Science.gov

Sample records for forming core elements

  1. 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.

  2. Core elements of a public psychiatry fellowship.

    PubMed

    Ranz, Jules M; Deakins, Susan M; LeMelle, Stephanie M; Rosenheck, Stephen D; Kellermann, Sara L

    2008-07-01

    As the oldest, largest, and best known program for training psychiatrists to become public-sector leaders, the Columbia University Public Psychiatry Fellowship (PPF) at New York State Psychiatric Institute has frequently been consulted by other departments of psychiatry planning public and community fellowship programs. PPF's faculty has developed seven core elements for such training programs. The fellowship's longevity and the career paths of its graduates suggest that these core elements represent a best-practices model for fellowship training in public-community psychiatry.

  3. Forming Process Simulation of Truss Core Panel

    NASA Astrophysics Data System (ADS)

    Tokura, Sunao; Hagiwara, Ichiro

    Honeycomb panel is widely used as flooring or wall material in various structure including buildings, aircraft, train and so on due to high stiffness and lightness at present. Honeycomb panel, however, has a disadvantage that adhesive used to glue honeycomb core and top plate may burn by fire. On the other hand truss core panel has equivalent stiffness as honeycomb panel and is expected to be an alternative to honeycomb panel as it is safer for fire. However, in general, difficulty exists to form truss core and forming techniques should be developed for practice use of truss core panel. In this paper, firstly theoretical forming limitation is discussed for tetrahedral truss core . Secondly single stage forming simulation of truss core panel using explicit FEM technique was performed for preliminary investigation to estimate formability and thickness distribution. Finally multi-stage forming simulation was presented and possibility to apply press forming for truss core panel production through the simulation. In addition some results of the simulation was compared with the experiment and good agreement of both results was shown.

  4. 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.

  5. 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.

  6. 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.

  7. 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…

  8. Nicolaus Taurellus on forms and elements.

    PubMed

    Blank, Andreas

    2014-12-01

    This article examines the conception of elements in the natural philosophy of Nicolaus Taurellus (1547-1606) and explores the theological motivation that stands behind this conception. By some of his early modern readers, Taurellus may have been understood as a proponent of material atoms. By contrast, I argue that considerations concerning the substantiality of the ultimate constituents of composites led Taurellus to an immaterialist ontology, according to which elements are immaterial forms that possess active and passive potencies as well as motion and extension. In Taurellus's view, immaterialism about elements provides support for the theological doctrine of creation ex nihilo. As he argues, the ontology of immaterial forms helps to explicate a sense in which creatures are substances, not accidents of the divine substance. In particular, he maintains that immaterial forms stand in suitable relations of ontological dependence to God: creation dependence (since forms would not exist without the divine act of creation), but neither subsistence dependence (since forms continue to exist without continued divine agency) nor activity dependence (since forms are active without requiring divine concurrence).

  9. 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.

  10. 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.

  11. 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.

  12. Elemental sulfur aerosol-forming mechanism

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Francisco, Joseph S.

    2017-01-01

    Elemental sulfur aerosols are ubiquitous in the atmospheres of Venus, ancient Earth, and Mars. There is now an evolving body of evidence suggesting that these aerosols have also played a role in the evolution of early life on Earth. However, the exact details of their formation mechanism remain an open question. The present theoretical calculations suggest a chemical mechanism that takes advantage of the interaction between sulfur oxides, SOn (n = 1, 2, 3) and hydrogen sulfide (nH2S), resulting in the efficient formation of a Sn+1 particle. Interestingly, the SOn + nH2S → Sn+1 + nH2O reactions occur via low-energy pathways under water or sulfuric acid catalysis. Once the Sn+1 particles are formed, they may further nucleate to form larger polysulfur aerosols, thus providing a chemical framework for understanding the formation mechanism of S0 aerosols in different environments.

  13. 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.

  14. Vanadium and Other Elements in Greenland Ice Cores

    DTIC Science & Technology

    1976-07-01

    Photograph by C’.C. Langway , Jr.) :1 CRREL Report 76-24 Vanadium and other elements in Greenland ice cores M.M. Herron, C.C. Langway , Jr., H.V. Weiss...Chemistry, San Diego State University; by Dr. C.C. Langway , Jr., Chairman of the Department of Geological Sciences, State University of New. York at Buffalo...the use of such commercial products. ij! 𔃼y\\ .j =3 VANADIUM AND OTHER ELEMENTS IN GREENLAND ICE CORES M.M. Herron;C.C. Langway , Jr., H.V.,Weiss, J

  15. Core Elements of Preparing Teachers for Culturally Relevant Practice.

    ERIC Educational Resources Information Center

    Ryan, Ann Marie

    Addressing the issue of teachers' low expectations for students of color and students in poverty poses significant challenges to teachers and teacher education alike. This article presents core elements of preparing teachers for culturally relevant practice based on an extensive review of current research in the field. It builds on the key…

  16. 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.

  17. 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.

  18. Trace elements in a dated ice core from Antarctica

    SciTech Connect

    Keshin, S.S.; Xudong Huang; Olmez, I. ); Langway, C.C. Jr. )

    1992-01-01

    Aerosol particles from both natural and anthropogenic sources are emitted into the atmosphere and transported by wind systems by various mechanisms. Once airborne, the particles, which contain various trace elements, accumulate on the earth's surface as either condensation nuclei or by dry fallout processes. In the polar regions, these particles are incorporated and deposited in snow layers in sequential time-unit increments. The trace analysis of elements contained in dated annual snow layers provides a measure of the elemental chemistry content of the atmosphere for the same time interval. A 164-m-deep, 10-cm-diam ice core was obtained at Byrd Station, Antarctica, in November 1989. Other physical and chemistry studies on this ice core have identified its detailed chronology in annual increments for the past 1360 yr. This study presents the results of the instrumental neutron activation analysis (INAA) measurements made on 26 individually dated samples of this core, selected between the 6.43- and 118.15-m depths.

  19. 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

  20. 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.

  1. A new algebra core for the minimal form' problem

    SciTech Connect

    Purtill, M.R. . Center for Communications Research); Oliveira, J.S.; Cook, G.O. Jr. )

    1991-12-20

    The demands of large-scale algebraic computation have led to the development of many new algorithms for manipulating algebraic objects in computer algebra systems. For instance, parallel versions of many important algorithms have been discovered. Simultaneously, more effective symbolic representations of algebraic objects have been sought. Also, while some clever techniques have been found for improving the speed of the algebraic simplification process, little attention has been given to the issue of restructuring expressions, or transforming them into minimal forms.'' By minimal form,'' we mean that form of an expression that involves a minimum number of operations. In a companion paper, we introduce some new algorithms that are very effective at finding minimal forms of expressions. These algorithms require algebraic and combinatorial machinery that is not readily available in most algebra systems. In this paper we describe a new algebra core that begins to provide the necessary capabilities.

  2. 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.

  3. Evidence of residual core material from the moon-forming impactor

    NASA Astrophysics Data System (ADS)

    Helffrich, George; Wood, Bernard

    2015-04-01

    Earth was accreted from smaller bodies initially dispersed over a wide range of heliocentric distances (Albarède, 2009; Morbidelli et al. 2012). Models of their assembly include timing constraints from short-lived isotopic systems (W-Hf (Allègre et al. 2008), Ag-Pd (Schönbächler et al. 2010)), physical condition constraints from metal-silicate element partitioning (W, Mo, Ni, Co, Cr, V, Si; Wade et al. (2012)) and orbital parameter constraints from accretion histories (Morbidelli et al. 2012). Current models invoke continuous or multi-stage core formation with later epochs being more oxidized and volatile rich (Wood, 2008; Schönbächler et al. 2010; Rubie et al. 2011). Here we show, using models of core liquid wavespeeds, that a volatile-enriched outermost outer core leads to the observed layering in it, as well as satisfying the relative abundances of W and Mo in the mantle and the volume of material added in late-stage core accretion. Layering can be explained by incomplete mixing of late-added core material. Densities of progressively accreted metal vary, initially mixing the growing core but then stratifying upon it. The topmost outer core's structure is consistent with it being a physical remnant of the Moon-forming impact.

  4. 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.

  5. 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.

  6. 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.

  7. Siderophile elements in IVA irons and the compaction of their parent asteroidal core

    NASA Astrophysics Data System (ADS)

    Albarède, Francis; Bouchet, Romain A.; Blichert-Toft, Janne

    2013-01-01

    The highly siderophile element concentrations of IVA irons constitute an excellent benchmark for asteroidal core processes and, so far, the paradigm, based on the negative correlation between Ni contents and crystallographic cooling rates, has been that they represent a suite of cumulates crystallizing inwards from a molten asteroidal core. It has, however, been recognized that fractional crystallization does not account for all of the siderophile concentration patterns. Here we use the experimental parameterization of siderophile element fractionation with respect to the sulfur content of molten iron (Chabot and Jones, 2003), least-squares techniques, and Monte Carlo error propagation to assess whether incremental changes in the series of IVA irons can be accounted for by fractional crystallization or rather by partial melting. We show that the apparent order of incompatibility during solid-melt segregation deduced from binary plots of siderophile elements is misleading as a result of the strong dependency of partition coefficients on the sulfur content of the melt. All models of fractional crystallization of an Fe-S melt corrected for this effect result in negative sulfur contents. The effect of interstitial melt on fractionation hence is negligible because the high sulfur content of the melts makes all the elements compatible. In contrast, residues left by the compaction of a molten asteroidal core that crystallized with traces of sulfides and silicates according to the incremental form of batch melting provide a successful representation of the IVA suite for a large number of elements. Misfit for some elements may be due to the presence of carbon or reflects memory of variations acquired during the crystallization of the core. It is likely that melting was triggered by 26Al and that melt extraction was enhanced by the high strain-rate of impacts. The calculated S content of the liquid reproduces the experimental value of the Fe-S eutectic (45% S). Inward

  8. Advanced solid elements for sheet metal forming simulation

    NASA Astrophysics Data System (ADS)

    Mataix, Vicente; Rossi, Riccardo; Oñate, Eugenio; Flores, Fernando G.

    2016-08-01

    The solid-shells are an attractive kind of element for the simulation of forming processes, due to the fact that any kind of generic 3D constitutive law can be employed without any additional hypothesis. The present work consists in the improvement of a triangular prism solid-shell originally developed by Flores[2, 3]. The solid-shell can be used in the analysis of thin/thick shell, undergoing large deformations. The element is formulated in total Lagrangian formulation, and employs the neighbour (adjacent) elements to perform a local patch to enrich the displacement field. In the original formulation a modified right Cauchy-Green deformation tensor (C) is obtained; in the present work a modified deformation gradient (F) is obtained, which allows to generalise the methodology and allows to employ the Pull-Back and Push-Forwards operations. The element is based in three modifications: (a) a classical assumed strain approach for transverse shear strains (b) an assumed strain approach for the in-plane components using information from neighbour elements and (c) an averaging of the volumetric strain over the element. The objective is to use this type of elements for the simulation of shells avoiding transverse shear locking, improving the membrane behaviour of the in-plane triangle and to handle quasi-incompressible materials or materials with isochoric plastic flow.

  9. 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.

  10. 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 process: Core elements of review. In adopting the procedures for review of matters described in... decisions are written; and (d) Applicants and enrollees have an opportunity to— (1) Represent themselves...

  11. 42 CFR 457.1140 - Program specific review process: Core elements of review.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 4 2013-10-01 2013-10-01 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...

  12. 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...

  13. 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).

  14. 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.

  15. 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.

  16. Role of the Hepatitis C Virus Core+1 Open Reading Frame and Core cis-Acting RNA Elements in Viral RNA Translation and Replication▿ †

    PubMed Central

    Vassilaki, Niki; Friebe, Peter; Meuleman, Philipe; Kallis, Stephanie; Kaul, Artur; Paranhos-Baccalà, Glaucia; Leroux-Roels, Geert; Mavromara, Penelope; Bartenschlager, Ralf

    2008-01-01

    Four conserved RNA stem-loop structures designated SL47, SL87, SL248, and SL443 have been predicted in the hepatitis C virus (HCV) core encoding region. Moreover, alternative translation products have been detected from a reading frame overlapping the core gene (core+1/ARFP/F). To study the importance of the core+1 frame and core-RNA structures for HCV replication in cell culture and in vivo, a panel of core gene silent mutations predicted to abolish core+1 translation and affecting core-RNA stem-loops were introduced into infectious-HCV genomes of the isolate JFH1. A mutation disrupting translation of all known forms of core+1 and affecting SL248 did not alter virus production in Huh7 cells and in mice xenografted with human liver tissue. However, a combination of mutations affecting core+1 at multiple codons and at the same time, SL47, SL87, and SL248, delayed RNA replication kinetics and substantially reduced virus titers. The in vivo infectivity of this mutant was impaired, and in virus genomes recovered from inoculated mice, SL87 was restored by reversion and pseudoreversion. Mutations disrupting the integrity of this stem-loop, as well as that of SL47, were detrimental for virus viability, whereas mutations disrupting SL248 and SL443 had no effect. This phenotype was not due to impaired RNA stability but to reduced RNA translation. Thus, SL47 and SL87 are important RNA elements contributing to HCV genome translation and robust replication in cell culture and in vivo. PMID:18799568

  17. Advanced neutron source reactor conceptual safety analysis report, three-element-core design: Chapter 15, accident analysis

    SciTech Connect

    Chen, N.C.J.; Wendel, M.W.; Yoder, G.L.; Harrington, R.M.

    1996-02-01

    In order to utilize reduced enrichment fuel, the three-element-core design for the Advanced Neutron Source has been proposed. The proposed core configuration consists of inner, middle, and outer elements, with the middle element offset axially beneath the inner and outer elements, which are axially aligned. The three-element-core RELAP5 model assumes that the reactor hardware is changed only within the core region, so that the loop piping, heat exchangers, and pumps remain as assumed for the two-element-core configuration. To assess the impact of changes in the core region configuration and the thermal-hydraulic steady-state conditions, the safety analysis has been updated. This report gives the safety margins for the loss-of-off-site power and pressure-boundary fault accidents based on the RELAP5 results. AU margins are greater for the three-element-core simulations than those calculated for the two-element core.

  18. 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).

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1988-07-01

    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.

  1. The spectral element dynamical core in the Community Atmosphere Model

    NASA Astrophysics Data System (ADS)

    Taylor, Mark

    2013-11-01

    I will describe our work developing CAM-SE, a highly scalable version of the Community Atmosphere Model (CAM). CAM-SE solves the hydrostatic equations with a spectral element horizontal descritization and the hybrid coordinate Simmons & Burridge (1981) vertical discretization. It uses a mimetic formulation of spectral elements which preserves the adjoint and annihilator properties of the divergence, gradient and curl operations. These mimetic properties result in local conservation (to machine precision) of mass, tracer mass and (2D) potential vorticity, and semi-discrete conservation (exact with exact time-discretization) of total energy. Hyper-viscsoity is used for all numerical dissipation. The spectral element method naturally supports unstructured/variable resolution grids. We are using this capability to perform simulations with 1/8 degree resolution over the central U.S., transitioning to 1 degree over most of the globe. This is a numerically efficient way to study the resolution sensitivity of CAM's many subgrid parameterizations.

  2. 34 CFR 200.26 - Core elements of a schoolwide program.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 34 Education 1 2011-07-01 2011-07-01 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...

  3. 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...

  4. 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...

  5. The aesthetic post and core: unifying radicular form and structure.

    PubMed

    Gluskin, Alan H; Ahmed, Irfan; Herrero, Dale B

    2002-05-01

    Use of a post system for the rehabilitation of endodontically treated teeth requires traditional planning for the function of the restoration as well as a structural and aesthetic strategy for novel technologies in ceramic and composite dentistry. Contemporary material options have greatly expanded the clinician's ability to rehabilitate the coronoradicular complex. Transilluminating posts, bondable fabrics, and high-technology ceramics create exciting possibilities in post and core design. The use of bondable materials allows the practitioner to unify the structure and morphology of root systems to provide creative solutions to challenges heretofore unmet.

  6. 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...

  7. 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

  8. Development and evaluation of a hydrostatic dynamical core using the spectral element/discontinuous Galerkin methods

    NASA Astrophysics Data System (ADS)

    Choi, S.-J.; Giraldo, F. X.

    2014-06-01

    In this paper, we present a dynamical core for the atmospheric primitive hydrostatic equations using a unified formulation of spectral element (SE) and discontinuous Galerkin (DG) methods in the horizontal direction with a finite difference (FD) method in the radial direction. The CG and DG horizontal discretization employs high-order nodal basis functions associated with Lagrange polynomials based on Gauss-Lobatto-Legendre (GLL) quadrature points, which define the common machinery. The atmospheric primitive hydrostatic equations are solved on the cubed-sphere grid using the flux form governing equations in a three-dimensional (3-D) Cartesian space. By using Cartesian space, we can avoid the pole singularity problem due to spherical coordinates and this also allows us to use any quadrilateral-based grid naturally. In order to consider an easy way for coupling the dynamics with existing physics packages, we use a FD in the radial direction. The models are verified by conducting conventional benchmark test cases: the Rossby-Haurwitz wavenumber 4, Jablonowski-Williamson tests for balanced initial state and baroclinic instability, and Held-Suarez tests. The results from those tests demonstrate that the present dynamical core can produce numerical solutions of good quality comparable to other models.

  9. 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

  10. 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.

  11. 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}.

  12. 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.

  13. 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.

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

    SciTech Connect

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

    2016-01-22

    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 ({sup 233}U), 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.

  15. 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.

  16. 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.

  17. 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

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

    PubMed

    Przybilski, Rita; Hammann, Christian

    2007-10-01

    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.

  19. New Evidence for the Theory of Chromosome Organization by Repetitive Elements (CORE).

    PubMed

    Tang, Shao-Jun

    2017-02-20

    Repetitive DNA elements were proposed to coordinate chromatin folding and interaction in chromosomes by their intrinsic homology-based clustering ability. A recent analysis of the data sets from chromosome-conformation-capture experiments confirms the spatial clustering of DNA repeats of the same family in the nuclear space, and thus provides strong new support for the CORE theory.

  20. New Evidence for the Theory of Chromosome Organization by Repetitive Elements (CORE)

    PubMed Central

    Tang, Shao-Jun

    2017-01-01

    Repetitive DNA elements were proposed to coordinate chromatin folding and interaction in chromosomes by their intrinsic homology-based clustering ability. A recent analysis of the data sets from chromosome-conformation-capture experiments confirms the spatial clustering of DNA repeats of the same family in the nuclear space, and thus provides strong new support for the CORE theory. PMID:28230735

  1. 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…

  2. 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)

  3. Factors affecting the reproducibility of trace element analyses of ice core samples

    NASA Astrophysics Data System (ADS)

    Rhodes, R. H.; Baker, J.; Millet, M.; Bertler, N.

    2010-12-01

    Ice cores provide high-resolution records of past atmospheric and environmental conditions. Increasingly, conventional stable isotope and major ion analyses of ice cores are being complimented by determination of ultra-trace levels of trace elements by inductively coupled plasma mass spectrometry (ICP-MS). Typically, these analyses are performed on acidified, melted, ice without removal of particulates by centrifugation or filtration. We have carried out a systematic investigation of the factors influencing the reproducibility of trace element determinations in ice core samples, which can be considered to contain three inorganic chemical components: marine salt, aerosol and mineral dust. The prevalent method of ICP-MS analysis of ice core samples involves analysing acidified samples (typically to 1% HNO3). To mimic these conditions, we undertook systematic leaching experiments on geochemically well-characterised, powdered, rock standards to examine how trace element measurements varied depending on the length of the acidification time, whether samples were frozen after acidification or not, dust lithology and the dust concentration. Four certified standards were leached at a dust concentration of 10 ppm in 1% HNO3 and leachates were sampled at regular time intervals up to a period of several months. The standards encompass a range of lithologies and textures, including basalt (BHVO-2), dolerite (W-2), granite (JG-2) and Fe-Mn oxyhydroxide (Nod P-1) materials. The basalt, dolerite and granite all have silicate mineralogies and showed some similar trace element trends during leaching. For example, the concentration of Al in the leachates increased by between 125% and 280% during the first 12 hr and did not stop rising after 8 weeks of leaching. In contrast, rare earth element and Y concentrations in the leachates became constant after just 2 hr. However, total element recovery differed between lithologies. After 12 hr of acidification the recovery of elements from Na

  4. Scalability of parallel finite element algorithms on multi-core platforms

    NASA Astrophysics Data System (ADS)

    Kopysov, S. P.; Novikov, A. K.; Nedozhogin, N. S.; Rychkov, V. N.

    2016-11-01

    The speedup of element-by-element FEM algorithms depends not only on peak processor performance but also on access time to shared mesh data. Eliminating memory boundness would significantly speed up unstructured mesh computations on hybrid multi-core architectures, where the gap between processor and memory performance continues to grow. The speedup can be achieved by ordering unknowns so that only those elements are processed in parallel which do not have common nodes. Therefore, memory conflicts are minimized. FEM assembly is performed with respect to the ordering, which defines how to compose vectors. Mesh can be partitioned into disjoint subdomains by using different layer-by-layer schemes. In this work, we evaluated several partitioning schemes (block, odd, even, and their modifications) on multi-core platforms, using Gunther's Universal Law of Computational Scalability. We performed numerical experiments with element-by-element matrix-vector multiplication on unstructured meshes on multi-core processors accelerated by MIC and GPU. With ordering, we achieved 5-times speedup on CPU, 40-times speedup on MIC, and 200- times speedup on GPU.

  5. 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.

  6. 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.

  7. Thermal, dynamic and compositional aspects of the core-forming Earth

    NASA Technical Reports Server (NTRS)

    Stevenson, D. J.

    1985-01-01

    Core formation is the most important and singular differentiation event in the history of a terrestrial planet. It almost certainly involved the downward migration of a partially or wholly molten iron alloy through a silicate and oxide mantle, and was contemporaneous with accretion. Several important, unresolved issues which have implications for mantle and core geochemistry, the thermal history of the Earth, and the origin of geomagnetism are addressed: whether the early Earth was molten; whether core formation involved low or high pressure geochemistry, or both; early Earth mantle homogenization; whether equilibration established between core forming material and the mantle through which it migrated; and how much iron is stranded and unable to reach the core.

  8. 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.

  9. 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)

  10. 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.

  11. 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.

  12. 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…

  13. 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

  14. 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.

  15. 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.

  16. Forming protostars in molecular clouds with shocked envelope expansion and core collapse

    NASA Astrophysics Data System (ADS)

    Lou, Yu-Qing; Gao, Yang

    2011-04-01

    Spectral observations of molecular line profiles reveal the so-called 'blue profiles' for double-peaked molecular spectral lines with stronger blue and weaker red peaks as notable features for star-forming cloud core collapses under the self-gravity. In contrast, ˜25-30 per cent of observed molecular spectral line profiles in star-forming clouds or cores also show the so-called double-peaked 'red profiles' with red peaks stronger than blue peaks. Gao & Lou show that these unexplained 'red profiles' can be signatures of global self-similar dynamics for envelope expansion with core collapse (EECC) within star-forming molecular clouds or cores. We demonstrate here that spatially resolved 'red profiles' of HCO+ (J= 1-0) and CS (J= 2-1) molecular transitions from the low-mass star-forming cloud core FeSt 1-457 together with its radial profile of column density inferred from dust extinction observations appear to reveal a self-similar hydrodynamic shock phase for global EECC. Observed spectral profiles of C18O (J= 1-0) are also fitted by the same EECC model. For further observational tests, the spatially resolved profiles of molecular transitions HCO+ (J= 3-2) and CS (J= 3-2) as well as the radial profiles of (sub)millimetre continuum emissions at three wavelengths of 1.2, 0.85 and 0.45 mm from FeSt 1-457 are also predicted.

  17. 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.

  18. Finite element simulation of laser scribed electrical steel for core loss reduction

    SciTech Connect

    Gurusamy, R.; Mohammed, M.; Molian, P.

    1996-12-31

    Laser scribing of electrical steels reduced core losses through magnetic domain refinement that occurred when thermal stresses were induced by laser heating. An experimental study with a 15 W, continuous wave diode laser for scribing and a finite element simulation model for determining the thermal stress distribution of cold-rolled, 3% silicon-steel were performed. The results showed that the maximum core loss reduction was attained only when the stresses reached the yield strength. In contrast, previous researchers attributed the maximum core loss reduction to the localized plastic deformation. This study also provided quantitative distribution of stresses in all three directions and clarified a controversy surrounding the type of stresses in the laser-scribed and rolled directions.

  19. Core elements of hospital antibiotic stewardship programs from the Centers for Disease Control and Prevention.

    PubMed

    Pollack, Loria A; Srinivasan, Arjun

    2014-10-15

    The proven benefits of antibiotic stewardship programs (ASPs) for optimizing antibiotic use and minimizing adverse events, such as Clostridium difficile and antibiotic resistance, have prompted the Centers for Disease Control and Prevention (CDC) to recommend that all hospitals have an ASP. This article summarizes Core Elements of Hospital Antibiotic Stewardship Programs, a recently released CDC document focused on defining the infrastructure and practices of coordinated multidisciplinary programs to improve antibiotic use and patient care in US hospitals.

  20. Defining core elements and outstanding practice in Nutritional Science through collaborative benchmarking.

    PubMed

    Samman, Samir; McCarthur, Jennifer O; Peat, Mary

    2006-01-01

    Benchmarking has been adopted by educational institutions as a potentially sensitive tool for improving learning and teaching. To date there has been limited application of benchmarking methodology in the Discipline of Nutritional Science. The aim of this survey was to define core elements and outstanding practice in Nutritional Science through collaborative benchmarking. Questionnaires that aimed to establish proposed core elements for Nutritional Science, and inquired about definitions of " good" and " outstanding" practice were posted to named representatives at eight Australian universities. Seven respondents identified core elements that included knowledge of nutrient metabolism and requirement, food production and processing, modern biomedical techniques that could be applied to understanding nutrition, and social and environmental issues as related to Nutritional Science. Four of the eight institutions who agreed to participate in the present survey identified the integration of teaching with research as an indicator of outstanding practice. Nutritional Science is a rapidly evolving discipline. Further and more comprehensive surveys are required to consolidate and update the definition of the discipline, and to identify the optimal way of teaching it. Global ideas and specific regional requirements also need to be considered.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Raising the Reliability of Forming Rolls by Alloying Their Core with Copper

    NASA Astrophysics Data System (ADS)

    Zhizhkina, N. A.

    2016-11-01

    The mechanical properties and the structure of forming rolls from cast irons of different compositions are studied. A novel iron including a copper additive that lowers its chilling and raises the homogeneity of the structure is suggested for the roll cores. The use of such iron should raise the reliability of the rolls in operation.

  6. Isomorphic coalescence of aster cores formed in vitro from microtubules and kinesin motors

    NASA Astrophysics Data System (ADS)

    Kim, K.; Sikora, A.; Nakazawa, H.; Umetsu, M.; Hwang, W.; Teizer, W.

    2016-10-01

    We report fluorescence microscopy studies of the formation of aster-like structures emerging from a cellular element-based active system and a novel analysis of the aster condensation. The system consists of rhodamine labeled microtubules which are dynamically coupled by functionalized kinesin motor proteins cross-linked via streptavidin-coated quantum dots (QDs). The aster-shaped objects contain core structures. The cores are aggregates of the QD-motor protein complexes, and result from the dynamic condensation of sub-clusters that are connected to each other randomly. The structural specificity of the aster core reflects a configuration of the initial connectivity between sub-clusters. Detailed image analysis allows us to extract a novel correlation between the condensation speed and the sub-cluster separation. The size of the core is scaled down during the condensation process, following a power law dependence on the distance between sub-clusters. The exponent of the power law is close to two, as expected from a geometric model. This single exponent common to all the contractile lines implies that there exists a time regime during which an isomorphic contraction of the aster core continues during the condensation process. We analyze the observed contraction by using a model system with potential applicability in a wide range of emergent phenomena in randomly coupled active networks, which are prevalent in the cellular environment.

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

    PubMed

    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

  8. 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

  9. 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

  10. Ionic High-Pressure Form of Elemental Boron

    SciTech Connect

    Oganov, A.; Chen, J; Gatti, C; Ma, Y; Ma, Y; Glass, C; Liu, Z; Yu, T; Kurakevych, O; et. al.

    2009-01-01

    This Letter presents the results of high-pressure experiments and ab initio evolutionary crystal structure predictions, and found a new boron phase that we named gamma-B28. This phase is comprised of icosahedral B12 clusters and B2 pairs in a NaCl-type arrangement, stable between 19 and 89 GPa, and exhibits evidence for charge transfer (for which our best estimate is delta approximately 0.48) between the constituent clusters to give (B2)delta+(B12)delta-. We have recently found that the same high-pressure boron phase may have given rise to the Bragg reflections reported by Wentorf in 1965 (ref. 1), although the chemical composition was not analysed and the data (subsequently deleted from the Powder Diffraction File database) seems to not have been used to propose a structure model. We also note that although we used the terms 'partially ionic' and 'ionic' to emphasize the polar nature of the high-pressure boron phase and the influence this polarity has on several physical properties of the elemental phase, the chemical bonding in gamma-B28 is predominantly covalent.

  11. 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.

  12. 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.

  13. 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

    2014-04-03

    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.

  14. 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.

  15. The Number of Catalytic Elements Is Crucial for the Emergence of Metabolic Cores

    PubMed Central

    De la Fuente, Ildefonso M.; Vadillo, Fernando; Pérez-Pinilla, Martín-Blas; Vera-López, Antonio; Veguillas, Juan

    2009-01-01

    Background Different studies show evidence that several unicellular organisms display a cellular metabolic structure characterized by a set of enzymes which are always in an active state (metabolic core), while the rest of the molecular catalytic reactions exhibit on-off changing states. This self-organized enzymatic configuration seems to be an intrinsic characteristic of metabolism, common to all living cellular organisms. In a recent analysis performed with dissipative metabolic networks (DMNs) we have shown that this global functional structure emerges in metabolic networks with a relatively high number of catalytic elements, under particular conditions of enzymatic covalent regulatory activity. Methodology/Principal Findings Here, to investigate the mechanism behind the emergence of this supramolecular organization of enzymes, we have performed extensive DMNs simulations (around 15,210,000 networks) taking into account the proportion of the allosterically regulated enzymes and covalent enzymes present in the networks, the variation in the number of substrate fluxes and regulatory signals per catalytic element, as well as the random selection of the catalytic elements that receive substrate fluxes from the exterior. The numerical approximations obtained show that the percentages of DMNs with metabolic cores grow with the number of catalytic elements, converging to 100% for all cases. Conclusions/Significance The results show evidence that the fundamental factor for the spontaneous emergence of this global self-organized enzymatic structure is the number of catalytic elements in the metabolic networks. Our analysis corroborates and expands on our previous studies illustrating a crucial property of the global structure of the cellular metabolism. These results also offer important insights into the mechanisms which ensure the robustness and stability of living cells. PMID:19888419

  16. Major and trace elements of a peat core from Yunnan, Southwest China: Implications for paleoclimatic proxies

    NASA Astrophysics Data System (ADS)

    Wei, Gangjian; Xie, Luhua; Sun, Yongge; Lu, Yuehan; Liu, Ying

    2012-09-01

    This study examines the accumulation of major and trace elements in peat deposits in central Yunnan Province, southwestern China. The ashes of an approximately 2 m long core spanning 32.7-11.4 ka are analyzed to assess the elemental contributions of organic materials and to identify elemental paleoclimatic proxies in peats. Peat ash, which is mainly composed of silicate materials, makes up 20-80% of each of the samples. The analysis shows that organic materials are a significant source of many of the elements in the ashes. Among these elements, P and V are the most typical, with their concentrations in the ashes closely correlating to the total organic carbon (TOC) content of the peats. Al, Na, Sc, Cr, Co, Ni, Cu, Ge, Pb, and Th are also associated with biogenic materials, particularly in the lower section (below 122 cm) of the core, where the organic material content is high. Ca, Sr, Mg, and Mn appear to have been part of carbonate deposits, such as authigenic FeCO3 and MnCO3 in the anoxic peats, whereas, K, Ti, Zn, Ga, Rb, Y, rare earth elements (REEs), Zr, Hf, Nb, Ta, Ba, and U are mainly associated with silicate materials. Local weathering products, rather than dust from northern China, are the main sources for the silicate materials in these peats. Some elemental ratios such as K/Rb and K2O/Na2O can reliably indicate changes in local chemical weathering intensity, and their variation patterns match the changes in the East Asian summer monsoon (EASM) very well. The less intensive chemical weathering indicated by lower K/Rb and K2O/Na2O ratios generally corresponds to weaker EASM strength during ˜30 to ˜10 ka, which is consistent with the fact that weaker summer monsoons may arouse drier climates, and do not favor intense chemical weathering. This suggests that select elemental ratios in peats/organic rich sediments may be informative proxies for monsoon climate changes.

  17. Computing ferrite core losses at high frequency by finite elements method including temperature influence

    SciTech Connect

    Ahmed, B.; Ahmad, J.; Guy, G.

    1994-09-01

    A finite elements method coupled with the Preisach model of hysteresis is used to compute-the ferrite losses in medium power transformers (10--60 kVA) working at relatively high frequencies (20--60 kHz) and with an excitation level of about 0.3 Tesla. The dynamic evolution of the permeability is taken into account. The simple and doubly cubic spline functions are used to account for temperature effects respectively on electric and on magnetic parameters of the ferrite cores. The results are compared with test data obtained with 3C8 and B50 ferrites at different frequencies.

  18. 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

  19. 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

  20. 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.

  1. Cognitive-graphic method for constructing of hierarchical forms of basic functions of biquadratic finite element

    NASA Astrophysics Data System (ADS)

    Astionenko, I. O.; Litvinenko, O. I.; Osipova, N. V.; Tuluchenko, G. Ya.; Khomchenko, A. N.

    2016-10-01

    Recently the interpolation bases of the hierarchical type have been used for the problem solving of the approximation of multiple arguments functions (such as in the finite-element method). In this work the cognitive graphical method of constructing of the hierarchical form bases on the serendipity finite elements is suggested, which allowed to get the alternative bases on a biquadratic finite element from the serendipity family without internal knots' inclusion. The cognitive-graphic method allowed to improve the known interpolation procedure of Taylor and to get the modified elements with irregular arrangement of knots. The proposed procedures are universal and are spread in the area of finite-elements.

  2. Closed form expressions for a consistent stress material nonlinear finite element

    NASA Astrophysics Data System (ADS)

    Knipe, Richard Lee

    Finite element expressions for two dimensional elasto-plasticity problems were implemented in closed form. These closed form expressions are based upon a distribution of the elasto-plastic constitutive relationship that is consistent with the interpolating functions used for the displacement. Closed form expressions for the element tangent stiffness matrix and initial stress nodal load vector were developed for the non hierarchic constant, linear, and quadratic strain triangle. Decreased solution times were obtained when using the closed form expressions instead of expressions based on numerical integration. The quality of the solutions obtained from the closed form expressions was measured against published solutions for two dimensional elasto-plasticity problems.

  3. 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.

  4. Test of tree core sampling for screening of toxic elements in soils from a Norwegian site.

    PubMed

    Algreen, Mette; Rein, Arno; Legind, Charlotte N; Amundsen, Carl Einar; Karlson, Ulrich Gosewinkel; Trapp, Stefan

    2012-04-01

    Tree core samples have been used to delineate organic subsurface plumes. In 2009 and 2010, samples were taken at trees growing on a former dump site in Norway and analyzed for arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn). Concentrations in wood were in averages (dw) 30 mg/kg for Zn, 2 mg/kg for Cu, and < 1 mg/kg for Cd, Cr, As and Ni. The concentrations in wood samples from the polluted test site were compared to those derived from a reference site. For all except one case, mean concentrations from the test site were higher than those from the reference site, but the difference was small and not always significant. Differences between tree species were usually higher than differences between reference and test site. Furthermore, all these elements occur naturally, and Cu, Ni, and Zn are essential minerals. Thus, all trees will have a natural background of these elements, and the occurrence alone does not indicate soil pollution. For the interpretation of the results, a comparison to wood samples from an unpolluted reference site with same species and similar soil conditions is required. This makes the tree core screening method less reliable for heavy metals than, e.g., for chlorinated solvents.

  5. Verification of a non-hydrostatic dynamical core using horizontally spectral element vertically finite difference method: 2-D aspects

    NASA Astrophysics Data System (ADS)

    Choi, S.-J.; Giraldo, F. X.; Kim, J.; Shin, S.

    2014-06-01

    The non-hydrostatic (NH) compressible Euler equations of dry atmosphere are 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. 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 terms and quadrature. The Euler equations used here are in a flux form based on the hydrostatic pressure vertical coordinate, which are the same as those used in the Weather Research and Forecasting (WRF) model, but a hybrid sigma-pressure vertical coordinate is implemented in this model. We verified the model by conducting widely used standard benchmark tests: the inertia-gravity wave, rising thermal bubble, density current wave, and linear hydrostatic mountain wave. The results from those tests demonstrate that the horizontally spectral element vertically finite difference model is accurate and robust. By using the 2-D slice model, we effectively show that the combined spatial discretization method of the spectral element and finite difference method in the horizontal and vertical directions, respectively, offers a viable method for the development of a NH dynamical core.

  6. Method for determining the elemental composition and distribution in semiconductor core-shell quantum dots.

    PubMed

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

    2011-02-01

    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 230 eV) 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 multiapproach methodology represent a significant advancement in the detailed surface science study of multilayer 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.

  7. Laser ablation inductively coupled plasma mass spectrometry: a new tool for trace element analysis in ice cores.

    PubMed

    Reinhardt, H; Kriews, M; Miller, H; Schrems, O; Lüdke, C; Hoffmann, E; Skole, J

    2001-07-01

    A new method for the detection of trace elements in polar ice cores using laser ablation with subsequent inductively coupled plasma mass spectrometry analysis is described. To enable direct analysis of frozen ice samples a special laser ablation chamber was constructed. Direct analysis reduces the risk of contamination. The defined removal of material from the ice surface by means of a laser beam leads to higher spatial resolution (300-1000 microm) in comparison to investigations with molten ice samples. This is helpful for the detection of element signatures in annual layers of ice cores. The method was applied to the successful determination of traces for the elements Mg, Al, Fe, Zn, Cd, Pb, some rare-earth elements (REE) and minor constituents such as Ca and Na in ice cores. These selected elements serve as tracer elements for certain sources and their element signatures detected in polar ice cores can give hints to climate changes in the past. We report results from measurements of frozen ice samples, the achievable signal intensities, standard deviations and calibration graphs as well as the first signal progression of 205Pb in an 8,000-year-old ice core sample from Greenland. In addition, the first picture of a crater on an ice surface burnt by an IR laser made by cryogenic scanning electron microscopy is presented.

  8. 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.

  9. DEUTERIUM BURNING IN MASSIVE GIANT PLANETS AND LOW-MASS BROWN DWARFS FORMED BY CORE-NUCLEATED ACCRETION

    SciTech Connect

    Bodenheimer, Peter; Fortney, Jonathan J.; Saumon, Didier E-mail: gennaro.dangelo@nasa.gov E-mail: jfortney@ucolick.org

    2013-06-20

    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{sub Circled-Plus }, are assumed to accrete gas up to final masses of 10-15 Jupiter masses (M{sub 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{sub 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{sub 50} fall in the range 11.6-13.6 M{sub 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{sub 50}. For masses above M{sub 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.

  10. A mesh re-zoning technique for finite element simulations of metal forming processes

    NASA Technical Reports Server (NTRS)

    Cheng, J.-C.; Kikuchi, N.

    1986-01-01

    Based on some fundamental properties of finite element approximations, a mesh re-zoning scheme is proposed for finite element simulations of metal forming problems. It is demonstrated that this technique is indispensable in analyzing many difficult forming processes, especially when there exist corners or very irregular shapes on the boundaries. The algorithm is tested by a backward extrusion process and direct extrusion through a square die.

  11. 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

  12. 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.

  13. 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

  14. Preparedness for clinical: evaluation of the core elements of the Clinical Immersion curriculum model.

    PubMed

    Diefenbeck, Cynthia; Herrman, Judith; Wade, Gail; Hayes, Evelyn; Voelmeck, Wayne; Cowperthwait, Amy; Norris, Susan

    2015-01-01

    The Clinical Immersion Model is an innovative baccalaureate nursing curriculum that has demonstrated successful outcomes over the past 10 years. For those intending to adopt the model, individual components in isolation may prove ineffective. This article describes three core components of the curriculum that form the foundation of preparation for the senior-year clinical immersion. Detailed student-centered outcomes evaluation of these critical components is shared. Results of a mixed-methods evaluation, including surveys and focus groups, are presented. Implications of this curricular evaluation and future directions are explored.

  15. Active learning: effects of core training design elements on self-regulatory processes, learning, and adaptability.

    PubMed

    Bell, Bradford S; Kozlowski, Steve W J

    2008-03-01

    This article describes a comprehensive examination of the cognitive, motivational, and emotional processes underlying active learning approaches; their effects on learning and transfer; and the core training design elements (exploration, training frame, emotion control) and individual differences (cognitive ability, trait goal orientation, trait anxiety) that shape these processes. Participants (N = 350) were trained to operate a complex, computer-based simulation. Exploratory learning and error-encouragement framing had a positive effect on adaptive transfer performance and interacted with cognitive ability and dispositional goal orientation to influence trainees' metacognition and state goal orientation. Trainees who received the emotion-control strategy had lower levels of state anxiety. Implications for development of an integrated theory of active learning, learner-centered design, and research extensions are discussed.

  16. Ab initio effective core potentials for molecular calculations. Potentials for main group elements Na to Bi

    SciTech Connect

    Wadt, W.R.; Hay, P.J.

    1985-01-01

    A consistent set of ab initio effective core potentials (ECP) has been generated for the main group elements from Na to Bi using the procedure originally developed by Kahn. The ECP's are derived from all-electron numerical Hartree--Fock atomic wave functions and fit to analytical representations for use in molecular calculations. For Rb to Bi the ECP's are generated from the relativistic Hartree--Fock atomic wave functions of Cowan which incorporate the Darwin and mass--velocity terms. Energy-optimized valence basis sets of (3s3p) primitive Gaussians are presented for use with the ECP's. Comparisons between all-electron and valence-electron ECP calculations are presented for NaF, NaCl, Cl/sub 2/, Cl/sub 2//sup -/, Br/sub 2/, Br/sub 2//sup -/, and Xe/sub 2//sup +/. The results show that the average errors introduced by the ECP's are generally only a few percent.

  17. Element Specific Observation of Ferromagnetic Interlayer Exchange Coupled Dual Vortex Core Nano Systems

    NASA Astrophysics Data System (ADS)

    Pulecio, Javier; Arena, Dario; Warnicke, Peter; Im, Mi-Young; Pollard, Shawn; Fischer, Peter; Zhu, Yimei

    2013-03-01

    We report on the magnetic evolution of magnetic vortices in nanoscale and multilayer disk structures. The tri-layer structure consists of Co and Permalloy (Py) layers, coupled across a thin (1nm) Cu spacer that provides strong coupling between the Co and Py layers. Element-resolved full-field XMCD microscopy is combined with ultra-high resolution Lorentz transmission electron microscopy, permitting measurement of both layer-resolved domain patterns and the vortex structure averaged across the tri-layer. We examine the evolution of the vortex structure while the nanostructure is cycled through the M-H hysteresis loop. In particular we will discuss the effects of strong interlayer exchanged coupling on a dual vortex core system, including analysis of the layer-resolved coercivity, and the evolution, deformation, annihilation, and nucleation of the vortices.

  18. Excitation dynamics of two spectral forms of the core complexes from photosynthetic bacterium Thermochromatium tepidum.

    PubMed

    Ma, Fei; Kimura, Yukihiro; Zhao, Xiao-Hui; Wu, Yi-Shi; Wang, Peng; Fu, Li-Min; Wang, Zheng-Yu; Zhang, Jian-Ping

    2008-10-01

    The intact core antenna-reaction center (LH1-RC) core complex of thermophilic photosynthetic bacterium Thermochromatium (Tch.) tepidum is peculiar in its long-wavelength LH1-Q(y) absorption (915 nm). We have attempted comparative studies on the excitation dynamics of bacteriochlorophyll (BChl) and carotenoid (Car) between the intact core complex and the EDTA-treated one with the Q(y) absorption at 889 nm. For both spectral forms, the overall Car-to-BChl excitation energy transfer efficiency is determined to be approximately 20%, which is considerably lower than the reported values, e.g., approximately 35%, for other photosynthetic purple bacteria containing the same kind of Car (spirilloxanthin). The RC trapping time constants are found to be 50 approximately 60 ps (170 approximately 200 ps) for RC in open (closed) state irrespective to the spectral forms and the wavelengths of Q(y) excitation. Despite the low-energy LH1-Q(y) absorption, the RC trapping time are comparable to those reported for other photosynthetic bacteria with normal LH1-Q(y) absorption at 880 nm. Selective excitation to Car results in distinct differences in the Q(y)-bleaching dynamics between the two different spectral forms. This, together with the Car band-shift signals in response to Q(y) excitation, reveals the presence of two major groups of BChls in the LH1 of Tch. tepidum with a spectral heterogeneity of approximately 240 cm(-1), as well as an alteration in BChl-Car geometry in the 889-nm preparation with respect to the native one.

  19. 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.

  20. Kinetic and thermodynamic characterization of the cobalt and manganese oxyhydroxide cores formed in horse spleen ferritin.

    PubMed

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

    2005-05-16

    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 (AH(2)), a two-electron reductant, effectively reduced the mineral cores; however, the reaction was incomplete and rapidly reached equilibrium. The addition of excess AH(2) shifted the reaction to completion with a M(3+)/AH(2) stoichiometry of 1.9-2.1, consistent with a single electron per metal atom reduction. The rate of reaction between M(O)OH and excess AH(2) 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(-1) min(-1), respectively, for Co- and Mn-HoSF at pH 9.0. From the variation of absorbance with increasing AH(2) 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 + AH(2) = 2M(OH)(2) + D, where AH(2) 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 AH(2). 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.

  1. 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.

  2. Quadratic solid-shell elements for nonlinear structural analysis and sheet metal forming simulation

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Chalal, Hocine; Abed-Meraim, Farid

    2017-01-01

    In this paper, two quadratic solid-shell (SHB) elements are proposed for the three-dimensional modeling of thin structures. These consist of a 20-node hexahedral solid-shell element, denoted SHB20, and its 15-node prismatic counterpart, denoted SHB15. The formulation of these elements is extended in this work to include geometric and material nonlinearities, for application to problems involving large displacements and rotations as well as plasticity. For this purpose, the SHB elements are coupled with large-strain anisotropic elasto-plastic constitutive equations for metallic materials. Although based on a purely three-dimensional approach, several modifications are introduced in the formulation of these elements to provide them with interesting shell features. In particular, a special direction is chosen to represent the thickness, along which a user-defined number of integration points are located. Furthermore, for efficiency requirements and for alleviating locking phenomena, an in-plane reduced-integration scheme is adopted. The resulting formulations are implemented into the finite element software ABAQUS/Standard and, to assess their performance, a variety of nonlinear benchmark problems are investigated. Attention is then focused on the simulation of various complex sheet metal forming processes, involving large strain, anisotropic plasticity, and double-sided contact. From all simulation results, it appears that the SHB elements represent an interesting alternative to traditional shell and solid elements, due to their versatility and capability of accurately modeling selective nonlinear benchmark problems as well as complex sheet metal forming processes.

  3. 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.

  4. Development of pressure-sensitive dosage forms with a core liquefying at body temperature.

    PubMed

    Wilde, Lisa; Bock, Mona; Wolf, Marieke; Glöckl, Gunnar; Garbacz, Grzegorz; Weitschies, Werner

    2014-04-01

    Pressure-sensitive dosage forms have been developed that are intended for pulsatile delivery of drugs to the proximal small intestine. The novel dosage forms are composed of insoluble shell and either a hard fat W32 or polyethylene glycol (PEG) 1000 core that are both liquidizing at body temperature. The release is triggered by predominant pressure waves such as contractions of the pylorus causing rupture of the shell and an immediate emptying of the liquefied filling containing the active ingredient. In consequence immediately after the trigger has been effective the total amount of the drug is intended to be available for absorption in the upper small intestine. Both core types were coated with a cellulose acetate film that creates a pressure-sensitive shell in which mechanical resistance is depending on the coating thickness. Results of the texture analysis confirmed a correlation between the polymer load of the coating and the mechanical resistance. The dissolution test performed under conditions of physiological meaningful mechanical stress showed that the drug release is triggered by pressure waves of ⩾300 mbar which are representing the maximal pressure occurring during the gastric emptying.

  5. 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.

  6. Radioactive Elements in Coal and Fly Ash: Abundance, Forms, and Environmental Significance

    USGS Publications Warehouse

    Zielinski, Robert A.; Finkelman, Robert B.

    1997-01-01

    Coal is largely composed of organic matter, but it is the inorganic matter in coal—minerals and trace elements— that have been cited as possible causes of health, environmental, and technological problems associated with the use of coal. Some trace elements in coal are naturally radioactive. These radioactive elements include uranium (U), thorium (Th), and their numerous decay products, including radium (Ra) and radon (Rn). Although these elements are less chemically toxic than other coal constituents such as arsenic, selenium, or mercury, questions have been raised concerning possible risk from radiation. In order to accurately address these questions and to predict the mobility of radioactive elements during the coal fuel-cycle, it is important to determine the concentration, distribution, and form of radioactive elements in coal and fly ash.

  7. The L723 Low-Mass Star Forming Protostellar System: Resolving a Double Core

    NASA Astrophysics Data System (ADS)

    Girart, J. M.; Rao, R.; Estalella, R.

    2009-03-01

    We present 1.35 mm Submillimeter Array (SMA) observations around the low-mass Class 0 source IRAS 19156+1906, at the center of the LDN 723 (L723) dark cloud. We detected emission from dust as well as emission from H2CO 30,3-20,2, DCN 3-2, and CN 2-1 lines, which arise from two cores, SMA 1 and SMA 2, separated by 2farcs9 (880 AU in projected distance). SMA 2 is associated with the previously detected source VLA 2. Weak SiO 5-4 emission is detected, possibly tracing a region of interaction between the dense envelope and the outflow. We modeled the dust and H2CO emission from the two cores. The results from the modeling show that the cores have similar physical properties (density and temperature distribution) but that SMA 2 has a larger p-H2CO abundance (by a factor of 3-10) than SMA 1. The p-H2CO abundances' findings are compatible with the value of the outer part of the circumstellar envelopes associated with Class 0 sources. SMA 2 is harboring an active multiple low-mass protostellar system and powering at least one molecular outflow. In contrast, there are no known signs of outflow activity toward SMA 1. This suggests that SMA 2 is more evolved than SMA 1. The kinematics of the two sources show marginal evidence of infall and rotation motions. The mass detected by the SMA observation, which trace scales of lsim1000 AU, is only a small fraction of the mass contained in the large-scale molecular envelope, which suggests that L723 is still in a very early phase of star formation. Despite the apparent quiescent nature of the L723, fragmentation is occurring at the center of the cloud at different scales. Thus, at sime1000 AU, the cloud has fragmented in two cores: SMA 1 and SMA 2. At the same time, at least one of these cores, SMA 2, has undergone additional fragmentation at scales of sime150 AU, forming a multiple stellar system.

  8. A simple finite element method for non-divergence form elliptic equation

    DOE PAGES

    Mu, Lin; Ye, Xiu

    2017-03-01

    Here, we develop a simple finite element method for solving second order elliptic equations in non-divergence form by combining least squares concept with discontinuous approximations. This simple method has a symmetric and positive definite system and can be easily analyzed and implemented. We could have also used general meshes with polytopal element and hanging node in the method. We prove that our finite element solution approaches to the true solution when the mesh size approaches to zero. Numerical examples are tested that demonstrate the robustness and flexibility of the method.

  9. 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.

  10. Challenges in Forming the Solar System's Giant Planet Cores via Pebble Accretion

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Though ~10 M ⊕ 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.

  11. A MASSIVE PROTOSTAR FORMING BY ORDERED COLLAPSE OF A DENSE, MASSIVE CORE

    SciTech Connect

    Zhang, Yichen; Tan, Jonathan C.; Telesco, Charles; De Buizer, James M.; Sandell, Goeran; Shuping, Ralph; Beltran, Maria T.; Churchwell, Ed; Whitney, Barbara; McKee, Christopher F.; Staff, Jan E.

    2013-04-10

    We present 30 and 40 {mu}m imaging of the massive protostar G35.20-0.74 with SOFIA-FORCAST. The high surface density of the natal core around the protostar leads to high extinction, even at these relatively long wavelengths, causing the observed flux to be dominated by that emerging from the near-facing outflow cavity. However, emission from the far-facing cavity is still clearly detected. We combine these results with fluxes from the near-infrared to mm to construct a spectral energy distribution (SED). For isotropic emission the bolometric luminosity would be 3.3 Multiplication-Sign 10{sup 4} L{sub Sun }. We perform radiative transfer modeling of a protostar forming by ordered, symmetric collapse from a massive core bounded by a clump with high-mass surface density, {Sigma}{sub cl}. To fit the SED requires protostellar masses {approx}20-34 M{sub Sun} depending on the outflow cavity opening angle (35 Degree-Sign -50 Degree-Sign ), and {Sigma}{sub cl} {approx} 0.4-1 g cm{sup -2}. After accounting for the foreground extinction and the flashlight effect, the true bolometric luminosity is {approx}(0.7-2.2) Multiplication-Sign 10{sup 5} L{sub Sun }. One of these models also has excellent agreement with the observed intensity profiles along the outflow axis at 10, 18, 31, and 37 {mu}m. Overall our results support a model of massive star formation involving the relatively ordered, symmetric collapse of a massive, dense core and the launching bipolar outflows that clear low-density cavities. Thus a unified model may apply for the formation of both low- and high-mass stars.

  12. Moving-mesh Simulations of Star-forming Cores in Magneto-gravo-turbulence

    NASA Astrophysics Data System (ADS)

    Mocz, Philip; Burkhart, Blakesley; Hernquist, Lars; McKee, Christopher F.; Springel, Volker

    2017-03-01

    Star formation in our Galaxy occurs in molecular clouds that are self-gravitating, highly turbulent, and magnetized. We study the conditions under which cloud cores inherit large-scale magnetic field morphologies and how the field is governed by cloud turbulence. We present four moving-mesh simulations of supersonic, turbulent, isothermal, self-gravitating gas with a range of magnetic mean-field strengths characterized by the Alfvénic Mach number {{ M }}{{A},0}, resolving prestellar core formation from parsec to a few astronomical unit scales. In our simulations with the turbulent kinetic energy density dominating over magnetic pressure ({{ M }}{{A},0}> 1), we find that the collapse is approximately isotropic with B ∝ ρ 2/3, core properties are similar regardless of initial mean-field strength, and the field direction on 100 au scales is uncorrelated with the mean field. However, in the case of a dominant large-scale magnetic field ({{ M }}{{A},0}=0.35), the collapse is anisotropic with B ∝ ρ 1/2. This transition at {{ M }}{{A},0}∼ 1 is not expected to be sharp, but clearly signifies two different paths for magnetic field evolution in star formation. Based on observations of different star-forming regions, we conclude that star formation in the interstellar medium may occur in both regimes. Magnetic field correlation with the mean field extends to smaller scales as {{ M }}{{A},0} decreases, making future Atacama Large Millimeter Array observations useful for constraining {{ M }}{{A},0} of the interstellar medium.

  13. Externally Heated Protostellar Cores in the Ophiuchus Star-forming Region

    NASA Astrophysics Data System (ADS)

    Lindberg, Johan E.; Charnley, Steven B.; Jørgensen, Jes K.; Cordiner, Martin A.; Bjerkeli, Per

    2017-01-01

    We present APEX 218 GHz observations of molecular emission in a complete sample of embedded protostars in the Ophiuchus star-forming region. To study the physical properties of the cores, we calculate H2CO and c-C3H2 rotational temperatures, both of which are good tracers of the kinetic temperature of the molecular gas. We find that the H2CO temperatures range between 16 K and 124 K, with the highest H2CO temperatures toward the hot corino source IRAS 16293-2422 (69–124 K) and the sources in the ρ Oph A cloud (23–49 K) located close to the luminous Herbig Be star S1, which externally irradiates the ρ Oph A cores. On the other hand, the c-C3H2 rotational temperature is consistently low (7–17 K) in all sources. Our results indicate that the c-C3H2 emission is primarily tracing more shielded parts of the envelope whereas the H2CO emission (at the angular scale of the APEX beam; 3600 au in Ophiuchus) mainly traces the outer irradiated envelopes, apart from in IRAS 16293-2422, where the hot corino emission dominates. In some sources, a secondary velocity component is also seen, possibly tracing the molecular outflow. Based on observations with the Atacama Pathfinder EXperiment (APEX) telescope. APEX is a collaboration between the Max Planck Institute for Radio Astronomy, the European Southern Observatory, and the Onsala Space Observatory.

  14. 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

  15. 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.

  16. 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.

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

    DOE PAGES

    Noack, Clinton W.; Jain, Jinesh C.; Stegmeier, John; ...

    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. 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.

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

    PubMed

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

    2015-01-01

    In this work, the geochemistry of the rare earth elements (REE) was studied 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.

  20. 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…

  1. 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.

  2. 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.

    2016-12-01

    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 time-scales for a helium atmosphere white dwarf, of no more than a few hundred years, 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 four times higher than for any white dwarf with a comparable diffusion time-scale. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. Major and trace elements in Mahogany zone oil shale in two cores from the Green River Formation, piceance basin, Colorado

    USGS Publications Warehouse

    Tuttle, M.L.; Dean, W.E.; Parduhn, N.L.

    1983-01-01

    The Parachute Creek Member of the lacustrine Green River Formation contains thick sequences of rich oil-shale. The richest sequence and the richest oil-shale bed occurring in the member are called the Mahogany zone and the Mahogany bed, respectively, and were deposited in ancient Lake Uinta. The name "Mahogany" is derived from the red-brown color imparted to the rock by its rich-kerogen content. Geochemical abundance and distribution of eight major and 18 trace elements were determined in the Mahogany zone sampled from two cores, U. S. Geological Survey core hole CR-2 and U. S. Bureau of Mines core hole O1-A (Figure 1). The oil shale from core hole CR-2 was deposited nearer the margin of Lake Uinta than oil shale from core hole O1-A. The major- and trace-element chemistry of the Mahogany zone from each of these two cores is compared using elemental abundances and Q-mode factor modeling. The results of chemical analyses of 44 CR-2 Mahogany samples and 76 O1-A Mahogany samples are summarized in Figure 2. The average geochemical abundances for shale (1) and black shale (2) are also plotted on Figure 2 for comparison. The elemental abundances in the samples from the two cores are similar for the majority of elements. Differences at the 95% probability level are higher concentrations of Ca, Cu, La, Ni, Sc and Zr in the samples from core hole CR-2 compared to samples from core hole O1-A and higher concentrations of As and Sr in samples from core hole O1-A compared to samples from core hole CR-2. These differences presumably reflect slight differences in depositional conditions or source material at the two sites. The Mahogany oil shale from the two cores has lower concentrations of most trace metals and higher concentrations of carbonate-related elements (Ca, Mg, Sr and Na) compared to the average shale and black shale. During deposition of the Mahogany oil shale, large quantities of carbonates were precipitated resulting in the enrichment of carbonate-related elements

  8. 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.

  9. 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.

  10. Structure of the Drosophila HeT-A transposon: a retrotransposon-like element forming telomeres.

    PubMed

    Danilevskaya, O; Slot, F; Pavlova, M; Pardue, M L

    1994-06-01

    Telomeres of Drosophila appear to be very different from those of other organisms. A transposable element, HeT-A, plays a major role in forming telomeres and may be the sole structural element, since telomerase-generated repeats are not found. HeT-A transposes only to chromosome ends. It appears to be a retrotransposon but has novel structural features, which may be related to its telomere functions. A consensus sequence from cloned HeT-A elements defines an element of approximately 6 kb. The coding region has retrotransposon-like overlapping open reading frames (ORFs) with a -1 frameshift in a sequence resembling the frameshift region of the mammalian HIV-1 retrovirus. Both the HeT-A ORFs contain motifs suggesting RNA binding. HeT-A-specific features include a long non-coding region, 3' of the ORFs, which makes up about half of the element. This region has a regular array of imperfect sequence repeats and ends with oligo(A), marking the end of the element and suggesting a polyadenylated RNA transposition intermediate. This 3' repeat region may have a structural role in heterochromatin. The most distal part of each complete HeT-A on the chromosome, the region 5' of the ORFs, has unusual conserved features, which might produce a terminal structure for the chromosome.

  11. A study on using pre-forming blank in single point incremental forming process by finite element analysis

    NASA Astrophysics Data System (ADS)

    Abass, K. I.

    2016-11-01

    Single Point Incremental Forming process (SPIF) is a forming technique of sheet material based on layered manufacturing principles. The edges of sheet material are clamped while the forming tool is moved along the tool path. The CNC milling machine is used to manufacturing the product. SPIF involves extensive plastic deformation and the description of the process is more complicated by highly nonlinear boundary conditions, namely contact and frictional effects have been accomplished. However, due to the complex nature of these models, numerical approaches dominated by Finite Element Analysis (FEA) are now in widespread use. The paper presents the data and main results of a study on effect of using preforming blank in SPIF through FEA. The considered SPIF has been studied under certain process conditions referring to the test work piece, tool, etc., applying ANSYS 11. The results show that the simulation model can predict an ideal profile of processing track, the behaviour of contact tool-workpiece, the product accuracy by evaluation its thickness, surface strain and the stress distribution along the deformed blank section during the deformation stages.

  12. Finite Element Modeling of a Non-Isothermal Superplastic-Like Forming Process

    SciTech Connect

    Liu Jun; Tan, Ming-Jen; Castagne, Sylvie; Jarfors, Anders E. W.; Fong, Kai-Soon; Bayraktar, Emin; Aue-u-lan, Yingyot

    2011-01-17

    Conventional superplastic forming (SPF) has been modified to increase the productivity and reduce some of the drawbacks, such as high forming temperature and high percentage thinning, to suit the automotive industries. One of the modifications was to combine between the conventional SPF and the use of a mechanical preformed blank to form the non-superplastic grade aluminum alloy (AA5083-O). The requirement of high temperature usually results in microstructural defects during forming process. In this paper, finite element modeling was adopted to investigate the superplastic-like forming process using the non-isothermal heating system. In the simulation, two phases (mechanical pre-forming and gas blow for ming) of the process were conducted under different temperatures, where the material was mechanically drawn into the die cavity at 200 deg. C in the first phase, and it formed with gas pressure applied at a global temperature increasing from 400 deg. C to 500 deg. C. Because of the non-isothermal heating of material, it was found that it had enough ductility to flow more easily in the specific zones (die corners and radius). Additionally, FEM results showed that a better formed part can be obtained by the increasing temperature forming, compared to the stable temperature phase.

  13. Ionic liquid crystals formed by self-assembly around an anionic anthracene core.

    PubMed

    Olivier, Jean-Hubert; Camerel, Franck; Barberá, Joaquín; Retailleau, Pascal; Ziessel, Raymond

    2009-08-17

    We have designed and synthesised a series of modular, mesogenic complexes based on anthracene-2,6-disulfonate and trialkoxybenzyl-functionalised imidazolium cations. Each complex contains a central, rigid, dianionic anthracene core and two flexible monocations bearing paraffin chains anchored on imidazolium rings. Anthracene-2,6-disulfonate can be crystallised with various simple alkylammonium ions and, in the case of +N(CH3)2(C16H33)2, a crystal structure determination has shown that the long paraffinic chains are intercalated between the anthracene moieties. The dianion forms columnar mesophases with trialkoxybenzylimidazolium cations, as identified by polarising optical microscopy and X-ray scattering measurements. Differential scanning calorimetry studies confirmed mesomorphic behaviour from room temperature to about 200 degrees C for alkyl chains containing 8, 12 and 16 carbon atoms. The strong luminescence of anthracene is maintained in the mesophase and fluorescence measurements confirmed the presence of J aggregates in all cases. The new functional materials described herein provide an easy access to stable and luminescent mesomorphic materials engineered by an ionic self-assembly process.

  14. EXPANDED VERY LARGE ARRAY OBSERVATIONS OF THE BARNARD 5 STAR-FORMING CORE: EMBEDDED FILAMENTS REVEALED

    SciTech Connect

    Pineda, Jaime E.; Longmore, Steven; Goodman, Alyssa A.; Arce, Hector G.; Caselli, Paola; Corder, Stuartt

    2011-09-20

    We present {approx}6.'5 x 8' Expanded Very Large Array (EVLA) mosaic observations of the NH{sub 3} (1,1) emission in the Barnard 5 region in Perseus, with an angular resolution of 6''. This map covers the coherent region, where the dense gas presents subsonic non-thermal motions (as seen from single dish observations with the Green Bank Telescope, GBT). The combined EVLA and GBT observations reveal, for the first time, a striking filamentary structure (20'' wide or 5000 AU at the distance of Perseus) in this low-mass star-forming region. The integrated intensity profile of this structure is consistent with models of an isothermal filament in hydrostatic equilibrium. The observed separation between the B5-IRS1 young stellar object (YSO), in the central region of the core, and the northern starless condensation matches the Jeans length of the dense gas. This suggests that the dense gas in the coherent region is fragmenting. The observed region displays a narrow velocity dispersion, where most of the gas shows evidence for subsonic turbulence and where little spatial variations are present. It is only close to the YSO where an increase in the velocity dispersion is found, but still displaying subsonic non-thermal motions.

  15. Secretin receptor oligomers form intracellularly during maturation through receptor core domains.

    PubMed

    Lisenbee, Cayle S; Miller, Laurence J

    2006-07-11

    Oligomerization of numerous G protein-coupled receptors has been documented, including the prototypic family B secretin receptor. The clinical significance of oligomerization of this receptor became clear with the recent observation that a misspliced form present in pancreatic cancer could associate with the wild-type receptor and act as a dominant negative inhibitor of its normal growth inhibitory function. Our goal was to explore the molecular mechanism of this interaction using bioluminescence (BRET) and fluorescence (FRET) resonance energy transfer and fluorescence microscopy with a variety of receptor constructs tagged with luciferase or cyan or yellow fluorescent proteins. BRET signals comparable to those obtained from cells coexpressing differentially tagged wild-type receptors were observed for similarly tagged secretin receptors in which all or part of the amino-terminal domain was deleted. As expected, neither of these constructs bound secretin, and only the partially truncated construct sorted to the plasma membrane. Receptors lacking the majority of the carboxyl-terminal domain, including that important for phosphorylation-mediated desensitization, also produced BRET signals above background. These findings suggested that the receptor's membrane-spanning core is responsible for secretin receptor oligomerization. Interestingly, alanine substitutions for a -GxxxG- helix interaction motif in transmembrane segment 7 created nonfunctional receptors that were capable of forming oligomers. Furthermore, treatment of receptor-expressing cells with brefeldin A did not eliminate the BRET signals, and morphologic FRET experiments confirmed the expected subcellular localizations of receptor oligomers. We conclude that secretin receptor oligomerization occurs through -GxxxG- motif-independent interactions of transmembrane segments during the maturation of nascent molecules.

  16. 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.

  17. Widespread Use of TATA Elements in the Core Promoters for RNA Polymerases III, II, and I in Fission Yeast

    PubMed Central

    Hamada, Mitsuhiro; Huang, Ying; Lowe, Todd M.; Maraia, Richard J.

    2001-01-01

    In addition to directing transcription initiation, core promoters integrate input from distal regulatory elements. Except for rare exceptions, it has been generally found that eukaryotic tRNA and rRNA genes do not contain TATA promoter elements and instead use protein-protein interactions to bring the TATA-binding protein (TBP), to the core promoter. Genomewide analysis revealed TATA elements in the core promoters of tRNA and 5S rRNA (Pol III), U1 to U5 snRNA (Pol II), and 37S rRNA (Pol I) genes in Schizosaccharomyces pombe. Using tRNA-dependent suppression and other in vivo assays, as well as in vitro transcription, we demonstrated an obligatory requirement for upstream TATA elements for tRNA and 5S rRNA expression in S. pombe. The Pol III initiation factor Brf is found in complexes with TFIIIC and Pol III in S. pombe, while TBP is not, consistent with independent recruitment of TBP by TATA. Template commitment assays are consistent with this and confirm that the mechanisms of transcription complex assembly and initiation by Pol III in S. pombe differ substantially from those in other model organisms. The results were extended to large-rRNA synthesis, as mutation of the TATA element in the Pol I promoter also abolishes rRNA expression in fission yeast. A survey of other organisms' genomes reveals that a substantial number of eukaryotes may use widespread TATAs for transcription. These results indicate the presence of TATA-unified transcription systems in contemporary eukaryotes and provide insight into the residual need for TBP by all three Pols in other eukaryotes despite a lack of TATA elements in their promoters. PMID:11564871

  18. Finite element simulation of flexible roll forming with supplemented material data and the experimental verification

    NASA Astrophysics Data System (ADS)

    Yan, Yu; Wang, Haibo; Li, Qiang; Guan, Yanzhi

    2016-03-01

    Flexible roll forming is a promising manufacturing method for the production of variable cross section products. Considering the large plastic strain in this forming process which is much larger than that of uniform deformation phase of uniaxial tensile test, the widely adopted method of simulating the forming processes with non-supplemented material data from uniaxial tensile test will certainly lead to large error. To reduce this error, the material data is supplemented based on three constitutive models. Then a finite element model of a six passes flexible roll forming process is established based on the supplemented material data and the original material data from the uniaxial tensile test. The flexible roll forming experiment of a B pillar reinforcing plate is carried out to verify the proposed method. Final cross section shapes of the experimental and the simulated results are compared. It is shown that the simulation calculated with supplemented material data based on Swift model agrees well with the experimental results, while the simulation based on original material data could not predict the actual deformation accurately. The results indicate that this material supplement method is reliable and indispensible, and the simulation model can well reflect the real metal forming process. Detailed analysis of the distribution and history of plastic strain at different positions are performed. A new material data supplement method is proposed to tackle the problem which is ignored in other roll forming simulations, and thus the forming process simulation accuracy can be greatly improved.

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

    PubMed Central

    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

  20. 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.

  1. 5'- and 3'-terminal nucleotides in the FGFR2 ISAR splicing element core have overlapping roles in exon IIIb activation and exon IIIc repression.

    PubMed

    Jones, R B; Carstens, R P; Luo, Y; McKeehan, W L

    2001-09-01

    The cell type-specific, mutually-exclusive alternative splicing of the fibroblast growth factor receptor 2 (FGFR2) pre-mRNA is tightly regulated. A sequence termed ISAR (intronic splicing activator and repressor) has been implicated as an important cis regulatory element in both activation of exon IIIb and repression of exon IIIc splicing in epithelial cells. In order to better understand how this single sequence could have dual roles, we transfected minigenes containing a series of 2-bp mutations in the 18 3'-most nucleotides of ISAR that we refer to as the ISAR core. Transfection of cells with dual-exon (IIIb and IIIc) minigenes revealed that mutation of terminal sequences of the core led to decreased exon IIIb inclusion and increased exon IIIc inclusion. Transfection of cells with single-exon IIIb minigenes and single-exon IIIc minigenes revealed that mutation of terminal sequences of the ISAR core led to decreased exon IIIb inclusion and increased exon IIIc inclusion, respectively. Nucleotides of the ISAR core responsible for exon IIIb activation appear to overlap very closely with those required for exon IIIc repression. We describe a model in which ISAR and a 5' intronic sequence known as IAS2 form a stem structure required for simultaneous exon IIIb activation and exon IIIc repression.

  2. Plasma-assisted synthesis and high-resolution characterization of anisotropic elemental and bimetallic core-shell magnetic nanoparticles.

    PubMed

    Hennes, M; Lotnyk, A; Mayr, S G

    2014-01-01

    Magnetically anisotropic as well as magnetic core-shell nanoparticles (CS-NPs) with controllable properties are highly desirable in a broad range of applications. With this background, a setup for the synthesis of heterostructured magnetic core-shell nanoparticles, which relies on (optionally pulsed) DC plasma gas condensation has been developed. We demonstrate the synthesis of elemental nickel nanoparticles with highly tunable sizes and shapes and Ni@Cu CS-NPs with an average shell thickness of 10 nm as determined with scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy measurements. An analytical model that relies on classical kinetic gas theory is used to describe the deposition of Cu shell atoms on top of existing Ni cores. Its predictive power and possible implications for the growth of heterostructured NP in gas condensation processes are discussed.

  3. 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.

  4. 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

  5. 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

  6. Continuous ice core melter system with discrete sampling for major ion, trace element and stable isotope analyses.

    PubMed

    Osterberg, Erich C; Handley, Michael J; Sneed, Sharon B; Mayewski, Paul A; Kreutz, Karl J

    2006-05-15

    We present a novel ice/firn core melter system that uses fraction collectors to collect discrete, high-resolution (<1 cm/sample possible), continuous, coregistered meltwater samples for analysis of eight major ions by ion chromatography (IC), >32 trace elements by inductively coupled plasma sectorfield mass spectrometry (ICP-SMS), and stable oxygen and hydrogen isotopes by isotope ratio mass spectrometry (IRMS). The new continuous melting with discrete sampling (CMDS) system preserves an archive of each sample, reduces the problem of incomplete particle dissolution in ICP-SMS samples, and provides more precise trace element data than previous ice melter models by using longer ICP-SMS scan times and washing the instrument between samples. CMDS detection limits are similar to or lower than those published for ice melter systems coupled directly to analytical instruments and are suitable for analyses of polar and mid-low-latitude ice cores. Analysis of total calcium and sulfur by ICP-SMS and calcium ion, sulfate, and methanesulfonate by IC from the Mt. Logan Prospector-Russell Col ice core confirms data accuracy and coregistration of the split fractions from each sample. The reproducibility of all data acquired by the CMDS system is confirmed by replicate analyses of parallel sections of the GISP2 D ice core.

  7. Structural Elements of Shallow Thermal Donors Formed in Nitrogen-Gas-Doped Silicon Crystals

    NASA Astrophysics Data System (ADS)

    Hara, Akito

    2007-02-01

    It has been reported that shallow thermal donors (STDs) are formed in oxygen-rich silicon (Si) crystals preannealed in nitrogen gas (N-gas-doped) and also in hydrogen-doped (H-doped) oxygen-rich Si crystals. The STDs formed in these crystals exhibit very similar electronic structures. Experiments using far-infrared optical absorption showed that several hydrogen-like STDs were formed at the same time and their energy levels in both the above-mentioned crystals were very similar. It has also been reported that the g-values of the STDs formed in both the crystals were identical. On the basis of electron-nucleus double resonance results, it has been strongly suggested that a hydrogen impurity is incorporated as a structural element of the STDs formed in the H-doped Si crystals. However, the origin of the STDs that are formed in N-gas-doped Si crystals is still unclear. To clarify this point, hydrogen detection in N-gas-doped Si was conducted and the annealing behaviors of STDs in N-gas-doped Si and H-doped Si were compared by electron spin resonance and far-infrared optical absorption measurement. It was concluded that the origin of the STDs formed in N-gas-doped Si crystals is not related to the hydrogen impurity.

  8. 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.

  9. 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

  10. Establishing the Structural Integrity of Core-Shell Nanoparticles against Elemental Migration using Luminescent Lanthanide Probes.

    PubMed

    Chen, Bing; Peng, Dengfeng; Chen, Xian; Qiao, Xvsheng; Fan, Xianping; Wang, Feng

    2015-10-19

    Core-shell structured nanoparticles are increasingly used to host luminescent lanthanide ions but the structural integrity of these nanoparticles still lacks sufficient understanding. Herein, we present a new approach to detect the diffusion of dopant ions in core-shell nanostructures using luminescent lanthanide probes whose emission profile and luminescence lifetime are sensitive to the chemical environment. We show that dopant ions in solution-synthesized core-shell nanoparticles are firmly confined in the designed locations. However, annealing at certain temperatures (greater than circa 350 °C) promotes diffusion of the dopant ions and leads to degradation of the integrity of the nanoparticles. These insights into core-shell nanostructures should enhance our ability to understand and use lanthanide-doped luminescent nanoparticles.

  11. Semiclassical form factor for spectral and matrix element fluctuations of multidimensional chaotic systems.

    PubMed

    Turek, Marko; Spehner, Dominique; Müller, Sebastian; Richter, Klaus

    2005-01-01

    We present a semiclassical calculation of the generalized form factor Kab(tau) which characterizes the fluctuations of matrix elements of the operators a and b in the eigenbasis of the Hamiltonian of a chaotic system. Our approach is based on some recently developed techniques for the spectral form factor of systems with hyperbolic and ergodic underlying classical dynamics and f = 2 degrees of freedom, that allow us to go beyond the diagonal approximation. First we extend these techniques to systems with f > 2. Then we use these results to calculate Kab(tau). We show that the dependence on the rescaled time tau (time in units of the Heisenberg time) is universal for both the spectral and the generalized form factor. Furthermore, we derive a relation between Kab(tau) and the classical time-correlation function of the Weyl symbols of a and b.

  12. 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

  13. 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.

  14. 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

  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 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.

  17. Forming the phosphate layer in reconstituted horse spleen ferritin and the role of phosphate in promoting core surface redox reactions.

    PubMed

    Johnson, J L; Cannon, M; Watt, R K; Frankel, R B; Watt, G D

    1999-05-18

    Apo horse spleen ferritin (apo HoSF) was reconstituted to various core sizes (100-3500 Fe3+/HoSF) by depositing Fe(OH)3 within the hollow HoSF interior by air oxidation of Fe2+. Fe2+ and phosphate (Pi) were then added anaerobically at a 1:4 ratio, and both Fe2+ and Pi were incorporated into the HoSF cores. The resulting Pi layer consisted of Fe2+ and Pi at about a 1:3 ratio which is strongly attached to the reconstituted ferritin mineral core surface and is stable even after air oxidation of the bound Fe2+. The total amount of Fe2+ and Pi bound to the iron core surface increases as the core volume increases up to a maximum near 2500 iron atoms, above which the size of the Pi layer decreases with increasing core size. Mössbauer spectroscopic measurements of the Pi-reconstituted HoSF cores using 57Fe2+ show that 57Fe3+ is the major species present under anaerobic conditions. This result suggests that the incoming 57Fe2+ undergoes an internal redox reaction to form 57Fe3+ during the formation of the Pi layer. Addition of bipyridine removes the 57Fe3+ bound in the Pi layer as [57Fe(bipy)3]2+, showing that the bound 57Fe2+ has not undergone irreversible oxidation. This result is related to previous studies showing that 57Fe2+ bound to native core is reversibly oxidized under anaerobic conditions in native holo bacterial and HoSF ferritins. Attempts to bury the Pi layer of native or reconstituted HoSF by adding 1000 additional iron atoms were not successful, suggesting that after its formation, the Pi layer "floats" on the developing iron mineral core.

  18. Volatile Siderophile Elements in Shergottites: Constraints on Core Formation and Magmatic Degassing

    NASA Technical Reports Server (NTRS)

    Righter, Kevin; Humayun, M.

    2012-01-01

    Volatile siderophile elements (e.g., As, Sb, Ge, Ga, In, Bi, Zn, Cd, Sn, Cu, Pb) can place constraints both on early differentiation as well as the origin of volatiles. This large group of elements has been used to constrain Earth accretion [1,2], and Earth-Moon geochemistry [3]. Application to Earth has been fostered by new experimental studies of these elements such as Ge, In, and Ga [4,5,6]. Application to Mars has been limited by the lack of data for many of these elements on martian meteorites. Many volatile elements are considered in the pioneering work by [7] but for only the small number of martian samples then available. We have made new measurements on a variety of martian meteorites in order to obtain more substantial datasets for these elements using the analytical approach of [8]. We use the new dataset, together with published data from the literature, to define martian mantle abundances of volatile siderophile elements. Then, we evaluate the possibility that these abundances could have been set by mid-mantle (14 GPa, 2100 C) metal-silicate equilibrium, as suggested by the moderately and slightly siderophile elements [9]. Finally, we examine the possibility that some elements were affected by volatility and magmatic degassing.

  19. 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.

  20. 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.

  1. 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.

  2. 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 ...

  3. 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

  4. Student construction of differential length elements in multivariable coordinate systems: A symbolic forms analysis

    NASA Astrophysics Data System (ADS)

    Thompson, John; Schermerhorn, Benjamin

    2017-01-01

    Analysis of properties of physical quantities represented by vector fields often involves symmetries and spatial relationships best expressed in non-Cartesian coordinate systems. Many important quantities are determined by integrals that can involve multivariable vector differential quantities. Four pairs of students in junior-level Electricity and Magnetism (E&M) were interviewed to investigate their understanding of the structure of non-Cartesian coordinate systems and the associated differential elements. Pairs were asked to construct differential length elements for an unconventional spherical coordinate system. In order to explore how student conceptual understanding interacts with their understanding of the specific structures of these expressions, a symbolic forms framework was used. Analysis of student reasoning revealed both known and novel forms as well as the general progression of students--use and combination of symbol templates during the construction process. Each group invoked and combined symbolic forms in a similar sequence. Difficulties with the construction of expressions seem to be related almost exclusively to the conceptual schema (e.g., neglecting the role of projection) rather than with symbol templates. Supported in part by NSF Grant PHY-1405726.

  5. Characteristics of correlation between climate and environmental elements from past 720,000 years in Dome Fuji ice core, Antarctica

    NASA Astrophysics Data System (ADS)

    Motoyama, H.; Project members, D.

    2011-12-01

    Two deep ice cores (DF1: 2503m and DF2: 3035m) at Dome Fuji, Antarctica have the in-depth information of global environmental change from present to the past 720,000 years. We made the data set of major ion concentration, dust concentration and stable isotope ratio which were analyzed 10cm sample every 50cm from 2400m to 3035m using the DF2 core. The age of this depth was covered from 300,000 to 720,000 years before. Using theDF1 core, major chemical species were carried out using 7-10cm ice samples cut out of the 50 cm-long spaced from 0.5 to 2.5m. All data was averaged by every 5 m. The Correlations between climate and environmental elements were calculated. The indexes of climate and environment are the following elements; MSA-, Cl-, NO3-, SO42-, H+ (calculated from pH.), Na+, NH4+, K+, Mg2+, Ca2+, ss-Na+, nss-Cl-, nss-SO42-, nss-K+, nss-Mg2+, nss-Ca2+, dD, d18O, d-excess, dust, pH and electrical conductivity. There is a feature in correlation respectively by the climatic stage. dD or d18O which becomes the index of the temperature and the environmental elements (for example, Na and Mg) indicate the strong negative correlation, but its degree is different depending on the climatic stages. In particular, environmental changes around Mid-Brunhes event and during AIM event were examined. Ice core drilling reached just near the bedrock in ice sheet. Liquid water which existed around the basal ice was soaked into the borehole. Its water was frozen and was picked up with drill machine. Characteristics of ion concentrations near the bedrock (i.e, from 3000m to 3035m) were reported.

  6. Reconstructing Quaternary precipitation periodicities with Santa Barbara Basin sediment cores: application of the siliciclastic detrital element proxy at annual resolution

    NASA Astrophysics Data System (ADS)

    Napier, T.; Hendy, I. L.; Hinnov, L.; Brown, E. T.

    2015-12-01

    Precipitation patterns in Southern California directly affect water availability, and extreme weather exacerbates water stress and subsequent societal impacts in this highly populated and vital agricultural region. In the future, mean annual precipitation is predicted to decrease in California, although frequency of heavy precipitation events may increase. To reconstruct annual precipitation history in Southern California, including both the magnitude and recurrence intervals, we analyze sediment from two Late Holocene (past ~150 years and past ~2 ka) and five Pleistocene (~400-450 ka [MIS 11 and 12] and ~735 ka [MIS 18]) cores collected in Santa Barbara Basin using data from XRF core scans for elements associated with the terrigenous siliciclastic detrital fraction of core sediment (Al, Fe, K, Rb, Si, Ti, Zr). We develop a floating annual age model for each core through identification of the annual signal in the siliciclastic detrital fraction. Siliciclastic detrital element concentrations increase in sediment associated with precipitation events and floods, and decrease in sediment associated with droughts. Variability in the concentrations of these elements can thus be used as a precipitation and river runoff proxy. We investigate changes in annual detrital sediment input during glacial, deglacial, and interglacial climate states, and changes due to rapid climate change (centennial to millennial time scales). Power spectral analysis of our annually tuned time series reveals precipitation periodicities associated with the Pacific Decadal Oscillation (15-25, 50-70 years) and El Niño-Southern Oscillation (2-7 years) that are dissimilar to common tidal perigee and nodal periods. These results provide information on the nature and response of precipitation patterns due to past changes in climate forcing, which will improve climate predictions for this region, especially interannual and decadal variability that impact climate on human timescales (i.e. <100 years).

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. The influence of various core designs on stress distribution in the veneered zirconia crown: a finite element analysis study

    PubMed Central

    Ha, Seung-Ryong; Kim, Sung-Hun; Yoo, Seung-Hyun; Jeong, Se-Chul; Lee, Jai-Bong; Yeo, In-Sung

    2013-01-01

    PURPOSE The purpose of this study was to evaluate various core designs on stress distribution within zirconia crowns. MATERIALS AND METHODS Three-dimensional finite element models, representing mandibular molars, comprising a prepared tooth, cement layer, zirconia core, and veneer porcelain were designed by computer software. The shoulder (1 mm in width) variations in core were incremental increases of 1 mm, 2 mm and 3 mm in proximal and lingual height, and buccal height respectively. To simulate masticatory force, loads of 280 N were applied from three directions (vertical, at a 45° angle, and horizontal). To simulate maximum bite force, a load of 700 N was applied vertically to the crowns. Maximum principal stress (MPS) was determined for each model, loading condition, and position. RESULTS In the maximum bite force simulation test, the MPSs on all crowns observed around the shoulder region and loading points. The compressive stresses were located in the shoulder region of the veneer-zirconia interface and at the occlusal region. In the test simulating masticatory force, the MPS was concentrated around the loading points, and the compressive stresses were located at the 3 mm height lingual shoulder region, when the load was applied horizontally. MPS increased in the shoulder region as the shoulder height increased. CONCLUSION This study suggested that reinforced shoulder play an essential role in the success of the zirconia restoration, and veneer fracture due to occlusal loading can be prevented by proper core design, such as shoulder. PMID:23755346

  14. 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

  15. 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

  16. 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

  17. Source tracing of rare earth elements: A case study of core 07 on the southern coast of Laizhou Bay

    NASA Astrophysics Data System (ADS)

    Fei, Guo; Maosheng, Gao; Guohua, Hou; Sen, Liu; Jing, Wang

    2017-03-01

    Rare earth elements (REEs) have proven to be useful indicators of sediment sources. To identify the group of elements most suitable for provenance identification, coastal sediment samples collected from core 07 in Laizhou Bay were analyzed for the presence of REEs. In addition, a corresponding analysis of contributions that different source made to multi-source sedimentary system and provenance discrimination study were undertaken, with the twofold purpose of assessing the effectiveness of REEs as source indicators, and evaluating relative inputs to the sedimentary system on the southern coast of Laizhou Bay from near source and distant origin rivers (i.e. the Bailang River and Yellow River, respectively). The study revealed that various REEs displayed similar cyclic variation in the vertical direction in core 07, with obvious changes at marine-continental stratigraphic boundaries, which could be used as stratigraphic division index. According to chondrite-normalized REE distribution patterns, the Bailang River and Yellow River comprise the main provenance of sediments in core 07. REE discrimination diagrams and the Provenance Index (PI) reveal that the sediments in early stage (Qp33 Qp31, 49.15-80.00 m) were primarily derived from Yellow River, and the sediments in late stage (Qh3 Qp33,5.80-49.15 m) were stemmed from Bailang River. Following extensive analysis, it was concluded that the main provenance of core 07 was the Bailang River, which has played an important role in the sedimentary system of the southern coast of Laizhou Bay since the early Late Pleistocene. Sediment from the Yellow River, rechannelled frequently in geological history, had limited influence in this area.

  18. 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

  19. An Oncogenic Super-Enhancer Formed Through Somatic Mutation of a Noncoding Intergenic Element

    PubMed Central

    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

    2016-01-01

    In certain human cancers, the expression of critical oncogenes is driven from large regulatory elements, called super-enhancers, which 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 it’s 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, suggesting 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

  20. 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

  1. 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.

  2. 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.

  3. DNC/HNC and N2D+/N2H+ ratios in high-mass star-forming cores

    NASA Astrophysics Data System (ADS)

    Fontani, F.; Sakai, T.; Furuya, K.; Sakai, N.; Aikawa, Y.; Yamamoto, S.

    2014-05-01

    Chemical models predict that the deuterated fraction (the column density ratio between a molecule containing D and its counterpart containing H) of N2H+, Dfrac(N2H+), high in massive pre-protostellar cores, is expected to rapidly drop by an order of magnitude after the protostar birth, while that of HNC, Dfrac(HNC), remains constant for much longer. We tested these predictions by deriving Dfrac(HNC) in 22 high-mass star-forming cores divided in three different evolutionary stages, from high-mass starless core candidates (HMSCs, eight) to high-mass protostellar objects (HMPOs, seven) to ultracompact H II regions (UCHIIs, seven). For all of them, Dfrac(N2H+) was already determined through IRAM 30 m Telescope observations, which confirmed the theoretical rapid decrease of Dfrac(N2H+) after protostar birth. Therefore, our comparative study is not affected by biases introduced by the source selection. We have found average Dfrac(HNC) of 0.012, 0.009 and 0.008 in HMSCs, HMPOs and UCHIIs, respectively, with no statistically significant differences among the three evolutionary groups. These findings confirm the predictions of the chemical models, and indicate that large values of Dfrac(N2H+) are more suitable than large values of Dfrac(HNC) to identify cores on the verge of forming high-mass stars, likewise what was found in the low-mass regime.

  4. 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…

  5. An investigation into the mechanics of double-sided incremental forming using finite element methods

    NASA Astrophysics Data System (ADS)

    Moser, Newell; Zhang, Zixuan; Ren, Huaqing; Ehmann, Kornel; Cao, Jian

    2016-10-01

    Double-Sided Incremental Forming (DSIF) is a developing sheet metal manufacturing process that has gained a lot of attention in recent years due to its inherent flexibility, low-overhead cost, and die-less nature. However, it can be challenging to define the tool gap so as to achieve a desired pressure through the sheet thickness since one must first predict sheet thinning. In this investigation, a novel part design is proposed which varies in-plane curvature as a function of depth. A finite element model for DSIF is developed and the strain histories in various regions are extracted. It was concluded that if the supporting tool loses contact with the sheet, localized necking can occur prior to part failure. Additionally, part geometry can have significant effects on the tool contact area which, consequently, affects the evolution of strain.

  6. 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

  7. 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.

  8. Toward new designed proteins derived from bovine pancreatic trypsin inhibitor (BPTI): covalent cross-linking of two 'core modules' by oxime-forming ligation.

    PubMed

    Carulla, N; Woodward, C; Barany, G

    2001-01-01

    A 25-residue disulfide-cross-linked peptide, termed 'oxidized core module' (OxCM), that includes essentially all of the secondary structural elements of bovine pancreatic trypsin inhibitor (BPTI) most refractory to hydrogen exchange, was shown previously to favor nativelike beta-sheet structure [Carulla, N., Woodward, C., and Barany, G. (2000) Synthesis and Characterization of a beta-Hairpin Peptide That Represents a 'Core Module' of Bovine Pancreatic Trypsin Inhibitor (BPTI). Biochemistry 39, 7927-7937]. The present work prepares to explore the hypothesis that the energies of nativelike conformations, relative to other possible conformations, could be decreased further by covalent linkage of two OxCMs. Optimized syntheses of six approximately 50-residue OxCM dimers are reported herein, featuring appropriate monomer modifications followed by oxime-forming ligation chemistry to create covalent cross-links at various positions and with differing lengths. Several side reactions were recognized through this work, and modified procedures to lessen or mitigate their occurrence were developed. Particularly noteworthy, guanidine or urea denaturants that were included as peptide-solubilizing components for some reaction mixtures were proven to form adducts with glyoxylyl moieties, thus affecting rates and outcomes. All six synthetic OxCM dimers were characterized by 1D (1)H NMR; three of them showed considerable chemical shift dispersion suggestive of self-association and mutual stabilization between the monomer units.

  9. 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

  10. 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.

  11. Nutrient, trace-element, and ecological history of Musky Bay, Lac Courte Oreilles, Wisconsin, as inferred from sediment cores

    USGS Publications Warehouse

    Fitzpatrick, Faith A.; Garrison, Paul J.; Fitzgerald, Sharon A.; Elder, John F.

    2003-01-01

    Sediment cores were collected from Musky Bay, Lac Courte Oreilles, and from surrounding areas in 1999 and 2001 to determine whether the water quality of Musky Bay has declined during the last 100 years or more as a result of human activity, specifically cottage development and cranberry farming. Selected cores were analyzed for sedimentation rates, nutrients, minor and trace elements, biogenic silica, diatom assemblages, and pollen over the past several decades. Two cranberry bogs constructed along Musky Bay in 1939 and the early 1950s were substantially expanded between 1950?62 and between 1980?98. Cottage development on Musky Bay has occurred at a steady rate since about 1930, although currently housing density on Musky Bay is one-third to one-half the housing density surrounding three other Lac Courte Oreilles bays. Sedimentation rates were reconstructed for a core from Musky Bay by use of three lead radioisotope models and the cesium-137 profile. The historical average mass and linear sedimentation rates for Musky Bay are 0.023 grams per square centimeter per year and 0.84 centimeters per year, respectively, for the period of about 1936?90. There is also limited evidence that sedimentation rates may have increased after the mid-1990s. Historical changes in input of organic carbon, nitrogen, phosphorus, and sulfur to Musky Bay could not be directly identified from concentration profiles of these elements because of the potential for postdepositional migration and recycling. Minor- and trace-element profiles from the Musky Bay core possibly reflect historical changes in the input of clastic material over time, as well as potential changes in atmospheric deposition inputs. The input of clastic material to the bay increased slightly after European settlement and possibly in the 1930s through 1950s. Concentrations of copper in the Musky Bay core increased steadily through the early to mid-1900s until about 1980 and appear to reflect inputs from atmospheric

  12. A MULTI-WAVELENGTH STUDY OF THE STAR-FORMING CORE AHEAD OF HH 80N

    SciTech Connect

    Masque, Josep M.; Estalella, Robert; Osorio, Mayra; Anglada, Guillem; Garay, Guido; Calvet, Nuria; Beltran, Maria T.

    2011-09-01

    We present observations of continuum emission in the mid-infrared to millimeter wavelength range, complemented with ammonia observations, of the dense core ahead of the radio Herbig-Haro (HH) object HH 80N, found in the GGD 27 region. The continuum emission in all the observed bands peaks at the same position, consistent with the presence of an embedded object, HH 80N-IRS1, within the core. The distribution of the Very Large Array ammonia emission is well correlated with that of the dust, suggesting that photochemical effects caused by the nearby HH object do not play an important role in shaping this particular molecular emission. In order to unveil the nature of HH 80N-IRS1, we analyzed the continuum data of this source, using self-consistent models of protostellar collapse. We find that a young protostar surrounded by a slowly rotating collapsing envelope of radius {approx}0.08 pc and 20 M{sub sun} plus a circumstellar disk of radius {approx}300 AU and 0.6 M{sub sun} provide a good fit to the observed spectral energy distribution and to the maps at 350 {mu}m, 1.2 mm, and 3.5 mm of HH 80N-IRS1. Besides, the Atacama Pathfinder Experiment and Plateau de Bure Interferometer continuum maps at 350 {mu}m and 3.5 mm, respectively, reveal additional clumps in the continuum emission. Given the modeling results and the observed morphology of the emission, we propose a scenario consisting of a central embedded Class 0 object, HH 80N-IRS1, with the rest of the material of the HH 80N core possibly undergoing fragmentation that may lead to the formation of several protostars.

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

    DOE PAGES

    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

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

    SciTech Connect

    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 effects 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.

  15. Melting and solid-melt partitioning in iron-light element systems under megabar conditions: Implications for the thermal state of the Core

    NASA Astrophysics Data System (ADS)

    Ohtani, E.; Kamada, S.; Sakai, T.; Terasaki, H.; Hayashi, H.

    2011-12-01

    The experimental study of the core was pioneered by H.K. Mao [1]. After his pioneering works, significant developments have been made in our high pressure science community to clarify the Earth's core. We have extended the pressure range of melting experiments of iron-light element compounds to pressures exceeding 100 GPa. Melting can be detected by using different criteria, i.e., a change of laser heating efficiency, in situ X-ray diffraction, and the textural change of the recovered samples after quenching from melts. These criteria are generally consistent with one another and enabled us to constrain the temperature, thermal state, and the composition of the core. Melting and phase relations of the Fe-Si, Fe-S, Fe-Ni-S and Fe-S-O systems were determined up to the core pressures based on the in situ X-ray diffraction and a change of laser heating efficiency and texture of the recovered samples by the laser heated diamond anvil cell [2,3,4]. The melting curves may provide constraints for temperatures at the core-mantle boundary (CMB) and the inner core boundary (ICB). Melting and phase relations of the Fe-Fe3S and Fe-S-O systems revealed that Fe3S dissolves first at the solidus before melting of the metallic iron alloy at the liquidus at least up to 180 GPa. The (FeNi)3S phase together with hcp-FeNi is stable up to the pressure above 200 GPa. Therefore, these phases are candidates for the constituent of the inner core. Solid-liquid partitioning experiments can be made by the laser heated diamond anvil cell. The partitioning experiment of Pt, Re, and Os between solid hcp-FeNi alloy and Fe-Ni-S liquid metals is an example of such experiments. It has been assumed that Os isotopic signatures showing coupled 186Os/188Os and 187Os/188Os enrichments in some plume magmas is originated from contamination of outer core materials formed by the inner core fractionation at the base of the lower mantle [5]. We conducted partitioning experiments of Pt, Re, and Os up to 100 GPa

  16. Examination of Environmental Trends in Hawaii Based on the Trace Element Distributions in Cores of the Kiawe tree (Prosopis pallida)

    NASA Astrophysics Data System (ADS)

    Parry, Y. S.; de Carlo, E. H.; Spengler, S. R.

    2003-12-01

    Annual growth rings of trees have the potential for providing a chronology of bioavailable contaminants extant in the environment in which the trees grow. Recent studies have documented a significant correlation between concentrations of metals in atmospheric particulate matter and those observed in surface and groundwater. The Kiawe (Prosopis pallida), a hardwood tree commonly found in Hawaii, represents a potential environmental tape recorder because of its life span on the order of multiple decades. Because the Kiawe is phreatophytic and has high transpiration rates, it may be ideally suited to examine past (temporal) and current (spatial) variability in the quality of groundwater where these trees grow. Because of the potential correlation between airborne and groundwater pollution we hypothesize that growth rings of Kiawe may yield clues to help unravel recent (50-100 yrs) changes in contamination patterns in Hawaii. We will present concentrations of trace elements (Cr, Mn, Co, Ni, Cu, Zn, Pb, Cd, Sb, and Pb) in cores of Kiawe trees growing on the island of Oahu, Hawaii. Oahu, the locus of more than 80 percent of the population of the State of Hawaii, is heavily urbanized, but other land uses include agriculture, conservation (rainforest), and military reservations, where live-fire military training activities over the past 60 years have raised public concern about potential contamination of natural resources. Preliminary analyses indicate that trace element concentrations in Kiawe wood range from a less than one to tens of micrograms per kilogram, depending on the element and the provenance of the tree.

  17. Far-infrared and submillimeter-wavelength observations of star-forming dense cores. I. Spectra

    SciTech Connect

    Ladd, E.F.; Adams, F.C.; Fuller, G.A.; Casey, S.; Davidson, J.A. Yerkes Observatory, Williams Bay, WI NASA, Ames Research Center, Moffett Field, CA )

    1991-01-01

    Far-infrared and submillimeter photometry of 10 low-mass star formation regions containing embedded IRAS sources is presented. These new observations define the peak of the spectral energy distributions of these objects and provide more precise estimates of their bolometric luminosities. Two new sources, L1527 and L483, are among the reddest known low-mass objects, with spectral energy distribution peaks at 100-200 microns and extremely steep IRAS slopes. These cold sources have spectra which are similar to blackbodies of 30-40 K but have significant excess emission on the Wien side. Models of the spectral energy distributions using a spherically symmetric core structure indicate that these sources have visual extinctions greater than 1000 mag. However, models with these large extinctions predict too little near-infrared emission. A nonspherically symmetric distribution of circumstellar material may play a role in the generation of the extra near-infrared emission. 64 refs.

  18. Not Only Columns: High Hole Mobility in a Discotic Nematic Mesophase Formed by Metal-Containing Porphyrin-Core Dendrimers.

    PubMed

    Concellón, Alberto; Marcos, Mercedes; Romero, Pilar; Serrano, José Luis; Termine, Roberto; Golemme, Attilio

    2017-01-24

    We report a new family of multifunctional liquid-crystalline porphyrin-core dendrimers that have coumarin functional groups around the porphyrin core. Porphyrin metalation strongly affects the photophysical properties, and therefore Zn(II) and Cu(II) derivatives have also been prepared. All the synthesized dendrimers form a nematic discotic mesophase. Their high tendency for homeotropic alignment makes these dendrimers excellent candidates for device applications, owing to their easy processability, spontaneous alignment between electrodes, and self-healing of defects because of their dynamic nature. The charge mobility values of these materials are the highest ever reported for a nematic discotic phase. Moreover, these values are similar to the highest values reported for ordered columnar mesophases, and this shows that a supramolecular organization in columns is not necessary to achieve high charge mobility.

  19. What controls the oxidative ratio of UK peats? A multi-site study of elemental CHNO concentrations in peat cores

    NASA Astrophysics Data System (ADS)

    Clay, Gareth; Worrall, Fred; Masiello, Carrie

    2013-04-01

    The oxidative ratio (OR) is the amount of CO2 sequestered in the terrestrial biosphere for each mol of O2 produced. The OR governs the effectiveness of a terrestrial biome to mitigate the impact of anthropogenic CO2 emissions and it has been used to calculate the balance of terrestrial and oceanic carbon sinks across the globe. However, few studies have investigated the controls of the variability in OR. What factors affect OR - climate? Soil type? Vegetation type? N deposition? Land use? Land use change? Small shifts in OR could have important implications in the global partitioning of CO2 between the atmosphere, biosphere, and oceans. This study looks at peat soils from a series of sites representing a climatic transect across the UK. Duplicate peat cores were taken, along with samples of above-ground vegetation and litter, from sites in northern Scotland (Forsinard), southern Scotland (Auchencorth), northern England (Moor House; Thorne Moor) through the Welsh borders (Whixhall Moss) and Somerset levels (Westhay Moor) to Dartmoor and Bodmin Moor in the south west of England. Sub-samples of the cores were analysed for their CHNO concentrations using a Costech ECS 4010 Elemental combustion system. Using the method of Masiello et al. (2008), OR values could be calculated from these elemental concentrations. Results show that OR values of UK peats varied between 0.82 and 1.27 with a median value of 1.08 which is within the range of world soils. There were significant differences in OR of the peat between sites with the data falling into two broad groupings - Group 1: Forsinard, Auchencorth, Dartmoor and Bodmin Moor; Group 2: Moor House, Thorne Moor, Westhay Moor, Whixhall Moss. Whilst there were significant changes (p < 0.05) in elemental ratios with increasing peat depth (increasing C:N ratio and decreasing O:C ratio) there was no significant difference overall in OR with depth. This paper will explore some of the possible controlling factors on these ratios. Local

  20. Mouse prenatal platelet-forming lineages share a core transcriptional program but divergent dependence on MPL.

    PubMed

    Potts, Kathryn S; Sargeant, Tobias J; Dawson, Caleb A; Josefsson, Emma C; Hilton, Douglas J; Alexander, Warren S; Taoudi, Samir

    2015-08-06

    The thrombopoietic environment of the neonate is established during prenatal life; therefore, a comprehensive understanding of platelet-forming cell development during embryogenesis is critical to understanding the etiology of early-onset thrombocytopenia. The recent discovery that the first platelet-forming cells of the conceptus are not megakaryocytes (MKs) but diploid platelet-forming cells (DPFCs) revealed a previously unappreciated complexity in thrombopoiesis. This raises important questions, including the following. When do conventional MKs appear? Do pathogenic genetic lesions of adult MKs affect DPFCs? What role does myeloproliferative leukemia virus (MPL), a key regulator of adult megakaryopoiesis, play in prenatal platelet-forming lineages? We performed a comprehensive study to determine the spatial and temporal appearance of prenatal platelet-forming lineages. We demonstrate that DPFCs originate in the yolk sac and then rapidly migrate to other extra- and intraembryonic tissues. Using gene disruption models of Gata1 and Nfe2, we demonstrate that perturbing essential adult MK genes causes an analogous phenotype in the early embryo before the onset of hematopoietic stem/progenitor cell-driven (definitive) hematopoiesis. Finally, we present the surprising finding that DPFC and MK commitment from their respective precursors is MPL independent in vivo but that completion of MK differentiation and establishment of the prenatal platelet mass is dependent on MPL expression.

  1. 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.

  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. Evolutionary status of dense cores in the NGC 1333 IRAS 4 star-forming region

    NASA Astrophysics Data System (ADS)

    Koumpia, E.; van der Tak, F. F. S.; Kwon, W.; Tobin, J. J.; Fuller, G. A.; Plume, R.

    2016-10-01

    Context. Protostellar evolution after the formation of the protostar is becoming reasonably well characterized, but the evolution from a prestellar core to a protostar is not well known, although the first hydrostatic core (FHSC) must be a pivotal step. Aims: NGC 1333 - IRAS 4C is a potentially very young object that we can directly compare with the nearby Class 0 objects IRAS 4A and IRAS 4B. Observational constraints are provided by spectral imaging from the JCMT Spectral Legacy Survey (330-373 GHz). We present integrated intensity and velocity maps of several species, including CO, H2CO and CH3OH. CARMA observations provide additional information with which we can distinguish IRAS 4C from other evolutionary stages. Methods: We present the observational signatures of the velocity of an observed outflow, the degree of CO depletion, the deuterium fractionation of [DCO+]/[HCO+], and gas kinetic temperatures. Results: We report differences between the three sources in four aspects: a) the kinetic temperature as probed using the H2CO lines is much lower toward IRAS 4C than the other two sources; b) the line profiles of the detected species show strong outflow activity toward IRAS 4A and IRAS 4B, but not toward IRAS 4C; c) the HCN/HNC is <1 toward IRAS 4C, which confirms the cold nature of the source; d) the degree of CO depletion and the deuteration are lowest toward the warmest of the sources, IRAS 4B. Conclusions: IRAS 4C seems to be in a different evolutionary state than the sources IRAS 4A and IRAS 4B. We can probably exclude the FHSC stage becaues of the relatively low Lsmm/Lbol ( 6%), and we investigate the earliest accretion phase of Class 0 stage and the transition between Class 0 to Class I. Our results do not show a consistent scenario for either case; the main problem is the absence of outflow activity and the cold nature of IRAS 4C. The number of FHSC candidates in Perseus is 10 times higher than current models predict, which suggests that the lifespan of

  4. 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%.

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

    PubMed

    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.

  6. 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

  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. 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.

  9. Comparison of antibody responses to different forms of HIV-1 core antigens by epitope mapping.

    PubMed

    Truong, C; Brand, D; Mallet, F; Roingeard, P; Barin, F

    1997-03-01

    The specificity of antibodies to HIV-1 capsid (p24CA) and matrix (p17MA) proteins, produced in mice against unprocessed immature assembled polyprotein (wild-type p55 virus-like particles or chimeric p55 virus-like particles) or against the monomeric mature form (rp24CA/rp17MA), was analyzed by a microplate epitope mapping assay using a panel of synthetic peptides covering the entire p24CA plus p17MA sequences of HIV-1LAI. All immunized mice developed anti-p24CA and anti-p17MA antibodies, although the spectrum of specificity of these antibodies was different. Four p24 CA epitopes (residues 176-192, 201-218, 233-253, 285-304) were recognized by anti-rp24CA/rp17MA antibodies, whereas one p17MA epitope (residues 11-25) and one p24CA epitope (residues 176-192) were constantly recognized by anti-p55 virus-like particle antibodies. These results suggest a different specificity pattern of anti-p24CA and anti-p17MA antibodies depending on whether they are produced against the soluble mature form or the immature assembled form of the gag proteins.

  10. 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

  11. Effectiveness of Rotation-free Triangular and Quadrilateral Shell Elements in Sheet-metal Forming Simulations

    NASA Astrophysics Data System (ADS)

    Brunet, M.; Sabourin, F.

    2005-08-01

    This paper is concerned with the effectiveness of triangular 3-node shell element without rotational d.o.f. and the extension to a new 4-node quadrilateral shell element called S4 with only 3 translational degrees of freedom per node and one-point integration. The curvatures are computed resorting to the surrounding elements. Extension from rotation-free triangular element to a quadrilateral element requires internal curvatures in order to avoid singular bending stiffness. Two numerical examples with regular and irregular meshes are performed to show the convergence and accuracy. Deep-drawing of a box, spring-back analysis of a U-shape strip sheet and the crash simulation of a beam-box complete the demonstration of the bending capabilities of the proposed rotation-free triangular and quadrilateral elements.

  12. Effectiveness of Rotation-free Triangular and Quadrilateral Shell Elements in Sheet-metal Forming Simulations

    SciTech Connect

    Brunet, M.; Sabourin, F.

    2005-08-05

    This paper is concerned with the effectiveness of triangular 3-node shell element without rotational d.o.f. and the extension to a new 4-node quadrilateral shell element called S4 with only 3 translational degrees of freedom per node and one-point integration. The curvatures are computed resorting to the surrounding elements. Extension from rotation-free triangular element to a quadrilateral element requires internal curvatures in order to avoid singular bending stiffness. Two numerical examples with regular and irregular meshes are performed to show the convergence and accuracy. Deep-drawing of a box, spring-back analysis of a U-shape strip sheet and the crash simulation of a beam-box complete the demonstration of the bending capabilities of the proposed rotation-free triangular and quadrilateral elements.

  13. 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.

  14. Characteristics of correlation between climate and environmental elements from past 700,000 years in Dome Fuji ice core, Antarctica

    NASA Astrophysics Data System (ADS)

    Motoyama, H.; Fuji Ice Core Project members, Dome

    2012-04-01

    Two deep ice cores (DF1: 2503m and DF2: 3035m) at Dome Fuji, Antarctica have the in-depth information of global environmental change from present to the past 700,000 years. We made the data set of major ion concentration, dust concentration and stable isotope ratio which were analyzed 10cm sample every 50cm from 2400m to 3035m using the DF2 core. The age of this depth was covered from 300,000 to 700,000 years before. Using the DF1 core, major chemical species were carried out using 7-10cm ice samples cut out of the 50 cm-long spaced from 0.5 to 2.5m. All data was averaged by every 5 m or every 1,000 years. The correlations between climate and environmental elements were calculated. The indexes of climate and environment are the following elements; MSA-, Cl-, NO3-, SO42-, H+ (calculated from pH), Na+, NH4+, K+, Mg2+, Ca2+, ss-Na+, nss-Cl-, nss-SO42-, nss-K+, nss-Mg2+, nss-Ca2+, δD, δ18O, d-excess, dust, pH and electrical conductivity. There is a feature in correlation respectively by the climatic stage. δD or δ18O which becomes the index of the temperature and the environmental elements (for example, Na+ and Mg2+) indicate the strong negative correlation, but its degree is different depending on the climatic stages. In particular, environmental changes around Mid-Brunhes event (i.e. 430kyrBP) were examined. Ice core drilling reached just near the bedrock in ice sheet. Liquid water which existed around the basal ice was soaked into the borehole. Its water was frozen and was picked up with drill machine. Characteristics of ion concentrations near the bedrock (i.e, from 3000m to 3035m) were reported. There was no big change in δ18O , δD and d-excess profiles in deeper part. Dust and nssCa2+ concentrations did not show the conspicuous change between 3000m to 3034m. They became high concentrations under 3034m. The concentration of Na+, SO42-, NO3- became small but Cl- became large from 3020m to 3033.5m. The concentrations of all ion components were suddenly

  15. On the use of solid-shell elements for thin structures: Application to impact and sheet metal forming simulations

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Chalal, Hocine; Abed-Meraim, Farid

    2016-10-01

    A family of linear and quadratic assumed-strain based solid-shell elements (SHB) is presented in this paper to simulate 3D thin structural problems including both quasi-static and dynamic analyses. The SHB solid-shell elements are based on a three-dimensional formulation, with only displacements as degrees of freedom, and a reduced integration technique with an arbitrary number of integration points along the thickness direction, which enables them to model 3D thin structures with only one layer of elements through the thickness. All SHB elements have been successfully implemented into ABAQUS dynamic/explicit and static/implicit codes. Several static and dynamic benchmark tests as well as sheet metal forming process simulations, involving large strain, material nonlinearity and contact, have been conducted to assess the performance of the SHB elements.

  16. On the increase of geometric accuracy with the help of stiffening elements for robot-based incremental sheet metal forming

    NASA Astrophysics Data System (ADS)

    Thyssen, Lars; Seim, Patrick; Störkle, Denis D.; Kuhlenkötter, Bernd

    2016-10-01

    This paper describes new developments in an incremental, robot-based sheet metal forming process (`Roboforming') for the production of sheet metal components for small lot sizes and prototypes. The incremental sheet forming (ISF) offers high geometrical form flexibility without the need of any part-dependent tools. To transfer the ISF to industrial applications, it is necessary to respond to the still existing constraints, e.g. the low geometrical accuracy. Especially the subsequent deformation resulting from the interaction of differently shaped elements causes geometrical deviations, which are limiting the scope of formable parts. The impact of the resulting forming forces will vary according to the shape of the individual elements. For this, the paper proposes and examines a new approach to stabilize the geometrical accuracy without losing the universal approach of Roboforming by inserting stiffening elements. Those elements with varying cross-sections at the initial area of various orientations must be examined on their stabilizing or subsequent distorting impact. Especially the different impacts of the subsequent forming of stiffness features in contrast to the direct forming are studied precisely.

  17. Mercury's core evolution

    NASA Astrophysics Data System (ADS)

    Deproost, Marie-Hélène; Rivoldini, Attilio; Van Hoolst, Tim

    2016-10-01

    Remote sensing data of Mercury's surface by MESSENGER indicate that Mercury formed under reducing conditions. As a consequence, silicon is likely the main light element in the core together with a possible small fraction of sulfur. Compared to sulfur, which does almost not partition into solid iron at Mercury's core conditions and strongly decreases the melting temperature, silicon partitions almost equally well between solid and liquid iron and is not very effective at reducing the melting temperature of iron. Silicon as the major light element constituent instead of sulfur therefore implies a significantly higher core liquidus temperature and a decrease in the vigor of compositional convection generated by the release of light elements upon inner core formation.Due to the immiscibility in liquid Fe-Si-S at low pressure (below 15 GPa), the core might also not be homogeneous and consist of an inner S-poor Fe-Si core below a thinner Si-poor Fe-S layer. Here, we study the consequences of a silicon-rich core and the effect of the blanketing Fe-S layer on the thermal evolution of Mercury's core and on the generation of a magnetic field.

  18. Observing Star Formation: From the Interstellar Medium to Star-Forming Cores

    NASA Astrophysics Data System (ADS)

    Goodman, Alyssa A.

    1995-12-01

    In the thirty years since the first mapping of molecular line emission from interstellar clouds, our ``picture" of the interstellar medium has evolved enormously. With only optical observations available, it was (correctly) hypothesized that new stars form from condensations of dense interstellar gas which appear optically as dark or bright nebulae. These early hypotheses often envisioned the overall collapse of whole clouds into stars, or fragmentation of entire clouds into ``Jeans mass"-size clumps. Thirty years of observing the clouds and the star-formation process which takes place within them has, alas, shown these hypotheses to be too simple. Radio-wavelength spectral-line mapping of interstellar gas, far-infrared and sub-millimeter continuum observations of thermal dust emission, and near-infrared and optical spectral and continuum observations of young stellar objects (YSO's) have revealed a detailed--yet nonetheless perplexing--view of the star-formation process. Molecular ``clouds" appear to be wispy, clumpy condensations of interstellar gas, with self-similar density and velocity structure on scales from hundreds of parsecs down to tenths of parsecs. Projected on density maxima in the gas distribution, one often finds point (or very compact) sources whose spectral colors are consistent with their being deeply embedded in dense gas. These sources are often the origin of powerful jets and outflows and are believed to be YSO's. The outflows, which can carry angular momentum away from a YSO, represent an important phase in the star-formation process. I will discuss the current observational ``picture" of star-forming molecular clouds, as well as some of the many theoretical models which have been proposed to explain cloud structure. Current theories and simulations include gravitational, magnetic and dynamical forces and seek to explain how these forces conspire to simultaneously regulate equilibrium, turbulent, and runaway (e.g. star-formation) processes

  19. 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

  20. Nonchiral polar smectic liquid crystals formed by bent-core molecules: weak coupling regime

    NASA Astrophysics Data System (ADS)

    Kranjc, Tomaz

    2002-12-01

    The structure and dynamic properties of achiral polar smectic liquid crystals formed by bow shaped molecules is considered and described by two two-dimensional order parameters, \\vec P and \\vec ξ. The first, polarization order parameter, gives the average projection of the arrow vectors on the smectic layer planes. The second, tilt order parameter, gives the average magnitude and direction of the tilt. To study the possible liquid crystal structures and their properties, a discrete phenomenological model taking into account the competing interactions between the nearest-neighbor smectic layers is used. The free energy of the system is expressed as a sum over smectic layers with terms modeling the appropriate intralayer and interlayer interactions and written only in terms of the arrow and the string order parameters. The free energy is then minimized in order to obtain stable structures and deduce their optical properties. There exist solutions for the case of strong coupling between the polarization and the tilt order parameters arising from attractive intralayer van der Waals and from steric interactions. In this contribution, we focus our attention to the case of weak coupling between the two order parameters and investigate possible structures and related optical properties of the system.

  1. 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

  2. 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.

  3. 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

  4. Using The Finite Element Method And Artificial Neural Networks To Predict Ductile Fracture In Cold Forming Processes

    NASA Astrophysics Data System (ADS)

    Klocke, F.; Breuer, D.

    2004-06-01

    Apart from the calculation of the plastic formability of metals the prediction of ductile cracks in cold forming processes is very important in order to design these processes efficiently. Therefore, many crack criteria have been developed and implemented in several FEM Programs. These criteria scale the crack prediction down to one value and they are qualified to detect the most endangered areas occurring cracks during the forming process quite well. All these criteria have two significant disadvantages: on one hand none of these criteria consider the whole forming history and on the other hand the detected critical value is not applicable to other forming processes. Therefore a new method to predict ductile fracture in cold forming processes has been developed. Various upsetting, bending and extrusion tests were designed in order to provoke a failure during the forming process. All these processes were modelled by means of the Finite Element Method to acquire the whole forming history (including the first principle stress, the equivalent stress and the equivalent strain starting with the first deformation to the first crack occurrence) for the area where the first fracture occurs. Basal in the results way a database with forming histories which all will lead to an failure during a forming process was built up. This database is used to train an artificial neural network. The artificial neural network will be able to predict a failure for new forming histories. The paper gives an overview over the use of the artificial neural network, the calculation of the forming histories and the used forming processes as well as the interaction between the Finite Element Method and the artificial neural network.

  5. 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.

  6. Material characterization and finite element simulations of aluminum alloy sheets during non-isothermal forming process

    NASA Astrophysics Data System (ADS)

    Zhang, Nan

    The utilization of more non-ferrous materials is one of the key factors to succeed out of the constantly increasing demand for lightweight vehicles in automotive sector. Aluminum-magnesium alloys have been identified as the most promising substitutions to the conventional steel without significant compromise in structural stiffness and strength. However, the conventional forming methods to deform the aluminum alloy sheets are either costly or insufficient in formability which limit the wide applications of aluminum alloy sheets. A recently proposed non-isothermal hot stamping approach, which is also referred as Hot Blank - Cold Die (HB-CD) stamping, aims at fitting the commercial grade aluminum alloy sheets, such as AA5XXX and AA7XXX, into high-volume and cost-effective production for automotive sector. In essence, HB-CD is a mutation of the conventional hot stamping approach for boron steel (22MnB5) which deforms the hot blank within the cold tool set. By elevating the operation temperature, the formability of aluminum alloy sheets can be significantly improved. Meanwhile, heating the blank only and deforming within the cold tool sets allow to reduce the energy and time consumed. This research work aims at conducting a comprehensive investigation of HB-CD with particular focuses on material characterization, constitutive modeling and coupled thermo-mechanical finite element simulations with validation. The material properties of AA5182-O, a popular commercial grade of aluminum alloy sheet in automotive sector, are obtained through isothermal tensile testing at temperatures from 25° to 300°, covering a quasi-static strain-rate range (0.001--0.1s-1). As the state-of-the-art non-contact strain measurement technique, digital image correlation (DIC) system is utilized to evaluate the stress-strain curves as well as to reveal the details of material deformation with full-field and multi-axis strain measurement. Material anisotropy is characterized by extracting the

  7. Molecular structure of a gypsy element of Drosophila subobscura (gypsyDs) constituting a degenerate form of insect retroviruses.

    PubMed Central

    Alberola, T M; de Frutos, R

    1996-01-01

    We have determined the nucleotide sequence of a 7.5 kb full-size gypsy element from Drosophila subobscura strain H-271. Comparative analyses were carried out on the sequence and molecular structure of gypsy elements of D.subobscura (gypsyDs), D.melanogaster (gypsyDm) and D.virilis (gypsyDv). The three elements show a structure that maintains a common mechanism of expression. ORF1 and ORF2 show typical motifs of gag and pol genes respectively in the three gypsy elements and could encode functional proteins necessary for intracellular expansion. In the three ORF1 proteins an arginine-rich region was found which could constitute a RNA binding motif. The main differences among the gypsy elements are found in ORF3 (env-like gene); gypsyDm encodes functional env proteins, whereas gypsyDs and gypsyDv ORF3s lack some motifs essential for functionality of this protein. On the basis of these results, while gypsyDm is the first insect retrovirus described, gypsyDs and gypsyDv could constitute degenerate forms of these retroviruses. In this context, we have found some evidence that gypsyDm could have recently infected some D.subobscura strains. Comparative analyses of divergence and phylogenetic relationships of gypsy elements indicate that the gypsy elements belonging to species of different subgenera (gypsyDs and gypsyDv) are closer than gypsy elements of species belonging to the same subgenus (gypsyDs and gypsyDm). These data are congruent with horizontal transfer of gypsy elements among different Drosophila spp. PMID:8600460

  8. Replacement of the human cytomegalovirus promoter with fish enhancer and core elements to control the expression of the G gene of viral haemorrhagic septicemia virus (VHSV).

    PubMed

    Martinez-Lopez, A; Chinchilla, B; Encinas, P; Gomez-Casado, E; Estepa, A; Coll, J M

    2012-12-15

    This work explores some of the possibilities to replace human cytomegalovirus (CMV) core and/or enhancer promoter control elements to create new expression vectors for use with fish. The work is relevant to fish vaccination, since DNA vaccines use eukaryotic expression plasmids controlled by the human cytomegalovirus (CMV) promoter to be effective against novirhabdoviruses, such as viral haemorrhagic septicemia virus (VHSV), one of the most devastating fish viral European diseases. To reduce possible homologous recombination with fish genome, core and enhancer sequences from fish origin, such as trout interferon-inducible myxovirus protein (Mx), zebrafish retrovirus long terminal repeat (LTR) and carp β-actin (AE6), were combined with those of CMV to design alternative hybrid promoters. The substitution of CMV core and/or enhancer with the corresponding elements of Mx or the LTR core maintained a similar in vitro protein G expression level than that obtained by using the CMV promoter. Vectors using the dsRNA-inducible Mx enhancer followed either by the LTR or the AE6 cores showed the highest in vitro protein G expression levels. Furthermore, synthetic constructs using the Mx enhancer maintained their polyI:C induction capabilities despite the core used. Some of these hybrid promoters might contribute to the development of all-fish-vectors for DNA vaccines while others might be useful for more basic studies.

  9. Characterization of organic matter in sediment cores of the Todos os Santos Bay, Bahia, Brazil, by elemental analysis and 13C NMR.

    PubMed

    Costa, A B; Novotny, E H; Bloise, A C; de Azevedo, E R; Bonagamba, T J; Zucchi, M R; Santos, V L C S; Azevedo, A E G

    2011-08-01

    The impact of human activity on the sediments of Todos os Santos Bay in Brazil was evaluated by elemental analysis and 13C Nuclear Magnetic Resonance (13C NMR). This article reports a study of six sediment cores collected at different depths and regions of Todos os Santos Bay. The elemental profiles of cores collected on the eastern side of Frades Island suggest an abrupt change in the sedimentation regime. Autoregressive Integrated Moving Average (ARIMA) analysis corroborates this result. The range of depths of the cores corresponds to about 50 years ago, coinciding with the implantation of major onshore industrial projects in the region. Principal Component Analysis of the 13C NMR spectra clearly differentiates sediment samples closer to the Subaé estuary, which have high contents of terrestrial organic matter, from those closer to a local oil refinery. The results presented in this article illustrate several important aspects of environmental impact of human activity on this bay.

  10. 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.

  11. 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.

  12. Impact of the Cooling Equipment on the Key Design Parameters of a Core-Form Power Transformer

    NASA Astrophysics Data System (ADS)

    Orosz, Tamás; Tamus, Zoltán Ádám

    2016-12-01

    The first step in the transformer design process is to find the active part's key design parameters. This is a non-linear mathematical optimisation task, which becomes more complex if the economic conditions are considered by the capitalisation of the losses. Geometric programming combined with the method of branch and bound can be an effective and accurate tool for this task even in the case of core-form power transformers, when formulating the short-circuit impedance in the required form is problematic. Most of the preliminary design methods consider only the active part of the transformer and the capitalised costs in order to determine the optimal key design parameters. In this paper, an extension of this meta-heuristic transformer optimisation model, which takes the cost of the insulating oil and the cooling equipment into consideration, is presented. Moreover, the impact of the new variables on the optimal key design parameters of a transformer design is examined and compared with the previous algorithm in two different economic scenarios. Significant difference can be found between the optimal set of key-design parameters if these new factors are considered.

  13. Early-stage star-forming cloud cores in Galactic Legacy Infrared Mid-Plane Survey (GLIMPSE) extended green objects (EGOs) as traced by organic species

    NASA Astrophysics Data System (ADS)

    Ge, J. X.; He, J. H.; Chen, X.; Takahashi, S.

    2014-12-01

    In order to investigate the physical and chemical properties of massive star-forming cores in the early stages, we analyse the excitation and abundance of four organic species, CH3OH, CH3OCH3, HCOOCH3 and CH3CH2CN, towards 29 extended green object (EGO) cloud cores that were observed by our previous single-dish spectral line survey. The EGO cloud cores are found to have similar methanol J3-J2 rotation temperatures of ˜44 K, a typical linear size of ˜0.036 pc and a typical beam-averaged methanol abundance of several 10-9 (the beam-corrected value could reach several 10-7). The abundances of the latter three species, normalized by that of methanol, are also found to be correlated across a large variety of clouds such as EGO cloud cores, hot corinos, massive hot cores and Galactic Centre clouds. The chemical properties of the EGO cloud cores lie between those of hot cores and hot corinos. However, the abundances and abundance ratios of the four species cannot be explained satisfactorily by recent chemical models, either among EGO cloud cores or among the various types of cloud core from literature.

  14. Biomechanical Evaluation of a Tooth Restored with High Performance Polymer PEKK Post-Core System: A 3D Finite Element Analysis

    PubMed Central

    Shin, Joo-Hee; Kim, Jong-Eun; Kim, Jee-Hwan; Lee, Won-Chang; Shin, Sang-Wan

    2017-01-01

    The aim of this study was to evaluate the biomechanical behavior and long-term safety of high performance polymer PEKK as an intraradicular dental post-core material through comparative finite element analysis (FEA) with other conventional post-core materials. A 3D FEA model of a maxillary central incisor was constructed. A cyclic loading force of 50 N was applied at an angle of 45° to the longitudinal axis of the tooth at the palatal surface of the crown. For comparison with traditionally used post-core materials, three materials (gold, fiberglass, and PEKK) were simulated to determine their post-core properties. PEKK, with a lower elastic modulus than root dentin, showed comparably high failure resistance and a more favorable stress distribution than conventional post-core material. However, the PEKK post-core system showed a higher probability of debonding and crown failure under long-term cyclic loading than the metal or fiberglass post-core systems. PMID:28386547

  15. 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

  16. ORGANIC CHEMISTRY OF LOW-MASS STAR-FORMING CORES. I. 7 mm SPECTROSCOPY OF CHAMAELEON MMS1

    SciTech Connect

    Cordiner, Martin A.; Charnley, Steven B.; Wirstroem, Eva S.; Smith, Robert G.

    2012-01-10

    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{sup 6} cm{sup -3} 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 non-equilibrium carbon chemistry; C{sub 6}H and HC{sub 7}N column densities are 5.9{sup +2.9}{sub -1.3} Multiplication-Sign 10{sup 11} cm{sup -2} and 3.3{sup +8.0}{sub -1.5} Multiplication-Sign 10{sup 12} cm{sup -2}, 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 C{sub 4}H{sup -} and C{sub 6}H{sup -}, with anion-to-neutral ratios [C{sub 4}H{sup -}]/[C{sub 4}H] < 0.02% and [C{sub 6}H{sup -}]/[C{sub 6}H] < 10%, consistent with previous observations in interstellar clouds and low-mass protostars. Deuterated HC{sub 3}N and c-C{sub 3}H{sub 2} were detected. The [DC{sub 3}N]/[HC{sub 3}N] ratio of approximately 4% is consistent with the value typically found in cold interstellar gas.

  17. 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.

  18. The mitochondrial genomes of sponges provide evidence for multiple invasions by Repetitive Hairpin-forming Elements (RHE)

    PubMed Central

    2009-01-01

    Background The mitochondrial (mt) genomes of sponges possess a variety of features, which appear to be intermediate between those of Eumetazoa and non-metazoan opisthokonts. Among these features is the presence of long intergenic regions, which are common in other eukaryotes, but generally absent in Eumetazoa. Here we analyse poriferan mitochondrial intergenic regions, paying particular attention to repetitive sequences within them. In this context we introduce the mitochondrial genome of Ircinia strobilina (Lamarck, 1816; Demospongiae: Dictyoceratida) and compare it with mtDNA of other sponges. Results Mt genomes of dictyoceratid sponges are identical in gene order and content but display major differences in size and organization of intergenic regions. An even higher degree of diversity in the structure of intergenic regions was found among different orders of demosponges. One interesting observation made from such comparisons was of what appears to be recurrent invasions of sponge mitochondrial genomes by repetitive hairpin-forming elements, which cause large genome size differences even among closely related taxa. These repetitive hairpin-forming elements are structurally and compositionally divergent and display a scattered distribution throughout various groups of demosponges. Conclusion Large intergenic regions of poriferan mt genomes are targets for insertions of repetitive hairpin- forming elements, similar to the ones found in non-metazoan opisthokonts. Such elements were likely present in some lineages early in animal mitochondrial genome evolution but were subsequently lost during the reduction of intergenic regions, which occurred in the Eumetazoa lineage after the split of Porifera. Porifera acquired their elements in several independent events. Patterns of their intra-genomic dispersal can be seen in the mt genome of Vaceletia sp. PMID:20003196

  19. A young Moon-forming giant impact at 70-110 million years accompanied by late-stage mixing, core formation and degassing of the Earth.

    PubMed

    Halliday, Alex N

    2008-11-28

    New W isotope data for lunar metals demonstrate that the Moon formed late in isotopic equilibrium with the bulk silicate Earth (BSE). On this basis, lunar Sr isotope data are used to define the former composition of the Earth and hence the Rb-Sr age of the Moon, which is 4.48+/-0.02Ga, or 70-110Ma (million years) after the start of the Solar System. This age is significantly later than had been deduced from W isotopes based on model assumptions or isotopic effects now known to be cosmogenic. The Sr age is in excellent agreement with earlier estimates based on the time of lunar Pb loss and the age of the early lunar crust (4.46+/-0.04Ga). Similar ages for the BSE are recorded by xenon and lead-lead, providing evidence of catastrophic terrestrial degassing, atmospheric blow-off and significant late core formation accompanying the ca 100Ma giant impact. Agreement between the age of the Moon based on the Earth's Rb/Sr and the lead-lead age of the Moon is consistent with no major losses of moderately volatile elements from the Earth during the giant impact. The W isotopic composition of the BSE can be explained by end member models of (i) gradual accretion with a mean life of roughly 35Ma or (ii) rapid growth with a mean life of roughly 10Ma, followed by a significant hiatus prior to the giant impact. The former assumes that approximately 60 per cent of the incoming metal from impactors is added directly to the core during accretion. The latter includes complete mixing of all the impactor material into the BSE during accretion. The identical W isotopic composition of the Moon and the BSE limits the amount of material that can be added as a late veneer to the Earth after the giant impact to less than 0.3+/-0.3 per cent of ordinary chondrite or less than 0.5+/-0.6 per cent CI carbonaceous chondrite based on their known W isotopic compositions. Neither of these on their own is sufficient to explain the inventories of both refractory siderophiles such as platinum group

  20. The Core Promoter and Redox-sensitive Cis-elements as Key Targets for Inactivation of the Lysyl Oxidase Gene by Cadmium

    PubMed Central

    Li, Jianmin; Cheng, Guang; Zheng, Maoguen; Zhao, Yinzhi; Zhou, Jing; Li, Wande

    2015-01-01

    Exposure of humans to cadmium (Cd) either from environmental contamination or from cigarette smoke, often induces lung emphysema and cancers. Lysyl oxidase (LOX), a copper-dependent enzyme essential for crosslinking of the extracellular matrix, displays antagonistic effects on emphysema and cancer pathogenesis. Our previous studies showed down-regulation of LOX in Cd-resistant (CdR) rat fetal lung fibroblasts (RFL6) derived from parental cells via long-term Cd exposure. The cloned rat LOX gene promoter −804/−1 (relative to ATG) with the maximal promoter activity contains the Inr-DPE core promoter, putative NFI binding sites, metal response elements (MRE) and antioxidant response elements (ARE). ChIP assays reported here further characterize the rat LOX gene promoter in response to Cd. CdR cells exhibited enhanced methylation of CpG at the LOX core promoter region and reduced activities of the NFI binding sites and MRE, but increased activity of the ARE in a dose-dependent manner. The collective effect of Cd on the LOX promoter is trans-inhibition of the LOX gene as shown by suppression of histone H3 acetylation in the LOX core promoter region. Thus, the LOX core promoter and redox-sensitive cis-elements are key Cd targets for down-regulation of LOX relevant to mechanisms for Cd-induced emphysema and lung cancers. PMID:25741534

  1. Forms of rare earth elements' sorption by quartz and goethite in the presence of bacteria Rhodopseudomonas palustris

    NASA Astrophysics Data System (ADS)

    Perelomov, L. V.; Perelomova, I. V.; Yoshida, S.

    2009-12-01

    The adsorption of a mixture of 16 isotopes of 14 rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) present in the initial solution in equal concentrations by quartz and goethite in the presence of bacteria Rhodopseudomonas palustris was studied under different acidity conditions. The solution pH was apparently the leading factor in the interaction of rare earth ions with the surface of mineral and biological sorbents. These interactions were controlled by electrostatic forces in acid (pH 4) and neutral (pH 7) solutions; the precipitation of elements from the solution was the predominant mechanism under alkaline conditions (pH 9). Microorganisms affected the adsorption of lanthanides by quartz in the entire pH range under study, especially at pH 7. In the presence of bacteria, the adsorption of the elements studied by goethite increased in an acid solution, remained unchanged under neutral conditions, and slightly decreased under alkaline conditions. Microorganisms increased the concentration of nonexchangeable forms of the elements adsorbed on the surface of quartz and goethite, which could be due to the formation of low-soluble complexes of rare earth elements with organic substances produced by bacteria.

  2. Finite element modelling of high air pressure forming processes for polymer sheets

    NASA Astrophysics Data System (ADS)

    Jiang, W.-G.; Warby, M. K.; Whiteman, J. R.; Abbott, S.; Shorter, W.; Warwick, P.; Wright, T.; Munro, A.; Munro, B.

    In this paper we describe the mathematical modelling and computational simulation of the high air pressure (HAP) thermoforming process which is used in the creation of thin walled polymeric structures. This involves, using data from material tests, an elastic-plastic constitutive equation valid for large deformations and a constrained deformation in which there is frictional contact between the polymeric sheet and a constraining surface (the mould surface). Despite a number of simplifying assumptions and some uncertainities in the mathematical model the finite element computations presented predict quite well the actual shape and thickness distribution which are found on sample products.

  3. Introduction of polycrystal constitutive laws in a finite element code with applications to zirconium forming

    SciTech Connect

    Maudlin, P.J.; Tome, C.N.; Kaschner, G.C.; Gray, G.T. III

    1998-08-01

    In this work the authors simulate the compressive deformation of heavily textured zirconium sheet using a finite element code with the constitutive response given by a polycrystal self-consistent model. They show that the strong anisotropy of the response can be explained in terms of the texture and the relative activity of prismatic (easy) and pyramidal (hard) slip modes. The simulations capture the yield anisotropy observed for so-called through-thickness and in-plane compression tests in terMs of the loading curves and final specimen geometries.

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

    NASA Astrophysics Data System (ADS)

    Seong, Dae-Yong; Jung, ChangGyun; Yang, Dong-Yol

    2007-05-01

    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.

  5. 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.

  6. 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)

  7. Advanced finite element analysis of die wear in sheet-bulk metal forming processes

    NASA Astrophysics Data System (ADS)

    Behrens, Bernd-Arno; Bouguecha, Anas; Vucetic, Milan; Chugreev, Alexander; Rosenbusch, Daniel

    2016-10-01

    The novel sheet-bulk metal forming (SBMF) technology allows the production of solid metal components with various functional design features out of flat sheet specimens. However, due to the high working pressures arising during the forming process the efficiency of SBMF is tightly related to the tool service life, which is mainly limited by die wear. In the forming processes involving high contact pressures (e.g. SBMF) the influence of contact normal stresses on the die wear can be overestimated. In order to provide a realistic estimation of the die wear, the shear friction stress must be considered. The presented paper introduces a die wear model that intends the tangential component of contact stress and its implementation in the commercial FE code.

  8. High-pressure melting experiments on Fe-Si alloys and implications for silicon as a light element in the core

    NASA Astrophysics Data System (ADS)

    Ozawa, Haruka; Hirose, Kei; Yonemitsu, Kyoko; Ohishi, Yasuo

    2016-12-01

    We carried out melting experiments on Fe-Si alloys to 127 GPa in a laser-heated diamond-anvil cell (DAC). On the basis of textural and chemical characterizations of samples recovered from a DAC, a change in eutectic liquid composition in the Fe-FeSi binary system was examined with increasing pressure. The chemical compositions of coexisting liquid and solid phases were quantitatively determined with field-emission-type electron microprobes. The results demonstrate that silicon content in the eutectic liquid decreases with increasing pressure to less than 1.5 ± 0.1 wt.% Si at 127 GPa. If silicon is a single light element in the core, 4.5 to 12 wt.% Si is required in the outer core in order to account for its density deficit from pure iron. However, such a liquid core, whose composition is on the Si-rich side of the eutectic point, crystallizes less dense solid, CsCl (B2)-type phase at the inner core boundary (ICB). Our data also show that the difference in silicon concentration between coexisting solid and liquid is too small to account for the observed density contrast across the ICB. These indicate that silicon cannot be the sole light element in the core. Previous geochemical and cosmochemical arguments, however, strongly require ∼6 wt.% Si in the core. It is possible that the Earth's core originally included ∼6 wt.% Si but then became depleted in silicon by crystallizing SiO2 or MgSiO3.

  9. 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

  10. The structured environments of embedded star-forming cores . PACS and SPIRE mapping of the enigmatic outflow source UYSO 1

    NASA Astrophysics Data System (ADS)

    Linz, H.; Krause, O.; Beuther, H.; Henning, Th.; Klein, R.; Nielbock, M.; Stecklum, B.; Steinacker, J.; Stutz, A.

    2010-07-01

    The intermediate-mass star-forming core UYSO 1 has previously been found to exhibit intriguing features. While deeply embedded and previously only identified by means of its (sub-)millimeter emission, it drives two powerful, dynamically young, molecular outflows. Although the process of star formation has obviously started, the chemical composition is still pristine. We present Herschel PACS and SPIRE continuum data of this presumably very young region. The now complete coverage of the spectral energy peak allows us to precisely constrain the elevated temperature of 26-28 K for the main bulge of gas associated with UYSO1, which is located at the interface between the hot H ii region Sh 2-297 and the cold dark nebula LDN 1657A. Furthermore, the data identify cooler compact far-infrared sources of just a few solar masses, hidden in this neighbouring dark cloud. Herschel is an ESA space observatory, with its science instruments PACS, SPIRE, and HIFI provided by European-led Principal Investigator consortia, and with important participation from NASA.

  11. Development of an object-oriented finite element program: application to metal-forming and impact simulations

    NASA Astrophysics Data System (ADS)

    Pantale, O.; Caperaa, S.; Rakotomalala, R.

    2004-07-01

    During the last 50 years, the development of better numerical methods and more powerful computers has been a major enterprise for the scientific community. In the same time, the finite element method has become a widely used tool for researchers and engineers. Recent advances in computational software have made possible to solve more physical and complex problems such as coupled problems, nonlinearities, high strain and high-strain rate problems. In this field, an accurate analysis of large deformation inelastic problems occurring in metal-forming or impact simulations is extremely important as a consequence of high amount of plastic flow. In this presentation, the object-oriented implementation, using the C++ language, of an explicit finite element code called DynELA is presented. The object-oriented programming (OOP) leads to better-structured codes for the finite element method and facilitates the development, the maintainability and the expandability of such codes. The most significant advantage of OOP is in the modeling of complex physical systems such as deformation processing where the overall complex problem is partitioned in individual sub-problems based on physical, mathematical or geometric reasoning. We first focus on the advantages of OOP for the development of scientific programs. Specific aspects of OOP, such as the inheritance mechanism, the operators overload procedure or the use of template classes are detailed. Then we present the approach used for the development of our finite element code through the presentation of the kinematics, conservative and constitutive laws and their respective implementation in C++. Finally, the efficiency and accuracy of our finite element program are investigated using a number of benchmark tests relative to metal forming and impact simulations.

  12. Dynamic Finite Element Analysis of Forming Process in long fibre reinforced hyperelastic materials

    NASA Astrophysics Data System (ADS)

    Erchiqui, F.; Bendada, A.; Gakwaya, A.; Kandil, N.

    2004-06-01

    In this work, we are interested in modeling and numerical simulation using the dynamic finite element method for the hyperelastic behaviour of a thin, transverse isotropic and incompressible thermoplastic membrane. The hyperelastic (Mooney -Rivlin) is considered. The thermoforming of the long fibre reinforced sheet is done under the action of a perfect gas. The load in pressure used in modelling is deduced from the law of perfect gases pressure. The lagrangian formulation together with the assumption of the membrane theory is used. The numerical analyze is performed by comparing the obtained results with measured experimental data for the polymeric ABS membrane inflation without long fibre. Moreover, the influence of the orientation of fibre on the thickness and on the stress distribution in the thermoforming sheet are analyzed.

  13. Finite Element Simulation of the Stretch-Forming of Aircraft Skins

    SciTech Connect

    Wisselink, H.H.; Boogaard, A.H. van den

    2005-08-05

    In the aerospace industry stretch forming is often used to produce skin parts. During stretch forming a sheet is clamped at two sides and stretched over a die, such that the sheet gets the shape of the die. However for complex shapes it is necessary to use expensive intermediate heat-treatments in order to avoid Lueders lines and still achieve large deformations.To optimize this process FEM simulations of this process are performed. A leading edge skin part, made of aluminium AA2024, has been chosen for a preliminary study. The material is modelled with the Vegter yield function, to account for the anisotropic behaviour of the aluminium sheet. Each annealing step is considered to reduce the work hardening completely. The strains in the part have been measured and are used for validation of the simulations. The used FEM model and the experimental results will be presented and conclusions and recommendations for future research will be given.

  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. 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.

  16. 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.

  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. Size and Structure of Clusters Formed by Shear Induced Coagulation: Modeling by Discrete Element Method.

    PubMed

    Kroupa, Martin; Vonka, Michal; Soos, Miroslav; Kosek, Juraj

    2015-07-21

    The coagulation process has a dramatic impact on the properties of dispersions of colloidal particles including the change of optical, rheological, as well as texture properties. We model the behavior of a colloidal dispersion with moderate particle volume fraction, that is, 5 wt %, subjected to high shear rates employing the time-dependent Discrete Element Method (DEM) in three spatial dimensions. The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was used to model noncontact interparticle interactions, while contact mechanics was described by the Johnson-Kendall-Roberts (JKR) theory of adhesion. The obtained results demonstrate that the steady-state size of the produced clusters is a strong function of the applied shear rate, primary particle size, and the surface energy of the particles. Furthermore, it was found that the cluster size is determined by the maximum adhesion force between the primary particles and not the adhesion energy. This observation is in agreement with several simulation studies and is valid for the case when the particle-particle contact is elastic and no plastic deformation occurs. These results are of major importance, especially for the emulsion polymerization process, during which the fouling of reactors and piping causes significant financial losses.

  19. Elements for the modeling of the thermal process in heating furnaces for steel forming

    NASA Astrophysics Data System (ADS)

    Constantinescu, D.; Carlan, A. B.

    2017-02-01

    In the present paper, by “modelling of thermal process” will be understood the thermal techniques modelling, applied to the heating of steel billets in a large scale, in view of processing by forming. These technologies are correlated with the particularities of the thermal aggregates, having as main objective the reducing of energy consumptions and the optimizing of the aggregate design. When heating the steel billets in view of processing by forming, the duration and the quality of heating are influenced by the modality that the billets are receiving the thermal flow. The reception of the thermal flow depends on the heated surface exposed to the thermal radiation in compliance with their position on the hearth of the heating aggregate. The present paper intends to establish some parameters in view of optimizing the heating process. A basic point of the work is also the determination of some components of a mathematical model for the proposed heating technology. The authors have in view the complexity of the technical evolutions of the furnaces.

  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. 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

  2. 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.

  3. 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.

  4. Foliar absorption of transuranic elements: influence of physiochemical form and environmental factors

    SciTech Connect

    Cataldo, D.A.; Garland, T.R.; Wildung, R.E.; Thomas, J.M.

    1980-07-01

    The accumulation of plutonium (/sup 238/Pu) and americium (/sup 241/Am) in seeds and roots of Phaseolus vulgaris L. was investigated following foliar interception. Under controlled conditions plants were exposed to well-characterized aerosols of fresh and aged Pu-dioxide, fresh Am-oxides, and Pu-nitrate and Pu-citrate complexes to assess the influence of chemical form and long-term weathering on foliar absorption and subsequent translocation to other plant parts. Mean values for Pu and Am accumulated in seeds and roots 28 days after foliar exposure ranged from 9 to 427 x 10/sup -4/% of that deposited on foilage. These results and previous plant uptake studies indicate that the foliar route is potentially of equal importance to the soil-root pathway as a route of transport. The levels of Pu and Am in seeds and roots resulting from foliar absorption and translocation from foilage were significantly affected by simulated rainfall and by the size of particles to which foilage was exposed. The influence of relative humidity and solution aging of oxides was less definitive; however, results suggest that either or both may infuence foliar absorption and subsequent translocation of Pu and Am to seeds and roots.

  5. The blood vasculature as the forming element of the uterus of the estrous donkey (Equus asinus).

    PubMed

    Abd-Elnaeim, M M; Zayed, A E; Leiser, R

    2001-01-01

    Light, scanning electron microscopy of endometrial surface and vascular casts were used to study the vascular architecture of the donkey uterus during estrous. The arterial blood supply of the uterus comes from three arteries: the uterine branch of the ovarian artery, the uterine artery of the external iliac artery, and the uterine branch of the urogenital artery. All arteries enter the uterus at its mesometrial border and divide into smaller ones. Segmentally constricted arteries are seen to circumscribe large veins at the perimetrium which become highly convoluted in the intermuscular vascular layer of the myometrium. Small arteries and arterioles originate at the borderline between the myometrium and the endometrium and radiate to the surface of the endometrium to constitute a system of numerous ridges and grooves by a widely meshed plexus of subepithelial capillary network. The post-capillary venules of the endometrium arise from the subepithelial capillary plexus to form slightly larger veins than the concurrent arteries which join up to the large tortuous veins in the intermuscular vascular layer of the uterus. This arrangement of blood vessels in the donkey uterus and particularly in the endometrium provides the requirement for instant blood flow on the arterial side and for the slow flow rate on the venous side to ameliorate the process of substances exchange.

  6. 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.

  7. 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

  8. 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).

  9. Elemental partitioning and isotopic fractionation of Zn between metal and silicate and geochemical estimation of the S content of the Earth's core

    NASA Astrophysics Data System (ADS)

    Mahan, Brandon; Siebert, Julien; Pringle, Emily A.; Moynier, Frédéric

    2017-01-01

    Zinc metal-silicate fractionation provides experimental access to the conditions of core formation and Zn has been used to estimate the S contents of the Earth's core and of the bulk Earth, assuming that they share similar volatility and that Zn was not partitioned into the Earth's core. Therefore, Zn provides both direct and indirect information into the origin and eventual fate of volatile and siderophile elements on Earth. However, the partitioning of Zn between metal and silicate - as well as the associated isotopic fractionation - is not well known. We have conducted a suite of partitioning experiments to characterize Zn elemental partitioning and isotopic fractionation between metal and silicate as a function of time, temperature, and composition. Experiments were conducted at 2 GPa and temperatures from 1473 K to 2273 K in a piston cylinder apparatus, with run durations from 5 to 240 min for four distinct starting materials. Chemical and isotopic equilibrium is achieved within 10 min of experimental outset. Zinc metal-silicate isotopic fractionation displays no resolvable dependence on temperature, composition, or oxygen fugacity within the data set. Therefore, the Zn isotopic composition of silicate phases can be used as a proxy for bulk telluric bodies. Partitioning results from this study and data from literature were used to robustly parameterize Zn metal-silicate partitioning as a function of temperature, pressure, and redox state. Using this parametric characterization and viable formation conditions, we have estimated a range of Zn contents in the cores of iron meteorite parent bodies (i.e. iron meteorites) of ∼0.1-150 ppm, in good agreement with natural observations. We have also calculated the first geochemical estimates for the Zn contents of the Earth's core and of the bulk Earth, at 242 ± 107 ppm and 114 ± 34 ppm (respectively), that consider the slightly siderophile behavior of Zn. These estimates of the Zn contents of the Earth's core and

  10. The major form of hepatitis C virus alternate reading frame protein is suppressed by core protein expression

    PubMed Central

    Wolf, Marie; Dimitrova, Maria; Baumert, Thomas F.; Schuster, Catherine

    2008-01-01

    Hepatitis C virus (HCV) is a human RNA virus encoding 10 proteins in a single open reading frame. In the +1 frame, an ‘alternate reading frame’ (ARF) overlaps with the core protein-encoding sequence and encodes the ARF protein (ARFP). Here, we investigated the molecular regulatory mechanisms of ARFP expression in HCV target cells. Chimeric HCV-luciferase reporter constructs derived from the infectious HCV prototype isolate H77 were transfected into hepatocyte-derived cell lines. Translation initiation was most efficient at the internal AUG codon at position 86/88, resulting in the synthesis of a truncated ARFP named 86/88ARFP. Interestingly, 86/88ARFP synthesis was markedly enhanced in constructs containing an inactivated core protein reading frame. This enhancement was reversed by co-expression of core protein in trans, demonstrating suppression of ARFP synthesis by HCV core protein. In conclusion, our results indicate that translation of ARFP occurs mainly by alternative internal initiation at position 86/88 and is regulated by HCV core protein expression. The suppression of ARFP translation by HCV core protein suggests that ARFP expression is inversely linked to the level of viral replication. These findings define key mechanisms regulating ARFP expression and set the stage for further studies addressing the function of ARFP within the viral life cycle. PMID:18400784

  11. The role of rare earth elements in the structures of FeB-based glass forming liquid alloys

    NASA Astrophysics Data System (ADS)

    Pan, S. P.; Qin, J. Y.; Gu, T. K.

    2010-02-01

    The structures of liquid Fe72RE6B22 (RE=Sc, Er, Ho, Dy, Y, Sm, Gd, Nd, and Ce) alloys were investigated by ab initio molecular dynamics simulation. The results show that the chemical affinity of Fe-RE and RE-B may influence the glass forming ability more than the atomic size of RE atom in these alloys. As expected, the ⟨0,3,6,0⟩ polyhedron dominates around B atoms and is significantly enriched by adding RE elements to the liquid Fe78B22 alloy. The good glass formers do not correspond to the larger percentages but to more RE atoms in the shell of ⟨0,3,6,0⟩ polyhedron. These features suggest that the effect of the chemical composition of ⟨0,3,6,0⟩ polyhedron on the glass forming ability may be larger than that of its quantity in these alloys.

  12. 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.

  13. Finite Element Modeling of Superplastic Sheet Forming Processes. Identification of Rheological and Tribological Parameters by Inverse Method

    NASA Astrophysics Data System (ADS)

    Bellet, Michel; Massoni, Elisabeth; Boude, Serge

    2004-06-01

    Superplastic forming is a thermoforming-like process commonly applied to titanium and aluminum alloys at high temperature and in specific conditions. This paper presents the application of an inverse analysis technique to the identification of rheological and tribological parameters. The method consists of two steps. First, two different kinds of forming tests have been carried out for rheological and tribological identification, using specific mold shapes. Accurate instrumentation and measurements have been done in order to feed an experimental database (values of appropriate observables). In a second step, the development of an inverse method has been carried out. It consists of the minimization of an objective function representative of the distance — in a least squares sense — between measured and calculated values of the observables. The algorithm, which is coupled with the finite element model FORGE2®, is based on a Gauss-Newton method, including a sensitivity matrix calculated by the semi-analytical method.

  14. 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)

  15. Closed-form analytical solutions of the time difference of arrival source location problem for minimal element monitoring arrays.

    PubMed

    Spencer, Steven J

    2010-05-01

    Closed-form analytical solutions are found for the time difference of arrival (TDOA) source location problem. Solutions are found for both two-dimensional (2D) and three-dimensional (3D) source location by formulating the TDOA equations in, respectively, polar and spherical coordinate systems, with the radial direction coincident with the assumed geodesic path of signal propagation to a reference sensor. Quadratic equations for TDOA 2D and 3D source location based on the spherical intersection (SX) scheme, in some cases permitting dual physical solutions, are found for three and four sensor element monitoring arrays, respectively. A method of spherical intersection subarrays (SXSAs) is developed to derive from these quadratic equations globally unique closed-form analytical solutions for TDOA 2D and 3D source location, for four and five sensor element monitoring arrays, respectively. Errors in 2D source location for introduced bias in time differences of arrival are shown to have a strong geometrical dependence. The SXSA and SX methods perform well in terms of accuracy and precision at high levels of arrival time bias for both 2D and 3D source location and are much more efficient than nonlinear least-squares schemes. The SXSA scheme may have particular applicability to accurately solving source location problems in demanding real-time situations.

  16. 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

  17. In-situ Ultrasonic Sound Velocity Measurements of Fe and Fe-Light Element Alloying Liquids at High Pressures with Implications to Planetary Cores

    NASA Astrophysics Data System (ADS)

    Jing, Z.; Wang, Y.; Yu, T.; Sakamaki, T.; Kono, Y.; Park, C.

    2012-12-01

    Liquid Fe-light element alloys are likely present in the Earth's outer core and the cores of other terrestrial planets and moons including Mercury, Mars, Earth's Moon, Ganymede, and Io, as suggested by geophysical and geochemical observations. In order to determine the abundances of light elements and their effects on the structure, dynamics, and evolution of planetary cores, it is crucial to determine the equation of state for Fe-X (X=S, Si, C, O, etc.) liquids under core conditions. However, equations of state for Fe-rich liquids are poorly constrained at planetary core pressures due to the scarcity of density data and the absence of sound velocity data for these liquids at high pressures. At GSECARS, we have developed techniques to directly measure the ultrasonic sound velocities of Fe-rich liquids at high pressures using both a Kawai-type multi-anvil apparatus and a Paris-Edinburgh cell. The sound velocity was determined by measuring the travel time difference between the sample echo and the buffer rod echo using a waveform generator and a digital oscilloscope and by measuring the sample thickness using X-ray radiographic images. X-ray diffraction was also used to determine the pressure of the experiments and to confirm the melting of the samples. Using this technique, we have successfully obtained sound velocities of three Fe-S liquid compositions (Fe-10wt%S, Fe-20wt%S, and Fe-27wt%S), two Fe-Si liquid compositions (Fe-17wt%Si and Fe-25wt%Si), and pure Fe liquid at high pressure and temperature conditions up to 8 GPa and 2073 K. Results show significant differences between Fe-S and Fe-Si liquids: (1) The velocity of liquid Fe decreases with increasing sulfur content, but increases with silicon content; (2) Velocity is nearly independent of temperature for Fe-S liquids, but decreases with increasing temperature for Fe-Si liquids. These data can provide tighter constraints on equations of state of Fe-light element liquids and adiabatic temperature gradients in

  18. 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.

  19. Designing of an artificial light energy converter in the form of short-chain dyad when combined with core-shell gold/silver nanocomposites.

    PubMed

    Dutta Pal, Gopa; Paul, Somnath; Bardhan, Munmun; De, Asish; Ganguly, Tapan

    2017-06-05

    UV-vis absorption, steady state and time resolved fluorescence and absorption spectroscopic investigations demonstrate that the short chain dyad MNTMA when combined with gold-silver core-shell (Au@Ag) nanocomposite , forms elongated conformers in the excited state whereas for the dyad - Ag (spherical) system the majority of dyads remains in a folded conformation. In the dyad-core-shell nanocomposite system, energy wasting charge recombination rate slows down primarily due to elongated conformation and thus it may be anticipated that this hybrid nanocomposite system may serve as a better light energy conversion device.

  20. 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

  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. 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.

  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. 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.

  5. Spontaneous core-shell elemental distribution in In-rich InxGa1-xN nanowires grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Gómez-Gómez, M.; Garro, N.; Segura-Ruiz, J.; Martinez-Criado, G.; Cantarero, A.; Mengistu, H. T.; García-Cristóbal, A.; Murcia-Mascarós, S.; Denker, C.; Malindretos, J.; Rizzi, A.

    2014-02-01

    The elemental distribution of self-organized In-rich InxGa1-xN nanowires grown by plasma-assisted molecular beam epitaxy has been investigated using three different techniques with spatial resolution on the nanoscale. Two-dimensional images and elemental profiles of single nanowires obtained by x-ray fluorescence and energy-dispersive x-ray spectroscopy, respectively, have revealed a radial gradient in the alloy composition of each individual nanowire. The spectral selectivity of resonant Raman scattering has been used to enhance the signal from very small volumes with different elemental composition within single nanowires. The combination of the three techniques has provided sufficient sensitivity and spatial resolution to prove the spontaneous formation of a core-shell nanowire and to quantify the thicknesses and alloy compositions of the core and shell regions. A theoretical model based on continuum elastic theory has been used to estimate the strain fields present in such inhomogeneous nanowires. These results suggest new strategies for achieving high quality non-polar heterostructures.

  6. Historical deposition of mercury and selected trace elements to high-elevation National Parks in the Western U.S. inferred from lake-sediment cores

    NASA Astrophysics Data System (ADS)

    Mast, M. Alisa; Manthorne, David J.; Roth, David A.

    2010-07-01

    Atmospheric deposition of Hg and selected trace elements was reconstructed over the past 150 years using sediment cores collected from nine remote, high-elevation lakes in Rocky Mountain National Park in Colorado and Glacier National Park in Montana. Cores were age dated by 210Pb, and sedimentation rates were determined using the constant rate of supply model. Hg concentrations in most of the cores began to increase around 1900, reaching a peak sometime after 1980. Other trace elements, particularly Pb and Cd, showed similar post-industrial increases in lake sediments, confirming that anthropogenic contaminants are reaching remote areas of the Rocky Mountains via atmospheric transport and deposition. Preindustrial (pre-1875) Hg fluxes in the sediment ranged from 5.7 to 42 μg m -2 yr -1 and modern (post-1985) fluxes ranged from 17.7 to 141 μg m -2 yr -1. The average ratio of modern to preindustrial fluxes was 3.2, which is similar to remote lakes elsewhere in North America. Estimates of net atmospheric deposition based on the cores were 3.1 μg m -2 yr -1 for preindustrial and 11.7 μg m -2 yr -1 for modern times. Current-day measurements of wet deposition range from 5.0 to 8.6 μg m -2 yr -1, which are lower than the modern sediment-based estimate of 11.7 μg m -2 yr -1, perhaps owing to inputs of dry-deposited Hg to the lakes.

  7. Historical deposition of mercury and selected trace elements to high-elevation National Parks in the Western U.S. inferred from lake-sediment cores

    USGS Publications Warehouse

    Mast, M. Alisa; Manthorne, David J.; Roth, David A.

    2010-01-01

    Atmospheric deposition of Hg and selected trace elements was reconstructed over the past 150 years using sediment cores collected from nine remote, high-elevation lakes in Rocky Mountain National Park in Colorado and Glacier National Park in Montana. Cores were age dated by 210Pb, and sedimentation rates were determined using the constant rate of supply model. Hg concentrations in most of the cores began to increase around 1900, reaching a peak sometime after 1980. Other trace elements, particularly Pb and Cd, showed similar post-industrial increases in lake sediments, confirming that anthropogenic contaminants are reaching remote areas of the Rocky Mountains via atmospheric transport and deposition. Preindustrial (pre-1875) Hg fluxes in the sediment ranged from 5.7 to 42 μg m−2 yr−1 and modern (post-1985) fluxes ranged from 17.7 to 141 μg m−2 yr−1. The average ratio of modern to preindustrial fluxes was 3.2, which is similar to remote lakes elsewhere in North America. Estimates of net atmospheric deposition based on the cores were 3.1 μg m−2 yr−1 for preindustrial and 11.7 μg m−2 yr−1for modern times. Current-day measurements of wet deposition range from 5.0 to 8.6 μg m−2 yr−1, which are lower than the modern sediment-based estimate of 11.7 μg m−2 yr−1, perhaps owing to inputs of dry-deposited Hg to the lakes.

  8. 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.

  9. 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)

  10. Verification of a Non-Hydrostatic Dynamical Core Using Horizontally Spectral Element Vertically Finite Difference Method: 2D Aspects

    DTIC Science & Technology

    2014-04-01

    ranges of ′θ ∈ −1.51×10−3,2.78 ×10−3⎡⎣ ⎤⎦ from the model based on 351 the spectral element and discontinuous Galerkin method. Also Li et al. (2013...2008: A study of spectral element and discontinuous Galerkin 457 methods for the Navier-Stokes equations in nonhydrostatic mesoscale 458 atmospheric...of Computational Physics, 117, 35-46. 467 468 Kelly, J. F. and F. X. Giraldo, 2012: Continuous and discontinuous Galerkin methods for a 469

  11. 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.

  12. Comparison of spectral and finite element methods applied to the study of the core-annular flow in an undulating tube

    NASA Astrophysics Data System (ADS)

    Kouris, Charalampos; Dimakopoulos, Yannis; Georgiou, Georgios; Tsamopoulos, John

    2002-05-01

    A Galerkin/finite element and a pseudo-spectral method, in conjunction with the primitive (velocity-pressure) and streamfunction-vorticity formulations, are tested for solving the two-phase flow in a tube, which has a periodically varying, circular cross section. Two immiscible, incompressible, Newtonian fluids are arranged so that one of them is around the axis of the tube (core fluid) and the other one surrounds it (annular fluid). The physical and flow parameters are such that the interface between the two fluids remains continuous and single-valued. This arrangement is usually referred to as Core-Annular flow. A non-orthogonal mapping is used to transform the uneven tube shape and the unknown, time dependent interface to fixed, cylindrical surfaces. With both methods and formulations, steady states are calculated first using the Newton-Raphson method. The most dangerous eigenvalues of the related linear stability problem are calculated using the Arnoldi method, and dynamic simulations are carried out using the implicit Euler method. It is shown that with a smooth tube shape the pseudo-spectral method exhibits exponential convergence, whereas the finite element method exhibits algebraic convergence, albeit of higher order than expected from the relevant theory. Thus the former method, especially when coupled with the streamfunction-vorticity formulation, is much more efficient. The finite element method becomes more advantageous when the tube shape contains a cusp, in which case the convergence rate of the pseudo-spectral method deteriorates exhibiting algebraic convergence with the number of the axial spectral modes, whereas the convergence rate of the finite element method remains unaffected. Copyright

  13. 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.

  14. 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

  15. 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.

  16. Analysis of core promoter sequences located downstream from the TATA element in the hsp70 promoter from Drosophila melanogaster.

    PubMed

    Wu, C H; Madabusi, L; Nishioka, H; Emanuel, P; Sypes, M; Arkhipova, I; Gilmour, D S

    2001-03-01

    TFIID recognizes multiple sequence elements in the hsp70 promoter of Drosophila. Here, we investigate the function of sequences downstream from the TATA element. A mutation in the initiator was identified that caused an eightfold reduction in binding of TFIID and a fourfold reduction in transcription in vitro. Another mutation in the +24 to +29 region was somewhat less inhibitory, but a mutation in the +14 to +19 region had essentially no effect. The normal promoter and the mutants in the initiator and the +24 to +29 region were transformed into flies by P element-mediated transformation. The initiator mutation reduced expression an average of twofold in adult flies, whereas the mutation in the +24 to +29 region had essentially no effect. In contrast, a promoter combining the two mutations was expressed an average of sixfold less than the wild type. The results suggest that the initiator and the +24 to +29 region could serve overlapping functions in vivo. Protein-DNA cross-linking was used to identify which subunits of TFIID contact the +24 to +29 region and the initiator. No specific subunits were found to cross-link to the +24 to +29 region. In contrast, the initiator cross-linked exclusively to dTAF230. Remarkably, dTAF230 cross-links approximately 10 times more efficiently to the nontranscribed strand than to the transcribed strand at the initiator.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. The Earliest Phases of Star formation (EPoS). Temperature, density, and kinematic structure of the star-forming core CB 17

    NASA Astrophysics Data System (ADS)

    Schmalzl, M.; Launhardt, R.; Stutz, A. M.; Linz, H.; Bourke, T. L.; Beuther, H.; Henning, Th.; Krause, O.; Nielbock, M.; Schmiedeke, A.

    2014-09-01

    Context. The initial conditions for the gravitational collapse of molecular cloud cores and the subsequent birth of stars are still not well constrained. The characteristic cold temperatures (~10 K) in such regions require observations at sub-millimetre and longer wavelengths. The Herschel Space Observatory and complementary ground-based observations presented in this paper have the unprecedented potential to reveal the structure and kinematics of a prototypical core region at the onset of stellar birth. Aims: This paper aims to determine the density, temperature, and velocity structure of the star-forming Bok globule CB 17. This isolated region is known to host (at least) two sources at different evolutionary stages: a dense core, SMM1, and a Class I protostar, IRS. Methods: We modeled the cold dust emission maps from 100 μm to 1.2 mm with both a modified blackbody technique to determine the optical depth-weighted line-of-sight temperature and column density and a ray-tracing technique to determine the core temperature and volume density structure. Furthermore, we analysed the kinematics of CB17 using the high-density gas tracer N2H+. Results: From the ray-tracing analysis, we find a temperature in the centre of SMM1 of T0 = 10.6 K, a flat density profile with radius 9.5 × 103 au, and a central volume density of nH,0 = 2.3 × 105 cm-3. The velocity structure of the N2H+ observations reveal global rotation with a velocity gradient of 4.3 km s-1 pc-1. Superposed on this rotation signature we find a more complex velocity field, which may be indicative of differential motions within the dense core. Conclusions: SMM is a core in an early evolutionary stage at the verge of being bound, but the question of whether it is a starless or a protostellar core remains unanswered. The Herschel data (Fig. 2) including N- and T-maps in Fig. 3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc

  4. 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.

  5. [(No) Fear of audits? Control is good, trust is better. Audits as a core element of quality management].

    PubMed

    Ertl-Wagner, B; Steinbrucker, S

    2011-10-01

    Quality management (QM) cannot be successfully implemented and performed without audits. The PDCA (Plan-Do-Check-Act) cycle is the core component of QM systems. In this cycle an audit represents the crucial step "check". Audits verify whether the performed actions and their results conform to the requirements. It is especially important to verify whether the principles of QM are omnipresent and fully implemented in a department or institution. The announcement of an audit may cause mixed feelings or even anxiety among the personnel to be audited. Without previous information and training the audit may be perceived as an act of control and intrusion into departmental affairs. The colleagues often fear sanctions if lapses are found or consider the audit to be a cross-examination. However, an audit is rather meant to be a helpful aid and a chance to continuously improve the departmental QM system by means of a constructive communication among colleagues. In the year 2009 the European Commission published guidelines for the performance of clinical audits in medical radiology, including diagnostic radiology, nuclear medicine and radiation therapy (Council Directive 97 / 43 / EURATOM). The aim is an optimal protection of the individual from the hazards of ionizing radiation and the directive expects radiological departments to perform clinical audits in accordance with national procedures.

  6. 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.

  7. 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

  8. Insertion of core CpG island element into human CMV promoter for enhancing recombinant protein expression stability in CHO cells.

    PubMed

    Mariati; Yeo, Jessna H M; Koh, Esther Y C; Ho, Steven C L; Yang, Yuansheng

    2014-01-01

    The human cytomegalovirus promoter (hCMV) is susceptible to gene silencing in CHO cells, most likely due to epigenetic events, such as DNA methylation and histone modifications. The core CpG island element (IE) from the hamster adenine phosphoribosyltransferase gene has been shown to prevent DNA methylation. A set of modified hCMV promoters was developed by inserting one or two copies of IE in either forward or reverse orientations either upstream of the hCMV enhancer, between the enhancer and core promoter (CP), or downstream of the CP. The modified hCMV with one copy of IE inserted between the enhancer and core promoter in reverse orientation (MR1) was most effective at enhancing expression stability without compromising expression level when compared with the wild-type (WT) hCMV. A third of 18 EGFP expressing clones generated using MR1 retained 70% of their starting expression level after 8 weeks of culture in the absence of selection pressure, while none of 18 WT hCMV generated clones had expression above 50%. MR1 also improved antibody expression stability of methotrexate (MTX) amplified CHO cell lines. Stably transfected pools generated using MR1 maintained 62% of their original monoclonal antibody titer after 8 weeks of culture in the absence of MTX, compared to only 37% for WT hCMV pools. Low levels of CpG methylation within both WT hCMV and MR1 were observed in all the analyzed cell lines and the methylation levels did not correlate to the expression stability, suggesting IE enhances expression stability by other mechanisms other than preventing methylation.

  9. Point mutations in the Moloney murine leukemia virus enhancer identify a lymphoid-specific viral core motif and 1,3-phorbol myristate acetate-inducible element.

    PubMed Central

    Speck, N A; Renjifo, B; Hopkins, N

    1990-01-01

    The transcriptional enhancer of the Moloney murine leukemia virus (MoMLV) is organized as a 75-base-pair repeat, and in each copy of the repeat there are multiple binding sites for nuclear factors. We have introduced point mutations into each of the known nuclear factor-binding sites in the MoMLV enhancer, in both copies of the direct repeat, and have analyzed the transcriptional activity conferred by the mutated enhancers by transient-expression assays in both hematopoietic and nonhematopoietic cell lines. Mutation of individual binding sites in the MoMLV enhancer has moderate effects (less than 2-fold to 20-fold) on transcription in six independent cell lines. Several mutations decreased transcription from the MoMLV enhancer ubiquitously (the leukemia virus factor b site and the glucocorticoid response element), whereas others affected transcription specifically in lymphoid cell lines (core motif) or, more significantly, in fibroblasts (nuclear factor 1 site). The transcriptional activity of the MoMLV enhancer can be induced 8- to 10-fold by 1,3-phorbol myristate acetate in Jurkat T cells. Mutations in any of three adjacent binding sites (leukemia virus factor b and c sites and the core motif) within a 28-base-pair region in the center of the direct repeat sequence of the MoMLV enhancer completely attenuate the response to 1,3-phorbol myristate acetate. Images PMID:2104942

  10. 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.

  11. Spontaneously formed interfacial metal silicates and their effect on the magnetism of superparamagnetic FeCo/SiO₂ core/shell nanoparticles.

    PubMed

    Desautels, Ryan D; Rowe, Michael P; Jones, Michael; Whallen, Amanda; van Lierop, Johan

    2015-03-10

    The integration of superparamagnetic core/shell nanoparticles into devices and other nanoscale technological applications requires a detailed understanding of how the intimate contact between core and shell nanophases affects the magnetism. We report how, for single-domain FeCo nanoparticles, an FeCo phase unique to the nanoscale with silica shells of increasing thicknesses spontaneously formed interfacial metal silicates between the core and shell (such as Fe2SiO4 and Co2SiO4) and altered the overall magnetism of the nanomaterial significantly. The influence of this previously overlooked phenomenon on magnetic properties is reported. Evidence of these metal silicate interfacial layers was observed by X-ray absorption spectroscopy (XAS) collected over the L3,2 absorption edges of Fe and X-ray photoelectron spectra (XPS) collected over the 2p transitions of Fe and Co. Through the correlation of magnetometry and XPS data, the evolution of nanoparticle magnetic anisotropy is shown to increase with the metal silicate.

  12. 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

  13. 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

  14. 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)

  15. 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.

  16. Spatial variation in diesel-related elemental and organic PM2.5 components during workweek hours across a downtown core.

    PubMed

    Tunno, Brett J; Shmool, Jessie L C; Michanowicz, Drew R; Tripathy, Sheila; Chubb, Lauren G; Kinnee, Ellen; Cambal, Leah; Roper, Courtney; Clougherty, Jane E

    2016-12-15

    Capturing intra-urban variation in diesel-related pollution exposures remains a challenge, given its complex chemical mix, and relatively few well-characterized ambient-air tracers for the multiple diesel sources in densely-populated urban areas. To capture fine-scale spatial resolution (50×50m grid cells) in diesel-related pollution, we used geographic information systems (GIS) to systematically allocate 36 sampling sites across downtown Pittsburgh, PA, USA (2.8km(2)), cross-stratifying to disentangle source impacts (i.e., truck density, bus route frequency, total traffic density). For buses, outbound and inbound trips per week were summed by route and a kernel density was calculated across sites. Programmable monitors collected fine particulate matter (PM2.5) samples specific to workweek hours (Monday-Friday, 7 am-7 pm), summer and winter 2013. Integrated filters were analyzed for black carbon (BC), elemental carbon (EC), organic carbon (OC), elemental constituents, and diesel-related organic compounds [i.e., polycyclic aromatic hydrocarbons (PAHs), hopanes, steranes]. To our knowledge, no studies have collected this suite of pollutants with such high sampling density, with the ability to capture spatial patterns during specific hours of interest. We hypothesized that we would find substantial spatial variation for each pollutant and significant associations with key sources (e.g. diesel and gasoline vehicles), with higher concentrations near the center of this small downtown core. Using a forward stepwise approach, we developed seasonal land use regression (LUR) models for PM2.5, BC, total EC, OC, PAHs, hopanes, steranes, aluminum (Al), calcium (Ca), and iron (Fe). Within this small domain, greater concentration differences were observed in most pollutants across sites, on average, than between seasons. Higher PM2.5 and BC concentrations were found in the downtown core compared to the boundaries. PAHs, hopanes, and steranes displayed different spatial

  17. Accumulation of rare earth elements by siderophore-forming Arthrobacter luteolus isolated from rare earth environment of Chavara, India.

    PubMed

    Emmanuel, E S Challaraj; Ananthi, T; Anandkumar, B; Maruthamuthu, S

    2012-03-01

    In this study, Arthrobacter luteolus, isolated from rare earth environment of Chavara (Quilon district, Kerala, India), were found to produce catechol-type siderophores. The bacterial strain accumulated rare earth elements such as samarium and scandium. The siderophores may play a role in the accumulation of rare earth elements. Catecholate siderophore and low-molecular-weight organic acids were found to be present in experiments with Arthrobacter luteolus. The influence of siderophore on the accumulation of rare earth elements by bacteria has been extensively discussed.

  18. 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.

  19. 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.

  20. A new N-hydroxyethyliminodiacetic acid modified core-shell silica phase for chelation ion chromatography of alkaline earth, transition and rare earth elements.

    PubMed

    McGillicuddy, Nicola; Nesterenko, Ekaterina P; Nesterenko, Pavel N; Stack, Elaine M; Omamogho, Jesse O; Glennon, Jeremy D; Paull, Brett

    2013-12-20

    Bare core-shell silica (1.7μm) has been modified with iminodiacetic acid functional groups via standard silane chemistry, forming a new N-hydroxyethyliminodiacetic acid (HEIDA) functionalised core-shell stationary phase. The column was applied in high-performance chelation ion chromatography and evaluated for the retention of alkaline earth, transition and heavy metal cations. The influence of nitric acid eluent concentration, addition of complexing agent dipicolinic acid, eluent pH and column temperature on the column performance was investigated. The efficiencies obtained for transition and heavy metal cations (and resultant separations) were comparable or better than those previously obtained for alternative fully porous silica based chelation stationary phases, and a similarly modified monolithic silica column, ranging from ∼15 to 56μm HETP. Increasing the ionic strength of the eluent with the addition of KNO3 (0.75M) and increasing the column temperature (70°C) facilitated the isocratic separation of a mixture of 14 lanthanides and yttrium in under 12min, with HETP averaging 18μm (7μm for Ce(III)).

  1. 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.

  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. Holographically formed three-dimensional Penrose-type photonic quasicrystal through a lab-made single diffractive optical element.

    PubMed

    Harb, Ahmad; Torres, Faraon; Ohlinger, Kris; Lin, Yuankun; Lozano, Karen; Xu, Di; Chen, Kevin P

    2010-09-13

    Large-area three-dimensional Penrose-type photonic quasicrystals are fabricated through a holographic lithography method using a lab-made diffractive optical element and a single laser exposure. The diffractive optical element consists of five polymer gratings symmetrically orientated around a central opening. The fabricated Penrose-type photonic quasicrystal shows ten-fold rotational symmetry. The Laue diffraction pattern from the photonic quasi-crystal is observed to be similar to that of the traditional alloy quasi-crystal. A golden ratio of 1.618 is also observed for the radii of diffraction rings, which has not been observed before in artificial photonic quasicrystals.

  4. 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.

  5. Synthesis of biocompatible poly(ɛ-caprolactone)- block-poly(propylene adipate) copolymers appropriate for drug nanoencapsulation in the form of core-shell nanoparticles.

    PubMed

    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.

  6. The T=1 capsid protein of Penicillium chrysogenum virus is formed by a repeated helix-rich core indicative of gene duplication.

    PubMed

    Luque, Daniel; González, José M; Garriga, Damiá; Ghabrial, Said A; Havens, Wendy M; Trus, Benes; Verdaguer, Nuria; Carrascosa, José L; Castón, José R

    2010-07-01

    Penicillium chrysogenum virus (PcV), a member of the Chrysoviridae family, is a double-stranded RNA (dsRNA) fungal virus with a multipartite genome, with each RNA molecule encapsidated in a separate particle. Chrysoviruses lack an extracellular route and are transmitted during sporogenesis and cell fusion. The PcV capsid, based on a T=1 lattice containing 60 subunits of the 982-amino-acid capsid protein, remains structurally undisturbed throughout the viral cycle, participates in genome metabolism, and isolates the virus genome from host defense mechanisms. Using three-dimensional cryoelectron microscopy, we determined the structure of the PcV virion at 8.0 A resolution. The capsid protein has a high content of rod-like densities characteristic of alpha-helices, forming a repeated alpha-helical core indicative of gene duplication. Whereas the PcV capsid protein has two motifs with the same fold, most dsRNA virus capsid subunits consist of dimers of a single protein with similar folds. The spatial arrangement of the alpha-helical core resembles that found in the capsid protein of the L-A virus, a fungal totivirus with an undivided genome, suggesting a conserved basic fold. The encapsidated genome is organized in concentric shells; whereas the inner dsRNA shells are well defined, the outermost layer is dense due to numerous interactions with the inner capsid surface, specifically, six interacting areas per monomer. The outermost genome layer is arranged in an icosahedral cage, sufficiently well ordered to allow for modeling of an A-form dsRNA. The genome ordering might constitute a framework for dsRNA transcription at the capsid interior and/or have a structural role for capsid stability.

  7. Interrater Reliability and Concurrent Validity of a New Rating Scale to Assess the Performance of Everyday Life Tasks in Dementia: The Core Elements Method.

    PubMed

    de Werd, Maartje M E; Hoelzenbein, Angela C; Boelen, Daniëlle H E; Rikkert, Marcel G M Olde; Hüell, Michael; Kessels, Roy P C; Voigt-Radloff, Sebastian

    2016-12-01

    Errorless learning (EL) is an instructional procedure involving error reduction during learning. Errorless learning is mostly examined by counting correctly executed task steps or by rating them using a Task Performance Scale (TPS). Here, we explore the validity and reliability of a new assessment procedure, the core elements method (CEM), which rates essential building blocks of activities rather than individual steps. Task performance was assessed in 35 patients with Alzheimer's dementia recruited from the Relearning methods on Daily Living task performance of persons with Dementia (REDALI-DEM) study using TPS and CEM independently. Results showed excellent interrater reliabilities for both measure methods (CEM: intraclass coefficient [ICC] = .85; TPS: ICC = .97). Also, both methods showed a high agreement (CEM: mean of measurement difference [MD] = -3.44, standard deviation [SD] = 14.72; TPS: MD = -0.41, SD = 7.89) and correlated highly (>.75). Based on these results, TPS and CEM are both valid for assessing task performance. However, since TPS is more complicated and time consuming, CEM may be the preferred method for future research projects.

  8. Finite element analysis of depth effect on measuring elastic modulus of a core-shell structure for application of instrumented indentation in tooth enamel.

    PubMed

    Jia, Yunfei; Xuan, Fu-Zhen; Yang, Fuqian

    2014-04-01

    Tooth enamel is a complex structure, consisting of numerous enamel rods surrounded by a protein-rich sheath. Considering the possible effect of the protein-rich sheath on the indentation deformation of an enamel rod and the limitation of the Oliver-Pharr method in measuring the elastic modulus of the enamel rod, we used a finite element method to analyze the indentation deformation of an elastic-perfectly plastic cylinder surrounded by an elastic-perfectly plastic film. A concept of the threshold indentation depth was proposed, at which the percentage error of the measured modulus of the cylinder is ±10%. For the indentation depth less than the threshold indentation depth, the elastic modulus measured from the indentation test can be approximated as the intrinsic elastic modulus of the cylinder. The normalized threshold indentation depth strongly depends on the modulus ratio of the film to the cylinder and the ratio of the film thickness to the cylinder radius. The results can be used to guide the use of the Oliver-Pharr method in characterizing the mechanical properties of tooth enamel and bio-composites with core-shell structures.

  9. 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

  10. The Cloud's Core Virtual Infrastructure Security

    NASA Astrophysics Data System (ADS)

    Tolnai, Annette; von Solms, Sebastiaan

    Cloud service providers (CSPs) should institute the necessary security controls, including restricting physical and logical access to hypervisor and other forms of employed virtualization layers. To enact relevant security measures, the core elements communicating with the hypervisor need to be secured. A proposed security model will introduce some of the aspects that need to be secured in the virtual environment to ensure a secure and sound cloud computing environment. This paper will discuss the core aspects of the virtualized architecture explaining the security risks, including a discussion pertaining to the relevant security core concepts to mitigate the risks.

  11. The dual sense of the term "element," attempts to derive the Madelung rule, and the optimal form of the periodic table, if any

    NASA Astrophysics Data System (ADS)

    Scerri, Eric R.

    This article concerns various foundational aspects of the periodic system of the elements. These issues include the dual nature of the concept of an "element" to include element as a "basic substance" and as a "simple substance." We will discuss the question of whether there is an optimal form of the periodic table, including whether the left-step table fulfils this role. We will also discuss the derivation or explanation of the [n + ℓ, n] or Madelung rule for electron-shell filling and whether indeed it is important to attempt to derive this rule from first principles. In particular, we examine the views of two chemists, Henry Bent and Eugen Schwarz, who have independently addressed many of these issues.

  12. A method for validation of finite element forming simulation on basis of a pointwise comparison of distance and curvature

    NASA Astrophysics Data System (ADS)

    Dörr, Dominik; Joppich, Tobias; Schirmaier, Fabian; Mosthaf, Tobias; Kärger, Luise; Henning, Frank

    2016-10-01

    Thermoforming of continuously fiber reinforced thermoplastics (CFRTP) is ideally suited to thin walled and complex shaped products. By means of forming simulation, an initial validation of the producibility of a specific geometry, an optimization of the forming process and the prediction of fiber-reorientation due to forming is possible. Nevertheless, applied methods need to be validated. Therefor a method is presented, which enables the calculation of error measures for the mismatch between simulation results and experimental tests, based on measurements with a conventional coordinate measuring device. As a quantitative measure, describing the curvature is provided, the presented method is also suitable for numerical or experimental sensitivity studies on wrinkling behavior. The applied methods for forming simulation, implemented in Abaqus explicit, are presented and applied to a generic geometry. The same geometry is tested experimentally and simulation and test results are compared by the proposed validation method.

  13. 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

  14. Pollutant element forms within sludges generated by treatment of two acid mine waters with lime, inorganic sulfide and sulfate reducing bacteria

    SciTech Connect

    Chatham, B.; Diebold, F.

    1995-10-01

    One of the research projects within the Mine Waste Technology Pilot Program conducted at Montana Tech under subcontract to MSE, Inc., Butte, MT is entitled {open_quotes}Formation, Properties and Stability of Sludge Generated During Treatment of Acid Mine Water.{close_quotes} One area of study within this activity is the determination of the element-solid associations within the three sludges being studied, namely, a lime initiated sludge, an inorganic sulfide initiated sludge and a sulfate reducing bacteria initiated sludge. These sludges are formed from treatment of two acid mine waters; one from an abandoned metal sulfide open pit mine (the Berkeley Pit in Butte, MT) and another from an abandoned metal sulfide underground mine (the Crystal Mine NW of Basin, MT). A sequential leaching scheme has been used to determine the form of the pollutant elements (Cu, Zn, Cd, Fe, Mn, and As) within these sludges. Significant differences are observed between these pollutant elements for each sludge. These data are interpreted in terms of the potential for release of the pollutant elements within a sludge containment pond storage system.

  15. 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

  16. FIRST MEASUREMENTS OF {sup 15}N FRACTIONATION IN N{sub 2}H{sup +} TOWARD HIGH-MASS STAR-FORMING CORES

    SciTech Connect

    Fontani, F.; Caselli, P.; Bizzocchi, L.; Palau, A.; Ceccarelli, C.

    2015-08-01

    We report on the first measurements of the isotopic ratio {sup 14}N/{sup 15}N in N{sub 2}H{sup +} toward a statistically significant sample of high-mass star-forming cores. The sources belong to the three main evolutionary categories of the high-mass star formation process: high-mass starless cores, high-mass protostellar objects, and ultracompact H ii regions. Simultaneous measurements of the {sup 14}N/{sup 15}N ratio in CN have been made. The {sup 14}N/{sup 15}N ratios derived from N{sub 2}H{sup +} show a large spread (from ∼180 up to ∼1300), while those derived from CN are in between the value measured in the terrestrial atmosphere (∼270) and that of the proto-solar nebula (∼440) for the large majority of the sources within the errors. However, this different spread might be due to the fact that the sources detected in the N{sub 2}H{sup +} isotopologues are more than those detected in the CN ones. The {sup 14}N/{sup 15}N ratio does not change significantly with the source evolutionary stage, which indicates that time seems to be irrelevant for the fractionation of nitrogen. We also find a possible anticorrelation between the {sup 14}N/{sup 15}N (as derived from N{sub 2}H{sup +}) and the H/D isotopic ratios. This suggests that {sup 15}N enrichment could not be linked to the parameters that cause D enrichment, in agreement with the prediction by recent chemical models. These models, however, are not able to reproduce the observed large spread in {sup 14}N/{sup 15}N, pointing out that some important routes of nitrogen fractionation could be still missing in the models.

  17. Core merging and stratification following giant impact

    NASA Astrophysics Data System (ADS)

    Landeau, Maylis; Olson, Peter; Deguen, Renaud; Hirsh, Benjamin H.

    2016-10-01

    A stratified layer below the core-mantle boundary has long been suspected on the basis of geomagnetic and seismic observations. It has been suggested that the outermost core has a stratified layer about 100 km thick that could be due to the diffusion of light elements. Recent seismological evidence, however, supports a layer exceeding 300 km in thickness of enigmatic origin. Here we show from turbulent mixing experiments that merging between projectile and planetary core following a giant impact can lead to a stratified layer at the top of the core. Scaling relationships between post-impact core structure and projectile properties suggest that merging between Earth's protocore and a projectile core that is enriched in light elements and 20 times less massive can produce the thick stratification inferred from seismic data. Our experiments favour Moon-forming impact scenarios involving a projectile smaller than the proto-Earth and suggest that entrainment of mantle silicates into the protocore led to metal-silicate equilibration under extreme pressure-temperature conditions. We conclude that the thick stratified layer detected at the top of Earth's core can be explained as a vestige of the Moon-forming giant impact during the late stages of planetary accretion.

  18. Core layering

    NASA Astrophysics Data System (ADS)

    Jacobson, S. A.; Rubie, D. C.; Hernlund, J. W.; Morbidelli, A.

    2015-12-01

    We have created a planetary accretion and differentiation model that self-consistently builds and evolves Earth's core. From this model, we show that the core grows stably stratified as the result of rising metal-silicate equilibration temperatures and pressures, which increases the concentrations of light element impurities into each newer core addition. This stable stratification would naturally resist convection and frustrate the onset of a geodynamo, however, late giant impacts could mechanically mix the distinct accreted core layers creating large homogenous regions. Within these regions, a geodynamo may operate. From this model, we interpret the difference between the planetary magnetic fields of Earth and Venus as a difference in giant impact histories. Our planetary accretion model is a numerical N-body integration of the Grand Tack scenario [1]—the most successful terrestrial planet formation model to date [2,3]. Then, we take the accretion histories of Earth-like and Venus-like planets from this model and post-process the growth of each terrestrial planet according to a well-tested planetary differentiation model [4,5]. This model fits Earth's mantle by modifying the oxygen content of the pre-cursor planetesimals and embryos as well as the conditions of metal-silicate equilibration. Other non-volatile major, minor and trace elements included in the model are assumed to be in CI chondrite proportions. The results from this model across many simulated terrestrial planet growth histories are robust. If the kinetic energy delivered by larger impacts is neglected, the core of each planet grows with a strong stable stratification that would significantly impede convection. However, if giant impact mixing is very efficient or if the impact history delivers large impacts late, than the stable stratification can be removed. [1] Walsh et al. Nature 475 (2011) [2] O'Brien et al. Icarus 223 (2014) [3] Jacobson & Morbidelli PTRSA 372 (2014) [4] Rubie et al. EPSL 301

  19. 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.

  20. 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.

  1. The high-mass star-forming core G35.2N: what have we learnt from SOFIA and ALMA observations?

    NASA Astrophysics Data System (ADS)

    Zinnecker, Hans; Sandell, Goeran

    2014-07-01

    G35.2N is a luminouos, star forming core in a filamentary cloud at a distance of 2.2 kpc. It is associated with a thermal N-S radio jet and a misaligned NE-SW CO outflow observed both with SOFIA FORCAST (30 and 40 microns, ~4" resolution; Zhang, Tan, de Buizer et al. 2013) and with ALMA band 7 (850 micron line and continuum, 0.4" resolution; Sanchez-Monge, Cesaroni, Beltran et al. 2013, 2014). The ALMA observations revealed a NW-SE Keplerian rotating disk in the CH3CN molecule (Sanchez-Monge et al.) with an enclosed protostellar mass of 18 +/- 3 Mo, whose orientation is inconsistent with the N-S radio jet, and whose protostellar mass is marginally inconsistent with the one inferred from the SED modelling (20-34 Mo, L ~ 10(5) Lo; Zhang et al.) We review the various assumptions involved in the derivation of the disk interpretation and the SED modelling. The dynamical mass could be in the form of a close binary (two 9 Mo stars, say) in which case the predicted total luminosity would be 3 x 10(4) Lo, close to the actually observed one (as opposed to the modelled one, which takes into account the flashlight effect and unmeasured radiation that escapes along a bipolar cavity). One the other hand, if the inferred higher-luminosity model is correct, the disk interpretation of ALMA rotation curve may have to be challenged, and what seems like a nice disk might be a more complex dynamical structure, such as a warped or precessing disk around a binary protostar or a different (outflow-related) velocity-structure altogether. These observations show the complexity of the interpretation of multi-wavelength observations of high-mass star forming regions when viewed with different spatial resolutions.

  2. Melting of the Earth's inner core.

    PubMed

    Gubbins, David; Sreenivasan, Binod; Mound, Jon; Rost, Sebastian

    2011-05-19

    The Earth's magnetic field is generated by a dynamo in the liquid iron core, which convects in response to cooling of the overlying rocky mantle. The core freezes from the innermost surface outward, growing the solid inner core and releasing light elements that drive compositional convection. Mantle convection extracts heat from the core at a rate that has enormous lateral variations. Here we use geodynamo simulations to show that these variations are transferred to the inner-core boundary and can be large enough to cause heat to flow into the inner core. If this were to occur in the Earth, it would cause localized melting. Melting releases heavy liquid that could form the variable-composition layer suggested by an anomaly in seismic velocity in the 150 kilometres immediately above the inner-core boundary. This provides a very simple explanation of the existence of this layer, which otherwise requires additional assumptions such as locking of the inner core to the mantle, translation from its geopotential centre or convection with temperature equal to the solidus but with composition varying from the outer to the inner core. The predominantly narrow downwellings associated with freezing and broad upwellings associated with melting mean that the area of melting could be quite large despite the average dominance of freezing necessary to keep the dynamo going. Localized melting and freezing also provides a strong mechanism for creating seismic anomalies in the inner core itself, much stronger than the effects of variations in heat flow so far considered.

  3. 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.

  4. Impact of the Parameter Identification of Plastic Potentials on the Finite Element Simulation of Sheet Metal Forming

    NASA Astrophysics Data System (ADS)

    Rabahallah, M.; Bouvier, S.; Balan, T.; Bacroix, B.; Teodosiu, C.

    2007-04-01

    In this work, an implicit, backward Euler time integration scheme is developed for an anisotropic, elastic-plastic model based on strain-rate potentials. The constitutive algorithm includes a sub-stepping procedure to deal with the strong nonlinearity of the plastic potentials when applied to FCC materials. The algorithm is implemented in the static implicit version of the Abaqus finite element code. Several recent plastic potentials have been implemented in this framework. The most accurate potentials require the identification of about twenty material parameters. Both mechanical tests and micromechanical simulations have been used for their identification, for a number of BCC and FCC materials. The impact of the identification procedure on the prediction of ears in cup drawing is investigated.

  5. Impact of the Parameter Identification of Plastic Potentials on the Finite Element Simulation of Sheet Metal Forming

    SciTech Connect

    Rabahallah, M.; Bouvier, S.; Bacroix, B.; Teodosiu, C.; Balan, T.

    2007-04-07

    In this work, an implicit, backward Euler time integration scheme is developed for an anisotropic, elastic-plastic model based on strain-rate potentials. The constitutive algorithm includes a sub-stepping procedure to deal with the strong nonlinearity of the plastic potentials when applied to FCC materials. The algorithm is implemented in the static implicit version of the Abaqus finite element code. Several recent plastic potentials have been implemented in this framework. The most accurate potentials require the identification of about twenty material parameters. Both mechanical tests and micromechanical simulations have been used for their identification, for a number of BCC and FCC materials. The impact of the identification procedure on the prediction of ears in cup drawing is investigated.

  6. Prediction of part shape and associated material properties in hot-press forming using Unite element analysis

    NASA Astrophysics Data System (ADS)

    Kim, Hwigeon; Ha, Jinjin; Lee, Myoung-Gyu; Barlat, Frederic

    2016-08-01

    The hot-press forming of a U-channel was conducted on a boron-steel blank. The die consisted of two separate parts in order to perform the partial quenching process. The cold die was initially at 25 °C while the heated die was set to five different temperatures, namely, 25, 120, 220, 320 and 400 °C. The cooling temperature history, Vickers hardness and springback of the channel were measured. A thermo-mechanical-metallurgical model, which accounts for the prior austenite deformation effect, was successfully implemented in the LS-DYNA explicit solver to simulate the hot-press forming process under partial quenching conditions. The predicted and experimental results were compared and found in reasonable agreement.

  7. 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.

  8. Advanced characterization of forms of chlorine, organic sulfur, and trace elements in available coals from operating Illinois mines. [Quarterly] technical report, September 1--November 30, 1994

    SciTech Connect

    Chou, M.I.M.; Demir, I.; Ruch, J.M.

    1994-12-31

    A set of 34 as-shipped coal samples from operating Illinois mines is available for this study to determine the forms of chlorine and sulfur and leachability of chlorine during wet grinding and froth flotation. The forms of chlorine may be inorganic, ionic, and organic. The forms of organic sulfur will include organic sulfide and thiophenic sulfur. Chlorine can be leached from coal during wet grinding. The potential for removal of chlorine from the samples during fine ({minus}200 mesh) and ultrafine ({minus}400 mesh) wet-grinding and during froth flotation designed primarily for removal of pyrite and ash will be determined. In addition, the organic/inorganic affinities of trace elements in as-shipped Illinois coals will be assessed so that the current physical coal cleaning results may be better interpreted.

  9. 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

  10. 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.

  11. 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

  12. Combined PIXE and SEM study of the behaviour of trace elements in gel formed around implant coated with bioactive glass

    NASA Astrophysics Data System (ADS)

    Oudadesse, H.; Irigaray, J. L.; Barbotteau, Y.; Brun, V.; Moretto, Ph.

    2002-05-01

    Bioactive glasses are used as coating biomaterials to facilitate anchorage of metallic prostheses implanted into the body. The aim of this work is to study the behavior of gel formed in contact with alloys and BVA and BVH bioactive glasses implanted. Cylinders of metallic implants composed by Ti, Al and V, are coated with bioactive glass. Three sheep were implanted for different time length: 3, 6 and 12 months in the femoral epiphysis. Results obtained with particle induced X-ray emission and scanning electron microscopy show that BVA coating induces a better contact between the metallic implant and bone. On the other hand, BVH coating prevents corrosion from the metallic implant.

  13. Stainless steel corrosion scale formed in reclaimed water: Characteristics, model for scale growth and metal element release.

    PubMed

    Cui, Yong; Liu, Shuming; Smith, Kate; Hu, Hongying; Tang, Fusheng; Li, Yuhong; Yu, Kanghua

    2016-10-01

    Stainless steels generally have extremely good corrosion resistance, but are still susceptible to pitting corrosion. As a result, corrosion scales can form on the surface of stainless steel after extended exposure to aggressive aqueous environments. Corrosion scales play an important role in affecting water quality. These research results showed that interior regions of stainless steel corrosion scales have a high percentage of chromium phases. We reveal the morphology, micro-structure and physicochemical characteristics of stainless steel corrosion scales. Stainless steel corrosion scale is identified as a podiform chromite deposit according to these characteristics, which is unlike deposit formed during iron corrosion. A conceptual model to explain the formation and growth of stainless steel corrosion scale is proposed based on its composition and structure. The scale growth process involves pitting corrosion on the stainless steel surface and the consecutive generation and homogeneous deposition of corrosion products, which is governed by a series of chemical and electrochemical reactions. This model shows the role of corrosion scales in the mechanism of iron and chromium release from pitting corroded stainless steel materials. The formation of corrosion scale is strongly related to water quality parameters. The presence of HClO results in higher ferric content inside the scales. Cl(-) and SO4(2-) ions in reclaimed water play an important role in corrosion pitting of stainless steel and promote the formation of scales.

  14. 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

  15. Study on the forming of ionic grating in paraelectric potassium tantalate-niobate crystals at large modulation depths based on the finite element method

    NASA Astrophysics Data System (ADS)

    Song, Yansheng; Ji, Jiarong; Dou, Wenhua; Wen, Changli

    2010-10-01

    A solution of the thermal fixing of holographic grating in paraelectric KTa1-xNbxO3 crystals based on flex-partial differential equation (FlexPDE) program has been proposed to solve the problem at large modulation depth. The Kukhtarev equations are rigorously solved by the algorithm of finite element method under the existing of nonlinear coupling effect. The distributions and time evolvement curves of space-charge filed, light-excitated electrons, ionized donors, compensating ionic species, and crystal refractive index are presented. The modulation of gratings becomes smaller along the propagating direction of writing beams because of the coupling effect. The simulation agrees well with the experimental result, and indicates that the finite element method is advantageous to reduce the difficulty of solving the Kukhtarev equations, and FlexPDE can display the forming of the fixed holographic grating dynamically on real time, with visualization.

  16. Elemental changes and alteration recorded by basaltic drill core samples recovered from in situ temperatures up to 345°C in the active, seawater-recharged Reykjanes geothermal system, Iceland

    NASA Astrophysics Data System (ADS)

    Fowler, Andrew P. G.; Zierenberg, Robert A.

    2016-11-01

    Hydrothermal activity results in element exchanges between seawater and oceanic crust that contribute to many aspects of ocean chemistry; therefore, improving knowledge of the associated chemical processes is of global significance. Hydrothermally altered basaltic drill core samples from the seawater-recharged Reykjanes geothermal system in Iceland record elemental gains and losses similar to those observed in samples of hydrothermally altered oceanic crust. At Reykjanes, rocks originally emplaced on the seafloor were buried by continued volcanism and subsided to the current depths (>2250 m below surface). These rocks integrate temperature-dependent elemental gains and losses from multiple stages of hydrothermal alteration that correspond to chemical exchanges observed in rocks from different crustal levels of submarine hydrothermal systems. Specifically, these lithologies have gained U, Mg, Zn, and Pb and have lost K, Rb, Ba, Cu, and light rare earth elements (La through Eu). Alteration and elemental gains and losses in lithologies emplaced on the seafloor can only be explained by a complex multistage hydrothermal alteration history. Reykjanes dolerite intrusions record alteration similar to that reported for the sheeted dike section of several examples of oceanic crust. Specifically, Reykjanes dolerites have lost K, Rb, Ba, and Pb, and gained Cu. The Reykjanes drill core samples provide a unique analog for seawater-oceanic crust reactions actively occurring at high temperatures (275-345°C) beneath a seafloor hydrothermal system.

  17. The atomic-scale mechanism for the enhanced glass-forming-ability of a Cu-Zr based bulk metallic glass with minor element additions

    NASA Astrophysics Data System (ADS)

    Wang, Q.; Liu, C. T.; Yang, Y.; Liu, J. B.; Dong, Y. D.; Lu, J.

    2014-04-01

    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.

  18. Silicon in the Earth's core.

    PubMed

    Georg, R Bastian; Halliday, Alex N; Schauble, Edwin A; Reynolds, Ben C

    2007-06-28

    Small isotopic differences between the silicate minerals in planets may have developed as a result of processes associated with core formation, or from evaporative losses during accretion as the planets were built up. Basalts from the Earth and the Moon do indeed appear to have iron isotopic compositions that are slightly heavy relative to those from Mars, Vesta and primitive undifferentiated meteorites (chondrites). Explanations for these differences have included evaporation during the 'giant impact' that created the Moon (when a Mars-sized body collided with the young Earth). However, lithium and magnesium, lighter elements with comparable volatility, reveal no such differences, rendering evaporation unlikely as an explanation. Here we show that the silicon isotopic compositions of basaltic rocks from the Earth and the Moon are also distinctly heavy. A likely cause is that silicon is one of the light elements in the Earth's core. We show that both the direction and magnitude of the silicon isotopic effect are in accord with current theory based on the stiffness of bonding in metal and silicate. The similar isotopic composition of the bulk silicate Earth and the Moon is consistent with the recent proposal that there was large-scale isotopic equilibration during the giant impact. We conclude that Si was already incorporated as a light element in the Earth's core before the Moon formed.

  19. An ultra-clean firn core from the Devon Island Ice Cap, Nunavut, Canada, retrieved using a titanium drill specially designed for trace element studies.

    PubMed

    Zheng, J; Fisher, D; Blake, E; Hall, G; Vaive, J; Krachler, M; Zdanowicz, C; Lam, J; Lawson, G; Shotyk, W

    2006-03-01

    An electromechanical drill with titanium barrels was used to recover a 63.7 m long firn core from Devon Island Ice Cap, Nunavut, Canada, representing 155 years of precipitation. The core was processed and analysed at the Geological Survey of Canada by following strict clean procedures for measurements of Pb and Cd at concentrations at or below the pg g(-1) level. This paper describes the effectiveness of the titanium drill with respect to contamination during ice core retrieval and evaluates sample-processing procedures in laboratories. The results demonstrate that: (1) ice cores retrieved with this titanium drill are of excellent quality with metal contamination one to four orders of magnitude less than those retrieved with conventional drills; (2) the core cleaning and sampling protocols used were effective, contamination-free, and adequate for analysis of the metals (Pb and Cd) at low pg g(-1) levels; and (3) results from 489 firn core samples analysed in this study are comparable with published data from other sites in the Arctic, Greenland and the Antarctic.

  20. A hemicentric inversion in the maize line knobless Tama flint created two sites of centromeric elements and moved the kinetochore-forming region.

    PubMed

    Lamb, Jonathan C; Meyer, Julie M; Birchler, James A

    2007-06-01

    A maize line, knobless Tama flint (KTF), was found to contain a version of chromosome 8 with two spatially distinct regions of centromeric elements, one at the original genetic position and the other at a novel location on the long arm. The new site of centromeric elements functions as the kinetochore-forming region resulting in a change of arm length ratio. Examination of fluorescence in situ hybridization markers on chromosome 8 revealed an inversion between the two centromere sites relative to standard maize lines, indicating that this chromosome 8 resulted from a hemicentric inversion with one breakpoint approximately 20 centi-McClintocks (cMc) on the long arm (20% of the total arm length from the centromere) and the other in the original cluster of centromere repeats. This inversion moved the kinetochore-forming region but left the remainder of the centromere repeats. In a hybrid between a standard line (Mo17) and KTF, both chromosome 8 homologues were completely synapsed at pachytene despite the inversion. Although the homologous centromeres were not paired, they were always correctly oriented at anaphase and migrated to opposite poles. Additionally, recombination on 8L was severely repressed in the hybrid.

  1. 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.

  2. Hydrogen exchange, core modules, and new designed proteins.

    PubMed

    Carulla, Natàlia; Barany, George; Woodward, Clare

    2002-12-10

    A strategy for design of new proteins that mimic folding properties of native proteins is based on peptides modeled on the slow exchange cores of natural proteins. We have synthesized peptides, called core modules, that correspond to the elements of secondary structure that carry the very slowest exchanging amides in a protein. The expectation is that, if soluble in water, core modules will form conformational ensembles that favor native-like structure. Core modules modeled on natural bovine pancreatic trypsin inhibitor have been shown by NMR studies to meet this expectation. The next step toward production of a native state mimic is to further shift the conformational bias of a core module toward more ordered structure by promoting module-module interactions that are mutually stabilizing. For this, two core modules were incorporated into a single molecule by means of a long cross-link. From a panel of several two-module peptides, one very promising lead emerged; it is called BetaCore. BetaCore is monomeric in water and forms a new fold composed of a four-stranded, antiparallel beta-sheet. The single, dominant conformation of BetaCore is characterized by various NMR experiments. Here we compare the individual core module to the two-module BetaCore and discuss the progressive stabilization of intramodule structure and the formation of new intermodule interactions.

  3. 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.

  4. Finite element analysis regarding the forming behaviour of symmetric hybrid structures consisting of two sheet metal outer layers and a thermoplastic core

    NASA Astrophysics Data System (ADS)

    Behrens, B.-A.; Bouguecha, A.; Bonk, C.; Schulze, H.

    2017-02-01

    To face challenges like damping effects or weight reduction in the automotive sector, new hybrid material combinations are developed. One possibility is the combination of several symmetric material layers with varying material characteristics to achieve in the component production less weight and appropriate stiffness in comparison to components produced with sheet metal. This article deals with the characterization of deep drawing behaviour of layered sandwich structures. The behaviour of the several layers and the layer interaction have been taken into account for the technical design of a deep drawing process. A material layer characterization is performed. Instabilities as interlaminar failures, ruptures or wrinkling of the structure have been investigated as part of additional experimental characterization tests on the basis of various deep drawing process parameters. Finally, the experimental data is used as input for the numerical modelling and simulation of layered structures. The FE simulation includes the material behaviour of the layers and layer interactions with cohesive zone modelling. Based on the results an important contribution for prediction accuracy in the numerical simulation has been provided.

  5. Wire core reactor for nuclear thermal propulsion

    NASA Astrophysics Data System (ADS)

    Harty, Richard B.; Brengle, Robert G.

    1993-01-01

    Studies have been performed of a compact high-performance nuclear rocket reactor that incorporates a tungsten alloy wire fuel element. This reactor, termed the wire core reactor, can deliver a specific impulse of 1,000 s using an expander cycle and a nozzle expansion ratio of 500 to 1. The core is constructed of layers of 0.8-mm-dia fueled tungsten wires wound over alternate layers of spacer wires, which forms a rugged annular lattice. Hydrogen flow in the core is annular, flowing from inside to outside. In addition to the concepts compact size and good heat transfer, the core has excellent power-flow matching features and can resist vibration and thermal stresses during star-up and shutdown.

  6. 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.

  7. 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.

  8. Dynamics of water around the complex structures formed between the KH domains of far upstream element binding protein and single-stranded DNA molecules.

    PubMed

    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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. Dimerization interfaces formed between the DNA binding domains determine the cooperative binding of RXR/RAR and RXR/TR heterodimers to DR5 and DR4 elements.

    PubMed Central

    Zechel, C; Shen, X Q; Chambon, P; Gronemeyer, H

    1994-01-01

    We have previously reported that the binding site repertoires of heterodimers formed between retinoid X receptor (RXR) and either retinoic acid receptor (RAR) or thyroid hormone receptor (TR) bound to response elements consisting of directly repeated PuG(G/T)TCA motifs spaced by 1-5 bp [direct repeat (DR) elements 1-5] are highly similar to those of their corresponding DNA binding domains (DBDs). We have now mapped the dimerization surfaces located in the DBDs of RXR, RAR and TR, which are responsible for cooperative interaction on DR4 (RXR and TR) and DR5 (RXR and RAR). The D-box of the C-terminal CII finger of RXR provides one of the surfaces which is specifically required for the formation of the heterodimerization interfaces on both DR4 and DR5. Heterodimerization with the RXR DBD on DR5 specifically requires the tip of the RAR CI finger as the complementary surface, while a 7 amino acid sequence encompassing the 'prefinger region', but not the TR CI finger, is specifically required for efficient dimerization of TR and RXR DBDs on DR4. Importantly, DBD swapping experiments demonstrate not only that the binding site repertoires of the full-length receptors are dictated by those of their DBDs, but also that the formation of distinct dimerization interfaces between the DBDs are the critical determinants for cooperative DNA binding of these receptors to specific DRs. Images PMID:8137825

  15. Combustion of Biosolids in a Bubbling Fluidized Bed, Part 1: Main Ash-Forming Elements and Ash Distribution with a Focus on Phosphorus.

    PubMed

    Skoglund, Nils; Grimm, Alejandro; Ohman, Marcus; Boström, Dan

    2014-02-20

    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 magnesium

  16. 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

  17. Held-Suarez simulations with the Community Atmosphere Model Spectral Element (CAM-SE) dynamical core: A global axial angular momentum analysis using Eulerian and floating Lagrangian vertical coordinates

    NASA Astrophysics Data System (ADS)

    Lauritzen, Peter H.; Bacmeister, Julio T.; Dubos, Thomas; Lebonnois, Sébastien; Taylor, Mark A.

    2014-03-01

    In this paper, an analysis of the global AAM conservation properties of NCAR's Community Atmosphere Model Spectral Element (CAM-SE) dynamical core under Held-Suarez forcing is presented. It is shown that the spurious sources/sinks of AAM in CAM-SE are 3 orders of magnitude smaller than the parameterized (physical) sources/sinks. The effect on AAM conservation by changing various numerical aspects of the dynamical core (e.g., different vertical coordinates, reduced formal order of accuracy, increased dissipation, and decreased divergence damping) is investigated. In particular, it is noted that changing from Eulerian (hybrid-sigma) to floating Lagrangian vertical coordinates does not alter the global AAM conservation properties of CAM-SE.

  18. 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.

  19. Improved fully-implicit spherical harmonics methods for first and second order forms of the transport equation using Galerkin Finite Element

    NASA Astrophysics Data System (ADS)

    Laboure, Vincent Matthieu

    In this dissertation, we focus on solving the linear Boltzmann equation -- or transport equation -- using spherical harmonics (PN) expansions with fully-implicit time-integration schemes and Galerkin Finite Element spatial discretizations within the Multiphysics Object Oriented Simulation Environment (MOOSE) framework. The presentation is composed of two main ensembles. On one hand, we study the first-order form of the transport equation in the context of Thermal Radiation Transport (TRT). This nonlinear application physically necessitates to maintain a positive material temperature while the PN approximation tends to create oscillations and negativity in the solution. To mitigate these flaws, we provide a fully-implicit implementation of the Filtered PN (FPN) method and investigate local filtering strategies. After analyzing its effect on the conditioning of the system and showing that it improves the convergence properties of the iterative solver, we numerically investigate the error estimates derived in the linear setting and observe that they hold in the non-linear case. Then, we illustrate the benefits of the method on a standard test problem and compare it with implicit Monte Carlo (IMC) simulations. On the other hand, we focus on second-order forms of the transport equation for neutronics applications. We mostly consider the Self-Adjoint Angular Flux (SAAF) and Least-Squares (LS) formulations, the former being globally conservative but void incompatible and the latter having -- in all generality -- the opposite properties. We study the relationship between these two methods based on the weakly-imposed LS boundary conditions. Equivalences between various parity-based PN methods are also established, in particular showing that second-order filters are not an appropriate fix to retrieve void compatibility. The importance of global conservation is highlighted on a heterogeneous multigroup k-eigenvalue test problem. Based on these considerations, we propose a new

  20. A DNA-binding factor specific for xenobiotic responsive elements of P-450c gene exists as a cryptic form in cytoplasm: Its possible translocation to nucleus

    SciTech Connect

    Fujisawa-Sehara, Atsuko; Yamane, Miyuki; Fujii-Kuriyama, Yoshiaki

    1988-08-01

    Transcription of the drug-metabolizing cytochrome P-450c gene is induced by 3-methylcholanthrene or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Previously, the authors defined two xenobiotic responsive elements (XREs) of {approx}15 base pairs, both of which activate transcription in cis in response to these xenobiotics. Using a gel mobility shift assay, they have identified a factor that specifically binds to the XREs. This factor appears in nuclei of mouse hepatoma cell line Hepa-1 only when the cells are treated with the xenobiotics, while the factor is undetectable in the nuclei of a 3-methylcholanthrene-treated mutant of Hepa-1 with defective function of a xenobiotic receptor. In addition, the nuclear factor bound to the XRE in the gel was found to be associated with ({sup 3}H)TCDD when the cells were treated with it, suggesting that the xenobiotic receptor is at least a component of the DNA-binding factor. The cytoplasmic fraction from nontreated Hepa-1 cells also contains the factor as a cryptic form and prominently reveals its DNA-binding activity by incubation with 3-methylcholanthrene in vitro. These results not only suggest the involvement of the XRE-binding factor in transcriptional activation via XREs but also provide evidence that the binding of ligands to the preexisting factor in a cryptic form induces its XRE-binding activity, which is probably followed by its translocation from cytoplasm to nucleus.

  1. 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.

  2. Determination of the Form Factors for the Decay B0 to D*- l+ nu_l and of the CKM Matrix Element |Vcb|

    SciTech Connect

    Aubert, B.

    2007-06-06

    We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V{sub cb}| and of the parameters {rho}{sup 2}, R{sub 1}(1), and R{sub 2}(1), which fully characterize the form factors for the B{sup 0} {yields} D*-{ell}+?{sub {ell}} decay in the framework of HQET. The results, based on a selected sample of about 52,800 B{sup 0} {yields} D*-{ell}+?{sub {ell}} decays, recorded by the BABAR detector, are {rho}{sup 2} = 1.156 {+-} 0.094 {+-} 0.028, R{sub 1}(1) = 1.329{+-}0.131{+-}0.044, R{sub 2}(1) = 0.859{+-}0.077{+-}0.022, and F(1)|V{sub cb}| = (35.0{+-}0.4{+-}1.1)x10-3. 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 ?t technique on a partial sample of the data, we improve the statistical precision of the result, {rho}{sup 2} = 1.179 {+-} 0.048 {+-} 0.028,R{sub 1}(1) = 1.417 {+-} 0.061 {+-} 0.044,R{sub 2}(1) = 0.836 {+-} 0.037 {+-} 0.022, and F(1)|V{sub cb}| = (34.7 {+-} 0.3 {+-} 1.1) x 10-3. Using lattice calculations for the axial form factor F(1), we extract |V{sub cb}| = (37.7{+-}0.3{+-}1.2{+-}{sup 1.2}{sub 1.4})x10{sup -3}, where the third error is due to the uncertainty in F(1). We also present a measurement of the exclusive branching fraction, B = (4.77 {+-} 0.04 {+-} 0.39)%.

  3. 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).

  4. 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

  5. Polymeric micelles based on poly(ethylene oxide) and α-carbon substituted poly(ɛ-caprolactone): An in vitro study on the effect of core forming block on polymeric micellar stability, biocompatibility, and immunogenicity.

    PubMed

    Garg, Shyam M; Vakili, Mohammad Reza; Lavasanifar, Afsaneh

    2015-08-01

    A series of block copolymers based on methoxy poly(ethylene oxide)-block-poly(ɛ-caprolactone) (PEO-b-PCL), PEO-b-PCL bearing side groups of benzyl carboxylate (PEO-b-PBCL), or free carboxyl (PEO-b-PCCL) on the PCL backbone with increasing degrees of polymerization of the PCL backbone were synthesized. Prepared block copolymers assembled to polymeric micelles by co-solvent evaporation. The physical stability of prepared micelles was assessed by measuring their tendency toward aggregation over time using dynamic light scattering (DLS). The resistance of micelles against dissociation in the presence of a micelle destabilizing agent, i.e., sodium dodecyl sulfate (SDS), was also investigated using DLS. The rate of micellar core degradation was determined using (1)H NMR for polymer molecular weight measurement upon incubation of micelles in PBS (pH=7.4) at 37°C followed by dialysis of the remaining polymer at different time intervals. The effect of pendent group chemistry in the micellar core on the adsorption of serum proteins to micellar structure was then evaluated using Bradford Protein assay kit. Finally, the effect of micellar core structure on the induction of bone marrow derived dendritic cell (BMDC) maturation and secretion of IL-12 was studied as a measure of micellar immunogenicity. The results showed micelle structures from polymers with higher degree of polymerization in the hydrophobic block and/or those with more hydrophobic substituents on the core-forming block, to be more stable. This was reflected by a decreased tendency for micellar aggregation, reduced dissociation of micelles in the presence of SDS, and diminished core degradation. All micelles were shown to have insignificant adsorption of serum protein suggesting that the hydrophilic PEO shell provided sufficient protection of the core. However, the protein adsorption increased with increase in the hydrophobicity and molecular weight of the core-forming block. Irrespective of the micellar core

  6. 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.

  7. Seismological constraints on core composition from Fe-O-S liquid immiscibility.

    PubMed

    Helffrich, George; Kaneshima, Satoshi

    2004-12-24

    Earth's core is composed primarily of iron (Fe) with about 10% by weight of lighter elements. The lighter elements are progressively enriched in the liquid outer core as the core cools and the inner core crystallizes. Thermodynamic modeling of Fe-O-S liquids shows that immiscible liquids can exist at outer-core pressures (136 to 330 gigapascals) at temperatures below 5200 kelvin and lead to layering in the outer core if the concentrations of the lighter elements are high enough. We found no evidence for layering in the outer core in the travel times and wave forms of P4KP seismic waves that reflect internally in the core. The absence of layers therefore constrains outer-core compositions in the Fe-O-S system to be no richer than 6 +/- 1 weight % (wt %) O and 2 to 15 wt % S. A single core liquid composition of 10.5 +/- 3.5 wt % S and 1.5 +/- 1.5 wt % O is compatible with wave speeds and densities throughout the outer core.

  8. 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.

  9. Held-Suarez simulations with the Community Atmosphere Model Spectral Element (CAM-SE) dynamical core: a detailed global axial angular momentum analysis using Eulerian and Floating Lagrangian vertical coordinates

    NASA Astrophysics Data System (ADS)

    Lauritzen, P. H.; Bacmeister, J. T.; Dubos, T.; Lebonnois, S.; Taylor, M.

    2013-12-01

    Conservation of Axial Angular Momentum (AAM) is a critical component of global general circulation models. For planets such as Venus and Titan super-rotation comes about through small imbalances in surface sources/sinks of AAM and are therefore susceptible to non-conservation errors in the dynamical core. In Earth's atmosphere the physical sources/sinks of AAM (e.g., resolved and parameterized mountain torques) are large so the lack of AAM may be less apparent. Nonetheless AAM conservation affects important phenomena such as the Quasi-Biennial Oscillation (QBO). In this paper a detailed analysis of the global AAM conservation properties of NCAR's Community Atmosphere Model Spectral Element (CAM-SE) dynamical core under Held-Suarez forcing is presented. It is shown that the spurious sources/sinks of AAM in CAM-SE are three orders of magnitude smaller than the parameterized (physical) sources/sinks. The effect on AAM conservation by changing various numerical aspects of the dynamical core (e.g., different vertical coordinates, reduced formal order of accuracy, increased dissipation and decreased divergence damping) is investigated. In particular it is noted that changing from Eulerian to Lagrangian vertical coordinates does not alter the excellent global AAM conservation properties of CAM-SE.

  10. 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

  11. 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

  12. Utilizing next-generation sequencing to resolve the backbone of the Core Goodeniaceae and inform future taxonomic and floral form studies.

    PubMed

    Gardner, Andrew G; Sessa, Emily B; Michener, Pryce; Johnson, Eden; Shepherd, Kelly A; Howarth, Dianella G; Jabaily, Rachel S

    2016-01-01

    Though considerable progress has been made in inferring phylogenetic relationships of many plant lineages, deep unresolved nodes remain a common problem that can impact downstream efforts, including taxonomic decision-making and character reconstruction. The Core Goodeniaceae is a group affected by this issue: data from the plastid regions trnL-trnF and matK have been insufficient to generate adequate support at key nodes along the backbone of the phylogeny. We performed genome skimming for 24 taxa representing major clades within Core Goodeniaceae. The plastome coding regions (CDS) and nuclear ribosomal repeats (NRR) were assembled and complemented with additional accessions sequenced for nuclear G3PDH and plastid trnL-trnF and matk. The CDS, NRR, and G3PDH alignments were analyzed independently and topology tests were used to detect the alignments' ability to reject alternative topologies. The CDS, NRR, and G3PDH alignments independently supported a Brunonia (Scaevola s.l. (Coopernookia (Goodenia s.l.))) backbone topology, but within Goodenia s.l., the strongly-supported plastome topology (Goodenia A (Goodenia B (Velleia+Goodenia C))) contrasts with the poorly supported nuclear topology ((Goodenia A+Goodenia B) (Velleia+Goodenia C)). A fully resolved and maximally supported topology for Core Goodeniaceae was recovered from the plastome CDS, and there is excellent support for most of the major clades and relationships among them in all alignments. The composition of these seven major clades renders many of the current taxonomic divisions non-monophyletic, prompting us to suggest that Goodenia may be split into several segregate genera.

  13. 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.

  14. A "core-top" screen for trace element proxies of environmental conditions and growth rates in the calcite skeletons of bamboo corals (Isididae)

    NASA Astrophysics Data System (ADS)

    Thresher, Ronald E.; Fallon, Stewart J.; Townsend, Ashley T.

    2016-11-01

    We test for trace element proxies in the high-magnesium calcite fraction of bamboo coral internodes by comparing environmental conditions and growth rates to the specimen-mean compositions of 73 corals that were live-caught at depths ranging from 3 to 3950 m and collected from habitats ranging from tropical coral reefs to the Antarctic slope. Comparisons were done at a large geographic scale (LGS) and for a well sampled area south of Australia, across depths at a single site, in order to help separate the effects of environmental variables that co-vary at one spatial scale, but not the other. Thirty-seven trace elements were measured using solution-based Sector Field ICP-MS, of which seventeen were significantly detected in more than a third of the specimens. Only eight element/calcium ratios correlated significantly with any environmental variable at the large geographic scale, and only four did so at the local level. At the LGS, the highest correlation was between ambient temperature and Mg/Ca, which accounted for 89% of the variance across specimens, spanned all four Isidid sub-families and was independently significant in the two best sampled sub-families.

  15. 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.

  16. 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

  17. [Clinical usefulness of urine-formed elements' information obtained from bacteria detection by flow cytometry method that uses nucleic acid staining].

    PubMed

    Nakagawa, Hiroko; Yuno, Tomoji; Itho, Kiichi

    2009-03-01

    Recently, specific detection method for Bacteria, by flow cytometry method using nucleic acid staining, was developed as a function of automated urine formed elements analyzer for routine urine testing. Here, we performed a basic study on this bacteria analysis method. In addition, we also have a comparison among urine sediment analysis, urine Gram staining and urine quantitative cultivation, the conventional methods performed up to now. As a result, the bacteria analysis with flow cytometry method that uses nucleic acid staining was excellent in reproducibility, and higher sensitivity compared with microscopic urinary sediment analysis. Based on the ROC curve analysis, which settled urine culture method as standard, cut-off level of 120/microL was defined and its sensitivity = 85.7%, specificity = 88.2%. In the analysis of scattergram, accompanied with urine culture method, among 90% of rod positive samples, 80% of dots were appeared in the area of 30 degrees from axis X. In addition, one case even indicated that analysis of bacteria by flow cytometry and scattergram of time series analysis might be helpful to trace the progress of causative bacteria therefore the information supposed to be clinically significant. Reporting bacteria information with nucleic acid staining flow cytometry method is expected to contribute to a rapid diagnostics and treatment of urinary tract infections. Besides, the contribution to screening examination of microbiology and clinical chemistry, will deliver a more efficient solution to urine analysis.

  18. Intricate interactions between the bloom-forming cyanobacterium Microcystis aeruginosa and foreign genetic elements, revealed by diversified clustered regularly interspaced short palindromic repeat (CRISPR) signatures.

    PubMed

    Kuno, Sotaro; Yoshida, Takashi; Kaneko, Takakazu; Sako, Yoshihiko

    2012-08-01

    Clustered regularly interspaced short palindromic repeats (CRISPR) confer sequence-dependent, adaptive resistance in prokaryotes against viruses and plasmids via incorporation of short sequences, called spacers, derived from foreign genetic elements. CRISPR loci are thus considered to provide records of past infections. To describe the host-parasite (i.e., cyanophages and plasmids) interactions involving the bloom-forming freshwater cyanobacterium Microcystis aeruginosa, we investigated CRISPR in four M. aeruginosa strains and in two previously sequenced genomes. The number of spacers in each locus was larger than the average among prokaryotes. All spacers were strain specific, except for a string of 11 spacers shared in two closely related strains, suggesting diversification of the loci. Using CRISPR repeat-based PCR, 24 CRISPR genotypes were identified in a natural cyanobacterial community. Among 995 unique spacers obtained, only 10 sequences showed similarity to M. aeruginosa phage Ma-LMM01. Of these, six spacers showed only silent or conservative nucleotide mutations compared to Ma-LMM01 sequences, suggesting a strategy by the cyanophage to avert CRISPR immunity dependent on nucleotide identity. These results imply that host-phage interactions can be divided into M. aeruginosa-cyanophage combinations rather than pandemics of population-wide infectious cyanophages. Spacer similarity also showed frequent exposure of M. aeruginosa to small cryptic plasmids that were observed only in a few strains. Thus, the diversification of CRISPR implies that M. aeruginosa has been challenged by diverse communities (almost entirely uncharacterized) of cyanophages and plasmids.

  19. 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

  20. 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)

  1. Modular core holder

    SciTech Connect

    Mueller, J.; Cole, C.W.; Hamid, S.; Lucas, J.K.

    1991-03-05

    This patent describes a modular core holder. It comprises: a sleeve, forming an internal cavity for receiving a core. The sleeve including segments; support means, overlying the sleeve, for supporting the sleeve; and access means, positioned between at least two of the segments of the sleeve, for allowing measurement of conditions within the internal cavity.

  2. 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.

  3. Structure and magnetism in Fe/FexPd1-x core/shell nanoparticles formed by alloying in Pd-embedded Fe nanoparticles.

    PubMed

    Baker, S H; Lees, M; Roy, M; Binns, C

    2013-09-25

    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.

  4. 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.

  5. Origin of the Elements

    NASA Astrophysics Data System (ADS)

    Truran, J. W., Jr.; Heger, A.

    2003-12-01

    Nucleosynthesis is the study of the nuclear processes responsible for the formation of the elements which constitute the baryonic matter of the Universe. The elements of which the Universe is composed indeed have a quite complicated nucleosynthesis history, which extends from the first three minutes of the Big Bang through to the present. Contemporary nucleosynthesis theory associates the production of certain elements/isotopes or groups of elements with a number of specific astrophysical settings, the most significant of which are: (i) the cosmological Big Bang, (ii) stars, and (iii) supernovae.Cosmological nucleosynthesis studies predict that the conditions characterizing the Big Bang are consistent with the synthesis only of the lightest elements: 1H, 2H, 3He, 4He, and 7Li (Burles et al., 2001; Cyburt et al., 2002). These contributions define the primordial compositions both of galaxies and of the first stars formed therein. Within galaxies, stars and supernovae play the dominant role both in synthesizing the elements from carbon to uranium and in returning heavy-element-enriched matter to the interstellar gas from which new stars are formed. The mass fraction of our solar system (formed ˜4.6 Gyr ago) in the form of heavy elements is ˜1.8%, and stars formed today in our galaxy can be a factor 2 or 3 more enriched (Edvardsson et al., 1993). It is the processes of nucleosynthesis operating in stars and supernovae that we will review in this chapter. We will confine our attention to three broad categories of stellar and supernova site with which specific nucleosynthesis products are understood to be identified: (i) intermediate mass stars, (ii) massive stars and associated type II supernovae, and (iii) type Ia supernovae. The first two of these sites are the straightforward consequence of the evolution of single stars, while type Ia supernovae are understood to result from binary stellar evolution.Stellar nucleosynthesis resulting from the evolution of single

  6. Evolution of fluid-rock interactions: fluid inclusion, isotopic, and major/minor element chemistry of hydrothermally altered volcanic rock in core RN-17B, Reykjanes, Iceland

    NASA Astrophysics Data System (ADS)

    Fowler, A. P.; Zierenberg, R. A.; Schiffman, P.; Marks, N. E.; Fridleifsson, G. O.

    2011-12-01

    The Reykjanes Peninsula, Iceland, hosts a seawater-dominated geothermal system. Previous studies indicate an evolution of the system from meteoric to seawater. The inclined 4-inch diameter RN-17B drill core was collected from 2798.5 m to 2808.5 m (~2555 m below surface) at in situ temperature of approximately 330°C. Samples for this study were obtained from the Iceland Deep Drilling Project (IDDP). The core contains hydrothermally altered rocks of basaltic composition. Hydrothermal alteration ranges from upper greenschist to lower amphibolite grade, dependent on protolith size and composition. Veins in the core grade inward from radial epidote + acicular hornblende + titanite + pyrite, to clearer equant and compositionally zoned epidote vein centers. Felted amphibole replaces hyaloclastite and smaller crystalline clasts within the core, but is absent from the centers of crystalline pillow basalt fragments. Amphibole in vein selvages and vesicle fillings is green and acicular. Electron microprobe analyses of amphibole indicate it spans a compositional range of ferrohornblende through paragasite. The pistacite component (Xps) of vein epidote ranges from 16.5 to 36.7. The Xps component shows both normal and reverse zoning within single epidote crystals across this range, and follows no distinct pattern. Vein epidote adjacent to the wall rock has a higher aluminum concentration than vein centers. This may be due to mobilization of aluminum from plagioclase in the wall rock during albitization. Solutions flowing through open fractures may have lower Al-content and thus precipitate more Fe-rich epidote than those next to the fracture walls. Primary fluid inclusions in epidote range in size from <1 to 10 μm in diameter. Secondary fluid inclusions are <1 μm in diameter and not measurable. Calculated fluid inclusion salinities range from 0.5 to 7.6 weight percent NaCl, with lower salinities adjacent to the wall rock and higher salinities in the vein centers

  7. New Constraints on the Earth's Core Chemical Composition

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    In the last forty years, there has been a considerable debate about which light element among sulfur, silicon, oxygen, carbon or hydrogen should be in the core [Poirier, Phys. Earth Planet. Int., 85, 319, 1994]. Not only the nature of these elements is a standing problem of prime importance, since it conditions the existence of a freezing point depression at the inner core boundary, but also their distribution within the core is unknown. It is indeed crucial to determine to what extent light elements are released in the liquid outer core, thus inducing solutal convection which in turn contributes to power the geodynamo [Loper, J. R. Astron. Soc., 54, 389, 1978]. In this respect, density and sound velocity measurements at high pressure in solid iron alloyed with different light elements are important to constrain core dynamics and coupling between liquid outer core and solid inner core. However, sound velocity data were not available until very recently, with sound velocity measurement in iron at high pressure [Fiquet et al.; Science, 291, 468, 2001; Mao et al., Science, 292, 914, 2001; Antonangeli et al., Earth Planet. Sci. Lett., 225, 243, 2004]. The question now is how to constrain the relative abundance of these light elements, and eventually rule out some of them based on a confrontation of seismic and mineralogical data. Here, we report direct measurements of acoustic sound velocity in iron alloyed with light elements supposedly entering in the composition of the Earth's core, i.e. oxygen, sulfur and silicon, and address the question of the composition of the core. In this work, we measured longitudinal sound velocities in light-element alloys of iron (FeS, FeO, FeS2, and FeSi) at high pressure by inelastic X-ray scattering. This data set provides a new mineralogical constraint on the composition of the Earth's core, and completes the previous set formed by compressibility and density measurements for these compounds. The combination of these data sets and

  8. 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.

  9. Thermochemical Evolution of Earth's Core with Magnesium Precipitation

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Vigorous convection within Earth's outer core drives a dynamo that has sustained a global magnetic field for at least 3.5 Gyr. Traditionally, people invoke three energy sources for the dynamo: thermal convection from cooling and freezing, compositional convection from light elements expelled by the growing inner core, and, perhaps, radiogenic heating from potassium-40. New theoretical and experimental work, however, indicates that the thermal and electrical conductivities of the outer core may be as much as three times higher than previously assumed. The implied increase in the adiabatic heat flux casts doubt on the ability of the usual mechanisms to explain the dynamo's longevity. Here, we present a quantitative model of the crystallization of magnesium-bearing minerals from the cooling core—a plausible candidate for the missing power source. Recent diamond-anvil cell experiments suggest that magnesium can partition into core material if thermodynamic equilibrium is achieved at high temperatures (>5000 K). We develop a model for core/mantle differentiation in which most of the core forms from material equilibrated at the base of a magma ocean as Earth slowly grows, but a small portion (~10%) equilibrated at extreme conditions in the aftermath of a giant impact. We calculate the posterior probability distribution for the original concentrations of magnesium and other light elements (chiefly oxygen and silicon) in the core, constrained by partitioning experiments and the observed depletion of siderophile elements in Earth's mantle. We then simulate the thermochemical evolution of cores with plausible compositions and thermal structures from the end of accretion to the present, focusing on the crystallization of a few percent of the initial core as ferropericlase and bridgmanite. Finally, we compute the associated energy release and verify that our final core compositions are consistent with the available seismological data.

  10. 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.

  11. 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.

  12. 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

  13. 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...

  14. ZnO-Ag core shell nanocomposite formed by green method using essential oil of wild ginger and their bactericidal and cytotoxic effects

    NASA Astrophysics Data System (ADS)

    Azizi, Susan; Mohamad, Rosfarizan; Rahim, Raha Abdul; Moghaddam, Amin Boroumand; Moniri, Mona; Ariff, Arbakariya; Saad, Wan Zuhainis; Namvab, Farideh

    2016-10-01

    In this paper, a novel green method for fabrication of zinc oxide-silver (ZnO-Ag) core-shell nanocomposite using essential oil of ginger (EO-G) is reported. The EO-G played two significant roles in the synthesis process: it could act as a reaction media for the formation of ZnO and reduce Ag+ to Ag0. The bioformed ZnO-Ag nanocomposite was compared with pure biosynthesized ZnO-NPs and characterized by UV-vis spectroscopy, TEM, EDX, XRD and FTIR. The characterization results confirmed that Ag-NPs had been embedded in ZnO hexagonal nanoparticles. Six Gram positive and negative pathogens were used to investigate the antibacterial effects of these samples. Ag-doping improves the bactericidal activity of ZnO-NPs. In vitro cytotoxicity studies on Vero cells, a dose dependent toxicity with non-toxic effect of concentration below 100 μg/mL was shown for ZnO-Ag nanocomposite. The biosynthesized ZnO-Ag nanocomposites were found to be comparable to those obtained from the conventional methods using hazardous materials which can be an excellent alternative for the synthesis of ZnO-Ag using biomass.

  15. 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.

  16. 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.

  17. Auxiliary basis sets for density-fitted correlated wavefunction calculations: weighted core-valence and ECP basis sets for post-d elements.

    PubMed

    Hättig, Christof; Schmitz, Gunnar; Kossmann, Jörg

    2012-05-14

    We report optimised auxiliary basis sets for the resolution-of-the-identity (or density-fitting) approximation of two-electron integrals in second-order Møller-Plesset perturbation theory (MP2) and similar electronic structure calculations with correlation-consistent basis sets for the post-d elements Ga-Kr, In-Xe, and Tl-Rn. The auxiliary basis sets are optimised such that the density-fitting error is negligible compared to the one-electron basis set error. To check to which extent this criterion is fulfilled we estimated for a test set of 80 molecules the basis set limit of the correlation energy at the MP2 level and evaluated the remaining density-fitting and the one-electron basis set errors. The resulting auxiliary basis sets are only 2-6 times larger than the corresponding one-electron basis sets and lead in MP2 calculations to speed-ups of the integral evaluation by one to three orders of magnitude. The density-fitting errors in the correlation energy are at least hundred times smaller than the one-electron basis set error, i.e. in the order of only 1-100 μH per atom.

  18. Identification of a negative regulatory cis-element in the enhancer core region of the prostate-specific antigen promoter: implications for intersection of androgen receptor and nuclear factor-kappaB signalling in prostate cancer cells.

    PubMed Central

    Cinar, Bekir; Yeung, Fan; Konaka, Hiroyuki; Mayo, Marty W; Freeman, Michael R; Zhau, Haiyen E; Chung, Leland W K

    2004-01-01

    The NF-kappaB (nuclear factor-kappaB) transcription factors mediate activation of a large number of gene promoters containing diverse kappaB-site sequences. Here, PSA (prostate-specific antigen) was used as an AR (androgen receptor)-responsive gene to examine the underlying mechanism by which the NF-kappaB p65 transcription factor down-regulates the transcriptional activity of AR in cells. We observed that activation of NF-kappaB by TNFalpha (tumour necrosis factor alpha) inhibited both basal and androgen-stimulated PSA expression, and that this down-regulation occurred at the promoter level, as confirmed by the super-repressor IkappaBalpha (S32A/S36A), a dominant negative inhibitor of NF-kappaB. Using a linker-scanning mutagenesis approach, we identified a cis -element, designated XBE (X-factor-binding element), in the AREc (androgen response element enhancer core) of the PSA promoter, which negatively regulated several AR-responsive promoters, including that of PSA. When three copies of XBE in tandem were juxtaposed to GRE4 (glucocorticoid response element 4), a 4-6-fold reduction of inducible GRE4 activity was detected in three different cell lines, LNCaP, ARCaP-AR and PC3-AR. Bioinformatics and molecular biochemical studies indicated that XBE is a kappaB-like element that binds specifically to the NF-kappaB p65 subunit; consistent with these observations, only NF-kappaB p65, but not the NF-kappaB p50 subunit, was capable of inhibiting AR-mediated PSA promoter transactivation in LNCaP cells. In addition, our data also showed that AR binds to XBE, as well as to the kappaB consensus site, and that the transfection of AR inhibits the kappaB-responsive promoter in transient co-transfection assays. Collectively, these data indicate that cross-modulation between AR and NF-kappaB p65 transcription factors may occur by a novel mechanism involving binding to a common cis -DNA element. PMID:14715080

  19. A Synthesis of Experimental Data Describing the Partitioning of Moderately Volatile Elements in Major Rock Forming Minerals: Implications for the Moon

    NASA Technical Reports Server (NTRS)

    Vander Kaaden, Kathleen E.; Draper, David S.; McCubbin, Francis M.; Neal, Clive R.; Taylor, G. Jeffrey

    2017-01-01

    Highly volatile elements [condensation temperatures below about 700 K] and water are highly informative about lunar bulk composition (hence origin), differentiation and magmatic evolution, and the role of impacts in delivering volatiles to the Moon. Fractionation of volatile elements compared to moderately volatile and refractory elements are informative about high-temperature conditions that operated in the proto-lunar disk. Existing data show clearly that the Moon is depleted in volatile elements compared to the bulk silicate Earth. For example, K/Th is 400-700 in the Moon compared to 2800-3000 in Earth. A complicating factor is that the abundances of the highly volatile elements in major lunar lithologies vary by approximately two orders of magnitude. Perhaps most interesting, H2O is not correlated with the concentration of volatile elements, indicating a decoupling of highly volatile elements from the even more volatile H2O. We contend that this decoupling could be a significant tracer of processes operating during lunar formation, differentiation, and bombardment, and the combination of analyzing both volatile elements and water is likely to provide significant insight into lunar geochemical history. This variation and lack of correlation raises the question: what were the relative contributions of crystallization in the magma ocean, subsequent mantle overturn, production of secondary magmas, and addition of volatiles by large impacts in producing this apparently large range in volatile abundances? This current study will produce new partitioning data relevant to the role and distribution of the volatile and non-volatile, yet geochemically significant elements (Co, Ni, Zn, Se, Rb, Sr, Mo, Ag, Cd, In, Sb, Ce, Yb, Tl, Pb, Bi) during the thermal and magmatic evolution of the Moon.

  20. 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.

  1. 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 using a molten core method. The cores were found to be amorphous as evidenced by X-ray diffraction and corroborated by Micro-Raman spectrum. Elemental analysis across the core/clad interface suggests that there is some diffusion of about 3 wt % oxygen in the core region. Phosphate glass-clad crystalline selenium core optical fibers were obtained by a postdrawing annealing process. A two-cm-long crystalline selenium semiconductor core optical fibers, electrically contacted to external circuitry through the fiber end facets, exhibit a three times change in conductivity between dark and illuminated states. Such crystalline selenium semiconductor core optical fibers have promising utility in optical switch and photoconductivity of optical fiber array.

  2. 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

  3. A Finite Element Analysis for Predicting the Residual Compressive Strength of Impact-Damaged Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.; Jackson, Wade C.

    2008-01-01

    A simple analysis method has been developed for predicting the residual compressive strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compressive loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

  4. A Finite Element Analysis for Predicting the Residual Compression Strength of Impact-Damaged Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.; Jackson, Wade C.

    2008-01-01

    A simple analysis method has been developed for predicting the residual compression strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compression loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

  5. Core-Cutoff Tool

    NASA Technical Reports Server (NTRS)

    Gheen, Darrell

    2007-01-01

    A tool makes a cut perpendicular to the cylindrical axis of a core hole at a predetermined depth to free the core at that depth. The tool does not damage the surrounding material from which the core was cut, and it operates within the core-hole kerf. Coring usually begins with use of a hole saw or a hollow cylindrical abrasive cutting tool to make an annular hole that leaves the core (sometimes called the plug ) in place. In this approach to coring as practiced heretofore, the core is removed forcibly in a manner chosen to shear the core, preferably at or near the greatest depth of the core hole. Unfortunately, such forcible removal often damages both the core and the surrounding material (see Figure 1). In an alternative prior approach, especially applicable to toxic or fragile material, a core is formed and freed by means of milling operations that generate much material waste. In contrast, the present tool eliminates the damage associated with the hole-saw approach and reduces the extent of milling operations (and, hence, reduces the waste) associated with the milling approach. The present tool (see Figure 2) includes an inner sleeve and an outer sleeve and resembles the hollow cylindrical tool used to cut the core hole. The sleeves are thin enough that this tool fits within the kerf of the core hole. The inner sleeve is attached to a shaft that, in turn, can be attached to a drill motor or handle for turning the tool. This tool also includes a cutting wire attached to the distal ends of both sleeves. The cutting wire is long enough that with sufficient relative rotation of the inner and outer sleeves, the wire can cut all the way to the center of the core. The tool is inserted in the kerf until its distal end is seated at the full depth. The inner sleeve is then turned. During turning, frictional drag on the outer core pulls the cutting wire into contact with the core. The cutting force of the wire against the core increases with the tension in the wire and

  6. The hydrogen exchange core and protein folding.

    PubMed Central

    Li, R.; Woodward, C.

    1999-01-01

    A database of hydrogen-deuterium exchange results has been compiled for proteins for which there are published rates of out-exchange in the native state, protection against exchange during folding, and out-exchange in partially folded forms. The question of whether the slow exchange core is the folding core (Woodward C, 1993, Trends Biochem Sci 18:359-360) is reexamined in a detailed comparison of the specific amide protons (NHs) and the elements of secondary structure on which they are located. For each pulsed exchange or competition experiment, probe NHs are shown explicitly; the large number and broad distribution of probe NHs support the validity of comparing out-exchange with pulsed-exchange/competition experiments. There is a strong tendency for the same elements of secondary structure to carry NHs most protected in the native state, NHs first protected during folding, and NHs most protected in partially folded species. There is not a one-to-one correspondence of individual NHs. Proteins for which there are published data for native state out-exchange and theta values are also reviewed. The elements of secondary structure containing the slowest exchanging NHs in native proteins tend to contain side chains with high theta values or be connected to a turn/loop with high theta values. A definition for a protein core is proposed, and the implications for protein folding are discussed. Apparently, during folding and in the native state, nonlocal interactions between core sequences are favored more than other possible nonlocal interactions. Other studies of partially folded bovine pancreatic trypsin inhibitor (Barbar E, Barany G, Woodward C, 1995, Biochemistry 34:11423-11434; Barber E, Hare M, Daragan V, Barany G, Woodward C, 1998, Biochemistry 37:7822-7833), suggest that developing cores have site-specific energy barriers between microstates, one disordered, and the other(s) more ordered. PMID:10452602

  7. 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.

  8. Magnetorotational iron core collapse

    NASA Technical Reports Server (NTRS)

    Symbalisty, E. M. D.

    1984-01-01

    During its final evolutionary stages, a massive star, as considered in current astrophysical theory, undergoes rapid collapse, thereby triggering a sequence of a catastrophic event which results in a Type II supernova explosion. A remnant neutron star or a black hole is left after the explosion. Stellar collapse occurs, when thermonuclear fusion has consumed the lighter elements present. At this stage, the core consists of iron. Difficulties arise regarding an appropriate model with respect to the core collapse. The present investigation is concerned with the evolution of a Type II supernova core including the effects of rotation and magnetic fields. A simple neutrino model is developed which reproduced the spherically symmetric results of Bowers and Wilson (1982). Several two-dimensional computational models of stellar collapse are studied, taking into account a case in which a 15 solar masses iron core was artificially given rotational and magnetic energy.

  9. INTEGRAL core programme

    NASA Technical Reports Server (NTRS)

    Gehrels, N.; Schoenfelder, V.; Ubertini, P.; Winkler, C.

    1997-01-01

    The International Gamma Ray Astrophysics Laboratory (INTEGRAL) mission is described with emphasis on the INTEGRAL core program. The progress made in the planning activities for the core program is reported on. The INTEGRAL mission has a nominal lifetime of two years with a five year extension option. The observing time will be divided between the core program (between 30 and 35 percent during the first two years) and general observations. The core program consists of three main elements: the deep survey of the Galactic plane in the central radian of the Galaxy; frequent scans of the Galactic plane in the search for transient sources, and pointed observations of several selected sources. The allocation of the observation time is detailed and the sensitivities of the observations are outlined.

  10. Helicobacter pylori CheZ(HP) and ChePep form a novel chemotaxis-regulatory complex distinct from the core chemotaxis signaling proteins and the flagellar motor.

    PubMed

    Lertsethtakarn, Paphavee; Howitt, Michael R; Castellon, Juan; Amieva, Manuel R; Ottemann, Karen M

    2015-09-01

    Chemotaxis is important for Helicobacter pylori to colonize the stomach. Like other bacteria, H. pylori uses chemoreceptors and conserved chemotaxis proteins to phosphorylate the flagellar rotational response regulator, CheY, and modulate the flagellar rotational direction. Phosphorylated CheY is returned to its non-phosphorylated state by phosphatases such as CheZ. In previously studied cases, chemotaxis phosphatases localize to the cellular poles by interactions with either the CheA chemotaxis kinase or flagellar motor proteins. We report here that the H. pylori CheZ, CheZ(HP), localizes to the poles independently of the flagellar motor, CheA, and all typical chemotaxis proteins. Instead, CheZ(HP) localization depends on the chemotaxis regulatory protein ChePep, and reciprocally, ChePep requires CheZ(HP) for its polar localization. We furthermore show that these proteins interact directly. Functional domain mapping of CheZ(HP) determined the polar localization motif lies within the central domain of the protein and that the protein has regions outside of the active site that participate in chemotaxis. Our results suggest that CheZ(HP) and ChePep form a distinct complex. These results therefore suggest the intriguing idea that some phosphatases localize independently of the other chemotaxis and motility proteins, possibly to confer unique regulation on these proteins' activities.

  11. Core bounce supernovae

    SciTech Connect

    Cooperstein, J.

    1987-01-01

    The gravitational collapse mechanism for Type II supernovae is considered, concentrating on the direct implosion - core bounce - hydrodynamic explosion picture. We examine the influence of the stiffness of the dense matter equation of state and discuss how the shock wave is formed. Its chances of success are determined by the equation of state, general relativistic effects, neutrino transport, and the size of presupernova iron core. 12 refs., 1 tab.

  12. Models of the earth's core

    NASA Technical Reports Server (NTRS)

    Stevenson, D. J.

    1981-01-01

    Combined inferences from seismology, high-pressure experiment and theory, geomagnetism, fluid dynamics, and current views of terrestrial planetary evolution lead to models of the earth's core with five basic properties. These are that core formation was contemporaneous with earth accretion; the core is not in chemical equilibrium with the mantle; the outer core is a fluid iron alloy containing significant quantities of lighter elements and is probably almost adiabatic and compositionally uniform; the more iron-rich inner solid core is a consequence of partial freezing of the outer core, and the energy release from this process sustains the earth's magnetic field; and the thermodynamic properties of the core are well constrained by the application of liquid-state theory to seismic and labroatory data.

  13. Models of the Earth's Core.

    PubMed

    Stevenson, D J

    1981-11-06

    Combined inferences from seismology, high-pressure experiment and theory, geomagnetism, fluid dynamics, and current views of terrestrial planetary evolution lead to models of the earth's core with the following properties. Core formation was contemporaneous with earth accretion; the core is not in chemical equilibrium with the mantle; the outer core is a fluid iron alloy containing significant quantities of lighter elements and is probably almost adiabatic and compositionally uniform; the more iron-rich inner solid core is a consequence of partial freezing of the outer core, and the energy release from this process sustains the earth's magnetic field; and the thermodynamic properties of the core are well constrained by the application of liquid-state theory to seismic and laboratory data.

  14. Sensitivities of Earth's core and mantle compositions to accretion and differentiation processes

    NASA Astrophysics Data System (ADS)

    Fischer, Rebecca A.; Campbell, Andrew J.; Ciesla, Fred J.

    2017-01-01

    The Earth and other terrestrial planets formed through the accretion of smaller bodies, with their core and mantle compositions primarily set by metal-silicate interactions during accretion. The conditions of these interactions are poorly understood, but could provide insight into the mechanisms of planetary core formation and the composition of Earth's core. Here we present modeling of Earth's core formation, combining results of 100 N-body accretion simulations with high pressure-temperature metal-silicate partitioning experiments. We explored how various aspects of accretion and core formation influence the resulting core and mantle chemistry: depth of equilibration, amounts of metal and silicate that equilibrate, initial distribution of oxidation states in the disk, temperature distribution in the planet, and target:impactor ratio of equilibrating silicate. Virtually all sets of model parameters that are able to reproduce the Earth's mantle composition result in at least several weight percent of both silicon and oxygen in the core, with more silicon than oxygen. This implies that the core's light element budget may be dominated by these elements, and is consistent with ≤1-2 wt% of other light elements. Reproducing geochemical and geophysical constraints requires that Earth formed from reduced materials that equilibrated at temperatures near or slightly above the mantle liquidus during accretion. The results indicate a strong tradeoff between the compositional effects of the depth of equilibration and the amounts of metal and silicate that equilibrate, so these aspects should be targeted in future studies aiming to better understand core formation conditions. Over the range of allowed parameter space, core and mantle compositions are most sensitive to these factors as well as stochastic variations in what the planet accreted as a function of time, so tighter constraints on these parameters will lead to an improved understanding of Earth's core composition.

  15. Vesta's Elemental Composition

    NASA Technical Reports Server (NTRS)

    Prettyman, T. H.; Beck, A. W.; Feldman, W. C.; Lawrence, D. J.; McCoy, T. J.; McSween, H. Y.; Mittlefehldt, D. W.; Peplowski, P. N.; Raymond, C. A.; Reedy, R. C.; Russell, C. T.; Titus, T. N.; Toplis, M. J.; Yamashita, N.

    2014-01-01

    Many lines of evidence (e.g. common geochemistry, chronology, O-isotope trends, and the presence of different HED rock types in polymict breccias) indicate that the howardite, eucrite, and diogenite (HED) meteorites originated from a single parent body. Meteorite studies show that this protoplanet underwent igneous differentiation to form a metallic core, an ultramafic mantle, and a basaltic crust. A spectroscopic match between the HEDs and 4 Vesta along with a plausible mechanism for their transfer to Earth, perhaps as chips off V-type asteroids ejected from Vesta's southern impact basin, supports the consensus view that many of these achondritic meteorites are samples of Vesta's crust and upper mantle. The HED-Vesta connection was put to the test by the NASA Dawn mission, which spent a year in close proximity to Vesta. Measurements by Dawn's three instruments, redundant Framing Cameras (FC), a Visible-InfraRed (VIR) spectrometer, and a Gamma Ray and Neutron Detector (GRaND), along with radio science have strengthened the link. Gravity measurements by Dawn are consistent with a differentiated, silicate body, with a dense Fe-rich core. The range of pyroxene compositions determined by VIR overlaps that of the howardites. Elemental abundances determined by nuclear spectroscopy are also consistent with HED-compositions. Observations by GRaND provided a new view of Vesta inaccessible by telescopic observations. Here, we summarize the results of Dawn's geochemical investigation of Vesta and their implications.

  16. Nuclear fuel elements having a composite cladding

    DOEpatents

    Gordon, Gerald M.; Cowan, II, Robert L.; Davies, John H.

    1983-09-20

    An improved nuclear fuel element is disclosed for use in the core of nuclear reactors. The improved nuclear fuel element has a composite cladding of an outer portion forming a substrate having on the inside surface a metal layer selected from the group consisting of copper, nickel, iron and alloys of the foregoing with a gap between the composite cladding and the core of nuclear fuel. The nuclear fuel element comprises a container of the elongated composite cladding, a central core of a body of nuclear fuel material disposed in and partially filling the container and forming an internal cavity in the container, an enclosure integrally secured and sealed at each end of said container and a nuclear fuel material retaining means positioned in the cavity. The metal layer of the composite cladding prevents perforations or failures in the cladding substrate from stress corrosion cracking or from fuel pellet-cladding interaction or both. The substrate of the composite cladding is selected from conventional cladding materials and preferably is a zirconium alloy.

  17. Auxiliary basis sets for density-fitting second-order Møller-Plesset perturbation theory: weighted core-valence correlation consistent basis sets for the 4d elements Y-Pd.

    PubMed

    Hill, J Grant

    2013-09-30

    Auxiliary basis sets (ABS) specifically matched to the cc-pwCVnZ-PP and aug-cc-pwCVnZ-PP orbital basis sets (OBS) have been developed and optimized for the 4d elements Y-Pd at the second-order Møller-Plesset perturbation theory level. Calculation of the core-valence electron correlation energies for small to medium sized transition metal complexes demonstrates that the error due to the use of these new sets in density fitting is three to four orders of magnitude smaller than that due to the OBS incompleteness, and hence is considered negligible. Utilizing the ABSs in the resolution-of-the-identity component of explicitly correlated calculations is also investigated, where it is shown that i-type functions are important to produce well-controlled errors in both integrals and correlation energy. Benchmarking at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations level indicates impressive convergence with respect to basis set size for the spectroscopic constants of 4d monofluorides; explicitly correlated double-ζ calculations produce results close to conventional quadruple-ζ, and triple-ζ is within chemical accuracy of the complete basis set limit.

  18. Geochemical constraints on Earth's core composition

    NASA Astrophysics Data System (ADS)

    Siebert, Julien

    2016-04-01

    The density of the core as measured from seismic-wave velocities is lower (by 10-15%) than that of pure iron, and therefore the core must also contain some light elements. Geophysical and cosmochemical constraints indicate that obvious candidates for these light elements include silicon, oxygen, and sulfur. These elements have been studied extensively for the past 30 years but a joint solution fulfilling all the requirements imposed by cosmochemistry and geochemistry, seismology, and models of Earth's accretion and core formation is still a highly controversial subject. Here are presented new experimental data in geochemistry used to place constraints on Earth's core composition. Metal-silicate partitioning experiments were performed at pressures and temperatures directly similar to those that prevailed in a deep magma ocean in the early Earth. The results show that core formation can reconcile the observed concentrations of siderophile elements in the silicate mantle with geophysical constraints on light elements in the core. Partitioning results also lead to a core containing less than 1 wt.% of sulfur, inconsistent with a S-rich layer to account for the observed structure of the outer core. Additionally, isotopic fractionations in core formation experiments are presented. This experimental tool merging the fields of experimental petrology and isotope geochemistry represents a promising approach, providing new independent constraints on the nature of light elements in the core.

  19. Selection of active elements in system reduction of vibration

    NASA Astrophysics Data System (ADS)

    Bialas, K.

    2016-11-01

    This work presents non-classical method of design of mechatronic systems. The purpose of this paper is also introduces synthesis of mechatronic system understand as design of mechatronic systems. The synthesis may be applied to modify the already existing systems in order to achieve a desired result. The system was consisted from mechanical and electrical elements. Electrical elements were used as subsystem reducing unwanted vibration of mechanical system. Electrical elements can be realized in the form of coils with movable core. The system was modelled in Matlab Simulink.

  20. 24. A CORE WORKER DISPLAYS THE CORE BOX AND CORES ...

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

    24. A CORE WORKER DISPLAYS THE CORE BOX AND CORES FOR A BRASS GATE VALVE BODY MADE ON A CORE BOX, CA. 1950. - Stockham Pipe & Fittings Company, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

  1. A Case of Extreme Simplicity of the Core Matrix in Three-Mode Principal Components Analysis.

    ERIC Educational Resources Information Center

    Murakami, Takashi; ten Berge, Jos M. F.; Kiers, Henk A. L.

    1998-01-01

    In three-mode principal components analysis, the P x Q x R core matrix "G" can be transformed to simple structure before it is interpreted. This paper shows that, when P=QR-1, G can be transformed to have nearly all the elements equal to values specified a priori. A closed-form solution for this transformation is offered. (SLD)

  2. The ab initio simulation of the Earth's core.

    PubMed

    Alfè, D; Gillan, M J; Vocadlo, L; Brodholt, J; Price, G D

    2002-06-15

    The Earth has a liquid outer and solid inner core. It is predominantly composed of Fe, alloyed with small amounts of light elements, such as S, O and Si. The detailed chemical and thermal structure of the core is poorly constrained, and it is difficult to perform experiments to establish the properties of core-forming phases at the pressures (ca. 300 GPa) and temperatures (ca. 5000-6000 K) to be found in the core. Here we present some major advances that have been made in using quantum mechanical methods to simulate the high-P/T properties of Fe alloys, which have been made possible by recent developments in high-performance computing. Specifically, we outline how we have calculated the Gibbs free energies of the crystalline and liquid forms of Fe alloys, and so conclude that the inner core of the Earth is composed of hexagonal close packed Fe containing ca. 8.5% S (or Si) and 0.2% O in equilibrium at 5600 K at the boundary between the inner and outer cores with a liquid Fe containing ca. 10% S (or Si) and 8% O.

  3. Wave propagation in sandwich panels with a poroelastic core.

    PubMed

    Liu, Hao; Finnveden, Svante; Barbagallo, Mathias; Arteaga, Ines Lopez

    2014-05-01

    Wave propagation in sandwich panels with a poroelastic core, which is modeled by Biot's theory, is investigated using the waveguide finite element method. A waveguide poroelastic element is developed based on a displacement-pressure weak form. The dispersion curves of the sandwich panel are first identified as propagating or evanescent waves by varying the damping in the panel, and wave characteristics are analyzed by examining their motions. The energy distributions are calculated to identify the dominant motions. Simplified analytical models are also devised to show the main physics of the corresponding waves. This wave propagation analysis provides insight into the vibro-acoustic behavior of sandwich panels lined with elastic porous materials.

  4. Analysis of biological properties of selected elements of haemostasis after treatment with the oxidized form of homocysteine in vitro.

    PubMed

    Malinowska, Joanna; Olas, Beata

    2011-01-01

    The elevated level of homocysteine (Hcys; hyperhomocysteinemia, in relation to the total plasma Hcys concentration, >15 µM) is associated with different diseases in human, including cardiovascular diseases. In plasma, Hcys occurs in various forms (the reduced Hcys, the oxidized Hcys, homocysteine thiolactone (HTL) and a component of proteins as a result of N- or S-homocysteinylation). The mechanisms by which hyperhomocysteinemia contributes to changes of haemostasis are complex and unclear. The role of different forms of Hcys, which may be involved in the modulation of haemostatic process during hyperhomocysteinemia is also not yet well-known. Our previous works have shown that both Hcys in the reduced form and the most reactive form of Hcys-its thiolactone may modify fibrinolysis, coagulation process and biological activity of blood platelets. The mechanism by which the oxidized Hcys exerts the prothrombotic effect and influences on blood platelets or plasma remains unclear. The aim of our study in vitro was to establish and compare the influence of the oxidized Hcys (at final doses of 0.01-1 mM), the reduced Hcys (at final doses of 0.01-1 mM) and HTL (at final doses of 0.1-1 µM) on selected haemostatic properties of blood platelets (platelet aggregation and platelet microparticle formation measured by flow cytometry) and plasma (fibrin polymerization and lysis). Here, our results indicate that the oxidized Hcys, like the reduced Hcys or HTL-augmented blood platelet aggregation, stimulated polymerization of fibrinogen and reduced the fibrin lysis in plasma. But, we suggest that the most reactive form of Hcys may be HTL (at lower concentrations than Hcys) during hyperhomocysteinemia-induced cardiovascular diseases.

  5. Practical determination of friction coefficient of Al 3003 for forming of backward extruded part using simple tip test and inverse finite element analysis

    NASA Astrophysics Data System (ADS)

    Bong, H. J.; Leem, D.; Kim, J. H.; Im, Y. T.; Lee, M. G.

    2016-05-01

    The friction coefficient for aluminum alloy 3003 was determined from a specially designed tip test and finite element (FE) simulations. Measured radial tip distance after the tip test was compared to the FE simulations by iteratively changing friction coefficient and the best fitting friction coefficient was determined. To consider strain rate effect on flow stress response during large plastic deformation, a new combined Hollomon- Voce hardening law was proposed. The friction under three different surface conditions was considered by the proposed inverse FE analysis. The results showed that there was obvious strain rate effect on the predicted punch load in the tip test. Moreover, the different friction coefficients were numerically determined for punch/workpiece and die/workpiece interfaces. Two possible causes of this difference were discussed by the analysis on contact normal pressure and slip velocity distributions of the two interfaces.

  6. Electromagnetic pump stator core

    DOEpatents

    Fanning, Alan W.; Olich, Eugene E.; Dahl, Leslie R.

    1995-01-01

    A stator core for supporting an electrical coil includes a plurality of groups of circumferentially abutting flat laminations which collectively form a bore and perimeter. A plurality of wedges are interposed between the groups, with each wedge having an inner edge and a thicker outer edge. The wedge outer edges abut adjacent ones of the groups to provide a continuous path around the perimeter.

  7. Banded electromagnetic stator core

    DOEpatents

    Fanning, Alan W.; Gonzales, Aaron A.; Patel, Mahadeo R.; Olich, Eugene E.

    1996-01-01

    A stator core for an electromagnetic pump includes a plurality of circumferentially adjoining groups of flat laminations disposed about a common centerline axis and collectively defining a central bore and a discontinuous outer perimeter, with adjacent groups diverging radially outwardly to form V-shaped gaps. An annular band surrounds the groups and is predeterminedly tensioned to clamp together the laminations, and has a predetermined flexibility in a radial direction to form substantially straight bridge sections between the adjacent groups.

  8. Banded electromagnetic stator core

    DOEpatents

    Fanning, A.W.; Gonzales, A.A.; Patel, M.R.; Olich, E.E.

    1994-04-05

    A stator core for an electromagnetic pump includes a plurality of circumferentially adjoining groups of flat laminations disposed about a common centerline axis and collectively defining a central bore and a discontinuous outer perimeter, with adjacent groups diverging radially outwardly to form V-shaped gaps. An annular band surrounds the groups and is predeterminedly tensioned to clamp together the laminations, and has a predetermined flexibility in a radial direction to form substantially straight bridge sections between the adjacent groups. 5 figures.

  9. Banded electromagnetic stator core

    DOEpatents

    Fanning, Alan W.; Gonzales, Aaron A.; Patel, Mahadeo R.; Olich, Eugene E.

    1994-01-01

    A stator core for an electromagnetic pump includes a plurality of circumferentially adjoining groups of flat laminations disposed about a common centerline axis and collectively defining a central bore and a discontinuous outer perimeter, with adjacent groups diverging radially outwardly to form V-shaped gaps. An annular band surrounds the groups and is predeterminedly tensioned to clamp together the laminations, and has a predetermined flexibility in a radial direction to form substantially straight bridge sections between the adjacent groups.

  10. Banded electromagnetic stator core

    DOEpatents

    Fanning, A.W.; Gonzales, A.A.; Patel, M.R.; Olich, E.E.

    1996-06-11

    A stator core for an electromagnetic pump includes a plurality of circumferentially adjoining groups of flat laminations disposed about a common centerline axis and collectively defining a central bore and a discontinuous outer perimeter, with adjacent groups diverging radially outwardly to form V-shaped gaps. An annular band surrounds the groups and is predeterminedly tensioned to clamp together the laminations, and has a predetermined flexibility in a radial direction to form substantially straight bridge sections between the adjacent groups. 5 figs.

  11. Variable depth core sampler

    DOEpatents

    Bourgeois, Peter M.; Reger, Robert J.

    1996-01-01

    A variable depth core sampler apparatus comprising a first circular hole saw member, having longitudinal sections that collapses to form a point and capture a sample, and a second circular hole saw member residing inside said first hole saw member to support the longitudinal sections of said first hole saw member and prevent them from collapsing to form a point. The second hole saw member may be raised and lowered inside said first hole saw member.

  12. Core Formation and Evolution of Asteroid 4 Vesta

    NASA Technical Reports Server (NTRS)

    Kiefer, Walter S.; Mittlefehldt, David W.

    2014-01-01

    The howardites, eucrites, and diogenites (HEDs) are a suite of related meteorite types that formed by igneous and impact processes on the same parent body. Multiple lines of evidence, including infrared spectroscopy of the asteroid belt and the petrology and geochemistry of the HEDs, suggest that the asteroid 4 Vesta is the parent body for the HEDs. Observations by NASA's Dawn spacecraft mission strongly support the conclusion that the HEDs are from Vesta. The abundances of the moderately siderophile elements Ni, Co, Mo, W, and P in eucrites require that most or all of the metallic phase in Vesta segregated to form a core prior to eucrite solidification. These observations place important constraints on the mode and timescale of core formation on Vesta. Possible core formation mechanisms include porous flow, which potentially could occur prior to initiation of silicate melting, and metallic rain in a largely molten silicate magma ocean. Once the core forms, convection within the core could possible sustain a magnetic dynamo for a period of time. We consider each process in turn.

  13. Common data elements for clinical research in Friedreich's ataxia.

    PubMed

    Lynch, David R; Pandolfo, Massimo; Schulz, Jorg B; Perlman, Susan; Delatycki, Martin B; Payne, R Mark; Shaddy, Robert; Fischbeck, Kenneth H; Farmer, Jennifer; Kantor, Paul; Raman, Subha V; Hunegs, Lisa; Odenkirchen, Joanne; Miller, Kristy; Kaufmann, Petra

    2013-02-01

    To reduce study start-up time, increase data sharing, and assist investigators conducting clinical studies, the National Institute of Neurological Disorders and Stroke embarked on an initiative to create common data elements for neuroscience clinical research. The Common Data Element Team developed general common data elements, which are commonly collected in clinical studies regardless of therapeutic area, such as demographics. In the present project, we applied such approaches to data collection in Friedreich's ataxia (FRDA), a neurological disorder that involves multiple organ systems. To develop FRDA common data elements, FRDA experts formed a working group and subgroups to define elements in the following: ataxia and performance measures; biomarkers; cardiac and other clinical outcomes; and demographics, laboratory tests, and medical history. The basic development process included identification of international experts in FRDA clinical research, meeting by teleconference to develop a draft of standardized common data elements recommendations, vetting of recommendations across the subgroups, and dissemination of recommendations to the research community for public comment. The full recommendations were published online in September 2011 at http://www.commondataelements.ninds.nih.gov/FA.aspx. The subgroups' recommendations are classified as core, supplemental, or exploratory. Template case report forms were created for many of the core tests. The present set of data elements should ideally lead to decreased initiation time for clinical research studies and greater ability to compare and analyze data across studies. Their incorporation into new, ongoing studies will be assessed in an ongoing fashion to define their utility in FRDA.

  14. Rare earth element and Pb isotope variations in a 52 kyr peat core from Lynch’s Crater (NE Queensland, Australia): Proxy development and application to paleoclimate in the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Kylander, M. E.; Muller, J.; Wüst, R. A. J.; Gallagher, K.; Garcia-Sanchez, R.; Coles, B. J.; Weiss, D. J.

    2007-02-01

    Accurate prediction of future climate scenarios is contingent on our understanding of past and present climate mechanisms. This is done in part through the reconstruction of historical climate changes using proxy records from terrestrial and marine archives. Terrestrial archives covering the Holocene and late Pleistocene are limited, most acutely in the Southern Hemisphere. Here, Rare earth elements (REE) and Pb isotopes are developed as inorganic geochemical proxies of mineral dust source changes and, by extension, climate change. Using a peat core from Lynch's Crater in NE Queensland, Australia, we present the first long-term (c. 52 kyr) terrestrial record of atmospheric REE and Pb deposition (with the exception of four wet events which represent periods of erosion from the crater itself) in the Southern Hemisphere covering both glacial and interglacial times. Based on a combination of correlation analyses, Al and Ti normalised profiles and elemental patterns, we establish REE are immobile within the peat deposit and not subject to significant post depositional diagenetic changes (important particularly for Ce). This is vital as REE can be mobile under acid and organic rich conditions like those that can occur during the development of a peat deposit. The volcanic provinces of eastern Australia have characteristic Eu anomaly signatures, which allowed their use in a novel way to detect changes in dust source to Lynch's Crater. Between 41,095 and 52,505 BP the deposit was under the influence of dust carried by long distance transport (>1500 km) from SE Australia. From 8525 to 40,815 BP regional sources (100-1500 km) dominated the deposited signals while between 1740 and 8390 BP the dust signal was controlled by local sources (<100 km). These findings were also confirmed by Pb isotope data. Changepoint modelling refined the timing of these changes in dust source, recognizing concurrent shifts in our tracing tools ((Eu/Eu ∗) PAAS and 206Pb/ 207Pb). These

  15. Computational Astrophysics at the Bleeding Edge: Simulating Core Collapse Supernovae

    NASA Astrophysics Data System (ADS)

    Mezzacappa, Anthony

    2013-04-01

    Core collapse supernovae are the single most important source of elements in the Universe, dominating the production of elements between oxygen and iron and likely responsible for half the elements heavier than iron. They result from the death throes of massive stars, beginning with stellar core collapse and the formation of a supernova shock wave that must ultimately disrupt such stars. Past, first-principles models most often led to the frustrating conclusion the shock wave stalls and is not revived, at least given the physics included in the models. However, recent progress in the context of two-dimensional, first-principles supernova models is reversing this trend, giving us hope we are on the right track toward a solution of one of the most important problems in astrophysics. Core collapse supernovae are multi-physics events, involving general relativity, hydrodynamics and magnetohydrodynamics, nuclear burning, and radiation transport in the form of neutrinos, along with a detailed nuclear physics equation of state and neutrino weak interactions. Computationally, simulating these catastrophic stellar events presents an exascale computing challenge. I will discuss past models and milestones in core collapse supernova theory, the state of the art, and future requirements. In this context, I will present the results and plans of the collaboration led by ORNL and the University of Tennessee.

  16. Organization of the cores of the mammalian pyruvate dehydrogenase complex formed by E2 and E2 plus the E3-binding protein and their capacities to bind the E1 and E3 components.

    PubMed

    Hiromasa, Yasuaki; Fujisawa, Tetsuro; Aso, Yoichi; Roche, Thomas E

    2004-02-20

    The subunits of the dihydrolipoyl acetyltransferase (E2) component of mammalian pyruvate dehydrogenase complex can form a 60-mer via association of the C-terminal I domain of E2 at the vertices of a dodecahedron. Exterior to this inner core structure, E2 has a pyruvate dehydrogenase component (E1)-binding domain followed by two lipoyl domains, all connected by mobile linker regions. The assembled core structure of mammalian pyruvate dehydrogenase complex also includes the dihydrolipoyl dehydrogenase (E3)-binding protein (E3BP) that binds the I domain of E2 by its C-terminal I' domain. E3BP similarly has linker regions connecting an E3-binding domain and a lipoyl domain. The composition of E2.E3BP was thought to be 60 E2 plus approximately 12 E3BP. We have prepared homogenous human components. E2 and E2.E3BP have s(20,w) values of 36 S and 31.8 S, respectively. Equilibrium sedimentation and small angle x-ray scattering studies indicate that E2.E3BP has lower total mass than E2, and small angle x-ray scattering showed that E3 binds to E2.E3BP outside the central dodecahedron. In the presence of saturating levels of E1, E2 bound approximately 60 E1 and maximally sedimented 64.4 +/- 1.5 S faster than E2, whereas E1-saturated E2.E3BP maximally sedimented 49.5 +/- 1.4 S faster than E2.E3BP. Based on the impact on sedimentation rates by bound E1, we estimate fewer E1 (approximately 12) were bound by E2.E3BP than by E2. The findings of a smaller E2.E3BP mass and a lower capacity to bind E1 support the smaller E3BP substituting for E2 subunits rather than adding to the 60-mer. We describe a substitution model in which 12 I' domains of E3BP replace 12 I domains of E2 by forming 6 dimer edges that are symmetrically located in the dodecahedron structure. Twelve E3 dimers were bound per E248.E3BP12 mass, which is consistent with this model.

  17. FUEL ELEMENT

    DOEpatents

    Fortescue, P.; Zumwalt, L.R.

    1961-11-28

    A fuel element was developed for a gas cooled nuclear reactor. The element is constructed in the form of a compacted fuel slug including carbides of fissionable material in some cases with a breeder material carbide and a moderator which slug is disposed in a canning jacket of relatively impermeable moderator material. Such canned fuel slugs are disposed in an elongated shell of moderator having greater gas permeability than the canning material wherefore application of reduced pressure to the space therebetween causes gas diffusing through the exterior shell to sweep fission products from the system. Integral fission product traps and/or exterior traps as well as a fission product monitoring system may be employed therewith. (AEC)

  18. NEUTRONIC REACTOR CORE INSTRUMENT

    DOEpatents

    Mims, L.S.

    1961-08-22

    A multi-purpose instrument for measuring neutron flux, coolant flow rate, and coolant temperature in a nuclear reactor is described. The device consists essentially of a hollow thimble containing a heat conducting element protruding from the inner wall, the element containing on its innermost end an amount of fissionsble materinl to function as a heat source when subjected to neutron flux irradiation. Thermocouple type temperature sensing means are placed on the heat conducting element adjacent the fissionable material and at a point spaced therefrom, and at a point on the thimble which is in contact with the coolant fluid. The temperature differentials measured between the thermocouples are determinative of the neutron flux, coolant flow, and temperature being measured. The device may be utilized as a probe or may be incorporated in a reactor core. (AE C)

  19. Tandemly Integrated HPV16 Can Form a Brd4-Dependent Super-Enhancer-Like Element That Drives Transcription of Viral Oncogenes

    PubMed Central

    Dooley, Katharine E.; Warburton, Alix

    2016-01-01

    ABSTRACT In cancer cells associated with human papillomavirus (HPV) infections, the viral genome is very often found integrated into the cellular genome. The viral oncogenes E6 and E7 are transcribed from the viral promoter, and integration events that alter transcriptional regulation of this promoter contribute to carcinogenic progression. In this study, we detected highly enriched binding of the super-enhancer markers Brd4, MED1, and H3K27ac, visible as a prominent nuclear focus by immunofluorescence, at the tandemly integrated copies of HPV16 in cells of the cervical neoplasia cell line W12 subclone 20861. Tumor cells are often addicted to super-enhancer-driven oncogenes and are particularly sensitive to disruption of transcription factor binding to the enhancers. Treatment of 20861 cells with bromodomain inhibitors displaced Brd4 from the HPV integration site, greatly decreased E6/E7 transcription, and inhibited cellular proliferation. Thus, Brd4 activates viral transcription at this integration site, and strong selection for E6/E7 expression can drive the formation of a super-enhancer-like element to promote oncogenesis. PMID:27624132

  20. Sediments at the top of Earth's core.

    PubMed

    Buffett, B A; Garnero, E J; Jeanloz, R

    2000-11-17

    Unusual physical properties at the core-mantle boundary have been inferred from seismic and geodetic observations in recent years. We show how both types of observations can be explained by a layer of silicate sediments, which accumulate at the top of the core as Earth cools. Compaction of the sediments expels most of the liquid iron but leaves behind a small amount of core material, which is entrained in mantle convection and may account for the isotopic signatures of core material in some hot spot plumes. Extraction of light elements from the liquid core also enhances the vigor of convection in the core and may increase the power available to the geodynamo.

  1. An early geodynamo driven by exsolution of mantle components from Earth’s core

    NASA Astrophysics Data System (ADS)

    Badro, James; Siebert, Julien; Nimmo, Francis

    2016-08-01

    Recent palaeomagnetic observations report the existence of a magnetic field on Earth that is at least 3.45 billion years old. Compositional buoyancy caused by inner-core growth is the primary driver of Earth’s present-day geodynamo, but the inner core is too young to explain the existence of a magnetic field before about one billion years ago. Theoretical models propose that the exsolution of magnesium oxide—the major constituent of Earth’s mantle—from the core provided a major source of the energy required to drive an early dynamo, but experimental evidence for the incorporation of mantle components into the core has been lacking. Indeed, terrestrial core formation occurred in the early molten Earth by gravitational segregation of immiscible metal and silicate melts, transporting iron-loving (siderophile) elements from the silicate mantle to the metallic core and leaving rock-loving (lithophile) mantle components behind. Here we present experiments showing that magnesium oxide dissolves in core-forming iron melt at very high temperatures. Using core-formation models, we show that extreme events during Earth’s accretion (such as the Moon-forming giant impact) could have contributed large amounts of magnesium to the early core. As the core subsequently cooled, exsolution of buoyant magnesium oxide would have taken place at the core-mantle boundary, generating a substantial amount of gravitational energy as a result of compositional buoyancy. This amount of energy is comparable to, if not more than, that produced by inner-core growth, resolving the conundrum posed by the existence of an ancient magnetic field prior to the formation of the inner core.

  2. Asteroid bombardment and the core of Theia as possible sources for the Earth's late veneer component

    NASA Astrophysics Data System (ADS)

    Sleep, Norman H.

    2016-07-01

    The silicate Earth contains Pt-group elements in roughly chondritic relative ratios, but with absolute concentrations <1% chondrite. This veneer implies addition of chondrite-like material with 0.3-0.7% mass of the Earth's mantle or an equivalent planet-wide thickness of 5-20 km. The veneer thickness, 200-300 m, within the lunar crust and mantle is much less. One hypothesis is that the terrestrial veneer arrived after the moon-forming impact within a few large asteroids that happened to miss the smaller Moon. Alternatively, most of terrestrial veneer came from the core of the moon-forming impactor, Theia. The Moon then likely contains iron from Theia's core. Mass balances lend plausibility. The lunar core mass is ˜1.6 × 1021 kg and the excess FeO component in the lunar mantle is 1.3-3.5 × 1021 kg as Fe, totaling 3-5 × 1021 kg or a few percent of Theia's core. This mass is comparable to the excess Fe of 2.3-10 × 1021 kg in the Earth's mantle inferred from the veneer component. Chemically in this hypothesis, Fe metal from Theia's core entered the Moon-forming disk. H2O and Fe2O3 in the disk oxidized part of the Fe, leaving the lunar mantle near a Fe-FeO buffer. The remaining iron metal condensed, gathered Pt-group elements eventually into the lunar core. The silicate Moon is strongly depleted in Pt-group elements. In contrast, the Earth's mantle contained excess oxidants, H2O and Fe2O3, which quantitatively oxidized the admixed Fe from Theia's core, retaining Pt-group elements. In this hypothesis, asteroid impacts were relatively benign with ˜1 terrestrial event that left only thermophile survivors.

  3. COVERING A CORE BY EXTRUSION

    DOEpatents

    Karnie, A.J.

    1963-07-16

    A method of covering a cylindrical fuel core with a cladding metal ms described. The metal is forced between dies around the core from both ends in two opposing skirts, and as these meet the ends turn outward into an annular recess in the dics. By cutting off the raised portion formed by the recess, oxide impurities are eliminated. (AEC)

  4. mXBP/CRE-BP2 and c-Jun form a complex which binds to the cyclic AMP, but not to the 12-O-tetradecanoylphorbol-13-acetate, response element.

    PubMed Central

    Ivashkiv, L B; Liou, H C; Kara, C J; Lamph, W W; Verma, I M; Glimcher, L H

    1990-01-01

    Proto-oncogene products c-Fos and c-Jun form a complex which binds with high affinity to the 12-O-tetradecanoylphorbol-13-acetate (TPA) response DNA element and which stimulates transcription of phorbol ester- inducible genes. We have previously identified, by screening a lambda gt11 expression library, murine protein mXBP, which binds to a sequence which overlaps the 3' end of the murine class II major histocompatibility complex A alpha gene X box, a conserved transcription element found upstream of all class II genes. Here, we demonstrate that the target sequence for mXBP is a consensus cyclic AMP response element (CRE). mXBP is a member of the leucine zipper family of DNA-binding proteins and has significant homology to oncoproteins c-Fos and c-Jun. The inferred amino acid sequence of mXBP shows near identity to human CRE-BP1, except it does not contain an internal proline-rich domain. Immunoprecipitation and glutaraldehyde cross-linking studies show that mXBP/CRE-BP2 can form a complex with c-Jun. Complex formation is dependent on intact leucine zipper domains in both proteins. mXBP-c-Jun complexes can coexist with c-Fos-c-Jun complexes and can bind with high affinity to CRE, but not to TPA response DNA element, sequences. These results suggest that changes in the expression of mXBP/CRE-BP2, c-Fos, and c-Jun, which alter the ratio of mXBP-c-Jun to c-Fos-c-Jun complexes, would affect the relative expression of cyclic AMP and phorbol ester-responsive genes. This provides support for a combinatorial model of gene regulation, whereby protein-protein interactions which alter the DNA binding specificity of protein complexes can expand the flexibility of cellular transcriptional responses. Images PMID:2138707

  5. Radiocarbon based source apportionment of black carbon in the form of PM10 elemental carbon aerosol particles at the Zeppelin Observatory, Svalbard

    NASA Astrophysics Data System (ADS)

    Winiger, Patrik; Andersson, August; Espen Yttri, Karl; Tunved, Peter; Gustafsson, Örjan

    2015-04-01

    Black carbon (BC) aerosol particles are formed from incomplete combustion of fossil fuel and biomass. Transported into the Arctic, they potentially contributes to climate warming. However, there are still large uncertainties related to the climate effects of BC, including aspects of radiative properties, mixing state of the particles, transport, atmospheric lifetime and sources. The current study aims to reduce source uncertainties by applying a top-down (observational) source-diagnostic isotope approach and comparing these to bottom-up (modeling) emission inventories to better constrain the source types and source regions. The use of natural abundance radiocarbon (Δ14C) is a powerful tool to distinguish between fossil (void of 14C) and biomass (contemporary 14C) combustion sources. Due to the well-defined end-members, 14C-measurements (alone) provide high precision (

  6. N,N{prime}-dicyclohexylcarbodiimide cross-linking suggests a central core of helices II in oligomers of URF13, the pore-forming T-toxin receptor of cms-T maize mitochondria

    SciTech Connect

    Rhoads, D.M. |; Kaspi, C.I.; Siedow, J.N.; Levings, C.S. III

    1994-08-16

    URF13 is a mitochondrially encoded, integral membrane protein found only in maize carrying the cms-T cytoplasm. URF13 is associated with cytoplasmic male sterility, Texas type, and causes susceptibility to the fungal pathogens Bipolaris maydis race T and Phyllosticta maydis. URF13 is predicted to contain three transmembrane {alpha}-helices and is a receptor for the pathotoxins (T-toxins) produced by B. maydis race T and P. maydis. Binding of T-toxin to URF13 leads to membrane permeability. Cross-linking of URF13 oligomers with N,N{prime}-dicyclohexylcarbodiimide (DCCD) protects Escherichia coli cells expressing URF13 and cms-T mitochondria from the permeability caused by T-toxin or methomyl. Using mutated forms of URF13 expressed in E. coli cells, the authors determined the molecular mechanism of DCCD protection. They separately changed Lys-37 in helix II to isoleucine (K37I-URF13) and Lys-32 in the helix I/helix II loop region to alanine (K32A-URF13). DCCD treatment of K37I-URF13-expressing cells did not protect the cells from permeability caused by T-toxin or methomyl. DCCD cross-linking was greatly reduced in K37I-URF13 and in D39V-URF13-expressing cells, but it was unaffected in K32A-URF13-expressing cells. Binding of methomyl or T-toxin decreases DCCD cross-linking of URF13 oligomers expressed in either E. coli or cms-T mitochondria. They conclude that Asp-39 in helix II is cross-linked by DCCD to Lys-37 in helix II of an adjacent URF13 molecule and that this cross-linking protects against toxin-mediated permeabilization. The results also indicate that helices II form a central core in URF13 oligomers.

  7. FUEL ELEMENTS FOR NEUTRONIC REACTORS

    DOEpatents

    Foote, F.G.; Jette, E.R.

    1963-05-01

    A fuel element for a nuclear reactor is described that consists of a jacket containing a unitary core of fissionable material and a filling of a metal of the group consisting of sodium and sodium-potassium alloys. (AEC)

  8. Common Core State Standards for English Language Arts & Literacy in History/Social Studies, Science, and Technical Subjects. Appendix A: Research Supporting Key Elements of the Standards, Glossary of Key Terms

    ERIC Educational Resources Information Center

    Common Core State Standards Initiative, 2010

    2010-01-01

    One of the key requirements of the Common Core State Standards for Reading is that all students must be able to comprehend texts of steadily increasing complexity as they progress through school. By the time they complete the core, students must be able to read and comprehend independently and proficiently the kinds of complex texts commonly found…

  9. Results from a preliminary review of scientific evidence for appropriateness of preparations, dosage forms and other product design elements for older adult patients.

    PubMed

    Messina, Rossella; Becker, Robert; van Riet-Nales, Diana A; Stegemann, Sven

    2015-01-30

    The aging population and the growing multimorbidity of the major patient population as well as the advanced (pharmaco)therapeutic treatment options are increasing the complexity of independent drug therapy management and administration. The increased complexity may have an impact on drug adherence (including any need for patients initiated coping strategies), and consequently on the safety and efficacy of the medicine. To overcome adherence issues caused by the design of the medicine, it is crucial that developers consider the age appropriateness of the medicine (route of administration, dosage form, excipients in the composition, frequency of dosing) in meeting patients' needs to manage their therapy without the support of a care giver. In order to understand the scientific evidence on such age appropriately designed medicines for use by older adults, a literature search was performed in the Medline database (all languages included). The search produced 34 publications that met the inclusion and exclusion criteria for the patient population of 65 years an older. An in-depth analysis of the included publications with respect to the methodological quality (study design, data collection, endpoints chosen) and results showed that none of these publications had adequately investigated the age appropriateness of the medicine for use by older adults. The authors consider that the knowledge gap in this area requires attention of all stakeholders in the healthcare community.

  10. Iron isotopic fractionation between silicate mantle and metallic core at high pressure

    NASA Astrophysics Data System (ADS)

    Liu, Jin; Dauphas, Nicolas; Roskosz, Mathieu; Hu, Michael Y.; Yang, Hong; Bi, Wenli; Zhao, Jiyong; Alp, Esen E.; Hu, Justin Y.; Lin, Jung-Fu

    2017-02-01

    The +0.1‰ elevated 56Fe/54Fe ratio of terrestrial basalts relative to chondrites was proposed to be a fingerprint of core-mantle segregation. However, the extent of iron isotopic fractionation between molten metal and silicate under high pressure-temperature conditions is poorly known. Here we show that iron forms chemical bonds of similar strengths in basaltic glasses and iron-rich alloys, even at high pressure. From the measured mean force constants of iron bonds, we calculate an equilibrium iron isotope fractionation between silicate and iron under core formation conditions in Earth of ~0-0.02‰, which is small relative to the +0.1‰ shift of terrestrial basalts. This result is unaffected by small amounts of nickel and candidate core-forming light elements, as the isotopic shifts associated with such alloying are small. This study suggests that the variability in iron isotopic composition in planetary objects cannot be due to core formation.

  11. Bacteria form tellurium nanocrystals

    USGS Publications Warehouse

    Oremland, R.S.

    2007-01-01

    A team of researchers have found two bacterial species that produce tellurium oxyanions as respiratory electron acceptors for growth, leaving elemental tellurium in the form of nanoparticles. The crystals from the two organisms exhibit distinctively different structures. Bacillus selenitireducens initially forms nanorods that cluster together to form rosettes. Sulfurospirillum barnesii forms irregularly-shaped nanospheres that coalesce into larger composite aggregates.

  12. Modeling Core Collapse Supernovae

    NASA Astrophysics Data System (ADS)

    Mezzacappa, Anthony

    2017-01-01

    Core collapse supernovae, or the death throes of massive stars, are general relativistic, neutrino-magneto-hydrodynamic events. The core collapse supernova mechanism is still not in hand, though key components have been illuminated, and the potential for multiple mechanisms for different progenitors exists. Core collapse supernovae are the single most important source of elements in the Universe, and serve other critical roles in galactic chemical and thermal evolution, the birth of neutron stars, pulsars, and stellar mass black holes, the production of a subclass of gamma-ray bursts, and as potential cosmic laboratories for fundamental nuclear and particle physics. Given this, the so called ``supernova problem'' is one of the most important unsolved problems in astrophysics. It has been fifty years since the first numerical simulations of core collapse supernovae were performed. Progress in the past decade, and especially within the past five years, has been exponential, yet much work remains. Spherically symmetric simulations over nearly four decades laid the foundation for this progress. Two-dimensional modeling that assumes axial symmetry is maturing. And three-dimensional modeling, while in its infancy, has begun in earnest. I will present some of the recent work from the ``Oak Ridge'' group, and will discuss this work in the context of the broader work by other researchers in the field. I will then point to future requirements and challenges. Connections with other experimental, observational, and theoretical efforts will be discussed, as well.

  13. NEUTRONIC REACTOR CORE

    DOEpatents

    Thomson, W.B.; Corbin, A. Jr.

    1961-07-18

    An improved core for a gas-cooled power reactor which admits gas coolant at high temperatures while affording strong integral supporting structure and efficient moderation of neutrons is described. The multiplicities of fuel elements constituting the critical amassment of fissionable material are supported and confined by a matrix of metallic structure which is interspersed therebetween. Thermal insulation is interposed between substantially all of the metallic matrix and the fuel elements; the insulation then defines the principal conduit system for conducting the coolant gas in heat-transfer relationship with the fuel elements. The metallic matrix itseif comprises a system of ducts through which an externally-cooled hydrogeneous liquid, such as water, is circulated to serve as the principal neutron moderant for the core and conjointly as the principal coolant for the insulated metallic structure. In this way, use of substantially neutron transparent metals, such as aluminum, becomes possible for the supporting structure, despite the high temperatures of the proximate gas. The Aircraft Nuclear Propulsion program's "R-1" reactor design is a preferred embodiment.

  14. Mars: a new core-crystallization regime.

    PubMed

    Stewart, Andrew J; Schmidt, Max W; van Westrenen, Wim; Liebske, Christian

    2007-06-01

    The evolution of the martian core is widely assumed to mirror the characteristics observed for Earth's core. Data from experiments performed on iron-sulfur and iron-nickel-sulfur systems at pressures corresponding to the center of Mars indicate that its core is presently completely liquid and that it will not form an outwardly crystallizing iron-rich inner core, as does Earth. Instead, planetary cooling will lead to core crystallization following either a "snowing-core" model, whereby iron-rich solids nucleate in the outer portions of the core and sink toward the center, or a "sulfide inner-core" model, where an iron-sulfide phase crystallizes to form a solid inner core.

  15. Pressure Core Characterization

    NASA Astrophysics Data System (ADS)

    Santamarina, J. C.

    2014-12-01

    Natural gas hydrates form under high fluid pressure and low temperature, and are found in permafrost, deep lakes or ocean sediments. Hydrate dissociation by depressurization and/or heating is accompanied by a multifold hydrate volume expansion and host sediments with low permeability experience massive destructuration. Proper characterization requires coring, recovery, manipulation and testing under P-T conditions within the stability field. Pressure core technology allows for the reliable characterization of hydrate bearing sediments within the stability field in order to address scientific and engineering needs, including the measurement of parameters used in hydro-thermo-mechanical analyses, and the monitoring of hydrate dissociation under controlled pressure, temperature, effective stress and chemical conditions. Inherent sampling effects remain and need to be addressed in test protocols and data interpretation. Pressure core technology has been deployed to study hydrate bearing sediments at several locations around the world. In addition to pressure core testing, a comprehensive characterization program should include sediment analysis, testing of reconstituted specimens (with and without synthetic hydrate), and in situ testing. Pressure core characterization technology can be used to study other gas-charged formations such as deep sea sediments, coal bed methane and gas shales.

  16. Doppler Scanning of Sediment Cores: A Useful Method for Studying Sedimentary Structures and Defining the Cutting Angle for Half Cores

    NASA Astrophysics Data System (ADS)

    Acar, Dursun; Cagatay, Namik; Biltekin, Demet; Eris, Kadir; Albut, Gulum; Ogretmen, Nazik; Arslan, Tugce; Sari, Erol

    2014-05-01

    We tested the doppler ultrasound scanning of sediment cores in PVC liners using 8 megahertz ultrasonic waves for detection of angular laminations. The method was tested with artificially prepared cores as well as marine and lake sediment cores, and proven to be a useful and fast technique for imaging and determining the vertical angularity of sedimentary structures, such as laminations and beddings. Random cutting axes provide two angularities on X and Y dimensions. In this study, the main scientific problem is 'sequential angular disconformity'. Importance of detection of these anomalies on whole cores before dividing into half cores based on determining the right cutting axes. Successful imaging was obtained from top three centimeter depth of the sediments below the PVC liner, using a linear Doppler probe. Other Doppler probes (e.g., convex probe) did not work for core scanning because of their wave-form and reflection characteristics. Longitudinal and rotational scanning with gap filler and ultrasonic wave conductive gel material for keeping energy range of wave is necessary for detecting the variation in the dip of the bedding and laminae in the cores before separation. Another angular reasoned problem is about horizontal surface and can be easily solved with adjustable position of sensor or ray source placement. Border of sampling points between two different lithology must be stay with regard to neighbour sediment angles. Vertical angularity correction is not easy and its effect on signal propagation, detection biases and effectible to mixed samples contamination during physical sampling (particle size analyzing). Determining the attitude of angled bedding before core splitting is important for further core analyses such as elemental analysis and digital X-ray radiography. After Doppler scanning, the splitting direction (i.e., vertical to bedding and lamination) can be determined. The method is cheap, quick and non- hazardous to health, unlike the x

  17. An early geodynamo driven by exsolution of mantle components from Earth's core.

    PubMed

    Badro, James; Siebert, Julien; Nimmo, Francis

    2016-08-18

    Recent palaeomagnetic observations report the existence of a magnetic field on Earth that is at least 3.45 billion years old. Compositional buoyancy caused by inner-core growth is the primary driver of Earth's present-day geodynamo, but the inner core is too young to explain the existence of a magnetic field before about one billion years ago. Theoretical models propose that the exsolution of magnesium oxide--the major constituent of Earth's mantle--f