measured before and after the NMES intervention period.

Results

All participants could use the system at a level that left them breathless and sweaty and with a heart rate over 120 beats per minute. Haemoglobin A1c levels improved by 0.8±0.7% from 7.4±1.3% (mean ± SD) to 6.6±1.0% (p=0.01). All participants considered the system suitable for people with diabetes, would recommend it and would continue to use it twice a week ‘to maintain improvements’.

Conclusions

These results suggest that aerobic NMES may be acceptable and have a beneficial effect on haemoglobin A1c of some men with diabetes. The treatment may be of particular benefit in those who will not or cannot do adequate amounts of voluntary exercise. A randomised control trial is required for conclusive efficacy data.
Is access to specialist assessment of chest pain equitable by age, gender, ethnicity and socioeconomic status? An enhanced ecological analysis
Authors: Sekhri Neha , Timmis Adam , Hemingway Harry , Walsh Niamh , Eldridge Sandra , Junghans Cornelia , Feder Gene
Published: June 2012

Objectives

To determine whether access to rapid access chest pain clinics of people with recent onset symptoms is equitable by age, socioeconomic status, ethnicity and gender, according to need.

Design

Retrospective cohort study with ecological analysis.

Setting

Patients referred from primary care to five rapid access chest pain clinics in secondary care, across England.

Participants

Of 8647 patients aged ≥35 years referred to chest pain clinics with new-onset stable chest pain but no known cardiac history, 7570 with documented census ward codes, age, gender and ethnicity comprised the study group. Patients excluded were those with missing date of birth, gender or ethnicity (n=782) and those with missing census ward codes (n=295).

Outcome measures

Effects of age, gender, ethnicity and socioeconomic status on clinic attendance were calculated as attendance rate ratios, with number of attendances as the outcome and resident population-years as the exposure in each stratum, using Poisson regression. Attendance rate ratios were then compared with coronary heart disease (CHD) mortality ratios to determine whether attendance was equitable according to need.

Results

Adjusted attendance rate ratios for patients aged >65 years were similar to younger patients (1.1, 95% CI 1.05 to 1.16), despite population CHD mortality rate ratios nearly 15 times higher in the older age group. Women had lower attendance rate ratios (0.81, 95% CI 0.77 to 0.84) and also lower population CHD mortality rate ratios compared with men. South Asians had higher attendance rates (1.67, 95% CI 1.57 to 1.77) compared with whites and had a higher standardised CHD mortality ratio of 1.46 (95% CI 1.41 to 1.51). Although univariable analysis showed that the most deprived patients (quintile 5) had an attendance rate twice that of less deprived quintiles, the adjusted analysis showed their attendance to be 13% lower (0.87, 95% CI 0.81 to 0.94) despite a higher population CHD mortality rate.

Conclusion

There is evidence of underutilisation of chest pain clinics by older people and those from lower socioeconomic status. More robust and patient focused administrative pathways need to be developed to detect inequity, correction of which has the potential to substantially reduce coronary mortality.
QUANTUM METROLOGY WITHOUT QUANTUM ENTANGLEMENT
Authors: DATTA ANIMESH , SHAJI ANIL
Published: June 2012

We scrutinize the role of quantum entanglement in quantum metrology and discuss recent advances in nonlinear quantum metrology that allow improved scalings of the measurement precision with respect to the available resources. Such schemes can surpass the conventional Heisenberg limited scaling of 1/N of quantum enhanced metrology. Without investing in the preparation of entangled states, we review how systems with intrinsic nonlinearities such as Bose–Einstein condensates and light-matter interfaces can provide improved scaling in single parameter estimation.
STUDY OF PLASMA POSITION BY THE ANALYTICAL SOLUTION OF GRAD–SHAFRANOV EQUATION FOR HT-7 TOKAMAK
Authors: ASIF M.
Published: June 2012

In this work, we present approximation of plasma position by two methods on HT-7 Tokamak. In the first method, solution of Grad–Shafranov equation are presented and one relation for plasma position is obtained. A generalized Grad–Shafranov-type equation has been used. Specific functional forms of plasma internal energy and current are used. In second method, according to magnetic fields distribution around the plasma, second relation for plasma position is obtained. Plasma position is obtained by magnetic probes. Results of the two methods are in good agreement with each other.
MULTIVARIATE HEAVY-TAILED MODELS FOR VALUE-AT-RISK ESTIMATION
Authors: MARINELLI CARLO , D'ADDONA STEFANO , RACHEV SVETLOZAR T.
Published: June 2012

For purposes of Value-at-Risk estimation, we consider several multivariate families of heavy-tailed distributions, which can be seen as multidimensional versions of Paretian stable and Student's t distributions allowing different marginals to have different indices of tail thickness. After a discussion of relevant estimation and simulation issues, we conduct a backtesting study on a set of portfolios containing derivative instruments, using historical US stock price data.
EFFECTS ON THE CHEMICAL STEREODYNAMICS OF THE INITIAL VIBRATIONAL EXCITATION IN THEF+LiH(v = 0-2, j = 0) →LiF+HREACTION
Authors: WANG TAO
Published: June 2012

In this work, the product polarization characteristics are reported for the reaction F + LiH (v = 0 - 2, j = 0) → LiF + H at the collision energy of 35 kcal/mol, by using the QCT method on the Aguado–Paniagua-potential energy surface (see Aguado et al.). The distribution of P(θr) which represents the K (reagent relative velocity vector) and J′ (product rotational angular momentum vector) correlation, the dihedral angle distribution of K-K′ (product relative velocity vector)-J′ P(φr), the angular distribution P(θr, φr) and the four polarization-dependent differential cross sections (2π/σ)(dσ00/dωt), (2π/σ)(dσ20/dωt), (2π/σ)(dσ22+/dωt), (2π/σ)(dσ21-/dωt) in each initial state are presented and discussed.
HYDROGEN BOND NETWORK OF 1-ALKYL-3-METHYLIMIDAZOLIUM IONIC LIQUIDS: A NETWORK THEORY ANALYSIS
Authors: XIONG ZICHANG , GAO JUN , ZHANG DONGJU , LIU CHENGBU
Published: June 2012

Hydrogen bond is a key factor in the determination of structures and properties of room-temperature ionic liquids. Connections of these hydrogen bonds form a network. In this work, we analyzed the hydrogen bond network of 1-alkyl-3-methylimidazolium ionic liquids using network theory. A two-dimensional view of the hydrogen bond network has been generated, the connection pattern shown that the average length of line shape connection is 2.44 to 2.77 for six 1-alkyl-3-methylimidazolium ionic liquids, and the connection patterns are different for short and long alkyl side chain length. The degree of each ion was calculated and analyzed. The nodes with zero degree were adopted to detect the boundary of the clusters in the ionic liquids, which have no hydrogen bond connected with neighbor ions. This work indicates that the network analysis method is useful for understanding and predicting the structure and function of RTILs.
ELEMENTAL AND MIXED ACTINIDE DIOXIDES: AN AB INITIO STUDY
Authors: MA LI , ATTA-FYNN RAYMOND , RAY ASOK K.
Published: June 2012

We present a systematic study of the electronic, geometric, and magnetic properties of the actinide dioxides, UO2 , PuO2 , AmO2 , U0.5Pu0.5O2 , U0.5Am0.5O2 and Pu0.5Am0.5O2 . For UO2 , PuO2 and AmO2 , both density functional and hybrid density functional theory (DFT and HDFT) have been used. The fractions of exact Hartree–Fock (HF) exchange chosen were 25% and 40% for the hybrid density functional. For U0.5Pu0.5O2 , U0.5Am0.5O2 and Pu0.5Am0.5O2 , only HDFT with 40% exact HF exchange was used. Each compound has been studied at the nonmagnetic, ferromagnetic and anti-ferromagnetic configurations, with and without spin–orbit coupling (SOC). The lattice parameters, magnetic structures, bulk moduli, band gaps and density of states have been computed and compared to available experimental data and other theoretical results. Pure DFT fails to provide a satisfactory qualitative description of the electronic and magnetic structures of the actinide dioxides. On the other hand, HDFT performs very well in the prediction and description of the properties of the actinide dioxides. Our total energy calculations clearly indicate that the ground-state structures are anti-ferromagnetic for all actinide dioxides considered here. The lattice constants and the band gaps expand with an increase of HF exchange in HDFT. The influence of SOC is found to be significant.
DENSITY FUNCTIONAL STUDY ON THE PROTON ASSISTED ISOMERIZATION OF 1H-IMIDAZO(4,5-b)PYRIDINE DERIVATIVES
Authors: DEKA R. P. , MEDHI C.
Published: June 2012

The proton assisted isomerization reactions of 1H-imidazo(4,5-b)pyridine (IMP) derivatives have been studied by using B3LYP/6-31G + (d,p) calculations, and the transition states of the reactions are analyzed with B3LYP/6-31+G(d,p) opt=qst3 route. It has been found that the prototropic transformation could be the feasible pathway of isomerization, since the energy gaps between the various protonated isomers are found closer compared to free molecules. The conversion of IMP-a1 to IMP-b1 may pass through several protrotopic isomerization, since the activation energy as well as the relative energy levels of these isomers are not small compared to other pathways. However, the results suggest that some of the reactions may take place simultaneously through protrotopic transformation. The relative variations of energy gaps in the excited states are smaller than the ground states. The protrotropic transformation in the excited states may be more feasible than the ground state.