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Sample records for forming core elements

  1. Core Formation Process and Light Elements in the Planetary Core

    NASA Astrophysics Data System (ADS)

    Ohtani, E.; Sakairi, T.; Watanabe, K.; Kamada, S.; Sakamaki, T.; Hirao, N.

    2015-12-01

    Si, O, and S are major candidates for light elements in the planetary core. In the early stage of the planetary formation, the core formation started by percolation of the metallic liquid though silicate matrix because Fe-S-O and Fe-S-Si eutectic temperatures are significantly lower than the solidus of the silicates. Therefore, in the early stage of accretion of the planets, the eutectic liquid with S enrichment was formed and separated into the core by percolation. The major light element in the core at this stage will be sulfur. The internal pressure and temperature increased with the growth of the planets, and the metal component depleted in S was molten. The metallic melt contained both Si and O at high pressure in the deep magma ocean in the later stage. Thus, the core contains S, Si, and O in this stage of core formation. Partitioning experiments between solid and liquid metals indicate that S is partitioned into the liquid metal, whereas O is weakly into the liquid. Partitioning of Si changes with the metallic iron phases, i.e., fcc iron-alloy coexisting with the metallic liquid below 30 GPa is depleted in Si. Whereas hcp-Fe alloy above 30 GPa coexisting with the liquid favors Si. This contrast of Si partitioning provides remarkable difference in compositions of the solid inner core and liquid outer core among different terrestrial planets. Our melting experiments of the Fe-S-Si and Fe-O-S systems at high pressure indicate the core-adiabats in small planets, Mercury and Mars, are greater than the slope of the solidus and liquidus curves of these systems. Thus, in these planets, the core crystallized at the top of the liquid core and 'snowing core' formation occurred during crystallization. The solid inner core is depleted in both Si and S whereas the liquid outer core is relatively enriched in Si and S in these planets. On the other hand, the core adiabats in large planets, Earth and Venus, are smaller than the solidus and liquidus curves of the systems. The

  2. NEUTRONIC REACTOR FUEL ELEMENT AND CORE SYSTEM

    DOEpatents

    Moore, W.T.

    1958-09-01

    This patent relates to neutronic reactors and in particular to an improved fuel element and a novel reactor core system for facilitating removal of contaminating fission products, as they are fermed, from association with the flssionable fuel, so as to mitigate the interferent effects of such fission products during reactor operation. The fuel elements are comprised of tubular members impervious to fluid and contatning on their interior surfaces a thin layer of fissionable material providing a central void. The core structure is comprised of a plurality of the tubular fuel elements arranged in parallel and a closed manifold connected to their ends. In the reactor the core structure is dispersed in a water moderator and coolant within a pressure vessel, and a means connected to said manifuld is provided for withdrawing and disposing of mobile fission product contamination from the interior of the feel tubes and manifold.

  3. Formed Core Sampler Hydraulic Conductivity Testing

    SciTech Connect

    Miller, D. H.; Reigel, M. M.

    2012-09-25

    A full-scale formed core sampler was designed and functionally tested for use in the Saltstone Disposal Facility (SDF). Savannah River National Laboratory (SRNL) was requested to compare properties of the formed core samples and core drilled samples taken from adjacent areas in the full-scale sampler. While several physical properties were evaluated, the primary property of interest was hydraulic conductivity. Differences in hydraulic conductivity between the samples from the formed core sampler and those representing the bulk material were noted with respect to the initial handling and storage of the samples. Due to testing conditions, the site port samples were exposed to uncontrolled temperature and humidity conditions prior to testing whereas the formed core samples were kept in sealed containers with minimal exposure to an uncontrolled environment prior to testing. Based on the results of the testing, no significant differences in porosity or density were found between the formed core samples and those representing the bulk material in the test stand.

  4. Chemical Models of Star-Forming Cores

    NASA Astrophysics Data System (ADS)

    Aikawa, Y.

    2013-10-01

    We review chemical models of low-mass star forming cores including our own work. Chemistry in molecular clouds are not in equilibrium. Molecular abundances in star forming cores change not only with physical conditions in cores but also with time. In prestellar cores, temperature stays almost constant ˜ 10 K, while the gas density increases as the core collapses. Three chemical phenomena are observed in this cold phase: molecular depletion, chemical fractionation, and deuterium enrichment. They are reproduced by chemical models combined with isothermal gravitational collapse. The collapse timescale of prestellar cores depends on the initial ratios of thermal, turbulent and magnetic pressure to gravitational energy. Since the chemical timescales, such as adsorption timescale of gas particle onto grains, are comparable to the collapse timescale, molecular abundances in cores should vary depending on the collapse timescale. Observations found that molecular abundances in some cores deviate from those in other cores, in spite of their similar central densities; it could originate in the pressure to gravity ratio in the cores. As the core contraction proceeds, compressional heating eventually overwhelms radiative cooling, and the core starts to warm up. Temperature of the infalling gas rises, as it approaches the central region. Grain-surface reactions of adsorbed molecules occur in this warm-up phase, as well as in prestellar phase. Hydrogenation is efficient at T ≤ 20 K, whereas radicals can migrate on grain surface and react with each other to form complex organic molecules (COMs) at T ≥ 30 K. Grain-surface species are sublimated to the gas phase and re-start gas-phase reactions; e.g. unsaturated carbon chains are formed from sublimated methane. Our model calculation predicts that COMs increases as the warm region extends outwards and the abundances of unsaturated carbon chains depend on the gas density in the CH4 sublimation zone. Recent detection of COMs in

  5. Explicit Instruction Elements in Core Reading Programs

    ERIC Educational Resources Information Center

    Child, Angela R.

    2012-01-01

    Classroom teachers are provided instructional recommendations for teaching reading from their adopted core reading programs (CRPs). Explicit instruction elements or what is also called instructional moves, including direct explanation, modeling, guided practice, independent practice, discussion, feedback, and monitoring, were examined within CRP…

  6. Light Elements in the Core: Constraints from Gallium Partitioning

    NASA Astrophysics Data System (ADS)

    Blanchard, I.; Badro, J.; Siebert, J.; Ryerson, F. J.

    2014-12-01

    The formation of Earth's core has left a compositional imprint on the mantle, depleting and fractionating most of its siderophile (iron-loving) elements. Gallium is a moderately siderophile, hence it should be strongly depleted in the mantle. However, gallium concentration in the mantle matches that of lithophile (silicate-loving) elements having the same volatility. That is to say that either gallium behaves as a lithophile element during core formation, or a large influx of gallium was brought to the Earth after the core had formed. Geochemical evidence does not support the latter hypothesis, as it would require all other lithophile elements with similar volatility to be enriched in the mantle, or for late accretion to be composed of anomalously gallium-rich objects. In order to mitigate this issue, experimental studies have tried to understand how gallium behaves during core segregation by gauging the effects of pressure, temperature and oxygen fugacity on the partitioning of gallium between metal and silicate. None of these parameters provided the first-order change required to match the observation. We investigated the influence of core composition on gallium partitioning. The core in known to contain light-elements (oxygen, silicon sulfur and carbon), and those can change the activity of gallium in the metal, and strongly affect the behavior of gallium during core formation. We performed a series of metal-silicate partitioning experiments (2 GPa, 1673-2073 K) in a piston-cylinder press. We varied the light-element composition of the metal and observed that Si and O have a very strong influence on the activity of gallium, making it more lithophile. We then modeled terrestrial accretion as a continuous process and tested different accretion histories; we can reproduce the mantle concentration of gallium if the core segregates in a deep magma ocean (>40 GPa) and contains large amounts of silicon or oxygen.

  7. Chemistry of Star-Forming Cores

    NASA Technical Reports Server (NTRS)

    Charnley, S. B.

    1994-01-01

    Chemical effects arising from the exchange of molecules between dust and gas in dense clumps are described. Selective desorption of CO and N2 from grains in cool cores can account for the presence of ammonia in several cores in the NGC 2024 cloud. Evaporation of ices containing methanol and ethanol can lead to detectable abundances of (C2H5)(sub 2)O and CH3OC2H5. Results are presented for the hot core chemistries of sulphur and phosphorus which are initiated by evaporated hydrogen sulphide and phosphine. The implications of these studies for understanding the nature of molecular mantles, the evolution of molecular complexity in the gas phase, and the presence of small-scale abundance gradients in star-forming regions, are briefly discussed.

  8. Element Partitioning Constraints on Formation and Composition of the Earth's Core

    NASA Technical Reports Server (NTRS)

    Li, J.; Agee, C. B.; Fei, Y.

    1998-01-01

    Element partitioning study provides a number of constraints on the formation and composition of the core. First, partitioning of siderophile elements between the core and mantle should explain the "excess" siderophile elements in the mantle. Second, partitioning of light element(s) between the core and mantle should supply the core with the right amount of light element(s) to account for the density deficit in the core. Third, partitioning of light element(s) between the inner and outer core should be consistent with the observed difference in density deficits (relative to pure Fe) between these two reservoirs. In this study, high-pressure and high-temperature experiments have been conducted to investigate the pressure, temperature, and composition effects on partitioning of siderophile elements Ni and Co between core-forming Fe alloy and mantle silicate melt and minerals, partitioning of light elements S, O, and Si between core-forming Fe alloy and mantle silicate melt and minerals, and partitioning of light elements S and C between solid and liquid Fe. The implications of these results for mechanism of core formation and the composition of the core are discussed.

  9. Making Mercury's Core with Light Elements

    NASA Technical Reports Server (NTRS)

    Vander Kaaden, Kathleen E.; McCubbin, Francis M.; Ross, D. Kent

    2016-01-01

    Recent results obtained from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft showed the surface of Mercury has low FeO abundances (less than 2 wt%) and high S abundances (approximately 4 wt%), suggesting the oxygen fugacity of Mercury's surface materials is somewhere between 3 to 7 log10 units below the IW buffer. The highly reducing nature of Mercury has resulted in a relatively thin mantle and a large core that has the potential to exhibit an exotic composition in comparison to the other terrestrial planets. This exotic composition may extend to include light elements (e.g., Si, C, S). Furthermore, has argued for a possible primary floatation crust on Mercury composed of graphite, which may require a core that is C-saturated. In order to investigate mercurian core compositions, we conducted piston cylinder experiments at 1 GPa, from 1300 C to 1700 C, using a range of starting compositions consisting of various Si-Fe metal mixtures (Si5Fe95, Si10Fe90, Si22Fe78, and Si35Fe65). All metals were loaded into graphite capsules used to ensure C-saturation during the duration of each experimental run. Our experiments show that Fe-Si metallic alloys exclude carbon relative to more Fe-rich metal. This exclusion of carbon commences within the range of 5 to 10 wt% Si. These results indicate that if Mercury has a Si-rich core (having more than approximately 5 wt% silicon), it would have saturated in carbon at low C abundances allowing for the possible formation of a graphite floatation crust as suggested by. These results have important implications for the thermal and magmatic evolution of Mercury.

  10. Siderophile elements, oxygen and single-stage core formation

    NASA Astrophysics Data System (ADS)

    Corgne, A.; Siebert, J.; Badro, J.

    2009-12-01

    The abundances of siderophile elements in the bulk silicate Earth (BSE) indicate that its iron-rich core most probably form at high pressure and high temperature in a magma ocean (e.g. Walker et al. 1993; Hillgren et al. 1994; Thibault & Walter 1995; Li & Agee, 1996). This is consistent with physical models of planetary accretion (Davies 1985; Benz & Cameron 1990; Tonks & Melosh 1993). Metal-silicate partitioning experiments have proposed that the BSE concentrations of several siderophile elements are consistent with a scenario of single-stage equilibration at the base of a deep magma ocean (Li & Agee 1996; Righter et al 1997; Chabot & Agee 2003). More recent models using temperature sensitive partitioning data for V and Nb have casted doubt on the single-stage event hypothesis since the required basal temperature should greatly exceed that of the mantle solidus (Wade & Wood 2005; Corgne et al. 2008; Wood et al. 2008). This temperature mismatch is meaningless in the framework of the magma ocean theory because the temperature at the base of the magma ocean should approximate that of the mantle solidus. To resolve this anomaly, it has been suggested that the building materials of the Earth were initially reduced materials and then became progressively oxidized with time (Wade & Wood 2005; Corgne et al. 2008; Wood et al. 2008). Thus, rather than resulting from a single-stage event at relatively fixed conditions of high pressure and high temperature, the Earth’s core may in fact have formed in a more complex event, imprinted by heterogeneous accretion and the progressive growth of the planet and its magma ocean. Here, we present an alternative to the dynamic model by showing that a single-stage core formation event could explain the mantle contents of the best-constrained siderophile elements (Ni, Co, V, Mn, Cr, Nb) provided that the core contains a few weight percents of oxygen. Our calculations based on partitioning and metallurgy data reveal that V and Nb become

  11. What Are the Core Elements of Your Curriculum?

    ERIC Educational Resources Information Center

    Exchange: The Early Childhood Leaders' Magazine Since 1978, 2009

    2009-01-01

    Several administrators discuss the core elements of their curriculum. These core elements are: (1) Child-centered; (2) Play; (3) Problem solving; (4) Respect; (5)Creativity; (6) Community; (7) Independence; (8) Curiosity; (9) Love of learning; (10) Relationship; (11) Cooperation; (12) Self-confidence; (13) Language; (14) Joy; (15) Nature; Natural…

  12. ElemeNT: a computational tool for detecting core promoter elements.

    PubMed

    Sloutskin, Anna; Danino, Yehuda M; Orenstein, Yaron; Zehavi, Yonathan; Doniger, Tirza; Shamir, Ron; Juven-Gershon, Tamar

    2015-01-01

    Core promoter elements play a pivotal role in the transcriptional output, yet they are often detected manually within sequences of interest. Here, we present 2 contributions to the detection and curation of core promoter elements within given sequences. First, the Elements Navigation Tool (ElemeNT) is a user-friendly web-based, interactive tool for prediction and display of putative core promoter elements and their biologically-relevant combinations. Second, the CORE database summarizes ElemeNT-predicted core promoter elements near CAGE and RNA-seq-defined Drosophila melanogaster transcription start sites (TSSs). ElemeNT's predictions are based on biologically-functional core promoter elements, and can be used to infer core promoter compositions. ElemeNT does not assume prior knowledge of the actual TSS position, and can therefore assist in annotation of any given sequence. These resources, freely accessible at http://lifefaculty.biu.ac.il/gershon-tamar/index.php/resources, facilitate the identification of core promoter elements as active contributors to gene expression. PMID:26226151

  13. Pressure Gradient Error of Spectral Element Dynamical Core associated with Topographic Forcing: Comparison with the Spherical Harmonics Dynamical Core

    NASA Astrophysics Data System (ADS)

    Kang, Hyun-Gyu; Cheong, Hyeong-Bin; Jeong, Han-Byeol; Kim, Won-Ho

    2015-04-01

    Response characteristics of the spectral element hydrostatic dynamical core on the cubed sphere to the global topographic forcing are investigated in terms of pressure gradient error, and it is compared with the spherical harmonics hydrostatic dynamical core. The vertical hybrid-pressure coordinate and finite difference method are introduced to both dynamical cores, and explicit and implicit hyper-diffusion schemes are applied to spectral element dynamical core and spherical harmonics dynamical core, respectively. The model atmosphere at initial time is set to the quiescent environment so that the term affecting on the time tendency of the momentum equation at the first time step is the pressure gradient term only which is influenced by the observed surface topography. During 6 days of time integration, the spurious flow is generated due to inaccurate numerical approximations of pressure gradient term for each dynamical core. High zonal wind speed which can be regarded as numerical error is occurred commonly in two dynamical cores around steep topography (e.g., the Tibetan Plateau, the Rocky Mountains, and the Andes Mountains), but the maximum zonal wind speed at day 6 of spectral element dynamical core is 8-9 times larger than that of spherical harmonics dynamical core. The vertically averaged kinetic energy spectrum at day 6 shows very different trend between two dynamical cores. By performing the experiments with the scale-separated topography, it turns out that these kinetic energy spectrum trends are mainly caused by the small-scale topography. A simple change of pressure gradient term into log-pressure form is found to significantly reduce numerical error (up to 63% of maximum wind speed in case of spectral element dynamical core) and noise-like small-scale phenomena.

  14. Experimental constraints on light elements in the Earth's outer core.

    PubMed

    Zhang, Youjun; Sekine, Toshimori; He, Hongliang; Yu, Yin; Liu, Fusheng; Zhang, Mingjian

    2016-01-01

    Earth's outer core is liquid and dominantly composed of iron and nickel (~5-10 wt%). Its density, however, is ~8% lower than that of liquid iron, and requires the presence of a significant amount of light element(s). A good way to specify the light element(s) is a direct comparison of density and sound velocity measurements between seismological data and those of possible candidate compositions at the core conditions. We report the sound velocity measurements of a model core composition in the Fe-Ni-Si system at the outer core conditions by shock-wave experiments. Combining with the previous studies, we found that the best estimate for the outer core's light elements is ~6 wt% Si, ~2 wt% S, and possible ~1-2.5 wt% O. This composition satisfies the requirements imposed by seismology, geochemistry, and some models of the early core formation. This finding may help us to further constrain the thermal structure of the Earth and the models of Earth's core formation. PMID:26932596

  15. Core-Mantle Partitioning of Volatile Elements and the Origin of Volatile Elements in Earth and Moon

    NASA Technical Reports Server (NTRS)

    Righter, K.; Pando, K.; Danielson, L.; Nickodem, K.

    2014-01-01

    Depletions of siderophile elements in mantles have placed constraints on the conditions on core segregation and differentiation in bodies such as Earth, Earth's Moon, Mars, and asteroid 4 Vesta. Among the siderophile elements there are a sub-set that are also volatile (volatile siderophile elements or VSE; Ga, Ge, In, As, Sb, Sn, Bi, Zn, Cu, Cd), and thus can help to constrain the origin of volatile elements in these bodies, and in particular the Earth and Moon. One of the fundamental observations of the geochemistry of the Moon is the overall depletion of volatile elements relative to the Earth, but a satisfactory explanation has remained elusive. Hypotheses for Earth include addition during accretion and core formation and mobilized into the metallic core, multiple stage origin, or addition after the core formed. Any explanation for volatile elements in the Earth's mantle must also be linked to an explanation of these elements in the lunar mantle. New metal-silicate partitioning data will be applied to the origin of volatile elements in both the Earth and Moon, and will evaluate theories for exogenous versus endogenous origin of volatile elements.

  16. Core-Mantle Partitioning of Volatile Siderophile Elements and the Origin of Volatile Elements in the Earth

    NASA Technical Reports Server (NTRS)

    Nickodem, K.; Righter, K.; Danielson, L.; Pando, K.; Lee, C.

    2012-01-01

    There are currently several hypotheses on the origin of volatile siderophile elements in the Earth. One hypothesis is that they were added during Earth s accretion and core formation and mobilized into the metallic core [1], others claim multiple stage origin [2], while some hypothesize that volatiles were added after the core already formed [3]. Several volatile siderophile elements are depleted in Earth s mantle relative to the chondrites, something which continues to puzzle many scientists. This depletion is likely due to a combination of volatility and core formation. The Earth s core is composed of Fe and some lighter constituents, although the abundances of these lighter elements are unknown [4]. Si is one of these potential light elements [5] although few studies have analyzed the effect of Si on metal-silicate partitioning, in particular the volatile elements. As, In, Ge, and Sb are trace volatile siderophile elements which are depleted in the mantle but have yet to be extensively studied. The metal-silicate partition coefficients of these elements will be measured to determine the effect of Si. Partition coefficients depend on temperature, pressure, oxygen fugacity, and metal and silicate composition and can constrain the concentrations of volatile, siderophile elements found in the mantle. Reported here are the results from 13 experiments examining the partitioning of As, In, Ge, and Sb between metallic and silicate liquid. These experiments will examine the effect of temperature, and metal-composition (i.e., Si content) on these elements in or-der to gain a greater understanding of the core-mantle separation which occurred during the Earth s early stages. The data can then be applied to the origin of volatile elements in the Earth.

  17. Alkali elements in the Earth's core: Evidence from enstatite meteorites

    NASA Technical Reports Server (NTRS)

    Lodders, K.

    1995-01-01

    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.

  18. Fiberglass honeycomb elements formed quickly and cheaply

    NASA Technical Reports Server (NTRS)

    Smith, R. H.

    1970-01-01

    Cookie cutter device initiates production of identical, double-contoured fiber glass elements used as shock absorbers. Three-bladed edges convert triangular honeycomb elements into hexagonal shapes which are then stamped to desired length by concave and convex dies. Sandpaper smoothing completes the process.

  19. Motions and Initial Conditions in Star-Forming Dense Cores

    NASA Technical Reports Server (NTRS)

    Myers, Philip C.

    2004-01-01

    The main focus was the study of star-forming regions through high spectral- and spatial resolution observations of mm-wavelength lines, and through models of the observations. The main accomplishments were a) demonstration that more than 15 starless cores show substantial evidence of extended inward motion at about half the sound speed; b) observations of infall asymmetry in several cores, in lines of N2H(+) and DCO(+), low- depletion tracers of the "inner core"; c) observation of "infall asymmetry" of spectral lines over approx. 0.5 pc in the NGC1333 cluster-forming region; d) observations indicating that cores are nearly at rest with respect to their envelopes; and e) development of analytic, power-series solutions to the equations of motions for condensing 1-D systems (layers, cylinders and spheres).

  20. NEUTRON RADIOGRAPHY (NRAD) REACTOR 64-ELEMENT CORE UPGRADE

    SciTech Connect

    John D. Bess

    2014-03-01

    The neutron radiography (NRAD) reactor is a 250 kW TRIGA (registered) (Training, Research, Isotopes, General Atomics) Mark II , tank-type research reactor currently located in the basement, below the main hot cell, of the Hot Fuel Examination Facility (HFEF) at the Idaho National Laboratory (INL). It is equipped with two beam tubes with separate radiography stations for the performance of neutron radiography irradiation on small test components. The interim critical configuration developed during the core upgrade, which contains only 62 fuel elements, has been evaluated as an acceptable benchmark experiment. The final 64-fuel-element operational core configuration of the NRAD LEU TRIGA reactor has also been evaluated as an acceptable benchmark experiment. Calculated eigenvalues differ significantly (approximately +/-1%) from the benchmark eigenvalue and have demonstrated sensitivity to the thermal scattering treatment of hydrogen in the U-Er-Zr-H fuel.

  1. Properties of Cores Formed by Retrograde Minor Mergers.

    NASA Astrophysics Data System (ADS)

    Bak, J.

    1999-09-01

    In the last 10 years over a dozen elliptical galaxies have been observed to posses a core which rotates counter to the rest of the galaxy. In one formation scenario, dynamical friction causes a compact companion to spiral into the center of a much larger elliptical galaxy on a retrograde orbit relative to the larger galaxy's rotation. If the core of the smaller galaxy is not tidally disrupted it may carry some of it's orbital angular momentum to the center. I present results from N-body simulations, which cover the parameter space over which satellite accretion is most likely to form counter rotating cores. The kinematic parts of the results are analyzed using the penalized likelihood method of Merritt to calculate 2D line-of-sight velocity fields, including third and fourth order Gauss-Hermite terms. By combining this method with IRAF, the photometric aspects of the results are analyzed and compared with observations. The results indicate that dissipationless satellite accretion can only form counter rotating cores when the larger galaxy's intrinsic angular momentum is almost perfectly antiparallel to the orbital angular momentum of the satellite. In most other cases a kinematically distinct core is formed. I present statistical properties of the cores, which include the deviations from pure isophote ellipses as well as deviations of the line-of-sight velocity profiles from a pure Gaussian form. To test the robustness of the results, some of the simulations are redone with a minor amount of dissipation added to the satellite. These simulations indicate that including small amounts of gas does not significantly effect the conclusions. I would like to thank the Student Stipend Committee for making this presentation possible.

  2. 25. CORES, WHICH FORM THE INTERIOR SURFACES OF MOLDS BY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    25. CORES, WHICH FORM THE INTERIOR SURFACES OF MOLDS BY PROVIDING A SOLID STRUCTURE FOR MOLTEN IRON TO FLOW AROUND ARE CAREFULLY PLACED INTO THE CAVITIES OF MOLDS IN THE BRASS FOUNDRY, CA. 1950. - Stockham Pipe & Fittings Company, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

  3. Oxygen as a light element: A solution to single-stage core formation

    NASA Astrophysics Data System (ADS)

    Corgne, Alexandre; Siebert, Julien; Badro, James

    2009-10-01

    The abundances of siderophile elements in the silicate Earth indicate that Earth's iron-rich core probably formed at high pressure and high temperature. A popular model of core formation considers that the concentrations of several moderately siderophile elements are consistent with a scenario of simple single-stage equilibration at the base of a magma ocean. However, recent work using temperature sensitive partitioning data for V and Nb have casted doubt on this interpretation since the required basal temperature would greatly exceed that of the mantle solidus. Here we show that single-stage core formation event could explain the mantle contents of siderophile elements best constrained by experiment (Ni, Co, V, Mn, Cr, and Nb) provided that the core contains a few weight percents of oxygen. Our calculations, based on partitioning and metallurgy data, reveal that V and Nb become significantly less siderophile with increasing the O content of core-forming materials, while the behaviour of Ni, Co, Cr and Mn is little affected. Since the other likely light element candidates C, Si and S do not drastically influence the siderophile behaviour, we conclude that a simple-equilibration scenario is a viable hypothesis only if O contributes partially to the core density deficit. This interpretation is consistent with the W budget of the silicate Earth and recently published W metal-silicate partitioning data. The presence of a few weight percents of oxygen in the core is also in agreement with recent high-pressure high-temperature solubility measurements in molten iron equilibrated with perovskite and ferropericlase.

  4. Siderophile Element Constraints on the Conditions of Core Formation in Mars

    NASA Technical Reports Server (NTRS)

    Righter, K.; Humayun, M.

    2012-01-01

    Siderophile element concentrations in planetary basalts and mantle samples have been used to estimate conditions of core formation for many years and have included applications to Earth, Moon, Mars and asteroid 4 Vesta [1]. For Earth, we have samples of mantle and a diverse collection of mantle melts which have provided a mature understanding of the how to reconstruct the concentration of siderophile elements in mantle materials, from only concentrations in surficial basalt (e.g., [2]). This approach has led to the consensus views that Earth underwent an early magma ocean stage to pressures of 40-50 GPa (e.g., [3,4]), Moon melted extensively and formed a small (approx. 2 mass %) metallic core [5], and 4 Vesta contains a metallic core that is approximately 18 mass % [6,7]. Based on new data from newly found meteorites, robotic spacecraft, and experimental partitioning studies, [8] showed that eight siderophile elements (Ni, Co, Mo, W, Ga, P, V and Cr) are consistent with equilibration of a 20 mass% S-rich metallic core with the mantle at pressures of 14 +/- 3 GPa. We aim to test this rather simple scenario with additional analyses of meteorites for a wide range of siderophile elements, and application of new experimental data for the volatile siderophile and highly siderophile elements.

  5. Finite element simulation of core inspection in helicopter rotor blades using guided waves.

    PubMed

    Chakrapani, Sunil Kishore; Barnard, Daniel; Dayal, Vinay

    2015-09-01

    This paper extends the work presented earlier on inspection of helicopter rotor blades using guided Lamb modes by focusing on inspecting the spar-core bond. In particular, this research focuses on structures which employ high stiffness, high density core materials. Wave propagation in such structures deviate from the generic Lamb wave propagation in sandwich panels. To understand the various mode conversions, finite element models of a generalized helicopter rotor blade were created and subjected to transient analysis using a commercial finite element code; ANSYS. Numerical simulations showed that a Lamb wave excited in the spar section of the blade gets converted into Rayleigh wave which travels across the spar-core section and mode converts back into Lamb wave. Dispersion of Rayleigh waves in multi-layered half-space was also explored. Damage was modeled in the form of a notch in the core section to simulate a cracked core, and delamination was modeled between the spar and core material to simulate spar-core disbond. Mode conversions under these damaged conditions were examined numerically. The numerical models help in assessing the difficulty of using nondestructive evaluation for complex structures and also highlight the physics behind the mode conversions which occur at various discontinuities. PMID:26048172

  6. Ferroelectric Smectic Phase Formed by Achiral Straight Core Mesogens

    NASA Astrophysics Data System (ADS)

    Stannarius, Ralf; Li, Jianjun; Weissflog, Wolfgang

    2003-01-01

    We report electro-optic experiments in liquid crystalline freestanding films of achiral hockey stick shaped mesogens with a straight aromatic core. The material forms two smectic mesophases. In the higher temperature phase, a spontaneous polarization exists in the smectic layer plane and the films show polar switching in electric fields. It is the first example of a ferroelectric phase formed by nearly rodlike achiral mesogens. Mirror symmetry of the phase is spontaneously broken. We propose a molecular configuration similar to a synclinic ferroelectric (CSPF) high temperature phase and an anticlinic, probably antiferroelectric (CAPA) low temperature phase.

  7. Alkali element depletion by core formation and vaporization on the early Earth

    NASA Technical Reports Server (NTRS)

    Lodders, K.; Fegley, B., Jr.

    1994-01-01

    The depletion of Na, K, Rb, and Cs in the Earth's upper mantle and crust relative to their abundances in chondrites is a long standing problem in geochemistry. Here we consider two commonly invoked mechanisms, namely core formation, and vaporization, for producing the observed depletions. Our models predict that a significant percentage of the Earth's bulk alkali element inventory is in the core (30 percent for Na, 52 percent for K, 74 percent for Rb, and 92 percent for Cs). These predictions agree with independent estimates from nebular volatility trends and (for K) from terrestrial heat flow data. Our models also predict that vaporization and thermal escape during planetary accretion are unlikely to produce the observed alkali element depletion pattern. However, loss during the putative giant impact which formed the Moon cannot be ruled out. Experimental, observational, and theoretical tests of our predictions are also described. Alkali element partitioning into the Earth's core was modeled by assuming that alkali element partitioning during core formation on the aubrite parent body (APB) is analogous to that on the early Earth. The analogy is reasonable for three reasons. First, the enstatite meteorites are the only known meteorites with the same oxygen isotope systematics as the Earth-Moon system. Second, the large core size of the Earth and the V depletion in the mantle requires accretion from planetesimals as reduced as the enstatite chondrites. Third, experimental studies of K partitioning between silicate and metal plus sulfide show that more K goes into the metal plus sulfide at higher pressures than at one atmosphere pressure. Thus partitioning in the relatively low pressure natural laboratory of the APB is a good guide to alkali elemental partitioning during the growth of the Earth.

  8. Harmonizing an opaque core network with transparent optical elements

    NASA Astrophysics Data System (ADS)

    Frankel, Michael Y.; Livas, Jeffrey

    2004-10-01

    Over the last decade, deployed core telecom networks have migrated from being based on single-channel SONET regeneration links to multi-span, multi-channel optically amplified systems. More recently, the industry has been aggressively pursuing a natural extension of this philosophy towards all-optical "analog" core networks, with each traffic demand touching electrical digital circuitry only at the in/egress nodes. This trend produced a substantial elimination of regeneration costs, increase in network capacity, and notionally simpler operation and service turn-up. At the same time, the optical "analog" network requires a large amount of sophisticated hardware and software for monitoring and manipulating high bit rate optical signals. The primary goal for current equipment suppliers is to provide cost effective system designs that are simple to deploy and operate. This paper will examine the trade-offs inherent in the technology and architecture choices needed to reach this goal through the "analog" transmission/all-optical ideal and concludes that it is difficult to improve on the present approach which uses a mix of transparent and opaque network elements.

  9. Effects of core deformations and collective rotational currents on electron-nucleus magnetic form factors

    SciTech Connect

    Lin, C.K.

    1983-01-01

    The collective model H/sub int/ + H/sub coll/ is used to study the magnetic form factors. For the intrinsic Hamiltonian, we use the Nilsson model to generate the intrinsic state. For the collective Hamiltonian, two models are considered, the rigid body model and the liquid soap model. We use the particle-rotor model to derive the collective operators and their reduced matrix elements, and then apply this model to the elastic M1 form factor of /sup 13/C. One sees clearly the interplay of the intrinsic form factor and the collective form factor. Since the form factor is essentially a Fourier transform of the current density operator, one also sees the effects of the collective current density distribution due to all the particles in addition to that of the intrinsic current due to the unpaired nucleons. The effects of core deformation are explored. This includes discussions on the difference between the variation before projection and the variation after projection. Analytic results are obtained in the case of weak deformations. The collective model focuses on the effects of the quadrupole deformation on the M1 form factor of /sup 13/C, whereas the calculation involving core polarization stresses the monopole effects. By introducing a quenching of the isovector g/sub s/, the fits by the collective models are very comparable to the fit by the core polarization, although the justification for this procedure in light nuclei is questionable.

  10. Methods to Identify Standard Data Elements in Clinical and Public Health Forms

    PubMed Central

    Abernethy, Neil F.; DeRimer, Kathy; Small, Peter M.

    2011-01-01

    The fragmentation of clinical and public health systems results in divergent information collection practices, presenting challenges to standardization and EHR certification efforts. Data forms employed in public health jurisdictions nationwide reflect these differences in patient treatment, monitoring and evaluation, and follow-up, presenting challenges for data integration. To study these variations, we surveyed tuberculosis contact investigation forms from all fifty states, three municipalities and two countries. We apply statistics and cluster analysis to analyze the divergent content of contact investigation forms with the goal of characterizing normative practices and identifying a common core of data fields. We found widespread variation in data elements between states in the study, with the “Name” field being the only ubiquitous data element. Our method reveals distinct groupings of data fields employed in certain regions, allowing the simultaneous identification of core standard data fields as well as variations in practice. PMID:22195051

  11. A survey of the core-congruential formulation for geometrically nonlinear TL finite elements

    NASA Technical Reports Server (NTRS)

    Felippa, Carlos A.; Crivelli, Luis A.; Haugen, Bjorn

    1994-01-01

    This article presents a survey of the core-congruential formulation (CCF) for geometrically nonlinear mechanical finite elements based on the total Lagrangian (TL) kinematic description. Although the key ideas behind the CCF can be traced back to Rajasekaran and Murray in 1973, it has not subsequently received serious attention. The CCF is distinguished by a two-phase development of the finite element stiffness equations. The initial phase developed equations for individual particles. These equations are expressed in terms of displacement gradients as degrees of freedom. The second phase involves congruential-type transformations that eventually binds the element particles of an individual element in terms of its node-displacement degrees of freedom. Two versions of the CCF, labeled direct and generalized, are distinguished. The direct CCF (DCCF) is first described in general form and then applied to the derivation of geometrically nonlinear bar, and plane stress elements using the Green-Lagrange strain measure. The more complex generalized CCF (GCCF) is described and applied to the derivation of 2D and 3D Timoshenko beam elements. Several advantages of the CCF, notably the physically clean separation of material and geometric stiffnesses, and its independence with respect to the ultimate choice of shape functions and element degrees of freedom, are noted. Application examples involving very large motions solved with the 3D beam element display the range of applicability of this formulation, which transcends the kinematic limitations commonly attributed to the TL description.

  12. Thoughts on practical core elements of an ethical anatomical education.

    PubMed

    Hildebrandt, Sabine

    2016-01-01

    While questions of ethics in body procurement have become a focus of attention in many medical schools around the world, the recent report by a medical student regarding disturbing incidences in an anatomical dissection course (Terry, ) underlines the importance of a discussion of ethical practices in anatomical education. Here thoughts on core elements of instruction are proposed which are based on the premise that both, ethical body procurement and ethical anatomical education, are the foundation for a humanism-based professional training of students in medicine. As the anatomical dissection course presents an exceptional situation for students, practical guidelines for a curriculum founded on ethical considerations are essential. They include a preparatory phase before the start of the course in which students are asked about their expectations and fears concerning anatomical dissection; an introduction to the history and ethics of anatomy; a time for reflection in the dissection room before the start of dissection; a regular opportunity for reflections on dissection in parallel to the course with students and faculty; and a memorial service for the donors organized by students for faculty, students and donor families. Finally, anatomical faculty should undergo training in ethical educational practices. Many anatomy programs have incorporated various of these ideas, while others have not done so. Guidelines for ethical anatomical practices can strengthen the foundation of a humanistic approach to medicine in future physicians and health care workers. PMID:26474826

  13. [Community health worker: a core element of health actions].

    PubMed

    Costa, Simone de Melo; Araújo, Flávia Ferreira; Martins, Laiara Versiani; Nobre, Lívia Lícia Rafael; Araújo, Fabrícia Magalhães; Rodrigues, Carlos Alberto Quintão

    2013-07-01

    This research sought to identify the actions developed by the Community Health Worker (CHW) in the context of family health in Montes Claros, State of Minas Gerais, Brazil. The research was conducted under the Program of Education through Work for Health-PET-SAÚDE, and is a quantitative study and census together with 241 CHWs. Most of them make family registrations and home visits, identify families with health risks and inform the health team. They also instruct families about available health services, arrange referrals and schedule consultations/exams, perform health education and teamwork reflections. Some also assist in the clinical environment. The majority who provide health education and those who are responsible for the referrals feel that they are professionally qualified for such tasks. CHWs are a core element of health actions, but the scope of performance requires investment in professional training to maintain the quality of the work executed by them in surveillance activities and teamwork reflection. In this way, the CHW can be jointly responsible for primary care and integrate the system of health care administration. PMID:23827919

  14. Spanwise variation of potential form drag. [finite element method

    NASA Technical Reports Server (NTRS)

    Clever, W. C.

    1977-01-01

    The finite element method is used to calculate the spanwise variation of potential form drag of a wing at subsonic and supersonic speeds using linearly varying panels. The wing may be of arbitrary planform and nonplanar provided the wing panels are parallel to the aircraft axis.

  15. Integrated particles sensor formed on single substrate using fringes formed by diffractive elements

    NASA Technical Reports Server (NTRS)

    Gharib, Morteza (Inventor); Fourguette, Dominique (Inventor); Modarress, Darius (Inventor); Taugwalder, Frederic (Inventor); Forouhar, Siamak (Inventor)

    2005-01-01

    Integrated sensors are described using lasers on substrates. In one embodiment, a first sensor forms a laser beam and uses a quartz substrate to sense particle motion by interference of the particles with a diffraction beam caused by a laser beam. A second sensor uses gradings to produce an interference. In another embodiment, an integrated sensor includes a laser element, producing a diverging beam, and a single substrate which includes a first diffractive optical element placed to receive the diverging beam and produce a fringe based thereon, a scattering element which scatters said fringe beam based on particles being detected, and a second diffractive element receiving scattered light.

  16. 42 CFR 457.1140 - Program specific review process: Core elements of review.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 4 2010-10-01 2010-10-01 false Program specific review process: Core elements of review. 457.1140 Section 457.1140 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF... review process: Core elements of review. In adopting the procedures for review of matters described...

  17. 42 CFR 457.1140 - Program specific review process: Core elements of review.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 4 2011-10-01 2011-10-01 false Program specific review process: Core elements of review. 457.1140 Section 457.1140 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF... review process: Core elements of review. In adopting the procedures for review of matters described...

  18. Verification of a non-hydrostatic dynamical core using horizontally spectral element vertically finite difference method

    NASA Astrophysics Data System (ADS)

    Choi, S. J.; Kim, J.; Shin, S.

    2014-12-01

    In this presentation, a new non-hydrostatic (NH) dynamical core using the spectral element method (SEM) in the horizontal discretization and the finite difference method (FDM) in the vertical discretization will be presented. By using horizontal SEM, which decomposes the physical domain into smaller pieces with a small communication stencil, we can achieve a high level of scalability. Also by using vertical FDM, we provide an easy way for coupling the dynamics and existing physics packages. The Euler equations used here are in a flux form based on the hybrid sigma hydrostatic pressure vertical coordinate, which are similar to those used in the Weather Research and Forecasting (WRF) model. Within these Euler equations, we use a time-split third-order Runge-Kutta (RK3) for the time discretization. In order to establish robustness, firstly the NH dynamical core is verified in a simplified two dimensional (2D) slice framework by conducting widely used standard benchmark tests, and then we verify the global three dimensional (3D) dynamical core on the cubed-sphere grid with several test cases introduced by Dynamical Core Model Intercomparison Project (DCMIP).

  19. Motions and Initial Conditions in Star-Forming Dense Cores

    NASA Technical Reports Server (NTRS)

    Myers, Philip C.

    2001-01-01

    Under this grant in the past year we have pursued spectral-line observations of star-forming regions over size scales from 0.01 pc to 0.5 pc. Our main goal has been to measure the systematic and turbulent motions of condensing and collapsing gas. In this area, our results include (1) in 67 starless dense cores, some 19 show clear evidence of spatially extended inward motions, with typical line-of-sight inward speed 0.05-0.09 km s(sup -1) and with typical plane-of-the-sky extent 0.1-0.3 pc, (2) In some 40 nearby regions with embedded groups and clusters, we see extended infall asymmetry in lines of CS and HCO(+) clearly in 4 regions and less clearly in 4 others, (3) Using finer resolution (15 arcsec or 0.01-0.02 pc) and lines tracing higher density, we see spatial concentration of infall asymmetry near the protostars in NGC 1333 IRS 4A and B, L483, and L1251B, and with still finer resolution (2 arcsec or 0.003 pc or 600 AU) we detect inverse P Cyg profiles, indicating absorption of continuum emission from the protostellar envelope by infalling gas in NGC 1333 IRS 4A and 4B. Further, at high resolution we identify regions of stellar mass and low turbulence ("kernels") which are good candidates to become the next generation of stars in embedded clusters. In addition we have completed a survey for the OH Zeeman effect in absorption against nearby H II regions, indicating that the large-scale magnetic field may be nearly critical if it typically threads a flattened structure. We have also developed a model of spatially extended infall motions based on dissipation of turbulence in a magnetized, selfgravitating layer. In the following we describe some of these results in more detail.

  20. Development of a short form of the elemental psychopathy assessment.

    PubMed

    Lynam, Donald R; Sherman, Emily D; Samuel, Douglas; Miller, Joshua D; Few, Lauren R; Widiger, Thomas A

    2013-12-01

    The Elemental Psychopathy Assessment (EPA) is a 178-item self-report measure designed to assess the basic elements of psychopathy from a Five-Factor Model perspective: Anger, Arrogance, Callousness, Coldness, Disobliged, Distrust, Dominance, Impersistence, Invulnerable, Manipulation, Opposition, Rashness, Self-Assurance, Self-Centered, Self-Contentment, Thrill-Seeking, Unconcern, and Urgency. The present article reports on the development of a short-form version of the EPA in two large undergraduate samples using item response theory. The validity of the resultant, 72-item, item response theory-derived short form is compared against the validity for the full scale in the undergraduate samples and smaller forensic sample. Results indicate that the 18 subscales of the EPA short form remain relatively reliable, possess an internal structure virtually identical to the full version, and manifest highly similar correlational profiles to a variety of criterion measures. The EPA short form is offered as a viable assessment of psychopathy when assessment time is limited. Implications of these findings are discussed. PMID:23996849

  1. Elastic constants for superplastically formed/diffusion-bonded corrugated sandwich core

    NASA Technical Reports Server (NTRS)

    Ko, W. L.

    1980-01-01

    Formulas and associated graphs for evaluating the effective elastic constants for a superplastically formed/diffusion bonded (SPF/DB) corrugated sandwich core, are presented. A comparison of structural stiffnesses of the sandwich core and a honeycomb core under conditions of equal sandwich core density was made. The stiffness in the thickness direction of the optimum SPF/DB corrugated core (that is, triangular truss core) is lower than that of the honeycomb core, and that the former has higher transverse shear stiffness than the latter.

  2. Novel core promoter elements and a cognate transcription factor in the divergent unicellular eukaryote Trichomonas vaginalis.

    PubMed

    Smith, Alias J; Chudnovsky, Lorissa; Simoes-Barbosa, Augusto; Delgadillo-Correa, Maria G; Jonsson, Zophonias O; Wohlschlegel, James A; Johnson, Patricia J

    2011-04-01

    A highly conserved DNA initiator (Inr) element has been the only core promoter element described in the divergent unicellular eukaryote Trichomonas vaginalis, although genome analyses reveal that only ∼75% of protein-coding genes appear to contain an Inr. In search of another core promoter element(s), a nonredundant database containing 5' untranslated regions of expressed T. vaginalis genes was searched for overrepresented DNA motifs and known eukaryotic core promoter elements. In addition to identifying the Inr, two elements that lack sequence similarity to the known protein-coding gene core promoter, motif 3 (M3) and motif 5 (M5), were identified. Mutational and functional analyses demonstrate that both are novel core promoter elements. M3 [(A/G/T)(A/G)C(G/C)G(T/C)T(T/A/G)] resembles a Myb recognition element (MRE) and is bound specifically by a unique protein with a Myb-like DNA binding domain. The M5 element (CCTTT) overlaps the transcription start site and replaces the Inr as an alternative, gene-specific initiator element. Transcription specifically initiates at the second cytosine within M5, in contrast to characteristic initiation by RNA polymerase II at an adenosine. In promoters that combine M3 with either M5 or Inr, transcription initiation is regulated by the M3 motif. PMID:21245378

  3. Isotopic variations in the rock-forming elements in meteorites

    NASA Technical Reports Server (NTRS)

    Clayton, R. N.; Hinton, R. W.; Davis, A. M.

    1988-01-01

    Variations in isotopic abundances of the major rock-forming elements can be used as tracers for chemical processes in the solar nebula, and may also provide links to the presolar cloud from which the solar nebula was derived. The paper reviews recent developments involving meteoritic abundances of the isotopes of O, Mg, Si, Ca, Ti, Cr, Fe, and Ni). Some of the effects observed are due to mass-dependent fractionation, and some are due to interaction of isotopically distinct reservoirs, reflecting incomplete homogenization of materials with different nucleosynthetic histories.

  4. PLANETARY CORE FORMATION WITH COLLISIONAL FRAGMENTATION AND ATMOSPHERE TO FORM GAS GIANT PLANETS

    SciTech Connect

    Kobayashi, Hiroshi; Krivov, Alexander V.; Tanaka, Hidekazu

    2011-09-01

    Massive planetary cores ({approx}10 Earth masses) trigger rapid gas accretion to form gas giant planets such as Jupiter and Saturn. We investigate the core growth and the possibilities for cores to reach such a critical core mass. At the late stage, planetary cores grow through collisions with small planetesimals. Collisional fragmentation of planetesimals, which is induced by gravitational interaction with planetary cores, reduces the amount of planetesimals surrounding them, and thus the final core masses. Starting from small planetesimals that the fragmentation rapidly removes, less massive cores are formed. However, planetary cores acquire atmospheres that enlarge their collisional cross section before rapid gas accretion. Once planetary cores exceed about Mars mass, atmospheres significantly accelerate the growth of cores. We show that, taking into account the effects of fragmentation and atmosphere, initially large planetesimals enable formation of sufficiently massive cores. On the other hand, because the growth of cores is slow for large planetesimals, a massive disk is necessary for cores to grow enough within a disk lifetime. If the disk with 100 km sized initial planetesimals is 10 times as massive as the minimum mass solar nebula, planetary cores can exceed 10 Earth masses in the Jovian planet region (>5 AU).

  5. Elemental abundances and temperatures of quiescent solar active region cores from X-ray observations

    NASA Astrophysics Data System (ADS)

    Del Zanna, G.; Mason, H. E.

    2014-05-01

    A brief review of studies of elemental abundances and emission measures in quiescent solar active region cores is presented. Hinode EUV Imaging Spectrometer (EIS) observations of strong iron spectral lines have shown sharply peaked distributions around 3 MK. EIS observations of lines emitted by a range of elements have allowed good estimates of abundances relative to iron. However, X-ray observations are required to measure the plasma emission above 3 MK and the abundances of oxygen and neon. We revisit, using up-to-date atomic data, older X-ray observations obtained by a sounding rocket and by the Solar Maximum Mission (SMM) Flat Crystal Spectrometer (FCS). We find that the Fe/O and Fe/Ne ratios are normally increased by a factor of 3.2, compared to the photospheric values. Similar results are obtained from FCS observations of six quiescent active region cores. The FCS observations also indicate that the emission measure above 3 MK has a very steep negative slope, with very little plasma observed at 5 MK or above. Appendix A is available in electronic form at http://www.aanda.org

  6. Investigation of Forming Performance of Laminated Steel Sheets Using Finite Element Analyses

    NASA Astrophysics Data System (ADS)

    Liu, Wenning; Sun, Xin; Ruokolainen, Robert; Gayden, Xiaohong

    2007-05-01

    Laminated steel sheets have been used in automotive structures for reducing in-cabin noise. However, due to the marked difference in material properties of the different laminated layers, integrating laminated steel parts into the manufacturing processes can be challenging. Especially, the behavior of laminated sheets during forming processes is very different from that of monolithic steel sheets. During the deep-draw forming process, large shear deformation and corresponding high interfacial stress may initiate and propagate interfacial cracks between the core polymer and the metal skin, hence degrading the performance of the laminated sheets. In this paper, the formability of the laminated steel sheets is investigated by means of numerical analysis. The goal of this work is to gain insight into the relationship between the individual properties of the laminated sheet layers and the corresponding formability of the laminated sheet as a whole, eventually leading to reliable design and successful forming process development of such materials. Finite element analyses of laminate sheet forming are presented. Effects of polymer core thickness and viscoelastic properties of the polymer core, as well as punching velocity, are also investigated.

  7. Conversion and evaluation of the THOR reactor core to TRIGA fuel elements

    SciTech Connect

    Li, S.-H.; Shiau, L.-C.

    1990-07-01

    The THOR reactor is a pool type 1 MW research reactor and has been operated since 1961. The original MTR fuel elements have been gradually replaced by TRIGA fuel elements since 1977 and the conversion completed in 1987. The calculations were performed for various core configurations by using computer codes, WIMS/CITATION. The computing results have been evaluated and compared with the core measurements after the fuel conversion. The analysis results are in good correspondence with the measurements. (author)

  8. 34 CFR 200.26 - Core elements of a schoolwide program.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 34 Education 1 2012-07-01 2012-07-01 false Core elements of a schoolwide program. 200.26 Section 200.26 Education Regulations of the Offices of the Department of Education OFFICE OF ELEMENTARY AND... Improving Basic Programs Operated by Local Educational Agencies Schoolwide Programs § 200.26 Core...

  9. 34 CFR 200.26 - Core elements of a schoolwide program.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false Core elements of a schoolwide program. 200.26 Section 200.26 Education Regulations of the Offices of the Department of Education OFFICE OF ELEMENTARY AND... Improving Basic Programs Operated by Local Educational Agencies Schoolwide Programs § 200.26 Core...

  10. 34 CFR 200.26 - Core elements of a schoolwide program.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 34 Education 1 2013-07-01 2013-07-01 false Core elements of a schoolwide program. 200.26 Section 200.26 Education Regulations of the Offices of the Department of Education OFFICE OF ELEMENTARY AND... Improving Basic Programs Operated by Local Educational Agencies Schoolwide Programs § 200.26 Core...

  11. 34 CFR 200.26 - Core elements of a schoolwide program.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 34 Education 1 2014-07-01 2014-07-01 false Core elements of a schoolwide program. 200.26 Section 200.26 Education Regulations of the Offices of the Department of Education OFFICE OF ELEMENTARY AND... Improving Basic Programs Operated by Local Educational Agencies Schoolwide Programs § 200.26 Core...

  12. Identification of the core sequence elements in Penaeus stylirostris densovirus promoters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This manuscript describes the role of different core elements in the transcriptional activity of promoters in a marine parvovirus, Penaeus stylirostris densovirus (PstDNV) that infects shrimp. Although comprehensive information on the role of different elements in the promoters of several animal par...

  13. CAM-SE: A scalable spectral element dynamical core for the Community Atmosphere Model.

    SciTech Connect

    Dennis, John; Edwards, Jim; Evans, Kate J; Guba, O; Lauritzen, Peter; Mirin, Art; St.-Cyr, Amik; Taylor, Mark; Worley, Patrick H

    2012-01-01

    The Community Atmosphere Model (CAM) version 5 includes a spectral element dynamical core option from NCAR's High-Order Method Modeling Environment. It is a continuous Galerkin spectral finite element method designed for fully unstructured quadrilateral meshes. The current configurations in CAM are based on the cubed-sphere grid. The main motivation for including a spectral element dynamical core is to improve the scalability of CAM by allowing quasi-uniform grids for the sphere that do not require polar filters. In addition, the approach provides other state-of-the-art capabilities such as improved conservation properties. Spectral elements are used for the horizontal discretization, while most other aspects of the dynamical core are a hybrid of well tested techniques from CAM's finite volume and global spectral dynamical core options. Here we first give a overview of the spectral element dynamical core as used in CAM. We then give scalability and performance results from CAM running with three different dynamical core options within the Community Earth System Model, using a pre-industrial time-slice configuration. We focus on high resolution simulations of 1/4 degree, 1/8 degree, and T340 spectral truncation.

  14. Experimental constraints on light elements in the Earth’s outer core

    PubMed Central

    Zhang, Youjun; Sekine, Toshimori; He, Hongliang; Yu, Yin; Liu, Fusheng; Zhang, Mingjian

    2016-01-01

    Earth’s outer core is liquid and dominantly composed of iron and nickel (~5–10 wt%). Its density, however, is ~8% lower than that of liquid iron, and requires the presence of a significant amount of light element(s). A good way to specify the light element(s) is a direct comparison of density and sound velocity measurements between seismological data and those of possible candidate compositions at the core conditions. We report the sound velocity measurements of a model core composition in the Fe-Ni-Si system at the outer core conditions by shock-wave experiments. Combining with the previous studies, we found that the best estimate for the outer core’s light elements is ~6 wt% Si, ~2 wt% S, and possible ~1–2.5 wt% O. This composition satisfies the requirements imposed by seismology, geochemistry, and some models of the early core formation. This finding may help us to further constrain the thermal structure of the Earth and the models of Earth’s core formation. PMID:26932596

  15. Experimental constraints on light elements in the Earth’s outer core

    NASA Astrophysics Data System (ADS)

    Zhang, Youjun; Sekine, Toshimori; He, Hongliang; Yu, Yin; Liu, Fusheng; Zhang, Mingjian

    2016-03-01

    Earth’s outer core is liquid and dominantly composed of iron and nickel (~5-10 wt%). Its density, however, is ~8% lower than that of liquid iron, and requires the presence of a significant amount of light element(s). A good way to specify the light element(s) is a direct comparison of density and sound velocity measurements between seismological data and those of possible candidate compositions at the core conditions. We report the sound velocity measurements of a model core composition in the Fe-Ni-Si system at the outer core conditions by shock-wave experiments. Combining with the previous studies, we found that the best estimate for the outer core’s light elements is ~6 wt% Si, ~2 wt% S, and possible ~1-2.5 wt% O. This composition satisfies the requirements imposed by seismology, geochemistry, and some models of the early core formation. This finding may help us to further constrain the thermal structure of the Earth and the models of Earth’s core formation.

  16. Structure, Motion, and Evolution of Star-Forming Dense Cores

    NASA Technical Reports Server (NTRS)

    Myers, Philip C.

    2003-01-01

    We have pursued spectral-line observations of star-forming regions over size scales from 0.01 pc to 0.5 pc. Our main goal has been to measure the systematic and turbulent motions of condensing and collapsing gas.

  17. Gravitational Wave Signatures in Black Hole Forming Core Collapse

    NASA Astrophysics Data System (ADS)

    Cerdá-Durán, Pablo; DeBrye, Nicolas; Aloy, Miguel A.; Font, José A.; Obergaulinger, Martin

    2013-12-01

    We present general relativistic numerical simulations of collapsing stellar cores. Our initial model consists of a low metallicity rapidly-rotating progenitor which is evolved in axisymmetry with the latest version of our general relativistic code CoCoNuT, which allows for black hole formation and includes the effects of a microphysical equation of state (LS220) and a neutrino leakage scheme to account for radiative losses. The motivation of our study is to analyze in detail the emission of gravitational waves in the collapsar scenario of long gamma-ray bursts. Our simulations show that the phase during which the proto-neutron star (PNS) survives before ultimately collapsing to a black hole is particularly optimal for gravitational wave emission. The high-amplitude waves last for several seconds and show a remarkable quasi-periodicity associated with the violent PNS dynamics, namely during the episodes of convection and the subsequent nonlinear development of the standing-accretion shock instability (SASI). By analyzing the spectrogram of our simulations we are able to identify the frequencies associated with the presence of g-modes and with the SASI motions at the PNS surface. We note that the gravitational waves emitted reach large enough amplitudes to be detected with third-generation detectors such as the Einstein Telescope within a Virgo Cluster volume at rates <~ 0.1 yr-1.

  18. GRAVITATIONAL WAVE SIGNATURES IN BLACK HOLE FORMING CORE COLLAPSE

    SciTech Connect

    Cerdá-Durán, Pablo; DeBrye, Nicolas; Aloy, Miguel A.; Font, José A.; Obergaulinger, Martin

    2013-12-20

    We present general relativistic numerical simulations of collapsing stellar cores. Our initial model consists of a low metallicity rapidly-rotating progenitor which is evolved in axisymmetry with the latest version of our general relativistic code CoCoNuT, which allows for black hole formation and includes the effects of a microphysical equation of state (LS220) and a neutrino leakage scheme to account for radiative losses. The motivation of our study is to analyze in detail the emission of gravitational waves in the collapsar scenario of long gamma-ray bursts. Our simulations show that the phase during which the proto-neutron star (PNS) survives before ultimately collapsing to a black hole is particularly optimal for gravitational wave emission. The high-amplitude waves last for several seconds and show a remarkable quasi-periodicity associated with the violent PNS dynamics, namely during the episodes of convection and the subsequent nonlinear development of the standing-accretion shock instability (SASI). By analyzing the spectrogram of our simulations we are able to identify the frequencies associated with the presence of g-modes and with the SASI motions at the PNS surface. We note that the gravitational waves emitted reach large enough amplitudes to be detected with third-generation detectors such as the Einstein Telescope within a Virgo Cluster volume at rates ≲ 0.1 yr{sup –1}.

  19. Structure, Motion, and Evolution of Star-Forming Dense Cores

    NASA Technical Reports Server (NTRS)

    Myers, Philip C.

    2002-01-01

    Under this grant in the past year we have pursued spectral-line observations of star-forming regions over size scales from 0.01 pc to 0.5 pc. Our main goal has been to measure the systematic and turbulent motions of condensing and collapsing gas. The following summary is excerpted from our recent application for a new three-year grant, submitted in June, 2002.

  20. Constraints on core formation in Vesta from metal-silicate partitioning of siderophile elements

    NASA Astrophysics Data System (ADS)

    Steenstra, E. S.; Knibbe, J. S.; Rai, N.; van Westrenen, W.

    2016-03-01

    It is now widely accepted that the asteroid 4-Vesta has an Fe-rich metallic core, but the composition of the core and the conditions prevailing during core-mantle differentiation are poorly constrained. In light of new constraints on Vesta's geophysical and geochemical properties obtained by the DAWN mission, we have re-examined the conditions at which core-mantle differentiation in Vesta may have occurred by linking the estimated mantle depletions of siderophile elements P, Co, Ni, Cu, Ga, Ge, Mo and W in the vestan mantle to newly derived predictive equations for core-mantle partitioning of these elements. We extend the number of elements previously considered in geochemical modeling of vestan core formation and use published metal-silicate partitioning data obtained at low pressures to characterize the dependence of metal/silicate partition coefficients (D) on pressure, temperature, oxygen fugacity and composition of the silicate and metallic melt. In our modeling we implement newly derived mantle depletions of P, Co, Ni and Ga through analysis of published HED meteorite analyses and assess two contrasting bulk compositional models for Vesta. Modeling results using Monte Carlo simulations constrain vestan core formation to have occurred at mildly reducing conditions of approximately 2 log units below the iron-wüstite (IW) buffer (ΔIW = -2.05 ± 0.20) if the two most likely bulk compositions (binary mixtures of H + CM or H + CV chondritic meteorites) are considered, assuming a temperature range between 1725 and 1850 K and a sulfur-free pure Fe core. If the core is assumed to be sulfur-rich (15 wt.% S) as predicted by the latter bulk compositional models, observed depletions for all eight siderophile elements can be simultaneously satisfied at ΔIW = -2.35 ± 0.10 and 1725-1850 K for the H + CV bulk composition and ΔIW = -2.30 ± 0.15 and 1725-1850 K for the H + CM bulk composition. More reducing conditions are not consistent with the observed siderophile

  1. Effect of Light Elements on the Sound Velocities in Solid Iron: Implications for the Composition of Earth's Core

    NASA Astrophysics Data System (ADS)

    Badro, J.; Fiquet, G.; Guyot, F.

    2006-12-01

    We measured compressional sound velocities in light-element alloys of iron (FeO, FeSi, FeS, and FeS2) at high pressure by inelastic x-ray scattering. This data set provides a mineralogical constraint on the composition of Earth's core, and completes the previous set formed by the pressure-density systematics for these compounds. Based on the combination of these data sets and their comparison with radial seismic models, we propose an average composition model of Earth's core. We show that sulphur cannot be the only light alloying element in the core, because it cannot satisfy both the compressibility, sound velocity and while retaining a reasonable abundance based on cosmochemical models. On the other hand, the incorporation of small amounts of silicon or oxygen is compatible with geophysical observations and geochemical abundances. From our data, the inner core contains 2.3 wt% silicon or 1.6 wt% oxygen. Using recent O and Si partitioning data, we build a new composite model of the core and discuss the effects of Nickel.

  2. Chemical tracers of pre-brown dwarf cores formed through turbulent fragmentation

    NASA Astrophysics Data System (ADS)

    Holdship, Jonathan; Viti, Serena

    2016-01-01

    A gas-grain time-dependent chemical code, UCL_CHEM, has been used to investigate the possibility of using chemical tracers to differentiate between the possible formation mechanisms of brown dwarfs. In this work, we model the formation of a pre-brown dwarf core through turbulent fragmentation by following the depth-dependent chemistry in a molecular cloud through the step change in density associated with an isothermal shock and the subsequent freefall collapse once a bound core is produced. Trends in the fractional abundance of molecules commonly observed in star-forming cores are then explored to find a diagnostic for identifying brown dwarf mass cores formed through turbulence. We find that the cores produced by our models would be bright in CO and NH3 but not in HCO+. This differentiates them from models using purely freefall collapse as such models produce cores that would have detectable transitions from all three molecules.

  3. Core-Mantle Partitioning of Volatile Elements and the Origin of Volatile Elements in Earth and Moon

    NASA Technical Reports Server (NTRS)

    Righter, Kevin; Pando, K.; Danielson, L.; Nickodem, K.

    2014-01-01

    Depletions of volatile siderophile elements (VSE; Ga, Ge, In, As, Sb, Sn, Bi, Zn, Cu, Cd) in mantles of Earth and Moon, constrain the origin of volatile elements in these bodies, and the overall depletion of volatile elements in Moon relative to Earth. A satisfactory explanation has remained elusive [1,2]. We examine the depletions of VSE in Earth and Moon and quantify the amount of depletion due to core formation and volatility of potential building blocks. We calculate the composition of the Earth's PUM during continuous accretion scenarios with constant and variable fO2. Results suggest that the VSE can be explained by a rather simple scenario of continuous accretion leading to a high PT metal-silicate equilibrium scenario that establishes the siderophile element content of Earth's PUM near the end of accretion [3]. Core formation models for the Moon explain most VSE, but calculated contents of In, Sn, and Zn (all with Tc < 750 K) are all still too high after core formation, and must therefore require an additional process to explain the depletions in the lunar mantle. We discuss possible processes including magmatic degassing, evaporation, condensation, and vapor-liquid fractionation in the lunar disk.

  4. Simulation on reactor TRIGA Puspati core kinetics fueled with thorium (Th) based fuel element

    NASA Astrophysics Data System (ADS)

    Mohammed, Abdul Aziz; Pauzi, Anas Muhamad; Rahman, Shaik Mohmmed Haikhal Abdul; Zin, Muhamad Rawi Muhammad; Jamro, Rafhayudi; Idris, Faridah Mohamad

    2016-01-01

    In confronting global energy requirement and the search for better technologies, there is a real case for widening the range of potential variations in the design of nuclear power plants. Smaller and simpler reactors are attractive, provided they can meet safety and security standards and non-proliferation issues. On fuel cycle aspect, thorium fuel cycles produce much less plutonium and other radioactive transuranic elements than uranium fuel cycles. Although not fissile itself, Th-232 will absorb slow neutrons to produce uranium-233 (233U), which is fissile. By introducing Thorium, the numbers of highly enriched uranium fuel element can be reduced while maintaining the core neutronic performance. This paper describes the core kinetic of a small research reactor core like TRIGA fueled with a Th filled fuel element matrix using a general purpose Monte Carlo N-Particle (MCNP) code.

  5. Element Redistribution in Fe-Ni-O Alloys by a Thermal Gradient: Implications for Siderophile Element Partitioning During Core Formation and Crystallization

    NASA Astrophysics Data System (ADS)

    Bennett, N.; Fei, Y.

    2014-12-01

    Experimentally determined partition coefficients for Fe-rich metallic systems are essential to constrain models of the formation and evolution of planetary cores. Solid metal-liquid metal partition coefficients (DSol/Liq) for many siderophile elements depend upon the light-element content of the liquid phase. This dependence can be described by an empirically determined interaction parameter (β). Oxygen is a potential light element in the cores of large planetary bodies. Direct measurements of the partition coefficients between solid and liquid alloys in the Fe-O system, however, are restricted to liquids with low O contents (<2.2 wt% O at 15 GPa; Langlade et al. LPSC, 2008). Measurements to derive β-values from Soret diffusion experiments allow us to extend our investigation to the larger compositional space present at higher temperature (Brenan & Bennett, EPSL, 2010). We performed experiments at 15 GPa in a 1500-tonne multi-anvil press, using starting materials that comprised Fe, Ni and FeO powders mixed with ~200 ppm each of the platinum group metals, W, Mn, Re and Au. Run-products were analysed by electron microprobe (Fe, Ni, O) and LA-ICP-MS (PGMs, W, Mn, Re, Au). Temperature along the sample was estimated from the thickness of a spinel layer formed at the interface between the Al2O3 capsule and MgO sleeve. Initial results show siderophile elements typically display O avoidance behavior and are concentrated toward the cold, Fe-rich portion of the sample. In one experiment however, that contains W and Re in weight percent concentrations, Mn and Re are concentrated toward the O-rich portion of the sample. Au concentrations remain approximately constant along the sample length. Results are used to predict the evolution of element ratios in the outer-core during inner-core crystallization. β-values may also be used to estimate changes to DMet/Sil that arise from O dissolved in core-forming metal.

  6. Did Jupiter's core form in the innermost parts of the Sun's protoplanetary disc?

    NASA Astrophysics Data System (ADS)

    Raymond, Sean N.; Izidoro, Andre; Bitsch, Bertram; Jacobson, Seth A.

    2016-05-01

    Jupiter's core is generally assumed to have formed beyond the snow line. Here we consider an alternative scenario that Jupiter's core may have accumulated in the innermost part of the protoplanetary disc. A growing body of research suggests that small particles (`pebbles') continually drift inward through the disc. If a fraction of drifting pebbles is trapped at the inner edge of the disc, several Earth-mass cores can quickly grow. Subsequently, the core may migrate outward beyond the snow line via planet-disc interactions. Of course, to reach the outer Solar system Jupiter's core must traverse the terrestrial planet-forming region. We use N-body simulations including synthetic forces from an underlying gaseous disc to study how the outward migration of Jupiter's core sculpts the terrestrial zone. If the outward migration is fast (τmig ˜ 104 yr), the core simply migrates past resident planetesimals and planetary embryos. However, if its migration is slower (τmig ˜ 105 yr) the core clears out solids in the inner disc by shepherding objects in mean motion resonances. In many cases, the disc interior to 0.5-1 AU is cleared of embryos and most planetesimals. By generating a mass deficit close to the Sun, the outward migration of Jupiter's core may thus explain the absence of terrestrial planets closer than Mercury. Jupiter's migrating core often stimulates the growth of another large (˜Earth-mass) core - that may provide a seed for Saturn's core - trapped in an exterior resonance. The migrating core also may transport a fraction of terrestrial planetesimals, such as the putative parent bodies of iron meteorites, to the asteroid belt.

  7. Inspection of spar-core bond in helicopter rotor blades using finite element analysis

    NASA Astrophysics Data System (ADS)

    Chakrapani, Sunil Kishore; Barnard, Daniel J.; Dayal, Vinay

    2015-03-01

    This work focuses on inspection of spar-core bond of a helicopter rotor blade using finite element analysis. Structures which have high density, high stiffness cores can be very difficult to inspect due to various mode conversions. FEM was used to capture these mode conversions effectively. The structure consists of a thin spar section followed by a spar-core half space and another thin spar section. A Lamb wave excited in the spar section can mode convert into a Rayleigh wave in the spar-core section due to the coupling of the core material. This in turn mode converts back into a Lamb wave upon interacting with the next spar section. This work focuses solely on capturing the mode conversions between Rayleigh and Lamb modes at different discontinuities in the geometry.

  8. The Native Form and Maturation Process of Hepatitis C Virus Core Protein

    PubMed Central

    Yasui, Kohichiroh; Wakita, Takaji; Tsukiyama-Kohara, Kyoko; Funahashi, Shin-Ichi; Ichikawa, Masumi; Kajita, Tadahiro; Moradpour, Darius; Wands, Jack R.; Kohara, Michinori

    1998-01-01

    The maturation and subcellular localization of hepatitis C virus (HCV) core protein were investigated with both a vaccinia virus expression system and CHO cell lines stably transformed with HCV cDNA. Two HCV core proteins, with molecular sizes of 21 kDa (p21) and 23 kDa (p23), were identified. The C-terminal end of p23 is amino acid 191 of the HCV polyprotein, and p21 is produced as a result of processing between amino acids 174 and 191. The subcellular localization of the HCV core protein was examined by confocal laser scanning microscopy. Although HCV core protein resided predominantly in the cytoplasm, it was also found in the nucleus and had the same molecular size as p21 in both locations, as determined by subcellular fractionation. The HCV core proteins had different immunoreactivities to a panel of monoclonal antibodies. Antibody 5E3 stained core protein in both the cytoplasm and the nucleus, C7-50 stained core protein only in the cytoplasm, and 499S stained core protein only in the nucleus. These results clearly indicate that the p23 form of HCV core protein is processed to p21 in the cytoplasm and that the core protein in the nucleus has a higher-order structure different from that of p21 in the cytoplasm. HCV core protein in sera of patients with HCV infection was analyzed in order to determine the molecular size of genuinely processed HCV core protein. HCV core protein in sera was found to have exactly the same molecular weight as the p21 protein. These results suggest that p21 core protein is a component of native viral particles. PMID:9621068

  9. Statistical Constraints from Siderophile Elements on Earth's Accretion, Differentiation, and Initial Core Stratification

    NASA Astrophysics Data System (ADS)

    O'Rourke, J. G.; Stevenson, D. J.

    2015-12-01

    Abundances of siderophile elements in the primitive mantle constrain the conditions of Earth's core/mantle differentiation. Core growth occurred as Earth accreted from collisions between planetesimals and larger embryos of unknown original provenance, so geochemistry is directly related to the overall dynamics of Solar System formation. Recent studies claim that only certain conditions of equilibration (pressure, temperature, and oxygen fugacity) during core formation can reproduce the available data. Typical analyses, however, only consider the effects of varying a few out of tens of free parameters in continuous core formation models. Here we describe the Markov chain Monte Carlo method, which simultaneously incorporates the large uncertainties on Earth's composition and the parameterizations that describe elemental partitioning between metal and silicate. This Bayesian technique is vastly more computationally efficient than a simple grid search and is well suited to models of planetary accretion that involve a plethora of variables. In contrast to previous work, we find that analyses of siderophile elements alone cannot yield a unique scenario for Earth's accretion. Our models predict a wide range of possible light element contents for the core, encompassing all combinations permitted by seismology and mineral physics. Specifically, we are agnostic between silicon and oxygen as the dominant light element, and the addition of carbon or sulfur is also permissible but not well constrained. Redox conditions may have remained roughly constant during Earth's accretion or relatively oxygen-rich material could have been incorporated before reduced embryos. Pressures and temperatures of equilibration, likewise, may only increase slowly throughout accretion. Therefore, we do not necessarily expect a thick (>500 km), compositionally stratified layer that is stable against convection to develop at the top of the core of Earth (or, by analogy, Venus). A thinner stable layer

  10. Using Elemental Literary Forms in the Composition Class

    ERIC Educational Resources Information Center

    Harp, Richard L.

    1978-01-01

    Concludes that imaginative literature is the best way to begin to teach writing and the literature to teach first should be the most basic and elemental types: fable, fairy tale, parable, proverb, and myth. (DD)

  11. Genome-wide computational prediction and analysis of core promoter elements across plant monocots and dicots

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transcription initiation, essential to gene expression regulation, involves recruitment of basal transcription factors to the core promoter elements (CPEs). The distribution of currently known CPEs across plant genomes is largely unknown. This is the first large scale genome-wide report on the compu...

  12. Study of Core Competency Elements and Factors Affecting Performance Efficiency of Government Teachers in Northeastern Thailand

    ERIC Educational Resources Information Center

    Chansirisira, Pacharawit

    2012-01-01

    The research aimed to investigate the core competency elements and the factors affecting the performance efficiency of the civil service teachers in the northeastern region, Thailand. The research procedure consisted of two steps. In the first step, the data were collected using a questionnaire with the reliability (Cronbach's Alpha) of 0.90. The…

  13. Communities That Care, Core Elements and Context: Research of Implementation in Two Countries

    PubMed Central

    Jonkman, H. B.; Haggerty, K. P.; Steketee, M.; Fagan, A.; Hanson, K.; Hawkins, J. D.

    2008-01-01

    This paper describes the degree to which implementation of the Communities That Care (CTC) prevention operating system was reached in 22 communities in 2 countries: the US (12 communities) and the Netherlands (10 communities). Core elements of CTC and results from two implementation measures conducted in both countries are reported here. Similarities and differences of the implementation process are discussed. PMID:19617929

  14. Solar Abundances of Rock Forming Elements, Extreme Oxygen and Hydrogen in a Young Polluted White Dwarf

    NASA Astrophysics Data System (ADS)

    Farihi, J.; Koester, D.; Zuckerman, B.; Vican, L.; Gänsicke, B. T.; Smith, N.; Walth, G.; Breedt, E.

    2016-09-01

    The Teff = 20 800 K white dwarf WD 1536+520 is shown to have broadly solar abundances of the major rock forming elements O, Mg, Al, Si, Ca, and Fe, together with a strong relative depletion in the volatile elements C and S. In addition to the highest metal abundances observed to date, including log (O/He) =-3.4, the helium-dominated atmosphere has an exceptional hydrogen abundance at log (H/He) =-1.7. Within the uncertainties, the metal-to-metal ratios are consistent with the accretion of an H2O-rich and rocky parent body, an interpretation supported by the anomalously high trace hydrogen. The mixed atmosphere yields unusually short diffusion timescales for a helium atmosphere white dwarf, of no more than a few hundred yr, and equivalent to those in a much cooler, hydrogen-rich star. The overall heavy element abundances of the disrupted parent body deviate modestly from a bulk Earth pattern, and suggest the deposition of some core-like material. The total inferred accretion rate is 4.2 × 109 g s-1, and at least 4 times higher than any white dwarf with a comparable diffusion timescale. Notably, when accretion is exhausted in this system, both metals and hydrogen will become undetectable within roughly 300 Myr, thus supporting a scenario where the trace hydrogen is related to the ongoing accretion of planetary debris.

  15. THE FRAGMENTATION OF MAGNETIZED, MASSIVE STAR-FORMING CORES WITH RADIATIVE FEEDBACK

    SciTech Connect

    Myers, Andrew T.; McKee, Christopher F.; Cunningham, Andrew J.; Klein, Richard I.; Krumholz, Mark R.

    2013-04-01

    We present a set of three-dimensional, radiation-magnetohydrodynamic calculations of the gravitational collapse of massive (300 M{sub Sun }), star-forming molecular cloud cores. We show that the combined effects of magnetic fields and radiative feedback strongly suppress core fragmentation, leading to the production of single-star systems rather than small clusters. We find that the two processes are efficient at suppressing fragmentation in different regimes, with the feedback most effective in the dense, central region and the magnetic field most effective in more diffuse, outer regions. Thus, the combination of the two is much more effective at suppressing fragmentation than either one considered in isolation. Our work suggests that typical massive cores, which have mass-to-flux ratios of about 2 relative to critical, likely form a single-star system, but that cores with weaker fields may form a small star cluster. This result helps us understand why the observed relationship between the core mass function and the stellar initial mass function holds even for {approx}100 M{sub Sun} cores with many thermal Jeans masses of material. We also demonstrate that a {approx}40 AU Keplerian disk is able to form in our simulations, despite the braking effect caused by the strong magnetic field.

  16. Modular Approach to Launch Vehicle Design Based on a Common Core Element

    NASA Technical Reports Server (NTRS)

    Creech, Dennis M.; Threet, Grady E., Jr.; Philips, Alan D.; Waters, Eric D.; Baysinger, Mike

    2010-01-01

    With a heavy lift launch vehicle as the centerpiece of our nation's next exploration architecture's infrastructure, the Advanced Concepts Office at NASA's Marshall Space Flight Center initiated a study to examine the utilization of elements derived from a heavy lift launch vehicle for other potential launch vehicle applications. The premise of this study is to take a vehicle concept, which has been optimized for Lunar Exploration, and utilize the core stage with other existing or near existing stages and boosters to determine lift capabilities for alternative missions. This approach not only yields a vehicle matrix with a wide array of capabilities, but also produces an evolutionary pathway to a vehicle family based on a minimum development and production cost approach to a launch vehicle system architecture, instead of a purely performance driven approach. The upper stages and solid rocket booster selected for this study were chosen to reflect a cross-section of: modified existing assets in the form of a modified Delta IV upper stage and Castor-type boosters; potential near term launch vehicle component designs including an Ares I upper stage and 5-segment boosters; and longer lead vehicle components such as a Shuttle External Tank diameter upper stage. The results of this approach to a modular launch system are given in this paper.

  17. Birefringence analysis of a two elliptical cores hollow fiber based on finite element method

    NASA Astrophysics Data System (ADS)

    Tian, Fengjun; Yuan, Libo; Dai, Qian; Liu, Zhihai; Zhang, Jianzhong

    2012-02-01

    We design and fabricate a two elliptical cores hollow optical fiber, which has an about 60μm diameter hollow air hole centrally, a 125μm diameter cladding, two 8μm/4μm (major axis/minor axis) elliptical cores, and a 2μm thickness silica cladding between core layer and air hole. Its mode birefringence is consisted of geometry birefringence and self-stress birefringence. Based on the finite element method the birefringence characteristics are analyzed numerically at 200nm- 1800nm wavelength. We expect that the two elliptical cores hollow fiber has some potential applications in in-fiber interferometers with polarization maintaining, poling fiber and Bio-sensor based on evanescent wave field.

  18. METHOD OF FORMING A FUEL ELEMENT FOR A NUCLEAR REACTOR

    DOEpatents

    Layer, E.H. Jr.; Peet, C.S.

    1962-01-23

    A method is given for preparing a fuel element for a nuclear reactor. The method includes the steps of sandblasting a body of uranium dioxide to roughen the surface thereof, depositing a thin layer of carbon thereon by thermal decomposition of methane, and cladding the uranium dioxide body with zirconium by gas pressure bonding. (AEC)

  19. The growth of Ho:YAG single crystals by Czochralski method and investigating the formed cores

    SciTech Connect

    Hasani Barbaran, J. Ghani Aragi, M. R.; Javaheri, I.; Baharvand, B.; Tabasi, M.; Layegh Ahan, R.; Jangjo, E.

    2015-12-15

    Ho:YAG single crystals were grown by Czochralski technique, and investigated by the X-ray diffraction (XRD) and optical methods. The crystals were cut and polished in order to observe and analyze their cores. It was found that the deviation of the cores formed in the Czochralski grown Ho:YAG single crystals are resulted from non-symmetrical status of thermal insulation around the Iridium crucible.

  20. AN ANALYSIS OF THE DEUTERIUM FRACTIONATION OF STAR-FORMING CORES IN THE PERSEUS MOLECULAR CLOUD

    SciTech Connect

    Friesen, R. K.; Kirk, H. M.; Shirley, Y. L.

    2013-03-01

    We have performed a pointed survey of N{sub 2}D{sup +} 2-1 and N{sub 2}D{sup +} 3-2 emission toward 64 N{sub 2}H{sup +}-bright starless and protostellar cores in the Perseus molecular cloud using the Arizona Radio Observatory Submillimeter Telescope and Kitt Peak 12 m telescope. We find a mean deuterium fractionation in N{sub 2}H{sup +}, R{sub D} = N(N{sub 2}D{sup +})/N(N{sub 2}H{sup +}), of 0.08, with a maximum R{sub D} = 0.2. In detected sources, we find no significant difference in the deuterium fractionation between starless and protostellar cores, nor between cores in clustered or isolated environments. We compare the deuterium fraction in N{sub 2}H{sup +} with parameters linked to advanced core evolution. We only find significant correlations between the deuterium fraction and increased H{sub 2} column density, as well as with increased central core density, for all cores. Toward protostellar sources, we additionally find a significant anticorrelation between R{sub D} and bolometric temperature. We show that the Perseus cores are characterized by low CO depletion values relative to previous studies of star-forming cores, similar to recent results in the Ophiuchus molecular cloud. We suggest that the low average CO depletion is the dominant mechanism that constrains the average deuterium fractionation in the Perseus cores to small values. While current equilibrium and dynamic chemical models are able to reproduce the range of deuterium fractionation values we find in Perseus, reproducing the scatter across the cores requires variation in parameters such as the ionization fraction or the ortho-to-para-H{sub 2} ratio across the cloud, or a range in core evolution timescales.

  1. An Analysis of the Deuterium Fractionation of Star-forming Cores in the Perseus Molecular Cloud

    NASA Astrophysics Data System (ADS)

    Friesen, R. K.; Kirk, H. M.; Shirley, Y. L.

    2013-03-01

    We have performed a pointed survey of N2D+ 2-1 and N2D+ 3-2 emission toward 64 N2H+-bright starless and protostellar cores in the Perseus molecular cloud using the Arizona Radio Observatory Submillimeter Telescope and Kitt Peak 12 m telescope. We find a mean deuterium fractionation in N2H+, RD = N(N2D+)/N(N2H+), of 0.08, with a maximum RD = 0.2. In detected sources, we find no significant difference in the deuterium fractionation between starless and protostellar cores, nor between cores in clustered or isolated environments. We compare the deuterium fraction in N2H+ with parameters linked to advanced core evolution. We only find significant correlations between the deuterium fraction and increased H2 column density, as well as with increased central core density, for all cores. Toward protostellar sources, we additionally find a significant anticorrelation between RD and bolometric temperature. We show that the Perseus cores are characterized by low CO depletion values relative to previous studies of star-forming cores, similar to recent results in the Ophiuchus molecular cloud. We suggest that the low average CO depletion is the dominant mechanism that constrains the average deuterium fractionation in the Perseus cores to small values. While current equilibrium and dynamic chemical models are able to reproduce the range of deuterium fractionation values we find in Perseus, reproducing the scatter across the cores requires variation in parameters such as the ionization fraction or the ortho-to-para-H2 ratio across the cloud, or a range in core evolution timescales.

  2. Modelling of Equilibrium Between Mantle and Core: Refractory, Volatile, and Highly Siderophile Elements

    NASA Technical Reports Server (NTRS)

    Righter, K.; Danielson, L.; Pando, K.; Shofner, G.; Lee, C. -T.

    2013-01-01

    Siderophile elements have been used to constrain conditions of core formation and differentiation for the Earth, Mars and other differentiated bodies [1]. Recent models for the Earth have concluded that the mantle and core did not fully equilibrate and the siderophile element contents of the mantle can only be explained under conditions where the oxygen fugacity changes from low to high during accretion and the mantle and core do not fully equilibrate [2,3]. However these conclusions go against several physical and chemical constraints. First, calculations suggest that even with the composition of accreting material changing from reduced to oxidized over time, the fO2 defined by metal-silicate equilibrium does not change substantially, only by approximately 1 logfO2 unit [4]. An increase of more than 2 logfO2 units in mantle oxidation are required in models of [2,3]. Secondly, calculations also show that metallic impacting material will become deformed and sheared during accretion to a large body, such that it becomes emulsified to a fine scale that allows equilibrium at nearly all conditions except for possibly the length scale for giant impacts [5] (contrary to conclusions of [6]). Using new data for D(Mo) metal/silicate at high pressures, together with updated partitioning expressions for many other elements, we will show that metal-silicate equilibrium across a long span of Earth s accretion history may explain the concentrations of many siderophile elements in Earth's mantle. The modeling includes refractory elements Ni, Co, Mo, and W, as well as highly siderophile elements Au, Pd and Pt, and volatile elements Cd, In, Bi, Sb, Ge and As.

  3. Flow formed by spanwise gaps between roughness elements

    NASA Technical Reports Server (NTRS)

    Logan, E.; Lin, S. H.; Islam, O.

    1985-01-01

    Measurements of the three mean velocity components and the three Reynolds shear stresses were made in the region downstream of gaps between wall-mounted roughness elements of square cross section and high aspect ratio in a thick turbulent boundary layer. The effect of small and large gaps was studied in a wind tunnel at a Reynolds number of 3600, based on obstacle height and free-stream velocity. The small gap produces retardation of the gap flow as with a two-dimensional roughness element, but a definite interaction between gap and wake flows is observed. The interaction is more intense for the large gap than for the small. Both gaps generate a secondary crossflow which moves fluid away from the centerline in the wall region and toward the centerline in the outer (y greater than 1.5H) region.

  4. EARTH’S CORE FORMATION: NEW CONSTRAINTS FROM SIDEROPHILE ELEMENTS PARTITIONING (Invited)

    NASA Astrophysics Data System (ADS)

    Siebert, J.; Corgne, A.; Ryerson, F. J.

    2009-12-01

    The abundances of siderophile elements in the Earth’s mantle are the result of core formation in the early Earth. Many variables are involved in the prediction of metal/silicate siderophile partition coefficients during core segregation: pressure, temperature, oxygen fugacity, silicate and metal compositions. Despite publications of numerous results of metal-silicate experiments, the experimental database and predictive expressions for elements partitioning are hampered by a lack of systematic study to separate and evaluate the effects of each variable. Only a relatively complete experimental database that describes Ni and Co partitioning now exists but is not sufficient to unambiguously decide between the most popular model for core formation with a single stage core-mantle equilibration at the bottom of a deep magma ocean (e.g. Li and Agee, 2001) and more recent alternative models (e.g. Wade and Wood, 2005; Rubie et al., 2007). In this experimental work, systematic study of metal-silicate partitioning is presented for elements normally regarded as moderately siderophile (Mo, As, Ge, W, P, Ni, Co), slightly siderophile (Zn, Ga, Mn, V, Cr) and refractory lithophile (Nb, Ta). New results are obtained for elements whose partitioning behavior is usually poorly constrained and not integrated into any accretion or core formation models. A new piston-cylinder design assembly allows us to present a suite of isobaric partitioning experiments at 3 GPa within a temperature range from 1600 to 2600 C and over a range of relative oxygen fugacity from IW-1.5 to IW-3.5. Silicate melts range from basaltic to peridotite in composition. The individual effect of pressure is also investigated through a combination of piston cylinder and multi anvil isothermal experiments from 0.5 to 18 GPa at 1900 C. Absolute measurements of partitioning coefficients combining EMP and LA-ICPMS analytical methods are provided. Moreover, thermodynamic calculations were performed to assess the effects

  5. Apollo 12 lunar samples: trace element analysis of a core and the uniformity of the regolith.

    PubMed

    Ganapathy, R; Keays, R R; Anders, E

    1970-10-30

    Four core and soil samples from Apollo 12 are enriched in a number of trace elements of meteoritic origin to virtually the same degree as Apollo 11 soil. An average meteoritic influx rate of about 4 x 10(-9) gram per square centimeter per year thus seems to be valid for the entire moon. A sample from a light gray, coarse-grained layer in the core resembles lunar basalts in composition, but is enriched by factors of 10(4) to 10(5) in bismuth and cadmium. PMID:17799707

  6. Properties of dense cores in clustered massive star-forming regions at high angular resolution

    NASA Astrophysics Data System (ADS)

    Sánchez-Monge, Álvaro; Palau, Aina; Fontani, Francesco; Busquet, Gemma; Juárez, Carmen; Estalella, Robert; Tan, Jonathan C.; Sepúlveda, Inma; Ho, Paul T. P.; Zhang, Qizhou; Kurtz, Stan

    2013-07-01

    We aim at characterizing dense cores in the clustered environments associated with intermediate-/high-mass star-forming regions. For this, we present a uniform analysis of Very Large Array NH3 (1,1) and (2,2) observations towards a sample of 15 intermediate-/high-mass star-forming regions, where we identify a total of 73 cores, classify them as protostellar, quiescent starless, or perturbed starless, and derive some physical properties. The average sizes and ammonia column densities of the total sample are ˜0.06 pc and ˜1015 cm-2, respectively, with no significant differences between the starless and protostellar cores, while the linewidth and rotational temperature of quiescent starless cores are smaller, ˜1.0 km s-1 and 16 K, than linewidths and temperatures of protostellar (˜1.8 km s-1 and 21 K), and perturbed starless (˜1.4 km s-1 and 19 K) cores. Such linewidths and temperatures for these quiescent starless cores in the surroundings of intermediate-/high-mass stars are still significantly larger than the typical linewidths and rotational temperatures measured in starless cores of low-mass star-forming regions, implying an important non-thermal component. We confirm at high angular resolutions (spatial scales ˜0.05 pc) the correlations previously found with single-dish telescopes (spatial scales ≳ 0.1 pc) between the linewidth and the rotational temperature of the cores, as well as between the rotational temperature and the linewidth with respect to the bolometric luminosity. In addition, we find a correlation between the temperature of each core and the incident flux from the most massive star in the cluster, suggesting that the large temperatures measured in the starless cores of our sample could be due to heating from the nearby massive star. A simple virial equilibrium analysis seems to suggest a scenario of a self-similar, self-gravitating, turbulent, virialized hierarchy of structures from clumps (˜0.1-10 pc) to cores (˜0.05 pc). A closer

  7. Sol-gel processing to form doped sol-gel monoliths inside hollow core optical fiber and sol-gel core fiber devices made thereby

    NASA Technical Reports Server (NTRS)

    Shaw, Harry C. (Inventor); Ott, Melanie N. (Inventor); Manuel, Michele V. (Inventor)

    2002-01-01

    A process of fabricating a fiber device includes providing a hollow core fiber, and forming a sol-gel material inside the hollow core fiber. The hollow core fiber is preferably an optical fiber, and the sol-gel material is doped with a dopant. Devices made in this manner includes a wide variety of sensors.

  8. Taxonomy for Strengthening the Identification of Core Elements for Evidence-Based Behavioral Interventions for HIV/AIDS Prevention

    ERIC Educational Resources Information Center

    Galbraith, Jennifer S.; Herbst, Jeffrey H.; Whittier, David K.; Jones, Patricia L.; Smith, Bryce D.; Uhl, Gary; Fisher, Holly H.

    2011-01-01

    The concept of core elements was developed to denote characteristics of an intervention, such as activities or delivery methods, presumed to be responsible for the efficacy of evidence-based behavioral interventions (EBIs) for HIV/AIDS prevention. This paper describes the development of a taxonomy of core elements based on a literature review of…

  9. Core-level binding-energy shifts for the metallic elements

    NASA Astrophysics Data System (ADS)

    Johansson, Börje; Mårtensson, Nils

    1980-05-01

    A general treatment of core-level binding-energy shifts in metals relative to the free atom is introduced and applied to all elemental metals in the Periodic Table. The crucial ingredients of the theoretical description are (a) the assumption of a fully screened final state in the metallic case and (b) the (Z+1) approximation for the screening valence charge distribution around the core-ionized site. This core-ionized site is, furthermore, treated as an impurity in an otherwise perfect metal. The combination of the complete screening picture and the (Z+1) approximation makes it possible to introduce a Born-Haber cycle which connects the initial state with the final state of the core-ionization process. From this cycle it becomes evident that the main contributions to the core-level shift are the cohesive energy difference between the (Z+1) and Z metal and an appropriate ionization energy of the (Z+1) atom (usually the first ionization potential). The appearance of the ionization potential in the shift originates from the assumption of a charge-neutral final state, while the contribution from the cohesive energies essentially describes the change of bonding properties between the initial and final state of the site. The calculated shifts show very good agreement with available experimental values (at present, for 19 elements). For the other elements we have made an effort to combine experimental ionization potentials with theoretical calculations in order to obtain accurate estimates of some of the atomic-core-level binding energies. Such energies together with measured metallic binding energies give "pseudoexperimental" shifts for many elements. Our calculated core-level shifts agree exceedingly well also with these data. For some of the transition elements the core-level shift shows a deviating behavior in comparison with that of neighboring elements. This is shown to be due to a difference in the atomic ground-state configuration, such as, for example, d5s in

  10. Nondestructive examination of 51 fuel and reflector elements from Fort St. Vrain Core Segment 1

    SciTech Connect

    Miller, C.M.; Saurwein, J.J.

    1980-12-01

    Fifty-one fuel and reflector elements irradiated in core segment 1 of the Fort St. Vrain High-Temperature Gas-Cooled Reactor (HTGR) were inspected dimensionally and visually in the Hot Service Facility at Fort St. Vrain in July 1979. Time- and volume-averaged graphite temperatures for the examined fuel elements ranged from approx. 400/sup 0/ to 750/sup 0/C. Fast neutron fluences varied from approx. 0.3 x 10/sup 25/ n/m/sup 2/ to 1.0 x 10/sup 25/ n/m/sup 2/ (E > 29 fJ)/sub HTGR/. Nearly all of the examined elements shrank in both axial and radial dimensions. The measured data were compared with strain and bow predictions obtained from SURVEY/STRESS, a computer code that employs viscoelastic beam theory to calculate stresses and deformations in HTGR fuel elements.

  11. Solid dispersions in the form of electrospun core-sheath nanofibers

    PubMed Central

    Yu, Deng-Guang; Zhu, Li-Min; Branford-White, Christopher J; Yang, Jun-He; Wang, Xia; Li, Ying; Qian, Wei

    2011-01-01

    Background The objective of this investigation was to develop a new type of solid dispersion in the form of core-sheath nanofibers using coaxial electrospinning for poorly water-soluble drugs. Different functional ingredients can be placed in various parts of core-sheath nanofibers to improve synergistically the dissolution and permeation properties of encapsulated drugs and to enable drugs to exert their actions. Methods Using acyclovir as a model drug, polyvinylpyrrolidone as the hydrophilic filament-forming polymer matrix, sodium dodecyl sulfate as a transmembrane enhancer, and sucralose as a sweetener, core-sheath nanofibers were successfully prepared, with the sheath part consisting of polyvinylpyrrolidone, sodium dodecyl sulfate, and sucralose, and the core part composed of polyvinylpyrrolidone and acyclovir. Results The core-sheath nanofibers had an average diameter of 410 ± 94 nm with a uniform structure and smooth surface. Differential scanning calorimetry and x-ray diffraction results demonstrated that acyclovir, sodium dodecyl sulfate, and sucralose were well distributed in the polyvinylpyrrolidone matrix in an amorphous state due to favoring of second-order interactions. In vitro dissolution and permeation studies showed that the core-sheath nanofiber solid dispersions could rapidly release acyclovir within one minute, with an over six-fold increased permeation rate across the sublingual mucosa compared with that of crude acyclovir particles. Conclusion The study reported here provides an example of the systematic design, preparation, characterization, and application of a novel type of solid dispersion consisting of multiple components and structural characteristics. PMID:22228995

  12. OUTFLOW, INFALL, AND PROTOSTARS IN THE STAR-FORMING CORE W3-SE

    SciTech Connect

    Zhu Lei; Zhao Junhui; Wright, M. C. H. E-mail: jzhao@cfa.harvard.edu

    2011-10-20

    We report new results on outflow and infall in the star-forming cores W3-SE SMA-1 and SMA-2 based on analysis of {approx}2.''5 resolution observations of the molecular lines HCN(3-2), HCO{sup +}(3-2), N{sub 2}H{sup +}(3-2), and CH{sub 3}OH(5{sub 2,3}-4{sub 1,3}) with the Submillimeter Array (SMA). A high-velocity bipolar outflow originating from the protostellar core SMA-1 was observed in the HCN(3-2) line, with a projected outflow axis at a position angle of 48{sup 0}. The detection of the outflow is confirmed from other molecular lines. An inverse P-Cygni profile in the HCN(3-2) line toward SMA-1 suggests that at least one of the double cores accretes matter from the molecular core. A filamentary structure in the molecular gas surrounds SMA-1 and SMA-2. Based on the SMA observations, our analysis suggests that the double pre-stellar cores SMA-1 and SMA-2 result from fragmentation in the collapsing massive molecular core W3-SE, and it is likely that they are forming intermediate- to high-mass stars which will be new members of a star cluster in the W3-SE region.

  13. Analysis of Moderately Siderophile Elements in Angrites: Implications for Core Formation of the Angrite Parent Body

    NASA Technical Reports Server (NTRS)

    Righter, K.; Shirai, N.; Irving, A.J.

    2009-01-01

    Angrites are an enigmatic group of achondrites, that constitute the largest group of basalts not affiliated with the Moon, Mars or Vesta (HEDs). Chemically, angrites are exceptionally refractory element- enriched (e.g., Al, Ca) and volatile element-depleted (e.g., Na and K) achondrites. Highly volatile siderophile and chalcophile elements (Zn, Ge and Se) may be less depleted than alkalis and Ga taken to imply a fractionation of plagiophile elements. Core formation on the angrite parent body (APB) is not well understood due to the dearth of moderately siderophile element (Ga, Ge, Mo, Sb, W) data for angrites, with the exception of Ni and Co [2]. In particular, there are no data for Mo abundances of angrites, while Sb and W abundances are reported for only 3 angrites, and have not always been determined on the same sample. The recent increase in angrite numbers (13) has greatly increased our knowledge of the compositional diversity of the angrite parent body (APB). In this study, we report new Co, Ni, Ga, Mo, Sb and W abundances for angrites by laser ablation inductively coupled plasma mass spectrometry (ICP-MS) in order to place constraints on core formation of the APB.

  14. Finite element analysis of the dynamic behavior of a laminated windscreen with frequency dependent viscoelastic core.

    PubMed

    Bouayed, Kaïss; Hamdi, Mohamed-Ali

    2012-08-01

    This paper presents numerical and experimental validation of results obtained by a shell finite element, which has been developed for modeling of the dynamic behavior of sandwich multilayered structures with a viscoelastic core. The proposed shell finite element is very easy to implement in existing finite element solvers, since it uses only the displacements as degrees of freedom at external faces and at inter-layer interfaces. The displacement field is linearly interpolated in the thickness direction of each layer, and analytical integration is made in the thickness direction in order to avoid meshing of each sandwich layer by solid elements. Only the two dimensional mid-surface of reference is meshed, facilitating the mesh generation task. A simplified modal approach using a real modal basis is also proposed to efficiently calculate the dynamic response of the sandwich structure. The proposed method reduces the memory size and computing time and takes into account the frequency-dependence of the polymer core mechanical properties. Results obtained by the proposed element in conjunction with the simplified modal method have been numerically and experimentally validated by comparison to results obtained by commercial software codes (MSC/NASTRAN and ESI/RAYON-VTM), and to measurements done on automobile windscreens. PMID:22894198

  15. Reactor physics analyses of the advanced neutron source three-element core

    SciTech Connect

    Gehin, J.C.

    1995-08-01

    A reactor physics analysis was performed for the Advanced Neutron Source reactor with a three-element core configuration. The analysis was performed with a two-dimensional r-z 20-energy-group finite-difference diffusion theory model of the 17-d fuel cycle. The model included equivalent r-z geometry representations of the central control rods, the irradiation and production targets, and reflector components. Calculated quantities include fuel cycle parameters, fuel element power distributions, unperturbed neutron fluxes in the reflector and target regions, reactivity perturbations, and neutron kinetics parameters.

  16. Tunable photonic elements at the surface of an optical fiber with piezoelectric core

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. V.; Sumetsky, M.

    2016-05-01

    Tunable photonic elements at the surface of an optical fiber with piezoelectric core are proposed and analyzed theoretically. These elements are based on whispering gallery modes whose propagation along the fiber is fully controlled by nanoscale variation of the effective fiber radius, which can be tuned by means of a piezoelectric actuator embedded into the core. The developed theory allows one to express the introduced effective radius variation through the shape of the actuator and the voltage applied to it. In particular, the design of a miniature tunable optical delay line and a miniature tunable dispersion compensator is presented. The potential application of the suggested model to the design of a miniature optical buffer is discussed.

  17. Tunable photonic elements at the surface of an optical fiber with piezoelectric core.

    PubMed

    Dmitriev, A V; Sumetsky, M

    2016-05-15

    Tunable photonic elements at the surface of an optical fiber with piezoelectric core are proposed and analyzed theoretically. These elements are based on whispering gallery modes whose propagation along the fiber is fully controlled by nanoscale variation of the effective fiber radius, which can be tuned by means of a piezoelectric actuator embedded into the core. The developed theory allows one to express the introduced effective radius variation through the shape of the actuator and the voltage applied to it. In particular, the designs of a miniature tunable optical delay line and a miniature tunable dispersion compensator are presented. The potential application of the suggested model to the design of a miniature optical buffer is also discussed. PMID:27176953

  18. Reassessment of True Core Collapse Differential Pressure Values for Filter Elements in Safety Critical Environments - 13076

    SciTech Connect

    Swain, Adam

    2013-07-01

    As the areas of application for diverse filter types increases, the mechanics and material sciences associated with the hardware and its relationship with more and more arduous process environments becomes critical to the successful and reliable operation of the filtration equipment. Where the filter is the last safe barrier between the process and the life environment, structural integrity and reliability is paramount in both the validation and the ethical acceptability of the designed equipment. Core collapse is a key factor influencing filter element selection, and is an extremely complex issue with a number of variables and failure mechanisms. It is becoming clear that the theory behind core collapse calculations is not always supported with real tested data. In exploring this issue we have found that the calculation method is not always reflective of the true as tested collapse value, with the calculated values being typically in excess or even an order of magnitude higher than the tested values. The above claim is supported by a case study performed by the author, which disproves most of what was previously understood to be true. This paper also aims to explore the various failure mechanisms of different configurations of filter core, comparing calculated collapse values against real tested values, with a view to understanding a method of calculating their true collapse value. As the technology is advancing, and filter elements are being used in higher temperature, higher pressure, more radioactive and more chemically aggressive environments, confidence in core collapse values and data is crucial. (authors)

  19. Redistribution of Core-forming Melt During Shear Deformation of Partially Molten Peridotite

    NASA Technical Reports Server (NTRS)

    Hustoft, J. W.; Kohlstedt, D. L.

    2002-01-01

    To investigate the role of deformation on the distribution of core-forming melt in a partially molten peridotite, samples of olivine-basalt-iron sulfide were sheared to large strains. Dramatic redistribution of sulfide and silicate melts occur during deformation. Additional information is contained in the original extended abstract.

  20. Major and trace elements in 35 lake and reservoir sediment cores from across the United States, 1994-2001

    USGS Publications Warehouse

    Van Metre, Peter C.; Mahler, Barbara J.; Wilson, Jennifer T.; Callender, Edward

    2006-01-01

    This report presents data on major and trace element concentrations in sediment cores collected from 35 lakes and reservoirs during 1994-2001. The lakes and reservoirs are located in or near 18 major urban areas across the United States and provide a geographically diverse coverage of urban land use for the country as well as some reference settings. Vertical intervals of the cores were analyzed for eight major elements and eight trace elements.

  1. The Human Disease-Associated Aβ Amyloid Core Sequence Forms Functional Amyloids in a Fungal Adhesin

    PubMed Central

    Rameau, Rachele D.; Jackson, Desmond N.; Beaussart, Audrey; Dufrêne, Yves F.

    2016-01-01

    ABSTRACT There is increasing evidence that many amyloids in living cells have physiological functions. On the surfaces of fungal cells, amyloid core sequences in adhesins can aggregate into 100- to 1,000-nm-wide patches to form high-avidity adhesion nanodomains on the cell surface. The nanodomains form through interactions that have amyloid-like properties: binding of amyloid dyes, perturbation by antiamyloid agents, and interaction with homologous sequences. To test whether these functional interactions are mediated by typical amyloid interactions, we substituted an amyloid core sequence, LVFFA, from human Aβ protein for the native sequence IVIVA in the 1,419-residue Candida albicans adhesin Als5p. The chimeric protein formed cell surface nanodomains and mediated cellular aggregation. The native sequence and chimeric adhesins responded similarly to the amyloid dye thioflavin T and to amyloid perturbants. However, unlike the native protein, the nanodomains formed by the chimeric protein were not force activated and formed less-robust aggregates under flow. These results showed the similarity of amyloid interactions in the amyloid core sequences of native Als5p and Aβ, but they also highlighted emergent properties of the native sequence. Also, a peptide composed of the Aβ amyloid sequence flanked by amino acids from the adhesin formed two-dimensional sheets with sizes similar to the cell surface patches of the adhesins. These results inform an initial model for the structure of fungal cell surface amyloid nanodomains. PMID:26758179

  2. Optical elements formed by compressed gases: Analysis and potential applications

    NASA Technical Reports Server (NTRS)

    Howes, W. L.

    1986-01-01

    Spherical, cylindrical, and conical shock waves are optically analogous to gas lenses. The geometrical optics of these shock configurations are analyzed as they pertain to flow visualization instruments, particularly the rainbow schlieren apparatus and single-pass interferometers. It is proposed that a lens or mirror formed by gas compressed between plastic sheets has potential as a fluid visualization test object; as the objective mirror in a very large space-based telescope, communication antenna, or energy collector; as the objective mirror in inexpensive commercial telescopes; and as a component in fluid visualization apparatuses.

  3. Surveying DNA Elements within Functional Genes of Heterocyst-Forming Cyanobacteria

    PubMed Central

    Hilton, Jason A.; Meeks, John C.; Zehr, Jonathan P.

    2016-01-01

    Some cyanobacteria are capable of differentiating a variety of cell types in response to environmental factors. For instance, in low nitrogen conditions, some cyanobacteria form heterocysts, which are specialized for N2 fixation. Many heterocyst-forming cyanobacteria have DNA elements interrupting key N2 fixation genes, elements that are excised during heterocyst differentiation. While the mechanism for the excision of the element has been well-studied, many questions remain regarding the introduction of the elements into the cyanobacterial lineage and whether they have been retained ever since or have been lost and reintroduced. To examine the evolutionary relationships and possible function of DNA sequences that interrupt genes of heterocyst-forming cyanobacteria, we identified and compared 101 interruption element sequences within genes from 38 heterocyst-forming cyanobacterial genomes. The interruption element lengths ranged from about 1 kb (the minimum able to encode the recombinase responsible for element excision), up to nearly 1 Mb. The recombinase gene sequences served as genetic markers that were common across the interruption elements and were used to track element evolution. Elements were found that interrupted 22 different orthologs, only five of which had been previously observed to be interrupted by an element. Most of the newly identified interrupted orthologs encode proteins that have been shown to have heterocyst-specific activity. However, the presence of interruption elements within genes with no known role in N2 fixation, as well as in three non-heterocyst-forming cyanobacteria, indicates that the processes that trigger the excision of elements may not be limited to heterocyst development or that the elements move randomly within genomes. This comprehensive analysis provides the framework to study the history and behavior of these unique sequences, and offers new insight regarding the frequency and persistence of interruption elements in

  4. Highly siderophile elements in Earth's mantle as a clock for the Moon-forming impact.

    PubMed

    Jacobson, Seth A; Morbidelli, Alessandro; Raymond, Sean N; O'Brien, David P; Walsh, Kevin J; Rubie, David C

    2014-04-01

    According to the generally accepted scenario, the last giant impact on Earth formed the Moon and initiated the final phase of core formation by melting Earth's mantle. A key goal of geochemistry is to date this event, but different ages have been proposed. Some argue for an early Moon-forming event, approximately 30 million years (Myr) after the condensation of the first solids in the Solar System, whereas others claim a date later than 50 Myr (and possibly as late as around 100 Myr) after condensation. Here we show that a Moon-forming event at 40 Myr after condensation, or earlier, is ruled out at a 99.9 per cent confidence level. We use a large number of N-body simulations to demonstrate a relationship between the time of the last giant impact on an Earth-like planet and the amount of mass subsequently added during the era known as Late Accretion. As the last giant impact is delayed, the late-accreted mass decreases in a predictable fashion. This relationship exists within both the classical scenario and the Grand Tack scenario of terrestrial planet formation, and holds across a wide range of disk conditions. The concentration of highly siderophile elements (HSEs) in Earth's mantle constrains the mass of chondritic material added to Earth during Late Accretion. Using HSE abundance measurements, we determine a Moon-formation age of 95 ± 32 Myr after condensation. The possibility exists that some late projectiles were differentiated and left an incomplete HSE record in Earth's mantle. Even in this case, various isotopic constraints strongly suggest that the late-accreted mass did not exceed 1 per cent of Earth's mass, and so the HSE clock still robustly limits the timing of the Moon-forming event to significantly later than 40 Myr after condensation. PMID:24695310

  5. Highly siderophile elements in Earth's mantle as a clock for the Moon-forming impact

    NASA Astrophysics Data System (ADS)

    Jacobson, Seth A.; Morbidelli, Alessandro; Raymond, Sean N.; O'Brien, David P.; Walsh, Kevin J.; Rubie, David C.

    2014-04-01

    According to the generally accepted scenario, the last giant impact on Earth formed the Moon and initiated the final phase of core formation by melting Earth's mantle. A key goal of geochemistry is to date this event, but different ages have been proposed. Some argue for an early Moon-forming event, approximately 30 million years (Myr) after the condensation of the first solids in the Solar System, whereas others claim a date later than 50 Myr (and possibly as late as around 100 Myr) after condensation. Here we show that a Moon-forming event at 40 Myr after condensation, or earlier, is ruled out at a 99.9 per cent confidence level. We use a large number of N-body simulations to demonstrate a relationship between the time of the last giant impact on an Earth-like planet and the amount of mass subsequently added during the era known as Late Accretion. As the last giant impact is delayed, the late-accreted mass decreases in a predictable fashion. This relationship exists within both the classical scenario and the Grand Tack scenario of terrestrial planet formation, and holds across a wide range of disk conditions. The concentration of highly siderophile elements (HSEs) in Earth's mantle constrains the mass of chondritic material added to Earth during Late Accretion. Using HSE abundance measurements, we determine a Moon-formation age of 95 +/- 32 Myr after condensation. The possibility exists that some late projectiles were differentiated and left an incomplete HSE record in Earth's mantle. Even in this case, various isotopic constraints strongly suggest that the late-accreted mass did not exceed 1 per cent of Earth's mass, and so the HSE clock still robustly limits the timing of the Moon-forming event to significantly later than 40 Myr after condensation.

  6. An interconnected network of core-forming melts produced by shear deformation

    PubMed

    Bruhn; Groebner; Kohlstedt

    2000-02-24

    The formation mechanism of terrestrial planetary cores is still poorly understood, and has been the subject of numerous experimental studies. Several mechanisms have been proposed by which metal--mainly iron with some nickel--could have been extracted from a silicate mantle to form the core. Most recent models involve gravitational sinking of molten metal or metal sulphide through a partially or fully molten mantle that is often referred to as a 'magma ocean'. Alternative models invoke percolation of molten metal along an interconnected network (that is, porous flow) through a solid silicate matrix. But experimental studies performed at high pressures have shown that, under hydrostatic conditions, these melts do not form an interconnected network, leading to the widespread assumption that formation of metallic cores requires a magma ocean. In contrast, here we present experiments which demonstrate that shear deformation to large strains can interconnect a significant fraction of initially isolated pockets of metal and metal sulphide melts in a solid matrix of polycrystalline olivine. Therefore, in a dynamic (non-hydrostatic) environment, percolation remains a viable mechanism for the segregation and migration of core-forming melts in a solid silicate mantle. PMID:10706283

  7. Elastic stability of superplastically formed/diffusion-bonded orthogonally corrugated core sandwich plates

    NASA Technical Reports Server (NTRS)

    Ko, W. L.

    1980-01-01

    The paper concerns the elastic buckling behavior of a newly developed superplastically formed/diffusion-bonded (SPF/DB) orthogonally corrugated core sandwich plate. Uniaxial buckling loads were calculated for this type of sandwich plate with simply supported edges by using orthotropic sandwich plate theory. The buckling behavior of this sandwich plate was then compared with that of an SPF/DB unidirectionally corrugated core sandwich plate under conditions of equal structural density. It was found that the buckling load for the former was considerably higher than that of the latter.

  8. Siderophile Element Depletion in the Angrite Parent Body (APB) Mantle: Due to Core Formation?

    NASA Technical Reports Server (NTRS)

    Righter, K.

    2008-01-01

    The origin of angrites has evaded scientists due in part to unusual mineralogy, oxidized character, and small numbers of samples. Increased interest in the origin of angrites has stemmed from the recovery of approximately 10 new angrites in the past decade. These new samples have allowed meteoriticists to recognize that angrites are compositionally diverse, old, and record very early differentiation. Also, a magma ocean has been proposed to have been involved in APB early differentiation, but this remains untested for siderophile elements which are commonly cited as one of the main lines of evidence for magma oceans on the early Earth, Moon, Mars and eucrite parent body (e.g., [6]). And recent suggestions that angrites may or may not be from Mercury have also peaked interest in these achondrites. Given all of this background, a detailed understanding of the early differentiation process is desired. Previous efforts at examining siderophile element (SE) concentrations with respect to core formation processes in the APB have not resulted in any definite conclusions regarding segregation of a metallic core. The goal of this study is to summarize what is known about SE concentrations in the suite, estimate depletions of SE compared to chondrites, and apply metal/silicate experimental partition coefficients to assess whether the APB had a core.

  9. Mobile elements drive recombination hotspots in the core genome of Staphylococcus aureus

    PubMed Central

    Everitt, Richard G.; Didelot, Xavier; Batty, Elizabeth M.; Miller, Ruth R; Knox, Kyle; Young, Bernadette C.; Bowden, Rory; Auton, Adam; Votintseva, Antonina; Larner-Svensson, Hanna; Charlesworth, Jane; Golubchik, Tanya; Ip, Camilla L. C.; Godwin, Heather; Fung, Rowena; Peto, Tim E. A.; Walker, A. Sarah; Crook, Derrick W.; Wilson, Daniel J.

    2014-01-01

    Horizontal gene transfer is an important driver of bacterial evolution, but genetic exchange in the core genome of clonal species, including the major pathogen Staphylococcus aureus, is incompletely understood. Here we reveal widespread homologous recombination in S. aureus at the species level, in contrast to its near-complete absence between closely related strains. We discover a patchwork of hotspots and coldspots at fine scales falling against a backdrop of broad-scale trends in rate variation. Over megabases, homoplasy rates fluctuate 1.9-fold, peaking towards the origin-of-replication. Over kilobases, we find core recombination hotspots of up to 2.5-fold enrichment situated near fault lines in the genome associated with mobile elements. The strongest hotspots include regions flanking conjugative transposon ICE6013, the staphylococcal cassette chromosome (SCC) and genomic island νSaα. Mobile element-driven core genome transfer represents an opportunity for adaptation and challenges our understanding of the recombination landscape in predominantly clonal pathogens, with important implications for genotype–phenotype mapping. PMID:24853639

  10. Finite Element Technology In Forming Simulations - Theoretical Aspects And Practical Applications Of A New Solid-Shell Element

    SciTech Connect

    Schwarze, M.; Reese, S.

    2007-05-17

    Finite element simulations of sheet metal forming processes are highly non-linear problems. The non-linearity arises not only from the kinematical relations and the material formulation, furthermore the contact between workpiece and the forming tools leads to an increased number of iterations within the Newton-Raphson scheme. This fact puts high demands on the robustness of finite element formulations. For this reason we study the enhanced assumed strain (EAS) concept as proposed in [1]. The goal is to improve the robustness of the solid-shell formulation in deep drawing simulations.

  11. In-line fiber-optic etalon formed by hollow-core photonic crystal fiber.

    PubMed

    Rao, Y J; Zhu, T; Yang, X C; Duan, D W

    2007-09-15

    A novel fiber-optic in-line etalon formed by splicing a section of hollow-core photonic crystal fiber (HCPCF) in between two single-mode fibers is proposed and demonstrated, for the first time to our knowledge. Such a HCPCF-based etalon acts as an excellent optical waveguide to form a Fabry-Perot interferometer and hence allows the cavity length to be as long as several centimeters with good visibility as the transmission loss of the HCPCF is much smaller than that of a hollow core fiber; this offers great potential to generate a practical dense fiber-optic sensor network with spatial frequency division-multiplexing. This novel etalon is demonstrated for strain measurement, and the experimental results show that a good visibility of 0.3 and a strain accuracy of better than +/- 5 microepsilon are achieved. PMID:17873927

  12. Carbon Solution in Core-Forming Magma Ocean Conditions: Implications for the Origin and Distribution of Terrestrial Carbon

    NASA Astrophysics Data System (ADS)

    Dasgupta, R.; Chi, H.; Walker, D.; Shimizu, N.; Buono, A. S.

    2012-12-01

    The origin of bulk silicate Earth carbon inventory is poorly known and the fate of the element during the early Earth differentiation and core formation is a missing link in the evolution of the terrestrial carbon cycle. Here we present high pressure-temperature experiments that simulate metal-silicate equilibria in a shallow magma ocean. Experiments were performed at 1-5 GPa, 1600-2100 °C on mixtures of synthetic or natural silicates (tholeiitic basalt/ alkali basalt/ komatiite/ fertile peridotite) and Fe-Ni-C±Co±S contained in graphite or MgO capsules. All the experiments produced immiscible Fe-rich metallic and silicate melts at oxygen fugacity (fO2) between ~IW-1.5 and IW-1.9. Carbon and hydrogen concentrations of basaltic glasses and non-glassy quenched silicate melts were determined using secondary ionization mass spectrometry (SIMS) and speciation of dissolved C-O-H volatiles in silicate glasses was constrained using Raman spectroscopy. Carbon contents of metallic melts were determined using both electron microprobe and SIMS. Our experiments indicate that at core-forming, reduced conditions, carbon in mafic-ultramafic magmas dissolves primarily as various hydrogenated species and the total carbon storage capacity, although is significantly higher than solubility of CO2 under similar conditions, remains low (<500 ppm). The total carbon content in our reduced melts at graphite saturation increases with increasing melt depolymerization (NBO/T), consistent with recent spectroscopic studies [1], and modestly with increasing hydration. Carbon behaves as a metal loving element during core-mantle separation and metal/silicate carbon partition coefficient, DC varies between ~3500 and ≥150 and increases with increasing pressure and decreases with increasing temperature and melt NBO/T. Extrapolation of our data to the plausible conditions of core-mantle equilibration suggest that if only a trace amount of carbon (~730 ppm C; [2]) was available during early Earth

  13. Global shielding analysis of the 2-element ANS core and reflector with photoneutrons

    SciTech Connect

    Bucholz, J.A.

    1996-04-01

    This paper describes the initial global 2-D shielding analyses for the 2-element, heavy-water cooled and reflected Advanced Neutron Source reactor which was to have been built in Oak Ridge, Tennessee. The portion of the system analyzed encompassed the highly enriched core, the 1.5-m-thick heavy-water reflector, the aluminum reflector vessel, and the first 0.2 m of light water beyond the reflector vessel. While some results are presented, this paper focuses primarily on the lessons learned during the analysis of this rather unique system.

  14. Recent Increase in Elemental Carbon Concentration and Deposition in a Svalbard Ice Core

    NASA Astrophysics Data System (ADS)

    Ruppel, M.; Isaksson, E. D.; Ström, J.; Svensson, J.; Beaudon, E.; Korhola, A.

    2013-12-01

    Black carbon (BC) is an aerosol produced by incomplete combustion of biomass and fossil fuels. Due to its strong light absorption it warms the atmosphere. Climate effects of BC are intensified in the Arctic where its deposition on snow and ice decreases surface albedo, causing earlier spring melt and associated feedbacks. Despite the significant role of BC in Arctic climate warming, there is little information on its concentrations and climate effects in the Arctic in time periods preceding direct observational data. Here we present first results on BC (here operationally defined as elemental carbon (EC)) concentrations and deposition on a Svalbard (European Arctic) glacier (Holtedahlfonna) from 1700 to 2004. The inner part of a 125 m deep ice core was melted, filtered and analyzed for apparent elemental carbon using a thermal optical method. EC concentrations (μg L-1) and the deposition (mg m-2 yr-1) were generally low in the pre-industrial era. Concentrations peaked around 1910 and again around 1950, whereas only the 1910 peak was recorded in the EC deposition, followed by decreasing deposition values. Strikingly, both EC concentration and deposition started to increase rapidly from the 1970s until 2004. This rise is not seen in any thus far published European or Arctic ice core, and it seems to contradict atmospheric BC measurements from the Arctic which indicate decreasing atmospheric BC concentrations since the beginning of the observations at the end of 1980s. However, the magnitude of the measured concentrations is in accordance with previous ice core EC measurements from the European Alps and a BC concentration and deposition peak around 1910 has also been recorded in Greenland ice cores. Work is continuing to disentangle the cause of the increasing EC values in the recent decades suggested by the present ice core. Contribution from any local sources has been ruled out. Back trajectory modeling is carried out to establish the EC source areas. The present

  15. Forming Giant Planet Cores by Pebble Accretion -- Why Slow and Steady wins the Race

    NASA Astrophysics Data System (ADS)

    Kretke, Katherine A.; Levison, Harold F.

    2014-05-01

    In recent years there has been a radical new solution proposed to solve the problem of giant planet core formation. "Pebbles", particles ranging from centimeters to meters in size, have been shown to accrete extremely efficiently due to aerodynamic drag. Large capture cross-sections combined with fast pebble drift rates can allow a single planetesimal to grow from Ceres size to 10s of Earth masses well within the lifetime of gaseous circumstellar disks. However, at large sizes, the the capture-cross section of pebbles goes with the Hill sphere, forcing pebble accretion to becomes a fundamentally "oligarchic-like" process. This makes it difficult to form a few giant planet cores; instead a more generic result is many 10s to 100s of competing oligarchs. In this work, we present a way to get around this oligarchic dilemma If pebbles are assumed to form slowly over a long period of time, then the planetesimal growth rates are slow enough for the planetesimals to dynamically excite each other. As the larger planetisimals/proto-planets stir their smaller companions, these smaller bodies are excited to such a degree that they spend only a small fraction of their orbits embedded in the cooler pebble disk. This allows the larger bodies to starve their neighbors and maintain a relative runaway growth rate to high mass, effectively forming the cores of giant planets.

  16. An Interconnected Network of Core-Forming Melts Produced by Shear Deformation

    NASA Technical Reports Server (NTRS)

    Bruhn, D.; Groebner, N.; Kohlstedt, D. L.

    2000-01-01

    The formation mechanism of terrestrial planetary is still poorly understood, and has been the subject of numerous experimental studies. Several mechanisms have been proposed by which metal-mainly iron with some nickel-could have been extracted from a silicate mantle to form the core. Most recent models involve gravitational sinking of molten metal or metal sulphide through a partially or fully molten mantle that is often referred to as a'magma ocean. Alternative models invoke percolation of molten metal along an interconnected network (that is, porous flow) through a solid silicate matrix. But experimental studies performed at high pressures have shown that, under hydrostatic conditions, these melts do not form an interconnected network, leading to the widespread assumption that formation of metallic cores requires a magma ocean. In contrast, here we present experiments which demonstrate that shear deformation to large strains can interconnect a significant fraction of initially isolated pockets of metal and metal sulphide melts in a solid matrix of polycrystalline olivine. Therefore, in a dynamic (nonhydrostatic) environment, percolation remains a viable mechanism for the segregation and migration of core-forming melts in a solid silicate mantle.

  17. Finite element numerical integration for first order approximations on multi- and many-core architectures

    NASA Astrophysics Data System (ADS)

    Banaś, Krzysztof; Krużel, Filip; Bielański, Jan

    2016-06-01

    The paper presents investigations on the implementation and performance of the finite element numerical integration algorithm for first order approximations and three processor architectures, popular in scientific computing, classical CPU, Intel Xeon Phi and NVIDIA Kepler GPU. A unifying programming model and portable OpenCL implementation is considered for all architectures. Variations of the algorithm due to different problems solved and different element types are investigated and several optimizations aimed at proper optimization and mapping of the algorithm to computer architectures are demonstrated. Performance models of execution are developed for different processors and tested in practical experiments. The results show the varying levels of performance for different architectures, but indicate that the algorithm can be effectively ported to all of them. The general conclusion is that the finite element numerical integration can achieve sufficient performance on different multi- and many-core architectures and should not become a performance bottleneck for finite element simulation codes. Specific observations lead to practical advises on how to optimize the kernels and what performance can be expected for the tested architectures.

  18. Modelling the core convection using finite element and finite difference methods

    NASA Astrophysics Data System (ADS)

    Chan, K. H.; Li, Ligang; Liao, Xinhao

    2006-08-01

    Applications of both parallel finite element and finite difference methods to thermal convection in a rotating spherical shell modelling the fluid dynamics of the Earth's outer core are presented. The numerical schemes are verified by reproducing the convection benchmark test by Christensen et al. [Christensen, U.R., Aubert, J., Cardin, P., Dormy, E., Gibbons, S., Glatzmaier, G.A., Grote, E., Honkura, Y., Jones, C., Kono, M., Matsushima, M., Sakuraba, A., Takahashi, F., Tilgner, A., Wilcht, J., Zhang, K., 2001. A numerical dynamo benchmark. Phys. Earth Planet. Interiors 128, 25-34.]. Both global average and local characteristics agree satisfactorily with the benchmark solution. With the element-by-element (EBE) parallelization technique, the finite element code demonstrates nearly optimal linear scalability in computational speed. The finite difference code is also efficient and scalable by utilizing a parallel library Aztec [Tuminaro, R.S., Heroux, M., Hutchinson, S.A., Shadid, J.N., 1999. Official AZTEC User's Guide: Version 2.1.].

  19. Deuterium Burning in Massive Giant Planets and Low-mass Brown Dwarfs Formed by Core-nucleated Accretion

    NASA Astrophysics Data System (ADS)

    Bodenheimer, Peter; D'Angelo, Gennaro; Lissauer, Jack J.; Fortney, Jonathan J.; Saumon, Didier

    2013-06-01

    Using detailed numerical simulations, we study the formation of bodies near the deuterium-burning limit according to the core-nucleated giant planet accretion scenario. The objects, with heavy-element cores in the range 5-30 M ⊕, are assumed to accrete gas up to final masses of 10-15 Jupiter masses (M Jup). After the formation process, which lasts 1-5 Myr and which ends with a "cold-start," low-entropy configuration, the bodies evolve at constant mass up to an age of several Gyr. Deuterium burning via proton capture is included in the calculation, and we determined the mass, M 50, above which more than 50% of the initial deuterium is burned. This often-quoted borderline between giant planets and brown dwarfs is found to depend only slightly on parameters, such as core mass, stellar mass, formation location, solid surface density in the protoplanetary disk, disk viscosity, and dust opacity. The values for M 50 fall in the range 11.6-13.6 M Jup, in agreement with previous determinations that do not take the formation process into account. For a given opacity law during the formation process, objects with higher core masses form more quickly. The result is higher entropy in the envelope at the completion of accretion, yielding lower values of M 50. For masses above M 50, during the deuterium-burning phase, objects expand and increase in luminosity by one to three orders of magnitude. Evolutionary tracks in the luminosity versus time diagram are compared with the observed position of the companion to Beta Pictoris.

  20. [Study on trace elements of lake sediments by ICP-AES and XRF core scanning].

    PubMed

    Cheng, Ai-Ying; Yu, Jun-Qing; Gao, Chun-Liang; Zhang, Li-Sha; He, Xian-Hu

    2013-07-01

    It is the first time to study sediment of Toson lake in Qaidam Basin. Trace elements including Cd, Cr, Cu, Zn and Pb in lake sediment were measured by ICP-AES method, studied and optimized from different resolution methods respectively, and finally determined a optimum pretreatment system for sediment of Toson lake, namely, HCl-HNO3-HF-HClO4-H2O2 system in the proportions of 5 : 5 : 5 : 1 : 1 was determined. At the same time, the data measured by XRF core scanning were compared, the use of moisture content correction method was analyzed, and the influence of the moisture content on the scanning method was discussed. The results showed that, compared to the background value, the contents of Cd and Zn were a little higher, the content of Cr, Cu and Pb was within the background value limits. XRF core scanning was controlled by sediment elements as well as water content in sediment to some extent. The results by the two methods showed a significant positive correlation, with the correlation coefficient up to 0.673-0.925, and they have a great comparability. PMID:24059207

  1. New Method for Determining the Elemental Composition and Distribution in Semiconductor Core-Shell Quantum Dots

    PubMed Central

    Zorn, Gilad; Dave, Shivang R.; Gao, Xiaohu; Castner, David G.

    2011-01-01

    In the biological sciences the use of core-shell quantum dots (QDs) has gained wide usage, but analytical challenges still exist for characterizing the QD structure. The application of energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy (XPS) to bulk materials is relatively straightforward, however, for meaningful applications of surface science techniques to multilayer nanoparticles requires novel modifications and analysis methods. To experimentally characterize the elemental composition and distribution in CdSe/CdS/ZnS QDs, we first develop a XPS signal subtraction technique capable of separating the overlapped selenium 3s (core) and sulfur 2s (shell) peaks (both peaks have binding energies near 230eV) with higher precision than is typically reported in the nanoparticle literature. This method is valid for any nanoparticle containing selenium and sulfur. Then we apply a correction formula to the XPS data and determine that the 2 nm stoichiometric CdSe core is surrounded by 2 CdS layers and a stoichimetric ZnS monolayer. These findings and the multi-approach methodology represent a significant advancement in the detailed surface science study of multi-layer nanoparticles. In agreement with recent surprising findings, the time-of-flight secondary mass spectrometry measurements suggest that the surface sites of the QDs used in this study are primarily covered with a mixture of octadecylphosphonic acid and trioctylphophine oxide. PMID:21226467

  2. Carbon and other light element contents in the Earth's core based on first-principles molecular dynamics.

    PubMed

    Zhang, Yigang; Yin, Qing-Zhu

    2012-11-27

    Carbon (C) is one of the candidate light elements proposed to account for the density deficit of the Earth's core. In addition, C significantly affects siderophile and chalcophile element partitioning between metal and silicate and thus the distribution of these elements in the Earth's core and mantle. Derivation of the accretion and core-mantle segregation history of the Earth requires, therefore, an accurate knowledge of the C abundance in the Earth's core. Previous estimates of the C content of the core differ by a factor of ∼20 due to differences in assumptions and methods, and because the metal-silicate partition coefficient of C was previously unknown. Here we use two-phase first-principles molecular dynamics to derive this partition coefficient of C between liquid iron and silicate melt. We calculate a value of 9 ± 3 at 3,200 K and 40 GPa. Using this partition coefficient and the most recent estimates of bulk Earth or mantle C contents, we infer that the Earth's core contains 0.1-0.7 wt% of C. Carbon thus plays a moderate role in the density deficit of the core and in the distribution of siderophile and chalcophile elements during core-mantle segregation processes. The partition coefficients of nitrogen (N), hydrogen, helium, phosphorus, magnesium, oxygen, and silicon are also inferred and found to be in close agreement with experiments and other geochemical constraints. Contents of these elements in the core derived from applying these partition coefficients match those derived by using the cosmochemical volatility curve and geochemical mass balance arguments. N is an exception, indicating its retention in a mantle phase instead of in the core. PMID:23150591

  3. Spf/db hollow core fan blade. [SuperPlastically Formed/Diffusion Bonded

    SciTech Connect

    Velicki, A.

    1993-08-31

    A hollow core rotor blade for a turbine engine, comprising: a generally airfoil-shaped outer structure comprised of a superplastically formed, diffusion bonded sheet material, the outer structure having a trailing edge and a leading edge and being comprised of a matrix structure, with generally longitudinally oriented composite fibers being embedded within the superplastically formed material to increase the bending stiffness of the blade, the leading edge having an outer surface; and a hollow core spacing enclosed by the outer structure; wherein the outer surface of the leading edge is formed from a single sheet of material and is therefore structurally continuous and seamless, thereby allowing the rotor blade to be relatively lightweight, efficient, and durable, wherein each surface layer is comprised of an antifretting material having sufficient strength to withstand stresses between the blade and rotor during engine operation and sufficient ductility for forming into the manufactured shape; and wherein the shim is disposed between the dovetail and the dovetail slot, such that a portion of the first surface layer of the shims contacts at least a portion of each side face of the dovetail, and such that a portion of the second surface layer of the shim contacts at least a portion of each side wall of the dovetail slot.

  4. DUST AND HCO{sup +} GAS IN THE STAR-FORMING CORE W3-SE

    SciTech Connect

    Zhu Lei; Zhao Junhui; Wright, M. C. H.; Wu Yuefang

    2010-03-20

    We report new results from recent Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of both continuum and HCO{sup +}(1-0) line emission at lambda3.4 mm from W3-SE, a molecular core of intermediate mass, together with the observations of continuum emission at lambda1.1 and lambda0.85/lambda0.45 mm with the Submillimeter Array (SMA) and the James Clerk Maxwell Telescope, respectively. A continuum emission core elongated from SE to NW, with a size of {approx}10'', has been observed at the millimeter and submillimeter wavelengths. The dust core has been resolved into a double source with the SMA at lambda1.1 mm. The angular separation between the two components is {approx}4''. Together with the measurements from the Spitzer Space Telescope and the Midcourse Space Experiment at mid-IR wavelengths, we determined the spectral energy distribution (SED) of the continuum emission from W3-SE and fit it with a thermal dust emission model. Our best fitting of the SED suggests the presence of two dust components with different temperatures. The emission at millimeter/submillimeter wavelengths is dominated by a major component that is characterized by a temperature of T{sub d} = 41 +- 6 K with a mass of 65 +- 10 M{sub sun}. In addition, there is a weaker hot component ({approx} 400 K) which accounts for emission in the mid-IR, suggesting that a small fraction of dust has been heated by newly formed stars. We also imaged the molecular core in the HCO{sup +}(1-0) line using CARMA at an angular resolution {approx}6''. In the central region of {approx}50'', the integrated HCO{sup +}(1-0) line emission shows a main component A that coincides with the dust core, as well as two substructures B and C which are located N and SE of the dust core, respectively. With the CARMA observations, we have verified the presence of a blue-dominated double peak profile toward this core. The line profile cannot be explained by infall alone. The broad velocity wings of the

  5. Recognition of Core Elements of Medical Professionalism among Medical Students and Faculty Members

    PubMed Central

    Jahan, Firdous; Siddiqui, Muhammad A; Al Zadjali, Najjat Mohammed; Qasim, Rizwan

    2016-01-01

    Objectives Medical students and future physicians have chosen to pursue a profession that requires personal integrity, compassion and a constant awareness of the commitment made by them. Professionalism includes personal behaviors, knowledge, and competency. It includes the attitudes and values one holds and that run through the profession as a whole. Medical students learn professionalism during the course by either direct teaching or experiential learning. We conducted this study to estimate the self-reported level of practice of the core elements of professionalism by medical students and medical faculty and compared the two groups. Methods One-hundred and nine students and 83 faculty members of Oman Medical College completed a professionalism questionnaire. The survey questions related to core elements of professionalism and were grouped under professional knowledge, professional skills, professional attitude, and qualities essential for professionalism. Results The response rate was 65.6% (109 of 166) among students and 75.5% (83 of 110) from faculty members. Response to the questions on professional skills between the student and faculty group was significantly different (p < 0.001). Similarly, there was a significant difference in the responses related to professional attitude between the student and faculty group (p < 0.001). Students and faculty members have a significant difference in opinion regarding up to date knowledge of basic and clinical sciences and clinical competency (p = 0.024). Similarly, significant differences in opinion regarding up to date knowledge of basic and clinical sciences and clinical competency in clinical and basic sciences faculty members (p = 0.001). Students identified good communication skills (82.6%), and faculty staff identified up to date professional knowledge (62.7%) as the most important aspect of professionalism. Conclusions Both students and teaching faculty agreed that the top most professional elements are up to

  6. New geochemical models of core formation in the Moon from metal-silicate partitioning of 15 siderophile elements

    NASA Astrophysics Data System (ADS)

    Steenstra, E. S.; Rai, N.; Knibbe, J. S.; Lin, Y. H.; van Westrenen, W.

    2016-05-01

    We re-examine the conditions at which core formation in the Moon may have occurred by linking the observed lunar mantle depletions of 15 siderophile elements, including volatile siderophile elements (VSE) to predictive equations derived from a database compilation of metal-silicate partition coefficients obtained at lunar-relevant pressure-temperature-oxygen fugacity (P- T- fO2) conditions. Our results suggest that at mantle temperatures between the solidus and liquidus the depletions for all elements considered can be satisfied, but only if the Moon was essentially fully molten at the time of core formation while assuming a S-rich (>8 wt%) core comprising 2.5 wt% of the mass of the Moon. However, we observe that at temperatures exceeding the mantle liquidus, with increasing temperature the core S content required to satisfy the element depletions is reduced. As a S-poor core is likely from recent lunar mantle estimates of S abundance, this suggests much higher temperatures during lunar core formation than previously proposed. We conclude that the VSE depletions in the lunar mantle can be solely explained by core formation depletion, suggesting that no significant devolatilization has occurred in later periods of lunar evolution. This is in agreement with the discovery of significant amounts of other volatiles in the lunar interior, but hard to reconcile with current lunar formation models.

  7. Correction of interstitial water changes in calibration methods applied to XRF core-scanning major elements in long sediment cores: Case study from the South China Sea

    NASA Astrophysics Data System (ADS)

    Chen, Quan; Kissel, Catherine; Govin, Aline; Liu, Zhifei; Xie, Xin

    2016-05-01

    Fast and nondestructive X-ray fluorescence (XRF) core scanning provides high-resolution element data that are widely used in paleoclimate studies. However, various matrix and specimen effects prevent the use of semiquantitative raw XRF core-scanning intensities for robust paleoenvironmental interpretations. We present here a case study of a 50.8 m-long piston Core MD12-3432 retrieved from the northern South China Sea. The absorption effect of interstitial water is identified as the major source of deviations between XRF core-scanning intensities and measured element concentrations. The existing two calibration methods, i.e., normalized median-scaled calibration (NMS) and multivariate log-ratio calibration (MLC), are tested with this sequence after the application of water absorption correction. The results indicate that an improvement is still required to appropriately correct the influence of downcore changes in interstitial water content in the long sediment core. Consequently, we implement a new polynomial water content correction in NMS and MLC methods, referred as NPS and P_MLC calibrations. Results calibrated by these two improved methods indicate that the influence of downcore water content changes is now appropriately corrected. We therefore recommend either of the two methods to be applied for robust paleoenvironmental interpretations of major elements measured by XRF-scanning in long sediment sequences with significant downcore interstitial water content changes.

  8. Siderophile and chalcophile element abundances in oceanic basalts, Pb isotope evolution and growth of the earth's core

    NASA Technical Reports Server (NTRS)

    Newsom, H. E.; White, W. M.; Jochum, K. P.; Hofmann, A. W.

    1986-01-01

    The hypothesis that the mantle Pb isotope ratios reflect continued extraction of Pb into the earth's core over geologic time is evaluated by studying the depeletion of chalcophile and siderophile elements in the mantle. Oceanic basalt samples are analyzed in order to determine the Pb, Sr, and Nd isotropic compositions and the abundances of siderophile and chalcophile elements and incompatible lithophile elements. The data reveal that there is no systematic variation of siderophile or chalcophile element abundances relative to abundances of lithophile elements and the Pb/Ce ratio of the mantle is constant. It is suggested that the crust formation involves nonmagmatic and magmatic processes.

  9. The Metabolic Core and Catalytic Switches Are Fundamental Elements in the Self-Regulation of the Systemic Metabolic Structure of Cells

    PubMed Central

    De la Fuente, Ildefonso M.; Cortes, Jesus M.; Perez-Pinilla, Martin B.; Ruiz-Rodriguez, Vicente; Veguillas, Juan

    2011-01-01

    Background Experimental observations and numerical studies with dissipative metabolic networks have shown that cellular enzymatic activity self-organizes spontaneously leading to the emergence of a metabolic core formed by a set of enzymatic reactions which are always active under all environmental conditions, while the rest of catalytic processes are only intermittently active. The reactions of the metabolic core are essential for biomass formation and to assure optimal metabolic performance. The on-off catalytic reactions and the metabolic core are essential elements of a Systemic Metabolic Structure which seems to be a key feature common to all cellular organisms. Methodology/Principal Findings In order to investigate the functional importance of the metabolic core we have studied different catalytic patterns of a dissipative metabolic network under different external conditions. The emerging biochemical data have been analysed using information-based dynamic tools, such as Pearson's correlation and Transfer Entropy (which measures effective functionality). Our results show that a functional structure of effective connectivity emerges which is dynamical and characterized by significant variations of bio-molecular information flows. Conclusions/Significance We have quantified essential aspects of the metabolic core functionality. The always active enzymatic reactions form a hub –with a high degree of effective connectivity- exhibiting a wide range of functional information values being able to act either as a source or as a sink of bio-molecular causal interactions. Likewise, we have found that the metabolic core is an essential part of an emergent functional structure characterized by catalytic modules and metabolic switches which allow critical transitions in enzymatic activity. Both, the metabolic core and the catalytic switches in which also intermittently-active enzymes are involved seem to be fundamental elements in the self-regulation of the Systemic

  10. Constraining the Depth of the Martian Magma Ocean during Core Formation using Element Partitioning

    NASA Astrophysics Data System (ADS)

    Wijbrans, Ineke; Tronche, Elodie; van Westrenen, Wim

    2010-05-01

    The depth of a planetary magma ocean places first order constraints on the thermal state of a young planet. For the Earth, the depth of the magma ocean is mostly constrained by the pressure-temperature conditions at which Fe-rich metal last equilibrated with the bulk silicate Earth (BSE). These equilibration conditions are thought to correspond to the conditions at the terrestrial magma ocean floor, as this is where the metal ponds before sinking to the core. This depth is estimated by combining the BSE contents of siderophile (iron-loving) elements with metal-silicate partition coefficients (D) at high temperatures and pressures [e.g. 1]. The extent and depth of a magma ocean on Mars are hotly debated. In the case of Mars, the sulphur content of the core is significantly higher than for Earth (10-16 wt% sulphur [2]). The presence of sulphur has been shown to have an effect on the metal-silicate partitioning of some siderophile elements [3], but the current data set is insufficient to be of use for direct application to Martian conditions. We have started an experimental programme to constrain siderophile element partition coefficients for Ni and Co between metal and silicate as a function of temperature, pressure and sulphur content in the metal-alloy. For the silicate composition we used a newly proposed bulk silicate Mars (BSM) [4]. We chose the above-mentioned siderophile elements because their BSM concentrations are reasonably known from studies of Martian meteorites. Our aim is to derive new constraints on the depth of the Martian magma ocean and the chemistry accompanying Martian core formation. Experimental methods: The starting material consisted of a 1:1 mixture of silicate glass + quench crystals in the FeO-CaO-MgO-Al2O3-SiO2 (FCMAS) system with a composition based on [4], and metal consisting of FeS, Fe, Ni, Co, FeP3. Four different metal compositions were used with sulphur contents of 0, 5, 15 and 25wt% respectively. Experiments were made in an end

  11. Forming ceria shell on Au-core by LSPR photothermal induced interface reaction

    NASA Astrophysics Data System (ADS)

    Qu, Y. H.; Liu, F.; Wei, Y.; Gu, C. L.; Zhang, L. H.; Liu, Y.

    2015-07-01

    A novel method for preparing core-shell structure of Au@ceria was presented, which is characterized with using photothermal effect from localized surface plasmon resonance (LSPR) to induce heat, and the heat can trigger the shell formation reactions confined on the surface of the Au nanoparticles (NPs). In short of the preparation procedure, aqueous sol of Au NPs, citric acid, ethylene glycol and cerous nitrate were irradiated with a Xe arc lamp, maintaining the temperature of the sol at 25 °C by cooling and stirring the sol. The Au NPs could generate heat from LSPR, and the heat induced polymerization reaction in the sol, resulting in cerium gel formation which enveloped each of the Au NPs, and the gel containing cerium formed only on the surface of the Au NPs. After calcination, Au@ceria was obtained. This method can be extended for preparing various core@shell nanocomposites in which metal cores possess LSPR effect and the shell formation can be induced by heat.

  12. Network-element view information model for an optical burst core switch

    NASA Astrophysics Data System (ADS)

    Kan, Chao; Balt, Halt; Michel, Stephane R.; Verchere, Dominique G.

    2001-10-01

    To natively support the bursty IP datagrams over all-optical Wavelength Division Multiplexing (WDM) networks, the Optical Burst Switching (OBS) WDM network has been proposed as a suitable architecture for future optical Internet backbone networks. However, managing the OBS network will be complicated due to the scale of the networks and the correlation between different technology layers. This paper presents an information model for the OBS core node, from the network-element view, to describe the management information flows between the optical burst layer and the traditional WDM transport layer, and how to model them using various Managed Objects (MOs). We also provide the structure of Management Information Base (MIB) used in SNMP management interface for managing the parameters identified at different layers.

  13. Kinetic and Thermodynamic Characterization of the Cobalt and Manganese Oxyhydroxide Cores Formed in Horse Spleen Ferritin

    NASA Technical Reports Server (NTRS)

    Zhang, Bo; Harb, John N.; Davis, Robert C.; Kim, Jae-Woo; Chu, Sang-Hyon; Choi, Sang; Miller, Tim; Watt, Gerald D.

    2004-01-01

    Horse spleen ferritin (HoSF) containing 800-1500 cobalt or 250-1200 manganese atoms as Co(O)OH and Mn(O)OH mineral cores within the HoSF interior (Co-HoSF and Mn-HoSF) was synthesized, and the chemical reactivity, kinetics of reduction, and the reduction potentials were measured. Microcoulometric and chemical reduction of HoSF containing the M(O)OH mineral core (M = Co or Mn) was rapid and quantitative with a reduction stoichiometry of 1.05+/-0.10 e/M forming a stable M(OH)2 mineral core. At pH 9.0, ascorbic acid (AH2), a two-electron reductant, effectively reduced the mineral cores; however, the reaction was incomplete and rapidly reached equilibrium. The addition of excess AH2 shifted the reaction to completion with a M(3+)/AH2 stoichiometry of 1.9-2.1, consistent with a single electron per metal atom reduction. The rate of reaction between M(0)OH and excess AH2 was measured by monitoring the decrease in mineral core absorbance with time. The reaction was first order in each reactant with second-order rate constants of 0.53 and 4.74/M/min, respectively, for Co- and Mn-HoSF at pH 9.0. From the variation of absorbance with increasing AH2 concentration, equilibrium constants at pH 9.0 of 5.0+/-1.9 for Co-HoSF and 2.9+/-0.9 for Mn-HoSF were calculated for 2M(O)OH + AH2 = 2M(OH)2 f D, where AH2 and D are ascorbic acid and dehydroascorbic acid, respectively. Consistent with these equilibrium constants, the standard potential for the reduction of Co(III)-HoSF is 42 mV more positive than that of the ascorbic acid reaction, while the standard potential of Mn(III)-HoSF is 27 mV positive relative to AH2. Fe(2+) in solution with Co- and Mn-HoSF under anaerobic conditions was oxidized to form Fe(O)OH within the HoSF interior, resulting in partial displacement of the Co or Mn by iron.

  14. Fully Integrated EAS-Based Solid-Shell Finite Elements in Implicit Sheet Metal Forming Simulations

    SciTech Connect

    Valente, R.A. Fontes; Cardoso, R.P.R.; Alves de Sousa, R.J.; Parente, M.P.L.; Jorge, R.M. Natal

    2005-08-05

    In this communication sheet metal forming problems are analyzed with the Finite Element Method and a fully-integrated solid-shell element, based on the Enhanced Assumed Strain (EAS) method. Among the solid-shell element's distinguish features, it should be mentioned the solely use of the EAS approach in dealing with either transverse and volumetric-based locking pathologies, thus avoiding the inclusion of other mixed methods into the formulation. The adopted methodology is then able to successfully deal with small thickness shell problems within the incompressible range, aspects commonly appearing in sheet metal forming modeling with solid elements.Simulations of this type of forming processes are mainly solved resorting to membrane and shell-type finite elements, included in explicit commercial programs. Nevertheless, the presented solid-shell formulation, within a fully implicit approach, provides reliable solutions when compared to experimental results. It is also worth mentioning that the present solid-shell formulation encompasses a minimum set of enhancing strain variables, if compared to other fully integrated hexahedral finite elements in the literature.In order to assess the performance of the presented formulation, the S-Rail Forming problem of an aluminum alloy is described and analyzed, with the results being compared to experimental and numerical simulation data.

  15. Carbon and other light element contents in the Earth’s core based on first-principles molecular dynamics

    PubMed Central

    Zhang, Yigang; Yin, Qing-Zhu

    2012-01-01

    Carbon (C) is one of the candidate light elements proposed to account for the density deficit of the Earth’s core. In addition, C significantly affects siderophile and chalcophile element partitioning between metal and silicate and thus the distribution of these elements in the Earth’s core and mantle. Derivation of the accretion and core–mantle segregation history of the Earth requires, therefore, an accurate knowledge of the C abundance in the Earth’s core. Previous estimates of the C content of the core differ by a factor of ∼20 due to differences in assumptions and methods, and because the metal–silicate partition coefficient of C was previously unknown. Here we use two-phase first-principles molecular dynamics to derive this partition coefficient of C between liquid iron and silicate melt. We calculate a value of 9 ± 3 at 3,200 K and 40 GPa. Using this partition coefficient and the most recent estimates of bulk Earth or mantle C contents, we infer that the Earth’s core contains 0.1–0.7 wt% of C. Carbon thus plays a moderate role in the density deficit of the core and in the distribution of siderophile and chalcophile elements during core–mantle segregation processes. The partition coefficients of nitrogen (N), hydrogen, helium, phosphorus, magnesium, oxygen, and silicon are also inferred and found to be in close agreement with experiments and other geochemical constraints. Contents of these elements in the core derived from applying these partition coefficients match those derived by using the cosmochemical volatility curve and geochemical mass balance arguments. N is an exception, indicating its retention in a mantle phase instead of in the core. PMID:23150591

  16. Shear strength of non-shear reinforced concrete elements. Part 3: Prestressed hollow-core slabs

    SciTech Connect

    Hoang, L.C.

    1997-12-31

    This paper deals with the shear strength of prestressed hollow-core slabs determined by the theory of plasticity. Two failure mechanisms are considered in order to derive the solutions. In the case of sliding failure in a diagonal crack, the shear strength is determined by means of the crack sliding model developed by Jin-Ping Zhang. The model takes into account the resistance against the formation of cracks due to prestressing as well as the variation of the prestressing force in the transfer zone. Due to the fact that the anchorage of the reinforcement takes place by bond, a rotation failure, which is indeed by a crack formed at the support with subsequent slip of the reinforcement, is also considered. This failure mode is likely to occur in cases with a high prestressing force combined with a short shear span. The theoretical calculations are compared with test results form the literature. A good agreement has been found.

  17. Electro-infiltration: A method to form nanocomposite soft magnetic cores for integrated magnetic devices

    NASA Astrophysics Data System (ADS)

    Wen, Xiao; Starr, Justin D.; Andrew, Jennifer S.; Arnold, David P.

    2014-09-01

    This article introduces a scalable, process-integrable manufacturing method for creating microstructured, nanocomposite soft magnetic cores on planar substrates such as silicon wafers or printed circuit boards. To demonstrate this electro-infiltration process, maghemite (γ-Fe2O3) nanoparticles less than 50 nm are first evaporatively consolidated from suspension into photoresist molds on a silicon substrate, forming dimensionally defined porous microstructures. Next, a high-saturation soft magnetic iron cobalt alloy (Fe-Co) is electroplated up from a conductive layer on the substrate to fill in the void spaces of the consolidated particles. The result is a dense, two-phase nanocomposite, where the maghemite nanoparticles form an inclusion phase in the electroplated metal matrix phase. Improved high-frequency permeability is observed in the 100 MHz-2 GHz range.

  18. CHEMICAL SEGREGATION TOWARD MASSIVE HOT CORES: THE AFGL2591 STAR-FORMING REGION

    SciTech Connect

    Jimenez-Serra, I.; Zhang, Q.; Viti, S.; Martin-Pintado, J.; De Wit, W.-J. E-mail: qzhang@cfa.harvard.edu E-mail: jmartin@cab.inta-csic.es

    2012-07-01

    We present high angular resolution observations (0.''5 Multiplication-Sign 0.''3) carried out with the Submillimeter Array (SMA) toward the AFGL2591 high-mass star-forming region. Our SMA images reveal a clear chemical segregation within the AFGL2591 VLA 3 hot core, where different molecular species (Types I, II, and III) appear distributed in three concentric shells. This is the first time that such a chemical segregation is ever reported at linear scales {<=}3000 AU within a hot core. While Type I species (H{sub 2}S and {sup 13}CS) peak at the AFGL2591 VLA 3 protostar, Type II molecules (HC{sub 3}N, OCS, SO, and SO{sub 2}) show a double-peaked structure circumventing the continuum peak. Type III species, represented by CH{sub 3}OH, form a ring-like structure surrounding the continuum emission. The excitation temperatures of SO{sub 2}, HC{sub 3}N, and CH{sub 3}OH (185 {+-} 11 K, 150 {+-} 20 K, and 124 {+-} 12 K, respectively) show a temperature gradient within the AFGL2591 VLA 3 envelope, consistent with previous observations and modeling of the source. By combining the H{sub 2}S, SO{sub 2}, and CH{sub 3}OH images, representative of the three concentric shells, we find that the global kinematics of the molecular gas follow Keplerian-like rotation around a 40 M{sub Sun} star. The chemical segregation observed toward AFGL2591 VLA 3 is explained by the combination of molecular UV photodissociation and a high-temperature ({approx}1000 K) gas-phase chemistry within the low extinction innermost region in the AFGL2591 VLA 3 hot core.

  19. Elementally specific electron-positron annihilation radiation emitted from ion cores of group-V impurity-vacancy complexes in germanium

    NASA Astrophysics Data System (ADS)

    Arutyunov, N. Yu.; Emtsev, V. V.

    2007-12-01

    High-momentum component (HMC) of the electron-positron annihilation has been detected by the angular correlation of annihilation radiation (ACAR) technique in order to obtain elementally specific information about the ion cores of the donor-vacancy complexes (DV) formed by irradiation with 60Co γ-rays at Tirr.≈280 K in oxygen-lean n-Ge doped with group-V donors (D=As, Sb, and Bi). The probability of annihilation of positrons with the core electrons of DV complexes reconstructed from ACAR spectra increases in passing from AsV to SbV and BiV complexes. This increase correlates with the shift of the D atom from its regular position towards the vacancy site predicted by the results of spin-density functional modeling study. The data obtained suggest inward relaxation of the ion cores of DV complexes (including the one directed inward towards the vacancy).

  20. Light element partitioning between silicate and metallic melts: Insights into the formation and composition of Earth's core

    NASA Astrophysics Data System (ADS)

    Myhill, R.; Rubie, D. C.; Frost, D. J.

    2015-12-01

    The mass deficit of the Earth's core, and the increasing solubility of light elements into metallic iron with increasing pressure demonstrate that the Earth's core must contain several weight percent of light elements such as Si, O, C and S. These light elements place important constraints on the depth of the primordial magma ocean(s), the chemical potentials of many of these elements in coexisting phases during differentiation, the temperature of the inner core boundary, and the composition of the bulk Earth. The P-wave velocity, Earth's mass deficit, and depth of the inner core boundary place two important constraints on the chemical composition of the core, but there are multiple trade-offs which cannot be resolved using seismology alone. In this study, we use a large experimental partitioning dataset to build activity-composition models for light elements in metallic melts in equilibrium with oxide and silicate phases (both solid and liquid). We avoid the use of epsilon models, which commonly fail at solute concentrations above a few weight percent. Instead we employ a modified subregular solution model, using intermediate species to calculate excess free energies of mixing. Flexible models like these are required to fit the experimental data which spans 0 - 100 GPa and 1500 - 5500 K. Several heuristics are used to reduce the number of free parameters where they are not independently constrained. We use our models to investigate the conditions of core formation and the chemical composition of the Earth's core using the approach of Rubie et al. (2015; Icarus v.248; pp 89-108).

  1. Challenges in forming the solar system's giant planet cores via pebble accretion

    SciTech Connect

    Kretke, K. A.; Levison, H. F.

    2014-12-01

    Though ∼10 M {sub ⊕} mass rocky/icy cores are commonly held as a prerequisite for the formation of gas giants, theoretical models still struggle to explain how these embryos can form within the lifetimes of gaseous circumstellar disks. In recent years, aerodynamic-aided accretion of 'pebbles', objects ranging from centimeters to meters in size, has been suggested as a potential solution to this long-standing problem. While pebble accretion has been demonstrated to be extremely effective in local simulations that look at the detailed behavior of these pebbles in the vicinity of a single planetary embryo, to date there have been no global simulations demonstrating the effectiveness of pebble accretion in a more complicated, multi-planet environment. Therefore, we have incorporated the aerodynamic-aided accretion physics into LIPAD, a Lagrangian code that can follow the collisional/accretional/dynamical evolution of a protoplanetary system, to investigate how pebble accretion manifests itself in the larger planet formation picture. We find that under generic circumstances, pebble accretion naturally leads to an 'oligarchic' type of growth in which a large number of planetesimals grow to similar-sized planets. In particular, our simulations tend to form hundreds of Mars- and Earth-mass objects between 4 and 10 AU. While merging of some oligarchs may grow massive enough to form giant planet cores, leftover oligarchs lead to planetary systems that cannot be consistent with our own solar system. We investigate various ideas presented in the literature (including evaporation fronts and planet traps) and find that none easily overcome this tendency toward oligarchic growth.

  2. Experiments on Lunar Core Composition: Phase Equilibrium Analysis of A Multi-Element (Fe-Ni-S-C) System

    NASA Technical Reports Server (NTRS)

    Go, B. M.; Righter, K.; Danielson, L.; Pando, K.

    2015-01-01

    Previous geochemical and geophysical experiments have proposed the presence of a small, metallic lunar core, but its composition is still being investigated. Knowledge of core composition can have a significant effect on understanding the thermal history of the Moon, the conditions surrounding the liquid-solid or liquid-liquid field, and siderophile element partitioning between mantle and core. However, experiments on complex bulk core compositions are very limited. One limitation comes from numerous studies that have only considered two or three element systems such as Fe-S or Fe-C, which do not supply a comprehensive understanding for complex systems such as Fe-Ni-S-Si-C. Recent geophysical data suggests the presence of up to 6% lighter elements. Reassessments of Apollo seismological analyses and samples have also shown the need to acquire more data for a broader range of pressures, temperatures, and compositions. This study considers a complex multi-element system (Fe-Ni-S-C) for a relevant pressure and temperature range to the Moon's core conditions.

  3. Rare earth elements in core marine sediments of coastal East Malaysia by instrumental neutron activation analysis.

    PubMed

    Ashraf, Ahmadreza; Saion, Elias; Gharibshahi, Elham; Kamari, Halimah Mohamed; Kong, Yap Chee; Hamzah, Mohd Suhaimi; Elias, Md Suhaimi

    2016-01-01

    A study was carried out on the concentration of REEs (Dy, Sm, Eu,Yb, Lu, La and Ce) that are present in the core marine sediments of East Malaysia from three locations at South China Sea and one location each at Sulu Sea and Sulawesi Sea. The sediment samples were collected at a depth of between 49 and 109 m, dried, and crushed to powdery form. The entire core sediments prepared for Instrumental Neutron Activation Analysis (INAA) were weighted approximately 0.0500 g to 0.1000 g for short irradiation and 0.1500 g to 0.2000 g for long irradiation. The samples were irradiated with a thermal neutron flux of 4.0×10(12) cm(-2) s(-1) in a TRIGA Mark II research reactor operated at 750 kW. Blank samples and standard reference materials SL-1 were also irradiated for calibration and quality control purposes. It was found that the concentration of REEs varies in the range from 0.11 to 36.84 mg/kg. The chondrite-normalized REEs for different stations suggest that all the REEs are from similar origins. There was no significant REEs contamination as the enrichment factors normalized for Fe fall in the range of 0.42-2.82. PMID:26405840

  4. Dendritic carbon architectures formed by nanotube core-directed diffusion-limited aggregation of nanoparticles.

    PubMed

    Liu, Zhenyu; Kong, Xiaohui

    2010-08-28

    A regular array of fractal patterns with macroscopic dendritic carbon architecture was prepared by catalytic chemical vapor deposition (CVD). The dendritic carbon architectures have micrometre-sized stems and hyperbranches evolved by lateral growth, and they are formed by diffusion-limited aggregation of carbon-encapsulated iron nanoparticle building blocks generated from catalytic pyrolysis of toluene, which is directed by carbon nanotube cores, and followed by subsequent restructuring from surface to bulk. Incorporation of such proposed processes in Monte Carlo simulations generates dendritic architectures similar to the morphologies observed from the experiments. The findings provide direct information to the time resolved evolution of the morphology and microstructure of the dendritic carbon architecture, which mimic the nature behavior as snowflake attaching on the tree branches. Those will be important to understand the growth of vapor grown carbon fibers and carbon filamentous structures, and further possibility to control branching out of vapor grown carbon fibers. PMID:20607160

  5. The Kinematic and Chemical Properties of a Potential Core-forming Clump: Perseus B1-E

    NASA Astrophysics Data System (ADS)

    Sadavoy, S. I.; Shirley, Y.; Di Francesco, J.; Henning, Th.; Currie, M. J.; André, Ph.; Pezzuto, S.

    2015-06-01

    We present 13CO and {{C}18}O (1-0), (2-1), and (3-2) maps toward the core-forming Perseus B1-E clump using observations from the James Clerk Maxwell Telescope, the Submillimeter Telescope of the Arizona Radio Observatory, and the IRAM 30 m telescope. We find that the 13CO and {{C}18}O line emission both have very complex velocity structures, indicative of multiple velocity components within the ambient gas. The (1-0) transitions reveal a radial velocity gradient across B1-E of ˜ 1 km {{s}-1} p{{c}-1} that increases from northwest to southeast, whereas the majority of the Perseus cloud has a radial velocity gradient increasing from southwest to northeast. In contrast, we see no evidence of a velocity gradient associated with the denser Herschel-identified substructures in B1-E. Additionally, the denser substructures have much lower systemic motions than the ambient clump material, which indicates that they are likely decoupled from the large-scale gas. Nevertheless, these substructures themselves have broad line widths (˜0.4 km {{s}-1}) similar to that of the {{C}18}O gas in the clump, which suggests they inherited their kinematic properties from the larger-scale, moderately dense gas. Finally, we find evidence of {{C}18}O depletion only toward one substructure, B1-E2, which is also the only object with narrow (transonic) line widths. We suggest that as prestellar cores form, their chemical and kinematic properties are linked in evolution, such that these objects must first dissipate their turbulence before they deplete in CO.

  6. Deuterium burning in objects forming via the core accretion scenario. Brown dwarfs or planets?

    NASA Astrophysics Data System (ADS)

    Mollière, P.; Mordasini, C.

    2012-11-01

    Aims: Our aim is to study deuterium burning in objects forming according to the core accretion scenario in the hot and cold start assumption and what minimum deuterium burning mass limit is found for these objects. We also study how the burning process influences the structure and luminosity of the objects. Furthermore we want to test and verify our results by comparing them to already existing hot start simulations which did not consider, however, the formation process. Methods: We present a new method to calculate deuterium burning of objects in a self-consistently coupled model of planet formation and evolution. We discuss which theory is used to describe the process of deuterium burning and how it was implemented. Results: We find that the objects forming according to a hot start scenario behave approximately in the same way as found in previous works of evolutionary calculations, which did not consider the formation. However, for cold start objects one finds that the objects expand during deuterium burning instead of being partially stabilized against contraction. In both cases, hot and cold start, the mass of the solid core has an influence on the minimum mass limit of deuterium burning. The general position of the mass limit, 13 MJ, stays however approximately the same. None of the investigated parameters was able to change this mass limit by more than 0.8 MJ. Due to deuterium burning, the luminosity of hot and cold start objects becomes comparable after ~200 Myr. Numerical data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/547/A105

  7. Stress Recovery Based h-Adaptive Finite Element Simulation of Sheet Forming Operations

    NASA Astrophysics Data System (ADS)

    Ahmed, Mohd.; Singh, Devinder

    2016-05-01

    In the present work, stress recovery techniques based adaptive finite element analysis of sheet forming operations is presented. An adaptive two dimensional finite element computer code allows the analysis of sheet forming operations and results in distribution of adaptively refined mesh, effective strain, and punch load, stress and strain rate tensor in the domain that has been developed. The recovery scheme for determining more accurate stress field is based on the least squares fitting of the computed stresses in an element patch surrounding and including a particular node. The solution error is estimated on the basis of an energy norm. It is shown with the help of an illustrative example of axi-symmetric stretching of a metal blank by a hemispherical punch that the adaptive analysis may be usefully employed to predict accurately deformation process, the seats of large deformations and locations of possible instability.

  8. Stress Recovery Based h-Adaptive Finite Element Simulation of Sheet Forming Operations

    NASA Astrophysics Data System (ADS)

    Ahmed, Mohd.; Singh, Devinder

    2016-07-01

    In the present work, stress recovery techniques based adaptive finite element analysis of sheet forming operations is presented. An adaptive two dimensional finite element computer code allows the analysis of sheet forming operations and results in distribution of adaptively refined mesh, effective strain, and punch load, stress and strain rate tensor in the domain that has been developed. The recovery scheme for determining more accurate stress field is based on the least squares fitting of the computed stresses in an element patch surrounding and including a particular node. The solution error is estimated on the basis of an energy norm. It is shown with the help of an illustrative example of axi-symmetric stretching of a metal blank by a hemispherical punch that the adaptive analysis may be usefully employed to predict accurately deformation process, the seats of large deformations and locations of possible instability.

  9. Spectral element simulation of precession driven flows in the outer cores of spheroidal planets

    NASA Astrophysics Data System (ADS)

    Vormann, Jan; Hansen, Ulrich

    2015-04-01

    A common feature of the planets in the solar system is the precession of the rotation axes, driven by the gravitational influence of another body (e.g. the Earth's moon). In a precessing body, the rotation axis itself is rotating around another axis, describing a cone during one precession period. Similar to the coriolis and centrifugal force appearing from the transformation to a rotating system, the addition of precession adds another term to the Navier-Stokes equation, the so called Poincaré force. The main geophysical motivation in studying precession driven flows comes from their ability to act as magnetohydrodynamic dynamos in planets and moons. Precession may either act as the only driving force or operate together with other forces such as thermochemical convection. One of the challenges in direct numerical simulations of such flows lies in the spheroidal shape of the fluid volume, which should not be neglected since it contributes an additional forcing trough pressure torques. Codes developed for the simulation of flows in spheres mostly use efficient global spectral algorithms that converge fast, but lack geometric flexibility, while local methods are usable in more complex shapes, but often lack high accuracy. We therefore adapted the spectral element code Nek5000, developed at Argonne National Laboratory, to the problem. The spectral element method is capable of solving for the flow in arbitrary geometries while still offering spectral convergence. We present first results for the simulation of a purely hydrodynamic, precession-driven flow in a spheroid with no-slip boundaries and an inner core. The driving by the Poincaré force is in a range where theoretical work predicts multiple solutions for a laminar flow. Our simulations indicate a transition to turbulent flows for Ekman numbers of 10-6 and lower.

  10. Understanding of Essential Elements Required in Informed Consent Form among Researchers and Institutional Review Board Members.

    PubMed

    Koonrungsesomboon, Nut; Laothavorn, Junjira; Karbwang, Juntra

    2015-06-01

    The process of informed consent remains a constant challenge in clinical research. The aim of the present study was to evaluate the understanding of researchers and members of Institutional Review Boards (IRBs) regarding the essential elements of an Informed Consent Form (ICF) as required by internationally recognized regulations. Using eight case studies to illustrate basic ethical elements, the study involved 107 participants, mainly from the Asia Pacific and African regions. The results showed that most of the participants had general knowledge regarding the essential elements required in an ICF. However, the issues of confidentiality of data and payment for study participation proved to be problematic for some participants, accounting for 35% and 28% of all incorrect answers respectively. This suggests that participants' understanding of the underlying concepts of the required ICF elements is limited. Ethical training of researchers and IRB members, particularly in the Asia Pacific and African regions, concerning valid informed consent is still needed. PMID:26161029

  11. Understanding of Essential Elements Required in Informed Consent Form among Researchers and Institutional Review Board Members

    PubMed Central

    Koonrungsesomboon, Nut; Laothavorn, Junjira; Karbwang, Juntra

    2015-01-01

    The process of informed consent remains a constant challenge in clinical research. The aim of the present study was to evaluate the understanding of researchers and members of Institutional Review Boards (IRBs) regarding the essential elements of an Informed Consent Form (ICF) as required by internationally recognized regulations. Using eight case studies to illustrate basic ethical elements, the study involved 107 participants, mainly from the Asia Pacific and African regions. The results showed that most of the participants had general knowledge regarding the essential elements required in an ICF. However, the issues of confidentiality of data and payment for study participation proved to be problematic for some participants, accounting for 35% and 28% of all incorrect answers respectively. This suggests that participants’ understanding of the underlying concepts of the required ICF elements is limited. Ethical training of researchers and IRB members, particularly in the Asia Pacific and African regions, concerning valid informed consent is still needed. PMID:26161029

  12. Error Analysis In Explicit Finite Element Analysis Of Incremental Sheet Forming

    SciTech Connect

    Bambach, M.; Hirt, G.

    2007-05-17

    Asymmetric incremental sheet forming (AISF) is a relatively new manufacturing process for the production of low volumes of sheet metal parts. Forming is accomplished by the CNC controlled movements of a simple ball-headed tool that follows a 3D trajectory to gradually shape a sheet metal blank. The local plastic deformation under the tool leads to a number of challenges for the Finite Element Modeling. Previous work indicates that implicit finite element methods are at present not efficient enough to allow for the simulation of AISF for industrially relevant parts, mostly due to the fact that the moving contact requires a very small time step. Explicit Finite Element methods can be speeded up by means of mass or load scaling to enable the simulation of large scale sheet metal forming problems, even for AISF. However, it is well known that the methods used to speed up the FE calculations can entail poor results when dynamic effects start to dominate the solution. Typically, the ratio of kinetic to internal energy is used as an assessment of the influence of dynamical effects. It has already been shown in the past that this global criterion can easily be violated locally for a patch of elements of the finite element mesh. This is particularly important for AISF with its highly localised loading and complex tool kinematics. The present paper details an investigation of dynamical effects in explicit Finite Element analysis of AISF. The interplay of mass or time scaling scheme and the smoothness of the tool trajectory is analysed with respect to the resulting errors. Models for tool path generation will be presented allowing for a generation of tool trajectories with predefined maximum speed and acceleration. Based on this, a strategy for error control is proposed which helps reduce the time for setting up reliable explicit finite element models for AISF.

  13. Error Analysis In Explicit Finite Element Analysis Of Incremental Sheet Forming

    NASA Astrophysics Data System (ADS)

    Bambach, M.; Hirt, G.

    2007-05-01

    Asymmetric incremental sheet forming (AISF) is a relatively new manufacturing process for the production of low volumes of sheet metal parts. Forming is accomplished by the CNC controlled movements of a simple ball-headed tool that follows a 3D trajectory to gradually shape a sheet metal blank. The local plastic deformation under the tool leads to a number of challenges for the Finite Element Modeling. Previous work indicates that implicit finite element methods are at present not efficient enough to allow for the simulation of AISF for industrially relevant parts, mostly due to the fact that the moving contact requires a very small time step. Explicit Finite Element methods can be speeded up by means of mass or load scaling to enable the simulation of large scale sheet metal forming problems, even for AISF. However, it is well known that the methods used to speed up the FE calculations can entail poor results when dynamic effects start to dominate the solution. Typically, the ratio of kinetic to internal energy is used as an assessment of the influence of dynamical effects. It has already been shown in the past that this global criterion can easily be violated locally for a patch of elements of the finite element mesh. This is particularly important for AISF with its highly localised loading and complex tool kinematics. The present paper details an investigation of dynamical effects in explicit Finite Element analysis of AISF. The interplay of mass or time scaling scheme and the smoothness of the tool trajectory is analysed with respect to the resulting errors. Models for tool path generation will be presented allowing for a generation of tool trajectories with predefined maximum speed and acceleration. Based on this, a strategy for error control is proposed which helps reduce the time for setting up reliable explicit finite element models for AISF.

  14. Coupled finite element simulation and optimization of single- and multi-stage sheet-forming processes

    NASA Astrophysics Data System (ADS)

    Tamasco, Cynthia M.; Rais-Rohani, Masoud; Buijk, Arjaan

    2013-03-01

    This article presents the development and application of a coupled finite element simulation and optimization framework that can be used for design and analysis of sheet-forming processes of varying complexity. The entire forming process from blank gripping and deep drawing to tool release and springback is modelled. The dies, holders, punch and workpiece are modelled with friction, temperature, holder force and punch speed controlled in the process simulation. Both single- and multi-stage sheet-forming processes are investigated. Process simulation is coupled with a nonlinear gradient-based optimization approach for optimizing single or multiple design objectives with imposed sheet-forming response constraints. A MATLAB program is developed and used for data-flow management between process simulation and optimization codes. Thinning, springback, damage and forming limit diagram are used to define failure in the forming process design optimization. Design sensitivity analysis and optimization results of the example problems are presented and discussed.

  15. The tolerance to exchanges of the Watson–Crick base pair in the hammerhead ribozyme core is determined by surrounding elements

    PubMed Central

    Przybilski, Rita; Hammann, Christian

    2007-01-01

    Tertiary interacting elements are important features of functional RNA molecules, for example, in all small nucleolytic ribozymes. The recent crystal structure of a tertiary stabilized type I hammerhead ribozyme revealed a conventional Watson–Crick base pair in the catalytic core, formed between nucleotides C3 and G8. We show that any Watson–Crick base pair between these positions retains cleavage competence in two type III ribozymes. In the Arabidopsis thaliana sequence, only moderate differences in cleavage rates are observed for the different base pairs, while the peach latent mosaic viroid (PLMVd) ribozyme exhibits a preference for a pyrimidine at position 3 and a purine at position 8. To understand these differences, we created a series of chimeric ribozymes in which we swapped sequence elements that surround the catalytic core. The kinetic characterization of the resulting ribozymes revealed that the tertiary interacting loop sequences of the PLMVd ribozyme are sufficient to induce the preference for Y3–R8 base pairs in the A. thaliana hammerhead ribozyme. In contrast to this, only when the entire stem–loops I and II of the A. thaliana sequences are grafted on the PLMVd ribozyme is any Watson–Crick base pair similarly tolerated. The data provide evidence for a complex interplay of secondary and tertiary structure elements that lead, mediated by long-range effects, to an individual modulation of the local structure in the catalytic core of different hammerhead ribozymes. PMID:17666711

  16. Rare earth element geochemistry of outcrop and core samples from the Marcellus Shale

    SciTech Connect

    Noack, Clinton W.; Jain, Jinesh C.; Stegmeier, John; Hakala, J. Alexandra; Karamalidis, Athanasios K.

    2015-06-26

    In this paper, we studied the geochemistry of the rare earth elements (REE) in eleven outcrop samples and six, depth-interval samples of a core from the Marcellus Shale. The REE are classically applied analytes for investigating depositional environments and inferring geochemical processes, making them of interest as potential, naturally occurring indicators of fluid sources as well as indicators of geochemical processes in solid waste disposal. However, little is known of the REE occurrence in the Marcellus Shale or its produced waters, and this study represents one of the first, thorough characterizations of the REE in the Marcellus Shale. In these samples, the abundance of REE and the fractionation of REE profiles were correlated with different mineral components of the shale. Namely, samples with a larger clay component were inferred to have higher absolute concentrations of REE but have less distinctive patterns. Conversely, samples with larger carbonate fractions exhibited a greater degree of fractionation, albeit with lower total abundance. Further study is necessary to determine release mechanisms, as well as REE fate-and-transport, however these results have implications for future brine and solid waste management applications.

  17. Rare earth element geochemistry of outcrop and core samples from the Marcellus Shale

    DOE PAGESBeta

    Noack, Clinton W.; Jain, Jinesh C.; Stegmeier, John; Hakala, J. Alexandra; Karamalidis, Athanasios K.

    2015-06-26

    In this paper, we studied the geochemistry of the rare earth elements (REE) in eleven outcrop samples and six, depth-interval samples of a core from the Marcellus Shale. The REE are classically applied analytes for investigating depositional environments and inferring geochemical processes, making them of interest as potential, naturally occurring indicators of fluid sources as well as indicators of geochemical processes in solid waste disposal. However, little is known of the REE occurrence in the Marcellus Shale or its produced waters, and this study represents one of the first, thorough characterizations of the REE in the Marcellus Shale. In thesemore » samples, the abundance of REE and the fractionation of REE profiles were correlated with different mineral components of the shale. Namely, samples with a larger clay component were inferred to have higher absolute concentrations of REE but have less distinctive patterns. Conversely, samples with larger carbonate fractions exhibited a greater degree of fractionation, albeit with lower total abundance. Further study is necessary to determine release mechanisms, as well as REE fate-and-transport, however these results have implications for future brine and solid waste management applications.« less

  18. Characteristics and Core Curricular Elements of Medical Simulation Fellowships in North America.

    PubMed

    Ahmed, Rami A; Frey, Jennifer; Gardner, Aimee K; Gordon, James A; Yudkowsky, Rachel; Tekian, Ara

    2016-05-01

    Background In the past few years, there has been rapid growth in the number of simulation fellowships for physicians in the United States and Canada, with the objective of producing faculty with expertise and leadership training in medical simulation. Relatively little is known about the collective content and structure of these new fellowship opportunities. Objective We sought to identify a common set of core curricular elements among existing simulation fellowships and to obtain demographic background information on participants and leadership. Methods We designed a web-based survey and circulated it to simulation fellowship directors in the United States and Canada. The questions explored aspects of the fellowship curriculum. A grounded theory approach was used to qualitatively analyze fellowship goals and objectives. Results Of the 29 program directors surveyed, 23 responded (79%). The most commonly listed goals and objectives were to increase skills in simulation curriculum development, simulation operations and training environment setup, research, educational theory, administration, and debriefing. The majority of the responding fellowship directors (17 of 22, 77%) indicated that a set of consensus national guidelines would benefit their fellowship program. Conclusions Simulation fellowships are experiencing a period of rapid growth. Development of a common set of program guidelines is a widely shared objective among fellowship directors. PMID:27168898

  19. Interactions between RNA polymerase and the core recognition element are a determinant of transcription start site selection.

    PubMed

    Vvedenskaya, Irina O; Vahedian-Movahed, Hanif; Zhang, Yuanchao; Taylor, Deanne M; Ebright, Richard H; Nickels, Bryce E

    2016-05-24

    During transcription initiation, RNA polymerase (RNAP) holoenzyme unwinds ∼13 bp of promoter DNA, forming an RNAP-promoter open complex (RPo) containing a single-stranded transcription bubble, and selects a template-strand nucleotide to serve as the transcription start site (TSS). In RPo, RNAP core enzyme makes sequence-specific protein-DNA interactions with the downstream part of the nontemplate strand of the transcription bubble ("core recognition element," CRE). Here, we investigated whether sequence-specific RNAP-CRE interactions affect TSS selection. To do this, we used two next-generation sequencing-based approaches to compare the TSS profile of WT RNAP to that of an RNAP derivative defective in sequence-specific RNAP-CRE interactions. First, using massively systematic transcript end readout, MASTER, we assessed effects of RNAP-CRE interactions on TSS selection in vitro and in vivo for a library of 4(7) (∼16,000) consensus promoters containing different TSS region sequences, and we observed that the TSS profile of the RNAP derivative defective in RNAP-CRE interactions differed from that of WT RNAP, in a manner that correlated with the presence of consensus CRE sequences in the TSS region. Second, using 5' merodiploid native-elongating-transcript sequencing, 5' mNET-seq, we assessed effects of RNAP-CRE interactions at natural promoters in Escherichia coli, and we identified 39 promoters at which RNAP-CRE interactions determine TSS selection. Our findings establish RNAP-CRE interactions are a functional determinant of TSS selection. We propose that RNAP-CRE interactions modulate the position of the downstream end of the transcription bubble in RPo, and thereby modulate TSS selection, which involves transcription bubble expansion or transcription bubble contraction (scrunching or antiscrunching). PMID:27162333

  20. Drill core major, trace and rare earth element anlayses from wells RN-17B and RN-30, Reykjanes, Iceland

    DOE Data Explorer

    Andrew Fowler

    2015-04-01

    Analytical results for X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) measurement of major, trace and rare earth elements in drill core from geothermal wells in Reykjanes, Iceland. Total Fe was analyzed as FeO, therefore is not included under the Fe2O3 column.

  1. Social and Emotional Learning (SEL) and Student Benefits: Implications for the Safe Schools/Healthy Students Core Elements

    ERIC Educational Resources Information Center

    Collaborative for Academic, Social, and Emotional Learning (NJ1), 2008

    2008-01-01

    This brief shares the latest research on the effects of social and emotional learning (SEL) on students and includes strategies for implementing SEL. It explains how SEL works, elaborates on how SEL can be an integrative prevention framework that addresses the Safe Schools/Healthy Students (SS/HS) core elements, and spells out implications of the…

  2. Somatic experiencing: using interoception and proprioception as core elements of trauma therapy

    PubMed Central

    Payne, Peter; Levine, Peter A.; Crane-Godreau, Mardi A.

    2015-01-01

    Here we present a theory of human trauma and chronic stress, based on the practice of Somatic Experiencing® (SE), a form of trauma therapy that emphasizes guiding the client's attention to interoceptive, kinesthetic, and proprioceptive experience. SE™ claims that this style of inner attention, in addition to the use of kinesthetic and interoceptive imagery, can lead to the resolution of symptoms resulting from chronic and traumatic stress. This is accomplished through the completion of thwarted, biologically based, self-protective and defensive responses, and the discharge and regulation of excess autonomic arousal. We present this theory through a composite case study of SE treatment; based on this example, we offer a possible neurophysiological rationale for the mechanisms involved, including a theory of trauma and chronic stress as a functional dysregulation of the complex dynamical system formed by the subcortical autonomic, limbic, motor and arousal systems, which we term the core response network (CRN). We demonstrate how the methods of SE help restore functionality to the CRN, and we emphasize the importance of taking into account the instinctive, bodily based protective reactions when dealing with stress and trauma, as well as the effectiveness of using attention to interoceptive, proprioceptive and kinesthetic sensation as a therapeutic tool. Finally, we point out that SE and similar somatic approaches offer a supplement to cognitive and exposure therapies, and that mechanisms similar to those discussed in the paper may also be involved in the benefits of meditation and other somatic practices. PMID:25699005

  3. Somatic experiencing: using interoception and proprioception as core elements of trauma therapy.

    PubMed

    Payne, Peter; Levine, Peter A; Crane-Godreau, Mardi A

    2015-01-01

    Here we present a theory of human trauma and chronic stress, based on the practice of Somatic Experiencing(®) (SE), a form of trauma therapy that emphasizes guiding the client's attention to interoceptive, kinesthetic, and proprioceptive experience. SE™ claims that this style of inner attention, in addition to the use of kinesthetic and interoceptive imagery, can lead to the resolution of symptoms resulting from chronic and traumatic stress. This is accomplished through the completion of thwarted, biologically based, self-protective and defensive responses, and the discharge and regulation of excess autonomic arousal. We present this theory through a composite case study of SE treatment; based on this example, we offer a possible neurophysiological rationale for the mechanisms involved, including a theory of trauma and chronic stress as a functional dysregulation of the complex dynamical system formed by the subcortical autonomic, limbic, motor and arousal systems, which we term the core response network (CRN). We demonstrate how the methods of SE help restore functionality to the CRN, and we emphasize the importance of taking into account the instinctive, bodily based protective reactions when dealing with stress and trauma, as well as the effectiveness of using attention to interoceptive, proprioceptive and kinesthetic sensation as a therapeutic tool. Finally, we point out that SE and similar somatic approaches offer a supplement to cognitive and exposure therapies, and that mechanisms similar to those discussed in the paper may also be involved in the benefits of meditation and other somatic practices. PMID:25699005

  4. Cluster form factor calculation in the ab initio no-core shell model

    SciTech Connect

    Navratil, Petr

    2004-11-01

    We derive expressions for cluster overlap integrals or channel cluster form factors for ab initio no-core shell model (NCSM) wave functions. These are used to obtain the spectroscopic factors and can serve as a starting point for the description of low-energy nuclear reactions. We consider the composite system and the target nucleus to be described in the Slater determinant (SD) harmonic oscillator (HO) basis while the projectile eigenstate to be expanded in the Jacobi coordinate HO basis. This is the most practical case. The spurious center of mass components present in the SD bases are removed exactly. The calculated cluster overlap integrals are translationally invariant. As an illustration, we present results of cluster form factor calculations for <{sup 5}He vertical bar{sup 4}He+n>, <{sup 5}He vertical bar{sup 3}H+d>, <{sup 6}Li vertical bar{sup 4}He+d>, <{sup 6}Be vertical bar{sup 3}He+{sup 3}He>, <{sup 7}Li vertical bar{sup 4}He+{sup 3}H>, <{sup 7}Li vertical bar{sup 6}Li+n>, <{sup 8}Be vertical bar{sup 6}Li+d>, <{sup 8}Be vertical bar{sup 7}Li+p>, <{sup 9}Li vertical bar{sup 8}Li+n>, and <{sup 13}C vertical bar{sup 12}C+n>, with all the nuclei described by multi-({Dirac_h}/2{pi}){omega} NCSM wave functions.

  5. The Effectiveness of L*a*b* Color Analysis in Determining the Elemental and Mineralogical Composition of Lake Sediment Cores

    NASA Astrophysics Data System (ADS)

    Dawson, S.; Lascu, I.; Myrbo, A.; Wittkop, C.

    2006-12-01

    High-resolution L*a*b color and x-ray fluorescence (XRF) elemental profiles were compared for a set of Midwestern U.S. lake sediment cores held in the National Lacustrine Core Repository. The cores all display centi- to decimeter scale light-dark banding (nicknamed "raccoon-tail banding"), determined by variations in carbonate versus organic matter content. Carbonate minerals are evidently depleted in the organic-rich strata due to carbonate dissolution in the hypolimnion and sediment column, which is the result of both external (i.e., climatic) and internal factors. XRF was performed at a resolution comparable to the L*a*b* image analysis of the core sections, which allowed the investigation of the relationship between sediment color and composition within a core. The "a" component in this image analysis is correlated with elemental iron abundance, and the "b" and "L" components are related to calcium (calcite) and organic carbon content. Overall, this study has determined that L*a*b* color analysis of high-resolution digital images is an easy and fast way to obtain preliminary information about the composition of core material. When used in conjunction with scanning XRF data, color analysis can replace lower-resolution geochemical analyses to produce sub-annual scale records of lake dynamics and responses to climate change.

  6. Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element

    SciTech Connect

    Moreau, P.; Gregoire, S.; Lochegnies, D.; Cesar de Sa, J.

    2007-05-17

    Numerical modeling of the glass forming processes requires the accurate knowledge of the heat exchange between the glass and the forming tools. A laboratory testing is developed to determine the evolution of the heat transfer coefficient in different glass/mould contact conditions (contact pressure, temperature, lubrication...). In this paper, trials are performed to determine heat transfer coefficient evolutions in experimental conditions close to the industrial blow-and-blow process conditions. In parallel of this work, a special interface element is implemented in a commercial Finite Element code in order to deal with heat transfer between glass and mould for non-meshing meshes and evolutive contact. This special interface element, implemented by using user subroutines, permits to introduce the previous heat transfer coefficient evolutions in the numerical modelings at the glass/mould interface in function of the local temperatures, contact pressures, contact time and kind of lubrication. The blow-and-blow forming simulation of a perfume bottle is finally performed to assess the special interface element performance.

  7. Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element

    NASA Astrophysics Data System (ADS)

    Moreau, P.; César de Sá, J.; Grégoire, S.; Lochegnies, D.

    2007-05-01

    Numerical modeling of the glass forming processes requires the accurate knowledge of the heat exchange between the glass and the forming tools. A laboratory testing is developed to determine the evolution of the heat transfer coefficient in different glass/mould contact conditions (contact pressure, temperature, lubrication…). In this paper, trials are performed to determine heat transfer coefficient evolutions in experimental conditions close to the industrial blow-and-blow process conditions. In parallel of this work, a special interface element is implemented in a commercial Finite Element code in order to deal with heat transfer between glass and mould for non-meshing meshes and evolutive contact. This special interface element, implemented by using user subroutines, permits to introduce the previous heat transfer coefficient evolutions in the numerical modelings at the glass/mould interface in function of the local temperatures, contact pressures, contact time and kind of lubrication. The blow-and-blow forming simulation of a perfume bottle is finally performed to assess the special interface element performance.

  8. Far-ultraviolet morphology of star-forming filaments in cool core brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Tremblay, G. R.; O'Dea, C. P.; Baum, S. A.; Mittal, R.; McDonald, M. A.; Combes, F.; Li, Y.; McNamara, B. R.; Bremer, M. N.; Clarke, T. E.; Donahue, M.; Edge, A. C.; Fabian, A. C.; Hamer, S. L.; Hogan, M. T.; Oonk, J. B. R.; Quillen, A. C.; Sanders, J. S.; Salomé, P.; Voit, G. M.

    2015-08-01

    We present a multiwavelength morphological analysis of star-forming clouds and filaments in the central (≲50 kpc) regions of 16 low-redshift (z < 0.3) cool core brightest cluster galaxies. New Hubble Space Telescope imaging of far-ultraviolet continuum emission from young (≲10 Myr), massive (≳5 M⊙) stars reveals filamentary and clumpy morphologies, which we quantify by means of structural indices. The FUV data are compared with X-ray, Lyα, narrow-band Hα, broad-band optical/IR, and radio maps, providing a high spatial resolution atlas of star formation locales relative to the ambient hot (˜107-8 K) and warm ionized (˜104 K) gas phases, as well as the old stellar population and radio-bright active galactic nucleus (AGN) outflows. Nearly half of the sample possesses kpc-scale filaments that, in projection, extend towards and around radio lobes and/or X-ray cavities. These filaments may have been uplifted by the propagating jet or buoyant X-ray bubble, or may have formed in situ by cloud collapse at the interface of a radio lobe or rapid cooling in a cavity's compressed shell. The morphological diversity of nearly the entire FUV sample is reproduced by recent hydrodynamical simulations in which the AGN powers a self-regulating rain of thermally unstable star-forming clouds that precipitate from the hot atmosphere. In this model, precipitation triggers where the cooling-to-free-fall time ratio is tcool/tff ˜ 10. This condition is roughly met at the maximal projected FUV radius for more than half of our sample, and clustering about this ratio is stronger for sources with higher star formation rates.

  9. Core shell micron-scale composites of titanium oxide and carbide formed through controlled thermal-plasma oxidation

    NASA Astrophysics Data System (ADS)

    Li, Ya-Li; Ishigaki, Takamasa

    2003-01-01

    Core-shell structured micron-scale spheres of titanium oxide and carbide were prepared by the controlled in-flight oxidation of a powder of irregularly shaped titanium-carbide particles in an argon-oxygen thermal plasma. Mono-dispersed core-shell particles with rutile shells and TiC cores were formed by an intermediate-rate input of oxygen to the plasma gas. The partial oxidation of the TiC particles in the liquid phase was accompanied by spheroidization of the surface oxide melt, thus giving rise to a core-shell composite under rapid quenching. TiO 2-TiC core-shell composites have potential as new materials for roles such as light-scattering media, photo-catalysts, and electro-rheorogical fluids.

  10. Three-dimensional finite element analysis of stress distribution in composite resin cores with fiber posts of varying diameters.

    PubMed

    Okamoto, Kazuhiko; Ino, Teruno; Iwase, Naoki; Shimizu, Eitaroh; Suzuki, Megumi; Satoh, Goh; Ohkawa, Shuji; Fujisawa, Masanori

    2008-01-01

    Using three-dimensional finite element analysis (3D-FEA), stress distributions in the remaining radicular tooth structure were investigated under the condition of varying diameters of fiber post for fiber post-reinforced composite resin cores (fiber post and core) in maxillary central incisors. Four 3D-FEA models were constructed: (1) fiber post (ø1.2, ø1.4, and ø1.6 mm) and composite resin core; and (2) gold-cast post and core. Maximum stresses in the tooth structure for fiber post and core were higher than that for gold-cast post and core. In the former models, stresses in the tooth structure as well as in the composite resin were slightly reduced with increase in fiber post diameter. These results thus suggested that to reduce stress in the remaining radicular tooth with a large coronal defect, it is recommended to accompany a composite resin core with a fiber post of a large diameter. PMID:18309611

  11. Finite Element Simulation of Sheet Metal Forming Process Using Local Interpolation for Tool Surfaces

    SciTech Connect

    Hama, Takayuki; Takuda, Hirohiko; Takamura, Masato; Makinouchi, Akitake; Teodosiu, Cristian

    2005-08-05

    Treatment of contact between a sheet and tools is one of the most difficult problems to deal with in finite-element simulations of sheet forming processes. In order to obtain more accurate tool models without increasing the number of elements, this paper describes a new formulation for contact problems using interpolation proposed by Nagata for tool surfaces. A contact search algorithm between sheet nodes and the interpolated tool surfaces was developed and was introduced into the static-explicit elastoplastic finite-element method code STAMP3D. Simulations of a square cup deep drawing process with a very coarsely discretized punch model were carried out. The simulated results showed that the proposed algorithm gave the proper drawn shape, demonstrating the validity of the proposed algorithm.

  12. Light Elements in the Core and Equilibration Degree with Silicate Mantle: Perspective from First-Principles Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Yin, Q.; Zhang, Y.

    2012-12-01

    The degree of chemical equilibration (hereafter as Ke), defined as the cumulative mass fraction of the metalic core in equilibrium with the silicate mantle during the Earth accretion processes, greatly influences determination of the timing of the Earth core formation [1]. If Ke is larger than ~0.4, Hf-W chronology implies a fast accretion in less than 30 Myr for the Earth. Otherwise, Hf-W data can only be used to constrain the Ke instead of timing [1]. Here we use the two-phase first-principles molecular dynamics (FPMD) [2] to constrain the solubility of light elements in liquid iron in equilibration with silicate melt at temperatures from 2500 to 4200 K, pressures from 20 to 120 GPa, and two compositions simplified from the "O-bearing" and "Si-bearing" bulk Earth model compositions of McDonough [3]. The solubility data are then used in the simulations of the many possible accretion scenarios of the Earth as outlined in [4], considering magma ocean depth, homogeneous vs heterogeneous accretion etc. For each accretion route, we calculate the effective core-mantle equilibration degree (Ke), where Kei and Wi are the core-mantle equilibration degree and the accreted mass fraction of the ith step, respectively. The successful Ke are selected based on the criterion that the resulting Earth's core must meet the required density deficit [5]. The Ke in those successful simulations are all found to be larger than 0.57, implying that the core-mantle differentiation has to occur early [1], within 30 millions years from the beginning of the solar system as originally stated [6]. Additional simulations (all at 3200 K and 40 GPa) are also made to calculate the partition coefficients of several other light elements. Combined with the bulk Earth compositions of these elements [3], it is found Si, O, and S are the major light elements in the core while C, P, Mg, H, N, and He are the minor elements in the core. We show [7] that FPMD calculations lend strong support to the classical

  13. Method of forming multi-element thin hot film sensors on polyimide film

    NASA Technical Reports Server (NTRS)

    Hopson, Jr., Purnell (Inventor)

    1996-01-01

    The invention comprises a method of forming a multi-element, thin hot film sensor on a polyimide film. The sensor is formed by first cleaning one surface of the polyimide. Then, under a continuous vacuum, the surface is simultaneously cleaned by ion bombardment while nickel is deposited by evaporation. The ion beam cleaning is discontinued and copper is then deposited to an initial thickness by evaporation without a break in the vacuum. The vacuum is then removed and a final thickness of copper is deposited by plating. Sensor patterns are then defined in the nickel and copper layers using conventional photolithography and etching techniques.

  14. LOOKING INTO THE HEARTS OF BOK GLOBULES: MILLIMETER AND SUBMILLIMETER CONTINUUM IMAGES OF ISOLATED STAR-FORMING CORES

    SciTech Connect

    Launhardt, R.; Henning, Th.; Khanzadyan, T.; Schmalzl, M.; Wolf, S.; Nutter, D.; Ward-Thompson, D.; Bourke, T. L.; Zylka, R.

    2010-05-15

    We present the results of a comprehensive infrared, submillimeter, and millimeter continuum emission study of isolated low-mass star-forming cores in 32 Bok globules, with the aim to investigate the process of star formation in these regions. The submillimeter and millimeter dust continuum emission maps together with the spectral energy distributions are used to model and derive the physical properties of the star-forming cores, such as luminosities, sizes, masses, densities, etc. Comparisons with ground-based near-infrared and space-based mid- and far-infrared images from Spitzer are used to reveal the stellar content of the Bok globules, association of embedded young stellar objects (YSOs) with the submillimeter dust cores, and the evolutionary stages of the individual sources. Submillimeter dust continuum emission was detected in 26 out of the 32 globule cores observed. For 18 globules with detected (sub)millimeter cores, we derive evolutionary stages and physical parameters of the embedded sources. We identify nine starless cores, most of which are presumably prestellar, nine Class 0 protostars, and twelve Class I YSOs. Specific source properties like bolometric temperature, core size, and central densities are discussed as a function of evolutionary stage. We find that at least two thirds (16 out of 24) of the star-forming globules studied here show evidence of forming multiple stars on scales between 1000 and 50,000 AU. However, we also find that most of these small prototstar and star groups are comprised of sources with different evolutionary stages, suggesting a picture of slow and sequential star formation in isolated globules.

  15. Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis Star Forming Core

    NASA Technical Reports Server (NTRS)

    Hamaguchi, Ken-Ji; Corcoran, Michael F.; Petre, Rob; White, Nicholas E.; Stelzer, Beate; Nedachi, Ko; Kobayashi, Naoto

    2004-01-01

    We detected three extremely embedded X-ray sources in the R Corona Australis (R CrA) star forming core, IRS 7 region. Two weak X-ray sources are associated with the VLA centimeter radio sources 10E & W, whereas the third brightest source detected in the two XMM-Newton observations on March 2003 has no counterpart at any wavelengths. The large K-band upper-limit (19.4m) measured with the University of Hawaii 88-inch Telescope and strong absorption derived in X-rays (N(sub H) approx. 2.8 x 10(exp 23)/sq cm equivalent to A(sub v) approx. 180 m) indicate that the source is younger than typical Class I protostars, i.e. a Class 0 protostar or an intermittent phase between Class 0 and Class I protostars. The X-ray luminosity was less than one thirtieth (log L(sub x) less than or approx. equals 29.3 ergs/s) in the former Chandra observation in October 2000, which suggests that the X-ray activity, probably generated by magnetic activity, is triggered by an intermittent mass accretion episode such as FU Ori type outbursts. Because the source was detected at high significance in the XMM-Newton observations (approx. 2,000 cnts), X-ray properties of such young protostars can be well investigated for the first time. The light curves were constant in the 1st observation and increased linearly by a factor of two during 30 ksec in the 2nd observation. Both spectra showed iron K lines originated in hot thin-thermal plasma and fluorescence by cold gas. They can be reproduced by an absorbed thin-thermal plasma model with a Gaussian component at 6.4 keV (kT approx. 3-4 keV, L(sub x) approx. 7-20 x 10(exp 30) ergs/s). The rising timescale of the light curves in the 2nd observation was too slow for magnetically generated X-ray flares, whereas large equivalent width of the fluorescence iron K line in the 1st observation (approx. 810 eV) requires strong partial covering of the X-ray source. These results suggest that a confined hot (perhaps accretion) spot on the protostellar core was

  16. Developmental activation of the lysozyme gene in chicken macrophage cells is linked to core histone acetylation at its enhancer elements.

    PubMed

    Myers, Fiona A; Lefevre, Pascal; Mantouvalou, Evangelia; Bruce, Kimberley; Lacroix, Claire; Bonifer, Constanze; Thorne, Alan W; Crane-Robinson, Colyn

    2006-01-01

    Native chromatin IP assays were used to define changes in core histone acetylation at the lysozyme locus during developmental maturation of chicken macrophages and stimulation to high-level expression by lipo-polysaccharide. In pluripotent precursors the lysozyme gene (Lys) is inactive and there is no acetylation of core histones at the gene, its promoter or at the upstream cis-control elements. In myeloblasts, where there is a very low level of Lys expression, H4 acetylation appears at the cis-control elements but not at the Lys gene or its promoter: neither H3 nor H2B become significantly acetylated in myeloblasts. In mature macrophages, Lys expression increases 5-fold: H4, H2B and H2A.Z are all acetylated at the cis-control elements but H3 remains unacetylated except at the -2.4 S silencer. Stimulation with LPS increases Lys expression a further 10-fold: this is accompanied by a rise in H3 acetylation throughout the cis-control elements; H4 and H2B acetylation remain substantial but acetylation at the Lys gene and its promoter remains low. Acetylation is thus concentrated at the cis-control elements, not at the Lys gene or its immediate promoter. H4 acetylation precedes H3 acetylation during development and H3 acetylation is most directly linked to high-level Lys expression. PMID:16914441

  17. Trace-element analyses of core samples from the 1967-1988 drillings of Kilauea Iki lava lake, Hawaii

    USGS Publications Warehouse

    Helz, Rosalind Tuthill

    2012-01-01

    This report presents previously unpublished analyses of trace elements in drill core samples from Kilauea Iki lava lake and from the 1959 eruption that fed the lava lake. The two types of data presented were obtained by instrumental neutron-activation analysis (INAA) and energy-dispersive X-ray fluorescence analysis (EDXRF). The analyses were performed in U.S. Geological Survey (USGS) laboratories from 1989 to 1994. This report contains 93 INAA analyses on 84 samples and 68 EDXRF analyses on 68 samples. The purpose of the study was to document trace-element variation during chemical differentiation, especially during the closed-system differentiation of Kilauea Iki lava lake.

  18. Linear Closed-form Solution and Finite-element Analysis of an Active Tensegrity Unit

    NASA Astrophysics Data System (ADS)

    Kmeť, Stanislav; Platko, Peter

    2012-11-01

    Results of the linear closed form solution of an active or adaptive tensegrity unit, as well as its numerical analysis using finite element method are presented in the paper. The shape of the unit is an octahedral cell with a square base and it is formed by thirteen members (four bottom and four top cables, four edge struts and one central strut). The central strut is designed as an actuator that allows for an adjustment of the shape of the unit which leads to changes of tensile forces in the cables. Due to the diagonal symmetry of the 3D tensegrity unit the closed-form analysis is based on the 2D solution of the equivalent planar biconvex cable system with one central strut under a vertical point load.

  19. EXPLORING MAGNETIC FIELD STRUCTURE IN STAR-FORMING CORES WITH POLARIZATION OF THERMAL DUST EMISSION

    SciTech Connect

    Kataoka, Akimasa; Machida, Masahiro N.; Tomisaka, Kohji

    2012-12-10

    The configuration and evolution of the magnetic field in star-forming cores are investigated in order to directly compare simulations and observations. We prepare four different initial clouds having different magnetic field strengths and rotation rates, in which magnetic field lines are aligned/misaligned with the rotation axis. First, we calculate the evolution of such clouds from the prestellar stage until long after protostar formation. Then, we calculate the polarization of thermal dust emission expected from the simulation data. We create polarization maps with arbitrary viewing angles and compare them with observations. Using this procedure, we confirmed that the polarization distribution projected on the celestial plane strongly depends on the viewing angle of the cloud. Thus, by comparing the observations with the polarization map predicted by the simulations, we can roughly determine the angle between the direction of the global magnetic field and the line of sight. The configuration of the polarization vectors also depends on the viewing angle. We find that an hourglass configuration of magnetic field lines is not always realized in a collapsing cloud when the global magnetic field is misaligned with the cloud rotation axis. Depending on the viewing angle, an S-shaped configuration of the magnetic field (or the polarization vectors) appears early in the protostellar accretion phase. This indicates that not only the magnetic field but also the cloud rotation affects the dynamical evolution of such a cloud. In addition, by comparing the simulated polarization with actual observations, we can estimate properties of the host cloud such as the evolutionary stage, magnetic field strength, and rotation rate.

  20. Distinct element method analyses of fuel spheres in the PBMR core using PFC{sup 3D}

    SciTech Connect

    Polson, Alexander G.

    2004-07-01

    The Pebble Bed Modular Reactor, or PBMR, is a High Temperature Gas Reactor that contains a large number of graphite fuel spheres that circulate in its core. The dynamics of these spheres, combined with thermal contraction and expansion, causes various loading cases on the reactor structures. A Distinct Element Method, or DEM, as implemented in the Particle Flow Code in 3D, or PFC{sup 3D}, is used at PBMR (Pty) Ltd to model the fuel sphere dynamics in the reactor core. This paper presents a few exploratory studies where PFC{sup 3D} was used to investigate the interaction between fuel spheres and structural components in the PBMR, as well as the packing efficiency of the spheres in the core. (author)

  1. A carbon, nitrogen, and sulfur elemental and isotopic study in dated sediment cores from the Louisiana Shelf

    USGS Publications Warehouse

    Rosenbauer, R.J.; Swarzenski, P.W.; Kendall, C.; Orem, W.H.; Hostettler, F.D.; Rollog, M.E.

    2009-01-01

    Three sediment cores were collected off the Mississippi River delta on the Louisiana Shelf at sites that are variably influenced by recurring, summer-time water-column hypoxia and fluvial loadings. The cores, with established chronology, were analyzed for their respective carbon, nitrogen, and sulfur elemental and isotopic composition to examine variable organic matter inputs, and to assess the sediment record for possible evidence of hypoxic events. Sediment from site MRJ03-3, which is located close to the Mississippi Canyon and generally not influenced by summer-time hypoxia, is typical of marine sediment in that it contains mostly marine algae and fine-grained material from the erosion of terrestrial C4 plants. Sediment from site MRJ03-2, located closer to the mouth of the Mississippi River and at the periphery of the hypoxic zone (annual recurrence of summer-time hypoxia >50%), is similar in composition to core MRJ03-3, but exhibits more isotopic and elemental variability down-core, suggesting that this site is more directly influenced by river discharge. Site MRJ03-5 is located in an area of recurring hypoxia (annual recurrence >75%), and is isotopically and elementally distinct from the other two cores. The carbon and nitrogen isotopic composition of this core prior to 1960 is similar to average particulate organic matter from the lower Mississippi River, and approaches the composition of C3 plants. This site likely receives a greater input of local terrestrial organic matter to the sediment. After 1960 and to the present, a gradual shift to higher values of ??13C and ??15N and lower C:N ratios suggests that algal input to these shelf sediments increased as a result of increased productivity and hypoxia. The values of C:S and ??34S reflect site-specific processes that may be influenced by the higher likelihood of recurring seasonal hypoxia. In particular, the temporal variations in the C:S and ??34S down-core are likely caused by changes in the rate of

  2. Myriad Triple-Helix-Forming Structures in the Transposable Element RNAs of Plants and Fungi.

    PubMed

    Tycowski, Kazimierz T; Shu, Mei-Di; Steitz, Joan A

    2016-05-10

    The ENE (element for nuclear expression) is a cis-acting RNA structure that protects viral or cellular noncoding RNAs (ncRNAs) from nuclear decay through triple-helix formation with the poly(A) tail or 3'-terminal A-rich tract. We expanded the roster of nine known ENEs by bioinformatic identification of ∼200 distinct ENEs that reside in transposable elements (TEs) of numerous non-metazoan and one fish species and in four Dicistrovirus genomes. Despite variation within the ENE core, none of the predicted triple-helical stacks exceeds five base triples. Increased accumulation of reporter transcripts in human cells demonstrated functionality for representative ENEs. Location close to the poly(A) tail argues that ENEs are active in TE transcripts. Their presence in intronless, but not intron-containing, hAT transposase genes supports the idea that TEs acquired ENEs to counteract the RNA-destabilizing effects of intron loss, a potential evolutionary consequence of TE horizontal transfer in organisms that couple RNA silencing to splicing deficits. PMID:27134163

  3. Myriad Triple-Helix-Forming Structures in the Transposable Element RNAs of Plants and Fungi

    PubMed Central

    Tycowski, Kazimierz T.; Shu, Mei-Di; Steitz, Joan A.

    2016-01-01

    SUMMARY The ENE (element for nuclear expression) is a cis-acting RNA structure that protects viral or cellular noncoding (nc)RNAs from nuclear decay through triple-helix formation with the poly(A) tail or 3′-terminal A-rich tract. We expanded the roster of 9 known ENEs by bioinformatic identification of ~200 distinct ENEs that reside in transposable elements (TEs) of numerous non-metazoan and one fish species, and in four Dicistrovirus genomes. Despite variation within the ENE core, none of the predicted triple-helical stacks exceeds five base triples. Increased accumulation of reporter transcripts in human cells demonstrated functionality for representative ENEs. Location close to the poly(A) tail argues that ENEs are active in TE transcripts. Their presence in intronless but not intron-containing hAT transposase genes supports the idea that TEs acquired ENEs to counteract the RNA-destabilizing effects of intron loss, a potential evolutionary consequence of TE horizontal transfer in organisms that couple RNA silencing to splicing deficits. PMID:27134163

  4. A tactile sensing element based on a hetero-core optical fiber for force measurement and texture detection

    NASA Astrophysics Data System (ADS)

    Yamazaki, Hiroshi; Koyama, Yuya; Watanabe, Kazuhiro

    2014-05-01

    Tactile sensing technology can measure a given property of an object through physical contact between a sensing element and the object. Various tactile sensing techniques have been developed for several applications such as intelligent robots, tactile interface, medical support and nursing care support. A desirable tactile sensing element for supporting human daily life can be embedded in the soft material with high sensitivity and accuracy in order to prevent from damaging to human or object physically. This report describes a new tactile sensing element. Hetero-core optical fibers have high sensitivity of macro-bending at local sensor portion and temperature independency, including advantages of optical fiber itself; thin size, light weight, flexible transmission line, and immunity to electro-magnetic interference. The proposed tactile sensing element could detect textures of touched objects through the optical loss caused by the force applied to the sensing element. The characteristics of the sensing element have been evaluated, in which the sensing element has the monotonic and non-linear sensitivity against the normal force ranged from 0 to 5 N with lower accuracy than 0.25 dB. Additionally, texture detection have been successfully demonstrated in which small surface figures of 0.1 mm in height were detected with spatial resolution of 0.4 mm.

  5. Semantic enrichment of medical forms - semi-automated coding of ODM-elements via web services.

    PubMed

    Breil, Bernhard; Watermann, Andreas; Haas, Peter; Dziuballe, Philipp; Dugas, Martin

    2012-01-01

    Semantic interoperability is an unsolved problem which occurs while working with medical forms from different information systems or institutions. Standards like ODM or CDA assure structural homogenization but in order to compare elements from different data models it is necessary to use semantic concepts and codes on an item level of those structures. We developed and implemented a web-based tool which enables a domain expert to perform semi-automated coding of ODM-files. For each item it is possible to inquire web services which result in unique concept codes without leaving the context of the document. Although it was not feasible to perform a totally automated coding we have implemented a dialog based method to perform an efficient coding of all data elements in the context of the whole document. The proportion of codable items was comparable to results from previous studies. PMID:22874367

  6. Non-contact high precision measurement of surface form tolerances and central thickness for optical elements

    NASA Astrophysics Data System (ADS)

    Lou, Ying

    2010-10-01

    The traditional contact measuring methods could not satisfy the current optical elements measuring requirements. Noncontact high precision measuring theory, principle and instrument of the surface form tolerances and central thickness for optical elements were studied in the paper. In comparison with other types of interferometers, such as Twyman-Green and Mach-Zehnder, a Fizeau interferometer has the advantages of having fewer optical components, greater accuracy, and is easier to use. Some relations among the 3/A(B/C), POWER/PV and N/ΔN were studied. The PV with POWER removed can be the reference number of ΔN. The chromatic longitudinal aberration of a special optical probe can be used for non-contanct central thickness measurement.

  7. Electrochemical machining process for forming surface roughness elements on a gas turbine shroud

    DOEpatents

    Lee, Ching-Pang; Johnson, Robert Alan; Wei, Bin; Wang, Hsin-Pang

    2002-01-01

    The back side recessed cooling surface of a shroud defining in part the hot gas path of a turbine is electrochemically machined to provide surface roughness elements and spaces therebetween to increase the heat transfer coefficient. To accomplish this, an electrode with insulating dielectric portions and non-insulating portions is disposed in opposition to the cooling surface. By passing an electrolyte between the cooling surface and electrode and applying an electrical current between the electrode and a shroud, roughness elements and spaces therebetween are formed in the cooling surface in opposition to the insulating and non-insulating portions of the electrode, hence increasing the surface area and heat transfer coefficient of the shroud.

  8. Hyper Text Mark-up Language and Dublin Core metadata element set usage in websites of Iranian State Universities’ libraries

    PubMed Central

    Zare-Farashbandi, Firoozeh; Ramezan-Shirazi, Mahtab; Ashrafi-Rizi, Hasan; Nouri, Rasool

    2014-01-01

    Introduction: Recent progress in providing innovative solutions in the organization of electronic resources and research in this area shows a global trend in the use of new strategies such as metadata to facilitate description, place for, organization and retrieval of resources in the web environment. In this context, library metadata standards have a special place; therefore, the purpose of the present study has been a comparative study on the Central Libraries’ Websites of Iran State Universities for Hyper Text Mark-up Language (HTML) and Dublin Core metadata elements usage in 2011. Materials and Methods: The method of this study is applied-descriptive and data collection tool is the check lists created by the researchers. Statistical community includes 98 websites of the Iranian State Universities of the Ministry of Health and Medical Education and Ministry of Science, Research and Technology and method of sampling is the census. Information was collected through observation and direct visits to websites and data analysis was prepared by Microsoft Excel software, 2011. Results: The results of this study indicate that none of the websites use Dublin Core (DC) metadata and that only a few of them have used overlaps elements between HTML meta tags and Dublin Core (DC) elements. The percentage of overlaps of DC elements centralization in the Ministry of Health were 56% for both description and keywords and, in the Ministry of Science, were 45% for the keywords and 39% for the description. But, HTML meta tags have moderate presence in both Ministries, as the most-used elements were keywords and description (56%) and the least-used elements were date and formatter (0%). Conclusion: It was observed that the Ministry of Health and Ministry of Science follows the same path for using Dublin Core standard on their websites in the future. Because Central Library Websites are an example of scientific web pages, special attention in designing them can help the researchers

  9. Global shielding analysis for the three-element core advanced neutron source reactor under normal operating conditions

    SciTech Connect

    Slater, C.O.; Bucholz, J.A.

    1995-08-01

    Two-dimensional discrete ordinates radiation transport calculations were performed for a model of the three-element core Advanced Neutron Source reactor design under normal operating conditions. The core consists of two concentric upper elements and a lower element radially centered in the annulus between the upper elements. The initial radiation transport calculations were performed with the DORT two-dimensional discrete ordinates radiation transport code using the 39-neutron-group/44-gamma-ray-group ANSL-V cross-section library, an S{sub 6} quadrature, and a P{sub 1} Legendre polynomial expansion of the cross sections to determine the fission neutron source distribution in the core fuel elements. These calculations were limited to neutron groups only. The final radiation transport calculations, also performed with DORT using the 39-neutron-group/44-gamma-ray-group ANSL-V cross-section library, an S{sub l0} quadrature, and a P{sub 3} Legendre polynomial expansion of the cross sections, produced neutron and gamma-ray fluxes over the full extent of the geometry model. Responses (or activities) at various locations in the model were then obtained by folding the appropriate response functions with the fluxes at those locations. Some comparisons were made with VENTURE-calculated (diffusion theory) 20-group neutron fluxes that were summed into four broad groups. Tne results were in reasonably good agreement when the effects of photoneutrons were not included, thus verifying the physics model upon which the shielding model was based. Photoneutrons increased the fast-neutron flux levels deep within the D{sub 2}0 several orders of magnitude. Results are presented as tables of activity values for selected radial and axial traverses, plots of the radial and axial traverse data, and activity contours superimposed on the calculational geometry model.

  10. NASA/JAXA's GPM Core Satellite Sees Heavy Rainfall as Danielle Forms

    NASA Video Gallery

    On June 19, NASA and the Japan Aerospace Exploration Agency's Global Precipitation Measurement or GPM core satellite showed intense showers falling at a rate of over 87 mm (3.4 inches) per hour in ...

  11. Paleomagnetic Reorientation of Structural Elements in Drill Cores: an example from Tolhuaca Geothermal Field

    NASA Astrophysics Data System (ADS)

    Perez-Flores, P.; Veloso, E. E.; Cembrano, J. M.; Sánchez, P.; Iriarte, S.; Lohmar, S.

    2013-12-01

    Reorientation of mesoscopic faults, veins and fractures recovered from drilling is critical to construct reliable structural models that can account for their architecture and deformation regime. However, oriented cores are expensive and time consuming to drill. Some techniques achieve reorientation by introducing tools into the borehole. Problems arise when boreholes are unstable or collapse. One alternative technique allowing reorientation is to obtain reliable paleomagnetic vectors to reorient each core piece after drilling. Here, we present stable and reliable remnant magnetic vectors calculated from the Tol-1 core to analyze the geometry of the fracture network and its relationship to regional tectonic. Tol-1 core is a vertical, 1073 m deep geothermal well, drilled at the Tolhuaca Geothermal Field in the Southern Volcanic Zone of the Andes by MRP Geothermal Chile Ltda (formerly GGE Chile SpA) in 2009. The core consists of basaltic/andesitic volcanic rocks with subordinate pyroclastic/volcaniclastic units, with probable Pleistocene age. Fault planes with slickenlines and mineral fiber kinematic indicators are common in the upper 700 m of the core. Calcite, quartz and calcite-quartz veins are recognized along of entire core, whereas epidote-quartz and calcite-epidote veins occur in the last 350 m, minor chlorite, anhydrite and clay-minerals are present. Orientations of structural features in the core were measured with a goniometer using the core's axis and a false north for each piece; hence, orientation data has a false strike but a real dip. To achieve total reorientation of the pieces, we collected 200 standard-size paleomagnetic specimens, ensuring that at least four of them were recovered from continuous pieces. Thermal (up to 700°C) and alternating field demagnetization (up to 90mT on steps of 2mT) methods were used to isolate a stable remnant magnetization (RM) vector, and each technique yielded similar results. RM vectors were recovered between 0 to 25

  12. Thermal Evolution Of The Core And Mantle Of Mars: Effects Of A Sequence Of Basin-Forming Impacts

    NASA Astrophysics Data System (ADS)

    Roberts, James; Arkani-Hamed, Jafar

    2015-04-01

    Several giant impact basins have been identified on Mars [1-2]. The youngest of these basins [1] are completely demagnetized [3], indicating that a global magnetic field [4] vanished in the mid-Noachian. Shock heating from the seven largest impacts penetrates below the core-mantle boundary (CMB) [5]. Previous investigations of coupled core cooling and mantle convection [5-6] showed that a single basin-forming impact could halt dynamo activity for 100 My, and that the core would not become fully convective again for nearly 1 Gy after the impact. However, the interval between impacts [1] is shorter than the timescale for dynamo activity to resume following an impact. Sub-sequent impacts may delay this recovery. Here, we expand this investigation into 3D and consider the full sequence of basin-forming impacts large enough to affect the core. Our goal is to obtain a better estimate of the timescale for resumption of dynamo activity. We compute the shock heating due to formation of the seven largest impact basins in the core and mantle using ray-tracing and scaling laws [7-8]. We model 3D mantle convection using CitcomS [9-10], and core cooling with a 1-D parametrization [5]. The temperature is initially adiabatic, with thermal boundary layers (TBL) at the surface and both sides of the CMB. At the time of each impact [1] we introduce a temperature perturbation resulting from shock heating into the core and mantle, and allow the core to stratify [11]. At a given timestep, we fix the mantle temperature and solve the 1D enthalpy equation in the core and lower TBL of the mantle over a time corresponding to a mantle timestep. We update the temperature at the CMB and TBL, and let the mantle convection progress for another timestep. We continue this iteration until the next impact occurs, or until the entire core is again convecting. Only the outermost core is affected by the impact heating. Because the conductivity of the core is higher than that of the mantle, the top of the

  13. Finite Element Development and Specifications of a Patched, Recessed Nomex Core Honeycomb Panel for Increased Sound Transmission Loss

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    2007-01-01

    This informal report summarizes the development and the design specifications of a recessed nomex core honeycomb panel in fulfillment of the deliverable in Task Order 13RBE, Revision 10, Subtask 17. The honeycomb panel, with 0.020-inch thick aluminum face sheets, has 0.016-inch thick aluminum patches applied to twenty-five, 6 by 6 inch, quarter inch thick recessed cores. A 10 dB higher transmission loss over the frequency range 250 - 1000 Hz was predicted by a MSC/NASTRAN finite element model when compared with the transmission loss of the base nomex core honeycomb panel. The static displacement, due to a unit force applied at either the core or recessed core area, was of the same order of magnitude as the static displacement of the base honeycomb panel when exposed to the same unit force. The mass of the new honeycomb design is 5.1% more than the base honeycomb panel. A physical model was constructed and is being tested.

  14. Finite element stress analysis of short-post core and over restorations prepared with different restorative materials.

    PubMed

    Gurbuz, Taskin; Sengul, Fatih; Altun, Ceyhan

    2008-07-01

    The present study was conducted to determine the effect on the distribution of stress with the use of short-post cores and over restorations composed of different materials. The restorative materials used were namely two different composite resin materials (Valux Plus and Tetric Flow), a polyacid-modified resin material (Dyract AP), and a woven polyethylene fiber combination (Ribbond Fiber + Bonding agent + Tetric Flow). Finite element analysis (FEA) was used to develop a model for the maxillary primary anterior teeth. A masticatory force of 100 N was applied at 148 degrees to the incisal edge of the palatal surface of the crown model. Stress distributions and stress values were compared using von Mises criteria. The tooth model was assumed to be isotropic, homogeneous, elastic, and asymmetrical. It was observed that the highest stress usually occurred in the cervical area of the tooth when Tetric Flow was used as the short-post core and over restoration material. The same maximum stress value was also obtained when Ribbond fiber + Tetric Flow material was used for the short-post core. The results of FEA showed that the mechanical properties and elastic modulus of the restorative material influenced the stresses generated in enamel, dentin, and restoration when short-post core restorations were loaded incisally. Resin-based restorative materials with higher elastic moduli were found to be unsuitable as short-post core materials in endodontically treated maxillary primary anterior teeth. PMID:18833762

  15. A finite element study of teeth restored with post and core: Effect of design, material, and ferrule

    PubMed Central

    Upadhyaya, Viram; Bhargava, Akshay; Parkash, Hari; Chittaranjan, B.; Kumar, Vivek

    2016-01-01

    Background: Different postdesigns and materials are available; however, no consensus exists regarding superiority for stress distribution. The aim of this study was to evaluate the effect of design and material of post with or without ferrule on stress distribution using finite element analysis. Materials and Methods: A total of 12 three-dimensional (3D) axisymmetric models of postretained central incisors were made: Six with ferrule design and six without it. Three of these six models had tapered posts, and three had parallel posts. The materials tested were titanium post with a composite resin core, nickel chromium cast post and core, and fiber reinforced composite (FRC) post with a composite resin core. The stress analysis was done using ANSYS software. The load of 100 N at an angle of 45΀ was applied 2 mm cervical to incisal edge on the palatal surface and results were analyzed using 3D von Mises criteria. Results: The highest amount of stress was in the cervical region. Overall, the stress in the tapered postsystem was more than the parallel one. FRC post and composite resin core recorded minimal stresses within the post but the stresses transmitted to cervical dentin were more as compared to other systems. Minimal stresses in cervical dentine were observed where the remaining coronal dentin was strengthen by ferrule. Conclusion: A rigid material with high modulus of elasticity for post and core system creates most uniform stress distribution pattern. Ferrule provides uniform distribution of stresses and decreases the cervical stresses. PMID:27274343

  16. Finite Element Prediction of Sheet Forming Defects Using Elastic-Plastic, Damage and Localization Models

    NASA Astrophysics Data System (ADS)

    Haddag, Badis; Abed-Meraim, Farid; Balan, Tudor

    2007-05-01

    In this work, an advanced anisotropic elastic-plasticity model is combined with a damage model and a strain localization criterion in the aim to describe accurately the mechanical behavior of sheet metals. Large strain, fully three-dimensional, implicit time integration algorithms are developed for this model and implemented in the finite element code Abaqus. The resulting code is used to predict the strain localization limits as well as the springback after forming of sheet steels. The impact of strain-path dependent hardening models on the limit strains and on the amount of springback is addressed.

  17. Continuous coring drill bit

    SciTech Connect

    Ford, G.A.

    1987-09-22

    A continuous coring drill bit is described comprising: (a) body means defining a vertical axis and adapted for connection to drill pipe and forming an internal body cavity disposed in eccentric relation with the vertical axis and a generally circular throat in communication with the body cavity for conducting drilling fluid. The throat defining a throat axis coincident with the vertical axis and being of a configuration permitting passage of a formation core into the body cavity; (b) a generally cylindrical tubular core breaker being rotatably mounted within the body cavity and defining a vertical axis of rotation of generally parallel and offset relation with the vertical axis of the body means; and (c) a buttress element extending inwardly from the core breaker and adapted to contact the formation core. Upon each rotation of the drill bit the buttress element applying transverse force to the core for fracturing of the core into sections sufficiently small for transport by the drilling fluid.

  18. Characterization of human glucocorticoid receptor complexes formed with DNA fragments containing or lacking glucocorticoid response elements

    SciTech Connect

    Tully, D.B.; Cidlowski, J.A. )

    1989-03-07

    Sucrose density gradient shift assays were used to study the interactions of human glucocorticoid receptors (GR) with small DNA fragments either containing or lacking glucocorticoid response element (GRE) DNA consensus sequences. When crude cytoplasmic extracts containing ({sup 3}H)triamcinolone acetonide (({sup 3}H)TA) labeled GR were incubated with unlabeled DNA under conditions of DNA excess, a GRE-containing DNA fragment obtained from the 5' long terminal repeat of mouse mammary tumor virus (MMTV LTR) formed a stable 12-16S complex with activated, but not nonactivated, ({sup 3}H)TA receptor. By contrast, if the cytosols were treated with calf thymus DNA-cellulose to deplete non-GR-DNA-binding proteins prior to heat activation, a smaller 7-10S complex was formed with the MMTV LTR DNA fragment. Activated ({sup 3}H)TA receptor from DNA-cellulose pretreated cytosols also interacted with two similarly sized fragments from pBR322 DNA. Stability of the complexes formed between GR and these three DNA fragments was strongly affected by even moderate alterations in either the salt concentration or the pH of the gradient buffer. Under all conditions tested, the complex formed with the MMTV LTR DNA fragment was more stable than the complexes formed with either of the pBR322 DNA fragments. Together these observations indicate that the formation of stable complexes between activated GR and isolated DNA fragments requires the presence of GRE consensus sequences in the DNA.

  19. Structure of Core Domain of Fibril-Forming PHF/Tau Fragments

    PubMed Central

    Inouye, Hideyo; Sharma, Deepak; Goux, Warren J.; Kirschner, Daniel A.

    2006-01-01

    Short peptide sequences within the microtubule binding domain of the protein Tau are proposed to be core nucleation sites for formation of amyloid fibrils displaying the paired helical filament (PHF) morphology characteristic of neurofibrillary tangles. To study the structure of these proposed nucleation sites, we analyzed the x-ray diffraction patterns from the assemblies formed by a variety of PHF/tau-related peptide constructs containing the motifs VQIINK (PHF6*) in the second repeat and VQIVYK (PHF6) in the third repeat of tau. Peptides included: tripeptide acetyl-VYK-amide (AcVYK), tetrapeptide acetyl-IVYK-amide (AcPHF4), hexapeptide acetyl-VQIVYK-amide (AcPHF6), and acetyl-GKVQIINKLDLSNVQKDNIKHGSVQIVYKPVDLSKVT-amide (AcTR4). All diffraction patterns showed reflections at spacings of 4.7 Å, 3.8 Å, and ∼8–10 Å, which are characteristic of an orthogonal unit cell of β-sheets having dimensions a = 9.4 Å, b = 6.6 Å, and c = ∼8–10 Å (where a, b, and c are the lattice constants in the H-bonding, chain, and intersheet directions). The sharp 4.7 Å reflections indicate that the β-crystallites are likely to be elongated along the H-bonding direction and in a cross-β conformation. The assembly of the AcTR4 peptide, which contains both the PHF6 and PHF6* motifs, consisted of twisted sheets, as indicated by a unique fanning of the diffuse equatorial scattering and meridional accentuation of the (210) reflection at 3.8 Å spacing. The diffraction data for AcVYK, AcPHF4, and AcPHF6 all were consistent with ∼50 Å-wide tubular assemblies having double-walls, where β-strands constitute the walls. In this structure, the peptides are H-bonded together in the fiber direction, and the intersheet direction is radial. The positive-charged lysine residues face the aqueous medium, and tyrosine-tyrosine aromatic interactions stabilize the intersheet (double-wall) layers. This particular contact, which may be involved in PHF fibril formation, is proposed here as a

  20. Origin of sedimentary humic acids, potential carriers of ore-forming elements

    NASA Astrophysics Data System (ADS)

    Hatcher, P. G.

    Humic acids are complex, macromolecular organic components of sediments and are defined by their solubility in dilute alkali insolubility in dilute acid. Because of their general structural characteristics (for example, their high proportion of oxygen functional groups), humic acids can complex with inorganic cations and may be important in forming ore deposits. In some instances (such as uranium ores), ore bodies are believed to have originated by mobilization of an ore-forming element complexed with humic acids and subsequent precipitation. Knowledge of the mechanism for the formation of humic acids is being applied to two major ore deposits. Carlin-type gold ores from Nevada show that humic acids may have been precursors. This suggests that the humic acids could have played a major role in the transport and accumulation of the ore.

  1. Finite Element modelling of laser forming at macro and micro scales

    NASA Astrophysics Data System (ADS)

    Griffiths, J.; Edwardson, S. P.; Dearden, G.; Watkins, K. G.

    Laser forming (LF) offers the industrial promise of controlled shaping of metallic and non-metallic components for prototyping, correction of design shape or distortion and precision adjustment applications. In order to fulfill this promise in a manufacturing environment the process must have a high degree of controllability, which can be achieved through a better understanding of its underlying mechanisms. At the macro scale, Finite Element (FE) modelling can be used to ascertain which of the various process parameters associated with the temperature gradient mechanism (such as graphite burn-off, geometrical effects, variation in absorption etc) contribute towards this phenomenon and subsequently the magnitude of their contribution. At the micro scale FE modelling can be used to determine the mechanism by which deformation occurs upon application of short pulses in laser micro forming (L μF).

  2. Formation of secondary messengers by blood-formed elements in low-power laser irradiation

    NASA Astrophysics Data System (ADS)

    Brill, Gregory E.; Proshina, Olga V.; Zhigalina, Valentina N.; Filimonovskaya, Lyudmila S.; Romanova, Tatyana P.; Petrisheva, Svetlana G.; Zolotarjova, Tamara M.

    1995-05-01

    Irradiation of heparinized rat blood by He-Ne laser light ((lambda) - 632.8 nm, power density - 5 mW/cm2) during 15 or 30 min was performed in vitro experiments. The complex of biochemical parameters of erythrocytes, plasma and cytochemical parameters of polymorphonuclear leucocytes was studied. Laser irradiation was stated to cause different metabolic changes in red blood cells and neutrophils depending on the dose. In both doses of irradiation glucose-6-phosphate dehydrogenase activity lowers in erythrocytes, succinate dehydrogenase activity and lysosomal cationic proteins content increase in neutrophils. Stimulation of oxygen active forms production in cellular membranes of blood formed elements results in plasma malonic dialdehyde level increase and in the change of the balance between primary and secondary lipid peroxidation products. Cooperative interaction between different blood cells in the process of realization of system response to laser exposure is supposed to exist.

  3. Recent development of a hydrostatic dynamical cores using the spectral element and the discontinuous Galerkin method at KIAPS (Invited)

    NASA Astrophysics Data System (ADS)

    Choi, S.; Giraldo, F. X.; Park, J.; Jun, S.; Yi, T.; Kang, S.; Oh, T.

    2013-12-01

    Korea Institute of Atmospheric Prediction Systems (KIAPS) was founded in 2011 by Korea Meteorological Administration (KMA) as a non-profit foundation to develop Korea's own global NWP system including it's framework, data assimilation, coupler and so on. The final goal of KIAPS is to develop a global non-hydrostatic NWP system by 2019 for operational use at KMA. In the first stage (2011-2013), we have developed a dynamical core for the Eulerian hydrostatic primitive equation as a initial effort. At the meeting, the progress and status of the core will be presented. The core is based on spectral element (SE; or continuous Galerkin method) and discontinuous Galerkin methods (DG). It is expected to take the advantages that the horizontal operators can be approximated by local high-order elements while scaling efficiently on multiprocessor computers with such high processor counts, since the properties of the methods are local in nature and have a small communication footprint. In order to overcome polar singularities and retain flexibility of the grid, we consider the hydrostatic primitive equations in 3D Cartesian space. This approach is used in Giraldo and Rosmond (MWR 2004). For the horizontal discretization, the cubed sphere grid is used for the sake of isotropy and due to the simplicity with which to use quadrilateral elements. For the vertical discretization, a Lorenz staggered grid is implemented with the terrain following σ-p coordinate. Currently, explicit time integrators, such as strong stability preserving Runge-Kutta (SSPRK) are implemented. In order to validate the developed core, some results are presented for test cases such as the Rossby-Haurwitz wavenumber 4 and the Jablonowski-Williamson balanced initial state and baroclinic instability test.

  4. Distribution and possible source of trace elements in the sediment cores of a tropical macrotidal estuary and their ecotoxicological significance.

    PubMed

    Chatterjee, M; Silva Filho, E V; Sarkar, S K; Sella, S M; Bhattacharya, A; Satpathy, K K; Prasad, M V R; Chakraborty, S; Bhattacharya, B D

    2007-04-01

    The paper presents the first document regarding concentration, distribution and possible sources of selected trace elements (Cu, Fe, Mn, Zn, Cr, Co, Ni, Pb, Al, B and Ba) in core sediments (<63 micro particle size) from the lower stretch of Hugli (Ganges) estuary, northeast coast of Bay of Bengal by ICP-AES and EDXRF to evaluate geochemical processes influencing their distribution and possible environmental consequences. The levels of elements showed a wide range of variations in different core depths, in upper and lower intertidal zones as well as among three sampling stations. The most interesting feature of the study is the downward increase of concentrations of majority of the elements reaching overall maximum values at a depth of 20-28 cm in upper littoral zone of the site located in the extreme downstream stretch of the estuary. Values of organic carbon showed very strong positive correlations with most of the elements as revealed by correlation matrix (r) values. The interelemental relationship revealed the identical behavior of element during its transport in the estuarine environment. The overall variation in concentration can be attributed to differential discharge of untreated effluents originating from industrial, agricultural, and aquacultural sources as well as from domestic sewage along with the fishing and boating activities. The resulting compositional dataset was tested by principal component analyses and cluster analyses. Pollution load index (PLI) and index of Geoaccumulation (Igeo) revealed overall low values but the enrichment factors (EFs) for Pb were typically high for all the stations. The mean concentrations of Zn and to some extent Cu exceeded the Effects Range-Low (ER-L) values in the majority of the cases indicating that there may be some ecotoxicological risk to organisms living in sediments. The concentration of the trace elements reported in this work is useful as baselines for comparison in future sediment quality studies. PMID

  5. Trace element seasonality in marine macroalgae of different functional-form groups.

    PubMed

    Malea, Paraskevi; Chatziapostolou, Anastasia; Kevrekidis, Theodoros

    2015-02-01

    Novel information on the seasonality of element accumulation in seaweeds is provided. Seasonal patterns of As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Sr, U, V and Zn concentrations in macroalgae belonging to different functional-form groups (Ulva intestinalis, Ulva rigida, Codium fragile, Gracilaria gracilis) from the Thessaloniki Gulf, Aegean Sea were determined and compared. Uni- and multivariate data analyses were applied. Element concentrations generally decreased during spring and/or summer, probably due to the growth effect, but a reverse trend, particularly in Ulva species, was also observed. Most elements (Cd, Co, Cr, Cu, Mo, Ni, Pb, Sr) in Ulva species displayed a comparatively low monthly variability, indicating that the extent of seasonal variation is closely related to thallus morphology and growth strategy. In particular, these data suggest that Cd, Co, Cr, Cu, Mo, Ni, Pb and Sr contents in fast-growing, sheet-like macroalgae are less influenced by the season, compared to their contents in coarsely-branched and thick-leathery macroalgae; therefore, sheet-like macroalgae may be more appropriate to be used in biomonitoring of coastal waters. The data presented could be utilized in the development of biomonitoring programmes for the protection of coastal environments. PMID:25460058

  6. Diamond-forming fluids in fibrous diamonds: The trace-element perspective

    NASA Astrophysics Data System (ADS)

    Weiss, Y.; Griffin, W. L.; Navon, O.

    2013-08-01

    processes leading to the formation of the “Ribbed” patterns. Percolation of an asthenospheric silicic HDF with “Planed” pattern through previously metasomatized lithosphere that carries accessory phlogopite and Fe-Ti oxides, closely reproduce the “Ribbed” pattern of silicic and low-Mg carbonatitic HDFs at fluid/rock ratios ≈ 0.1%. The initial trace-element pattern of the lithosphere influences the more compatible elements of the HDF (Sr-Lu). However, in the Cs-Pr range, the presence of phlogopite and Ti-Fe oxides controls the evolution of the “Ribbed” pattern. Percolation explains the observed decoupling between major- and trace-elements in HDFs and the resemblance of trace-element patterns in HDFs from different cratons. It may also explain the limited variation of δ13C in fibrous diamonds (-6±2‰). The two patterns escape the circular “chicken and egg” reasoning that calls for an enriched source for the formation of highly fractionated melts: it suggests that diamond-forming fluids can come directly from the asthenosphere (with no need for a pre-metasomatized source) and that they can be further modified in the lithosphere.

  7. Secondary structure in the core of amyloid fibrils formed from human β₂m and its truncated variant ΔN6.

    PubMed

    Su, Yongchao; Sarell, Claire J; Eddy, Matthew T; Debelouchina, Galia T; Andreas, Loren B; Pashley, Clare L; Radford, Sheena E; Griffin, Robert G

    2014-04-30

    Amyloid fibrils formed from initially soluble proteins with diverse sequences are associated with an array of human diseases. In the human disorder, dialysis-related amyloidosis (DRA), fibrils contain two major constituents, full-length human β2-microglobulin (hβ2m) and a truncation variant, ΔN6 which lacks the N-terminal six amino acids. These fibrils are assembled from initially natively folded proteins with an all antiparallel β-stranded structure. Here, backbone conformations of wild-type hβ2m and ΔN6 in their amyloid forms have been determined using a combination of dilute isotopic labeling strategies and multidimensional magic angle spinning (MAS) NMR techniques at high magnetic fields, providing valuable structural information at the atomic-level about the fibril architecture. The secondary structures of both fibril types, determined by the assignment of ~80% of the backbone resonances of these 100- and 94-residue proteins, respectively, reveal substantial backbone rearrangement compared with the location of β-strands in their native immunoglobulin folds. The identification of seven β-strands in hβ2m fibrils indicates that approximately 70 residues are in a β-strand conformation in the fibril core. By contrast, nine β-strands comprise the fibrils formed from ΔN6, indicating a more extensive core. The precise location and length of β-strands in the two fibril forms also differ. The results indicate fibrils of ΔN6 and hβ2m have an extensive core architecture involving the majority of residues in the polypeptide sequence. The common elements of the backbone structure of the two proteins likely facilitates their ability to copolymerize during amyloid fibril assembly. PMID:24679070

  8. Secondary Structure in the Core of Amyloid Fibrils Formed from Human β2m and its Truncated Variant ΔN6

    PubMed Central

    2014-01-01

    Amyloid fibrils formed from initially soluble proteins with diverse sequences are associated with an array of human diseases. In the human disorder, dialysis-related amyloidosis (DRA), fibrils contain two major constituents, full-length human β2-microglobulin (hβ2m) and a truncation variant, ΔN6 which lacks the N-terminal six amino acids. These fibrils are assembled from initially natively folded proteins with an all antiparallel β-stranded structure. Here, backbone conformations of wild-type hβ2m and ΔN6 in their amyloid forms have been determined using a combination of dilute isotopic labeling strategies and multidimensional magic angle spinning (MAS) NMR techniques at high magnetic fields, providing valuable structural information at the atomic-level about the fibril architecture. The secondary structures of both fibril types, determined by the assignment of ∼80% of the backbone resonances of these 100- and 94-residue proteins, respectively, reveal substantial backbone rearrangement compared with the location of β-strands in their native immunoglobulin folds. The identification of seven β-strands in hβ2m fibrils indicates that approximately 70 residues are in a β-strand conformation in the fibril core. By contrast, nine β-strands comprise the fibrils formed from ΔN6, indicating a more extensive core. The precise location and length of β-strands in the two fibril forms also differ. The results indicate fibrils of ΔN6 and hβ2m have an extensive core architecture involving the majority of residues in the polypeptide sequence. The common elements of the backbone structure of the two proteins likely facilitates their ability to copolymerize during amyloid fibril assembly. PMID:24679070

  9. Systematics of metal-silicate partitioning for many siderophile elements applied to Earth’s core formation

    NASA Astrophysics Data System (ADS)

    Siebert, Julien; Corgne, Alexandre; Ryerson, Frederick J.

    2011-03-01

    Superliquidus metal-silicate partitioning was investigated for a number of moderately siderophile (Mo, As, Ge, W, P, Ni, Co), slightly siderophile (Zn, Ga, Mn, V, Cr) and refractory lithophile (Nb, Ta) elements. To provide independent constrains on the effects of temperature, oxygen fugacity and silicate melt composition, isobaric (3 GPa) experiments were conducted in piston cylinder apparatus at temperature between 1600 and 2600 °C, relative oxygen fugacities of IW-1.5 to IW-3.5, and for silicate melt compositions ranging from basalt to peridotite. The effect of pressure was investigated through a combination of piston cylinder and multi-anvil isothermal experiments between 0.5 and 18 GPa at 1900 °C. Oxidation states of siderophile elements in the silicate melt as well as effect of carbon saturation on partitioning are also derived from these results. For some elements (e.g. Ga, Ge, W, V, Zn) the observed temperature dependence does not define trends parallel to those modeled using metal-metal oxide free energy data. We correct partitioning data for solute interactions in the metallic liquid and provide a parameterization utilized in extrapolating these results to the P- T- X conditions proposed by various core formation models. A single-stage core formation model reproduces the mantle abundances of several siderophile elements (Ni, Co, Cr, Mn, Mo, W, Zn) for core-mantle equilibration at pressures from 32 to 42 GPa along the solidus of a deep peridotitic magma ocean (˜3000 K for this pressure range) and oxygen fugacities relevant to the FeO content of the present-day mantle. However, these P- T- fO 2 conditions cannot produce the observed concentrations of Ga, Ge, V, Nb, As and P. For more reducing conditions, the P- T solution domain for single stage core formation occurs at subsolidus conditions and still cannot account for the abundances of Ge, Nb and P. Continuous core formation at the base of a magma ocean at P- T conditions constrained by the peridotite

  10. Simulated Verification of Fuel Element Inventory in a Small Reactor Core Using the Nuclear Materials Identification System (NMIS)

    SciTech Connect

    Grogan, Brandon R; Mihalczo, John T

    2009-01-01

    The International Panel on Climate Change projects that by 2050 the world energy demand may double. Although the primary focus for new nuclear power plants in industrialized nations is on large plants in the 1000-1600 MWe range, there is an increasing demand for small and medium reactors (SMRs). About half of the innovative SMR concepts are for small (<300 MWe) reactors with a 5-30 year life without on-site refueling. This type of reactor is also known as a battery-type reactor. These reactors are particularly attractive to countries with small power grids and for non-electrical purposes such as heating, hydrogen production, and seawater desalination. Traditionally, this type of reactor has been used in a nautical propulsion role. This type of reactor is designed as a permanently sealed unit to prevent the diversion of the uranium in the core by the user. However, after initial fabrication it will be necessary to verify that the newly fabricated reactor core contains the quantity of uranium that initially entered the fuel fabrication plant. In most instances, traditional inspection techniques can be used to perform this verification, but in certain situations the core design will be considered sensitive. Non-intrusive verification techniques must be utilized in these situations. The Nuclear Materials Identification System (NMIS) with imaging uses active interrogation and a fast time correlation processor to characterize fissile material. The MCNP-PoliMi computer code was used to simulate NMIS measurements of a small, sealed reactor core. Because most battery-type reactor designs are still in the early design phase, a more traditional design based on a Russian icebreaker core was used in the simulations. These simulations show how the radiography capabilities of the NMIS could be used to detect the diversion of fissile material by detecting void areas in the assembled core where fuel elements have been removed.

  11. The connection between prestellar cores and filaments in cluster-forming clumps of the Aquila Rift complex

    NASA Astrophysics Data System (ADS)

    Könyves, Vera; André, Philippe; Maury, Anaëlle

    2015-08-01

    One of the main goals of the Herschel Gould Belt survey (André et al. 2010) is to elucidate the physicalmechanisms responsible for the formation and evolution of prestellar cores in molecular clouds. In theAquila cloud complex imaged with Herschel/SPIRE-PACS between 70-500 μm, we have recently identifieda complete sample of 651 starless cores, 446 of them are gravitationally-bound prestellar cores, likelyforming stars in the future. We also detected 58 protostellar cores (Könyves et al. 2010 and 2015, subm.- see http://gouldbelt-herschel.cea.fr/archives). This region is dominated by two (proto)clusters which arecurrently active sites of clustered star formation (SF): the filamentary Serpens South cloud and the W40HII region. The latter is powered by massive young stars, and a 2nd-generation SF can be witnessed inthe surroundings (Maury et al. 2011).Our Herschel observations also provide an unprecedented census of filaments in Aquila and suggest aclose connection between them and the formation process of prestellar cores, where both structures arehighly concentrated around the protoclusters. About 10-20% of the gas mass is in the form of filamentsbelow Av~7, while ~50-75% of the dense gas mass above Av~7-10 is in filamentary structures.Furthermore, ~90% of our prestellar cores are located above a background column density correspondingto Av~7, and ~75% of them lie within the densest filamentary structures with supercritical masses per unitlength >16 M⊙/pc. Indeed, a strong correlation is found between the spatial distribution of prestellar coresand the densest filaments.Comparing the statistics of cores and filaments with the number of young stellar objects found by Spitzerin the same complex, we also infer a typical timescale ~1 Myr for the formation and evolution of bothprestellar cores and filaments.In summary, our Herschel findings in Aquila support a filamentary paradigm for the early stages of SF,where the cores result from the gravitational fragmentation

  12. Oncogene regulation. An oncogenic super-enhancer formed through somatic mutation of a noncoding intergenic element.

    PubMed

    Mansour, Marc R; Abraham, Brian J; Anders, Lars; Berezovskaya, Alla; Gutierrez, Alejandro; Durbin, Adam D; Etchin, Julia; Lawton, Lee; Sallan, Stephen E; Silverman, Lewis B; Loh, Mignon L; Hunger, Stephen P; Sanda, Takaomi; Young, Richard A; Look, A Thomas

    2014-12-12

    In certain human cancers, the expression of critical oncogenes is driven from large regulatory elements, called super-enhancers, that recruit much of the cell's transcriptional apparatus and are defined by extensive acetylation of histone H3 lysine 27 (H3K27ac). In a subset of T-cell acute lymphoblastic leukemia (T-ALL) cases, we found that heterozygous somatic mutations are acquired that introduce binding motifs for the MYB transcription factor in a precise noncoding site, which creates a super-enhancer upstream of the TAL1 oncogene. MYB binds to this new site and recruits its H3K27 acetylase-binding partner CBP, as well as core components of a major leukemogenic transcriptional complex that contains RUNX1, GATA-3, and TAL1 itself. Additionally, most endogenous super-enhancers found in T-ALL cells are occupied by MYB and CBP, which suggests a general role for MYB in super-enhancer initiation. Thus, this study identifies a genetic mechanism responsible for the generation of oncogenic super-enhancers in malignant cells. PMID:25394790

  13. Platinum group elements provide no indication of a meteoritic component in ICDP cores from the Bosumtwi crater, Ghana

    NASA Astrophysics Data System (ADS)

    Goderis, S.; Tagle, R.; Schmitt, R. T.; Erzinger, J.; Claeys, P. H.

    In an attempt to identify the type of projectile, 14 samples from the Bosumtwi crater in Ghana were analyzed for platinum group element (PGE) concentrations by nickel sulfide fire assay inductively coupled plasma-mass spectrometry (ICP-MS). The majority of the samples come from the impactite material recovered by cores LB-07A and LB-08A, which were drilled by the International Continental Scientific Drilling program (ICDP). One sample originates from the fallback material found at the contact between the impactite and the overlying lake sediment in core LB-05B. No clear signature of a meteoritic contamination was identified in the 13 impactite samples. The target rock apparently dominates the PGE contribution in the impactites. These results agree with the PGE concentrations reported for the suevites collected at the crater rim and in other parts of the Bosumtwi ICDP cores. However, based on Cr and Os isotopic signatures, a meteoritic component could be present in the sample of fallback material, supporting the reports of the existence of meteoritic material in the Ivory Coast tektites. Further analyses of the fallback material from the Bosumtwi drill cores should confirm (or not) this first result.

  14. Rapid, dynamic segregation of core forming melts: Results from in-situ High Pressure- High Temperature X-ray Tomography

    NASA Astrophysics Data System (ADS)

    Watson, H. C.; Yu, T.; Wang, Y.

    2011-12-01

    The timing and mechanisms of core formation in the Earth, as well as in Earth-forming planetesimals is a problem of significant importance in our understanding of the early evolution of terrestrial planets . W-Hf isotopic signatures in meteorites indicate that core formation in small pre-differentiated planetesimals was relatively rapid, and occurred over the span of a few million years. This time scale is difficult to achieve by percolative flow of the metallic phase through a silicate matrix in textural equilibrium. It has been suggested that during this active time in the early solar system, dynamic processes such as impacts may have caused significant deformation in the differentiating planetesimals, which could lead to much higher permeability of the core forming melts. Here, we have measured the change in permeability of core forming melts in a silicate matrix due to deformation. Mixtures of San Carlos olivine and FeS close to the equilibrium percolation threshold (~5 vol%FeS) were pre-synthesized to achieve an equilibrium microstructure, and then loaded into the rotational Drickamer apparatus at GSE-CARS, sector 13-BMD, at the Advanced Photon Source (Argonne National Laboratory). The samples were subsequently pressed to ~2GPa, and heated to 1100°C. Alternating cycles of rotation to collect X-ray tomography images, and twisting to deform the sample were conducted until the sample had been twisted by 1080°. Qualitative and quantitative analyses were performed on the resulting 3-dimensional x-ray tomographic images to evaluate the effect of shear deformation on permeability and migration velocity. Lattice-Boltzmann simulations were conducted, and show a marked increase in the permeability with increasing deformation, which would allow for much more rapid core formation in planetesimals.

  15. Constraints on core formation from systematic study of metal-silicate partitioning on a great number of siderophile elements

    SciTech Connect

    Siebert, J; Ryerson, F J

    2008-10-27

    The abundances of siderophile elements in the Earth's mantle are the result of core formation in the early Earth. Many variables are involved in the prediction of metal/silicate siderophile partition coefficients during core segregation: pressure, temperature, oxygen fugacity, silicate and metal compositions. Despite publications of numerous results of metal-silicate experiments, the experimental database and predictive expressions for elements partitioning are hampered by a lack of systematic study to separate and evaluate the effects of each variable. Only a relatively complete experimental database that describes Ni and Co partitioning now exists but is not sufficient to unambiguously decide between the most popular model for core formation with a single stage core-mantle equilibration at the bottom of a deep magma ocean (e.g. Li and Agee, 2001) and more recent alternative models (e.g. Wade and Wood, 2005; Rubie et al., 2007). In this experimental work, systematic study of metal silicate partitioning is presented for elements normally regarded as moderately siderophile (Mo, As, Ge, W, P, Ni, Co), slightly siderophile (Zn, Ga, Mn, V, Cr) and refractory lithophile (Nb, Ta). Using a new piston-cylinder design assembly allows us to present a suite of isobaric partitioning experiments at 3 GPa within a temperature range from 1600 to 2600 C and over a range of relative oxygen fugacity from IW-1.5 to IW-3.5. Silicate melts range from basaltic to peridotite in composition. The individual effect of pressure is also investigated through a combination of piston cylinder and multi anvil isothermal experiments from 0.5 to 18 GPa at 1900 C. Absolute measurements of partitioning coefficients combining EMP and LA-ICPMS analytical methods are provided. New results are obtained for elements whose partitioning behavior is usually poorly constrained and not integrated into any accretion or core formation models. We find notably that Ge, As, Mo become less siderophile with

  16. Chemical Exchange Between the Core and the Convecting Mantle of the Earth: Evidence from Highly Siderophile Elements (HSE)

    NASA Astrophysics Data System (ADS)

    Schmidt, G.; Palme, H.; Kratz, K. L.

    1995-09-01

    Core formation is a major physical and chemical event in the evolution of a differentiated planet. The core is the dominant repository of HSE in the Earth. Element ratios of HSE in peridotites provide insights into the accretion processes of the Earth and the effect of core formation. Depletion of HSE in the Earth's mantle results from core formation. Refractory siderophile elements are about a factor of > 100 depleted in the Earth's mantle compared to CI carbonaceous chondrites. Nevertheless, the concentrations of PGE, Re and Au (7.1 +/- 0.8 x 10^-3 CI chondrite abundances) are higher than would be expected from metal-silicate partitioning during core formation [1]. Several different explanations have been suggested to explain the low absolute abundances of these elements. (1) Os, Re, Ir, Ru, Rh, Pd, Pt, and Au were added with a late chondritic veneer containing less than 1% of a CI component [2-9]. (2) Insufficient core formation, i.e. some metallic Fe-Ni was retained in the upper mantle during core formation [10]. (3) Disequilibrium during core formation; Segregation of metal from the upper mantle in later stages of accretion was so rapid that equilibrium was not attained [4,11,12]. (4) There was continuous formation of the core during accretion; Equilibrium between sinking metal grains and a molten magma ocean at high temperatures (3000-3500 K) [13]. (5) Increase in silicate/metal partition coefficients by pressure, temperature, or high f(O2) [5,14]; Solution of FeO in the core raises the f(O2) conditions at the core-mantle interface sufficiently to increase the equilibrium concentrations of the siderophile elements in the mantle [15]. Studies of mantle-derived samples such as massif peridotites and peridotite xenoliths provide direct information on the nature and composition of the upper mantle. Massive peridotitic rocks from Zabargad island (Red Sea), Lanzo (Italy), Ronda (Spain) and peridotitic xenoliths from Mongolia were analysed for Os, Re, Ir, Ru, Rh, Pd

  17. Star-forming regions of the Aquila rift cloud complex. II. Turbulence in molecular cores probed by NH3 emission

    NASA Astrophysics Data System (ADS)

    Levshakov, S. A.; Henkel, C.; Reimers, D.; Wang, M.

    2014-07-01

    Aims: We intend to derive statistical properties of stochastic gas motion inside the dense, low-mass star-forming molecular cores that are traced by NH3(1, 1) and (2, 2) emission lines. Methods: We use the spatial two-point autocorrelation (ACF) and structure functions calculated from maps of the radial velocity fields. Results: The observed ammonia cores are characterized by complex intrinsic motions of stochastic nature. The measured kinetic temperature ranges between 8.8 K and 15.1 K. From NH3 excitation temperatures of 3.5-7.3 K, we determine H2 densities with typical values of nH2~ (1-6) × 104 cm-3. The ammonia abundance, X = [NH3]/[H2], varies from 2 × 10-8 to 1.5 × 10-7. We find oscillating ACFs, which eventually decay to zero with increasing lags on scales of 0.04 ≲ ℓ ≲ 0.5 pc. The current paradigm supposes that the star-formation process is controlled by the interplay between gravitation and turbulence with the latter preventing molecular cores from a rapid collapse due to their own gravity. Thus, oscillating ACFs may indicate a damping of the developed turbulent flows surrounding the dense but less turbulent core, a transition to dominating gravitational forces and, hence, to gravitational collapse. Appendix A is available in electronic form at http://www.aanda.org

  18. Detailed history of atmospheric trace elements from the Quelccaya ice core (Southern Peru) during the last 1200 years

    NASA Astrophysics Data System (ADS)

    Uglietti, C.; Gabrielli, P.; Thompson, L. G.

    2013-12-01

    The recent increase in trace element concentrations, for example Cr, Cu, Zn, Ag, Pb, Bi, and U, in polar snow and ice has provided compelling evidence of a hemispheric change in atmospheric composition since the nineteenth century. This change has been concomitant with the expansion of the Industrial Revolution and points towards an anthropogenic source of trace elements in the atmosphere. There are very few low latitude trace element ice core records and these are believed to be sensitive to perturbations of regional significance. To date, these records have not been used to document a preindustrial anthropogenic impact on atmospheric composition at low latitudes. Ice cores retrieved from the tropical Andes are particularly interesting because they have the potential to reveal detailed information about the evolution and environmental consequences of mineral exploitation related to the Pre Inca Civilizations, the Inca Empire (1438-1533 AD) and the subsequent Spanish invasion and dominance (1532-1833 AD). The chemical record preserved in the ice of the Quelccaya ice cap (southern Peruvian Andes) offers the exceptional opportunity to geochemically constrain the composition of the tropical atmosphere at high resolution over the last ~1200 years. Quantification of twenty trace elements (Ag, Al, As, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Rb, Sb, Sn, Ti, Tl, U, V, and Zn) was performed by ICP-SFMS over 105 m of the Quelccaya North Dome core (5600 m asl, 128.57 m) by analyzing 2450 samples. This provides the first atmospheric trace element record in South America spanning continuously and at high resolution for the time period between 1990 and 790 AD. Ag, As, Bi, Cd, Cr, Co, Cu, Mn, Mo, Sb, Sn, Pb and Zn show increases in concentration and crustal enrichment factor starting at different times between 1450 and 1550 AD, in concomitance with the expansions of the Inca Empire and, subsequently, the Spanish Empire well before the inception of the Industrial Revolution. This

  19. The light element component of the Earth’s core: Constraints from in situ X-Radiography in the LHDAC

    NASA Astrophysics Data System (ADS)

    Lord, O. T.; Walter, M. J.; Walker, D.; Clark, S. M.

    2009-12-01

    The light element budget of the Earth’s core depends in part on the high-pressure melting relations of the relevant iron rich binary systems. Candidate alloying elements include H, C, O, Si and S, due to their cosmochemical abundance. Many of these systems are known to contain eutectic points, the temperatures and compositions of which are critical to reconstructing the phase relations of these systems. Thus far most studies reporting the composition of eutectic liquids depend on ex situ analysis with a potential for systematic errors introduced by quench induced exsolution. To circumvent this issue we have developed an in situ technique for the determination of liquid compositions in iron-rich binary systems at simultaneous high-pressure and high-temperature conditions. Samples consist of Fe(1-x)O or FeS, surrounded by a ring of iron forming a ‘donut’ with a diameter of ~100μm and a thickness of ~20μm. Pressure is monitored by ruby fluorescence. The sample is heated at the boundary between the iron and light element compound using two 100 W IR lasers in a double-sided configuration at beamline 12.2.2 at the Advanced Light Source. Temperature is measured by spectroradiometry. Before, during and after melting, X-radiographic images of the sample are taken by shining a defocused beam of synchrotron X-rays through the sample and onto a CdWO4 phosphor. The visible light from the phosphor is then focused onto a high resolution CCD, where absorption contrast images are recorded. The absorption of the molten region is then determined, and it’s composition calculated by comparison to the absorption of the two solid end members. In previous work we measured the composition of the Fe-FeS eutectic to 20 GPa and the Fe-Fe3C eutectic to 44 GPa [1,2]. Further, we saw no discernible solubility of oxygen in liquid iron up to 43 GPa [1]. Here we extend the data for sulfur up to 70 GPa and for oxygen up to 63 GPa. Our new sulfur data fit well with previous studies at lower

  20. Kinetic analysis of data obtained from studies on microbial degradation of cement waste forms, using shrinking core models.

    PubMed

    Idachaba, M A; Nyavor, K; Egiebor, N O

    2003-04-01

    Model equations based on analytical solutions of two shrinking core models (acid dissolution or shrinking unreacted core (SUC) model, and bulk diffusion model), were used to analyze the kinetics of microbial degradation of cement waste forms. Two current approaches of waste form microbial stability evaluation (Nuclear Regulatory Commission (NRC) method and refined biofilm formation) were used to generate the data. Good linear correlations with R(2)>0.95 were obtained for the leaching data from both the NRC and biofilm approaches, using the model equation based on the bulk diffusion concept. Analyses using the model equation based on the acid dissolution model generally gave poor correlations except when data obtained from biofilm formation method was normalized. PMID:12686024

  1. Optimization and Openmp Parallelization of a Discrete Element Code for Convex Polyhedra on Multi-Core Machines

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Matuttis, Hans-Georg

    2013-02-01

    We report our experiences with the optimization and parallelization of a discrete element code for convex polyhedra on multi-core machines and introduce a novel variant of the sort-and-sweep neighborhood algorithm. While in theory the whole code in itself parallelizes ideally, in practice the results on different architectures with different compilers and performance measurement tools depend very much on the particle number and optimization of the code. After difficulties with the interpretation of the data for speedup and efficiency are overcome, respectable parallelization speedups could be obtained.

  2. Structure of a Folding Intermediate Reveals the Interplay Between Core and Peripheral Elements in RNA Folding

    SciTech Connect

    Baird, Nathan J.; Westhof, Eric; Qin, Hong; Pan, Tao; Sosnick, Tobin R.

    2010-07-13

    Though the molecular architecture of many native RNA structures has been characterized, the structures of folding intermediates are poorly defined. Here, we present a nucleotide-level model of a highly structured equilibrium folding intermediate of the specificity domain of the Bacillus subtilis RNase P RNA, obtained using chemical and nuclease mapping, circular dichroism spectroscopy, small-angle X-ray scattering and molecular modeling. The crystal structure indicates that the 154 nucleotide specificity domain is composed of several secondary and tertiary structural modules. The structure of the intermediate contains modules composed of secondary structures and short-range tertiary interactions, implying a sequential order of tertiary structure formation during folding. The intermediate lacks the native core and several long-range interactions among peripheral regions, such as a GAAA tetraloop and its receptor. Folding to the native structure requires the local rearrangement of a T-loop in the core in concert with the formation of the GAAA tetraloop-receptor interaction. The interplay of core and peripheral structure formation rationalizes the high degree of cooperativity observed in the folding transition leading to the native structure.

  3. A distance-limited sample of massive star-forming cores from the RMS

    NASA Astrophysics Data System (ADS)

    Maud, L. T.; Lumsden, S. L.; Moore, T. J. T.; Mottram, J. C.; Urquhart, J. S.; Cicchini, A.

    2015-09-01

    We analyse C18O (J = 3-2) data from a sample of 99 infrared (IR)-bright massive young stellar objects (MYSOs) and compact H II regions that were identified as potential molecular-outflow sources in the Red MSX Source survey. We extract a distance-limited (D < 6 kpc) sample shown to be representative of star formation covering the transition between the source types. At the spatial resolution probed, Larson-like relationships are found for these cores, though the alternative explanation, that Larson's relations arise where surface-density-limited samples are considered, is also consistent with our data. There are no significant differences found between source properties for the MYSOs and H II regions, suggesting that the core properties are established prior to the formation of massive stars, which subsequently have little impact at the later evolutionary stages investigated. There is a strong correlation between dust-continuum and C18O-gas masses, supporting the interpretation that both trace the same material in these IR-bright sources. A clear linear relationship is seen between the independently established core masses and luminosities. The position of MYSOs and compact H II regions in the mass-luminosity plane is consistent with the luminosity expected from the most massive protostar in the cluster when using an ˜40 per cent star formation efficiency and indicates that they are at a similar evolutionary stage, near the end of the accretion phase.

  4. Oxygen fugacity of basaltic magmas and the role of gas-forming elements

    NASA Technical Reports Server (NTRS)

    Sato, M.

    1978-01-01

    It is suggested that major variations in the relative oxygen fugacity of a basaltic magma are caused primarily by gas-forming elements, especially carbon and hydrogen. According to this theory, carbon, present in the source region of a basaltic magma, reduces the host magma during ascent, as isothermally carbon becomes more reducing with decreasing pressure. For an anhydrous magma such as lunar basalts, this reduction continues through the extrusive phase and the relative oxygen fugacity decreases rapidly until buffered by the precipitation of a metallic phase. For hydrous magmas such as terrestrial basalts, reduction by carbon is eventually superceded by oxidation due to loss of H2 generated by the reaction of C with H2O and by thermal dissociation of H2O. The relative oxygen fugacity of a hydrous magma initially decreases as a magma ascends from the source region and then increases until magnetite crystallization curbs the rising trend of the relative oxygen fugacity.

  5. Production and evolution of light elements in active star-forming regions.

    PubMed

    Cassé, M; Lehoucq, R; Vangioni-Flam, E

    1995-01-26

    Collisions between cosmic rays (energetic protons and alpha-particles) and carbon, nitrogen and oxygen in the interstellar medium have been considered to be the main source of lithium, beryllium and boron, through fragmentation of the larger nuclei. But this mechanism is unable to account for the observed Solar System abundances of the isotopes 7Li and 11B. The recent detection of an excess of gamma-rays in the direction of the star-forming region in the Orion cloud has been interpreted as arising from the excitation of carbon and oxygen nuclei ejected from supernovae when they collide with the surrounding gas, which is primarily molecular and atomic hydrogen. Here we investigate the consequences of the two-body interactions of the ejected carbon and oxygen nuclei (and the alpha-particles ejected with them) with the hydrogen and helium in the surrounding gas, using a model developed previously. We show that these interactions offer a way to make lithium, beryllium and boron that is independent of the abundance of heavy elements in the surrounding medium. Such supernova-driven interactions, combined with the effect of galactic cosmic rays, can explain the observed Solar System abundances of these light elements. PMID:7830765

  6. The Formation of Glycine in Hot Cores: New Gas-grain Chemical Simulations of Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Garrod, Robin

    2012-07-01

    Organic molecules of increasing complexity have been detected in the warm envelopes of star-forming cores, commonly referred to as "hot cores". Spectroscopic searches at mm/sub-mm wavelengths have uncovered both amines and carboxylic acids in these regions, as well as a range of other compounds including alcohols, ethers, esters, and nitriles. However, the simplest amino acid, glycine (NH2CH2COOH), has not yet been reliably detected in the ISM. There has been much interest in this molecule, due to its importance to the formation of proteins, and to life, while the positive identification of interstellar molecules of similar or greater complexity suggests that its existence in star-forming regions is plausible. I will present the results of recent models of hot-core chemistry that simulate the formation of both simple and complex molecules on the surfaces or within the ice mantles of dust grains. I will also present results from the first gas-grain astrochemical model to approach the question of amino-acid formation in hot cores. The formation of glycine in moderate abundance is found to be as efficient as that for similarly complex species, while its sublimation from the grains occurs at somewhat higher temperatures. However, simulated emission spectra based on the model results show that the degree of compactness of high-abundance regions, and the density and temperature profiles of the cores may be the key variables affecting the future detection of glycine, as well as other amino acids, and may explain its non-detection to date.

  7. The Job Dimensions Underlying the Job Elements of the Position Analysis Questionnaire (PAQ) (Form B). Report No. 4.

    ERIC Educational Resources Information Center

    Marquardt, Lloyd D.; McCormick, Ernest J.

    This study was concerned with the identification of the job dimension underlying the job elements of the Position Analysis Questionnaire (PAQ), Form B. The PAQ is a structured job analysis instrument consisting of 187 worker-oriented job elements which are divided into six a priori major divisions. The statistical procedure of principal components…

  8. Forum Guide to Core Finance Data Elements. NFES 2007-801

    ERIC Educational Resources Information Center

    National Forum on Education Statistics, 2007

    2007-01-01

    This document provides an overview of key finance data terms and is designed to accompany the "Financial Accounting for Local and State School Systems: 2003 Edition" by identifying common reporting requirements and defining frequently used indicators and calculations using data elements from accounting and other data systems. It also covers the…

  9. Finite element analysis of effective mechanical properties, vibration and acoustic performance of auxetic chiral core sandwich structures

    NASA Astrophysics Data System (ADS)

    Joshi, Hrishikesh Ravindra

    Honeycomb cellular materials are widely used in engineering applications due to their high strength to weight ratio and controllable effective mechanical properties. The effective properties are controlled by varying the geometry of the repetitive unit cells of honeycomb structure. Sandwich panels made of honeycomb cores are beneficial in many applications including vibration isolation and sound transmission reduction. Sandwich panels with standard honeycomb core configurations have previously been studied with regards to sound transmission behavior. It has been established that the auxetic honeycomb cores, having negative in-plane Poisson's ratio, exhibit higher sound transmission loss as compared to regular honeycomb cores. In this study, the vibration and sound transmission response of novel auxetic chiral honeycomb structures (both hexa-chiral and anti-tetra chiral), have been investigated in detail using finite element analysis with two-dimensional plane elasticity elements. Chiral honeycomb structures are made up of a linear tessellation of periodic unit cell, which consists of circular nodes of radius ' r ' connected to each other by tangent ligaments of length ' L '. The distance between two adjacent circular nodes is ' R '. These geometric parameters are tailored to obtain the chiral structure with desired effective mechanical properties of in-plane Poisson's ratio, Young's modulus and shear modulus. Results show that, for both the hexa-chiral and anti-tetra-chiral configurations with same thickness, structures with smaller node radius 'r' have higher in-plane negative Poisson's ratio, effective Young's modulus, and shear modulus. The Poisson's ratio of anti-tetra-chiral structure with small node radius and thickness is found to approach the limit of -1. A steady state dynamic response of the chiral honeycomb sandwich panel subjected to uniform pressure load on the bottom face-sheet is also investigated over a frequency range of 1 Hz to 2000 Hz. It is

  10. Plane strain finite element analysis of sheet forming operations including bending effects

    NASA Astrophysics Data System (ADS)

    Cho, Uk Youn

    1993-01-01

    An improved finite element method suitable for the plane-strain analysis of sheet metal forming operations is presented. The method incorporates a computationally efficient shell model and a consistent frictional contact algorithm through an implicit updated Lagrangian formulation. The workpiece material model is rigid-viscoplastic with a choice of power law hardening and plastic normal anisotropy and is capable of modeling a wide variety of sheet metals. A simplified nonlinear incremental shell theory is employed along with an optional reduced integration through the thickness for computational efficiency, while retaining the advantages of the kinematic model containing the bending effects. Complex tool geometry can be handled by discrete data points, by primitives (lines and arcs), or by analytical functions. The capabilities of the method are demonstrated through verification problems and comparisons with experimental data, benchmark results, and published data for several practical problems of the sheet metal forming industry. The problems include stretching and/or deep drawing operations, simulation of automobile panel section, and brake bending operation. As an independent investigation from the first portion of the dissertation, measured data from a set of simple bending experiments of two types of aluminum are presented and analyzed. Generated data from the experiments include strain histories (loading and unloading), spring back information (spring back angle and strains), and friction coefficients. As a by-product, a simple way of estimating the friction coefficient (Coulomb's law) during a bending operation is proposed and demonstrated.

  11. Current Thoughts on Reactive Element Effects in Alumina-Forming Systems: In Memory of John Stringer

    DOE PAGESBeta

    Naumenko, D.; Pint, B. A.; Quadakkers, W. J.

    2016-05-06

    In memory of John Stringer (1934–2014), one of the leaders in studying the reactive element (RE) effects, this paper reviews the current status of understanding of the effect of RE dopants on high-temperature oxidation behavior, with an emphasis on recent research related to deploying alumina-forming alloys and coatings with optimal performance in commercial systems. Additionally, to the well-known interaction between indigenous sulfur and RE additions, effects have been observed with C, N, and O found in commercial alloys and coatings. While there are many similarities between alumina-forming alloys and coatings, the latter bring additional complicating factors such as the effectsmore » of O incorporation during thermal spraying MCrAlY coatings, coating roughness, and heat treatments that must be considered in optimizing the beneficial dopant addition. We can see analogies between RE effects in alloys and in the substrates beneath diffusion M–Al coatings. Recently, there has been more interest in the influence of mixed oxidant environments, since these may modify the manifestation of the RE effect. Some thoughts are provided on optimizing the RE benefit and modeling oxidation of RE-doped alloys.« less

  12. Effect of Silicon on Activity Coefficients of Siderophile Elements (P, Au, Pd, As, Ge, Sb, and In) in Liquid Fe, with Application to Core Formation

    NASA Technical Reports Server (NTRS)

    Righter, K.; Pando, K.; Danielson, L. R.; Humayun, M.; Righter, M.; Lapen, T.; Boujibar, A.

    2016-01-01

    Earth's core contains approximately 10 percent light elements that are likely a combination of S, C, Si, and O, with Si possibly being the most abundant. Si dissolved into Fe liquids can have a large effect on the magnitude of the activity coefficient of siderophile elements (SE) in Fe liquids, and thus the partitioning behavior of those elements between core and mantle. The effect of Si can be small such as for Ni and Co, or large such as for Mo, Ge, Sb, As. The effect of Si on many siderophile elements is unknown yet could be an important, and as yet unquantified, influence on the core-mantle partitioning of SE. Here we report new experiments designed to quantify the effect of Si on the partitioning of P, Au, Pd, and many other SE between metal and silicate melt. The results will be applied to Earth, for which we have excellent constraints on the mantle siderophile element concentrations.

  13. Search for a meteoritic component in drill cores from the Bosumtwi impact structure, Ghana: Platinum group element contents and osmium isotopic characteristics

    NASA Astrophysics Data System (ADS)

    McDonald, Iain; Peucker-Ehrenbrink, Bernhard; Coney, Louise; Ferrière, Ludovic; Reimold, Wolf Uwe; Koeberl, Christian

    An attempt was made to detect a meteoritic component in both crater-fill (fallback) impact breccias and fallout suevites (outside the crater rim) at the Bosumtwi impact structure in Ghana. Thus far, the only clear indication for an extraterrestrial component related to this structure has been the discovery of a meteoritic signature in Ivory Coast tektites, which formed during the Bosumtwi impact event. Earlier work at Bosumtwi indicated unusually high levels of elements that are commonly used for the identification of meteoritic contamination (i.e., siderophile elements, including the platinum group elements [PGE]) in both target rocks and impact breccias from surface exposures around the crater structure, which does not allow unambiguous verification of an extraterrestrial signature. The present work, involving PGE abundance determinations and Os isotope measurements on drill core samples from inside and outside the crater rim, arrives at the same conclusion. Despite the potential of the Os isotope system to detect even small amounts of extraterrestrial contribution, the wide range in PGE concentrations and Os isotope composition observed in the target rocks makes the interpretation of unradiogenic, high-concentration samples as an impact signature ambiguous.

  14. Using lead isotopes and trace element records from two contrasting Lake Tanganyika sediment cores to assess watershed – Lake exchange

    USGS Publications Warehouse

    Odigie, Kingsley; Cohen, A.D.; Swarzenski, Peter W.; Flegal, R

    2014-01-01

    Lead isotopic and trace element records of two contrasting sediment cores were examined to reconstruct historic, industrial contaminant inputs to Lake Tanganyika, Africa. Observed fluxes of Co, Cu, Mn, Ni, Pb, and Zn in age-dated sediments collected from the lake varied both spatially and temporally over the past two to four centuries. The fluxes of trace elements were lower (up to 10-fold) at a mid-lake site (MC1) than at a nearshore site (LT-98-58), which is directly downstream from the Kahama and Nyasanga River watersheds and adjacent to the relatively pristine Gombe Stream National Park. Trace element fluxes at that nearshore site did not measurably change over the last two centuries (1815–1998), while the distal, mid-lake site exhibited substantial changes in the fluxes of trace elements – likely caused by changes in land use – over that period. For example, the flux of Pb increased by ∼300% from 1871 to 1991. That apparent accelerated weathering and detrital mobilization of lithogenic trace elements was further evidenced by (i) positive correlations (r = 0.77–0.99, p < 0.05) between the fluxes of Co, Cu, Mn, Ni, Pb, and Zn and those of iron (Fe) at both sites, (ii) positive correlations (r = 0.82–0.98, p < 0.01, n = 9) between the fluxes of elements (Al, Co, Cu, Fe, Mn, Ni, Pb, and Zn) and the mass accumulation rates at the offshore site, (iii) the low enrichment factors (EF < 5) of those trace elements, and (iv) the temporal consistencies of the isotopic composition of Pb in the sediment. These measurements indicate that accelerated weathering, rather than industrialization, accounts for most of the increases in trace element fluxes to Lake Tanganyika in spite of the development of mining and smelting operations within the lake’s watershed over the past century. The data also indicate that the mid-lake site is a much more sensitive and useful recorder of environmental changes than the nearshore site. Furthermore, the lead isotopic compositions

  15. Core Outcomes and Common Data Elements in Chronic Subdural Hematoma: A Systematic Review of the Literature Focusing on Baseline and Peri-Operative Care Data Elements.

    PubMed

    Chari, Aswin; Hocking, Katie C; Edlmann, Ellie; Turner, Carole; Santarius, Thomas; Hutchinson, Peter J; Kolias, Angelos G

    2016-09-01

    Chronic subdural hematoma (CSDH) is an increasingly common subtype of head injury, especially in the elderly population. The optimization of treatment strategies has been hampered by the collection of heterogeneous outcome measures and data elements, precluding cross-study comparisons. This study aimed to quantify the heterogeneity of data elements in the pre-operative, operative, and post-operative phases of care, and build the basis for the development of a set of common data elements (CDEs) for CSDH. This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and was registered with the PROSPERO register of systematic reviews (CRD42014007266). All full-text English studies with more than 10 patients (prospective) or more than 100 patients (retrospective) published after 1990 examining clinical outcomes in CSDH were eligible for inclusion. One hundred two eligible studies were found. Only 40 studies (39.2%) reported the main presenting symptom/feature and 24 (23.5%) reported additional symptoms/features. Admitting neurological/functional status was classified by the Glasgow Coma Scale (25 studies; 24.5%), the Markwalder Score (26 studies; 25.5%) and the modified Rankin Scale (three studies; 2.9%). Fifty-four studies (52.9%) made some mention of patient comorbidities and 58 studies (56.9%) reported the proportion or excluded patients on anticoagulant medication. Eighteen studies (17.6%) reported baseline coagulation status. Sixty-four studies (62.7%) stratified or assessed severity based on radiological findings, although the methods used varied widely. There was variable reporting of surgical technique and post-operative care; 32 studies (31.4%) made no mention of whether the operations were performed under general or local anesthetic. This study, a part of the Core Outcomes and Common Data Elements in CSDH (CODE-CSDH) project, confirms and quantifies the heterogeneity of data elements collected and

  16. Release of quercetin from micellar nanoparticles with saturated and unsaturated core forming polyesters--a combined computational and experimental study.

    PubMed

    Hassanzadeh, Salman; Khoee, Sepideh; Beheshti, Abolghasem; Hakkarainen, Minna

    2015-01-01

    Computational and experimental studies were combined to obtain new insight into the widely reported anomalous release mechanism of hydrophobic drug (quercetin) from polymeric micellar nanoparticles. Saturated and unsaturated amphiphilic triblock copolymers from monomethoxy polyethylene glycol (mPEG), poly(butylene adipate) (PBA) and poly(cis-2-butene adipate) (PCBA) (mPEG-PBA-mPEG and mPEG-PCBA-mPEG) were utilized as model polymers to specify the contribution of polymer-micelle degradation and polymer-drug interactions on the observed differences in the release rates by applicable computational investigation and experimental evaluations. Monitoring the size of the micelles through the releasing process together with hydrolytic degradation studies of the core forming polymers proved that the contribution of polymer hydrolysis and micelle degradation on the observed differences in the release rates during the release time window was minimal. The compatibility between quercetin and the core forming polymer is another factor influencing the drug encapsulation and the relative release rate and it was therefore investigated theoretically (using density functional theory (DFT) at B3LYP/6-311(++)G level of theory) and experimentally (FT-IR imaging). The drug-polymer interactions in the core were shown to be much more important than the polymer and/or micelle swelling-dissociation-degradation processes under the studied conditions. PMID:25492006

  17. Modeling the Submillimeter Dust Continuum Emission from Nearby Low Mass Star Forming Cores

    NASA Astrophysics Data System (ADS)

    Shirley, Y. L.; Young, C. H.; Evans, N. J., II; Rawlings, J. M. C.

    2001-12-01

    Current theories of a low mass star formation predict the evolution of the density distribution, n({r}, t), temperature distribution, T({r}, t), and the velocity field ,{v}({r}, t), of the envelope of protostellar cores with time. Optically thin dust emission at submillimeter wavelengths provides a powerful diagnostic to constrain the envelope density and temperature structure. In this study, thirty-nine low mass cores were mapped with SCUBA at 850 and 450 μ m on the JCMT during sixteen nights between January 1998 and February 2000. The sources were selected from the earliest phases (pre-T Tauri) in the proposed evolutionary scheme for low mass protostars (6 Pre-protostellar Cores (PPCs), 15 Class 0, 18 Class I) with luminosities indicative of low mass star formation (Lbol < 50 Lsun) and with distances less than 450 pc. High signal-to-noise maps allowed azimuthally averaged radial profiling out to 60 arcseconds from the continuum centroid. The similarities and differences in the submillimeter continuum emission properties of the envelopes of PPCs, Class 0, and Class I sources on 103 to 104 AU scales are summarized. We have modeled the normalized radial intensity distributions and spectral energy distributions (SED) for sixteen sources from the SCUBA survey (3 PPCs, 7 Class 0, and 6 Class I) using a one dimensional radiative transfer code (Egan, Leung, & Spagna 1988) with internal heating from a central protostar (Class 0 and I objects) and external heating from the interstellar radiation field (all objects) to calculate the dust temperature distribution. Power law, Bonnor-Ebert, Shu inside-out collapse, and Plummer density distributions were tested to match the observed normalized radial profiles and observed SED simultaneously. Realistic beam profiles and chopping were used to simulate the observations. We find Bonnor-Ebert spheres with central densities of 105 to 106 cm-3 reproduce the PPC radial profiles while power law models (n(r) ~ r-p, p = 1.1 - 2

  18. Intrinsic electrostatic resonances of heterostructures with negative permittivity from finite-element calculations: Application to core-shell inclusions

    NASA Astrophysics Data System (ADS)

    Mejdoubi, Abdelilah; Brosseau, Christian

    2007-11-01

    Herein, we report finite-element calculations of the effective (relative) permittivity of composite materials consisting of inclusions and inclusion arrays with a core-shell structure embedded in a surrounding host. The material making up the core of the two-dimensional structures, or cross sections of infinite three-dimensional objects (parallel, infinitely long, and identical cylinders) where the properties and characteristics are invariant along the perpendicular cross sectional plane, is assumed to have a negative real part of the permittivity, while the coating material (annular shell) is considered to be lossless. While strictly valid only in a dc situation, our analysis can be extended to treat electric fields that oscillate with time, provided that the wavelengths and attenuation lengths associated with the fields are much larger than the microstructure dimension in order that the homogeneous (effective-medium) representation of the composite structure makes sense. While one may identify features of the electrostatic resonance (ER) which are common to core-shell structures characterized by permittivities with real parts of opposite signs, it appears that the predicted ER positions are sensitive to the shell thickness and can be tuned through varying this geometric parameter. For example, we observe that the ER is broadened and shifted as the loss and the shell thickness are increased, respectively. We also argue that such core shell may also be valuable in controlling ER characteristics via polarization in an external electric field. In addition, by considering calculations of the electric field distribution, we find that the ER results in very strong and local-field enhancements into small parts of the shell perimeter. Our findings open up possibilities for the development of hybrid structures that could exploit the ER features for a particular application.

  19. Multiple glass singularities and isodynamics in a core-softened model for glass-forming systems.

    PubMed

    Gnan, Nicoletta; Das, Gayatri; Sperl, Matthias; Sciortino, Francesco; Zaccarelli, Emanuela

    2014-12-19

    We investigate the slow dynamics of a simple glass former whose interaction potential is the sum of a hard core and a square shoulder repulsion. According to mode coupling theory, the competition between the two repulsive length scales gives rise to a complex dynamic scenario: besides the fluid-glass line, the theory predicts a glass-glass line in the temperature-packing fraction plane with two end points. Interestingly, for critical values of the square-shoulder parameters, such end points can be accessed from the liquid phase. We verify, via extensive numerical simulations, the existence of both points through the observation of an unconventional subdiffusive/logarithmic dynamical behavior. Unexpectedly, we also discover that the simultaneous presence of two end points generates special loci in the state diagram along which the dynamics is identical at all length and time scales. PMID:25554913

  20. Characterization of atmospheric trace elements in the Puruogangri ice core: a preliminary account of Tibetan Plateau environmental and contamination histories

    NASA Astrophysics Data System (ADS)

    Beaudon, E.; Gabrielli, P.; Sierra Hernandez, R.; Wegner, A.; Thompson, L. G.

    2014-12-01

    Asia is facing enormous challenges including large-scale environmental changes, rapid population growth and industrialization. The inherent generated pollution contributes to half of all Earth's anthropogenic trace metals emissions that, when deposited to glaciers of the surrounding mountains of the Third Pole region, leave a characteristic chemical fingerprint. Records of past atmospheric deposition preserved in snow and ice from Third Pole glaciers provide unique insights into changes of the chemical composition of the atmosphere and into the nature and intensity of the regional atmospheric circulation systems. The determination of the elemental composition of aeolian dust stored in Himalayan and Tibetan Plateau glaciers can help to qualify the potential contamination of glacial meltwater as a part of the greater fresh Asian water source. The 215 m long Puruogangri ice core retrieved in 2000 at 6500 m a.s.l. in central Tibetan Plateau (Western Tanggula Shan, China) provides one of the first multi-millennium-long environmental archives (spanning the last 7000 years and annually resolved for the last 400 years) obtained from the Tibetan Plateau region. The Puruogangri's area is climatologically of particular interest because of its location at the boundary between the monsoon (wet) and the westerly (dry) dominated atmospheric circulation. The major objective of this study is to determine the concentration of trace and ultra-trace elements in the Puruogangri ice core between 1600 and 2000 AD in order to characterize the atmospheric aerosols entrapped in the ice. Particular attention is given to assess the amount of trace elements originating from anthropogenic sources during both the pre-industrial and industrial periods. The distinction between the anthropogenic contribution and the crustal background may rely on the precise decoupling of the dry and wet seasons signals, the former being largely influenced by dust contribution.

  1. Highly siderophile element (HSE) abundances in the mantle of Mars are due to core formation at high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Righter, K.; Danielson, L. R.; Pando, K. M.; Williams, J.; Humayun, M.; Hervig, R. L.; Sharp, T. G.

    2015-04-01

    Highly siderophile elements (HSEs) can be used to understand accretion and core formation in differentiated bodies, due to their strong affinity for FeNi metal and sulfides. Coupling experimental studies of metal-silicate partitioning with analyses of HSE contents of Martian meteorites can thus offer important constraints on the early history of Mars. Here, we report new metal-silicate partitioning data for the PGEs and Au and Re across a wide range of pressure and temperature space, with three series designed to complement existing experimental data sets for HSE. The first series examines temperature effects for D(HSE) in two metallic liquid compositions—C-bearing and C-free. The second series examines temperature effects for D(Re) in FeO-bearing silicate melts and FeNi-rich alloys. The third series presents the first systematic study of high pressure and temperature effects for D(Au). We then combine our data with previously published partitioning data to derive predictive expressions for metal-silicate partitioning of the HSE, which are subsequently used to calculate HSE concentrations of the Martian mantle during continuous accretion of Mars. Our results show that at midmantle depths in an early magma ocean (equivalent to approximately 14 GPa, 2100 °C), the HSE contents of the silicate fraction are similar to those observed in the Martian meteorite suite. This is in concert with previous studies on moderately siderophile elements. We then consider model calculations that examine the role of melting, fractional crystallization, and sulfide saturation/undersaturation in establishing the range of HSE contents in Martian meteorites derived from melting of the postcore formation mantle. The core formation modeling indicates that the HSE contents can be established by metal-silicate equilibrium early in the history of Mars, thus obviating the need for a late veneer for HSE, and by extension volatile siderophile elements, or volatiles in general.

  2. Rare-element pegmatite-forming melt during Variscan orogeny: genesis, propagation and consolidation

    NASA Astrophysics Data System (ADS)

    Deveaud, Sarah; Guillou-Frottier, Laurent; Millot, Romain

    2015-04-01

    The Variscan rare-element pegmatite fields mainly enriched in Li, Nb and Ta are subject to increasing mining exploration in the last few years. Indeed, Li from pegmatite deposits is recognised to be less sensitive to supply disruptions than Li from brine deposits. Thus, new metallogenic guides need to be defined in order to meet the growing demand for Li, Nb and Ta metals, and to ensure supply of strategic metals at the European scale. Three Variscan rare-element pegmatite fields have been selected to apply a multi-approach study in order to understand the genesis of pegmatite-forming melt, their propagation and their clustered consolidation at the crustal scale. The Monts d'Ambazac (French Massif Central), Barroso-Alvão (Portugal) and Forcarei-Lalin (Galicia, Spain) pegmatite fields present a similar age (~305-315 Ma), a similar geodynamical context (syn- to post-collisional) and same kind of mineralisations (LiCsTa type) but show distinct intensity of deformation affecting various country-rocks. Firstly, spatial statistical analyses have been developed to constrain the spatial distribution of the Monts d'Ambazac and the Barroso-Alvão pegmatite fields. Secondly, Li-isotopic analyses in micas have been used to investigate the role of δ7Li as geochemical tracer of LCT-pegmatites (from the less to the more evolved and lithium-rich pegmatite type). Finally, spatial and temporal relationships between pegmatites and hosting-rocks have been discriminated with structural field data mainly obtained on the Monts d'Ambazac and Forcarei-Lalin pegmatite fields. In addition, Li- isotopes results corroborate that Li-fractionation is neither affected by fractional crystallisation nor by crustal anatexis processes in a significant way. These δ7Li values (‰ ) being independent from the degree of magmatic fractionation (K/Rb ratio) and ranging from -3.5 to +3.5 ‰, tend to confirm that these pegmatite-forming melts evolve independently of each other. Our results demonstrate

  3. Geochemical variations of rare earth elements in Marcellus shale flowback waters and multiple-source cores in the Appalachian Basin

    NASA Astrophysics Data System (ADS)

    Noack, C.; Jain, J.; Hakala, A.; Schroeder, K.; Dzombak, D. A.; Karamalidis, A.

    2013-12-01

    Rare earth elements (REE) - encompassing the naturally occurring lanthanides, yttrium, and scandium - are potential tracers for subsurface groundwater-brine flows and geochemical processes. Application of these elements as naturally occurring tracers during shale gas development is reliant on accurate quantitation of trace metals in hypersaline brines. We have modified and validated a liquid-liquid technique for extraction and pre-concentration of REE from saline produced waters from shale gas extraction wells with quantitative analysis by ICP-MS. This method was used to analyze time-series samples of Marcellus shale flowback and produced waters. Additionally, the total REE content of core samples of various strata throughout the Appalachian Basin were determined using HF/HNO3 digestion and ICP-MS analysis. A primary goal of the study is to elucidate systematic geochemical variations as a function of location or shale characteristics. Statistical testing will be performed to study temporal variability of inter-element relationships and explore associations between REE abundance and major solution chemistry. The results of these analyses and discussion of their significance will be presented.

  4. Organic matter formed from hydrolysis of metal carbides of the iron peak of cosmic elemental abundance

    NASA Astrophysics Data System (ADS)

    Cataldo, Franco

    2003-01-01

    This work is a modern revisitation of an old idea of great chemists of the past such as Berthelot, Mendeleev, Cloez and Moissan: the formation of organic matter under pre-biotic conditions starting from the hydrolysis of metal carbides. This idea was originally proposed for the formation of petroleum in the Earth and was extended to other bodies of the solar system by Sokolov at the end of the 19th century. The reason for this revisitation lies in the fact that complex organic matter resembling a petroleum fraction may exist in certain protoplanetary nebulae. The present work starts with a survey of the theory of the inorganic origin of petroleum and reports on current evidence for its derivation from residues of formerly living matter, but also considers theories that admit both a biogenic and an abiogenic origin for petroleum. By considering the cosmic abundance of elements and the evidence concerning the presence of carbides in meteorites, we discuss the formation, structure and hydrolysis products derived from the metal carbides of the iron peak of cosmic elemental abundance. Chromium carbide (Cr3C2) has then been used as a model compound for all the key carbides of the iron peak of the cosmic abundance (Cr, Fe, Ni, V, Mn, Co) and it has been hydrolysed under different conditions and the hydrocarbons formed have been analysed using electronic spectroscopy, high-performance liquid chromatography with a diode-array detector (HPLC-DAD) and by Fourier-transform infrared (FT-IR) spectroscopy. Methane, a series of about 20 different alkenes with single and conjugated double bonds have been detected. Paraffins are formed simultaneously with the alkene series but no acetylenic hydrocarbons have been detected. This study confirms early works considering the easy hydrolysis of the carbides of Cr, Fe, Ni, Mn and Co with the formation of H2, a series of alkanes including methane and a series of alkenes including ethylene. The peculiar behaviour of copper carbide (copper is

  5. Parallel High-order Global Implicit Filter for the Spectral Element Dynamical Core on the Cubed Sphere

    NASA Astrophysics Data System (ADS)

    Kang, H. G.; Cheong, H. B.

    2015-12-01

    Parallel-friendly high-order global implicit filter for the spectral element dynamical core on the cubed sphere is developed to control small-scale numerical noises efficiently. The global discrete Laplacian operator matrix constructed by assembling the local discrete Laplacian operator matrix is used to make the Helmholtz-type global filter matrix. By preparing the inverted filter matrix in advance, only forward operation which is the multiplication of the inverted filter matrix and the global grid vector is required to carry out the filtering process. Also, the magnitude of inverted filter matrix components vary in significantly large range from (O-40) to (O -1) so that negligible matrix components less than a certain threshold value such as 10-15 or 10-10 can be removed reduce the operation count. It is found that the number of the matrix components after removal process is maintained with the help of diffusion coefficient and model time step size even though the horizontal resolution increases. This feature has advantages in parallelization of filtering process. Parallel scalability of filtering process only is nearly perfect to 512 CPUs. Scalability of the fully-equipped model is now under test and will be presented. Forward operating high-order filter is implemented in the spectral element hydrostatic dynamical core. Performance of forward operating high-order filter is evaluated using the dynamical core model intercomparison project (DCMIP) test cases and compared to explicit hyper-viscosity. Test case 2-0-0 which is steady-state atmosphere at rest in the presence of bottom topography is chosen, and we changed its moderately-steep orography to non-smoothed observed one to generate small-scale noise sufficiently. During 6 days of time integration, spurious flow was generated by the pressure gradient error. For a large time step size the model with explicit diffusion was found unstable, finally blowing-up at day 1. However, the model with second-order implicit

  6. TiO2@C Core-Shell Nanoparticles Formed by Polymeric Nano-Encapsulation

    NASA Astrophysics Data System (ADS)

    Vasei, Mitra; Das, Paramita; Cherfouh, Hayet; Marsan, Benoit; Claverie, Jerome

    2014-07-01

    TiO2 semiconducting nanoparticles are known to be photocatalysts of moderate activity due to their high band-gap and high rate of electron-hole recombination. The formation of a shell of carbon around the core of TiO2, i.e. the formation of TiO2@C nanoparticles, is believed to partly alleviate these problems. It is usually achieved by a hydrothermal treatment in a presence of a sugar derivative. We present here a novel method for the formation of highly uniform C shell around TiO2 nanoparticles. For this purpose, TiO2 nanoparticles were dispersed in water using an oligomeric dispersant prepared by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. Then the nanoparticles were engaged into an emulsion polymerization of acrylonitrile, resulting in the formation of a shell of polyacrylonitrile (PAN) around each TiO2 nanoparticles. Upon pyrolisis, the PAN was transformed into carbon, resulting in the formation of TiO2@C nanoparticles. The structure of the resulting particles was elucidated by X-Ray diffraction, FTIR, UV-VIS and Raman spectroscopy as well as TEM microscopy. Preliminary results about the use of the TiO2@C particles as photocatalysts for the splitting of water are presented. They indicate that the presence of the C shell is responsible for a significant enhancement of the photocurrent.

  7. Nanostructures formed in pure quartz glass under irradiation in the reactor core

    NASA Astrophysics Data System (ADS)

    Ibragimova, E. M.; Mussaeva, M. A.; Kalanov, M. U.

    2014-04-01

    Optical spectroscopy and X-ray diffraction techniques were used for studying nanoscale particles grown in pure SiO2 glass under irradiation with fast neutron fluencies within 6×1016-5·1019 cm-2 and gamma-quanta ~1.8×1020 cm-2 in the reactor core in water. The neutron irradiation results in destroying of the initial α- and β-quartz mesoscopic order of 1.7 and 1.2 nm sizes and growing of cristobalite and tridymite nanocrystals of 16 and 8 nm sizes in the thermal peaks of displacements reapectively. The point defects (oxygen deficient E‧s, E'1, E'2 and non-bridging oxygen centers) induced by the γ-irradiation are accumulated in the nanocrystals shell of 0.65-0.85 nm thickness. Interaction of close point defects at the nanocrystal-glass interface causes the splitting of optical absorption bands into the intensive (D~2-4) resonances characteristic for local interband electron transitions, having the width of 10-15 nm close to the nanocrystals' sizes and the energy depending on their structure.

  8. TiO2@C core-shell nanoparticles formed by polymeric nano-encapsulation

    PubMed Central

    Vasei, Mitra; Das, Paramita; Cherfouth, Hayet; Marsan, Benoît; Claverie, Jerome P.

    2014-01-01

    TiO2 semiconducting nanoparticles are known to be photocatalysts of moderate activity due to their high band-gap and high rate of electron-hole recombination. The formation of a shell of carbon around the core of TiO2, i.e., the formation of TiO2@C nanoparticles, is believed to partly alleviate these problems. It is usually achieved by a hydrothermal treatment in a presence of a sugar derivative. We present here a novel method for the formation of highly uniform C shell around TiO2 nanoparticles. For this purpose, TiO2 nanoparticles were dispersed in water using an oligomeric dispersant prepared by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization. Then the nanoparticles were engaged into an emulsion polymerization of acrylonitrile, resulting in the formation of a shell of polyacrylonitrile (PAN) around each TiO2 nanoparticles. Upon pyrolysis, the PAN was transformed into carbon, resulting in the formation of TiO2@C nanoparticles. The structure of the resulting particles was elucidated by X-Ray diffraction, FTIR, UV-VIS and Raman spectroscopy as well as TEM microscopy. Preliminary results about the use of the TiO2@C particles as photocatalysts for the splitting of water are presented. They indicate that the presence of the C shell is responsible for a significant enhancement of the photocurrent. PMID:25072054

  9. Boundary Element Modeling of Fault Cored Anticlines and Associated Blind Thrust Faults in Central California

    NASA Astrophysics Data System (ADS)

    Williams, M. K.; Johnson, K. M.

    2015-12-01

    Recent literature investigating active folding indicates that crustal-scale anticlines grow primarily through slip on underlying faults. Such studies use the geometry and uplift rates of active fault-related folds to infer fault slip rate based upon an assumed kinematic relationship between fault slip and particle motion in the surrounding crust. Our method uses a boundary element model of flexural slip folding called BEAFS (Boundary Element Analysis of Flexural Slip), allowing us to focus on the mechanics of deformation.In many cases, the shallow geometry (<5km) of natural folds are well constrained by subsurface data. However, the geometry of the causative blind thrust faults are often not well imaged. By comparing our numerical simulations with published subsurface and surface data on naturally occurring active folds, we can determine fault geometry and the extent to which various mechanisms are controlling fold evolution. For this work, we present our model results for the underlying faults at Kettleman Hills South Dome, Kettleman Hills North Dome, and Coalinga Anticline in the San Joaquin Valley of Central California. The rupturing of blind thrust faults associated with actively growing anticlines such as these pose a significant global seismic hazard. Our study area is of particular interest as it is the site of two such recent earthquakes—a Mw=6.5 earthquake in 1983 at Coalinga and a Mw=6.1 in 1985 at Kettleman Hills North Dome. Thus, we can compare the published earthquake data from these events to the parameters predicted by our model results from BEAFS.

  10. Bent LC molecules with a 60° central core that can form B7 and B2 phases (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Watanabe, Junji

    2015-10-01

    We synthesized small-angle bent-core liquid-crystalline (LC) molecules based on a 1,2-bis(phenylethylene) benzene central core, containing seven aromatic rings and alkoxy tails with carbon numbers of 12, 16 and 18. This ortho-bistolane central core offers a 60° bend angle. Irrespective of this unusually small angle, these molecules can form banana smectic phases with a ferroelectric B7-antiferroelectric B2 phase sequence upon cooling as clarified from the micoscopic, X-ray and opto-electric observations. This indicates that despite of the low bend angle of 60°, these are able to be still packed into a layer with the polar bent direction parallel to the layer like ordinal banana molecules. The present result is striking since it had been believed that banana phases can only be stabilized when the bending angle is in the range from 110-140°, providing additional insight into the nature of banana-shaped molecules.

  11. Element redistribution during hydrothermal alteration of rhyolite in an active geothermal system: Yellowstone drill cores Y-7 and Y-8

    NASA Astrophysics Data System (ADS)

    Sturchio, Neil C.; Muehlenbachs, Karlis; Seitz, Martin G.

    1986-08-01

    Hydrothermal alteration of the 0.54 Ma Biscuit Basin rhyolite flow in Yellowstone drill cores Y-7 and Y-8 has involved significant changes in Ti-normalized whole rock concentrations of Li, Mg, Ca, Na, K, Mn, Rb, Sr, Sb, Cs, Ba, and U, whereas such changes have generally not occurred for Al, Fe, Sc, Co, Y, Zr, REE, Hf, Ta, and Th. The relatively mobile elements have been redistributed over distances from 2-5 cm to more than 10-100 m, and are associated mainly with zeolites and clays, in thoroughly altered samples; average whole rock changes in Ti-normalized mass range from about 0.5-17 g/Kg (9-49%) for major elements and 0.1-280 mg/Kg (19-4260%) for minor and trace elements. Compositional changes correlate with hydrothermal mineralogy. The relatively immobile elements have been redistributed over a distance of at least 10-100 μm but less than 2-5 cm, and are associated mainly with clays, in thoroughly altered samples. Addition of SiO 2 ranges from 110-890 g/Kg in samples where porosity has been thoroughly sealed by silica deposition. Thermal water is not in oxygen isotopic equilibrium with any primary or secondary phases analyzed except calcite. Modest depletions of 18O (1-2%) due to exchange with thermal water apparently have occurred in Y-8 plagioclase and obsidian. Oxygen isotope ratios in obsidian-replacing smectite and in veinlet celadonite and β-cristobalite suggest that these phases precipitated from water locally enriched in 18O (up to ~8% heavier than present thermal water). The minimum integrated water/rock mass ratio in Y-7 and Y-8 is 10 3-10 4 (assuming advective transport).

  12. Recessive TTN truncating mutations define novel forms of core myopathy with heart disease

    PubMed Central

    Chauveau, Claire; Bonnemann, Carsten G.; Julien, Cedric; Kho, Ay Lin; Marks, Harold; Talim, Beril; Maury, Philippe; Arne-Bes, Marie Christine; Uro-Coste, Emmanuelle; Alexandrovich, Alexander; Vihola, Anna; Schafer, Sebastian; Kaufmann, Beth; Medne, Livija; Hübner, Norbert; Foley, A. Reghan; Santi, Mariarita; Udd, Bjarne; Topaloglu, Haluk; Moore, Steven A.; Gotthardt, Michael; Samuels, Mark E.; Gautel, Mathias; Ferreiro, Ana

    2014-01-01

    Core myopathies (CM), the main non-dystrophic myopathies in childhood, remain genetically unexplained in many cases. Heart disease is not considered part of the typical CM spectrum. No congenital heart defect has been reported, and childhood-onset cardiomyopathy has been documented in only two CM families with homozygous mutations of the TTN gene. TTN encodes titin, a giant protein of striated muscles. Recently, heterozygous TTN truncating mutations have also been reported as a major cause of dominant dilated cardiomyopathy. However, relatively few TTN mutations and phenotypes are known, and titin pathophysiological role in cardiac and skeletal muscle conditions is incompletely understood. We analyzed a series of 23 families with congenital CM and primary heart disease using TTN M-line-targeted sequencing followed in selected patients by whole-exome sequencing and functional studies. We identified seven novel homozygous or compound heterozygous TTN mutations (five in the M-line, five truncating) in 17% patients. Heterozygous parents were healthy. Phenotype analysis identified four novel titinopathies, including cardiac septal defects, left ventricular non-compaction, Emery–Dreifuss muscular dystrophy or arthrogryposis. Additionally, in vitro studies documented the first-reported absence of a functional titin kinase domain in humans, leading to a severe antenatal phenotype. We establish that CM are associated with a large range of heart conditions of which TTN mutations are a major cause, thereby expanding the TTN mutational and phenotypic spectrum. Additionally, our results suggest titin kinase implication in cardiac morphogenesis and demonstrate that heterozygous TTN truncating mutations may not manifest unless associated with a second mutation, reassessing the paradigm of their dominant expression. PMID:24105469

  13. Recessive TTN truncating mutations define novel forms of core myopathy with heart disease.

    PubMed

    Chauveau, Claire; Bonnemann, Carsten G; Julien, Cedric; Kho, Ay Lin; Marks, Harold; Talim, Beril; Maury, Philippe; Arne-Bes, Marie Christine; Uro-Coste, Emmanuelle; Alexandrovich, Alexander; Vihola, Anna; Schafer, Sebastian; Kaufmann, Beth; Medne, Livija; Hübner, Norbert; Foley, A Reghan; Santi, Mariarita; Udd, Bjarne; Topaloglu, Haluk; Moore, Steven A; Gotthardt, Michael; Samuels, Mark E; Gautel, Mathias; Ferreiro, Ana

    2014-02-15

    Core myopathies (CM), the main non-dystrophic myopathies in childhood, remain genetically unexplained in many cases. Heart disease is not considered part of the typical CM spectrum. No congenital heart defect has been reported, and childhood-onset cardiomyopathy has been documented in only two CM families with homozygous mutations of the TTN gene. TTN encodes titin, a giant protein of striated muscles. Recently, heterozygous TTN truncating mutations have also been reported as a major cause of dominant dilated cardiomyopathy. However, relatively few TTN mutations and phenotypes are known, and titin pathophysiological role in cardiac and skeletal muscle conditions is incompletely understood. We analyzed a series of 23 families with congenital CM and primary heart disease using TTN M-line-targeted sequencing followed in selected patients by whole-exome sequencing and functional studies. We identified seven novel homozygous or compound heterozygous TTN mutations (five in the M-line, five truncating) in 17% patients. Heterozygous parents were healthy. Phenotype analysis identified four novel titinopathies, including cardiac septal defects, left ventricular non-compaction, Emery-Dreifuss muscular dystrophy or arthrogryposis. Additionally, in vitro studies documented the first-reported absence of a functional titin kinase domain in humans, leading to a severe antenatal phenotype. We establish that CM are associated with a large range of heart conditions of which TTN mutations are a major cause, thereby expanding the TTN mutational and phenotypic spectrum. Additionally, our results suggest titin kinase implication in cardiac morphogenesis and demonstrate that heterozygous TTN truncating mutations may not manifest unless associated with a second mutation, reassessing the paradigm of their dominant expression. PMID:24105469

  14. Using Virtual Field Trips to Connect Students with University Scientists: Core Elements and Evaluation of zipTrips™

    NASA Astrophysics Data System (ADS)

    Adedokun, Omolola A.; Hetzel, Kristin; Parker, Loran Carleton; Loizzo, Jamie; Burgess, Wilella D.; Paul Robinson, J.

    2012-10-01

    Physical field trips to scientists' work places have been shown to enhance student perceptions of science, scientists and science careers. Although virtual field trips (VFTs) have emerged as viable alternatives (or supplements) to traditional physical fieldtrips, little is known about the potential of virtual field trips to provide the same or similar science career exploration advantages as physical field trips. The overarching goal of this paper is to describe a VFT, zipTrips™, designed to provide middle school students, especially those in resource limited rural areas, with access to university scientists. Using zipTrips as a case example, the paper identifies and describes some of the core characteristics and elements of high quality authentic VFTs that foster student-scientist interactions. In addition, the paper uses program evaluation data to examine the impact of zipTrips on student perceptions of scientists.

  15. A global non-hydrostatic dynamical core using the spectral element method on a cubed-sphere grid

    NASA Astrophysics Data System (ADS)

    Choi, Suk-Jin; Hong, Song-You

    2016-06-01

    A new global model with a non-hydrostatic (NH) dynamical core is developed. It employs the spectral element method (SEM) in the horizontal discretization and the finite difference method (FDM) in the vertical discretization. The solver includes a time-split third-order Runge-Kutta (RK3) time-integration technique. Pursuing the quasi-uniform and pole singularity-free spherical geometry, a cubed-sphere grid is employed. To assess the performance of the developed dynamical solver, the results from a number of idealized benchmark tests for hydrostatic and non-hydrostatic flows are presented and compared. The results indicate that the non-hydrostatic dynamical solver is able to produce solutions with good accuracy and consistency comparable to reference solutions. Further evaluation of the model with a full-physics package demonstrates its capability in reproducing heavy rainfall over the Korean Peninsula, which confirms that coupling of the dynamical solver and full-physics package is robust.

  16. A new method based on low background instrumental neutron activation analysis for major, trace and ultra-trace element determination in atmospheric mineral dust from polar ice cores.

    PubMed

    Baccolo, Giovanni; Clemenza, Massimiliano; Delmonte, Barbara; Maffezzoli, Niccolò; Nastasi, Massimiliano; Previtali, Ezio; Prata, Michele; Salvini, Andrea; Maggi, Valter

    2016-05-30

    Dust found in polar ice core samples present extremely low concentrations, in addition the availability of such samples is usually strictly limited. For these reasons the chemical and physical analysis of polar ice cores is an analytical challenge. In this work a new method based on low background instrumental neutron activation analysis (LB-INAA) for the multi-elemental characterization of the insoluble fraction of dust from polar ice cores is presented. Thanks to an accurate selection of the most proper materials and procedures it was possible to reach unprecedented analytical performances, suitable for ice core analyses. The method was applied to Antarctic ice core samples. Five samples of atmospheric dust (μg size) from ice sections of the Antarctic Talos Dome ice core were prepared and analyzed. A set of 37 elements was quantified, spanning from all the major elements (Na, Mg, Al, Si, K, Ca, Ti, Mn and Fe) to trace ones, including 10 (La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb and Lu) of the 14 natural occurring lanthanides. The detection limits are in the range of 10(-13)-10(-6) g, improving previous results of 1-3 orders of magnitude depending on the element; uncertainties lies between 4% and 60%. PMID:27154827

  17. Myc versus USF: discrimination at the cad gene is determined by core promoter elements.

    PubMed Central

    Boyd, K E; Farnham, P J

    1997-01-01

    Carbamoyl-phosphate synthase/aspartate carbamoyltransferase/dihydroorotase, which is encoded by the cad gene, is required for the first three rate-limiting steps of de novo pyrimidine biosynthesis. It has been previously demonstrated that cad transcription increases at the G1/S-phase boundary, as quiescent cells reenter the proliferative cell cycle. The growth-responsive element has been mapped to an E box at +65 in the hamster cad promoter. Using an in vivo UV cross-linking and immunoprecipitation assay, we show that Myc, Max, and upstream stimulatory factor (USF) bind to the chromosomal cad promoter. To determine whether binding of Myc-Max or USF is critical for cad growth regulation, we analyzed promoter constructs which contain mutations in the nucleotides flanking the E box. We demonstrate that altering nucleotides which flank the cad E box to sequences which decrease Myc-Max binding in vitro correlates with a loss of cad G1/S-phase transcriptional activation. This result supports the conclusion that binding of Myc-Max, but not USF, is essential for cad regulation. Our investigations demonstrate that the endogenous cad E box can be bound by more than one transcription factor, but growth-induced cad expression is achieved only by Myc. PMID:9111322

  18. Core Outcomes and Common Data Elements in Chronic Subdural Hematoma: A Systematic Review of the Literature Focusing on Reported Outcomes.

    PubMed

    Chari, Aswin; Hocking, Katie C; Broughton, Ellie; Turner, Carole; Santarius, Thomas; Hutchinson, Peter J; Kolias, Angelos G

    2016-07-01

    The plethora of studies in chronic subdural hematoma (CSDH) has not resulted in the development of an evidence-based treatment strategy, largely due to heterogeneous outcome measures that preclude cross-study comparisons and guideline development. This study aimed to identify and quantify the heterogeneity of outcome measures reported in the CSDH literature and to build a case for the development of a consensus-based core outcome set. This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and was registered with the PROSPERO international prospective register of systematic reviews (CRD42014007266). All full-text English language studies with >10 patients (prospective) or >100 patients (retrospective) published after 1990 examining clinical outcomes in CSDH were eligible for inclusion. One hundred two eligible studies were found. There were 14 (13.7%) randomized controlled trials, one single arm trial (1.0%), 25 (24.5%) cohort comparison studies, and 62 (60.8%) prospective or retrospective cohort studies. Outcome domains reported by the studies included mortality (63.8% of included studies), recurrence (94.1%), complications (48.0%), functional outcomes (40.2%), and radiological (38.2%) outcomes. There was significant heterogeneity in the definitions of the outcome measures, as evidenced by the seven different definitions of the term "recurrence," with no definition given in 19 studies. The time-points of assessment for all the outcome domains varied greatly from inpatient/hospital discharge to 18 months. This study establishes and quantifies the heterogeneity of outcome measure reporting in CSDH and builds the case for the development of a robust consensus-based core outcome set for future studies to adhere to as part of the Core Outcomes and Common Data Elements in CSDH (CODE-CSDH) project. PMID:26295586

  19. Suppression of grp78 core promoter element-mediated stress induction by the dbpA and dbpB (YB-1) cold shock domain proteins.

    PubMed Central

    Li, W W; Hsiung, Y; Wong, V; Galvin, K; Zhou, Y; Shi, Y; Lee, A S

    1997-01-01

    The highly conserved grp78 core promoter element plays an important role in the induction of grp78 under diverse stress signals. Previous studies have established a functional region in the 3' half of the core (stress-inducible change region [SICR]) which exhibits stress-inducible changes in stressed nuclei. The human transcription factor YY1 is shown to bind the SICR and transactivate the core element under stress conditions. Here we report that expression library screening with the core element has identified two new core binding proteins, YB-1 and dbpA. Both proteins belong to the Y-box family of proteins characterized by an evolutionarily conserved DNA binding motif, the cold shock domain (CSD). In contrast to YY1, which binds only double-stranded SICR, the Y-box/CSD proteins much prefer the lower strand of the SICR. The Y-box proteins can repress the inducibility of the grp78 core element mediated by treatment of cells with A23187, thapsigargin, and tunicamycin. In gel shift assays, YY1 binding to the core element is inhibited by either YB-1 or dbpA. A yeast interaction trap screen using LexA-YY1 as a bait and a HeLa cell cDNA-acid patch fusion library identified YB-1 as a YY1-interacting protein. In cotransfection experiments, the Y-box proteins antagonize the YY1-mediated enhancement of transcription directed by the grp78 core in stressed cells. Thus, the CSD proteins may be part of the stress signal transduction mechanism in the mammalian system. PMID:8972186

  20. Rare earth element compositions of core sediments from the shelf of the South Sea, Korea: Their controls and origins

    NASA Astrophysics Data System (ADS)

    Jung, Hoi-Soo; Lim, Dhongil; Choi, Jin-Yong; Yoo, Hae-Soo; Rho, Kyung-Chan; Lee, Hyun-Bok

    2012-10-01

    Rare earth elements (REEs) of bulk sediments and heavy mineral samples of core sediments from the South Sea shelf, Korea, were analyzed to determine the constraints on REE concentrations and distribution patterns as well as to investigate their potential applicability for discriminating sediment provenance. Bulk sediment REEs showed large variation in concentrations and distribution patterns primarily due to grain size and carbonate dilution effects, as well as due to an abundance of heavy minerals. In the fine sandy sediments (cores EZ02-15 and 19), in particular, heavy minerals (primarily monazite and titanite/sphene) largely influenced REE compositions. Upper continental crust-normalized REE patterns of these sand-dominated sediments are characterized by enriched light REEs (LREEs), because of inclusion of heavy minerals with very high concentrations in LREEs. Notably, such a strong LREE enrichment is also observed in Korean river sediments. So, a great care must be taken when using the REE concentrations and distribution patterns of sandy and coarse silty shelf sediments as a proxy for discriminating sediment provenance. In the fine-grained muddy sediments with low heavy mineral abundance, in contrast, REE fractionation ratios and their UCC-normalized patterns seem to be reliable proxies for assessing sediment provenance. The resultant sediment origin suggested a long lateral transportation of some fine-grained Chinese river sediments (probably the Changjiang River) to the South Sea of Korea across the shelf of the northern East China Sea.

  1. Origins of hematite and redox-sensitive elements in a 3.46 Ga jasper-basalt sequence in ABDP #1 core from Pilbara, Western Australia

    NASA Astrophysics Data System (ADS)

    Ohmoto, H.; Bevacqua, D. C.; Watanabe, Y.

    2010-12-01

    Previous researchers suggested that the abundant hematite crystals in surface outcrops of 3.46 Ga jasper and submarine basalt in the Marble Bar area, Western Australia were modern oxidation products of siderite and pyrite. Drilling at ABDP #1 site (260 m long at ~50° angle) was carried out to obtain modern oxidation-free samples of the jasper and submarine basalt and to conduct research aimed at constraining the redox state of the Archean oceans and atmosphere. The deep drill core samples were found to contain hematite crystals as abundantly as those in surface outcrops, suggesting that the hematite crystals are not modern oxidation products. We have conducted petrological, mineralogical, and geochemical investigations on more than 100 samples of chert/jasper and basalt. Based partly on the textural relationships among minerals in SEM and TEM images, we (Hoashi et al., Nature Geosciences, 2009) have concluded that the hematite crystals in the jasper beds formed at >60°C on and/or near the deep (>200 m) ocean floor by the mixing of ferrous iron-rich hydrothermal fluids and oxygen-rich deep ocean water. Hematite crystals in basalts, which occur at below, inter bedded with, and above the jasper beds, were most likely formed by the same processes. Hematite-rich jaspers and basalts in ABDP #1 core show significant enrichments of many redox-sensitive elements (e.g., Fe3+, Mn, U, Mo, REEs), as well as some non-redox sensitive elements (e.g., Li, Ba, Sr). Negative Ce anomalies are commonly found in these samples. These characteristics are essentially identical to those in jaspers and basalts in many modern submarine hydrothermal systems. These data suggest that since at least ~3.46 Ga ago: (1) the geochemistry and mineralogy of submarine hydrothermal deposits and associated basalts have been dictated by reducing (Fe- and Mn rich) hydrothermal fluids and oxidizing deep ocean water; (2) the concentrations of many redox-senstive (and other) elements in the oceans have been

  2. Scaled up low-mass star formation in massive star-forming cores in the G333 giant molecular cloud

    NASA Astrophysics Data System (ADS)

    Wiles, B.; Lo, N.; Redman, M. P.; Cunningham, M. R.; Jones, P. A.; Burton, M. G.; Bronfman, L.

    2016-06-01

    Three bright molecular line sources in G333 have recently been shown to exhibit signatures of infall. We describe a molecular line radiative transfer (RT) modelling process which is required to extract the infall signature from Mopra and Nanten2 data. The observed line profiles differ greatly between individual sources but are reproduced well by variations upon a common unified model where the outflow viewing angle is the most significant difference between the sources. The models and data together suggest that the observed properties of the high-mass star-forming regions such as infall, turbulence and mass are consistent with scaled-up versions of the low-mass case with turbulent velocities that are supersonic and an order of magnitude larger than those found in low-mass star-forming regions. Using detailed RT modelling, we show that the G333 cores are essentially undergoing a scaled-up version of low-mass star formation. This is an extension of earlier work in that the degree of infall and the chemical abundances are constrained by the RT modelling in a way that is not practical with a standard analysis of observational data. We also find high velocity infall and high infall mass rates, possibly suggesting accelerated collapse due to external pressure. Molecular depletion due to freeze-out on to dust grains in central regions of the cores is suggested by low molecular abundances of several species. Strong evidence for a local enhancement of 13C-bearing species towards the outflow cloud cores is discussed, consistent with the presence of shocks caused by the supersonic motions within them.

  3. Metal-core piezoelectric fiber-based smart layer for damage detection using sparse virtual element boundary measurement

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Cheng, Li; Qiu, Jinhao; Wang, Hongyuan

    2016-04-01

    Metal-core Piezoelectric Fiber (MPF) was shown to have great potential to be a structurally integrated sensor for structural health monitoring (SHM) applications. Compared with the typical foil strain gauge, MPF is more suitable for high frequency strain measurement and can create direct conversion of mechanical energy into electric energy without the need for complex signal conditioners or gauge bridges. In this paper, a MPF-based smart layer is developed as an embedded network of distributed strain sensors that can be surface-mounted on a thin-walled structure. Each pair of the adjacent MPFs divides the entire structure into several "virtual elements (VEs)". By exciting the structure at the natural frequency of the VE, a "weak" formulation of the previously developed Pseudo-excitation (PE) approach based on sparse virtual element boundary measurement (VEBM) is proposed to detect the damage. To validate the effectiveness of the VEBM based approach, experiments are conducted to locate a small crack in a cantilever beam by using a MPF- based smart layer and a Laser Doppler Vibrometer (LDV). Results demonstrate that the proposed VEBM approach not only inherits the enhanced noise immunity capability of the "weak" formulation of the PE approach, but also allows a significant reduction in the number of measurement points as compared to the original version of the PE approach.

  4. Patient Experience and Satisfaction with Inpatient Service: Development of Short Form Survey Instrument Measuring the Core Aspect of Inpatient Experience

    PubMed Central

    Wong, Eliza L. Y.; Coulter, Angela; Hewitson, Paul; Cheung, Annie W. L.; Yam, Carrie H. K.; Lui, Siu fai; Tam, Wilson W. S.; Yeoh, Eng-kiong

    2015-01-01

    Patient experience reflects quality of care from the patients’ perspective; therefore, patients’ experiences are important data in the evaluation of the quality of health services. The development of an abbreviated, reliable and valid instrument for measuring inpatients’ experience would reflect the key aspect of inpatient care from patients’ perspective as well as facilitate quality improvement by cultivating patient engagement and allow the trends in patient satisfaction and experience to be measured regularly. The study developed a short-form inpatient instrument and tested its ability to capture a core set of inpatients’ experiences. The Hong Kong Inpatient Experience Questionnaire (HKIEQ) was established in 2010; it is an adaptation of the General Inpatient Questionnaire of the Care Quality Commission created by the Picker Institute in United Kingdom. This study used a consensus conference and a cross-sectional validation survey to create and validate a short-form of the Hong Kong Inpatient Experience Questionnaire (SF-HKIEQ). The short-form, the SF-HKIEQ, consisted of 18 items derived from the HKIEQ. The 18 items mainly covered relational aspects of care under four dimensions of the patient’s journey: hospital staff, patient care and treatment, information on leaving the hospital, and overall impression. The SF-HKIEQ had a high degree of face validity, construct validity and internal reliability. The validated SF-HKIEQ reflects the relevant core aspects of inpatients’ experience in a hospital setting. It provides a quick reference tool for quality improvement purposes and a platform that allows both healthcare staff and patients to monitor the quality of hospital care over time. PMID:25860775

  5. Preservation of deep Himalayan PT conditions that formed during multiple events in garnet cores: Mylonitization produces erroneous results for rims

    NASA Astrophysics Data System (ADS)

    Sapkota, J.; Sanislav, I. V.

    2013-03-01

    The Kathmandu Thrust Sheet, which overlies the Lesser Himalayas along the southern part of the Main Central Thrust (MCT) and forms the leading edge of the Higher Himalayan crystalline rocks, is folded at a regional scale by the Gorkha-Kathmandu fold couplet in Central Nepal. Garnet porphyroblasts lying close to the MCT within this thrust sheet preserve structural and metamorphic history that predates mylonitization during thrust emplacement. The succession of five FIA sets preserved within these porphyroblasts formed due to changes in the direction of India's motion relative to Asia after they collided. The intersection of Fe, Ca and Mn isopleths for garnet cores reveals that FIA sets 1, 2, 3, 4 and 5 nucleated respectively at 6.2 kbar and 515 °C, 6-7 kbar and 545-550 °C, 6.6 kbar and 530 °C, 5.6-6.2 kbar and 525-550 °C and 6.8-6.9 kbar and 520-560 °C. The average PT mode of THERMOCALC, which relies on equilibrium being achieved between the garnet rims and the matrix, gives pressures around 11 kbar that do not accord with the lengthy succession of lower core pressures. The many foliations in the matrix, which formed during top to the south thrusting plus subsequent deformations that eventually led to these rocks reaching the surface, truncate all foliations preserved within the porphyroblasts that are defined by inclusion trails. This has resulted in the garnet rims not being in equilibrium with the matrix and the anomalously high pressures. The garnet rims may have been affected by slow dissolution and solution transfer over the period of time that the matrix was deforming plastically at high strain rates as the rocks were uplifted. The assumption of equilibrium between garnet rims and surrounding silicates used by various rim geothermobarometric methods does not hold for these rocks.

  6. Thin Film XRF measurements (Wet and dry) of Black Sea Sediment Samples And Their Elemental Comparisons With Same Core U Channel Sample.

    NASA Astrophysics Data System (ADS)

    Acar, Dursun; Eris, Kadir; Sarı, Erol; Genc, S. Can

    2015-04-01

    This paper presents the XRF data from about 0.3mm thin film sediment core. We prepared 3 different model from same sediment core. The main aim is the finding for elemental changing of spectra variety and their comparison with physical changes of samples about mass and water content. Our XRF measurements were carried out by ITRAX (Cox System), and we have documented the some useful and more precision tricks; a) the first point is that the wet or dry nature of the core, b) the second is the use of U channel sample or thin film sample. For base referencing for the selected elements, we prepared normal wet U channel sample with the thickness of 1.5 cm. We used thin material (film) for keeping the humidty of every core sample's surface. Because humidity loss very high on thin film core sample and very effective to get bad results related to changing of topography and beam emission related to loss of pore water. Our XRF measurements have revealed that the Zn, Ti, Si, V,S, Cr, Mn, Ba, K and Ca elements were measured more precisely and accurate using by the dry thin film sample than those of wet U channel and wet thin sediment sample experiments. Beside this, Y, Zr, Nb, Rb, Sr, Ir, Fe,Co, Ni and Al elements were measured from the wet U channeled core more reliable with respect to the former. Lead (Pb) and Cd elements have behaved constantly during the three types of measurements. Keywords: Thin film XRF, U channel, Elements, Sediment, Measurement

  7. Two approaches to form antibacterial surface: Doping with bactericidal element and drug loading

    NASA Astrophysics Data System (ADS)

    Sukhorukova, I. V.; Sheveyko, A. N.; Kiryukhantsev-Korneev, Ph. V.; Anisimova, N. Y.; Gloushankova, N. A.; Zhitnyak, I. Y.; Benesova, J.; Amler, E.; Shtansky, D. V.

    2015-03-01

    Two approaches (surface doping with bactericidal element and loading of antibiotic into specially formed surface microcontainers) to the fabrication of antibacterial yet biocompatible and bioactive surfaces are described. A network structure with square-shaped blind pores of 2.6 ± 0.6 × 10-3 mm3 for drug loading was obtained by selective laser sintering (SLS). The SLS-fabricated samples were loaded with 0.03, 0.3, 2.4, and 4 mg/cm2 of co-amoxiclav (amoxicillin and clavulanic acid). Ag-doped TiCaPCON films with 0.4, 1.2, and 4.0 at.% of Ag were obtained by co-sputtering of composite TiC0.5-Ca3(PO4)2 and metallic Ag targets. The surface structure of SLS-prepared samples and cross-sectional morphology of TiCaPCON-Ag films were studied by scanning electron microscopy. The through-thickness of Ag distribution in the TiCaPCON-Ag films was obtained by glow discharge optical emission spectroscopy. The kinetics of Ag ion release in normal saline solution was studied using inductively coupled plasma mass spectrometry. Bacterial activity of the samples was evaluated against S. epidermidis, S. aureus, and K. pneum. ozaenae using the agar diffusion test and photometric method by controlling the variation of optical density of the bacterial suspension over time. Cytocompatibility of the Ag-doped TiCaPCON films was observed in vitro using chondrocytic and MC3T3-E1 osteoblastic cells. The viability and proliferation of chondrocytic cells were determined using the MTS assay and PicoGreen assay tests, respectively. The alkaline phosphatase (ALP) activity of the SLS-fabricated samples loaded with co-amoxiclav was also studied. The obtained results showed that the moderate bacteriostatic effect of the Ag-doped TiCaPCON films is mainly manifested in the change of bacterial colony morphology and optical densities of bacteria suspensions. In contrast, the SLS-prepared samples showed a very rapid initial drug release resulting in strong bactericidal effect just from the start of the

  8. A/T gap tolerance in the core sequence and flanking sequence requirements of non-canonical p53 response elements.

    PubMed

    Cai, Bi-He; Chao, Chung-Faye; Lin, Hwang-Chi; Huang, Hua-Ying; Kannagi, Reiji; Chen, Jang-Yi

    2016-06-01

    The canonical core sequence of the p53 response element, CATG, has a two-base A/T gap. Previously, we found that p53 can also activate a non-canonical four-base A/T gap CATATG core sequence. In this study, we investigated the possible number of A/T bases used by p53 and showed that a six-base A/T gap CATATATG core sequence was the maximum A/T gap in the p53 response element that could be upregulated by p53 and p63. Canonical and non-canonical p53 response elements also have three-base flanking sequences. A/T bases could be substituted by G/C bases, including CACACG and CGTGTG, but not CGCGCG. We found that the SV40 promoter with functional six- and two-base A/T gap core sequences could be activated by TAp63γ and that TAp63γ could upregulate SV40 small and large T antigens expression in COS7 cells. We also found that the distal region of PUMA promoter with functional two six-base A/T gap core sequences could be activated by TAp63γ in 293T cells. These new findings could provide novel rules for the non-canonical p53 family response element and could extend the entire p53 family regulation network. PMID:26823482

  9. [Exclusive elemental enteral diet in cortico-resistant and cortico-dependent forms of Crohn's disease].

    PubMed

    Le Quintrec, Y; Cosnes, J; Le Quintrec, M; Contou, J F; Baumer, P; Bellanger, J; Gendre, J P

    1987-01-01

    The aim of this study was to investigate the value of elemental diet in steroid-resistant and steroid-dependent Crohn's disease. Elemental diet (Vivonex HN, 39.4 +/- 9.2 kcal/kg/d) was delivered through a nasogastric tube at a constant rate. Twenty therapeutic periods lasting from 20 to 74 days (median, 32 days) were undertaken in 18 patients. Elemental diet was well tolerated. Mean values of hemoglobin, serum albumin, and serum transferrin increased significantly through the therapeutic period; body weight and anthropometric data did not change significantly. The short-term response to elemental diet was excellent in 11 cases, demonstrated by achievement of clinical remission and steroid withdrawal; six patients had an incomplete remission and remained slightly active or had to be maintained under low dose steroids; three patients did not respond to therapy and had to be operated upon. During the follow-up (6-30 months), 8 patients out of 17 had a relapse. Relapse was controlled by medical therapy in 5 cases and led to surgery in the 3 other cases. We conclude that elemental diet, as total parenteral nutrition, is an effective therapy of steroid-resistant and steroid-dependent Crohn's disease. However, elemental diet does not prevent relapse. PMID:3111930

  10. Organic Chemistry of Low-Mass Star-Forming Cores. I. 7 mm Spectroscopy of Chamaeleon MMSl

    NASA Technical Reports Server (NTRS)

    Cordiner, Martn A.; Charnley, Steven B.; Wirtstroem, Eva S.; Smith, Robert G.

    2012-01-01

    Observations are presented of emission lines from organic molecules at frequencies 32-50 GHz in the vicinity of Chamaeleon MMS1. This chemically rich dense cloud core harbors an extremely young, very low luminosity protostellar object and is a candidate first hydrostatic core. Column densities are derived and emission maps are presented for species including polyynes, cyanopolyynes, sulphuretted carbon chains, and methanol. The polyyne emission peak lies about 5000 AU from the protostar, whereas methanol peaks about 15,000 AU away. Averaged over the telescope beam, the molecular hydrogen number density is calculated to be 10(exp 6) / cubic cm and the gas kinetic temperature is in the range 5-7 K. The abundances of long carbon chains are very large and are indicative of a nonequilibrium carbon chemistry; C6H and HC7N column densities are 5.9(sup +2.9) (sub -1.3) x 10(exp 11) /cubic cm and 3.3 (sup +8.0)(sub -1.5) x 10(exp 12)/sq cm, respectively, which are similar to the values found in the most carbon-chain-rich protostars and prestellar cores known, and are unusually large for star-forming gas. Column density upper limits were obtained for the carbon chain anions C4H(-) and C6H(-), with anion-to-neutral ratios [C4H(-)]/[C4H] < 0.02% and [C6H(-l)]/[C6H] < 10%, consistent with previous observations in interstellar clouds and low-mass protostars. Deuterated HC,3 and c-C3H2 were detected. The [DC3N]/[HC,N] ratio of approximately 4% is consistent with the value typically found in cold interstellar gas.

  11. The effect of acidified sample storage time on the determination of trace element concentration in ice cores by ICP-SFMS

    NASA Astrophysics Data System (ADS)

    Uglietti, C.; Gabrielli, P.; Lutton, A.; Olesik, J.; Thompson, L. G.

    2012-12-01

    Trace elements in micro-particles entrapped in ice cores are a valuable proxy of past climate and environmental variations. Inductively coupled plasma sector field mass spectrometry (ICP-SFMS) is generally recognized as a sensitive and accurate technique for the quantification of ultra-trace element concentrations in ice cores. Usually, ICP-SFMS analyses of ice core samples are performed by melting and acidifying aliquots. Acidification is important to transfer trace elements from particles into solution by partial and/or complete dissolution. Only elements in solution and in sufficiently small particles will be vaporized and converted to elemental ions in the plasma for detection by ICP-SFMS. However, experimental results indicate that differences in acidified sample storage time at room temperature may lead to the recovery of different trace element fractions. Moreover, different lithologies of the relatively abundant crustal material entrapped in the ice matrix could also influence the fraction of trace elements that are converted into elemental ions in the plasma. These factors might affect the determination of trace elements concentrations in ice core samples and hamper the comparison of results obtained from ice cores from different locations and/or epochs. In order to monitor the transfer of elements from particles into solution in acidified melted ice core samples during storage, a test was performed on sections from nine ice cores retrieved from low latitude drilling sites around the world. When compared to ice cores from polar regions, these samples are characterized by a relative high content of micro-particles that may leach trace elements into solution differently. Of the nine ice cores, five are from the Tibetan Plateau (Dasuopu, Guliya, Naimonanyi, Puruogangri and Dunde), two from the Andes (Quelccaya and Huascaran), one from Africa (Kilimanjaro) and one from the Eastern Alps (Ortles). These samples were decontaminated by triple rinsing, melted and

  12. Supported Ag-TiO(2) core-shell nanofibres formed at low temperature by plasma deposition.

    PubMed

    Borrás, Ana; Barranco, Angel; Yubero, Francisco; González-Elipe, Agustín R

    2006-07-28

    Ag-TiO(2) nanofibres (about three microm long and 30-150 nm thick) formed by a single-crystalline silver wire (20-30 nm thick) and an external layer of amorphous TiO(2) of variable thickness are prepared at 403 K by oxygen plasma activation of a silver substrate followed by plasma deposition of TiO(2). Thicker fibres of anatase crystallites surrounding the silver wire were prepared when plasma deposition was carried out at 523 K. The fibres have been analysed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray photoemission spectroscopy (XPS). The plasmon losses of the silver core wire have been characterized by electron energy loss spectroscopy in the TEM microscope. Based on the experimental evidence, a new volcano-type mechanism of formation of these core-shell fibres is proposed, whereby the effect of the plasma and the high mobility of the silver would be key factors determining their morphology and dimensions. PMID:19661598

  13. Finemet nanocrystalline soft magnetic alloy: Investigation of glass forming ability, crystallization mechanism, production techniques, magnetic softness and the effect of replacing the main constituents by other elements

    NASA Astrophysics Data System (ADS)

    Gheiratmand, T.; Hosseini, H. R. Madaah

    2016-06-01

    Finemet soft magnetic alloy has been in the focus of interest in the last years due to its high saturation magnetization, high permeability and low core loss. The great quantity of papers has been devoted to the study of its structural and magnetic properties, confirms this claim. This paper reviews the different researches performed on Finemet up to now. The criteria that should be satisfied in order to have the high glass forming ability in an alloy and also the techniques applied for production of Finemet ribbons, powders and bulk samples have been explained. In addition, the mechanism of devitrification, nanocrystallization and magnetic softness in this applicable magnetic alloy has been discussed in detail. Finally, the effect of different elements substituted with the main constituents in Finemet has been summarized through the studies on the characterization and magnetic properties of different Finemet-type alloys.

  14. High Resolution Aqua Planet Simulations With the Community Atmospheric Model (CAM) Using the HOMME Spectral Element Dynamical Core

    NASA Astrophysics Data System (ADS)

    Taylor, M.; Edwards, J.; St. Cyr, A.; Lauritzen, P.

    2008-12-01

    We will describe recent high resolution Aqua planet simulation results from CAM/HOMME, a highly scalable cubed-sphere based atmospheric model that has been integrated into the Community Climate System Model (CCSM). Aqua planet simulations have no known "correct" answer, so we evaluate the simulations using the Williamson equivalent resolution model inter-comparison methodology. Our highest resolution simulations, performed using 56,000 processors of the LLNL BG/L system at 1/8 degree horizontal result ion, show a well resolved Nastrom-Gage type transition from k-3 to k-5/3 in the kinetic energy spectra. CAM/HOMME uses a 4th order spectral element discretization for the dynamics coupled with monotone (2nd order) or sign-preserving (3rd order) advection scheme and a hyper-viscosity term for dissipation. We use a new, "compatible" formulation of the spectral element method, meaning it has discrete analogs of several key properties of the spherical div, grad and curl operators. This allows the method to locally conserve both mass and energy and (in 2D) relative vorticity. The conservation is possible even when the equations are not written in conservation form, making it the first atmospheric model in the CCSM to conserve both mass and energy. The tracer advection is consistent with the hydrostatic mass equation. Monotone or sign-preserving tracer advection is obtained with the spectral element horizontal discretization on vertically Lagrangian surfaces combined with a PPM based vertical remap.

  15. Fe-liquid segregation in deforming planetesimals: Coupling Core-Forming compositions with transport phenomena [rapid communication

    NASA Astrophysics Data System (ADS)

    Rushmer, Tracy; Petford, Nick; Humayun, Munir; Campbell, Andrew J.

    2005-11-01

    The segregation and macroscopic transport phenomena leading ultimately to the formation of metallic cores in planetary silicate mantles is a fundamental yet poorly understood process. Here we report the results of a series of deformation experiments on a sample of partially molten Kernouve H6 chondrite ( T = 900-1050 °C) aimed at determining the siderophile concentrations and associated partition coefficients in both Fe-S-Ni-O quench and Fe-Ni metal as a function of degree of melting, and to provide insight into the melt segregation mechanism(s). The geochemical results show the S content in the segregated Fe-rich liquid metal decreases with increasing degree of melting. As the S content of the liquid metal also strongly affects the partitioning of highly siderophile elements between solid and liquid metal, an increase in porosity (Fe liquid melt fraction) from c. 5% to 30% lowers DSM/LM for HSE by several orders of magnitude. The relationship between melt fraction and porosity is used to compare the migration rate of liquid metal driven by buoyancy pressure gradients with a new theoretical model of melt segregation in a deforming porous medium that takes into account the coupling between volume strain (dilatancy) and shear stress. For buoyancy driven porous flow, highest transport velocities occur at highest porosities, implying the fastest flow velocities will carry Fe-rich liquid metal with low sulfur contents, preferentially enriched in incompatible HSEs. Predicted characteristic timescales of liquid metal transport due to buoyancy effects (diapirism and porous flow) for a c. 100 km-sized planetesimal are contrasted with shear-induced segregation velocities set up in response to external perturbations via impacts, an important process during the final stages of planetary accretion. A novel feature of our analysis is that liquid metal segregated previously into a planetary core by buoyancy instabilities (e.g., porous flow or a raining mechanism), might be drawn

  16. 3D microoptical elements formed in a photostructurable germanium silicate by direct laser writing

    NASA Astrophysics Data System (ADS)

    Malinauskas, M.; Žukauskas, A.; Purlys, V.; Gaidukevičiu¯tė, A.; Balevičius, Z.; Piskarskas, A.; Fotakis, C.; Pissadakis, S.; Gray, D.; Gadonas, R.; Vamvakaki, M.; Farsari, M.

    2012-12-01

    We present our investigations into the fabrication of three-dimensional microoptical elements by the direct femtosecond laser writing of a germanium-silicon photosensitive hybrid material. Germanium glass composites are very interesting for optical applications as they are photosensitive, and maintain high optical transparency in the visible and near-infrared bands of the spectrum. Here, we have used a germanium containing hybrid material to make nanophotonic structures and microoptical elements such as photonic crystal templates, prisms and spatial polarization plates, both on flat surfaces and fiber tips. Our results show that this germanium silicate composite is an excellent material for microoptics fabrication.

  17. Design, tolerance, and fabrication of an optical see-through head-mounted display with free-form surface elements.

    PubMed

    Wang, Qingfeng; Cheng, Dewen; Wang, Yongtian; Hua, Hong; Jin, Guofan

    2013-03-01

    Free-form surfaces (FFSs) provide more freedom to design an optical system with fewer elements and hence to reduce the size and weight of the overall system than rotationally symmetric optical surfaces. In this paper, an optical see-through (OST), head-mounted display (HMD) consisting of a free-form, wedge-shaped prism and a free-form lens is designed and fabricated through the injection molding method. The free-form prism for the projection system is designed with a field-of-view (FOV) of 36°; the free-form lens is cemented to the prism for the see-through system to achieve a FOV of 50°. The free-form prism and lens are expanded at the edge area during the design stage in order to reduce the effects of surface deformation in the working area in molding fabrication process and to improve ergonomic fit with the head of a user. The tolerance analyzes considering the mold design for the free-form optical systems are carried out using the Monte Carlo method. The FFS optical elements are successfully fabricated and the system performance is carefully examined. The results indicate that the performance of the OST-HMD is sufficient for both entertainment and scientific applications. PMID:23458822

  18. Multireference study of spin-orbit coupling in the hydrides of the 6p-block elements using the model core potential method

    NASA Astrophysics Data System (ADS)

    Zeng, Tao; Fedorov, Dmitri G.; Klobukowski, Mariusz

    2010-02-01

    Careful spin-orbit multireference studies were carried out for the late p-block elements Tl, Pb, Bi, Po, At, and Rn and their hydrides using the model core potentials developed in the present work. The model core potentials were designed to treat the scalar-relativistic and spin-orbit coupling effects at the Douglas-Kroll level. The variational stability of the spin-orbit coupling operator was discussed in terms of the relativistic kinematic operators and depicted graphically. A detailed analysis of the spin-orbit multireference dissociation curves of the 6p element hydrides as well as of their atomic spectra allowed to establish the accuracy of the model core potentials with respect to all-electron calculations to be within several mÅ for re, meV (ceV) for De at the correlation level of configuration interaction (multireference perturbation theory), 30 cm-1 for ωe, and about 350 cm-1 for the low-lying atomic and molecular term and level energies. These values are expected to be the maximum error limits for the model core potentials of all the np-block elements (n =2-6). Furthermore, a good agreement with experiment requires that many terms be coupled in the spin-orbit coupling calculations. A timing study of Tl and TlH computations indicates that the model core potentials lead to 20-fold (6-fold) speedup at the level of configuration interaction (multireference perturbation theory) calculations.

  19. A New Innovative Spherical Cermet Nuclear Fuel Element to Achieve an Ultra-Long Core Life for use in Grid-Appropriate LWRs

    SciTech Connect

    Senor, David J.; Painter, Chad L.; Geelhood, Ken J.; Wootan, David W.; Meriwether, George H.; Cuta, Judith M.; Adkins, Harold E.; Matson, Dean W.; Abrego, Celestino P.

    2007-12-01

    Spherical cermet fuel elements are proposed for use in the Atoms For Peace Reactor (AFPR-100) concept. AFPR-100 is a small-scale, inherently safe, proliferation-resistant reactor that would be ideal for deployment to nations with emerging economies that decide to select nuclear power for the generation of carbon-free electricity. The basic concept of the AFPR core is a water-cooled fixed particle bed, randomly packed with spherical fuel elements. The flow of coolant within the particle bed is at such a low rate that the bed does not fluidize. This report summarizes an approach to fuel fabrication, results associated with fuel performance modeling, core neutronics and thermal hydraulics analyses demonstrating a ~20 year core life, and a conclusion that the proliferation resistance of the AFPR reactor concept is high.

  20. Finite Element Based Stress Analysis of Graphite Component in High Temperature Gas Cooled Reactor Core Using Linear and Nonlinear Irradiation Creep Models

    SciTech Connect

    Mohanty, Subhasish; Majumdar, Saurindranath

    2015-01-01

    Irradiation creep plays a major role in the structural integrity of the graphite components in high temperature gas cooled reactors. Finite element procedures combined with a suitable irradiation creep model can be used to simulate the time-integrated structural integrity of complex shapes, such as the reactor core graphite reflector and fuel bricks. In the present work a comparative study was undertaken to understand the effect of linear and nonlinear irradiation creep on results of finite element based stress analysis. Numerical results were generated through finite element simulations of a typical graphite reflector.

  1. Large-scale volcaniclastic turbidites from subaerial caldera-forming eruptions at Dominica: insights from IODP site U1398 cores

    NASA Astrophysics Data System (ADS)

    Maeno, F.; Ishizuka, O.; Kataoka, K.; Le Friant, A.; Boudon, G.; Villemant, B.

    2014-12-01

    Volcaniclastic turbidity currents can be caused by subaerial explosive eruptions. However, their flow and emplacement processes in oceanic environment are still ambiguous. Core data obtained by deep-ocean drilling give constraints on the origin of such turbidity currents and resultant deposits. In this presentation, stratigraphy and grain data of volcaniclastic deposits from IODP site U1398 cores are shown and the origin of the deposit is discussed. The site is located 120 km southwest of Dominica Island. The uppermost unit that we study extends 0-40 mbsf. The main part is composed of a series of thick massive volcaniclastic turbidites, and is divided into several subunits. Each subunit has a few to 10 m thick and is separated by thin layers of fine materials or hemipelagic mud. Most of the layers are massive, composed of sorted, medium to coarse sand, and poor in fines. Some are normally graded. The upper turbidite is thick and massive, and contains abundant pumice clasts. They tend to concentrate in middle or upper part of the layer. Components of matrix are represented by pumice, massive lava, crystals (pl, opx, cpx, qz, hbl, titanomagnetite), and sparse carbonates. Generally, in normally graded layers, upper finer part is rich in pumice and bioclasts, and lower part is richer in crystals. In some layers, crystal concentration in matrix vary in proportion up to 80 wt.%, and its variation is correlated with magnetic susceptibility data. Grain size and component characteristics and their variations are thought to reflect emplacement process of volcaniclastic turbidity currents. Importantly, the grain characteristics are almost identical to the previous description for subaerial deposits or piston core data of the Roseau Tuff (~30 ka B.P.) that originated from the largest eruption in the Lesser Antilles in the last 200,000 years. The eruption formed caldera(s) on land in Dominica, and the most of the materials were deposited beneath the sea. Also it has been

  2. Platinum-Group Elements in Kerguelen Plateau Basalts: a Tale of Crystal Fractionation, the Core-Mantle Boundary, and no Sulfide Segregation.

    NASA Astrophysics Data System (ADS)

    Chazey, W. J.; Neal, C. R.

    2001-12-01

    Basalt samples from the Kerguelen Plateau in the southern Indian Ocean (ODP Leg 183) were analyzed for major and trace elements including the platinum-group elements (PGEs: Os, Ir, Ru, Rh, Pt, Pd). PGE abundances range from 0.1 (Os-, Ir, Ru) to 5 times primitive mantle (i.e., Pt). Olivine and Cr-spinel were fractionating phases, which probably accentuated the depletion of Os, Ir, and Ru relative to Rh, Pt, and Pd in primitive mantle-normalized profiles. Primitive mantle-normalized profiles show a relatively flat transition form Pt and Pd to Y, although a slight negative Pd anomaly is present in some samples. Sulfide immiscibility has the potential to preferentially remove Pd, but would also deplete all of the PGEs relative to Y. Plots of PGE/Y vs. Y/Cu demonstrate that the Pd anomaly was not caused by separation of a sulfide-rich fluid. Downhole variation of Pt in the Site 1138 basalt sequence is similar to that of other incompatible elements demonstrating that Pt is behaving as a lithophile element and from which we infer that the magma is undersaturated with respect to S. Finally, if sulfide immiscibility had occurred, Ru/Ir ratios would increase due to the greater affinity of Ir for sulfide liquid (vs. silicate melt), but these ratios are within error of the primitive mantle value. The depletion in Pd is attributed to it being preferentially removed during secondary alteration of the KP basalts. There seems to be very little consistent variation in PGE concentrations between ODP Sites 1136, 1137, 1138, 1141 and 1142. The PGEs in Sites 1136, 1141, and 1142 samples are generally lower in abundance than those from Sites 1137 and 1138. Overall, the PGEs in the Kerguelen plateau basalts are present in relatively high abundances. When plotted with MORBs, for example, all of the Kerguelen basalts are much higher in abundance, even though the KP basalts are derived from a much higher degree of partial melting. Most MORBs, however, appear to have experienced sulfide

  3. Characterization of elemental and structural composition of corrosion scales and deposits formed in drinking water distribution systems.

    PubMed

    Peng, Ching-Yu; Korshin, Gregory V; Valentine, Richard L; Hill, Andrew S; Friedman, Melinda J; Reiber, Steve H

    2010-08-01

    Corrosion scales and deposits formed within drinking water distribution systems (DWDSs) have the potential to retain inorganic contaminants. The objective of this study was to characterize the elemental and structural composition of extracted pipe solids and hydraulically-mobile deposits originating from representative DWDSs. Goethite (alpha-FeOOH), magnetite (Fe(3)O(4)) and siderite (FeCO(3)) were the primary crystalline phases identified in most of the selected samples. Among the major constituent elements of the deposits, iron was most prevalent followed, in the order of decreasing prevalence, by sulfur, organic carbon, calcium, inorganic carbon, phosphorus, manganese, magnesium, aluminum and zinc. The cumulative occurrence profiles of iron, sulfur, calcium and phosphorus for pipe specimens and flushed solids were similar. Comparison of relative occurrences of these elements indicates that hydraulic disturbances may have relatively less impact on the release of manganese, aluminum and zinc, but more impact on the release of organic carbon, inorganic carbon, and magnesium. PMID:20576284

  4. Toxicity characteristic leaching procedure fails to extract oxoanion-forming elements that are extracted by municipal solid waste leachates

    SciTech Connect

    Hooper, K.; Iskander, M.; Sivia, G.

    1998-12-01

    US EPA and state regulatory agencies rely on standard extraction tests to identify wastes that have the potential to contaminate surface water or groundwater. To evaluate the predictive abilities of these extraction tests, the Toxicity Characteristic Leaching Procedure (TCLP), the Waste Extraction Test (WET), and the Synthetic Precipitation Leaching Procedure (SPLP) were compared with actual municipal solid waste leachates (MSWLs) for their ability to extract regulated elements from a variety of industrial solid wastes in short- and long-term extractions. Short-term extractions used MSWLs from a variety of California landfills. Long-term sequential extractions simulated longer term leaching, as might occur in MSW landfills. For most regulated elements, the TCLP roughly predicted the maximum concentrations extracted by the MSWLs. For regulated elements that form oxoanions (e.g., Sb, As, Mo, Se, V), however the TCLP underpredicted the levels extracted by the MSWL. None of the standard tests adequately predicted these levels. The results emphasize the need for better standardized techniques to identify wastes that have the potential to contaminate groundwater with oxoanion-forming elements, particularly arsenic.

  5. The N-terminal half of the connexin protein contains the core elements of the pore and voltage gates

    PubMed Central

    Kronengold, Jack; Srinivas, Miduturu; Verselis, Vytas K.

    2013-01-01

    Connexins form channels with large aqueous pores that mediate fluxes of inorganic ions and biological signaling molecules. Studies aimed at identifying the connexin pore now include a crystal structure that provides details of putative pore-lining residues that need to be verified using independent biophysical approaches. Here we extended our initial cysteine-scanning studies of the TM1/E1 region of Cx46 hemichannels to include TM2 and TM3 transmembrane segments. No evidence of reactivity was observed in either TM2 or TM3 probed with small or large thiol-modifying reagents. Several identified pore residues in E1 of Cx46 have been verified in different Cx isoforms. Use of variety of thiol reagents indicates that the connexin hemichannel pore is large and flexible enough, at least in the extracellular part of the pore funnel, to accommodate uncommonly large side chains. We also find that that gating characteristics are largely determined by the same domains that constitute the pore. These data indicate that biophysical and structural studies are converging towards a view that the N-terminal half of the Cx protein contains the principal components of the pore and gating elements, with NT, TM1 and E1 forming the pore funnel. PMID:22825713

  6. Constraints on the Mineral Evolution of Terrestrial Planets Using Statistical Correlations Among the Mineral-Forming Elements

    NASA Astrophysics Data System (ADS)

    Hummer, D. R.; Hazen, R. M.; Golden, J.; Downs, R. T.

    2015-12-01

    The mineralogy of terrestrial planets is governed not only by size, bulk chemical composition, planetary differentiation processes, and secondary geochemical processes, but also by the fundamental way in which a planet's constituent elements parse themselves into mineral species. To gain insight into which elements tend to associate with each other to form minerals, we have used the IMA mineralogical database (rruff.info/ima) to conduct a statistical analysis of the number of known mineral species containing each of the 72 mineral-forming elements, as well as how many species contain both X and Y for every possible X-Y pair of elements. The frequency with which elements X and Y occur together in the nominal chemical formulae of minerals was compared with the expected rate of co-occurrence (assuming that elements are distributed among mineral species randomly). The results reveal that among the most strongly correlated element pairs are H-O, Na-Si, Al-Si, S-Ag, O-Si, Si-Ca, and O-Ca. Examples of strongly anti-correlated pairs are O-S, O-Ag, Si-S, O-Sb, O-Se, H-Ag, and Si-As. The strength of these correlations and anti-correlations varied by many orders of magnitude (as measured by their p-value in a chi-squared test for variable dependence), ranging from near 1 to an astounding 10-304. Out of 2520 unique element pairs, 1688 were statistically significant (p-value <0.05). These pair correlations can be attributed to an array of geochemical factors, including but not limited to 1) the mutual exclusivity of sulfide vs. silicate anionic groups, 2) crystal chemical considerations of size and charge similarities among cations, especially within silicate structures, 3) group relationships on the periodic table, and 4) soft vs. hard ion relationships. These principles, along with the specific correlations they produce, can serve as a valuable guide in explaining the mineral evolution of Earth's crust, and predicting the mineralogy of terrestrial planets even when the bulk

  7. Computationally Efficient Finite Element Analysis Method Incorporating Virtual Equivalent Projected Model For Metallic Sandwich Panels With Pyramidal Truss Cores

    SciTech Connect

    Seong, Dae-Yong; Jung, Chang Gyun; Yang, Dong-Yol

    2007-05-17

    Metallic sandwich panels composed of two face sheets and cores with low relative density have lightweight characteristics and various static and dynamic load bearing functions. To predict the forming characteristics, performance, and formability of these structured materials, full 3D modeling and analysis involving tremendous computational time and memory are required. Some constitutive continuum models including homogenization approaches to solve these problems have limitations with respect to the prediction of local buckling of face sheets and inner structures. In this work, a computationally efficient FE-analysis method incorporating a virtual equivalent projected model that enables the simulation of local buckling modes is newly introduced for analysis of metallic sandwich panels. Two-dimensional models using the projected shapes of 3D structures have the same equivalent elastic-plastic properties with original geometries that have anisotropic stiffness, yield strength, and hardening function. The sizes and isotropic properties of the virtual equivalent projected model have been estimated analytically with the same equivalent properties and face buckling strength of the full model. The 3-point bending processes with quasi-two-dimensional loads and boundary conditions are simulated to establish the validity of the proposed method. The deformed shapes and load-displacement curves of the virtual equivalent projected model are found to be almost the same as those of a full three-dimensional FE-analysis while reducing computational time drastically.

  8. TADPOL: A 1.3 mm SURVEY OF DUST POLARIZATION IN STAR-FORMING CORES AND REGIONS

    SciTech Connect

    Hull, Charles L. H.; Plambeck, Richard L.; Bower, Geoffrey C.; Heiles, Carl; Kwon, Woojin; Carpenter, John M.; Lamb, James W.; Pillai, Thushara; Crutcher, Richard M.; Hakobian, Nicholas S.; Looney, Leslie W.; Fiege, Jason D.; Franzmann, Erica; Houde, Martin; Hughes, A. Meredith; Marrone, Daniel P.; Matthews, Brenda C.; Pound, Marc W.; Rahman, Nurur; Sandell, Göran; and others

    2014-07-01

    We present λ 1.3 mm Combined Array for Research in Millimeter-wave Astronomy observations of dust polarization toward 30 star-forming cores and eight star-forming regions from the TADPOL survey. We show maps of all sources, and compare the ∼2.''5 resolution TADPOL maps with ∼20'' resolution polarization maps from single-dish submillimeter telescopes. Here we do not attempt to interpret the detailed B-field morphology of each object. Rather, we use average B-field orientations to derive conclusions in a statistical sense from the ensemble of sources, bearing in mind that these average orientations can be quite uncertain. We discuss three main findings. (1) A subset of the sources have consistent magnetic field (B-field) orientations between large (∼20'') and small (∼2.''5) scales. Those same sources also tend to have higher fractional polarizations than the sources with inconsistent large-to-small-scale fields. We interpret this to mean that in at least some cases B-fields play a role in regulating the infall of material all the way down to the ∼1000 AU scales of protostellar envelopes. (2) Outflows appear to be randomly aligned with B-fields; although, in sources with low polarization fractions there is a hint that outflows are preferentially perpendicular to small-scale B-fields, which suggests that in these sources the fields have been wrapped up by envelope rotation. (3) Finally, even at ∼2.''5 resolution we see the so-called polarization hole effect, where the fractional polarization drops significantly near the total intensity peak. All data are publicly available in the electronic edition of this article.

  9. TADPOL: A 1.3 mm Survey of Dust Polarization in Star-forming Cores and Regions

    NASA Astrophysics Data System (ADS)

    Hull, Charles L. H.; Plambeck, Richard L.; Kwon, Woojin; Bower, Geoffrey C.; Carpenter, John M.; Crutcher, Richard M.; Fiege, Jason D.; Franzmann, Erica; Hakobian, Nicholas S.; Heiles, Carl; Houde, Martin; Hughes, A. Meredith; Lamb, James W.; Looney, Leslie W.; Marrone, Daniel P.; Matthews, Brenda C.; Pillai, Thushara; Pound, Marc W.; Rahman, Nurur; Sandell, Göran; Stephens, Ian W.; Tobin, John J.; Vaillancourt, John E.; Volgenau, N. H.; Wright, Melvyn C. H.

    2014-07-01

    We present λ 1.3 mm Combined Array for Research in Millimeter-wave Astronomy observations of dust polarization toward 30 star-forming cores and eight star-forming regions from the TADPOL survey. We show maps of all sources, and compare the ~2.''5 resolution TADPOL maps with ~20'' resolution polarization maps from single-dish submillimeter telescopes. Here we do not attempt to interpret the detailed B-field morphology of each object. Rather, we use average B-field orientations to derive conclusions in a statistical sense from the ensemble of sources, bearing in mind that these average orientations can be quite uncertain. We discuss three main findings. (1) A subset of the sources have consistent magnetic field (B-field) orientations between large (~20'') and small (~2.''5) scales. Those same sources also tend to have higher fractional polarizations than the sources with inconsistent large-to-small-scale fields. We interpret this to mean that in at least some cases B-fields play a role in regulating the infall of material all the way down to the ~1000 AU scales of protostellar envelopes. (2) Outflows appear to be randomly aligned with B-fields; although, in sources with low polarization fractions there is a hint that outflows are preferentially perpendicular to small-scale B-fields, which suggests that in these sources the fields have been wrapped up by envelope rotation. (3) Finally, even at ~2.''5 resolution we see the so-called polarization hole effect, where the fractional polarization drops significantly near the total intensity peak. All data are publicly available in the electronic edition of this article.

  10. Structure of the protein core of translation initiation factor 2 in apo, GTP-bound and GDP-bound forms

    SciTech Connect

    Simonetti, Angelita; Fabbretti, Attilio; Hazemann, Isabelle; Jenner, Lasse; Gualerzi, Claudio O.; Klaholz, Bruno P.

    2013-06-01

    The crystal structures of the eubacterial translation initiation factor 2 in apo form and with bound GDP and GTP reveal conformational changes upon nucleotide binding and hydrolysis, notably of the catalytically important histidine in the switch II region. Translation initiation factor 2 (IF2) is involved in the early steps of bacterial protein synthesis. It promotes the stabilization of the initiator tRNA on the 30S initiation complex (IC) and triggers GTP hydrolysis upon ribosomal subunit joining. While the structure of an archaeal homologue (a/eIF5B) is known, there are significant sequence and functional differences in eubacterial IF2, while the trimeric eukaryotic IF2 is completely unrelated. Here, the crystal structure of the apo IF2 protein core from Thermus thermophilus has been determined by MAD phasing and the structures of GTP and GDP complexes were also obtained. The IF2–GTP complex was trapped by soaking with GTP in the cryoprotectant. The structures revealed conformational changes of the protein upon nucleotide binding, in particular in the P-loop region, which extend to the functionally relevant switch II region. The latter carries a catalytically important and conserved histidine residue which is observed in different conformations in the GTP and GDP complexes. Overall, this work provides the first crystal structure of a eubacterial IF2 and suggests that activation of GTP hydrolysis may occur by a conformational repositioning of the histidine residue.

  11. Observations of two ``millimetre-only'' cores as candidates for early high-mass star-forming regions

    NASA Astrophysics Data System (ADS)

    Balnozan, Egon; Lo, Nadia; Jones, Paul; Cunningham, Maria; Hill, Tracey; Bronfman, Leonardo

    2013-04-01

    We wish to image at high spectral resolution two “millimetre-only” sources from a subset of 10 identified by Hill et al. (2005) in a 1.2-mm continuum survey. These very bright mm-only sources (also featuring strong NH3 emission) are believed to be excellent candidates for early-stage protostars (C2102-2009JULS) through their characteristic similarity to known massive star-forming sources, despite lacking typical features of massive star formation such as methanol masers and radio continuum. We present evidence of methanol emission in these sources from a recent spectral analysis, along with other molecular species indicative of very early-stage star-formation in cores featuring outflows but devoid of HII regions. High-resolution observations are critical in discriminating between maser and thermal methanol line emission mechanisms that can distinguish between early-stage massive star formation and lower-mass objects. These observations will allow us to quantify the frequency, spatial position and scale of molecular emission to further understanding of the chemistry that distinguishes between low and high-mass star formation, investigate the possible relation between mm-only radio sources and massive protostars, while also gathering data relevant to creating chemical timelines of their early evolution.

  12. Ten-Year Results From the Natrelle 410 Anatomical Form-Stable Silicone Breast Implant Core Study

    PubMed Central

    Maxwell, G. Patrick; Van Natta, Bruce W.; Bengtson, Bradley P.; Murphy, Diane K.

    2015-01-01

    Background Silicone breast implants have long been used for breast augmentation and reconstruction. During this time, these medical devices have gone through a number of modifications to improve their safety, quality, and clinical outcome performance. Objectives The authors conducted a 10-year study to determine the safety and effectiveness of Natrelle 410 silicone breast implants. Methods This prospective, multicenter study enrolled 941 subjects who were undergoing either augmentation, augmentation revision, reconstruction, or reconstruction revision. Data on complications, reoperations, explantations, and subject satisfaction were collected at annual clinic visits, and one-third of subjects underwent biennial magnetic resonance imaging (MRI) to screen for implant rupture. The authors used the Kaplan-Meier estimator to calculate risk rates for local complications, reoperations, and explantations. Results Capsular contracture rates increased approximately 1% per year from the previously reported 6-year rates. The rates were significantly lower than those from the Natrelle round gel core study. The overall rate of confirmed ruptured implants in subjects who underwent MRI was 5.7%. Eleven late seromas were reported. The most common reason for explantation was a subject requesting a size or style change. Satisfaction rates remained high through 10 years, with most subjects saying they were somewhat or definitely satisfied with their implants. Conclusions This 10-year prospective trial demonstrated the long-term safety and effectiveness of Natrelle 410 anatomical form-stable implants. The complication rates were low and the satisfaction rates were high. Level of Evidence: 1 Therapeutic PMID:25717116

  13. FUEL ELEMENT CONSTRUCTION

    DOEpatents

    Zumwalt, L.R.

    1961-08-01

    Fuel elements having a solid core of fissionable material encased in a cladding material are described. A conversion material is provided within the cladding to react with the fission products to form stable, relatively non- volatile compounds thereby minimizing the migration of the fission products into the coolant. The conversion material is preferably a metallic fluoride, such as lead difluoride, and may be in the form of a coating on the fuel core or interior of the cladding, or dispersed within the fuel core. (AEC)

  14. Finite element simulation of sheet metal forming and springback using a crystal plasticity approach

    SciTech Connect

    Bertram, A.; Boehlke, T.; Krawietz, A.; Schulze, V.

    2007-05-17

    In this paper the application of a crystal plasticity model for body-centered cubic crystals in the simulation of a sheet metal forming process is discussed. The material model parameters are identified by a combination of a texture approximation procedure and a conventional parameter identification scheme. In the application of a cup drawing process the model shows an improvement of the strain and earing prediction as well as the qualitative springback results in comparison with a conventional phenomenological model.

  15. Forming flat-topped element patterns in antenna arrays with corrugated structures

    NASA Astrophysics Data System (ADS)

    Korotkov, V. D.; Skobelev, S. P.

    1994-05-01

    The problem of electromagnetic wave radiation from a periodic ribbed structure of plane-parallel waveguides, one part of which is excited by T-waves with a given amplitude and the other part includes short-circuits, is considered. A technique for structure analysis, and the calculation results of its partial directional pattern and efficiency characterizing the possibilities of the structure on forming sector partial directional patterns are presented.

  16. Rare earth element concentrations in dissolved and acid available particulate forms for eastern UK rivers

    NASA Astrophysics Data System (ADS)

    Neal, C.

    2007-01-01

    Variations in concentration of yttrium (Y), lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm) and gadolinium (Gd) among rivers of eastern England and the border with Scotland are described in relation to the dissolved (<0.45 µM) fraction and acid-available particulate (AAP) fractions. The rivers cover a range of rural, agricultural and urban/industrial environments. Yttrium and the lanthanides show significant levels of both dissolved and acid-available particulate forms (typically about 40% in the dissolved form). For the dissolved phase, Y and the lanthanides are linearly correlated with each other and with iron: most of this dissolved component may be in a micro-particulate/colloidal form. The Y and lanthanide relationships show marked scatter and there are anomalously high La concentrations at times for the rivers Great Ouse, Thames and Wear that are probably linked to pollutant sources. For the Ouse, and especially for one of its tributaries, the Swale, relatively high Sm concentrations are probably associated with mineralisation within the catchment and contamination of the associated flood plain. For the AAP components, there are strong linear relationships with Y and the lanthanides across all the rivers. There is also a strong link between these AAP associated REE and AAP iron, although the scatter is greater and the industrial rivers have a lower lanthanide to iron ratio, probably due to iron-rich contaminants.

  17. SN 2008jb: A 'LOST' CORE-COLLAPSE SUPERNOVA IN A STAR-FORMING DWARF GALAXY AT {approx}10 Mpc

    SciTech Connect

    Prieto, J. L.; Lee, J. C.; Drake, A. J.; Djorgovski, S. G.; McNaught, R.; Garradd, G.; Beacom, J. F.; Beshore, E.; Catelan, M.; Pojmanski, G.; Stanek, K. Z.; Szczygiel, D. M.

    2012-01-20

    } for the star formation complex, assuming a single-age starburst. These properties are consistent with the expanding H{alpha} supershells observed in many well-studied nearby dwarf galaxies, which are tell-tale signs of feedback from the cumulative effect of massive star winds and supernovae. The age estimated for the star-forming region where SN 2008jb exploded suggests a relatively high-mass progenitor star with an initial mass M {approx} 20 M{sub Sun} and warrants further study. We discuss the implications of these findings in the study of core-collapse supernova progenitors.

  18. Parallel Computing of Multi-scale Finite Element Sheet Forming Analyses Based on Crystallographic Homogenization Method

    SciTech Connect

    Kuramae, Hiroyuki; Okada, Kenji; Uetsuji, Yasutomo; Nakamachi, Eiji; Tam, Nguyen Ngoc; Nakamura, Yasunori

    2005-08-05

    Since the multi-scale finite element analysis (FEA) requires large computation time, development of the parallel computing technique for the multi-scale analysis is inevitable. A parallel elastic/crystalline viscoplastic FEA code based on a crystallographic homogenization method has been developed using PC cluster. The homogenization scheme is introduced to compute macro-continuum plastic deformations and material properties by considering a polycrystal texture. Since the dynamic explicit method is applied to this method, the analysis using micro crystal structures computes the homogenized stresses in parallel based on domain partitioning of macro-continuum without solving simultaneous linear equations. The micro-structure is defined by the Scanning Electron Microscope (SEM) and the Electron Back Scan Diffraction (EBSD) measurement based crystal orientations. In order to improve parallel performance of elastoplasticity analysis, which dynamically and partially increases computational costs during the analysis, a dynamic workload balancing technique is introduced to the parallel analysis. The technique, which is an automatic task distribution method, is realized by adaptation of subdomain size for macro-continuum to maintain the computational load balancing among cluster nodes. The analysis code is applied to estimate the polycrystalline sheet metal formability.

  19. Forensic firearm identification of semiautomatic handguns using laser formed microstamping elements

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd E.; Ohar, Orest

    2008-08-01

    For well over one hundred years the science of Firearm and Tool Mark Identification has relied on the theory that unintentional random tooling marks generated during the manufacture of a firearm onto its interior surfaces are unique to each individual firearm.[1][2] Forensic Firearm and Tool Mark Examiners have had to rely on the analysis of these randomly formed unintentional striations, or scratches and dings, transferred onto ammunition components from firearms used to commit crimes, as a way of developing clues and evidence. Such transfers take place during the cycle of fire and ejection of the cartridge from the firearm during the commission of a crime. The typical striations on the cartridge casings are caused by tooling marks that are randomly formed during the machining of interior surfaces of the manufactured firearm and by other firearm components that come in contact with the cycling ammunition. Components like the firing pin, extractor and ejector, impact the surfaces of the cartridges as they are fed, fired and ejected from the firearm. When found at a crime scene, these striae constitute ballistic evidence when effectively analyzed by a Forensic Firearm and Tool Mark Examiner. Examiners categorize these striations looking for matches to be made between the components that created the marks and the recovered firearm. Reality is that nearly 50% of firearms used in violent crimes are not recovered at a crime scene, requiring the analysis to be processed and logged into evidence files or imaged into reference image databases for future comparison whenever a firearm might be recovered. This paper will present a unique law enforcement technology, embedded into firearms for tracking the sources of illegally trafficked firearms, called Microstamping. Microstamping is a laser based micromachining process that forms microscopic "intentional structures and marks" on components within a firearm. Thus when the firearm is fired, these microstamp structures transfer

  20. Magnetic nanoparticles formed in glasses co-doped with iron and larger radius elements

    SciTech Connect

    Edelman, I.; Ivanova, O.; Ivantsov, R.; Velikanov, D.; Zabluda, V.; Zubavichus, Y.; Veligzhanin, A.; Zaikovskiy, V.; Stepanov, S.; Artemenko, A.; Curely, J.; Kliava, J.

    2012-10-15

    A new type of nanoparticle-containing glasses based on borate glasses co-doped with low contents of iron and larger radius elements, Dy, Tb, Gd, Ho, Er, Y, and Bi, is studied. Heat treatment of these glasses results in formation of magnetic nanoparticles, radically changing their physical properties. Transmission electron microscopy and synchrotron radiation-based techniques: x-ray diffraction, extended x-ray absorption fine structure, x-ray absorption near-edge structure, and small-angle x-ray scattering, show a broad distribution of nanoparticle sizes with characteristics depending on the treatment regime; a crystalline structure of these nanoparticles is detected in heat treated samples. Magnetic circular dichroism (MCD) studies of samples subjected to heat treatment as well as of maghemite, magnetite, and iron garnet allow to unambiguously assign the nanoparticle structure to maghemite, independently of co-dopant nature and of heat treatment regime used. Different features observed in the MCD spectra are related to different electron transitions in Fe{sup 3+} ions gathered in the nanoparticles. The static magnetization in heat treated samples has non-linear dependence on the magnetizing field with hysteresis. Zero-field cooled magnetization curves show that at higher temperatures the nanoparticles occur in superparamagnetic state with blocking temperatures above 100 K. Below ca. 20 K, a considerable contribution to both zero field-cooled and field-cooled magnetizations occurs from diluted paramagnetic ions. Variable-temperature electron magnetic resonance (EMR) studies unambiguously show that in as-prepared glasses paramagnetic ions are in diluted state and confirm the formation of magnetic nanoparticles already at earlier stages of heat treatment. Computer simulations of the EMR spectra corroborate the broad distribution of nanoparticle sizes found by 'direct' techniques as well as superparamagnetic nanoparticle behaviour demonstrated in the magnetization

  1. Climatic Impact on Major and Trace Elements in Deltaic Core Sediments: Evidence from Muthupet Lagoon, se Coast of India

    NASA Astrophysics Data System (ADS)

    Jayaprakash, M.; Urban, B.; Murugan, P. M. V.; Dharan, L.; Seshachalam, S.; Jonathan, M.

    2013-12-01

    Geochemistry of lagoon deposits provides a continuous record of climatic changes, and such core sediments at successive deeper and older layers have long been utilized for sedimentologic and organic geochemical studies. These ecosystems present a mechanism for trapping sediment and therefore record climatic changes in the form of geochemical imprints. The aim of the present study is to evaluate the climatic and depositional controls in the Muthupet lagoon, situated at the southern most end of the Cauvery delta, south east India. The variations of geochemical parameters with depth and their ratios were employed to reveal the characteristics of Holocene climate and associated paleoenvironmental implications of this region. Moderate values of the Chemical Index of Alteration (CIA) suggest intermediate chemical weathering of the source rock under tropical to subtropical climatic conditions. Index of Composition Variability (ICV) values indicate low proportion of non clay silicate minerals in these sediments. V/Cr ratio has been used as a paleo-oxygenation indicator and in the present study, the ratio V/Cr was found to be < 2 indicating oxic-depositional conditions prevailing in this lagoon. Fe/Ti and Fe/Al ratios reveal valuable information on the impact of climate changes on the sedimentation in the study area. Na and S, indicators of paleosalinity and marine flooding were evaluated. The increase in concentration of Na at various depths was identified and marine incursions characterized. Abrupt changes in the values at certain depths were directly related to major climatic events using the available rainfall and 210Pb data. Key words: Climate change, Weathering Pattern, Muthupet Mangroves, SE coast of India. Location map of the study area

  2. ALU repeats in promoters are position-dependent co-response elements (coRE) that enhance or repress transcription by dimeric and monomeric progesterone receptors.

    PubMed

    Jacobsen, Britta M; Jambal, Purevsuren; Schittone, Stephanie A; Horwitz, Kathryn B

    2009-07-01

    We have conducted an in silico analysis of progesterone response elements (PRE) in progesterone receptor (PR) up-regulated promoters. Imperfect inverted repeats, direct repeats, and half-site PRE are widespread, not only in PR-regulated, but also in non-PR-regulated and random promoters. Few resemble the commonly used palindromic PRE with three nucleotide (nt) spacers. We speculated that PRE may be necessary but insufficient to control endogenous PR-dependent transcription. A search for PRE partners identified a highly conserved 234-nt sequence invariably located within 1-2 kb of transcription start sites. It resembles ALU repeats and contains binding sites for 11 transcription factors. The 234-nt sequence of the PR-regulated 8-oxoguanine DNA glycosylase promoter was cloned in the forward or reverse orientation in front of zero, one, or two inverted repeat PRE, and one or tandem PRE half-sites, driving luciferase. Under these conditions the 234-nt sequence functions as a co-response element (coRE). From the PRE or tandem half-sites, the reverse coRE is a strong activator of PR and glucocorticoid receptor-dependent transcription. The forward coRE is a powerful repressor. The prevalence of PRE half-sites in natural promoters suggested that PR monomers regulate transcription. Indeed, dimerization-domain mutant PR monomers were stronger transactivators than wild-type PR on PRE or tandem half-sites. This was repressed by the forward coRE. We propose that in natural promoters the coRE functions as a composite response element with imperfect PRE and half-sites to present variable, orientation-dependent transcription factors for interaction with nearby PR. PMID:19372234

  3. Toward Connecting Core-Collapse Supernova Theory with Observations: Nucleosynthetic Yields and Distribution of Elements in a 15 M⊙ Blue Supergiant Progenitor with SN 1987A Energetics

    NASA Astrophysics Data System (ADS)

    Plewa, Tomasz; Handy, Timothy; Odrzywolek, Andrzej

    2014-03-01

    We compute and discuss the process of nucleosynthesis in a series of core-collapse explosion models of a 15 solar mass, blue supergiant progenitor. We obtain nucleosynthetic yields and study the evolution of the chemical element distribution from the moment of core bounce until young supernova remnant phase. Our models show how the process of energy deposition due to radioactive decay modifies the dynamics and the core ejecta structure on small and intermediate scales. The results are compared against observations of young supernova remnants including Cas A and the recent data obtained for SN 1987A. The work has been supported by the NSF grant AST-1109113 and DOE grant DE-FG52-09NA29548. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the U.S. DoE under Contract No. DE-AC02-05CH11231.

  4. Nonlinear acceleration of a continuous finite element discretization of the self-adjoint angular flux form of the transport equation

    SciTech Connect

    Sanchez, R.

    2012-07-01

    Nonlinear acceleration of a continuous finite element (CFE) discretization of the transport equation requires a modification of the transport solution in order to achieve local conservation, a condition used in nonlinear acceleration to define the stopping criterion. In this work we implement a coarse-mesh finite difference acceleration for a CFE discretization of the second-order self adjoint angular flux (SAAF) form of the transport equation and use a post processing to enforce local conservation. Numerical results are given for one-group source calculations of one-dimensional slabs. We also give a formal derivation of the boundary conditions for the SAAF. (authors)

  5. Nonlinear Acceleration of a Continuous Finite Element Discretization of the Self-Adjoint Angular Flux Form of the Transport Equation

    SciTech Connect

    Richard Sanchez; Cristian Rabiti; Yaqi Wang

    2013-11-01

    Nonlinear acceleration of a continuous finite element (CFE) discretization of the transport equation requires a modification of the transport solution in order to achieve local conservation, a condition used in nonlinear acceleration to define the stopping criterion. In this work we implement a coarse-mesh finite difference acceleration for a CFE discretization of the second-order self-adjoint angular flux (SAAF) form of the transport equation and use a postprocessing to enforce local conservation. Numerical results are given for one-group source calculations of one-dimensional slabs. We also give a novel formal derivation of the boundary conditions for the SAAF.

  6. Complexes as the main agents of transport for amphoteric and complex-forming elements in the lithosphere

    SciTech Connect

    Beus, A.A.

    1987-04-01

    Geochemical studies of the association of metals with halogens (particularly fluorine), carbonates, and sulfur indicate an important role for complexes in the transport of amphoteric and complex-forming elements in hot solutions, especially because theory clearly indicates that most of these metals cannot be transported as simple halides, carbonates, and sulfides in natural hydrothermal solutions. The author has considered the implications of complexing for a much broader range of transport processes, reaching the scale of differentiation of the earth's shells. This paper reviews his work. 24 references.

  7. Study Of Various Initial Blank Shapes To Minimize The Earing In The Different Shaped Formed Parts Using Finite Element Analysis

    SciTech Connect

    Desai, Sharvari G.; Date, P P.; Pardeshi, R. H.

    2005-08-05

    In deep drawing process planar anisotropy is found to be a major problem. A high planar anisotropy causes earing in the formed cup (formation of wavy edge at the top). In this paper anisotropic behavior of stainless steel sheet is studied for drawn rectangular, circular and octagonal shaped parts. Finite element based simulation software PAMSTAMP2G is used to simulate the forming of the octagonal deep drawn cup. It is well known that the blank shape and size greatly affects the strain distribution in deep drawing process. Earing is a major problem due to highly anisotropic behavior of the selected material. To optimize the initial blank shape to minimize earing, the flow of material was observed at various steps during the forming and accordingly blank shapes were modified. Four blank shapes were considered to minimize earing for the forming of octagonal product. Finally a circular blank was used for forming of the octagonal part which gave minimum earing. The thickness strain distribution for circular shaped blank is better as compared to other blank shapes.

  8. DUBLIN CORE

    EPA Science Inventory

    The Dublin Core is a metadata element set intended to facilitate discovery of electronic resources. It was originally conceived for author-generated descriptions of Web resources, and the Dublin Core has attracted broad ranging international and interdisciplinary support. The cha...

  9. Crystallographic Stability of Metastable Phase Formed by Containerless Processing in REFeO3 (RE: Rare-Earth Element)

    NASA Technical Reports Server (NTRS)

    Kuribayashi, Kazuhiko; Kumar, M. S. Vijaya

    2012-01-01

    Undercooling a melt often facilitates a metastable phase to nucleate preferentially. Although the classical nucleation theory shows that the most critical factor for forming a metastable phase is the interface free energy, the crystallographic stability is also indispensable for the phase to be frozen at ambient temperature. In compound materials such as oxides, authors have suggested that the decisive factors for forming a critical nucleus are not only the free energy difference but also the difference of the entropy of fusion between stable and metastable phases. In the present study, using REFeO3 (RE: rare-earth element) as a model material, we investigate the formation of a metastable phase from undercooled melts with respect to the competitive nucleation and crystallographical stabilities of both phases.

  10. Trace elements profiles, notably Hg, from a preliminary study of the Apollo 15 deep-drill core.

    NASA Technical Reports Server (NTRS)

    Jovanovic, S.; Reed, G. W., Jr.

    1972-01-01

    The possible thermal gradient near the surface during a lunation is considered together with the heat flow from the interior, the physical process of Hg migration, the results from core and trench samples from previous missions, and other temperature sensitive phenomena that may help understand the processes. U, Os, and Ru concentrations in the deep drill core samples are of potential interest and are summarized in a table. The Os tends to parallel the Hg profile with depth.

  11. Nano-sized Minerals of Elemental Selenium and Tellurium Formed by Bacterial Dissimilatory Reduction of Se- and Te-Oxyanions.

    NASA Astrophysics Data System (ADS)

    Oremland, R. S.

    2007-12-01

    Selenium and tellurium are both Group 16 elements that have curious opto-electrical properties making them of potential interest for photovoltaic applications. The process of dissimilatory reduction of selenate and selenite by 3 diverse species of anaerobes, Bacillus selenitireducens, Sulfurospirillum barnesii, and Selenihalanaerobacter shriftii resulted in the accumulation of many uniformly-sized nanospheres (diameter = approx. 300 nm) that aggregated on the outside of their cell envelopes (Oremland et al., 2004). Despite their uniformity of shape, purified Se-nanospheres from the 3 different species displayed significantly different spectral properties (UV- visible light and Raman) indicating differing internal arrangements of their Se atoms. Se-nanospheres from all 3 species also had lower bandgap energies than that of elemental selenium formed by chemical means. We subsequently determined that S. barnesii and B. selenitireducens could grow by dissimilatory reduction of Te- oxyanions, although progress was hampered by the fact that Te concentrations above 0.6 mM proved toxic to cells (Baesman et al., 2007). Unlike the case for Se-nanospheres, the Te-nanoparticles formed by the two microbes were entirely different. S. barnesii formed small, irregularly shaped spheroids (smaller than 50 nm diameter) that coalesced into larger aggregates. In contrast, B. selenitreducens formed nano-rods (10 nm diameter x 200 nm length) that coalesced into larger shards which formed even larger rosette-shaped aggregates once they sloughed off the cells. Spectroscopy of purified Te-rosettes indicated an internal trigonally-shaped array of Te atoms. Future research on Te(0) nano-materials formed by anaerobic bacteria would be aided by isolation of novel species adapted to growth at high batch culture concentrations of Te-oxyanions (approx. 10 mM). Furthermore, the ability of microbes like B. selenitreducens to form selenide by reduction of Se(0) suggests an application in the

  12. NEUTRONIC REACTOR FUEL ELEMENT

    DOEpatents

    Shackleford, M.H.

    1958-12-16

    A fuel element possessing good stability and heat conducting properties is described. The fuel element comprises an outer tube formed of material selected from the group consisting of stainhess steel, V, Ti. Mo. or Zr, a fuel tube concentrically fitting within the outer tube and containing an oxide of an isotope selected from the group consisting of U/sup 235/, U/sup 233/, and Pu/sup 239/, and a hollow, porous core concentrically fitting within the fuel tube and formed of an oxide of an element selected from the group consisting of Mg, Be, and Zr.

  13. Verification of a non-hydrostatic dynamical core using the horizontal spectral element method and vertical finite difference method: 2-D aspects

    NASA Astrophysics Data System (ADS)

    Choi, S.-J.; Giraldo, F. X.; Kim, J.; Shin, S.

    2014-11-01

    The non-hydrostatic (NH) compressible Euler equations for dry atmosphere were solved in a simplified two-dimensional (2-D) slice framework employing a spectral element method (SEM) for the horizontal discretization and a finite difference method (FDM) for the vertical discretization. By using horizontal SEM, which decomposes the physical domain into smaller pieces with a small communication stencil, a high level of scalability can be achieved. By using vertical FDM, an easy method for coupling the dynamics and existing physics packages can be provided. The SEM uses high-order nodal basis functions associated with Lagrange polynomials based on Gauss-Lobatto-Legendre (GLL) quadrature points. The FDM employs a third-order upwind-biased scheme for the vertical flux terms and a centered finite difference scheme for the vertical derivative and integral terms. For temporal integration, a time-split, third-order Runge-Kutta (RK3) integration technique was applied. The Euler equations that were used here are in flux form based on the hydrostatic pressure vertical coordinate. The equations are the same as those used in the Weather Research and Forecasting (WRF) model, but a hybrid sigma-pressure vertical coordinate was implemented in this model. We validated the model by conducting the widely used standard tests: linear hydrostatic mountain wave, tracer advection, and gravity wave over the Schär-type mountain, as well as density current, inertia-gravity wave, and rising thermal bubble. The results from these tests demonstrated that the model using the horizontal SEM and the vertical FDM is accurate and robust provided sufficient diffusion is applied. The results with various horizontal resolutions also showed convergence of second-order accuracy due to the accuracy of the time integration scheme and that of the vertical direction, although high-order basis functions were used in the horizontal. By using the 2-D slice model, we effectively showed that the combined spatial

  14. Synthesis of pyrite/carbon shells on cobalt nanowires forming core/branch arrays as high-performance cathode for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Cao, F.; Pan, G. X.; Chen, J.; Zhang, Y. J.; Xia, X. H.

    2016-01-01

    Construction of self-supported porous metal sulfide arrays is critical for the development of high-performance electrochemical energy storage devices. Herein we report hierarchical porous Co/FeS2-C core/branch nanowires arrays by the combination of facile solution-based methods. FeS2-C nanoflakes branch is uniformly coated on the Co nanowire core forming composite core/branch arrays. The as-prepared Co/FeS2-C core/branch nanowire arrays possess combined properties of highly porous structure and strong mechanical stability. As cathode of lithium ion batteries, the Co/FeS2-C core/branch nanowire arrays exhibit good electrochemical performances with initial discharge capacity of 850 mAh g-1 at 0.25 °C and stable high-rate cycling life (539 mAh g-1 after 70 cycles at 0.25 °C). The hierarchical core/branch architecture provides positive roles in the enhancement of electrochemical properties, including fast transportation path of electron, short diffusion of ions and high contact area between the active material and electrolyte.

  15. Finite element modelling of shot peening and peen forming processes and characterisation of peened AA2024-T351 aluminium alloy

    NASA Astrophysics Data System (ADS)

    Gariepy, Alexandre

    The main purpose of this thesis was to develop and validate finite element (FE) simulation tools for shot peening and peen forming. The specific aim was to achieve quantitatively accurate predictions for both processes and demonstrate the potential of reliable FE modelling for scientific investigation and industrial applications. First, an improved dynamic impact model that takes into account the stochastic nature of shot peening was proposed by carefully studying its dimensions, introducing a dispersion of shot sizes and significantly reducing its computational cost. In addition, cyclic mechanical testing was conducted to define a suitable material constitutive theory for aluminium alloy (AA) 2024-T3/T351 subjected to shot peening. By combining a realistic shot peening model with an appropriate material law, fairly good residual stress predictions were achieved for three different sets of shot peening parameters. Second, an experimental and numerical characterization of AA2024-T351 shot peened with parameters representative of fatigue life improvement applications was conducted. Multiple techniques, such as micro-indentation, residual stress determination and electron backscatter diffraction, were combined to gain a better understanding of the influence of shot peening on the material. The potential uses of finite element simulation to complement experimental data were also studied. The material heterogeneity arising from the random impact sequence was investigated and it was found that the impact modelling methodology could provide useful information on such heterogeneities. Third, a novel peen forming simulation methodology was introduced. The impact model provided the necessary input data as part of a multiscale approach. Numerically calculated unbalanced induced stress profiles were input into shell elements and the deformed shape after peen forming was computed as a springback analysis. In addition, a simple interpolation method was proposed to model the

  16. Unexpected increase in elemental carbon concentrations and deposition in a Svalbard ice core since 1970 and its implications for Arctic warming

    NASA Astrophysics Data System (ADS)

    Ruppel, Meri; Isaksson, Elisabeth; Ström, Johan; Beaudon, Emilie; Svensson, Jonas; Pedersen, Christina A.; Korhola, Atte

    2014-05-01

    Changes in albedo and related feedbacks in the Arctic have been suggested to be one of the driving mechanisms for the observed amplified Arctic warming. Black carbon (BC) is an aerosol produced by incomplete combustion of biomass and fossil fuels. Due to its strong light absorption it warms the atmosphere. Its climate effects are intensified in the Arctic where its deposition on snow and ice decreases surface albedo. BC has been suggested to have caused 20% of the Arctic melting hitherto. Despite the significant role of BC in Arctic warming, there is little information on its concentrations and climate effects in the area in the past. Here we present results on elemental carbon (EC, proxy for BC) concentrations and deposition on a Svalbard glacier (Holtedahlfonna) from 1700 to 2004. The inner part of a 125 m deep ice core was melted, filtered through a quartz fiber filter and analyzed for EC using a thermal optical method. The EC values increased after 1850 and peaked around 1910, similar to previous ice core records from Greenland. Strikingly, EC values increase abruptly since 1970. Such a rise is not seen in Greenland ice cores, and it seems to contradict atmospheric measurements indicating decreasing atmospheric BC concentrations since 1989 in the Arctic. However, the trend gains additional credence from a melt index derived from the same ice core indicating increased summer melt since 1970. The rise in EC values since 1970 is possibly explained by increased washout ratio of BC especially due to increased temperatures. In addition, post-depositional processes, such as increased melt, may enrich EC in most recent ice layers. These processes enable rising EC values in the ice core while atmospheric concentrations have decreased. Possible explanations for the differences in the recorded ice core BC trends from Greenland and Svalbard in the recent decades are partly different sources and the vertical distribution of emissions in the atmosphere. Specifically, the

  17. Grain-size distribution and selected major and trace element concentrations in bed-sediment cores from the Lower Granite Reservoir and Snake and Clearwater Rivers, eastern Washington and northern Idaho, 2010

    USGS Publications Warehouse

    Braun, Christopher L.; Wilson, Jennifer T.; Van Metre, Peter C.; Weakland, Rhonda J.; Fosness, Ryan L.; Williams, Marshall L.

    2012-01-01

    Fifty subsamples from 15 cores were analyzed for major and trace elements. Concentrations of trace elements were low, with respect to sediment quality guidelines, in most cores. Typically, major and trace element concentrations were lower in the subsamples collected from the Snake River compared to those collected from the Clearwater River, the confluence of the Snake and Clearwater Rivers, and Lower Granite Reservoir. Generally, lower concentrations of major and trace elements were associated with coarser sediments (larger than 0.0625 millimeter) and higher concentrations of major and trace elements were associated with finer sediments (smaller than 0.0625 millimeter).

  18. CORE SATURATION BLOCKING OSCILLATOR

    DOEpatents

    Spinrad, R.J.

    1961-10-17

    A blocking oscillator which relies on core saturation regulation to control the output pulse width is described. In this arrangement an external magnetic loop is provided in which a saturable portion forms the core of a feedback transformer used with the thermionic or semi-conductor active element. A first stationary magnetic loop establishes a level of flux through the saturation portion of the loop. A second adjustable magnet moves the flux level to select a saturation point giving the desired output pulse width. (AEC)

  19. Influence of the Shell Thickness and Ratio Between Core Elements on Photostability of the CdTe/CdS Core/Shell Quantum Dots Embedded in a Polymer Matrix.

    PubMed

    Doskaliuk, Nataliia; Khalavka, Yuriy; Fochuk, Petro

    2016-12-01

    This paper reports a study of photooxidation and photomodification processes of the CdTe/CdS quantum dots embedded in a polymer matrix under ambient condition. During the first few minutes of irradiation, the quasi-inverse increase in photoluminescence intensity has been observed indicating the passivation of the nanocrystal surface traps by water molecules. A prolonged irradiation of the polymer film containing CdTe/CdS quantum dots leads to a significant decrease in the photoluminescence intensity together with the "blue shift" of the photoluminescence peak energy associated with quantum dot photooxidation. The mechanisms of the CdTe/CdS core/shell quantum dot photooxidation and photomodification in a polymer matrix are discussed. We have found a correlation between the photostability of the quantum dots and the CdS shell thickness as well as the ratio of core elements. PMID:27102905

  20. Influence of the Shell Thickness and Ratio Between Core Elements on Photostability of the CdTe/CdS Core/Shell Quantum Dots Embedded in a Polymer Matrix

    NASA Astrophysics Data System (ADS)

    Doskaliuk, Nataliia; Khalavka, Yuriy; Fochuk, Petro

    2016-04-01

    This paper reports a study of photooxidation and photomodification processes of the CdTe/CdS quantum dots embedded in a polymer matrix under ambient condition. During the first few minutes of irradiation, the quasi-inverse increase in photoluminescence intensity has been observed indicating the passivation of the nanocrystal surface traps by water molecules. A prolonged irradiation of the polymer film containing CdTe/CdS quantum dots leads to a significant decrease in the photoluminescence intensity together with the "blue shift" of the photoluminescence peak energy associated with quantum dot photooxidation. The mechanisms of the CdTe/CdS core/shell quantum dot photooxidation and photomodification in a polymer matrix are discussed. We have found a correlation between the photostability of the quantum dots and the CdS shell thickness as well as the ratio of core elements.

  1. Origins of diamond-forming fluids: An isotopic and trace element study of diamonds and silicates from diamondiferous xenoliths

    NASA Astrophysics Data System (ADS)

    Laiginhas, Fernando; Pearson, D. Graham; McNeill, John; Gurney, John; Nowell, Geoff; Ottley, Chris

    2010-05-01

    While there is increasing understanding of the age of formation and nature of "gem" diamonds, significant debate revolves around the nature of the fluids/melts from which they form. Stable C and N isotopes have been shown to be highly variable and yet the role of subduction-related fluids remains strongly debated. Recent studies on fibrous diamonds have yielded new trace and major element data (e.g., Weiss et al., 2009) that, together with new radiogenic isotope data (Klein BenDavid et al., 2010) indicate such diamonds grow from fluids that comprise mixtures of hydrous silicic, hydrous saline and carbonatitic fluids, derived from different source components of asthenospheric and lithospheric origin. However, until now such data has been lacking from gem diamonds. Using a new laser-based technique (McNeill et al., 2009), we have analysed a suite of diamonds plus co-existing host silicates from several diamondiferous xenoliths (6 harzburgites, 1 eclogite) from the Finsch and Newlands kimberlites in order to try to understand the fluid compositions that produce gem diamonds and better understand their effects of their mantle wall rocks. Diamonds from the xenoliths show a wide variety of trace element enrichment levels. While the eclogitic diamond shows similar trace element systematics to some of the harzburgitic diamonds there are significant differences within the harzburgitic diamonds from different xenoliths, with those from Finsch being significantly enriched in Ba, Sr and Pb relative to other elements. Nd isotope data on the host silicates is variable and dominantly unradiogenic, indicative of long-term enrichment typically associated with the source of some diamond-forming fluids. We will present Sr isotopic data on host silicates and diamond fluids to constrain whether the "gem" diamonds require the complex sources of fluids that characterise the growth of fibrous diamonds. 1) Y. Weiss, R. Kessel, W.L. Griffin, I. Kiflawi, O. Klein-BenDavid, D.R. Bell, J

  2. Observation of the core of the Perseus cluster with the Einstein solid state spectrometer: Cooling gas and elemental abundances

    NASA Technical Reports Server (NTRS)

    Mushotzky, R. F.; Holt, S. S.; Smith, B. W.; Boldt, E. A.; Serlemitsos, P. J.

    1980-01-01

    Solid State Spectrometer observations of the core of the Perseus cluster have resulted in the detection of X-ray emission lines due to Si, S, and Fe. Analysis of the spectrum indicates that the X-ray emission has at least two characteristic temperatures. This is interpreted in the framework of radiative accretion in the core of the cluster. The derived parameters are a cooling time tc less than 2 x 109 yrs for the low temperature gas, a mass accretion rate of approximately 300 Mo/yr and a characteristic size of 10 to 20 Kpc for the cool gas. The Fe abundance in the core, approximately 0.4, is similar to the Fe abundance averaged over the whole cluster indicating that Fe emission is not strongly concentrated about NGC 1275. The Si and S abundances are consistent with solar values.

  3. The sources and time-integrated evolution of diamond-forming fluids - Trace elements and isotopic evidence

    NASA Astrophysics Data System (ADS)

    Klein-BenDavid, Ofra; Pearson, D. Graham; Nowell, Geoff M.; Ottley, Chris; McNeill, John C. R.; Logvinova, Alla; Sobolev, Nikolay V.

    2014-01-01

    Sub-micrometer inclusions in fibrous diamond growth zones carry high-density fluids (HDF) from which the host diamonds have precipitated. The chemistry of these fluids is our best opportunity of characterizing the diamond-forming environment. The major and trace element patterns of diamond-forming fluids vary widely. Such elemental signatures can be easily modified by a variety of mantle processes whereas radiogenic isotopes give a clear fingerprint of the time-integrated evolution of the fluid source region. Thus, the combination of elemental and isotope data is a powerful tool in constraining the origin of fluids from which diamonds precipitate. Here we present combined trace element composition (34 diamonds) and Sr isotopic data (23 diamonds) for fluid-rich diamonds from six worldwide locations. The Nd and Pb isotopic composition of two of the diamonds were also obtained. Several of the samples were analyzed in at least 2 locations to investigate variations in the fluid during diamond growth. The data was acquired using an off-line laser sampling technique followed by solution ICPMS and TIMS analysis. The Sr isotopic compositions of diamond fluids from the different suites range between convecting mantle values for Udachnaya (87Sr/86Sr363 = 0.70300 ± 16 to 0.70361 ± 4), to highly enriched values, up to 87Sr/86Sr = 0.72330 ± 3, for a diamond from Congo. No isochronous relationships were observed in any of the suites. The lowest Nd isotopic composition recorded so far in a diamond is from Congo (εNd71 = -40.4), which also contains the most radiogenic Sr isotopic composition. In contrast, a less enriched but still rather unradiogenic Nd isotope composition (εNd540 = -11) was obtained for a diamond from Snap Lake, which has moderately radiogenic Sr isotopic enrichment (87Sr/86Sr540 = 0.70821 ± 1). The Pb isotopic system measured in one diamond indicates a complex evolution for the fluid source, with extreme 207Pb/204Pb ratio (15.810 ± 3) and moderate

  4. Star Forming Dense Cloud Cores in the TeV -ray SNR RX J1713.7-3946

    SciTech Connect

    Sano, H.; Sato, J.; Yamamoto, H.; Hayakawa, T.; Torii, K.; Moribe, N.; Kawamura, A.; Okuda, T.; Mizuno, N.; Onishi, T.; Maezawa, H.; Inoue, T.; Inutsuka, S.; Tanaka, T.; Mizuno, A.; Ogawa, H.; Stutzki, J.; Bertoldi, F.; Anderl, S.; Bronfman, L.; Koo, B.C.

    2010-10-27

    RX J1713.7-3946 is one of the TeV {gamma}-ray supernova remnants (SNRs) emitting synchrotron X rays. The SNR is associated with molecular gas located at {approx}1 kpc. We made new molecular observations toward the dense cloud cores, peaks A, C and D, in the SNR in the {sup 12}CO(J=2-1) and {sup 13}CO(J=2-1) transitions at angular resolution of 90 degrees. The most intense core in {sup 13}CO, peak C, was also mapped in the {sup 12}CO(J=4-3) transition at angular resolution of 38 degrees. Peak C shows strong signs of active star formation including bipolar outflow and a far-infrared protostellar source and has a steep gradient with a r{sup -2.2 {+-} 0.4} variation in the average density within radius r. Peak C and the other dense cloud cores are rim-brightened in synchrotron X rays, suggesting that the dense cloud cores are embedded within or on the outer boundary of the SNR shell. This confirms the earlier suggestion that the X rays are physically associated with the molecular gas (Fukui et al. 2003). We present a scenario where the densest molecular core, peak C, survived against the blast wave and is now embedded within the SNR. Numerical simulations of the shock-cloud interaction indicate that a dense clump can indeed survive shock erosion, since shock propagation speed is stalled in the dense clump. Additionally, the shock-cloud interaction induces turbulence and magnetic field amplification around the dense clump that may facilitate particle acceleration in the lower-density inter-clump space leading to the enhanced synchrotron X rays around dense cores.

  5. Removal plan for Shippingport pressurized water reactor core 2 blanket fuel assemblies form T plant to the canister storage building

    SciTech Connect

    Lata

    1996-09-26

    This document presents the current strategy and path forward for removal of the Shippingport Pressurized Water Reactor Core 2 blanket fuel assemblies from their existing storage configuration (wet storage within the T Plant canyon) and transport to the Canister Storage Building (designed and managed by the Spent Nuclear Fuel. Division). The removal plan identifies all processes, equipment, facility interfaces, and documentation (safety, permitting, procedures, etc.) required to facilitate the PWR Core 2 assembly removal (from T Plant), transport (to the Canister storage Building), and storage to the Canister Storage Building. The plan also provides schedules, associated milestones, and cost estimates for all handling activities.

  6. Trace elements in South America aerosol during 20th century inferred from a Nevado Illimani ice core, Eastern Bolivian Andes (6350 m asl)

    NASA Astrophysics Data System (ADS)

    Correia, A.; Freydier, R.; Delmas, R. J.; Simões, J. C.; Taupin, J.-D.; Dupré, B.; Artaxo, P.

    2003-09-01

    A 137 m ice core drilled in 1999 from Eastern Bolivian Andes at the summit of Nevado Illimani (16º 37' S, 67º 46' W, 6350 m asl) was analyzed at high temporal resolution, allowing a characterization of trace elements in Andean aerosol trapped in the ice during the 20th century. The upper 50 m of the ice core were dated by multi-proxy analysis of stable isotopes (d18O and d2H), 137Cs and Ca+2 content, electrical conductivity, and insoluble microparticle content, together with reference historical horizons from atmospheric nuclear tests and known volcanic eruptions. This 50 m section corresponds to a record of environmental variations spanning about 80 years from 1919 to 1999. It was cut in 744 sub-samples under laminar flow in a clean bench, which were analyzed by Ion Chromatography for major ionic concentration, by a particle counter for insoluble aerosol content, and by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for the concentration of 45 chemical species from Li to U. This paper focuses on results of trace element concentrations measured by ICP-MS. The high temporal resolution used in the analyses allowed classifying samples as belonging to dry or wet seasons. During wet season elemental concentrations are low and samples show high crustal enrichment factors. During dry seasons the situation is opposite, with high elemental concentrations and low crustal enrichments. For example, with salt lakes as main sources in the region, average Li concentration during the 20th century is 0.035 and 0.90 ng g-1 for wet and dry seasons, respectively. Illimani average seasonal concentration ranges cover the spectrum of elemental concentration measurements at another Andean ice core site (Sajama) for most soil-related elements. Regional crustal dust load in the deposits was found to be overwhelming during dry season, obfuscating the contribution of biomass burning material. Marked temporal trends from the onset of 20th century to more recent years were identified

  7. Effect of a degraded core on the mechanical behaviour of tissue-engineered cartilage constructs: a poro-elastic finite element analysis.

    PubMed

    Kelly, D J; Prendergast, P J

    2004-01-01

    The structure and functionality of tissue-engineered cartilage is determined by the tissue culture conditions and mechanical conditioning during growth. The quality of tissue-engineered cartilage can be evaluated using tests such as the confined compression test. Tissue-engineered cartilage constructs usually consist of an outer layer of cartilage and an inner core of either undeveloped cartilage or degrading scaffold material. A biphasic poro-elastic finite element model was used to demonstrate how such a core influences the reaction force-time curve obtained from a confined compression test. The finite element model predicted that higher volumes of degraded scaffold in the inner core would reduce the aggregate modulus calculated from the confined compression test and raised the estimate of tissue permeability. The predicted aggregate modulus reduced from 0.135 MPa, for a homogenous construct, to 0.068 MPa, for a construct that was only 70% cartilaginous. It was found that biphasic poro-elastic finite modelling should be used in preference to a one-dimensional model that assumed homogeneity in estimating the properties of tissue-engineered cartilage. PMID:14977217

  8. Experimental detailed power distribution in a fast spectrum thermionic reactor fuel element at the core/BeO reflector interface region

    NASA Technical Reports Server (NTRS)

    Klann, P. G.; Lantz, E.

    1973-01-01

    A zero-power critical assembly was designed, constructed, and operated for the prupose of conducting a series of benchmark experiments dealing with the physics characteristics of a UN-fueled, Li-7-cooled, Mo-reflected, drum-controlled compact fast reactor for use with a space-power conversion system. The critical assembly was modified to simulate a fast spectrum advanced thermionics reactor by: (1) using BeO as a reflector in place of some of the existing molybdenum, (2) substituting Nb-1Zr tubing for some of the existing Ta tubing, and (3) inserting four full-scale mockups of thermionic type fuel elements near the core and BeO reflector boundary. These mockups were surrounded with a buffer zone having the equivalent thermionic core composition. In addition to measuring the critical mass of this thermionic configuration, a detailed power distribution in one of the thermionic element stages in the mixed spectrum region was measured. A power peak to average ratio of two was observed for this fuel stage at the midplane of the core and adjacent to the reflector. Also, the power on the outer surface adjacent to the BeO was slightly more than a factor of two larger than the power on the inside surface of a 5.08 cm (2.0 in.) high annular fuel segment with a 2.52 cm (0.993 in. ) o.d. and a 1.86 cm (0.731 in.) i.d.

  9. Sequence Elements Upstream of the Core Promoter Are Necessary for Full Transcription of the Capsule Gene Operon in Streptococcus pneumoniae Strain D39

    PubMed Central

    Wen, Zhensong; Sertil, Odeniel; Cheng, Yongxin; Zhang, Shanshan; Liu, Xue; Wang, Wen-Ching

    2015-01-01

    Streptococcus pneumoniae is a major bacterial pathogen in humans. Its polysaccharide capsule is a key virulence factor that promotes bacterial evasion of human phagocytic killing. While S. pneumoniae produces at least 94 antigenically different types of capsule, the genes for biosynthesis of almost all capsular types are arranged in the same locus. The transcription of the capsular polysaccharide (cps) locus is not well understood. This study determined the transcriptional features of the cps locus in the type 2 virulent strain D39. The initial analysis revealed that the cps genes are cotranscribed from a major transcription start site at the −25 nucleotide (G) upstream of cps2A, the first gene in the locus. Using unmarked chromosomal truncations and a luciferase-based transcriptional reporter, we showed that the full transcription of the cps genes not only depends on the core promoter immediately upstream of cps2A, but also requires additional elements upstream of the core promoter, particularly a 59-bp sequence immediately upstream of the core promoter. Unmarked deletions of these promoter elements in the D39 genome also led to significant reduction in CPS production and virulence in mice. Lastly, common cps gene (cps2ABCD) mutants did not show significant abnormality in cps transcription, although they produced significantly less CPS, indicating that the CpsABCD proteins are involved in the encapsulation of S. pneumoniae in a posttranscriptional manner. This study has yielded important information on the transcriptional characteristics of the cps locus in S. pneumoniae. PMID:25733517

  10. Novel core promoter elements in the oomycete pathogen Phytophthora infestans and their influence on expression detected by genome-wide analysis

    PubMed Central

    2013-01-01

    Background The core promoter is the region flanking the transcription start site (TSS) that directs formation of the pre-initiation complex. Core promoters have been studied intensively in mammals and yeast, but not in more diverse eukaryotes. Here we investigate core promoters in oomycetes, a group within the Stramenopile kingdom that includes important plant and animal pathogens. Prior studies of a small collection of genes proposed that oomycete core promoters contain a 16 to 19 nt motif bearing an Initiator-like sequence (INR) flanked by a novel sequence named FPR, but this has not been extended to whole-genome analysis. Results We used expectation maximization to find over-represented motifs near TSSs of Phytophthora infestans, the potato blight pathogen. The motifs corresponded to INR, FPR, and a new element found about 25 nt downstream of the TSS called DPEP. TATA boxes were not detected. Assays of DPEP function by mutagenesis were consistent with its role as a core motif. Genome-wide searches found a well-conserved combined INR+FPR in only about 13% of genes after correcting for false discovery, which contradicted prior reports that INR and FPR are found together in most genes. INR or FPR were found alone near TSSs in 18% and 7% of genes, respectively. Promoters lacking the motifs had pyrimidine-rich regions near the TSS. The combined INR+FPR motif was linked to higher than average mRNA levels, developmentally-regulated transcription, and functions related to plant infection, while DPEP and FPR were over-represented in constitutively-expressed genes. The INR, FPR, and combined INR+FPR motifs were detected in other oomycetes including Hyaloperonospora arabidopsidis, Phytophthora sojae, Pythium ultimum, and Saprolegnia parasitica, while DPEP was found in all but S. parasitica. Only INR seemed present in a non-oomycete stramenopile. Conclusions The absence of a TATA box and presence of novel motifs show that the oomycete core promoter is diverged from that of

  11. Core Elements of the European (Higher) Education Policy: Market-Driven Restructuring or Impetus for Intercultural Rapprochement?

    ERIC Educational Resources Information Center

    Starkie, Elisa Gavari

    2008-01-01

    For many years there has been a debate about the existence or not, of a common European education policy. In this article I argue that there has been a real European education policy since the approval of the Maastricht Treaty, with a proper content and which offers many new possibilities to students. The core of this policy is the setting up of…

  12. A Catalog of Low-mass Star-forming Cores Observed with SHARC-II at 350 μm

    NASA Astrophysics Data System (ADS)

    Suresh, Akshaya; Dunham, Michael M.; Arce, Héctor G.; Evans, Neal J., II; Bourke, Tyler L.; Merello, Manuel; Wu, Jingwen

    2016-08-01

    We present a catalog of low-mass dense cores observed with the SHARC-II instrument at 350 μm. Our observations have an effective angular resolution of 10″, approximately 2.5 times higher than observations at the same wavelength obtained with the Herschel Space Observatory, albeit with lower sensitivity, especially to extended emission. The catalog includes 81 maps covering a total of 164 detected sources. For each detected source, we tabulate basic source properties including position, peak intensity, flux density in fixed apertures, and radius. We examine the uncertainties in the pointing model applied to all SHARC-II data and conservatively find that the model corrections are good to within ∼3″, approximately 1/3 of the SHARC-II beam. We examine the differences between two array scan modes and find that the instrument calibration, beam size, and beam shape are similar between the two modes. We also show that the same flux densities are measured when sources are observed in the two different modes, indicating that there are no systematic effects introduced into our catalog by utilizing two different scan patterns during the course of taking observations. We find a detection rate of 95% for protostellar cores but only 45% for starless cores, and demonstrate the existence of a SHARC-II detection bias against all but the most massive and compact starless cores. Finally, we discuss the improvements in protostellar classification enabled by these 350 μm observations.

  13. The influence of the root cross-section on the stress distribution in teeth restored with a positive-locking post and core design: a finite element study.

    PubMed

    Schilling, Kai-Uwe; Rottner, Kurt; Boldt, Julian; Proff, Peter; Gredes, Tomasz; Richter, Ernst-Jürgen; Reicheneder, Claudia

    2008-10-01

    Human teeth with substantial coronal defects are subject to reconstruction by means of post and core restorations. Typically, such a restoration comprises a slightly cylindrical post onto which an abutment of varying shape, depending on the designated restoration, is attached. As clinical results are not satisfactory to date, we proposed a new proprietary post and core design which makes use of positive locking. As this prefabricated system is not customised to an individual root's cross-sectional geometry (usually oval), a varying amount of radicular dentin is left in periphery of the core's outer edge. The aim of this study was to assess the implications of this fact, i.e., whether the root has to endure higher overall stress levels which ultimately may lead to failure of one of the components involved. A series of finite element simulations were performed to evaluate stress and strain on the system, in which the proposed post and core was embedded into a virtual dentin cylinder of different diameters, ranging from flush mounting of the restoration to a dentin excess of 4 mm, and subsequently loaded with forces with two angles of attack (90 degrees and 130 degrees ). The results show that flush mounting yields an agreeable stress and strain distribution within the radicular dentin, but overall stress levels drop significantly with an excess of 0.5 mm of surrounding dentin. More than 1 mm excess was not found to have profound positive effects. PMID:18803526

  14. Multiple magma evolution and ore-forming processes of the Hongge layered intrusion, SW China: Insights from Sr-Nd isotopes, trace elements and platinum-group elements

    NASA Astrophysics Data System (ADS)

    Liao, Mingyang; Tao, Yan; Song, Xieyan; Li, Yubang; Xiong, Feng

    2015-12-01

    The Hongge layered intrusion (259 Ma), which is located in the inner zone of the Emeishan large igneous province (ELIP), is one of the most typical Fe-Ti-V ore deposits in the Pan-Xi area. Mafic-ultramafic layered intrusions of the ELIP have attracted a lot of attention lately because these intrusions host world class Fe-Ti-V oxide deposits plus interesting Cu-Ni-(PGE) mineralization which may have economic potential. This paper, reports new whole-rock major and trace element compositions, PGE abundances and Sr-Nd isotopic data for selected cumulate rocks and basalts. We use these data to investigate the nature of parental magmas and the controls on its evolution from the source mantle en route to the surface involving the Hongge ore-bearing intrusion. Two abrupt changes in Mt/Ilm and trace element ratios such as Ba/Th with depths in the Hongge layered intrusion indicate that this intrusion formed by at least two pluses of relatively primitive magma. The whole rock Sr-Nd isotopic data of basaltic and intrusive rocks plot in the region of Emeishan low-Ti basalts and the compositions of residual liquid (at ∼1260 °C and 1155 °C) calculated by MELTS are similar to our actual high-Ti (BFQ-2) and low-Ti (BC-1) basltic samples, indicate they are co-magmatic rather than derivation from a distinct source. Total PGE abundances in the Hongge samples are extremely low, ranging from 0.5 to 10 ppb. Sulfide-bearing rocks in the Hongge intrusion and the nearby coeval Banfangqing and Baicao basalts have similar mantle-like Pd/Pt ratios (2-6) and extremely high Cu/Pd ratios (3 × 104 to 4 × 105), indicating that sulfide segregation took place at depth prior to emplacement at Hongge and eruption in this region. Sulfide saturation in the Hongge magma may have resulted from such crustal contamination event. Crystallization of silicate minerals under the anhydrous magma, magma hydration plus Fe-Ti enrichments in the parental magma are three critical factors for the formation of Fe

  15. Trace Element Geochemistry of Basaltic Tephra in Maar Cores; Implications for Centre Correlation, Field Evolution, and Mantle Source Characteristics of the Auckland Volcanic Field, New Zealand

    NASA Astrophysics Data System (ADS)

    Hopkins, J. L.; Leonard, G.; Timm, C.; Wilson, C. J. N.; Neil, H.; Millet, M. A.

    2014-12-01

    Establishing volcanic hazard and risk management strategies hinges on a detailed understanding of the type, timing and tephra dispersal of past eruptions. In order to unravel the pyroclastic eruption history of a volcanic field, genetic links between the deposits and eruption source centre need to be established. The Auckland Volcanic Field (AVF; New Zealand) has been active for ca. 200 kyr and comprises ca. 53 individual centres covering an area of ca. 360km2. These centres show a range of sizes and eruptive styles from maar craters and tuff rings, to scoria cones and lava flows consistent with both phreatomagmatic and magmatic eruptions. Superimposition of the metropolitan area of Auckland (ca. 1.4 million inhabitants) on the volcanic field makes it critically important to assess the characteristics of the volcanic activity, on which to base assessment and management of the consequent hazards. Here we present a geochemical approach for correlating tephra deposits to their source centres. To acquire the most complete stratigraphic record of pyroclastic events, maar crater cores from different locations, covering various depths and thus ages across the field were selected. Magnetic susceptibility and x-ray density scanning of the cores was used to identify the basaltic tephra horizons, which were sampled and in-situ analysis of individual shards undertaken for major and trace elements using EPMA and LA-ICP-MS techniques, respectively. Our results show that tephra shard trace element ratios are comparable and complementary to the AVF whole rock database. The use of specific trace element ratios (e.g. Gd/Yb vs. Zr/Yb) allows us to fingerprint and cross correlate tephra horizons between cores and, when coupled with newly acquired 40Ar-39Ar age dating and eruption size estimates, correlate horizons to their source centres. This integrated style of study can provide valuable information to help volcanic hazard management and forecasting, and mitigation of related risks.

  16. Component mode synthesis methods applied to 3D heterogeneous core calculations, using the mixed dual finite element solver MINOS

    SciTech Connect

    Guerin, P.; Baudron, A. M.; Lautard, J. J.

    2006-07-01

    This paper describes a new technique for determining the pin power in heterogeneous core calculations. It is based on a domain decomposition with overlapping sub-domains and a component mode synthesis technique for the global flux determination. Local basis functions are used to span a discrete space that allows fundamental global mode approximation through a Galerkin technique. Two approaches are given to obtain these local basis functions: in the first one (Component Mode Synthesis method), the first few spatial eigenfunctions are computed on each sub-domain, using periodic boundary conditions. In the second one (Factorized Component Mode Synthesis method), only the fundamental mode is computed, and we use a factorization principle for the flux in order to replace the higher order Eigenmodes. These different local spatial functions are extended to the global domain by defining them as zero outside the sub-domain. These methods are well-fitted for heterogeneous core calculations because the spatial interface modes are taken into account in the domain decomposition. Although these methods could be applied to higher order angular approximations - particularly easily to a SPN approximation - the numerical results we provide are obtained using a diffusion model. We show the methods' accuracy for reactor cores loaded with UOX and MOX assemblies, for which standard reconstruction techniques are known to perform poorly. Furthermore, we show that our methods are highly and easily parallelizable. (authors)

  17. Explosive Nucleosynthesis of Weak R-Process Elements in Extremely Metal-Poor Core-Collapse Supernovae

    NASA Astrophysics Data System (ADS)

    Izutani, Natsuko; Umeda, Hideyuki; Tominaga, Nozomu

    2009-02-01

    There have been attempts to fit the abundance patterns of extremely metal-poor (EMP) stars with supernova (SN) nucleosynthesis models for the elements lighter than Zn. Observations have revealed the presence of EMP stars with a peculiarly high ratio of "weak r-process elements" Sr, Y, and Zr. Although several possible processes were suggested for the origin of these elements, a complete solution for reproducing those ratios has not yet been found. In order to reproduce the abundance patterns of such stars, we investigate a model with neutron-rich matter ejection from the inner region of the conventional mass-cut. We find that explosive nucleosynthesis in a high energy SN (or "hypernova") can reproduce the high abundances of Sr, Y, and Zr but that the enhancements of Sr, Y, and Zr are not achieved by nucleosynthesis in a normal SN. Our results imply that, if these elements are ejected from a normal SN, nucleosynthesis in higher entropy flow than that of the SN shock is required.

  18. A Dual Modulated Homochiral Helical Nanofilament Phase with Local Columnar Ordering Formed by Bent Core Liquid Crystals: Effects of Molecular Chirality.

    PubMed

    Li, Lin; Salamonczyk, Miroslaw; Jákli, Antal; Hegmann, Torsten

    2016-08-01

    Helical nanofilament (HNF) phases form as a result of an intralayer mismatch between top and bottom molecular halves in bent-core liquid crystals (BC-LCs) that is relieved by local saddle-splay geometry. HNFs are immensely attractive for photovoltaic and chiral separation applications and as templates for the chiral spatial assembly of guest molecules. Here, the synthesis and characterization of two unichiral BC-LCs and one racemic mixture with tris-biphenyl-diester cores featuring chiral (R,R) and (S,S) or racemic 2-octyloxy aliphatic side chains are presented. In comparison to the achiral compound with linear side chains forming an intralayer modulated HNF phase (HNFmod ), synchrotron small angle X-ray diffraction indicates that the unichiral derivatives form a dual modulated HNF phase with intra- as well as interlayer modulations (HNFmod2 ) suggesting a columnar local structure of the nanofilaments. Transmission electron microscopy and circular dichroism spectropolarimetry confirm that the unichiral materials exclusively form homochiral HNFs with a twist sense-matching secondary twist. A contact preparation provides the first example of two identical chiral liquid crystal phases only differing in their handedness that do not mix and form an achiral liquid crystal phase with an entirely different structure in the contact zone. PMID:27334846

  19. Assessment of trace element contamination in sediment cores from the Pearl River and estuary, South China: geochemical and multivariate analysis approaches.

    PubMed

    Yang, Yongqiang; Liu, Zhuli; Chen, Fanrong; Wu, Shijun; Zhang, Ling; Kang, Mingliang; Li, Jie

    2014-12-01

    Twenty-four major and trace elements and the mineralogical composition of four sediment cores along the Pearl River and estuary were analyzed using ICP-AES, ICP-MS, and X-ray diffraction (XRD) to evaluate contamination levels. The dominant minerals were quartz, kaolinite, and illite, followed by montmorillonite and feldspars, while small amounts of halite and calcite were also observed in a few samples. Cluster analysis (CA) and principal component analysis (PCA) were performed to identify the element sources. The highest metal concentrations were found at Huangpu, primarily due to wastewater treatment plant discharge and/or the surreptitious dumping of sludge, and these data differed from those of other sources. Excluding the data from Huangpu, the PCA showed that most elements could be considered as lithogenic; few elements are the combination of lithogenic and anthropogenic sources. An antagonistic relationship between the anthropogenic source metals (K, Ba, Zn, Pb, Cd, Ag, Tl, and U) and marine source metals (Na, Mg, Ti, V, and Ca) was observed. The resulting normalized Al enrichment factor (EF) indicated very high or significant pollution of Cd, Ag, Cu, Zn, Mo, and Pb at Huangpu, which may cause serious environmental effects. Conflicting results between the PCA and EF can be attributed to the background values used, indicating that background values must be selected carefully. PMID:25159811

  20. Liprotides made of α-lactalbumin and cis fatty acids form core-shell and multi-layer structures with a common membrane-targeting mechanism.

    PubMed

    Frislev, Henriette S; Jessen, Christian M; Oliveira, Cristiano L P; Pedersen, Jan Skov; Otzen, Daniel E

    2016-07-01

    α-Lactalbumin (aLA) has been shown to form complexes with oleic acid (OA), which may target cancer cells. We recently showed that aLA and several other proteins all form protein-OA complexes called liprotides with a generic structure consisting of a micellar OA core surrounded by a shell of partially denatured protein. Here we report that a heat treatment and an alkaline treatment method both allow us to prepare liprotide complexes composed of aLA and a range of unsaturated fatty acids (FA), provided the FAs contain cis (but not trans) double bonds. All liprotides containing cis-FA form both small and large species, which all consist of partially denatured aLA, though the overall shape of the species differs. Small liprotides have a simple core-shell structure while the larger liprotides are multi-layered, i.e. they have an additional layer of both FA and aLA surrounding the outside of the core-shell structure. All liprotides can transfer their entire FA content to vesicles, releasing aLA as monomers and softening the lipid membrane. The more similar to OA, the more efficiently the different FAs induce hemolysis. We conclude that aLA can take up and transfer a wide variety of FA to membranes, provided they contain a cis-bond. This highlights liprotides as a general class of complexes where both protein and cis-FA component can be varied without departing from a generic (though sometimes multi-layered) core-shell structure. PMID:27068540

  1. H2D(+) observations give an age of at least one million years for a cloud core forming Sun-like stars.

    PubMed

    Brünken, Sandra; Sipilä, Olli; Chambers, Edward T; Harju, Jorma; Caselli, Paola; Asvany, Oskar; Honingh, Cornelia E; Kamiński, Tomasz; Menten, Karl M; Stutzki, Jürgen; Schlemmer, Stephan

    2014-12-11

    The age of dense interstellar cloud cores, where stars and planets form, is a crucial parameter in star formation and difficult to measure. Some models predict rapid collapse, whereas others predict timescales of more than one million years (ref. 3). One possible approach to determining the age is through chemical changes as cloud contraction occurs, in particular through indirect measurements of the ratio of the two spin isomers (ortho/para) of molecular hydrogen, H2, which decreases monotonically with age. This has been done for the dense cloud core L183, for which the deuterium fractionation of diazenylium (N2H(+)) was used as a chemical clock to infer that the core has contracted rapidly (on a timescale of less than 700,000 years). Among astronomically observable molecules, the spin isomers of the deuterated trihydrogen cation, ortho-H2D(+) and para-H2D(+), have the most direct chemical connections to H2 (refs 8, 9, 10, 11, 12) and their abundance ratio provides a chemical clock that is sensitive to greater cloud core ages. So far this ratio has not been determined because para-H2D(+) is very difficult to observe. The detection of its rotational ground-state line has only now become possible thanks to accurate measurements of its transition frequency in the laboratory, and recent progress in instrumentation technology. Here we report observations of ortho- and para-H2D(+) emission and absorption, respectively, from the dense cloud core hosting IRAS 16293-2422 A/B, a group of nascent solar-type stars (with ages of less than 100,000 years). Using the ortho/para ratio in conjunction with chemical models, we find that the dense core has been chemically processed for at least one million years. The apparent discrepancy with the earlier N2H(+) work arises because that chemical clock turns off sooner than the H2D(+) clock, but both results imply that star-forming dense cores have ages of about one million years, rather than 100,000 years. PMID:25409140

  2. H2D+ observations give an age of at least one million years for a cloud core forming Sun-like stars

    NASA Astrophysics Data System (ADS)

    Brünken, Sandra; Sipilä, Olli; Chambers, Edward T.; Harju, Jorma; Caselli, Paola; Asvany, Oskar; Honingh, Cornelia E.; Kamiński, Tomasz; Menten, Karl M.; Stutzki, Jürgen; Schlemmer, Stephan

    2014-12-01

    The age of dense interstellar cloud cores, where stars and planets form, is a crucial parameter in star formation and difficult to measure. Some models predict rapid collapse, whereas others predict timescales of more than one million years (ref. 3). One possible approach to determining the age is through chemical changes as cloud contraction occurs, in particular through indirect measurements of the ratio of the two spin isomers (ortho/para) of molecular hydrogen, H2, which decreases monotonically with age. This has been done for the dense cloud core L183, for which the deuterium fractionation of diazenylium (N2H+) was used as a chemical clock to infer that the core has contracted rapidly (on a timescale of less than 700,000 years). Among astronomically observable molecules, the spin isomers of the deuterated trihydrogen cation, ortho-H2D+ and para-H2D+, have the most direct chemical connections to H2 (refs 8, 9, 10, 11, 12) and their abundance ratio provides a chemical clock that is sensitive to greater cloud core ages. So far this ratio has not been determined because para-H2D+ is very difficult to observe. The detection of its rotational ground-state line has only now become possible thanks to accurate measurements of its transition frequency in the laboratory, and recent progress in instrumentation technology. Here we report observations of ortho- and para-H2D+ emission and absorption, respectively, from the dense cloud core hosting IRAS 16293-2422 A/B, a group of nascent solar-type stars (with ages of less than 100,000 years). Using the ortho/para ratio in conjunction with chemical models, we find that the dense core has been chemically processed for at least one million years. The apparent discrepancy with the earlier N2H+ work arises because that chemical clock turns off sooner than the H2D+ clock, but both results imply that star-forming dense cores have ages of about one million years, rather than 100,000 years.

  3. Partitioning of Moderately Siderophile Elements Among Olivine, Silicate Melt, and Sulfide Melt: Constraints on Core Formation in the Earth and Mars

    NASA Technical Reports Server (NTRS)

    Gaetani, Glenn A.; Grove, Timothy L.

    1997-01-01

    This study investigates the effects of Variations in the fugacities of oxygen and sulfur on the partitioning of first series transition metals (V, Cr, Mn, Fe, Co, Ni. and Cu) and W among coexisting sulfide melt, silicate melt, and olivine. Experiments were performed at 1 atm pressure, 1350 C, with the fugacities of oxygen and sulfur controlled by mixing CO2, CO, and SO2 gases. Starting compositions consisted of a CaO-MgO-Al2O3-SiO2-FeO-Na2O analog for a barred olivine chondrule from an ordinary chondrite and a synthetic komatiite. The f(sub O2)/f(sub S2), conditions ranged from log of f(sub O2) = -7.9 to - 10.6, with log of f(sub S2) values ranging from - 1.0 to -2.5. Our experimental results demonstrate that the f(sub O2)/f(sub S2) dependencies of sulfide melt/silicate melt partition coefficients for the first series transition metals arc proportional to their valence states. The f(sub O2)/f(sub S2) dependencies for the partitioning of Fe, Co, Ni, and Cu are weaker than predicted on the basis of their valence states. Variations in conditions have no significant effect on olivine/melt partitioning other than those resulting from f(sub O2)-induced changes in the valence state of a given element. The strong f(sub O2)/f(sub S2) dependence for the olivine/silicate melt partitioning of V is attributable to a change of valence state, from 4+ to 3+, with decreasing f(sub O2). Our experimentally determined partition coefficients are used to develop models for the segregation of sulfide and metal from the silicate portion of the early Earth and the Shergottite parent body (Mars). We find that the influence of S is not sufficient to explain the overabundance of siderophile and chalcophile elements that remained in the mantle of the Earth following core formation. Important constraints on core formation in Mars are provided by our experimental determination of the partitioning of Cu between silicate and sulfide melts. When combined with existing estimates for siderophile

  4. Program ELM: A tool for rapid thermal-hydraulic analysis of solid-core nuclear rocket fuel elements

    NASA Technical Reports Server (NTRS)

    Walton, James T.

    1992-01-01

    This report reviews the state of the art of thermal-hydraulic analysis codes and presents a new code, Program ELM, for analysis of fuel elements. ELM is a concise computational tool for modeling the steady-state thermal-hydraulics of propellant flow through fuel element coolant channels in a nuclear thermal rocket reactor with axial coolant passages. The program was developed as a tool to swiftly evaluate various heat transfer coefficient and friction factor correlations generated for turbulent pipe flow with heat addition which have been used in previous programs. Thus, a consistent comparison of these correlations was performed, as well as a comparison with data from the NRX reactor experiments from the Nuclear Engine for Rocket Vehicle Applications (NERVA) project. This report describes the ELM Program algorithm, input/output, and validation efforts and provides a listing of the code.

  5. Trace element geochemistry of the 1991 Mt. Pinatubo silicic melts, Philippines: Implications for ore-forming potential of adakitic magmatism

    NASA Astrophysics Data System (ADS)

    Borisova, Anastassia Yu.; Pichavant, Michel; Polvé, Mireille; Wiedenbeck, Michael; Freydier, Remi; Candaudap, Frédéric

    2006-07-01

    The dacite pumice erupted from Mt. Pinatubo on June 15, 1991 (whole-rock, rhyolitic groundmass glasses and homogenized melt inclusions) has been analyzed using inductively coupled plasma-mass spectrometry (ICP-MS), nanosecond and femtosecond laser ablation ICP-MS and secondary ion mass spectrometry (SIMS) to evaluate its ore-forming potential. Data suggest that adakite magmas are metal-rich and concentrate ore metals during magmatic differentiation. Sulfides segregate in limited amounts under the hydrous, oxidizing conditions typical of adakitic magmas resulting in incompatible behavior for Au (6-22 ppb), Cu (26-77 ppm), and Pb, Mo, As, and Sb in melts of dacitic to rhyolitic compositions. Metal transfer from this adakite magma to the coexisting aqueous phase was favored by the peraluminous composition of the rhyolitic melt and high aqueous chloride concentrations. Mass balance calculations suggest that the pre-eruptive aqueous phase could have extracted a minimum of 100 t Au and 5 × 10 5 t Cu from the Mt. Pinatubo magma. Our data suggest that intrusives having adakitic signatures are genetically associated with Au-Cu and Cu-Mo mineralization, auriferous porphyry copper deposits, and epithermal gold veins. High H 2O, Cl, Sr/Y, Pb/Ce, Mo/Ce, As/Ce and Sb/Ce in Mt. Pinatubo melts reflect the contribution of deep fluids derived from subducted sediments and altered MORBs in the dacite genesis. The slab-derived fluids carrying mobile elements are likely responsible for the enrichment of adakite magmas in gold, associated metals and H 2O, and may explain the exceptional ore-forming potential of adakite magmatism.

  6. Metallic elements in fossil fuel combustion products: amounts and form of emissions and evaluation of carcinogenicity and mutagenicity.

    PubMed Central

    Vouk, V B; Piver, W T

    1983-01-01

    Metallic elements contained in coal, oil and gasoline are mobilized by combustion processes and may be emitted into the atmosphere, mainly as components of submicron particles. The information about the amounts, composition and form of metal compounds is reviewed for some fuels and combustion processes. Since metal compounds are always contained in urban air pollutants, they have to be considered whenever an evaluation of biological impact of air pollutants is made. The value of currently used bioassays for the evaluation of the role of trace metal compounds, either as major biologically active components or as modifiers of biological effects of organic compounds is assessed. The whole animal bioassays for carcinogenicity do not seem to be an appropriate approach. They are costly, time-consuming and not easily amenable to the testing of complex mixtures. Some problems related to the application and interpretation of short-term bioassays are considered, and the usefulness of such bioassays for the evaluation of trace metal components contained in complex air pollution mixtures is examined. PMID:6337825

  7. cis-Active elements of Friend spleen focus-forming virus: from disease induction to disease prevention.

    PubMed

    Baum, C; Hunt, N; Hildinger, M; Eckert, H G; Zaehres, H; Richters, A; John, J; Löhler, J; Ostertag, W

    1998-01-01

    The polycythemic strain of the Friend spleen focus-forming virus (SFFVp) is a replication-defective, acutely transforming retrovirus inducing a bistage erythroleukemia in susceptible mice. The first stage of the disease is an acute polyclonal erythroblastosis induced by the proliferation-promoting effect of gp55. gp55 is expressed from a spliced subgenomic message of SFFVp and stimulates the cellular receptor for erythropoietin. Using a selectable SFFVp that otherwise mimics the specificity of the disease, we demonstrate that the kinetics of the polyclonal expansion depends on the transcriptional strength of the retroviral cis-active elements. By exchanging gp55 for apathogenic genes, we show that SFFVp enhancer and splice signals can be successfully utilized for the development of retroviral vectors mediating very efficient transgene expression in hematopoietic cells. Apathogenic selectable SFFVp-based vectors carrying distinct enhancer alterations are a valuable tool to analyze transcriptional control of leukemia viruses in the absence of oncogenic proteins. Moreover they might have therapeutic potential. PMID:9587397

  8. Core-to-valence spectroscopic detection of the CH{sub 2}Br radical and element-specific femtosecond photodissociation dynamics of CH{sub 2}IBr

    SciTech Connect

    Attar, Andrew R.; Piticco, Lorena; Leone, Stephen R.

    2014-10-28

    Element-specific single photon photodissociation dynamics of CH{sub 2}IBr and core-to-valence absorption spectroscopy of CH{sub 2}Br radicals are investigated using femtosecond high-harmonic extreme ultraviolet (XUV) transient absorption spectroscopy. Photodissociation of CH{sub 2}IBr along both the C–I or C–Br reaction coordinates is observed in real-time following excitation at 266 nm. At this wavelength, C–I dissociation is the dominant reaction channel and C–Br dissociation is observed as a minor pathway. Both photodissociation pathways are probed simultaneously through individual 4d(I) N{sub 4/5} and 3d(Br) M{sub 4/5} core-to-valence transitions. The 3d(Br) M{sub 4/5} pre-edge absorption spectrum of the CH{sub 2}Br radical photoproduct corresponding to the C–I dissociation channel is characterized for the first time. Although the radical's singly occupied molecular orbital (SOMO) is mostly localized on the central carbon atom, the 3d(Br) → π{sup *}(SOMO) resonances at 68.5 eV and 69.5 eV are detected 2 eV below the parent molecule 3d(Br) → σ{sup *}(LUMO) transitions. Core-to-valence XUV absorption spectroscopy provides a unique probe of the local electronic structure of the radical species in reference to the Br reporter atom. The measured times for C–I dissociation leading to I and I{sup *} atomic products are 48 ± 12 fs and 44 ± 4 fs, respectively, while the measured C–Br dissociation time leading to atomic Br is 114 ± 17 fs. The investigation performed here demonstrates the capability of femtosecond time-resolved core-level spectroscopy utilizing multiple reporter atoms simultaneously.

  9. Water transport from collapsing prestellar cores to forming disks: evolution of the HDO/H2O ratio

    NASA Astrophysics Data System (ADS)

    Furuya, K.; Drozdovskaya, M. N.; Walsh, C.; van Dishoeck, E. F.

    2016-05-01

    We investigate the transport of H2O and HDO ices from the collapse of rotating cores to the formation of disks. We adopt a two-dimensional physical model in order to trace fluid parcels, in which molecular evolution is simulated using a gas-ice chemical model. We find that water ice accreting from the protostellar envelope onto the disks can have a variation of the HDO/H2O ratio, reproducing the variation of the HDO/H2O ratio observed in comets. The result suggests that processing of water in the disk itself is not necessarily required to account for the variation of the HDO/H2O ratio in comets.

  10. Trace Element Determination from the Guliya Ice Core to Characterize Aerosol Deposition over the Western Tibetan Plateau during the Last 500 Years

    NASA Astrophysics Data System (ADS)

    Sierra Hernandez, R.; Gabrielli, P.; Beaudon, E.; Wegner, A.; Thompson, L. G.

    2014-12-01

    The Tibetan Plateau or Third Pole covers over 5 million km2, and has ~46,000 glaciers that collectively contain one of the Earth's largest stores of fresh water. The Guliya ice cap located in the western Kunlun Shan on the Qinghai-Tibetan Plateau, China, is the largest (> 200 km2) ice cap in the subtropical zone. In 1992, a 308.6 m ice core to bedrock was recovered from the Guliya ice cap. The deepest 20 meters yielded the first record extending back through the last glacial cycle found outside of the Polar Regions. Because of its continental location on the northwestern side of the Tibetan Plateau, the atmospheric circulation over the Guliya ice cap is dominated by westerly air flow from the Eurasian region. Therefore the site is expected to be unaffected by the fallout of anthropogenic trace metals originating from the inner Asian continent and rather may serve to characterize trace metal emissions from the western countries. Here we present preliminary results of the determination of 29 trace elements, Rb, Sr, Nb, Mo, Ag, Cd, Sn, Sb, Cs, Ba, Ta, Tl, Pb, Bi, U, Li, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, and As, from Guliya ice core samples spanning the period 1500 - 1992 AD at seasonal (1750-1992 AD) and annual (1500-1750 AD) resolution. This Guliya trace element record will complement the developing records from the Dasuopu glacier, central Himalaya, and from the Puruogangri ice cap in the western Tanggula Shan in central Tibetan Plateau, which in contrast to Guliya are influenced by the monsoon. We investigate the possible sources both natural and anthropogenic of atmospheric trace elements and their fluxes over the Tibetan Plateau during the last 500 years.

  11. Testing the ureilite projectile hypothesis for the El'gygytgyn impact: Determination of siderophile element abundances and Os isotope ratios in ICDP drill core samples and melt rocks

    NASA Astrophysics Data System (ADS)

    Goderis, S.; Wittmann, A.; Zaiss, J.; Elburg, M.; Ravizza, G.; Vanhaecke, F.; Deutsch, A.; Claeys, P.

    2013-07-01

    The geochemical nature of the impactites from International Continental Scientific Drilling Project—El'gygytgyn lake drill core 1C is compared with that of impact melt rock fragments collected near the western rim of the structure and literature data. Concentrations of major and trace elements, with special focus on siderophile metals Cr, Co, Ni, and the platinum group elements, and isotope ratios of osmium (Os), were determined to test the hypothesis of an ureilite impactor at El'gygytgyn. Least squares mixing calculations suggest that the upper volcanic succession of rhyolites, dacites, and andesites were the main contributors to the polymict impact breccias. Additions of 2-13.5 vol% of basaltic inclusions recovered from drill core intervals between 391.6 and 423.0 mblf can almost entirely account for the compositional differences observed for the bottom of a reworked fallout deposit at 318.9 mblf, a polymict impact breccia at 471.4 mblf, and three impact melt rock fragments. However, the measured Os isotope ratios and slightly elevated PGE content (up to 0.262 ng g-1 Ir) of certain impactite samples, for which the CI-normalized logarithmic PGE signature displays a relatively flat (i.e., chondritic) pattern, can only be explained by the incorporation of a small meteoritic contribution. This component is also required to explain the exceptionally high siderophile element contents and corresponding Ni/Cr, Ni/Co, and Cr/Co ratios of impact glass spherules and spherule fragments that were recovered from the reworked fallout deposits and from terrace outcrops of the Enmyvaam River approximately 10 km southeast of the crater center. Mixing calculations support the presence of approximately 0.05 wt% and 0.50-18 wt% of ordinary chondrite (possibly type-LL) in several impactites and in the glassy spherules, respectively. The heterogeneous distribution of the meteoritic component provides clues for emplacement mechanisms of the various impactite units.

  12. Climatic Impact on Major and Trace Elements in Deltaic Core Sediments: Evidence from Muthupet Lagoon, South East Coast of India

    NASA Astrophysics Data System (ADS)

    Jayaprakash, M.; Velmurugan, P. M.; Giridharan, L.; Urban, B.

    2013-05-01

    Geochemistry of lagoon deposits provides a continuous record of climatic changes, and such core sediments at successive deeper and older layers have long been utilized for sedimentologic, and organic geochemical studies. These ecosystems provide a mechanism for trapping sediment and can act as a recorder of climatic changes via geochemical imprints. The aim of the present study is to evaluate the climatic and depositional controls in the Muthupet lagoon, Southeast coast of India, situated at the southern most end of the Cauvery delta. The down core variations of geochemical parameters and their ratios were employed to reveal the characteristics of Holocene climate and associated paleoenvironmental implications of the study area. Moderate values of the Chemical Index of Alteration (CIA) suggest intensive chemical weathering of the source rock under tropical to subtropical climatic conditions. Index of Composition Variability (ICV) values indicate low proportion of nonclay silicate minerals in these sediments. V/Cr ratio has been used as a paleo-oxygenation indicator and in the present study, the ratio V/Cr was found to be < 2 indicating oxic-depositional conditions prevailing in this lagoon. Ni/Co, Ni/V and (Cu+Mg)/Zn ratios of the sediments are evaluated and the variations are interpreted to reflect the changes in the input from the marine environment. Fe/Ti and Fe/Al ratios yields valuable information on the impact of climate changes on the sedimentation of the study areas. Na and S, indicators of paleosalinity and marine flooding have been evaluated. The increase in the concentration of Na at various depths was identified and the marine incursions were characterized.

  13. Trace elements in South America aerosol during 20th century inferred from a Nevado Illimani ice core, Eastern Bolivian Andes (6350 m a.s.l.)

    NASA Astrophysics Data System (ADS)

    Correia, A.; Freydier, R.; Delmas, R. J.; Simões, J. C.; Taupin, J.-D.; Dupré, B.; Artaxo, P.

    2003-05-01

    A 137 m ice core drilled in 1999 from Eastern Bolivian Andes at the summit of Nevado Illimani (16° 37' S, 67° 46' W, 6350 m a.s.l.) was analyzed at high temporal resolution, allowing a characterization of trace elements in Andean aerosol trapped in the ice during the 20th century. The upper 50 m of the ice core were dated by multi-proxy analysis of stable isotopes (d18O and d2H), 137Cs and Ca+2 content, electrical conductivity, and insoluble microparticle content, together with reference historical horizons from atmospheric nuclear tests and known volcanic eruptions. This 50 m section corresponds to a record of environmental variations spanning about 80 years from 1919 to 1999. It was cut in 744 sub-samples under laminar flow in a clean bench, which were analyzed by Ion Chromatography for major ionic concentration, by a particle counter for insoluble aerosol content, and by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for the concentration of 45 chemical species from Li to U. This paper focuses on results of trace element concentrations measured by ICP-MS. The high temporal resolution used in the analyses allowed classifying samples as belonging to dry or wet seasons. During wet season elemental concentrations are low and samples show high crustal enrichment factors. During dry seasons the situation is opposite, with high elemental concentrations and low crustal enrichments. For example, with salt lakes as main sources in the region, average Li concentration during the 20th century is 0.035 and 0.90 ng g-1 for wet and dry seasons, respectively. Illimani average seasonal concentration ranges cover the spectrum of elemental concentration measurements at another Andean ice core site (Sajama) for most soil-related elements. Regional crustal dust load in the deposits was found to be overwhelming during dry season, obfuscating the contribution of biomass burning material. Marked temporal trends from the onset of 20th century to more recent years were

  14. Paleoceanographic changes in the Ulleung Basin, East (Japan) Sea, during the last 20,000 years: Evidence from variations in element composition of core sediments

    NASA Astrophysics Data System (ADS)

    Lim, Dhongil; Xu, Zhaokai; Choi, Jinyong; Kim, Soyoung; Kim, Eunhee; Kang, Sora; Jung, Hoisoo

    2011-01-01

    A millennial-scale paleoceanographic record of the Ulleung Basin in the southern part of the East (Japan) Sea (ES) for the last 20,000 years was reconstructed based on variations in the element compositions of core sediment. Most of the elements showed relatively wide content ranges throughout the core, largely because of different sediment types, their grain size spectra, biological components, and geochemical conditions (i.e., redox conditions). In particular, biogenic components (Ca, Sr, Ba, and CaCO 3) and some minor elements (Cu, Mn, Mo, U, Cd, Zn, and V) revealed three distinct intervals of major paleoceanographic changes. Interval 1 (∼18-9.3 kyr BP) is characterized by a rhythmic alternation of dark- and light-colored sediment bands. Distinctive differences in the abundance of organic carbon, carbonate, and redox-elements between the dark- and light-colored-sediment layers are probably attributable to especially those associated with bottom-water redox variations combined with the enhanced primary productivity and water stratification in the Ulleung Basin. These alternations perhaps reflect fluctuations in paleo-discharge from Chinese and/or Korean rivers during the last deglaciation. From a global perspective, the repetition of dark sapropelic sediment layers suggests a possible teleconnection between oceanographic change and development of the East Asian summer monsoon and consequent fluctuations in fluvial discharge from Korean and Chinese rivers to the East Sea basin. In Interval 2 (9.3-6.5 kyr BP), a remarkable increase in the concentrations of organic carbon and redox elements is probably linked to the intrusion of the warm/saline Tsushima Current to the basin, which would have enhanced ventilation and upwelling of nutrient-rich sub-surface waters. In parallel, a pronounced decrease in carbonate content indicates extensive carbonate dissolution due to the consumption of large amounts of free pore-water oxygen in surface sediments that would have

  15. Amyloid Core Formed of Full-Length Recombinant Mouse Prion Protein Involves Sequence 127–143 but Not Sequence 107–126

    PubMed Central

    Chatterjee, Biswanath; Lee, Chung-Yu; Lin, Chen; Chen, Eric H.-L.; Huang, Chao-Li; Yang, Chien-Chih; Chen, Rita P.-Y.

    2013-01-01

    The principal event underlying the development of prion disease is the conversion of soluble cellular prion protein (PrPC) into its disease-causing isoform, PrPSc. This conversion is associated with a marked change in secondary structure from predominantly α-helical to a high β-sheet content, ultimately leading to the formation of aggregates consisting of ordered fibrillar assemblies referred to as amyloid. In vitro, recombinant prion proteins and short prion peptides from various species have been shown to form amyloid under various conditions and it has been proposed that, theoretically, any protein and peptide could form amyloid under appropriate conditions. To identify the peptide segment involved in the amyloid core formed from recombinant full-length mouse prion protein mPrP(23–230), we carried out seed-induced amyloid formation from recombinant prion protein in the presence of seeds generated from the short prion peptides mPrP(107–143), mPrP(107–126), and mPrP(127–143). Our results showed that the amyloid fibrils formed from mPrP(107–143) and mPrP(127–143), but not those formed from mPrP(107–126), were able to seed the amyloidogenesis of mPrP(23–230), showing that the segment residing in sequence 127–143 was used to form the amyloid core in the fibrillization of mPrP(23–230). PMID:23844138

  16. Trace element fluxes and natural potential risks from 210Pb-dated sediment cores in lacustrine environments at the Central Mexican Plateau.

    PubMed

    Ontiveros-Cuadras, J F; Ruiz-Fernández, A C; Sanchez-Cabeza, J A; Pérez-Bernal, L H; Sericano, J L; Preda, M; Wee Kwong, L Liong; Páez-Osuna, F

    2014-01-15

    The accumulation, enrichment and provenance of selected trace metals (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, V and Zn) were studied in sediment cores collected from three lakes located in the Central Mexican Plateau, selected on the basis of their contrasting degree of urbanization: Santa Elena Lake, in a rural and remote area; El Tule Lake, in a rural and slightly urbanized area; and Chapala Lake, in a highly urbanized area. Grain size, magnetic susceptibility and sedimentary constituents such as organic carbon, calcium carbonate, as well as major (Al, Fe, Mn) and minor (Ca, Li, Rb, Sr, Th) elements were analyzed to explain the concentration trends of trace metals. Factor analysis (FA) was used to assess the provenance of the trace elements. The highest metal enrichment factor (EF) above natural concentration levels was found at Chapala Lake for Ag (EF = 3.9), although other trace element EF in all lakes was <2.0, indicating slight contamination. However, the concentration levels of Cr and Ni in all lakes, Hg and Zn in Chapala Lake, Cu in El Tule Lake and As in Santa Elena Lake were above international benchmarks for which adverse effects are expected to occur frequently, even for those metals only slightly enriched (e.g. As, Cr). Through FA, the terrigenous contribution was identified as the most important source of trace metals to the three lakes, most likely related to deforestation and erosion of the surrounding areas, followed by atmospheric transport of volcanic ashes, rather than to direct sources. PMID:24061059

  17. NUCLEAR REACTOR CORE DESIGN

    DOEpatents

    Mahlmeister, J.E.; Peck, W.S.; Haberer, W.V.; Williams, A.C.

    1960-03-22

    An improved core design for a sodium-cooled, graphitemoderated nuclear reactor is described. The improved reactor core comprises a number of blocks of moderator material, each block being in the shape of a regular prism. A number of channels, extending the length of each block, are disposed around the periphery. When several blocks are placed in contact to form the reactor core, the channels in adjacent blocks correspond with each other to form closed conduits extending the length of the core. Fuel element clusters are disposed in these closed conduits, and liquid coolant is forced through the annulus between the fuel cluster and the inner surface of the conduit. In a preferred embodiment of the invention, the moderator blocks are in the form of hexagonal prisms with longitudinal channels cut into the corners of the hexagon. The main advantage of an "edge-loaded" moderator block is that fewer thermal neutrons are absorbed by the moderator cladding, as compared with a conventional centrally loaded moderator block.

  18. The structure of a tetrameric α-carbonic anhydrase from Thermovibrio ammonificans reveals a core formed around intermolecular disulfides that contribute to its thermostability.

    PubMed

    James, Paul; Isupov, Michail N; Sayer, Christopher; Saneei, Vahid; Berg, Svein; Lioliou, Maria; Kotlar, Hans Kristian; Littlechild, Jennifer A

    2014-10-01

    Carbonic anhydrase enzymes catalyse the reversible hydration of carbon dioxide to bicarbonate. A thermophilic Thermovibrio ammonificans α-carbonic anhydrase (TaCA) has been expressed in Escherichia coli and structurally and biochemically characterized. The crystal structure of TaCA has been determined in its native form and in two complexes with bound inhibitors. The tetrameric enzyme is stabilized by a unique core in the centre of the molecule formed by two intersubunit disulfides and a single lysine residue from each monomer that is involved in intersubunit ionic interactions. The structure of this core protects the intersubunit disulfides from reduction, whereas the conserved intrasubunit disulfides are not formed in the reducing environment of the E. coli host cytosol. When oxidized to mimic the environment of the periplasmic space, TaCA has increased thermostability, retaining 90% activity after incubation at 70°C for 1 h, making it a good candidate for industrial carbon-dioxide capture. The reduction of all TaCA cysteines resulted in dissociation of the tetrameric molecule into monomers with lower activity and reduced thermostability. Unlike other characterized α-carbonic anhydrases, TaCA does not display esterase activity towards p-nitrophenyl acetate, which appears to result from the increased rigidity of its protein scaffold. PMID:25286845

  19. Mobile 3D television: development of core technological elements and user-centered evaluation methods toward an optimized system

    NASA Astrophysics Data System (ADS)

    Gotchev, Atanas; Smolic, Aljoscha; Jumisko-Pyykkö, Satu; Strohmeier, Dominik; Bozdagi Akar, Gozde; Merkle, Philipp; Daskalov, Nikolai

    2009-02-01

    A European consortium of six partners has been developing core technological components of a mobile 3D television system over DVB-H channel. In this overview paper, we present our current results on developing optimal methods for stereo-video content creation, coding and transmission and emphasize their significance for the power-constrained mobile platform, equipped with auto-stereoscopic display. We address the user requirements by applying modern usercentered approaches taking into account different user groups and usage contexts in contrast to the laboratory assessment methods which, though standardized, offer limited applicability to real applications. To this end, we have been aiming at developing a methodological framework for the whole system development process. One of our goals has been to further develop the user-centered approach towards experienced quality of critical system components. In this paper, we classify different research methods and technological solutions analyzing their pros and constraints. Based on this analysis we present the user-centered methodological framework being used throughout the whole development process of the system and aimed at achieving the best performance and quality appealing to the end user.

  20. The CCAN recruits CENP-A to the centromere and forms the structural core for kinetochore assembly

    PubMed Central

    Hori, Tetsuya; Shang, Wei-Hao; Takeuchi, Kozo

    2013-01-01

    CENP-A acts as an important epigenetic marker for kinetochore specification. However, the mechanisms by which CENP-A is incorporated into centromeres and the structural basis for kinetochore formation downstream of CENP-A remain unclear. Here, we used a unique chromosome-engineering system in which kinetochore proteins are targeted to a noncentromeric site after the endogenous centromere is conditionally removed. Using this system, we created two distinct types of engineered kinetochores, both of which were stably maintained in chicken DT40 cells. Ectopic targeting of full-length HJURP, CENP-C, CENP-I, or the CENP-C C terminus generated engineered kinetochores containing major kinetochore components, including CENP-A. In contrast, ectopic targeting of the CENP-T or CENP-C N terminus generated functional kinetochores that recruit the microtubule-binding Ndc80 complex and chromosome passenger complex (CPC), but lack CENP-A and most constitutive centromere-associated network (CCAN) proteins. Based on the analysis of these different engineered kinetochores, we conclude that the CCAN has two distinct roles: recruiting CENP-A to establish the kinetochore and serving as a structural core to directly recruit kinetochore proteins. PMID:23277427

  1. ELM - A SIMPLE TOOL FOR THERMAL-HYDRAULIC ANALYSIS OF SOLID-CORE NUCLEAR ROCKET FUEL ELEMENTS

    NASA Technical Reports Server (NTRS)

    Walton, J. T.

    1994-01-01

    ELM is a simple computational tool for modeling the steady-state thermal-hydraulics of propellant flow through fuel element coolant channels in nuclear thermal rockets. Written for the nuclear propulsion project of the Space Exploration Initiative, ELM evaluates the various heat transfer coefficient and friction factor correlations available for turbulent pipe flow with heat addition. In the past, these correlations were found in different reactor analysis codes, but now comparisons are possible within one program. The logic of ELM is based on the one-dimensional conservation of energy in combination with Newton's Law of Cooling to determine the bulk flow temperature and the wall temperature across a control volume. Since the control volume is an incremental length of tube, the corresponding pressure drop is determined by application of the Law of Conservation of Momentum. The size, speed, and accuracy of ELM make it a simple tool for use in fuel element parametric studies. ELM is a machine independent program written in FORTRAN 77. It has been successfully compiled on an IBM PC compatible running MS-DOS using Lahey FORTRAN 77, a DEC VAX series computer running VMS, and a Sun4 series computer running SunOS UNIX. ELM requires 565K of RAM under SunOS 4.1, 360K of RAM under VMS 5.4, and 406K of RAM under MS-DOS. Because this program is machine independent, no executable is provided on the distribution media. The standard distribution medium for ELM is one 5.25 inch 360K MS-DOS format diskette. ELM was developed in 1991. DEC, VAX, and VMS are trademarks of Digital Equipment Corporation. Sun4 and SunOS are trademarks of Sun Microsystems, Inc. IBM PC is a registered trademark of International Business Machines. MS-DOS is a registered trademark of Microsoft Corporation.

  2. Major Cation, Carbon System and Trace Element Chemistry in Pore Waters from a Depth Transect of Cores on the Iberian Margin: Implications for Paleoproxies.

    NASA Astrophysics Data System (ADS)

    Greaves, M.; Elderfield, H.; Hodell, D. A.; Skinner, L. C.; Sevilgen, D.; Grauel, A. L.; de la Fuente, M.; Misra, S.

    2014-12-01

    A significant body of work exists on the chemistry of pore waters from DSDP and ODP drilling cores (e.g. Gieskes 1975; Sayles 1981) showing large gradients in sea salt cations and anions interpreted in terms of diagenetic reactions such as the formation of Mg-rich clays and dolomite formation (Higgins and Schrag, 2010). Another class of diagenetic reactions involves the breakdown of organic matter and trace element behaviour (Froelich et al., 1979). The translation of chemical gradients into fluxes requires estimates of pore water chemistry across the sea water - sediment surface boundary. Additionally, the use of the chemistry of benthic foraminiferal calcite for seawater paleochemistry requires estimation of the chemistry of pore waters which may differ from that of bottom seawater because of diagenetic reactions. In this work we have collected multi core samples from 10 core sites on cruise RRS James Cook JC089 on the southwest Iberian continental margin. Pore waters were extracted from the core surface and at 1 cm depth intervals down core (typically to ~40 cm depth) using Rhizon samplers and analysed for Alkalinity, DIC, ∂13C and Na, K, Mg, Ca, Li, Mn, Fe, Ba, B, Sr by atomic emission spectrophotometry as well as O2 penetration and pH by microelectrodes. This has allowed us to inspect chemical behavior at the bottom water - sediment interface. Some examples of results are a large gradient in ∂13C of DIC, the similarity of zero O2 penetration followed by an increase in Mn concentration and then decrease to zero, the similarity of Li to Mn and, in contrast to much DSDP/ODP work, Ca2+ and Mg2+both decrease with depth in pore waters near the sediment surface. References: Gieskes J.M. Annu. Rev. Earth Planet. Sci. 3, 433 (1975). Sayles F. L. Geochim. Cosmochim. Acta45, 1061 (1981). Higgins J.A. and D.P. Schrag. Geochim. Cosmochim. Acta.74, 5039 (2010). Froelich, P.N., et al., Geochim. Cosmochim. Acta. 43, 1075 (1979).

  3. On the effective implementation of a boundary element code on graphics processing units unsing an out-of-core LU algorithm

    SciTech Connect

    D'Azevedo, Ed F; Nintcheu Fata, Sylvain

    2012-01-01

    A collocation boundary element code for solving the three-dimensional Laplace equation, publicly available from \\url{http://www.intetec.org}, has been adapted to run on an Nvidia Tesla general purpose graphics processing unit (GPU). Global matrix assembly and LU factorization of the resulting dense matrix were performed on the GPU. Out-of-core techniques were used to solve problems larger than available GPU memory. The code achieved over eight times speedup in matrix assembly and about 56~Gflops/sec in the LU factorization using only 512~Mbytes of GPU memory. Details of the GPU implementation and comparisons with the standard sequential algorithm are included to illustrate the performance of the GPU code.

  4. APEX/SABOCA observations of small-scale structure of infrared-dark clouds . I. Early evolutionary stages of star-forming cores

    NASA Astrophysics Data System (ADS)

    Ragan, Sarah E.; Henning, Thomas; Beuther, Henrik

    2013-11-01

    Infrared-dark clouds (IRDCs) harbor the early phases of cluster and high-mass star formation and are comprised of cold (~20 K), dense (n > 104 cm-3) gas. The spectral energy distribution (SED) of IRDCs is dominated by the far-infrared and millimeter wavelength regime, and our initial Herschel study examined IRDCs at the peak of the SED with high angular resolution. Here we present a follow-up study using the SABOCA instrument on APEX which delivers 7.8″ angular resolution at 350 μm, matching the resolution we achieved with Herschel/PACS, and allowing us to characterize substructure on ~0.1 pc scales. Our sample of 11 nearby IRDCs are a mix of filamentary and clumpy morphologies, and the filamentary clouds show significant hierarchical structure, while the clumpy IRDCs exhibit little hierarchical structure. All IRDCs, regardless of morphology, have about 14% of their total mass in small scale core-like structures which roughly follow a trend of constant volume density over all size scales. Out of the 89 protostellar cores we identified in this sample with Herschel, we recover 40 of the brightest and re-fit their SEDs and find their properties agree fairly well with our previous estimates (⟨ T ⟩ ~ 19 K). We detect a new population of "cold cores" which have no 70 μm counterpart, but are 100 and 160 μm-bright, with colder temperatures (⟨ T ⟩ ~ 16 K). This latter population, along with SABOCA-only detections, are predominantly low-mass objects, but their evolutionary diagnostics are consistent with the earliest starless or prestellar phase of cores in IRDCs. Based on observations carried out with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between Max Planck Institut für Radioastronomie (MPIfR), Onsala Space Observatory (OSO), and the European Southern Observatory (ESO).Appendices are available in electronic form at http://www.aanda.org

  5. Systematically convergent basis sets with relativistic pseudopotentials. II. Small-core pseudopotentials and correlation consistent basis sets for the post-d group 16-18 elements

    SciTech Connect

    Peterson, Kirk A.; Figgen, Detlev; Goll, Erich; Stoll, Hermann; Dolg, Michael F.

    2003-12-01

    Series of correlation consistent basis sets have been developed for the post-d group 16-18 elements in conjunction with small-core relativistic pseudopotentials (PPs) of the energy-consistent variety. The latter were adjusted to multiconfiguration Dirac-Hartree-Fock data based on the Dirac-Coulomb-Breit Hamiltonian. The outer-core (n-1)spd shells are explicitly treated together with the nsp valence shell with these PPs. The accompanying cc-pVnZ-PP and aug-cc-pVnZ-PP basis sets range in size from DZ to 5Z quality and yield systematic convergence of both Hartree-Fock and correlated total energies. In addition to the calculation of atomic electron affinities and dipole polarizabilities of the rare gas atoms, numerous molecular benchmark calculations (HBr, HI, HAt, Br2, I2, At2, SiSe, SiTe, SiPo, KrH+, XeH+, and RnH+) are also reported at the coupled cluster level of theory. For the purposes of comparison, all-electron calculations using the Douglas-Kroll-Hess Hamiltonian have also been carried out for the halogen-containing molecules using basis sets of 5Z quality.

  6. Micro-patterns of Au@SiO 2 core-shell nanoparticles formed by electrostatic interactions

    NASA Astrophysics Data System (ADS)

    Qi, Youli; Chen, Miao; Liang, Shan; Yang, Wu; Zhao, Jing

    2008-01-01

    In this paper, silica-coated Au nanoparticles (Au@SiO 2) were prepared by the technique of vortex mixing. Subsequently, these monodisperse Au@SiO 2 nanoparticles were functionalized by the silane reagents 3-aminopropyltriethoxysilane (APS) and 3-mercaptopropyltriethoxysilane (MPTS) respectively. Then, these NH 2-terminated and SO 32--terminated Au@SiO 2 nanoparticles were respectively assembled onto the substrates, which have been patterned with different self-assembly monolayers (SAMs), to form close-packed two-dimensional Au@SiO 2 nanoparticle arrays by electrostatic interactions. The morphologies and the optical properties of Au@SiO 2 nanoparticles with different silica-shell thicknesses were characterized by TEM and UV-vis. The compositions and zeta potentials of the functionalized Au@SiO 2 nanoparticles were examined by X-ray photoelectron spectroscopy (XPS) and dynamic light scattering (DLS). The morphologies of the patterns formed on different templates were characterized by atomic force microscopy (AFM).

  7. An N-terminal extension to the hepatitis B virus core protein forms a poorly ordered trimeric spike in assembled virus-like particles

    PubMed Central

    McGonigle, Richard; Yap, Wei Boon; Ong, Swee Tin; Gatherer, Derek; Bakker, Saskia E.; Tan, Wen Siang; Bhella, David

    2015-01-01

    Virus-like particles composed of the core antigen of hepatitis B virus (HBcAg) have been shown to be an effective platform for the display of foreign epitopes in vaccine development. Heterologous sequences have been successfully inserted at both amino and carboxy termini as well as internally at the major immunodominant epitope. We used cryogenic electron microscopy (CryoEM) and three-dimensional image reconstruction to investigate the structure of VLPs assembled from an N-terminal extended HBcAg that contained a polyhistidine tag. The insert was seen to form a trimeric spike on the capsid surface that was poorly resolved, most likely owing to it being flexible. We hypothesise that the capacity of N-terminal inserts to form trimers may have application in the development of multivalent vaccines to trimeric antigens. Our analysis also highlights the value of tools for local resolution assessment in studies of partially disordered macromolecular assemblies by cryoEM. PMID:25557498

  8. Element partitioning during core-mantle differentiation in a magma ocean: New high-pressure data on CI- and EH-chondrite model compositions

    NASA Astrophysics Data System (ADS)

    Corgne, A.; Keshav, S.; McDonough, W. F.; Fei, Y.

    2005-12-01

    High-pressure metal-silicate partitioning experiments demonstrate that the mantle contents of some siderophile elements are consistent with equilibration between molten silicate and molten metal at high pressures and high temperatures. This conclusion is a solid argument for the `magma ocean theory'. This study is aimed at constraining the factors affecting major and trace element partitioning during core formation in a magma ocean. We report on a series of partitioning experiments between molten metal and silicate melt on CI- and EH-chondrite model compositions. Two CI-model compositions are used, one S-free and one with 2 wt% S. Oxidation state ranges from IW-2.2 in runs using CI chondrites to IW-4.6 in the runs using EH chondrite. Data were obtained by EPMA and LA-ICPMS at 3.6 and 7.7 GPa. As expected, partition coefficient (D) for S increases with increasing pressure (DS=15 at 3.6 GPa, 90 at 7.7 GPa). Fe, Si, Ti, Cr, Mn, Ga, Nb and Ta have Ds significantly higher at lower oxygen fugacity, with DSi=0.4 and DFe=200 at IW-4.6 (DSi<0.0004 and DFe=10 at IW-2.2). Cr, Mn, Nb, and Ta become compatible (D>1) in molten metal at IW-4.6. At both 3.6 and 7.7 GPa, DCr=25, DMn=1.7 and DTa=10. In contrast DNb increases with increasing pressure at IW-4.6: DNb=130 at 3.6 GPa and DNb=240 at 7.7 GPa. Similarly, at IW-4.6, DGa increases with increasing pressure: DGa=50 at 3.6 GPa and DGa=100 at 7.7 GPa. This behavior is opposite to the one observed at higher oxygen fugacity (IW-2.2) where DGa decreases with increasing pressure: DGa=5-6.5 at 3.6 GPa and DGa=1.3-1.5 at 7.7 GPa, for S-bearing and S-free CI-chondrite respectively. Also, Ti is affected by the oxidation state and pressure conditions: DTi<0.1 at IW-2.2, but at IW-4.6 DTi=0.4 at 3.6 GPa and DTi=0.25 at 7.7 GPa. Our results show that over the conditions of pressure-temperature-oxygen fugacity of this study refractory lithophile elements are highly incompatible in molten metal: DAl<0.004, DMg<0.0004, DCa<0.01, DSc<0.05, DNd

  9. Magnetic Signatures of Nectarian-Aged Lunar Basin-Forming Impacts: Probable Evidence for a Former Core Dynamo

    NASA Astrophysics Data System (ADS)

    Hood, Lon

    2010-05-01

    Previous analyses of Lunar Prospector magnetometer (MAG) and electron reflectometer (ER) data have shown that impact processes played an important role in producing the observed crustal magnetization. In particular, the largest areas of strong anomalies occur antipodal to the youngest large basins and correlative studies indicate that basin ejecta materials are important anomaly sources. Models suggest that transient fields generated by the expansion of impact vapor-melt clouds in the presence of an initial solar wind magnetic field are sufficient to explain the antipodal anomalies (Hood and Artemieva, Icarus, v. 193, p. 485, 2008). However, analyses of ER data have also shown that some anomalies are present within Nectarian-aged basins including Moscoviense, Mendel-Rydberg, and Crisium (Halekas et al., Meteorit. Planet. Sci., v. 38, p. 565, 2003). These latter anomalies could be due either to thermoremanence (TRM) in impact melt or to shock remanence in the central uplift. The former interpretation would require a long-lived, steady magnetizing field, consistent with a core dynamo, while the latter interpretation could in principle be explained by an impact-generated field. Here, LP MAG data are applied to produce more detailed regional maps of magnetic anomalies within selected Nectarian basins. Anomalies within the Crisium basin, in particular, are located inside the inner rim edges and are clearly genetically associated with the basin (rather than being due to ejecta from younger basins superposed on Crisium). An analysis of the vector field components shows that the directions of magnetization of the two main sources are close to parallel within the errors of the modeling. These anomalies are therefore most probably due to TRM of impact melt that cooled in a steady, large-scale field. In addition, the paleomagnetic pole position calculated for the strongest and most isolated anomaly lies close to the present rotational pole. Assuming no true polar wander since

  10. Study of the core-corona structure formed during the explosion of an aluminum wire in vacuum

    SciTech Connect

    Tkachenko, S. I.; Mingaleev, A. R.; Pikuz, S. A.; Romanova, V. M.; Khattatov, T. A.; Shelkovenko, T. A.; Ol'khovskaya, O. G.; Gasilov, V. A.; Kalinin, Yu. G.

    2012-01-15

    The time evolution of the matter parameters and current distribution in the discharge channel formed during a nanosecond explosion of a 25-{mu}m-diameter 12-mm-long aluminum wire was studied in a series of experiments with the following parameters: the discharge voltage was U{sub 0} = 20 kV, the current amplitude was I{sub max} {approx} 8 kA, and the current rise rate was dI/dt {approx} 40 A/ns. Optical shadow and schlieren images of the discharge channel were obtained using the second harmonic of a YAG: Nd{sup +3} laser, and UV images of the discharge channel self-radiation were recorded using a four-frame camera with a microchannel plate. The process of aluminum wire explosion was simulated numerically (including simulations performed from the 'cold start'). The numerical results were compared with the experimental data.

  11. FUEL ELEMENT FOR NUCLEAR REACTORS

    DOEpatents

    Dickson, J.J.

    1963-09-24

    A method is described whereby fuel tubes or pins are cut, loaded with fuel pellets and a heat transfer medium, sealed at each end with slotted fittings, and assembled into a rectangular tube bundle to form a fuel element. The tubes comprising the fuel element are laterally connected between their ends by clips and tabs to form a linear group of spaced parallel tubes, which receive their vertical support by resting on a grid. The advantages of this method are that it permits elimination of structural material (e.g., fuel-element cans) within the reactor core, and removal of at least one fuel pin from an element and replacement thereof so that a burnable poison may be utilized during the core lifetime. (AEC)

  12. Two-component relativistic density-functional calculations of the dimers of the halogens from bromine through element 117 using effective core potential and all-electron methods.

    PubMed

    Mitin, Alexander V; van Wüllen, Christoph

    2006-02-14

    A two-component quasirelativistic Hamiltonian based on spin-dependent effective core potentials is used to calculate ionization energies and electron affinities of the heavy halogen atom bromine through the superheavy element 117 (eka-astatine) as well as spectroscopic constants of the homonuclear dimers of these atoms. We describe a two-component Hartree-Fock and density-functional program that treats spin-orbit coupling self-consistently within the orbital optimization procedure. A comparison with results from high-order Douglas-Kroll calculations--for the superheavy systems also with zeroth-order regular approximation and four-component Dirac results--demonstrates the validity of the pseudopotential approximation. The density-functional (but not the Hartree-Fock) results show very satisfactory agreement with theoretical coupled cluster as well as experimental data where available, such that the theoretical results can serve as an estimate for the hitherto unknown properties of astatine, element 117, and their dimers. PMID:16483205

  13. Nuclear fuel element

    DOEpatents

    Armijo, Joseph S.; Coffin, Jr., Louis F.

    1980-04-29

    A nuclear fuel element for use in the core of a nuclear reactor is disclosed and has an improved composite cladding comprised of a moderate purity metal barrier of zirconium metallurgically bonded on the inside surface of a zirconium alloy tube. The metal barrier forms a shield between the alloy tube and a core of nuclear fuel material enclosed in the composite cladding. There is a gap between the cladding and the core. The metal barrier forms about 1 to about 30 percent of the thickness of the composite cladding and has low neutron absorption characteristics. The metal barrier serves as a preferential reaction site for gaseous impurities and fission products and protects the alloy tube from contact and reaction with such impurities and fission products. Methods of manufacturing the composite cladding are also disclosed.

  14. Monitoring arrangement for vented nuclear fuel elements

    DOEpatents

    Campana, Robert J.

    1981-01-01

    In a nuclear fuel reactor core, fuel elements are arranged in a closely packed hexagonal configuration, each fuel element having diametrically opposed vents permitting 180.degree. rotation of the fuel elements to counteract bowing. A grid plate engages the fuel elements and forms passages for communicating sets of three, four or six individual vents with respective monitor lines in order to communicate vented radioactive gases from the fuel elements to suitable monitor means in a manner readily permitting detection of leakage in individual fuel elements.

  15. The origin of metamorphic core complexes and detachment faults formed during Tertiary continental extension in the northern Colorado River region, U.S.A.

    NASA Astrophysics Data System (ADS)

    Lister, Gordon S.; Davis, Gregory A.

    Metamorphic core complexes form as the result of major continental extension, when the middle and lower continental crust is dragged out from beneath the fracturing, extending upper crust. Movement zones capable of producing such effects evolve in space as well as with time. Deforming rocks in the footwall are uplifted through a progression of different metamorphic and deformational environments, producing a characteristic sequence of (overprinted) meso- and microstructures. The movement zone is folded as the result of the bowing upwards of the lower crust to form a broad basement culmination, as the result of isostatic rebound due to tectonic denudation, but most likely also as the result of local isostatic adjustments due to granite intrusion in the middle crust. A succession of splays branch off from the master detachment fault at depth, excising substantial portions of the lower portions of the upper plate as successive detachment faults eat upwards through it. At the same time, detachment faults incise into progressively deeper levels of the lower plate, although the amount of incision is limited, because the locus of movement remains at approximately the same level in the lower plate. The detachment faults presently observed in the metamorphic core complexes are relatively young features, formed late in the geological evolution of these bodies, and are only the last in a succession of low-angle normal faults that sliced through the upper crust at the upward terminations of major, shallow-dipping, ductile shear zones in the extending Cordilleran orogen. Excisement of listric fault bottoms can explain some of the enigmatic domino-like fault blocks, and other structural relations observed in these terranes. Evidence in support of this model is illustrated from detachment terranes in the northern Colorado River region of southern Nevada, southeastern California and western Arizona, where multiple generations of detachment faults have produced remarkable

  16. Polar Order and Symmetry Breaking at the Boundary between Bent-Core and Rodlike Molecular Forms: When 4-Cyanoresorcinol Meets the Carbosilane End Group.

    PubMed

    Westphal, Eduard; Gallardo, Hugo; Caramori, Giovanni Finoto; Sebastián, Nerea; Tamba, Maria-Gabriela; Eremin, Alexey; Kawauchi, Susumu; Prehm, Marko; Tschierske, Carsten

    2016-06-01

    Two isomeric achiral bent-core liquid crystals involving a 4-cyanoresorcinol core and containing a carbosilane unit as nanosegregating segment were synthesized and were shown to form ferroelectric liquid-crystalline phases. Inversion of the direction of one of the COO groups in these molecules leads to a distinct distribution of the electrostatic potential along the surface of the molecule and to a strong change of the molecular dipole moments. Thus, a distinct degree of segregation of the carbosilane units and consequent modification of the phase structure and coherence length of polar order result. For the compound with larger dipole moment (CN1) segregation of the carbosilane units is suppressed, and this compound forms paraelectric SmA and SmC phases; polar order is only achieved after transition to a new LC phase, namely, the ferroelectric leaning phase (SmCLs PS ) with the unique feature that tilt direction and polar direction coincide. The isomeric compound CN2 with a smaller dipole moment forms separate layers of the carbosilane groups and shows a randomized polar SmA phase (SmAPAR ) and ferroelectric polydomain SmCs PS phases with orthogonal combination of tilt and polar direction and much higher polarizations. Thus, surprisingly, the compound with the smaller molecular dipole moment shows increased polar order in the LC phases. Besides ferroelectricity, mirror-symmetry breaking with formation of a conglomerate of macroscopic chiral domains was observed in one of the SmC phases of CN1. These investigations contribute to the general understanding of the development of polar order and chirality in soft matter. PMID:27143620

  17. Modal element method for potential flow in non-uniform ducts: Combining closed form analysis with CFD

    NASA Technical Reports Server (NTRS)

    Baumeister, Kenneth J.; Baumeister, Joseph F.

    1994-01-01

    An analytical procedure is presented, called the modal element method, that combines numerical grid based algorithms with eigenfunction expansions developed by separation of variables. A modal element method is presented for solving potential flow in a channel with two-dimensional cylindrical like obstacles. The infinite computational region is divided into three subdomains; the bounded finite element domain, which is characterized by the cylindrical obstacle and the surrounding unbounded uniform channel entrance and exit domains. The velocity potential is represented approximately in the grid based domain by a finite element solution and is represented analytically by an eigenfunction expansion in the uniform semi-infinite entrance and exit domains. The calculated flow fields are in excellent agreement with exact analytical solutions. By eliminating the grid surrounding the obstacle, the modal element method reduces the numerical grid size, employs a more precise far field boundary condition, as well as giving theoretical insight to the interaction of the obstacle with the mean flow. Although the analysis focuses on a specific geometry, the formulation is general and can be applied to a variety of problems as seen by a comparison to companion theories in aeroacoustics and electromagnetics.

  18. On the implementation of the continuum shell finite element SHB8PS and application to sheet forming simulation

    NASA Astrophysics Data System (ADS)

    Salahouelhadj, A.; Abed-Meraim, F.; Chalal, H.; Balan, T.

    2011-05-01

    In this contribution, the formulation of the SHB8PS continuum shell finite element is extended to anisotropic elastic-plastic behavior models with combined isotropic-kinematic hardening at large deformations. The resulting element is then implemented into the commercial implicit finite element code Abaqus/Standard via the UEL subroutine. The SHB8PS element is an eight-node, three-dimensional brick with displacements as the only degrees of freedom and a preferential direction called the thickness. A reduced integration scheme is adopted using an arbitrary number of integration points along the thickness direction and only one integration point in the other directions. The hourglass modes due to this reduced integration are controlled using a physical stabilization technique together with an assumed strain method for the elimination of locking. Therefore, the element can be used to model thin structures while providing an accurate description of the various through-thickness phenomena. Its performance is assessed through several applications involving different types of non-linearities: geometric, material and that induced by contact. Particular attention is given to springback prediction for a NUMISHEET benchmark problem.

  19. SUBMILLIMETER ARRAY OBSERVATIONS OF MAGNETIC FIELDS IN G240.31+0.07: AN HOURGLASS IN A MASSIVE CLUSTER-FORMING CORE

    SciTech Connect

    Qiu, Keping; Zhang, Qizhou; Menten, Karl M.; Liu, Hauyu B.; Tang, Ya-Wen; Girart, Josep M.

    2014-10-10

    We report the first detection of an hourglass magnetic field aligned with a well-defined outflow rotation system in a high-mass, star-forming region. The observations were performed with the Submillimeter Array toward G240.31+0.07, which harbors a massive, flattened, and fragmenting molecular cloud core and a wide-angle bipolar outflow. The polarized dust emission at 0.88 mm reveals a clear hourglass-shaped magnetic field aligned within 20° of the outflow axis. Maps of high-density tracing spectral lines, e.g., H{sup 13}CO{sup +} (4-3), show that the core is rotating about its minor axis, which is also aligned with the magnetic field axis. Therefore, both the magnetic field and kinematic properties observed in this region are surprisingly consistent with the theoretical predictions of the classic paradigm of isolated low-mass star formation. The strength of the magnetic field in the plane of sky is estimated to be ∼1.1 mG, resulting in a mass-to-magnetic flux ratio of 1.4 times the critical value and a turbulent-to-ordered magnetic energy ratio of 0.4. We also find that the specific angular momentum almost linearly decreases from r ∼ 0.6 pc to 0.03 pc scales, which is most likely attributed to magnetic braking.

  20. Synthesis of biocompatible poly(ɛ-caprolactone)- block-poly(propylene adipate) copolymers appropriate for drug nanoencapsulation in the form of core-shell nanoparticles

    PubMed Central

    Nanaki, Stavroula G; Pantopoulos, Kostas; Bikiaris, Dimitrios N

    2011-01-01

    Poly(propylene adipate)-block-poly(ɛ-caprolactone) copolymers were synthesized using a combination of polycondensation and ring-opening polymerization of ɛ-caprolactone in the presence of poly(propylene adipate). Gel permeation chromatography was used for molecular weight determination, whereas hydrogen-1 nuclear magnetic resonance and carbon-13 nuclear magnetic resonance spectroscopy were employed for copolymer characterization and composition evaluation. The copolymers were found to be block while their composition was similar to the feeding ratio. They formed semicrystalline structures, while only poly(ɛ-caprolactone) formed crystals, as shown by wide angle X-ray diffraction. Differential scanning calorimetry data suggest that the melting point and heat of fusion of copolymers decreased by increasing the poly(propylene adipate) amount. The synthesized polymers exhibited low cytotoxicity and were used to encapsulate desferrioxamine, an iron-chelating drug. The desferrioxamine nanoparticles were self-assembled into core shell structures, had mean particle size <250 nm, and the drug remained in crystalline form. Further studies revealed that the dissolution rate was mainly related to the melting temperature, as well as to the degree of crystallinity of copolymers. PMID:22162656

  1. Elemental carbon and polycyclic aromatic compounds in a 150-year sediment core from Lake Qinghai, Tibetan Plateau, China: influence of regional and local sources and transport pathways.

    PubMed

    Han, Y M; Wei, C; Bandowe, B A M; Wilcke, W; Cao, J J; Xu, B Q; Gao, S P; Tie, X X; Li, G H; Jin, Z D; An, Z S

    2015-04-01

    Elemental carbon (EC) and polycyclic aromatic compounds (PACs) are potential proxies for the reconstruction of change in human activities and the origin of air masses in historic times. In this study, the historic deposition of char and soot (the two subtypes of EC) and PACs in a 150-year sediment core from different topographic subbasins of Lake Qinghai on the Qinghai Tibetan Plateau (QTP) were reconstructed. The objective was to explore how the variations in the concentrations of EC and PACs, in the ratios of char to soot and of oxygenated polycyclic aromatic hydrocarbons (OPAHs) to parent PAHs, and in the composition of the PAC mixtures reflect historical changes in climate and human activity and the origin of air masses arriving at the QTP. The deposition fluxes of soot in the different subbasins were similar, averaging 0.18 (range of 0.15-0.25) and 0.16 (0.13-0.23) g m(-2) year(-1), respectively, but they varied for char (averaging 0.11 and 0.22 g m(-2) year(-1), respectively), suggesting ubiquitous atmospheric deposition of soot and local river inputs of char. The different vertical distributions of the char/soot ratios in the different subbasins can be interpreted in terms of the different transport mechanisms of char and soot. An abrupt increase in soot concentrations since 1980 coincides with results from the QTP ice cores that were interpreted to be indicative of soot transport from South Asia. Similar concentration patterns of PAHs with soot and 9,10-anthraquinone/anthracene (9,10-AQ/ANT) ratios all >2.0 suggest regional PAC sources. Increasing PAH/soot ratios and decreasing 9,10-AQ/ANT ratios since the beginning of the 1970s indicate increasing local emissions. The historical trends of these diagnostic ratios indicate an increase in the fossil-fuel contribution since the beginning of the 1970s. The increase of perylene concentrations with increasing core depth and the ratio of perylene to its penta-aromatic isomers indicate that perylene originates

  2. Controls on the distribution and fractionation of yttrium and rare earth elements in core sediments from the Mandovi estuary, western India

    NASA Astrophysics Data System (ADS)

    Prajith, A.; Rao, V. Purnachandra; Kessarkar, Pratima M.

    2015-01-01

    Mineralogy, major elements (Fe, Mn and Al), rare earths and yttrium (REY) of bulk sediments were analyzed in four gravity cores recovered along the main channel of the Mandovi estuary, western India, to determine the sources and controls on REY distribution. The accelerator mass spectrometer (AMS) ages of total organic carbon indicated modern age for the sediments of the upper estuary and, maximum mean ages of 1588 years AD and 539 years AD for the bottom sediments of the cores in the lower estuary and bay, respectively. The sediments of the upper/middle estuary showed abundant hematite, magnetite and goethite and high Fe, Mn, total-REE (ΣREE) and Y, while those in the lower estuary/bay showed abundant silicate minerals and relatively low Fe, Mn, ΣREE and Y. ΣREE showed significant correlation with clay and silt fractions and Y, Al and organic carbon (OC) content of the sediments. The light to heavy REE ratios (LREE/HREE) of sediments were lower than in Post-Archean Australian Shale (PAAS). The PAAS-normalized rare earths and yttrium (REY; Y inserted between Dy and Ho) patterns of sediments showed middle REE (MREE)- and HREE-enrichment with positive Eu anomaly (Eu/Eu*) and variable Ce anomaly (Ce/Ce*). The REY of sediments is primarily controlled by its texture and REE of source sediment, which is ore material-dominated in the upper/middle estuary and silicate material-dominated in the lower estuary/bay. Low LREE/HREE ratios suggest that very fine-grained sediments were carried away from the estuary because of high-energy conditions. Fractionations of REY (Y/Ho, Sm/Nd, Ce/Ce* and Eu/Eu*) are controlled by different mechanisms. High Y/Ho ratios in clayey silts are due to redistribution of Y and Ho by adsorption onto organic-rich, clays. Variations in Sm/Nd ratios are similar to that of Eu/Eu* in cores from the lower estuary/bay and are controlled by mineral constituents of the sediments. Positive Ce and Eu anomalies are inherited from ore material, and ore

  3. The downstream core promoter element, DPE, is conserved from Drosophila to humans and is recognized by TAFII60 of Drosophila

    PubMed Central

    Burke, Thomas W.; Kadonaga, James T.

    1997-01-01

    We analyzed the function of the downstream promoter element (DPE), a distinct 7-nucleotide core promoter element that is ∼30 nucleotides downstream of the transcription start site of many TATA-box-deficient (TATA-less) promoters in Drosophila. There is a strict requirement for spacing between the Inr and DPE motifs, as an increase or decrease of 3 nucleotides in the distance between the Inr and DPE causes a seven- to eightfold reduction in transcription as well as a significant reduction in the binding of purified TFIID. These results suggest a specific and somewhat rigid interaction of TFIID with the Inr and DPE sequences. Photo-cross-linking analysis of purified TFIID with a TATA-less DPE-containing promoter revealed specific cross-linking of dTAFII60 and dTAFII40 to the DPE, with a higher efficiency of cross-linking to dTAFII60 than to dTAFII40. These data, combined with the previously well-characterized interactions between the two TAFs and their homology to histones H4 and H3, suggest that a dTAFII60–dTAFII40 heterotetramer binds to the DPE. Human and Drosophila transcription factors exhibit essentially the same requirements for DPE sequence and for Inr–DPE spacing. In addition, the TATA-less promoter of the human interferon regulatory factor-1 (IRF-1) gene contains a DPE that is important for transcriptional activity both in vitro and in cultured cells. Hence, these studies provide evidence for a direct role of TAFs in basal transcription of TATA-less DPE-containing genes and collectively indicate that the DPE is, in many respects, a downstream counterpart to the TATA box that is present in Drosophila to humans. PMID:9367984

  4. Herschel/HIFI observations of spectrally resolved methylidyne signatures toward the high-mass star-forming core NGC 6334I

    NASA Astrophysics Data System (ADS)

    van der Wiel, M. H. D.; van der Tak, F. F. S.; Lis, D. C.; Bell, T.; Bergin, E. A.; Comito, C.; Emprechtinger, M.; Schilke, P.; Caux, E.; Ceccarelli, C.; Baudry, A.; Goldsmith, P. F.; Herbst, E.; Langer, W.; Lord, S.; Neufeld, D.; Pearson, J.; Phillips, T.; Rolffs, R.; Yorke, H.; Bacmann, A.; Benedettini, M.; Blake, G. A.; Boogert, A.; Bottinelli, S.; Cabrit, S.; Caselli, P.; Castets, A.; Cernicharo, J.; Codella, C.; Coutens, A.; Crimier, N.; Demyk, K.; Dominik, C.; Encrenaz, P.; Falgarone, E.; Fuente, A.; Gerin, M.; Helmich, F.; Hennebelle, P.; Henning, T.; Hily-Blant, P.; Jacq, T.; Kahane, C.; Kama, M.; Klotz, A.; Lefloch, B.; Lorenzani, A.; Maret, S.; Melnick, G.; Nisini, B.; Pacheco, S.; Pagani, L.; Parise, B.; Salez, M.; Saraceno, P.; Schuster, K.; Tielens, A. G. G. M.; Vastel, C.; Viti, S.; Wakelam, V.; Walters, A.; Wyrowski, F.; Edwards, K.; Zmuidzinas, J.; Morris, P.; Samoska, L. A.; Teyssier, D.

    2010-10-01

    Context. In contrast to the more extensively studied dense star-forming cores, little is known about diffuse gas surrounding star-forming regions. Aims: We study the molecular gas in the Galactic high-mass star-forming region NGC 6334I, which contains diffuse, quiescent components that are inconspicuous in widely used molecular tracers such as CO. Methods: We present Herschel/HIFI observations of methylidyne (CH) toward NGC 6334I observed as part of the “Chemical HErschel Survey of Star forming regions” (CHESS) key program. HIFI resolves each of the six hyperfine components of the lowest rotational transition (J = 3/2 - 1/2) of CH, observed in both emission and absorption. Results: The CH emission features appear close to the systemic velocity of NGC 6334I, while its measured FWHM linewidth of 3 km s-1 is smaller than previously observed in dense gas tracers such as NH3 and SiO. The CH abundance in the hot core is ~7 × 10-11, two to three orders of magnitude lower than in diffuse clouds. While other studies find distinct outflows in, e.g., CO and H2O toward NGC 6334I, we do not detect any outflow signatures in CH. At least two redshifted components of cold absorbing material must be present at -3.0 and +6.5 km s-1 to explain the absorption signatures. We derive a CH column density (NCH) of 7 × 1013 and 3 × 1013 cm-2 for these two absorbing clouds. We find evidence of two additional absorbing clouds at +8.0 and 0.0 km s-1, both with NCH ≈ 2 × 1013 cm-2. Turbulent linewidths for the four absorption components vary between 1.5 and 5.0 km s-1 in FWHM. We constrain the physical properties and locations of the clouds by matching our CH absorbers with the absorption signatures seen in other molecular tracers. Conclusions: In the hot core, molecules such as H2O and CO trace gas that is heated and dynamically influenced by outflow activity, whereas the CH molecule traces more quiescent material. The four CH absorbing clouds have column densities and turbulent

  5. Core Forensics: Earth's Accretion and Differentiation

    NASA Astrophysics Data System (ADS)

    Badro, J.; Brodholt, J. P.; Siebert, J.; Piet, H.; Ryerson, F. J.

    2013-12-01

    Earth's accretion and its primitive differentiation are intimately interlinked processes. One way to constrain accretionary processes is by looking at the major differentiation event that took place during accretion: core formation. Understanding core formation and core composition can certainly shed a new light on early and late accretionary processes. On the other hand, testing certain accretionary models and hypothesis (fluxes, chemistries, timing) allows -short of validating them- at the very least to unambiguously refute them, through the 'filter'' of core formation and composition. Earth's core formed during accretion as a result of melting, phase-separation, and segregation of accretionary building blocks (from meteorites to planetesimals). The bulk composition of the core and mantle depends on the evolution (pressure, temperature, composition) of core extraction during accretion. The entire process left a compositional imprint on both reservoirs: (1) in the silicate Earth, in terms of siderophile trace-element (Ni, Co, V, Cr, among others) concentrations and isotopic fractionation (Si, Cu, among others), a record that is observed in present-day mantle rocks; and (2) on the core, in terms of major element composition and light elements dissolved in the metal, a record that is observed by seismology through the core density-deficit. This imprint constitutes actually a fairly impressive set of evidence (siderophile element concentration and fractionation, volatile and siderophile element isotopic fractionation), can be used today to trace back the primordial processes that occurred 4.5 billion years ago. We are seeking to provide an overhaul of the standard core formation/composition models, by using a new rationale that bridges geophysics and geochemistry. The new ingredients are (1) new laser-heated diamond anvil cell partitioning data, dramatically extending the previous P-T conditions for experimental work, (2) ab initio molecular dynamics calculations to

  6. The Tom Core Complex

    PubMed Central

    Ahting, Uwe; Thun, Clemens; Hegerl, Reiner; Typke, Dieter; Nargang, Frank E.; Neupert, Walter; Nussberger, Stephan

    1999-01-01

    Translocation of nuclear-encoded preproteins across the outer membrane of mitochondria is mediated by the multicomponent transmembrane TOM complex. We have isolated the TOM core complex of Neurospora crassa by removing the receptors Tom70 and Tom20 from the isolated TOM holo complex by treatment with the detergent dodecyl maltoside. It consists of Tom40, Tom22, and the small Tom components, Tom6 and Tom7. This core complex was also purified directly from mitochondria after solubilization with dodecyl maltoside. The TOM core complex has the characteristics of the general insertion pore; it contains high-conductance channels and binds preprotein in a targeting sequence-dependent manner. It forms a double ring structure that, in contrast to the holo complex, lacks the third density seen in the latter particles. Three-dimensional reconstruction by electron tomography exhibits two open pores traversing the complex with a diameter of ∼2.1 nm and a height of ∼7 nm. Tom40 is the key structural element of the TOM core complex. PMID:10579717

  7. Internal deformation in layered Zechstein-III K-Mg salts. Structures formed by complex deformation and high contrasts in viscosity observed in drill cores.

    NASA Astrophysics Data System (ADS)

    Raith, Alexander; Urai, Janos L.

    2016-04-01

    During the evaporation of a massive salt body, alternations of interrupted and full evaporation sequences can form a complex layering of different lithologies. Viscosity contrasts of up to five orders of magnitude between these different lithologies are possible in this environment. During the late stage of an evaporation cycle potassium and magnesium (K-Mg) salts are precipitated. These K-Mg salts are of economic interest but also a known drilling hazard due to their very low viscosity. How up to 200m thick layers of these evaporites affect salt deformation at different scales is not well known. A better understanding of salt tectonics with extreme mechanical stratification is needed for better exploration and production of potassium-magnesium salts and to predict the internal structure of potential nuclear waste repositories in salt. To gain a better understanding of the internal deformation of these layers we analyzed K-Mg salt rich drill cores out of the Zechstein III-1b subunit from the Veendam Pillow 10 km southeast of Groningen, near the city Veendam in the NE Netherlands. The study area has a complex geological history with multiple tectonic phases of extension and compression forming internal deformation in the pillow but also conserving most of the original layering. Beside halite the most common minerals in the ZIII-1b are carnallite, kieserite, anhydrite and bischofite alternating in thin layers of simple composition. Seismic interpretation revealed that the internal structure of the Veendam Pillow shows areas, in which the K-Mg salt rich ZIII 1b layer is much thicker than elsewhere, as a result of salt deformation. The internal structure of the ZIII-1b on the other hand, remains unknown. The core analysis shows a strong strain concentration in the weaker Bischofite (MgCl2*6H20) and Carnallite (KMgCl3*6H20) rich layers producing tectonic breccias and highly strained layers completely overprinting the original layering. Layers formed by alternating beds

  8. Laminated metal composite formed from low flow stress layers and high flow stress layers using flow constraining elements and making same

    DOEpatents

    Syn, C.K.; Lesuer, D.R.

    1995-07-04

    A laminated metal composite of low flow stress layers and high flow stress layers is described which is formed using flow constraining elements, preferably in the shape of rings, individually placed around each of the low flow stress layers while pressure is applied to the stack to bond the layers of the composite together, to thereby restrain the flow of the low flow stress layers from the stack during the bonding. The laminated metal composite of the invention is made by the steps of forming a stack of alternate layers of low flow stress layers and high flow stress layers with each layer of low flow stress material surrounded by an individual flow constraining element, such as a ring, and then applying pressure to the top and bottom surfaces of the resulting stack to bond the dissimilar layers together, for example, by compression rolling the stack. In a preferred embodiment, the individual flow constraining elements surrounding the layers of low flow stress material are formed of a material which may either be the same material as the material comprising the high flow stress layers, or have similar flow stress characteristics to the material comprising the high flow stress layers. Additional sacrificial layers may be added to the top and bottom of the stack to avoid damage to the stack during the bonding step; and these additional layers may then be removed after the bonding step. 5 figs.

  9. Laminated metal composite formed from low flow stress layers and high flow stress layers using flow constraining elements and making same

    DOEpatents

    Syn, Chol K.; Lesuer, Donald R.

    1995-01-01

    A laminated metal composite of low flow stress layers and high flow stress layers is described which is formed using flow constraining elements, preferably in the shape of rings, individually placed around each of the low flow stress layers while pressure is applied to the stack to bond the layers of the composite together, to thereby restrain the flow of the low flow stress layers from the stack during the bonding. The laminated metal composite of the invention is made by the steps of forming a stack of alternate layers of low flow stress layers and high flow stress layers with each layer of low flow stress material surrounded by an individual flow constraining element, such as a ring, and then applying pressure to the top and bottom surfaces of the resulting stack to bond the dissimilar layers together, for example, by compression rolling the stack. In a preferred embodiment, the individual flow constraining elements surrounding the layers of low flow stress material are formed of a material which may either be the same material as the material comprising the high flow stress layers, or have similar flow stress characteristics to the material comprising the high flow stress layers. Additional sacrificial layers may be added to the top and bottom of the stack to avoid damage to the stack during the bonding step; and these additional layers may then be removed after the bonding step.

  10. Self-seeding in one dimension: a route to uniform fiber-like nanostructures from block copolymers with a crystallizable core-forming block.

    PubMed

    Qian, Jieshu; Lu, Yijie; Chia, Anselina; Zhang, Meng; Rupar, Paul A; Gunari, Nikhil; Walker, Gilbert C; Cambridge, Graeme; He, Feng; Guerin, Gerald; Manners, Ian; Winnik, Mitchell A

    2013-05-28

    One-dimensional micelles formed by the self-assembly of crystalline-coil poly(ferrocenyldimethylsilane) (PFS) block copolymers exhibit self-seeding behavior when solutions of short micelle fragments are heated above a certain temperature and then cooled back to room temperature. In this process, a fraction of the fragments (the least crystalline fragments) dissolves at elevated temperature, but the dissolved polymer crystallizes onto the ends of the remaining seed fragments upon cooling. This process yields longer nanostructures (up to 1 μm) with uniform width (ca. 15 nm) and a narrow length distribution. In this paper, we describe a systematic investigation of factors that affect the self-seeding behavior of PFS block copolymer micelle fragments. For PI(1000)-PFS(50) (the subscripts refer to the number average degree of polymerization) in decane, these factors include the presence of a good solvent (THF) for PFS and the effect of annealing the fragments prior to the self-seeding experiments. THF promoted the dissolution of the micelle fragments, while preannealing improved their stability. We also extended our experiments to other PFS block copolymers with different corona-forming blocks. These included PI(637)-PFS(53) in decane, PFS(60)-PDMS(660) in decane (PDMS = polydimethylsiloxane), and PFS(30)-P2VP(300) in 2-propanol (P2VP = poly(2-vinylpyridine)). The most remarkable result of these experiments is our finding that the corona-forming chain plays an important role in affecting how the PFS chains crystallize in the core of the micelles and, subsequently, the range of temperatures over which the micelle fragments dissolve. Our results also show that self-seeding is a versatile approach to generate uniform PFS fiber-like nanostructures, and in principle, the method should be extendable to a wide variety of crystalline-coil block copolymers. PMID:23586519

  11. High-affinity homologous peptide nucleic acid probes for targeting a quadruplex-forming sequence from a MYC promoter element.

    PubMed

    Roy, Subhadeep; Tanious, Farial A; Wilson, W David; Ly, Danith H; Armitage, Bruce A

    2007-09-18

    Guanine-rich DNA and RNA sequences are known to fold into secondary structures known as G-quadruplexes. Recent biochemical evidence along with the discovery of an increasing number of sequences in functionally important regions of the genome capable of forming G-quadruplexes strongly indicates important biological roles for these structures. Thus, molecular probes that can selectively target quadruplex-forming sequences (QFSs) are envisioned as tools to delineate biological functions of quadruplexes as well as potential therapeutic agents. Guanine-rich peptide nucleic acids have been previously shown to hybridize to homologous DNA or RNA sequences forming PNA-DNA (or RNA) quadruplexes. For this paper we studied the hybridization of an eight-mer G-rich PNA to a quadruplex-forming sequence derived from the promoter region of the MYC proto-oncogene. UV melting analysis, fluorescence assays, and surface plasmon resonance experiments reveal that this PNA binds to the MYC QFS in a 2:1 stoichiometry and with an average binding constant Ka = (2.0 +/- 0.2) x 10(8) M(-1) or Kd = 5.0 nM. In addition, experiments carried out with short DNA targets revealed a dependence of the affinity on the sequence of bases in the loop region of the DNA. A structural model for the hybrid quadruplex is proposed, and implications for gene targeting by G-rich PNAs are discussed. PMID:17718513

  12. Mercury's thermal evolution and core crystallization regime

    NASA Astrophysics Data System (ADS)

    Rivoldini, A.; Van Hoolst, T.; Dumberry, M.; Steinle-Neumann, G.

    2015-10-01

    Unlike the Earth, where the liquid core isentrope is shallower than the core liquidus, at the lower pressures inside Mercury's core the isentrope can be steeper than the melting temperature. As a consequence, upon cooling, the isentrope may first enter a solid stability field near the core mantle boundary and produce ironrich snow that sinks under gravity and produces buoyant upwellings of iron depleted fluid. Similar to bottom up crystallization, crystallization initiated near the top might generate sufficient buoyancy flux to drive magnetic field generation by compositional convection.In this study we model Mercury's thermal evolution by taking into account the formation of iron-rich snow to assess when the conditions for an internally magnetic field can be satisfied. We employ a thermodynamic consistent description of the iron high-pressure phase diagram and thermoelastic properties of iron alloys as well as the most recent data about the thermal conductivity of core materials. We use a 1-dimensional parametrized thermal evolution model in the stagnant lid regime for the mantle (e.g. [1]) that is coupled to the core. The model for the mantle takes into account the formation of the crust due to melting at depth. Mantle convection is driven by heat producing radioactive elements, heat loss from secular cooling and from the heat supplied by the core. The heat generated inside the core is mainly provided from secular cooling, from the latent heat released at iron freezing, and from gravitational energy resulting form the release of light elements at the inner core-outer core boundary as well as from the sinking of iron-rich snow and subsequent upwellings of light elements in the snow zone. If the heat flow out of the core is smaller than the heat transported along the core isentrope a thermal boundary will from at the top of the outer core. To determine the extension of the convecting region inside the liquid core we calculate the convective power [2]. Finally, we

  13. LASERS: Spatial and angular characteristics of the radiation from high-power lasers utilizing solutions of organic compounds with active elements in the form of hollow cylinders

    NASA Astrophysics Data System (ADS)

    Korobkov, A. M.; Nikolaev, S. V.

    1989-08-01

    A study was made of the characteristic features of the output radiation pattern of a rhodamine laser with cells in the form of hollow cylinders excited from outside and from inside by linear flashlamps. Different methods of suppressing nonaxial rays were proposed and tested. It was found that when a cell in the form of a hollow cylinder was excited from the inside, the active medium acquired the properties of a negative lens and the paths of the rays in the resonator became similar to those in an unstable resonator. This made it possible to increase the radiation brightness by more than an order of magnitude and also to demonstrate the advantages of using internally excited active elements in the form of hollow cylinders in high-power low-divergence dye solution lasers.

  14. Crystallization in Earth's Core after High-Temperature Core Formation

    NASA Astrophysics Data System (ADS)

    Hirose, K.; Morard, G.; Hernlund, J. W.; Helffrich, G. R.; Ozawa, H.

    2015-12-01

    Recent core formation models based on the metal-silicate partitioning of siderophile elements suggest that the Earth's core was formed by metal segregation at high pressure and high temperature in a deep magma ocean. It is also thought that the simultaneous solubility of silicon and oxygen in liquid iron are strongly enhanced at high pressure and high temperature, such that at the end of accretion the core was rich in both silicon and oxygen. Here we performed crystallization experiments on the Fe-Si binary and Fe-Si-O ternary systems up to core pressure in a laser-heated diamond-anvil cell. The starting material for the latter was a homogeneous mixture of fine-grain Fe-Si and SiO2 (<1 µm). We prepared cross sections of samples recovered from the DAC using a focused ion beam (FIB) and subsequently performed textural and chemical characterization with field-emission-type electron microprobe (FE-EPMA). Quenched liquid alloy was found at the hottest part coexisting with a solid phase (liquidus phase) at the periphery. These results combined with literature data on the melting phase relations in the Fe-FeO binary system demonstrate that the liquidus field of SiO2 is very wide at the Fe-rich portion of the Fe-Si-O ternary system at the core pressure range. It indicates that the original Fe-Si-O core liquid should have crystallized a large amount SiO2 until it lost either silicon or oxygen. The recent finding of high thermal conductivity of the core suggests that core thermal convection is difficult to sustain without extreme degrees of secular cooling. However, even for modest degrees of joint Si-O incorporation into the early core, the buoyancy released by crystallization of SiO2 is sufficient to overcome thermal stratification and sustain the geodynamo.

  15. Cluster of Genes That Encode Positive and Negative Elements Influencing Filament Length in a Heterocyst-Forming Cyanobacterium

    PubMed Central

    Merino-Puerto, Victoria; Herrero, Antonia

    2013-01-01

    The filamentous, heterocyst-forming cyanobacteria perform oxygenic photosynthesis in vegetative cells and nitrogen fixation in heterocysts, and their filaments can be hundreds of cells long. In the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120, the genes in the fraC-fraD-fraE operon are required for filament integrity mainly under conditions of nitrogen deprivation. The fraC operon transcript partially overlaps gene all2395, which lies in the opposite DNA strand and ends 1 bp beyond fraE. Gene all2395 produces transcripts of 1.35 kb (major transcript) and 2.2 kb (minor transcript) that overlap fraE and whose expression is dependent on the N-control transcription factor NtcA. Insertion of a gene cassette containing transcriptional terminators between fraE and all2395 prevented production of the antisense RNAs and resulted in an increased length of the cyanobacterial filaments. Deletion of all2395 resulted in a larger increase of filament length and in impaired growth, mainly under N2-fixing conditions and specifically on solid medium. We denote all2395 the fraF gene, which encodes a protein restricting filament length. A FraF-green fluorescent protein (GFP) fusion protein accumulated significantly in heterocysts. Similar to some heterocyst differentiation-related proteins such as HglK, HetL, and PatL, FraF is a pentapeptide repeat protein. We conclude that the fraC-fraD-fraE←fraF gene cluster (where the arrow indicates a change in orientation), in which cis antisense RNAs are produced, regulates morphology by encoding proteins that influence positively (FraC, FraD, FraE) or negatively (FraF) the length of the filament mainly under conditions of nitrogen deprivation. This gene cluster is often conserved in heterocyst-forming cyanobacteria. PMID:23813733

  16. µ-XRF Analysis of Trace Elements in Lapis Lazuli-Forming Minerals for a Provenance Study.

    PubMed

    Angelici, Debora; Borghi, Alessandro; Chiarelli, Fabrizia; Cossio, Roberto; Gariani, Gianluca; Lo Giudice, Alessandro; Re, Alessandro; Pratesi, Giovanni; Vaggelli, Gloria

    2015-04-01

    This paper presents new developments on the provenance study of lapis lazuli started by our group in 2008: during the years a multi-technique approach has been exploited to obtain minero-petrographic characterization and creation of a database considering only rock samples of known provenance. Since the final aim of the study is to develop a method to analyze archeological findings and artworks made with lapis lazuli in a completely non-invasive way, ion beam analysis techniques were employed to trace the provenance of the raw material used for the production of artifacts. Continuing this goal and focusing the analysis on determination of more significant minero-chemical markers for the provenance study of trace elements in different minerals, the method was extended with the use of micro X-ray fluorescence (µ-XRF), to test the potential of the technique for this application. The analyzes were focused on diopside and pyrite in lapis lazuli samples of known provenance (Afghanistan, Tajikistan, and Siberia). In addition, µ-XRF data were compared with micro proton-induced X-ray emission (µ-PIXE) results to verify the agreement between the two databases and to compare the analytical performance of both techniques for this application. PMID:25782348

  17. Photochemically Generated Elemental Selenium Forms Conjugates with Serum Proteins that Are Preferentially Cytotoxic to Leukemia and Selected Solid Tumor Cells

    PubMed Central

    Daziano, Jean-Pierre; Günther, Wolfgang H.H.; Krieg, Marianne; Tsujino, Ichiro; Miyagi, Kiyoko; Anderson, Gregory S.; Sampson, Reynée W.; Ostrowski, Martin D.; Muir, Sarah A.; Bula, Raymond J.; Sieber, Fritz

    2012-01-01

    The objective of this study was to determine if and how photoproducts contribute to the anti-tumor effect of merocyanine-mediated PDT. A panel of barbituric, thiobarbituric and selenobarbituric acid analogues of Merocyanine 540 was photobleached, and the resulting photoproducts were characterized by absorption, fluorescence emission, mass, energy dispersive X-ray, and X-ray photoelectron spectroscopy, and tested for cytotoxic activity against tumor cell lines and freshly explanted bone marrow cells. While all dyes were readily photobleached, only photoproducts of selone dyes showed cytotoxic activity. One-hour incubations with micromolar concentrations of selone-derived photoproducts were sufficient to reduce leukemia/lymphoma cells ≥10,000 fold while preserving virtually all normal CD34-positive bone marrow cells. Of 6 multi-drug resistant tumor cell lines tested, 5 were as sensitive or more sensitive to photoproducts than the corresponding wild-type lines. Physicochemical characterizations of the cytotoxic activity indicated that it consisted of conjugates of subnano particles of elemental selenium and (lipo)proteins. The discovery of cytotoxic Se-protein conjugates provides a rare example of photoproducts contributing substantially to the anti-tumor effect of PDT and challenges the long-held view that Se in oxidation state zero is biologically inert. Agents modeled after our Se-protein conjugates may prove useful for the treatment of leukemia. PMID:22211823

  18. Double-diffusive inner core translation

    NASA Astrophysics Data System (ADS)

    Deguen, Renaud; Alboussière, Thierry; Labrosse, Stéphane

    2015-04-01

    The hemispherical asymmetry of the inner core has recently been interpreted as resulting form a high-viscosity mode of inner core convection, consisting in a translation of the inner core. With melting on one hemisphere and crystallization on the other one, inner core translation would impose a strongly asymmetric buoyancy flux at the bottom of the outer core, with likely strong implications for the dynamics of the outer core and the geodynamo. The main requirement for convective instability in the inner core is an adverse radial density gradient. While older estimates of the inner core thermal conductivity favored a superadiabatic temperature gradient and the existence of thermal convection, the much higher values recently proposed make thermal convection unlikely. Compositional convection might be a viable alternative to thermal convection: an unstable compositional gradient may arise in the inner core either because the light elements present in the core are predicted to become increasingly incompatible as the inner core grows (Gubbins et al. 2013), or because of a possibly positive feedback of the development of the F-layer on inner core convection. Though the magnitude of the destabilizing effect of the compositional field is predicted to be similar to or smaller than the stabilizing effect of the thermal field, the huge difference between thermal and chemical diffusivities implies that double-diffusive instabilities may still arise even if the net density decreases upward. We propose here a theoretical (linear stability analysis) and numerical study of double diffusive convection in the inner core, focusing on the translation mode, and discuss in what conditions inner core translation can develop.

  19. Mixing of fluids in hydrothermal ore-forming (Sn,W) systems: stable isotope and rare earth elements data

    NASA Astrophysics Data System (ADS)

    Sushchevskaya, T. M.; Popova, J. A.; Velivetskaya, T. A.; Ignatiev, A. V.; Matveeva, S. S.; Limantseva, O. A.

    2012-04-01

    Experimental and physico-chemical modeling data witness to important role of mixing of different type of fluids during tin and tungsten ore formation in hydrothermal systems. Mixing of magmatogeneous fluids, exsolved from granite melts, with exogenic, initially meteoric waters in hydrothermal ore-forming systems may change chemical composition of ore-forming fluid, causing cassiterite and/or wolframite precipitation (Heinrich, 1990; Sushchevskaya, Ryzhenko, 2002). We studied the process of genetically different fluids mixing for two economic Sn-W deposits, situated in the Iultin ore region (North-East of Russia, Chukotka Penninsula). The Iultin and Svetloe deposits are located in the apical parts of close situated leucogranite stocks, formed at the final stage of the Iultin complex emplacement. Both deposits are composed of a series of quartz veins among the flyschoid rocks (T 1-2), cut by the dikes (K1) of lamprophyre, granodiorite porphyre and alpite. The veins of the deposits are dominated by the productive quartz-wolframite-cassiterite-arsenopyrite-muscovite mineral assemblage. Topaz, beryl, fluorite, and albite occur sporadically. The later sulfide (loellingite-stannite-chalcopyrite) and quartz-fluorite-calcite assemblages show insignificant development. The preore quartz veinlets in host hornfels contain disseminated iron sulfides, chalcopyrite, muscovite. Isotopic (H, O, Ar) study of minerals, supplemented by oxygen isotope data of host granites and metamorphic rocks gave us possibility to conclude, that at the Iultin and the Svetloye deposits fluid mixing was fixed on the early stages of deposit formation and could be regarded as probable cause of metal (W, Sn) precipitation. During postore time the intensive involvement of isotopically light exogenic waters have changed: a) the initial character of oxygen isotope zonality; b) the initial hydrogen isotope composition of muscovites, up to meteoric calculated values for productive fluid (while the δ18O

  20. Sulfur in Earth's Mantle and Its Behavior During Core Formation

    NASA Technical Reports Server (NTRS)

    Chabot, Nancy L.; Righter,Kevin

    2006-01-01

    The density of Earth's outer core requires that about 5-10% of the outer core be composed of elements lighter than Fe-Ni; proposed choices for the "light element" component of Earth's core include H, C, O, Si, S, and combinations of these elements [e.g. 1]. Though samples of Earth's core are not available, mantle samples contain elemental signatures left behind from the formation of Earth's core. The abundances of siderophile (metal-loving) elements in Earth's mantle have been used to gain insight into the early accretion and differentiation history of Earth, the process by which the core and mantle formed, and the composition of the core [e.g. 2-4]. Similarly, the abundance of potential light elements in Earth's mantle could also provide constraints on Earth's evolution and core composition. The S abundance in Earth's mantle is 250 ( 50) ppm [5]. It has been suggested that 250 ppm S is too high to be due to equilibrium core formation in a high pressure, high temperature magma ocean on early Earth and that the addition of S to the mantle from the subsequent accretion of a late veneer is consequently required [6]. However, this earlier work of Li and Agee [6] did not parameterize the metalsilicate partitioning behavior of S as a function of thermodynamic variables, limiting the different pressure and temperature conditions during core formation that could be explored. Here, the question of explaining the mantle abundance of S is revisited, through parameterizing existing metal-silicate partitioning data for S and applying the parameterization to core formation in Earth.

  1. The rare earth element geochemistry on surface sediments, shallow cores and lithological units of Lake Acıgöl basin, Denizli, Turkey

    NASA Astrophysics Data System (ADS)

    Budakoglu, Murat; Abdelnasser, Amr; Karaman, Muhittin; Kumral, Mustafa

    2015-11-01

    The sediments in Lake Acıgöl, located in SW Anatolia, Turkey, were formed under tectono-sedimentary events. REE geochemical investigations of the Lake Acıgöl sediments, from surface and shallow core sediments at different depths (0-10 cm, 10-20 cm and 20-30 cm) are presented to clarify the characteristics of REE and the nature of source rocks in the lake sediments' and to deduce their paleoenvironmental proxies. The chondrite-normalized REE patterns of these sediments are shown as light enrichment in LREE and flat HREE with a negative Eu anomaly that is close to the continental collision basin (CCB) in its profile; this is not comparable with PAAS and UCC. Inorganic detrital materials control the REE characteristics of the Lake Acıgöl sediments and these sediments were accumulated in oxic and dysoxic depositional conditions and/or at passive margins derived from oceanic island arc rocks. They were affected by low chemical weathering, either at the original source or during transport, before deposition under arid or subtropical humid climatic conditions. In addition, we used GIS techniques (such as Inverse Distance Weighted (IDW) and Geographically Weighted Regression (GWR)) to investigate the spatial interpolation and spatial correlation of the REEs from the lake surface sediments in Lake Acıgöl and its surrounding lithological units. GIS techniques showed that the lithological units (e.g., Hayrettin Formation) north of Lake Acıgöl have high REE contents; however, Eu/Eu∗ values were higher in some lake surface sediments than in lithological units, and that refers to a negative Eu-anomaly. Therefore, Lake Acıgöl sediments are derived from the weathered products, mainly from local, highly basic bedrock around the lake from the Archean crust. The chronology of Lake Acıgöl sediment was conducted using the Constant Rate of Supply (CRS) model. Using the CRS methods for the calculation of sedimentation rate, we obtained a 0.012 g/cm2/year value which is an

  2. Characteristics of altered layers formed by sputtering with a massive molecular ion containing diverse elements with large mass differences

    SciTech Connect

    Fujiwara, Yukio; Kondou, Kouji; Nonaka, Hidehiko; Saito, Naoaki; Fujimoto, Toshiyuki; Kurokawa, Akira; Ichimura, Shingo; Tomita, Mitsuhiro

    2007-10-01

    Tetrairidium dodecacarbonyl (Ir{sub 4}(CO){sub 12}) is an organometallic compound called metal cluster complex which has a molecular weight of 1104.9. To investigate its irradiation effect, silicon substrates sputtered with 10 keV Ir{sub 4}(CO){sub 7}{sup +} were analyzed by high resolution Rutherford backscattering spectrometry. Experimental results were examined on the basis of a conventional theory of simultaneous implantation and sputtering. The introduction of oxygen gas during sputtering proved to form a thick oxide layer in the substrate, resulting in iridium segregation at the silicon-oxide interface and carbon accumulation near the surface. It was confirmed that oxygen partial pressure significantly affected the characteristics of an altered layer beneath a sputtered surface.

  3. On the representation of elements of a von Neumann algebra in the form of finite sums of products of projections. III. Commutators in C*-algebras

    SciTech Connect

    Bikchentaev, A M

    2008-04-30

    It is proved that every skew-Hermitian element of any properly infinite von Neumann algebra can be represented in the form of a finite sum of commutators of projections in this algebra. A new commutation condition for projections in terms of their upper (lower) bound in the lattice of all projections of the algebra is obtained. For the full matrix algebra the set of operators with canonical trace zero is described in terms of finite sums of commutators of projections and the domain in which the trace is positive is described in terms of finite sums of pairwise products of projections. Applications to AF-algebras are obtained. Bibliography: 33 titles.

  4. Most of the structural elements of the globular domain of murine prion protein form fibrils with predominant beta-sheet structure.

    PubMed

    Jamin, Nadège; Coïc, Yves-Marie; Landon, Céline; Ovtracht, Ludmila; Baleux, Françoise; Neumann, Jean-Michel; Sanson, Alain

    2002-10-01

    The conversion of the cellular prion protein into the beta-sheet-rich scrapie prion protein is thought to be the key step in the pathogenesis of prion diseases. To gain insight into this structural conversion, we analyzed the intrinsic structural propensity of the amino acid sequence of the murine prion C-terminal domain. For that purpose, this globular domain was dissected into its secondary structural elements and the structural propensity of the protein fragments was determined. Our results show that all these fragments, excepted that strictly encompassing helix 1, have a very high propensity to form structured aggregates with a dominant content of beta-sheet structures. PMID:12372610

  5. Detection of Chemical Interactions Between the Core and Mantle

    NASA Astrophysics Data System (ADS)

    Walker, R. J.

    2002-05-01

    . These elemental pairs form two short-lived systems. If core segregation occurred sufficiently early, depleted 182W and enriched 107Ag may be characteristic of the outer core.

  6. Environmental exposure to lead, but not other neurotoxic metals, relates to core elements of ADHD in Romanian children: performance and questionnaire data.

    PubMed

    Nicolescu, Rodica; Petcu, Cristian; Cordeanu, Aurelia; Fabritius, Klaus; Schlumpf, Margret; Krebs, Rolf; Krämer, Ursula; Winneke, Gerhard

    2010-07-01

    Neurobehavioral measures of attention, and clinical features of the attention-deficit hyperactivity disorder (ADHD) have been studied in pediatric environmental lead research. However rarely, if ever, have performance measures of attention or executive functions and questionnaire-based quantitative ADHD-observations been studied in the same subjects. We examined associations between pediatric blood lead concentrations (PbB), as well as those of mercury (Hg), and aluminum (Al), and performance in four different attention tasks, as well as behavioral ratings from an ICD-10 (hyperactivity) and DSM-IV-coded (attention deficit) German questionnaire (FBB-ADHS). Asymptomatic, 8-12 year old children from two Romanian cities were studied, namely Bucharest and Pantelimon, a city near a metal-processing plant. Blood was analyzed for Pb, Al, and Hg. Data from 83 children were available for final analysis. We assessed attention performance by means of four tasks of the computer-based ADHD-taylored German KITAP-battery. We also received questionnaire ratings from parents and teachers covering three ADHD-dimensions. Multiple linear regression analysis was used to estimate associations between the three neurotoxic trace metals in blood and the different ADHD features. After adjusting for eleven potentially confounding variables we found consistent borderline to significant associations between Pb, but not other metals, in blood and various performance- and questionnaire data. False alarm responses (FAR) in the KITAP subtests rather than response latencies exhibited positive associations with PbB. Questionnaire ratings for ADHD dimensions also revealed PbB-related adversity. With any two-fold increase of PbB outcome changed markedly, namely up to 35%. Restriction to children with PbBs<10mug/dl had only a marginal influence on outcome.The converging evidence from performance- and questionnaire data confirms that core elements of ADHD are adversely affected by low environmental Pb

  7. Excitation and abundance of C3 in star forming cores. Herschel/HIFI observations of the sight-lines to W31C and W49N

    NASA Astrophysics Data System (ADS)

    Mookerjea, B.; Giesen, T.; Stutzki, J.; Cernicharo, J.; Goicoechea, J. R.; de Luca, M.; Bell, T. A.; Gupta, H.; Gerin, M.; Persson, C. M.; Sonnentrucker, P.; Makai, Z.; Black, J.; Boulanger, F.; Coutens, A.; Dartois, E.; Encrenaz, P.; Falgarone, E.; Geballe, T.; Godard, B.; Goldsmith, P. F.; Gry, C.; Hennebelle, P.; Herbst, E.; Hily-Blant, P.; Joblin, C.; Kaźmierczak, M.; Kołos, R.; Krełowski, J.; Lis, D. C.; Martin-Pintado, J.; Menten, K. M.; Monje, R.; Pearson, J. C.; Perault, M.; Phillips, T. G.; Plume, R.; Salez, M.; Schlemmer, S.; Schmidt, M.; Teyssier, D.; Vastel, C.; Yu, S.; Dieleman, P.; Güsten, R.; Honingh, C. E.; Morris, P.; Roelfsema, P.; Schieder, R.; Tielens, A. G. G. M.; Zmuidzinas, J.

    2010-10-01

    We present spectrally resolved observations of triatomic carbon (C3) in several ro-vibrational transitions between the vibrational ground state and the low-energy ν2 bending mode at frequencies between 1654-1897 GHz along the sight-lines to the submillimeter continuum sources W31C and W49N, using Herschel's HIFI instrument. We detect C3 in absorption arising from the warm envelope surrounding the hot core, as indicated by the velocity peak position and shape of the line profile. The sensitivity does not allow to detect C3 absorption due to diffuse foreground clouds. From the column densities of the rotational levels in the vibrational ground state probed by the absorption we derive a rotation temperature (Trot) of ~50-70 K, which is a good measure of the kinetic temperature of the absorbing gas, as radiative transitions within the vibrational ground state are forbidden. It is also in good agreement with the dust temperatures for W31C and W49N. Applying the partition function correction based on the derived Trot, we get column densities N(C3) ~ 7-9 × 1014 cm-2 and abundance x(C3) ~ 10-8 with respect to H2. For W31C, using a radiative transfer model including far-infrared pumping by the dust continuum and a temperature gradient within the source along the line of sight we find that a model with x(C3) = 10-8, Tkin = 30-50 K, N(C3) = 1.5 × 1015 cm-2 fits the observations reasonably well and provides parameters in very good agreement with the simple excitation analysis. Appendix A (page 5) is only available in electronic form at http://www.aanda.orgHerschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  8. Effect of the existing form of Cu element on the mechanical properties, bio-corrosion and antibacterial properties of Ti-Cu alloys for biomedical application.

    PubMed

    Zhang, Erlin; Wang, Xiaoyan; Chen, Mian; Hou, Bing

    2016-12-01

    Ti-Cu alloys have exhibited strong antibacterial ability, but Ti-Cu alloys prepared by different processes showed different antibacterial ability. In order to reveal the controlling mechanism, Ti-Cu alloys with different existing forms of Cu element were prepared in this paper. The effects of the Cu existing form on the microstructure, mechanical, corrosion and antibacterial properties of Ti-Cu alloys have been systematically investigated. Results have shown that the as-cast Ti-Cu alloys showed a higher hardness and mechanical strength as well as a higher antibacterial rate (51-64%) but a relatively lower corrosion resistance than pure titanium. Treatment at 900°C/2h (T4) significantly increased the hardness and the strength, improved the corrosion resistance but had little effect on the antibacterial property. Treatment at 900°C/2h+400°C/12h (T6) increased further the hardness and the mechanical strength, improved the corrosion resistance and but also enhanced the antibacterial rate (>90%) significantly. It was demonstrated that the Cu element in solid solution state showed high strengthening ability but low antibacterial property while Cu element in Ti2Cu phase exhibited strong strengthening ability and strong antibacterial property. Ti2Cu phase played a key role in the antibacterial mechanism. The antibacterial ability of Ti-Cu alloy was strongly proportional to the Cu content and the surface area of Ti2Cu phase. High Cu content and fine Ti2Cu phase would contribute to a high strength and a strong antibacterial ability. PMID:27612819

  9. Trace elements mineral-melt partitioning in diamond-forming peridotite-carbonatite system (experimental study at 8.5 GPa)

    NASA Astrophysics Data System (ADS)

    Kuzyura, A.; Litvin, Y.; Vasilisev, P.; Jeffries, T.; Wall, F.

    2012-04-01

    The upper mantle peridotite-carbonatite system of the model composition [(Ol36-60Opx16Cpx12-24Grt12-24)30Carb70]99TE01represents ultra-basic parental medium for diamond and paragenetic mineral inclusions therein. This experimental study is focused onto geochemical behavior of trace elements (TE) during formation of diamond in heterogeneous parental medium consisting of completely miscible carbonate-silicate melt and peridotitic minerals which are paragenetic to diamond (olivine Ol, orthopyroxene Opx, clinopyroxene Cpx and garnet Grt). The TE mixture consists of Li, Rb, Cs, Ba, Th, U, Ta, Nb, La, Ce, Pb, Pr, Sr, Nd, Zr, Hf, Sm, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb, Lu, Sc, and Zn. The trace elements were mainly introduced into the system as oxides. In experiments at 8.5 GPa and 1510oC, quite large (more than 100 μm) garnet, clinopyroxenes, and olivine crystals were formed in completely miscible carbonate-silicate (carbonatite) melts Orthopyrohene was not formed. After quenching, the melt phase was presented as cryptocrystalline aggregate which was analyzed over areas of 10-10 - 100-100 μm size with the use of microprobe and LA-ICP-MS methods. The methods were used in analyzing TE content in single crystalline olivine, clinopyroxene and garnet submerged into the quenched melt. Coefficients of inter-phase TE partitioning Kd for the coupled phases olivine-melt, clinopyroxene-melt, garnet-melt, and olivine-garnet were calculated, based on the results of LA-ICP-MS determination of the TE contents. Spydergram characterizing clearly the inter-phase TE partitions is plotted. By the spydergram, garnet and olivine are the major phases in TE inter-phase mineral-melt partitioning for the diamond-forming peridotite-carbonatite system. The feature is that light REE elements (La, Ce, Pr) are mainly distributed into the melt phase where as the medium and heavy elements (Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) - into garnet (Kd = 1 - 6). Such heavy elements as Zr, Hf, Y, and Sc

  10. Advanced characterization of forms of chlorine, organic sulfur and trace elements in available coals from operating Illinois mines. Quarterly report, 1 December 1994--28 February 1995

    SciTech Connect

    Chou, M.I.M.; Demir, I.; Ruch, R.R.; Lytle, S.

    1995-12-31

    The goals of the study are (1) to use X-ray absorption near-edge spectroscopy (XANES) to determine forms of chlorine (inorganic, ionic, and organic) and forms of organic sulfur (organic sulfide and thiophenic sulfur) in as-shipped coals from Illinois mines, (2) to obtain basic data on chlorine removal via froth flotation at fine ({minus}200 mesh) and ultrafine ({minus}400 mesh) particle sizes, and (3) to evaluate XANES for direct assessment of the organic/inorganic affinities of trace elements. This is a cooperative effort among the Illinois State Geological Survey, the University of Kentucky, and Western Kentucky University. In this quarter, chlorine leachability during fine wet grinding of 21 coal samples was examined. The results show a general improvement in chlorine removal by grinding coals to {minus}200 mesh, but do not show further improvement by additional grinding to {minus}400 mesh. The chlorine and sulfur spectra of five coals , each from a distinct geographic location in Illinois, were examined. The chlorine XANES spectra for the five coals are similar and chloride anion was determined to be the predominant form of chlorine. The sulfur XANES data for the same coals show that a majority (61% to 82%) of organic sulfur in the coals is contributed from thiophenic sulfur. The distribution of organic sulfur shows that the high sulfur coals tend to have more organic sulfide than low sulfur coals. A more detailed interpretation may be possible after a complete analysis of all the samples selected. Evaluating the possibility of XANES for direct assessment of the organic/inorganic affinities of trace elements in an Illinois coal was completed.

  11. Dynamics of water around the complex structures formed between the KH domains of far upstream element binding protein and single-stranded DNA molecules

    SciTech Connect

    Chakraborty, Kaushik; Bandyopadhyay, Sanjoy

    2015-07-28

    Single-stranded DNA (ss-DNA) binding proteins specifically bind to the single-stranded regions of the DNA and protect it from premature annealing, thereby stabilizing the DNA structure. We have carried out atomistic molecular dynamics simulations of the aqueous solutions of two DNA binding K homology (KH) domains (KH3 and KH4) of the far upstream element binding protein complexed with two short ss-DNA segments. Attempts have been made to explore the influence of the formation of such complex structures on the microscopic dynamics and hydrogen bond properties of the interfacial water molecules. It is found that the water molecules involved in bridging the ss-DNA segments and the protein domains form a highly constrained thin layer with extremely retarded mobility. These water molecules play important roles in freezing the conformational oscillations of the ss-DNA oligomers and thereby forming rigid complex structures. Further, it is demonstrated that the effect of complexation on the slow long-time relaxations of hydrogen bonds at the interface is correlated with hindered motions of the surrounding water molecules. Importantly, it is observed that the highly restricted motions of the water molecules bridging the protein and the DNA components in the complexed forms originate from more frequent hydrogen bond reformations.

  12. Dynamics of water around the complex structures formed between the KH domains of far upstream element binding protein and single-stranded DNA molecules

    NASA Astrophysics Data System (ADS)

    Chakraborty, Kaushik; Bandyopadhyay, Sanjoy

    2015-07-01

    Single-stranded DNA (ss-DNA) binding proteins specifically bind to the single-stranded regions of the DNA and protect it from premature annealing, thereby stabilizing the DNA structure. We have carried out atomistic molecular dynamics simulations of the aqueous solutions of two DNA binding K homology (KH) domains (KH3 and KH4) of the far upstream element binding protein complexed with two short ss-DNA segments. Attempts have been made to explore the influence of the formation of such complex structures on the microscopic dynamics and hydrogen bond properties of the interfacial water molecules. It is found that the water molecules involved in bridging the ss-DNA segments and the protein domains form a highly constrained thin layer with extremely retarded mobility. These water molecules play important roles in freezing the conformational oscillations of the ss-DNA oligomers and thereby forming rigid complex structures. Further, it is demonstrated that the effect of complexation on the slow long-time relaxations of hydrogen bonds at the interface is correlated with hindered motions of the surrounding water molecules. Importantly, it is observed that the highly restricted motions of the water molecules bridging the protein and the DNA components in the complexed forms originate from more frequent hydrogen bond reformations.

  13. Improved stratigraphic dating at a low accumulation Alpine ice core through laser ablation trace element profiling at sub-mm depth resolution

    NASA Astrophysics Data System (ADS)

    Bohleber, Pascal; Spaulding, Nicole; Mayewski, Paul; Sneed, Sharon; Handley, Mike; Erhardt, Tobias; Wagenbach, Dietmar

    2015-04-01

    The small scale Colle Gnifetti glacier saddle (4450 m asl, Monte Rosa region) is the only ice core drilling site in the European Alps with a net accumulation low enough to offer multi-millennia climate records. However, a robust interpretation of such long term records (i.e. mineral dust, stable water isotopes) at the Colle Gnifetti (CG) multi core array is strongly challenged by depositional noise associated with a highly irregular annual layer stratigraphy. In combination with a relatively large vertical strain rate and rapid layer thinning, annual layer counting gets increasingly ambiguous as of approximately 100 years. In addition, this prevents clear attribution of likely volcanic horizons to historical eruption dates. To improve stratigraphic dating under such intricate conditions, we deployed laser ablation (LA) ICP-MS at sub-mm sample resolution. We present here the first LA impurity profiles from a new Colle Gnifetti ice core drilled 73 m to bedrock in 2013 at a site where the net snow accumulation is around 20 cm w.e. per year. We contrast the LA signal variability (including Ca, Fe, Na) to continuous flow analyses (CFA) records at cm-resolution (Ca, Na, melt water conductivity, micro- particle) recorded over the whole core length. Of special concern are the lower 28 m to bedrock, which have been continuously profiled in LA Ca, thus offering the direct comparison of Ca-signals between CFA and LA. By this means, we first validate at upper depths LA based annual layer identification through agreement with CFA based counting efforts before demonstrating the LA based counting still works at depths where CFA derived annual layers become spurious since embedded in strong, multi-year cycles. Finally, LA ice core profiling of our CG core has potential for not only dating improvement but also reveals benefits in resolving highly thinned basal ice sections including accounting for micro-structural features such as grain boundaries.

  14. STAR-FORMING DENSE CLOUD CORES IN THE TeV GAMMA-RAY SNR RX J1713.7-3946

    SciTech Connect

    Sano, H.; Sato, J.; Horachi, H.; Moribe, N.; Yamamoto, H.; Hayakawa, T.; Torii, K.; Kawamura, A.; Okuda, T.; Mizuno, N.; Onishi, T.; Inutsuka, S.; Matsumoto, H.; Maezawa, H.; Mizuno, A.; Inoue, T.; Tanaka, T.; Ogawa, H.; Stutzki, J.; Bertoldi, F.

    2010-11-20

    RX J1713.7-3946 is one of the TeV {gamma}-ray supernova remnants (SNRs) emitting synchrotron X-rays. The SNR is associated with molecular gas located at {approx}1 kpc. We made new molecular observations toward the dense cloud cores, peaks A, C, and D, in the SNR in the {sup 12}CO(J = 2-1) and {sup 13}CO(J = 2-1) transitions at an angular resolution of 90''. The most intense core in {sup 13}CO, peak C, was also mapped in the {sup 12}CO(J = 4-3) transition at an angular resolution of 38''. Peak C shows strong signs of active star formation including bipolar outflow and a far-infrared protostellar source, and has a steep gradient with a r {sup -2.2{+-}0.4} variation in the average density within radius r. Peak C and the other dense cloud cores are rim-brightened in synchrotron X-rays, suggesting that the dense cloud cores are embedded within or on the outer boundary of the SNR shell. This confirms the earlier suggestion that the X-rays are physically associated with the molecular gas. We present a scenario where the densest molecular core, peak C, survived the blast wave and is now embedded within the SNR. Numerical simulations of the shock-cloud interaction indicate that a dense clump can indeed survive shock erosion, since the shock propagation speed is stalled in the dense clump. Additionally, the shock-cloud interaction induces turbulence and magnetic field amplification around the dense clump that may facilitate particle acceleration in the lower-density inter-clump space leading to enhanced synchrotron X-rays around dense cores.

  15. The atomic-scale mechanism for the enhanced glass-forming-ability of a Cu-Zr based bulk metallic glass with minor element additions

    PubMed Central

    Wang, Q.; Liu, C. T.; Yang, Y.; Liu, J. B.; Dong, Y. D.; Lu, J.

    2014-01-01

    It is known that the glass forming-ability (GFA) of bulk metallic glasses (BMGs) can be greatly enhanced via minor element additions. However, direct evidence has been lacking to reveal its structural origin despite different theories hitherto proposed. Through the high-resolution transmission-electron-microscopy (HRTEM) analysis, here we show that the content of local crystal-like orders increases significantly in a Cu-Zr-Al BMG after a 2-at% Y addition. Contrasting the previous studies, our current results indicate that the formation of crystal-like order at the atomic scale plays an important role in enhancing the GFA of the Cu-Zr-Al base BMG. PMID:24721927

  16. Process for producing organic products containing silicon, hydrogen, nitrogen, and carbon by the direct reaction between elemental silicon and organic amines and products formed thereby

    DOEpatents

    Pugar, E.A.; Morgan, P.E.D.

    1988-04-04

    A process is disclosed for producing, at a low temperature, a high purity organic reaction product consisting essentially of silicon, hydrogen, nitrogen, and carbon. The process comprises reacting together a particulate elemental high purity silicon with a high purity reactive amine reactant in a liquid state at a temperature of from about O/degree/C up to about 300/degree/C. A high purity silicon carbide/silicon nitride ceramic product can be formed from this intermediate product, if desired, by heating the intermediate product at a temperature of from about 1200-1700/degree/C for a period from about 15 minutes up to about 2 hours or the organic reaction product may be employed in other chemical uses.

  17. Measuring the Internal Structure and Physical Conditions in Star and Planet Forming Clouds Core: Toward a Quantitative Description of Cloud Evolution

    NASA Technical Reports Server (NTRS)

    Lada, Charles J.

    2005-01-01

    This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular cloud cores and investigate the physical conditions which give rise to star and planet formation. The goals of this program are to acquire, reduce and analyze deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds in order to internal structure of starless cloud cores and to quantitatively investigate the evolution of such structure through the star and planet formation process. During the second year of this grant, progress toward these goals is discussed.

  18. Measuring the Internal Structure and Physical Conditions in Star and Planet Forming Clouds Cores: Towards a Quantitative Description of Cloud Evolution

    NASA Technical Reports Server (NTRS)

    Lada, Charles J.

    2004-01-01

    This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular cloud cores and investigate the physical conditions which give rise to star and planet formation. The goals of this program are to acquire, reduce and analyze deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds in order to determine the detailed initial conditions for star formation from quantitative measurements of the internal structure of starless cloud cores and to quantitatively investigate the evolution of such structure through the star and planet formation process.

  19. Combustion of Biosolids in a Bubbling Fluidized Bed, Part 1: Main Ash-Forming Elements and Ash Distribution with a Focus on Phosphorus

    PubMed Central

    2014-01-01

    This is the first in a series of three papers describing combustion of biosolids in a 5-kW bubbling fluidized bed, the ash chemistry, and possible application of the ash produced as a fertilizing agent. This part of the study aims to clarify whether the distribution of main ash forming elements from biosolids can be changed by modifying the fuel matrix, the crystalline compounds of which can be identified in the raw materials and what role the total composition may play for which compounds are formed during combustion. The biosolids were subjected to low-temperature ashing to investigate which crystalline compounds that were present in the raw materials. Combustion experiments of two different types of biosolids were conducted in a 5-kW benchscale bubbling fluidized bed at two different bed temperatures and with two different additives. The additives were chosen to investigate whether the addition of alkali (K2CO3) and alkaline-earth metal (CaCO3) would affect the speciation of phosphorus, so the molar ratios targeted in modified fuels were P:K = 1:1 and P:K:Ca = 1:1:1, respectively. After combustion the ash fractions were collected, the ash distribution was determined and the ash fractions were analyzed with regards to elemental composition (ICP-AES and SEM-EDS) and part of the bed ash was also analyzed qualitatively using XRD. There was no evidence of zeolites in the unmodified fuels, based on low-temperature ashing. During combustion, the biosolid pellets formed large bed ash particles, ash pellets, which contained most of the total ash content (54%–95% (w/w)). This ash fraction contained most of the phosphorus found in the ash and the only phosphate that was identified was a whitlockite, Ca9(K,Mg,Fe)(PO4)7, for all fuels and fuel mixtures. With the addition of potassium, cristobalite (SiO2) could no longer be identified via X-ray diffraction (XRD) in the bed ash particles and leucite (KAlSi2O6) was formed. Most of the alkaline-earth metals calcium and

  20. On the Evolution of Stars That Form Electron-degenerate Cores Processed by Carbon Burning. II. Isotope Abundances and Thermal Pulses in a 10 Msun Model with an ONe Core and Applications to Long-Period Variables, Classical Novae, and Accretion-induced Collapse

    NASA Astrophysics Data System (ADS)

    Ritossa, Claudio; Garcia-Berro, Enrique; Iben, Icko, Jr.

    1996-03-01

    A 10 Msun model of Population I composition is evolved from the hydrogen-burning main sequence to the thermally pulsing `super' asymptotic giant branch (TPSAGB) stage, where it has an oxygen-neon (ONe) core of mass 1.196 Msun and is experiencing thermal pulses driven by helium-burning thermonuclear flashes. Interior abundance characteristics are relevant to an understanding of the core collapse of massive acereting white dwarfs in close binary star systems. At mass point 0.2 Msun., abundances by mass are X(16O) = 0.656, X(20Ne) = 0.215, X(23Na) = 0.0467, X(24Mg) = 0.0325, X(25Mg) = 0.0115, X(12 C)= 0.0112, X(22Ne) = 0.00893, X(21Ne) = 0.00689, X(26Mg) = 0.00560, and X(27Al) = 0.00528. Abundances near the surface of the core are relevant to an understanding of nova outbursts in cataclysmic variables. At mass point 1.17 Msun, abundances by mass are X(16O) = 0.511, X(20Ne) = 0.313, X(23Na) = 0.0644, X(24Mg) = 0.0548, X(25Mg) = 0.0158, X(27 Al)= 0.0108, X(12C) = 0.00916, X(26Mg) = 0.00989, X(21Ne) = 0.00598, and X(22Ne) = 0.00431. Carbon burning is quenched at the beginning of the thermally pulsing phase, and a layer of CO matter of mass 0.015 Msun separates the ONe core from overlying helium- and hydrogen-rich layers. The outer 0.01 M of the CO layer contains essentially no neon: very little new 20Ne has been made, and most of the 22Ne which has been made from the original CNO elements has been converted into 25Mg and neutrons which have been captured to form neutron-rich isotopes. If the observational counterpart of the model is in a close binary and fills its Roche lobe near the end of the carbon-burning phase, and if the binary evolves into a cataclysmic variable, one expects that the ejecta of approximately 1000 nova outbursts will exhibit an under- abundance of neon and overabundance of carbon, oxygen, and magnesium. During the TPSAGB phase, characteristics of a pulse cycle approach local limit-cycle values after ˜30 pulses. Helium-shell flashes are of about the

  1. Advanced characterization of forms of chlorine, organic sulfur and trace elements in available coals from operating Illinois mines. Quarterly report, 1 March 1995--31 May 1995

    SciTech Connect

    Chou, M.I.M.; Demir, I; Ruch, R.R.; Lytle, J.M.; Bhagway, S; Li, Y.C.; Chou, C.L.; Huggins, F.E.; Huffman, G.P.

    1995-12-31

    The goals of the study are (1) to use X-ray absorption near-edge spectroscopy (XANES) to determine forms of chlorine (inorganic, ionic, and organic) and forms of organic sulfur (organic sulfide and thiophenic sulfur) in as-shipped coals from Illinois mines, (2) to obtain basic data on chlorine removal via froth flotation at fine ({minus}200 mesh) and ultrafine ({minus}400 mesh) particle sizes, and (3) to evaluate XANES for direct assessment of the organic/inorganic affinities of trace elements. In the last quarter, chlorine leachability during fine wet grinding of 21 coal samples was examined. In this quarter, the effect of froth flotation/release analysis (FF/RA) on the Cl contents of coals ground to {minus}200 and {minus}400 mesh sizes is completed. The results indicate that a combination of wet grinding and FF/RA reduced Cl contents in most samples from regions 1,2, and 3 by 29--81% and in one sample from region 4S by 60%. The chlorine and sulfur spectra of 21 coals, from five distinct geographic locations in Illinois, were examined. The chlorine XANES spectra for the coals are similar and chloride anion was determined to be the predominant form of chlorine. The sulfur XANES data for these coals show that a majority (61% to 82%) of organic sulfur in the thiophenic form. The ratios of thiophenic sulfur to total organic sulfur show a correlation with sample location. For samples from regions 1 and 2, the ratios are relatively lower (61% to 64%), whereas, for samples from regions 3, 4H, and 4S, the ratios are relatively higher (64% to 82%). A more detailed interpretation in these correlations will be discussed in the next report.

  2. A vascular tissue engineering scaffold with core-shell structured nano-fibers formed by coaxial electrospinning and its biocompatibility evaluation.

    PubMed

    Duan, Nannan; Geng, Xue; Ye, Lin; Zhang, Aiying; Feng, Zengguo; Guo, Lianrui; Gu, Yongquan

    2016-01-01

    In this article, a tubular vascular tissue engineering scaffold with core-shell structured fibers was produced by coaxial electrospinning at an appropriate flow rate ratio between the inner and outer solution. PCL was selected as the core to provide the mechanical property and integrity to the scaffold while collagen was used as the shell to improve the attachment and proliferation of vascular cells due to its excellent biocompatibility. The fine core-shell structured fibers were demonstrated by scanning electron microscope and transmission electron microscope observations. Subsequently, the collagen shell was crosslinked by genipin and further bound with heparin. The crosslinking process was confirmed by the increasing of tensile strength, swelling ratio and thermogravimetric analysis measurements while the surface heparin content was characterized by means of a UV-spectrophotometer and activated partial thromboplastin time tests. Furthermore, the mechanical properties such as stitch strength and bursting pressure of the as-prepared scaffold were measured. Moreover, the biocompatibility of the scaffold was evaluated by cytotoxicity investigation with L929 cells via MTT assay. Endothelial cell adhesion assessments were conducted to reveal the possibility of the formation of an endothelial cell layer on the scaffold surface, while the ability of smooth muscle cell penetration into the scaffold wall was also assessed by confocal laser scanning microscopy. The as-prepared core-shell structured scaffold showed promising potential for use in vascular tissue engineering. PMID:27206161

  3. Experiments pertaining to the formation and equilibration of planetary cores

    NASA Technical Reports Server (NTRS)

    Jeanloz, Raymond; Knittle, Elise; Williams, Quentin

    1987-01-01

    The phase diagram of FeO was experimentally determined to pressures of 155 GPa and temperatures of 4000 K using shock wave and diamond-cell techniques. Researchers discovered a metallic phase of FeO at pressures greater than 70 GPa and temperatures exceeding 1000 K. The metallization of FeO at high pressures implies that oxygen can be present as the light alloying element of the Earth's outer core, in accord with the geochemical predictions of Ringwood. The high pressures necessry for this metallization suggest that the core has acquired its composition well after the initial stages of the Earth's accretion. The core forming alloy can react chemically with oxides such as those forming the mantle. The core and mantle may never have reached complete chemical equilibrium, however. If this is the case, the core-mantle boundary is likely to be a zone of active chemical reactions.

  4. Chemical protection of ZnO nanorods at ultralow pH To form a hierarchical BiFeO3/ZnO core-shell structure.

    PubMed

    Loh, Leonard; Briscoe, Joe; Dunn, Steve

    2015-01-14

    ZnO is an interesting material for photoactive and optoelectronic devices because of the wide range of available nanostructures and advantageous semiconducting properties. However, a significant drawback of ZnO is the low stability in high or low pH solutions. This has limited the development of ZnO core-shell materials for use in Z-scheme systems or photovoltaics, where any secondary phase is produced using chemical solution processing at low or high pH. Here, we show a simple process to produce an organic capping layer of 3-aminopropyltriethoxysilane that can successfully stabilize nanostructured ZnO for processing below pH 1. We demonstrate that this process can be used to produce a ZnO-BiFeO3 (BFO) core-shell structure by a sol-gel process. Using a range of physical and analytical techniques, we show that BFO is highly crystalline and produces a conformal coating with a thickness of 2.5 nm. X-ray photoelectron spectroscopy and X-ray diffraction confirm the phase and expected chemical composition of BFO. Finally we are able to demonstrate that diodes produced using the ZnO-BFO core-shell structure have improved performance with a rectification ratio at ±3 V of 2800 because of the reduction in reverse current typically associated with surface recombination on ZnO. Our process opens a route to producing a range of hitherto prohibited ZnO core-shell structures that may have applications ranging from photovoltaic devices to core-shell photocatalysts. PMID:25247787

  5. Laminated metal composite formed from low flow stress layers and high flow stress layers using flow constraining elements and method of making same

    SciTech Connect

    Syn, C.K.; Lesuer, D.R.

    1994-12-31

    This invention relates to a laminated metal composite, comprising alternating layers of low flow stress material and high flow stress material, and formed using flow constraining elements around each low flow stress layer; and a method of making same. A composite is a combination of at least two chemically distinct materials with a distinct interface separating the two materials. A metal matrix composite (MMC) is a composite material composed of a metal and a nonmetallic reinforcing agent such as silicon carbide (SiC) or graphite in continuous or discontinuous fiber, whisker, or discrete particulate form. A laminate is a material composed of several bonded layers. It is possible to have a laminate composed of multi-layers of a single type of material bonded to each other. However, such a laminate would not be considered to be a composite. The term {open_quotes}laminated metal composite{close_quotes} (LMC), as used herein, is intended to include a structural material composed of: (1) layers of metal or metal alloys interleaved with (2) a different metal, a metal alloy, or a metal matrix composite (MMC) containing strengthening agents.

  6. Processing of Activated Core Components

    SciTech Connect

    Friske, A.; Gestermann, G.; Finkbeiner, R.

    2003-02-26

    Used activated components from the core of a NPP like control elements, water channels from a BWR, and others like in-core measurement devices need to be processed into waste forms suitable for interim storage, and for the final waste repository. Processing of the activated materials can be undertaken by underwater cutting and packaging or by cutting and high-pressure compaction in a hot cell. A hot cell is available in Germany as a joint investment between GNS and the Karlsruhe Research Center at the latter's site. Special transport equipment is available to transport the components ''as-is'' to the hot cell. Newly designed underwater processing equipment has been designed, constructed, and operated for the special application of NPP decommissioning. This equipment integrates an underwater cutting device with an 80 ton force underwater in-drum compactor.

  7. Banded transformer cores

    NASA Technical Reports Server (NTRS)

    Mclyman, C. W. T. (Inventor)

    1974-01-01

    A banded transformer core formed by positioning a pair of mated, similar core halves on a supporting pedestal. The core halves are encircled with a strap, selectively applying tension whereby a compressive force is applied to the core edge for reducing the innate air gap. A dc magnetic field is employed in supporting the core halves during initial phases of the banding operation, while an ac magnetic field subsequently is employed for detecting dimension changes occurring in the air gaps as tension is applied to the strap.

  8. Determination of the Form Factors for the Decay B0 -> D*-l+nu_l and of the CKM Matrix Element |Vcb|

    SciTech Connect

    Aubert, B.

    2006-09-26

    The authors present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V{sub cb}| and of the parameters {rho}{sup 2}, R{sub 1}, and R{sub 2}, which fully characterize the form factors of the B{sup 0} {yields} D*{sup -}{ell}{sup +}{nu}{sub {ell}} decay in the framework of HQET, based on a sample of about 52,800 B{sup 0} {yields} D*{sup -}{ell}{sup +}{nu}{sub {ell}} decays recorded by the BABAR detector. The kinematical information of the fully reconstructed decay is used to extract the following values for the parameters (where the first errors are statistical and the second systematic): {rho}{sup 2} = 1.156 {+-} 0.094 {+-} 0.028, R{sub 1} = 1.329 {+-} 0.131 {+-} 0.044, R{sub 2} = 0.859 {+-} 0.077 {+-} 0.022, F(1)|V{sub cb}| = (35.03 {+-} 0.39 {+-} 1.15) x 10{sup -3}. By combining these measurements with the previous BABAR measurements of the form factors which employs a different technique on a partial sample of the data, they improve the statistical accuracy of the measurement, obtaining: {rho}{sup 2} = 1.179 {+-} 0.048 {+-} 0.028, R{sub 1} = 1.417 {+-} 0.061 {+-} 0.044, R{sub 2}, = 0.836 {+-} 0.037 {+-} 0.022, and F(1)|V{sub cb}| = (34.68 {+-} 0.32 {+-} 1.15) x 10{sup -3}. Using the lattice calculations for the axial form factor F(1), they extract |V{sub cb}| = (37.74 {+-} 0.35 {+-} 1.25 {+-} {sub 1.44}{sup 1.23}) x 10{sup -3}, where the third error is due to the uncertainty in F(1).

  9. Determination of the form factors for the decay B0→D*-l+νl and of the CKM matrix element |Vcb|

    NASA Astrophysics Data System (ADS)

    Aubert, B.; Bona, M.; Boutigny, D.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prudent, X.; Tisserand, V.; Zghiche, A.; Tico, J. Garra; Grauges, E.; Lopez, L.; Palano, A.; Eigen, G.; Ofte, I.; Stugu, B.; Sun, L.; Abrams, G. S.; Battaglia, M.; Brown, D. N.; Button-Shafer, J.; Cahn, R. N.; Groysman, Y.; Jacobsen, R. G.; Kadyk, J. A.; Kerth, L. T.; Kolomensky, Yu. G.; Kukartsev, G.; Pegna, D. Lopes; Lynch, G.; Mir, L. M.; Orimoto, T. J.; Pripstein, M.; Roe, N. A.; Ronan, M. T.; Tackmann, K.; Wenzel, W. A.; Del Amo Sanchez, P.; Hawkes, C. M.; Watson, A. T.; Held, T.; Koch, H.; Lewandowski, B.; Pelizaeus, M.; Schroeder, T.; Steinke, M.; Cottingham, W. N.; Walker, D.; Asgeirsson, D. J.; Cuhadar-Donszelmann, T.; Fulsom, B. G.; Hearty, C.; Knecht, N. S.; Mattison, T. S.; McKenna, J. A.; Khan, A.; Saleem, M.; Teodorescu, L.; Blinov, V. E.; Bukin, A. D.; Druzhinin, V. P.; Golubev, V. B.; Onuchin, A. P.; Serednyakov, S. I.; Skovpen, Yu. I.; Solodov, E. P.; Todyshev, K. Yu; Bondioli, M.; Curry, S.; Eschrich, I.; Kirkby, D.; Lankford, A. J.; Lund, P.; Mandelkern, M.; Martin, E. C.; Stoker, D. P.; Abachi, S.; Buchanan, C.; Foulkes, S. D.; Gary, J. W.; Liu, F.; Long, O.; Shen, B. C.; Zhang, L.; Paar, H. P.; Rahatlou, S.; Sharma, V.; Berryhill, J. W.; Campagnari, C.; Cunha, A.; Dahmes, B.; Hong, T. M.; Kovalskyi, D.; Richman, J. D.; Beck, T. W.; Eisner, A. M.; Flacco, C. J.; Heusch, C. A.; Kroseberg, J.; Lockman, W. S.; Schalk, T.; Schumm, B. A.; Seiden, A.; Williams, D. C.; Wilson, M. G.; Winstrom, L. O.; Chen, E.; Cheng, C. H.; Dvoretskii, A.; Fang, F.; Hitlin, D. G.; Narsky, I.; Piatenko, T.; Porter, F. C.; Mancinelli, G.; Meadows, B. T.; Mishra, K.; Sokoloff, M. D.; Blanc, F.; Bloom, P. C.; Chen, S.; Ford, W. T.; Hirschauer, J. F.; Kreisel, A.; Nagel, M.; Nauenberg, U.; Olivas, A.; Smith, J. G.; Ulmer, K. A.; Wagner, S. R.; Zhang, J.; Gabareen, A. M.; Soffer, A.; Toki, W. H.; Wilson, R. J.; Winklmeier, F.; Zeng, Q.; Altenburg, D. D.; Feltresi, E.; Hauke, A.; Jasper, H.; Merkel, J.; Petzold, A.; Spaan, B.; Wacker, K.; Brandt, T.; Klose, V.; Lacker, H. M.; Mader, W. F.; Nogowski, R.; Schubert, J.; Schubert, K. R.; Schwierz, R.; Sundermann, J. E.; Volk, A.; Bernard, D.; Bonneaud, G. R.; Latour, E.; Lombardo, V.; Thiebaux, Ch.; Verderi, M.; Clark, P. J.; Gradl, W.; Muheim, F.; Playfer, S.; Robertson, A. I.; Xie, Y.; Andreotti, M.; Bettoni, D.; Bozzi, C.; Calabrese, R.; Cecchi, A.; Cibinetto, G.; Franchini, P.; Luppi, E.; Negrini, M.; Petrella, A.; Piemontese, L.; Prencipe, E.; Santoro, V.; Anulli, F.; Baldini-Ferroli, R.; Calcaterra, A.; de Sangro, R.; Finocchiaro, G.; Pacetti, S.; Patteri, P.; Peruzzi, I. M.; Piccolo, M.; Rama, M.; Zallo, A.; Buzzo, A.; Contri, R.; Lo Vetere, M.; Macri, M. M.; Monge, M. R.; Passaggio, S.; Patrignani, C.; Robutti, E.; Santroni, A.; Tosi, S.; Chaisanguanthum, K. S.; Morii, M.; Wu, J.; Dubitzky, R. S.; Marks, J.; Schenk, S.; Uwer, U.; Bard, D. J.; Dauncey, P. D.; Flack, R. L.; Nash, J. A.; Nikolich, M. B.; Vazquez, W. Panduro; Behera, P. K.; Chai, X.; Charles, M. J.; Mallik, U.; Meyer, N. T.; Ziegler, V.; Cochran, J.; Crawley, H. B.; Dong, L.; Eyges, V.; Meyer, W. T.; Prell, S.; Rosenberg, E. I.; Rubin, A. E.; Gritsan, A. V.; Guo, Z. J.; Lae, C. K.; Denig, A. G.; Fritsch, M.; Schott, G.; Arnaud, N.; Béquilleux, J.; Davier, M.; Grosdidier, G.; Höcker, A.; Lepeltier, V.; Le Diberder, F.; Lutz, A. M.; Pruvot, S.; Rodier, S.; Roudeau, P.; Schune, M. H.; Serrano, J.; Sordini, V.; Stocchi, A.; Wang, W. F.; Wormser, G.; Lange, D. J.; Wright, D. M.; Chavez, C. A.; Forster, I. J.; Fry, J. R.; Gabathuler, E.; Gamet, R.; Hutchcroft, D. E.; Payne, D. J.; Schofield, K. C.; Touramanis, C.; Bevan, A. J.; di Lodovico, F.; George, K. A.; Menges, W.; Sacco, R.; Cowan, G.; Flaecher, H. U.; Hopkins, D. A.; Jackson, P. S.; McMahon, T. R.; Salvatore, F.; Wren, A. C.; Brown, D. N.; Davis, C. L.; Allison, J.; Barlow, N. R.; Barlow, R. J.; Chia, Y. M.; Edgar, C. L.; Lafferty, G. D.; West, T. J.; Yi, J. I.; Anderson, J.; Chen, C.; Jawahery, A.; Roberts, D. A.; Simi, G.; Tuggle, J. M.; Blaylock, G.; Dallapiccola, C.; Hertzbach, S. S.; Li, X.; Moore, T. B.; Salvati, E.; Saremi, S.; Cowan, R.; Fisher, P. H.; Sciolla, G.; Sekula, S. J.; Spitznagel, M.; Taylor, F.; Yamamoto, R. K.; McLachlin, S. E.; Patel, P. M.; Robertson, S. H.; Lazzaro, A.; Palombo, F.; Bauer, J. M.; Cremaldi, L.; Eschenburg, V.; Godang, R.; Kroeger, R.; Sanders, D. A.; Summers, D. J.; Zhao, H. W.; Brunet, S.; Côté, D.; Simard, M.; Taras, P.; Viaud, F. B.; Nicholson, H.; de Nardo, G.; Fabozzi, F.; Lista, L.; Monorchio, D.; Sciacca, C.; Baak, M. A.; Raven, G.; Snoek, H. L.; Jessop, C. P.; Losecco, J. M.; Benelli, G.; Corwin, L. A.; Gan, K. K.; Honscheid, K.; Hufnagel, D.; Kagan, H.; Kass, R.; Morris, J. P.; Rahimi, A. M.; Regensburger, J. J.; Ter-Antonyan, R.; Wong, Q. K.; Blount, N. L.; Brau, J.; Frey, R.; Igonkina, O.; Kolb, J. A.; Lu, M.; Rahmat, R.; Sinev, N. B.; Strom, D.; Strube, J.; Torrence, E.; Gagliardi, N.; Gaz, A.; Margoni, M.; Morandin, M.; Pompili, A.; Posocco, M.; Rotondo, M.; Simonetto, F.; Stroili, R.; Voci, C.; Ben-Haim, E.; Briand, H.; Chauveau, J.; David, P.; Del Buono, L.; de La Vaissière, Ch.; Hamon, O.; Hartfiel, B. L.; Leruste, Ph.; Malclès, J.; Ocariz, J.; Perez, A.; Gladney, L.; Biasini, M.; Covarelli, R.; Manoni, E.; Angelini, C.; Batignani, G.; Bettarini, S.; Calderini, G.; Carpinelli, M.; Cenci, R.; Cervelli, A.; Forti, F.; Giorgi, M. A.; Lusiani, A.; Marchiori, G.; Mazur, M. A.; Morganti, M.; Neri, N.; Paoloni, E.; Rizzo, G.; Walsh, J. J.; Haire, M.; Biesiada, J.; Elmer, P.; Lau, Y. P.; Lu, C.; Olsen, J.; Smith, A. J. S.; Telnov, A. V.; Baracchini, E.; Bellini, F.; Cavoto, G.; D'Orazio, A.; Del Re, D.; di Marco, E.; Faccini, R.; Ferrarotto, F.; Ferroni, F.; Gaspero, M.; Jackson, P. D.; Gioi, L. Li; Mazzoni, M. A.; Morganti, S.; Piredda, G.; Polci, F.; Renga, F.; Voena, C.; Ebert, M.; Schröder, H.; Waldi, R.; Adye, T.; Castelli, G.; Franek, B.; Olaiya, E. O.; Ricciardi, S.; Roethel, W.; Wilson, F. F.; Aleksan, R.; Emery, S.; Escalier, M.; Gaidot, A.; Ganzhur, S. F.; de Monchenault, G. Hamel; Kozanecki, W.; Legendre, M.; Vasseur, G.; Yèche, Ch.; Zito, M.; Chen, X. R.; Liu, H.; Park, W.; Purohit, M. V.; Wilson, J. R.; Allen, M. T.; Aston, D.; Bartoldus, R.; Bechtle, P.; Berger, N.; Claus, R.; Coleman, J. P.; Convery, M. R.; Dingfelder, J. C.; Dorfan, J.; Dubois-Felsmann, G. P.; Dujmic, D.; Dunwoodie, W.; Field, R. C.; Glanzman, T.; Gowdy, S. J.; Graham, M. T.; Grenier, P.; Hast, C.; Hryn'Ova, T.; Innes, W. R.; Kelsey, M. H.; Kim, H.; Kim, P.; Leith, D. W. G. S.; Li, S.; Luitz, S.; Luth, V.; Lynch, H. L.; Macfarlane, D. B.; Marsiske, H.; Messner, R.; Muller, D. R.; O'Grady, C. P.; Perazzo, A.; Perl, M.; Pulliam, T.; Ratcliff, B. N.; Roodman, A.; Salnikov, A. A.; Schindler, R. H.; Schwiening, J.; Snyder, A.; Stelzer, J.; Su, D.; Sullivan, M. K.; Suzuki, K.; Swain, S. K.; Thompson, J. M.; Va'Vra, J.; van Bakel, N.; Wagner, A. P.; Weaver, M.; Wisniewski, W. J.; Wittgen, M.; Wright, D. H.; Yarritu, A. K.; Yi, K.; Young, C. C.; Burchat, P. R.; Edwards, A. J.; Majewski, S. A.; Petersen, B. A.; Wilden, L.; Ahmed, S.; Alam, M. S.; Bula, R.; Ernst, J. A.; Jain, V.; Pan, B.; Saeed, M. A.; Wappler, F. R.; Zain, S. B.; Bugg, W.; Krishnamurthy, M.; Spanier, S. M.; Eckmann, R.; Ritchie, J. L.; Ruland, A. M.; Schilling, C. J.; Schwitters, R. F.; Izen, J. M.; Lou, X. C.; Ye, S.; Bianchi, F.; Gallo, F.; Gamba, D.; Pelliccioni, M.; Bomben, M.; Bosisio, L.; Cartaro, C.; Cossutti, F.; Della Ricca, G.; Lanceri, L.; Vitale, L.; Azzolini, V.; Lopez-March, N.; Martinez-Vidal, F.; Milanes, D. A.; Oyanguren, A.; Albert, J.; Banerjee, Sw.; Bhuyan, B.; Hamano, K.; Kowalewski, R.; Nugent, I. M.; Roney, J. M.; Sobie, R. J.; Back, J. J.; Harrison, P. F.; Latham, T. E.; Mohanty, G. B.; Pappagallo, M.; Band, H. R.; Chen, X.; Dasu, S.; Flood, K. T.; Hollar, J. J.; Kutter, P. E.; Pan, Y.; Pierini, M.; Prepost, R.; Wu, S. L.; Yu, Z.; Neal, H.

    2008-02-01

    We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| and of the parameters ρ2, R1(1), and R2(1), which fully characterize the form factors for the B0→D*-ℓ+νℓ decay in the framework of heavy-quark effective field theory. The results, based on a selected sample of about 52 800 B0→D*-ℓ+νℓ decays, recorded by the BABAR detector, are ρ2=1.157±0.094±0.027, R1(1)=1.327±0.131±0.043, R2(1)=0.859±0.077±0.021, and F(1)|Vcb|=(34.7±0.4±1.0)×10-3. The first error is the statistical and the second is the systematic uncertainty. Combining these measurements with the previous BABAR measurement of the form factors, which employs a different fit technique on a partial sample of the data, we improve the statistical precision of the result, ρ2=1.191±0.048±0.028, R1(1)=1.429±0.061±0.044, R2(1)=0.827±0.038±0.022, and F(1)|Vcb|=(34.4±0.3±1.1)×10-3. Using lattice calculations for the axial form factor F(1), we extract |Vcb|=(37.4±0.3±1.2±1.41.2)×10-3, where the third error is due to the uncertainty in F(1). We also present a measurement of the exclusive branching fraction, B=(4.69±0.04±0.34)%.

  10. Building the Frequency Profile of the Core Promoter Element Patterns in the Three ChromHMM Promoter States at 200bp Intervals: A Statistical Perspective

    PubMed Central

    Lent, Heather; Lee, Kyung-Eun

    2015-01-01

    Recently, the Encyclopedia of DNA Elements (ENCODE) Analysis Working Group converted data from ChIP-seq analyses from the Broad Histone track into 15 corresponding chromatic maps that label sequences with different kinds of histone modifications in promoter regions. Here, we publish a frequency profile of the three ChromHMM promoter states, at 200-bp intervals, with particular reference to the existence of sequence patterns of promoter elements, GC-richness, and transcription starting sites. Through detailed and diligent analysis of promoter regions, researchers will be able to uncover new and significant information about transcription initiation and gene function. PMID:26865847

  11. Limits on the Core Mass of Jupiter

    NASA Astrophysics Data System (ADS)

    Stevenson, D. J.

    2015-12-01

    The core is here defined as the central concentration of elements heavier than hydrogen and helium (it need not be solid and it need not be purely heavy elements and it will not have a sharp boundary). Its determination is a major goal of the Juno mission (2016-17) and it will be difficult to determine because it is expected to be only a few percent of the total mass. It has long been known that there is no prospect of determining the nature of this core (e.g., its density) from gravity measurements, even though the mass can be estimated. By consideration of simple models that are nonetheless faithful to the essential physics, it is further shown that should the core be contaminated with light elements (hydrogen and helium) then the gravity data can tell us the core mass as defined (with some caveats about the fuzziness of its boundary) but not the total mass within some small radius (which could include any light elements mixed in). This is both good and bad news: Good in that the core is thought to be diagnostic of the conditions under which the planet formed but bad in that the admixture also tells us more about both formation process and core erosion. Further, a linear perturbation theory has been developed that provides an easy approximate way of determining how errors in the equation of state (EOS) propagate into errors in the estimated core mass or envelope enrichment in heavies in models that nonetheless satisfy all observables. This theory does not require detailed models of the planet but provides an integral mapping from changes in the EOS into approximate changes in radius at fixed mass, and low degree gravity (or moment of inertia, MOI). This procedure also shows that there exist perturbations that leave the radius, mass and MOI unchanged but cause a change in J2, though in practice the non-uniqueness of structure by this consideration (~0.2% or less in MOI for example) is less than the non-uniqueness arising from likely EOS uncertainties (~1% in total

  12. Drill cutting and core major, trace and rare earth element anlayses from wells RN-17B and RN-30, Reykjanes, Iceland

    SciTech Connect

    Andrew Fowler

    2015-05-01

    Analytical results for x-ray fluorescence (XRF) and Inductively Couple Plasma Mass Spectrometry (ICP-MS) measurement of major, trace and rare earth elements in drill cuttings from geothermal wells in Reykjanes, Iceland. Total Fe was analyzed as FeO, therefore is not included under the Fe2O3 column.

  13. An AP-1 binding site in the enhancer/core element of the HIV-1 promoter controls the ability of HIV-1 to establish latent infection.

    PubMed

    Duverger, Alexandra; Wolschendorf, Frank; Zhang, Mingce; Wagner, Fredric; Hatcher, Brandon; Jones, Jennifer; Cron, Randall Q; van der Sluis, Renee M; Jeeninga, Rienk E; Berkhout, Ben; Kutsch, Olaf

    2013-02-01

    Following integration, HIV-1 in most cases produces active infection events; however, in some rare instances, latent infection events are established. The latter have major clinical implications, as latent infection allows the virus to persist despite antiretroviral therapy. Both the cellular factors and the viral elements that potentially determine whether HIV-1 establishes active or latent infection events remain largely elusive. We detail here the contribution of different long terminal repeat (LTR) sequences for the establishment of latent HIV-1 infection. Using a panel of full-length replication-competent virus constructs that reflect naturally occurring differences of HIV-1 subtype-specific LTRs and targeted LTR mutants, we found the primary ability of HIV-1 to establish latent infection in this system to be controlled by a four-nucleotide (nt) AP-1 element just upstream of the NF-κB element in the viral promoter. Deletion of this AP-1 site mostly deprived HIV-1 of the ability to establish latent HIV-1 infection. Extension of this site to a 7-nt AP-1 sequence massively promoted latency establishment, suggesting that this promoter region represents a latency establishment element (LEE). Given that these minimal changes in a transcription factor binding site affect latency establishment to such large extent, our data support the notion that HIV-1 latency is a transcription factor restriction phenomenon. PMID:23236059

  14. An AP-1 Binding Site in the Enhancer/Core Element of the HIV-1 Promoter Controls the Ability of HIV-1 To Establish Latent Infection

    PubMed Central

    Duverger, Alexandra; Wolschendorf, Frank; Zhang, Mingce; Wagner, Fredric; Hatcher, Brandon; Jones, Jennifer; Cron, Randall Q.; van der Sluis, Renee M.; Jeeninga, Rienk E.; Berkhout, Ben

    2013-01-01

    Following integration, HIV-1 in most cases produces active infection events; however, in some rare instances, latent infection events are established. The latter have major clinical implications, as latent infection allows the virus to persist despite antiretroviral therapy. Both the cellular factors and the viral elements that potentially determine whether HIV-1 establishes active or latent infection events remain largely elusive. We detail here the contribution of different long terminal repeat (LTR) sequences for the establishment of latent HIV-1 infection. Using a panel of full-length replication-competent virus constructs that reflect naturally occurring differences of HIV-1 subtype-specific LTRs and targeted LTR mutants, we found the primary ability of HIV-1 to establish latent infection in this system to be controlled by a four-nucleotide (nt) AP-1 element just upstream of the NF-κB element in the viral promoter. Deletion of this AP-1 site mostly deprived HIV-1 of the ability to establish latent HIV-1 infection. Extension of this site to a 7-nt AP-1 sequence massively promoted latency establishment, suggesting that this promoter region represents a latency establishment element (LEE). Given that these minimal changes in a transcription factor binding site affect latency establishment to such large extent, our data support the notion that HIV-1 latency is a transcription factor restriction phenomenon. PMID:23236059

  15. Examining the role of magma mixing with major and minor element distribution patterns in rock-forming minerals in the Tuolumne batholith, Sierra Nevada, CA

    NASA Astrophysics Data System (ADS)

    Krause, J.; Memeti, V.; Paterson, S. R.

    2009-12-01

    Recent geochemical and geochronologic studies emphasize the role of incremental growth of large magma chambers and associated complex magma processes. One of the major results of these studies is that volcanic and plutonic rocks tend to consist of different crystal populations recording complex individual histories. Detailed geochemical observations of individual minerals provide direct access to petrogenetic processes, which are averaged in whole rock analyses. Recent field, U/Pb zircon geochronology and geochemistry data on the 95-85 Ma Tuolumne batholith (TB), Sierra Nevada, CA, have shown ample evidence for extensive mixing between different magmas and internal magma chamber recycling of older marginal units into younger central units within the long lived, main batholith. Its southern lobes are interpreted to represent shorter lived and simpler magma bodies since their composition is attributed to fractionation of magma derived from a single source. In order to test this hypothesis on the mineral scale, X-ray element distribution maps and quantitative analyses have been performed with the electron microprobe on samples from different structural positions both in the lobes and the main chamber of the TB. K-feldspars, ≤ 5 mm large, of the central Kuna Crest lobe, the porphyritic Half Dome lobe, and from the margin of the northern Half Dome lobe often show simple Ba zoning patterns with elevated contents in the center (Ba = 0.8-1.2 wt%) decreasing towards the rim (Ba = 0.4-0.5 wt%). Other K-feldspars ≤ 1.5 mm within the same thin section have reversed zoning with low Ba contents in the core (Ba = 0.1-0.2 wt%) increasing towards the rim (Ba = 0.4-0.6 wt%). A sample from the center of the Cathedral Peak lobe contains idiomorphic K-feldspar phenocrysts ≤ 12 mm with concentric oscillatory Ba-zoning (Ba = 0.6-1.9 wt%) and abundant inclusions of plagioclase. In addition, this sample contains idiomorphic K-feldspars ≤ 1.5 mm with homogeneous cores free of

  16. Fully Crystalline Faceted Fe-Au Core-Shell Nanoparticles.

    PubMed

    Langlois, C; Benzo, P; Arenal, R; Benoit, M; Nicolai, J; Combe, N; Ponchet, A; Casanove, M J

    2015-08-12

    Fe-Au core-shell nanoparticles displaying an original polyhedral morphology have been successfully synthesized through a physical route. Analyses using transmission electron microscopy show that the Au shell forms truncated pyramids epitaxially grown on the (100) facets of the iron cubic core. The evolution of the elastic energy and strain field in the nanoparticles as a function of their geometry and composition is calculated using the finite-element method. The stability of the remarkable centered core-shell morphology experimentally observed is attributed to the weak elastic energy resulting from the low misfit at the Fe/Au (100) interface compared to the surface energy contribution. PMID:26146846

  17. Tbx1 is required autonomously for cell survival and fate in the pharyngeal core mesoderm to form the muscles of mastication.

    PubMed

    Kong, Ping; Racedo, Silvia E; Macchiarulo, Stephania; Hu, Zunju; Carpenter, Courtney; Guo, Tingwei; Wang, Tao; Zheng, Deyou; Morrow, Bernice E

    2014-08-15

    Velo-cardio-facial/DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a congenital anomaly disorder characterized by craniofacial anomalies including velo-pharyngeal insufficiency, facial muscle hypotonia and feeding difficulties, in part due to hypoplasia of the branchiomeric muscles. Inactivation of both alleles of mouse Tbx1, encoding a T-box transcription factor, deleted on chromosome 22q11.2, results in reduction or loss of branchiomeric muscles. To identify downstream pathways, we performed gene profiling of microdissected pharyngeal arch one (PA1) from Tbx1(+/+) and Tbx1(-/-) embryos at stages E9.5 (somites 20-25) and E10.5 (somites 30-35). Basic helix-loop-helix (bHLH) transcription factors were reduced, while secondary heart field genes were increased in expression early and were replaced by an increase in expression of cellular stress response genes later, suggesting a change in gene expression patterns or cell populations. Lineage tracing studies using Mesp1(Cre) and T-Cre drivers showed that core mesoderm cells within PA1 were present at E9.5 but were greatly reduced by E10.5 in Tbx1(-/-) embryos. Using Tbx1(Cre) knock-in mice, we found that cells are lost due to apoptosis, consistent with increase in expression of cellular stress response genes at E10.5. To determine whether Tbx1 is required autonomously in the core mesoderm, we used Mesp1(Cre) and T-Cre mesodermal drivers in combination with inactivate Tbx1 and found reduction or loss of branchiomeric muscles from PA1. These mechanistic studies inform us that Tbx1 is required upstream of key myogenic genes needed for core mesoderm cell survival and fate, between E9.5 and E10.5, resulting in formation of the branchiomeric muscles. PMID:24705356

  18. Tbx1 is required autonomously for cell survival and fate in the pharyngeal core mesoderm to form the muscles of mastication

    PubMed Central

    Kong, Ping; Racedo, Silvia E.; Macchiarulo, Stephania; Hu, Zunju; Carpenter, Courtney; Guo, Tingwei; Wang, Tao; Zheng, Deyou; Morrow, Bernice E.

    2014-01-01

    Velo-cardio-facial/DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a congenital anomaly disorder characterized by craniofacial anomalies including velo-pharyngeal insufficiency, facial muscle hypotonia and feeding difficulties, in part due to hypoplasia of the branchiomeric muscles. Inactivation of both alleles of mouse Tbx1, encoding a T-box transcription factor, deleted on chromosome 22q11.2, results in reduction or loss of branchiomeric muscles. To identify downstream pathways, we performed gene profiling of microdissected pharyngeal arch one (PA1) from Tbx1+/+ and Tbx1−/− embryos at stages E9.5 (somites 20–25) and E10.5 (somites 30–35). Basic helix–loop–helix (bHLH) transcription factors were reduced, while secondary heart field genes were increased in expression early and were replaced by an increase in expression of cellular stress response genes later, suggesting a change in gene expression patterns or cell populations. Lineage tracing studies using Mesp1Cre and T-Cre drivers showed that core mesoderm cells within PA1 were present at E9.5 but were greatly reduced by E10.5 in Tbx1−/− embryos. Using Tbx1Cre knock-in mice, we found that cells are lost due to apoptosis, consistent with increase in expression of cellular stress response genes at E10.5. To determine whether Tbx1 is required autonomously in the core mesoderm, we used Mesp1Cre and T-Cre mesodermal drivers in combination with inactivate Tbx1 and found reduction or loss of branchiomeric muscles from PA1. These mechanistic studies inform us that Tbx1 is required upstream of key myogenic genes needed for core mesoderm cell survival and fate, between E9.5 and E10.5, resulting in formation of the branchiomeric muscles. PMID:24705356

  19. Solar and volcanic forcing of summer air temperatures - a combined ice core and tree ring perspective form the Carpathian Mts. (Europe)

    NASA Astrophysics Data System (ADS)

    Perşoiu, Aurel; Popa, Ionel

    2014-05-01

    In order to improve our understanding of natural and anthropogenic influences on climate, high resolution reconstruction of the climate changes (and associated forcings) during the recent past (last millennium) are strongly needed. While these types of records are available for numerous regions, they are still scarce and with low resolution in the Eastern half of the European continent. In this paper, we present a high-resolution (decadal and better) reconstruction of summer air temperatures from the Carpathian Mts. (Romania), using water stable isotopes in cave ice cores (from Scărişoara Ice Cave) and tree-rings as proxies for summer air temperatures (late and early, respectively). Our combined results show that periods of low solar activity (Wolf, Spörer and Dalton) and the main volcanic eruptions of the past millennium had had a clearly visible - in both isotope and tree ring data - impact on summer temperatures in the area. Worth to mention is that the "year without a summer" occurred in 1818 in both records, two years later than in most of the reconstructions in the vicinity. The Medieval Warm Period is seen as a relatively warm (~0.5 °C warmer than the 1960-1990 period) and stable period in the ice core data, but it's not clearly recorded by the tree rings, while the Little Ice Age (starting at around 1350 in the 14C-dated ice core chronology, and in 1370 in the annually resolved tree ring data) is marked by lower than present (by ~ 1 °C) air temperatures and increased variability. The ice core record stops at 1870 AD due to enhanced ice melting in the 20th century, associated with drier and warmer summer, as seen in the tree ring reconstruction. Our results provide a unique picture of the climate during the past millennium for a region where such information is mostly missing, strengthening the general view of 1) a relatively variable climate during the past 1000 years and 2) rapid warming during the past ~100 years.

  20. Nuclear fuel element

    DOEpatents

    Armijo, Joseph S.; Coffin, Jr., Louis F.

    1983-01-01

    A nuclear fuel element for use in the core of a nuclear reactor is disclosed and has a composite cladding having a substrate and a metal barrier metallurgically bonded on the inside surface of the substrate so that the metal barrier forms a shield between the substrate and the nuclear fuel material held within the cladding. The metal barrier forms about 1 to about 30 percent of the thickness of the cladding and is comprised of a low neutron absorption metal of substantially pure zirconium. The metal barrier serves as a preferential reaction site for gaseous impurities and fission products and protects the substrate from contact and reaction with such impurities and fission products. The substrate of the composite cladding is selected from conventional cladding materials and preferably is a zirconium alloy. Methods of manufacturing the composite cladding are also disclosed.

  1. The role of the sutures in biomechanical dynamic simulation of a macaque cranial finite element model: implications for the evolution of craniofacial form.

    PubMed

    Wang, Qian; Wood, Sarah A; Grosse, Ian R; Ross, Callum F; Zapata, Uriel; Byron, Craig D; Wright, Barth W; Strait, David S

    2012-02-01

    The global biomechanical impact of cranial sutures on the face and cranium during dynamic conditions is not well understood. It is hypothesized that sutures act as energy absorbers protecting skulls subjected to dynamic loads. This hypothesis predicts that sutures have a significant impact on global patterns of strain and cranial structural stiffness when analyzed using dynamic simulations; and that this global impact is influenced by suture material properties. In a finite element model developed from a juvenile Rhesus macaque cranium, five different sets of suture material properties for the zygomaticotemporal sutures were tested. The static and dynamic analyses produced similar results in terms of strain patterns and reaction forces, indicating that the zygomaticotemporal sutures have limited impact on global skull mechanics regardless of loading design. Contrary to the functional hypothesis tested in this study, the zygomaticotemporal sutures did not absorb significant amounts of energy during dynamic simulations regardless of loading speed. It is alternatively hypothesized that sutures are mechanically significant only insofar as they are weak points on the cranium that must be shielded from unduly high stresses so as not to disrupt vitally important growth processes. Thus, sutural and overall cranial form in some vertebrates may be optimized to minimize or otherwise modulate sutural stress and strain. PMID:22190334

  2. The role of the sutures in biomechanical dynamic simulation of a macaque cranial finite element model: Implications for the evolution of craniofacial form

    PubMed Central

    Wang, Qian; Wood, Sarah A.; Grosse, Ian R.; Ross, Callum F.; Zapata, Uriel; Byron, Craig D.; Wright, Barth W.; Strait, David S.

    2012-01-01

    The global biomechanical impact of cranial sutures on the face and cranium during dynamic conditions is not well understood. It is hypothesized that sutures act as energy absorbers protecting skulls subjected to dynamic loads. This hypothesis predicts that sutures have a significant impact on global patterns of strain and cranial structural stiffness when analyzed using dynamic simulations; and that this global impact is influenced by suture material properties. In a finite element model developed from a juvenile Rhesus macaque cranium, five different sets of suture material properties for the zygomaticotemporal sutures were tested. The static and dynamic analyses produced similar results in terms of strain patterns and reaction forces, indicating that the zygomaticotemporal sutures have limited impact on global skull mechanics regardless of loading design. Contrary to the functional hypothesis tested here, the zygomaticotemporal sutures did not absorb significant amounts of energy during dynamic simulations regardless of loading speed. It is alternatively hypothesized that sutures are mechanically significant only insofar as they are weak points on the cranium that must be shielded from unduly high stresses so as not to disrupt vitally important growth processes. Thus, sutural and overall cranial form in some vertebrates may be optimized to minimize or otherwise modulate sutural stress and strain. PMID:22190334

  3. [Changes in the contents of phosphoinositides in formed elements of blood and endometrial tissue in patients with hyperplastic processes and cancer of the endometrium].

    PubMed

    Damirov, M M; Kulakov, V I; Sliusar', N N; Bakuleva, L P

    1995-01-01

    The levels of phosphoinositides were measured in blood macrophages, platelets, lymphocytes, granulocytes, neutrophils, and red cells, as well as in endometrial tissue of 175 patients with glandular hyperplasia of the endometrium, atypical hyperplasia, endometrial polyps and cancer. A reliable reduction of the content of phosphatidyl inositides and phosphatidyl inositide-S-phosphates was observed in all formed elements of the blood, the most marked decrease being observed in endometrial cancer. On the contrary, the content of phosphatidyl inositide-4-phosphates and phosphatidyl inositide-4.5-diphosphates in the macrophages, lymphocytes, and granulocytes was reliably increased in the patients as against healthy women. The process of phosphatidylinositide phosphorylation run an absolutely different course in pathologically altered endometrial tissue than in comparison with that in blood cells. A new phosphatidyl inositide-signal mechanism was revealed, which is unrelated to inositol-1.4.5-triphosphate, as a result of which the potentiality of appearance of new secondary messengers actively participating in cell growth increases. PMID:7485761

  4. Ground-state properties of alkali dimers and their cations (including the elements Li, Na, and K) from ab initio calculations with effective core polarization potentials

    NASA Astrophysics Data System (ADS)

    Müller, Wolfgang; Meyer, Wilfried

    1984-04-01

    Extensive all-electron SCF and valence CI calculations are presented for alkali dimer systems with consideration of intershell correlation effects by use of an effective core polarization potential (CPP), which contains only a single adjustable atomic parameter. High accuracy is obtained for the ground-state spectroscopic constants of the studied molecules. The maximum deviations from accurate experimental data are as follows: 1% or 0.03 Å for Re, 2% or 100 cm-1 for De, 0.5% or 1 cm-1 for ωe, and 0.2% or 100 cm-1 for ionization energies. For experimentally uncertain or unknown values reliable predictions can thus be made. The calculated dipole moments for LiK and NaK agree with experiment to within 0.1%, but for LiNa we obtain a deviation of 8% or 0.036 D. An analysis of molecular core polarization contributions reveals the reasons for some systematic defects in previous pseudopotential calculations.

  5. Structure and magnetism in Fe/FexPd1-x core/shell nanoparticles formed by alloying in Pd-embedded Fe nanoparticles

    NASA Astrophysics Data System (ADS)

    Baker, S. H.; Lees, M.; Roy, M.; Binns, C.

    2013-09-01

    We have investigated atomic structure and magnetism in Fe nanoparticles with a diameter of 2 nm embedded in a Pd matrix. The samples for these studies were prepared directly from the gas phase by co-deposition, using a gas aggregation source and an MBE-type source for the Fe nanoparticles and Pd matrix respectively. Extended absorption fine structure (EXAFS) measurements indicate that there is an appreciable degree of alloying at the nanoparticle/matrix interface; at dilute nanoparticle concentrations, more than half of the Fe atoms are alloyed with Pd. This leads to a core/shell structure in the embedded nanoparticles, with an FexPd1-x shell surrounding a reduced pure Fe core. Magnetism in the nanocomposite samples was probed by means of magnetometry measurements, which were interpreted in the light of their atomic structure. These point to a magnetized cloud of Pd atoms surrounding the embedded nanoparticles which is significantly larger than around single Fe atoms in Pd. The coercivities in the Fe/Pd nanocomposite samples are larger than in FexPd1-x atomic alloys of corresponding composition, which is consistent with exchange coupling between the magnetically harder and softer regions in the nanocomposite samples.

  6. Constraints on the Nature of Terrestrial Core-Forming Melts: Ultra-High Pressure Transport Property Measurements and X-Ray Computed Tomography Final Report

    SciTech Connect

    Roberts, J J; Kinney, J H; Ryerson, F J

    2006-01-20

    A key issue in models of planetary core formation is the interconnectness and potential percolation of iron-sulfide melts in contact with silicates at high temperature and pressure. To address this issue an integrated study of the electrical conductivity-texture-permeability relationships of olivine-sulfide partial-melt samples was performed. This work has application to the interpretation of high conductivity zones in the Earth as revealed by electromagnetic studies and to the origin and development of the Earth's core. The project consisted of three main tasks. (1) Synthesis and characterization of olivine-sulfide partial-melts. (2) Electrical conductivity measurements of the partial-melt and the individual melt and crystalline phases. (3) X-ray microtomographic determination of the 3-D structure and interconnectedness of the melt phase. The results are used to determine a model of permeability of a partially molten solid that incorporates the melt distribution, a goal that has never before been achieved. Material synthesis was accomplished in the piston cylinder apparatus and electrical conductivity measurements were performed at one atmosphere. X-ray computed tomography was performed on recovered samples at the ALS. This work makes use of and further enhances LLNL's strengths in high-pressure material properties, x-ray micro- and nanoscale imaging and development of transport theory.

  7. Double-diffusive inner core convective translation

    NASA Astrophysics Data System (ADS)

    Deguen, Renaud; Alboussière, Thierry; Labrosse, Stéphane

    2016-04-01

    The hemispherical asymmetry of the inner core has been interpreted as resulting form a high-viscosity mode of inner core convection, consisting in a translation of the inner core. With melting on one hemisphere and crystallization on the other one, inner core translation would impose a strongly asymmetric buoyancy flux at the bottom of the outer core, with likely strong implications for the dynamics of the outer core and the geodynamo. The main requirement for convective instability in the inner core is an adverse radial density gradient. While older estimates of the inner core thermal conductivity favored a superadiabatic temperature gradient and the existence of thermal convection, the much higher values recently proposed makes thermal convection very unlikely. Compositional convection might be a viable alternative to thermal convection: an unstable compositional gradient may arise in the inner core either because the light elements present in the core are predicted to become increasingly incompatible as the inner core grows (Gubbins et al. 2013), or because of a possibly positive feedback of the development of the F-layer on inner core convection. Though the magnitude of the destabilizing effect of the compositional field is predicted to be similar to or smaller than the stabilizing effect of the thermal field, the huge difference between thermal and chemical diffusivities implies that double-diffusive instabilities can still arise even if the net density decreases upward. We propose here a theoretical and numerical study of double diffusive convection in the inner core that demonstrate that a translation mode can indeed exist if the compositional field is destabilizing, even if the temperature profile is subadiabatic, and irrespectively of the relative magnitude of the destabilizing compositional gradient and stabilizing temperature field. The predicted inner core translation rate is similar to the mean inner core growth rate, which is more consistent with

  8. Trace element partitioning in Earth's lower mantle and implications for geochemical consequences of partial melting at the core-mantle boundary

    NASA Astrophysics Data System (ADS)

    Hirose, Kei; Shimizu, Nobumichi; van Westrenen, Wim; Fei, Yingwei

    2004-08-01

    Trace element partitioning data between CaSiO 3-perovskite (CaPv), MgSiO 3-perovskite (MgPv), calcium-aluminum silicate (CAS-phase), and coexisting melts in peridotite and mid-ocean ridge basalt (MORB) compositions were obtained at 25-27 GPa and 2400-2530 °C using multi-anvil apparatus and ion microprobe. Results clearly show that CaPv is the predominant host for large ion lithophile elements (LILE) in the lower mantle. Because of the overwhelmingly high CaPv/melt partition coefficients (>10 for many of the LILE), partial melting in the lower mantle causes strong enrichment of LILE in the CaPv-bearing solid phase residue. CaPv has the following partitioning characteristics: (1) uniformly high partition coefficients for heavy rare earth elements (HREE) (e.g. 15 for Yb), decreasing toward light REE (e.g. 7 for La), (2) systematically lower partition coefficients for high field strength elements (Nb, Zr, Ti) and Sr relative to neighboring REE, (3) high Th and U, and systematically low Pb partition coefficients. Previous high-pressure studies have shown that the stability field of CaPv above solidus temperature is much wider in basaltic composition than in peridotite, indicating that melting of subducted oceanic crust in the lower mantle could produce significant geochemical CaPv signatures. Strong enrichment in Th and U relative to Pb in CaPv would result in radiogenic Pb isotopic compositions of the CaPv-bearing solid residue. Some clinopyroxenes in plume mantle peridotite xenoliths possess trace element patterns closely resembling those of natural CaPv found in diamonds and CaPv from the present experiments, suggesting that they were inherited from the CaPv-bearing precursor. In contrast, CaPv is the first phase to disappear during partial melting of peridotite above 24 GPa, and its geochemical signature may not be observable in nature. (MgPv + CaPv) fractional crystallization from a magma ocean has previously been put forward as a mechanism for Si depletion of the

  9. Composite Cores

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Spang & Company's new configuration of converter transformer cores is a composite of gapped and ungapped cores assembled together in concentric relationship. The net effect of the composite design is to combine the protection from saturation offered by the gapped core with the lower magnetizing requirement of the ungapped core. The uncut core functions under normal operating conditions and the cut core takes over during abnormal operation to prevent power surges and their potentially destructive effect on transistors. Principal customers are aerospace and defense manufacturers. Cores also have applicability in commercial products where precise power regulation is required, as in the power supplies for large mainframe computers.

  10. Making an Ice Core.

    ERIC Educational Resources Information Center

    Kopaska-Merkel, David C.

    1995-01-01

    Explains an activity in which students construct a simulated ice core. Materials required include only a freezer, food coloring, a bottle, and water. This hands-on exercise demonstrates how a glacier is formed, how ice cores are studied, and the nature of precision and accuracy in measurement. Suitable for grades three through eight. (Author/PVD)

  11. Effects of urbanization and long-term rainfall on the occurrence of organic compounds and trace elements in reservoir sediment cores, streambed sediment, and fish tissue from the Santa Ana River basin, California, 1998

    USGS Publications Warehouse

    Burton, Carmen A.

    2002-01-01

    Organcochlorine compounds, semivolatile-organic compounds (SVOC), and trace elements were analyzed in reservoir sediment cores, streambed sediment, and fish tissue in the Santa Ana River Basin as part of the U.S. Geological Survey's National Water-Quality Assessment Program. Three reservoirs were sampled in areas that have different degrees of urbanization. Streambed sediment and fish tissue collected at 12 sites were divided into two groups, urban and nonurban. More organochlorine compounds were detected in reservoir sediment cores, streambed sediment and fish tissue, and at higher concentrations at urban sites than at nonurban sites. At all sites, except West Street Basin, concentrations of organochlorine compounds were lower than the probable-effect concentration (PEC). At the highly urbanized West Street Basin, chlordane and p,p'-DDE exceeded the PEC throughout the historical record. The less stringent threshold-effect concentration (TEC) was exceeded for six compounds at eight sites. Most of the organochlorine compounds detected in streambed sediment and fish tissue were at urban sites on the Santa Ana River as opposed to its tributaries, suggesting accumulation and persistence in the river. More SVOCs were detected in reservoir sediment cores and streambed sediment, and at higher concentrations, at urban sites than at nonurban sites. At all the sites, except West Street Basin, concentrations of SVOCs were lower than the PEC. At West Street Basin, chrysene, pyrene, and total polycyclic-aromatic hydrocarbons exceeded the PEC throughout the historical record. The TEC was exceeded for 10 compounds at 3 sites. Most of the SVOCs were detected in streambed sediment at urban sites on tributaries to the Santa Ana River rather than the mainstem itself. The less frequent occurrence and lower concentrations in the Santa Ana River suggest that SVOCs are less persistent than organochlorine compounds, possibly as a result of volatization, gradation, or dilution. Most trace-element

  12. Trace elements in organic- and iron-rich surficial fluids of the boreal zone: Assessing colloidal forms via dialysis and ultrafiltration

    NASA Astrophysics Data System (ADS)

    Vasyukova, E. V.; Pokrovsky, O. S.; Viers, J.; Oliva, P.; Dupré, B.; Martin, F.; Candaudap, F.

    2010-01-01

    On-site size fractionation of about 40 major and trace elements (TE) was performed on waters from boreal small rivers and their estuaries in the Karelia region of North-West Russia around the "Vetreny Belt" mountain range and in Paanajärvi National Park (Northern Karelia). Samples were filtered in the field using a progressively decreasing pore size (5 μm, 2.5 (3) μm, 0.22 (0.45) μm, 100 kDa, 10 and 1 kDa) by means of frontal filtration and ultrafiltration (UF) techniques and employing in-situ dialysis with 10 and 1 kDa membranes followed by ICP-MS analysis. For most samples, dialysis yields a systematically higher (factor of 2-3) proportion of colloidal forms compared to UF. Nevertheless, dialysis is able to provide a fast and artefact-free in-situ separation of colloidal and dissolved components. Similar to previous studies in European subarctic zones, poor correlation of iron concentration with that of organic carbon (OC) in (ultra)filtrates and dialysates reflect the presence of two pools of colloids composed of organic-rich and Fe-rich particles. All major anions and silica are present as dissolved species (or solutes) passing through the 1-kDa membrane. Size-separation ultrafiltration experiments show the existence of larger or smaller pools of colloidal particles different for each of the considered elements. The effect of rock lithology (acidic versus basic) on the colloidal speciation of TE is seen solely in the increase of Fe and some accompanying TE concentrations in catchment areas dominated by basic rocks compared to granitic catchments. Neither the ultrafiltration pattern nor the relative proportions of colloidal versus truly dissolved TE are affected by the lithology of the underlying rocks: within ±10% uncertainty, the two colloidal (10 kDa-0.22 μm and 1-10 kDa) and the truly dissolved (<1 kDa) pools show no difference in percentage of TE distribution between two types of bedrock lithology. The same conclusion is held for organic- and Fe

  13. Nuclear core positioning system

    DOEpatents

    Garkisch, Hans D.; Yant, Howard W.; Patterson, John F.

    1979-01-01

    A structural support system for the core of a nuclear reactor which achieves relatively restricted clearances at operating conditions and yet allows sufficient clearance between fuel assemblies at refueling temperatures. Axially displaced spacer pads having variable between pad spacing and a temperature compensated radial restraint system are utilized to maintain clearances between the fuel elements. The core support plates are constructed of metals specially chosen such that differential thermal expansion produces positive restraint at operating temperatures.

  14. Mechanochemical surface functionalisation of superparamagnetic microparticles with in situ formed crystalline metal-complexes: a fast novel core-shell particle formation method.

    PubMed

    Brede, F A; Mandel, K; Schneider, M; Sextl, G; Müller-Buschbaum, K

    2015-05-21

    An innovative mechanochemical method is reported for the in situ formation of crystalline metal-complexes on the surface of superparamagnetic nanocomposite microparticles. The process is demonstrated for coating Fe3O4 multicore-silica matrix particles with the 1,2,4-1H-triazole complex [ZnCl2(TzH)2]. The use of mechanochemistry demonstrates a flexible process to obtain functional shells on magnetic particle cores without the need for complicated surface-functionalisation reactions in solution. Simple mixing of the desired shell-precursors ZnCl2 and 1,2,4-1H-triazole (TzH) with the magnetic particles in a ball mill is sufficient to tailor the particle surfaces with novel functionalities while retaining the superparamagnetic behaviour. PMID:25907694

  15. "Snowing" Core in Earth?

    NASA Astrophysics Data System (ADS)

    Li, J.; Chen, B.; Cormier, V.; Gao, L.; Gubbins, D.; Kharlamova, S. A.; He, K.; Yang, H.

    2008-12-01

    As a planet cools, an initially molten core gradually solidifies. Solidification occurs at shallow depths in the form of "snow", if the liquidus temperature gradient of the core composition is smaller than the adiabatic temperature gradient in the core. Experimental data on the melting behavior of iron-sulfur binary system suggest that the cores of Mercury and Ganymede are probably snowing at the present time. The Martian core is predicted to snow in the future, provided that the sulfur content falls into the range of 10 to 14 weight percent. Is the Earth's core snowing? If so, what are the surface manifestations? If the Earth's core snowed in the past, how did it affect the formation of the solid inner core and the geodynamo? Here, we evaluate the likelihood and consequences of a snowing core throughout the Earth's history, on the basis of mineral physics data describing the melting behavior, equation-of-state, and thermodynamic properties of iron-rich alloys at high pressures. We discuss if snowing in the present-day Earth can reproduce the shallow gradients of compressional wave velocity above the inner-core boundary, and whether or not snowing in the early Earth may reconcile the apparent young age of the solid inner core with a long-lived geodynamo.

  16. Net-b, a Ras-insensitive factor that forms ternary complexes with serum response factor on the serum response element of the fos promoter.

    PubMed

    Giovane, A; Sobieszczuk, P; Ayadi, A; Maira, S M; Wasylyk, B

    1997-10-01

    The Ras signalling pathway targets transcription factors such as the ternary complex factors that are recruited by the serum response factor to form complexes on the serum response element (SRE) of the fos promoter. We have identified a new ternary complex factor, Net-b. We report the features of the net gene and show that it produces several splice variants, net-b and net-c. net-b RNA and protein are expressed in a variety of tissues and cell lines. net-c RNA is expressed at low levels, and the protein was not detected, raising the possibility that it is a cryptic splice variant. We have studied the composition of ternary complexes that form on the SRE of the fos promoter with extracts from fibroblasts (NIH 3T3) cultured under various conditions and pre-B cells (70Z/3) before and after differentiation with lipopolysaccharide (LPS). The fibroblast complexes contain mainly Net-b followed by Sap1 and Elk1. Net-b complexes, as well as Sap1 and Elk1, are induced by epidermal growth factor (EGF) stimulation of cells cultured in low serum. Pre-B-cell complexes contain mainly Sap1, with less of Net-b and little of Elk1. There is little change upon LPS-induced differentiation compared to the increase with EGF in fibroblasts. We have also found that Net-b is a nuclear protein that constitutively represses transcription. Net-b is not activated by Ras signalling, in contrast to Net, Sap1a, and Elk1. We have previously reported that down-regulation of Net proteins with antisense RNA increases SRE activity. The increase in SRE activity is observed at low serum levels and is even greater after serum stimulation, showing that the SRE is under negative regulation by Net proteins and the level of repression increases during induction. Net-b, the predominant factor in ternary complexes in fibroblasts, may both keep the activity of the SRE low in the absence of strong inducing conditions and rapidly shut the activity off after stimulation. PMID:9315625

  17. Evolution of ore forming fluid in the orogenic type gold deposit in Tavt, Mongolia: trace element geochemistry and fluid inclusions in quartz

    NASA Astrophysics Data System (ADS)

    Lee, K.; Oyungerel, S.; Lee, I.

    2011-12-01

    The Tavt gold deposit of Dzhida-Selengisky metallogenic belt is located in the Dzhida terrane, northern Mongolia. This deposit commonly occurs with massive auriferous quartz veins that contain sulfides and less commonly occurs with disseminated- and stockwork-type quartz veins. Such gold-bearing quartz veins have an average grade of 6.3 g/t Au, 29.4 g/t Ag, and 1.3% Cu. This gold deposit is composed of three stages of quartz vein groups. The first stage quartz group is widely spread with medium to large grain size, showing white-grey and milky white colors. It underwent intensive cataclasis with strong cuts via fractures and includes a small amount of sulfides, secondary minerals and Au. The second stage quartz group is grey and includes an oxidation zone. The oxidation zone distributed on the outside of the vein is brown and green-grey; it is also enriched with sulfide minerals containing gold. This quartz group is located in a brittle and cataclastic zone with the first stage quartz group. The main mineralization process for gold is related to this second stage quartz group. The transition between the first and second groups is not clear, and their contact relationship is complex. The third stage quartz group is transparent to translucent, and has small euhedral crystals that were formed in the second stage quartz group. The third stage of quartz is partly associated with chlorite and montmorillonite that was formed in the latest stage. Each generation of quartz was analyzed by SEM-CL, EPMA, and ICP-MS. Fluid inclusion data were collected from the USGS gas-flow heating/freezing stage and Raman-spectroscopy. The electron microprobe data show the distribution of Al, Ca, K and Fe among distinguished CL intensities and textures of quartz from different stages. The prepared pure quartz samples were analyzed by ICP-MS. The analysis also shows different patterns of trace elements according to the quartz stages.

  18. Net-b, a Ras-insensitive factor that forms ternary complexes with serum response factor on the serum response element of the fos promoter.

    PubMed Central

    Giovane, A; Sobieszczuk, P; Ayadi, A; Maira, S M; Wasylyk, B

    1997-01-01

    The Ras signalling pathway targets transcription factors such as the ternary complex factors that are recruited by the serum response factor to form complexes on the serum response element (SRE) of the fos promoter. We have identified a new ternary complex factor, Net-b. We report the features of the net gene and show that it produces several splice variants, net-b and net-c. net-b RNA and protein are expressed in a variety of tissues and cell lines. net-c RNA is expressed at low levels, and the protein was not detected, raising the possibility that it is a cryptic splice variant. We have studied the composition of ternary complexes that form on the SRE of the fos promoter with extracts from fibroblasts (NIH 3T3) cultured under various conditions and pre-B cells (70Z/3) before and after differentiation with lipopolysaccharide (LPS). The fibroblast complexes contain mainly Net-b followed by Sap1 and Elk1. Net-b complexes, as well as Sap1 and Elk1, are induced by epidermal growth factor (EGF) stimulation of cells cultured in low serum. Pre-B-cell complexes contain mainly Sap1, with less of Net-b and little of Elk1. There is little change upon LPS-induced differentiation compared to the increase with EGF in fibroblasts. We have also found that Net-b is a nuclear protein that constitutively represses transcription. Net-b is not activated by Ras signalling, in contrast to Net, Sap1a, and Elk1. We have previously reported that down-regulation of Net proteins with antisense RNA increases SRE activity. The increase in SRE activity is observed at low serum levels and is even greater after serum stimulation, showing that the SRE is under negative regulation by Net proteins and the level of repression increases during induction. Net-b, the predominant factor in ternary complexes in fibroblasts, may both keep the activity of the SRE low in the absence of strong inducing conditions and rapidly shut the activity off after stimulation. PMID:9315625

  19. Trace element partitioning in rock forming minerals of co-genetic, subduction-related alkaline and tholeiitic mafic rocks in the Ural Mountains, Russia

    NASA Astrophysics Data System (ADS)

    Krause, J.; Brügmann, G. E.; Pushkarev, E. V.

    2009-04-01

    The partitioning of trace elements between rock forming minerals in igneous rocks is largely controlled by physical and chemical parameters e.g. temperature, pressure and chemical composition of the minerals and the coexisting melt. In the present study partition coefficients for REE between hornblende, orthopyroxene, feldspars, apatite and clinopyroxene in a suite of co-genetic alkaline and tholeiitic mafic rocks from the Ural Mountains (Russia) were calculated. The results give insights to the influence of the chemical composition of the parental melt on the partitioning behaviour of the REE. Nepheline-bearing, alkaline melanogabbros (tilaites) are assumed to represent the most fractionated products of the melt that formed the ultramafic cumulates in zoned mafic-ultramafic complexes in the Ural Mountains. Co-genetic with the latter is a suite of olivine gabbros, gabbronorites and hornblende gabbros formed from a tholeiitic parental melt. Negative anomalies for the HFSE along with low Nb and Ta contents and a positive Sr anomaly indicate a subduction related origin of all parental melts. The nepheline gabbros consist predominantly of coarse-grained clinopyroxene phenocrysts in a matrix of fine grained clinopyroxene, olivine, plagioclase, K-feldspar and nepheline with accessory apatite. The tholeiitic gabbros have equigranular to porphyric textures with phenocrysts of olivine, pyroxene and hornblende in a plagioclase rich matrix with olivine hornblende, pyroxene and accessory apatite. Element concentrations of adjacent matrix grains and rims of phenochrysts were measured with LA-ICPMS. The distribution of REE between hornblende and clinopyroxene in the tholeiitic rocks is similar for most of the elements (DHbl•Cpx(La-Tm) = 2.7-2.8, decreasing to 2.6 and 2.4 for Yb and Lu, respectively). These values are about two times higher than published data (e.g. Ionov et al. 1997). Partition coefficients for orthopyroxene/clinopyroxene systematically decrease from the HREE

  20. Evaluation of a barley core collection for spot form net blotch reaction reveals distinct genotype specific pathogen virulence and host susceptibility

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spot form net blotch (SFNB) caused by Pyrenophora teres Drechs. f. maculata Smedeg., (anamorph Drechslera teres [Sacc.] Shoem.) is a major foliar disease of barley (Hordeum vulgare L.) worldwide. SFNB epidemics have recently been observed in major barley producing countries, suggesting that the loca...

  1. Siderophile element partitioning between cohenite and liquid in the Fe-Ni-S-C system and implications for geochemistry of planetary cores and mantles

    NASA Astrophysics Data System (ADS)

    Buono, Antonio S.; Dasgupta, Rajdeep; Lee, Cin-Ty A.; Walker, David

    2013-11-01

    We experimentally investigated the effects of pressure and S content on partition coefficients (D) between crystalline cohenite and liquid in the Fe-Ni-S-C system. Compositions with S contents of 0, 4.72, and 14.15 wt.%, in an Fe-rich mix containing a constant C (4.72 wt.%), Ni (5.23 wt.%), and W, Re, Os, Pt, and Co (totaling 0.43 wt.%) were equilibrated at 1150 °C and 3 and 6 GPa. Our cohenite-melt D data are compared to literature Fe-Ni-S and Fe-Ni-C experiments involving a crystalline phase of Fe. There is a change in D when the solid is cohenite rather than crystalline iron. Compared to solid-Fe/melt Ds, cohenite/melt Ds are lower for all elements except W.

  2. Core shroud corner joints

    DOEpatents

    Gilmore, Charles B.; Forsyth, David R.

    2013-09-10

    A core shroud is provided, which includes a number of planar members, a number of unitary corners, and a number of subassemblies each comprising a combination of the planar members and the unitary corners. Each unitary corner comprises a unitary extrusion including a first planar portion and a second planar portion disposed perpendicularly with respect to the first planar portion. At least one of the subassemblies comprises a plurality of the unitary corners disposed side-by-side in an alternating opposing relationship. A plurality of the subassemblies can be combined to form a quarter perimeter segment of the core shroud. Four quarter perimeter segments join together to form the core shroud.

  3. Lunar core: occam's razor?

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    Whether or not the earth's moon has a core is a much bandied question. Like many notions about the properties of the moon, ideas of a lunar core changed drastically after the Apollo studies. A review of the development of these ideas was given a scholarly treatment by S.K. Runcorn recently (Nature, 304, 589-596, 1983). In contrast, L.L. Hood, C.P. Sonett, and L.J. Srnka have questioned the concept in serious detail (Nature, 307, 661-662, 1984).Whether or not the moon actually has or has had a fluid metallic core is of great consequence for a number of geophysical theories about the solar system. Most investigators concede that the possible existence of a lunar core remains one of the major unanswered, and yet most critical, questions about the moon. A lot rides on the answer: Can a lunar-sized body have a core? Is the core metallic? How is the core related to lunar magnetism and its paleomagnetism? Is or was a lunar core related to lunar volcanism? If the moon can have a core, is planetary core formation in the solar system a simple matter of gravitationally segregating metallic fragments that were formed elsewhere? Implications of the questions are without limit. There is, perhaps, no more valid issue about the moon to explore scientifically.

  4. Solubilization of Hexafluorobenzene by the Micellar Aromatic Core Formed from Aggregation of Amphiphilic (2,3-O-Dibenzyl-6-O-sulfobutyl) Cyclodextrins.

    PubMed

    McKee, James A; Green, Thomas K

    2016-05-01

    Aggregation colloids that possess an aromatic pseudophase in an aqueous system could provide new avenues of research including micellar catalysis, aqueous remediation, and emulsion polymerization studies. The apparent aggregation of two macrocyclic surfactants, hexakis (2,3-O-dibenzyl-6-O-sulfobutyl) cyclomaltohexaose (DBSBA) and heptakis (2,3-O-dibenzyl-6-O-sulfobutyl) cyclomaltoheptaose (DBSBB), was investigated using diffusion ordered nuclear magnetic resonance (NMR) spectroscopy (DOSY), conductivity, and pyrene fluorescence techniques. These amphiphiles were found to possess near spherical symmetry at critical micelle concentrations of approximately 0.1 mM in all techniques used to study the phenomenon. Aggregation of both surfactants was found to be entropically driven at low temperatures but enthalpically driven at higher temperatures. The calculated compensation temperatures of DBSBA and DBSBB were determined to be 317 and 307 K, respectively. These surfactants contain a high percentage of aromatic moieties in their structures, which affects the thermodynamics of aggregation and their interior micellar environment. The proposed aromatic micellar core was tested using hexafluorobenzene (HFB) as a molecular probe in (19)F NMR experiments. (19)F NMR relaxation and chemical shift studies found the HFB quantitatively partitioned into the micellar interiors. Global regression analysis found that HFB interaction with DBSBA micelles possessed at least two association constants, differing by an order of magnitude, the largest being in excess of 8300 M(-1). DBSBB micellar interactions with HFB were found to be weaker, although in excess of 1100 M(-1), with a subsequent association constant of similar magnitude. Benzyl substituents of DBSBB are required for solubilization of HFB. Heteronuclear Overhauser effect spectroscopy (HOESY, (19)F-(1)H) of the DBSBB:HFB complex revealed strong interaction of HFB with benzyl substituents but not the cyclodextrin cavity. PMID

  5. NEUTRONIC REACTOR FUEL ELEMENT

    DOEpatents

    Stacy, J.T.

    1958-12-01

    A reactor fuel element having a core of molybdenum-uranium alloy jacketed in stainless steel is described. A barrier layer of tungsten, tantalum, molybdenum, columbium, or silver is interposed between the core and jacket to prevent formation of a low melting eutectic between uranium and the varlous alloy constituents of the stainless steel.

  6. JACKETED REACTOR FUEL ELEMENT

    DOEpatents

    Smith, K.F.; Van Thyne, R.J.

    1958-12-01

    A fuel element is described for fast reactors comprised of a core of uranium metal containing material and a jacket around the core, the jacket consisting of from 2.5 to 15 percent of titanium, from 1 to 5 percent of niobium, and from 80 to 96.5 percent of vanadium.

  7. Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses

    SciTech Connect

    Zhang, Kai; Fan, Meng; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O’Hern, Corey S.

    2015-11-14

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate R{sub c}, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. R{sub c} (or the corresponding critical casting thickness d{sub c}) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small R{sub c} < 10{sup −2} K/s, pure metals and most alloys are typically poor glass-formers with large R{sub c} > 10{sup 10} K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with R{sub c} approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for

  8. Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Fan, Meng; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2015-11-01

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate Rc, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. Rc (or the corresponding critical casting thickness dc) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small Rc < 10-2 K/s, pure metals and most alloys are typically poor glass-formers with large Rc > 1010 K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with Rc approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for designing BMGs with cm or greater casting thickness.

  9. Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses.

    PubMed

    Zhang, Kai; Fan, Meng; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2015-11-14

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate Rc, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. Rc (or the corresponding critical casting thickness dc) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small Rc < 10(-2) K/s, pure metals and most alloys are typically poor glass-formers with large Rc > 10(10) K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with Rc approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for designing BMGs with cm or greater casting

  10. Constraints on the flux of meteoritic and cometary water on the Moon from volatile element (N-Ar) analyses of single lunar soil grains, Luna 24 core

    NASA Astrophysics Data System (ADS)

    Füri, Evelyn; Marty, Bernard; Assonov, Sergey S.

    2012-03-01

    We report new nitrogen and argon isotope and abundance results for single breccia clasts and agglutinates from four different sections of the Luna 24 drill core in order to re-evaluate the provenance of N trapped in lunar regolith, and to place limits on the flux of planetary material to the Moon’s surface. Single Luna 24 grains with 40Ar/36Ar ratios <1 show δ15N values between -54.5‰ and +123.3‰ relative to terrestrial atmosphere. Thus, low-antiquity lunar soils record both positive and negative δ15N signatures, and the secular increase of the δ15N value previously postulated by Kerridge (Kerridge, J.F. [1975]. Science 188(4184), 162-164. doi:10.1126/science.188.4184.162) is no longer apparent when the Luna and Apollo data are combined. Instead, the N isotope signatures, corrected for cosmogenic 15N, are consistent with binary mixing between isotopically light solar wind (SW) N and a planetary N component with a δ15N value of +100‰ to +160‰. The lower δ15N values of Luna 24 grains compared to Apollo samples reflect a higher relative proportion of solar N, resulting from the higher SW fluence in the region of Mare Crisium compared to the central near side of the Moon. Carbonaceous chondrite-like micro-impactors match well the required isotope characteristics of the non-solar N component trapped in low-antiquity lunar regolith. In contrast, a possible cometary contribution to the non-solar N flux is constrained to be ⩽3-13%. Based on the mixing ratio of SW to planetary N obtained for recently exposed lunar soils, we estimate the flux of micro-impactors to be (2.2-5.7) × 103 tons yr-1 at the surface of the Moon. Our estimate for Luna 24 agrees well with that for young Apollo regolith, indicating that the supply of planetary material does not depend on lunar location. Thus, the continuous influx of water-bearing cosmic dust may have represented an important source of water for the lunar surface over the past ∼1 Ga, provided that water removal rates

  11. PROCESS FOR JACKETING A CORE

    DOEpatents

    Last, G.A.

    1960-07-19

    A process is given for enclosing the uranium core of a nuclear fuel element by placing the core in an aluminum cup and closing the open end of the cup over the core. As the metal of the cup is brought together in a weld over the center of the end of the core, it is extruded inwardly as internal projection into a central recess in the core and outwardly as an external projection. Thus oxide inclusions in the weld of the cup are spread out into the internal and external projections and do not interfere with the integrity of the weld.

  12. Alkali metal and rare earth element evolution of rock-forming minerals from the Gatumba area pegmatites (Rwanda): Quantitative assessment of crystal-melt fractionation in the regional zonation of pegmatite groups

    NASA Astrophysics Data System (ADS)

    Hulsbosch, Niels; Hertogen, Jan; Dewaele, Stijn; André, Luc; Muchez, Philippe

    2014-05-01

    This study presents a general model for the evaluation of Rayleigh fractional crystallisation as the principal differentiation mechanism in the formation of regionally zoned common and rare-element pegmatites. The magmatic evolution of these systems from a granitic source is reconstructed by means of alkali element and rare earth element (REE) analyses of rock-forming minerals (feldspars, micas and tourmaline), which represent a whole sequence of regional pegmatite zonation. The Gatumba pegmatite field (Rwanda, Central Africa) is chosen as case study area because of its well-developed regional zonation sequence. The pegmatites are spatially and temporally related to peraluminous G4-granites (986 ± 10 Ma). The regional zonation is developed around a G4-granite and the proximal pegmatites grade outwardly into biotite, two-mica and muscovite pegmatites. Rare-element (Nb-Ta-Sn) pegmatites occur most distal from the granite.

  13. Iras-Selected Galactic Star-Forming Regions - Part One - New 6/16-5/23 Water Maser Detections in Molecular Cores North of DEC +15DEG

    NASA Astrophysics Data System (ADS)

    Palumbo, G. G. C.; Scappini, F.; Pareschi, G.; Codella, C.; Caselli, P.; Attolini, M. R.

    1994-01-01

    The results are presented of a survey, performed with the Medicina 32-m parabolic reflector, of a sample of IRAS-selected sources associated with molecular clouds for water masers at 22 GHz (616 → 523). The final aim is to study the occurrence of maser emission from star-forming regions in the very early stages of evolution. The whole sample consists of 1409 IRAS sources selected by applying Emerson's colour criteria. In the present paper, results are given for sources with declinations greater than +15°, belonging to two subsamples that satisfy more restrictive colour criteria which should identify ultracompact H II regions (subsample A, 288 sources) and H II regions (subsample B, 133 sources). The main result of the present study is that 59 IRAS sources in the samples are water maser emitters, 11 of which are new detections from the present survey.

  14. Selenium semiconductor core optical fibers

    SciTech Connect

    Tang, G. W.; Qian, Q. Peng, K. L.; Wen, X.; Zhou, G. X.; Sun, M.; Chen, X. D.; Yang, Z. M.

    2015-02-15

    Phosphate glass-clad optical fibers containing selenium (Se) semiconductor core were fabricated u