bluuebunny/crossref_metadata_2025 huggingface dataset:
Isotope source table for a 25 M⊙ supernova
Authors: Meyer Bradley S. , Weaver Thomas A. , Woosley Stanford E.
Published: June 2012

Abstract— We present a table giving the yields of 103 isotopes in eight distinct zones in the ejecta from the explosion of a 25 M star. Each zone in the ejecta is distinct isotopically due to the evolution and explosion of the star. Thus the table not only gives the yields of isotopes in the different zones of the ejecta but also provides information about the chemical environments in which each isotope is injected into the interstellar medium.

The table is a summary of the nuclear yields from a single numerical model of the explosion of a massive star. The yields from a real supernova will vary from those in this table because of uncertainties in the input physics to the numerical model and because the real star may differ in mass, mass‐loss rate, or metallicity from the modeled star. We argue that these uncertainties and variations, for the most part, will not change the direction of the largest isotopic effects in the different zones of the ejecta. This means that the table is quite generally applicable as a guide to understanding the ejecta of supernovae and as a characterization of possible chemical environments in which isotopes are injected into the interstellar medium.
Laser probe argon‐40/argon‐39 dating of coesite‐ and stishovite‐bearing pseudotachylytes and the age of the Vredefort impact event
Authors: Spray John G. , Kelley Simon P. , Reimold W. Uwe
Published: June 2012

Abstract— Age determinations have been made on pseudotachylytic rocks from the controversial Vredefort structure of South Africa using the laser microprobe 40Ar/39Ar dating technique. Coesite‐ and stishovitebearing veins in a quartzite from the Central Rand Group of the collar rocks were dated using a 10‐μm diameter focused ultra‐violet laser beam. These yielded a weighted mean age of 2027 ± 18 Ma (2σ). Six pseudotachylytes, sampled from four different locations within the Outer Granite Gneiss of the core, were dated using an 50–100‐μm diameter focused infrared laser beam. These pseudotachylytes exhibit altered vein margins with apparent ages considerably younger than ages obtained from the fresher centres of veins. The best weighted mean pseudotachylyte matrix age obtained was 2018 ± 14 Ma (2σ). Most of the clasts within the pseudotachylyte matrices retain significantly older (e.g., Archean) ages, indicative of their parent rock history. Our results show that five of the seven dated samples possess matrix ages of ∼2000 Ma, similar to the age of the Granophyre (Walraven et al., 1990), a supposed impact melt rock (French and Nielsen, 1990). The dating of coesite‐ and stishovite‐bearing veins equates the shock event with pseudotachylyte formation, generation of the Granophyre and creation of the Vredefort structure. The results affirm that the Vredefort Dome is a meteorite impact structure and show that it formed at 2018 ± 14 Ma (2σ).
Impact‐induced chondrule flattening in the Allende CV3 carbonaceous chondrite: Shock experiments
Authors: Nakamura Tomoki , Tomeoka Kazushige , Sekine Toshimori , Takeda Hiroshi
Published: June 2012

Abstract— We have carried out shock‐recovery experiments on the Allende CV3 carbonaceous chondrite using a single‐stage propellant gun and succeeded in reproducing oriented, flattened chondrules like those observed in some natural CV3 chondrites. The Allende samples were shocked at equilibrium pressures of 11 and 21 GPa, which are close to the highest values in shock stages S2 and S3, respectively (Stöffler et al., 1991). Chondrules are flattened nearly perpendicular to the compaction axis with mean aspect ratios of 1.34 and 1.62 at pressures of 11 and 21 GPa, respectively; thus, the degree of chondrule flattening is proportional to the shock intensity. The chondrule flattening and foliation are mainly due to collapse of pores in the matrix under shock pressure. High matrix abundance of CV3 chondrites could result in much apparent chondrule flattening relative to ordinary chondrites. Optical and electron microscope observations show that textural and mineralogical characteristics of chondrules and matrix in the shock‐loaded samples are very similar to those observed in naturally shocked CV3 chondrites. Our results provide strong support for the interpretation that the chondrule flattening and foliation in CV3 chondrites were caused by shock‐induced pressure due to hypervelocity impacts on the meteorite parent bodies.
Nierite (Si3N4), a new mineral from ordinary and enstatite chondrites
Authors: Lee Martin R. , Russell Sara S. , Arden John W. , Pillinger C. T.
Published: June 2012

Abstract— Nierite (Si3N4) is a new mineral that has been found in perchloric acid‐resistant residues of three ordinary chondrites (Adrar 003 [LL3.2], Inman [L3.4] and Tieschitz [H3.6]) and one enstatite chondrite (Indarch [EH4]). This mineral occurs as very small (∼2 × 0.4 μm) lath‐shaped grains, which have been characterised by transmission electron microscopy. The d‐spacings of nierite are, within errors, comparable to those of synthetic α‐Si3N4, which has trigonal symmetry (P31c, a = 0.7758 nm, c = 0.5623 nm, V = 0.2931 nm3 Z = 4). Energy‐dispersive x‐ray analyses confirm that nierite is a Si‐ and N‐rich mineral. A few nierite crystals in the Indarch, Inman and Tieschitz residues are intergrown with whiskers of another nitride. Only two crystals of this additional nitride were found that were of sufficient size to give electron diffraction patterns uncontaminated by nierite reflections. The d‐spacings of this second nitride are comparable to those of β‐Si3N4, the hexagonal polymorph of synthetic Si3N4.

The majority of nierite crystals in Indarch are interpreted to have formed by exsolution of Si and N from kamacite, perryite and schreibersite during parent‐body metamorphism. Some grains have evidence for two discrete episodes of nierite crystallization. The origin of nierite in Adrar 003, Inman and Tieschitz is not known, but formation during exsolution is again possible. The petrographic relationships between nierite and β‐Si3N4 in Indarch, Inman and Tieschitz suggests that the β‐Si3N4 whiskers predated nierite and acted as a seed on which nierite crystals later nucleated. The nierite/β‐Si3N4 ratio in ordinary chondrites is controlled by their metamorphic grade and possibly also their oxidation state.
The isotopic composition and origins of silicon nitride from ordinary and enstatite chondrites
Authors: Russell S. S. , Lee M. R. , Arden J. W. , Pillinger C. T.
Published: June 2012

Abstract— The N‐isotopic composition of acid‐resistant residues of three low petrologic type ordinary chondrites (Adrar 003, LL3.2; Inman, L3.4; Tieschitz, H3.6) and an enstatite chondrite (Indarch, EH4) have been measured by static mass spectrometry. All of these samples have been shown by transmission electron microscopy (TEM) to contain silicon nitride (Si3N4), and no other nitrides were detected in any of the residues (Lee et al., 1995). Stepped combustion has demonstrated the presence of at least two components with low C/N ratios, which have been interpreted as Si3N4. The most abundant component, common to all the meteorites studied, released during combustion at temperatures >1150 °C, may have formed during metamorphism of the meteorite's parent body. In addition, the ordinary chondrites Tieschitz and Inman show evidence for a second component of Si3N4 that is less stable to combustion than the first and is enriched in 15N. The unusual N‐isotope signature suggests that this second type of Si3N4 may constitute a new type of interstellar grain. A comparison of the isotope and microscope data suggests that the >1150 °C component can be related to nierite (α‐Si3N4) and the less stable component to β‐Si3N4.
Iodine‐xenon studies of Bjurböle and Parnallee using RELAX
Authors: Gilmour J. D. , Ash R. D. , Hutchison R. , Bridges J. C. , Lyon I. C. , Turner G.
Published: June 2012

Abstract— Iodine‐xenon analyses of chondrules from the Bjurböle L4 and Parnallee LL3.6 meteorites have been made using a continuous wave laser microprobe and the resonance ionisation mass spectrometer RELAX. The excess 129Xe content released from the Bjurböle chondrule is lower than previous stepped‐heating studies have found, suggesting that the technique does not completely degas the samples. Nonetheless, clear isochrons were produced, and data for initial 129Xe/130Xe are consistent with earlier work. A correlation is evident in each chondrule between 131Xe* and 128Xe* perhaps indicating a common host‐phase for their parent nuclides, a condition possibly fulfilled by a Te‐ and I‐bearing sulfide. The I‐Xe system of a Parnallee macrochondrule exhibits no excess 129Xe, possibly as a result of thermal alteration or deformation before accumulation of the meteorite. A cristobalite‐bearing chondrule depleted in 16O yields an I‐Xe age of 4.5 ± 0.5 Ma after the mean Bjurböle age.
Fractionation of refractory siderophile elements in metal from the Rose City meteorite
Authors: Rubin Alan E.
Published: June 2012

Abstract— An ∼4 × 9 × 12‐mm concentration of metal (dubbed RC1) situated between silicate melt and a relict chondritic clast in the Rose City H5 impact‐melt breccia is compositionally heterogeneous. Approximately 65 wt% of RC1 is enriched in the refractory siderophile elements, Os and Ir, by 30–40% relative to bulk H chondrite metal; ∼20 wt% is depleted in these elements by 31–35%; and 15 wt% is depleted by a considerably greater amount (75%). Common and volatile siderophile elements are essentially unfractionated in all three regions; W is fractionated to only a moderate degree. The compositions of the different regions of RC1 are similar to those of previously analyzed metal nodules and veins in shocked but unmelted ordinary chondrites. All of these objects probably formed by a complex process involving vaporization of chondritic material, rapidly followed by oxidation of W to form volatile oxides, fractional condensation of refractory siderophile elements, transport of the residual vapor (containing common and volatile siderophile elements as well as W oxide) and condensation of this vapor in fractures and voids or on metallic liquid substrates. The common occurrence of vugs in shock‐heated chondrites and the pervasiveness of vaporization effects recorded in metal masses and veins underscores the important role of superheating in the formation of impact breccias.
Sulfur and selenium in chondritic meteorites
Authors: Dreibus G. , Palme H. , Spettel B. , Zipfel J. , Wänke H.
Published: June 2012

Abstract— We report here new analyses of S and Se in carbonaceous chondrites (2 CIs, 11 CMs, 6 CO3s, 7 CV3s, 2 C4s, 4 CRs, and 1 CH), 2 rumurutiites, ordinary chondrites (2 Hs, 2 Ls, and 1 LL), 3 anomalous chondrites, 3 acapulcoites, 3 lodranites, and in silicate inclusions of the Landes IAB iron meteorite. To avoid problems from inhomogeneous distribution of sulfides, the same samples that had been analysed for Se by INAA were analysed for S using a Leybold Heraeus Carbon and Sulfur Analyser (CSA 2002).

With the measured CI contents of 5.41% S and 21.4 ppm Se a CI S/Se ratio of 2540 is obtained. A nearly identical S/Se ratio of 2560 ± 150 is found for carbonaceous chondrites (average of falls). The average ratio of all meteorite falls analysed in this study was 2500 ± 270. These data suggest that the new S content of Orgueil with 5.41% provides a reliable estimate for the average Solar System. The new solar system abundance of S of 4.62 × 105 (atoms/106 Si) is in good agreement with the solar photospheric abundance of 7.21 (log (a(H)) = E12) (Anders and Grevesse, 1989).

Among the 50 analysed meteorites, 24 were finds from hot (Australia, Africa) and cold (Antarctica) deserts. Weathering effects in the carbonaceous chondrites and in one lodranite from the hot deserts resulted in losses of S, Se, Na and occasionally Ni. Sulfur is apparently more affected by weathering than Se. No losses were observed in ordinary chondrite finds and in meteorites collected in the Antarctica, except for the obvious loss of Na in the CM‐chondrite Y 74662.

The low S‐content of 0.096% in Gibson, a lodranite, is probably not representative of this group of meteorites. Gibson is a find from the Australian desert and has lost S and also Se by weathering. Two other lodranites, finds from Antarctica, have about 2% S.
Volatiles in unequilibrated ordinary chondrites: Abundances, sources and implications for explosive volcanism on differentiated asteroids
Authors: Muenow D. W. , Keil K. , McCoy T. J.
Published: June 2012

Abstract— Keil and Wilson (1993) proposed that, during partial melting of some asteroidal meteorite parent bodies, explosive pyroclastic volcanism accelerated S‐rich Fe, Ni‐FeS cotectic partial melts into space. These authors argued that this process was responsible for the S‐depletion of many of the magmas from which the magmatic iron meteorites formed. This process only requires the presence of a few hundred to thousand ppm of volatiles in asteroids < ∼100 km in radius. If the precursor materials of these magmatic iron meteorite groups were similar in composition to unequilibrated ordinary chondrites, then the volatile contents of the latter may be a measure of the potential effectiveness of the process. Analysis of volatile contents of seven unequilibrated ordinary chondrite falls by dynamic high‐temperature mass spectrometry revealed that thousands of ppm of indigeneous volatiles, mostly CO, Cl, Na and S, are released at temperatures near the Fe, Ni‐FeS cotectic melting temperature of ∼980 °C. If these volatiles are largely retained in the asteroidal parent bodies until onset of partial melting, S depletion of the residual melt might have been achieved by ejection of S‐rich partial Fe, Ni‐FeS melts by pyroclastic volcanism.
Noble gases and strontium isotopes in the unique meteorite Divnoe
Authors: Shukolyukov Yu. A. , Assonov S. S. , Smoliar M. I. , Kolesnikov E. M.
Published: June 2012

Abstract— We present an isotope study of noble gases in Divnoe, an anomalous meteorite, and also Rb‐Sr and K‐Ar dating of this meteorite. The relatively young Rb‐Sr age obtained (3.39 Ga) seems doubtful and, most probably, results from weathering or contamination. The ancient K‐Ar age (4.67+0.20–0.40), together with clear excess of 129Xe, allows the suggestion of very early formation of the Divnoe meteorite.

Concentrations and isotope ratios of noble gases in Divnoe are: 17.9 ≤ 3He ≤ 29.0 × 10−8; 20Ne = 6.22 × 10−8; 2.44 ≤ 36Ar ≤ 5.10 × 10−8; 130Xe = 41.3 × 10−12 cm3/g; 0.079 ≤ 3He/4He ≤ 0.193; 20Ne/22Ne = 0.860; 21Ne/22Ne = 0.927; 3.47 ≤ 40Ar/36Ar ≤ 9.47; 2.22 ≤ 36Ar/38Ar ≤ 3.27; 129Xe/132Xe = 1.09. The exposure age calculated from cosmogenic 3He, 21Ne, and 38Ar is 17.9 ± 0.9 Ma.

On the basis of the isotope data for the noble gases and O, and abundances of K, Rb, and Sr, an attempt was made to estimate the relationship of Divnoe to other meteorite types. The O‐isotope characteristics of Divnoe are clearly distinct from those of ordinary chondrites, acapulcoites/lodranites, and SNC meteorites (Petaev et al., 1994, Clayton, 1993). In plots of 136Xe vs. 129Xe/130Xe, the Divnoe data fall outside of the data fields for carbonaceous and enstatite chondrites. The light noble gas data, especially the 40Ar/38Ar ratio, and the 40Ar, 38Ar, 3He, and 4He contents of Divnoe differ significantly from those of all meteorite types except diogenites. The K, Rb, and Sr abundances in Divnoe are substantially lower than in most other meteorites. In the concentrations of these elements, as well as in the REE pattern, the Divnoe meteorite is similar only to diogenites. Divnoe probably should be treated as a restite remaining after partial melting of the chondritic mantle of a parent asteroid body.
Detailed abundances of rare earth elements, thorium and uranium in chondritic meteorites: An ICP‐MS study
Authors: Shinotsuka Kazunori , Hidaka Hiroshi , Ebihara Mitsuru
Published: June 2012

Abstract— Inductively coupled plasma mass spectrometry (ICP‐MS) was successfully applied to bulk samples of Allende, Jilin, Modoc, Saint‐Séverin and Atlanta for the determination of rare earth elements (REE) (Y and 14 lanthanoids), Th and U. The results of ICP‐MS showed good agreement with recommended values, and their reproducibilities were high enough to discuss the detailed abundances of lanthanoids and actinoids in chondritic meteorites. For the Allende reference sample issued by the Smithsonian Institution, a positive anomaly of Tm, a fractionation between light REE and heavy REE and a high Th/U ratio were observed in the CI‐normalized abundances of REE, Th and U. These features are common for group II inclusions in Allende, suggesting that the abundances of refractory lithophiles in Allende are somewhat influenced by those in a specific constituent. For the other chondritic meteorites, a zigzag alteration was commonly observed in the heavy‐REE region of their CI‐normalized abundance patterns. It is suggested that such a zigzag pattern is attributable to erratically high abundances of monoisotopic REE (Tb, Ho and Tm) in the CI values. Abundances of REE, Th and U in the bulk samples are also discussed separately in detail.
Planar deformation features in quartz grains from the resurge deposit of the Lockne structure, Sweden
Authors: Therriault A. M. , Lindström M.
Published: June 2012

Abstract— Microscopic planar deformation features (PDFs) in quartz grains are diagnostic of shock meta‐morphism during hypervelocity impact cratering. Measurements of the poles of sets of PDFs and the optic axis of 25 quartz grains were carried out for a sample of the Loftarsten deposit from the Lockne area, Sweden. The most abundant PDFs observed in the sample from the Lockne area correspond to those found at known impact craters (i.e., ω (1013} and π (1012). This study confirms the previous suggestion that the Lockne structure is an impact crater. The Loftarsten is, therefore, interpreted as the final stage of resurge deposition after a marine impact at Lockne in the Middle Ordovician.
Chemical and physical studies of type 3 chondrites XII: The metamorphic history of CV chondrites and their components
Authors: Guimon R. Kyle , Symes Steven J. K. , Sears Derek W. G. , Benoit Paul H.
Published: June 2012

Abstract— The induced thermoluminescence (TL) properties of 16 CV and CV‐related chondrites, four CK chondrites and Renazzo (CR2) have been measured in order to investigate their metamorphic history. The petrographic, mineralogical and bulk compositional differences among the CV chondrites indicate that the TL sensitivity of the ∼130 °C TL peak is reflecting the abundance of ordered feldspar, especially in chondrule mesostasis, which in turn reflects parent‐body metamorphism. The TL properties of 18 samples of homogenized Allende powder heated at a variety of times and temperatures, and cathodoluminescence mosaics of Axtell and Coolidge, showed results consistent with this conclusion. Five refractory inclusions from Allende, and separates from those inclusions, were also examined and yielded trends reflecting variations in mineralogy indicative of high peak temperatures (either metamorphic or igneous) and fairly rapid cooling. The CK chondrites are unique among metamorphosed chondrites in showing no detectable induced TL, which is consistent with literature data that suggests very unusual feldspar in these meteorites. Using TL sensitivity and several mineral systems and allowing for the differences in the oxidized and reduced subgroups, the CV and CV‐related meteorites can be divided into petrologic types analogous to those of the ordinary and CO type 3 chondrites. Axtell, Kaba, Leoville, Bali, Arch and ALHA81003 are type 3.0–3.1, while ALH84018, Efremovka, Grosnaja, Allende and Vigarano are type 3.2–3.3 and Coolidge and Loongana 001 are type 3.8. Mokoia is probably a breccia with regions ranging in petrologic type from 3.0 to 3.2. Renazzo often plots at the end of the reduced and oxidized CV chondrite trends, even when those trends diverge, suggesting that in many respects it resembles the unmetamorphosed precursors of the CV chondrites. The low‐petrographic types and low‐TL peak temperatures of all samples, including the CV3.8 chondrites, indicates metamorphism in the stability field of low feldspar (i.e., <800 °C) and a metamorphic history similar to that of the CO chondrites but unlike that of the ordinary chondrites.
Solar‐proton‐produced neon in shergottite meteorites and implications for their origin
Authors: Garrison D. H. , Rao M. N. , Bogard D. D.
Published: June 2012

Abstract— Measured Ne isotopes in samples of shergottite ALHA77005 show variations in 21Ne/22Ne ratios and 21Ne abundances that are consistent with the presence of two cosmogenic components: a component produced by nuclear interactions of galactic cosmic rays (GCR) and a component produced at shallow shielding depths (∼0–3 cm) by energetic solar flare protons (SCR). We suggest that the 21Ne/22Ne ratio generally can be used to distinguish between SCR and GCR components in many meteorite types. Analysis of cosmogenic Ne produced in chondrite mineral separates, eucrites, and anorthositic lunar rocks, all having diverse major element compositions, indicate that the GCR 21Ne/22Ne ratio increases modestly with relative Mg content. Data for hundreds of chondrite analyses suggest that SCR Ne is present in no more than a very small fraction of chondrites. Examination of literature data for other shergottites, however, indicate that all of these meteorites contain SCR Ne but that it is apparently absent in other SNC meteorites. The ubiquitous presence of SCR Ne in shergottites, in contrast to most other types of meteorites, suggests that the martian origin of shergottites gave them different orbital parameters compared to other meteorites. This in turn may have contributed to slower entry velocities and lesser surface ablation in the atmosphere or even to higher SCR production rates.
Mineralogical and chemical modification of components in CV3 chondrites: Nebular or asteroidal processing?
Authors: Krot Alexander N. , Scott Edward R. D. , Zolensky Michael E.
Published: June 2012

Abstract— Calcium‐ and aluminum‐rich inclusions (CAIs), chondrules, dark inclusions and matrices in certain CV3 carbonaceous chondrites appear to have been modified by different degrees of late‐stage alteration processes that caused significant variations in mineralogy and chemistry. Some chondrules and CAIs are rimmed with fayalitic olivine. Metal in all components may be oxidized and sulphidized to magnetite, Ni‐rich metal and sulfides. Silicates in all components are aqueously altered to different degrees to phyllosilicates. Primary minerals in some CAIs experienced Fe‐alkali‐halogen metasomatism forming nepheline, sodalite, wollastonite, hedenbergite and other secondary minerals. In CV3 chondrites with metasomatized CAIs, nepheline, sodalite, etc. are also present in chondrule mesostases and in matrices. McSween's (1977b) reduced subgroup of CV3 chondrites generally shows minimal alteration of all components and may represent the unaltered precursors for the oxidized CV3 chondrites, which generally show major alteration. Most studies have been focused on specific components in CV3 chondrites and have not considered possible relationships between alteration processes. We infer from the correlated occurrences of the alteration features that they were closely related in time and space and review nebular and asteroidal models for their origins. We prefer an asteroidal model.
Recovery of three ordinary chondrites, Rooikop 001–003, from the Namib Desert in Western Namibia
Authors: Reid A.M. , Jakes P. , Zolensky M. E. , Miller R. McG.
Published: June 2012

Abstract— Reconnaissance searches for meteorites were made in five selected areas of western Namibia in 1991. Three new ordinary chondrites (H5, L5, L4/5) were recovered from one of the areas searched.
Acfer 094, a uniquely primitive carbonaceous chondrite from the Sahara
Authors: Newton J. , Bischoff A. , Arden J. W. , Franchi I. A. , Geiger T. , Greshake A. , Pillinger C. T.
Published: June 2012

Abstract— The Saharan meteorite Acfer 094 is a unique type of carbonaceous chondrite. Mineralogical and petrological considerations and O isotopes are unable to distinguish unambiguously between a CO3 vs. CM2 classification. The other important light elements, C and N, have systematics that do not match any previously recognised meteorite group. Particularly important in this respect is the very low C/N ratio and δ13C of the macromolecular C. Acfer 094 has more diamond and SiC, especially X type grains, than any other specimen studied, suggesting minimal thermal or aqueous processing to decrease its very primitive status.
Carbon, nitrogen and hydrogen in Saharan chondrites: The importance of weathering
Authors: Ash R. D. , Pillinger C. T.
Published: June 2012

Abstract— The Sahara Desert is a region of high diurnal temperature variation and sporadic rainfall that has recently yielded over 450 meteorites. Eighteen of these Saharan samples are carbonaceous chondrites, of which we have analysed 17 for C content and isotopic composition. Ten of the 18 are paired CR chondrites, of which four have also had N and H contents and compositions determined. A primitive ordinary chondrite (L/LL3.2) found in the region has also been analysed for C, N and H contents and isotopic composition.

Saharan samples contain between 21% and 45% of the light elements of their non‐Saharan counterparts. Paired Saharan samples show a greater heterogeneity in both C content and isotopic composition than multiple analyses of non‐Saharan samples.

The cause of the observed isotopic and abundance effects is due to the hot desert weathering processes experienced by these samples. Peak temperatures of meteorites on the desert floor may be in excess of 100 °C, leading to low‐temperature hydrous pyrolysis and oxidation reactions, liberating volatile organics and CO2. This may also cause the remaining material to become partially solubilised and ultimately lost during rainfall. The low δD of the CR and ordinary chondrites can be attributed to the destruction and loss of organic material through dehydrogenation and exchange reactions on the desert surface. The increased 13C abundance suggests that the less tightly bound C from the macromolecular organic material is isotopically lighter than the remaining C. Carbon contents and isotopic compositions are also affected by the addition of terrestrial calcitic evaporite deposits, up to 10,000 ppm carbonate has been measured, with a δ13C of between 0 and −10%0.
Alkali elements in the Earth's core: Evidence from enstatite meteorites
Authors: Lodders K.
Published: June 2012

Abstract—The abundances of alkali elements in the Earth's core are predicted by assuming that accretion of the Earth started from material similar in composition to enstatite chondrites and that enstatite achondrites (aubrites) provide a natural laboratory to study core‐mantle differentiation under extremely reducing conditions. If core formation on the aubrite parent body is comparable with core formation on the early Earth, it is found that 2600 (±1000) ppm Na, 550 (±260) ppm K, 3.4 (±2.1) ppm Rb, and 0.31 (±0.24) ppm Cs can reside in the Earth's core. The alkali‐element abundances are consistent with those predicted by independent estimates based on nebula condensation calculations and heat flow data.
Mitochondrial Import Efficiency of ATFS-1 Regulates Mitochondrial UPR Activation
Authors: Nargund Amrita M. , Pellegrino Mark W. , Fiorese Christopher J. , Baker Brooke M. , Haynes Cole M.
Published: June 2012

Initiating Mitochondrial Repair

The mitochondrial unfolded protein response (UPRmt) mediates the up-regulation of nuclear encoded mitochondrial chaperone genes in response to mitochondrial dysfunction. How mitochondrial dysfunction is communicated to the nucleus is unclear, but requires the transcription factor, ATFS-1.

Nargund
et al.

(p.
587
, published online 14 June) found that the key point of regulation in UPRmt signaling is mitochondrial protein import efficiency of ATFS-1. In addition to a nuclear localization sequence (NLS), ATFS-1 has a mitochondrial targeting sequence (MTS) that is necessary for UPRmt repression. ATFS-1 is normally imported efficiently into mitochondria and degraded by the Lon protease. However, in the presence of stress, some ATFS-1 fails to be imported into mitochondria and is trafficked to the nucleus. The juxtaposition of a C-terminal NLS to an N-terminal MTS in a transcriptional activator thus couples unfolded protein load in the mitochondrial matrix to a rectifying transcriptional response in the nucleus.
Universities, Key to Prosperity
Authors: Holliday Charles O.
Published: June 2012

By almost any measure, U.S. Research Universities are consistently ranked among the best in the world. Beginning with the Morrill Act (Land Grant College Act) of 1862, federal and state policies have underscored the nation's commitment to building the finest research institutions. As such, U.S. universities have been the incubators of the nation's prosperity. E. I. du Pont de Nemours and Company, which I once headed, is a great example. One of its key products, nylon, was made possible because of a Harvard-educated polymer researcher who brought his knowledge to DuPont. Today, that kind of connection is everywhere, from high-tech Silicon Valley startups to cutting-edge East Coast biomedical facilities. The talent and knowledge produced by research universities underpin many of the finest U.S. achievements, from seeding the modern agricultural system to enabling the World Wide Web. But new challenges are putting these important national assets in danger. The National Research Council (NRC) committee that I chaired to assess the capacities of U.S. universities has now released recommendations for maintaining their role in national prosperity.
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Conservative management in a rare case of spontaneous bilateral cerebellar haemorrhage
Authors: Lalla Rakesh , Malhotra Hardeep Singh , Garg Ravindra Kumar , Verma Rajesh
Published: June 2012

Intracranial haemorrhage is usually associated with various risk factors such as hypertension, aneurysm, bleeding diatheses, anticoagulant use, amyloid angiopathy and remote bleed occurring after supratentorial and spinal surgery. Simultaneous bilateral cerebellar haemorrhage is rarely observed outside the setting of known precipitants and may follow a rapid downhill course. We present an unusual case of a young man who presented to us with sudden-onset cerebellar signs due to haemorrhage occurring in both the cerebellar hemispheres. Our patient had a favourable outcome with conservative management despite having bilateral cerebellar haematoma with partial obliteration of the fourth ventricle.
Closure of non-healing chronic ulcer in Klippel–Trenaunay syndrome using low-level laser therapy
Authors: Dixit Snehil , Maiya Arun G , Umakanth Shashikiran , Shastry Barkur A
Published: June 2012

A 69-year-old man diagnosed with Klippel–Trenaunay syndrome (KTS) reported to the physiotherapy outpatient clinic with the complaint of a non-healing ulcer over the right medial malleolus, for a 6-month duration, that was non-granulating and had moderate pus discharge with foul odour at initial assessment. There was a decrease in scores of the Pressure Ulcer Scale of Healing, a significant increase in granulation tissue, a decrease in the amount of discharge and foul odour along with complete closure of the chronic wound after irradiation with a light-emitting diode (LED). This is a novel case study analysing the possible effect of a helium–neon laser  and LEDs on non-healing chronic ulcers associated with KTS, where the complete closure of the chronic ulcer that was initially not responsive to standard medical care was observed.
CURIE TEMPERATURE OF 3d TRANSITION-METAL-DOPED GaAs
Authors: CHEN YU , ZHAO CHUNWANG , GUAN YUQIN , ZHANG ZHENDUO
Published: June 2012

The Zener model of ferromagnetism predicts that higher values of Curie temperature (CT) can be achieved by materials containing greater doping concentrations and hole concentrations. However, the prediction value is significantly higher than those from experiments with high doping concentrations. This discrepancy is resolved by an improved theoretical prediction for CT of 3d transition-metal-doped GaAs . Cr -doping results in higher CT than the Mn -doped GaAs. Maximum CT of Ga 1-x Mn x As is 215 K with 13.9% doping concentration. Room temperature CT can be achieved by 11.3% Cr -doped GaAs . Maximum CT of Ga 1-x Cr x As can reach 514.4 K with 31.7% doping concentration.
A QUADRATIC HEDGING APPROACH TO COMPARISON OF CATASTROPHE INDICES
Authors: NORBERG RAGNAR , SAVINA OKSANA
Published: June 2012

The present study addresses the problem of designing a catastrophe derivative that insurers can use to hedge catastrophe-related losses in an incomplete market. The losses are modeled as a doubly stochastic compound Poisson process with shot-noise intensity. The hedging capability of a derivative is measured by the reduction of the mean squared hedging error resulting from optimal trading in the derivative. A general form of this measure is obtained in terms of the coefficients in the martingale dynamics of the loss process and the price process of the derivative. Six specific derivatives, with pay-offs depending in different ways on available catastrophe indices and portfolio data, are compared by the proposed criterion.
FAST COMPUTATION OF VANILLA PRICES IN TIME-CHANGED MODELS AND IMPLIED VOLATILITIES USING RATIONAL APPROXIMATIONS
Authors: PISTORIUS MARTIJN , STOLTE JOHANNES
Published: June 2012

We present a new numerical method to price vanilla options quickly in time-changed Brownian motion models. The method is based on rational function approximations of the Black-Scholes formula. Detailed numerical results are given for a number of widely used models. In particular, we use the variance-gamma model, the CGMY model and the Heston model without correlation to illustrate our results. Comparison to the standard fast Fourier transform method with respect to accuracy and speed appears to favour the newly developed method in the cases considered. We present error estimates for the option prices. Additionally, we use this method to derive a procedure to compute, for a given set of arbitrage-free European call option prices, the corresponding Black-Scholes implied volatility surface. To achieve this, rational function approximations of the inverse of the Black-Scholes formula are used. We are thus able to work out implied volatilities more efficiently than one can by the use of other common methods. Error estimates are presented for a wide range of parameters.
TRANSPORTATION NETWORK STABILITY: A CASE STUDY OF CITY TRANSIT
Authors: BERCHE BERTRAND , FERBER CHRISTIAN VON , HOLOVATCH TARAS , HOLOVATCH YURIJ
Published: June 2012

The goals of this paper are to present criteria, that allow to a priori quantify the attack stability of real world correlated networks of finite size and to check how these criteria correspond to analytic results available for infinite uncorrelated networks. As a case study, we consider public transportation networks (PTN) of several major cities of the world. To analyze their resilience against attacks, either the network nodes or edges are removed in specific sequences (attack scenarios). During each scenario the size S(c) of the largest remaining network component is observed as function of the removed share c of nodes or edges. To quantify the PTN stability with respect to different attack scenarios we use the area below the curve described by S(c) for c ∈ [0, 1] recently introduced (Schneider, C. M. et al. [PNAS 108 (2011) 3838]) as a numerical measure of network robustness. This measure captures the network reaction over the whole attack sequence. We present results of the analysis of PTN stability against node and link-targeted attacks.
POTENTIAL ENERGY SURFACE, MICROWAVE AND INFRARED SPECTRA OF THE Xe–CO2 COMPLEX FROM AB INITIO CALCULATIONS
Authors: CHEN MIN , ZHU HUA
Published: June 2012

We present a new three-dimensional potential energy surface for Xe–CO2 including the Q3 normal mode for the υ3 antisymmetric stretching vibration of the CO2 molecule. Two vibrationally adiabatic potentials with CO2 in both the ground (υ3 = 0) and the first excited (υ3 = 1) states are generated by the integration of this potential over the Q3 coordinate. Each potential is found to have a T-shaped global minimum. The radial DVR/angular FBR method and the Lanczos algorithm are employed to calculate the rovibrational energy levels. The calculated band origin shifts, microwave and infrared spectra based on the two averaged potentials are in good agreement with the available experimental data.
THEORETICAL STUDIES ON THE MECHANISM OF CYCLIC NUCLEOTIDE MONOPHOSPHATE HYDROLYSIS WITHIN PHOSPHODIESTERASES
Authors: CAO XIAORAN , LIU CHENGBU , LIU YONGJUN
Published: June 2012

As the only metabolizing enzyme for the degradation of second messenger cAMP and cGMP, phosphodiesterase (PDE) has been the clinical target of various human diseases. But the hydrolysis procedure of PDE is still unclear. To investigate the mechanism of PDE catalysis, three types of PDE (PDE4d, PDE5a and PDE10a) were selected and studied by using molecular dynamics (MD) simulation and quantum mechanics (QM) calculation methods. MD Simulation results indicate that different PDEs share a similar hydrolysis area in the active sites, and the phosphate parts of cyclic nucleotides take the same orientation and are partly surrounded by water molecules. Based on the statistical data of MD simulation, the QM calculation models were built. The calculation results indicate that in aqueous solution, the nucleophile hydroxide ion that attacks the phosphor atom of the cyclic nucleotide in the hydrolysis may migrate between the two metal ions in the active site. To help the ring-open reaction, it is the water molecule that provides proton to the O3′ atom of cyclic nucleotide, and generates another hydroxide ion complexed with the metal ion.
ON THE ENSEMBLE AVERAGE OF GENERALIZED TRUNCATED RANDOM WALK
Authors: ZABIHINPOUR ZAHRA , GHAEMI MEHRDAD
Published: June 2012

A new analytical solution is developed for the one- and two- dimensional generalized discrete time random walk with discrete and finite length of jumping. It is shown that the ensemble average of the mean square displacement has a linear relation with time. This result is general and independent of mathematical form of distribution function but magnitude of diffusion coefficient depends on the distribution function. This result confirms our previous numerical work. The truncated Levy flight is studied as a special case and the diffusion coefficient for different maximum length of jump is calculated numerically. The obtained results are in good agreement with the analytical solution.
Control-flow analysis of functional programs
Authors: Midtgaard Jan
Published: June 2012

We present a survey of control-flow analysis of functional programs, which has been the subject of extensive investigation throughout the past 30 years. Analyses of the control flow of functional programs have been formulated in multiple settings and have led to many different approximations, starting with the seminal works of Jones, Shivers, and Sestoft. In this article, we survey control-flow analysis of functional programs by structuring the multitude of formulations and approximations and comparing them.
Mitigating program security vulnerabilities
Authors: Shahriar Hossain , Zulkernine Mohammad
Published: June 2012

Programs are implemented in a variety of languages and contain serious vulnerabilities which might be exploited to cause security breaches. These vulnerabilities have been exploited in real life and caused damages to related stakeholders such as program users. As many security vulnerabilities belong to program code, many techniques have been applied to mitigate these vulnerabilities before program deployment. Unfortunately, there is no comprehensive comparative analysis of different vulnerability mitigation works. As a result, there exists an obscure mapping between the techniques, the addressed vulnerabilities, and the limitations of different approaches. This article attempts to address these issues. The work extensively compares and contrasts the existing program security vulnerability mitigation techniques, namely testing, static analysis, and hybrid analysis. We also discuss three other approaches employed to mitigate the most common program security vulnerabilities: secure programming, program transformation, and patching. The survey provides a comprehensive understanding of the current program security vulnerability mitigation approaches and challenges as well as their key characteristics and limitations. Moreover, our discussion highlights the open issues and future research directions in the area of program security vulnerability mitigation.
Runtime countermeasures for code injection attacks against C and C++ programs
Authors: Younan Yves , Joosen Wouter , Piessens Frank
Published: June 2012

The lack of memory safety in C/C++ often leads to vulnerabilities.
Code injection attacks
exploit these vulnerabilities to gain control over the execution flow of applications. These attacks have played a key role in many major security incidents. Consequently, a huge body of research on countermeasures exists. We provide a comprehensive and structured survey of vulnerabilities and countermeasures that operate at runtime. These countermeasures make different trade-offs in terms of performance, effectivity, compatibility, etc., making it hard to evaluate and compare countermeasures in a given context. We define a classification and evaluation framework on the basis of which countermeasures can be assessed.
Gaze-contingent visual presentation technique with electro-ocular-graph-based saccade detection
Authors: Watanabe Junji , Maeda Taro , Ando Hideyuki
Published: June 2012

When a single column of light sources flashes quickly in a temporal pattern during a horizontal saccade eye movement, two-dimensional images can be perceived in the space neighboring the light source. This perceptual phenomenon has been applied to light devices for visual arts and entertainment. However, a serious drawback in exploiting this perceptual phenomenon for a visual information display is that a two-dimensional image cannot be viewed if there is any discrepancy between the ocular motility and the flicker timing. We overcame this drawback by combining the saccade-based display with an electro-ocular-graph-based sensor for detecting the saccade. The saccade onset is measured with the electro-ocular-graph-based sensor in real time and the saccade-based display is activated instantaneously as the saccade begins. The psychophysical experiments described in this article demonstrates that the method that we used can detect saccades with low latency and allows the saccade-based display to convey visual information more effectively than when the light sources continuously blink regardless of the observer's eye movements.
Parametric time-frequency representation of spatial sound in virtual worlds
Authors: Laitinen Mikko-Ville , Pihlajamäki Tapani , Erkut Cumhur , Pulkki Ville
Published: June 2012

Directional audio coding (DirAC) is a parametric time-frequency domain method for processing spatial audio based on psychophysical assumptions and on energetic analysis of the sound field. Methods to use DirAC in spatial sound synthesis for virtual worlds are presented in this article. Formal listening tests are used to show that DirAC can be used to position and to control the spatial extent of virtual sound sources with good audio quality. It is also shown that DirAC can be used to generate reverberation for N-channel horizontal listening with only two monophonic reverberators without a prominent loss in quality when compared with quality obtained with N-channel reverberators.
Real-time adaptive blur for reducing eye strain in stereoscopic displays
Authors: Leroy Laure , Fuchs Philippe , Moreau Guillaume
Published: June 2012

Stereoscopic devices are widely used (immersion-based working environments, stereoscopically-viewed movies, auto-stereoscopic screens). In some instances, exposure to stereoscopic immersion techniques can be lengthy, and so eye strain sets in. We propose a method for reducing eye strain induced by stereoscopic vision. After reviewing sources of eye strain linked to stereoscopic vision, we focus on one of these sources: images with high frequency content associated with large disparities. We put forward an algorithm for removing the irritating high frequencies in high horizontal disparity zones (i.e., for virtual objects appearing far from the real screen level). We elaborate on our testing protocol to establish that our image processing method reduces eye strain caused by stereoscopic vision, both objectively and subjectively. We subsequently quantify the positive effects of our algorithm on the relief of eye strain and discuss further research perspectives.
A unified optimizing compiler framework for different GPGPU architectures
Authors: Yang Yi , Xiang Ping , Kong Jingfei , Mantor Mike , Zhou Huiyang
Published: June 2012

This article presents a novel optimizing compiler for general purpose computation on graphics processing units (GPGPU). It addresses two major challenges of developing high performance GPGPU programs: effective utilization of GPU memory hierarchy and judicious management of parallelism. The input to our compiler is a naïve GPU kernel function, which is functionally correct but without any consideration for performance optimization. The compiler generates two kernels, one optimized for global memories and the other for texture memories. The proposed compilation process is effective for both AMD/ATI and NVIDIA GPUs. The experiments show that our optimized code achieves very high performance, either superior or very close to highly fine-tuned libraries.
Automatic code overlay generation and partially redundant code fetch elimination
Authors: Jang Choonki , Lee Jaejin , Egger Bernhard , Ryu Soojung
Published: June 2012

There is an increasing interest in explicitly managed memory hierarchies, where a hierarchy of distinct memories is exposed to the programmer and managed explicitly in software. These hierarchies can be found in typical embedded systems and an emerging class of multicore architectures. To run an application that requires more code memory than the available higher-level memory, typically an overlay structure is needed. The overlay structure is generated manually by the programmer or automatically by a specialized linker. Manual code overlaying requires the programmer to deeply understand the program structure for maximum memory savings as well as minimum performance degradation. Although the linker can automatically generate the code overlay structure, its memory savings are limited and it even brings significant performance degradation because traditional techniques do not consider the program context. In this article, we propose an automatic code overlay generation technique that overcomes the limitations of traditional automatic code overlaying techniques. We are dealing with a system context that imposes two distinct constraints: (1) no hardware support for address translation and (2) a spatially and temporally coarse grained faulting mechanism at the function level. Our approach addresses those two constraints as efficiently as possible. Our technique statically computes the Worst-Case Number of Conflict misses (WCNC) between two different code segments using path expressions. Then, it constructs a static temporal relationship graph with the WCNCs and emits an overlay structure for a given higher-level memory size. We also propose an inter-procedural partial redundancy elimination technique that minimizes redundant code copying caused by the generated overlay structure. Experimental results show that our approach is promising.