Temperature distribution of thick thermoset composites

NASA Astrophysics Data System (ADS)

Guo, Zhan-Sheng; Du, Shanyi; Zhang, Boming

2004-05-01

The development of temperature distribution of thick polymeric matrix laminates during an autoclave vacuum bag process was measured and compared with numerically calculated results. The finite element formulation of the transient heat transfer problem was carried out for polymeric matrix composite materials from the heat transfer differential equations including internal heat generation produced by exothermic chemical reactions. Software based on the general finite element software package was developed for numerical simulation of the entire composite process. From the experimental and numerical results, it was found that the measured temperature profiles were in good agreement with the numerical ones, and conventional cure cycles recommended by prepreg manufacturers for thin laminates should be modified to prevent temperature overshoot.

Residual thermal stress control in composite reinforced metal structures. [by mechanical loading of metal component prior to bonding

NASA Technical Reports Server (NTRS)

Kelly, J. B.; June, R. R.

1972-01-01

Advanced composite materials, composed of boron or graphite fibers and a supporting matrix, make significant structural efficiency improvements available to aircraft and aerospace designers. Residual stress induced during bonding of composite reinforcement to metal structural elements can be reduced or eliminated through suitable modification to the manufacturing processes. The most successful method employed during this program used a steel tool capable of mechanically loading the metal component in compression prior to the adhesive bonding cycle. Compression loading combined with heating to 350 F during the bond cycle can result in creep deformation in aluminum components. The magnitude of the deformation increases with increasing stress level during exposure to 350 F.

Scale-dependent variation in nitrogen cycling and soil fungal communities along gradients of forest composition and age in regenerating tropical dry forests.

PubMed

Waring, Bonnie G; Adams, Rachel; Branco, Sara; Powers, Jennifer S

2016-01-01

Rates of ecosystem nitrogen (N) cycling may be mediated by the presence of ectomycorrhizal fungi, which compete directly with free-living microbes for N. In the regenerating tropical dry forests of Central America, the distribution of ectomycorrhizal trees is affected by succession and soil parent material, both of which may exert independent influence over soil N fluxes. In order to quantify these interacting controls, we used a scale-explicit sampling strategy to examine soil N cycling at scales ranging from the microsite to ecosystem level. We measured fungal community composition, total and inorganic N pools, gross proteolytic rate, net N mineralization and microbial extracellular enzyme activity at multiple locations within 18 permanent plots that span dramatic gradients of soil N concentration, stand age and forest composition. The ratio of inorganic to organic N cycling was correlated with variation in fungal community structure, consistent with a strong influence of ectomycorrhiza on ecosystem-scale N cycling. However, on average, > 61% of the variation in soil biogeochemistry occurred within plots, and the effects of forest composition were mediated by this local-scale heterogeneity in total soil N concentrations. These cross-scale interactions demonstrate the importance of a spatially explicit approach towards an understanding of controls on element cycling. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Lunar atmosphere. How surface composition and meteoroid impacts mediate sodium and potassium in the lunar exosphere.

PubMed

Colaprete, A; Sarantos, M; Wooden, D H; Stubbs, T J; Cook, A M; Shirley, M

2016-01-15

Despite being trace constituents of the lunar exosphere, sodium and potassium are the most readily observed species due to their bright line emission. Measurements of these species by the Ultraviolet and Visible Spectrometer (UVS) on the Lunar Atmosphere and Dust Environment Explorer (LADEE) have revealed unambiguous temporal and spatial variations indicative of a strong role for meteoroid bombardment and surface composition in determining the composition and local time dependence of the Moon's exosphere. Observations show distinct lunar day (monthly) cycles for both species as well as an annual cycle for sodium. The first continuous measurements for potassium show a more repeatable variation across lunations and an enhancement over KREEP (Potassium Rare Earth Elements and Phosphorus) surface regions, revealing a strong dependence on surface composition. Copyright © 2016, American Association for the Advancement of Science.

Elemental concentration variations in Plio-Pleistocene sediments from ODP Site 1143 (southern South China Sea) obtained by XRF analyses

NASA Astrophysics Data System (ADS)

Tian, J.; Xie, X.; Jin, H.; Wang, P.; Jian, Z.

2009-12-01

Energy dispersive X-ray fluorescence (XRF) scanning technology provides the most accurate and most economic analytical methods for the determination of major and minor elements of the deep-sea sediment ranging from sodium (11) to uranium (92). Scanning on the smooth core surface by XRF Core scanner is reliable and non-destructive to the sediment, requiring little or no time to prepare the core. This method overcomes the drawback of the traditional analytical method by ICP-AES or ICP-MS which requires long time for sample preparation. Thus, it makes it viable to reconstruct long and high-resolution elemental time series from sediment cores. We have performed relatively elemental concentration analyses on the deep sea sediment cores from ODP site 1143 (southern SCS) down to 190.77 mcd (meters composite depth) by XRF core scanner. The depth resolution of the scanning is 1 cm, equivalent to a time resolution of ~250 years. The age model is based on tuning the benthic foraminiferal d18O at Site 1143 to obliquity and precession (Tian et al., 2002) which indicates that the 190.77 meters long sediment spans the past 5 Myr. We compared the records between 99.5 and 136.46 mcd with the elemental records from the same site obtained by Philips PW 2400 X-ray spectrometer (Wehausen et al., online publication). Comparison reveals, regardless of the absolute changes of the elements, that the elemental records (Si, Ti, Al, Fe, Mn, Ca, K, P, Ba, Rb, Sr) obtained by two methods are nearly the same. Results show that the relative concentration variations of the productivity related elements such as Ba and Ca display distinctive glacial-interglacial cycles for the past 5 Myr. These productivity cycles recorded show one-on-one relationship with the glacial-interglacial cycles of the global ice volume change recorded in the benthic foraminiferal d18O. The glacial-interglacial cycles in productivity and global ice volume changes are consistent with each other not only in amplitude but also in secular variations. The benthic d18O implies the final formation of the northern hemisphere glaciation between ~2.5 Ma and ~3.3 Ma, as indicated by gradually increased values of d18O. During this period, both Ba and Ca show gradually increased values of relative concentration, indicating increased productivity which was probably caused by intensified East Asia summer monsoon. The close relationship of the productivity related elemental variations with benthic foraminiferal d18O reveals that the Plio-Pleistocene variations of the East Asian monsoon have been greatly dominated by global ice volume change. Although the elements related to terrigenous detrital matter composition of site 1143 such as Ti, Fe, As, Co and Ni display distinct glacial-interglacial cycles for the past 5 Myr, they display different patterns in secular variation with that of the benthic foraminiferal d18O. The mismatch indicates that besides northern hemisphere glaciation other multiple processes including changes in provenance and weathering intensity caused by monsoonal climate variability and sea level fluctuations could have affected the terrigenous detrital matter composition of site 1143.

Advanced manufacturing development of a composite empennage component for L-1011 aircraft. Phase 3: Production readiness verification testing

NASA Technical Reports Server (NTRS)

Jackson, A.; Sandifer, J.; Sandorff, P.; Vancleave, R.

1984-01-01

Twenty-two specimens of each of two key structural elements of the Advance Composite Vertical Fin (ACVF) were fabricated and tested. One element represented the front spar at the fuselage attachment area and the other element represented the cover at the fuselage joint area. Ten specimens of each element were selected for static testing. The coefficient of variation resulting from the tests was 3.28 percent for the ten cover specimens and 6.11 percent for the ten spar specimens, which compare well with metallic structures. The remaining twelve cover and twelve spar specimens were durability tested in environmental chambers which permitted the temperature and humidity environment to be cycled as well as the applied loads. Results of the durability tests indicated that such components will survive the service environment.

Modeling and Depletion Simulations for a High Flux Isotope Reactor Cycle with a Representative Experiment Loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandler, David; Betzler, Ben; Hirtz, Gregory John

2016-09-01

The purpose of this report is to document a high-fidelity VESTA/MCNP High Flux Isotope Reactor (HFIR) core model that features a new, representative experiment loading. This model, which represents the current, high-enriched uranium fuel core, will serve as a reference for low-enriched uranium conversion studies, safety-basis calculations, and other research activities. A new experiment loading model was developed to better represent current, typical experiment loadings, in comparison to the experiment loading included in the model for Cycle 400 (operated in 2004). The new experiment loading model for the flux trap target region includes full length 252Cf production targets, 75Se productionmore » capsules, 63Ni production capsules, a 188W production capsule, and various materials irradiation targets. Fully loaded 238Pu production targets are modeled in eleven vertical experiment facilities located in the beryllium reflector. Other changes compared to the Cycle 400 model are the high-fidelity modeling of the fuel element side plates and the material composition of the control elements. Results obtained from the depletion simulations with the new model are presented, with a focus on time-dependent isotopic composition of irradiated fuel and single cycle isotope production metrics.« less

Spatial variability of organic matter molecular composition and elemental geochemistry in surface sediments of a small boreal Swedish lake

NASA Astrophysics Data System (ADS)

Tolu, Julie; Rydberg, Johan; Meyer-Jacob, Carsten; Gerber, Lorenz; Bindler, Richard

2017-04-01

The composition of sediment organic matter (OM) exerts a strong control on biogeochemical processes in lakes, such as those involved in the fate of carbon, nutrients and trace metals. While between-lake spatial variability of OM quality is increasingly investigated, we explored in this study how the molecular composition of sediment OM varies spatially within a single lake and related this variability to physical parameters and elemental geochemistry. Surface sediment samples (0-10 cm) from 42 locations in Härsvatten - a small boreal forest lake with a complex basin morphometry - were analyzed for OM molecular composition using pyrolysis gas chromatography mass spectrometry for the contents of 23 major and trace elements and biogenic silica. We identified 162 organic compounds belonging to different biochemical classes of OM (e.g., carbohydrates, lignin and lipids). Close relationships were found between the spatial patterns of sediment OM molecular composition and elemental geochemistry. Differences in the source types of OM (i.e., terrestrial, aquatic plant and algal) were linked to the individual basin morphometries and chemical status of the lake. The variability in OM molecular composition was further driven by the degradation status of these different source pools, which appeared to be related to sedimentary physicochemical parameters (e.g., redox conditions) and to the molecular structure of the organic compounds. Given the high spatial variation in OM molecular composition within Härsvatten and its close relationship with elemental geochemistry, the potential for large spatial variability across lakes should be considered when studying biogeochemical processes involved in the cycling of carbon, nutrients and trace elements or when assessing lake budgets.

Adhesion characterization and defect sizing of sandwich honeycomb composites.

PubMed

Ndiaye, Elhadji Barra; Maréchal, Pierre; Duflo, Hugues

2015-09-01

Defects may appear in composite structures during their life cycle. A 10MHz 128 elements phased array transducer was investigated to characterize join bonds and defects in sandwich honeycomb composite structures. An adequate focal law throughout the composite skin gives the ultrasonic dispersive properties of the composite skin and glue layer behind. The resulting B-scan cartographies allow characterizing locally the honeycomb adhesion. Experimental measurements are compared in good agreement with the Debye Series Method (DSM). In the processed C-scan image, flaws are detectable and measurable, localized both in the scanning plane and in the thickness of the composite skin. Copyright © 2015 Elsevier B.V. All rights reserved.

Integral blow moulding for cycle time reduction of CFR-TP aluminium contour joint processing

NASA Astrophysics Data System (ADS)

Barfuss, Daniel; Würfel, Veit; Grützner, Raik; Gude, Maik; Müller, Roland

2018-05-01

Integral blow moulding (IBM) as a joining technology of carbon fibre reinforced thermoplastic (CFR-TP) hollow profiles with metallic load introduction elements enables significant cycle time reduction by shortening of the process chain. As the composite part is joined to the metallic part during its consolidation process subsequent joining steps are omitted. In combination with a multi-scale structured load introduction element its form closure function enables to pass very high loads and is capable to achieve high degrees of material utilization. This paper first shows the process set-up utilizing thermoplastic tape braided preforms and two-staged press and internal hydro formed load introduction elements. Second focuses on heating technologies and process optimization. Aiming at cycle time reduction convection and induction heating in regard to the resulting product quality is inspected by photo micrographs and computer tomographic scans. Concluding remarks give final recommendations for the process design in regard to the structural design.

Rare earth elements in the sedimentary cycle - A pilot study of the first leg

NASA Technical Reports Server (NTRS)

Basu, A.; Blanchard, D. P.; Brannon, J. C.

1982-01-01

The effects of source rock composition and climate on the natural abundances of rare elements (REE) in the first leg of the sedimentary cycle are evaluated using a study with Holocene fluvia sands. The medium grained sand fraction of samples collected from first order streams exclusively draining granitic plutons in Montana (semi-arid), Georgia (humid), and South Carolina (humid) are analyzed. It is found that the REE distribution patterns (but not the total absolute abundances) of the daughter sands are very similar, despite compositional differences between parent plutons. Averages of the three areas are determined to have a La/Lu ratio of about 103, showing a depletion of heavy REE with respect to an average granite (La/Lu = 79) or the composition of North American Shales (La/Lu = 55). However, the Eu/Sm ratio in sands from these areas is about 0.22, which is very close to this ratio in North American Shales (0.21), although the overall REE distribution of these sands is not similar to that of the North American Shales in any way. It is concluded that the major rock type, but neither its minor subdivisions nor the climate, controls the REE distribution patterns in first cycle daughter sands, although the total and the parent rock-normalized abundances of REE in sands from humid areas are much lower than those in sands from arid areas.

Fatigue Analysis of Notched Laminates: A Time-Efficient Macro-Mechanical Approach

NASA Technical Reports Server (NTRS)

Naghipour, P.; Pineda, E. J.; Bednarcyk, B. A.; Arnold, S. M.; Waas, A. M.

2016-01-01

A coupled transversely isotropic deformation and damage fatigue model is implemented within the finite element method and was utilized along with a static progressive damage model to predict the fatigue life, stiffness degradation as a function of number of cycles, and post-fatigue tension and compression response of notched, multidirectional laminates. Initially, the material parameters for the fatigue model were obtained utilizing micromechanics simulations and the provided [0], [90] and [plus or minus 45] experimental composite laminate S-N (stress-cycle) data. Within the fatigue damage model, the transverse and shear properties of the plies were degraded with an isotropic scalar damage variable. The damage in the longitudinal (fiber) ply direction was suppressed, and only the strength of the fiber was degraded as a function of fatigue cycles. A maximum strain criterion was used to capture the failure in each element, and once this criterion was satisfied, the longitudinal stiffness of the element was decreased by a factor of 10 (sup 4). The resulting, degraded properties were then used to calculate the new stress state. This procedure was repeated until final failure of the composite laminate was achieved or a specified number of cycles reached. For post-fatigue tension and compression behavior, four internal state variables were used to control the damage and failure. The predictive capability of the above-mentioned approach was assessed by performing blind predictions of the notched multidirectional IM7/977-3 composite laminates response under fatigue and post-fatigue tensile and compressive loading, followed by a recalibration phase. Although three different multidirectional laminates were analyzed in the course of this study, only detailed results (i.e., stiffness degradation and post-fatigue stress-train curves as well as damage evolution states for a single laminate ([30/60/90/minus 30/minus 60] (sub 2s)) are discussed in detail here.

Environmental, mechanical and life-cycle cost analysis of bridge columns.

DOT National Transportation Integrated Search

2014-08-01

Corrosion of RC bridge element is one of the major deterioration distresses in US Highway Bridges. FRP composites jackets can be : the economic and effective corrosion repair in future, though its practices and field installation as a means of corros...

Non-volatile copolymer compositions for fabricating gel element microarrays

PubMed Central

Golova, Julia B.; Chernov, Boris K.; Perov, Alexander N.; Reynolds, Jennifer; Linger, Yvonne L.; Kukhtin, Alexander; Chandler, Darrell P.

2011-01-01

By modifying polymer compositions and cross-linking reagents, we have developed a simple yet effective manufacturing strategy for copolymerized three-dimensional gel element arrays. A new gel-forming monomer (2-(hydroxyethyl) methacrylamide; HEMAA) was used that possesses low volatility and improves the stability of copolymerized gel element arrays to on-chip thermal cycling procedures relative to previously used monomers. Probe immobilization efficiency within the new polymer was 55%, equivalent to that obtained with acrylamide (AA) and methacrylamide (MA) monomers. Non-specific binding of single stranded targets was equivalent for all monomers. Increasing cross-linker chain length improved hybridization kinetics and end-point signal intensities relative to N,N-methylenebisacrylamide (Bis). The new copolymer formulation was successfully applied to a model orthopox array. Because HEMAA greatly simplifies gel element array manufacture, we expect it (in combination with new cross-linkers described herein) to find widespread application in microarray science. PMID:22033291

Modelling of Fiber/Matrix Debonding of Composites Under Cyclic Loading

NASA Technical Reports Server (NTRS)

Naghipour, Paria; Pineda, Evan J.; Bednarcyk, Brett A.; Arnold, Steven M.

2013-01-01

The micromechanics theory, generalized method of cells (GMC), was employed to simulate the debonding of fiber/matrix interfaces, within a repeating unit cell subjected to global, cyclic loading, utilizing a cyclic crack growth law. Cycle dependent, interfacial debonding was implemented as a new module to the available GMC formulation. The degradation of interfacial stresses, with applied load cycles, was achieved via progressive evolution of the interfacial compliance. A periodic repeating unit cell, representing the fiber/matrix architecture of a composite, was subjected to combined normal and shear loadings, and degradation of the global transverse stress in successive cycles was monitored. The obtained results were compared to values from a corresponding finite element model. Reasonable agreement was achieved for combined normal and shear loading conditions, with minimal variation for pure loading cases. The local effects of interfacial debonding, and fatigue damage will later be combined as sub-models to predict the experimentally obtained fatigue life of Ti-15-3/Sic composites at the laminate level.

Geochemical and isotopic (Nd-Pb-Sr-O) variations bearing on the genesis of volcanic rocks from Vesuvius, Italy

USGS Publications Warehouse

Ayuso, R.A.; de Vivo, B.; Rolandi, G.; Seal, R.R.; Paone, A.

1998-01-01

Alkaline volcanism produced by Monte Somma-Vesuvius volcano includes explosive plinian and subplinian activity in addition to effusive lava flows. Pumice, scoria, and lava (150 samples) exhibit major- and trace-element gradients as a function of SiO2 (58.9-47.2 wt%) and MgO (0-7.8 wt%); Mg value are ???50. Internally gradational chemical groups or cycles are distinguished by age: (1) 25 000 to 14 000 yr B.P.; (2) 8000 yr B.P. to A.D. 79; and (3) A.D. 79 to 1944. A small number of lavas, dikes and scora were also analysed from the Somma formation (~ 35 000 to 25 000 yr B.P.). Within each group, contents of Na2O + K2O increas with decreasing MgO along distinct rocks. Nb/Y values are variable from 0.66 to 3.14 (at SiO2 ??? 50 wt%) generally in the range of alkaline and ultra-alkaline rocks. Variations in contents of some majro elements (e.g., P and Ti), and trace elements (e.g., Th, Nb, Ta, Zr, Hf, Pb, La, and Sc), as well as contrasting trends in ratios of various elements (e.g., Ta/Yb, Hf/U, Th/Ta, Th/Hf, Th/Yb, etc.) are also generally consistent with the group subdivisions. For example, Th/Hf increases from ??? 5 to ??? 10 with decreasing age for the Vesuvius system as a whole, yielding similar compositions in the least evolved rocks (low-silica, high-MgO, imcompatible element-poor) erupted at the end of each cycle. Internal variations within individual eruptions also systematically changed generally towards a common mafic composition at the end of each cycle, thus reflecting the dominanit volume in the magma chamber. At the start of a new eruptive cycle, the rocks are relatively enriched in incompatible elements; younger groups also contain higher abundances than other groups. N-MORB-normalized multielement diagrams exhibit selective enrichments of Sr, K, Rb, Th, and the light rare-earth elements; deep Nb and Ta negative anomalies commonly seen in rocks generated at orogenic margins are absent in the light rare-earth elements; deep Nb and Ta netgative anomalies commonly seen in rocks generated at orogenic margins are absent in our samples. Sr isotopic compositions are known to be variable within some of the units, in agreement with our data (87Sr/86Sr ~ 0.70699 to 0.70803) and with contributions from several isotopic components. Isotopic compositions for ??18O (7.3 to 10.2%), Pb for mineral separates and whole rocks (206Pb/204Pb ~ 18.947 to 19.178, 207Pb/204/Pb ~ 15.617 to 15.769, 208Pb/204Pb ~38.915 to 39.345), and Nd (143Nd ~ 0.51228 to 0.51251) also show variability. Oxygen isotope data show that pumices have higher ??18O values than cogenetic lavas, and that ??18O values and SiO2 are correlated. Radiogenic and stable isotope data plot within range of isotopic compositions for the Roman comagmatic province. Fractional crystallization cannot account for the radiogenic isotopic compositions of the Vesuvius magmas. We favor instead the combined effects of heterogeneous magma sources, together with isotopic exchange near the roof of the magma chamber. We suggest that metasomatized continental mantle lithosphere is the principal source of the magmas. This kind of enriched mantle was melted and reactivated in an area of continental extension (incipient rift setting) without direct reliance on contemporaneous subduction processes but possibly with input from mantle sources that resemble those that produce ocean island basalts.

Finite Element Modeling of Fragment Penetration of Thin Structural Composite Laminates

DTIC Science & Technology

1991-12-01

his direction and assistance provided during the program. The following are registered trade names: Kevlar-29, 3M Co., Scotchply, Owens Corning Fiberglass...grains, are used. Composite laminates such as Owens Corning Fiberglass (R) panels, 3M Scotchply 1002 (R) panels and Kevlar-29 (R) reinforced plastic...results [2]: 1. Owens Corning Fiberglass (OCF) Structural Panels. Woven S-2 glass and a typical resin type, contert, sizing, and cure cycle at 220

Biogeochemical Mg cycle in the Barton Peninsula, King George Island, West Antarctica

NASA Astrophysics Data System (ADS)

Choi, H. B.; Ryu, J. S.; Lee, J.; Lim, H. S.; Yoon, H.

2016-12-01

Understanding of biogeochemical Mg cycle is important in terms of plant growth as well as global climate because Mg participates in numerous biogeochemical processes. Here, we collected rock, soil, water and moss samples in the Barton peninsula, King George Island, West Antarctica, and measured their elemental and Mg isotope compositions in order to quantify and understand the biogeochemical processes of the Mg cycle. Elemental results show that the input of seawater derived Mg mainly controls dissolved Mg in meltwater. Mg isotope compositions in rocks and soils are consistent within the error, -0.03 ± 0.15‰ (n=6) and +0.03 ± 0.07‰ (n=8), respectively. However, δ26Mg values of meltwater and moss are -0.69 ± 0.09‰ (n=34) and -0.46 ± 0.19‰ (n=16), respectively, indicating that mosses display higher δ26Mg values compared to meltwater they uptake. This implies an isotope fractionation in favor of heavy isotopes during moss growth. The apparent Mg isotope fractionation between moss and meltwater (Δ26Mgmoss-meltwater) ranges from 0.02‰ to 0.55‰, with an average of +0.29‰ (n=6), which is within the range previously reported during higher plant growth. Our finding suggests that enhanced plant growth in Arctic and Antarctica due to climate change and global warming may play an important role in the biogeochemical Mg cycle globally.

Hierarchical sulfur-based cathode materials with long cycle life for rechargeable lithium batteries.

PubMed

Wang, Jiulin; Yin, Lichao; Jia, Hao; Yu, Haitao; He, Yushi; Yang, Jun; Monroe, Charles W

2014-02-01

Composite materials of porous pyrolyzed polyacrylonitrile-sulfur@graphene nanosheet (pPAN-S@GNS) are fabricated through a bottom-up strategy. Microspherical particles are formed by spray drying of a mixed aqueous colloid of PAN nanoparticles and graphene nanosheets, followed by a simple heat treatment with elemental sulfur. The pPAN-S primary nanoparticles are wrapped homogeneously and loosely within a three-dimensional network of graphene nanosheets (GNS). The hierarchical pPAN-S@GNS composite shows a high reversible capacity of 1449.3 mAh g(-1) sulfur or 681.2 mAh g(-1) composite in the second cycle; after 300 cycles at a 0.2 C charge/discharge rate the capacity retention is 88.8 % of its initial reversible value. Additionally, the coulombic efficiency (CE) during cycling is near 100 %, apart from in the first cycle, in which CE is 81.1 %. A remarkable capacity of near 700 mAh g(-1) sulfur is obtained, even at a high discharge rate of 10 C. The superior performance of pPAN-S@GNS is ascribed to the spherical secondary GNS structure that creates an electronically conductive 3D framework and also reinforces structural stability. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Pengfei; Nie, Anmin; Zheng, Jianming

Voltage and capacity fading of layer structured lithium and manganese rich (LMR) transition metal oxide is directly related to the structural and composition evolution of the material during the cycling of the battery. However, understanding such evolution at atomic level remains elusive. Based on atomic level structural imaging, elemental mapping of the pristine and cycled samples and density functional theory calculations, it is found that accompanying the hoping of Li ions is the simultaneous migration of Ni ions towards the surface from the bulk lattice, leading to the gradual depletion of Ni in the bulk lattice and thickening of amore » Ni enriched surface reconstruction layer (SRL). Furthermore, Ni and Mn also exhibit concentration partitions within the thin layer of SRL in the cycled samples where Ni is almost depleted at the very surface of the SRL, indicating the preferential dissolution of Ni ions in the electrolyte. Accompanying the elemental composition evolution, significant structural evolution is also observed and identified as a sequential phase transition of C2/m →I41→Spinel. For the first time, it is found that the surface facet terminated with pure cation is more stable than that with a mixture of cation and anion. These findings firmly established how the elemental species in the lattice of LMR cathode transfer from the bulk lattice to surface layer and further into the electrolyte, clarifying the long standing confusion and debate on the structure and chemistry of the surface layer and their correlation with the voltage fading and capacity decaying of LMR cathode. Therefore, this work provides critical insights for designing of cathode materials with both high capacity and voltage stability during cycling.« less

Germanium and Tin Based Anode Materials for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Ji, Dongsheng

The discovery of safe anode materials with high energy density for lithium-ion batteries has always been a significant topic. Group IV elements have been under intensive study for their high capability of alloying with lithium. Batteries with graphite and tin based anode material have already been applied in cell phones and vehicles. In order to apply group IV elements, their dramatic volume change during lithiation and delithiation processes is the key point to work on. Reducing the particle size is the most common method to buffer the volume expansion. This strategy has been applied on both germanium and tin based materials. Germanium based anode material has been made by two different synthesis methods. The amorphous Ge-C-Ti composite material was made by ball milling method and performed much better than other germanium alloy including Ge-Mg, Ge-Fe and Ge-Fe.Germanium sphere nano particles with diameter of around 50 nm have been made by solution method. After ball milled with graphite, the resulted product performed stable capacity over 500 mAh˙g-1 for more than 20 cycles. Ball milled graphite in the composite plays an important role of buffering volume change and stabilizing germanium. Sn-Fe alloy is one of the feasible solutions to stabilize tin. Sn 2Fe-C composite has been made by ball milling method. After optimizations of the ratio of precursors, reaction time, milling balls and electrolyte additives, the electrochemistry performance was improved. The anode performed 420 mAh˙ -1 at 1.0 mA/cm2 and maintained its structure after cycling at 2.0 mA/cm2. At 0.3 mA/cm2 cycling rate, the anode performed 978 mAh/cm3 after 500 cycles, which still exceeds the theoretical capacity of graphite.

URANIUM COMPOSITIONS

DOEpatents

Allen, N.P.; Grogan, J.D.

1959-05-12

This patent relates to high purity uranium alloys characterized by improved stability to thermal cycling and low thermal neutron absorption. The high purity uranium alloy contains less than 0.1 per cent by weight in total amount of any ore or more of the elements such as aluminum, silicon, phosphorous, tin, lead, bismuth, niobium, and zinc.

Elemental composition and functional groups in soil labile organic matter fractions

USDA-ARS?s Scientific Manuscript database

Labile organic matter fractions are major components involved in nutrient cycle in soil. In this chapter, we examine three labile organic matter fraction: light fraction (LF), humic acid (HA) and fulvic acid (HA) in Alabama cotton soils (ultisol) amended with chemical fertilizer (NH4NO3) and poult...

Optimal cure cycle design of a resin-fiber composite laminate

NASA Technical Reports Server (NTRS)

Hou, Jean W.; Sheen, Jeenson

1987-01-01

A unified computed aided design method was studied for the cure cycle design that incorporates an optimal design technique with the analytical model of a composite cure process. The preliminary results of using this proposed method for optimal cure cycle design are reported and discussed. The cure process of interest is the compression molding of a polyester which is described by a diffusion reaction system. The finite element method is employed to convert the initial boundary value problem into a set of first order differential equations which are solved simultaneously by the DE program. The equations for thermal design sensitivities are derived by using the direct differentiation method and are solved by the DE program. A recursive quadratic programming algorithm with an active set strategy called a linearization method is used to optimally design the cure cycle, subjected to the given design performance requirements. The difficulty of casting the cure cycle design process into a proper mathematical form is recognized. Various optimal design problems are formulated to address theses aspects. The optimal solutions of these formulations are compared and discussed.

Hard-Soft Composite Carbon as a Long-Cycling and High-Rate Anode for Potassium-Ion Batteries

DOE PAGES

Jian, Zelang; Hwang, Sooyeon; Li, Zhifei; ...

2017-05-05

There exist tremendous needs for sustainable storage solutions for intermittent renewable energy sources, such as solar and wind energy. Thus, systems based on Earth-abundant elements deserve much attention. Potassium-ion batteries represent a promising candidate because of the abundance of potassium resources. As for the choices of anodes, graphite exhibits encouraging potassium-ion storage properties; however, it suffers limited rate capability and poor cycling stability. Here in this paper, nongraphitic carbons as K-ion anodes with sodium carboxymethyl cellulose as the binder are systematically investigated. Compared to hard carbon and soft carbon, a hard–soft composite carbon with 20 wt% soft carbon distributed inmore » the matrix phase of hard carbon microspheres exhibits highly amenable performance: high capacity, high rate capability, and very stable long-term cycling. In contrast, pure hard carbon suffers limited rate capability, while the capacity of pure soft carbon fades more rapidly.« less

Hard-Soft Composite Carbon as a Long-Cycling and High-Rate Anode for Potassium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jian, Zelang; Hwang, Sooyeon; Li, Zhifei

There exist tremendous needs for sustainable storage solutions for intermittent renewable energy sources, such as solar and wind energy. Thus, systems based on Earth-abundant elements deserve much attention. Potassium-ion batteries represent a promising candidate because of the abundance of potassium resources. As for the choices of anodes, graphite exhibits encouraging potassium-ion storage properties; however, it suffers limited rate capability and poor cycling stability. Here in this paper, nongraphitic carbons as K-ion anodes with sodium carboxymethyl cellulose as the binder are systematically investigated. Compared to hard carbon and soft carbon, a hard–soft composite carbon with 20 wt% soft carbon distributed inmore » the matrix phase of hard carbon microspheres exhibits highly amenable performance: high capacity, high rate capability, and very stable long-term cycling. In contrast, pure hard carbon suffers limited rate capability, while the capacity of pure soft carbon fades more rapidly.« less

Understanding spatial heterogeneity in soil carbon and nitrogen cycling in regenerating tropical dry forests

NASA Astrophysics Data System (ADS)

Waring, B. G.; Powers, J. S.; Branco, S.; Adams, R.; Schilling, E.

2015-12-01

Tropical dry forests (TDFs) currently store significant amounts of carbon in their biomass and soils, but these highly seasonal ecosystems may be uniquely sensitive to altered climates. The ability to quantitatively predict C cycling in TDFs under global change is constrained by tremendous spatial heterogeneity in soil parent material, land-use history, and plant community composition. To explore this variation, we examined soil carbon and nitrogen dynamics in 18 permanent plots spanning orthogonal gradients of stand age and soil fertility. Soil C and N pools, microbial biomass, and microbial extracellular enzyme activities were most variable at small (m2) spatial scales. However, the ratio of organic vs. inorganic N cycling was consistently higher in forest stands dominated by slow-growing, evergreen trees that associate with ectomycorrhizal fungi. Similarly, although bulk litter stocks and turnover rates varied greatly among plots, litter decomposition tended to be slower in ectomycorrhizae-dominated stands. Soil N cycling tended to be more conservative in older plots, although the relationship between stand age and element cycling was weak. Our results emphasize that microscale processes, particularly interactions between mycorrhizal fungi and free-living decomposers, are important controls on ecosystem-scale element cycling.

Micromechanics, Fracture Mechanics and Gas Permeability of Composite Laminates for Cryogenic Storage Systems

NASA Technical Reports Server (NTRS)

Choi, Sukjoo; Sankar, Bhavani; Ebaugh, Newton C.

2005-01-01

A micromechanics method is developed to investigate microcrack propagation in a liquid hydrogen composite tank at cryogenic temperature. The unit cell is modeled using square and hexagonal shapes depends on fiber and matrix layout from microscopic images of composite laminates. Periodic boundary conditions are applied to the unit cell. The temperature dependent properties are taken into account in the analysis. The laminate properties estimated by the micromechanics method are compared with empirical solutions using constituent properties. The micro stresses in the fiber and matrix phases based on boundary conditions in laminate level are calculated to predict the formation of microcracks in the matrix. The method is applied to an actual liquid hydrogen storage system. The analysis predicts micro stresses in the matrix phase are large enough to cause microcracks in the composite. Stress singularity of a transverse crack normal to a ply-interface is investigated to predict the fracture behavior at cryogenic conditions using analytical and finite element analysis. When a transverse crack touches a ply-interface of a composite layer with same fiber orientation, the stress singularity is equal to 1/2. When the transverse crack propagates to a stiffer layer normal to the ply-direction, the singularity becomes less than 1/2 and vice versa. Finite element analysis is performed to predict the fracture toughness of a laminated beam subjected to fracture loads measured by four-point bending tests at room and cryogenic temperatures. As results, the fracture load at cryogenic temperature is significantly lower than that at room temperature. However, when thermal stresses are taken into consideration, for both cases of room and cryogenic temperatures, the difference of the fracture toughness becomes insignificant. The result indicates fracture toughness is a characteristic property, which is independent to temperature changes. The experimental analysis is performed to investigate the effect of cryogenic cycling on permeability for various composite material systems. Textile composites have lower permeability than laminated composites even with increasing number of cryogenic cycle. Nano-particles dispersed in laminated composites do not show improvement on permeability. The optical inspection is performed to investigate the microcrack propagation and void content in laminated composites and compared the microscopic results before and after cryogenic cycling.

VARIATIONS IN SOLAR WIND FRACTIONATION AS SEEN BY ACE/SWICS AND THE IMPLICATIONS FOR GENESIS MISSION RESULTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pilleri, P.; Wiens, R. C.; Reisenfeld, D. B.

We use Advanced Composition Explorer (ACE)/Solar Wind Ion Composition Spectrometer (SWICS) elemental composition data to compare the variations in solar wind (SW) fractionation as measured by SWICS during the last solar maximum (1999–2001), the solar minimum (2006–2009), and the period in which the Genesis spacecraft was collecting SW (late 2001—early 2004). We differentiate our analysis in terms of SW regimes (i.e., originating from interstream or coronal hole flows, or coronal mass ejecta). Abundances are normalized to the low-first ionization potential (low-FIP) ion magnesium to uncover correlations that are not apparent when normalizing to high-FIP ions. We find that relative tomore » magnesium, the other low-FIP elements are measurably fractionated, but the degree of fractionation does not vary significantly over the solar cycle. For the high-FIP ions, variation in fractionation over the solar cycle is significant: greatest for Ne/Mg and C/Mg, less so for O/Mg, and the least for He/Mg. When abundance ratios are examined as a function of SW speed, we find a strong correlation, with the remarkable observation that the degree of fractionation follows a mass-dependent trend. We discuss the implications for correcting the Genesis sample return results to photospheric abundances.« less

COARSEMAP: synthesis of observations and models for coarse-mode aerosols

NASA Astrophysics Data System (ADS)

Wiedinmyer, C.; Lihavainen, H.; Mahowald, N. M.; Alastuey, A.; Albani, S.; Artaxo, P.; Bergametti, G.; Batterman, S.; Brahney, J.; Duce, R. A.; Feng, Y.; Buck, C.; Ginoux, P. A.; Chen, Y.; Guieu, C.; Cohen, D.; Hand, J. L.; Harrison, R. M.; Herut, B.; Ito, A.; Losno, R.; Gomez, D.; Kanakidou, M.; Landing, W. M.; Laurent, B.; Mihalopoulos, N.; Mackey, K.; Maenhaut, W.; Hueglin, C.; Milando, C.; Miller, R. L.; Myriokefaitakis, S.; Neff, J. C.; Pandolfi, M.; Paytan, A.; Perez Garcia-Pando, C.; Prank, M.; Prospero, J. M.; Tamburo, E.; Varrica, D.; Wong, M.; Zhang, Y.

2017-12-01

Coarse mode aerosols influence Earth's climate and biogeochemistry by interacting with long-wave radiation, promoting ice nucleation, and contributing important elements to biogeochemical cycles during deposition. Yet coarse mode aerosols have received less emphasis in the scientific literature. Here we present first efforts to globally synthesize available mass concentration, composition and optical depth data and modeling for the coarse mode aerosols (<10 µm) in a new project called "COARSEMAP" (http://www.geo.cornell.edu/eas/PeoplePlaces/Faculty/mahowald/COARSEMAP/). We seek more collaborators who have observational data, especially including elemental or composition data, and/or who are interested in detailed modeling of the coarse mode. The goal will be publications synthesizing data with models, as well as providing synthesized results to the wider community.

Numerical model for an epoxy beam reinforced with superelastic shape memory alloy wires

NASA Astrophysics Data System (ADS)

Viet, N. V.; Zaki, W.; Umer, R.

2018-03-01

We present a numerical solution for a smart composite beam consisting of an epoxy matrix reinforced with unidirectional superelastic shape memory alloy (SMA) fibers with uniform circular cross section. The beam is loaded by a tip load, which is then removed resulting in shape recovery due to superelasticity of the SMA wires. The analysis is carried out considering a representative volume element (RVE) of the beam consisting of one SMA wire embedded in epoxy. The analytical model is developed for a superelastic SMA/epoxy composite beam subjected to a complete loading cycle in bending. Using the proposed model, the moment-curvature profile, martensite volume fraction variation, and axial stress are determined. The results are validated against three-dimensional finite element analysis (3D FEA) for the same conditions. The proposed work is a contribution toward better understanding of the bending behavior of superelastic SMA-reinforced composites.

FIP effect for minor heavy solar wind ions as seen with SOHO/CELIAS/MTOF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heidrich-Meisner, Verena, E-mail: heidrich@physik.uni-kiel.de; Berger, Lars; Wimmer-Schweingruber, Robert F.

A recent paper [Shearer et al., 2014] reported that during solar maximum Ne showed a surprisingly low abundance. This leads to the question whether other elements show the same behavior. The good mass resolution of Mass-Time-Of-Flight (MTOF) as part of the Charge ELement and Isotope Analysis System (CELIAS) on the Solar Helioshperic Observatory (SOHO) allows to investigate the composition of heavy minor elements in different types of solar wind. We restrict this study to slow solar wind, where the characterisation of slow solar wind is taken from Xu and Borovsky, 2014. This classification scheme requires magnet field information. Since SOHOmore » does not carry a magnetometer, we use the Magnetometer (MAG) of the Advanced Composition Explorer (ACE) instead. The Solar Wind Ion Composition Spectrometer (ACE/SWICS) also provides composition data for cross-calibration and charge-state distributions as input for the transmission function of MTOF whenever the two spacecraft can be expected to observe the same type of wind. We illustrate the MTOF’s capability to determine the solar wind abundance compared to the photospheric abundance (called the FIP ratio in the following) for rare elements like Ti or Cr on long-time scales as a proof of concept for our analysis. And in this brief study, measurements with both ACE/SWICS indicate that the observed elements exhibit a (weak) dependence on the solar cycle, whereas the MTOF measurements are inconclusive.« less

Evaluation of different approaches for improving the cycle life of MgNi-based electrodes for Ni-MH batteries

NASA Astrophysics Data System (ADS)

Rongeat, C.; Grosjean, M.-H.; Ruggeri, S.; Dehmas, M.; Bourlot, S.; Marcotte, S.; Roué, L.

Several methods have been investigated to enhance the cycle life of amorphous MgNi used as the negative electrode for Ni-MH batteries. The first approach involves modifying its surface composition in different ways, including the electroless deposition of a chromate conversion coating, the addition of chromate salt or NaF into the electrolyte and the mechanical coating of the particles with various compounds (e.g. TiO 2). Another approach consists of developing (MgNi + AB 5) composite materials. However, the cycle life of these modified MgNi electrodes remains unsatisfactory. On the other hand, the modification of the bulk composition of the MgNi alloy with elements such as Ti and Al appears to be more effective. For instance, a Mg 0.9Ti 0.1NiAl 0.05 electrode retains 67% of its initial discharge capacity (404 mAh g -1) after 15 cycles compared to 29% for MgNi. The charging conditions also have a great influence on the electrode cycle life as demonstrated by the existence of a charge input threshold below which minor capacity decay occurs. In addition, the particle size has a major influence on the electrode performance. We have developed an optimized electrode constituted of Mg 0.9Ti 0.1NiAl 0.05 particles with the appropriate size (>150 μm) showing a capacity decay rate as low as ∼0.2% per cycle when charged at 300 mAh g -1.

Statistical clumped isotope signatures

PubMed Central

Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

2016-01-01

High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

Ultrasmall TiO2-Coated Reduced Graphene Oxide Composite as a High-Rate and Long-Cycle-Life Anode Material for Sodium-Ion Batteries.

PubMed

Liu, Yao; Liu, Jingyuan; Bin, Duan; Hou, Mengyan; Tamirat, Andebet Gedamu; Wang, Yonggang; Xia, Yongyao

2018-05-02

Because of the low cost and abundant nature of the sodium element, sodium-ion batteries (SIBs) are attracting extensive attention, and a variety of SIB cathode materials have been discovered. However, the lack of high-performance anode materials is a major challenge of SIBs. Herein, we have synthesized ultrasmall TiO 2 -nanoparticle-coated reduced graphene oxide (TiO 2 @RGO) composites by using a one-pot hydrolysis method, which are then investigated as anode materials for SIBs. The morphology of TiO 2 @RGO has been characterized using transmission electron microscopy, indicating that the TiO 2 nanospheres uniformly grow on the surface of the RGO nanosheet. As-prepared TiO 2 @RGO composites exhibited a promising electrochemical performance in terms of cycling stability and rate capability, especially the initial cycle Coulombic efficiency of 60.7%, which is higher than that in previous reports. The kinetics of the electrode reaction has been investigated by cyclic voltammetry. The results indicate that the sodium-ion intercalation/extraction behavior is not controlled by the semiinfinite diffusion process, which gives rise to an outstanding rate performance. In addition, the electrochemical performance of TiO 2 @RGO composites in full cells, coupled with carbon-coated Na 3 V 2 (PO 4 ) 3 as the positive material, has been investigated. The discharge specific capacity was up to 117.2 mAh g -1 , and it remained at 84.6 mAh g -1 after 500 cycles under a current density of 2 A g -1 , which shows excellent cycling stability.

The General Laws of Chemical Elements Composition Dynamics in the Biosphere

NASA Astrophysics Data System (ADS)

Korzh, Vyacheslav D.

2013-04-01

The key point of investigation of the specificity of the biosphere elemental composition formation is determination of patterns of redistribution of elemental average concentrations among various phases, like solid - liquid ( the lithosphere - the hydrosphere), which occurs as a result of a global continuous processing of inert matter by living substances. Our task here is to investigate this process in the system "lithosphere - hydrosphere" in view of the integrated involvement of living material in it. This process is most active in biogeochemical barriers, i.e. in places of "the life condensation" and runs under a nonlinear regularity that has been unknown before. It is established that this process results in a general relative increase in concentrations of chemical elements in the solid phase in proportion as their prevalence in the environment is reduced. This process running in various natural systems has practically the same parameter of nonlinearity (v) approximately equal to 0.7. For proto-lithosphere -"living material" - soil v = 0.75. For river - "living material" - ocean v = 0.67. For the contemporary factual awareness level these estimations of nonlinearity indices are practically negligible. Hence, it is for the first time that the existence of a universal constant of nonlinearity of elemental composition evolution in the biosphere has been proved and its quantitative evaluation has been made. REFERENCES 1. Korzh V.D. 1974. Some general laws governing the turnover of substance within the ocean-atmosphere-continent-ocean cycle. // Journal de Recherches Atmospheriques. Vol. 8. P. 653-660. 2. Korzh V.D. 2008. The general laws in the formation of the elemental composition of the Hydrosphere and Biosphere.// J. Ecologica, Vol. XV, P. 13-21. 3. Korzh V.D. 2012. Determination of general laws of elemental composition in Hydrosphere // Water: chemistry & ecology, Journal of water science and its practical application. # 1, P.56-62.

Elemental economy: microbial strategies for optimizing growth in the face of nutrient limitation.

PubMed

Merchant, Sabeeha S; Helmann, John D

2012-01-01

Microorganisms play a dominant role in the biogeochemical cycling of nutrients. They are rightly praised for their facility for fixing both carbon and nitrogen into organic matter, and microbial driven processes have tangibly altered the chemical composition of the biosphere and its surrounding atmosphere. Despite their prodigious capacity for molecular transformations, microorganisms are powerless in the face of the immutability of the elements. Limitations for specific elements, either fleeting or persisting over eons, have left an indelible trace on microbial genomes, physiology, and their very atomic composition. We here review the impact of elemental limitation on microbes, with a focus on selected genetic model systems and representative microbes from the ocean ecosystem. Evolutionary adaptations that enhance growth in the face of persistent or recurrent elemental limitations are evident from genome and proteome analyses. These range from the extreme (such as dispensing with a requirement for a hard to obtain element) to the extremely subtle (changes in protein amino acid sequences that slightly, but significantly, reduce cellular carbon, nitrogen, or sulfur demand). One near-universal adaptation is the development of sophisticated acclimation programs by which cells adjust their chemical composition in response to a changing environment. When specific elements become limiting, acclimation typically begins with an increased commitment to acquisition and a concomitant mobilization of stored resources. If elemental limitation persists, the cell implements austerity measures including elemental sparing and elemental recycling. Insights into these fundamental cellular properties have emerged from studies at many different levels, including ecology, biological oceanography, biogeochemistry, molecular genetics, genomics, and microbial physiology. Here, we present a synthesis of these diverse studies and attempt to discern some overarching themes. Copyright © 2012 Elsevier Ltd. All rights reserved.

Elemental Economy: microbial strategies for optimizing growth in the face of nutrient limitation

PubMed Central

Merchant, Sabeeha S.; Helmann, John D.

2014-01-01

Microorganisms play a dominant role in the biogeochemical cycling of nutrients. They are rightly praised for their facility at fixing both carbon and nitrogen into organic matter, and microbial driven processes have tangibly altered the chemical composition of the biosphere and its surrounding atmosphere. Despite their prodigious capacity for molecular transformations, microorganisms are powerless in the face of the immutability of the elements. Limitations for specific elements, either fleeting or persisting over eons, have left an indelible trace on microbial genomes, physiology, and their very atomic composition. We here review the impact of elemental limitation on microbes, with a focus on selected genetic model systems and representative microbes from the ocean ecosystem. Evolutionary adaptations that enhance growth in the face of persistent or recurrent elemental limitations are evident from genome and proteome analyses. These range from the extreme (such as dispensing with a requirement for a hard to obtain element) to the extremely subtle (changes in protein amino acid sequences that slightly, but significantly, reduce cellular carbon, nitrogen, or sulfur demand). One near universal adaptation is the development of sophisticated acclimation programs by which cells adjust their chemical composition in response to a changing environment. When specific elements become limiting, acclimation typically begins with an increased commitment to acquisition and a concomitant mobilization of stored resources. If elemental limitation persists, the cell implements austerity measures including elemental-sparing and elemental-recycling. Insights into these fundamental cellular properties have emerged from studies at many different levels; including ecology, biological oceanography, biogeochemistry, molecular genetics, genomics, and microbial physiology. Here, we present a synthesis of these diverse studies and attempt to discern some overarching themes. PMID:22633059

VICI (Venus In Situ Composition Investigations): The Next Step in Understanding Venus Climate Evolution

NASA Astrophysics Data System (ADS)

Glaze, L. S.; Garvin, J. B.

2017-12-01

Venus provides a natural laboratory to explore an example of terrestrial planet evolution that may be cosmically ubiquitous. By better understanding the composition of the Venus atmosphere and surface, we can better constrain the efficiency of the Venusian greenhouse. VICI is a proposed NASA New Frontiers mission that delivers two landers to Venus on two separate Venus fly-bys. Following six orbital remote sensing missions to Venus (since 1978), VICI would be the first mission to land on the Venus surface since 1985, and the first U.S. mission to enter the Venus atmosphere in 49 years. The four major VICI science objectives are: Atmospheric origin and evolution: Understand the origin of the Venus atmosphere, how it has evolved, including how recently Venus lost its oceans, and how and why it is different from the atmospheres of Earth and Mars, through in situ measurements of key noble gases, nitrogen, and hydrogen. Atmospheric composition and structure: Reveal the unknown chemical processes and structure in Venus' deepest atmosphere that dominate the current climate through two comprehensive, in situ vertical profiles. Surface properties and geologic evolution: For the first time ever, explore the tessera from the surface, specifically to test hypotheses of ancient content-building cycles, erosion, and links to past climates using multi-point mineralogy, elemental chemistry, imaging and topography. Surface-atmosphere interactions: Characterize Venus' surface weathering environment and provide insight into the sulfur cycle at the surface-atmosphere interface by integrating rich atmospheric composition and structure datasets with imaging, surface mineralogy, and elemental rock composition. VICI is designed to study Venus' climate history through detailed atmospheric composition measurements not possible on earlier missions. In addition, VICI images the tessera surface during descent enabling detailed topography to be generated. Finally, VICI makes multiple elemental chemistry measurements, including depth profiles through the weathering rind and subsurface, and the first ever direct mineralogy measurements on the Venus surface. VICI's payloads build on the success of the Mars Science Laboratory (MSL) by carrying the same instrumentation that has delivered high-impact science results on Mars.

Source/process apportionment of major and trace elements in sinking particles in the Sargasso sea

NASA Astrophysics Data System (ADS)

Huang, S.; Conte, M. H.

2009-01-01

Elemental composition of the particle flux at the Oceanic Flux Program (OFP) time-series site off Bermuda was measured from January 2002 to March 2005. Eighteen elements (Mg, Al, Si, P, Ca, Sc, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Sr, Cd, Ba and Pb) in sediment trap material from 500, 1500 and 3200 m depths were quantified using fusion-HR-ICPMS. Positive Matrix Factorization (PMF) was used to elucidate sources, elemental associations and processes that affect geochemical behavior in the water column. Results provide evidence for intense elemental cycling between the sinking flux material and the dissolved and suspended pools within mesopelagic and bathypelagic waters. Biological processing and remineralization rapidly deplete the sinking flux material in organic matter and associated elements (N, P, Cd, Zn) between 500 and 1500 m depth. Suspended particle aggregation, authigenic mineral precipitation, and chemical scavenging enriches the flux material in lithogenic minerals, barite and redox sensitive elements (Mn, Co, V, Fe). A large increase in the flux of lithogenic elements is observed with depth and confirms that the northeast Sargasso is a significant sink for advected continental materials, likely supplied via Gulf Stream circulation. PMF resolved major sources that contribute to sinking flux at all depths (carbonate, high-Mg carbonate, opal, organic matter, lithogenic material, and barite) as well as additional depth-specific elemental associations that contribute about half of the compositional variability in the flux. PMF solutions indicate close geochemical associations of barite-opal, Cd-P, Zn-Co, Zn-Pb and redox sensitive elements in the sinking flux material at 500 m depth. Major reorganizations of element associations occur as labile carrier phases break down and elements redistribute among new carrier phases deeper in the water column. Factor scores show strong covariation and similar temporal phasing among the three trap depths and indicate a tight coupling in particle flux compositional variability throughout the water column. Seasonality in flux composition is primarily driven by dilution of the lithogenic component with freshly-produced biogenic material during the late winter primary production maximum. Temporal trends in scores reveal subtle non-seasonal changes in flux composition occurring on month long timescales. This non-seasonal variability may be driven by changes in the biogeochemical properties of intermediate water masses that pass through the region and which affect rates of chemical scavenging and/or aggregation within the water column.

Before Biology: Geologic Habitability and Setting the Chemical and Physical Foundations for Life

NASA Astrophysics Data System (ADS)

Unterborn, Cayman Thomas

The Earth is a habitable, dynamic planet, with plate tectonics creating a deep water and carbon cycle. These cycles regulate surface and atmospheric C and water abundances, and therefore long-term climate, which is vital to Earths habitability. The driving force behind plate tectonics is the convection of the mantle. The fact that the Earth transports its interior heat via convection instead of conduction is a result of a confluence of factors that include the internal energy budget as well as mantle size and composition. Relative to the Sun stars that host extrasolar planets vary in their refractory rock-building element proportions relative to Si by an order of magnitude. This variation will create terrestrial planets with unique mineralogies and dynamical behavior. How similar these planets are to Earth, chemically and physically, is the focus of this proposal with the end goal being to answer: "What variation in planetary chemical composition is capable of supporting the geochemical cycles necessary for life?".

Accumulation and Translocation of Essential and Nonessential Elements by Tomato Plants (Solanum lycopersicum) Cultivated in Open-Air Plots under Organic or Conventional Farming Techniques.

PubMed

Liñero, Olaia; Cidad, Maite; Carrero, Jose Antonio; Nguyen, Christophe; de Diego, Alberto

2015-11-04

A 5-month experiment was performed to study the accumulation of several inorganic elements in tomato plants cultivated using organic or synthetic fertilizer. Plants were harvested in triplicate at six sampling dates during their life cycle. Statistical and chemometric analysis of data indicated the sequestration of toxic elements and of Na, Zn, Fe, and Co in roots, while the rest of the elements, including Cd, were mainly translocated to aboveground organs. A general decreasing trend in element concentrations with time was observed for most of them. A negative correlation between some element concentrations and ripening stage of fruits was identified. Conventionally grown plants seemed to accumulate more Cd and Tl in their tissues, while organic ones were richer in some nutrients. However, there was no clear effect of the fertilizer used (organic vs synthetic) on the elemental composition of fruits.

Bottom-Up Catalytic Approach towards Nitrogen-Enriched Mesoporous Carbons/Sulfur Composites for Superior Li-S Cathodes

PubMed Central

Sun, Fugen; Wang, Jitong; Chen, Huichao; Qiao, Wenming; Ling, Licheng; Long, Donghui

2013-01-01

We demonstrate a sustainable and efficient approach to produce high performance sulfur/carbon composite cathodes via a bottom-up catalytic approach. The selective oxidation of H2S by a nitrogen-enriched mesoporous carbon catalyst can produce elemental sulfur as a by-product which in-situ deposit onto the carbon framework. Due to the metal-free catalytic characteristic and high catalytic selectivity, the resulting sulfur/carbon composites have almost no impurities that thus can be used as cathode materials with compromising battery performance. The layer-by-layer sulfur deposition allows atomic sulfur binding strongly with carbon framework, providing efficient immobilization of sulfur. The nitrogen atoms doped on the carbon framework can increase the surface interactions with polysulfides, leading to the improvement in the trapping of polysulfides. Thus, the composites exhibit a reversible capacity of 939 mAh g−1 after 100 cycles at 0.2 C and an excellent rate capability of 527 mAh g−1 at 5 C after 70 cycles. PMID:24084754

Scanning and Transmission Electron Microscopy of High Temperature Materials

NASA Technical Reports Server (NTRS)

1994-01-01

Software and hardware updates to further extend the capability of the electron microscope were carried out. A range of materials such as intermetallics, metal-matrix composites, ceramic-matrix composites, ceramics and intermetallic compounds, based on refractory elements were examined under this research. Crystal structure, size, shape and volume fraction distribution of various phases which constitute the microstructures were examined. Deformed materials were studied to understand the effect of interfacial microstructure on the deformation and fracture behavior of these materials. Specimens tested for a range of mechanical property requirements, such as stress rupture, creep, low cycle fatigue, high cycle fatigue, thermomechanical fatigue, etc. were examined. Microstructural and microchemical stability of these materials exposed to simulated operating environments were investigated. The EOIM Shuttle post-flight samples were also examined to understand the influence of low gravity processing on microstructure. In addition, fractographic analyses of Nb-Zr-W, titanium aluminide, molybdenum silicide and silicon carbide samples were carried out. Extensive characterization of sapphire fibers in the fiber-reinforced composites made by powder cloth processing was made. Finally, pressure infiltration casting of metal-matrix composites was carried out.

Microtomography evaluation of dental tissue wear surface induced by in vitro simulated chewing cycles on human and composite teeth.

PubMed

Bedini, Rossella; Pecci, Raffaella; Notarangelo, Gianluca; Zuppante, Francesca; Persico, Salvatore; Di Carlo, Fabio

2012-01-01

In this study a 3D microtomography display of tooth surfaces after in vitro dental wear tests has been obtained. Natural teeth have been compared with prosthetic teeth, manufactured by three different polyceramic composite materials. The prosthetic dental element samples, similar to molars, have been placed in opposition to human teeth extracted by paradontology diseases. After microtomography analysis, samples have been subjected to in vitro fatigue test cycles by servo-hydraulic mechanical testing machine. After the fatigue test, each sample has been subjected again to microtomography analysis to obtain volumetric value changes and dental wear surface images. Wear surface images were obtained by 3D reconstruction software and volumetric value changes were measured by CT analyser software. The aim of this work has been to show the potential of microtomography technique to display very clear and reliable wear surface images. Microtomography analysis methods to evaluate volumetric value changes have been used to quantify dental tissue and composite material wear.

LOW ACTIVATION JOINING OF SIC/SIC COMPOSITES FOR FUSION APPLICATIONS: MODELING DUAL-PHASE MICROSTRUCTURES AND DISSIMILAR MATERIAL JOINTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henager, Charles H.; Nguyen, Ba Nghiep; Kurtz, Richard J.

2016-03-31

Finite element continuum damage models (FE-CDM) have been developed to simulate and model dual-phase joints and cracked joints for improved analysis of SiC materials in nuclear environments. This report extends the analysis from the last reporting cycle by including results from dual-phase models and from cracked joint models.

Eddy current sensing of intermetallic composite consolidation

NASA Technical Reports Server (NTRS)

Dharmasena, Kumar P.; Wadley, Haydn N. G.

1991-01-01

A finite element method is used to explore the feasibility and optimization of a probe-type eddy current sensor for determining the thickness of plate specimens during a hot isostatic pressing cycle. The dependence of the sensor's impedance upon sample-sensor separation in the high frequency limit is calculated, and factors that maximize sensitivity to the final stages of densification are identified.

Highly Stretchable Supercapacitors Based on Aligned Carbon Nanotube/Molybdenum Disulfide Composites.

PubMed

Lv, Tian; Yao, Yao; Li, Ning; Chen, Tao

2016-08-01

Stretchable supercapacitors that can sustain their performance under unpredictable tensile force are important elements for practical applications of various portable and wearable electronics. However, the stretchability of most reported supercapacitors was often lower than 100 % because of the limitation of the electrodes used. Herein we developed all-solid-state supercapacitors with a stretchability as high as 240 % by using aligned carbon nanotube composites with compact structure as electrodes. By combined with pseudocapacitive molybdenum disulfide nanosheets, the newly developed supercapacitor showed a specific capacitance of 13.16 F cm(-3) , and also showed excellent cycling retention (98 %) after 10 000 charge-discharge cycles. This work also presents a general and effective approach in developing high-performance electrodes for flexible and stretchable electronics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluations of Silica Aerogel-Based Flexible Blanket as Passive Thermal Control Element for Spacecraft Applications

NASA Astrophysics Data System (ADS)

Hasan, Mohammed Adnan; Rashmi, S.; Esther, A. Carmel Mary; Bhavanisankar, Prudhivi Yashwantkumar; Sherikar, Baburao N.; Sridhara, N.; Dey, Arjun

2018-03-01

The feasibility of utilizing commercially available silica aerogel-based flexible composite blankets as passive thermal control element in applications such as extraterrestrial environments is investigated. Differential scanning calorimetry showed that aerogel blanket was thermally stable over - 150 to 126 °C. The outgassing behavior, e.g., total mass loss, collected volatile condensable materials, water vapor regained and recovered mass loss, was within acceptable range recommended for the space applications. ASTM tension and tear tests confirmed the material's mechanical integrity. The thermo-optical properties remained nearly unaltered in simulated space environmental tests such as relative humidity, thermal cycling and thermo-vacuum tests and confirmed the space worthiness of the aerogel. Aluminized Kapton stitched or anchored to the blanket could be used to control the optical transparency of the aerogel. These outcomes highlight the potential of commercial aerogel composite blankets as passive thermal control element in spacecraft. Structural and chemical characterization of the material was also done using scanning electron microscopy, Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy.

Physiological, biomass elemental composition and proteomic analyses of Escherichia coli ammonium-limited chemostat growth, and comparison with iron- and glucose-limited chemostat growth

PubMed Central

Folsom, James Patrick

2015-01-01

Escherichia coli physiological, biomass elemental composition and proteome acclimations to ammonium-limited chemostat growth were measured at four levels of nutrient scarcity controlled via chemostat dilution rate. These data were compared with published iron- and glucose-limited growth data collected from the same strain and at the same dilution rates to quantify general and nutrient-specific responses. Severe nutrient scarcity resulted in an overflow metabolism with differing organic byproduct profiles based on limiting nutrient and dilution rate. Ammonium-limited cultures secreted up to 35  % of the metabolized glucose carbon as organic byproducts with acetate representing the largest fraction; in comparison, iron-limited cultures secreted up to 70  % of the metabolized glucose carbon as lactate, and glucose-limited cultures secreted up to 4  % of the metabolized glucose carbon as formate. Biomass elemental composition differed with nutrient limitation; biomass from ammonium-limited cultures had a lower nitrogen content than biomass from either iron- or glucose-limited cultures. Proteomic analysis of central metabolism enzymes revealed that ammonium- and iron-limited cultures had a lower abundance of key tricarboxylic acid (TCA) cycle enzymes and higher abundance of key glycolysis enzymes compared with glucose-limited cultures. The overall results are largely consistent with cellular economics concepts, including metabolic tradeoff theory where the limiting nutrient is invested into essential pathways such as glycolysis instead of higher ATP-yielding, but non-essential, pathways such as the TCA cycle. The data provide a detailed insight into ecologically competitive metabolic strategies selected by evolution, templates for controlling metabolism for bioprocesses and a comprehensive dataset for validating in silico representations of metabolism. PMID:26018546

Brazed graphite/refractory metal composites for first-wall protection elements

NASA Astrophysics Data System (ADS)

Šmid, I.; Croessmann, C. D.; Salmonson, J. C.; Whitley, J. B.; Kny, E.; Reheis, N.; Kneringer, G.; Nickel, H.

1991-03-01

The peak surface heat flux deposition on divertor elements of near term fusion devices is expected to exceed 10 MW/m 2. The needed reliability of brazed plasma interactive components, particularly under abnormal operating conditions with peak surface temperatures well beyond 1000°C, makes refractory metallic substrates and brazes with a high melting point very attractive. TZM, a high temperature alloy of molybdenum, and isotropic graphite, materials very closely matched in their thermal expansion, were brazed with four high-temperature brazes. The brazes used were Zr, 90Ni/10Ti, 90Cu/10Ti and 70Ag/27Cu/3Ti (nominal composition prior to brazing, wt%). The resulting composite tiles of 50 × 50 mm2 with a TZM thickness of 5 mm and a graphite thickness of 10 mm have been tested in high heat flux simulation for their thermal fatigue properties. Up to 600 loading cycles were carried out with an average heat flux of 10 MW/m 2 for 0.5 s pulses. The maximum surface temperature was 1100°C. In support of the experiment, the thermal response and temperature gradients of the samples were investigated using a finite element model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatsumi, Yoshiyuki; Kimura, Nobukazu; Itaya, Tetsumaru

K-Ar dates and chemical compositions of basalts in the Gregory Rift, Kenya, demonstrate marked secular variation of lava chemistry. Two magmatic cycles characterized by incompatible element relative depletion are recognized; both occurring immediately after the peak of basaltic volcanism and coeval with both trachyte/phonolite volcanism and domal uplift of the region. These cycles may be attributed to increasing degree of partial melting of mantle source material in association with thinning of the lithosphere by thermal erosion through contact with hot upwelling asthenospheric mantle. Cyclic variation in asthenosphere upwelling may be considered an important controlling process in the evolution of themore » Gregory Rift.« less

Fabrication, characterization, and modeling of piezoelectric fiber composites

NASA Astrophysics Data System (ADS)

Lin, Xiujuan; Zhou, Kechao; Button, Tim W.; Zhang, Dou

2013-07-01

Piezoelectric fiber composites (PFCs) with interdigitated electrodes have attracted increasing interest in a variety of industrial, commercial, and aerospace markets due to their unique flexibility, adaptability, and improved transverse actuation performance. Viscous plastic processing technique was utilized for the fabrication of PFCs with customized feature sizes. The assembly parameters showed great influence on the performance of PFCs, which was verified by the finite element analysis. The cracks were identified in the fibers underneath the electrode finger after several millions cycles due to the stress and electric field concentration. The electrode finger width was an important structural parameter and showed great influence on the actuation performance and the stress distribution in the PFCs. The finite element analysis revealed that wider electrode finger would be beneficial for reducing the risk of materials failure with slight influence on the actuation performance.

Biogeochemical Cycling of Fe, S, C, N, and Mo in the 3.2 Ga ocean: Constraints from DXCL-DP Black Shales from Pilbara, Western Australia

NASA Astrophysics Data System (ADS)

Yamaguchi, K. E.; Naraoka, H.; Ikehara, M.; Ito, T.; Kiyokawa, S.

2014-12-01

Records of geochemical cycling of bio-essential, redox-sensitive elements have keys to decipher mysteries of the co-evolution of Earth and life. To obtain insight into biogeochemical cycling of those elements and early evolution of microbial biosphere from high-quality samples, we drilled through Mesoarchean strata in coastal Pilbara (Dixon Island-Cleaverville Drilling Project, see Yamaguchi et al., 2009; Kiyokawa et al., 2012), and obtained 3.2 Ga old drillcores (CL1, CL2, and DX) of sulfide-rich black shales in the Cleaverville Group, Pilbara Supergroup. We conducted a systematic geochemical study involving sequential extractions of Fe, S, C, and N for phase-dependent contents (e.g., pyrite-Fe, reactive-Fe, highly reactive-Fe, unreactive-Fe, pyrite-S, sulfate-S, organic-S, elemental-S, Corg, Ccarb, Norg, and Nclay) and their stable isotope compositions, micro FT-IR and laser Raman spectroscopy for extracted kerogen, in addition to major and trace (redox-sensitive; e.g., Mo) element analysis, for >100 samples. Here we integrate our recent multidisciplinary investigations into the redox state of ocean and nature of microbial biosphere in the ocean 3.2 Ga ago. All of the obtained data are very difficult to explain only by geochemical processes in strictly anoxic environments, where both atmosphere and oceans were completely anoxic, like an environment before the inferred "Great Oxidation Event" when pO2 was lower than 0.00001 PAL (e.g., Holland, 1994). Our extensive data set consistently suggests that oxygenic photosynthesis, bacterial sulfate reduction, and microbially mediated redox-cycling of nitrogen, possibly involving denitrification and N2-fixation, are very likely to have been operating, and may be used as a strong evidence for at least local and temporal existence of oxidized environment as far back as 3.2 Ga ago. Modern-style biogeochemical cycling of Fe, S, C, N, and Mo has been operating since then. The atmosphere-hydrosphere system 3.2 Ga ago would have been sufficiently oxidized to allow redox-cycling of elements during deposition of the sediments, ~800 Ma earlier than commonly thought. Our suggestions have far-reaching and astrobiological implications for earlier evolution of the surface environment, especially redox state, and marine microbial biosphere.

STATISTICAL CHARACTERISTICS OF ELEMENTAL ABUNDANCE RATIOS: OBSERVATIONS FROM THE ACE SPACECRAFT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, L.-L.; Zhang, H.

We statistically analyze the elemental galactic cosmic ray (GCR) composition measurements of elements 5 ≤ Z ≤ 28 within the energy range 30–500 MeV/nucleon from the CRIS instrument on board the ACE spacecraft in orbit about the L1 Lagrange point during the period from 1997 to 2014. Similarly to the last unusual solar minimum, the elevated elemental intensities of all heavy nuclei during the current weak solar maximum in 2014 are ∼40% higher than that of the previous solar maximum in 2002, which has been attributed to the weak modulation associated with low solar activity levels during the ongoing weakestmore » solar maximum since the dawn of space age. In addition, the abundance ratios of heavy nuclei with respect to elemental oxygen are generally independent of kinetic energy per nucleon in the energy region 60–200 MeV/nuc, in good agreement with previous experiments. Furthermore, the abundance ratios of most relatively abundant species, except carbon, exhibit considerable solar-cycle variation, which are obviously positively correlated with the sunspot numbers with about one-year time lag. We also find that the percentage variation of abundance ratios for most elements are approximately identical. These preliminary results provide valuable insights into the characteristics of elemental heavy nuclei composition and place new and significant constraints on future GCR heavy nuclei propagation and modulation models.« less

Nitrogen, phosphorus, and cation use efficiency in stands of regenerating tropical dry forest.

PubMed

Waring, Bonnie G; Becknell, Justin M; Powers, Jennifer S

2015-07-01

Plants on infertile soils exhibit physiological and morphological traits that support conservative internal nutrient cycling. However, potential trade-offs among use efficiencies for N, P, and cations are not well explored in species-rich habitats where multiple elements may limit plant production. We examined uptake efficiency and use efficiency of N, P, K, Ca, Mg, Al, and Na in plots of regenerating tropical dry forests spanning a gradient of soil fertility. Our aim was to determine whether plant responses to multiple elements are correlated, or whether there are trade-offs among exploitation strategies across stands varying in community composition, soil quality, and successional stage. For all elements, both uptake efficiency and use efficiency decreased as availability of the corresponding element increased. Plant responses to N, Na, and Al were uncoupled from uptake and use efficiencies for P and essential base cations, which were tightly correlated. N and P use efficiencies were associated with shifts in plant species composition along the soil fertility gradient, and there was also a trend towards increasing N use efficiency with stand age. N uptake efficiency was positively correlated with the abundance of tree species that associate with ectomycorrhizal fungi. Taken together, our results suggest that successional processes and local species composition interact to regulate plant responses to availability of multiple resources. Successional tropical dry forests appear to employ different strategies to maximize response to N vs. P and K.

Elemental Anisotropic Growth and Atomic-Scale Structure of Shape-Controlled Octahedral Pt-Ni-Co Alloy Nanocatalysts.

PubMed

Arán-Ais, Rosa M; Dionigi, Fabio; Merzdorf, Thomas; Gocyla, Martin; Heggen, Marc; Dunin-Borkowski, Rafal E; Gliech, Manuel; Solla-Gullón, José; Herrero, Enrique; Feliu, Juan M; Strasser, Peter

2015-11-11

Multimetallic shape-controlled nanoparticles offer great opportunities to tune the activity, selectivity, and stability of electrocatalytic surface reactions. However, in many cases, our synthetic control over particle size, composition, and shape is limited requiring trial and error. Deeper atomic-scale insight in the particle formation process would enable more rational syntheses. Here we exemplify this using a family of trimetallic PtNiCo nanooctahedra obtained via a low-temperature, surfactant-free solvothermal synthesis. We analyze the competition between Ni and Co precursors under coreduction "one-step" conditions when the Ni reduction rates prevailed. To tune the Co reduction rate and final content, we develop a "two-step" route and track the evolution of the composition and morphology of the particles at the atomic scale. To achieve this, scanning transmission electron microscopy and energy dispersive X-ray elemental mapping techniques are used. We provide evidence of a heterogeneous element distribution caused by element-specific anisotropic growth and create octahedral nanoparticles with tailored atomic composition like Pt1.5M, PtM, and PtM1.5 (M = Ni + Co). These trimetallic electrocatalysts have been tested toward the oxygen reduction reaction (ORR), showing a greatly enhanced mass activity related to commercial Pt/C and less activity loss than binary PtNi and PtCo after 4000 potential cycles.

Nonlinear flutter analysis of composite panels

NASA Astrophysics Data System (ADS)

An, Xiaomin; Wang, Yan

2018-05-01

Nonlinear panel flutter is an interesting subject of fluid-structure interaction. In this paper, nonlinear flutter characteristics of curved composite panels are studied in very low supersonic flow. The composite panel with geometric nonlinearity is modeled by a nonlinear finite element method; and the responses are computed by the nonlinear Newmark algorithm. An unsteady aerodynamic solver, which contains a flux splitting scheme and dual time marching technology, is employed in calculating the unsteady pressure of the motion of the panel. Based on a half-step staggered coupled solution, the aeroelastic responses of two composite panels with different radius of R = 5 and R = 2.5 are computed and compared with each other at different dynamic pressure for Ma = 1.05. The nonlinear flutter characteristics comprising limited cycle oscillations and chaos are analyzed and discussed.

Effect of Processing Parameters on Thermal Cycling Behavior of Al2O3-Al2O3 Brazed Joints

NASA Astrophysics Data System (ADS)

Dandapat, Nandadulal; Ghosh, Sumana; Guha, Bichitra Kumar; Datta, Someswar; Balla, Vamsi Krishna

2016-10-01

In the present study, alumina ceramics were active metal brazed at different temperatures ranging from 1163 K to 1183 K (890 °C to 910 °C) using TICUSIL (68.8Ag-26.7Cu-4.5Ti in wt pct) foil as filler alloy of different thicknesses. The brazed joints were subjected to thermal cycling for 100 cycles between 323 K and 873 K (50 °C and 600 °C). The microstructural and elemental composition analysis of the brazed joints were performed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) before and after thermal cycling. Helium (He) leak test and brazing strength measurement were also conducted after thermal cycling for 100 cycles. The joint could withstand up to 1 × 10-9 Torr pressure and brazing strength was higher than 20 MPa. The experimental results demonstrated that joints brazed at the higher temperature with thinner filler alloy produced strong Al2O3-Al2O3 joints.

Analysis and Testing of a Metallic Repair Applicable to Pressurized Composite Aircraft Structure

NASA Technical Reports Server (NTRS)

Przekop, Adam; Jegley, Dawn C.; Rouse, Marshall; Lovejoy, Andrew E.

2014-01-01

Development of repair technology is vital to the long-term application of new structural concepts on aircraft structure. The design, analysis, and testing of a repair concept applicable to a stiffened composite panel based on the Pultruded Rod Stitched Efficient Unitized Structure was recently completed. The damage scenario considered was a mid-bay to mid-bay saw-cut with a severed stiffener, flange, and skin. A bolted metallic repair was selected so that it could be easily applied in the operational environment. The present work describes results obtained from tension and pressure panel tests conducted to validate both the repair concept and finite element analysis techniques used in the design effort. Simulation and experimental strain and displacement results show good correlation, indicating that the finite element modeling techniques applied in the effort are an appropriate compromise between required fidelity and computational effort. Static tests under tension and pressure loadings proved that the proposed repair concept is capable of sustaining load levels that are higher than those resulting from the current working stress allowables. Furthermore, the pressure repair panel was subjected to 55,000 pressure load cycles to verify that the design can withstand a life cycle representative for a transport category aircraft. These findings enable upward revision of the stress allowables that had been kept at an overly-conservative level due to concerns associated with repairability of the panels. This conclusion enables more weight efficient structural designs utilizing the composite concept under investigation.

Optimization of Layered Cathode Materials for Lithium-Ion Batteries

PubMed Central

Julien, Christian; Mauger, Alain; Zaghib, Karim; Groult, Henri

2016-01-01

This review presents a survey of the literature on recent progress in lithium-ion batteries, with the active sub-micron-sized particles of the positive electrode chosen in the family of lamellar compounds LiMO2, where M stands for a mixture of Ni, Mn, Co elements, and in the family of yLi2MnO3•(1 − y)LiNi½Mn½O2 layered-layered integrated materials. The structural, physical, and chemical properties of these cathode elements are reported and discussed as a function of all the synthesis parameters, which include the choice of the precursors and of the chelating agent, and as a function of the relative concentrations of the M cations and composition y. Their electrochemical properties are also reported and discussed to determine the optimum compositions in order to obtain the best electrochemical performance while maintaining the structural integrity of the electrode lattice during cycling. PMID:28773717

Composites of aluminum alloy and magnesium alloy with graphite showing low thermal expansion and high specific thermal conductivity

NASA Astrophysics Data System (ADS)

Oddone, Valerio; Boerner, Benji; Reich, Stephanie

2017-12-01

High thermal conductivity, low thermal expansion and low density are three important features in novel materials for high performance electronics, mobile applications and aerospace. Spark plasma sintering was used to produce light metal-graphite composites with an excellent combination of these three properties. By adding up to 50 vol.% of macroscopic graphite flakes, the thermal expansion coefficient of magnesium and aluminum alloys was tuned down to zero or negative values, while the specific thermal conductivity was over four times higher than in copper. No degradation of the samples was observed after thermal stress tests and thermal cycling. Tensile strength and hardness measurements proved sufficient mechanical stability for most thermal management applications. For the production of the alloys, both prealloyed powders and elemental mixtures were used; the addition of trace elements to cope with the oxidation of the powders was studied.

Composites of aluminum alloy and magnesium alloy with graphite showing low thermal expansion and high specific thermal conductivity

PubMed Central

Oddone, Valerio; Boerner, Benji; Reich, Stephanie

2017-01-01

Abstract High thermal conductivity, low thermal expansion and low density are three important features in novel materials for high performance electronics, mobile applications and aerospace. Spark plasma sintering was used to produce light metal–graphite composites with an excellent combination of these three properties. By adding up to 50 vol.% of macroscopic graphite flakes, the thermal expansion coefficient of magnesium and aluminum alloys was tuned down to zero or negative values, while the specific thermal conductivity was over four times higher than in copper. No degradation of the samples was observed after thermal stress tests and thermal cycling. Tensile strength and hardness measurements proved sufficient mechanical stability for most thermal management applications. For the production of the alloys, both prealloyed powders and elemental mixtures were used; the addition of trace elements to cope with the oxidation of the powders was studied. PMID:28458742

Composites of aluminum alloy and magnesium alloy with graphite showing low thermal expansion and high specific thermal conductivity.

PubMed

Oddone, Valerio; Boerner, Benji; Reich, Stephanie

2017-01-01

High thermal conductivity, low thermal expansion and low density are three important features in novel materials for high performance electronics, mobile applications and aerospace. Spark plasma sintering was used to produce light metal-graphite composites with an excellent combination of these three properties. By adding up to 50 vol.% of macroscopic graphite flakes, the thermal expansion coefficient of magnesium and aluminum alloys was tuned down to zero or negative values, while the specific thermal conductivity was over four times higher than in copper. No degradation of the samples was observed after thermal stress tests and thermal cycling. Tensile strength and hardness measurements proved sufficient mechanical stability for most thermal management applications. For the production of the alloys, both prealloyed powders and elemental mixtures were used; the addition of trace elements to cope with the oxidation of the powders was studied.

Synthesis and Characterization of Pt–Ag Alloy Nanocages with Enhanced Activity and Durability toward Oxygen Reduction

DOE PAGES

Yang, Xuan; Roling, Luke T.; Vara, Madeline; ...

2016-09-23

Engineering the elemental composition of metal nanocrystals offers an effective strategy for the development of catalysts or electrocatalysts with greatly enhanced activity. Herein, we report the synthesis of Pt–Ag alloy nanocages with an outer edge length of 18 nm and a wall thickness of about 3 nm. Such nanocages with a composition of Pt 19Ag 81 could be readily prepared in one step through the galvanic replacement reaction between Ag nanocubes and a Pt(II) precursor. Here, after 10 000 cycles of potential cycling in the range of 0.60–1.0 V as in an accelerated durability test, the composition of the nanocagesmore » changed to Pt 56Ag 44, together with a specific activity of 1.23 mA cm –2 toward oxygen reduction, which was 3.3 times that of a state-of-the-art commercial Pt/C catalyst (0.37 mA cm –2) prior to durability testing. Density functional theory calculations attributed the increased activity to the stabilization of the transition state for breaking the O–O bond in molecular oxygen. Even after 30 000 cycles of potential cycling, the mass activity of the nanocages only dropped from 0.64 to 0.33 A mg –1 Pt, which was still about two times that of the pristine Pt/C catalyst (0.19 A mg –1 Pt).« less

Synthesis and Characterization of Pt–Ag Alloy Nanocages with Enhanced Activity and Durability toward Oxygen Reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Xuan; Roling, Luke T.; Vara, Madeline

Engineering the elemental composition of metal nanocrystals offers an effective strategy for the development of catalysts or electrocatalysts with greatly enhanced activity. Herein, we report the synthesis of Pt–Ag alloy nanocages with an outer edge length of 18 nm and a wall thickness of about 3 nm. Such nanocages with a composition of Pt 19Ag 81 could be readily prepared in one step through the galvanic replacement reaction between Ag nanocubes and a Pt(II) precursor. Here, after 10 000 cycles of potential cycling in the range of 0.60–1.0 V as in an accelerated durability test, the composition of the nanocagesmore » changed to Pt 56Ag 44, together with a specific activity of 1.23 mA cm –2 toward oxygen reduction, which was 3.3 times that of a state-of-the-art commercial Pt/C catalyst (0.37 mA cm –2) prior to durability testing. Density functional theory calculations attributed the increased activity to the stabilization of the transition state for breaking the O–O bond in molecular oxygen. Even after 30 000 cycles of potential cycling, the mass activity of the nanocages only dropped from 0.64 to 0.33 A mg –1 Pt, which was still about two times that of the pristine Pt/C catalyst (0.19 A mg –1 Pt).« less

Mixed-Mode Decohesion Finite Elements for the Simulation of Delamination in Composite Materials

NASA Technical Reports Server (NTRS)

Camanho, Pedro P.; Davila, Carlos G.

2002-01-01

A new decohesion element with mixed-mode capability is proposed and demonstrated. The element is used at the interface between solid finite elements to model the initiation and non-self-similar growth of delaminations. A single relative displacement-based damage parameter is applied in a softening law to track the damage state of the interface and to prevent the restoration of the cohesive state during unloading. The softening law for mixed-mode delamination propagation can be applied to any mode interaction criterion such as the two-parameter power law or the three-parameter Benzeggagh-Kenane criterion. To demonstrate the accuracy of the predictions and the irreversibility capability of the constitutive law, steady-state delamination growth is simulated for quasistatic loading-unloading cycles of various single mode and mixed-mode delamination test specimens.

Interlaminar shear fracture toughness and fatigue thresholds for composite materials

NASA Technical Reports Server (NTRS)

Obrien, T. Kevin; Murri, Gretchen B.; Salpekar, Satish A.

1987-01-01

Static and cyclic end notched flexure tests were conducted on a graphite epoxy, a glass epoxy, and graphite thermoplastic to determine their interlaminar shear fracture toughness and fatigue thresholds for delamination in terms of limiting values of the mode II strain energy release rate, G-II, for delamination growth. The influence of precracking and data reduction schemes are discussed. Finite element analysis indicated that the beam theory calculation for G-II with the transverse shear contribution included was reasonably accurate over the entire range of crack lengths. Cyclic loading significantly reduced the critical G-II for delamination. A threshold value of the maximum cyclic G-II below which no delamination occurred after one million cycles was identified for each material. Also, residual static toughness tests were conducted on glass epoxy specimens that had undergone one million cycles without delamination. A linear mixed-mode delamination criteria was used to characterize the static toughness of several composite materials; however, a total G threshold criterion appears to characterize the fatigue delamination durability of composite materials with a wide range of static toughness.

Natural Cycles, Gases

NASA Technical Reports Server (NTRS)

Douglass, Anne R.; Jackman, Charles H.; Rood, R. B.; Aikin, A. C.; Stolarski, R. S.; Mccormick, M. P.; Fahey, David W.

1992-01-01

The major gaseous components of the exhaust of stratospheric aircraft are expected to be the products of combustion (CO2 and H2O), odd nitrogen (NO, NO2 HNO3), and products indicating combustion inefficiencies (CO and total unburned hydrocarbons). The species distributions are produced by a balance of photochemical and transport processes. A necessary element in evaluating the impact of aircraft exhaust on the lower stratospheric composition is to place the aircraft emissions in perspective within the natural cycles of stratospheric species. Following are a description of mass transport in the lower stratosphere and a discussion of the natural behavior of the major gaseous components of the stratospheric aircraft exhaust.

Low Activation Joining of SiC/SiC Composites for Fusion Applications: Thermomechanical Modeling of Dual-Phase Microstructures and Dissimilar Material Joints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ba Nghiep; Henager, Charles H.; Kurtz, Richard J.

2016-09-30

Finite element (FE) continuum damage mechanics (CDM) models have been developed to simulate and model dual-phase joints and cracked joints for improved analysis of SiC materials in nuclear environments. This report extends the analysis from the last reporting cycle by including preliminary thermomechanical analyses of cracked joints and implementation of dual-phase damage models.

Modelling and simulation of the consolidation behavior during thermoplastic prepreg composites forming process

NASA Astrophysics Data System (ADS)

Xiong, H.; Hamila, N.; Boisse, P.

2017-10-01

Pre-impregnated thermoplastic composites have recently attached increasing interest in the automotive industry for their excellent mechanical properties and their rapid cycle manufacturing process, modelling and numerical simulations of forming processes for composites parts with complex geometry is necessary to predict and optimize manufacturing practices, especially for the consolidation effects. A viscoelastic relaxation model is proposed to characterize the consolidation behavior of thermoplastic prepregs based on compaction tests with a range of temperatures. The intimate contact model is employed to predict the evolution of the consolidation which permits the microstructure prediction of void presented through the prepreg. Within a hyperelastic framework, several simulation tests are launched by combining a new developed solid shell finite element and the consolidation models.

Mars

NASA Astrophysics Data System (ADS)

McSween, H. Y., Jr.; McLennan, S. M.

Of all the planets, Mars is the most Earthlike, inviting geochemical comparisons. Geochemical data for Mars are derived from spacecraft remote sensing, surface measurements and Martian meteorites. These analyses of exposed crustal materials enable estimates of bulk planet composition and inferences about its iron-rich mantle and core, as well as constraints on planetary differentiation and crust-mantle evolution. Mars probably had an early magma ocean, but there is no evidence for plate tectonics or crustal recycling any time in its history. The crust is basaltic in composition and lithologically heterogeneous, with radiometric crystallization ages ranging from ~4 billion years to within the last several hundred million years. Mantle sources for magmas vary considerably in incompatible element abundances. Although Mars is volatile element-rich, estimations of the amount of water delivered to the surface by volcanism are controversial. Low-temperature aqueous alteration affected the ancient Martian surface, producing clay minerals, sulfates, and other secondary minerals. Weathering and diagenetic trends are distinct from terrestrial chemical alteration, indicating different aqueous conditions. Organic matter has been found in Martian meteorites, but no geochemical signal of life has yet been discovered. Dynamic geochemical cycles for some volatile elements are revealed by stable isotope measurements. Long-term secular changes in chemical and mineralogical compositions of igneous rocks and sediments have been documented but are not well understood.

Studies of behavior of the fuel compound based on the U-Zr micro-heterogeneous quasialloy during cyclic thermal tests

NASA Astrophysics Data System (ADS)

Zaytsev, D. A.; Repnikov, V. M.; Soldatkin, D. M.; Solntsev, V. A.

2017-11-01

This paper provides the description of temperature cycle testing of U-Zr heterogeneous fuel composition. The composition is essentially a niobium-doped zirconium matrix with metallic uranium filaments evenly distributed over the cross section. The test samples 150 mm long had been fabricated using a fiber-filament technology. The samples were essentially two-bladed spiral mandrel fuel elements parts. In the course of experiments the following temperatures were applied: 350, 675, 780 and 1140 °C with total exposure periods equal to 200, 30, 30 and 6 hours respectively. The fuel element samples underwent post-exposure material science examination including: geometry measurements, metallographic analysis, X-ray phase analysis and electron-microscopic analysis as well as micro-hardness measurement. It has been found that no significant thermal swelling of the samples occurs throughout the whole temperature range from 350 °C up to 1140 °C. The paper presents the structural changes and redistribution of the fuel component over the fuel element cross section with rising temperature.

Modeling Fatigue Damage Onset and Progression in Composites Using an Element-Based Virtual Crack Closure Technique Combined With the Floating Node Method

NASA Technical Reports Server (NTRS)

De Carvalho, Nelson V.; Krueger, Ronald

2016-01-01

A new methodology is proposed to model the onset and propagation of matrix cracks and delaminations in carbon-epoxy composites subject to fatigue loading. An extended interface element, based on the Floating Node Method, is developed to represent delaminations and matrix cracks explicitly in a mesh independent fashion. Crack propagation is determined using an element-based Virtual Crack Closure Technique approach to determine mixed-mode energy release rates, and the Paris-Law relationship to obtain crack growth rate. Crack onset is determined using a stressbased onset criterion coupled with a stress vs. cycle curve and Palmgren-Miner rule to account for fatigue damage accumulation. The approach is implemented in Abaqus/Standard® via the user subroutine functionality. Verification exercises are performed to assess the accuracy and correct implementation of the approach. Finally, it was demonstrated that this approach captured the differences in failure morphology in fatigue for two laminates of identical stiffness, but with layups containing ?deg plies that were either stacked in a single group, or distributed through the laminate thickness.

Crustal forensics in arc magmas

NASA Astrophysics Data System (ADS)

Davidson, Jon P.; Hora, John M.; Garrison, Jennifer M.; Dungan, Michael A.

2005-01-01

The geochemical characteristics of continental crust are present in nearly all arc magmas. These characteristics may reflect a specific source process, such as fluid fluxing, common to both arc magmas and the continental crust, and/or may reflect the incorporation of continental crust into arc magmas either at source via subducted sediment, or via contamination during differentiation. Resolving the relative mass contributions of juvenile, mantle-derived material, versus that derived from pre-existing crust of the upper plate, and providing these estimates on an element-by-element basis, is important because: (1) we want to constrain crustal growth rates; (2) we want to quantitatively track element cycling at convergent margins; and (3) we want to determine the origin of economically important elements and compounds. Traditional geochemical approaches for determining the contributions of various components to arc magmas are particularly successful when applied on a comparative basis. Studies of suites from multiple magmatic systems along arcs, for which differentiation effects can be individually constrained, can be used to extrapolate to potential source compositions. In the Lesser Antilles Arc, for example, differentiation trends from individual volcanoes are consistent with open-system evolution. However, such trends do not project back to a common primitive magma composition, suggesting that differentiation modifies magmas that were derived from distinct mantle sources. We propose that such approaches should now be complemented by petrographically constrained mineral-scale isotope and trace element analysis to unravel the contributing components to arc magmas. This innovative approach can: (1) better constrain true end-member compositions by returning wider ranges in geochemical compositions among constituent minerals than is found in whole rocks; (2) better determine magmatic evolution processes from core-rim isotopic or trace element profiles from the phases contained in magmas; and (3) constrain rates of differentiation by applying diffusion-controlled timescales to element profiles. An example from Nguaruhoe Volcano, New Zealand, underscores the importance of such a microsampling approach, showing that mineral isotopic compositions encompass wide ranges, that whole-rock isotopic compositions are consequently simply element-weighted averages of the heterogeneous crystal cargo, and that open-system evolution is proved by core-rim variations in Sr isotope ratios. Nguaruhoe is just one of many systems examined through microanalytical approaches. The overwhelming conclusion of these studies is that crystal cargoes are not truly phenocrystic, but are inherited from various sources. The implication of this realization is that the interpretation of whole-rock isotopic data, including the currently popular U-series, needs careful evaluation in the context of petrographic observations.

An Irreversible Constitutive Law for Modeling the Delamination Process using Interface Elements

NASA Technical Reports Server (NTRS)

Goyal, Vinay K.; Johnson, Eric R.; Davila, Carlos G.; Jaunky, Navin; Ambur, Damodar (Technical Monitor)

2002-01-01

An irreversible constitutive law is postulated for the formulation of interface elements to predict initiation and progression of delamination in composite structures. An exponential function is used for the constitutive law such that it satisfies a multi-axial stress criterion for the onset of delamination, and satisfies a mixed mode fracture criterion for the progression of delamination. A damage parameter is included to prevent the restoration of the previous cohesive state between the interfacial surfaces. To demonstrate the irreversibility capability of the constitutive law, steady-state crack growth is simulated for quasi-static loading-unloading cycle of various fracture test specimens.

An Irreversible Constitutive Law for Modeling the Delamination Process Using Interface Elements

NASA Technical Reports Server (NTRS)

Goyal, Vinay K.; Johnson, Eric R.; Davila, Carlos G.; Jaunky, Navin; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

An irreversible constitutive law is postulated for the formulation of interface elements to predict initiation and progression of delamination in composite structures. An exponential function is used for the constitutive law such that it satisfies a multi-axial stress criterion for the onset of delamination, and satisfies a mixed mode fracture criterion for the progression of delamination. A damage parameter is included to prevent the restoration of the previous cohesive state between the interfacial surfaces. To demonstrate the irreversibility capability of the constitutive law, steady-state crack growth is simulated for quasi-static loading-unloading cycle of various fracture test specimens.

Characterizing marine particles and their impact on biogeochemical cycles in the GEOTRACES program

NASA Astrophysics Data System (ADS)

Anderson, Robert F.; Hayes, Christopher T.

2015-04-01

Trace elements and their isotopes (TEIs) are of priority interest in several subdisciplines of oceanography. For example, the vital role of trace element micronutrients in regulating the growth of marine organisms, which, in turn, may influence the structure and composition of marine ecosystems, is now well established (Morel and Price, 2003; Twining and Baines, 2013). Natural distributions of some TEIs have been severely impacted by anthropogenic emissions, leading to substantial perturbations of natural ocean inventories. Pb and Hg, for example, (Lamborg et al., 2002; Schaule and Patterson, 1981), may represent a significant threat to human food supply. Furthermore, much of our knowledge of past variability in the ocean environment, including the ocean's role in climate change, has been developed using TEI proxies archived in marine substrates such as sediments, corals and microfossils. Research in each of these areas relies on a comprehensive knowledge of the distributions of TEIs in the ocean, and on the sensitivity of these distributions to changing environmental conditions. With numerous processes affecting the regional supply and removal of TEIs in the ocean, a comprehensive understanding of the marine biogeochemical cycles of TEIs can be attained only by a global, coordinated, international effort. GEOTRACES, an international program designed to study the marine biogeochemical cycles of trace elements and their isotopes (Anderson et al., 2014; Henderson et al., 2007), aims to achieve these goals.

The impact of fish and the commercial marine harvest on the ocean iron cycle.

PubMed

Moreno, Allison R; Haffa, Arlene L M

2014-01-01

Although iron is the fourth most abundant element in the Earth's crust, bioavailable iron limits marine primary production in about one third of the ocean. This lack of iron availability has implications in climate change because the removal of carbon dioxide from the atmosphere by phytoplankton requires iron. Using literature values for global fish biomass estimates, and elemental composition data we estimate that fish biota store between 0.7-7 × 10(11) g of iron. Additionally, the global fish population recycles through excretion between 0.4-1.5 × 10(12) g of iron per year, which is of a similar magnitude as major recognized sources of iron (e.g. dust, sediments, ice sheet melting). In terms of biological impact this iron could be superior to dust inputs due to the distributed deposition and to the greater solubility of fecal pellets compared to inorganic minerals. To estimate a loss term due to anthropogenic activity the total commercial catch for 1950 to 2010 was obtained from the Food and Agriculture Organization of the United Nations. Marine catch data were separated by taxa. High and low end values for elemental composition were obtained for each taxonomic category from the literature and used to calculate iron per mass of total harvest over time. The marine commercial catch is estimated to have removed 1-6 × 10(9) g of iron in 1950, the lowest values on record. There is an annual increase to 0.7-3 × 10(10) g in 1996, which declines to 0.6-2 × 10(10) g in 2010. While small compared to the total iron terms in the cycle, these could have compounding effects on distribution and concentration patterns globally over time. These storage, recycling, and export terms of biotic iron are not currently included in ocean iron mass balance calculations. These data suggest that fish and anthropogenic activity should be included in global oceanic iron cycles.

Analysis of Ageing Effect on Li-Polymer Batteries

PubMed Central

Barcellona, Simone; Brenna, Morris; Foiadelli, Federica; Longo, Michela; Piegari, Luigi

2015-01-01

Lithium-ion batteries are a key technology for current and future energy storage in mobile and stationary application. In particular, they play an important role in the electrification of mobility and therefore the battery lifetime prediction is a fundamental aspect for successful market introduction. Numerous studies developed ageing models capable of predicting battery life span. Most of the previous works compared the effect of the ageing factors to a battery's cycle life. These cycles are identical, which is not the case for electric vehicles applications. Indeed, most of the available information is based on results from laboratory testing, under very controlled environments, and using ageing protocols, which may not correctly reflect the actual utilization. For this reason, it is important to link the effect of duty cycles with the ageing of the batteries. This paper proposes a simple method to investigate the effect of the duty cycle on the batteries lifetime through tests performed on different cells for different kinds of cycle. In this way, a generic complex cycle can be seen as a composition of elemental cycles by means of Rainflow procedures. Consequently, the ageing due to any cycle can be estimated starting from the knowledge of simpler cycles. PMID:26236775

A physics-based model of the electrical impedance of ionic polymer metal composites

NASA Astrophysics Data System (ADS)

Cha, Youngsu; Aureli, Matteo; Porfiri, Maurizio

2012-06-01

In this paper, we analyze the chemoelectrical behavior of ionic polymer metal composites (IPMCs) in the small voltage range with a novel hypothesis on the charge dynamics in proximity of the electrodes. In particular, we homogenize the microscopic properties of the interfacial region through a so-called composite layer which extends between the polymer membrane and the metal electrode. This layer accounts for the dissimilar properties of its constituents by describing the charge distribution via two species of charge carriers, that is, electrons and mobile counterions. We model the charge dynamics in the IPMC by adapting the multiphysics formulation based on the Poisson-Nernst-Planck (PNP) framework, which is enriched through an additional term to capture the electron transport in the composite layer. Under the hypothesis of small voltage input, we use the linearized PNP model to derive an equivalent IPMC circuit model with lumped elements. The equivalent model comprises a resistor connected in series with the parallel of a capacitor and a Warburg impedance element. These elements idealize the phenomena of charge build up in the double layer region and the faradaic impedance related to mass transfer, respectively. We validate the equivalent model through measurements on in-house fabricated samples addressing both IPMC step response and impedance, while assessing the influence of repeated plating cycles on the electrical properties of IPMCs. Experimental results are compared with theoretical findings to identify the equivalent circuit parameters. Findings from this study are compared with alternative impedance models proposed in the literature.

Propulsion system needs

NASA Technical Reports Server (NTRS)

Gunn, Stanley

1991-01-01

The needs of the designer of a solid core nuclear rocket engine are discussed. Some of the topics covered include: (1) a flight thrust module/feed system module assembly; (2) a nuclear thermal rocket (NTR), expander cycle, dual T/P; (3) turbopump operating conditions; (4) typical system parameters; (5) growth capability composite fuel elements; (6) a NTR radiation cooled nozzle extension; (7) a NFS-3B Feed System; and (8) a NTR Integrated Pneumatic-Fluidics Control System.

Residual Tensile Property of Plain Woven Jute Fiber/Poly(Lactic Acid) Green Composites during Thermal Cycling

PubMed Central

Katogi, Hideaki; Takemura, Kenichi; Akiyama, Motoki

2016-01-01

This study investigated the residual tensile properties of plain woven jute fiber reinforced poly(lactic acid) (PLA) during thermal cycling. Temperature ranges of thermal cycling tests were 35–45 °C and 35–55 °C. The maximum number of cycles was 103 cycles. The quasi-static tensile tests of jute fiber, PLA, and composite were conducted after thermal cycling tests. Thermal mechanical analyses of jute fiber and PLA were conducted after thermal cycling tests. Results led to the following conclusions. For temperatures of 35–45 °C, tensile strength of composite at 103 cycles decreased 10% compared to that of composite at 0 cycles. For temperatures of 35–55 °C, tensile strength and Young’s modulus of composite at 103 cycles decreased 15% and 10%, respectively, compared to that of composite at 0 cycles. Tensile properties and the coefficient of linear expansion of PLA and jute fiber remained almost unchanged after thermal cycling tests. From observation of a fracture surface, the length of fiber pull out in the fracture surface of composite at 103 cycles was longer than that of composite at 0 cycles. Therefore, tensile properties of the composite during thermal cycling were decreased, probably because of the decrease of interfacial adhesion between the fiber and resin. PMID:28773694

Partitioning the relative contributions of inorganic plant composition and soil characteristics to the quality of Helichrysum italicum subsp. italicum (Roth) G. Don fil. essential oil.

PubMed

Bianchini, Ange; Santoni, François; Paolini, Julien; Bernardini, Antoine-François; Mouillot, David; Costa, Jean

2009-07-01

Composition of Helichrysum italicum subsp. italicum essential oil showed chemical variability according to vegetation cycle, environment, and geographic origins. In the present work, 48 individuals of this plant at different development stages and the corresponding root soils were sampled: i) 28 volatile components were identified and measured in essential oil by using GC and GC/MS; ii) ten elements from plants and soils have been estimated using colorimetry in continuous flux, flame atomic absorption spectrometry, or emission spectrometry (FAAS/FAES); iii) texture and acidity (real and potential) of soil samples were also reported. Relationships between the essential-oil composition, the inorganic plant composition, and the soil characteristics (inorganic composition, texture, and acidity) have been established using multivariate analysis such as Principal Component Analysis (PCA) and partial Redundancy Analysis (RDA). This study demonstrates a high level of intraspecific differences in oil composition due to environmental factors and, more particularly, soil characteristics.

Robocast Pb(Zr{sub 0.95}Ti{sub 0.05})O{sub 3} Ceramic Monoliths and Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

TUTTLE,BRUCE A.; SMAY,JAMES E.; CESARANO III,JOSEPH

2000-07-18

Robocasting, a computer controlled slurry deposition technique, was used to fabricate ceramic monoliths and composites of chemically prepared Pb(Zr{sub 0.95}Ti{sub 0.05})O{sub 3} (PZT 95/5) ceramics. Densities and electrical properties of the robocast samples were equivalent to those obtained for cold isostatically pressed (CIP) parts formed at 200 MPa. Robocast composites consisting of alternate layers of the following sintered densities: (93.9%--96.1%--93.9%), were fabricated using different levels of organic pore former additions. Modification from a single to a multiple material deposition robocaster was essential to the fabrication of composites that could withstand repeated cycles of saturated polarization switching under 30 kV/cm fields.more » Further, these composites withstood 500 MPa hydrostatic pressure induced poled ferroelectric (FE) to antiferroelectric (AFE) phase transformation during which strain differences on the order of 0.8% occurred between composite elements.« less

The System of Chemical Elements Distribution in the Hydrosphere

NASA Astrophysics Data System (ADS)

Korzh, Vyacheslav D.

2013-04-01

The chemical composition of the hydrosphere is a result of substance migration and transformation on lithosphere-river, river-sea, and ocean-atmosphere boundaries. The chemical elements composition of oceanic water is a fundamental multi-dimensional constant for our planet. Detailed studies revealed three types of chemical element distribution in the ocean: 1) Conservative: concentration normalized to salinity is the constant in space and time; 2) Nutrient-type: element concentration in the surface waters decreases due to the biosphere consumption; and 3) Litho-generative: complex character of distribution of elements, which enter the ocean with the river runoff and interred almost entirely in sediments. The correlation between the chemical elements compositions of the river and oceanic water is high (r = 0.94). We conclude that biogeochemical features of each chemical element are determined by the relationship between its average concentration in the ocean and the intensity of its migration through hydrosphere boundary zones. In our presentation, we shall show intensities of global migration and average concentrations in the ocean in the co ordinates lgC - lg [tau], where C is an average element concentration and [tau] is its residence time in the ocean. We have derived a relationship between three main geochemical parameters of the dissolved forms of chemical elements in the hydrosphere: 1) average concentration in the ocean, 2) average concentration in the river runoff and 3) the type of distribution in oceanic water. Using knowledge of two of these parameters, it allows gaining theoretical knowledge of the third. The System covers all chemical elements for the entire range of observed concentrations. It even allows to predict the values of the annual river transport of dissolved Be, C, N, Ge, Tl, Re, to refine such estimates for P, V, Zn, Br, I, and to determine the character of distribution in the ocean for Au and U. Furthermore, the System allowed estimating natural (unaffected by anthropogenic influence) mean concentrations of elements in the river runoff and using them as ecological reference data. Finally, due to the long response time of the ocean, the mean concentrations of elements and patterns of their distribution in the ocean can be used to determine pre-techno-generative concentrations of elements in the river runoff. In our presentation, we shall show several examples of implementation of the System for studying the sediments' transport by the rivers of the Arctic slope of Northern Eurasia. References 1. Korzh V.D. 1974: Some general laws governing the turnover of substance within the ocean-atmosphere-continent-ocean cycle. Journal de Recherches Atmospheriques, 8, 653-660. 2. Korzh V.D. 2008: The general laws in the formation of the element composition of the Hydrosphere and Biosphere. J. Ecologica, 15, 13-21. 3. Korzh V.D. 2012: Determination of general laws of the chemical element composition in Hydrosphere. Water: Chemistry & Ecology, Journal of Water Science and its Practical Application. No. 1, 56-62.

Effects of cyclic impacts on the performance of a piezo-composite electricity generating element in a d33 mode energy harvesting.

PubMed

Pham, Van Lai; Ha, Ngoc San; Goo, Nam Seo; Choo, Jinkyo F

2014-10-01

The increasing use of piezoelectric generators to harvest energy from various ambient sources requires the establishment of durability data for piezoelectric materials. In this paper, a d3 mode piezocomposite electricity generating element (PCGE) was tested for its durability under cyclic impact loading. For this purpose, a motor driven lever system was designed to apply constant impact force on PCGEs. To investigate the durability of PCGEs, the output voltage of the PCGEs was observed upon repeated application of an impact force until eventual loss of the generated voltage. The experimental results enabled to determine the number of cycles until which PCGEs can be used without loss of their electricity generation performance with respect to the stress level applied on the PCGEs. At low stress level (around 0.76 MPa or lower), the PCGE showed almost insignificant degradation even after 2 million cycles whereas degradation occurred sooner (after 8 x 10(5) cycles) at higher stress levels (around 0.92 MPa or higher). The effects of impact loading on the durability of the PCGEs were also examined by X-ray photographs of the specimens.

Fabrication of 3D lawn-shaped N-doped porous carbon matrix/polyaniline nanocomposite as the electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Zhang, Xiuling; Ma, Li; Gan, Mengyu; Fu, Gang; Jin, Meng; Lei, Yao; Yang, Peishu; Yan, Maofa

2017-02-01

A facile approach to acquire electrode materials with prominent electrochemical property is pivotal to the progress of supercapacitors. 3D nitrogen-doped porous carbon matrix (PCM), with high specific surface area (SSA) up to 2720 m2 g-1, was obtained from the carbonization and activation of the nitrogen-enriched composite precursor (graphene/polyaniline). Then 3D lawn-shaped PCM/PANI composite was obtained by the simple in-situ polymerization. The morphology and structure of these resulting composites were characterized by combining SEM and TEM measurements, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) spectroscopy analyses and Raman spectroscope. The element content of all samples was evaluated using CHN analysis. The results of electrochemical testing indicated that the PCM/PANI composite displays a higher capacitance value of 527 F g-1 at 1 A g-1 compared to 338 F g-1 for pure PANI, and exhibits appreciable rate capability with a retention of 76% at 20 A g-1 as well as fine long-term cycling performance (with 88% retention of specific capacitance after 1000 cycles at 10 A g-1). Simultaneously, the excellent capacitance performance coupled with the facile synthesis of PCM/PANI indicates it is a promising electrode material for supercapacitors.

Tropical Mosquito Assemblages Demonstrate ‘Textbook’ Annual Cycles

PubMed Central

Franklin, Donald C.; Whelan, Peter I.

2009-01-01

Background Annual biological rhythms are often depicted as predictably cyclic, but quantitative evaluations are few and rarely both cyclic and constant among years. In the monsoon tropics, the intense seasonality of rainfall frequently drives fluctuations in the populations of short-lived aquatic organisms. However, it is unclear how predictably assemblage composition will fluctuate because the intensity, onset and cessation of the wet season varies greatly among years. Methodology/Principal Findings Adult mosquitoes were sampled using EVS suction traps baited with carbon dioxide around swamplands adjacent to the city of Darwin in northern Australia. Eleven sites were sampled weekly for five years, and one site weekly for 24 years, the sample of c. 1.4 million mosquitoes yielding 63 species. Mosquito abundance, species richness and diversity fluctuated seasonally, species richness being highly predictable. Ordination of assemblage composition demonstrated striking annual cycles that varied little from year to year. The mosquito assemblage was temporally structured by a succession of species peaks in abundance. Conclusion/Significance Ordination provided strong visual representation of annual rhythms in assemblage composition and the means to evaluate variability among years. Because most mosquitoes breed in shallow freshwater which fluctuates with rainfall, we did not anticipate such repeatability; we conclude that mosquito assemblage composition appears adapted to predictable elements of the rainfall. PMID:20011531

Stable isotopes of transition and post-transition metals as tracers in environmental studies

USGS Publications Warehouse

Bullen, Thomas D.; Baskaran, Mark

2011-01-01

The transition and post-transition metals, which include the elements in Groups 3–12 of the Periodic Table, have a broad range of geological and biological roles as well as industrial applications and thus are widespread in the environment. Interdisciplinary research over the past decade has resulted in a broad understanding of the isotope systematics of this important group of elements and revealed largely unexpected variability in isotope composition for natural materials. Significant kinetic and equilibrium isotope fractionation has been observed for redox sensitive metals such as iron, chromium, copper, molybdenum and mercury, and for metals that are not redox sensitive in nature such as cadmium and zinc. In the environmental sciences, the isotopes are increasingly being used to understand important issues such as tracing of metal contaminant sources and fates, unraveling metal redox cycles, deciphering metal nutrient pathways and cycles, and developing isotope biosignatures that can indicate the role of biological activity in ancient and modern planetary systems.

(abstract) Effect of Electrolyte Composition on Carbon Electrode Performance

NASA Technical Reports Server (NTRS)

Huang, C-K.; Surampudi, S.; Shen, D. H.; Halpert, G.

1993-01-01

Rechargeable lithium cells containing lithium foil anodes are reported to have limited cycle life (at 100% DOD) performance and safety problems. These limitations are understood to be due to the high reactivity of elemental Li with the electrolyte and the formation of high surface area Li during cycling. To mitigate these problems, several lithium alloys and lithium intercalation compounds are being investigated as alternate lithium anode materials. Li(sub x)C has been identified as a promising lithium anode material due to its low equivalent weight, low voltage vs. Li, and improved stability towards various electrolytes. In this paper, we report the results of our studies on the electrolyte evaluation for the Li(sub x)C anode.

Material property for designing, analyzing, and fabricating space structures

NASA Technical Reports Server (NTRS)

Kolkailah, Faysal A.

1991-01-01

An analytical study was made of plasma assisted bullet projectile. The finite element analysis and the micro-macromechanic analysis was applied to an optimum design technique for the multilayered graphite-epoxy composite projectile that will achieve hypervelocity of 6 to 10 Km/s. The feasibility was determined of dialectics to monitor cure of graphite-epoxies. Several panels were fabricated, cured, and tested with encouraging results of monitoring the cure of graphite-epoxies. The optimum cure process for large structures was determined. Different orientation were used and three different curing cycles were employed. A uniaxial tensile test was performed on all specimens. The optimum orientation with the optimum cure cycle were concluded.

Life cycle assessment of metal alloys for structural applications

NASA Astrophysics Data System (ADS)

Malovrh Rebec, K.; Markoli, B.; Leskovar, B.

2018-03-01

The study compared environmental footprints of two types of Al-alloys: well-known 5083 aluminium alloy with magnesium and traces of manganese and chromium in its composition. This material is highly resistant to seawater corrosion and the influence of industrial chemicals. Furthermore, it retains exceptional strength after welding. The comparisons were made to an innovative alloy where the aluminium based matrix is reinforced by metastable quasicrystals (QC), thus avoiding magnesium in its composition. Furthermore, we checked other aluminium ingots’ footprints and compared European average and Germany country specific production data. Environmental footprints were assessed via cradle to gate life cycle assessment. Our findings normalized to 1 m2 plate suggest, that newly proposed alloy could save around 50 % in value of parameters abiotic resources depletion of fossil fuels, acidification, eutrophication, global warming potential and photochemical ozone creation potential if we compare Qc5 to 6 mm 5083 alloy plate. Only abiotic resources depletion of elements and ozone depletion parameters increase for Qc5 compared to 6 mm 5083 alloy plate.

Biomass Waste Inspired Highly Porous Carbon for High Performance Lithium/Sulfur Batteries

PubMed Central

Zhao, Yan; Ren, Jun; Tan, Taizhe; Babaa, Moulay-Rachid; Bakenov, Zhumabay; Liu, Ning; Zhang, Yongguang

2017-01-01

The synthesis of highly porous carbon (HPC) materials from poplar catkin by KOH chemical activation and hydrothermal carbonization as a conductive additive to a lithium-sulfur cathode is reported. Elemental sulfur was composited with as-prepared HPC through a melt diffusion method to form a S/HPC nanocomposite. Structure and morphology characterization revealed a hierarchically sponge-like structure of HPC with high pore volume (0.62 cm3∙g−1) and large specific surface area (1261.7 m2∙g−1). When tested in Li/S batteries, the resulting compound demonstrated excellent cycling stability, delivering a second-specific capacity of 1154 mAh∙g−1 as well as presenting 74% retention of value after 100 cycles at 0.1 C. Therefore, the porous structure of HPC plays an important role in enhancing electrochemical properties, which provides conditions for effective charge transfer and effective trapping of soluble polysulfide intermediates, and remarkably improves the electrochemical performance of S/HPC composite cathodes. PMID:28878149

Sustainable Sulfur-rich Copolymer/Graphene Composite as Lithium-Sulfur Battery Cathode with Excellent Electrochemical Performance

PubMed Central

Ghosh, Arnab; Shukla, Swapnil; Khosla, Gaganpreet Singh; Lochab, Bimlesh; Mitra, Sagar

2016-01-01

A sulfur-rich copolymer, poly(S-r-C-a) has been synthesized via a sustainable route, showing the utility of two major industrial wastes- elemental sulfur (petroleum waste) and cardanol (agro waste), to explore its potential as cathode material for Li-S batteries. The sulfur-rich copolymer exhibited a reduction in the active material dissolution into the electrolyte and a low self-discharge rate behavior during the rest time compared to an elemental sulfur cathode, indicating the chemical confinement of sulfur units. The presence of organosulfur moieties in copolymer suppress the irreversible deposition of end-discharge products on electrode surfaces and thus improve the electrochemical performances of Li-S batteries. This sulfur copolymer offered a reversible capacity of 892 mA h g−1 at 2nd cycle and maintained the capacity of 528 mA h g−1 after 50 cycles at 200 mA g−1. Reduced graphene oxide (rGO) prepared via a sustainable route was used as a conductive filler to extract the better electrochemical performances from this sulfur copolymer. Such sustainable origin batteries prepared via economically viable showed an improved specific capacity of ~975 mA h g−1 after 100 cycles at 200 mA g−1 current rate with capacity fading of 0.15% per cycle and maintained a stable performance over 500 cycles at 2000 mA g−1. PMID:27121089

Stress analysis in curved composites due to thermal loading

NASA Astrophysics Data System (ADS)

Polk, Jared Cornelius

Many structures in aircraft, cars, trucks, ships, machines, tools, bridges, and buildings, consist of curved sections. These sections vary from straight line segments that have curvature at either one or both ends, segments with compound curvatures, segments with two mutually perpendicular curvatures or Gaussian curvatures, and segments with a simple curvature. With the advancements made in multi-purpose composites over the past 60 years, composites slowly but steadily have been appearing in these various vehicles, compound structures, and buildings. These composite sections provide added benefits over isotropic, polymeric, and ceramic materials by generally having a higher specific strength, higher specific stiffnesses, longer fatigue life, lower density, possibilities in reduction of life cycle and/or acquisition cost, and greater adaptability to intended function of structure via material composition and geometry. To be able to design and manufacture a safe composite laminate or structure, it is imperative that the stress distributions, their causes, and effects are thoroughly understood in order to successfully accomplish mission objectives and manufacture a safe and reliable composite. The objective of the thesis work is to expand upon the knowledge of simply curved composite structures by exploring and ascertaining all pertinent parameters, phenomenon, and trends in stress variations in curved laminates due to thermal loading. The simply curved composites consist of composites with one radius of curvature throughout the span of the specimen about only one axis. Analytical beam theory, classical lamination theory, and finite element analysis were used to ascertain stress variations in a flat, isotropic beam. An analytical method was developed to ascertain the stress variations in an isotropic, simply curved beam under thermal loading that is under both free-free and fixed-fixed constraint conditions. This is the first such solution to Author's best knowledge of such a problem. It was ascertained and proven that the general, non-modified (original) version of classical lamination theory cannot be used for an analytical solution for a simply curved beam or any other structure that would require rotations of laminates out their planes in space. Finite element analysis was used to ascertain stress variations in a simply curved beam. It was verified that these solutions reduce to the flat beam solutions as the radius of curvature of the beams tends to infinity. MATLAB was used to conduct the classical lamination theory numerical analysis. A MATLAB program was written to conduct the finite element analysis for the flat and curved beams, isotropic and composite. It does not require incompatibility techniques used in mechanics of isotropic materials for indeterminate structures that are equivalent to fixed-beam problems. Finally, it has the ability to enable the user to define and create unique elements not accessible in commercial software, and modify finite element procedures to take advantage of new paradigms.

Molecular Engineering for Mechanically Resilient and Stretchable Electronic Polymers and Composites

DTIC Science & Technology

2016-06-08

CONTRACT NUMBER 5b. GRANT NUMBER FA9550-13-1-0156 5c. PROGRAM ELEMENT NUMBER 6 . AUTHOR(S) Darren J. Lipomi 5d. PROJECT NUMBER 5e. TASK NUMBER...CA 92093-0448 8. PERFORMING ORGANIZATION REPORT NUMBER 9 . SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) Air Force Office of Scientific...these results to produce a new type of ultra-thin, skin-wearable solar cell that could survive many cycles of deformation without degrading

Impact resonance method for damage detection in RC beams strengthened with composites

NASA Astrophysics Data System (ADS)

Gheorghiu, Catalin; Rhazi, Jamal E.; Labossiere, Pierre

2005-05-01

There are numerous successful applications of fibre-reinforced composites for strengthening the civil engineering infrastructure. Most of these repairs are being continuously or intermittently monitored for assessing their effectiveness and safety. The impact resonance method (IRM), a non-destructive technique, utilized in civil engineering exclusively for determining the dynamic concrete properties, could be a valuable and viable damage detection tool for structural elements. The IRM gives useful information about the dynamic characteristics of rectangular and circular concrete members such as beams and columns. In this experimental program, a 1.2-m-long reinforced concrete beam strengthened with a carbon fibre-reinforced polymer (CFRP) plate has been employed. The CFRP-strengthened beam has been loaded in fatigue for two million cycles at 3 Hz. The load amplitude was from 15 to 35% of the anticipated yielding load of the beam. Throughout fatigue testing the cycling was stopped for IRM measurements to be taken. The obtained data provided information about changes in modal properties such as natural frequencies of vibration. These results have shown the successful use of the IRM for detecting fatigue damage in concrete members strengthened with composites.

Solar Corona/Wind Composition and Origins of the Solar Wind

NASA Astrophysics Data System (ADS)

Lepri, S. T.; Gilbert, J. A.; Landi, E.; Shearer, P.; von Steiger, R.; Zurbuchen, T.

2014-12-01

Measurements from ACE and Ulysses have revealed a multifaceted solar wind, with distinctly different kinetic and compositional properties dependent on the source region of the wind. One of the major outstanding issues in heliophysics concerns the origin and also predictability of quasi-stationary slow solar wind. While the fast solar wind is now proven to originate within large polar coronal holes, the source of the slow solar wind remains particularly elusive and has been the subject of long debate, leading to models that are stationary and also reconnection based - such as interchange or so-called S-web based models. Our talk will focus on observational constraints of solar wind sources and their evolution during the solar cycle. In particular, we will point out long-term variations of wind composition and dynamic properties, particularly focused on the abundance of elements with low First Ionization Potential (FIP), which have been routinely measured on both ACE and Ulysses spacecraft. We will use these in situ observations, and remote sensing data where available, to provide constraints for solar wind origin during the solar cycle, and on their correspondence to predictions for models of the solar wind.

Biodeterioration of the Cement Composites

NASA Astrophysics Data System (ADS)

Luptáková, Alena; Eštoková, Adriana; Mačingová, Eva; Kovalčíková, Martina; Jenčárová, Jana

2016-10-01

The destruction of natural and synthetic materials is the spontaneous and irreversible process of the elements cycling in nature. It can by accelerated or decelerated by physical, chemical and biological influences. Biological influences are represented by the influence of the vegetation and microorganisms (MO). The destruction of cement composites by different MO through the diverse mechanisms is entitled as the concrete biodeterioration. Several sulphur compounds and species of MO are involved in this complex process. Heterotrophic and chemolithotrophic bacteria together with fungi have all been found in samples of corroding cement composites. The MO involved in the process metabolise the presented sulphur compounds (hydrogen sulphide, elemental sulphur etc.) to sulphuric acid reacting with concrete. When sulphuric acid reacts with a concrete matrix, the first step involves a reaction between the acid and the calcium hydroxide forming calcium sulphate. This is subsequently hydrated to form gypsum, the appearance of which on the surface of concrete pipes takes the form of a white, mushy substance which has no cohesive properties. In the continuing attack, the gypsum would react with the calcium aluminate hydrate to form ettringite, an expansive product. The use supplementary cementing composite materials have been reported to improve the resistance of concrete to biodeterioration. The aim of this work was the study of the cement composites biodeterioration by the bacteria Acidithiobacillus thiooxidans. Experimental works were focused on the comparison of special cement composites and its resistance affected by the activities of used sulphur-oxidising

Multi-element microelectropolishing method

DOEpatents

Lee, Peter J.

1994-01-01

A method is provided for microelectropolishing a transmission electron microscopy nonhomogeneous multi-element compound foil. The foil is electrolyzed at different polishing rates for different elements by rapidly cycling between different current densities. During a first portion of each cycle at a first voltage a first element electrolyzes at a higher current density than a second element such that the material of the first element leaves the anode foil at a faster rate than the second element and creates a solid surface film, and such that the solid surface film is removed at a faster rate than the first element leaves the anode foil. During a second portion of each cycle at a second voltage the second element electrolyzes at a higher current density than the first element, and the material of the second element leaves the anode foil at a faster rate than the first element and creates a solid surface film, and the solid surface film is removed at a slower rate than the second element leaves the foil. The solid surface film is built up during the second portion of the cycle, and removed during the first portion of the cycle.

Fatigue Life Methodology for Tapered Hybrid Composite Flexbeams

NASA Technical Reports Server (NTRS)

urri, Gretchen B.; Schaff, Jeffery R.

2006-01-01

Nonlinear-tapered flexbeam specimens from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. Two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) associated with simulated delamination growth in the flexbeams are presented from both codes. These results compare well with each other and suggest that the initial delamination growth from the tip of the ply-drop toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves for comparison with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared well with the test results.

Tracing halogen and B cycling in subduction zones based on obducted, subducted and forearc serpentinites of the Dominican Republic.

PubMed

Pagé, Lilianne; Hattori, Keiko

2017-12-19

Serpentinites are important reservoirs of fluid-mobile elements in subduction zones, contributing to volatiles in arc magmas and their transport into the Earth's mantle. This paper reports halogen (F, Cl, Br, I) and B abundances of serpentinites from the Dominican Republic, including obducted and subducted abyssal serpentinites and forearc mantle serpentinites. Abyssal serpentinite compositions indicate the incorporation of these elements from seawater and sediments during serpentinization on the seafloor and at slab bending. During their subduction and subsequent lizardite-antigorite transition, F and B are retained in serpentinites, whilst Cl, Br and I are expelled. Forearc mantle serpentinite compositions suggest their hydration by fluids released from subducting altered oceanic crust and abyssal serpentinites, with only minor sediment contribution. This finding is consistent with the minimal subduction of sediments in the Dominican Republic. Forearc mantle serpentinites have F/Cl and B/Cl ratios similar to arc magmas, suggesting the importance of serpentinite dehydration in the generation of arc magmatism in the mantle wedge.

Evolution of a Quaternary peralkaline volcano: Mayor Island, New Zealand

USGS Publications Warehouse

Houghton, Bruce F.; Weaver, S.D.; Wilson, C.J.N.; Lanphere, M.A.

1992-01-01

Mayor Island is a Holocene pantelleritic volcano showing a wide range of dispersive power and eruptive intensity despite a very limited range in magma composition of only 2% SiO2. The primary controls on this range appear to have been the magmatic gas content on eruption and a varying involvement of basaltic magma, rather than major-element chemistry of the rhyolites. The ca. 130 ka subaerial history of the volcano contains portions of three geochemical cycles with abrupt changes in trace-element chemistry following episodes of caldera collapse. The uniform major-element chemistry of the magma may relate to a fine balance between rates of eruption and supply and the higher density of the more evolved (Ferich) magmas which could be tapped only after caldera-forming events had removed significant volumes of less evolved but lighter magma. ?? 1992.

Canopy Nutrient Cycling In Afromontane Tropical Forests At Different Successional Stages

NASA Astrophysics Data System (ADS)

Nyirambangutse, B.; Zibera, E.; Dusenge, M. E.; Nsabimana, D.; Pleijel, H.; Uddling, J.; Wallin, G.

2017-12-01

Canopy nutrient composition and cycling control biogeochemical processes and tree growth in forests. However, the understanding of nutrient limitations and cycling in tropical montane forests (TMF) is currently limited, in particular for Afromontane forests. In this study we investigated leaf nutrient composition and resorption, canopy nutrient cycling and soil carbon and nutrient content in 15 permanent plots at different successional stages in a TMF (elevation 1950 to 2550 m a.s.l.) in Rwanda, Central Africa. Leaf concentrations of 12 elements were analyzed in attached green leaves as well as in shed leaves of 10 early (ES) and 10 late (LS) successional tree species. Leaf nutrient concentrations mostly did not differ between ES and LS species (exception: K was 20% higher in ES), but the ratios of P, K and Mg to N were significantly higher in ES species. Mean resorption efficiencies of N (37%), P (48%) and K (46%) were much higher than for other nutrients. Nutrient resorption efficiency exhibited very large interspecific variation, did not differ between ES and LS species, and was not related to the leaf concentration of the respective element. Total leaf litterfall was on average 4.9 t ha-1 yr-1 (66% of total litterfall) and was independent of the successional stage of the forest. The total content of C, N, P and K in leaf litterfall did not differ between ES and LS stands. Ground litter turnover rates of C and N were 0.98 and 0.78 y-1, respectively. High leaf N concentrations, intermediate N:P ratios and low resorption efficiencies compared to values reported for other TMFs indicate high fertility and likely co-limitation by N and P, however progressively increasing towards P limitation during the course of succession. Our results further demonstrate that resorption efficiency and canopy litterfall inputs to soil mostly do not differ between ES and LS species in Afromontane tropical forests.

Influence of dental restorations and mastication loadings on dentine fatigue behaviour: Image-based modelling approach.

PubMed

Vukicevic, Arso M; Zelic, Ksenija; Jovicic, Gordana; Djuric, Marija; Filipovic, Nenad

2015-05-01

The aim of this study was to use Finite Element Analysis (FEA) to estimate the influence of various mastication loads and different tooth treatments (composite restoration and endodontic treatment) on dentine fatigue. The analysis of fatigue behaviour of human dentine in intact and composite restored teeth with root-canal-treatment using FEA and fatigue theory was performed. Dentine fatigue behaviour was analysed in three virtual models: intact, composite-restored and endodontically-treated tooth. Volumetric change during the polymerization of composite was modelled by thermal expansion in a heat transfer analysis. Low and high shrinkage stresses were obtained by varying the linear shrinkage of composite. Mastication forces were applied occlusally with the load of 100, 150 and 200N. Assuming one million cycles, Fatigue Failure Index (FFI) was determined using Goodman's criterion while residual fatigue lifetime assessment was performed using Paris-power law. The analysis of the Goodman diagram gave both maximal allowed crack size and maximal number of cycles for the given stress ratio. The size of cracks was measured on virtual models. For the given conditions, fatigue-failure is not likely to happen neither in the intact tooth nor in treated teeth with low shrinkage stress. In the cases of high shrinkage stress, crack length was much larger than the maximal allowed crack and failure occurred with 150 and 200N loads. The maximal allowed crack size was slightly lower in the tooth with root canal treatment which induced somewhat higher FFI than in the case of tooth with only composite restoration. Main factors that lead to dentine fatigue are levels of occlusal load and polymerization stress. However, root canal treatment has small influence on dentine fatigue. The methodology proposed in this study provides a new insight into the fatigue behaviour of teeth after dental treatments. Furthermore, it estimates maximal allowed crack size and maximal number of cycles for a specific case. Copyright © 2015 Elsevier Ltd. All rights reserved.

An investigation into the impact of cryogenic environment on mechanical stresses in FRP composites

NASA Astrophysics Data System (ADS)

Fifo, O.; Basu, B.

2015-07-01

Fibre reinforced polymer (FRP) composites are fast becoming a highly utilised engineering material for high performance applications due to their light weight and high strength. Carbon fibre and other high strength fibres are commonly used in design of aerospace structures, wind turbine blades, etc. and potentially for propellant tanks of launch vehicles. For the aforementioned fields of application, stability of the material is essential over a wide range of temperature particularly for structures in hostile environments. Many studies have been conducted, experimentally, over the last decade to investigate the mechanical behaviour of FRP materials at varying subzero temperature. Likewise, tests on aging and cycling effect (room to low temperature) on the mechanical response of FRP have been reported. However, a relatively lesser focused area has been the mechanical behaviour of FRP composites under cryogenic environment. This article reports a finite element method of investigating the changes in the mechanical characteristics of an FRP material when temperature based analysis falls below zero. The simulated tests are carried out using a finite element package with close material properties used in the cited literatures. Tensile test was conducted and the results indicate that the mechanical responses agree with those reported in the literature sited.

Building Block Approach' for Structural Analysis of Thermoplastic Composite Components for Automotive Applications

NASA Astrophysics Data System (ADS)

Carello, M.; Amirth, N.; Airale, A. G.; Monti, M.; Romeo, A.

2017-12-01

Advanced thermoplastic prepreg composite materials stand out with regard to their ability to allow complex designs with high specific strength and stiffness. This makes them an excellent choice for lightweight automotive components to reduce mass and increase fuel efficiency, while maintaining the functionality of traditional thermosetting prepreg (and mechanical characteristics) and with a production cycle time and recyclability suited to mass production manufacturing. Currently, the aerospace and automotive sectors struggle to carry out accurate Finite Elements (FE) component analyses and in some cases are unable to validate the obtained results. In this study, structural Finite Elements Analysis (FEA) has been done on a thermoplastic fiber reinforced component designed and manufactured through an integrated injection molding process, which consists in thermoforming the prepreg laminate and overmolding the other parts. This process is usually referred to as hybrid molding, and has the provision to reinforce the zones subjected to additional stresses with thermoformed themoplastic prepreg as required and overmolded with a shortfiber thermoplastic resin in single process. This paper aims to establish an accurate predictive model on a rational basis and an innovative methodology for the structural analysis of thermoplastic composite components by comparison with the experimental tests results.

Amorphous V-O-C composite nanofibers electrospun from solution precursors as binder- and conductive additive-free electrodes for supercapacitors with outstanding performance

NASA Astrophysics Data System (ADS)

Chen, Xia; Zhao, Bote; Cai, Yong; Tadé, Moses O.; Shao, Zongping

2013-11-01

Flexible V-O-C composite nanofibers were fabricated from solution precursors via electrospinning and were investigated as free-standing and additive-free film electrodes for supercapacitors. Specifically, composite nanofibers (V0, V5, V10 and V20) with different vanadyl acetylacetonate (VO(acac)2) contents of 0, 5, 10 and 20 wt% with respect to polyacrylonitrile (PAN) were prepared. The composite nanofibers were comparatively studied using XRD, Raman spectroscopy, XPS, N2 adsorption-desorption, FE-SEM, TEM and S-TEM. The vanadium element was found to be well-dispersed in the carbon nanofibers, free from the formation of an aggregated crystalline phase, even in the case of V20. A specific surface area of 587.9 m2 g-1 was reached for V10 after calcination, which is approximately twice that of the vanadium-free carbon nanofibers (V0, 300.9 m2 g-1). To perform as an electrode for supercapacitors in an aqueous electrolyte, the V10 film delivered a specific capacitance of 463 F g-1 at 1 A g-1. V10 was also able to retain a specific capacitance of 380 F g-1, even at a current density of 10 A g-1. Additionally, very stable cycling stability was achieved, maintaining an outstanding specific capacitance of 400 F g-1 at 5 A g-1 after charge-discharge cycling 5000 times. Thus, V-O-C composite nanofibers are highly attractive electrode materials for flexible, high-power, thin film energy storage devices and applications.Flexible V-O-C composite nanofibers were fabricated from solution precursors via electrospinning and were investigated as free-standing and additive-free film electrodes for supercapacitors. Specifically, composite nanofibers (V0, V5, V10 and V20) with different vanadyl acetylacetonate (VO(acac)2) contents of 0, 5, 10 and 20 wt% with respect to polyacrylonitrile (PAN) were prepared. The composite nanofibers were comparatively studied using XRD, Raman spectroscopy, XPS, N2 adsorption-desorption, FE-SEM, TEM and S-TEM. The vanadium element was found to be well-dispersed in the carbon nanofibers, free from the formation of an aggregated crystalline phase, even in the case of V20. A specific surface area of 587.9 m2 g-1 was reached for V10 after calcination, which is approximately twice that of the vanadium-free carbon nanofibers (V0, 300.9 m2 g-1). To perform as an electrode for supercapacitors in an aqueous electrolyte, the V10 film delivered a specific capacitance of 463 F g-1 at 1 A g-1. V10 was also able to retain a specific capacitance of 380 F g-1, even at a current density of 10 A g-1. Additionally, very stable cycling stability was achieved, maintaining an outstanding specific capacitance of 400 F g-1 at 5 A g-1 after charge-discharge cycling 5000 times. Thus, V-O-C composite nanofibers are highly attractive electrode materials for flexible, high-power, thin film energy storage devices and applications. Electronic supplementary information (ESI) available: FE-SEM image. See DOI: 10.1039/c3nr04484j

Structural and Electrical Properties of Lithium-Ion Rechargeable Battery Using the LiFePO4/Carbon Cathode Material.

PubMed

Kim, Young-Sung; Jeoung, Tae-Hoon; Nam, Sung-Pill; Lee, Seung-Hwan; Kim, Jea-Chul; Lee, Sung-Gap

2015-03-01

LiFePO4/C composite powder as cathode material and graphite powder as anode material for Li-ion batteries were synthesized by using the sol-gel method. An electrochemical improvement of LiFePO4 materials has been achieved by adding polyvinyl alcohol as a carbon source into as-prepared materials. The samples were characterized by elemental analysis (EA), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-EM). The chemical composition of LiFePO4/C powders was in a good agreement with that of the starting solution. The capacity loss after 500 cycles of LiFePO4/C cell is 11.1% in room temperature. These superior electrochemical properties show that LiFePO4/C composite materials are promising candidates as cathode materials.

Transcriptional Changes Underlying Elemental Stoichiometry Shifts in a Marine Heterotrophic Bacterium

PubMed Central

Chan, Leong-Keat; Newton, Ryan J.; Sharma, Shalabh; Smith, Christa B.; Rayapati, Pratibha; Limardo, Alexander J.; Meile, Christof; Moran, Mary Ann

2012-01-01

Marine bacteria drive the biogeochemical processing of oceanic dissolved organic carbon (DOC), a 750-Tg C reservoir that is a critical component of the global C cycle. Catabolism of DOC is thought to be regulated by the biomass composition of heterotrophic bacteria, as cells maintain a C:N:P ratio of ∼50:10:1 during DOC processing. Yet a complicating factor in stoichiometry-based analyses is that bacteria can change the C:N:P ratio of their biomass in response to resource composition. We investigated the physiological mechanisms of resource-driven shifts in biomass stoichiometry in continuous cultures of the marine heterotrophic bacterium Ruegeria pomeroyi (a member of the Roseobacter clade) under four element limitation regimes (C, N, P, and S). Microarray analysis indicated that the bacterium scavenged for alternate sources of the scarce element when cells were C-, N-, or P-limited; reworked the ratios of biomolecules when C- and P- limited; and exerted tighter control over import/export and cytoplasmic pools when N-limited. Under S limitation, a scenario not existing naturally for surface ocean microbes, stress responses dominated transcriptional changes. Resource-driven changes in C:N ratios of up to 2.5-fold and in C:P ratios of up to sixfold were measured in R. pomeroyi biomass. These changes were best explained if the C and P content of the cells was flexible in the face of shifting resources but N content was not, achieved through the net balance of different transcriptional strategies. The cellular-level metabolic trade-offs that govern biomass stoichiometry in R. pomeroyi may have implications for global carbon cycling if extendable to other heterotrophic bacteria. Strong homeostatic responses to N limitation by marine bacteria would intensify competition with autotrophs. Modification of cellular inventories in C- and P-limited heterotrophs would vary the elemental ratio of particulate organic matter sequestered in the deep ocean. PMID:22783226

Diel cycling of trace elements in streams draining mineralized areas: a review

USGS Publications Warehouse

Gammons, Christopher H.; Nimick, David A.; Parker, Stephen R.

2015-01-01

Many trace elements exhibit persistent diel, or 24-h, concentration cycles in streams draining mineralized areas. These cycles can be caused by various physical and biogeochemical mechanisms including streamflow variation, photosynthesis and respiration, as well as reactions involving photochemistry, adsorption and desorption, mineral precipitation and dissolution, and plant assimilation. Iron is the primary trace element that exhibits diel cycling in acidic streams. In contrast, many cationic and anionic trace elements exhibit diel cycling in near-neutral and alkaline streams. Maximum reported changes in concentration for these diel cycles have been as much as a factor of 10 (988% change in Zn concentration over a 24-h period). Thus, monitoring and scientific studies must account for diel trace-element cycling to ensure that water-quality data collected in streams appropriately represent the conditions intended to be studied.

Design/Analysis of Metal/Composite Bonded Joints for Survivability at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Bartoszyk, Andrew E.

2004-01-01

A major design and analysis challenge for the JWST ISM structure is the metal/composite bonded joints that will be required to survive down to an operational ultra-low temperature of 30K (-405 F). The initial and current baseline design for the plug-type joint consists of a titanium thin walled fitting (1-3mm thick) bonded to the interior surface of an M555/954-6 composite truss square tube with an axially stiff biased lay-up. Metallic fittings are required at various nodes of the truss structure to accommodate instrument and lift-point bolted interfaces. Analytical experience and design work done on metal/composite bonded joints at temperatures below liquid nitrogen are limited and important analysis tools, material properties, and failure criteria for composites at cryogenic temperatures are virtually nonexistent. Increasing the challenge is the difficulty in testing for these required tools and parameters at 30K. A preliminary finite element analysis shows that failure due to CTE mismatch between the biased composite and titanium or aluminum is likely. Failure is less likely with Invar, however an initial mass estimate of Invar fittings demonstrates that Invar is not an automatic alternative. In order to gain confidence in analyzing and designing the ISM joints, a comprehensive joint development testing program has been planned and is currently running. The test program is designed for the correlation of the analysis methodology, including tuning finite element model parameters, and developing a composite failure criterion for the effect of multi-axial composite stresses on the strength of a bonded joint at 30K. The testing program will also consider stress mitigation using compliant composite layers and potential strength degradation due to multiple thermal cycles. Not only will the finite element analysis be correlated to the test data, but the FEA will be used to guide the design of the test. The first phase of the test program has been completed and the preliminary analysis has been revisited based on the test data In this work, we present an overview of the test plan, results today, and resulting design improvements.

Inert matrix fuel neutronic, thermal-hydraulic, and transient behavior in a light water reactor

NASA Astrophysics Data System (ADS)

Carmack, W. J.; Todosow, M.; Meyer, M. K.; Pasamehmetoglu, K. O.

2006-06-01

Currently, commercial power reactors in the United States operate on a once-through or open cycle, with the spent nuclear fuel eventually destined for long-term storage in a geologic repository. Since the fissile and transuranic (TRU) elements in the spent nuclear fuel present a proliferation risk, limit the repository capacity, and are the major contributors to the long-term toxicity and dose from the repository, methods and systems are needed to reduce the amount of TRU that will eventually require long-term storage. An option to achieve a reduction in the amount, and modify the isotopic composition of TRU requiring geological disposal is 'burning' the TRU in commercial light water reactors (LWRs) and/or fast reactors. Fuel forms under consideration for TRU destruction in light water reactors (LWRs) include mixed-oxide (MOX), advanced mixed-oxide, and inert matrix fuels. Fertile-free inert matrix fuel (IMF) has been proposed for use in many forms and studied by several researchers. IMF offers several advantages relative to MOX, principally it provides a means for reducing the TRU in the fuel cycle by burning the fissile isotopes and transmuting the minor actinides while producing no new TRU elements from fertile isotopes. This paper will present and discuss the results of a four-bundle, neutronic, thermal-hydraulic, and transient analyses of proposed inert matrix materials in comparison with the results of similar analyses for reference UOX fuel bundles. The results of this work are to be used for screening purposes to identify the general feasibility of utilizing specific inert matrix fuel compositions in existing and future light water reactors. Compositions identified as feasible using the results of these analyses still require further detailed neutronic, thermal-hydraulic, and transient analysis study coupled with rigorous experimental testing and qualification.

Effects of sea-level changes on mid-ocean ridge magmatism and implications for emission rates of carbon.

NASA Astrophysics Data System (ADS)

Cerpa, N.; Katz, R. F.; Keller, T.

2017-12-01

Glacial cycles move water between ice sheets and the ocean, and hence cause regional pressure changes in the solid Earth. The rate of sea-level (SL) change during this cycle is comparable to the rate of mantle upwelling beneath mid-ocean ridges (MORs), and hence we expect the induced pressure variations to modify the rate and depth of silicate melting. SL variations may therefore induce changes in the supply and composition of magma at MORs, which could affect the flux of carbon into the climate system. Likewise, the trace-element geochemistry of magmas tapped by ridge volcanism may vary during these cycles due to variations in melt flux. Such variations may have been recorded by sediment-hosted volcanic glass fragments [Ferguson et al., 2017]. We investigate these questions using computational models of melt production and transport in which volatiles participate in the thermodynamics of melting. Published models of the effect of SL on MORs predict up to 10% variation in carbon emission rates for absolute changes in SL of 50-100 m with possible lag times of several tens of kyrs [Burley et al., 2015; Hasenclever et al., 2017]. A major assumption of those models is that water and carbon are passive, incompatible elements. But small concentrations of those volatiles affect the solidus of mantle peridotite and increase the volume of upper mantle undergoing partial melting. Hence the current predictions of variation in MOR carbon emission might be an underestimate. Moreover, published models neglect the effects of volatiles on melt transport. Recents studies have demonstrated that volatiles can induce channelized transport [Keller and Katz 2016], potentially affecting the rate at which carbon is extracted from the mantle. In this study, we investigate the interplay between SL variations, melting, and segregation of volatile-rich melts. We use two-phase magma/mantle dynamics coupled to melting models that treat water and carbon dioxide as thermodynamic components. We compare models of equilibrium and disequilibrium melting to assess the influence of reaction kinetics on magma productivity at MORs during SL variations. Our calculations provide new estimates of the lag and amplitude of carbon emissions during glacial cycles. We address the impact of SL variations on the trace-element composition of magmas.

Cadmium cycling in the water column of the Kuroshio-Oyashio Extension region: Insights from dissolved and particulate isotopic composition

NASA Astrophysics Data System (ADS)

Yang, Shun-Chung; Zhang, Jing; Sohrin, Yoshiki; Ho, Tung-Yuan

2018-07-01

We measured dissolved and particulate Cd isotopic composition in the water column of a meridional transect across the Kuroshio-Oyashio Extension region in a Japanese GEOTRACES cruise to investigate the relative influence of physical and biogeochemical processes on Cd cycling in the Northwestern Pacific Ocean. Located at 30-50°N along 165°E, the transect across the extension region possesses dramatic hydrographic contrast. Cold surface water and a relatively narrow and shallow thermocline characterizes the Oyashio Extension region in contrast to a relatively warm and highly stratified surface water and thermocline in the Kuroshio Extension region. The contrasting hydrographic distinction at the study site provides us with an ideal platform to investigate the spatial variations of Cd isotope fractionation systems in the ocean. Particulate samples demonstrated biologically preferential uptake of light Cd isotopes, and the fractionation effect varied dramatically in the surface water of the two regions, with relatively large fractionation factors in the Oyashio region. Based on the relationship of dissolved Cd concentrations and isotopic composition, we found that a closed system fractionation model can reasonably explain the relationship in the Kuroshio region. However, using dissolved Cd isotopic data, either a closed system or steady-state open system fractionation model may explain the relationship in the surface water of the Oyashio region. Particulate δ114/110Cd data further supports that the surface water of the Oyashio region matches a steady-state open system model more closely. Contrary to the surface water, the distribution of potential density exhibits comparable patterns with Cd elemental and isotopic composition in the thermocline and deep water in the two extension regions, showing that physical processes are the dominant forcing controlling Cd cycling in the deep waters. The results demonstrate that Cd isotope fractionation can match either a closed or open system Rayleigh fractionation model, depending on the relative contribution of physical and biogeochemical processes on its cycling.

High-rate and ultralong cycle-life LiFePO4 nanocrystals coated by boron-doped carbon as positive electrode for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Feng, Jinpeng; Wang, Youlan

2016-12-01

An evolutionary modification approach, boron-doped carbon coating, has been used to improve the electrochemical performances of positive electrodes for lithium-ion batteries, and demonstrates apparent and significant modification effects. In this study, the boron-doped carbon coating is firstly adopted and used to decorate the performance of LiFePO4. The obtained composite exhibits a unique core-shell structure with an average diameter of 140 nm and a 4 nm thick boron-doped carbon shell that uniformly encapsulates the core. Owing to the boron element which could induce high amount of defects in the carbon, the electronic conductivity of LiFePO4 is greatly ameliorated. Thus, the boron-doped composite shows superior rate capability and cycle stability than the undoped sample. For instance, the reversible specific capacity of LiFePO4@B0.4-C can reach 164.1 mAh g-1 at 0.1C, which is approximately 96.5% of the theoretical capacity (170 mAh g-1). Even at high rate of 10C, it still shows a high specific capacity of 126.8 mAh g-1 and can be maintained at 124.5 mAh g-1 after 100 cycles with capacity retention ratio of about 98.2%. This outstanding Li-storage property enable the present design strategy to open up the possibility of fabricating the LiFePO4@B-C composite for high-performance lithium-ion batteries.

Linking morphology with activity through the lifetime of pretreated PtNi nanostructured thin film catalysts

DOE PAGES

Cullen, David A.; Lopez-Haro, Miguel; Bayle-Guillemaud, Pascale; ...

2015-04-10

In this study, the nanoscale morphology of highly active Pt 3Ni 7 nanostructured thin film fuel cell catalysts is linked with catalyst surface area and activity following catalyst pretreatments, conditioning and potential cycling. The significant role of fuel cell conditioning on the structure and composition of these extended surface catalysts is demonstrated by high resolution imaging, elemental mapping and tomography. The dissolution of Ni during fuel cell conditioning leads to highly complex, porous structures which were visualized in 3D by electron tomography. Quantification of the rendered surfaces following catalyst pretreatment, conditioning, and cycling shows the important role pore structure playsmore » in surface area, activity, and durability.« less

Multi-element microelectropolishing method

DOEpatents

Lee, P.J.

1994-10-11

A method is provided for microelectropolishing a transmission electron microscopy nonhomogeneous multi-element compound foil. The foil is electrolyzed at different polishing rates for different elements by rapidly cycling between different current densities. During a first portion of each cycle at a first voltage a first element electrolyzes at a higher current density than a second element such that the material of the first element leaves the anode foil at a faster rate than the second element and creates a solid surface film, and such that the solid surface film is removed at a faster rate than the first element leaves the anode foil. During a second portion of each cycle at a second voltage the second element electrolyzes at a higher current density than the first element, and the material of the second element leaves the anode foil at a faster rate than the first element and creates a solid surface film, and the solid surface film is removed at a slower rate than the second element leaves the foil. The solid surface film is built up during the second portion of the cycle, and removed during the first portion of the cycle. 10 figs.

Anthropogenic Cycles of Rare Earth Elements

NASA Astrophysics Data System (ADS)

Du, X.; Graedel, T. E.

2009-12-01

This research will develop quantitatively resolved anthropogenic cycles and in-use stocks for the rare earth metals specifically cerium, lanthanum and dysprosium in Japan, China, and the U.S. for the year of 2007. Rare earth elements (REE) is a group of 17 scare metals widely used in a growing number of emerging technologies and have been in high demand for emerging technologies as raw materials during past the three decades. New market participants from newly industrializing countries, primarily China, have had strong impacts on the demand of share. Consequently, the importance to sustain a reliable, steady, uninterrupted supply on global market triggered comprehensive research to recognize and understand the life cycles of rare earths. Moreover, because China plays a dominant role in mining production since 1990, it requires the assessment for the countries, which are almost completely dependent on imports from China with respect to rare earth resources. The study aims to analyze the flows and stocks of rare earth elements individually as elemental form in spite of their natural geological co-occurrence and mixed composition in applications. By applying the method of Material Flow Analysis (MFA) work has been done on evaluating current and historical flows of specific technologically significant materials, for example, copper, zinc, nickel, etc., determining the stocks available in different types of reservoirs (e.g., lithosphere, in-use) and the flows among the reservoirs, developing scenarios of possible futures of metal use, and assessing the environmental and policy implications of the results. Therefore, REE as a new target deserves inclusion because of its potential demand-supply conflict and importance to secure the competitive advantage of technical innovation in future. This work will generate a quantitatively resolved anthropogenic life cycle and in-use stocks for REE for the main target countries for a chosen year, 2007, providing flows and stocks from mining to use to recycling quantifying the cycles for Japan, China and the U.S. as three representative types of consumers and paying attention to aspects of resource sustainability. Being well aware of the stages in the metal life cycle helps the sustainable development and policy making in long term. The goal is to consider REE resource availability, sustainability, and development strategies in the future that can sustain a reliable, steady, uninterrupted REE supply on the global market.

Sulfur isotopic evidence for the origin of elemental sulfur in gas hydrate-bearing sediments of the northern South China Sea

NASA Astrophysics Data System (ADS)

Lin, Zhiyong; Sun, Xiaoming; Strauss, Harald; Lu, Yang; Xu, Li; Lu, Hongfeng; Teichert, Barbara M. A.; Peckmann, Jörn

2017-04-01

Elemental sulfur is a common intermediate in the sulfur cycle and contributes significantly to the fractionation of stable sulfur isotopes in different reservoirs in shelfal marine sediments (e.g., Canfield and Thamdrup, 1994). However, no study dedicated to the isotopic composition of elemental sulfur in seep environments has been conducted to the best of our knowledge, thus limiting further insight into the biochemical pathways involving elemental sulfur in such environments. In this study, elemental sulfur and pyrite were extracted from the sediment of a 200-m long gas hydrate-bearing core, which was obtained from the gas hydrate drilling expedition to the northern South China Sea in 2013 (Zhang et al., 2015). The sulfur isotopic composition of elemental sulfur was found to vary from -16 to +23 per mill, and pyrite yielded values ranging from -34 to +18 per mill. Interestingly, elemental sulfur revealed higher 34S contents (up to 30 per mill) than the associated pyrite in most sediment layers. Since elemental sulfur is only produced during oxidative pathways in the sulfur cycle, the studied elemental sulfur apparently represents the oxidation product of hydrogen sulfide by various electron acceptors such as Mn(IV) oxides or Fe(III) oxides (e.g., Thamdrup et al., 1993; Yao and Millero, 1996). Since there is little sulfur isotope fractionation for oxidative processes (Fry et al., 1986), the enrichment of elemental sulfur in 34S points to a pool of hydrogen sulfide depleted in 32S, which is best interpreted to result from sulfate-driven anaerobic oxidation of methane. References: Canfield D.E. and Thamdrup B. (1994) The production of 34S-depleted sulfide during bacterial disproportionation of elemental sulfur. Science 266, 1973. Fry B., Cox J., Gest H. and Hayer J.M. (1986) Discrimination between 34S and32S during bacterial metabolism of inorganic sulfur compounds. J. Bacteriol. 165, 328-330. Thamdrup B., Finster K., Hansen W. and Bak F. (1993) Bacterial disproportionation of elemental sulfur coupled to chemical reduction of iron and manganese. Appl. Env. Microbiol. 59, 101-108. Yao W. and Millero F.J. (1996) Oxidation of hydrogen sulfide by hydrous Fe(III) oxides in seawater. Mar. Chem. 52, 1-16. Zhang G., Liang J., Lu J.A., Yang S., Zhang M., Holland M., Schultheiss P., Su X., Sha Z., Xu H., Gong Y., Fu S., Wang L. and Kuang Z. (2015) Geological features, controlling factors and potential prospects of the gas hydrate occurrence in the east part of the Pearl River Mouth Basin, South China Sea. Mar. Pet. Geol. 67, 356-367.

Geology and geochemistry of endoroique basin case of Baghdad chott southern of Algeria

NASA Astrophysics Data System (ADS)

Lamini, Abdellah; Hacini, Messaoud

2018-05-01

Chott Baghdad is an inland saline lake of the type Na-(Mg)-CI-(SO4). It is situated in septontrional Algerian sahara basin (northern of Africa).these small depression is fall dawn about 31m below sea level. One of characteristic of this zone is dry climate in summer when temperature reach 45°C and decrease in winter 5 °C. Chott Baghdad irrigate with surface water zone, continental saharan aquifer and precipitated water. Evaporative lakes without river outlets are common and their chemical composition has been reported to exhibit a wide diversity (Hardie and Eugster, 1970; Eugster and Hardie, 1978). Geologics and gitologic characteristics of deposed evaporates in Baghdad basin, small closed lagon take place with brines rich in ions SO42 - , Ca2+, Na+, Cl- and under the effect of evaporation generate the rock salt and gypsum precipitation. The objective of this study is to simulate evolution the geochemical cycle inside of chott Baghdad, in addition try to interpreter behavior of major element which constructs this small depression. The most important thing is to calculate saturated index of evaporated mineral and compare it with DRX result. To reach this study, monthly brine samples were collected from January to December. Different analytic methods were used: physico-chemical analytic (PH, temperature and conductivity). In addition, spectrophotometer and titration, phlameemissions were done to calculate major element concentration. From this study, we can conclude that major element behavior (Na+, Cl-, SO42 - , Mg+, K+, HCO3-, and Ca2+) is as follow: Chlore and sodium was decreasing at end of geochemical cycle. In addition, Bicarbonate, potassium and magnesium have characteristic evolution, where they increase at the beginning of geochemical cycle till summer then decrease steadily at the end of cycle. Where us, Calcium is quit steady during one year cycle.

Fatigue failure of dentin-composite disks subjected to cyclic diametral compression

PubMed Central

Li, Yuping; Carrera, Carola; Chen, Ruoqiong; Li, Jianying; Chen, Yungchung; Lenton, Patricia; Rudney, Joel. D.; Jones, Robert S.; Aparicio, Conrado; Fok, Alex

2015-01-01

Objective Our aim was to establish the relationship between cyclic loading and fatigue life of the dentin-composite interface using the newly developed disk in diametral compression tests. The results were then used to estimate the fatigue life of restored teeth under occlusal loading. Methods Disk specimens (5mm dia. × 2mm thick) were prepared using bovine incisors and restored with either a methacrylate-based composite Z100™ with Adper Single Bond Plus (Z100) or silorane-based composite Filtek ™ LS with LS System adhesive (LS). The dentin-composite disks were tested under cyclic diametral compression to determine the number of cycles to failure (Nf) at three load levels (n = 3 per group). Finite element analysis (FEA) was used to calculate the interfacial stresses (σ) within the specimen, to establish the σ vs. Nf curves, and those within a restored tooth under normal chewing forces (15N maximum). These were then used to estimate the lifetime of the restored tooth for the two restorative systems. Results The disks restored with LS had a higher fatigue resistance than those restored with Z100. The maximum interfacial stress in the restored tooth determined by FEA was ∼0.5MPa. Based on the estimate of 300,000 cycles of chewing per year, the predicted lifetime under occlusal loading for teeth restored with LS and Z100 was 33 and 10 years, respectively. Significance The disk in cyclic diametral compression has been used successfully to provide fatigue data which allows the lifetime of composite-restored teeth under occlusal loading to be predicted using numerical simulation. PMID:25958269

Fabrication and lithium storage performance of sugar apple-shaped SiOx@C nanocomposite spheres

NASA Astrophysics Data System (ADS)

Li, Mingqi; Zeng, Ying; Ren, Yurong; Zeng, Chunmei; Gu, Jingwei; Feng, Xiaofang; He, Hongyan

2015-08-01

Nonstoichiometric SiOx is a kind of very attractive anode material for high-energy lithium-ion batteries because of a high specific capacity and facile synthesis. However, the poor electrical conductivity and unstable electrode structure of SiOx severely limit its electrochemical performance as anode in lithium-ion batteries. In this work, highly durable sugar apple-shaped SiOx@C nanocomposite spheres are fabricated to achieve significantly improved electrochemical performance. The composite is synthesized by homogenous one-pot synthesis, using ethyltriethoxysilanes (EtSi(OEt)3) and resorcinol/formaldehyde (RF) as starting materials. The morphology, composition and structure of the composite are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis (EA) and X-ray photoelectron spectroscopy (XPS). At a current density of 50 mA g-1, the sugar apple-shaped SiOx@C spheres exhibit a stable discharge capacity of about 630 mAh g-1 calculated on the total mass of both SiOx and C. At a current density of 100 mA g-1, a stable discharge capacity of about 550 mAh g-1 is obtained and the capacity has been kept up to 400 cycles. The excellent cycling performance is attributed to the homogeneous dispersion of SiOx in disordered carbon at the nanometer scale and the unique structure of the composite.

Molten salt reactor neutronics and fuel cycle modeling and simulation with SCALE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Betzler, Benjamin R.; Powers, Jeffrey J.; Worrall, Andrew

Current interest in advanced nuclear energy and molten salt reactor (MSR) concepts has enhanced interest in building the tools necessary to analyze these systems. A Python script known as ChemTriton has been developed to simulate equilibrium MSR fuel cycle performance by modeling the changing isotopic composition of an irradiated fuel salt using SCALE for neutron transport and depletion calculations. Some capabilities in ChemTriton that have improved, include a generic geometry capable of modeling multi-zone and multi-fluid systems, enhanced time-dependent feed and separations, and a critical concentration search. Although more generally applicable, the capabilities developed to date are illustrated in thismore » paper in three applied problems: (1) simulating the startup of a thorium-based MSR fuel cycle (a likely scenario requires the first of these MSRs to be started without available 233U); (2) determining the effect of the removal of different fission products on MSR operations; and (3) obtaining the equilibrium concentration of a mixed-oxide light-water reactor fuel in a two-stage fuel cycle with a sodium fast reactor. Moreover, the third problem is chosen to demonstrate versatility in an application to analyze the fuel cycle of a non-MSR system. During the first application, the initial fuel salt compositions fueled with different sources of fissile material are made feasible after (1) removing the associated nonfissile actinides after much of the initial fissile isotopes have burned and (2) optimizing the thorium concentration to maintain a critical configuration without significantly reducing breeding capability. In the second application, noble metal, volatile gas, and rare earth element fission products are shown to have a strong negative effect on criticality in a uranium-fueled thermal-spectrum MSR; their removal significantly increases core lifetime (by 30%) and fuel utilization. In the third application, the fuel of a mixed-oxide light-water reactor approaches an equilibrium composition after 20 depletion steps, demonstrating the potential for the longer time scales required to achieve equilibrium for solid-fueled systems over liquid fuel systems. This time to equilibrium can be reduced by starting with an initial fuel composition closer to that of the equilibrium fuel, reducing the need to handle time-dependent fuel compositions.« less

Molten salt reactor neutronics and fuel cycle modeling and simulation with SCALE

DOE PAGES

Betzler, Benjamin R.; Powers, Jeffrey J.; Worrall, Andrew

2017-03-01

Current interest in advanced nuclear energy and molten salt reactor (MSR) concepts has enhanced interest in building the tools necessary to analyze these systems. A Python script known as ChemTriton has been developed to simulate equilibrium MSR fuel cycle performance by modeling the changing isotopic composition of an irradiated fuel salt using SCALE for neutron transport and depletion calculations. Some capabilities in ChemTriton that have improved, include a generic geometry capable of modeling multi-zone and multi-fluid systems, enhanced time-dependent feed and separations, and a critical concentration search. Although more generally applicable, the capabilities developed to date are illustrated in thismore » paper in three applied problems: (1) simulating the startup of a thorium-based MSR fuel cycle (a likely scenario requires the first of these MSRs to be started without available 233U); (2) determining the effect of the removal of different fission products on MSR operations; and (3) obtaining the equilibrium concentration of a mixed-oxide light-water reactor fuel in a two-stage fuel cycle with a sodium fast reactor. Moreover, the third problem is chosen to demonstrate versatility in an application to analyze the fuel cycle of a non-MSR system. During the first application, the initial fuel salt compositions fueled with different sources of fissile material are made feasible after (1) removing the associated nonfissile actinides after much of the initial fissile isotopes have burned and (2) optimizing the thorium concentration to maintain a critical configuration without significantly reducing breeding capability. In the second application, noble metal, volatile gas, and rare earth element fission products are shown to have a strong negative effect on criticality in a uranium-fueled thermal-spectrum MSR; their removal significantly increases core lifetime (by 30%) and fuel utilization. In the third application, the fuel of a mixed-oxide light-water reactor approaches an equilibrium composition after 20 depletion steps, demonstrating the potential for the longer time scales required to achieve equilibrium for solid-fueled systems over liquid fuel systems. This time to equilibrium can be reduced by starting with an initial fuel composition closer to that of the equilibrium fuel, reducing the need to handle time-dependent fuel compositions.« less

Investigating the origins of rhythmic major-element zoning in HP/LT garnets from worldwide subduction mélanges

NASA Astrophysics Data System (ADS)

Viete, D. R.; Hacker, B. R.; Seward, G.; Allen, M. B.

2016-12-01

Rhythmic major-element zoning has been documented in garnets from high pressure/low temperature (HP/LT) lenses within a number of worldwide subduction mélanges (e.g. California, Chinese Tianshan, Cuba, Greek Cyclades, Guatemala, Japan, Venezuela). The origin of these features has implications for the nature of subduction-zone processes. Conditions of rhythmic zoning acquirement in HP/LT garnets of California and Venezuela were investigated by use of Raman and FTIR microspectroscopy, and thermodynamic modelling of phase equilibria. Quartz-in-garnet Raman barometry reveals varying P—on the order of 100­-300 MPa, over radial distances of 10s of µm—in association with the high-Mn (and low-Mg) bands that define the fine-scale rhythmic zoning. Results from FTIR microspectroscopy demonstrate association between the high-Mn bands and locally depressed (structural) OH and elevated (molecular) H2O concentrations. The microspectroscopy results suggest changes in P and fluid activity attended development of the cryptic rhythmic zoning. Perple_X modelling of phase equilibria shows that, for specific rock chemistry and subduction P-T conditions, garnet modal abundance is extremely sensitive to changes in P (e.g. 10-20 vol.% growth/dissolution for ΔP = 200 MPa). Rhythmic major-element zoning may reflect P- and/or fluid-driven cycles of garnet stability-instability and/or varying reaction progress/kinetics during subduction. Steep compositional gradients that define the rhythmic major-element zoning limit time scales at subduction T, requiring that such individual stability-instability and/or accelerated reaction cycles were extremely brief. Seismic cycles or porosity waves represent ephemeral phenomena capable of accounting for development of rhythmic major-element zoning in HP/LT garnet, during subduction, as a result of fluctuations in both P and fluids. Metamorphic rocks may well carry detailed records of the catastrophism that punctuates longer-term tectonometamorphic processes.

Development and demonstration of manufacturing processes for fabricating graphite/Larc-160 polyimide structural elements, part 4, paragraph C

NASA Technical Reports Server (NTRS)

1981-01-01

Progress in the development of processes for production of Celion/LARC-160 graphite-polyimide materials, quality control methods, and the fabrication of Space Shuttle composite structure components is reported. The formulation and processing limits for three batches of resin are presented. Process improvements for simplification of the imidizing and autoclave cure cycles are described. Imidized and autoclave cured test panels were prepared. Celion/LARC-160 cure process verification and the fabrication of honeycomb sandwich panel elements and skin/stringer panels are described. C-scans of laminates imidized at 163 C to 218 C for periods from 30 to 180 minutes, and of process verification laminates made from different batches of prepreg are presented. Failure modes and load/strain characteristics of sandwich elements and C-scans of stringer to skin bond joints are also given.

The epsomitic phototrophic microbial mat of Hot Lake, Washington: community structural responses to seasonal cycling

PubMed Central

Lindemann, Stephen R.; Moran, James J.; Stegen, James C.; Renslow, Ryan S.; Hutchison, Janine R.; Cole, Jessica K.; Dohnalkova, Alice C.; Tremblay, Julien; Singh, Kanwar; Malfatti, Stephanie A.; Chen, Feng; Tringe, Susannah G.; Beyenal, Haluk; Fredrickson, James K.

2013-01-01

Phototrophic microbial mats are compact ecosystems composed of highly interactive organisms in which energy and element cycling take place over millimeter-to-centimeter-scale distances. Although microbial mats are common in hypersaline environments, they have not been extensively characterized in systems dominated by divalent ions. Hot Lake is a meromictic, epsomitic lake that occupies a small, endorheic basin in north-central Washington. The lake harbors a benthic, phototrophic mat that assembles each spring, disassembles each fall, and is subject to greater than tenfold variation in salinity (primarily Mg2+ and SO2−4) and irradiation over the annual cycle. We examined spatiotemporal variation in the mat community at five time points throughout the annual cycle with respect to prevailing physicochemical parameters by amplicon sequencing of the V4 region of the 16S rRNA gene coupled to near-full-length 16S RNA clone sequences. The composition of these microbial communities was relatively stable over the seasonal cycle and included dominant populations of Cyanobacteria, primarily a group IV cyanobacterium (Leptolyngbya), and Alphaproteobacteria (specifically, members of Rhodobacteraceae and Geminicoccus). Members of Gammaproteobacteria (e.g., Thioalkalivibrio and Halochromatium) and Deltaproteobacteria (e.g., Desulfofustis) that are likely to be involved in sulfur cycling peaked in summer and declined significantly by mid-fall, mirroring larger trends in mat community richness and evenness. Phylogenetic turnover analysis of abundant phylotypes employing environmental metadata suggests that seasonal shifts in light variability exert a dominant influence on the composition of Hot Lake microbial mat communities. The seasonal development and organization of these structured microbial mats provide opportunities for analysis of the temporal and physical dynamics that feed back to community function. PMID:24312082

The Epsomitic Phototrophic Microbial Mat of Hot Lake, Washington. Community Structural Responses to Seasonal Cycling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindemann, Stephen R.; Moran, James J.; Stegen, James C.

2013-11-13

Phototrophic microbial mats are compact ecosystems composed of highly interactive organisms in which energy and element cycling take place over millimeter-to-centimeter-scale distances. Although microbial mats are common in hypersaline environments, they have not been extensively characterized in systems dominated by divalent ions. Hot Lake is a meromictic, epsomitic lake that occupies a small, endorheic basin in north-central Washington. The lake harbors a benthic, phototrophic mat that assembles each spring, disassembles each fall, and is subject to greater than tenfold variation in salinity (primarily Mg 2+ and SO 2 -4) and irradiation over the annual cycle. We examined spatiotemporal variation inmore » the mat community at five time points throughout the annual cycle with respect to prevailing physicochemical parameters by amplicon sequencing of the V4 region of the 16S rRNA gene coupled to near-full-length 16S RNA clone sequences. The composition of these microbial communities was relatively stable over the seasonal cycle and included dominant populations of Cyanobacteria, primarily a group IV cyanobacterium (Leptolyngbya), and Alphaproteobacteria (specifically, members of Rhodobacteraceae and Geminicoccus). Members of Gammaproteobacteria (e.g., Thioalkalivibrio and Halochromatium) and Deltaproteobacteria (e.g., Desulfofustis) that are likely to be involved in sulfur cycling peaked in summer and declined significantly by mid-fall, mirroring larger trends in mat community richness and evenness. Phylogenetic turnover analysis of abundant phylotypes employing environmental metadata suggests that seasonal shifts in light variability exert a dominant influence on the composition of Hot Lake microbial mat communities. The seasonal development and organization of these structured microbial mats provide opportunities for analysis of the temporal and physical dynamics that feed back to community function.« less

From Gene Expression to the Earth System: Isotopic Constraints on Nitrogen Cycling Across Scales

NASA Astrophysics Data System (ADS)

Houlton, B. Z.

2015-12-01

A central motivation of the Biogeosciences is to understand the cycling of biologically essential elements over multiple scales of space and time. This charge is vital to basic knowledge of Earth system functioning. It is also relevant to many of the global challenges we face, such as climate change, biodiversity conservation, and the multifaceted role of global fertilizer use in maximizing human health and well-being. Nitrogen is connected to all of these; yet it has been one of the more vexing elements to quantitatively appraise across systems and scales. Here I discuss how research in my group has been exploring the use of natural nitrogen isotope abundance (15N/14N) as a biogeochemical tracer - from the level of gene expression to nitrogen's role in global climate change. First, I present evidence for a positive correlation between the bacterial genes that encode for gaseous nitrogen production (i.e., nirS) and the 15N/14N of soil extractable nitrate pools across an array of terrestrial ecosystems. Second, I demonstrate how these local-scale results fit with our work on ecosystem-scale nitrogen isotope budgets, where we quantify a uniformly small isotope effect (i.e., < 1 per mil) of nitrogen leaching losses from tropical rainforest to highly disturbed arid sites. Third, I present results from our global isotope model, which is based on results from our field investigations, providing a new nitrogen "benchmarking" scheme for global computational models and climate change forecasts. Finally, I move to a new research frontier where we have been developing a technique to measure the nitrogen isotope composition of ancient terrestrial plant compounds (i.e., chlorins) buried in the soil. This research aims to address the response of the nitrogen cycle to glacial-interglacial transitions over millennia, which is beyond the window of experimental testing. Together, this research highlights the utility of nitrogen isotope composition in addressing the myriad scales of this element's interaction with Earth's environment, and supports the working hypothesis that bacterial denitrification is the major fractionating pathway of nitrogen loss from the terrestrial biosphere, much like the global ocean.

Elemental and isotopic behaviour of Zn in Deccan basalt weathering profiles: Chemical weathering from bedrock to laterite and links to Zn deficiency in tropical soils.

PubMed

Suhr, Nils; Schoenberg, Ronny; Chew, David; Rosca, Carolina; Widdowson, Mike; Kamber, Balz S

2018-04-01

Zinc (Zn) is a micronutrient for organisms and essential for plant growth, therefore knowledge of its elemental cycling in the surface environment is important regarding wider aspects of human nutrition and health. To explore the nature of Zn cycling, we compared its weathering behaviour in a sub-recent regolith versus an ancient laterite profile of the Deccan Traps, India - an area of known soil Zn deficiency. We demonstrate that progressive breakdown of primary minerals and the associated formation of phyllosilicates and iron oxides leads to a depletion in Zn, ultimately resulting in a loss of 80% in lateritic residues. This residue is mainly composed of resistant iron oxides and hydroxides ultimately delivering insufficient amounts of bio-available Zn. Moreover, (sub)-tropical weathering in regions experiencing extended tectonic quiescence (e.g., cratons) further enhance the development of old and deep soil profiles that become deficient in Zn. This situation is clearly revealed by the spatial correlation of the global distribution of laterites, cratons (Africa, India, South America and Australia) and known regions of Zn deficient soils that result in health problems for humans whose diet is derived from such land. We also investigate whether this elemental depletion of Zn is accompanied by isotope fractionation. In the saprolitic horizons of both weathering profiles, compositions of δ 66 Zn JMC-Lyon lie within the "crustal average" of +0.27±0.07‰ δ 66 Zn JMC-Lyon . By contrast, soil horizons enriched in secondary oxides show lighter isotope compositions. The isotopic signature of Zn (Δ 66 Zn sample-protolith up to ~ -0.65‰) during the formation of the ferruginous-lateritic weathering profile likely resulted from a combination of biotically- and kinetically-controlled sorption reactions on Fe-oxyhydroxides. Our findings suggest that oxide rich soil types/horizons in (sub)-tropical regions likely exert a control on riverine Zn isotope compositions such that these become heavier than the crustal average. This isotopic behaviour invites a broader study of global soils to test whether light isotope composition alone could serve as an indicator for reduced bioavailability of Zn. Copyright © 2017 Elsevier B.V. All rights reserved.

Composition of commercial media used for human embryo culture.

PubMed

Morbeck, Dean E; Krisher, Rebecca L; Herrick, Jason R; Baumann, Nikola A; Matern, Dietrich; Moyer, Thomas

2014-09-01

To determine the composition of commercially available culture media and test whether differences in composition are biologically relevant in a murine model. Experimental laboratory study. University-based laboratory. Cryopreserved hybrid mouse one-cell embryos were used in experiments. Amino acid, organic acid, ions, and metal content were determined for two different lots of media from Cook, In Vitro Care, Origio, Sage, Vitrolife, Irvine CSC, and Global. To determine whether differences in the composition of these media are biologically relevant, mouse one-cell embryos were thawed and cultured for 120 hours in each culture media at 5% and 20% oxygen in the presence or absence of protein in an EmbryoScope time-lapse incubator. The compositions of seven culture media were analyzed for concentrations of 39 individual amino acids, organic acids, ions, and elements. Blastocyst rates and cell cycle timings were calculated at 96 hours of culture, and the experiments were repeated in triplicate. Of the 39 analytes, concentrations of glucose, lactate, pyruvate, amino acids, phosphate, calcium, and magnesium were present in variable concentrations, likely reflecting differences in the interpretation of animal studies. Essential trace elements, such as copper and zinc, were not detected. Mouse embryos failed to develop in one culture medium and were differentially affected by oxygen in two other media. Culture media composition varies widely, with differences in pyruvate, lactate, and amino acids especially notable. Blastocyst development was culture media dependent and showed an interaction with oxygen concentration and presence of protein. Copyright © 2014 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Microbial Transformations of Nitrogen, Sulfur, and Iron Dictate Vegetation Composition in Wetlands: A Review

PubMed Central

Lamers, Leon P. M.; van Diggelen, Josepha M. H.; Op den Camp, Huub J. M.; Visser, Eric J. W.; Lucassen, Esther C. H. E. T.; Vile, Melanie A.; Jetten, Mike S. M.; Smolders, Alfons J. P.; Roelofs, Jan G. M.

2012-01-01

The majority of studies on rhizospheric interactions focus on pathogens, mycorrhizal symbiosis, or carbon transformations. Although the biogeochemical transformations of N, S, and Fe have profound effects on vegetation, these effects have received far less attention. This review, meant for microbiologists, biogeochemists, and plant scientists includes a call for interdisciplinary research by providing a number of challenging topics for future ecosystem research. Firstly, all three elements are plant nutrients, and microbial activity significantly changes their availability. Secondly, microbial oxidation with oxygen supplied by radial oxygen loss from roots in wetlands causes acidification, while reduction using alternative electron acceptors leads to generation of alkalinity, affecting pH in the rhizosphere, and hence plant composition. Thirdly, reduced species of all three elements may become phytotoxic. In addition, Fe cycling is tightly linked to that of S and P. As water level fluctuations are very common in wetlands, rapid changes in the availability of oxygen and alternative terminal electron acceptors will result in strong changes in the prevalent microbial redox reactions, with significant effects on plant growth. Depending on geological and hydrological settings, these interacting microbial transformations change the conditions and resource availability for plants, which are both strong drivers of vegetation development and composition by changing relative competitive strengths. Conversely, microbial composition is strongly driven by vegetation composition. Therefore, the combination of microbiological and plant ecological knowledge is essential to understand the biogeochemical and biological key factors driving heterogeneity and total (i.e., microorganisms and vegetation) community composition at different spatial and temporal scales. PMID:22539932

Polypyrrole polyvinylidene difluoride composite stripe and zigzag actuators for use in facial robotics

NASA Astrophysics Data System (ADS)

Tadesse, Yonas; Priya, Shashank; Ramannair Chenthamarakshan, C.; de Tacconi, Norma R.; Rajeshwar, Krishnan

2008-04-01

Composite stripe and zigzag actuators consisting of a sandwich polypyrrole (PPy)/polyvinylidene difluoride (PVDF)/PPy structure were synthesized using potentiodynamic film growth on gold electrodes. The synthesis was done from an aqueous solution containing tetrabutylammonium perchlorate and pyrrole by polymerization at room temperature. The actuator displacement was modeled using finite element simulations. For depositing thin PPy films and thereby minimizing the response time, experimental optimization of the deposition conditions was performed. The number of current-potential (potentiodynamic) growth cycles and the thickness of the deposited PPy film were highly correlated in the initial stages of polymer film growth. The actuation response measurements indicate that the zigzag shaped actuators provide promising properties to develop artificial muscle.

Galactic cosmic ray composition and energy spectra

NASA Technical Reports Server (NTRS)

Mewaldt, R. A.

1994-01-01

Galactic cosmic ray nuclei represent a significant risk to long-duration spaceflight outside the magnetosphere. We review briefly existing measurements of the composition and energy spectra of heavy cosmic ray nuclei, pointing out which species and energy ranges are most critical to assessing cosmic ray risks for spaceflight. Key data sets are identified and a table of cosmic ray abundances is presented for elements from H to Ni (Z = 1 to 28). Because of the 22-year nature of the solar modulation cycle, data from the approaching 1998 solar minimum is especially important to reducing uncertainties in the cosmic ray radiation hazard. It is recommended that efforts to model this hazard take advantage of approaches that have been developed to model the astrophysical aspects of cosmic rays.

Fluid-rock interaction recorded in fault rocks of the Nobeoka Thrust, fossilized megasplay fault in an ancient accretionary complex

NASA Astrophysics Data System (ADS)

Hasegawa, R.; Yamaguchi, A.; Fukuchi, R.; Kitamura, Y.; Kimura, G.; Hamada, Y.; Ashi, J.; Ishikawa, T.

2017-12-01

The relationship between faulting and fluid behavior has been in debate. In this study, we clarify the fluid-rock interaction in the Nobeoka Thrust by major/trace element composition analysis using the boring core of the Nobeoka Thrust, an exhumed analogue of an ancient megasplay fault in Shimanto accretionary complex, southwest Japan. The hanging wall and the footwall of the Nobeoka Thrust show difference in lithology and metamorphic grade, and their maximum burial temperature is estimated from vitrinite reflectance analysis to be 320 330°C and 250 270°C, respectively (Kondo et al., 2005). The fault zone was formed in a fluid-rich condition, as evidenced by warm fluid migration suggested by fluid inclusion analysis (Kondo et al., 2005), implosion brecciation accompanied by carbonate precipitation followed by formation of pseudotachylyte (Okamoto et al., 2006), ankerite veins coseismically formed under reducing conditions (Yamaguchi et al., 2011), and quartz veins recording stress rotation in seismic cycles (Otsubo et al., 2016). In this study, first we analyzed the major/trace element composition across the principal slip zone (PSZ) of the Nobeoka Thrust by using fragments of borehole cores penetrated through the Nobeoka Thrust. Many elements fluctuated just above the PSZ, whereas K increase and Na, Si decrease suggesting illitization of plagioclase, as well as positive anomalies in Li and Cs were found within the PSZ. For more detail understanding, we observed polished slabs and thin sections of the PSZ. Although grain size reduction of deformed clast and weak development of foliation were observed entirely in the PSZ by macroscopic observation, remarkable development of composite planar fabric nor evidence of friction melting were absent. In this presentation, we show the result of major/trace element composition corresponding to the internal structure of PSZ, and discuss fluid-rock interaction and its impact to megasplay fault activity in subduction zones.

Effects of build orientation and element partitioning on microstructure and mechanical properties of biomedical Ti-6Al-4V alloy produced by laser sintering.

PubMed

Mengucci, P; Gatto, A; Bassoli, E; Denti, L; Fiori, F; Girardin, E; Bastianoni, P; Rutkowski, B; Czyrska-Filemonowicz, A; Barucca, G

2017-07-01

Direct Metal Laser Sintering (DMLS) technology was used to produce tensile and flexural samples based on the Ti-6Al-4V biomedical composition. Tensile samples were produced in three different orientations in order to investigate the effect of building direction on the mechanical behavior. On the other hand, flexural samples were submitted to thermal treatments to simulate the firing cycle commonly used to veneer metallic devices with ceramics in dental applications. Roughness and hardness measurements as well as tensile and flexural mechanical tests were performed to study the mechanical response of the alloy while X-ray diffraction (XRD), electron microscopy (SEM, TEM, STEM) techniques and microanalysis (EDX) were used to investigate sample microstructure. Results evidenced a difference in the mechanical response of tensile samples built in orthogonal directions. In terms of microstructure, samples not submitted to the firing cycle show a single phase acicular α' (hcp) structure typical of metal parts subject to high cooling rates. After the firing cycle, samples show a reduction of hardness and strength due to the formation of laths of the β (bcc) phase at the boundaries of the primary formed α' plates as well as to lattice parameters variation of the hcp phase. Element partitioning during the firing cycle gives rise to high concentration of V atoms (up to 20wt%) at the plate boundaries where the β phase preferentially forms. Copyright © 2017 Elsevier Ltd. All rights reserved.

Designing added functions in engineered cementitious composites

NASA Astrophysics Data System (ADS)

Yang, En-Hua

In this dissertation, a new and systematic material design approach is developed for ECC with added functions through material microstructures linkage to composite macroscopic behavior. The thesis research embodies theoretical development by building on previous ECC micromechanical models, and experimental investigations into three specific new versions of ECC with added functions aimed at addressing societal demands of our built infrastructure. Specifically, the theoretical study includes three important ECC modeling elements: Steady-state crack propagation analyses and simulation, predictive accuracy of the fiber bridging constitutive model, and development of the rate-dependent strain-hardening criteria. The first element establishes the steady-state cracking criterion as a fundamental requirement for multiple cracking behavior in brittle matrix composites. The second element improves the accuracy of crack-width prediction in ECC. The third element establishes the micromechanics basis for impact-resistant ECC design. Three new ECCs with added functions were developed and experimentally verified in this thesis research through the enhanced theoretical framework. A green ECC incorporating a large volume of industrial waste was demonstrated to possess reduced crack width and drying shrinkage. The self-healing ECC designed with tight crack width was demonstrated to recover transport and mechanical properties after microcrack damage when exposed to wet and dry cycles. The impact-resistant ECC was demonstrated to retain tensile ductility with increased strength under moderately high strain-rate loading. These new versions of ECC with added functions are expected to contribute greatly to enhancing the sustainability, durability, and safety of civil infrastructure built with ECC. This research establishes the effectiveness of micromechanics-based design and material ingredient tailoring for ECC with added new attributes but without losing its basic tensile ductile characteristics.

In operando quantitation of Li concentration for a commercial Li-ion rechargeable battery using high-energy X-ray Compton scattering.

PubMed

Suzuki, Kosuke; Suzuki, Ayahito; Ishikawa, Taiki; Itou, Masayoshi; Yamashige, Hisao; Orikasa, Yuki; Uchimoto, Yoshiharu; Sakurai, Yoshiharu; Sakurai, Hiroshi

2017-09-01

Compton scattering is one of the most promising probes for quantitating Li under in operando conditions, since high-energy X-rays, which have high penetration power, are used as the incident beam and the Compton-scattered energy spectrum has specific line-shapes for each element. An in operando quantitation method to determine the Li composition in electrodes has been developed by using line-shape (S-parameter) analysis of the Compton-scattered energy spectrum. In this study, S-parameter analysis has been applied to a commercial coin cell Li-ion rechargeable battery and the variation of the S-parameters during the charge/discharge cycle at the positive and negative electrodes has been obtained. By using calibration curves for Li composition in the electrodes, the change in Li composition of the positive and negative electrodes has been determined using the S-parameters simultaneously.

Pechini process-derived tin oxide and tin oxide-graphite composites for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhang, R.; Lee, Jim Y.; Liu, Z. L.

The Pechini process [Ceram. Bull. 68 (1989) 1002] is used to obtain fine tin oxide powders that reduce the specific volume change in Li + insertion and extraction reactions. The suitability of these tin oxides as active materials for negative electrodes in lithium-ion batteries is investigated. From elemental analysis, it is found that the templating polymer network is almost completely obliterated after heating at 500 °C. The best tin oxide does not exhibit extensive crystallization of tin atoms even after 30 cycles of alloying and de-alloying reactions with Li. The structure and the specific capacity of the oxides are dependent on the heat treatment and remnants of the polymeric CH network can impose an unfavorable outcome. A capacity of 600 mAh g -1, which is unchanged for 30 cycles, can be obtained from tin oxide heat treated at 1000 °C. Composites of graphite and SnO 2 are also prepared and exhibit synergistic interactions between graphite and tin oxide which are similar to those reported previously [Electrochem. Solid State Lett. 3 (2000) 167].

The NO/ONOO-Cycle as the Central Cause of Heart Failure

PubMed Central

Pall, Martin L.

2013-01-01

The NO/ONOO-cycle is a primarily local, biochemical vicious cycle mechanism, centered on elevated peroxynitrite and oxidative stress, but also involving 10 additional elements: NF-κB, inflammatory cytokines, iNOS, nitric oxide (NO), superoxide, mitochondrial dysfunction (lowered energy charge, ATP), NMDA activity, intracellular Ca2+, TRP receptors and tetrahydrobiopterin depletion. All 12 of these elements have causal roles in heart failure (HF) and each is linked through a total of 87 studies to specific correlates of HF. Two apparent causal factors of HF, RhoA and endothelin-1, each act as tissue-limited cycle elements. Nineteen stressors that initiate cases of HF, each act to raise multiple cycle elements, potentially initiating the cycle in this way. Different types of HF, left vs. right ventricular HF, with or without arrhythmia, etc., may differ from one another in the regions of the myocardium most impacted by the cycle. None of the elements of the cycle or the mechanisms linking them are original, but they collectively produce the robust nature of the NO/ONOO-cycle which creates a major challenge for treatment of HF or other proposed NO/ONOO-cycle diseases. Elevated peroxynitrite/NO ratio and consequent oxidative stress are essential to both HF and the NO/ONOO-cycle. PMID:24232452

The Experiment and Numerical Simulation of Composite Countersunk-head Fasteners Pull-through Mechanical Behavior

NASA Astrophysics Data System (ADS)

Mu, Junwu; Guan, Zhidong; Bian, Tianya; Li, Zengshan; Wang, Kailun; Liu, Sui

2014-10-01

Fasteners made of the anisotropic carbon/carbon (C/C) composite material have been developed for joining C/C composite material components in the high-temperature environment. The fastener specimens are fabricated from the C/C composites which are made from laminated carbon cloths with Z-direction carbon fibers being punctured as perform. Densification process cycles such as the thermal gradient chemical vapor infiltration (CVI) technology were repeated to obtain high density C/C composites fastener. The fasteners were machined parallel to the carbon cloths (X-Y direction). A method was proposed to test pull-through mechanical behavior of the countersunk-head C/C composite material fasteners. The damage morphologies of the fasteners were observed through the charge coupled device (CCD) and the scanning electron microscope (SEM). The internal micro-structure were observed through the high-resolution Mirco-CT systems. Finally, an excellent simulation of the C/C composite countersunk-head fasteners were performed with the finite element method (FEM), in which the damage evolution model of the fastener was established based on continuum damage mechanics. The simulation is correspond well with the test result . The damage evolution process and the relation between the countersunk depth and the ultimate load was investigated.

Chemical weathering from the CoDA (Compositional Data Analysis) point of view: new insights for the Alpine rivers geochemistry

NASA Astrophysics Data System (ADS)

Gozzi, Caterina; Buccianti, Antonella; Frondini, Francesco

2017-04-01

The aim of this contribution is to explore the relationship among weathering reactions, the sample space of compositional data and fractals by means of distributional analysis. Weathering reactions represent the transfer of heat and entropy to the environment in geochemical cycles. Chemical weathering is a key process for understanding the global cycle of elements, both on long and short-terms and chemical weathering rates are complex functions of many factors including dissolution kinetics of minerals, mechanical erosion, lithology. Compositional data express the relative (proportional) abundance of chemical elements/species in a given total (i.e. volume or weight) so that compositions pertaining to the peculiar geometry of the simplex sample space. Fractals are temporal or spatial objects with self-similarity and scale invariance, so that internal structures repeat themselves over multiple levels of magnification or scales of measurement. Gibbs's free energy and the application of the Law Mass Action can be used to model weathering reactions, under the hypothesis of chemical equilibrium. Compositional data are obtained in the analytical phase after the determination of the concentrations of chemicals in sampled solid, liquid or gaseous materials. Fractals can be measured by using their fractal dimensions. The presence of fractal structures can be observed when the frequency distribution of isometric log-ratio coordinates is investigated, showing the logarithm of the cumulative number of samples exceeding a certain coordinate value plotted against the coordinate value itself. Isometric log-ratio coordinates (or balances) can be constructed by using the sequential binary partition (SBP) method. The balances can be identified to maintain, as far as possible, the similarity with a corresponding weathering reaction (Buccianti & Zuo, 2016). As an alternative, balances can be derived after the multivariate investigation of the variance-covariance structure of the compositional matrix. In both cases the idea is to probe the behaviour of geochemical processes to be analysed in time or space. An application example is presented for the chemistry of the surficial waters of the Alpine region (Donnini et al., 2016). The emergence of fractal structures indicates the presence of dissipative systems, which require complexity, large numbers of inter-connected elements and stochasticity requiring caution in the use of classical spatial methods to represent geochemical phenomena. Buccianti A. & Zuo R., 2016. Weathering reactions and isometric log-ratio coordinates: Do they speak to each other? Applied Geochemistry, 75, 189-199. Donnini M., Frondini F., Probst J.L., Probst A., Cardellini C., Marchesini I., Guzzetti F., 2016. Chemical weathering and consumption of atmospheric carbon dioxide in the Alpine region. Global and Planetary Change, 136 (2016) 65-81.

Crack detection and fatigue related delamination in FRP composites applied to concrete

NASA Astrophysics Data System (ADS)

Brown, Jeff; Baker, Rebecca; Kallemeyn, Lisa; Zendler, Andrew

2008-03-01

Reinforced concrete beams are designed to allow minor concrete cracking in the tension zone. The severity of cracking in a beam element is a good indicator of how well a structure is performing and whether or not repairs are needed to prevent structural failure. FRP composites are commonly used to increase the flexural and shear capacity of RC beam elements, but one potential disadvantage of this method is that strengthened surfaces are no longer visible and cracks or delaminations that result from excessive loading or fatigue may go undetected. This research investigated thermal imaging techniques for detecting load induced cracking in the concrete substrate and delamination of FRP strengthening systems applied to reinforced concrete (RC). One small-scale RC beam (5 in. x 6 in. x 60 in.) was strengthened with FRP and loaded to failure monotonically. An infrared thermography inspection was performed after failure. A second strengthened beam was loaded cyclically for 1,750,000 cycles to investigate how fatigue might affect substrate cracking and delamination growth throughout the service-life of a repaired element. No changes were observed in the FRP bond during/after the cyclic loading. The thermal imaging component of this research included pixel normalization to enhance detectability and characterization of this specific type of damage.

Cell cycle nucleic acids, polypeptides and uses thereof

DOEpatents

Gordon-Kamm, William J [Urbandale, IA; Lowe, Keith S [Johnston, IA; Larkins, Brian A [Tucson, AZ; Dilkes, Brian R [Tucson, AZ; Sun, Yuejin [Westfield, IN

2007-08-14

The invention provides isolated nucleic acids and their encoded proteins that are involved in cell cycle regulation. The invention further provides recombinant expression cassettes, host cells, transgenic plants, and antibody compositions. The present invention provides methods and compositions relating to altering cell cycle protein content, cell cycle progression, cell number and/or composition of plants.

ACE/SWICS OBSERVATIONS OF HEAVY ION DROPOUTS WITHIN THE SOLAR WIND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weberg, Micah J.; Zurbuchen, Thomas H.; Lepri, Susan T., E-mail: mjweberg@umich.edu, E-mail: thomasz@umich.edu, E-mail: slepri@umich.edu

2012-11-20

We present the first in situ observations of heavy ion dropouts within the slow solar wind, observed for select elements ranging from helium to iron. For iron, these dropouts manifest themselves as depletions of the Fe/H ratio by factors up to {approx}25. The events often exhibit mass-dependent fractionation and are contained in slow, unsteady wind found within a few days from known stream interfaces. We propose that such dropouts are evidence of gravitational settling within large coronal loops, which later undergo interchange reconnection and become source regions of slow, unsteady wind. Previously, spectroscopic studies by Raymond et al. in 1997more » (and later Feldman et al. in 1999) have yielded strong evidence for gravitational settling within these loops. However, their expected in situ signature plasma with heavy elements fractionated by mass was not observed prior to this study. Using data from the SWICS instrument on board the Advanced Composition Explorer (ACE), we investigate the composition of the solar wind within these dropouts and explore long term trends over most of a solar cycle.« less

The role of silver in self-lubricating coatings for use at extreme temperatures

NASA Technical Reports Server (NTRS)

Sliney, H. E.

1985-01-01

The advantages and disadvantages of elemental silver as a tribological material are discussed. It is demonstrated that the relatively high melting point of 961 deg C, softness, marked plasticity, and thermochemical stability of silver combine to make this metal useful in thin film solid lubricant coatings over a wide temperature range. Disadvantages of silver during sliding, except when used as a thin film, are shown to be gross ploughing due to plastic deformation under load with associated high friction and excessive transfer to counterface surfaces. This transfer generates an irregular surface topography with consequent undesirable changes in bearing clearance distribution. Research to overcome these disadvantages of element silver is described. A comparison is made of the tribological behavior of pure silver with that of silver formulated with other metals and high-temperature solid lubricants. The composite materials are prepared by co-depositing the powdered components with an airbrush followed by furnace heat treatment or by plasma-spraying. Composite coatings were formulated which are shown to be self-lubricating over repeated, temperature cycles from low temperature to about 900 deg C.

The use of silver in self-lubricating coatings for extreme temperatures

NASA Technical Reports Server (NTRS)

Sliney, H. E.

1986-01-01

The advantages and disadvantages of elemental silver as a tribological material are discussed. It is demonstrated that the relatively high melting point of 961 deg C, softness, marked plasticity, and thermochemical stability of silver combine to make this metal useful in thin film solid lubricant coatings over a wide temperature range. Disadvantages of silver during sliding, except when used as a thin film, are shown to be gross ploughing due to plastic deformation under load with associated high friction and excessive transfer to counterface surfaces. This transfer generates an irregular surface topography with consequent undesirable changes in bearing clearance distribution. Research to overcome these disadvantages of element silver is described. A comparison is made of the tribological behavior of pure silver with that of silver formulated with other metals and high-temperature solid lubricants. The composite materials are prepared by co-depositing the powdered components with an airbrush followed by furnace heat treatment or by plasma-spraying. Composite coatings were formulated which are shown to be self-lubricating over repeated, temperature cycles from low temperature to about 900 deg C.

Fatigue Life Analysis of Tapered Hybrid Composite Flexbeams

NASA Technical Reports Server (NTRS)

Murri, Gretchen B.; Schaff, Jeffery R.; Dobyns, Alan L.

2002-01-01

Nonlinear-tapered flexbeam laminates from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. The two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) obtained from the above codes using the virtual crack closure technique (VCCT) at a resin crack location in the flexbeams are presented for both hybrid material types. These results compare well with each other and suggest that the initial delamination growth from the resin crack toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves and compared with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared reasonably well with the test results.

Evolution of the Structural-Phase State of a Ti-Al- V-Mo Alloy During Severe Plastic Deformation and SubSequent Annealing

NASA Astrophysics Data System (ADS)

Grabovetskaya, G. P.; Ratochka, I. V.; Mishin, I. P.; Zabudchenko, O. V.; Lykova, O. N.

2016-05-01

The effect of the initial phase composition of a Ti-Al-V-Mo alloy (VT16 according to Russian classification) on the evolution of its structural-phase state during the formation of ultrafine-grained structure and subsequent annealing is investigated by methods of optical and transmission electron microscopy and x-ray diffraction analysis. The structure is produced by cyclic pressing with a change of the deformation axis in each cycle combined with a gradual decrease of the pressing temperature from 1073 to 723 K. As this takes place, α″ → α + β and β → α phase transitions are found to develop in the test alloy. The phase state of the ultrafinegrained material thus produced depends for the most part on its elemental composition and severe plastic deformation regime. Annealing below the recrystallization temperature is shown to give rise to a β→α phase transition and alloying element redistribution. The foregoing processes allow for retaining a high level of the strength properties of the alloy.

Reliability and Creep/Fatigue Analysis of a CMC Component

NASA Technical Reports Server (NTRS)

Murthy, Pappu L. N.; Mital, Subodh K.; Gyekenyesi, John Z.; Gyekenyesi, John P.

2007-01-01

High temperature ceramic matrix composites (CMC) are being explored as viable candidate materials for hot section gas turbine components. These advanced composites can potentially lead to reduced weight and enable higher operating temperatures requiring less cooling; thus leading to increased engine efficiencies. There is a need for convenient design tools that can accommodate various loading conditions and material data with their associated uncertainties to estimate the minimum predicted life as well as the failure probabilities of a structural component. This paper presents a review of the life prediction and probabilistic analyses performed for a CMC turbine stator vane. A computer code, NASALife, is used to predict the life of a 2-D woven silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) turbine stator vane due to a mission cycle which induces low cycle fatigue and creep. The output from this program includes damage from creep loading, damage due to cyclic loading and the combined damage due to the given loading cycle. Results indicate that the trends predicted by NASALife are as expected for the loading conditions used for this study. In addition, a combination of woven composite micromechanics, finite element structural analysis and Fast Probability Integration (FPI) techniques has been used to evaluate the maximum stress and its probabilistic distribution in a CMC turbine stator vane. Input variables causing scatter are identified and ranked based upon their sensitivity magnitude. Results indicate that reducing the scatter in proportional limit strength of the vane material has the greatest effect in improving the overall reliability of the CMC vane.

Effect of mission cycling on the fatigue performance of SiC-coated carbon-carbon composites

NASA Technical Reports Server (NTRS)

Mahfuz, H.; Das, P. S.; Jeelani, S.; Baker, D. M.; Johnson, S. A.

1993-01-01

The effects of thermal and pressure cycling on the fatigue performance of carbon-carbon composites, and the influence of mission cycling on these effects, were investigated by subjecting both virgin and mission-cycled two-dimensional specimens of SiC-coated carbon-carbon composites to fatigue tests, conducted at room temperature in three-point bending, with a stress ratio of 0.2 and a frequency of 1 Hz. It was found that the fatigue strength of C-C composites is high (about 90 percent of the ultimate flexural strength), but decreased with the mission cycling. The lowering of the fatigue strength with mission cycling is attributed to the increase in interfacial bond strength due to thermal and pressure cycling of the material. The already high sensitivity of C-C composites to stress during cyclic loading increases further with the amount of mission cycling. Results of NDE suggest that the damage growth in virgin C-C, in the high-cycle range, is slow at the initial stage of the cyclic life, but propagates rapidly after certain threshold cycles of the fatigue life.

Amorphous V-O-C composite nanofibers electrospun from solution precursors as binder- and conductive additive-free electrodes for supercapacitors with outstanding performance.

PubMed

Chen, Xia; Zhao, Bote; Cai, Yong; Tadé, Moses O; Shao, Zongping

2013-12-21

Flexible V-O-C composite nanofibers were fabricated from solution precursors via electrospinning and were investigated as free-standing and additive-free film electrodes for supercapacitors. Specifically, composite nanofibers (V0, V5, V10 and V20) with different vanadyl acetylacetonate (VO(acac)2) contents of 0, 5, 10 and 20 wt% with respect to polyacrylonitrile (PAN) were prepared. The composite nanofibers were comparatively studied using XRD, Raman spectroscopy, XPS, N2 adsorption-desorption, FE-SEM, TEM and S-TEM. The vanadium element was found to be well-dispersed in the carbon nanofibers, free from the formation of an aggregated crystalline phase, even in the case of V20. A specific surface area of 587.9 m(2) g(-1) was reached for V10 after calcination, which is approximately twice that of the vanadium-free carbon nanofibers (V0, 300.9 m(2) g(-1)). To perform as an electrode for supercapacitors in an aqueous electrolyte, the V10 film delivered a specific capacitance of 463 F g(-1) at 1 A g(-1). V10 was also able to retain a specific capacitance of 380 F g(-1), even at a current density of 10 A g(-1). Additionally, very stable cycling stability was achieved, maintaining an outstanding specific capacitance of 400 F g(-1) at 5 A g(-1) after charge-discharge cycling 5000 times. Thus, V-O-C composite nanofibers are highly attractive electrode materials for flexible, high-power, thin film energy storage devices and applications.

Sources of the solar wind - the heliospheric point of view

NASA Astrophysics Data System (ADS)

Von Steiger, Rudolf; Shearer, Paul; Zurbuchen, Thomas

The solar wind as observed in the heliosphere has several properties that can be interpreted as signatures of conditions and processes at its source in the solar atmosphere. Traditionally it has been customary to distinguish between solar wind types solely based on its speed, "fast" and "slow" wind. Over the last couple of decades new instruments resolving not only the main constituents (protons and alpha particles) but also heavy ions from C to Fe have added new observables, in particular the charge state and elemental composition of these ions. The charge states are indicators of the coronal temperature at the source region; they have confirmed that the "fast" wind emanates from the relatively cool coronal hole regions, while the "slow" wind originates from hotter sources such as the streamer belt and active regions. Thus they are more reliable indicators of solar wind source than the speed alone could be because they readily discriminate between "fast" wind from coronal holes and fast coronal mass ejections (CMEs). The elemental composition in the solar wind compared to the abundances in the photosphere shows a typical fractionation that depends on the first ionization potential (FIP) of the elements. Since that fractionation occurs beneath the corona, in the chromosphere, its strength is indicative of the conditions in that layer. While the "fast" wind is very similar to photospheric composition, the fractionation of the "slow" wind and of CMEs is higher and strongly variable. We will review the observations of the SWICS composition instruments on both the ACE and the Ulysses missions, which have made composition observations between 1 and 5 AU and at all latitudes in the heliosphere over the last two decades. Specifically, analysis of the "slow" wind observations at all time scales, from hours to complete solar cycles, will be used to better characterize its source regions.

Probabilistic fracture finite elements

NASA Technical Reports Server (NTRS)

Liu, W. K.; Belytschko, T.; Lua, Y. J.

1991-01-01

The Probabilistic Fracture Mechanics (PFM) is a promising method for estimating the fatigue life and inspection cycles for mechanical and structural components. The Probability Finite Element Method (PFEM), which is based on second moment analysis, has proved to be a promising, practical approach to handle problems with uncertainties. As the PFEM provides a powerful computational tool to determine first and second moment of random parameters, the second moment reliability method can be easily combined with PFEM to obtain measures of the reliability of the structural system. The method is also being applied to fatigue crack growth. Uncertainties in the material properties of advanced materials such as polycrystalline alloys, ceramics, and composites are commonly observed from experimental tests. This is mainly attributed to intrinsic microcracks, which are randomly distributed as a result of the applied load and the residual stress.

Probabilistic fracture finite elements

NASA Astrophysics Data System (ADS)

Liu, W. K.; Belytschko, T.; Lua, Y. J.

1991-05-01

The Probabilistic Fracture Mechanics (PFM) is a promising method for estimating the fatigue life and inspection cycles for mechanical and structural components. The Probability Finite Element Method (PFEM), which is based on second moment analysis, has proved to be a promising, practical approach to handle problems with uncertainties. As the PFEM provides a powerful computational tool to determine first and second moment of random parameters, the second moment reliability method can be easily combined with PFEM to obtain measures of the reliability of the structural system. The method is also being applied to fatigue crack growth. Uncertainties in the material properties of advanced materials such as polycrystalline alloys, ceramics, and composites are commonly observed from experimental tests. This is mainly attributed to intrinsic microcracks, which are randomly distributed as a result of the applied load and the residual stress.

Rational design of anode materials based on Group IVA elements (Si, Ge, and Sn) for lithium-ion batteries.

PubMed

Wu, Xing-Long; Guo, Yu-Guo; Wan, Li-Jun

2013-09-01

Lithium-ion batteries (LIBs) represent the state-of-the-art technology in rechargeable energy-storage devices and they currently occupy the prime position in the marketplace for powering an increasingly diverse range of applications. However, the fast development of these applications has led to increasing demands being placed on advanced LIBs in terms of higher energy/power densities and longer life cycles. For LIBs to meet these requirements, researchers have focused on active electrode materials, owing to their crucial roles in the electrochemical performance of batteries. For anode materials, compounds based on Group IVA (Si, Ge, and Sn) elements represent one of the directions in the development of high-capacity anodes. Although these compounds have many significant advantages when used as anode materials for LIBs, there are still some critical problems to be solved before they can meet the high requirements for practical applications. In this Focus Review, we summarize a series of rational designs for Group IVA-based anode materials, in terms of their chemical compositions and structures, that could address these problems, that is, huge volume variations during cycling, unstable surfaces/interfaces, and invalidation of transport pathways for electrons upon cycling. These designs should at least include one of the following structural benefits: 1) Contain a sufficient number of voids to accommodate the volume variations during cycling; 2) adopt a "plum-pudding"-like structure to limit the volume variations during cycling; 3) facilitate an efficient and permanent transport pathway for electrons and lithium ions; or 4) show stable surfaces/interfaces to stabilize the in situ formed SEI layers. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Variability in magnesium, carbon and oxygen isotope compositions, and trace element contents of brachiopod shells: implications for paleoceanographic studies

NASA Astrophysics Data System (ADS)

Rollion-Bard, Claire; Saulnier, Ségolène; Vigier, Nathalie; Schumacher, Aimryc; Chaussidon, Marc; Lécuyer, Christophe

2016-04-01

Magnesium content in the ocean is ≈ 1290 ppm and is one of the most abundant elements. It is involved in the carbon cycle via the dissolution and precipitation of carbonates, especially Mg-rich carbonates as dolomites. The Mg/Ca ratio of the ocean is believed to have changed through time. The causes of these variations, i.e. hydrothermal activity change or enhanced precipitation of dolomite, could be constrained using the magnesium isotope composition (δ26Mg) of carbonates. Brachiopods, as marine environmental proxies, have the advantage to occur worldwide in a depth range from intertidal to abyssal, and have been found in the geological record since the Cambrian. Moreover, as their shell is in low-Mg calcite, they are quite resistant to diagenetic processes. Here we report δ26Mg, δ18O, δ13C values along with trace element contents of one modern brachiopod specimen (Terebratalia transversa) and one fossil specimen (Terebratula scillae, 2.3 Ma). We combined δ26Mg values with oxygen and carbon isotope compositions and trace element contents to look for possible shell geochemical heterogeneities in order to investigate the processes that control the Mg isotope composition of brachiopod shells. We also evaluate the potential of brachiopods as a proxy of past seawater δ26Mg values. The two investigated brachiopod shells present the same range of δ26Mg variation (up to 2 ‰)). This variation cannot be ascribed to changes in environmental parameters, i.e. temperature or pH. As previously observed, the primary layer of calcite shows the largest degree of oxygen and carbon isotope disequilibrium relative to seawater. In contrast, the δ26Mg value of this layer is comparable to that of the secondary calcite layer value. In both T. scillae and T. transversa, negative trends are observable between magnesium isotopic compositions and oxygen and carbon isotopic compositions. These trends, combined to linear relationships between δ26Mg values and REE contents, are best explained by kinetic effects linked to changes in growth rate during the brachiopod life. The innermost calcite layer of T. transversa is in isotopic equilibrium for both oxygen and magnesium and could therefore be the best target for reconstructing past δ26Mg values of seawater.

Role of Soil Erosion in Biogeochemical Cycling of Essential Elements: Carbon, Nitrogen, and Phosphorus

NASA Astrophysics Data System (ADS)

Berhe, Asmeret Asefaw; Barnes, Rebecca T.; Six, Johan; Marín-Spiotta, Erika

2018-05-01

Most of Earth's terrestrial surface is made up of sloping landscapes. The lateral distribution of topsoil by erosion controls the availability, stock, and persistence of essential elements in the terrestrial ecosystem. Over the last two decades, the role of soil erosion in biogeochemical cycling of essential elements has gained considerable interest from the climate, global change, and biogeochemistry communities after soil erosion and terrestrial sedimentation were found to induce a previously unaccounted terrestrial sink for atmospheric carbon dioxide. More recent studies have highlighted the role of erosion in the persistence of organic matter in soil and in the biogeochemical cycling of elements beyond carbon . Here we synthesize available knowledge and data on how erosion serves as a major driver of biogeochemical cycling of essential elements. We address implications of erosion-driven changes in biogeochemical cycles on the availability of essential elements for primary production, on the magnitude of elemental exports downstream, and on the exchange of greenhouse gases from the terrestrial ecosystem to the atmosphere. Furthermore, we explore fates of eroded material and how terrestrial mass movement events play major roles in modifying Earth's climate.

Exobiochemistry

NASA Technical Reports Server (NTRS)

Jones, Harry

2001-01-01

Exobiochemistry is the putative biochemistry of extraterrestrial life. It suggests the possible energy and material bases of extraterrestrial life and could help detect it. The diverse biochemistry of Earth indicates that a wide range of exobiochemistry is possible on other planets. An exobiochemistry will probably use the same energy sources as Earths ecology, light, biological organic material, and more rarely abiotic chemicals. Extraterrestrial life will be based on familiar chemical principles and probably capture, store, and release energy using oxidation-reduction reactions. Extraterrestrial life will give chemical indications of its existence. Key elements will be concentrated, stored, and recycled, altering their availability and isotopic composition. Any significant departure from chemical equilibrium would be good evidence for exobiochemistry, but an integrated system of departures from the expected equilibrium would be better. Exobiochemistry can be expected to include closed biogeochemical cycles of the major life supporting elements and may well show the complex dynamic close-coupled interactions that characterize the terrestrial biosphere. Terrestrial biochemistry provides a basis for generalization and extrapolation but it does not set bounds on exobiochemistry. In exobiochemistry we can expect: 1. closed chemical cycles that recycle materials, nutrients, and catalysts, 2. organisms with complementary metabolisms that cooperate to close the chemical cycles, 3. a high probability of a carbon and water chemistry, but some possibility of a non-carbon or non-water chemistry in extreme environments, and, 4. life similar to bacteria more prevalent than higher plants and animals.

Elemental cycling response of an Adirondack subalpine spruce-fir forest to atmospheric and environmental change

Treesearch

Andrew J. Friedland; Eric K. Miller

1996-01-01

Patterns and trends in forest elemental cycling can become more apparent in the presence of atmospheric perturbations. High-elevation forests of the northeastern United States have received large amounts of atmospheric deposition of pollutants, which have altered natural elemental cycling and retention rates in a variety of ways. This study examined atmospheric...

Composite turbine blade design options for Claude (open) cycle OTEC power systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penney, T R

1985-11-01

Small-scale turbine rotors made from composites offer several technical advantages for a Claude (open) cycle ocean thermal energy conversion (OTEC) power system. Westinghouse Electric Corporation has designed a composite turbine rotor/disk using state-of-the-art analysis methods for large-scale (100-MW/sub e/) open cycle OTEC applications. Near-term demonstrations using conventional low-pressure turbine blade shapes with composite material would achieve feasibility and modern credibility of the open cycle OTEC power system. Application of composite blades for low-pressure turbo-machinery potentially improves the reliability of conventional metal blades affected by stress corrosion.

Asphalt pavement aging and temperature dependent properties using functionally graded viscoelastic model

NASA Astrophysics Data System (ADS)

Dave, Eshan V.

Asphalt concrete pavements are inherently graded viscoelastic structures. Oxidative aging of asphalt binder and temperature cycling due to climatic conditions being the major cause of non-homogeneity. Current pavement analysis and simulation procedures dwell on the use of layered approach to account for these non-homogeneities. The conventional finite-element modeling (FEM) technique discretizes the problem domain into smaller elements, each with a unique constitutive property. However the assignment of unique material property description to an element in the FEM approach makes it an unattractive choice for simulation of problems with material non-homogeneities. Specialized elements such as "graded elements" allow for non-homogenous material property definitions within an element. This dissertation describes the development of graded viscoelastic finite element analysis method and its application for analysis of asphalt concrete pavements. Results show that the present research improves efficiency and accuracy of simulations for asphalt pavement systems. Some of the practical implications of this work include the new technique's capability for accurate analysis and design of asphalt pavements and overlay systems and for the determination of pavement performance with varying climatic conditions and amount of in-service age. Other application areas include simulation of functionally graded fiber-reinforced concrete, geotechnical materials, metal and metal composites at high temperatures, polymers, and several other naturally existing and engineered materials.

Towards better monitoring of technology critical elements in Europe: Coupling of natural and anthropogenic cycles.

PubMed

Nuss, Philip; Blengini, Gian Andrea

2018-02-01

The characterization of elemental cycles has a rich history in biogeochemistry. Well known examples include the global carbon cycle, or the cycles of the 'grand nutrients' nitrogen, phosphorus, and sulfur. More recently, efforts have increased to better understand the natural cycling of technology critical elements (TCEs), i.e. elements with a high supply risk and economic importance in the EU. On the other hand, tools such as material-flow analysis (MFA) can help to understand how substances and goods are transported and accumulated in man-made technological systems ('anthroposphere'). However, to date both biogeochemical cycles and MFA studies suffer from narrow system boundaries, failing to fully illustrate relative anthropogenic and natural flow magnitude and the degree to which human activity has perturbed the natural cycling of elements. We discuss important interconnections between natural and anthropogenic cycles and relevant EU raw material dossiers. Increased integration of both cycles could help to better capture the transport and fate of elements in nature including their environmental/human health impacts, highlight potential future material stocks in the anthroposphere (in-use stocks) and in nature (e.g., in soils, tailings, or mining wastes), and estimate anticipated emissions of TCEs to nature in the future (based on dynamic stock modeling). A preliminary assessment of natural versus anthropogenic element fluxes indicates that anthropogenic fluxes induced by the EU-28 of palladium, platinum, and antimony (as a result of materials uses) might be greater than the respective global natural fluxes. Increased combination of MFA and natural cycle data at EU level could help to derive more complete material cycles and initiate a discussion between the research communities of biogeochemists and material flow analysts to more holistically address the issues of sustainable resource management. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

How causal analysis can reveal autonomy in models of biological systems

NASA Astrophysics Data System (ADS)

Marshall, William; Kim, Hyunju; Walker, Sara I.; Tononi, Giulio; Albantakis, Larissa

2017-11-01

Standard techniques for studying biological systems largely focus on their dynamical or, more recently, their informational properties, usually taking either a reductionist or holistic perspective. Yet, studying only individual system elements or the dynamics of the system as a whole disregards the organizational structure of the system-whether there are subsets of elements with joint causes or effects, and whether the system is strongly integrated or composed of several loosely interacting components. Integrated information theory offers a theoretical framework to (1) investigate the compositional cause-effect structure of a system and to (2) identify causal borders of highly integrated elements comprising local maxima of intrinsic cause-effect power. Here we apply this comprehensive causal analysis to a Boolean network model of the fission yeast (Schizosaccharomyces pombe) cell cycle. We demonstrate that this biological model features a non-trivial causal architecture, whose discovery may provide insights about the real cell cycle that could not be gained from holistic or reductionist approaches. We also show how some specific properties of this underlying causal architecture relate to the biological notion of autonomy. Ultimately, we suggest that analysing the causal organization of a system, including key features like intrinsic control and stable causal borders, should prove relevant for distinguishing life from non-life, and thus could also illuminate the origin of life problem. This article is part of the themed issue 'Reconceptualizing the origins of life'.

Nanoconfined phosphorus film coating on interconnected carbon nanotubes as ultrastable anodes for lithium ion batteries

NASA Astrophysics Data System (ADS)

Xu, Zhiwei; Zeng, Yan; Wang, Liyuan; Li, Nan; Chen, Cheng; Li, Cuiyu; Li, Jing; Lv, Hanming; Kuang, Liyun; Tian, Xu

2017-07-01

Elemental phosphorus (P) is extensively explored as promising anode candidates due to its abundance, low-cost and high theoretical specific capacity. However, it is of great challenge for P-based materials as practical high-energy-density and long-cycling anodes for its large volume expansion and low conductibility. Here, we significantly improve both cycling and rate performance of red P by cladding the nanoconfined P film on interconnected multi-walled carbon nanotube networks (P-MWCNTs composite) via facile wet ball-milling. The red P-MWCNTs anode presents a superior high reversible capacity of 1396.6 mAh g-1 on the basis of P-MWCNTs composite weight at 50 mA g-1 with capacity retention reaching at ∼90% over 50 cycles. Even at 1000 mA g-1, it still maintains remarkable specific reversible capacity of 934.0 mAh g-1. This markedly enhanced performance is ascribed to synergistic advantages of this unique structure: Intimate contacts between nanosized red P and entangled MWCNTs not only shorten the transmission routes of ions through MWCNTs toward red P, but also motivate the access with electrolyte to open structures of P film. Besides, the confined nanosized P film moderate volume expansions effectively and the entangled MWCNTs networks acted as conductive channels activate high ionic/electronic conductivity of the whole electrodes.

Element Cycles: An Environmental Chemistry Board Game

ERIC Educational Resources Information Center

Pippins, Tracy; Anderson, Cody M.; Poindexter, Eric F.; Sultemeier, S. Whitney; Schultz, Linda D.

2011-01-01

"Element Cycles" is an activity designed to reinforce correlation of essential elements and their different forms in the ecosystem. Students are assigned essential elements to research as homework, then share results, and construct game boards with four ecosphere sections: geosphere (earth), hydrosphere (water), atmosphere (air), and biosphere…

Differences in the Activities of Eight Enzymes from Ten Soil Fungi and Their Possible Influences on the Surface Structure, Functional Groups, and Element Composition of Soil Colloids

PubMed Central

Wang, Wenjie; Li, Yanhong; Wang, Huimei; Zu, Yuangang

2014-01-01

How soil fungi function in soil carbon and nutrient cycling is not well understood by using fungal enzymatic differences and their interactions with soil colloids. Eight extracellular enzymes, EEAs (chitinase, carboxymethyl cellulase, β-glucosidase, protease, acid phosphatase, polyphenol oxidase, laccase, and guaiacol oxidase) secreted by ten fungi were compared, and then the fungi that showed low and high enzymatic activity were co-cultured with soil colloids for the purpose of finding fungi-soil interactions. Some fungi (Gomphidius rutilus, Russula integra, Pholiota adiposa, and Geastrum mammosum) secreted 3–4 enzymes with weak activities, while others (Cyathus striatus, Suillus granulate, Phallus impudicus, Collybia dryophila, Agaricus sylvicola, and Lactarius deliciosus) could secret over 5 enzymes with high activities. The differences in these fungi contributed to the alterations of functional groups (stretching bands of O-H, N-H, C-H, C = O, COO- decreased by 11–60%, while P = O, C-O stretching, O-H bending and Si-O-Si stretching increased 9–22%), surface appearance (disappearance of adhesive organic materials), and elemental compositions (11–49% decreases in C1s) in soil colloids. Moreover, more evident changes were generally in high enzymatic fungi (C. striatus) compared with low enzymatic fungi (G. rutilus). Our findings indicate that inter-fungi differences in EEA types and activities might be responsible for physical and chemical changes in soil colloids (the most active component of soil matrix), highlighting the important roles of soil fungi in soil nutrient cycling and functional maintenance. PMID:25398013

Differences in the activities of eight enzymes from ten soil fungi and their possible influences on the surface structure, functional groups, and element composition of soil colloids.

PubMed

Wang, Wenjie; Li, Yanhong; Wang, Huimei; Zu, Yuangang

2014-01-01

How soil fungi function in soil carbon and nutrient cycling is not well understood by using fungal enzymatic differences and their interactions with soil colloids. Eight extracellular enzymes, EEAs (chitinase, carboxymethyl cellulase, β-glucosidase, protease, acid phosphatase, polyphenol oxidase, laccase, and guaiacol oxidase) secreted by ten fungi were compared, and then the fungi that showed low and high enzymatic activity were co-cultured with soil colloids for the purpose of finding fungi-soil interactions. Some fungi (Gomphidius rutilus, Russula integra, Pholiota adiposa, and Geastrum mammosum) secreted 3-4 enzymes with weak activities, while others (Cyathus striatus, Suillus granulate, Phallus impudicus, Collybia dryophila, Agaricus sylvicola, and Lactarius deliciosus) could secret over 5 enzymes with high activities. The differences in these fungi contributed to the alterations of functional groups (stretching bands of O-H, N-H, C-H, C = O, COO- decreased by 11-60%, while P = O, C-O stretching, O-H bending and Si-O-Si stretching increased 9-22%), surface appearance (disappearance of adhesive organic materials), and elemental compositions (11-49% decreases in C1s) in soil colloids. Moreover, more evident changes were generally in high enzymatic fungi (C. striatus) compared with low enzymatic fungi (G. rutilus). Our findings indicate that inter-fungi differences in EEA types and activities might be responsible for physical and chemical changes in soil colloids (the most active component of soil matrix), highlighting the important roles of soil fungi in soil nutrient cycling and functional maintenance.

Implications for metal and volatile cycles from the pH of subduction zone fluids

NASA Astrophysics Data System (ADS)

Galvez, Matthieu E.; Connolly, James A. D.; Manning, Craig E.

2016-11-01

The chemistry of aqueous fluids controls the transport and exchange—the cycles—of metals and volatile elements on Earth. Subduction zones, where oceanic plates sink into the Earth’s interior, are the most important geodynamic setting for this fluid-mediated chemical exchange. Characterizing the ionic speciation and pH of fluids equilibrated with rocks at subduction zone conditions has long been a major challenge in Earth science. Here we report thermodynamic predictions of fluid-rock equilibria that tie together models of the thermal structure, mineralogy and fluid speciation of subduction zones. We find that the pH of fluids in subducted crustal lithologies is confined to a mildly alkaline range, modulated by rock volatile and chlorine contents. Cold subduction typical of the Phanerozoic eon favours the preservation of oxidized carbon in subducting slabs. In contrast, the pH of mantle wedge fluids is very sensitive to minor variations in rock composition. These variations may be caused by intramantle differentiation, or by infiltration of fluids enriched in alkali components extracted from the subducted crust. The sensitivity of pH to soluble elements in low abundance in the host rocks, such as carbon, alkali metals and halogens, illustrates a feedback between the chemistry of the Earth’s atmosphere-ocean system and the speciation of subduction zone fluids via the composition of the seawater-altered oceanic lithosphere. Our findings provide a perspective on the controlling reactions that have coupled metal and volatile cycles in subduction zones for more than 3 billion years7.

Plant-soil distribution of potentially toxic elements in response to elevated atmospheric CO2.

PubMed

Duval, Benjamin D; Dijkstra, Paul; Natali, Susan M; Megonigal, J Patrick; Ketterer, Michael E; Drake, Bert G; Lerdau, Manuel T; Gordon, Gwyneth; Anbar, Ariel D; Hungate, Bruce A

2011-04-01

The distribution of contaminant elements within ecosystems is an environmental concern because of these elements' potential toxicity to animals and plants and their ability to hinder microbial ecosystem services. As with nutrients, contaminants are cycled within and through ecosystems. Elevated atmospheric CO2 generally increases plant productivity and alters nutrient element cycling, but whether CO2 causes similar effects on the cycling of contaminant elements is unknown. Here we show that 11 years of experimental CO2 enrichment in a sandy soil with low organic matter content causes plants to accumulate contaminants in plant biomass, with declines in the extractable contaminant element pools in surface soils. These results indicate that CO2 alters the distribution of contaminant elements in ecosystems, with plant element accumulation and declining soil availability both likely explained by the CO2 stimulation of plant biomass. Our results highlight the interdependence of element cycles and the importance of taking a broad view of the periodic table when the effects of global environmental change on ecosystem biogeochemistry are considered.

Structural transformation of macroporous silicon anodes as a result of cyclic lithiation processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, G. V.; Kulova, T. L.; Tolmachev, V. A., E-mail: tva@mail.ioffe.ru

2013-09-15

Anodes based on a regular lattice of macroporous silicon with different periods, sizes, and shapes of pore cross sections are studied. The discharge capacity and its degradation during cycling (embedding and extraction of lithium) are examined. Scanning electron microscopy is used to analyze changes in the electrode structure upon the lithiation/delithiation of Si and to evaluate the elemental composition of the porous material. An ex situ morphological analysis of the electrodes demonstrates that, on the whole, the porous structure is preserved upon cycling and the thickness of silicon walls increases. The degree of Si-wall destruction depends on their initial thickness.more » Estimates show that the electrolyte reduction process mainly occurs according to the two-electron mechanism, with inorganic salts of lithium formed as a result.« less

No One's Home: the Fate of Carbon on Lifeless Earths

NASA Astrophysics Data System (ADS)

Neveu, Marc

Although several thousands of exoplanets are now known, including many terrestrial planets, their possible geology and climates remain poorly understood and understudied. Yet, understanding how elements such as carbon are cycled between a planet's interior, surface, and atmosphere is crucial to predict how lifeless planets operate and, by contrast, be able to detect deviations from abiotic backgrounds due to biology, the holy grail of exoplanet science. As a first, feasible step towards the difficult, long-term goal of understanding how key reactive elements (H, C, N, O, S) are cycled in the atmospheres, surfaces, and interiors of terrestrial exoplanets through time, we propose to carry out a self-consistent theoretical study of the fate of carbon in the atmospheres and at the surfaces of Earth-like, lifeless exoplanets. We will: 1. Model the near-surface geochemistry and geophysics of the carbon cycle to determine net carbon gas fluxes as a function of terrestrial planet size and redox conditions; 2. Model the atmospheric fate of carbon species as a function of stellar input; 3. Perform simulations that self-consistently combine geological and atmospheric processes; 4. Convert resulting atmospheric compositions to spectra to be archived as a public database for use by observers. We will track the abiotic fate of carbon and its atmospheric expression on Earth-like planets as a function of three key parameters: planet size, surface and atmospheric redox conditions, and stellar irradiation. To do so, we will further develop and use state-of-theart planetary geological ("Geo") and atmospheric ("Atmos") models. We have previously developed a code that couples geophysical evolution and water-rock geochemistry (Neveu et al. 2015, GRL 42, 10197). Using this code, we will calculate the speciation of carbon species versus depth in subaerial oceans, their possible incorporation into the crust by water-rock interaction at the seafloor or by subduction of sediments, and outgassing as a function of temperature, pressure, and fluid/rock composition. We will expand this code with benchmarked parameterizations of land and seafloor weathering and outgassing rates. This modeling will result in detailed boundary conditions to be implemented into an existing atmospheric photochemical-climate model (DomagalGoldman et al. 2014, ApJ 792, 90). The atmospheric model will be used to predict species mixing ratios from net surface fluxes, given planetary and stellar parameters. The models will be benchmarked against what is known of the surfaces and atmospheres of the Earth (present and prior to atmospheric oxygenation) and Titan. Atmospheric model outputs will be fed back into the geological model in combined simulations of carbon cycling. We will investigate in detail the mutual feedbacks between geological and atmospheric processes, so far understudied for terrestrial exoplanets. The resulting atmospheric compositions will be converted to predicted exoplanet spectra using the Spectral Mapping Atmospheric Radiative Transfer model (SMART; Meadows & Crisp 1996, JGR 101, 4595). This grid of spectra will be made freely available to the exoplanet community. This proposal is relevant to the Exoplanets Research Program (E.3) objectives, as it "supports directly the scientific goals of advancing our knowledge and understanding of exoplanetary systems." It involves the "characterization of exoplanets (including their surfaces, interiors, and atmospheres) [...] including the determination of their compositions, dynamics, energetics, and chemical behaviors." This investigation will also advance "understanding the chemical and physical processes of exoplanets (including the state and evolution of their surfaces, interiors, and atmospheres)." Furthermore, this proposal is not "aimed at investigating the habitability of an exoplanet" and therefore not relevant to the Habitable Worlds program element (E.4).

Multimodal Characterization of the Morphology and Functional Interfaces in Composite Electrodes for Li-S Batteries by Li Ion and Electron Beams.

PubMed

Oleshko, Vladimir P; Herzing, Andrew A; Twedt, Kevin A; Griebel, Jared J; McClelland, Jabez J; Pyun, Jeffrey; Soles, Christopher L

2017-09-19

We report the characterization of multiscale 3D structural architectures of novel poly[sulfur-random-(1,3-diisopropenylbenzene)] copolymer-based cathodes for high-energy-density Li-S batteries capable of realizing discharge capacities >1000 mAh/g and long cycling lifetimes >500 cycles. Hierarchical morphologies and interfacial structures have been investigated by a combination of focused Li ion beam (LiFIB) and analytical electron microscopy in relation to the electrochemical performance and physicomechanical stability of the cathodes. Charge-free surface topography and composition-sensitive imaging of the electrodes was performed using recently introduced low-energy scanning LiFIB with Li + probe sizes of a few tens of nanometers at 5 keV energy and 1 pA probe current. Furthermore, we demonstrate that LiFIB has the ability to inject a certain number of Li cations into the material with nanoscale precision, potentially enabling control of the state of discharge in the selected area. We show that chemical modification of the cathodes by replacing the elemental sulfur with organosulfur copolymers significantly improves its structural integrity and compositional homogeneity down to the sub-5-nm length scale, resulting in the creation of (a) robust functional interfaces and percolated conductive pathways involving graphitic-like outer shells of aggregated nanocarbons and (b) extended micro- and mesoscale porosities required for effective ion transport.

Geochemical characterization of critical dust source regions in the American West

NASA Astrophysics Data System (ADS)

Aarons, Sarah M.; Blakowski, Molly A.; Aciego, Sarah M.; Stevenson, Emily I.; Sims, Kenneth W. W.; Scott, Sean R.; Aarons, Charles

2017-10-01

The generation, transport, and deposition of mineral dust are detectable in paleoclimate records from land, ocean, and ice, providing valuable insight into earth surface conditions and cycles on a range of timescales. Dust deposited in marine and terrestrial ecosystems can provide critical nutrients to nutrient-limited ecosystems, and variations in dust provenance can indicate changes in dust production, sources and transport pathways as a function of climate variability and land use change. Thus, temporal changes in locations of dust source areas and transport pathways have implications for understanding interactions between mineral dust, global climate, and biogeochemical cycles. This work characterizes dust from areas in the American West known for dust events and/or affected by increasing human settlement and livestock grazing during the last 150 years. Dust generation and uplift from these dust source areas depends on climate and land use practices, and the relative contribution of dust has likely changed since the expansion of industrialization and agriculture into the western United States. We present elemental and isotopic analysis of 28 potential dust source area samples analyzed using Thermal Ionization Mass Spectrometry (TIMS) for 87Sr/86Sr and 143Nd/144Nd composition and Multi-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS) for 176Hf/177Hf composition, and ICPMS for major and trace element concentrations. We find significant variability in the Sr, Nd, and Hf isotope compositions of potential source areas of dust throughout western North America, ranging from 87Sr/86Sr = 0.703699 to 0.740236, εNd = -26.6 to 2.4, and εHf = -21.7 to -0.1. We also report differences in the trace metal and phosphorus concentrations in the geologic provinces sampled. This research provides an important resource for the geochemical tracing of dust sources and sinks in western North America, and will aid in modeling the biogeochemical impacts of increased dust generation and deposition caused by higher drought frequency and human activity.

Cadmium and zinc isotopes of organic-rich marine sediments during Oceanic Anoxic Event 2

NASA Astrophysics Data System (ADS)

Sweere, T.; Dickson, A. J.; Jenkyns, H. C.; Porcelli, D.; Henderson, G. M.; van den Boorn, S.

2017-12-01

Mesozoic Oceanic Anoxic Events (OAEs) are characterized by widespread deposition of organic-rich sediments and the spread of low-oxygen marine environments. To drive and sustain unusually efficient carbon-burial during these events requires high export productivity rates, which has to be supported by an abundance of nutrients in the surface ocean. The presence of redox-sensitive bio-essential micronutrients may be particularly important, and potentially bio-limiting, during such events as they may be drawn down into sediment under low-oxygen conditions. Cadmium and zinc isotopes have potential as tracers for past (micro)nutrient dynamics considering their nutrient-like distribution in the modern ocean and isotope fractionation with uptake by primary producers. The modern deep ocean is generally well mixed for Cd and Zn while short-term cycling of these elements in the surface ocean imposes regional variation. Additional regional variation may be caused by sulfide formation and associated isotope fractionation in euxinic environments. The impact of such regional environmental conditions on the Cd- and Zn-isotope composition of the sediment therefore needs to be addressed in order to explore the use of these elements as a proxy for past nutrient conditions. Here we present an extensive dataset of cadmium- and zinc-isotope compositions of organic-rich marine sediments from different basins deposited during OAE 2 (Late Cretaceous). This comparison highlights regional differences in Cd- and Zn-isotope compositions. However, despite regional environmental controls, a correlation between δ114Cd and δ66Zn across the different sites is observed, which implies a largely similar control on the two isotope systems. When regional environmental controls are accounted for, the data may provide insight in the δ66Zn and δ114Cd evolution of global seawater during OAE 2 as well as information on the global cycling of redox-sensitive micronutrients during the event

Hybrid lithium-ion capacitor with LiFePO4/AC composite cathode - Long term cycle life study, rate effect and charge sharing analysis

NASA Astrophysics Data System (ADS)

Shellikeri, A.; Yturriaga, S.; Zheng, J. S.; Cao, W.; Hagen, M.; Read, J. A.; Jow, T. R.; Zheng, J. P.

2018-07-01

Energy storage devices, which can combine the advantages of lithium-ion battery with that of electric double layer capacitor, are of prime interest. Recently, composite cathodes, which combine a battery material with capacitor material, have shown promise in enhancing life cycle and energy/power performances. Lithium-ion capacitor (LIC), with unique charge storage mechanism of combining a pre-lithiated battery anode with a capacitor cathode, is one such device which has the potential to synergistically incorporate the composite cathode to enhance capacity and cycle life. We report here a hybrid LIC consisting of a lithium iron phosphate (LiFePO4-LFP)/Activated Carbon composite cathode in combination with a hard carbon anode, by integrating the cycle life and capacity enhancing strategies of a dry method of electrode fabrication, anode pre-lithiation and a 3:1 anode to cathode capacity ratio, demonstrating a long cycle life, while elaborating on the charge sharing between the faradaic and non-faradaic mechanism in the battery and capacitor materials, respectively in the composite cathode. An excellent cell capacity retention of 94% (1000 cycles at 1C) and 92% (100,000 cycles at 60C) were demonstrated, while retaining 78% (over 6000 cycles at 2.7C) and 67% (over 70,000 cycles at 43C) of the LFP capacity in the composite cathode.

Do the monomers release from the composite resins after artificial aging?

PubMed

Tokay, Ugur; Koyuturk, Alp Erdin; Aksoy, Abdurrahman; Ozmen, Bilal

2015-04-01

The aim of this study is to measure the effect of thermal cycling on the amount of monomer released from three different composite materials by HPLC analysis method. Three different composite materials, inlay composite, posterior composite and micro-hybrid composite were used. Sixty cylinder specimens each with a dimension of approximately 1 cm width and 3 mm depth, were prepared before experiments were carried out. Inlay composite material was polymerized according to manufacturers' instructions. Thermal cycling device was used to simulate thermal differences which occur in the mouth media. Monomers were analyzed using HPLC technic after thermal cycling process. The amount of ethoxylated Bis-GMA and urethane dimethacrylate (UDMA) in inlay composite material, the amount of ethoxylated Bis-GMA in posterior composite material, the amount of ethoxylated Bis-GMA and triethyleneglycol dimethacrylate (TEGDMA) in micro-hybrid composite material were investigated. Monomer release of thermal cycles levels showed a linear increase in UDMA and TEGDMA (P < 0.05). In terms of thermal cycles levels, Bis-EMA released from posterior composite showed a cubic change (P < 0.001). It was observed that use of additional polymerization processes might have positive effect on the decrease of residual monomer. In the light of the results, we suggest that indirect composite resins have more outstanding features than direct composite resins in terms of biocompatibility. © 2015 Wiley Periodicals, Inc.

Composite materials for space applications

NASA Technical Reports Server (NTRS)

Rawal, Suraj P.; Misra, Mohan S.; Wendt, Robert G.

1990-01-01

The objectives of the program were to: generate mechanical, thermal, and physical property test data for as-fabricated advanced materials; design and fabricate an accelerated thermal cycling chamber; and determine the effect of thermal cycling on thermomechanical properties and dimensional stability of composites. In the current program, extensive mechanical and thermophysical property tests of various organic matrix, metal matrix, glass matrix, and carbon-carbon composites were conducted, and a reliable database was constructed for spacecraft material selection. Material property results for the majority of the as-fabricated composites were consistent with the predicted values, providing a measure of consolidation integrity attained during fabrication. To determine the effect of thermal cycling on mechanical properties, microcracking, and thermal expansion behavior, approximately 500 composite specimens were exposed to 10,000 cycles between -150 and +150 F. These specimens were placed in a large (18 cu ft work space) thermal cycling chamber that was specially designed and fabricated to simulate one year low earth orbital (LEO) thermal cycling in 20 days. With this rate of thermal cycling, this is the largest thermal cycling unit in the country. Material property measurements of the thermal cycled organic matrix composite laminate specimens exhibited less than 24 percent decrease in strength, whereas, the remaining materials exhibited less than 8 percent decrease in strength. The thermal expansion response of each of the thermal cycled specimens revealed significant reduction in hysteresis and residual strain, and the average CTE values were close to the predicted values.

Cell-Sediment Separation and Elemental Stoichiometries in Extreme Environments

NASA Astrophysics Data System (ADS)

Neveu, M.; Poret-peterson, A. T.; Lee, Z. M.; Anbar, A. D.; Elser, J. J.

2012-12-01

Better understanding of the coupling of major biogeochemical cycles requires knowledge of the cellular elemental composition of key microbes. This is difficult in benthic sediments and mats, because of the contributions of non-living components. We are particularly interested in microbial extremophiles, and therefore sought to determine and interpret bulk and cellular elemental ratios in complex field-collected sediment samples from diverse hot spring ecosystems of Yellowstone National Park (YNP). These samples covered a broad range of temperature, pH, and chemical composition. We also sought to extend stoichiometric analysis to a broader suite of elements, including metals (Fe, Ni, Cu, Zn, Mo, etc.) of biological importance (Sterner and Elser, 2002). To overcome the challenge of rigorously isolating communities from their complex mineral matrices (Havig et al., 2011), we adapted a cell-sediment separation procedure from Amalfitano and Fazi (2008). The method involves chemical (use of a detergent and a chelating agent) and physical methods (stirring, gentle sonication, and gradient centrifugation) to break the microbe-mineral bonds. C and N elemental and isotopic abundances were determined by elemental analysis - isotope ratio - mass spectrometry (EA-IR-MS), while P, Na, Mg, Al, K, Ca, V, Cr, Fe, Co, Ni, Cu, Zn, and Mo contents were determined by inductively coupled plasma - mass spectrometry (ICP-MS). We sought to assess the existence of an "Extended Redfield Ratio" (ERR) for these microbes; that is, to establish the multi-element stoichiometric envelope within which extremophilic microbes must operate. Elemental and isotopic mass balance analyses of cultured E. coli before and after separation showed that our procedure preserved cellular C, N, P, Fe, and trace metal contents: neither loss of these elements (e.g., by cell lysis) nor contamination by reagents were observed. On the other hand, cation-forming elements (Na, Mg, K, Ca), were not conserved. Cell counting by epifluorescence microscopy indicated a cell recovery yield between 6 and 40% in field-collected samples (95% for cultured E. coli). Aluminum, assumed to be non-biological in origin, was used to estimate the extent of mineral contamination of isolated cell communities. These results show that our method is successful at separating microbial cells from sediment collected in extreme environments and preserving them for analysis of a broad suite of elements. Photosynthetic sites yielded much more cell material than hotter, chemosynthetic sites (Cox et al., 2011). We are currently measuring cellular elemental abundances and ratios in samples from relatively low-temperature (25 to 65°C), photosynthetic areas, spanning a wide range of pH (2 to 9.5) and composition. These measurements will be compared to existing datasets on the bulk sediment stoichiometry of these ecosystems, and to previous observations of cellular elemental composition. References: Redfield, A.C. (1934) In Daniel, R.J. [Ed.], James Johnstone Memorial Volume, pp. 176-192, Univ. Press Liverpool. Sterner, R.W., Elser, J.J. (2002) Ecological Stoichiometry Princeton Univ. Press, 441p. Havig, J.R., et al. (2011) JGR 116, G01005. Amalfitano, S., Fazi, S. (2008) J. of Microbiol. Methods 75, 237-243. Cox, A., et al. (2011) Chem. Geol. 280, 344-351.

[Effect of thermal cycling on surface microstructure of different light-curing composite resins].

PubMed

Lv, Da; Liu, Kai-Lei; Yao, Yao; Zhang, Wei-Sheng; Liao, Chu-Hong; Jiang, Hong

2015-04-01

To evaluate the effect of thermal cycling on surface microstructure of different light-curing composite resins. A nanofilled composite (Z350) and 4 microhybrid composites (P60, Z250, Spectrum, and AP-X) were fabricated from lateral to center to form cubic specimens. The lateral surfaces were abrased and polished before water storage and 40 000 thermal cycles (5/55 degrees celsius;). The mean surface roughness (Ra) were measured and compared before and after thermal cycling, and the changes of microstructure were observed under scanning electron microscope (SEM). Significant decreases of Ra were observed in the composites, especially in Spectrum (from 0.164±0.024 µm to 0.140±0.017 µm, P<0.001) and Z250 (from 0.169±0.035 µm to 0.144±0.033 µm, P<0.001), whose Ra approximated that of P60 (0.121±0.028 µm) with smoothly polished surface. SEM revealed scratches and shallower pits on the surface of all the 5 resins, and fissures occurred on Z350 following the thermal cycling. Water storage and thermal cycling may produce polishing effect on composite resins and cause fissures on nanofilled composite resins.

Thermal degradation of the tensile properties of undirectionally reinforced FP-AI203/EZ 33 magnesium composites

NASA Technical Reports Server (NTRS)

Bhatt, R. T.; Grimes, H. H.

1982-01-01

The effects of isothermal and cyclic exposure on the room temperature axial and transverse tensile strength and dynamic flexural modulus of 35 volume percent and 55 volume percent FP-Al2O3/EZ 33 magnesium composites were studied. The composite specimens were continuously heated in a sand bath maintained at 350 C for up to 150 hours or thermally cycled between 50 and 250 C or 50 and 350 C for up to 3000 cycles. Each thermal cycle lasted for a total of six minutes with a hold time of two minutes at the maximum temperature. Results indicate to significant loss in the room temperature axial tensile strength and dynamic flexural modulus of composites thermally cycled between 50 and 250 C or of composites isothermally heated at 350 C for up to 150 hours from the strength and modulus data for the untreated, as fabricated composites. In contrast, thermal cycling between 50 and 350 C caused considerable loss in both room temperature strength and modulus. Fractographic analysis and measurement of composite transverse strength and matrix hardness of thermally cycled and isothermally heated composites indicated matrix softening and fiber/matrix debonding due to void growth at the interface and matrix cracking as the likely causes of the strength and modulus loss behavior.

Light element geochemistry of the Apollo 16 site

NASA Technical Reports Server (NTRS)

Kerridge, J. F.; Kaplan, I. R.; Petrowski, C.; Chang, S.

1975-01-01

The abundance and isotopic composition of carbon, sulfur, and nitrogen, the abundance of helium and hydrogen, and the content of metallic iron are reported for lunar surface samples from the Apollo 16 landing site at Cayley-Descartes. The light elements show marked interstation variability at the site. The abundances in soils of C, N, He, and H are apparently controlled mainly by exposure to the solar wind, through implantation or stripping processes. Carbon abundances (but not observed isotopic distributions) are compatible with a model in which equilibrium is established after 10,000-100,000 yr between solar wind input and loss by proton stripping. Sulfur abundances in soils are apparently controlled by abundances in local country rocks, but the lunar S cycle is quite complex. A metallic iron component may have originated by solar wind reduction of lunar Fe(2+).

The 'North American shale composite' - Its compilation, major and trace element characteristics

NASA Technical Reports Server (NTRS)

Gromet, L. P.; Dymek, R. F.; Haskin, L. A.; Korotev, R. L.

1984-01-01

North American shale composite (NASC) major element composition and compilation are presented, together with rare earth element (REE) redeterminations obtained by high precision analytical methods. The major element composition of the NASC compares closely with other average shale compositions, and significant portions of the REE and some other trace elements are contained in minor phases. The uneven REE distribution in NASC powder appears to yield the heterogeneity in analyzed aliquants. REE distributions of detrital sediments may to some extent be dependent on their minor mineral assemblages and the sedimentological factors controlling these assemblages.

Development and flight test of metal-lined CFRP cryogenic tank for reusable rocket

NASA Astrophysics Data System (ADS)

Higuchi, Ken; Takeuchi, Shinsuke; Sato, Eiichi; Naruo, Yoshihiro; Inatani, Yoshifumi; Namiki, Fumiharu; Tanaka, Kohtaro; Watabe, Yoko

2005-07-01

A cryogenic tank made of carbon fiber reinforced plastic (CFRP) shell with aluminum thin liner has been designed as a liquid hydrogen (LH2) tank for an ISAS reusable launch vehicle, and the function of it has been proven by repeated flights onboard the test vehicle called reusable vehicle testing (RVT) in October 2003. The liquid hydrogen tank has to be a pressure vessel, because the fuel of the engine of the test vehicle is supplied by fuel pressure. The pressure vessel of a combination of the outer shell of CFRP for strength element at a cryogenic temperature and the inner liner of aluminum for gas barrier has shown excellent weight merit for this purpose. Interfaces such as tank outline shape, bulk capacity, maximum expected operating pressure (MEOP), thermal insulation, pipe arrangement, and measurement of data are also designed to be ready onboard. This research has many aims, not only development of reusable cryogenic composite tank but also the demonstration of repeated operation including thermal cycle and stress cycle, familiarization with test techniques of operation of cryogenic composite tanks, and the accumulation of data for future design of tanks, vehicle structures, safety evaluation, and total operation systems.

Behaviour of aluminium in forest soils with different lithology and herb vegetation cover.

PubMed

Hubová, Petra; Tejnecký, Václav; Češková, Michaela; Borůvka, Luboš; Němeček, Karel; Drábek, Ondřej

2018-04-01

The aim of this study was to determine the content, distribution and behaviour of Al in soils under beech forest with different parent rock, and to assess the role of herbaceous vegetation on soil Al behaviour. We hypothesize that the contents of elements in the soil sorption complex (Al etc.) are strongly influenced by vegetation cover. Also, low molecular mass organic acids (LMMOA) can be considered as an indicator of soil organic matter (SOM) decomposition and vegetation litter turnover. Speciation of LMMOA, nutrition content (PO 4 3- , Ca 2+ , K + ) and element composition in aqueous extracts were determined by means of ion chromatography and inductively coupled plasma - optical emission spectrometry (ICP-OES) respectively. Active and exchangeable pH, sorption characteristics and exchangeable Al (Al ex ) were determined in BaCl 2 extracts by ICP-OES. Elemental composition of parent rocks was assessed by means of X-ray fluorescence spectroscopy. Herb-poor localities showed lower pH, less nutrients (PO 4 3- , Ca 2+ , K + ), less LMMOA, a larger stock of SOM and greater cation exchange capacity. There was also lower mobilisation of Al in organic horizons, which explains the larger pools of Al. Generally, we can conclude that LMMOA, and thus soil vegetation cover, play an important role in the Al soil cycle. Copyright © 2017 Elsevier Inc. All rights reserved.

Program Helps Generate Boundary-Element Mathematical Models

NASA Technical Reports Server (NTRS)

Goldberg, R. K.

1995-01-01

Composite Model Generation-Boundary Element Method (COM-GEN-BEM) computer program significantly reduces time and effort needed to construct boundary-element mathematical models of continuous-fiber composite materials at micro-mechanical (constituent) scale. Generates boundary-element models compatible with BEST-CMS boundary-element code for anlaysis of micromechanics of composite material. Written in PATRAN Command Language (PCL).

Natural and anthropic effects on hydrochemistry and major and trace elements in the water mass of a Spanish Pyrenean glacial lake set.

PubMed

Santolaria, Zoe; Arruebo, Tomás; Pardo, Alfonso; Rodríguez-Casals, Carlos; Matesanz, José María; Lanaja, Francisco Javier; Urieta, José Santiago

2017-07-01

This study presents the key hydrochemical characteristics and concentration levels of major (Ca, Mg, Na, Si, K, Sr, Fe) and trace (Ba, Sc, Cr, Mn, Al, As, Li, Co, Cu, U, Pb, Hg, Au, Sn, Zn, Cd, Ag, Ni) elements in the water mass of four selected Pyrenean cirque glacial lakes (Sabocos, Baños, Truchas and Escalar tarns) with different catchment features, between 2010 and 2013. Resulting data set is statistically analyzed to discriminate between the natural or anthropic origin of the elements. Analyses indicate that in all cases, the main source of most major and trace elements is geological weathering, being thus individual bedrock composition the main driver of differences between lakes. Several anthropogenic sources of airborne Cu, Sc, Co, and Cr must be also considered. The shallowness of the lake is also a factor that may influence element cycling and concentration levels in its water mass. Concentrations of anthropogenic elements were low, comparable to those reported in other glacial lakes, way below the WHO, US EPA, EC, and Spanish legal limits for drinking water quality, indicating the absence of serious pollution. Toxic heavy metals Cd, Pb, Hg, and Zn were not detected in any of the tarns.

Tracing the secular evolution of the UCC using the iron isotope composition of ancient glacial diamictites

NASA Astrophysics Data System (ADS)

Liu, X. M.; Gaschnig, R. M.; Rudnick, R. L.; Hazen, R. M.; Shahar, A.

2014-12-01

Iron is the fourth most abundant element in the continental crust and influences global climate and biogeochemical cycles in the ocean1. Continental inputs, including river waters, sediments and atmospheric dust are dominant sources (>95%) of iron into the ocean2. Therefore, understanding how continental inputs may have changed through time is important in understanding the secular evolution of the marine Fe cycle. We analysed the Fe isotopic composition of twenty-four glacial diamictite composites, upper continental crust (UCC) proxies, with ages ranging from the Mesoarchean to the Paleozoic eras to characterize the secular evolution of the UCC. The diamictites all have elevated chemical index of alteration (CIA) and other characteristics of weathered regolith (e.g., strong depletion in soluble elements such as Sr), which they inherited from their upper crustal source region3. δ56Fe in the diamictite composites range from -0.59 to +0.23‰, however, most diamictites cluster with an average δ56Fe of 0.11± 0.20 (2s), overlapping juvenile continental material such as island arc basalts (IABs), which show a narrow range in δ56Fe from -0.04 to +0.14 ‰4. There is no obvious correlation between δ56Fe of the glacial diamictites and the CIA, except that the diamictite with the lowest δ56Fe at -0.59 ‰ also has the highest CIA = 89 (the Paleoproterozoic Makganyene Fm.). The data suggest that the Fe isotope compositions in the upper continental crust did not vary throughout Earth history. Interestingly, chemical weathering and sedimentary transport likely play only a minor role in producing Fe isotope variations in the upper continental crust. Anoxic weathering pre-GOE (Great Oxidation Event) does not seem to generate different Fe isotopic signatures from the post-GOE oxidative weathering environment in the upper continental crust. Therefore, large Fe isotopic fractionations observed in various marine sedimentary records are likely due to other processes occurring in the ocean (e.g., biological activity) instead of abiotic redox reactions on the continent. References: 1.Martin (1990) Paleoceanography. 2.Fantle and DePaolo (2004) EPSL. 3. Gaschnig et al. (2014) EPSL. 4. Dauphas et al. (2009) EPSL.

Tracing the secular evolution of the UCC using the iron isotope composition of ancient glacial diamictites

NASA Astrophysics Data System (ADS)

Liu, X. M.; Gaschnig, R. M.; Rudnick, R. L.; Hazen, R. M.; Shahar, A.

2015-12-01

Iron is the fourth most abundant element in the continental crust and influences global climate and biogeochemical cycles in the ocean1. Continental inputs, including river waters, sediments and atmospheric dust are dominant sources (>95%) of iron into the ocean2. Therefore, understanding how continental inputs may have changed through time is important in understanding the secular evolution of the marine Fe cycle. We analysed the Fe isotopic composition of twenty-four glacial diamictite composites, upper continental crust (UCC) proxies, with ages ranging from the Mesoarchean to the Paleozoic eras to characterize the secular evolution of the UCC. The diamictites all have elevated chemical index of alteration (CIA) and other characteristics of weathered regolith (e.g., strong depletion in soluble elements such as Sr), which they inherited from their upper crustal source region3. δ56Fe in the diamictite composites range from -0.59 to +0.23‰, however, most diamictites cluster with an average δ56Fe of 0.11± 0.20 (2s), overlapping juvenile continental material such as island arc basalts (IABs), which show a narrow range in δ56Fe from -0.04 to +0.14 ‰4. There is no obvious correlation between δ56Fe of the glacial diamictites and the CIA, except that the diamictite with the lowest δ56Fe at -0.59 ‰ also has the highest CIA = 89 (the Paleoproterozoic Makganyene Fm.). The data suggest that the Fe isotope compositions in the upper continental crust did not vary throughout Earth history. Interestingly, chemical weathering and sedimentary transport likely play only a minor role in producing Fe isotope variations in the upper continental crust. Anoxic weathering pre-GOE (Great Oxidation Event) does not seem to generate different Fe isotopic signatures from the post-GOE oxidative weathering environment in the upper continental crust. Therefore, large Fe isotopic fractionations observed in various marine sedimentary records are likely due to other processes occurring in the ocean (e.g., biological activity) instead of abiotic redox reactions on the continent. References: 1.Martin (1990) Paleoceanography. 2.Fantle and DePaolo (2004) EPSL. 3. Gaschnig et al. (2014) EPSL. 4. Dauphas et al. (2009) EPSL.

Effect of thermal cycling on composites reinforced with two differently sized silica-glass fibers.

PubMed

Meriç, Gökçe; Ruyter, I Eystein

2007-09-01

To evaluate the effects of thermal cycling on the flexural properties of composites reinforced with two differently sized fibers. Acid-washed, woven, fused silica-glass fibers, were heat-treated at 500 degrees C, silanized and sized with one of two sizing resins (linear poly(butyl methacrylate)) (PBMA), cross-linked poly(methyl methacrylate) (PMMA). Subsequently the fibers were incorporated into a polymer matrix. Two test groups with fibers and one control group without fibers were prepared. The flexural properties of the composite reinforced with linear PBMA-sized fibers were evaluated by 3-point bend testing before thermal cycling. The specimens from all three groups were thermally cycled in water (12,000 cycles, 5/55 degrees C, dwell time 30 s), and afterwards tested by 3-point bending. SEM micrographs were taken of the fibers and of the fractured fiber reinforced composites (FRC). The reduction of ultimate flexural strength after thermal cycling was less than 20% of that prior to thermal cycling for composites reinforced with linear PBMA-sized silica-glass fibers. The flexural strength of the composite reinforced with cross-linked PMMA-sized fibers was reduced to less than half of the initial value. This study demonstrated that thermal cycling differently influences the flexural properties of composites reinforced with different sized silica-glass fibers. The interfacial linear PBMA-sizing polymer acts as a stress-bearing component for the high interfacial stresses during thermal cycling due to the flexible structure of the linear PBMA above Tg. The cross-linked PMMA-sizing, however, acts as a rigid component and therefore causes adhesive fracture between the fibers and matrix after the fatigue process of thermal cycling and flexural fracture.

Phytoplankton bloom dynamics in coastal ecosystems: A review with some general lessons from sustained investigation of San Francisco Bay, California

USGS Publications Warehouse

Cloern, James E.

1996-01-01

Phytoplankton blooms are prominent features of biological variability in shallow coastal ecosystems such as estuaries, lagoons, bays, and tidal rivers. Long-term observation and research in San Francisco Bay illustrates some patterns of phytoplankton spatial and temporal variability and the underlying mechanisms of this variability. Blooms are events of rapid production and accumulation of phytoplankton biomass that are usually responses to changing physical forcings originating in the coastal ocean (e.g., tides), the atmosphere (wind), or on the land surface (precipitation and river runoff). These physical forcings have different timescales of variability, so algal blooms can be short-term episodic events, recurrent seasonal phenomena, or rare events associated with exceptional climatic or hydrologic conditions. The biogeochemical role of phytoplankton primary production is to transform and incorporate reactive inorganic elements into organic forms, and these transformations are rapid and lead to measurable geochemical change during blooms. Examples include the depletion of inorganic nutrients (N, P, Si), supersaturation of oxygen and removal of carbon dioxide, shifts in the isotopic composition of reactive elements (C, N), production of climatically active trace gases (methyl bromide, dimethylsulfide), changes in the chemical form and toxicity of trace metals (As, Cd, Ni, Zn), changes in the biochemical composition and reactivity of the suspended particulate matter, and synthesis of organic matter required for the reproduction and growth of heterotrophs, including bacteria, zooplankton, and benthic consumer animals. Some classes of phytoplankton play special roles in the cycling of elements or synthesis of specific organic molecules, but we have only rudimentary understanding of the forces that select for and promote blooms of these species. Mounting evidence suggests that the natural cycles of bloom variability are being altered on a global scale by human activities including the input of toxic contaminants and nutrients, manipulation of river flows, and translocation of species. This hypothesis will be a key component of our effort to understand global change at the land-sea interface. Pursuit of this hypothesis will require creative approaches for distinguishing natural and anthropogenic sources of phytoplankton population variability, as well as recognition that the modes of human disturbance of coastal bloom cycles operate interactively and cannot be studied as isolated processes.

40 CFR Appendix Vi to Part 1039 - Nonroad Compression-ignition Composite Transient Cycle

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Nonroad Compression-ignition Composite Transient Cycle VI Appendix VI to Part 1039 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... ENGINES Pt. 1039, App. VI Appendix VI to Part 1039—Nonroad Compression-ignition Composite Transient Cycle...

Taxonomic and Environmental Variability in the Elemental Composition and Stoichiometry of Individual Dinoflagellate and Diatom Cells from the NW Mediterranean Sea

PubMed Central

2016-01-01

Here we present, for the first time, the elemental concentration, including C, N and O, of single phytoplankton cells collected from the sea. Plankton elemental concentration and stoichiometry are key variables in phytoplankton ecophysiology and ocean biogeochemistry, and are used to link cells and ecosystems. However, most field studies rely on bulk techniques that overestimate carbon and nitrogen because the samples include organic matter other than plankton organisms. Here we used X-ray microanalysis (XRMA), a technique that, unlike bulk analyses, gives simultaneous quotas of C, N, O, Mg, Si, P, and S, in single-cell organisms that can be collected directly from the sea. We analysed the elemental composition of dinoflagellates and diatoms (largely Chaetoceros spp.) collected from different sites of the Catalan coast (NW Mediterranean Sea). As expected, a lower C content is found in our cells compared to historical values of cultured cells. Our results indicate that, except for Si and O in diatoms, the mass of all elements is not a constant fraction of cell volume but rather decreases with increasing cell volume. Also, diatoms are significantly less dense in all the measured elements, except Si, compared to dinoflagellates. The N:P ratio of both groups is higher than the Redfield ratio, as it is the N:P nutrient ratio in deep NW Mediterranean Sea waters (N:P = 20–23). The results suggest that the P requirement is highest for bacterioplankton, followed by dinoflagellates, and lowest for diatoms, giving them a clear ecological advantage in P-limited environments like the Mediterranean Sea. Finally, the P concentration of cells of the same genera but growing under different nutrient conditions was the same, suggesting that the P quota of these cells is at a critical level. Our results indicate that XRMA is an accurate technique to determine single cell elemental quotas and derived conversion factors used to understand and model ocean biogeochemical cycles. PMID:27111067

The influence of day/night cycles on biomass yield and composition of Neochloris oleoabundans.

PubMed

de Winter, Lenneke; Cabanelas, Iago Teles Dominguez; Martens, Dirk E; Wijffels, René H; Barbosa, Maria J

2017-01-01

Day/night cycles regulate the circadian clock of organisms to program daily activities. Many species of microalgae have a synchronized cell division when grown under a day/night cycle, and synchronization might influence biomass yield and composition. Therefore, the aim of this study was to study the influence of day/night cycle on biomass yield and composition of the green microalgae Neochloris oleoabundans . Hence, we compared continuous turbidostat cultures grown under continuous light with cultures grown under simulated day/night cycles. Under day/night cycles, cultures were synchronized as cell division was scheduled in the night, whereas under continuous light cell division occurred randomly synchronized cultures were able to use the light 10-15% more efficiently than non-synchronized cultures. Our results indicate that the efficiency of light use varies over the cell cycle and that synchronized cell division provides a fitness benefit to microalgae. Biomass composition under day/night cycles was similar to continuous light, with the exception of starch content. The starch content was higher in cultures under continuous light, most likely because the cells never had to respire starch to cover for maintenance during dark periods. Day/night cycles were provided in a 'block' (continuous light intensity during the light period) and in a 'sine' (using a sine function to simulate light intensities from sunrise to sunset). There were no differences in biomass yield or composition between these two ways of providing light (in a 'block' or in a 'sine'). The biomass yield and composition of N. oleoabundans were influenced by day/night cycles. These results are important to better understand the relations between research done under continuous light conditions and with day/night cycle conditions. Our findings also imply that more research should be done under day/night cycles.

Aggregated filter-feeding consumers alter nutrient limitation: consequences for ecosystem and community dynamics.

PubMed

Atkinson, Carla L; Vaughn, Caryn C; Forshay, Kenneth J; Cooper, Joshua T

2013-06-01

Nutrient cycling is a key process linking organisms in ecosystems. This is especially apparent in stream environments in which nutrients are taken up readily and cycled through the system in a downstream trajectory. Ecological stoichiometry predicts that biogeochemical cycles of different elements are interdependent because the organisms that drive these cycles require fixed ratios of nutrients. There is growing recognition that animals play an important role in biogeochemical cycling across ecosystems. In particular, dense aggregations of consumers can create biogeochemical hotspots in aquatic ecosystems via nutrient translocation. We predicted that filter-feeding freshwater mussels, which occur as speciose, high-biomass aggregates, would create biogeochemical hotspots in streams by altering nutrient limitation and algal dynamics. In a field study, we manipulated nitrogen and phosphorus using nutrient-diffusing substrates in areas with high and low mussel abundance, recorded algal growth and community composition, and determined in situ mussel excretion stoichiometry at 18 sites in three rivers (Kiamichi, Little, and Mountain Fork Rivers, south-central United States). Our results indicate that mussels greatly influence ecosystem processes by modifying the nutrients that limit primary productivity. Sites without mussels were N-limited with -26% higher relative abundances of N-fixing blue-green algae, while sites with high mussel densities were co-limited (N and P) and dominated by diatoms. These results corroborated the results of our excretion experiments; our path analysis indicated that mussel excretion has a strong influence on stream water column N:P. Due to the high N:P of mussel excretion, strict N-limitation was alleviated, and the system switched to being co-limited by both N and P. This shows that translocation of nutrients by mussel aggregations is important to nutrient dynamics and algal species composition in these rivers. Our study highlights the importance of consumers and this imperiled faunal group on nutrient cycling and community dynamics in aquatic ecosystems.

Application of inorganic element ratios to chemometrics for determination of the geographic origin of welsh onions.

PubMed

Ariyama, Kaoru; Horita, Hiroshi; Yasui, Akemi

2004-09-22

The composition of concentration ratios of 19 inorganic elements to Mg (hereinafter referred to as 19-element/Mg composition) was applied to chemometric techniques to determine the geographic origin (Japan or China) of Welsh onions (Allium fistulosum L.). Using a composition of element ratios has the advantage of simplified sample preparation, and it was possible to determine the geographic origin of a Welsh onion within 2 days. The classical technique based on 20 element concentrations was also used along with the new simpler one based on 19 elements/Mg in order to validate the new technique. Twenty elements, Na, P, K, Ca, Mg, Mn, Fe, Cu, Zn, Sr, Ba, Co, Ni, Rb, Mo, Cd, Cs, La, Ce, and Tl, in 244 Welsh onion samples were analyzed by flame atomic absorption spectroscopy, inductively coupled plasma atomic emission spectrometry, and inductively coupled plasma mass spectrometry. Linear discriminant analysis (LDA) on 20-element concentrations and 19-element/Mg composition was applied to these analytical data, and soft independent modeling of class analogy (SIMCA) on 19-element/Mg composition was applied to these analytical data. The results showed that techniques based on 19-element/Mg composition were effective. LDA, based on 19-element/Mg composition for classification of samples from Japan and from Shandong, Shanghai, and Fujian in China, classified 101 samples used for modeling 97% correctly and predicted another 119 samples excluding 24 nonauthentic samples 93% correctly. In discriminations by 10 times of SIMCA based on 19-element/Mg composition modeled using 101 samples, 220 samples from known production areas including samples used for modeling and excluding 24 nonauthentic samples were predicted 92% correctly.

Controlled ecological life support system - biological problems

NASA Technical Reports Server (NTRS)

Moore, B., III (Editor); Macelroy, R. D. (Editor)

1982-01-01

The general processes and controls associated with two distinct experimental paradigms are examined. Specific areas for research related to biotic production (food production) and biotic decomposition (waste management) are explored. The workshop discussions were directed toward Elemental cycles and the biological factors that affect the transformations of nutrients into food, of food material into waste, and of waste into nutrients were discussed. To focus on biological issues, the discussion assumed that (1) food production would be by biological means (thus excluding chemical synthesis), (2) energy would not be a limiting factor, and (3) engineering capacity for composition and leak rate would be adequate.

Implications of a reducing and warm (not hot) Archaean ambient mantle for ancient element cycles

NASA Astrophysics Data System (ADS)

Aulbach, Sonja

2016-04-01

There is considerable uncertainty regarding the oxygen partial pressure (fO2) and potential temperature (TP) of the ambient convecting mantle throughout Earth's history. Rare Archaean eclogite suites have elemental and isotopic compositions indicative of formation of crustal protoliths in oceanic spreading ridges, hence unaffected by continental sources. These include some eclogite xenoliths derived from cratonic mantle lithosphere and orogenic eclogites marking the exhumation of oceanic crust at Pacific-type margins. Their compositions may retain a memory of the thermal and redox state of the Archaean convecting mantle sources that gave rise to their low-pressure protoliths. Archaean eclogites have TiO2-REE relationships consistent with fractional crystallisation of olivine±plagioclase and cpx during formation of picritic protoliths from a melt that separated from a garnet-free peridotite source, implying intersection of the solidus at ≤2.5 to 3.0 GPa [1]. Low melt fractions (<0.25) inferred from samples with the least fractionated (lowest TiO2) protoliths further argue against deep intersection of the mantle solidus. This suggests a moderately elevated TP ~ 1420-1470 degrees C (lower than some estimates for the ambient convecting mantle at that time [2]), which would support an early onset of plate tectonics [3] and emergence of continents [4], heralding a transition to modern chemical cycles. Moderate TP further indicates that deep recycling of carbon and water, though reduced compared to today, may have been possible in the Archaean [5,6]. Carefully screened eclogites have V/Sc (reflecting the redox state of the ambient mantle during protolith formation [7]) corresponding to ΔFMQ corrected to 1 GPa as low as -1.7 at 3 Ga [1]. Such low oxygen fugacities have consequences for the location of the peridotite solidus and for the types of melts generated during redox melting [5,8]. They also modulate the redox state of volatiles liberated at oceanic spreading ridges [7] in the Archaean, with implications for the composition and oxygenation of the palaeo-atmosphere. Subsequent subduction of such reducing oceanic crust must have also affected the cycling of volatile elements (soluble instead of molecular species [9]) and of redox-sensitive ore-forming metals [10] during metamorphic dehydration and melting reactions. [1] Aulbach&Viljoen (2015) Earth Planet Sci Lett 431; [2] Herzberg et al. (2010) Earth Planet Sci Lett 292; [3] Sizova et al. (2010) Lithos 116; [4] Rey&Coltice (2008) Geology 36; [5] Dasgupta (2013) RIMG 75; [6] Magni et al. (2014) G3 15; [7] Li&Lee (2004) EPSL 228; [8] Stagno et al. (2013) Nature 493; [9] Sverjensky et al. (2014) Nat Geosci 7; [10] Evans & Tomkins (2011) Earth Planet Sci Lett 308.

The geochemistry of loess: Asian and North American deposits compared

USGS Publications Warehouse

Muhs, Daniel R.

2018-01-01

Loess is widely distributed over Asia and North America and constitutes one of the most important surficial deposits that serve as terrestrial records of the Quaternary. The oldest Pleistocene loess in China is likely ∼2.6 Ma, thus spanning much or all of the Pleistocene. In North America, most loess is no older than the penultimate glacial period, with the exception of Alaska, where the record may go back to ∼3.0 Ma. On both continents, loess deposits date primarily to glacial periods, and interglacial or interstadial periods are represented by paleosols. Both glacial and non-glacial sources of silts that comprise the bulk of loess deposits are found on both continents. Although loess has been considered to be representative of the average upper continental crust, there are regionally distinctive compositions of loess in both Asia and North America. Loess deposits in Asia from Yakutia, Tajikistan, and China have compositionally distinct major element compositions, due to varying abundances of silicate minerals, carbonate minerals, and clay minerals. In North America, loess in the Mississippi River valley, the Great Plains, and Alaska are also distinguishable with regard to major element composition that reflects highly diverse source sediments. Trace element geochemistry (Sc-Th-Zr and the rare earth elements) also shows regional diversity of loess bodies, in both Asia and North America. On both continents, most loess bodies show significant contributions from later-cycle, altered sedimentary rocks, as opposed to direct derivation from igneous rocks. Further, some loess bodies have detectable contributions from mafic igneous rocks as well as major contributions from average, upper-crustal, felsic rocks. Intercalated paleosols in loess sections show geochemical compositions that differ significantly from the underlying loess parent materials. Ratios of soluble-to-insoluble elements show depletions in paleosols due to chemical weathering losses of calcite, dolomite, plagioclase, mica, apatite, and smectite. In Asia and North America, the last interglacial paleosol is more weathered than equivalent modern soils, which could be due either to a climate that was warmer and more humid, a longer period of pedogenesis, or both. In Asia, early Pleistocene loess and paleosols are both more weathered than those from the middle and late Pleistocene, forming prior to a mid-Pleistocene aridification of Asia from uplift of the Tibetan Plateau. Understanding the geochemistry of loess and paleosols can tell us much about past atmospheric circulation, past temperature and moisture regimes, and even tectonic processes.

The geochemistry of loess: Asian and North American deposits compared

NASA Astrophysics Data System (ADS)

Muhs, Daniel R.

2018-04-01

Loess is widely distributed over Asia and North America and constitutes one of the most important surficial deposits that serve as terrestrial records of the Quaternary. The oldest Pleistocene loess in China is likely ∼2.6 Ma, thus spanning much or all of the Pleistocene. In North America, most loess is no older than the penultimate glacial period, with the exception of Alaska, where the record may go back to ∼3.0 Ma. On both continents, loess deposits date primarily to glacial periods, and interglacial or interstadial periods are represented by paleosols. Both glacial and non-glacial sources of silts that comprise the bulk of loess deposits are found on both continents. Although loess has been considered to be representative of the average upper continental crust, there are regionally distinctive compositions of loess in both Asia and North America. Loess deposits in Asia from Yakutia, Tajikistan, and China have compositionally distinct major element compositions, due to varying abundances of silicate minerals, carbonate minerals, and clay minerals. In North America, loess in the Mississippi River valley, the Great Plains, and Alaska are also distinguishable with regard to major element composition that reflects highly diverse source sediments. Trace element geochemistry (Sc-Th-Zr and the rare earth elements) also shows regional diversity of loess bodies, in both Asia and North America. On both continents, most loess bodies show significant contributions from later-cycle, altered sedimentary rocks, as opposed to direct derivation from igneous rocks. Further, some loess bodies have detectable contributions from mafic igneous rocks as well as major contributions from average, upper-crustal, felsic rocks. Intercalated paleosols in loess sections show geochemical compositions that differ significantly from the underlying loess parent materials. Ratios of soluble-to-insoluble elements show depletions in paleosols due to chemical weathering losses of calcite, dolomite, plagioclase, mica, apatite, and smectite. In Asia and North America, the last interglacial paleosol is more weathered than equivalent modern soils, which could be due either to a climate that was warmer and more humid, a longer period of pedogenesis, or both. In Asia, early Pleistocene loess and paleosols are both more weathered than those from the middle and late Pleistocene, forming prior to a mid-Pleistocene aridification of Asia from uplift of the Tibetan Plateau. Understanding the geochemistry of loess and paleosols can tell us much about past atmospheric circulation, past temperature and moisture regimes, and even tectonic processes.

Real-time measurement of size-resolved elemental composition ratio for flame synthesized composite nanoparticle aggregates using a tandem SMPS-ICP-OES

PubMed Central

Reed, Nathan; Fang, Jiaxi; Chavalmane, Sanmathi; Biswas, Pratim

2017-01-01

Composite nanoparticles find application in catalysis, drug delivery, and energy storage and require increasingly fine control of their physical properties and composition. While composite nanoparticles have been widely synthesized and characterized, little work has systematically correlated the initial concentration of precursors and the final composition of flame synthesized composite nanoparticles. This relationship is explored in a diffusion flame aerosol reactor by coupling a scanning mobility particle sizer (SMPS) with an inductively coupled plasma optical emission spectrometer (ICP-OES). A framework for studying the relationship between the initial precursor concentrations of different elements and the final nanoparticle composition is explored. The size-resolved elemental composition was measured by directly injecting size-selected fractions of aggregated magnetite and silicon dioxide composite nanoparticles into the ICP-OES plasma. This work showed a correlation between precursor molar ratio and the measured elemental ratio in the mobility size range of 50 to 140 nm. Building on previous work studying size resolved elemental composition of engineered nanoparticles, the analysis is extended to flame synthesized composite nanoparticle aggregates in this work. PMID:28435179

Real-time measurement of size-resolved elemental composition ratio for flame synthesized composite nanoparticle aggregates using a tandem SMPS-ICP-OES.

PubMed

Reed, Nathan; Fang, Jiaxi; Chavalmane, Sanmathi; Biswas, Pratim

2017-01-01

Composite nanoparticles find application in catalysis, drug delivery, and energy storage and require increasingly fine control of their physical properties and composition. While composite nanoparticles have been widely synthesized and characterized, little work has systematically correlated the initial concentration of precursors and the final composition of flame synthesized composite nanoparticles. This relationship is explored in a diffusion flame aerosol reactor by coupling a scanning mobility particle sizer (SMPS) with an inductively coupled plasma optical emission spectrometer (ICP-OES). A framework for studying the relationship between the initial precursor concentrations of different elements and the final nanoparticle composition is explored. The size-resolved elemental composition was measured by directly injecting size-selected fractions of aggregated magnetite and silicon dioxide composite nanoparticles into the ICP-OES plasma. This work showed a correlation between precursor molar ratio and the measured elemental ratio in the mobility size range of 50 to 140 nm. Building on previous work studying size resolved elemental composition of engineered nanoparticles, the analysis is extended to flame synthesized composite nanoparticle aggregates in this work.

High resolution analysis of trace elements in corals by laser ablation ICP-MS

NASA Astrophysics Data System (ADS)

Sinclair, Daniel J.; Kinsley, Leslie P. J.; McCulloch, Malcolm T.

1998-06-01

A method has been developed using laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) for rapid high resolution analysis of B, Mg, Sr, Ba, and U in corals. Corals represent a challenge for a microbeam technique due to their compositional and structural heterogeneity, their nonsilicate matrix, and their unusual range of trace element compositions relative to available standards. The method employs an argon-fluoride excimer laser (λ = 193 nm), masked to produce a beam 600 μm wide by 20 μm across to average ablation sampling over a range of structural features. Coral sections are scanned at a constant rate beneath the laser to produce a continuous sampling of the coral surface. Sensitivity drift is controlled by careful preconditioning of the ICP-MS to carbonate material, and standardisation is carried out by bracketing each traverse down the coral sample by analyses of a CaSiO 3 glass synthesised from coral powder. The method demonstrates excellent reproducibility of both the shape and magnitude of coralline trace element profiles, with typical precisions of between 1.0 and 3.7% based on analysis of the synthetic standard. Accuracy varies between 3.8% for B and 31% for U. Discrepancies are attributed to heterogeneities in the synthetic standard, and matrix differences between the silicate standard and carbonate sample. The method is demonstrated by analysis of a coral collected from Australia's Great Barrier Reef near a weather station recording in-situ sea-surface-temperature (SST). The elements B, Mg, Sr, and U show seasonal compositional cycles, and tentative calibrations against SST have been derived. Using independent ICP-MS solution estimates of the coral composition to correct for standardisation uncertainties, the following calibrations have been derived: B/Ca (μmol/mol)= 1000 (±20)- 20.6 (±0.8)× SSTMg/Ca (mmol/mol)= 0.0 (±0.3)+ 0.16 (±0.01)× SSTSr/Ca (mmol/mol)= 10.8 (±0.1)- 0.070 (±0.004)× SSTU/Ca (μmol/mol)= 2.24 (±0.07)- 0.046 (±0.003)× SSTl These calibrations agree with literature within experimental errors, except for Mg which displays a 35% greater temperature dependence than reported previously. None of the elements in the coral appear to be sensitive to decreases in salinity associated with heavy rainfall in the summer of 1991/1992.

Operando Spectromicroscopy of Sulfur Species in Lithium-Sulfur Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Elizabeth C.; Kasse, Robert M.; Heath, Khloe N.

Here, a novel cross-sectional battery cell was developed to characterize lithium-sulfur batteries using X-ray spectromicroscopy. Chemically sensitive X-ray maps were collected operando at energies relevant to the expected sulfur species and were used to correlate changes in sulfur species with electrochemistry. Significant changes in the sulfur/carbon composite electrode were observed from cycle to cycle including rearrangement of the elemental sulfur matrix and PEO10LiTFSI binder. Polysulfide concentration and area of spatial diffusion increased with cycling, indicating that some polysulfide dissolution is irreversible, leading to polysulfide shuttle. Fitting of the maps using standard sulfur and polysulfide XANES spectra indicated that upon subsequentmore » discharge/charge cycles, the initial sulfur concentration was not fully recovered; polysulfides and lithium sulfide remained at the cathodes with higher order polysulfides as the primary species in the region of interest. Quantification of the polysulfide concentration across the electrolyte and electrode interfaces shows that the polysulfide concentration before the first discharge and after the third charge is constant within the electrolyte, but while cycling, a significant increase in polysulfides and a gradient toward the lithium metal anode forms. Finally, this chemically and spatially sensitive characterization and analysis provides a foundation for further operando spectromicroscopy of lithium-sulfur batteries.« less

Native Mussels Alter Nutrient Availability and Reduce Blue ...

EPA Pesticide Factsheets

Nutrient cycling is a key process that ties all organisms together. This is especially apparent in stream environments in which nutrients are taken up readily and cycled through the system in a downstream trajectory. Ecological stoichiometry predicts that biogeochemical cycles of different elements are interdependent because the organisms that drive these cycles require fixed ratios of nutrients. There is growing recognition that animals play an important role in biogeochemical cycling across ecosystems. In particular, dense aggregations of consumers can create biogeochemical hotspots in aquatic ecosystems via nutrient translocation. We predicted that filter-feeding freshwater mussels, which occur as speciose, high biomass aggregates, would create biogeochemical hotspots in streams by altering nutrient limitation and algal dynamics. In a field study, we manipulated nitrogen and phosphorus using nutrient-diffusing substrates in areas with high and low mussel abundance, recorded algal growth and community composition, and determined in situ mussel excretion stoichiometry at 18 sites in 3 rivers (Kiamichi, Little, and Mt. Fork rivers, southcentral U.S.). Our results indicate that mussels greatly influence ecosystem processes by modifying the nutrients that limit primary productivity. Sites without mussels were N-limited with ~26% higher abundances of N-fixing blue-green algae, while sites with high mussel densities were co-limited (N and P) and dominated by diatoms

Renewable hydrogen production via thermochemical/electrochemical coupling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ambrosini, Andrea; Babiniec, Sean Michael; Miller, James E.

A coupled electrochemical/thermochemical cycle was investigated to produce hydrogen from renewable resources. Like a conventional thermochemical cycle, this cycle leverages chemical energy stored in a thermochemical working material that is reduced thermally by solar energy. However, in this concept, the stored chemical energy only needs to be partially, but not fully, capable of splitting steam to produce hydrogen. To complete the process, a proton-conducting membrane is driven to separate hydrogen as it is produced, thus shifting the thermodynamics toward further hydrogen production. This novel coupled-cycle concept provides several benefits. First, the required oxidation enthalpy of the reversible thermochemical material ismore » reduced, enabling the process to occur at lower temperatures. Second, removing the requirement for spontaneous steam-splitting widens the scope of materials compositions, allowing for less expensive/more abundant elements to be used. Lastly, thermodynamics calculations suggest that this concept can potentially reach higher efficiencies than photovoltaic-to-electrolysis hydrogen production methods. This Exploratory Express LDRD involved assessing the practical feasibility of the proposed coupled cycle. A test stand was designed and constructed and proton-conducting membranes were synthesized. While the full proof of concept was not achieved, the individual components of the experiment were validated and new capabilities that can be leveraged by a variety of programs were developed.« less

Thermal Conductivity Changes Due to Degradation of Cathode Film Subjected to Charge-Discharge Cycles in a Li Ion Battery

NASA Astrophysics Data System (ADS)

Jagannadham, K.

2018-05-01

A battery device with graphene platelets as anode, lithium nickel manganese oxide as cathode, and solid-state electrolyte consisting of layers of lithium phosphorous oxynitride and lithium lanthanum titanate is assembled on the stainless steel substrate. The battery in a polymer enclosure is subjected to several electrical tests consisting of charge and discharge cycles at different current and voltage levels. Thermal conductivity of the cathode layer is determined at the end of charge-discharge cycles using transient thermoreflectance. The microstructure and composition of the cathode layer and the interface between the cathode, the anode, and the electrolyte are characterized using scanning electron microscopy and elemental mapping. The decrease in the thermal conductivity of the same cathode observed after each set of electrical test cycles is correlated with the volume changes and formation of low ionic and thermal conductivity lithium oxide and lithium oxychloride at the interface and along porous regions. The interface between the metal current collector and the cathode is also found to be responsible for the increase in thermal resistance. The results indicate that changes in the thermal conductivity of the electrodes provide a measure of the resistance to heat transfer and degradation of ionic transport in the cathode accompanying the charge-discharge cycles in the batteries.

Operando Spectromicroscopy of Sulfur Species in Lithium-Sulfur Batteries

DOE PAGES

Miller, Elizabeth C.; Kasse, Robert M.; Heath, Khloe N.; ...

2017-11-03

Here, a novel cross-sectional battery cell was developed to characterize lithium-sulfur batteries using X-ray spectromicroscopy. Chemically sensitive X-ray maps were collected operando at energies relevant to the expected sulfur species and were used to correlate changes in sulfur species with electrochemistry. Significant changes in the sulfur/carbon composite electrode were observed from cycle to cycle including rearrangement of the elemental sulfur matrix and PEO10LiTFSI binder. Polysulfide concentration and area of spatial diffusion increased with cycling, indicating that some polysulfide dissolution is irreversible, leading to polysulfide shuttle. Fitting of the maps using standard sulfur and polysulfide XANES spectra indicated that upon subsequentmore » discharge/charge cycles, the initial sulfur concentration was not fully recovered; polysulfides and lithium sulfide remained at the cathodes with higher order polysulfides as the primary species in the region of interest. Quantification of the polysulfide concentration across the electrolyte and electrode interfaces shows that the polysulfide concentration before the first discharge and after the third charge is constant within the electrolyte, but while cycling, a significant increase in polysulfides and a gradient toward the lithium metal anode forms. Finally, this chemically and spatially sensitive characterization and analysis provides a foundation for further operando spectromicroscopy of lithium-sulfur batteries.« less

Influence of Silicate Melt Composition on Metal/Silicate Partitioning of W, Ge, Ga and Ni

NASA Technical Reports Server (NTRS)

Singletary, S. J.; Domanik, K.; Drake, M. J.

2005-01-01

The depletion of the siderophile elements in the Earth's upper mantle relative to the chondritic meteorites is a geochemical imprint of core segregation. Therefore, metal/silicate partition coefficients (Dm/s) for siderophile elements are essential to investigations of core formation when used in conjunction with the pattern of elemental abundances in the Earth's mantle. The partitioning of siderophile elements is controlled by temperature, pressure, oxygen fugacity, and by the compositions of the metal and silicate phases. Several recent studies have shown the importance of silicate melt composition on the partitioning of siderophile elements between silicate and metallic liquids. It has been demonstrated that many elements display increased solubility in less polymerized (mafic) melts. However, the importance of silicate melt composition was believed to be minor compared to the influence of oxygen fugacity until studies showed that melt composition is an important factor at high pressures and temperatures. It was found that melt composition is also important for partitioning of high valency siderophile elements. Atmospheric experiments were conducted, varying only silicate melt composition, to assess the importance of silicate melt composition for the partitioning of W, Co and Ga and found that the valence of the dissolving species plays an important role in determining the effect of composition on solubility. In this study, we extend the data set to higher pressures and investigate the role of silicate melt composition on the partitioning of the siderophile elements W, Ge, Ga and Ni between metallic and silicate liquid.

The effects of simulated space environmental parameters on six commercially available composite materials

NASA Technical Reports Server (NTRS)

Funk, Joan G.; Sykes, George F., Jr.

1989-01-01

The effects of simulated space environmental parameters on microdamage induced by the environment in a series of commercially available graphite-fiber-reinforced composite materials were determined. Composites with both thermoset and thermoplastic resin systems were studied. Low-Earth-Orbit (LEO) exposures were simulated by thermal cycling; geosynchronous-orbit (GEO) exposures were simulated by electron irradiation plus thermal cycling. The thermal cycling temperature range was -250 F to either 200 F or 150 F. The upper limits of the thermal cycles were different to ensure that an individual composite material was not cycled above its glass transition temperature. Material response was characterized through assessment of the induced microcracking and its influence on mechanical property changes at both room temperature and -250 F. Microdamage was induced in both thermoset and thermoplastic advanced composite materials exposed to the simulated LEO environment. However, a 350 F cure single-phase toughened epoxy composite was not damaged during exposure to the LEO environment. The simuated GEO environment produced microdamage in all materials tested.

Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

NASA Technical Reports Server (NTRS)

Gao, Xiujie; Burton, Deborah; Turner, Travis L.; Brinson, Catherine

2005-01-01

Shape memory alloy hybrid composites with adaptive-stiffening or morphing functions are simulated using finite element analysis. The composite structure is a laminated fiber-polymer composite beam with embedded SMA ribbons at various positions with respect to the neutral axis of the beam. Adaptive stiffening or morphing is activated via selective resistance heating of the SMA ribbons or uniform thermal loads on the beam. The thermomechanical behavior of these composites was simulated in ABAQUS using user-defined SMA elements. The examples demonstrate the usefulness of the methods for the design and simulation of SMA hybrid composites. Keywords: shape memory alloys, Nitinol, ABAQUS, finite element analysis, post-buckling control, shape control, deflection control, adaptive stiffening, morphing, constitutive modeling, user element

Simulated Nitrogen Deposition has Minor Effects on Ecosystem Pools and Fluxes of Energy, Elements, and Biochemicals in a Northern Hardwoods Forest

NASA Astrophysics Data System (ADS)

Talhelm, A. F.; Pregitzer, K. S.; Burton, A. J.; Xia, M.; Zak, D. R.

2017-12-01

The elemental and biochemical composition of plant tissues is an important influence on primary productivity, decomposition, and other aspects of biogeochemistry. Human activity has greatly altered biogeochemical cycles in ecosystems downwind of industrialized regions through atmospheric nitrogen deposition, but most research on these effects focuses on individual elements or steps in biogeochemical cycles. Here, we quantified pools and fluxes of biomass, the four major organic elements (carbon, oxygen, hydrogen, nitrogen), four biochemical fractions (lignin, structural carbohydrates, cell walls, and soluble material), and energy in a mature northern hardwoods forest in Michigan. We sampled the organic and mineral soil, fine and coarse roots, leaf litter, green leaves, and wood for chemical analyses. We then combined these data with previously published and archival information on pools and fluxes within this forest, which included replicated plots receiving either ambient deposition or simulated nitrogen deposition (3 g N m-2 yr-1 for 18 years). Live wood was the largest pool of energy and all elements and biochemical fractions. However, the production of wood, leaf litter, and fine roots represented similar fluxes of carbon, hydrogen, oxygen, cell wall material, and energy, while nitrogen fluxes were dominated by leaf litter and fine roots. Notably, the flux of lignin via fine roots was 70% higher than any other flux. Experimental nitrogen deposition had relatively few significant effects, increasing foliar nitrogen, increasing the concentration of lignin in the soil organic horizon and decreasing pools of all elements and biochemical fractions in the soil organic horizon except nitrogen, lignin, and structural carbohydrates. Overall, we found that differences in tissue chemistry concentrations were important determinants of ecosystem-level pools and fluxes, but that nitrogen deposition had little effect on concentrations, pools, or fluxes in this mature forest. Disclaimer: The views expressed in this poster are those of the authors and do not necessarily represent the views or policies of the U.S. EPA.

Particulate sulfur-containing lipids: Production and cycling from the epipelagic to the abyssopelagic zone

NASA Astrophysics Data System (ADS)

Gašparović, Blaženka; Penezić, Abra; Frka, Sanja; Kazazić, Saša; Lampitt, Richard S.; Holguin, F. Omar; Sudasinghe, Nilusha; Schaub, Tanner

2018-04-01

There are major gaps in our understanding of the distribution and role of lipids in the open ocean especially with regard to sulfur-containing lipids (S-lipids). Here, we employ a powerful analytical approach based on high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to elucidate depth-related S-lipid production and molecular transformations in suspended particulate matter from the Northeast Atlantic Ocean in this depth range. We show that within the open-ocean environment S-lipids contribute up to 4.2% of the particulate organic carbon, and that up to 95% of these compounds have elemental compositions that do not match those found in the Nature Lipidomics Gateway database (termed "novel"). Among the remaining 5% of lipids that match the database, we find that sulphoquinovosyldiacylglycerol (SQDG) are efficiently removed while sinking through the mesopelagic zone. The relative abundance of other assigned lipids (sulphoquinovosylmonoacylglycerol (SQMG), sulfite and sulfate lipids, Vitamin D2 and D3 derivatives, and sphingolipids) did not change substantially with depth. The novel S-lipids, represented by hundreds of distinct elemental compositions (160-300 molecules at any one depth), contribute increasingly to the lipid and particulate organic matter pools with increased depth. Depth-related transformations cause (i) incomplete degradation/transformation of unsaturated S-lipids which leads to the depth-related accumulation of the refractory saturated compounds with reduced molecular weight (average 455 Da) and (ii) formation of highly unsaturated S-lipids (average abyssopelagic molecular double bond equivalents, DBE=7.8) with lower molecular weight (average 567 Da) than surface S-lipids (average 592 Da). A depth-related increase in molecular oxygen content is observed for all novel S-lipids and indicates that oxidation has a significant role in their transformation while (bio)hydrogenation possibly impacts the formation of saturated compounds. The instrumentation approach applied here represents a step change in our comprehension of marine S-lipid diversity and the potential role of these compounds in the oceanic carbon cycle. We describe a very much higher number of compounds than previously reported, albeit at the level of elemental composition and fold-change quantitation with depth, rather than isomeric confirmation and absolute quantitation of individual lipids. We emphasize that saturated S-lipids have the potential to transfer carbon from the upper ocean to depth and hence are significant vectors for carbon sequestration.

A highly oxidized atmosphere-ocean system and oceanic molybdenum drawdown during the Paleoproterozoic

NASA Astrophysics Data System (ADS)

Goto, K. T.; Ito, T.; Suzuki, K.; Anbar, A. D.; Gordon, G. W.; Kashiwabara, T.; Takaya, Y.; Shimoda, G.; Nozaki, T.; Kiyokawa, S.; Tetteh, G. M.; Nyame, F. K.

2014-12-01

Multiple lines of evidence suggest that the first major oxidation of the atmosphere-ocean system occurred during the Paleoproterozoic. However, the course of this redox transition remains elusive. A number of large Mn deposits are distributed in Paleoproterozoic sedimentary successions. As Mn is a redox-sensitive element characterized by high redox potential, knowledge of the Mn cycle in Paleoproterozoic seawater may provide insight into redox evolution during this period. Here, we investigate the Mn cycle in Paleoproterozoic seawater based on the Re-Os and Mo isotope compositions, and the abundance of major and trace elements, in Mn-rich sedimentary rocks from the Nsuta deposit of the Birimian Supergroup, Ghana. The Mn ore is composed mainly of rhodochrosite and is distributed at the boundaries between sedimentary rocks and tholeiitic volcanic rocks. The Re-Os isochron age (2217 ± 100 Ma) we obtained was consistent with U-Pb zircon ages of the volcanic rocks. The manganophile elements, except for Mo, show no enrichment, which is similar to modern hydrothermal Mn oxides. The PAAS-normalized REE compositions show positive Ce anomaly, indicative of Ce enrichment due to the oxidation of Ce(III) by Mn(IV). These findings suggest that Mn ore formed from primary precipitation of Mn oxides from hydrothermal fluids as they were mixed with bottom seawater at ~2.2 Ga. Thus, the bottom seawater would have been sufficiently oxygenated for the precipitation of Mn oxides at ~2.2 Ga. The Nsuta ore samples exhibit slight Mo enrichment, but Mo/Mn ratios are orders of magnitude lower than those in modern hydrothermal Mn oxides. We also found that the Mo isotopes in the Nsuta ore are ~0.7‰ heavier than those in modern hydrothermal and hydrogenous Mn oxides. As Mo in hydrothermal Mn oxides is sourced primarily from seawater (Goto et al., in prep), these results may reflect smaller oceanic Mo inventory and heavier seawater Mo isotope composition at 2.2 Ga than those of present-day. Our calculation using a simple mass balance model suggests that substantial removal of light Mo by Mn oxides may have caused such oceanic conditions. Our findings are consistent with the recently proposed 'oxygen overshoot' model (Bekker and Holland, 2012) and low Mo contents in ~2.2-Ga black shales and sedimentary pyrites (e.g., Scott et al., 2008).

Predator-driven elemental cycling: the impact of predation and risk effects on ecosystem stoichiometry.

PubMed

Leroux, Shawn J; Schmitz, Oswald J

2015-11-01

Empirical evidence is beginning to show that predators can be important drivers of elemental cycling within ecosystems by propagating indirect effects that determine the distribution of elements among trophic levels as well as determine the chemical content of organic matter that becomes decomposed by microbes. These indirect effects can be propagated by predator consumptive effects on prey, nonconsumptive (risk) effects, or a combination of both. Currently, there is insufficient theory to predict how such predator effects should propagate throughout ecosystems. We present here a theoretical framework for exploring predator effects on ecosystem elemental cycling to encourage further empirical quantification. We use a classic ecosystem trophic compartment model as a basis for our analyses but infuse principles from ecological stoichiometry into the analyses of elemental cycling. Using a combined analytical-numerical approach, we compare how predators affect cycling through consumptive effects in which they control the flux of nutrients up trophic chains; through risk effects in which they change the homeostatic elemental balance of herbivore prey which accordingly changes the element ratio herbivores select from plants; and through a combination of both effects. Our analysis reveals that predators can have quantitatively important effects on elemental cycling, relative to a model formalism that excludes predator effects. Furthermore, the feedbacks due to predator nonconsumptive effects often have the quantitatively strongest impact on whole ecosystem elemental stocks, production and efficiency rates, and recycling fluxes by changing the stoichiometric balance of all trophic levels. Our modeling framework predictably shows how bottom-up control by microbes and top-down control by predators on ecosystems become interdependent when top predator effects permeate ecosystems.

Temperature dependence of the biaxial modulus, intrinsic stress and composition of plasma deposited silicon oxynitride films

NASA Technical Reports Server (NTRS)

Harding, David R.; Ogbuji, Linus U. T.; Freeman, Mathieu J.

1995-01-01

Silicon oxynitride films were deposited by plasma-enhanced chemical-vapor deposition. The elemental composition was varied between silicon nitride and silicon dioxide: SiO(0.3)N(1.0), SiO(0.7)N(1.6), SiO(0.7)N(1.1), and SiO(1.7)N(0.%). These films were annealed in air, at temperatures of 40-240 C above the deposition temperature (260 C), to determine the stability and behavior or each composition. the biaxial modulus, biaxial intrinsic stress, and elemental composition were measured at discrete intervals within the annealing cycle. Films deposited from primarily ammonia possessed considerable hydrogen (up to 38 at.%) and lost nitrogen and hydrogen at anneal temperatures (260-300 C) only marginally higher than the deposition temperature. As the initial oxygen content increased a different mechanism controlled the behavior or the film: The temperature threshold for change rose to approximately equal to 350 C and the loss of nitrogen was compensated by an equivalent rise in the oxygen content. The transformation from silicon oxynitride to silica was completed after 50 h at 400 C. The initial biaxial modulus of all compositions was 21-3- GPa and the intrinsic stress was -30 to 85 MPa. Increasing the oxygen content raised the temperature threshold where cracking first occurred; the two film compositions with the highest initial oxygen content did not crack, even at the highest temperature (450 C) investigated. At 450 C the biaxial modulus increased to approximately equal to 100 GPa and the intrinsic stress was approximately equal to 200 MPa. These increases could be correlated with the observed change in the film's composition. When nitrogen was replaced by oxygen, the induced stress remained lower than the biaxial strength of the material, but, when nitrogen and hydrogen were lost, stress-relieving microcracking occurred.

Changes of the elemental distributions in marine diatoms as a reporter of sample preparation artefacts. A nuclear microscopy application

NASA Astrophysics Data System (ADS)

Godinho, R. M.; Cabrita, M. T.; Alves, L. C.; Pinheiro, T.

2015-04-01

Studies of the elemental composition of whole marine diatoms cells have high interest as they constitute a direct measurement of environmental changes, and allow anticipating consequences of anthropogenic alterations to organisms, ecosystems and global marine geochemical cycles. Nuclear microscopy is a powerful tool allowing direct measurement of whole cells giving qualitative imaging of distribution, and quantitative determination of intracellular concentration. Major obstacles to the analysis of marine microalgae are high medium salinity and the recurrent presence of extracellular exudates produced by algae to maintain colonies in natural media and in vitro. The objective of this paper was to optimize the methodology of sample preparation of marine unicellular algae for elemental analysis with nuclear microscopy, allowing further studies on cellular response to metals. Primary cultures of Coscinodiscus wailesii maintained in vitro were used to optimize protocols for elemental analysis with nuclear microscopy techniques. Adequate cell preparation procedures to isolate the cells from media components and exudates were established. The use of chemical agents proved to be inappropriate for elemental determination and for intracellular morphological analysis. The assessment of morphology and elemental partitioning in cell compartments obtained with nuclear microscopy techniques enabled to infer their function in natural environment and imbalances in exposure condition. Exposure to metal affected C. wailesii morphology and internal elemental distribution.

Standardization of the neutron probe for the assessment of masonry deterioration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Livingston, R.A.

1992-01-01

The repair of the infrastructure will require nondestructive methods to assess the condition of existing buildings and other structures, many of which are constructed of masonry. One possible technology is the neutron probe, a prompt-gamma neutron activation (PGNA) technique that can perform non- destructive elemental analyses in the field. It is based on a very low intensity [sup 252]Cf neutron source and a high-purity germanium detector for the gamma rays emitted by neutron capture within the material. The thermal neutron capture cross sections for hydrogen and chlorine are very large, and in masonry, these elements are found primarily in moisturemore » and chlorides. These are major causes of deterioration in porous materials such as brick masonry. The moisture damages the material through expansive stresses during freeze-thaw cycles. Chlorides also generate expansive stresses through periodic cycles of dissolution and recrystallization in response to relative humidity cycles in the atmosphere. Similar problems also occur in reinforced concrete, where chlorides cause additional damage through corrosion of the reinforcing steel. The sensitivity of the neutron probe to hydrogen and chlorine thus means it can be used to map the distribution of these agents of deterioration. Preliminary field work at Colonial Williamsburg and Venice, Italy, showed that the technique could yield useful qualitative information. However, to be a quantitative method, the neutron probe had to be standardized in the laboratory on materials of known composition and specified moisture and chloride content.« less

The Effect of a Receding Saline Lake (The Salton Sea) on Airborne Particulate Matter Composition.

PubMed

Frie, Alexander L; Dingle, Justin H; Ying, Samantha C; Bahreini, Roya

2017-08-01

The composition of ambient particulate matter (PM) and its sources were investigated at the Salton Sea, a shrinking saline lake in California. To investigate the influence of playa exposure on PM composition, PM samples were collected during two seasons and at two sites around the Salton Sea. To characterize source composition, soil samples were collected from local playa and desert surfaces. PM and soil samples were analyzed for 15 elements using mass spectrometry and X-ray diffraction. The contribution of sources to PM mass and composition was investigated using Al-referenced enrichment factors (EFs) and source factors resolved from positive matrix factorization (PMF). Playa soils were found to be significantly enriched in Ca, Na, and Se relative to desert soils. PMF analysis resolved the PM 10 data with four source factors, identified as Playa-like, Desert-like, Ca-rich, and Se. Playa-like and desert-like sources were estimated to contribute to a daily average of 8.9% and 45% of PM 10 mass, respectively. Additionally, playa sources were estimated to contribute to 38-68% of PM 10 Na. PM 10 Se concentrations showed strong seasonal variations, suggesting a seasonal cycle of Se volatilization and recondensation. These results support the importance of playas as a source of PM mass and a controlling factor of PM composition.

Long-term thermal degradation and alloying constituent effects on five boron/aluminum composites

NASA Technical Reports Server (NTRS)

Olsen, G. C.

1982-01-01

Thermal exposure effects on the properties of five boron/aluminum composite systems were experimentally investigated. The composite systems were 49 volume percent boron fibers (203 micron diameter) in aluminum-alloy matrices 1100 Al, 2024 Al, 3003 Al, 5052 Al, and 6061 Al. Specimens were thermally exposed up to 10,000 hours at 500 K and 590 K, up to 500 hours at 730 K, and up to 10,000 hours at 500 K and 590 K, up to 500 hours at 730 K, and up to 2000 thermal cycles between 200 K and 590 K. Composite longitudinal and transverse tensile strengths, longitudinal compression strength, and in-plane shear strength were determined. None of the systems was severely degraded by exposure at 590 K. The best performing system was B-2024 Al. Effects of matrix alloys on degradation mechanisms were experimentally investigated. Composite specimens and individual fibers were metallurgically analyzed with a scanning electron microscope and an electron microprobe to determine failure characteristics, chemical element distribution, and reaction layer morphology. Alloying constituents were found to be affect the composite degradation mechanisms as follows: alloys containing iron, but without manganese as a stabilizer, caused increased low-temperature degradation; alloys containing magnesium, iron, or manganese caused increased degradation; and alloys containing copper caused increased fiber strength.

Ion microprobe analyses of aluminous lunar glasses - A test of the 'rock type' hypothesis

NASA Technical Reports Server (NTRS)

Meyer, C., Jr.

1978-01-01

Previous soil survey investigations found that there are natural groupings of glass compositions in lunar soils and that the average major element composition of some of these groupings is the same at widely separated lunar landing sites. This led soil survey enthusiasts to promote the hypothesis that the average composition of glass groupings represents the composition of primary lunar 'rock types'. In this investigation the trace element composition of numerous aluminous glass particles was determined by the ion microprobe method as a test of the above mentioned 'rock type' hypothesis. It was found that within any grouping of aluminous lunar glasses by major element content, there is considerable scatter in the refractory trace element content. In addition, aluminous glasses grouped by major elements were found to have different average trace element contents at different sites (Apollo 15, 16 and Luna 20). This evidence argues that natural groupings in glass compositions are determined by regolith processes and may not represent the composition of primary lunar 'rock types'.

CYCLING OF DISSOLVED ELEMENTAL MERCURY IN ARCTIC ALASKAN LAKES. (R829796)

EPA Science Inventory

Aqueous production and water-air exchange of elemental mercury (Hg⁰) are important features of the environmental cycling of Hg. We investigated Hg⁰ cycling in ten Arctic Alaskan lakes that spanned a wide range in physicochemical characteristics. Dissolved...

Analytical model for a laminated shape memory alloy beam with piezoelectric layers

NASA Astrophysics Data System (ADS)

Viet, N. V.; Zaki, W.; Umer, R.

2018-03-01

We propose an analytical model for a laminated beam consisting of a superelastic shape memory alloy (SMA) core layer bonded to two piezoelectric layers on its top and bottom surfaces. The model accounts for forward and reverse phase transformation between austenite and martensite during a full isothermal loading-unloading cycle starting a full austenite in the SMA layer. In particular, the laminated composite beam has a rectangular cross section and is fixed at one end while the other end is subjected to a concentrated transverse force acting at the tip. The moment-curvature relation is analytically derived. The generated electric displacement output from the piezoelectric layers is then determined using the linear piezoelectric theory. The results are compared to 3D simulations using finite element analysis (FEA). The comparison shows good agreement in terms of electric displacement, in general, throughout the loading cycle.

Long cycle life rechargeable lithium batteries

NASA Technical Reports Server (NTRS)

Pasquariello, D. M.; Willstaedt, E. B.; Abraham, K. M.

1992-01-01

Cycle life and safety of delta-LiAl/TiS2 cells were evaluated using laboratory and AA-size cells. Analysis of the alloys (which contained 60, 70, 80, or 85 wt-pct. lithium and are designated 60 LiAl etc.) showed them to contain a mixture of elemental Li and Al4Li9. Cycling efficiencies correlated with the amount of free lithium in the anode. Using an electrolyte with the composition 48 v/o THF:48 v/o 2-MeTHF:4 v/o 2-MeF/LiAsF6(1.5M), a 70 LiAl/TiS2 laboratory cell yielded a cycling efficiency of 96.4 pct. when cycled at a 100 pct. discharge depth which compares well with Li anode cycling efficiencies of 96 to 97.5 pct. obtained previously in this electrolyte. The highest cycling efficiency of any delta-LiAl/TiS2 laboratory cell was 96.7 pct. when the 60 LiAl alloy was used with the 35 v/o PC:35 v/o EC:30 v/o triglyme/LiAsF6(1.0M) electrolyte. The 70 LiAl alloy was selected for further testing in AA cells since it was malleable for the fabrication of spirally wound electrodes, and its overall cycling performance was sufficiently good. AA-size 70 LiAl/TiS2 cells appear to have capacity/rate properties similar to those for identical Li/TiS2 cells. The use of the delta-LiAl alloy anodes does not appear to offer any safety advantage when cycled cells are shorted or heated.

A micromechanical study of the damage mechanics of acrylic particulate composites under thermomechanical loading

NASA Astrophysics Data System (ADS)

Nie, Shihua

The main aim of this dissertation was to characterize the damage mechanism and fatigue behavior of the acrylic particulate composite. This dissertation also investigated how the failure mechanism is influenced by changes in certain parameters including the volume fraction of particle, the interfacial bonding strength, the stiffness and thickness of the interphase, and the CTE mismatch between the particle and the matrix. Monotonic uniaxial tensile and compressive testing under various temperatures and strain rates, isothermal low-cycle mechanical testing and thermal cycling of a plate with a cutout were performed. The influence of the interfacial bonding strength between the particle and the matrix on the failure mechanism of the ATH filled PMMA was investigated using in situ observations under uniaxial loading conditions. For composites with weak interfacial bonding, the debonding is the major damage mode. For composites with strong interfacial bonding, the breakage of the agglomerate of particles is the major damage mode. Experimental studies also demonstrated the significant influence of interfacial bonding strength on the fatigue life of the ATH filled PMMA. The damage was characterized in terms of the elastic modulus degradation, the load-drop parameter, the plastic strain range and the hysteresis dissipation. Identifying the internal state variables that quantify material degradation under thermomechanical loading is an active research field. In this dissertation, the entropy production, which is a measure of the irreversibility of the thermodynamic system, is used as the metric for damage. The close correlation between the damage measured in terms of elastic modulus degradation and that obtained from the finite element simulation results validates the entropy based damage evolution function. A micromechanical model for acrylic particulate composites with imperfect interfacial bonds was proposed. Acrylic particulate composites are treated as three-phase composites consisting of agglomerated particles, bulk matrix and an interfacial transition zone around the agglomerate. The influence of the interfacial bonding and the CTE mismatch between the matrix and the filler on the overall thermomechanical behavior of composites is studied analytically and experimentally. The comparison of analytical simulation with experimental data demonstrated the validity of the proposed micromechanical model for acrylic particulate composites with an imperfect interface. (Abstract shortened by UMI.)

The effect of melt composition on the partitioning of trace elements between titanite and silicate melt

NASA Astrophysics Data System (ADS)

Prowatke, S.; Klemme, S.

2003-04-01

The aim of this study is to systematically investigate the influence of melt composition on the partitioning of trace elements between titanite and different silicate melts. Titanite was chosen because of its important role as an accessory mineral, particularly with regard to intermediate to silicic alkaline and calc-alkaline magmas [e.g. 1] and of its relative constant mineral composition over a wide range of bulk compositions. Experiments at atmospheric pressure were performed at temperatures between 1150°C and 1050°C. Bulk compositions were chosen to represent a basaltic andesite (SH3 - 53% SiO2), a dacite (SH2 - 65 SiO2) and a rhyolite (SH1 - 71% SiO2). Furthermore, two additional experimental series were conducted to investigate the effect of Al-Na and the Na-K ratio of melts on partitioning. Starting materials consisted of glasses that were doped with 23 trace elements including some selected rare earth elements (La, Ce, Pr, Sm, Gd, Lu), high field strength elements (Zr, Hf, Nb, Ta) and large ion lithophile elements (Cs, Rb, Ba) and Th and U. The experimental run products were analysed for trace elements using secondary ion mass spectrometry at Heidelberg University. Preliminary results indicate a strong effect of melt composition on trace element partition coefficients. Partition coefficients for rare-earth elements uniformly show a convex-upward shape [2, 3], since titanite accommodates the middle rare-earth elements more readily than the light rare-earth elements or the heavy rare-earth elements. Partition coefficients for the rare-earth elements follow a parabolic trend when plotted against ionic radius. The shape of the parabola is very similar for all studied bulk compositions, the position of the parabola, however, is strongly dependent on bulk composition. For example, isothermal rare-earth element partition coefficients (such as La) are incompatible (D<1) in alkali-rich silicate melts and strongly compatible (D>>1) in alkali-poor melt compositions. From our experimental data we present an model that combines the influence of the crystal lattice on partitioning with the effect of melt composition on trace element partition coefficients. [1] Nakada, S. (1991) Am. Mineral. 76: 548-560 [2] Green, T.H. and Pearson, N.J. (1986) Chem. Geol. 55: 105-119 [3] Tiepolo, M.; Oberti, R. and Vannucci, R. (2002) Chem. Geol. 191: 105-119

Geochemical and Isotopic (Sr, U) Tracing of Weathering Processes Controlling the Recent Geochemical Evolution of Soil Solutions in the Strengbach Catchment (Vosges, France)

NASA Astrophysics Data System (ADS)

Chabaux, F. J.; Prunier, J.; Pierret, M.; Stille, P.

2012-12-01

The characterization of the present-day weathering processes controlling the chemical composition of waters and soils in natural ecosystems is an important issue to predict and to model the response of ecosystems to recent environmental changes. It is proposed here to highlight the interest of a multi-tracer geochemical approach combining measurement of major and trace element concentrations along with U and Sr isotopic ratios to progress in this topic. This approach has been applied to the small granitic Strengbah Catchment, located in the Vosges Mountain (France), used and equipped as a hydro-geochemical observatory since 1986 (Observatoire Hydro-Géochimique de l'Environnement; http://ohge.u-strasbg.fr). This study includes the analysis of major and trace element concentrations and (U-Sr) isotope ratios in soil solutions collected within two soil profiles located on two experimental plots of this watershed, as well as the analysis of soil samples and vegetation samples from these two plots The depth variation of elemental concentration of soil solutions confirms the important influence of the vegetation cycling on the budget of Ca, K, Rb and Sr, whereas Mg and Si budget in soil solutions are quasi exclusively controlled by weathering processes. Variation of Sr, and U isotopic ratios with depth also demonstrates that the sources and biogeochemical processes controlling the Sr budget of soil solutions is different in the uppermost soil horizons and in the deeper ones, and clearly influence by the vegetation cycling.

In Search of a Time Efficient Approach to Crack and Delamination Growth Predictions in Composites

NASA Technical Reports Server (NTRS)

Krueger, Ronald; Carvalho, Nelson

2016-01-01

Analysis benchmarking was used to assess the accuracy and time efficiency of algorithms suitable for automated delamination growth analysis. First, the Floating Node Method (FNM) was introduced and its combination with a simple exponential growth law (Paris Law) and Virtual Crack Closure technique (VCCT) was discussed. Implementation of the method into a user element (UEL) in Abaqus/Standard(Registered TradeMark) was also presented. For the assessment of growth prediction capabilities, an existing benchmark case based on the Double Cantilever Beam (DCB) specimen was briefly summarized. Additionally, the development of new benchmark cases based on the Mixed-Mode Bending (MMB) specimen to assess the growth prediction capabilities under mixed-mode I/II conditions was discussed in detail. A comparison was presented, in which the benchmark cases were used to assess the existing low-cycle fatigue analysis tool in Abaqus/Standard(Registered TradeMark) in comparison to the FNM-VCCT fatigue growth analysis implementation. The low-cycle fatigue analysis tool in Abaqus/Standard(Registered TradeMark) was able to yield results that were in good agreement with the DCB benchmark example. Results for the MMB benchmark cases, however, only captured the trend correctly. The user element (FNM-VCCT) always yielded results that were in excellent agreement with all benchmark cases, at a fraction of the analysis time. The ability to assess the implementation of two methods in one finite element code illustrated the value of establishing benchmark solutions.

Effect of salinity on metal mobility in Sečovlje salina sediment (northern Adriatic, Slovenia)

NASA Astrophysics Data System (ADS)

Kovač, N.; Ramšak, T.; Glavaš, N.; Dolenec, M.; Rogan Šmuc, N.

2016-12-01

Saline sediment (saline healing mud or "fango") from the Sečovlje Salina (northern Adriatic, Slovenia) is traditionally used in the coastal health resorts as a virgin material for medical treatment, wellness and relax purposes. Therapeutic qualities of the healing mud depend on its mineralogical composition and physical, mineralogical, geochemical and biological properties. Their microbial and potentially toxic elements contamination are the most important features affecting user safety. However, the degree of metal toxicity (and its regulation) for natural healing mud is still under discussion. Therefore, the influence of the overlying water salinity on the mobility of heavy metals (and some other geochemical characteristic) was studied for saline sediments of the Sečovlje Salina. Experiments takes place in tanks under defined conditions i.e. at day (21 °C): night (16 °C) cycle for three months. Sediment was covered with water of different salinities (36, 155, 323 g NaCl L-1 and distillate water) and mixed/stirred every week during the experimental period. At the same time, the evaporated water was replaced with distilled water. The mud samples were analyzed, at the beginning and at the end of experiment, for mineral (XRD), elemental composition (ICP-MS) and organic content (% TOC, % TN). Geochemical analysis of the aqueous phase (content of cations and anions) have also been carried out in an accredited Canadian laboratory Actlabs (Activation Laboratories, Canada). Salinity and maturation of sediment does not significantly affect its mineral composition. The samples taken at the end of the experiment have higher percent of water but lower organic carbon concentration. Concentrations of investigated elements are comparable to that in surface sediments from Central Adriatic Sea. In the water phase, concentrations of most elements (As, Ba, Cu, Mo, Mn, Ni, Sr, Sb) rise from the beginning to the end of the experiment, whereas the metal (potentially toxic elements) decreasing trend in mud was observed at that time. These data contribute to the knowledge of natural healing muds and that of diagenetic processes on metals in hypersaline sediments.

The dynamical structure of intense Mediterranean cyclones

NASA Astrophysics Data System (ADS)

Flaounas, Emmanouil; Raveh-Rubin, Shira; Wernli, Heini; Drobinski, Philippe; Bastin, Sophie

2015-05-01

This paper presents and analyzes the three-dimensional dynamical structure of intense Mediterranean cyclones. The analysis is based on a composite approach of the 200 most intense cyclones during the period 1989-2008 that have been identified and tracked using the output of a coupled ocean-atmosphere regional simulation with 20 km horizontal grid spacing and 3-hourly output. It is shown that the most intense Mediterranean cyclones have a common baroclinic life cycle with a potential vorticity (PV) streamer associated with an upper-level cyclonic Rossby wave breaking, which precedes cyclogenesis in the region and triggers baroclinic instability. It is argued that this common baroclinic life cycle is due to the strongly horizontally sheared environment in the Mediterranean basin, on the poleward flank of the quasi-persistent subtropical jet. The composite life cycle of the cyclones is further analyzed considering the evolution of key atmospheric elements as potential temperature and PV, as well as the cyclones' thermodynamic profiles and rainfall. It is shown that most intense Mediterranean cyclones are associated with warm conveyor belts and dry air intrusions, similar to those of other strong extratropical cyclones, but of rather small scale. Before cyclones reach their mature stage, the streamer's role is crucial to advect moist and warm air towards the cyclones center. These dynamical characteristics, typical for very intense extratropical cyclones in the main storm track regions, are also valid for these Mediterranean cases that have features that are visually similar to tropical cyclones.

Disturbance decouples biogeochemical cycles across forests of the southeastern US

Treesearch

Ashley D. Keiser; Jennifer D. Knoepp; Mark A. Bradford

2016-01-01

Biogeochemical cycles are inherently linked through the stoichiometric demands of the organisms that cycle the elements. Landscape disturbance can alter element availability and thus the rates of biogeochemical cycling. Nitrification is a fundamental biogeochemical process positively related to plant productivity and nitrogen loss from soils to aquatic systems, and the...

Fatigue Life Methodology for Tapered Composite Flexbeam Laminates

NASA Technical Reports Server (NTRS)

Murri, Gretchen B.; OBrien, T. Kevin; Rousseau, Carl Q.

1997-01-01

The viability of a method for determining the fatigue life of composite rotor hub flexbeam laminates using delamination fatigue characterization data and a geometric non-linear finite element (FE) analysis was studied. Combined tension and bending loading was applied to non-linear tapered flexbeam laminates with internal ply drops. These laminates, consisting of coupon specimens cut from a full-size S2/E7T1 glass-epoxy flexbeam were tested in a hydraulic load frame under combined axial-tension and transverse cyclic bending. The magnitude of the axial load remained constant and the direction of the load rotated with the specimen as the cyclic bending load was applied. The first delamination damage observed in the specimens occurred at the area around the tip of the outermost ply-drop group. Subsequently, unstable delamination occurred by complete delamination along the length of the specimen. Continued cycling resulted in multiple delaminations. A 2D finite element model of the flexbeam was developed and a geometrically non-linear analysis was performed. The global responses of the model and test specimens agreed very well in terms of the transverse displacement. The FE model was used to calculate strain energy release rates (G) for delaminations initiating at the tip of the outer ply-drop area and growing toward the thick or thin regions of the flexbeam, as was observed in the specimens. The delamination growth toward the thick region was primarily mode 2, whereas delamination growth toward the thin region was almost completely mode 1. Material characterization data from cyclic double-cantilevered beam tests was used with the peak calculated G values to generate a curve predicting fatigue failure by unstable delamination as a function of the number of loading cycles. The calculated fatigue lives compared well with the test data.

Fatigue Life Methodology for Tapered Composite Flexbeam Laminates

NASA Technical Reports Server (NTRS)

Murri, Gretchen B.; O''Brien, T. Kevin; Rousseau, Carl Q.

1997-01-01

The viability of a method for determining the fatigue life of composite rotor hub flexbeam laminates using delamination fatigue characterization data and a geometric non-linear finite element (FE) analysis was studied. Combined tension and bending loading was applied to nonlinear tapered flexbeam laminates with internal ply drops. These laminates, consisting of coupon specimens cut from a full-size S2/E7T1 glass-epoxy flexbeam were tested in a hydraulic load frame under combined axial-tension and transverse cyclic bending loads. The magnitude of the axial load remained constant and the direction of the load rotated with the specimen as the cyclic bending load was applied. The first delamination damage observed in the specimens occurred at the area around the tip of the outermost ply-drop group. Subsequently, unstable delamination occurred by complete delamination along the length of the specimen. Continued cycling resulted in multiple delaminations. A 2D finite element model of the flexbeam was developed and a geometrically non-linear analysis was performed. The global responses of the model and test specimens agreed very well in terms of the transverse flexbeam tip-displacement and flapping angle. The FE model was used to calculate strain energy release rates (G) for delaminations initiating at the tip of the outer ply-drop area and growing toward the thick or thin regions of the flexbeam, as was observed in the specimens. The delamination growth toward the thick region was primarily mode 2, whereas delamination growth toward the thin region was almost completely mode 1. Material characterization data from cyclic double-cantilevered beam tests was used with the peak calculated G values to generate a curve predicting fatigue failure by unstable delamination as a function of the number of loading cycles. The calculated fatigue lives compared well with the test data.

Effects of thermal cycling on graphie-fiber-reinforced 6061 aluminum

NASA Technical Reports Server (NTRS)

Dries, G. A.; Tompkins, S. S.

1986-01-01

Graphite-reinforced aluminum alloy metal-matrix composites are among materials being considered for structural components in dimensionally stable space structures. This application requires materials with low values of thermal expansions and high specific stiffnesses. They must remain stable during exposures to the space environment for periods extending to 20 years. The effects of thermal cycling on the thermal expansion behavior and mechanical properties of Thornel P100 graphite 6061 aluminum composites, as fabricated and after thermal processing to eliminate thermal strain hysteresis, have been investigated. Two groups of composites were studied: one was fabricated by hot roll bonding and the other by diffusion bonding. Processing significantly reduced strain hysteresis during thermal cycling in both groups and improved the ultimate tensile strength and modulus in the diffusion-bonded composites. Thermal cycling stabilized the as-fabricated composites by reducing the residual fabrication stress and increased the matrix strength by metallurgical aging. Thermal expansion behavior of both groups after processing was insensitive to thermal cycling. Data scatter was too large to determine effects of thermal cycling on the mechanical properties. The primary effects of processing and thermal cycling can be attributed to changes in the metallurgical condition and stress state of the matrix.

40 CFR Appendix II to Part 1048 - Large Spark-ignition (SI) Composite Transient Cycle

Code of Federal Regulations, 2010 CFR

2010-07-01

... Transient Cycle II Appendix II to Part 1048 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY.... 1048, App. II Appendix II to Part 1048—Large Spark-ignition (SI) Composite Transient Cycle The following table shows the transient duty-cycle for engines that are not constant-speed engines, as described...

Effects of thermal cycling parameters on residual stresses in alumina scales of CoNiCrAlY and NiCoCrAlY bond coats

DOE PAGES

Nordhorn, Christian; Mücke, Robert; Unocic, Kinga A.; ...

2014-08-20

In this paper, furnace cycling experiments were performed on free-standing high-velocity oxygen-fuel bond coat samples to investigate the effect of material composition, surface texture, and cycling conditions on the average stresses in the formed oxide scales after cooling. The oxide scale thicknesses were determined by SEM image analyses and information about the stresses were acquired by photo-stimulated luminescence-spectroscopy. Additionally, the scale thickness dependent stress fields were calculated in finite-element analyses including approximation functions for the surface roughness derived on the basis of profilometry data. The evolution of the average residual stress as a function of oxide scale thickness was subjectmore » to stochastic fluctuations predominantly caused by local scale spallations. In comparison to the supplemental modeling results, thermal stresses due to mismatch of thermal expansion coefficients are identified as the main contribution to the residual stresses. Finally, the theoretical results emphasize that analyses of spectroscopic data acquired for average stress investigations of alumina scales rely on detailed information about microstructural features.« less

Menstrual cycle perturbation by organohalogens and elements in the Cree of James Bay, Canada.

PubMed

Wainman, Bruce C; Kesner, James S; Martin, Ian D; Meadows, Juliana W; Krieg, Edward F; Nieboer, Evert; Tsuji, Leonard J

2016-04-01

Persistent organohalogens (POHs) and metals have been linked to alterations in menstrual cycle function and fertility in humans. The Cree First Nations people living near James Bay in Ontario and Quebec, Canada, have elevated levels of POHs, mercury and lead compared to other Canadians. The present study examines the interrelationships between selected POHs and elements on menstrual cycle function in these Cree women. Menstrual cycle characteristics were derived from structured daily diaries and endocrine measurements from daily urine samples collected during one cycle for 42 women age 19-42. We measured 31 POHs in blood plasma and 18 elements in whole blood, for 31 of the participants. POHs and elements detected in ≥ 70% of the participants were transformed by principal component (PC) analysis to reduce the contaminant exposure data to fewer, uncorrelated PCA variables. Multiple regression analysis revealed that, after adjusting for confounders, PC-3 values showed significant negative association with cycle length, after adjusting for confounders (p = 0.002). PC-3 accounted for 9.2% of the variance and shows positive loadings for cadmium, selenium, and PBDE congeners 47 and 153, and a negative loading for copper. Sensitivity analysis of the model to quantify likely effect sizes showed a range of menstrual cycle length from 25.3 to 28.3 days using the lower and upper 95% confidence limits of mean measured contaminant concentrations to predict cycle length. Our observations support the hypothesis that the menstrual cycle function of these women may be altered by exposure to POHs and elements from their environment. Copyright © 2015. Published by Elsevier Ltd.

Convergent responses of nitrogen and phosphorus resorption to nitrogen inputs in a semiarid grassland

USGS Publications Warehouse

Lü, Xiao-Tao; Reed, Sasha; Yu, Qiang; He, Nian-Peng; Wang, Zheng-Wen; Han, Xing-Guo

2013-01-01

Human activities have significantly altered nitrogen (N) availability in most terrestrial ecosystems, with consequences for community composition and ecosystem functioning. Although studies of how changes in N availability affect biodiversity and community composition are relatively common, much less remains known about the effects of N inputs on the coupled biogeochemical cycling of N and phosphorus (P), and still fewer data exist regarding how increased N inputs affect the internal cycling of these two elements in plants. Nutrient resorption is an important driver of plant nutrient economies and of the quality of litter plants produce. Accordingly, resorption patterns have marked ecological implications for plant population and community fitness, as well as for ecosystem nutrient cycling. In a semiarid grassland in northern China, we studied the effects of a wide range of N inputs on foliar nutrient resorption of two dominant grasses, Leymus chinensis and Stipa grandis. After 4 years of treatments, N and P availability in soil and N and P concentrations in green and senesced grass leaves increased with increasing rates of N addition. Foliar N and P resorption significantly decreased along the N addition gradient, implying a resorption-mediated, positive plant–soil feedback induced by N inputs. Furthermore, N : P resorption ratios were negatively correlated with the rates of N addition, indicating the sensitivity of plant N and P stoichiometry to N inputs. Taken together, the results demonstrate that N additions accelerate ecosystem uptake and turnover of both N and P in the temperate steppe and that N and P cycles are coupled in dynamic ways. The convergence of N and P resorption in response to N inputs emphasizes the importance of nutrient resorption as a pathway by which plants and ecosystems adjust in the face of increasing N availability.

A textural and compositional investigation on the source and timing of iron oxidation and titanium enrichment in high-pressure serpentinites

NASA Astrophysics Data System (ADS)

Crossley, R.; Evans, K. A.; Reddy, S.; Lester, G. W.

2016-12-01

The redox state, quantity and composition of subduction zone fluids influence the transport and precipitation of elements including those which are redox-sensitive, of economic importance such as Cu, Au and Ag, and those considered to be immobile, which include Fe3+. However, subduction zone fluids remain poorly understood. The redox state of Fe in high-pressure ultramafic rocks, which host a significant proportion of Fe3+, can be used to provide an insight into Fe cycling and constrain the composition and possible source of subduction zone fluids. In this work, we use a combination of oxide mineral textures, mineral parageneses, mineral composition data, and whole rock geochemistry of high-pressure retrogressed ultramafic rocks from the Zermatt-Saas Zone to constrain the distribution and oxidation state of iron, and to provide insights on the nature of fluids at depth within subduction zones. Oxide minerals host the bulk of the iron, particularly Fe3+. The increase in mode of magnetite during initial retrogression is most consistent with oxidation of existing iron via the infiltration of an oxidising fluids since it is difficult to reconcile addition of Fe3+ with the known limited solubility of this species. In addition, fluid-mediated or mechanical mixing with other lithologies in the slab could introduce elements and alter the bulk composition of serpentinites. However, the high Ti content of one sample cannot be explained by simple mixing of a depleted mantle protolith with the nearby Allalin gabbros, and provides the tantalising possibility that Ti, an element generally perceived as immobile, has been added to the rock. While we cannot completely exclude the possibility of pre-subduction Ti addition, textural analysis of Ti-rich minerals suggest mobilisation of Ti during subduction on at least a centimetre scale. If Ti addition has occurred, then the introduction of Fe3+, also generally considered to be immobile, cannot be disregarded. The Al-rich nature of the sample may be consistent with aluminosilicate complexing as the transport vector for Ti and/or Fe3+.

Dust in Rain During Drought: An Overlooked Pathway for Elemental Flux to Ecosystems

NASA Astrophysics Data System (ADS)

Ponette-González, A.; Collins, J. D., Jr.; Manuel, J. E.; Byers, T. A.; Glass, G. A.; Weathers, K. C.; Gill, T. E.

2017-12-01

Airborne dust has the potential to alter ecosystem productivity and biogeochemical cycles at local to global scales by enhancing atmospheric deposition of critical limiting nutrients and toxic pollutants. Suspended dust particles are delivered to ecosystems directly via dry deposition or in precipitation (wet deposition) by rainout and washout. Compared to dry deposition, dust removal by precipitation (dust-in-rain) is a seldom quantified yet potentially significant flux between the atmosphere and ecosystems. We quantified dust effects on the ionic and elemental composition of precipitation and on wet deposition rates at a National Atmospheric Deposition Program (NADP) monitoring site in west Texas during the extreme 2012 drought. Dust events were identified using meteorological data for stations within a 150-km radius buffer surrounding the NADP site. Data on the dissolved chemistry of weekly wet deposition samples and elemental analysis of the particulate fraction were analyzed. Calcium was the dominant dissolved ion in rainwater, comprising 61% of the total measured solute content during dust-in rain weeks. In the particulate fraction, Fe alone made up 81% of the elemental composition during dust-in-rain weeks. At this site, five dust-in-rain weeks delivered 19% of the annual water input (51 mm water). However, these weeks contributed 46-70% of the annual dissolved Ca2+, Mg2+, K+, Na+, PO43-, and Cl- flux and >55% of the particulate Fe, Ti, V, Ni, Rb, Ga, and Br flux. Sourcing analysis, conducted using an End-Member Mixing Algorithm (EMMA) on the particulate fraction identified Fe, Cu, Rb, and Sr end-members, representing 87% of the total elemental variance. In addition, EMMA showed that dust-in-rain weeks were more well mixed than other rainfall weeks. Preliminary findings for this west Texas site show that infrequent dust-in-rain events constitute an important but overlooked proportion of the elemental flux to ecosystems during severe drought.

Element geochemical analysis of the contribution of aeolian sand to suspended sediment in desert stream flash floods.

PubMed

Jia, Xiaopeng; Wang, Haibing

2014-01-01

The interaction of wind and water in semiarid and arid areas usually leads to low-frequency flash flood events in desert rivers, which have adverse effects on river systems and ecology. In arid zones, many aeolian dune-fields terminate in stream channels and deliver aeolian sand to the channels. Although aeolian processes are common to many desert rivers, whether the aeolian processes contribute to fluvial sediment loss is still unknown. Here, we identified the aeolian-fluvial cycling process responsible for the high rate of suspended sediment transport in the Sudalaer desert stream in the Ordos plateau of China. On the basis of element geochemistry data analysis, we found that aeolian sand was similar to suspended sediment in element composition, which suggests that aeolian sand contributes to suspended sediment in flash floods. Scatter plots of some elements further confirm that aeolian sand is the major source of the suspended sediment. Factor analysis and the relation between some elements and suspended sediment concentration prove that the greater the aeolian process, the higher the suspended sediment concentration and the greater the contribution of aeolian sand to suspended sediment yield. We conclude that aeolian sand is the greatest contributor to flash floods in the Sudalaer desert stream.

Element Geochemical Analysis of the Contribution of Aeolian Sand to Suspended Sediment in Desert Stream Flash Floods

PubMed Central

Wang, Haibing

2014-01-01

The interaction of wind and water in semiarid and arid areas usually leads to low-frequency flash flood events in desert rivers, which have adverse effects on river systems and ecology. In arid zones, many aeolian dune-fields terminate in stream channels and deliver aeolian sand to the channels. Although aeolian processes are common to many desert rivers, whether the aeolian processes contribute to fluvial sediment loss is still unknown. Here, we identified the aeolian-fluvial cycling process responsible for the high rate of suspended sediment transport in the Sudalaer desert stream in the Ordos plateau of China. On the basis of element geochemistry data analysis, we found that aeolian sand was similar to suspended sediment in element composition, which suggests that aeolian sand contributes to suspended sediment in flash floods. Scatter plots of some elements further confirm that aeolian sand is the major source of the suspended sediment. Factor analysis and the relation between some elements and suspended sediment concentration prove that the greater the aeolian process, the higher the suspended sediment concentration and the greater the contribution of aeolian sand to suspended sediment yield. We conclude that aeolian sand is the greatest contributor to flash floods in the Sudalaer desert stream. PMID:25089295

Structural Evolution of Sub-10 nm Octahedral Platinum$-$Nickel Bimetallic Nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Qiaowan; Xu, Yuan; Duan, Zhiyuan

Octahedral Pt alloy nanocrystals (NCs) have shown excellent activities as electrocatalysts toward oxygen reduction reaction (ORR). As the activity and stability of NCs are highly dependent on their structure and the elemental distribution, it is of great importance to understand the formation mechanism of octahedral NCs and to rationally synthesize shape-controlled alloy catalysts with optimized ORR activity and stability. However, the factors controlling the structural and compositional evolution during the synthesis have not been well understood yet. Here in this paper, we systematically investigated the structure and composition evolution pathways of Pt–Ni octahedra synthesized with the assistance of W(CO) 6more » and revealed a unique core–shell structure consisting of a Pt core and a Pt–Ni alloy shell. Below 140 °C, sphere-like pure Pt NCs with the diameter of 3–4 nm first nucleated, followed by the isotropic growth of Pt–Ni alloy on the seeds at temperatures between 170 and 230 °C forming Pt@Pt–Ni core–shell octahedra with {111} facets. Owing to its unique structure, the Pt@Pt–Ni octahedra show an unparalleled stability during potential cycling, that is, no activity drop after 10 000 cycles between 0.6 and 1.0 V. This work proposes the Pt@Pt–Ni octahedra as a high profile electrocatalyst for ORR and reveals the structural and composition evolution pathways of Pt-based bimetallic NCs.« less

Structural Evolution of Sub-10 nm Octahedral Platinum$-$Nickel Bimetallic Nanocrystals

DOE PAGES

Chang, Qiaowan; Xu, Yuan; Duan, Zhiyuan; ...

2017-05-11

Octahedral Pt alloy nanocrystals (NCs) have shown excellent activities as electrocatalysts toward oxygen reduction reaction (ORR). As the activity and stability of NCs are highly dependent on their structure and the elemental distribution, it is of great importance to understand the formation mechanism of octahedral NCs and to rationally synthesize shape-controlled alloy catalysts with optimized ORR activity and stability. However, the factors controlling the structural and compositional evolution during the synthesis have not been well understood yet. Here in this paper, we systematically investigated the structure and composition evolution pathways of Pt–Ni octahedra synthesized with the assistance of W(CO) 6more » and revealed a unique core–shell structure consisting of a Pt core and a Pt–Ni alloy shell. Below 140 °C, sphere-like pure Pt NCs with the diameter of 3–4 nm first nucleated, followed by the isotropic growth of Pt–Ni alloy on the seeds at temperatures between 170 and 230 °C forming Pt@Pt–Ni core–shell octahedra with {111} facets. Owing to its unique structure, the Pt@Pt–Ni octahedra show an unparalleled stability during potential cycling, that is, no activity drop after 10 000 cycles between 0.6 and 1.0 V. This work proposes the Pt@Pt–Ni octahedra as a high profile electrocatalyst for ORR and reveals the structural and composition evolution pathways of Pt-based bimetallic NCs.« less

Small-scale geochemical cycles and the distribution of uranium in central and north Florida organic deposits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bond, P.A.

1993-03-01

The global geochemical cycle for an element tracks its path from its various sources to its sinks via processes of weathering and transportation. The cycle may then be quantified in a necessarily approximate manner. The geochemical cycle (thus quantified) reveals constraints (known and unknown) on an element's behavior imposed by the various processes which act on it. In the context of a global geochemical cycle, a continent becomes essentially a source term. If, however, an element's behavior is examined in a local or regional context, sources and their related sinks may be identified. This suggests that small-scale geochemical cycles maymore » be superimposed on global geochemical cycles. Definition of such sub-cycles may clarify the distribution of an element in the earth's near-surface environment. In Florida, phosphate minerals of the Hawthorn Group act as a widely distributed source of uranium. Uranium is transported by surface- and ground-waters. Florida is the site of extensive wetlands and peatlands. The organic matter associated with these deposits adsorbs uranium and may act as a local sink depending on its hydrogeologic setting. This work examines the role of organic matter in the distribution of uranium in the surface and shallow subsurface environments of central and north Florida.« less

Diffusion in the chromosphere and the composition of the solar corona and energetic particles

NASA Technical Reports Server (NTRS)

Vauclair, S.; Meyer, J. P.

1985-01-01

Composition observations, in the solar photosphere, and in the upper transition region (TR) and corona imply a change of composition of the solar atmosphere somewhere between the photosphere and the upper TR. Heavy elements with first ionization potential (FIP) 9 eV (high-FIP element) are approx. 4 times less abundant in the TR and corona than in the photosphere, as compared to both hydrogen and heavy elements with lower low-FIP elements. A separation is suggested between neutral and ionized elements in a region where the high-FIP elements are mostly neutral, and the low-FIP elements ionized. This occurs in the chromosphere at altitudes above 600 km and below 2000 km above Photosphere. Whether the diffusion processes can explain the observed change in composition is investigated.

Structural Acoustic Physics Based Modeling of Curved Composite Shells

DTIC Science & Technology

2017-09-19

Results show that the finite element computational models accurately match analytical calculations, and that the composite material studied in this...products. 15. SUBJECT TERMS Finite Element Analysis, Structural Acoustics, Fiber-Reinforced Composites, Physics-Based Modeling 16. SECURITY...2 4 FINITE ELEMENT MODEL DESCRIPTION

Evidence for Cyclical Fractional Crystallization, Recharge, and Assimilation in Basalts of the Kimama Core, Central Snake River Plain, Idaho: A 5.5-million-year Highlight Reel of Petrogenetic processes in a Mid-Crustal Sill Complex

NASA Astrophysics Data System (ADS)

Potter, Katherine E.; Shervais, John W.; Christiansen, Eric H.; Vetter, Scott K.

2018-02-01

Basalts erupted in the Snake River Plain of central Idaho and sampled in the Kimama drill core link eruptive processes to the construction of mafic intrusions over 5.5 Ma. Cyclic variations in basalt composition reveal temporal chemical heterogeneity related to fractional crystallization and the assimilation of previously-intruded mafic sills. A range of compositional types are identified within 1912 m of continuous drill core: Snake River olivine tholeiite (SROT), low K SROT, high Fe-Ti, and evolved and high K-Fe lavas similar to those erupted at Craters of the Moon National Monument. Detailed lithologic and geophysical logs document 432 flow units comprising 183 distinct lava flows and 78 flow groups. Each lava flow represents a single eruptive episode, while flow groups document chemically and temporally related flows that formed over extended periods of time. Temporal chemical variation demonstrates the importance of source heterogeneity and magma processing in basalt petrogenesis. Low-K SROT and high Fe-Ti basalts are genetically related to SROT as, respectively, hydrothermally-altered and fractionated daughters. Cyclic variations in the chemical composition of Kimama flow groups are apparent as 21 upward fractionation cycles, six recharge cycles, eight recharge-fractionation cycles, and five fractionation-recharge cycles. We propose that most Kimama basalt flows represent typical fractionation and recharge patterns, consistent with the repeated influx of primitive SROT parental magmas and extensive fractional crystallization coupled with varying degrees of assimilation of gabbroic to ferrodioritic sills at shallow to intermediate depths over short durations. Trace element models show that parental SROT basalts were generated by 5-10% partial melting of enriched mantle at shallow depths above the garnet-spinel lherzolite transition. The distinctive evolved and high K-Fe lavas are rare. Found at four depths, 319 m, 1045 m, 1078 m, and 1189 m, evolved and high K-Fe flows are compositionally unrelated to SROT magmas and represent highly fractionated basalt, probably accompanied by crustal assimilation. These evolved lavas may be sourced from the Craters of the Moon/Great Rift system to the northeast. The Kimama drill core is the longest record of geochemical variation in the central Snake River Plain and reinforces the concept of magma processing in a layered complex.

A minimal mathematical model combining several regulatory cycles from the budding yeast cell cycle.

PubMed

Sriram, K; Bernot, G; Képès, F

2007-11-01

A novel topology of regulatory networks abstracted from the budding yeast cell cycle is studied by constructing a simple nonlinear model. A ternary positive feedback loop with only positive regulations is constructed with elements that activates the subsequent element in a clockwise fashion. A ternary negative feedback loop with only negative regulations is constructed with the elements that inhibit the subsequent element in an anticlockwise fashion. Positive feedback loop exhibits bistability, whereas the negative feedback loop exhibits limit cycle oscillations. The novelty of the topology is that the corresponding elements in these two homogeneous feedback loops are linked by the binary positive feedback loops with only positive regulations. This results in the emergence of mixed feedback loops in the network that displays complex behaviour like the coexistence of multiple steady states, relaxation oscillations and chaos. Importantly, the arrangement of the feedback loops brings in the notion of checkpoint in the model. The model also exhibits domino-like behaviour, where the limit cycle oscillations take place in a stepwise fashion. As the aforementioned topology is abstracted from the budding yeast cell cycle, the events that govern the cell cycle are considered for the present study. In budding yeast, the sequential activation of the transcription factors, cyclins and their inhibitors form mixed feedback loops. The transcription factors that involve in the positive regulation in a clockwise orientation generates ternary positive feedback loop, while the cyclins and their inhibitors that involve in the negative regulation in an anticlockwise orientation generates ternary negative feedback loop. The mutual regulation between the corresponding elements in the transcription factors and the cyclins and their inhibitors generates binary positive feedback loops. The bifurcation diagram constructed for the whole system can be related to the different events of the cell cycle in terms of dynamical system theory. The checkpoint mechanism that plays an important role in different phases of the cell cycle are accounted for by silencing appropriate feedback loops in the model.

The Nature of Variations in Anomalies of the Chemical Composition of the Solar Corona with the 11-Year Cycle

NASA Astrophysics Data System (ADS)

Pipin, V. V.; Tomozov, V. M.

2018-04-01

Evidence that the distribution of the abundances of admixtures with low first-ionization potentials (FIP < 10 eV) in the lower solar corona could be associated with the typology of the largescale magnetic field is presented. Solar observations show an enhancement in the abundances of elements with low FIPs compared to elements with high FIPs (>10 eV) in active regions and closed magnetic configurations in the lower corona. Observations with the ULYSSES spacecraft and at the Stanford Solar Observatory have revealed strong correlations between the manifestation of the FIP effect in the solar wind, the strength of the open magnetic flux (without regard to sign), and the ratio of the large-scale toroidal and poloidal magnetic fields at the solar surface. Analyses of observations of the Sun as a star show that the enhancement of the abundances of admixtures with low FIPs in the corona compared to their abundances in the photosphere (the FIP effect) is closely related to the solar-activity cycle and also with variations in the topology of the large-scale magnetic field. A possible mechanism for the relationship between the FIP effect and the spectral type of a star is discussed in the framework of solar-stellar analogies.

Fabrication characteristics and hydrogenation behavior of hydrogen storage alloys for sealed Ni-MH batteries

NASA Astrophysics Data System (ADS)

Kim, Ho-Sung; Kim, Jeon Min; Kim, Tae-Won; Oh, Ik-Hyun; Choi, Jeon; Park, Choong Nyeon

2008-08-01

Hydrogen storage alloys based on LmNi4.2Co0.2Mn0.3Al0.3 were fabricated to study the equilibrium hydrogen pressure and electrochemical performance. The surface morphology and structure of the alloys were analyzed by SEM and XRD, and then the hydrogenation behaviors of all alloys were evaluated by PCT and electrochemical half-cell. We studied the hydrogenation behavior of the Lm-based alloy with changes in composition elements such as Mn, Al, and Co and investigated the optimal design for Lm-based alloy in a sealed battery system. As a result of studying the hydrogenation characterization of alloys with the substitution elements, hydrogen storage alloys such as LmNi3.75Co0.15Mn0.5Al0.3 and LmNi3.5Co0.5Mn0.5Al0.5 were obtained to correspond with the characteristics of a sealed battery with a higher capacity, long life cycle, lower internal pressure, and lower battery cost. The capacity preservation rate of LmNi3.5Co0.5Mn0.5Al0.5 was greatly improved to 92.7% (255 mAh/g) at 60 cycles, indicating a low equilibrium hydrogen pressure of 0.03 atm in PCT devices.

Marine sponges with contrasting life histories can be complementary biomonitors of heavy metal pollution in coastal ecosystems.

PubMed

Batista, Daniela; Muricy, Guilherme; Rocha, Rafael Chávez; Miekeley, Norbert F

2014-05-01

In this study, we compared the usefulness of a long-living sponge (Hymeniacidon heliophila, Class Demospongiae) and a short-living one (Paraleucilla magna, Class Calcarea) as biomonitors of metallic pollution. The concentrations of 16 heavy metals were analyzed in both species along a gradient of decreasing pollution from the heavily polluted Guanabara Bay to the less impacted coastal islands in Rio de Janeiro, SE Brazil (SW Atlantic). The levels of most elements analyzed were higher in H. heliophila (Al, Co, Cr, Cu, Fe, Mn, Ni, Hg, Ni, and Sn) and P. magna (Ni, Cu, Mn, Al, Ti, Fe, Pb, Co, Cr, Zn, and V) collected from the heavily polluted bay when compared with the cleanest sites. Hymeniacidon heliophila accumulates 11 elements more efficiently than P. magna. This difference may be related to their skeleton composition, histological organization, symbiont bacteria and especially to their life cycle. Both species can be used as a biomonitors of metallic pollution, but while Hymeniacidon heliophila was more effective in concentrating most metals, Paraleucilla magna is more indicated to detect recent pollutant discharges due to its shorter life cycle. We suggest that the complementary use of species with contrasting life histories can be an effective monitoring strategy of heavy metals in coastal environments.

Seasonal Cyclicity in Trace Elements and Stable Isotopes of Modern Horse Enamel.

PubMed

de Winter, Niels J; Snoeck, Christophe; Claeys, Philippe

2016-01-01

The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal's diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet.

Seasonal Cyclicity in Trace Elements and Stable Isotopes of Modern Horse Enamel

PubMed Central

Snoeck, Christophe; Claeys, Philippe

2016-01-01

The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal’s diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet. PMID:27875538

Manganese, Metallogenium, and Martian Microfossils

NASA Technical Reports Server (NTRS)

Stein, L. Y.; Nealson, K. H.

1999-01-01

Manganese could easily be considered an abundant element in the Martian regolith, assuming that the composition of martian meteorites reflects the composition of the planet. Mineralogical analyses of 5 SNC meteorites have revealed an average manganese oxide concentration of 0.48%, relative to the 0.1% concentration of manganese found in the Earth's crust. On the Earth, the accumulation of manganese oxides in oceans, soils, rocks, sedimentary ores, fresh water systems, and hydrothermal vents can be largely attributed to microbial activity. Manganese is also a required trace nutrient for most life forms and participates in many critical enzymatic reactions such as photosynthesis. The wide-spread process of bacterial manganese cycling on Earth suggests that manganese is an important element to both geology and biology. Furthermore, there is evidence that bacteria can be fossilized within manganese ores, implying that manganese beds may be good repositories for preserved biomarkers. A particular genus of bacteria, known historically as Metallogenium, can form star-shaped manganese oxide minerals (called metallogenium) through the action of manganese oxide precipitation along its surface. Fossilized structures that resemble metallogenium have been found in Precambrian sedimentary formations and in Cretaceous-Paleogene cherts. The Cretaceous-Paleogene formations are highly enriched in manganese and have concentrations of trace elements (Fe, Zn, Cu, and Co) similar to modern-day manganese oxide deposits in marine environments. The appearance of metallogenium-like fossils associated with manganese deposits suggests that bacteria may be preserved within the minerals that they form. Additional information is contained in the original extended abstract.

Thermal cycling effects on adhesion of resin-bovine enamel junction among different composite resins.

PubMed

Chen, Wen-Cheng; Ko, Chia-Ling; Wu, Hui-Yu; Lai, Pei-Ling; Shih, Chi-Jen

2014-10-01

Thermal cycling is used to mimic the changes in oral cavity temperature experienced by composite resins when used clinically. The purpose of this study is to assess the thermal cycling effects of in-house produced composite resin on bonding strength. The dicalcium phosphate anhydrous filler surfaces are modified using nanocrystals and silanization (w/NP/Si). The resin is compared with commercially available composite resins Filtek Z250, Z350, and glass ionomer restorative material GIC Fuji-II LC (control). Different composite resins were filled into the dental enamel of bovine teeth. The bond force and resin-enamel junction graphical structures of the samples were determined after thermal cycling between 5 and 55°C in deionized water for 600 cycles. After thermal cycling, the w/NP/Si 30wt%, 50wt% and Filtek Z250, Z350 groups showed higher shear forces than glass ionomer GIC, and w/NP/Si 50wt% had the highest shear force. Through SEM observations, more of the fillings with w/NP/Si 30wt% and w/NP/Si 50wt% groups flowed into the enamel tubule, forming closed tubules with the composite resins. The push-out force is proportional to the resin flow depth and uniformity. The push-out tubule pore and resin shear pattern is the most uniform and consistent in the w/NP/Si 50wt% group. Accordingly, this developed composite resin maintains great mechanical properties after thermal cycling. Thus, it has the potential to be used in a clinical setting when restoring non-carious cervical lesions. Copyright © 2014 Elsevier Ltd. All rights reserved.

A Shear Deformable Shell Element for Laminated Composites

NASA Technical Reports Server (NTRS)

Chao, W. C.; Reddy, J. N.

1984-01-01

A three-dimensional element based on the total Lagrangian description of the motion of a layered anisotropic composite medium is developed, validated, and used to analyze layered composite shells. The element contains the following features: geometric nonlinearity, dynamic (transient) behavior, and arbitrary lamination scheme and lamina properties. Numerical results of nonlinear bending, natural vibration, and transient response are presented to illustrate the capabilities of the element.

Use of Encapsulated Zinc Particles in a Eutectic Chloride Salt to Enhance Thermal Energy Storage Capacity for Concentrated Solar Power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cingarapu, Sreeram; Singh, Dileep; Timofeeva, Elena V.

2015-08-01

Concentrated Solar Power (CSP) is considered as a viable large-scale renewable energy source to produce electricity. However, current costs to produce electricity from CSP are not cost competitive as compared to the traditional energy generation technologies based on fossil fuels and nuclear. It is envisioned that development of high efficiency and high heat capacity thermal storage fluids will increase system efficiency, reduce structural storage volume, and hence, contribute to reducing costs. Particularly, with respect to CSP, current high temperature energy storage fluids, such as molten salts, are relatively limited in terms of their thermal energy storage capacity and thermal conductivity.more » The current work explores possibility of boosting the thermal storage capacity of molten salts through latent heat of added phase change materials. We studied the advantage Of adding coated Zn micron-sized particles to alkali chloride salt eutectic for enhanced thermal energy storage. Zinc particles (0.6 mu m and 5 mu m) obtained from commercial source were coated with an organo-phosphorus shell to improve chemical stability and to prevent individual particles from coalescing with one another during melt/freeze cycles. Thermal cycling tests (200 melt/freeze cycles) showed that coated Zn particles have good thermal stability and are chemically inert to alkali chloride salt eutectic in both N-2 and in air atmospheres. Elemental mapping of the cross-sectional view of coated Zn particles from the composite after thermal cycles showed no signs of oxidation, agglomeration or other type of particle degradation. The measured enhancement in volumetric thermal storage capacity of the composite with just similar to 10 vol% of coated Zn particles over the base chloride salt eutectic varies from 15% to 34% depending on cycling temperature range (Delta T = 50 degrees C -100 degrees C. (C) 2015 Elsevier Ltd. All rights reserved.« less

Mineral Nutrition of Plants. Chapter 9

NASA Technical Reports Server (NTRS)

Wignarajah, Kanapathipillai

1995-01-01

The ultimate source of nutrients for all living organisms consists of the inanimate nutrient reserves found on earth. Of the elements known to exist, seven are considered essential to plants in large amounts (macronutrients), and many others are required in smaller quantities (micronutrients). Essentiality of a nutrient is defined according to the following concepts: (a) A deficiency of the element makes it impossible for the plant to complete the vegetative or reproductive stage of its cycle; (b) such deficiency is specific to the element in question and can be prevented or corrected only by supplying this element; (c) the element is directly involved in the nutrition of the plant quite apart from its possible effects in correcting some unfavorable microbiological or chemical condition of the soil or other culture medium. From that standpoint a favorable response from adding a given element to the culture medium does not constitute conclusive evidence of its indispensability in plant nutrition. All the elements occurring in the outer part of the earth are in constant turnover among the different components of earth. This overall migration is referred to as geochemical cycling. When cycling includes a role for biological organisms, it is referred to as "biogeochemical cycling." Like most cyclical processes in nature, the biogeochemical cycling of elements is not continuous, nor does it proceed in a well-defined direction. At stages, it may be halted or short-circuited, or it may change. Any changes will eventually impact the survival, evolution, and development of biological species in the system. The relationship of the various systems is represented in a schematic manner. To assess the efficiency of operation of the biogeochemical cycles, it is important to include both natural and human activities. Often reliable values on use by man are difficult to obtain for a number of reasons, such as lack of international cooperation, and lack of proper bookkeeping and auditing by individual nations. However, a general estimate of the annual world consumption of elements and their compounds is presented.

Nano-Ni induced surface modification relevant to the hydrogenation performances in La-Mg based alloys

NASA Astrophysics Data System (ADS)

Zhang, Huaiwei; Fu, Li; Xuan, Weidong; Li, Xingguo

2018-05-01

Nano-Ni drived modification in LaMg3/Ni composite is investigated. The new phases of LaMg2 and MgNi2 can be formed on the sample surface during the milling process. There is almost no electric charge transfer process between Ni and La element through XPS analyses. The amorphization structure can be found on the alloy surface with the increasing of reaction duration, and the capacity and cycle stability are also greatly promoted. On the other hand, the milled alloys show the lower charge transfer resistance, better anti-corrosion ability and higher oxidation current density.

Simulation of Structural Transformations in Heating of Alloy Steel

NASA Astrophysics Data System (ADS)

Kurkin, A. S.; Makarov, E. L.; Kurkin, A. B.; Rubtsov, D. E.; Rubtsov, M. E.

2017-07-01

Amathematical model for computer simulation of structural transformations in an alloy steel under the conditions of the thermal cycle of multipass welding is presented. The austenitic transformation under the heating and the processes of decomposition of bainite and martensite under repeated heating are considered. Amethod for determining the necessary temperature-time parameters of the model from the chemical composition of the steel is described. Published data are processed and the results used to derive regression models of the temperature ranges and parameters of transformation kinetics of alloy steels. The method developed is used in computer simulation of the process of multipass welding of pipes by the finite-element method.

A Geochemical Comparison of the Northern Peninsular Ranges Batholith in Southern California and the Coastal Batholith in Southern Peru

NASA Astrophysics Data System (ADS)

Clausen, B. L.; Martínez Ardila, A. M.; Morton, D. M.

2010-12-01

An extensive geochemical data set from the northern Peninsular Ranges Batholith (PRB) in southern California is compared and contrasted with the Arequipa segment of the Peruvian Coastal Batholith, including new granitoid samples recently collected near Ica (14°S, 76°W). The data include major and trace elements and Sr isotope ratios. This is part of an on-going study of subduction-related magmatism to refine a petrogenetic model of crust formation at plate boundaries, with a particular interest in the role of magma mixing. Research in the northern PRB suggests that continental crust is formed in several cycles: (1) mantle melting to give mafic volcanics and gabbroic intrusives, (2) basalt/gabbro melting to give felsic granitoids uncontaminated by continental crust and having low initial 87Sr/86Sr (Sri) values less than 0.704, and (3) crustal melting to give high Sri values greater than 0.704. Geochemical evidence was used to determine the extent of mixing between mafic and felsic magma that produced rocks of intermediate SiO2 composition. These differentiation cycles formed a west to east chronologic sequence and yielded granitoids of gabbro, tonalite, and granodiorite composition. Using principal component analysis on the northern PRB granitoids, the four factors affecting geochemical composition were categorized as differentiation, crustal contamination, depth of magma source, and conditions that yield a range from calcic to more alkaline granitoids. A similar major and trace element analysis is being done for a classic result of subduction in the Peruvian Coastal Batholith. The Peruvian samples recently collected include granitoids of the upper Cretaceous Coastal Batholith, as well as the associated volcanics of Cretaceous and Jurassic age. The Coastal Batholith samples include a range of granitoids from the early gabbros and from the four batholithic super-units (from west to east: Linga, Pampahuasi, Tiabaya, and Incahuasi) containing a combination of diorite, tonalite, monzonite, and granodiorite. In addition, samples were taken from the adjacent Precambrian basement and Paleozoic San Nicolas batholith in order to estimate the local geochemistry for continental crust contamination and to compare with published crustal averages. For this part of the Coastal Batholith, gabbroic plutons that formed during extension have little contamination from continental crust; the time-separated super-units form distinct assemblages; some of the super-units went through several differentiation cycles; parts of the Linga super-unit have low Sri ratios below 0.704; and magma mixing played an important role. The Coastal Batholith of western Peru (similar to the eastern PRB) has an intermediate calc-alkaline composition, in comparison to batholiths in Chile (similar to the western PRB) that are more calcic and those in eastern Peru (similar to the Sierra Nevadas) that are more alkaline.

Apollo 15 green glass - Compositional distribution and petrogenesis

NASA Technical Reports Server (NTRS)

Steele, Alison M.; Colson, Russell O.; Korotev, Randy L.; Haskin, Larry A.

1992-01-01

We have characterized a comprehensive suite of individual green-glass beads from Apollo 15 soil to determine interelement behavior and to constrain petrogenetic relationships. We analyzed 365 particles for trace elements by instrumental neutron activation analysis and analyzed 52 of them, selected to cover the compositional ranges observed for trace elements, for major elements by electron microprobe analysis. We confirm the observation of Delano (1979) that the beads comprise discrete compositional groups, although two of the groups he defined are further split on the basis of trace-element compositions. Each of the resulting seven groups has distinct average rare-earth abundances. The coherence between major- and trace-element data was masked in previous studies by imprecision, correlated error, and nonrepresentative sampling of the different groups. Most of the compositional characteristics of the green glasses can be explained by a model for batch equilibrium melting of a nearly homogeneous, ultramafic source region, when the complicating effects of high pressure and low oxygen fugacity are taken into account. The previously puzzling behavior of Ni and Co as apparently incompatible elements may arise from partial reduction of those elements to the zero oxidation state, resulting in low mineral/melt partition coefficients. The model also offers explanations for why the green glasses form boomerang-shaped trends on many two-element variation diagrams and why certain compositions (Groups A and D) are more abundant than glasses with other compositions.

Overview of the mechanisms that could explain the 'Boundary Exchange' at the land-ocean contact.

PubMed

Jeandel, Catherine

2016-11-28

Land to ocean transfer of material largely controls the chemical composition of seawater and the global element cycles. Oceanic isotopic budgets of chemical species, macro- and micronutrients (e.g. Nd, Sr, Si, Mg, Zn, Mo and Ni) have revealed an imbalance between their sources and sinks. Radiogenic isotope budgets underlined the importance of taking into account continental margins as a source of elements to oceans. They also highlighted that the net land-ocean inputs of chemical species probably result from particle-dissolved exchange processes, named 'Boundary Exchange'. Yet, locations where 'Boundary Exchange' occurs are not clearly identified and reviewed here: discharge of huge amount of freshly weathered particles at the river mouths, submarine weathering of deposited sediments along the margins, submarine groundwater discharges and subterranean estuaries. As a whole, we conclude that all of them might contribute to 'Boundary Exchange'. Highlighting their specific roles and the processes at play is a key scientific issue for the second half of GEOTRACES.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

Overview of the mechanisms that could explain the ‘Boundary Exchange’ at the land–ocean contact

PubMed Central

2016-01-01

Land to ocean transfer of material largely controls the chemical composition of seawater and the global element cycles. Oceanic isotopic budgets of chemical species, macro- and micronutrients (e.g. Nd, Sr, Si, Mg, Zn, Mo and Ni) have revealed an imbalance between their sources and sinks. Radiogenic isotope budgets underlined the importance of taking into account continental margins as a source of elements to oceans. They also highlighted that the net land–ocean inputs of chemical species probably result from particle-dissolved exchange processes, named ‘Boundary Exchange’. Yet, locations where ‘Boundary Exchange’ occurs are not clearly identified and reviewed here: discharge of huge amount of freshly weathered particles at the river mouths, submarine weathering of deposited sediments along the margins, submarine groundwater discharges and subterranean estuaries. As a whole, we conclude that all of them might contribute to ‘Boundary Exchange’. Highlighting their specific roles and the processes at play is a key scientific issue for the second half of GEOTRACES. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’. PMID:29035253

Super-active shape memory alloy composites

NASA Astrophysics Data System (ADS)

Barrett, Ronald M.; Gross, R. Steven

1995-05-01

A new type of very low stiffness super-active composite material is presented. This laminate uses shape-memory alloy (SMA) filaments which are embedded within a low Durometer silicone matrix. The purpose is to develop an active composite in which the local strains within the SMA actuator material will be approximately 1% while the laminate strains will be at least an order of magnitude larger. This type of laminate will be useful for biomimetic, biomedical, surgical and prosthetic applications in which the very high actuator strength of conventional SMA filaments is too great for biological tissues. A modified form of moment and force-balance analysis is used to model the performance of the super-active shape-memory alloy composite (SASMAC). The analytical models are used to predict the performance of a SASMAC pull-pull actuator which uses 10 mil diameter Tinel alloy K actuators embedded in a 0.10' thick, 25 Durometer silicon matrix. The results of testing demonstrate that the laminate is capable of straining up to 10% with theory and experiment in good agreement. Fatigue testing was conducted on the actuator for 1,000 cycles. Because the local strains within the SMA were kept to less than 1%, the element showed no degradation in performance.

Super-active shape-memory alloy composites

NASA Astrophysics Data System (ADS)

Barrett, Ron; Gross, R. Steven

1996-06-01

A new type of very-low-stiffness super-active composite material is presented. This laminate uses shape-memory alloy (SMA) filaments which are embedded within a low-hardness silicone matrix. The purpose is to develop an active composite in which the local strains within the SMA actuator material will be approximately 1%, while the laminate strains will be at least an order of magnitude larger. This type of laminate will be useful for biomimetic, biomedical, surgical and prosthetic applications in which the very high stiffness and actuation strength of conventional SMA filaments are too great for biological tissues. A modified form of moment and force-balance analysis is used to model the performance of the super-active shape-memory alloy composite (SASMAC). The analytical models are used to predict the performance of a SASMAC pull - pull actuator which uses 10 mil diameter Tinel alloy K actuators embedded in a 0.10" thick, 25 Durometer silicone matrix. The results of testing demonstrate that the laminate is capable of straining up to 10% with theory and experiment in good agreement. Fatigue testing was conducted on the actuator for 1 000 cycles. Because the local strains within the SMA were kept to less than 1%, the element showed no degradation in performance.

Vertically aligned CNT-Cu nano-composite material for stacked through-silicon-via interconnects.

PubMed

Sun, Shuangxi; Mu, Wei; Edwards, Michael; Mencarelli, Davide; Pierantoni, Luca; Fu, Yifeng; Jeppson, Kjell; Liu, Johan

2016-08-19

For future miniaturization of electronic systems using 3D chip stacking, new fine-pitch materials for through-silicon-via (TSV) applications are likely required. In this paper, we propose a novel carbon nanotube (CNT)/copper nanocomposite material consisting of high aspect ratio, vertically aligned CNT bundles coated with copper. These bundles, consisting of hundreds of tiny CNTs, were uniformly coated by copper through electroplating, and aspect ratios as high as 300:1 were obtained. The resistivity of this nanomaterial was found to be as low as ∼10(-8) Ω m, which is of the same order of magnitude as the resistivity of copper, and its temperature coefficient was found to be only half of that of pure copper. The main advantage of the composite TSV nanomaterial is that its coefficient of thermal expansion (CTE) is similar to that of silicon, a key reliability factor. A finite element model was set up to demonstrate the reliability of this composite material and thermal cycle simulations predicted very promising results. In conclusion, this composite nanomaterial appears to be a very promising material for future 3D TSV applications offering both a low resistivity and a low CTE similar to that of silicon.

Active shape control of composite blades using shape memory actuation

NASA Astrophysics Data System (ADS)

Chandra, Ramesh

2001-10-01

This paper presents active shape control of composite beams using shape memory actuation. Shape memory alloy (SMA) bender elements trained to memorize bending shape were used to induce bending and twisting deformations in composite beams. Bending-torsion coupled graphite-epoxy and kevlar-epoxy composite beams with Teflon inserts were manufactured using an autoclave-molding technique. Teflon inserts were replaced by trained SMA bender elements. Composite beams with SMA bender elements were activated by heating these using electrical resistive heating and the bending and twisting deformations of the beams were measured using a mirror and laser system. The structural response of the composite beams activated by SMA elements was predicted using the Vlasov theory, where these beams were modeled as open sections with many branches. The bending moment induced by a SMA bender element was calculated from its experimentally determined memorized shape. The bending, torsion, and bending-torsion coupling stiffness coefficients of these beams were obtained using analytical formulation of an open-section composite beam with many branches (Vlasov theory).

Alloys for hydrogen storage in nickel/hydrogen and nickel/metal hydride batteries

NASA Technical Reports Server (NTRS)

Anani, Anaba; Visintin, Arnaldo; Petrov, Konstantin; Srinivasan, Supramaniam; Reilly, James J.; Johnson, John R.; Schwarz, Ricardo B.; Desch, Paul B.

1993-01-01

Since 1990, there has been an ongoing collaboration among the authors in the three laboratories to (1) prepare alloys of the AB(sub 5) and AB(sub 2) types, using arc-melting/annealing and mechanical alloying/annealing techniques; (2) examine their physico-chemical characteristics (morphology, composition); (3) determine the hydrogen absorption/desorption behavior (pressure-composition isotherms as a function of temperature); and (4) evaluate their performance characteristics as hydride electrodes (charge/discharge, capacity retention, cycle life, high rate capability). The work carried out on representative AB(sub 5) and AB(sub 2) type modified alloys (by partial substitution or with small additives of other elements) is presented. The purpose of the modification was to optimize the thermodynamics and kinetics of the hydriding/dehydriding reactions and enhance the stabilities of the alloys for the desired battery applications. The results of our collaboration, to date, demonstrate that (1) alloys prepared by arc melting/annealing and mechanical alloying/annealing techniques exhibit similar morphology, composition and hydriding/dehydriding characteristics; (2) alloys with the appropriate small amounts of substituent or additive elements: (1) retain the single phase structure, (2) improve the hydriding/dehydriding reactions for the battery applications, and (3) enhance the stability in the battery environment; and (3) the AB(sub 2) type alloys exhibit higher energy densities than the AB(sub 5) type alloys but the state-of-the-art, commercialized batteries are predominantly manufactured using Ab(sub 5) type alloys.

Mercury in litterfall and sediment using elemental and isotopic composition of carbon and nitrogen in the mangrove of Southeastern Brazil

NASA Astrophysics Data System (ADS)

Fragoso, Cynara Pedrosa; Bernini, Elaine; Araújo, Beatriz Ferreira; Almeida, Marcelo Gomes de; Rezende, Carlos Eduardo de

2018-03-01

Mercury and elemental and isotopic compositions of carbon and nitrogen were determined in litterfall and sediments from the mangrove of the Paraíba do Sul River, Rio de Janeiro, Brazil. Total mercury (THg) and monomethylmercury (MMHg) concentrations in sediment ranged from 33 to 123 ng g-1 and 0.20-1.38 ng g-1, respectively. The δ13C in sediment varied from -29.4 to -26.5‰ and from 2.4 to 5.8‰ in δ15N. The THg concentration in litterfall and its annual input to the mangrove was 21 ± 2 ng g-1 and 16 ± 4 μg m-2 for the species Laguncularia racemosa, 18 ± 1 ng g-1 and 17 ± 3 μg m-2 for Rhizophora mangle, and 53 ± 4 ng g-1 and 33 ± 4 μg m-2 for Avicennia germinans, respectively. The isotopic composition of leaf litter ranged from -28.6 to -26.9‰ for δ13C and 4.5-7.2‰ for δ15N. Both the highest annual Hg input via litterfall and highest sediment Hg concentration were observed in areas dominated by A. germinans. These results suggest that the rate of litterfall of plant species and the atmospheric deposition have played an important role in the Hg biogeochemical cycle in the mangrove ecosystem.

Effects of mechanical and thermal cycling on composite and hybrid laminates with residual stresses

NASA Technical Reports Server (NTRS)

Daniel, I. M.; Liber, T.

1977-01-01

The effects of tensile load cycling and thermal cycling on residual stiffness and strength properties of the following composite and hybrid angle-ply laminates were studied: boron/epoxy, boron/polyimide, graphite/low-modulus epoxy, graphite/high-modulus epoxy, graphite/polyimide, S-glass/epoxy, graphite/Kevlar 49/epoxy, and graphite/S-glass/epoxy. Specimens of the first six types were mechanically cycled up to 90% of static strength. Those that survived 10 million cycles were tested statically to failure, and no significant changes in residual strength and modulus were noted. Specimens of all types were subjected to thermal cycling between room temperature and 411 K for the epoxy-matrix composites and 533 K for the polyimide-matrix composites. The residual strength and stiffness remained largely unchanged, except for the graphite/low-modulus epoxy, which showed reductions in both of approximately 35%. When low-temperature thermal cycling under tensile load was applied, there was a noticeable reduction in modulus and strength in the graphite/low-modulus epoxy and some strength reduction in the S-glass/epoxy.

Drivers of interannual variability in virioplankton abundance at the coastal western Antarctic peninsula and the potential effects of climate change.

PubMed

Evans, Claire; Brandsma, Joost; Pond, David W; Venables, Hugh J; Meredith, Michael P; Witte, Harry J; Stammerjohn, Sharon; Wilson, William H; Clarke, Andrew; Brussaard, Corina P D

2017-02-01

An 8-year time-series in the Western Antarctic Peninsula (WAP) with an approximately weekly sampling frequency was used to elucidate changes in virioplankton abundance and their drivers in this climatically sensitive region. Virioplankton abundances at the coastal WAP show a pronounced seasonal cycle with interannual variability in the timing and magnitude of the summer maxima. Bacterioplankton abundance is the most influential driving factor of the virioplankton, and exhibit closely coupled dynamics. Sea ice cover and duration predetermine levels of phytoplankton stock and thus, influence virioplankton by dictating the substrates available to the bacterioplankton. However, variations in the composition of the phytoplankton community and particularly the prominence of Diatoms inferred from silicate drawdown, drive interannual differences in the magnitude of the virioplankton bloom; likely again mediated through changes in the bacterioplankton. Their findings suggest that future warming within the WAP will cause changes in sea ice that will influence viruses and their microbial hosts through changes in the timing, magnitude and composition of the phytoplankton bloom. Thus, the flow of matter and energy through the viral shunt may be decreased with consequences for the Antarctic food web and element cycling. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Pt-Richcore/Sn-Richsubsurface/Ptskin Nanocubes As Highly Active and Stable Electrocatalysts for the Ethanol Oxidation Reaction.

PubMed

Rizo, Rubén; Arán-Ais, Rosa M; Padgett, Elliot; Muller, David A; Lázaro, Ma Jesús; Solla-Gullón, José; Feliu, Juan M; Pastor, Elena; Abruña, Héctor D

2018-03-14

Direct ethanol fuel cells are one of the most promising electrochemical energy conversion devices for portable, mobile and stationary power applications. However, more efficient and stable and less expensive electrocatalysts are still required. Interestingly, the electrochemical performance of the electrocatalysts toward the ethanol oxidation reaction can be remarkably enhanced by exploiting the benefits of structural and compositional sensitivity and control. Here, we describe the synthesis, characterization, and electrochemical behavior of cubic Pt-Sn nanoparticles. The electrochemical activity of the cubic Pt-Sn nanoparticles was found to be about three times higher than that obtained with unshaped Pt-Sn nanoparticles and six times higher than that of Pt nanocubes. In addition, stability tests indicated the electrocatalyst preserves its morphology and remains well-dispersed on the carbon support after 5000 potential cycles, while a cubic (pure) Pt catalyst exhibited severe agglomeration of the nanoparticles after a similar stability testing protocol. A detailed analysis of the elemental distribution in the nanoparticles by STEM-EELS indicated that Sn dissolves from the outer part of the shell after potential cycling, forming a ∼0.5 nm Pt skin. This particular atomic composition profile having a Pt-rich core, a Sn-rich subsurface layer, and a Pt-skin surface structure is responsible for the high activity and stability.

SOLAR WIND HEAVY IONS OVER SOLAR CYCLE 23: ACE/SWICS MEASUREMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lepri, S. T.; Landi, E.; Zurbuchen, T. H.

2013-05-01

Solar wind plasma and compositional properties reflect the physical properties of the corona and its evolution over time. Studies comparing the previous solar minimum with the most recent, unusual solar minimum indicate that significant environmental changes are occurring globally on the Sun. For example, the magnetic field decreased 30% between the last two solar minima, and the ionic charge states of O have been reported to change toward lower values in the fast wind. In this work, we systematically and comprehensively analyze the compositional changes of the solar wind during cycle 23 from 2000 to 2010 while the Sun movedmore » from solar maximum to solar minimum. We find a systematic change of C, O, Si, and Fe ionic charge states toward lower ionization distributions. We also discuss long-term changes in elemental abundances and show that there is a {approx}50% decrease of heavy ion abundances (He, C, O, Si, and Fe) relative to H as the Sun went from solar maximum to solar minimum. During this time, the relative abundances in the slow wind remain organized by their first ionization potential. We discuss these results and their implications for models of the evolution of the solar atmosphere, and for the identification of the fast and slow wind themselves.« less

A new perspective of using sequential extraction: To predict the deficiency of trace elements during anaerobic digestion.

PubMed

Cai, Yafan; Wang, Jungang; Zhao, Yubin; Zhao, Xiaoling; Zheng, Zehui; Wen, Boting; Cui, Zongjun; Wang, Xiaofen

2018-09-01

Trace elements were commonly used as additives to facilitate anaerobic digestion. However, their addition is often blind because of the complexity of reaction conditions, which has impeded their widespread application. Therefore, this study was conducted to evaluate deficiencies in trace elements during anaerobic digestion by establishing relationships between changes in trace element bioavailability (the degree to which elements are available for interaction with biological systems) and digestion performance. To accomplish this, two batch experiments were conducted. In the first, sequential extraction was used to detect changes in trace element fractions and then to evaluate trace element bioavailability in the whole digestion cycle. In the second batch experiment, trace elements (Co, Fe, Cu, Zn, Mn, Mo and Se) were added to the reaction system at three concentrations (low, medium and high) and their effects were monitored. The results showed that sequential extraction was a suitable method for assessment of the bioavailability of trace elements (appropriate coefficient of variation and recovery rate). The results revealed that Se had the highest (44.2%-70.9%) bioavailability, while Fe had the lowest (1.7%-3.0%). A lack of trace elements was not directly related to their absolute bioavailability, but was instead associated with changes in their bioavailability throughout the digestion cycle. Trace elements were insufficient when their bioavailability was steady or increased over the digestion cycle. These results indicate that changes in trace element bioavailability during the digestion cycle can be used to predict their deficiency. Copyright © 2018 Elsevier Ltd. All rights reserved.

Phylogenetic and structural response of heterotrophic bacteria to dissolved organic matter of different chemical composition in a continuous culture study.

PubMed

Landa, M; Cottrell, M T; Kirchman, D L; Kaiser, K; Medeiros, P M; Tremblay, L; Batailler, N; Caparros, J; Catala, P; Escoubeyrou, K; Oriol, L; Blain, S; Obernosterer, I

2014-06-01

Dissolved organic matter (DOM) and heterotrophic bacteria are highly diverse components of the ocean system, and their interactions are key in regulating the biogeochemical cycles of major elements. How chemical and phylogenetic diversity are linked remains largely unexplored to date. To investigate interactions between bacterial diversity and DOM, we followed the response of natural bacterial communities to two sources of phytoplankton-derived DOM over six bacterial generation times in continuous cultures. Analyses of total hydrolysable neutral sugars and amino acids, and ultrahigh resolution mass spectrometry revealed large differences in the chemical composition of the two DOM sources. According to 454 pyrosequences of 16S ribosomal ribonucleic acid genes, diatom-derived DOM sustained higher levels of bacterial richness, evenness and phylogenetic diversity than cyanobacteria-derived DOM. These distinct community structures were, however, not associated with specific taxa. Grazing pressure affected bacterial community composition without changing the overall pattern of bacterial diversity levels set by DOM. Our results demonstrate that resource composition can shape several facets of bacterial diversity without influencing the phylogenetic composition of bacterial communities, suggesting functional redundancy at different taxonomic levels for the degradation of phytoplankton-derived DOM. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

Application of an Instrumental and Computational Approach for Improving the Vibration Behavior of Structural Panels Using a Lightweight Multilayer Composite

PubMed Central

Sánchez, Alberto; García, Manuel; Sebastián, Miguel Angel; Camacho, Ana María

2014-01-01

This work presents a hybrid (experimental-computational) application for improving the vibration behavior of structural components using a lightweight multilayer composite. The vibration behavior of a flat steel plate has been improved by the gluing of a lightweight composite formed by a core of polyurethane foam and two paper mats placed on its faces. This composite enables the natural frequencies to be increased and the modal density of the plate to be reduced, moving about the natural frequencies of the plate out of excitation range, thereby improving the vibration behavior of the plate. A specific experimental model for measuring the Operating Deflection Shape (ODS) has been developed, which enables an evaluation of the goodness of the natural frequencies obtained with the computational model simulated by the finite element method (FEM). The model of composite + flat steel plate determined by FEM was used to conduct parametric study, and the most influential factors for 1st, 2nd and 3rd mode were identified using a multifactor analysis of variance (Multifactor-ANOVA). The presented results can be easily particularized for other cases, as it may be used in cycles of continuous improvement as well as in the product development at the material, piece, and complete-system levels. PMID:24618779

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yates, K.R.; Schreiber, A.M.; Rudolph, A.W.

The US Nuclear Regulatory Commission has initiated the Fuel Cycle Risk Assessment Program to provide risk assessment methods for assistance in the regulatory process for nuclear fuel cycle facilities other than reactors. Both the once-through cycle and plutonium recycle are being considered. A previous report generated by this program defines and describes fuel cycle facilities, or elements, considered in the program. This report, the second from the program, describes the survey and computer compilation of fuel cycle risk-related literature. Sources of available information on the design, safety, and risk associated with the defined set of fuel cycle elements were searchedmore » and documents obtained were catalogued and characterized with respect to fuel cycle elements and specific risk/safety information. Both US and foreign surveys were conducted. Battelle's computer-based BASIS information management system was used to facilitate the establishment of the literature compilation. A complete listing of the literature compilation and several useful indexes are included. Future updates of the literature compilation will be published periodically. 760 annotated citations are included.« less

Summary of the Effects of Two Years of Hygro-Thermal Cycling on a Carbon/Epoxy Composite Material

NASA Technical Reports Server (NTRS)

Kohlman, Lee W.; Binienda, Wieslaw K.; Roberts, Gary D.; Miller, Sandi G.; Pereira, J. Michael; Bail, Justin L.

2011-01-01

Composite materials are beginning to be used for structures in the fan section of commercial gas turbine engines. This paper explores the type of damage that could occur within one type of composite material after exposure to hygrothermal cycles (temperature/humidity cycles) that are representative of the environment in the fan section of an engine. The effect of this damage on composite material properties is measured. Chemical changes in the matrix material were limited to the exposed surface. Microcrack formation was identified in the composite material. This damage did not cause a significant reduction in tensile strength or impact penetration resistance of the composite material. Additional data is needed to assess the effect of damage on compressive strength.

MnO2 Nanorods Intercalating Graphene Oxide/Polyaniline Ternary Composites for Robust High-Performance Supercapacitors

NASA Astrophysics Data System (ADS)

Han, Guangqiang; Liu, Yun; Zhang, Lingling; Kan, Erjun; Zhang, Shaopeng; Tang, Jian; Tang, Weihua

2014-04-01

New ternary composites of MnO2 nanorods, polyaniline (PANI) and graphene oxide (GO) have been prepared by a two-step process. The 100 nm-long MnO2 nanorods with a diameter ~20 nm are conformably coated with PANI layers and fastened between GO layers. The MnO2 nanorods incorporated ternary composites electrode exhibits significantly increased specific capacitance than PANI/GO binary composite in supercapacitors. The ternary composite with 70% MnO2 exhibits a highest specific capacitance reaching 512 F/g and outstanding cycling performance, with ~97% capacitance retained over 5000 cycles. The ternary composite approach offers an effective solution to enhance the device performance of metal-oxide based supercapacitors for long cycling applications.

Expression of a major surface protein of Trypanosoma brucei insect forms is controlled by the activity of mitochondrial enzymes.

PubMed

Vassella, Erik; Probst, Matthias; Schneider, André; Studer, Erwin; Renggli, Christina Kunz; Roditi, Isabel

2004-09-01

In cycling between the mammalian host and the tsetse fly vector, trypanosomes undergo major changes in energy metabolism and surface coat composition. Early procyclic (insect) forms in the tsetse fly midgut are coated by glycoproteins known as EP and GPEET procyclins. EP expression continues in late procyclic forms, whereas GPEET is down-regulated. In culture, expression of GPEET is modulated by glycerol or glucose. Here, we demonstrate that a glycerol-responsive element of 25 nucleotides within the 3' untranslated region of GPEET mRNA also controls expression by glucose and during development in the fly. In trypanosomes, mitochondrial ATP is produced mainly by the acetate: succinate-CoA transferase/succinyl-CoA synthetase (ASCT) cycle, the citric acid cycle, and the cytochromes. Silencing of the pyruvate dehydrogenase or succinyl-CoA synthetase from the ASCT cycle by RNA interference induces reexpression of GPEET in late procyclic forms, whereas inhibition of the citric acid cycle or the cytochromes has no effect. In contrast, inhibition of the alternative oxidase, the second branch of the electron transport chain, with salicylhydroxamic acid overrides the effect of glucose or glycerol and causes a reduction in the level of GPEET mRNA. Our results reveal a new mechanism by which expression of a surface glycoprotein is controlled by the activity of mitochondrial enzymes.

Layer by Layer Ex-Situ Deposited Cobalt-Manganese Oxide as Composite Electrode Material for Electrochemical Capacitor

PubMed Central

Rusi; Chan, P. Y.; Majid, S. R.

2015-01-01

The composite metal oxide electrode films were fabricated using ex situ electrodeposition method with further heating treatment at 300°C. The obtained composite metal oxide film had a spherical structure with mass loading from 0.13 to 0.21 mg cm-2. The structure and elements of the composite was investigated using X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The electrochemical performance of different composite metal oxides was studied by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD). As an active electrode material for a supercapacitor, the Co-Mn composite electrode exhibits a specific capacitance of 285 Fg-1 at current density of 1.85 Ag-1 in 0.5M Na2SO4 electrolyte. The best composite electrode, Co-Mn electrode was then further studied in various electrolytes (i.e., 0.5M KOH and 0.5M KOH/0.04M K3Fe(CN) 6 electrolytes). The pseudocapacitive nature of the material of Co-Mn lead to a high specific capacitance of 2.2 x 103 Fg-1 and an energy density of 309 Whkg-1 in a 0.5MKOH/0.04MK3Fe(CN) 6 electrolyte at a current density of 10 Ag-1. The specific capacitance retention obtained 67% of its initial value after 750 cycles. The results indicate that the ex situ deposited composite metal oxide nanoparticles have promising potential in future practical applications. PMID:26158447

Layer by Layer Ex-Situ Deposited Cobalt-Manganese Oxide as Composite Electrode Material for Electrochemical Capacitor.

PubMed

Rusi; Chan, P Y; Majid, S R

2015-01-01

The composite metal oxide electrode films were fabricated using ex situ electrodeposition method with further heating treatment at 300°C. The obtained composite metal oxide film had a spherical structure with mass loading from 0.13 to 0.21 mg cm(-2). The structure and elements of the composite was investigated using X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The electrochemical performance of different composite metal oxides was studied by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD). As an active electrode material for a supercapacitor, the Co-Mn composite electrode exhibits a specific capacitance of 285 Fg(-1) at current density of 1.85 Ag(-1) in 0.5 M Na2SO4 electrolyte. The best composite electrode, Co-Mn electrode was then further studied in various electrolytes (i.e., 0.5 M KOH and 0.5 M KOH/0.04 M K3Fe(CN) 6 electrolytes). The pseudocapacitive nature of the material of Co-Mn lead to a high specific capacitance of 2.2 x 10(3) Fg(-1) and an energy density of 309 Whkg(-1) in a 0.5 M KOH/0.04 M K3Fe(CN) 6 electrolyte at a current density of 10 Ag(-1). The specific capacitance retention obtained 67% of its initial value after 750 cycles. The results indicate that the ex situ deposited composite metal oxide nanoparticles have promising potential in future practical applications.

Biogeochemistry of carbon and related major and trace elements in peat bog soils of the middle taiga of Western Siberia (Russia).

NASA Astrophysics Data System (ADS)

Stepanova, V. A.; Mironycheva-Tokareva, N. P.; Pokrovsky, O. S.

2012-04-01

Global climate changes impact the status of wetland ecosystems shifting the balances of the carbon, macro-, and microelements cycles. This study aims to establish the features of accumulation and distribution of major- and trace elements in the organic layer of peat bog soils, belonging to different ecosystems of the oligotrophic bog complex located in the middle taiga of Western Siberia (Khanty-Mansiysk region, Russia). Key areas which are selected for this study include the following bog conjugate elementary ecosystems: higher ryam, lower ryam, ridge-hollow complex, and oligotrophic poor fen as characterized previously [1]. We have sampled various peat types along the entire length of the soil column (every 10 cm down to 3 m). Peat samples were analyzed for a wide range of macro- and microelements using an ICP-MS technique following full acid digestion in a microwave oven. These measurements allowed quantitative estimates of major- and trace elements in the peat deposits within the whole bog complex and individual elementary landscapes. Based on the data obtained, the lateral and radial geochemical structures of the bog landscapes were determined and clarified for the first time for middle taiga of the West Siberian plain. The similar regime of mineral nutrition during the complete bog landscape formation was detected for the peat deposits based on the measurements of some major- and trace elements (Ca, Fe, Mg, etc.). The vertical distribution of some major and some trace elements along the profile of peat column is rather uniform with relatively strong increase in the bottom organic layers. This strongly suggests the similarity of the processes of element accumulation in the peat and relatively weak post depositional redistribution of elements within the peat soil profile. Overall, obtained corroborate the existing view on chemical composition of peats being determined by botanical peat's components (which forms this peat deposit), atmospheric precipitation, position of ecosystems in the landscape (lateral migration) and types of bedrocks [2]. The results allow better understanding of the coupling between biogeochemical cycles of carbon and major and trace elements in peat soils in order to predict the future changes in both concentrations and stocks of chemical elements in the Western Siberia peat bog systems under climate warming.

Element cycling in upland/peatland watersheds Chapter 8.

Treesearch

Noel Urban; Elon S. Verry; Steven Eisenreich; David F. Grigal; Stephen D. Sebestyen

2011-01-01

Studies at the Marcell Experimental Forest (MEF) have measured the pools, cycling, and transport of a variety of elements in both the upland and peatland components of the landscape. Peatlands are important zones of element retention and biogeochemical reactions that greatly influence the chemistry of surface water. In this chapter, we summarize findings on nitrogen (N...

Finite Element Models and Properties of a Stiffened Floor-Equipped Composite Cylinder

NASA Technical Reports Server (NTRS)

Grosveld, Ferdinand W.; Schiller, Noah H.; Cabell, Randolph H.

2010-01-01

Finite element models were developed of a floor-equipped, frame and stringer stiffened composite cylinder including a coarse finite element model of the structural components, a coarse finite element model of the acoustic cavities above and below the beam-supported plywood floor, and two dense models consisting of only the structural components. The report summarizes the geometry, the element properties, the material and mechanical properties, the beam cross-section characteristics, the beam element representations and the boundary conditions of the composite cylinder models. The expressions used to calculate the group speeds for the cylinder components are presented.

Remediation using trace element humate surfactant

DOEpatents

Riddle, Catherine Lynn; Taylor, Steven Cheney; Bruhn, Debra Fox

2016-08-30

A method of remediation at a remediation site having one or more undesirable conditions in which one or more soil characteristics, preferably soil pH and/or elemental concentrations, are measured at a remediation site. A trace element humate surfactant composition is prepared comprising a humate solution, element solution and at least one surfactant. The prepared trace element humate surfactant composition is then dispensed onto the remediation site whereby the trace element humate surfactant composition will reduce the amount of undesirable compounds by promoting growth of native species activity. By promoting native species activity, remediation occurs quickly and environmental impact is minimal.

Atomic Layer Deposition of Aluminum Sulfide: Growth Mechanism and Electrochemical Evaluation in Lithium-Ion Batteries

DOE PAGES

Meng, Xiangbo; Cao, Yanqiang; Libera, Joseph A.; ...

2017-10-01

This work describes the synthesis of aluminum sulfide (AlS x) thin films by atomic layer deposition (ALD) using tris(dimethylamido)aluminum and hydrogen sulfide. We employed a suite of in situ measurement techniques to explore the ALD AlS x growth mechanism, including quartz crystal microbalance, quadrupole mass spectrometry, and Fourier transform infrared spectroscopy. A variety of ex situ characterization techniques were used to determine the growth characteristics, morphology, elemental composition, and crystallinity of the resultant AlS x films. This study revealed that the AlS x growth was self-limiting in the temperature range 100–250 °C, and the growth per cycle decreased linearly withmore » increasing temperature from ~0.45 Å/cycle at 100 °C to ~0.1 Å/cycle at 250 °C. The AlSx films were amorphous in this temperature range. We conducted electrochemical testing to evaluate the ALD AlS x as a potential anode material for lithium-ion batteries (LIBs). Finally, the ALD AlS x exhibited reliable cyclability over 60 discharge–charge cycles with a sustainable discharge capacity of 640 mAh/g at a current density of 100 mA/g in the voltage window of 0.6–3.5 V.« less

Atomic Layer Deposition of Aluminum Sulfide: Growth Mechanism and Electrochemical Evaluation in Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Xiangbo; Cao, Yanqiang; Libera, Joseph A.

This work describes the synthesis of aluminum sulfide (AlS x) thin films by atomic layer deposition (ALD) using tris(dimethylamido)aluminum and hydrogen sulfide. We employed a suite of in situ measurement techniques to explore the ALD AlS x growth mechanism, including quartz crystal microbalance, quadrupole mass spectrometry, and Fourier transform infrared spectroscopy. A variety of ex situ characterization techniques were used to determine the growth characteristics, morphology, elemental composition, and crystallinity of the resultant AlS x films. This study revealed that the AlS x growth was self-limiting in the temperature range 100–250 °C, and the growth per cycle decreased linearly withmore » increasing temperature from ~0.45 Å/cycle at 100 °C to ~0.1 Å/cycle at 250 °C. The AlSx films were amorphous in this temperature range. We conducted electrochemical testing to evaluate the ALD AlS x as a potential anode material for lithium-ion batteries (LIBs). Finally, the ALD AlS x exhibited reliable cyclability over 60 discharge–charge cycles with a sustainable discharge capacity of 640 mAh/g at a current density of 100 mA/g in the voltage window of 0.6–3.5 V.« less

Novel polyoxometalate silica nano-sized spheres: efficient catalysts for olefin oxidation and the deep desulfurization process.

PubMed

Nogueira, Lucie S; Ribeiro, Susana; Granadeiro, Carlos M; Pereira, Eulália; Feio, Gabriel; Cunha-Silva, Luís; Balula, Salete S

2014-07-07

A novel method to prepare silica nano-sized particles incorporating polyoxometalates was developed leading to a new efficient heterogeneous oxidative catalyst. Zinc-substituted polyoxotungstate [PW11Zn(H2O)O39](5-) (PW11Zn) was encapsulated into silica nanoparticles using a cross-linked organic-inorganic core, performed through successive spontaneous reactions in water. The potassium salt of PW11Zn and the composite formed, PW11Zn-APTES@SiO2, were characterized by a myriad of solid-state methods such as FT-IR, FT-Raman, (31)P and (13)C CP/MAS solid-state NMR, elemental analysis and SEM-EDS, confirming the integrity of the PW11Zn structure immobilized in the silica nanoparticles. The new composite has shown to be a versatile catalyst for the oxidation of olefins and also to catalyze the desulfurization of a model oil using H2O2 as the oxidant and acetonitrile as the solvent. The novel composite material was capable of being recycled without significant loss of activity and maintaining its structural stability for consecutive desulfurization and olefin oxidative cycles.

Time-dependent deformation of titanium metal matrix composites

NASA Technical Reports Server (NTRS)

Bigelow, C. A.; Bahei-El-din, Y. A.; Mirdamadi, M.

1995-01-01

A three-dimensional finite element program called VISCOPAC was developed and used to conduct a micromechanics analysis of titanium metal matrix composites. The VISCOPAC program uses a modified Eisenberg-Yen thermo-viscoplastic constitutive model to predict matrix behavior under thermomechanical fatigue loading. The analysis incorporated temperature-dependent elastic properties in the fiber and temperature-dependent viscoplastic properties in the matrix. The material model was described and the necessary material constants were determined experimentally. Fiber-matrix interfacial behavior was analyzed using a discrete fiber-matrix model. The thermal residual stresses due to the fabrication cycle were predicted with a failed interface, The failed interface resulted in lower thermal residual stresses in the matrix and fiber. Stresses due to a uniform transverse load were calculated at two temperatures, room temperature and an elevated temperature of 650 C. At both temperatures, a large stress concentration was calculated when the interface had failed. The results indicate the importance of accuracy accounting for fiber-matrix interface failure and the need for a micromechanics-based analytical technique to understand and predict the behavior of titanium metal matrix composites.

Anthropogenic osmium in rain and snow reveals global-scale atmospheric contamination.

PubMed

Chen, Cynthia; Sedwick, Peter N; Sharma, Mukul

2009-05-12

Osmium is one of the rarer elements in seawater, with typical concentration of approximately 10 x 10(-15) g g(-1) (5.3 x 10(-14) mol kg(-1)). The osmium isotope composition ((187)Os/(188)Os ratio) of deep oceans is 1.05, reflecting a balance between inputs from continental crust (approximately 1.3) and mantle/cosmic dust (approximately 0.13). Here, we show that the (187)Os/(188)Os ratios measured in rain and snow collected around the world range from 0.16 to 0.48, much lower than expected (>1), but similar to the isotope composition of ores (approximately 0.2) that are processed to extract platinum and other metals to be used primarily in automobile catalytic converters. Present-day surface seawater has a lower (187)Os/(188)Os ratio (approximately 0.95) than deep waters, suggesting that human activities have altered the isotope composition of the world's oceans and impacted the global geochemical cycle of osmium. The contamination of the surface ocean is particularly remarkable given that osmium has few industrial uses. The pollution may increase with growing demand for platinum-based catalysts.

Study of the dynamics of Zn, Fe, and Cu in the soil-plant system during leaf litter decomposition using isotopic compositions

NASA Astrophysics Data System (ADS)

Pichat, S.; Fekiacova, Z.

2013-12-01

Litter decomposition is a key process in the cycle of the elements in the soil-plant system. We have investigated the dynamics of three essential micronutrients (Zn, Fe, and Cu) in the vegetal cover, litter, organic horizons, and upper soil horizon (0-2 and 5-10 cm) using both element concentrations and isotopic compositions. The study was conducted on the O3HP (Oak Observatory at the Haute-Provence Observatory) experimental field site in southern France. O3HP is located far from pollution sources. It has been a fallow land for 70 years with the tree cover represented mainly by oak trees (Quercus pubescens). The soil is a thin layer of Calcisol developed under Mediterranean climate. The area has been subdivided in four zones as a function of plant cover. The results for two of these zones, dominated by respectively Poaceae and Genista hispanica, are reported here. We found that the concentrations of the three elements increase from the Ol to the Of horizon. Copper concentration in the Of horizon is close to that of the soil, whereas it is lower for Fe and Zn. For isotopic compositions, the behavior of the three elements is, however, different, which suggests different processes of redistribution for these elements. An enrichment in light Fe isotopes was observed from the Ol to the Of horizon, the latter having an isotopic composition similar to that of the soil. Zinc isotopic compositions are also similar in the Of horizon and the soil but they are isotopically heavier than in the Ol horizon. For Cu, the O horizons are isotopically heavier than the soil, with Of being the heaviest horizon. In addition, for Cu and Zn, the profiles in the O-horizons in the Poaceae-dominated and Genista hispanica-dominated areas are similar but their values are offset, suggesting an influence of the vegetal cover. The increase in concentration for Cu, Zn and Fe with age/depth in the O horizons is in agreement with what is commonly observed in litter-bag experiments, e.g. 1,2. Two mechanisms have been invoked to explain this phenomenon: 1) addition of metals by aerial dust and wet deposition or 2) absorption of metals from the soil by organisms that develop on the litter. Our vertical profiles of isotopic compositions in the O horizons show that the first hypothesis is unlikely. Instead, they suggest a downward transfer of isotopically light metals from the fresh litter to the base of the O horizon. In addition, the assumption of an upward transfer of isopically heavy Cu and Zn from the upper soil horizon to the Of horizon is needed to fully explain the profiles we observed. 1 Lomander and Johansson (2001) Water, Air, and Soil Pollut. 132, 165-184 2 Scheid et al. (2009) Eur. J. Soil Sci. 60, 613-621

The effects of diagenesis and dolomitization on Ca and Mg isotopes in marine platform carbonates: Implications for the geochemical cycles of Ca and Mg

NASA Astrophysics Data System (ADS)

Fantle, Matthew S.; Higgins, John

2014-10-01

The Ca, Mg, O, and C isotopic and trace elemental compositions of marine limestones and dolostones from ODP Site 1196A, which range in depth (∼58 to 627 mbsf) and in depositional age (∼5 and 23 Ma), are presented. The objectives of the study are to explore the potential for non-traditional isotope systems to fingerprint diagenesis, to quantify the extent to which geochemical proxies are altered during diagenesis, and to investigate the importance of diagenesis within the global Ca and Mg geochemical cycles. The data suggest that Ca, which has a relatively high solid to fluid mass ratio, can be isotopically altered during diagenesis. In addition, the alteration of Ca correlates with the alteration of Mg in such a way that both can serve as useful tools for deciphering diagenesis in ancient rocks. Bulk carbonate δ44Ca values vary between 0.60 and 1.31‰ (SRM-915a scale); the average limestone δ44Ca is 0.97 ± 0.24‰ (1SD), identical within error to the average dolostone (1.03 ± 0.15 1SD ‰). Magnesium isotopic compositions (δ26Mg, DSM-3 scale) range between -2.59‰ and -3.91‰, and limestones (-3.60 ± 0.25‰) and dolostones (-2.68 ± 0.07‰) are isotopically distinct. Carbon isotopic compositions (δ13C, PDB scale) vary between 0.86‰ and 2.47‰, with average limestone (1.96 ± 0.31‰) marginally offset relative to average dolostone (1.68 ± 0.57‰). The oxygen isotopic compositions (δ18O, PDB scale) of limestones (-1.22 ± 0.94‰) are substantially lower than the dolostones measured (2.72 ± 1.07‰). The isotopic data from 1196A suggest distinct and coherent trends in isotopic and elemental compositions that are interpreted in terms of diagenetic trajectories. Numerical modeling supports the contention that such trends can be interpreted as diagenetic, and suggests that the appropriate distribution coefficient (KMg) associated with limestone diagenesis is ∼1 to 5 × 10-3, distinctly lower than those values (>0.015) reported in laboratory studies. With respect to Mg isotopes, the modeling also suggest that diagenetic fractionation factors of ∼0.9955 (-4.5‰) and 0.9980 (-2‰) are appropriate for limestone diagenesis and dolomitization, respectively.

The Composition of Dramatic Experience: The Play Element in Student Electronic Projects.

ERIC Educational Resources Information Center

Rouzie, Albert

2000-01-01

Analyzes two student group Hypertext projects and a MOO (multiuser domain, object-oriented) project. Finds the play element can enrich readerly experience through the creation of a dramatic experience of information. Suggests that composition instructors need to recognize the play element in computer-based composition and encourage the development…

A molecular investigation of soil organic carbon composition across a subalpine catchment

USGS Publications Warehouse

Hsu, Hsiao-Tieh; Lawrence, Corey R.; Winnick, Matthew J.; Bargar, John R.; Maher, Katharine

2018-01-01

The dynamics of soil organic carbon (SOC) storage and turnover are a critical component of the global carbon cycle. Mechanistic models seeking to represent these complex dynamics require detailed SOC compositions, which are currently difficult to characterize quantitatively. Here, we address this challenge by using a novel approach that combines Fourier transform infrared spectroscopy (FT-IR) and bulk carbon X-ray absorption spectroscopy (XAS) to determine the abundance of SOC functional groups, using elemental analysis (EA) to constrain the total amount of SOC. We used this SOC functional group abundance (SOC-fga) method to compare variability in SOC compositions as a function of depth across a subalpine watershed (East River, Colorado, USA) and found a large degree of variability in SOC functional group abundances between sites at different elevations. Soils at a lower elevation are predominantly composed of polysaccharides, while soils at a higher elevation have more substantial portions of carbonyl, phenolic, or aromatic carbon. We discuss the potential drivers of differences in SOC composition between these sites, including vegetation inputs, internal processing and losses, and elevation-driven environmental factors. Although numerical models would facilitate the understanding and evaluation of the observed SOC distributions, quantitative and meaningful measurements of SOC molecular compositions are required to guide such models. Comparison among commonly used characterization techniques on shared reference materials is a critical next step for advancing our understanding of the complex processes controlling SOC compositions.

Application of the boundary element method to the micromechanical analysis of composite materials

NASA Technical Reports Server (NTRS)

Goldberg, R. K.; Hopkins, D. A.

1995-01-01

A new boundary element formulation for the micromechanical analysis of composite materials is presented in this study. A unique feature of the formulation is the use of circular shape functions to convert the two-dimensional integrations of the composite fibers to one-dimensional integrations. To demonstrate the applicability of the formulations, several example problems including elastic and thermal analysis of laminated composites and elastic analyses of woven composites are presented and the boundary element results compared to experimental observations and/or results obtained through alternate analytical procedures. While several issues remain to be addressed in order to make the methodology more robust, the formulations presented here show the potential in providing an alternative to traditional finite element methods, particularly for complex composite architectures.

Lithogenic sources, composition and intra-annual variability of suspended particulate matter supplied from rivers to the Northern Galician Rias (Bay of Biscay)

NASA Astrophysics Data System (ADS)

Bernárdez, Patricia; Prego, Ricardo; Filgueiras, Ana Virginia; Ospina-Álvarez, Natalia; Santos-Echeandía, Juan; Álvarez-Vázquez, Miguel Angel; Caetano, Miguel

2017-12-01

Scarce research about small European rivers from non-human impacted areas to determine their natural background state has been undertaken. During the annual hydrological cycle of 2008-9 the patterns of particulate supply (SPM, POC, PON, Al, Cd, Co, Cr, Cu, Fe, Ni, Pb, V, Zn) from the rivers Sor, Mera Landro, Lourido and Landoi to the Northern Galician Rias (SW Bay of Biscay) were tackled. No differences in the composition of the SPM were detected for the studied rivers regarding Al, Fe and POC but the relative percentage of particulate trace elements (PTE) discriminate the rivers. So, Cr, Co and Ni in the Lourido, and Landoi rivers, and Cu in the Mera River, are controlled by watershed minerals of Ortegal Geological Complex while for the rest rivers PTE are by granitic and Ollo de Sapo bedrock watershed. Therefore, the imprint of PTE in the parental rocks of the river basins is reflected on the coastal sediments of the Rias. The main process controlling the dynamics and variations of chemical elements in the particulate form is the river discharge. This fact exemplifies that these rivers presents a natural behavior not being highly influenced by anthropogenic activities.

Cyclin Polynucleotides, Polypeptides And Uses Thereof.

DOEpatents

Lowe, Keith S.; Tao, Yumin; Gordon-Kamm, William J.; Gregory, Carolyn A.; Hoerster, George J.; McElver, John A.

2003-02-11

The invention provides isolated polynucleotides and their encoded proteins that are involved in cell cycle regulation. The invention further provides recombinant expression cassettes, host cells, transgenic plants, and antibody compositions. The present invention provides methods and compositions relating to altering cell cycle protein content and/or composition of plants.

Studies of finite element analysis of composite material structures

NASA Technical Reports Server (NTRS)

Douglas, D. O.; Holzmacher, D. E.; Lane, Z. C.; Thornton, E. A.

1975-01-01

Research in the area of finite element analysis is summarized. Topics discussed include finite element analysis of a picture frame shear test, BANSAP (a bandwidth reduction program for SAP IV), FEMESH (a finite element mesh generation program based on isoparametric zones), and finite element analysis of a composite bolted joint specimens.

Cure Cycle Design Methodology for Fabricating Reactive Resin Matrix Fiber Reinforced Composites: A Protocol for Producing Void-free Quality Laminates

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung

2014-01-01

For the fabrication of resin matrix fiber reinforced composite laminates, a workable cure cycle (i.e., temperature and pressure profiles as a function of processing time) is needed and is critical for achieving void-free laminate consolidation. Design of such a cure cycle is not trivial, especially when dealing with reactive matrix resins. An empirical "trial and error" approach has been used as common practice in the composite industry. Such an approach is not only costly, but also ineffective at establishing the optimal processing conditions for a specific resin/fiber composite system. In this report, a rational "processing science" based approach is established, and a universal cure cycle design protocol is proposed. Following this protocol, a workable and optimal cure cycle can be readily and rationally designed for most reactive resin systems in a cost effective way. This design protocol has been validated through experimental studies of several reactive polyimide composites for a wide spectrum of usage that has been documented in the previous publications.

Effects of temperature and humidity cycling on the strengths of textile reinforced carbon/epoxy composite materials

NASA Technical Reports Server (NTRS)

Cano, Roberto J.; Furrow, Keith W.

1993-01-01

Results are presented from an experimental evaluation of the combined effects of temperature and humidity cycling on AS4/3501-6 composites (unstitched, Kevlar 29 stitched, and S-2 glass stitched uniweave fabric) and AS4/E905L composites (2-D, S-2 glass stitched 2-D, and 3-D braided fabric). The AS4/3501-6 uniweave material had a quasi-isotropic layup, whereas the AS4/E905L materials were braided in a (+/-30 deg/0 deg)(sub s) orientation. Data presented include compression strengths and compression-compression fatigue results for uncycled composites and cycled composites (160, 480, 720, and 1280 cycles from 140 deg F at 95 percent relative humidity to -67 deg F). To observe the presence of microcracking within the laminates, photomicrographs were taken of each material type at the end of each cycling period. Microcracks were found to be more prevalent within stitched laminates, predominantly around individual stitches. The glass stitched laminates showed significant microcracking even before cycling. Less microcracking was evident in the Kevlar stitched materials, whereas the unstitched uniweave material developed microcracks only after cycling. The 3-D braid did not develop microcracks. The static compression strengths of the unstitched and Kevlar stitched uniweave materials were degraded by about 10 percent after 1280 temperature/humidity cycles, whereas the reduction in compression strength for the glass stitched uniweave was less than 3 percent. The reduction in compression strength for the glass stitched 2-D braid was less than 8 percent. The unstitched 2-D and 3-D braids did not lose strength from temperature/humidity cycling. The compression-compression fatigue properties of all six material types were not affected by temperature/humidity cycling.

MnO2 Nanorods Intercalating Graphene Oxide/Polyaniline Ternary Composites for Robust High-Performance Supercapacitors

PubMed Central

Han, Guangqiang; Liu, Yun; Zhang, Lingling; Kan, Erjun; Zhang, Shaopeng; Tang, Jian; Tang, Weihua

2014-01-01

New ternary composites of MnO2 nanorods, polyaniline (PANI) and graphene oxide (GO) have been prepared by a two-step process. The 100 nm-long MnO2 nanorods with a diameter ~20 nm are conformably coated with PANI layers and fastened between GO layers. The MnO2 nanorods incorporated ternary composites electrode exhibits significantly increased specific capacitance than PANI/GO binary composite in supercapacitors. The ternary composite with 70% MnO2 exhibits a highest specific capacitance reaching 512 F/g and outstanding cycling performance, with ~97% capacitance retained over 5000 cycles. The ternary composite approach offers an effective solution to enhance the device performance of metal-oxide based supercapacitors for long cycling applications. PMID:24769835

Fungal Bioweathering of Mimetite and a General Geomycological Model for Lead Apatite Mineral Biotransformations

PubMed Central

Ceci, Andrea; Kierans, Martin; Hillier, Stephen; Persiani, Anna Maria

2015-01-01

Fungi play important roles in biogeochemical processes such as organic matter decomposition, bioweathering of minerals and rocks, and metal transformations and therefore influence elemental cycles for essential and potentially toxic elements, e.g., P, S, Pb, and As. Arsenic is a potentially toxic metalloid for most organisms and naturally occurs in trace quantities in soil, rocks, water, air, and living organisms. Among more than 300 arsenic minerals occurring in nature, mimetite [Pb5(AsO4)3Cl] is the most stable lead arsenate and holds considerable promise in metal stabilization for in situ and ex situ sequestration and remediation through precipitation, as do other insoluble lead apatites, such as pyromorphite [Pb5(PO4)3Cl] and vanadinite [Pb5(VO4)3Cl]. Despite the insolubility of mimetite, the organic acid-producing soil fungus Aspergillus niger was able to solubilize mimetite with simultaneous precipitation of lead oxalate as a new mycogenic biomineral. Since fungal biotransformation of both pyromorphite and vanadinite has been previously documented, a new biogeochemical model for the biogenic transformation of lead apatites (mimetite, pyromorphite, and vanadinite) by fungi is hypothesized in this study by application of geochemical modeling together with experimental data. The models closely agreed with experimental data and provided accurate simulation of As and Pb complexation and biomineral formation dependent on, e.g., pH, cation-anion composition, and concentration. A general pattern for fungal biotransformation of lead apatite minerals is proposed, proving new understanding of ecological implications of the biogeochemical cycling of component elements as well as industrial applications in metal stabilization, bioremediation, and biorecovery. PMID:25979898

An optimized chronology for a stalagmite using seasonal trace element cycles from Shihua Cave, Beijing, North China

NASA Astrophysics Data System (ADS)

Ban, F.; Baker, A.; Marjo, C.; Duan, W.; Li, X.; Coleborn, K.; Akter, R.; Nagra, G.

2017-12-01

Stalagmites play an increasingly important role in the paleoclimatic reconstruction from seasonal to orbital timescales. One of the important reasons is that 230Th-dating can provide an absolute age enabling more accurate knowledge of the stalagmite growth. Additionally, annual trace element and optical layers can provide complementary method for determining a precise age and seasonal resolution. The trace elements of a stalagmite (XMG) in Beijing Shihua Cave, which is located in the East Asian monsoon region, were analyzed by laser ablation ICP-MS and compared with stalagmite laminae. The results show that: (1) the polished section of the topmost 4 mm of stalagmite XMG has obvious bi-optical layers (fluorescence and visible light) under a conventional transmission microscope. In the rest of the sample laminae are not observed using this method. (2) The variations of P/Ca, Sr/Ca, Ba/Ca, U/Ca and Mg/Ca show seasonal cycles throughout the sample. Sr/Ca is inversely correlated to P/Ca, and its peaks correspond with the (non-fluorescing) white layers, which deposit in late winter and spring when the climate is dry. The peaks of P/Ca match closely with the (fluorescing) opaque layers, because P is a soil-derived element which increases in the high rainfall monsoon period. (3) The PCA of the five trace elements showed that the cycles of PC1 could represent the annual cycle. This stalagmite was deposited over 148 ± 4 years through peak counting and the cycles of PC1 correspond well with the annual layers. Trace element cyclicity as shown by PC1 can increase the accuracy of stalagmite dating, especially in the absence of obvious laminae. The trace elements can be used as the marker of seasonal changes in a strongly contrasting wet-dry monsoon climate regime. Keywords: high-precision dating; LA-ICP-MS; stalagmite; trace elements; seasonal cycles; Shihua Cave

Carbon-Coated Na3.32 Fe2.34 (P2 O7 )2 Cathode Material for High-Rate and Long-Life Sodium-Ion Batteries.

PubMed

Chen, Mingzhe; Chen, Lingna; Hu, Zhe; Liu, Qiannan; Zhang, Binwei; Hu, Yuxiang; Gu, Qinfen; Wang, Jian-Li; Wang, Lian-Zhou; Guo, Xiaodong; Chou, Shu-Lei; Dou, Shi-Xue

2017-06-01

Rechargeable sodium-ion batteries are proposed as the most appropriate alternative to lithium batteries due to the fast consumption of the limited lithium resources. Due to their improved safety, polyanion framework compounds have recently gained attention as potential candidates. With the earth-abundant element Fe being the redox center, the uniform carbon-coated Na 3.32 Fe 2.34 (P 2 O 7 ) 2 /C composite represents a promising alternative for sodium-ion batteries. The electrochemical results show that the as-prepared Na 3.32 Fe 2.34 (P 2 O 7 ) 2 /C composite can deliver capacity of ≈100 mA h g -1 at 0.1 C (1 C = 120 mA g -1 ), with capacity retention of 92.3% at 0.5 C after 300 cycles. After adding fluoroethylene carbonate additive to the electrolyte, 89.6% of the initial capacity is maintained, even after 1100 cycles at 5 C. The electrochemical mechanism is systematically investigated via both in situ synchrotron X-ray diffraction and density functional theory calculations. The results show that the sodiation and desodiation are single-phase-transition processes with two 1D sodium paths, which facilitates fast ionic diffusion. A small volume change, nearly 100% first-cycle Coulombic efficiency, and a pseudocapacitance contribution are also demonstrated. This research indicates that this new compound could be a potential competitor for other iron-based cathode electrodes for application in large-scale Na rechargeable batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemostratigraphy and evolution of the Paraná Igneous Province volcanism in the central portion of the state of Paraná, Southern Brazil

NASA Astrophysics Data System (ADS)

Gomes, Allan Silva; Licht, Otavio Augusto Boni; Vasconcellos, Eleonora Maria Gouvêa; Soares, Jan Savaris

2018-04-01

Analysis of borehole samples offers the potential to investigate the chemostratigraphic variations of a large igneous province in subsurface. New geochemical data based on multielement analyses of 829 chip samples that were obtained during the drilling of seven deep boreholes is presented for the central area of the Paraná Igneous Province (PIP). In order to detail the compositional variations found within the two main types from the Central-Northern Subprovince (CNSP), simple statistical treatment was carried out for part this database. Thus, the combination of low (L) and high (H) contents of Th, Nb, La and Yb was used as a means to create 16 geochemical subtypes for the Type 4 (LSi-LZr-HTi-HP) sequence. Likewise, other four elements (Cr, Ni, Cu and Pd) were selected with the same intention for the Type 1 (Central-Northern) (LSi-LZr-LTi-LP) sequence. When subtypes are plotted in the cross section, it is possible to observe that those with similar characteristics tend to be associated in groups (cycles). This analysis showed that the volcanic pile can be divided into at least eleven different cycles and also that they are laterally continuous throughout the section. The compositional changes observed in these volcanic cycles also display correlations with Mg#, Zr, Ti/Y and La/SmN ratios, for example. Therefore, since the reservoir is marked by periods of injection of more differentiated or more mafic magmas, it could be suggested that it was periodically recharged with batches of magma from the parental source.

Microbiome succession during ammonification in eelgrass bed sediments.

PubMed

Ettinger, Cassandra L; Williams, Susan L; Abbott, Jessica M; Stachowicz, John J; Eisen, Jonathan A

2017-01-01

Eelgrass ( Zostera marina ) is a marine angiosperm and foundation species that plays an important ecological role in primary production, food web support, and elemental cycling in coastal ecosystems. As with other plants, the microbial communities living in, on, and near eelgrass are thought to be intimately connected to the ecology and biology of eelgrass. Here we characterized the microbial communities in eelgrass sediments throughout an experiment to quantify the rate of ammonification, the first step in early remineralization of organic matter, also known as diagenesis, from plots at a field site in Bodega Bay, CA. Sediment was collected from 72 plots from a 15 month long field experiment in which eelgrass genotypic richness and relatedness were manipulated. In the laboratory, we placed sediment samples ( n  = 4 per plot) under a N 2 atmosphere, incubated them at in situ temperatures (15 °C) and sampled them initially and after 4, 7, 13, and 19 days to determine the ammonification rate. Comparative microbiome analysis using high throughput sequencing of 16S rRNA genes was performed on sediment samples taken initially and at seven, 13 and 19 days to characterize changes in the relative abundances of microbial taxa throughout ammonification. Within-sample diversity of the sediment microbial communities across all plots decreased after the initial timepoint using both richness based (observed number of OTUs, Chao1) and richness and evenness based diversity metrics (Shannon, Inverse Simpson). Additionally, microbial community composition changed across the different timepoints. Many of the observed changes in relative abundance of taxonomic groups between timepoints appeared driven by sulfur cycling with observed decreases in predicted sulfur reducers ( Desulfobacterales ) and corresponding increases in predicted sulfide oxidizers ( Thiotrichales ). None of these changes in composition or richness were associated with variation in ammonification rates. Our results showed that the microbiome of sediment from different plots followed similar successional patterns, which we infer to be due to changes related to sulfur metabolism. These large changes likely overwhelmed any potential changes in sediment microbiome related to ammonification rate. We found no relationship between eelgrass presence or genetic composition and the microbiome. This was likely due to our sampling of bulk sediments to measure ammonification rates rather than sampling microbes in sediment directly in contact with the plants and suggests that eelgrass influence on the sediment microbiome may be limited in spatial extent. More in-depth functional studies associated with eelgrass microbiome will be required in order to fully understand the implications of these microbial communities in broader host-plant and ecosystem functions (e.g., elemental cycling and eelgrass-microbe interactions).

Binding of Cd by ferrihydrite organo-mineral composites: Implications for Cd mobility and fate in natural and contaminated environments.

PubMed

Du, Huihui; Peacock, Caroline L; Chen, Wenli; Huang, Qiaoyun

2018-09-01

Adsorption and coprecipitation of organic matter with iron (hydr)oxides can alter iron (hydr)oxide surface properties and their reactivity towards nutrient elements and heavy metals. Organo-mineral composites were synthesized using humic acid (HA) and iron oxide, during coprecipitation with ferrihydrite (Fh) and adsorption to pre-formed Fh with two C loadings. The Fh-HA coprecipitated composites have a higher C content and smaller surface area compared to the equivalent adsorbed composites. NanoSIMS shows there is a high degree of spatial correlation between Fe and C for both composites, but C distribution is more uniform in the coprecipitated composites. The C 1s NEXAFS reveals a similar C composition between the Fh-HA coprecipitated and adsorbed composites. However composites at high carbon loading are more enriched in aromatic C, likely due to preferential binding of carboxyl functional groups on aromatic rings in the HA. The amount of Cd sorbed is independent of the composite type, either coprecipitated or adsorbed, but is a function of the C loading. Composites with low C loading show Cd sorption that is almost identical to pure Fh, while composites with high C loading show Cd sorption that is intermediate between pure Fh and pure HA, with sorption significantly enhanced over pure Fh at pH < 6.5. A bidentate edge-sharing binding was identified for Cd on pure Fh and Cd-carboxyl binding on pure HA. These findings have significant implications not only for the sequestration of Cd in contaminated environments but also the coupled biogeochemical cycling of Cd, Fe and C in the critical zone. Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.

Igneous fractionation and subsolidus equilibration of diogenite meteorites

NASA Technical Reports Server (NTRS)

Mittlefehldt, David W.

1993-01-01

Diogenites are coarse-grained orthopyroxenite breccias of remarkably uniform major element composition. Most diogenites contain homogeneous pyroxene fragments up to 5 cm across of Wo2En74Fs24 composition. Common minor constituents are chromite, olivine, trolite and metal, while silica, plagioclase, merrillite and diopside are trace phases. Diogenites are generally believed to be cumulates from the eucrite parent body, although their relationship with eucrites remains obscure. It has been suggested that some diogenites are residues after partial melting. I have performed EMPA and INAA for major, minor and trace elements on most diogenites, concentrating on coarse-grained mineral and lithic clasts in order to elucidate their igneous formation and subsequent metamorphic history. Major element compositions of diogenites are decoupled from minor and trace element compositions; the latter record an igneous fractionation sequence that is not preserved in the former. Low equilibration temperatures indicate that major element diffusion continued long after crystallization. Diffusion coefficients for trivalent and tetravalent elements in pyroxene are lower than those of divalent elements. Therefore, major element compositions of diogenites may represent means of unknown portions of a cumulate homogenized by diffusion, while minor and trace elements still yield information on their igneous history. The scale of major element equilibration is unknown, but is likely to be on the order of a few cm. Therefore, the diogenite precursors may have consisted largely of cm-sized, igneously zoned orthopyroxene grains, which were subsequently annealed during slow cooling, obliterating major element zoning but preserving minor and trace incompatible element zoning.

Compositional classification and sedimentological interpretation of the laminated lacustrine sediments at Baumkrichen (Western Austria) using XRF core scanning data

NASA Astrophysics Data System (ADS)

Barrett, Samuel; Tjallingii, Rik; Bloemsma, Menno; Brauer, Achim; Starnberger, Reinhard; Spötl, Christoph; Dulski, Peter

2015-04-01

The outcrop at Baumkirchen (Austria) encloses part of a unique sequence of laminated lacustrine sediments deposited during the last glacial cycle. A ~250m long composite sediment record recovered at this location now continuously covers the periods ~33 to ~45 ka BP (MIS 3) and ~59 to ~73 ka BP (MIS 4), which are separated by a hiatus. The well-laminated (mm-cm scale) and almost entirely clastic sediments reveal alternations of clayey silt and medium silt to very-fine sand layers. Although radiocarbon and optically stimulated luminescence (OSL) dating provide a robust chronology, accurate dating of the sediment laminations appears to be problematic due to very high sedimentation rates (3-8 cm/yr). X-ray fluorescence (XRF) core scanning provided a detailed ~150m long record of compositional changes of the sediments at Baumkirchen. Changes in the sediments are subtle and classification into different facies based on individual elements is therefore subjective. We applied a statistically robust clustering analysis to provide an objective compositional classification without prior knowledge, based on XRF measurements for 15 analysed elements (all those with an acceptable signal-noise ratio: Zr, Sr, Ca, Mn, Cu, Zn, Rb, Ni, Fe, K, Cr, V, Si, Ba, T). The clustering analysis indicates a distinct compositional change between sediments deposited below and above the stratigraphic hiatus, but also differentiates between individual different laminae. Preliminary results suggest variations in the sequence are largely controlled by the relative occurrence of different kinds of sediment represented by different clusters. Three clusters identify well-laminated sediments, visually similar in appearance, each dominated by an anti-correlation between Ca and one or more of the detrital elements K, Zr, Ti, Si and Fe. Two of these clusters occur throughout the entire sequence, one frequently and the other restricted to short sections, while the third occurs almost exclusively below the hiatus, indicating a geochemically distinct component that possibly represents a specific sediment source. In a similar manner, three other clusters identify event layers with different compositions of which two occur exclusively above the hiatus and one exclusively below. The variations in the occurrence of these clusters revealing distinct event layers suggest variations in dominant sediment source both above and below the hiatus and within the section above it. More detailed comparisons between compositional variations of the individual clusters obtained from biplots and microscopic observations on thin sections, grain-size analyses, and mineralogical analyses are needed to further differentiate between sediment sources and transport mechanisms.

Ultrathin dendrimer-graphene oxide composite film for stable cycling lithium-sulfur batteries.

PubMed

Liu, Wen; Jiang, Jianbing; Yang, Ke R; Mi, Yingying; Kumaravadivel, Piranavan; Zhong, Yiren; Fan, Qi; Weng, Zhe; Wu, Zishan; Cha, Judy J; Zhou, Henghui; Batista, Victor S; Brudvig, Gary W; Wang, Hailiang

2017-04-04

Lithium-sulfur batteries (Li-S batteries) have attracted intense interest because of their high specific capacity and low cost, although they are still hindered by severe capacity loss upon cycling caused by the soluble lithium polysulfide intermediates. Although many structure innovations at the material and device levels have been explored for the ultimate goal of realizing long cycle life of Li-S batteries, it remains a major challenge to achieve stable cycling while avoiding energy and power density compromises caused by the introduction of significant dead weight/volume and increased electrochemical resistance. Here we introduce an ultrathin composite film consisting of naphthalimide-functionalized poly(amidoamine) dendrimers and graphene oxide nanosheets as a cycling stabilizer. Combining the dendrimer structure that can confine polysulfide intermediates chemically and physically together with the graphene oxide that renders the film robust and thin (<1% of the thickness of the active sulfur layer), the composite film is designed to enable stable cycling of sulfur cathodes without compromising the energy and power densities. Our sulfur electrodes coated with the composite film exhibit very good cycling stability, together with high sulfur content, large areal capacity, and improved power rate.

Fire Frequency and Vegetation Composition Influence Soil Nitrogen Cycling and Base Cations in an Oak Savanna Ecosystem

NASA Astrophysics Data System (ADS)

McLauchlan, K. K.; Nelson, D. M.; Perakis, S.; Marcotte, A. L.

2017-12-01

Fire frequency is crucial for maintaining savannas in the transition between forests and grasslands. In general, increasing fire frequency has two effects: it increases herbaceous plant cover more than woody plant cover, and it lowers soil organic matter stocks. These effects have been demonstrated at a long-term prescribed fire experiment in an oak savanna ecosystem at Cedar Creek Ecosystem Science Reserve, Minnesota, U.S.A. The fire experiment began in 1964 and oak savannas are burned at various frequencies ranging from every year to not at all. This has led to changes in vegetation ranging from almost 100% grassland to 100% oak forest. Additionally, nitrogen stocks almost doubled in the sites that were not burned, as it accumulated in the trees, leaf litter, and soil. We addressed additional soil changes taking place at this experiment by asking the question: How have fire and oak-grass balance affected soil nutrients, specifically nitrogen and base cations? Surface soils were collected from 12 plots on the oak savanna burn experiment. Soils were collected in increments to 100 cm depth, from under grass-dominated vegetation and from under tree-dominated vegetation. We non-destructively estimated soil base cations by measuring elemental concentrations of dried soil subsamples with a handheld x-ray fluorescence analyzer. We also measured carbon and nitrogen concentrations and isotopic composition of the soil samples. Soils in plots with high fire frequency had higher concentrations of calcium than soils in unburned plots (low fire frequency). Similar trends were seen for soil potassium, magnesium, and phosphorus concentrations. In contrast, soils in plots with high fire frequency had dramatically lowered nitrogen cycling rates and stocks across the oak savanna. The contrast between the responses of different nutrients to changing fire frequency has important implications for the consequences of fire and tree-grass composition on nutrient cycling dynamics.

Influence of particle composition on thorium cycling along the U.S. GEOTRACES North Atlantic Section

NASA Astrophysics Data System (ADS)

Lerner, Paul; Marchal, Olivier; Lam, Phoebe

2017-04-01

Our current knowledge about the behaviour of particle-reactive substances in the ocean stems largely from measurements of thorium radio-isotopes (Th-228, Th-230, Th-234) on seawater samples. The oceanic Th database has increased dramatically over the recent years, thanks in particular to the GEOTRACES program, an international study of the marine biogeochemical cycles of trace elements and their isotopes. Here we present an analysis of data collected at several stations of the U.S. GEOTRACES North Atlantic section (section GA03). Data originating from eleven stations situated west and east of the Middle-Atlantic Ridge are analyzed. First, at each station, the rate parameters of a single-particle class model of Th and particle cycling in the ocean water column are estimated from a least-squares fit to an eclectic data set, including (i) measurements of Th-228, Th-230, Th-234 activities in different size fractions, (ii) measurements of particle concentration, and (iii) measurements, or observational estimates, of the activities of the radio-active parents Ra-228, U-234, and U-238. Among our most salient results is a significant decrease in the apparent rate constant of Th adsorption (k1) with depth, with maxima in the meso-pelagic zone (ca. 100 - 1000 m) and minima below, at most stations. Second, we explore whether our k1 estimates can be related to changes in particle composition, both along the water column and laterally along GA03. We apply (i) multiple linear regression to quantify the amount of variance in k1 that can be explained by linear regression against particle composition data, and (ii) relative importance analysis to determine the relative contribution of different particulate phases to the explained variance in k1. Finally, the implications of our results for the interpretation of field Th isotope data and for the description of particle scavenging in ocean-biogeochemistry models are clarified.

Effects of drying-wetting and freezing-thawing cycle on leachability of metallic elements in mine soils

NASA Astrophysics Data System (ADS)

Bang, H.; Kim, J.; Hyun, S.

2016-12-01

Mine leachate derived from contaminated mine sites with metallic elements can pose serious risks on human society and environment. Only labile fraction of metallic elements in mine soils is subject to leaching and movement by rainfall. Lability of metallic element in soil is a function of bond strengths between metal and soil surfaces, which is influenced by environmental condition (e.g., rainfall intensity, duration, temperature, etc.) The purpose of this study was to elucidate the effects of various climate conditions on the leaching patterns and lability of metallic elements in mine soils. To do this, two mine soils were sampled from two abandoned mine sites located in Korea. Leaching test were conducted using batch decant-refill method. Various climatic conditions were employed in leaching test such as (1) oven drying (40oC) - wetting cycles, (2) air drying (20oC) - wetting cycle, and (3) freezing (-40oC) - thawing cycles. Duration of drying and freezing were varied from 4 days to 2 weeks. Concentration of metallic elements, pH, Eh and concentration of dissolved iron and sulfate in leachate from each leaching process was measured. To identify the changes of labile fraction in mine soils after each of drying or freezing period, sequential extraction procedure (five fraction) was used to compare labile fraction (i.e., F1 + F2) of metallic elements. The concentration of metallic elements in mine leachate was increased after drying and freezing procedure. The amounts of released metallic element from mine soils was changed depending on their drying or freezing period. In addition, labile fraction of metallic elements in soil was also changed after drying and freezing. The changes in labile fraction after drying and freezing might be due to the increased soil surface area by pore water volume expansion. Further study is therefore needed to evaluate the impact of altered physical properties of soils such as hydration of soil surface area and shrinking by drying and freezing cycles.

Optimal cure cycle design of a resin-fiber composite laminate

NASA Technical Reports Server (NTRS)

Hou, Jean W.; Hou, Tan H.; Sheen, Jeen S.

1987-01-01

Fibers reinforced composites are used in many applications. The composite parts and structures are often manufactured by curing the prepreg or unmolded material. The magnitudes and durations of the cure temperature and the cure pressure applied during the cure process have significant consequences on the performance of the finished product. The goal of this study is to exploit the potential of applying the optimization technique to the cure cycle design. The press molding process of a polyester is used as an example. Various optimization formulations for the cure cycle design are investigated. Recommendations are given for further research in computerizing the cure cycle design.

Enhanced capacitance and rate capability of graphene/polypyrrole composite as electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Zhang, Dacheng; Zhang, Xiong; Chen, Yao; Yu, Peng; Wang, Changhui; Ma, Yanwei

Graphene and polypyrrole composite (PPy/GNS) is synthesized via in situ polymerization of pyrrole monomer in the presence of graphene under acid conditions. The structure and morphology of the composite are characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectrometer (FTIR), X-rays photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). It is found that a uniform composite is formed with polypyrrole being homogeneously surrounded by graphene nanosheets (GNS). The composite is a promising candidate for supercapacitors to have higher specific capacitance, better rate capability and cycling stability than those of pure polypyrrole. The specific capacitance of PPy/GNS composite based on the three-electrode cell configuration is as high as 482 F g -1 at a current density of 0.5 A g -1. After 1000 cycles, the attenuation of the specific capacitance is less than 5%, indicating that composite has excellent cycling performance.

Conducting Polymer Coated Graphene Oxide Electrode for Rechargeable Lithium-Sulfur Batteries.

PubMed

Lee, Hee-Yoon; Jung, Yongju; Kim, Seok

2016-03-01

Poly(diallyldimethylammonium chloride) (PDDA)/graphene oxide-sulfur composites were prepared by a chemical oxidation method. For the PDDA-GO composites, conducting polymers (PDDA) were coated on the surface of GO sheets. PDDA-GO composites could be expected to increase electrical conductivity and protect restacking of graphene sheets. And then, sulfur particles were dispersed into the PDDA-GO composites by mixing in the CS2 solvent. It is expected the PDDA-GO/S composites show the limited release of polysulfides due to the fact that it can provide high surface area, because conducting polymer can be used as spacer between graphene sheets. Electrochemical performances of prepared composites were characterized by cyclic voltammetry (CV). The PDDA-GO/S composites showed a high discharge capacity of 1102 mAh g(-1) at the first cycle and a good cycle retention of 60% after 100 cycles.

Simulations of carbon fiber composite delamination tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kay, G

2007-10-25

Simulations of mode I interlaminar fracture toughness tests of a carbon-reinforced composite material (BMS 8-212) were conducted with LSDYNA. The fracture toughness tests were performed by U.C. Berkeley. The simulations were performed to investigate the validity and practicality of employing decohesive elements to represent interlaminar bond failures that are prevalent in carbon-fiber composite structure penetration events. The simulations employed a decohesive element formulation that was verified on a simple two element model before being employed to perform the full model simulations. Care was required during the simulations to ensure that the explicit time integration of LSDYNA duplicate the near steady-statemore » testing conditions. In general, this study validated the use of employing decohesive elements to represent the interlaminar bond failures seen in carbon-fiber composite structures, but the practicality of employing the elements to represent the bond failures seen in carbon-fiber composite structures during penetration events was not established.« less

Synthesis and characterization of sulfur–carbon–vanadium pentoxide composites for improved electrochemical properties of lithium–sulfur batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kong, Long; Handa, Yusuke; Taniguchi, Izumi, E-mail: taniguchi.i.aa@m.titech.ac.jp

2016-01-15

Highlights: • A wet ball milling was conducted to synthesis S–C–V{sub 2}O{sub 5} composite electrode. • V{sub 2}O{sub 5} additive led to further improve electrochemical performance of S-cathode. • S–C–V{sub 2}O{sub 5} composite electrode exhibited a first discharge capacity of 951 mAh g{sup −1}. • The electrode (60 wt.%—S, 30 wt.%—V{sub 2}O{sub 5}, 10 wt.%—C) showed best battery performance. - Abstract: Sulfur (S)–carbon (C)–vanadium pentoxide (V{sub 2}O{sub 5}) composites were prepared by wet ball milling, and their physical and electrochemical properties were evaluated. Firstly, the effect of the carbon content of S–C composite electrodes on their physical and electrochemical propertiesmore » was investigated. The S–C composite electrode with 60 wt.% S delivers a first discharge capacity of 1077 mAh g{sup −1}. However, its capacity markedly decreases to 606 mAh g{sup −1} after 10 cycles, which corresponds to a capacity fading rate of 47 mAh g{sup −1} per cycle. To improve the electrochemical performance of the S–C composite electrode, carbon was partially replaced by V{sub 2}O{sub 5}. The S–C–V{sub 2}O{sub 5} composite electrode with a composition of 60 wt.%—S, 30 wt.%—V{sub 2}O{sub 5} and 10 wt.%—C exhibits a lower capacity fading rate of 23 mAh g{sup −1} per cycle in the first 10 cycles and better capacity retention than the S–C composite electrode over 50 cycles.« less

Trace element and major ion composition of wet and dry depositon in Ankara, Turkey

NASA Astrophysics Data System (ADS)

Kaya, Güven; Tuncel, Gürdal

Daily, wet-only precipitation samples collected over a two year period were analyzed for SO 42-, NO 3-, Cl -, NH 4+, H +, Ca, Mg, K, Na, Al, Cu, Cd, Cr, Zn, V and Ni. Weekly dry-deposition samples collected on petri-dishes over the same period were analyzed only for major ions. Concentrations of ions and elements in Ankara precipitation are comparable with concentrations reported in literature for other urban areas. However, the wet deposition fluxes are the lowest among literature values, owing to small annual precipitation in the region. Although, annual average pH in precipitation is 4.7, episodic rain events with fairly low pH's were observed. Approximately half of the acidity in Ankara precipitation is neutralized in the winter season, while the acidity is completely neutralized by airborne soil particles that are rich in CaCO 3 in the summer precipitation. The SO 42- and NO 3- contributes approximately equally on the free acidity in winter. Main forms of SO 42- and NO 3- in precipitation are CaSO 4 and Ca(NO 3) 2, respectively. Crustal elements and ions have higher concentrations during summer season, while anthropogenic ions and elements did not show well-defined seasonal cycles. The lack of industrial activity in Ankara has profound influence on the temporal behavior of elements and ions.

Experimental evaluation of thermal ratcheting behavior in UO2 fuel elements

NASA Technical Reports Server (NTRS)

Phillips, W. M.

1973-01-01

The effects of thermal cycling of UO2 at high temperatures has been experimentally evaluated to determine the rates of distortion of UO2/clad fuel elements. Two capsules were rested in the 1500 C range, one with a 50 C thermal cycle, the other with a 100 C thermal cycle. It was observed that eight hours at the lower cycle temperature produced sufficient UO2 redistribution to cause clad distortion. The amount of distortion produced by the 100 C cycle was less than double that produced by the 50 C, indicating smaller thermal cycles would result in clad distortion. An incubation period was observed to occur before the onset of distortion with cycling similar to fuel swelling observed in-pile at these temperatures.

Mechanical ball-milling preparation of fullerene/cobalt core/shell nanocomposites with high electrochemical hydrogen storage ability.

PubMed

Bao, Di; Gao, Peng; Shen, Xiande; Chang, Cheng; Wang, Longqiang; Wang, Ying; Chen, Yujin; Zhou, Xiaoming; Sun, Shuchao; Li, Guobao; Yang, Piaoping

2014-02-26

The design and synthesis of new hydrogen storage nanomaterials with high capacity at low cost is extremely desirable but remains challenging for today's development of hydrogen economy. Because of the special honeycomb structures and excellent physical and chemical characters, fullerenes have been extensively considered as ideal materials for hydrogen storage materials. To take the most advantage of its distinctive symmetrical carbon cage structure, we have uniformly coated C60's surface with metal cobalt in nanoscale to form a core/shell structure through a simple ball-milling process in this work. The X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectra, high-solution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrometry (EDX) elemental mappings, and X-ray photoelectron spectroscopy (XPS) measurements have been conducted to evaluate the size and the composition of the composites. In addition, the blue shift of C60 pentagonal pinch mode demonstrates the formation of Co-C chemical bond, and which enhances the stability of the as-obtained nanocomposites. And their electrochemical experimental results demonstrate that the as-obtained C60/Co composites have excellent electrochemical hydrogen storage cycle reversibility and considerably high hydrogen storage capacities of 907 mAh/g (3.32 wt % hydrogen) under room temperature and ambient pressure, which is very close to the theoretical hydrogen storage capacities of individual metal Co (3.33 wt % hydrogen). Furthermore, their hydrogen storage processes and the mechanism have also been investigated, in which the quasi-reversible C60/Co↔C60/Co-Hx reaction is the dominant cycle process.

Molecular Insights on Dissolved Organic Matter Transformation by Supraglacial Microbial Communities.

PubMed

Antony, Runa; Willoughby, Amanda S; Grannas, Amanda M; Catanzano, Victoria; Sleighter, Rachel L; Thamban, Meloth; Hatcher, Patrick G; Nair, Shanta

2017-04-18

Snow overlays the majority of Antarctica and is an important repository of dissolved organic matter (DOM). DOM transformations by supraglacial microbes are not well understood. We use ultrahigh resolution mass spectrometry to elucidate molecular changes in snowpack DOM by in situ microbial processes (up to 55 days) in a coastal Antarctic site. Both autochthonous and allochthonous DOM is highly bioavailable and is transformed by resident microbial communities through parallel processes of degradation and synthesis. DOM thought to be of a more refractory nature, such as dissolved black carbon and carboxylic-rich alicyclic molecules, was also rapidly and extensively reworked. Microbially reworked DOM exhibits an increase in the number and magnitude of N-, S-, and P-containing formulas, is less oxygenated, and more aromatic when compared to the initial DOM. Shifts in the heteroatom composition suggest that microbial processes may be important in the cycling of not only C, but other elements such as N, S, and P. Microbial reworking also produces photoreactive compounds, with potential implications for DOM photochemistry. Refined measurements of supraglacial DOM and their cycling by microbes is critical for improving our understanding of supraglacial DOM cycling and the biogeochemical and ecological impacts of DOM export to downstream environments.

An Investigation of Black Carbon Degradation Potential in a Forest Soil Environment

NASA Astrophysics Data System (ADS)

William, H. C.; Lee, E.; Grannas, A.; Hatcher, P. G.

2003-12-01

Except for emission processes, there is currently little understanding of the mechanisms driving the degradation and biogeochemical cycling of black carbon (BC). Considering current estimates of the global BC pool (>2,500x1015gC), and its annual emission rates (55-205x1012 gC/year), BC represents roughly 16% of Earth's actively cycling organic carbon. Without significant chemical and biological degradation pathways, all of the actively cycling carbon on earth would have accumulated as charcoal in <100,000 years. This investigation show that charcoals recovered from experimental forest fires are altered significantly by microbial colonization, and mineral complexation during exposure to soil processes. Charcoal surface morphology and elemental composition were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and BET surface area measurements. The influence of 90 years aging upon carbon functionality was probed by solid-state 13C NMR spectroscopy. The prevalence of fungal mycorhizae in these forest soil charcoals also motivated an investigation of black carbon degradation via extracellular enzymes and acids known be exuded by mycelia. Degradation is quantified by carbon loss, and soluble products are examined by mass spectrometry.

Nitrogen cycling in an extreme hyperarid environment inferred from δ(15)N analyses of plants, soils and herbivore diet.

PubMed

Díaz, Francisca P; Frugone, Matías; Gutiérrez, Rodrigo A; Latorre, Claudio

2016-03-09

Climate controls on the nitrogen cycle are suggested by the negative correlation between precipitation and δ(15)N values across different ecosystems. For arid ecosystems this is unclear, as water limitation among other factors can confound this relationship. We measured herbivore feces, foliar and soil δ(15)N and δ(13)C values and chemically characterized soils (pH and elemental composition) along an elevational/climatic gradient in the Atacama Desert, northern Chile. Although very positive δ(15)N values span the entire gradient, soil δ(15)N values show a positive correlation with aridity as expected. In contrast, foliar δ(15)N values and herbivore feces show a hump-shaped relationship with elevation, suggesting that plants are using a different N source, possibly of biotic origin. Thus at the extreme limits of plant life, biotic interactions may be just as important as abiotic processes, such as climate in explaining ecosystem δ(15)N values.

The ecological impact of membrane-based extraction of phenolic compounds--a life cycle assessment study.

PubMed

Bayer, C; Follmann, M; Melin, T; Wintgens, T; Larsson, K; Almemark, M

2010-01-01

Many phenolic compounds show high boiling points, low molecular weights, moderate polarities or high toxicities. Therefore, conventional wastewater treatment is limited or expensive. Recycling of the separated compounds is often not possible. But, if liquid-liquid reactive extraction is linked to a non-porous membrane, some or all of the above mentioned limitations may be overcome. The key element is a composite membrane with a dense, hydrophobic top layer which avoids the mixing of the two aqueous fluid streams. The dilute phenol stream is one of them, the other is caustic soda as stripping solvent. Since the basics of this technology have been discussed before, the scope of this study is to facilitate process implementation and integration. To this end, a life cycle assessment framework is used to identify the optimal equipment size for the treatment of wastewater that may, for example, originate from the production of polycarbonate. Limiting for this application is not the environmental performance though, but most likely process economics.

Effect of Nickel Coated Multi-Walled Carbon Nanotubes on Electrochemical Performance of Lithium-Sulfur Rechargeable Batteries.

PubMed

Wu, Xiao; Yao, Shanshan; Hou, Jinli; Jing, Maoxiang; Qian, Xinye; Shen, Xiangqian; Xiang, Jun; Xi, Xiaoming

2017-04-01

Conventional lithium-sulfur batteries suffer from severe capacity fade, which is induced by low electron conductivity and high dissolution of intermediated polysulfides. Recent studies have shown the metal (Pt, Au, Ni) as electrocatalyst of lithium polysulfides and improved the performance for lithium sulfur batteries. In this work, we present the nickel coated multi-walled carbon nanotubes (Ni-MWNTs) as additive materials for elemental sulfur positive electrodes for lithium-sulfur rechargeable batteries. Compared with MWNTs, the obtained Ni-MWNTs/sulfur composite cathode demonstrate a reversible specific capacity approaching 545 mAh after 200 cycles at a rate of 0.5C as well as improved cycling stability and excellent rate capacity. The improved electrochemical performance can be attributed to the fact the MWNTs shows a vital role on polysulfides adsorption and nickel has a catalytic effect on the redox reactions during charge–discharge process. Meanwhile, the Ni-MWNTs is a good electric conductor for sulfur cathode.

Electrolytic conditioning of a magnesium aluminum chloride complex for reversible magnesium deposition

DOE PAGES

Barile, Christopher J.; Barile, Elizabeth C.; Zavadil, Kevin R.; ...

2014-12-04

We describe in this report the electrochemistry of Mg deposition and dissolution from the magnesium aluminum chloride complex (MACC). The results define the requirements for reversible Mg deposition and definitively establish that voltammetric cycling of the electrolyte significantly alters its composition and performance. Elemental analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDS) results demonstrate that irreversible Mg and Al deposits form during early cycles. Electrospray ionization-mass spectrometry (ESI-MS) data show that inhibitory oligomers develop in THF-based solutions. These oligomers form via the well-established mechanism of a cationic ring-opening polymerization of THF during the initial synthesis of the MACC andmore » under resting conditions. In contrast, MACC solutions in 1,2-dimethoxyethane (DME), an acyclic solvent, do not evolve as dramatically at open circuit potential. Furthermore, we propose a mechanism describing how the conditioning process of the MACC in THF improves its performance by both tuning the Mg:Al stoichiometry and eliminating oligomers.« less

Enhancement of anticorrosion property of 304 stainless steel using silane coatings

NASA Astrophysics Data System (ADS)

Akhtar, Sultan; Matin, Asif; Madhan Kumar, A.; Ibrahim, Ahmed; Laoui, Tahar

2018-05-01

In the present work, silane coatings based on glycidoxypropyltrimethoxysilane/methyltrimethoxysilane (GPTMS/MTMS) and silica nanoparticles were prepared by a sol-gel method. A simple dip-coating method was applied for film deposition and the effect of immersion time and number of immersion cycles on corrosion behavior of 304 stainless steel (SS) was investigated. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS) was used to study the surface morphology and elemental composition of the modified surfaces. The corrosion behavior of the coated and uncoated SS substrates was studied by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.6 M sodium chloride solution. Our results showed that the presence of coatings improved the anti-corrosion property of SS substrates. The coating with a dipping time of 10 min and 3 dipping cycles exhibited the best protection efficiency compared to other coatings and the uncoated substrate. SEM/EDS findings and contact angle measurements supported the conclusions drawn from the corrosion study.

Nitrogen cycling in an extreme hyperarid environment inferred from δ15N analyses of plants, soils and herbivore diet

NASA Astrophysics Data System (ADS)

Díaz, Francisca P.; Frugone, Matías; Gutiérrez, Rodrigo A.; Latorre, Claudio

2016-03-01

Climate controls on the nitrogen cycle are suggested by the negative correlation between precipitation and δ15N values across different ecosystems. For arid ecosystems this is unclear, as water limitation among other factors can confound this relationship. We measured herbivore feces, foliar and soil δ15N and δ13C values and chemically characterized soils (pH and elemental composition) along an elevational/climatic gradient in the Atacama Desert, northern Chile. Although very positive δ15N values span the entire gradient, soil δ15N values show a positive correlation with aridity as expected. In contrast, foliar δ15N values and herbivore feces show a hump-shaped relationship with elevation, suggesting that plants are using a different N source, possibly of biotic origin. Thus at the extreme limits of plant life, biotic interactions may be just as important as abiotic processes, such as climate in explaining ecosystem δ15N values.

Nitrogen cycling in an extreme hyperarid environment inferred from δ15N analyses of plants, soils and herbivore diet

PubMed Central

Díaz, Francisca P.; Frugone, Matías; Gutiérrez, Rodrigo A.; Latorre, Claudio

2016-01-01

Climate controls on the nitrogen cycle are suggested by the negative correlation between precipitation and δ15N values across different ecosystems. For arid ecosystems this is unclear, as water limitation among other factors can confound this relationship. We measured herbivore feces, foliar and soil δ15N and δ13C values and chemically characterized soils (pH and elemental composition) along an elevational/climatic gradient in the Atacama Desert, northern Chile. Although very positive δ15N values span the entire gradient, soil δ15N values show a positive correlation with aridity as expected. In contrast, foliar δ15N values and herbivore feces show a hump-shaped relationship with elevation, suggesting that plants are using a different N source, possibly of biotic origin. Thus at the extreme limits of plant life, biotic interactions may be just as important as abiotic processes, such as climate in explaining ecosystem δ15N values. PMID:26956399

Nitrogen isotope fractionation by alternative nitrogenases and past ocean anoxia

PubMed Central

Zhang, Xinning; Sigman, Daniel M.; Morel, François M. M.; Kraepiel, Anne M. L.

2014-01-01

Biological nitrogen fixation constitutes the main input of fixed nitrogen to Earth’s ecosystems, and its isotope effect is a key parameter in isotope-based interpretations of the N cycle. The nitrogen isotopic composition (δ15N) of newly fixed N is currently believed to be ∼–1‰, based on measurements of organic matter from diazotrophs using molybdenum (Mo)-nitrogenases. We show that the vanadium (V)- and iron (Fe)-only “alternative” nitrogenases produce fixed N with significantly lower δ15N (–6 to –7‰). An important contribution of alternative nitrogenases to N2 fixation provides a simple explanation for the anomalously low δ15N (<–2‰) in sediments from the Cretaceous Oceanic Anoxic Events and the Archean Eon. A significant role for the alternative nitrogenases over Mo-nitrogenase is also consistent with evidence of Mo scarcity during these geologic periods, suggesting an additional dimension to the coupling between the global cycles of trace elements and nitrogen. PMID:24639508

The synthesis of ZrO2-Y2O3 ceramic fibers by the method of impregnation of viscous threads

NASA Astrophysics Data System (ADS)

Titova, S. M.; Obabkov, N. V.; Zakirova, A. F.; Zakirov, I. F.; Dokuchaev, V. S.; Shak, A. V.

2017-09-01

The possibility of synthesis of ZrO2-Y2O3 oxide fibers and their applicatiuon for reinforcing porous ceramics of the same composition was investigated. Ceramic fibers were obtained by impregnating viscose strings with solutions of zirconyl and yttrium nitrates. The method allows synthesis of the fibers with a diameter of 400 µm and length of 5 to 20 mm. The strength of the synthesized fibers was determined. The maximum tensile strength (132.45 MPa) was demonstrated by fibers obtained with a working solution concentration of 500 g oxides/L. Repeated impregnation of the viscose yarn led to an increase in the strength of the fibers to 205 MPa. Ceramic fibers can be used as reinforcing elements of oxide ceramics. The bending strength of the reinforced ceramics was 3 MPa. After 10 cycles of thermal cycling (heating to 1100 °C and cooling in water) the bending strength was reduced to 1 MPa.

Composite lithium metal anode by melt infusion of lithium into a 3D conducting scaffold with lithiophilic coating.

PubMed

Liang, Zheng; Lin, Dingchang; Zhao, Jie; Lu, Zhenda; Liu, Yayuan; Liu, Chong; Lu, Yingying; Wang, Haotian; Yan, Kai; Tao, Xinyong; Cui, Yi

2016-03-15

Lithium metal-based battery is considered one of the best energy storage systems due to its high theoretical capacity and lowest anode potential of all. However, dendritic growth and virtually relative infinity volume change during long-term cycling often lead to severe safety hazards and catastrophic failure. Here, a stable lithium-scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with "lithiophilic" coating. Lithium is uniformly entrapped on the matrix surface and in the 3D structure. The resulting composite electrode possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling. We showed stable cycling of this composite electrode with small Li plating/stripping overpotential (<90 mV) at a high current density of 3 mA/cm(2) over 80 cycles.

High-speed optical phase-shifting apparatus

DOEpatents

Zortman, William A.

2016-11-08

An optical phase shifter includes an optical waveguide, a plurality of partial phase shifting elements arranged sequentially, and control circuitry electrically coupled to the partial phase shifting elements. The control circuitry is adapted to provide an activating signal to each of the N partial phase shifting elements such that the signal is delayed by a clock cycle between adjacent partial phase shifting elements in the sequence. The transit time for a guided optical pulse train between the input edges of consecutive partial phase shifting elements in the sequence is arranged to be equal to a clock cycle, thereby enabling pipelined processing of the optical pulses.

Laser ablation-miniature mass spectrometer for elemental and isotopic analysis of rocks.

PubMed

Sinha, M P; Neidholdt, E L; Hurowitz, J; Sturhahn, W; Beard, B; Hecht, M H

2011-09-01

A laser ablation-miniature mass spectrometer (LA-MMS) for the chemical and isotopic measurement of rocks and minerals is described. In the LA-MMS method, neutral atoms ablated by a pulsed laser are led into an electron impact ionization source, where they are ionized by a 70 eV electron beam. This results in a secondary ion pulse typically 10-100 μs wide, compared to the original 5-10 ns laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer (MMS) and measured in parallel by a modified CCD array detector capable of detecting ions directly. Compared to conventional scanning techniques, simultaneous measurement of the ion pulse along the focal plane effectively offers a 100% duty cycle over a wide mass range. LA-MMS offers a more quantitative assessment of elemental composition than techniques that detect ions directly generated by the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the wavelength of the laser beam, and the not well characterized ionization efficiencies of the elements in the process. The above problems attendant to the direct ion analysis has been minimized in the LA-MMS by analyzing the ablated neutral species after their post-ionization by electron impaction. These neutral species are much more abundant than the directly ablated ions in the ablated vapor plume and are, therefore, expected to be characteristic of the chemical composition of the solid. Also, the electron impact ionization of elements is well studied and their ionization cross sections are known and easy to find in databases. Currently, the LA-MMS limit of detection is 0.4 wt.%. Here we describe LA-MMS elemental composition measurements of various minerals including microcline, lepidolite, anorthoclase, and USGS BCR-2G samples. The measurements of high precision isotopic ratios including (41)K/(39)K (0.077 ± 0.004) and (29)Si/(28)Si (0.052 ± 0.006) in these minerals by LA-MMS are also described. The LA-MMS has been developed as a prototype instrument system for space applications for geochemical and geochronological measurements on the surface of extraterrestrial bodies. © 2011 American Institute of Physics

The effect of thermal cycling on the structure and properties of a Co, Cr, Ni-TaC directionally solidified eutectic composite

NASA Technical Reports Server (NTRS)

Dunlevey, F. M.; Wallace, J. F.

1973-01-01

The effect of thermal cycling on the structure and properties of a cobalt, chromium, nickel, tantalum carbide directionally solidified eutectic composite is reported. It was determined that the stress rupture properties of the alloy were decreased by the thermal cycling. The loss in stress rupture properties varied with the number of cycles with the loss in properties after about 200 cycles being relatively high. The formation of serrations and the resulting changes in the mechanical properties of the material are discussed.

Compensation for electrical converter nonlinearities

DOEpatents

Perisic, Milun; Ransom, Ray M; Kajouke, Lateef A

2013-11-19

Systems and methods are provided for delivering energy from an input interface to an output interface. An electrical system includes an input interface, an output interface, an energy conversion module between the input interface and the output interface, an inductive element between the input interface and the energy conversion module, and a control module. The control module determines a compensated duty cycle control value for operating the energy conversion module to produce a desired voltage at the output interface and operates the energy conversion module to deliver energy to the output interface with a duty cycle that is influenced by the compensated duty cycle control value. The compensated duty cycle control value is influenced by the current through the inductive element and accounts for voltage across the switching elements of the energy conversion module.

Early Diagenesis of Trace Elements in Modern Fjord Sediments of the High Arctic

NASA Astrophysics Data System (ADS)

Herbert, L.; Riedinger, N.; Aller, R. C.; Jørgensen, B. B.; Wehrmann, L.

2017-12-01

Marine sediments are critical repositories for elements that are only available at trace concentrations in seawater, such as Fe, Mn, Co, Ni, As, Mo, and U. The behavior of these trace elements in the sediment is governed by a dynamic interplay of diagenetic reactions involving organic carbon, Fe and Mn oxides, and sulfur phases. In the Arctic fjords of Svalbard, glacial meltwater delivers large amounts of reactive Fe and Mn oxides to the sediment, while organic carbon is deposited episodically and diluted by lithogenic material. These conditions result in pronounced Fe and Mn cycling, which in turn drives other diagenetic processes such as rapid sulfide oxidation. These conditions make the Svalbard fjords ideal sites for investigating trace element diagenesis because they allow resolution of the interconnections between Fe and Mn dynamics and trace element cycling. In August 2016, we collected sediment cores from three Svalbard fjords and analyzed trace elements in the pore water and solid sediment over the top meter. Initial results reveal the dynamic nature of these fjords, which are dominated by non-steady state processes and episodic events such as meltwater pulses and phytoplankton blooms. Within this system, the distribution of As appears to be strongly linked to the Fe cycle, while Co and Ni follow Mn; thus, these three elements may be released from the sediment through diffusion and bioturbation along with Fe and Mn. The pore water profiles of U and Mo indicate removal processes that are independent from Fe or Mn, and which are rather unexpected given the apparent diagenetic conditions. Our results will help elucidate the processes controlling trace element cycling in a dynamic, glacially impacted environment and will ultimately contribute to our understanding of the role of fjords in the biogeochemical cycling of trace elements in a rapidly changing Arctic Ocean.

Energy Finite Element Analysis Developments for Vibration Analysis of Composite Aircraft Structures

NASA Technical Reports Server (NTRS)

Vlahopoulos, Nickolas; Schiller, Noah H.

2011-01-01

The Energy Finite Element Analysis (EFEA) has been utilized successfully for modeling complex structural-acoustic systems with isotropic structural material properties. In this paper, a formulation for modeling structures made out of composite materials is presented. An approach based on spectral finite element analysis is utilized first for developing the equivalent material properties for the composite material. These equivalent properties are employed in the EFEA governing differential equations for representing the composite materials and deriving the element level matrices. The power transmission characteristics at connections between members made out of non-isotropic composite material are considered for deriving suitable power transmission coefficients at junctions of interconnected members. These coefficients are utilized for computing the joint matrix that is needed to assemble the global system of EFEA equations. The global system of EFEA equations is solved numerically and the vibration levels within the entire system can be computed. The new EFEA formulation for modeling composite laminate structures is validated through comparison to test data collected from a representative composite aircraft fuselage that is made out of a composite outer shell and composite frames and stiffeners. NASA Langley constructed the composite cylinder and conducted the test measurements utilized in this work.

Modification of a Macromechanical Finite-Element Based Model for Impact Analysis of Triaxially-Braided Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Blinzler, Brina J.; Binienda, Wieslaw K.

2010-01-01

A macro level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. For the current analytical approach, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The constitutive model requires stiffness and strength properties of an equivalent unidirectional composite. Simplified micromechanics methods are used to determine the equivalent stiffness properties, and results from coupon level tests on the braided composite are utilized to back out the required strength properties. Simulations of quasi-static coupon tests of several representative braided composites are conducted to demonstrate the correlation of the model. Impact simulations of a represented braided composites are conducted to demonstrate the capability of the model to predict the penetration velocity and damage patterns obtained experimentally.

Organic molecules, ions, and rare isotopologues in the remnant of the stellar-merger candidate, CK Vulpeculae (Nova 1670)

NASA Astrophysics Data System (ADS)

Kamiński, T.; Menten, K. M.; Tylenda, R.; Karakas, A.; Belloche, A.; Patel, N. A.

2017-11-01

Context. CK Vulpeculae (CK Vul) is an enigmatic star whose outburst was observed in 1670-72. A stellar-merger event was proposed to explain its ancient eruption. Aims: We aim to investigate the composition of the molecular gas recently discovered in the remnant of CK Vul. Deriving the chemical, elemental, and isotopic composition is crucial for identifying the nature of the object and obtaining clues on its progenitor(s). Methods: We observed millimeter and submillimeter-wave spectra of CK Vul using the IRAM 30 m and APEX telescopes. Radiative-transfer modeling of the observed molecular features was performed to yield isotopic ratios for various elements. Results: The spectra of CK Vul reveal a very rich molecular environment of low excitation (Tex ≲ 12 K). Atomic carbon and twenty-seven different molecules, including two ions, were identified. They range from simple diatomic to complex polyatomic species of up to seven atoms large. The chemical composition of the molecular gas is indicative of carbon and nitrogen-driven chemistry but oxides are also present. Additionally, the abundance of fluorine may be enhanced. The spectra are rich in isotopologues that are very rare in most known sources. All stable isotopes of C, N, O, Si, and S are observed and their isotopic ratios are derived. Conclusions: The composition of the remnant's molecular gas is most peculiar and gives rise to a very unique millimeter and submillimeter spectrum. The observation of ions and complex molecules suggests the presence of a photoionizing source but its nature (a central star or shocks) remains unknown. The elemental and isotopic composition of the gas cannot be easily reconciled with standard stellar nucleosynthesis but processing in hot CNO cycles and partial helium burning can explain most of the chemical peculiarities. The isotopic ratios of CK Vul are remarkably close to those of presolar "nova grains" but the link of Nova 1670 to objects responsible for these grains is unclear. The accuracy of isotopic ratios can be improved by future observations at higher angular resolutions and with realistic models of the kinematical structure of the remnant. The reduced spectra are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A78

Effect of variable hydrothermal conditions on sulfur speciation and isotopic compositions mediated by two Thiomicrospira strains

NASA Astrophysics Data System (ADS)

Houghton, J.; Wills, E.; Fike, D. A.

2012-12-01

Microbially mediated reactions involving elemental sulfur in low temperature hydrothermal environments are a critical component of the net hydrothermal flux of sulfur to the global oceans. We assess here the physiological impact on sulfur speciation and isotopic composition of two microbial strains at a range of pH conditions consistent with the sharp gradients found in seafloor hydrothermal environments. Thiomicrospira thermophila and T. crunogena, both isolated from hydrothermal vents at East Pacific Rise, were grown with thiosulfate as the electron donor under aerobic, closed system conditions at controlled pH and optimal temperature (35°C). T. thermophila at pH 8 produced sulfate at a 1:1 ratio with thiosulfate consumption during exponential growth, with the ratio decreasing as pH decreases. This stoichiometric ratio decreases more steeply as a function of pH during metabolism by T. crunogena. Sulfate:thiosulfate ratios less than one indicate the production of alternative oxidized sulfur compounds such as polythionates. The rate of sulfate production is comparable in both strains and is dependent on pH, decreasing from 0.8mM/hr at pH 8 to 0.2mM/hr at pH 5.6. Fractionation of 34S expressed as Δ34S between reactant and product range from 0‰ to 3‰ for both sulfate and elemental sulfur produced, with no difference between products in pH buffered experiments (pH 5.6 and 8.0). However, in unbuffered experiments during which growth causes pH to decrease from 7 to below 4.5, Δ34S(S2O3-SO4) is consistently larger than Δ34S(S2O3-S) in both strains by a factor of 2. The metabolic activity of these (and similar) strains indicate that complex and cryptic sulfur cycling may be occurring in the subsurface, associated with only minimal variation in the δ34S isotopic composition of sulfate and elemental sulfur.

Trace Element Geochemistry as a Tool for the Reconstruction of Upwelling Patterns at 12oS off Peru since the Last Glacial Maximum (LGM)

NASA Astrophysics Data System (ADS)

Boening, P.; Brumsack, H.; Wolf, A.

2002-05-01

Laminated sediments (core 106KL), recovered during R/V Sonne cruise 147 from the Peruvian upper slope mud lens at 12oS, were analyzed for bulk parameters (TOC, TIC, TS) and opal as well as major and trace element composition by XRF and ICP-MS in 5 cm intervals. The composition of the terrigenous-detrital sediment fraction is comparable to average shale. The sediments exhibit slight increases in biogenic silica (diatoms) and carbonate contents (foraminifera) in varying layers. The experimentally determined opal contents correlate well with Si/Al ratios. High TOC and P contents are due to enhanced primary productivity, high sedimentation rates and corresponding organic matter preservation under a strong OMZ. We distinguish between three different groups of elements: 1.) trace elements involved in bio-cycling (e.g. Cd, Ag, Ni, Cu) are highly enriched in the sediments due to their association with plankton, high sedimentation rates (preventing remobilization from the sediments) and fixation as sulfides. 2.) redox-sensitive elements (e.g. Re, Mo) are significantly enriched probably due to reduction and precipitation under suboxic/anoxic conditions. Diffusion of these elements from the water column into sub/anoxic sediments seems to be the controlling factor, besides sulfide precipitation. An average Re/Mo ratio of 1.3 indicates anoxic sedimentary conditions. Most trace elements correlate well with the TOC content presumably documenting productivity events. 3.) Al, Zr and Y are well correlated, presumably representing sporadic high-energy fluvial input from the continent or enhanced current velocities. The three element groups were used to reconstruct the upwelling patterns off Lima since the LGM: TOC content and Al-normalized trace element patterns from the bio/redox-sensitive fractions represent the signal from the water column, whereas Al, Y and Zr reflect the terrigenous input. During the LGM (about 17 ky BP) the site was hardly affected by upwelling as the upwelling cell was located more basinward. As the sea level rose during the Late Glacial (17-10 ky BP) the upwelling cell shifted towards the coast. The Early Holocene (10-5 ky BP) is not documented likely because strong currents (presumably the Peru counter current) eroded the slope. In the Late Holocene the upwelling cell was established at the site. However, a higher terrrigenous proportion and lower input from the water column suggest a basinward shifting of the upwelling cell during the Second Neoglacial (2000-2700 BP). Stronger Element/Al and TOC variabilities indicate the influence of El Nino during the Late Holocene.

Hydrogen Permeability of Polymer Matrix Composites at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Grenoble, Ray W.; Gates, Thomas S

2005-01-01

This paper presents experimental methods and results of an ongoing study of the correlation between damage state and hydrogen gas permeability of laminated composite materials under mechanical strains and thermal loads. A specimen made from IM-7/977-2 composite material has been mechanically cycled at room temperature to induce microcrack damage. Crack density and tensile modulus were observed as functions of number of cycles. Damage development was found to occur most quickly in the off-axis plies near the outside of the laminate. Permeability measurements were made after 170,000 cycles and 430,000 cycles. Leak rate was found to depend on applied mechanical strain, crack density, and test temperature.

Trends in Trace Element Fractionation Between Foraminiferal Species and the Role of Biomineralization

NASA Astrophysics Data System (ADS)

Reichart, G. J.; Nooijer, L. D.; Geerken, E.; Mezger, E.; van Dijk, I. V.; Daemmer, L. K.

2017-12-01

Reconstructions of past climate and environments are largely based on stable isotopes and trace element concentrations measured on fossil foraminiferal calcite. Their element and isotope composition roughly reflects seawater composition and physical conditions, which in turn, are related to paleoceanographic parameters. More recently, attempts are being made to infer ranges in environmental parameters using the observed differences in the composition within individual tests. Remarkably, inter-species differences in trace element incorporation are well-correlated over a wide range of environmental conditions. This is particularly remarkable knowing that different environmental factors influence incorporation of these elements at various magnitudes. Most likely the complex biomineralization of foraminifera potentially offsets trace elements similarly at all these scales and also between different species. This suggests that at least parts of the mechanisms underlying foraminiferal biomineralization are similar for all species, which in turn provides important clues on the cellular mechanisms operating during calcification. Moreover, the systematics in trace element partitioning between species could potentially provide important clues for unravelling past changes in trace element composition of the ancient ocean.

Depleted δ13C Values in Salt Dome Cap Rock Organic Matter and Implications for Microbial Metabolism and Fixation

NASA Astrophysics Data System (ADS)

Loyd, S. J.; Lu, L.; Caesar, K. H.; Kyle, R.

2015-12-01

Salt domes occur throughout the Gulf Coast Region USA and are often associated with trapped hydrocarbons. These salt domes can be capped by sulfate and carbonate minerals that result from complex digenetic interactions in the subsurface. The specific natures of these interactions are poorly understood, in particular the role of microbes in facilitating mineralization and element cycling. Carbon isotope compositions of cap rock calcites (δ13Ccarb) are highly variable and range from near neutral to less than -40‰ (VPDB) indicative of methane-sourced carbon. These low values and the common coexistence of elemental sulfur and metal sulfides have spurred hypotheses invoking microbial sulfate reduction as driving carbonate mineral authigenesis. Here, we present new organic carbon isotope (δ13Corg) data that, similar to δ13Ccarb, exhibit depletions below -30 to -25‰. These δ13Corg values are lower than local liquid hydrocarbons and "normal" marine organic matter reflecting either microbial fixation of methane-sourced carbon or microbial fractionation from liquid hydrocarbon sources. The combined carbon isotope data (δ13Ccarb and δ13Corg) indicate that methane likely plays an important role in microbial cycling in salt domes. The δ13Corg values are similar to those of anaerobic oxidation of methane (AOM) related communities from methane-sulfate controlled marine sediments. Ultimately, salt dome environments may share some important characteristics with AOM systems.

Photoluminescence Characteristics of Yag:Ce, Gd Based Phosphors with Different Prehistories

NASA Astrophysics Data System (ADS)

Lisitsyn, V. M.; Soshchin, N. P.; Yang yang, Yu; Stepanov, S. A.; Lisitsyna, L. A.; Tulegenova, A. T.; Abdullin, Kh. A.

2017-09-01

Luminescence characteristics of yttrium-aluminum garnet based phosphor samples differed by their elemental composition and prehistory of synthesis are studied. The morphology, structure, and elemental composition of phosphor samples, their excitation and emission spectra, efficiency of phosphor conversion of chip emission, and kinetics of luminescence decay are measured. The emission characteristics of phosphors are compared with their structural properties and elemental composition.

Application of finite element substructuring to composite micromechanics. M.S. Thesis - Akron Univ., May 1984

NASA Technical Reports Server (NTRS)

Caruso, J. J.

1984-01-01

Finite element substructuring is used to predict unidirectional fiber composite hygral (moisture), thermal, and mechanical properties. COSMIC NASTRAN and MSC/NASTRAN are used to perform the finite element analysis. The results obtained from the finite element model are compared with those obtained from the simplified composite micromechanics equations. A unidirectional composite structure made of boron/HM-epoxy, S-glass/IMHS-epoxy and AS/IMHS-epoxy are studied. The finite element analysis is performed using three dimensional isoparametric brick elements and two distinct models. The first model consists of a single cell (one fiber surrounded by matrix) to form a square. The second model uses the single cell and substructuring to form a nine cell square array. To compare computer time and results with the nine cell superelement model, another nine cell model is constructed using conventional mesh generation techniques. An independent computer program consisting of the simplified micromechanics equation is developed to predict the hygral, thermal, and mechanical properties for this comparison. The results indicate that advanced techniques can be used advantageously for fiber composite micromechanics.

Geometrically nonlinear analysis of layered composite plates and shells

NASA Technical Reports Server (NTRS)

Chao, W. C.; Reddy, J. N.

1983-01-01

A degenerated three dimensional finite element, based on the incremental total Lagrangian formulation of a three dimensional layered anisotropic medium was developed. Its use in the geometrically nonlinear, static and dynamic, analysis of layered composite plates and shells is demonstrated. A two dimenisonal finite element based on the Sanders shell theory with the von Karman (nonlinear) strains was developed. It is shown that the deflections obtained by the 2D shell element deviate from those obtained by the more accurate 3D element for deep shells. The 3D degenerated element can be used to model general shells that are not necessarily doubly curved. The 3D degenerated element is computationally more demanding than the 2D shell theory element for a given problem. It is found that the 3D element is an efficient element for the analysis of layered composite plates and shells undergoing large displacements and transient motion.

[Aging of silorane- and methacrylate-based composite resins: effects on color and translucency].

PubMed

Liu, Chang; Pan, Jie; Lin, Hong; Shen, Song

2015-10-01

To evaluate the color stability and translucency of silorane-based low shrinkage composite after in vitro aging procedures of thermal cycling and water storage respectively, and to compare with those of conventional methacrylate-based posterior composite. Three light-cured composite resins, dimethacrylate-based composite A (Filtek™ Z350), B (Filtek™ P60) and silorane-based composite C (Filtek™ P90), were tested in this study. Ten specimens (10 mm in diameter, 1 mm in height) of each composite were prepared. The ten specimens in each group were then divided into two subgroups (n = 5). One subgroup underwent thermal cycling [(5.0 ± 0.5)~(55.0 ± 1.0) °C, 10 000 cycles] and the other was stored in 37 C° distilled water for 180 days. With a spectrophotometer, the CIE L * a * b * parameters of the specimens were tested before and after artificial aging against white, medium grey and black backgrounds, respectively. △E, TP and △TP were calculated and data were analyzed using independent-samples t test and partial analysis (P < 0.05). With regard to color stability, silorane-based composite showed color alteration above the clinically acceptable levels (△E > 3.3), and also showed higher △E with a statistically significant difference in comparison with the other composites (B and C) (P < 0.05) after artificial aging. With regard to translucency, composite C showed more alteration compared with composite B (P < 0.05) after thermal cycling. It may be concluded that the silorane-based composite underwent greater alteration with regard to color stability and translucency.

Radionuclide inventories : ORIGEN2.2 isotopic depletion calculation for high burnup low-enriched uranium and weapons-grade mixed-oxide pressurized-water reactor fuel assemblies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gauntt, Randall O.; Ross, Kyle W.; Smith, James Dean

2010-04-01

The Oak Ridge National Laboratory computer code, ORIGEN2.2 (CCC-371, 2002), was used to obtain the elemental composition of irradiated low-enriched uranium (LEU)/mixed-oxide (MOX) pressurized-water reactor fuel assemblies. Described in this report are the input parameters for the ORIGEN2.2 calculations. The rationale for performing the ORIGEN2.2 calculation was to generate inventories to be used to populate MELCOR radionuclide classes. Therefore the ORIGEN2.2 output was subsequently manipulated. The procedures performed in this data reduction process are also described herein. A listing of the ORIGEN2.2 input deck for two-cycle MOX is provided in the appendix. The final output from this data reduction processmore » was three tables containing the radionuclide inventories for LEU/MOX in elemental form. Masses, thermal powers, and activities were reported for each category.« less

Trace element analyses of fluid-bearing diamonds from Jwaneng, Botswana

NASA Astrophysics Data System (ADS)

Schrauder, Marcus; Koeberl, Christian; Navon, Oded

1996-12-01

Fibrous diamonds from Botswana contain abundant micro-inclusions, which represent syngenetic mantle fluids under high pressure. The major element composition of the fluids within individual diamonds was found to be uniform, but a significant compositional variation exists between different diamond specimens. The composition of the fluids varies between a carbonatitic and a hydrous endmember. To constrain the composition of fluids in the mantle, the trace element contents of thirteen micro-inclusion-bearing fibrous diamonds from Botswana was studied using neutron activation analysis. The concentrations of incompatible elements (including K, Na, Br, Rb, Sr, Zr, Cs, Ba, Hf, Ta, Th, U, and the LREEs) in the fluids are higher than those of mantle-derived rocks and melt inclusions. The compatible elements (e.g., Cr, Co, Ni) have abundances that are similar to those of the primitive mantle. The concentrations of most trace elements decrease by a factor of two from the carbonate-rich fluids to the hydrous fluids. Several models may explain the observed elemental variations. Minerals in equilibrium with the fluid were most likely enriched in incompatible elements, which does not agree with derivation of the fluids by partial melting of common peridotites or eclogites. Fractional crystallization of a kimberlite-like magma at depth may yield carbonatitic fluids with low mg numbers (atomic ratio [Mg/(Mg+Fe)]) and high trace element contents. Fractionation of carbonates and additional phases (e.g., rutile, apatite, zircon) may, in general, explain the concentrations of incompatible elements in the fluids, which preferably partition into these phases. Alternatively, mixing of fluids with compositions similar to those of the two endmembers may explain the observed variation of the elemental contents. The fluids in fibrous diamonds might have equilibrated with mineral inclusions in eclogitic diamonds, while peridotitic diamonds do not show evidence of interaction with these fluids. The chemical composition of the fluids in fibrous diamonds indicates that, at p, T conditions that are characteristic for diamond formation, carbonatitic and hydrous fluids are efficient carriers of incompatible elements.

Isotopic Compositions of the Elements, 2001

NASA Astrophysics Data System (ADS)

Böhlke, J. K.; de Laeter, J. R.; De Bièvre, P.; Hidaka, H.; Peiser, H. S.; Rosman, K. J. R.; Taylor, P. D. P.

2005-03-01

The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the "best measurement" of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001.

Structural health monitoring in composite materials using frequency response methods

NASA Astrophysics Data System (ADS)

Kessler, Seth S.; Spearing, S. Mark; Atalla, Mauro J.; Cesnik, Carlos E. S.; Soutis, Constantinos

2001-08-01

Cost effective and reliable damage detection is critical for the utilization of composite materials in structural applications. Non-destructive evaluation techniques (e.g. ultrasound, radiography, infra-red imaging) are available for use during standard repair and maintenance cycles, however by comparison to the techniques used for metals these are relatively expensive and time consuming. This paper presents part of an experimental and analytical survey of candidate methods for the detection of damage in composite materials. The experimental results are presented for the application of modal analysis techniques applied to rectangular laminated graphite/epoxy specimens containing representative damage modes, including delamination, transverse ply cracks and through-holes. Changes in natural frequencies and modes were then found using a scanning laser vibrometer, and 2-D finite element models were created for comparison with the experimental results. The models accurately predicted the response of the specimems at low frequencies, but the local excitation and coalescence of higher frequency modes make mode-dependent damage detection difficult and most likely impractical for structural applications. The frequency response method was found to be reliable for detecting even small amounts of damage in a simple composite structure, however the potentially important information about damage type, size, location and orientation were lost using this method since several combinations of these variables can yield identical response signatures.

Lunar Ferroan Anorthosite Petrogenesis: Clues from Trace Element Distributions in FAN Subgroups

NASA Astrophysics Data System (ADS)

Floss, Christine; James, Odette B.; McGee, James J.; Crozaz, Ghislaine

1998-04-01

The rare earth elements (REE) and selected other trace elements were measured in plagioclase and pyroxene from nine samples of the lunar ferroan anorthosite (FAN) suite of rocks. Samples were selected from each of four FAN subgroups previously defined by James et al. (1989). Plagioclase compositions are homogeneous within each sample, but high- and low-Ca pyroxenes from lithic clasts typically have different REE abundances from their counterparts in the surrounding granulated matrices. Measured plagioclase/low-Ca pyroxene concentration ratios for the REE have steeper patterns than experimentally determined plagioclase/low-Ca pyroxene partition coefficients in most samples. Textural and trace element evidence suggest that, although subsolidus equilibration may be responsible for some of the discrepancy, plagioclase compositions in most samples have been largely unaffected by intermineral redistribution of the REE. The REE systematics of plagioclase from the four subgroups are broadly consistent with their derivation through crystallization from a single evolving magma. However, samples from some of the subgroups exhibit a decoupling of plagioclase and pyroxene compositions that probably reflects the complexities inherent in crystallization from a large-scale magmatic system. For example, two anorthosites with very magnesian mafic minerals have highly evolved trace element compositions; major element compositions in plagioclase also do not reflect the evolutionary sequence recorded by their REE compositions. Finally, a noritic anorthosite breccia with relatively ferroan mafic minerals contains several clasts with high and variable REE and other trace element abundances. Although plagioclase REE compositions are consistent with their derivation from a magma with a KREEPy trace element signature, very shallow REE patterns in the pyroxenes suggest the addition of a component enriched in the light REE.

Analysis of grain elements and identification of best genotypes for Fe and P in Afghan wheat landraces

PubMed Central

Kondou, Youichi; Manickavelu, Alagu; Komatsu, Kenji; Arifi, Mujiburahman; Kawashima, Mika; Ishii, Takayoshi; Hattori, Tomohiro; Iwata, Hiroyoshi; Tsujimoto, Hisashi; Ban, Tomohiro; Matsui, Minami

2016-01-01

This study was carried out with the aim of developing the methodology to determine elemental composition in wheat and identify the best germplasm for further research. Orphan and genetically diverse Afghan wheat landraces were chosen and EDXRF was used to measure the content of some of the elements to establish elemental composition in grains of 266 landraces using 10 reference lines. Four elements, K, Mg, P, and Fe, were measured by standardizing sample preparation. The results of hierarchical cluster analysis using elemental composition data sets indicated that the Fe content has an opposite pattern to the other elements, especially that of K. By systematic analysis the best wheat germplasms for P content and Fe content were identified. In order to compare the sensitivity of EDXRF, the ICP method was also used and the similar results obtained confirmed the EDXRF methodology. The sampling method for measurement using EDXRF was optimized resulting in high-throughput profiling of elemental composition in wheat grains at low cost. Using this method, we have characterized the Afghan wheat landraces and isolated the best genotypes that have high-elemental content and have the potential to be used in crop improvement. PMID:28163583

Composite lithium metal anode by melt infusion of lithium into a 3D conducting scaffold with lithiophilic coating

PubMed Central

Liang, Zheng; Lin, Dingchang; Zhao, Jie; Lu, Zhenda; Liu, Yayuan; Liu, Chong; Lu, Yingying; Wang, Haotian; Yan, Kai; Tao, Xinyong; Cui, Yi

2016-01-01

Lithium metal-based battery is considered one of the best energy storage systems due to its high theoretical capacity and lowest anode potential of all. However, dendritic growth and virtually relative infinity volume change during long-term cycling often lead to severe safety hazards and catastrophic failure. Here, a stable lithium–scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with “lithiophilic” coating. Lithium is uniformly entrapped on the matrix surface and in the 3D structure. The resulting composite electrode possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling. We showed stable cycling of this composite electrode with small Li plating/stripping overpotential (<90 mV) at a high current density of 3 mA/cm2 over 80 cycles. PMID:26929378

The role of the seagrass Posidonia oceanica in the cycling of trace elements

NASA Astrophysics Data System (ADS)

Sanz-Lázaro, C.; Malea, P.; Apostolaki, E. T.; Kalantzi, I.; Marín, A.; Karakassis, I.

2012-03-01

The aim of this work was to study the role of the seagrass Posidonia oceanica on the cycling of a wide set of trace elements (Ag, As, Ba, Bi, Cd, Co, Cr, Cs, Cu, Fe, Ga, Li, Mn, Ni, Pb, Rb, Sr, Tl, V and Zn). We measured the concentration of these trace elements in the different compartments of P. oceanica (leaves, rhizomes, roots and epibiota) in a non-polluted seagrass meadow representative of the Mediterranean and calculated the annual budget from a mass balance. We provide novel data on accumulation dynamics of many trace elements in P. oceanica compartments and demonstrate that trace element accumulation patterns are mainly determined by plant compartment rather than by temporal variability. Epibiota was the compartment which showed the greatest concentrations for most trace elements. Thus, they constitute a key compartment when estimating trace element transfer to higher trophic levels by P. oceanica. For most trace elements, translocation seemed to be low and acropetal. Zn, Cd, Sr and Rb were the trace elements that showed the highest release rate through decomposition of plant detritus, while Cs, Tl and Bi the lowest. P. oceanica acts as a sink of potentially toxic trace elements (Ni, Cr, As and Ag), which can be sequestered, decreasing their bioavailability. P. oceanica may have a relevant role in the cycling of trace elements in the Mediterranean.

The role of the seagrass Posidonia oceanica in the cycling of trace elements

NASA Astrophysics Data System (ADS)

Sanz-Lázaro, C.; Malea, P.; Apostolaki, E. T.; Kalantzi, I.; Marín, A.; Karakassis, I.

2012-07-01

The aim of this study was to investigate the role of the seagrass Posidonia oceanica on the cycling of a wide set of trace elements (Ag, As, Ba, Bi, Cd, Co, Cr, Cs, Cu, Fe, Ga, Li, Mn, Ni, Pb, Rb, Sr, Tl, V and Zn). We measured the concentration of these trace elements in different compartments of P. oceanica (leaves, rhizomes, roots and epiphytes) in a non-polluted seagrass meadow representative of the Mediterranean and calculated the annual budget from a mass balance. We provide novel data on accumulation dynamics of many trace elements in P. oceanica compartments and demonstrate that trace element accumulation patterns are mainly determined by plant compartment rather than by temporal variability. Epiphytes were the compartment, which showed the greatest concentrations for most trace elements. Thus, they constitute a key compartment when estimating trace element transfer to higher trophic levels by P. oceanica. Trace element translocation in P. oceanica seemed to be low and acropetal in most cases. Zn, Cd, Sr and Rb were the trace elements that showed the highest release rate through decomposition of plant detritus, while Cs, Tl and Bi showed the lowest. P. oceanica acts as a sink of potentially toxic trace elements (Ni, Cr, As and Ag), which can be sequestered, decreasing their bioavailability. P. oceanica may have a relevant role in the cycling of trace elements in the Mediterranean.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiang, N. B.; Qu, Z. N., E-mail: znqu@ynao.ac.cn

The ensemble empirical mode decomposition (EEMD) analysis is utilized to extract the intrinsic mode functions (IMFs) of the solar mean magnetic field (SMMF) observed at the Wilcox Solar Observatory of Stanford University from 1975 to 2014, and then we analyze the periods of these IMFs as well as the relation of IMFs (SMMF) with some solar activity indices. The two special rotation cycles of 26.6 and 28.5 days should be derived from different magnetic flux elements in the SMMF. The rotation cycle of the weak magnetic flux element in the SMMF is 26.6 days, while the rotation cycle of themore » strong magnetic flux element in the SMMF is 28.5 days. The two rotation periods of the structure of the interplanetary magnetic field near the ecliptic plane are essentially related to weak and strong magnetic flux elements in the SMMF, respectively. The rotation cycle of weak magnetic flux in the SMMF did not vary over the last 40 years because the weak magnetic flux element derived from the weak magnetic activity on the full disk is not influenced by latitudinal migration. Neither the internal rotation of the Sun nor the solar magnetic activity on the disk (including the solar polar fields) causes the annual variation of SMMF. The variation of SMMF at timescales of a solar cycle is more related to weak magnetic activity on the full solar disk.« less

Fair performance comparison of different carbon blacks in lithium-sulfur batteries with practical mass loadings - Simple design competes with complex cathode architecture

NASA Astrophysics Data System (ADS)

Jozwiuk, Anna; Sommer, Heino; Janek, Jürgen; Brezesinski, Torsten

2015-11-01

The lithium-sulfur system is one of the most promising next generation battery systems, as elemental sulfur is cheap, abundant and has a high theoretical specific capacity. Although much research is conducted on complex sulfur/carbon composites and architectures, it is difficult to compare the performance of the cathodes to one another. Factors, such as different electrolyte composition and cell components strongly affect the cyclability of the battery. Here, we show the importance of optimizing ;standard; conditions to allow for fair performance comparison of different carbon blacks. Our optimal electrolyte-to-sulfur ratio is 11 μL mgsulfur-1 and high concentrations of LiNO3 (>0.6 M) are needed because nitrate is consumed continuously during cycling. Utilizing these standard conditions, we tested the cycling behavior of four types of cathodes with individual carbon blacks having different specific surface areas, namely Printex-A, Super C65, Printex XE-2 and Ketjenblack EC-600JD. Both the specific capacity and polysulfide adsorption capability clearly correlate with the surface area of the carbon being used. High specific capacities (>1000 mAh gsulfur-1 at C/5) are achieved with high surface area carbons. We also demonstrate that a simple cathode using Ketjenblack EC-600JD as the conductive matrix material can well compete with those having complex architectures or additives.

Influence of dipping cycles on physical, optical, and electrical properties of Cu 2 NiSnS 4 : Direct solution dip coating for photovoltaic applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mokurala, Krishnaiah; Mallick, Sudhanshu; Bhargava, Parag

Direct solution coating technique has emerged as a promising economically viable process for earth abundant chalcogenide absorber materials for photovoltaic applications. Here, direct ethanol based dip coating of earth abundant Cu2NiSnS4 (CNTS) films on soda lime glass (SLG), molybdenum coated glass (Mo), and fluorine doped tin oxide coated glass (FTO) substrates is investigated. The structural and morphological properties of pre-annealed and sulfurized CNTS films coated on SLG, FTO, and Mo substrates are reported. The influence of dipping cycles on composition and optoelectronic properties of pre-annealed and sulfurized CNTS films deposited on SLG substrate is presented. Energy dispersive spectroscopy (EDS) andmore » X-ray fluorescence (XRF) analysis reveal how changes in thickness and elemental composition affect morphology and optoelectronic properties. The obtained absorption coefficient, optical bandgap, resistivity and mobility of pre - annealed and sulfurized films are found to be 104 cm-1, 1.5 eV, 0.48 Ocm, 3.4 cm2/Vs and 104 cm-1, 1.29 eV, 0.14 Ocm, 11.0 cm2/Vs, respectively. These properties are well suited for photovoltaic applications and lead to the conclusion that the direct ethanol based dip coating can be an alternative economically viable process for the fabrication of earth abundant CNTS absorber layers for thin film solar cells.« less

The effect of nutrient enrichment on the growth, nucleic acid concentrations, and elemental stoichiometry of coral reef macroalgae.

PubMed

Reef, Ruth; Pandolfi, John M; Lovelock, Catherine E

2012-08-01

The growth rate hypothesis (GRH) links growth rates with organism elemental stoichiometry. Support for the GRH was found for many animal species, but less so for plants. This is the first study to test the GRH in macroalgae. Tropical coral reef macroalgae from three lineages, Caulerpa serrulata (Chlorophyta), Laurencia intricata (Rhodophyta), and Sargassum polyphyllum (Phaeophyceae) were grown enriched with nitrogen or phosphorous and under control conditions at Heron Island on the Great Barrier Reef, Australia. Growth rate, photosynthesis, nucleic acid composition, and elemental stoichiometry were measured. Nutrient enrichment had positive effects on photosynthetic rates and on investment in RNA. However, growth rate was not correlated with either photosynthetic rates or RNA content; thus, we did not find support for the GRH in tropical macroalgae. Macroalgae, especially L. intricata, accumulated P to very high levels (>0.6% of dry weight). The growth rate response to tissue P concentrations was unimodal. Above 0.21%, P accumulation had negative effects on growth. Nitrogen was not stored, but evidence of futile cycling was observed. The capacity to store large amounts of P is probably an adaptation to the low and patchy nutrient environment of the tropical oceans.

The effect of nutrient enrichment on the growth, nucleic acid concentrations, and elemental stoichiometry of coral reef macroalgae

PubMed Central

Reef, Ruth; Pandolfi, John M; Lovelock, Catherine E

2012-01-01

The growth rate hypothesis (GRH) links growth rates with organism elemental stoichiometry. Support for the GRH was found for many animal species, but less so for plants. This is the first study to test the GRH in macroalgae. Tropical coral reef macroalgae from three lineages, Caulerpa serrulata (Chlorophyta), Laurencia intricata (Rhodophyta), and Sargassum polyphyllum (Phaeophyceae) were grown enriched with nitrogen or phosphorous and under control conditions at Heron Island on the Great Barrier Reef, Australia. Growth rate, photosynthesis, nucleic acid composition, and elemental stoichiometry were measured. Nutrient enrichment had positive effects on photosynthetic rates and on investment in RNA. However, growth rate was not correlated with either photosynthetic rates or RNA content; thus, we did not find support for the GRH in tropical macroalgae. Macroalgae, especially L. intricata, accumulated P to very high levels (>0.6% of dry weight). The growth rate response to tissue P concentrations was unimodal. Above 0.21%, P accumulation had negative effects on growth. Nitrogen was not stored, but evidence of futile cycling was observed. The capacity to store large amounts of P is probably an adaptation to the low and patchy nutrient environment of the tropical oceans. PMID:22957199

Analysis of the effects of simulated synergistic LEO environment on solar panels

NASA Astrophysics Data System (ADS)

Allegri, G.; Corradi, S.; Marchetti, M.; Scaglione, S.

2007-02-01

The effects due to the LEO environment exposure of a solar array primary structure are here presented and discussed in detail. The synergistic damaging components featuring LEO environment are high vacuum, thermal cycling, neutral gas, ultraviolet (UV) radiation and cold plasma. The synergistic effects due to these environmental elements are simulated by "on ground" tests, performed in the Space Environment Simulator (SAS) at the University of Rome "La Sapienza"; numerical simulations are performed by the Space Environment Information System (SPENVIS), developed by the European Space Agency (ESA). A "safe life" design for a solar array primary structure is developed, taking into consideration the combined damaging action of the LEO environment components; therefore results from both numerical and experimental simulations are coupled within the framework of a standard finite element method (FEM) based design. The expected durability of the solar array primary structure, made of laminated sandwich composite, is evaluated assuming that the loads exerted on the structure itself are essentially dependent on thermo-elastic stresses. The optical degradation of surface materials and the stiffness and strength degradation of structural elements are taken into account to assess the global structural durability of the solar array under characteristic operative conditions in LEO environment.

Fatigue delamination onset prediction in tapered composite laminates

NASA Technical Reports Server (NTRS)

Murri, Gretchen Bostaph; Salpekar, Satish A.; Obrien, T. Kevin

1989-01-01

Tapered (0 deg) laminates of S2/CE9000 and S2/SP250 glass/epoxies, and IM6/1827I graphite/epoxy were tested in cyclic tension. The specimens usually showed some initial stable delaminations in the tapered region, but these did not affect the stiffness of the specimens, and loading was continued until the specimens either delaminated unstably, or reached 10(exp 6) to 2 x 10(exp 7) million cycles with no unstable delamination. The final unstable delamination originated at the junction of the thin and tapered regions. A finite-element model was developed for the tapered laminate with and without the initial stable delaminations observed in the tests. The analysis showed that for both cases the most likely place for an opening (Mode 1) delamination to originate is at the junction of the taper and thin regions. For each material type, the models were used to calculate the strain energy release rate, G, associated with delaminations originating at that junction and growing either into the thin region or tapered region. For the materials tested, cyclic G(sub Imax) values from DCB tests were used with the maximum strain energy release rates calculated from the finite-element analysis to predict the onset of unstable delamination at the junction as a function of fatigue cycles. The predictions were compared to experimental values of maximum cyclic load as a function of cycles to unstable delamination from fatigue tests in tapered laminates. For the IM6/1827I and S2/SP250 laminates, the predictions agreed very well with the test data. Predicted values for the S2/CE9000 were conservative compared to the test data.

Ion processing element with composite media

DOEpatents

Mann, Nick R.; Tranter, Troy J.; Todd, Terry A.; Sebesta, Ferdinand

2003-02-04

An ion processing element employing composite media disposed in a porous substrate, for facilitating removal of selected chemical species from a fluid stream. The ion processing element includes a porous fibrous glass substrate impregnated by composite media having one or more active components supported by a matrix material of polyacrylonitrile. The active components are effective in removing, by various mechanisms, one or more constituents from a fluid stream passing through the ion processing element. Due to the porosity and large surface area of both the composite medium and the substrate in which it is disposed, a high degree of contact is achieved between the active component and the fluid stream being processed. Further, the porosity of the matrix material and the substrate facilitates use of the ion processing element in high volume applications where it is desired to effectively process a high volume flows.

Ion processing element with composite media

DOEpatents

Mann, Nick R [Blackfoot, ID; Tranter, Troy J [Idaho Falls, ID; Todd, Terry A [Aberdeen, ID; Sebesta, Ferdinand [Prague, CZ

2009-03-24

An ion processing element employing composite media disposed in a porous substrate, for facilitating removal of selected chemical species from a fluid stream. The ion processing element includes a porous fibrous glass substrate impregnated by composite media having one or more active components supported by a matrix material of polyacrylonitrile. The active components are effective in removing, by various mechanisms, one or more constituents from a fluid stream passing through the ion processing element. Due to the porosity and large surface area of both the composite medium and the substrate in which it is disposed, a high degree of contact is achieved between the active component and the fluid stream being processed. Further, the porosity of the matrix material and the substrate facilitates use of the ion processing element in high volume applications where it is desired to effectively process a high volume flows.

SRXRF determination of the multielement composition of the hair and blood of the children of Tundra Nenetz population

NASA Astrophysics Data System (ADS)

Chankina, O. V.; Kovalskaya, G. A.; Koutzenogii, K. P.; Osipova, L. P.; Savchenko, T. I.

2001-09-01

SRXRF has been used to determine the multielement composition of the hair and blood of Tundra Nenetz children. The method allows one to simultaneously determine 21 elements in the blood and 22 elements in the hair. Individual differences have been revealed in the element composition of the hair and blood. Sexual and age changes have been revealed in the content of some elements in the hair. A technique has been developed to prepare blood and hair samples for measuring the element composition by the SRXRF method. The blood samples were prepared by spreading 20 μl over the 1 cm 2 Whatman filter. The hair samples were obtained by pressing in the form of tablets of 1 cm in diameter and a mass of 10-40 mg.

Layerwise Finite Elements for Smart Piezoceramic Composite Plates in Thermal Environments

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.; Lee, Ho-Jun

1996-01-01

Analytical formulations are presented which account for the coupled mechanical, electrical, and thermal response of piezoelectric composite laminates and plate structures. A layerwise theory is formulated with the inherent capability to explicitly model the active and sensory response of piezoelectric composite plates having arbitrary laminate configurations in thermal environments. Finite element equations are derived and implemented for a bilinear 4-noded plate element. Application cases demonstrate the capability to manage thermally induced bending and twisting deformations in symmetric and antisymmetric composite plates with piezoelectric actuators, and show the corresponding electrical response of distributed piezoelectric sensors. Finally, the resultant stresses in the thermal piezoelectric composite laminates are investigated.

Nuclear matrix - structure, function and pathogenesis.

PubMed

Wasąg, Piotr; Lenartowski, Robert

2016-12-20

The nuclear matrix (NM), or nuclear skeleton, is the non-chromatin, ribonucleoproteinaceous framework that is resistant to high ionic strength buffers, nonionic detergents, and nucleolytic enzymes. The NM fulfills a structural role in eukaryotic cells and is responsible for maintaining the shape of the nucleus and the spatial organization of chromatin. Moreover, the NM participates in several cellular processes, such as DNA replication/repair, gene expression, RNA transport, cell signaling and differentiation, cell cycle regulation, apoptosis and carcinogenesis. Short nucleotide sequences called scaffold/matrix attachment regions (S/MAR) anchor the chromatin loops to the NM proteins (NMP). The NMP composition is dynamic and depends on the cell type and differentiation stage or metabolic activity. Alterations in the NMP composition affect anchoring of the S/MARs and thus alter gene expression. This review aims to systematize information about the skeletal structure of the nucleus, with particular emphasis on the organization of the NM and its role in selected cellular processes. We also discuss several diseases that are caused by aberrant NM structure or dysfunction of individual NM elements.

Marine Bioinorganic Chemistry: The Role of Trace Metals in the Oceanic Cycles of Major Nutrients

NASA Astrophysics Data System (ADS)

Morel, F. M. M.; Milligan, A. J.; Saito, M. A.

2003-12-01

The bulk of living biomass is chiefly made up of only a dozen "major" elements - carbon, hydrogen, oxygen, nitrogen, phosphorus, sodium, potassium, chlorine, calcium, magnesium, sulfur (and silicon in diatoms) - whose proportions vary within a relatively narrow range in most organisms. A number of trace elements, particularly first row transition metals - manganese, iron, nickel, cobalt, copper, and zinc - are also "essential" for the growth of organisms. At the molecular level, the chemical mechanisms by which such elements function as active centers or structural factors in enzymes and by which they are accumulated and stored by organisms is the central topic of bioinorganic chemistry. At the scale of ocean basins, the interplay of physical, chemical, and biological processes that govern the cycling of biologically essential elements in seawater is the subject of marine biogeochemistry. For those interested in the growth of marine organisms, particularly in the one-half of the Earth's primary production contributed by marine phytoplankton, bioinorganic chemistry and marine biogeochemistry are critically linked by the extraordinary paucity of essential trace elements in surface seawater, which results from their biological utilization and incorporation in sinking organic matter. How marine organisms acquire elements that are present at nano- or picomolar concentrations in surface seawater; how they perform critical enzymatic functions when necessary metal cofactors are almost unavailable are the central topics of "marine bioinorganic chemistry." The central aim of this field is to elucidate at the molecular level the metal-dependent biological processes involved in the major biogeochemical cycles.By examining the solutions that emerged from the problems posed by the scarcity of essential trace elements, marine bioinorganic chemists bring to light hitherto unknown ways to take up or utilize trace elements, new molecules, and newer "essential" elements. Focusing on molecular mechanisms involved in such processes as inorganic carbon fixation, organic carbon respiration, or nitrogen transformation, they explain how the cycles of trace elements are critically linked to those of major nutrients such as carbon or nitrogen. But we have relatively little understanding of the binding molecules and the enzymes that mediate the biochemical role of trace metals in the marine environment. In this sense, this chapter is more a "preview" than a review of the field of marine bioinorganic chemistry. To exemplify the concepts and methods of this field, we have chosen to focus on one of its most important topics: the potentially limiting role of trace elements in primary marine production. As a result we center our discussion on particular subsets of organisms, biogeochemical cycles, and trace elements. Our chief actors are marine phytoplankton, particularly eukaryotes, while heterotrophic bacteria make only cameo appearances. The biogeochemical cycles that will serve as our plot are those of the elements involved in phytoplankton growth, the major algal nutrients - carbon, nitrogen, phosphorus, and silicon - leaving aside, e.g., the interesting topic of the marine sulfur cycle. Seven trace metals provide the intrigue: manganese, iron, nickel, cobalt, copper, zinc, and cadmium. But several other trace elements such as selenium, vanadium, molybdenum, and tungsten (and, probably, others not yet identified) will assuredly add further twists in future episodes.We begin this chapter by discussing what we know of the concentrations of trace elements in marine microorganisms and of the relevant mechanisms and kinetics of trace-metal uptake. We then review the biochemical role of trace elements in the marine cycles of carbon, nitrogen, phosphorus, and silicon. Using this information, we examine the evidence, emanating from both laboratory cultures and field measurements, relevant to the mechanisms and the extent of control by trace metals of marine biogeochemical cycles. Before concluding with a wistful glimpse of the future of marine bioinorganic chemistry we discuss briefly some paleoceanographic aspects of this new field: how the chemistry of the planet "Earth" - particularly the concentrations of trace elements in the oceans - has evolved since its origin, chiefly as a result of biological processes and how the evolution of life has, in turn, been affected by the availability of essential trace elements.

The long-term carbon cycle, fossil fuels and atmospheric composition.

PubMed

Berner, Robert A

2003-11-20

The long-term carbon cycle operates over millions of years and involves the exchange of carbon between rocks and the Earth's surface. There are many complex feedback pathways between carbon burial, nutrient cycling, atmospheric carbon dioxide and oxygen, and climate. New calculations of carbon fluxes during the Phanerozoic eon (the past 550 million years) illustrate how the long-term carbon cycle has affected the burial of organic matter and fossil-fuel formation, as well as the evolution of atmospheric composition.

Characterizing Observed Limit Cycles in the Cassini Main Engine Guidance Control System

NASA Technical Reports Server (NTRS)

Rizvi, Farheen; Weitl, Raquel M.

2011-01-01

The Cassini spacecraft dynamics-related telemetry during long Main Engine (ME) burns has indicated the presence of stable limit cycles between 0.03-0.04 Hz frequencies. These stable limit cycles cause the spacecraft to possess non-zero oscillating rates for extended periods of time. This indicates that the linear ME guidance control system does not model the complete dynamics of the spacecraft. In this study, we propose that the observed limit cycles in the spacecraft dynamics telemetry appear from a stable interaction between the unmodeled nonlinear elements in the ME guidance control system. Many nonlinearities in the control system emerge from translating the linear engine gimbal actuator (EGA) motion into a spacecraft rotation. One such nonlinearity comes from the gear backlash in the EGA system, which is the focus of this paper. The limit cycle characteristics and behavior can be predicted by modeling this gear backlash nonlinear element via a describing function and studying the interaction of this describing function with the overall dynamics of the spacecraft. The linear ME guidance controller and gear backlash nonlinearity are modeled analytically. The frequency, magnitude, and nature of the limit cycle are obtained from the frequency response of the ME guidance controller and nonlinear element. In addition, the ME guidance controller along with the nonlinearity is simulated. The simulation response contains a limit cycle with similar characterstics as predicted analytically: 0.03-0.04 Hz frequency and stable, sustained oscillations. The analytical and simulated limit cycle responses are compared to the flight telemetry for long burns such as the Saturn Orbit Insertion and Main Engine Orbit Trim Maneuvers. The analytical and simulated limit cycle characteristics compare well with the actual observed limit cycles in the flight telemetry. Both have frequencies between 0.03-0.04 Hz and stable oscillations. This work shows that the stable limit cycles occur due to the interaction between the unmodeled nonlinear elements and linear ME guidance controller.

Thermal Shock Properties of a 2D-C/SiC Composite Prepared by Chemical Vapor Infiltration

NASA Astrophysics Data System (ADS)

Zhang, Chengyu; Wang, Xuanwei; Wang, Bo; Liu, Yongsheng; Han, Dong; Qiao, Shengru; Guo, Yong

2013-06-01

The thermal shock properties of a two-dimensional carbon fiber-reinforced silicon carbide composite with a multilayered self-healing coating (2D-C/SiC) were investigated in air. The composite was prepared by low-pressure chemical vapor infiltration. 2D-C/SiC specimens were thermally shocked for different cycles between 900 and 300 °C. The thermal shock resistance was characterized by residual tensile properties and mass variation. The change of the surface morphology and microstructural evolution of the composite were examined by a scanning electron microscope. In addition, the phase evolution on the surfaces was identified using an X-ray diffractometer. It is found that the composite retains its tensile strength within 20 thermal shock cycles. However, the modulus of 2D-C/SiC decreases gradually with increasing thermal shock cycles. Extensive pullout of fibers on the fractured surface and peeling off of the coating suggest that the damage caused by the thermal shock involves weakening of the bonding strength of coating/composite and fiber/matrix. In addition, the carbon fibers in the near-surface zone were oxidized through the matrix cracks, and the fiber/matrix interfaces delaminated when the composite was subjected to a larger number of thermal shock cycles.

Current state of nuclear fuel cycles in nuclear engineering and trends in their development according to the environmental safety requirements

NASA Astrophysics Data System (ADS)

Vislov, I. S.; Pischulin, V. P.; Kladiev, S. N.; Slobodyan, S. M.

2016-08-01

The state and trends in the development of nuclear fuel cycles in nuclear engineering, taking into account the ecological aspects of using nuclear power plants, are considered. An analysis of advantages and disadvantages of nuclear engineering, compared with thermal engineering based on organic fuel types, was carried out. Spent nuclear fuel (SNF) reprocessing is an important task in the nuclear industry, since fuel unloaded from modern reactors of any type contains a large amount of radioactive elements that are harmful to the environment. On the other hand, the newly generated isotopes of uranium and plutonium should be reused to fabricate new nuclear fuel. The spent nuclear fuel also includes other types of fission products. Conditions for SNF handling are determined by ecological and economic factors. When choosing a certain handling method, one should assess these factors at all stages of its implementation. There are two main methods of SNF handling: open nuclear fuel cycle, with spent nuclear fuel assemblies (NFAs) that are held in storage facilities with their consequent disposal, and closed nuclear fuel cycle, with separation of uranium and plutonium, their purification from fission products, and use for producing new fuel batches. The development of effective closed fuel cycles using mixed uranium-plutonium fuel can provide a successful development of the nuclear industry only under the conditions of implementation of novel effective technological treatment processes that meet strict requirements of environmental safety and reliability of process equipment being applied. The diversity of technological processes is determined by different types of NFA devices and construction materials being used, as well as by the composition that depends on nuclear fuel components and operational conditions for assemblies in the nuclear power reactor. This work provides an overview of technological processes of SNF treatment and methods of handling of nuclear fuel assemblies. Based on analysis of modern engineering solutions on SNF regeneration, it has been concluded that new reprocessing technologies should meet the ecological safety requirements, provide a more extensive use of the resource base of nuclear engineering, allow the production of valuable and trace elements on an industrial scale, and decrease radioactive waste release.

Improved Damage Resistant Composite Materials Incorporating Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Paine, Jeffrey S. N.; Rogers, Craig A.

1996-01-01

Metallic shape memory alloys (SMA) such as nitinol have unique shape recovery behavior and mechanical properties associated with a material phase change that have been used in a variety of sensing and actuation applications. Recent studies have shown that integrating nitinol-SMA actuators into composite materials increases the composite material's functionality. Hybrid composites of conventional graphite/epoxy or glass/epoxy and nitinol-SMA elements can perform functions in applications where monolithic composites perform inadequately. One such application is the use of hybrid composites to function both in load bearing and armor capacities. While monolithic composites with high strength-to-weight ratios function efficiently as loadbearing structures, because of their brittle nature, impact loading can cause significant catastrophic damage. Initial composite failure modes such as delamination and matrix cracking dissipate some impact energy, but when stress exceeds the composite's ultimate strength, fiber fracture and material perforation become dominant. One of the few methods that has been developed to reduce material perforation is hybridizing polymer matrix composites with tough kevlar or high modulus polyethynylene plies. The tough fibers increase the impact resistance and the stiffer and stronger graphite fibers carry the majority of the load. Similarly, by adding nitinol-SMA elements that absorb impact energy through the stress-induced martensitic phase transformation, the composites' impact perforation resistance can be greatly enhanced. The results of drop-weight and high velocity gas-gun impact testing of various composite materials will be presented. The results demonstrate that hybridizing composites with nitinol-SMA elements significantly increases perforation resistance compared to other traditional toughening elements. Inspection of the composite specimens at various stages of perforation by optical microscope illustrates the mechanisms by which perforation is initiated. Results suggest that the out-of-plane transverse shear properties of the composite and nitinol elements have a significant effect on the perforation resistance. Applications that can utilize the hybrid composites effectively will also be presented with the experimental studies.

Influence of delayed gadolinium enhanced MRI of cartilage (dGEMRIC) protocol on T2-mapping: is it possible to comprehensively assess knee cartilage composition in one post-contrast MR examination at 3 Tesla?

PubMed

Verschueren, J; van Tiel, J; Reijman, M; Bron, E E; Klein, S; Verhaar, J A N; Bierma-Zeinstra, S M A; Krestin, G P; Wielopolski, P A; Oei, E H G

2017-09-01

To evaluate the possibility of assessing knee cartilage with T2-mapping and delayed gadolinium enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) in one post-contrast MR examination at 3 Tesla (T). T2 mapping was performed in 10 healthy volunteers at baseline; directly after baseline; after 10 min of cycling; and after 90 min delay, and in 16 osteoarthritis patients before and after intravenous administration of a double dose gadolinium dimeglumine contrast agent, reflecting key dGEMRIC protocol elements. Differences in T2 relaxation times between each timepoint and baseline were calculated for 6 cartilage regions using paired t tests or Wilcoxon signed-rank tests and the smallest detectable change (SDC). After cycling, a significant change in T2 relaxation times was found in the lateral weight-bearing tibial plateau (+1.0 ms, P = 0.04). After 90 min delay, significant changes were found in the lateral weight-bearing femoral condyle (+1.2 ms, P = 0.03) and the lateral weight-bearing tibial plateau (+1.3 ms, P = 0.01). In these regions of interests (ROIs), absolute differences were small and lower than the corresponding SDCs. T2-mapping after contrast administration only showed statistically significantly lower T2 relaxation times in the medial posterior femoral condyle (-2.4 ms, P < 0.001) with a change exceeding the SDC. Because dGEMRIC protocol elements resulted in only small differences in T2 relaxation times that were not consistent and lower than the SDC in the majority of regions, our results suggest that T2-mapping and dGEMRIC can be performed reliably in a single imaging session to assess cartilage biochemical composition in knee osteoarthritis (OA) at 3 T. Copyright © 2017 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Polyethylene-glycol-doped polypyrrole increases the rate performance of the cathode in lithium-sulfur batteries.

PubMed

Wu, Feng; Chen, Junzheng; Li, Li; Zhao, Teng; Liu, Zhen; Chen, Renjie

2013-08-01

Polypyrrole-polyethylene glycol (PPy/PEG)-modified sulfur/aligned carbon nanotubes (PPy/PEG-S/A-CNTs) were synthesized by using an in situ polymerization method. The ratio of PPy to PEG equaled 31.7:1 after polymerization, and the PEG served as a cation dopant in the polymerization and electrochemical reactions. Elemental analysis, FTIR, Raman spectroscopy, XRD, and electrochemical methods were performed to measure the physicochemical properties of the composite. Elemental analysis demonstrated that the sulfur, PPy, PEG, A-CNT, and chloride content in the synthesized material was 64.6%, 22.1%, 0.7%, 12.1%, and 0.5%, respectively. The thickness of the polymer shell was about 15-25 nm, and FTIR confirmed the successful PPy/PEG synthesis. The cathode exhibited a high initial specific capacity of 1355 mAh g(-1) , and a sulfur usage of 81.1%. The reversible capacity of 924 mAh g(-1) was obtained after 100 cycles, showing a remarkably improved cyclability compared to equivalent systems without PEG doping and without any coatings. PPy/PEG provided an effective electronically conductive network and a stable interface structure for the cathode. Rate performance of the PPy/PEG- S/A-CNT composite was more than double that of the unmodified S/A-CNTs. Remarkably, the battery could work at a very high current density of 8 A g(-1) and reached an initial capacity of 542 mAh g(-1) ; it also retained a capacity of 480 mAh g(-1) after 100 cycles. The addition of PEG as a dopant in the PPy shell contributed to this prominent rate improvement. Lithium ions and electrons were available everywhere on the surfaces of the particles, and thus could greatly improve the electrochemical reaction; PEG is a well-known solvent for lithium salts and a very good lithium-ion catcher. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Bioinorganic chemical composition of the lens and methods of its investigation].

PubMed

Avetisov, S E; Novikov, I A; Pakhomova, N A; Motalov, V G

2018-01-01

Bioinorganic chemical composition of the lens of human and experimental animals (cows, dogs, rats, rabbits) have been analyzed in various studies. In most cases, the studies employed different methods to determine the gross (total) composition of chemical elements and their concentrations in the examined samples. Less frequently, they included an assessment of the distribution of chemical elements in the lens and correlation of their concentration with its morphological changes. Chemical elements from all groups (series) of the periodic classification system were discovered in the lens substance. Despite similar investigation methods, different authors obtained contradicting results on the chemical composition of the lens. This article presents data suggesting possible correlation between inorganic chemical elements in the lens substance with the development and formation of lenticular opacities. All currently employed methods are known to only analyze limited number of select chemical elements in the tissues and do not consider the whole range of elements that can be analyzed with existing technology; furthermore, the majority of studies are conducted on the animal model lens. Therefore, it is feasible to continue the development of the chemical microanalysis method by increasing the sensitivity of Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) with the purpose of assessing the gross chemical composition and distribution of the elements in the lens substance, as well as revealing possible correlation between element concentration and morphological changes in the lens.

Fungal Bioweathering of Mimetite and a General Geomycological Model for Lead Apatite Mineral Biotransformations.

PubMed

Ceci, Andrea; Kierans, Martin; Hillier, Stephen; Persiani, Anna Maria; Gadd, Geoffrey Michael

2015-08-01

Fungi play important roles in biogeochemical processes such as organic matter decomposition, bioweathering of minerals and rocks, and metal transformations and therefore influence elemental cycles for essential and potentially toxic elements, e.g., P, S, Pb, and As. Arsenic is a potentially toxic metalloid for most organisms and naturally occurs in trace quantities in soil, rocks, water, air, and living organisms. Among more than 300 arsenic minerals occurring in nature, mimetite [Pb5(AsO4)3Cl] is the most stable lead arsenate and holds considerable promise in metal stabilization for in situ and ex situ sequestration and remediation through precipitation, as do other insoluble lead apatites, such as pyromorphite [Pb5(PO4)3Cl] and vanadinite [Pb5(VO4)3Cl]. Despite the insolubility of mimetite, the organic acid-producing soil fungus Aspergillus niger was able to solubilize mimetite with simultaneous precipitation of lead oxalate as a new mycogenic biomineral. Since fungal biotransformation of both pyromorphite and vanadinite has been previously documented, a new biogeochemical model for the biogenic transformation of lead apatites (mimetite, pyromorphite, and vanadinite) by fungi is hypothesized in this study by application of geochemical modeling together with experimental data. The models closely agreed with experimental data and provided accurate simulation of As and Pb complexation and biomineral formation dependent on, e.g., pH, cation-anion composition, and concentration. A general pattern for fungal biotransformation of lead apatite minerals is proposed, proving new understanding of ecological implications of the biogeochemical cycling of component elements as well as industrial applications in metal stabilization, bioremediation, and biorecovery. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Changes in element accumulation, phenolic metabolism, and antioxidative enzyme activities in the red-skin roots of Panax ginseng.

PubMed

Zhou, Ying; Yang, Zhenming; Gao, Lingling; Liu, Wen; Liu, Rongkun; Zhao, Junting; You, Jiangfeng

2017-07-01

Red-skin root disease has seriously decreased the quality and production of Panax ginseng (ginseng). To explore the disease's origin, comparative analysis was performed in different parts of the plant, particularly the epidermis, cortex, and/or fibrous roots of 5-yr-old healthy and diseased red-skin ginseng. The inorganic element composition, phenolic compound concentration, reactive oxidation system, antioxidant concentrations such as ascorbate and glutathione, activities of enzymes related to phenolic metabolism and oxidation, and antioxidative system particularly the ascorbate-glutathione cycle were examined using conventional methods. Aluminum (Al), iron (Fe), magnesium, and phosphorus were increased, whereas manganese was unchanged and calcium was decreased in the epidermis and fibrous root of red-skin ginseng, which also contained higher levels of phenolic compounds, higher activities of the phenolic compound-synthesizing enzyme phenylalanine ammonia-lyase and the phenolic compound oxidation-related enzymes guaiacol peroxidase and polyphenoloxidase. As the substrate of guaiacol peroxidase, higher levels of H 2 O 2 and correspondingly higher activities of superoxide dismutase and catalase were found in red-skin ginseng. Increased levels of ascorbate and glutathione; increased activities of l-galactose 1-dehydrogenase, ascorbate peroxidase, ascorbic acid oxidase, and glutathione reductase; and lower activities of dehydroascorbate reductase, monodehydroascorbate reductase, and glutathione peroxidase were found in red-skin ginseng. Glutathione- S -transferase activity remained constant. Hence, higher element accumulation, particularly Al and Fe, activated multiple enzymes related to accumulation of phenolic compounds and their oxidation. This might contribute to red-skin symptoms in ginseng. It is proposed that antioxidant and antioxidative enzymes, especially those involved in ascorbate-glutathione cycles, are activated to protect against phenolic compound oxidation.

Improvement of production layout based on optimum production balancing scale results by using Moodie Young and Comsoal method

NASA Astrophysics Data System (ADS)

Ikhsan, Siregar; Ulina Anastasia Sipangkar, Tri; Prasetio, Aji

2017-09-01

This research was conducted at a make to order production system company which is engaged in the car body of the vehicle. One of the products produced is dump truck which is one kind of transportation for the transport of goods equipped with hydraulics to facilitate goods’ loading and unloading process. The company has 7 work stations with different cycle times. Companies often experience delays in order delivery. The production process on the production floor has not been done optimally where there is a build up of work in process in some work centres. The build up of work in process (WIP) products is seen in the welding and painting stations. Stacking that occurs on the production line may cause the company to be liable for damages due to delays in product completion. The WIP occurs due to unbalanced paths can be seen from the variance of cycle time of each station is very diverse. The time difference of each work element is due to the allocation of work elements to each work centre unevenly. On the basis of the allocation of uneven work elements, the dump truck assembly line is made. The analysis is done by using Moodie Young and Comsoal method to do the balancing of production line. The result of layout improvement by using systematic layout planning (SLP) method is change the composition of the work centre from 7 into 4 work centre which enables the movement of material to be more effective and efficient so that it can get an efficient and effective production trajectory and can solve existing problems. The result of the track balancing is then used as a guide in constructing a new layout based on the balancing result with the most optimum method.

Fatigue Debonding of the Roughened Stem–Cement Interface: Effects of Surface Roughness and Stem Heating Conditions

PubMed Central

Damron, Leatha A.; Kim, Do-Gyoon; Mann, Kenneth A.

2007-01-01

The aim of this study was to determine the effects of cyclic loading on the debond process of a roughened stem– cement interface used in total hip arthroplasty. The specific goals were to assess the effects of two surgeon-controlled variables (stem heating and degree of stem surface roughness) and to determine if an independent finite element-based fracture mechanics model could be used to predict the debond response. A clamped cantilever beam geometry was used to determine the fatigue debond response of the stem– cement interface and was created using an experimental mold that simulated in vivo cementing conditions. A second experiment was performed using a torsion-loading model representative of the stem– cement–bone composite. For both experiments, two stem heating (room temperature and 50°C) and surface roughness conditions (grit blasted: Ra = 2.3 and 5.1 μm) were used. Finally, a finite element model of the torsion experiment with provision for crack growth was developed and compared with the experimental results. Results from both experiments revealed that neither stem preheating nor use of a stem with a greater surface roughness had a marked effect on the fatigue debond response. There was substantial variability in the debond response for all cases; this may be due to microscopic gaps at the interface for all interface conditions. The debond rate from the finite element simulation (10−7.31 m/cycle) had a magnitude similar to the experimental torsion model (10− (6.77 ± 1.25) m/cycle). This suggests that within the context of the experimental conditions studied here that the debond response could be assessed using a linear elastic fracture mechanics-type approach. PMID:16292769

Adhesive strength of paint-on resins to crown and bridge composites.

PubMed

Kanie, Takahito; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2004-12-01

This paper examined the adhesive strength of paint-on resin to crown and bridge composites after soaking in water and thermal-cycling. Three shades of paint-on resin were coated on three kinds of crown and bridge composite under four surface treatment conditions (a combination of sandblaster and pretreatment liquid). These specimens were soaked in water at 37 degrees C for 1 day, 1 month, and 1 year, and at 4 degrees C and 60 degrees C alternatively for 1-minute periods for 10,000 cycles by thermal-cycling machine. The adhesive strengths were obtained by shear test. There were no significant differences among the adhesive strengths of three shades of paint-on resin to three composites after storage (p > 0.05). The adhesive strengths to composites with sandblasting showed higher values than those without it (p < 0.01).

In vitro wear of Ionofil Molar AC quick glass-ionomer cement.

PubMed

Abesi, Farida; Safarcherati, Hengameh; Sadati, Javad; Kheirollahi, Hossein

2011-01-01

The aim of this study was to evaluate the three-body wear-resistance of one type of restorative glass-ionomer cement (GIC). Specimen including conventional GIC (Ionofil Molar AC Quick: IMACQ), hybrid ionomer (Fuji II LC), and composite resin (Heliomolar) were tested in a wearing machine. In this machine, a 6 kg load was applied via pressable chromium-cobalt bar at 5,000, 10,000, 20,000, 40,000, 80,000, 120,000 cycles. Specimen weight was measured by an electronical weight balance before and after each cycle. Data were analyzed using one-way analysis of variance (ANOVA) followed by a t-test, and a paired t-test at P≤0.05. The highest weight loss has been found in Fuji II LC, then in GIC IMACQ and the least wear rate has been reported in heliomolar composite in all cycles except 120,000 cycles. In 120,000 cycles, the highest weight loss was seen in GIC IMACQ, then Fuji II LC, and finally heliomolar composite. There was a statistically significant difference in weight loss between GIC IMACQ and heliomolar composite (P=0/001). The wear rate of GIC IMACQ was between those of heliomolar composite and Fuji II LC glass ionomer in all cycles except 120,000 cycles. The most important advantage of this new-generation glass ionomer is its good manipulability and also high wear-resistance compared to the hybrid ionomer. Therefore, it is suggested that it can be used as restorative material in class I restorations in primary teeth.

Isotopic compositions of the elements, 2001

USGS Publications Warehouse

Böhlke, J.K.; De Laeter, J. R.; De Bievre, P.; Hidaka, H.; Peiser, H.S.; Rosman, K.J.R.; Taylor, P.D.P.

2005-01-01

The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the “best measurement” of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E)">Ar(E)Ar(E) and its uncertainty U[Ar(E)]">U[Ar(E)]U[Ar(E)] recommended by CAWIA in 2001.

Evaluating the cave carbonate chemical signal as a proxy for rain patterns in Mallorca Island

NASA Astrophysics Data System (ADS)

Cacho, Isabel; Cisneros, Mercé; Torner, Judit; Català, Albert; Moreno, Ana; Stoll, Heather; Iglesias, Miguel; Bladé, Ileana; Fornos, Joan

2017-04-01

Mallorca's climate is marked by a strong seasonal cycle in both temperatures and precipitations which is likely to be recorded in the carbonate precipitates formed in its extended karst systems. Here we present isotopes and trace elements measured in dripwaters collected at weakly and/or seasonal bases since spring 2013 in three caves from Mallorca that represent the eastern and S-eastern sector of the island. This information is complemented with isotopic composition of rain events in the same region, other cave environmental parameters and chemistry of seasonal farmed carbonates in the same caves. Drip water results are very consistent between the different studied caves and indicate an important attenuation of the rainfall isotopic signal in the epikarst and only extreme climate conditions such as the severe dry conditions in summer 2015. Farmed carbonates present a clear seasonal cycle with low values, in both carbon and oxygen isotopes, in summer and autumn and high values in winter and spring. This cyclicity can not be attributed to amount effect or rain composition and we propose a close relation to cave environmental conditions. High CO2 concentrations in summer and autumn would avoid degasification reducing the PCP process and resulting in more negative isotopic relationships in both oxygen and carbon isotopes. Coherently, this CO2 cycles are in phase with those of temperature since both reflect ventilation rates in the cave. Nevertheless, ultra-high resolution profiles of Mg/Ca ratios measured by laser ablation on last century carbonate precipitates in the same caves, reveal a inter-annual variability with a persistent cyclicity which show coherent patterns with the instrumental rain records from Mallorca. This comparison reveals the potential of the Mallorca carbonates to reveal the long-term precipitation evolution of the island.

Innovative Processing of Composites for Ultra-High Temperature Applications. Book 3

DTIC Science & Technology

1993-11-01

SiC Samples Prepared with Four Preceramic Polymer Infiltration / Pyrolysis (at 15750C) Cycles Figure 21 Scanning Electron...Micrograph of Large Pores near the Surface of Siliconized SIC Sample with Four Preceramic Polymer Infiltration / Pyrolysis (at 1575*C) Cycles II...In order to achieve dense, bulk composites with maximum SiC /Si ratio, two infiltration / pyrolysis cycles were used. S (4) After siliconization,

Sources and mobility of carbonate melts beneath cratons, with implications for deep carbon cycling, metasomatism and rift initiation

NASA Astrophysics Data System (ADS)

Tappe, Sebastian; Romer, Rolf L.; Stracke, Andreas; Steenfelt, Agnete; Smart, Katie A.; Muehlenbachs, Karlis; Torsvik, Trond H.

2017-05-01

Kimberlite and carbonatite magmas that intrude cratonic lithosphere are among the deepest probes of the terrestrial carbon cycle. Their co-existence on thick continental shields is commonly attributed to continuous partial melting sequences of carbonated peridotite at >150 km depths, possibly as deep as the mantle transition zone. At Tikiusaaq on the North Atlantic craton in West Greenland, approximately 160 Ma old ultrafresh kimberlite dykes and carbonatite sheets provide a rare opportunity to study the origin and evolution of carbonate-rich melts beneath cratons. Although their Sr-Nd-Hf-Pb-Li isotopic compositions suggest a common convecting upper mantle source that includes depleted and recycled oceanic crust components (e.g., negative ΔεHf coupled with > + 5 ‰ δ7Li), incompatible trace element modelling identifies only the kimberlites as near-primary low-degree partial melts (0.05-3%) of carbonated peridotite. In contrast, the trace element systematics of the carbonatites are difficult to reproduce by partial melting of carbonated peridotite, and the heavy carbon isotopic signatures (-3.6 to - 2.4 ‰ δ13C for carbonatites versus -5.7 to - 3.6 ‰ δ13C for kimberlites) require open-system fractionation at magmatic temperatures. Given that the oxidation state of Earth's mantle at >150 km depth is too reduced to enable larger volumes of 'pure' carbonate melt to migrate, it is reasonable to speculate that percolating near-solidus melts of carbonated peridotite must be silicate-dominated with only dilute carbonate contents, similar to the Tikiusaaq kimberlite compositions (e.g., 16-33 wt.% SiO2). This concept is supported by our findings from the North Atlantic craton where kimberlite and other deeply derived carbonated silicate melts, such as aillikites, exsolve their carbonate components within the shallow lithosphere en route to the Earth's surface, thereby producing carbonatite magmas. The relative abundances of trace elements of such highly differentiated 'cratonic carbonatites' have only little in common with those of metasomatic agents that act on the deeper lithosphere. Consequently, carbonatite trace element systematics should only be used with caution when constraining carbon mobility and metasomatism at mantle depths. Regardless of the exact nature of carbonate-bearing melts within the mantle lithosphere, they play an important role in enrichment processes, thereby decreasing the stability of buoyant cratons and promoting rift initiation - as exemplified by the Mesozoic-Cenozoic breakup of the North Atlantic craton.

Lamination residual stresses in fiber composites

NASA Technical Reports Server (NTRS)

Daniel, I. M.; Liber, T.

1975-01-01

An experimental investigation was conducted to determine the magnitude of lamination residual stresses in angle-ply composites and to evaluate their effects on composite structural integrity. The materials investigated were boron/epoxy, boron/polyimide, graphite/low modulus epoxy, graphite/high modulus epoxy, graphite/polyimide and s-glass/epoxy. These materials were fully characterized. Static properties of laminates were also determined. Experimental techniques using embedded strain gages were developed and used to measure residual strains during curing. The extent of relaxation of lamination residual stresses was investigated. It was concluded that the degree of such relaxation is low. The behavior of angle-ply laminates subjected to thermal cycling, tensile load cycling, and combined thermal cycling with tensile load was investigated. In most cases these cycling programs did not have any measurable influence on residual strength and stiffness of the laminates. In the tensile load cycling tests, the graphite/polyimide shows the highest endurance with 10 million cycle runouts at loads up to 90 percent of the static strength.

Wavelet Spectral Finite Elements for Wave Propagation in Composite Plates with Damages - Years 3-4

DTIC Science & Technology

2014-05-23

study of Lamb wave interactions with holes and through thickness defects in thin metal plates . Distribution Code A: Approved for public release...Propagation in Composite Plates with Damages - Years 3-4 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA23861214005 5c. PROGRAM ELEMENT NUMBER 6...14. ABSTRACT The objective of the proposed efforts: -Formulated Wavelet Spectral element for a healthy composite plates and used the formulated

Development of metal hydride composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Congdon, J.W.

1992-12-01

Most of current hydride technology at Savannah River Site is based on beds of metal hydride powders; the expansion upon hydridation and the cycling results in continued breakdown into finer particles. Goal is to develop a composite which will contain the fines in a dimensionally stable matrix, for use in processes which require a stable gas flow through a hydride bed. Metal hydride composites would benefit the advanced Thermal Cycling Absorption process (hydrogen isotope separation), and the Replacement Tritium Facility (storage, pumping, compression, purification of hydrogen isotopes). These composites were fabricated by cold compaction of a mixture of metal hydridemore » granules and coarse copper powder; the porosity in the granules was introduced by means of ammonium carbonate. The composite pellets were cycled 138 times in hydrogen with the loss of LANA0.75 (LaNi{sub 4.25}Al{sub 0.75}) limited to the surface. Vacuum sintering can provide additional strength at the edges. Without a coating, the metal hydride particles exposed at the pellet surface can be removed by cycling several times in hydrogen.« less

Analytical and experimental investigation of aircraft metal structures reinforced with filamentary composites. Phase 2: Structural fatigue, thermal cycling, creep, and residual strength

NASA Technical Reports Server (NTRS)

Blichfeldt, B.; Mccarty, J. E.

1972-01-01

Specimens representative of metal aircraft structural components reinforced with boron filamentary composites were manufactured and tested under cyclic loading, cyclic temperature, or continuously applied loading to evaluate some of the factors that affect structural integrity under cyclic conditions. Bonded, stepped joints were used throughout to provide composite-to-metal transition regions at load introduction points. Honeycomb panels with titanium or aluminum faces reinforced with unidirectional boron composite were fatigue tested at constant amplitude under completely reversed loading. Results indicated that the matrix material was the most fatigue-sensitive part of the design, with debonding initiating in the stepped joints. However, comparisons with equal weight all-metal specimens show a 10 to 50 times improved fatigue life. Fatigue crack propagation and residual strength were studied for several different stiffened panel concepts, and were found to vary considerably depending on the configuration. Composite-reinforced metal specimens were also subjected to creep and thermal cycling tests. Thermal cycling of stepped joint tensile specimens resulted in a ten percent decrease in residual strength after 4000 cycles.

Synergetic Effect of Yolk-Shell Structure and Uniform Mixing of SnS-MoS₂ Nanocrystals for Improved Na-Ion Storage Capabilities.

PubMed

Choi, Seung Ho; Kang, Yun Chan

2015-11-11

Mixed metal sulfide composite microspheres with a yolk-shell structure for sodium-ion batteries are studied. Tin-molybdenum oxide yolk-shell microspheres prepared by a one-pot spray pyrolysis process transform into yolk-shell SnS-MoS2 composite microspheres. The discharge capacities of the yolk-shell and dense-structured SnS-MoS2 composite microspheres for the 100th cycle are 396 and 207 mA h g(-1), and their capacity retentions measured from the second cycle are 89 and 47%, respectively. The yolk-shell SnS-MoS2 composite microspheres with high structural stability during repeated sodium insertion and desertion processes have low charge-transfer resistance even after long-term cycling. The synergetic effect of the yolk-shell structure and uniform mixing of the SnS and MoS2 nanocrystals result in the excellent sodium-ion storage properties of the yolk-shell SnS-MoS2 composite microspheres by improving their structural stability during cycling.

Metallurgically lithiated SiOx anode with high capacity and ambient air compatibility

PubMed Central

Zhao, Jie; Lee, Hyun-Wook; Sun, Jie; Yan, Kai; Liu, Yayuan; Liu, Wei; Lu, Zhenda; Lin, Dingchang; Zhou, Guangmin; Cui, Yi

2016-01-01

A common issue plaguing battery anodes is the large consumption of lithium in the initial cycle as a result of the formation of a solid electrolyte interphase followed by gradual loss in subsequent cycles. It presents a need for prelithiation to compensate for the loss. However, anode prelithiation faces the challenge of high chemical reactivity because of the low anode potential. Previous efforts have produced prelithiated Si nanoparticles with dry air stability, which cannot be stabilized under ambient air. Here, we developed a one-pot metallurgical process to synthesize LixSi/Li2O composites by using low-cost SiO or SiO2 as the starting material. The resulting composites consist of homogeneously dispersed LixSi nanodomains embedded in a highly crystalline Li2O matrix, providing the composite excellent stability even in ambient air with 40% relative humidity. The composites are readily mixed with various anode materials to achieve high first cycle Coulombic efficiency (CE) of >100% or serve as an excellent anode material by itself with stable cyclability and consistently high CEs (99.81% at the seventh cycle and ∼99.87% for subsequent cycles). Therefore, LixSi/Li2O composites achieved balanced reactivity and stability, promising a significant boost to lithium ion batteries. PMID:27313206

Post-Crazing Stress Analysis of Glass-Epoxy Laminates.

DTIC Science & Technology

1979-05-01

element Stress concentrations Thick-shell element b. Identiflers/Open-Ended Terms Thick-plate element Glass-epoxy Laminates Composite materials Failure...number) / Glass-Epoxy Angle Plys Finite Elements’ Laminates Shear Testing Isoparametric.,lement Composite Materials Compression Testing Doubly-Curved...with light weight. This favorable strength- weight ratio makes the material attractive for some flight structures as well as other machines and

Anthropogenic osmium in rain and snow reveals global-scale atmospheric contamination

PubMed Central

Chen, Cynthia; Sedwick, Peter N.; Sharma, Mukul

2009-01-01

Osmium is one of the rarer elements in seawater, with typical concentration of ≈10 × 10−15 g g−1 (5.3 × 10−14 mol kg−1). The osmium isotope composition (187Os/188Os ratio) of deep oceans is 1.05, reflecting a balance between inputs from continental crust (≈1.3) and mantle/cosmic dust (≈0.13). Here, we show that the 187Os/188Os ratios measured in rain and snow collected around the world range from 0.16 to 0.48, much lower than expected (>1), but similar to the isotope composition of ores (≈0.2) that are processed to extract platinum and other metals to be used primarily in automobile catalytic converters. Present-day surface seawater has a lower 187Os/188Os ratio (≈0.95) than deep waters, suggesting that human activities have altered the isotope composition of the world's oceans and impacted the global geochemical cycle of osmium. The contamination of the surface ocean is particularly remarkable given that osmium has few industrial uses. The pollution may increase with growing demand for platinum-based catalysts. PMID:19416862

Trilateral Design and Test Code for Military Bridging and Gap-Crossing Equipment

DTIC Science & Technology

2005-05-01

Property data should be provided for individual lamina and for the ( laminat - ed) composite . The required lamina properties are identified in...Resistance Welding ....... a Brazing ......................... X Machining ..................... a Chemical Composition : Element... Machining .................. b Chemical Composition : Element % Si .................................. 0.2 max Fe

Elemental composition and energy spectra of galactic cosmic rays

NASA Technical Reports Server (NTRS)

Mewaldt, R. A.

1988-01-01

A brief review is presented of the major features of the elemental composition and energy spectra of galactic cosmic rays. The requirements for phenomenological models of cosmic ray composition and energy spectra are discussed, and possible improvements to an existing model are suggested.

Origin and evolution of SINEs in eukaryotic genomes.

PubMed

Kramerov, D A; Vassetzky, N S

2011-12-01

Short interspersed elements (SINEs) are one of the two most prolific mobile genomic elements in most of the higher eukaryotes. Although their biology is still not thoroughly understood, unusual life cycle of these simple elements amplified as genomic parasites makes their evolution unique in many ways. In contrast to most genetic elements including other transposons, SINEs emerged de novo many times in evolution from available molecules (for example, tRNA). The involvement of reverse transcription in their amplification cycle, huge number of genomic copies and modular structure allow variation mechanisms in SINEs uncommon or rare in other genetic elements (module exchange between SINE families, dimerization, and so on.). Overall, SINE evolution includes their emergence, progressive optimization and counteraction to the cell's defense against mobile genetic elements.

Simplified Calculation Model and Experimental Study of Latticed Concrete-Gypsum Composite Panels

PubMed Central

Jiang, Nan; Ma, Shaochun

2015-01-01

In order to address the performance complexity of the various constituent materials of (dense-column) latticed concrete-gypsum composite panels and the difficulty in the determination of the various elastic constants, this paper presented a detailed structural analysis of the (dense-column) latticed concrete-gypsum composite panel and proposed a feasible technical solution to simplified calculation. In conformity with mechanical rules, a typical panel element was selected and divided into two homogenous composite sub-elements and a secondary homogenous element, respectively for solution, thus establishing an equivalence of the composite panel to a simple homogenous panel and obtaining the effective formulas for calculating the various elastic constants. Finally, the calculation results and the experimental results were compared, which revealed that the calculation method was correct and reliable and could meet the calculation needs of practical engineering and provide a theoretical basis for simplified calculation for studies on composite panel elements and structures as well as a reference for calculations of other panels. PMID:28793631

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.

Simplified Calculation Model and Experimental Study of Latticed Concrete-Gypsum Composite Panels.

PubMed

Jiang, Nan; Ma, Shaochun

2015-10-27

In order to address the performance complexity of the various constituent materials of (dense-column) latticed concrete-gypsum composite panels and the difficulty in the determination of the various elastic constants, this paper presented a detailed structural analysis of the (dense-column) latticed concrete-gypsum composite panel and proposed a feasible technical solution to simplified calculation. In conformity with mechanical rules, a typical panel element was selected and divided into two homogenous composite sub-elements and a secondary homogenous element, respectively for solution, thus establishing an equivalence of the composite panel to a simple homogenous panel and obtaining the effective formulas for calculating the various elastic constants. Finally, the calculation results and the experimental results were compared, which revealed that the calculation method was correct and reliable and could meet the calculation needs of practical engineering and provide a theoretical basis for simplified calculation for studies on composite panel elements and structures as well as a reference for calculations of other panels.

Tetrathionate and Elemental Sulfur Shape the Isotope Composition of Sulfate in Acid Mine Drainage

PubMed Central

Balci, Nurgul; Brunner, Benjamin; Turchyn, Alexandra V.

2017-01-01

Sulfur compounds in intermediate valence states, for example elemental sulfur, thiosulfate, and tetrathionate, are important players in the biogeochemical sulfur cycle. However, key understanding about the pathways of oxidation involving mixed-valance state sulfur species is still missing. Here we report the sulfur and oxygen isotope fractionation effects during the oxidation of tetrathionate (S4O62−) and elemental sulfur (S°) to sulfate in bacterial cultures in acidic conditions. Oxidation of tetrathionate by Acidithiobacillus thiooxidans produced thiosulfate, elemental sulfur and sulfate. Up to 34% of the tetrathionate consumed by the bacteria could not be accounted for in sulfate or other intermediate-valence state sulfur species over the experiments. The oxidation of tetrathionate yielded sulfate that was initially enriched in 34S (ε34SSO4−S4O6) by +7.9‰, followed by a decrease to +1.4‰ over the experiment duration, with an average ε34SSO4−S4O6 of +3.5 ± 0.2‰ after a month of incubation. We attribute this significant sulfur isotope fractionation to enzymatic disproportionation reactions occurring during tetrathionate decomposition, and to the incomplete transformation of tetrathionate into sulfate. The oxygen isotope composition of sulfate (δ18OSO4) from the tetrathionate oxidation experiments indicate that 62% of the oxygen in the formed sulfate was derived from water. The remaining 38% of the oxygen was either inherited from the supplied tetrathionate, or supplied from dissolved atmospheric oxygen (O2). During the oxidation of elemental sulfur, the product sulfate became depleted in 34S between −1.8 and 0‰ relative to the elemental sulfur with an average for ε34SSO4−S0 of −0.9 ± 0.2‰ and all the oxygen atoms in the sulfate derived from water with an average normal oxygen isotope fractionation (ε18OSO4−H2O) of −4.4‰. The differences observed in δ18OSO4 and the sulfur isotope composition of sulfate (δ34SSO4), acid production, and mixed valence state sulfur species generated by the oxidation of the two different substrates suggests a metabolic flexibility in response to sulfur substrate availability. Our results demonstrate that microbial processing of mixed-valence-state sulfur species generates a significant sulfur isotope fractionation in acidic environments and oxidation of mixed-valence state sulfur species may produce sulfate with characteristic sulfur and oxygen isotope signatures. Elemental sulfur and tetrathionate are not only intermediate-valence state sulfur compounds that play a central role in sulfur oxidation pathways, but also key factors in shaping these isotope patterns. PMID:28861071

Minor Elements in Nakhlite Pyroxenes: Cr in MIL00346

NASA Technical Reports Server (NTRS)

McKay, G. A.; Schwandt, C.; Le, L.; Makishima, J.; Kurihara, T.

2006-01-01

Nakhlites are olivine-bearing clinopyroxene cumulates. Based on petrographic characteristics, they may be divided into groups that cooled at different rates and may have been formed at different depths in a single flow. The order of cooling rate from slowest to fastest is NWA998

Finite element modeling of frictionally restrained composite interfaces

NASA Technical Reports Server (NTRS)

Ballarini, Roberto; Ahmed, Shamim

1989-01-01

The use of special interface finite elements to model frictional restraint in composite interfaces is described. These elements simulate Coulomb friction at the interface, and are incorporated into a standard finite element analysis of a two-dimensional isolated fiber pullout test. Various interfacial characteristics, such as the distribution of stresses at the interface, the extent of slip and delamination, load diffusion from fiber to matrix, and the amount of fiber extraction or depression are studied for different friction coefficients. The results are compared to those obtained analytically using a singular integral equation approach, and those obtained by assuming a constant interface shear strength. The usefulness of these elements in micromechanical modeling of fiber-reinforced composite materials is highlighted.

Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pratt, Joseph William; Cordaro, Joseph Gabriel; Sartor, George B.

2012-02-01

In an attempt to mitigate the hazards associated with storing large quantities of reactive metal hydrides, polymer composite materials were synthesized and tested under simulated usage and accident conditions. The composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride. Composites with vinyl-containing siloxane oligomers were also polymerized with and without added styrene and divinyl benzene. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride reduced the inherent hydrogen storage capacity of the material. The composites were found to be initially effective at reducing the amount of heatmore » released during oxidation. However, upon cycling the composites, the mitigating behavior was lost. While the polymer composites we investigated have mitigating potential and are physically robust, they undergo a chemical change upon cycling that makes them subsequently ineffective at mitigating heat release upon oxidation of the metal hydride. Acknowledgements The authors would like to thank the following people who participated in this project: Ned Stetson (U.S. Department of Energy) for sponsorship and support of the project. Ken Stewart (Sandia) for building the flow-through calorimeter and cycling test stations. Isidro Ruvalcaba, Jr. (Sandia) for qualitative experiments on the interaction of sodium alanate with water. Terry Johnson (Sandia) for sharing his expertise and knowledge of metal hydrides, and sodium alanate in particular. Marcina Moreno (Sandia) for programmatic assistance. John Khalil (United Technologies Research Corp) for insight into the hazards of reactive metal hydrides and real-world accident scenario experiments. Summary In an attempt to mitigate and/or manage hazards associated with storing bulk quantities of reactive metal hydrides, polymer composite materials (a mixture of a mitigating polymer and a metal hydride) were synthesized and tested under simulated usage and accident conditions. Mitigating the hazards associated with reactive metal hydrides during an accident while finding a way to keep the original capability of the active material intact during normal use has been the focus of this work. These composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride, in this case a prepared sodium alanate (chosen as a representative reactive metal hydride). It was found that the polymerization of styrene and divinyl benzene could be initiated using AIBN in toluene at 70°C. The resulting composite materials can be either hard or brittle solids depending on the cross-linking density. Thermal decomposition of these styrene-based composite materials is lower than neat polystyrene indicating that the chemical nature of the polymer is affected by the formation of the composite. The char-forming nature of cross-linked polystyrene is low and therefore, not an ideal polymer for hazard mitigation. To obtain composite materials containing a polymer with higher char-forming potential, siloxane-based monomers were investigated. Four vinyl-containing siloxane oligomers were polymerized with and without added styrene and divinyl benzene. Like the styrene materials, these composite materials exhibited thermal decomposition behavior significantly different than the neat polymers. Specifically, the thermal decomposition temperature was shifted approximately 100 °C lower than the neat polymer signifying a major chemical change to the polymer network. Thermal analysis of the cycled samples was performed on the siloxane-based composite materials. It was found that after 30 cycles the siloxane-containing polymer composite material has similar TGA/DSC-MS traces as the virgin composite material indicating that the polymer is physically intact upon cycling. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride in the form of a composite material reduced the inherent hydrogen storage capacity of the material. This reduction in capacity was observed to be independent of the amount of charge/discharge cycles except for the composites containing siloxane, which showed less of an impact on hydrogen storage capacity as it was cycled further. While the reason for this is not clear, it may be due to a chemically stabilizing effect of the siloxane on the metal hydride. Flow-through calorimetry was used to characterize the mitigating effectiveness of the different composites relative to the neat (no polymer) material. The composites were found to be initially effective at reducing the amount of heat released during oxidation, and the best performing material was the siloxane-containing composite which reduced the heat release to less than 50% of the value of the neat material. However, upon cycling the composites, all mitigating behavior was lost. The combined results of the flow-through calorimetry, hydrogen capacity, and thermogravimetric analysis tests lead to the proposed conclusion that while the polymer composites have mitigating potential and are physically robust under cycling, they undergo a chemical change upon cycling that makes them ineffective at mitigating heat release upon oxidation of the metal hydride.« less

The research and realization of digital management platform for ultra-precision optical elements within life-cycle

NASA Astrophysics Data System (ADS)

Wang, Juan; Wang, Jian; Li, Lijuan; Zhou, Kun

2014-08-01

In order to solve the information fusion, process integration, collaborative design and manufacturing for ultra-precision optical elements within life-cycle management, this paper presents a digital management platform which is based on product data and business processes by adopting the modern manufacturing technique, information technique and modern management technique. The architecture and system integration of the digital management platform are discussed in this paper. The digital management platform can realize information sharing and interaction for information-flow, control-flow and value-stream from user's needs to offline in life-cycle, and it can also enhance process control, collaborative research and service ability of ultra-precision optical elements.

Plutonium segregation in glassy aerodynamic fallout from a nuclear weapon test

DOE PAGES

Holliday, K. S.; Dierken, J. M.; Monroe, M. L.; ...

2017-01-11

Our study combines electron microscopy equipped with energy dispersive spectroscopy to probe major element composition and autoradiography to map plutonium in order to examine the spatial relationships between plutonium and fallout composition in aerodynamic glassy fallout from a nuclear weapon test. We interrogated a sample set of 48 individual fallout specimens in order to reveal that the significant chemical heterogeneity of this sample set could be described compositionally with a relatively small number of compositional endmembers. Furthermore, high concentrations of plutonium were never associated with several endmember compositions and concentrated with the so-called mafic glass endmember. Our result suggests thatmore » it is the physical characteristics of the compositional endmembers and not the chemical characteristics of the individual component elements that govern the un-burnt plutonium distribution with respect to major element composition in fallout.« less

Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

NASA Technical Reports Server (NTRS)

Gao, Xiu-Jie; Turner, Travis L.; Burton, Deborah; Brinson, L. Catherine

2005-01-01

The usage of shape memory materials has extended rapidly to many fields, including medical devices, actuators, composites, structures and MEMS devices. For these various applications, shape memory alloys (SMAs) are available in various forms: bulk, wire, ribbon, thin film, and porous. In this work, the focus is on SMA hybrid composites with adaptive-stiffening or morphing functions. These composites are created by using SMA ribbons or wires embedded in a polymeric based composite panel/beam. Adaptive stiffening or morphing is activated via selective resistance heating or uniform thermal loads. To simulate the thermomechanical behavior of these composites, a SMA model was implemented using ABAQUS user element interface and finite element simulations of the systems were studied. Several examples are presented which show that the implemented model can be a very useful design and simulation tool for SMA hybrid composites.

The link between composition and balance in masterworks vs. paintings of lower artistic quality.

PubMed

Vartanian, Oshin; Martindale, Colin; Podsiadlo, Jacob; Overbay, Shane; Borkum, Jonathan

2005-11-01

In painting, composition is commonly defined as the two-dimensional arrangement of elements within the canvas. Each element is considered to have a perceptual weight. The arrangement of these weighted elements determines how balanced a painting is. It has been suggested that due to superior composition, masterworks may be more balanced than works of lower artistic quality. We tested this hypothesis by instructing our participants to rate masterworks and selections of lower artistic quality on balance. This hypothesis was not supported. Second, it has been suggested that rearranging elements within a painting may have a more detrimental effect on composition (and by extension balance) in masterworks than in selections of lower artistic quality. This view associates works of higher artistic quality with visual rightness, thereby predicting that compositional change would be more likely to cause deviations from a visually right state in masterworks. We tested this hypothesis by displacing an element within each painting to a different location, and measuring the effect on balance. In accordance with recent findings in the literature, we also took into account the severity of the compositional alterations. The results demonstrated that compositional alteration affected balance ratings equally across masterworks and selections of lower artistic quality. These results demonstrate that, although balance is a function of compositional structure, balance on its own is not sufficient to distinguish between works of varying artistic quality. To the extent that balance is considered a function of composition, the results suggest that masterworks are distinguished from works of lower artistic quality for reasons other than solely composition.

Computing Fiber/Matrix Interfacial Effects In SiC/RBSN

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Hopkins, Dale A.

1996-01-01

Computational study conducted to demonstrate use of boundary-element method in analyzing effects of fiber/matrix interface on elastic and thermal behaviors of representative laminated composite materials. In study, boundary-element method implemented by Boundary Element Solution Technology - Composite Modeling System (BEST-CMS) computer program.

Subsurface In Situ Elemental Composition Measurements with PING

NASA Technical Reports Server (NTRS)

Parsons, Ann; McClanahan, Timothy; Bodnarik, Julia; Evans, Larry; Nowicki, Suzanne; Schweitzer, Jeffrey; Starr, Richard

2013-01-01

This paper describes the Probing In situ with Neutron and Gamma rays (PING) instrument, that can measure the subsurface elemental composition in situ for any rocky body in the solar system without the need for digging into the surface. PING consists of a Pulsed Neutron Generator (PNG), a gamma ray spectrometer and neutron detectors. Subsurface elements are stimulated by high-energy neutrons to emit gamma rays at characteristic energies. This paper will show how the detection of these gamma rays results in a measurement of elemental composition. Examples of the basalt to granite ratios for aluminum and silicon abundance are provided.

Symmetry considerations in the scattering of identical composite bodies

NASA Technical Reports Server (NTRS)

Norbury, J. W.; Townsend, L. W.; Deutchman, P. A.

1986-01-01

Previous studies of the interactions between composite particles were extended to the case in which the composites are identical. The form of the total interaction potential matrix elements was obtained, and guidelines for their explicit evaluation were given. For the case of elastic scattering of identical composites, the matrix element approach was shown to be equivalent to the scattering amplitude method.

Ocean acidification changes the structure of an Antarctic coastal protistan community

NASA Astrophysics Data System (ADS)

Hancock, Alyce M.; Davidson, Andrew T.; McKinlay, John; McMinn, Andrew; Schulz, Kai G.; van den Enden, Rick L.

2018-04-01

Antarctic near-shore waters are amongst the most sensitive in the world to ocean acidification. Microbes occupying these waters are critical drivers of ecosystem productivity, elemental cycling and ocean biogeochemistry, yet little is known about their sensitivity to ocean acidification. A six-level, dose-response experiment was conducted using 650 L incubation tanks (minicosms) adjusted to a gradient in fugacity of carbon dioxide (fCO2) from 343 to 1641 µatm. The six minicosms were filled with near-shore water from Prydz Bay, East Antarctica, and the protistan composition and abundance was determined by microscopy during 18 days of incubation. No CO2-related change in the protistan community composition was observed during the initial 8 day acclimation period under low light. Thereafter, the response of both autotrophic and heterotrophic protists to fCO2 was species-specific. The response of diatoms was mainly cell size related; microplanktonic diatoms ( > 20 µm) increased in abundance with low to moderate fCO2 (343-634 µatm) but decreased at fCO2 ≥ 953 µatm. Similarly, the abundance of Phaeocystis antarctica increased with increasing fCO2 peaking at 634 µatm. Above this threshold the abundance of micro-sized diatoms and P. antarctica fell dramatically, and nanoplanktonic diatoms ( ≤ 20 µm) dominated, therefore culminating in a significant change in the protistan community composition. Comparisons of these results with previous experiments conducted at this site show that the fCO2 thresholds are similar, despite seasonal and interannual differences in the physical and biotic environment. This suggests that near-shore microbial communities are likely to change significantly near the end of this century if anthropogenic CO2 release continues unabated, with profound ramifications for near-shore Antarctic ecosystem food webs and biogeochemical cycling.

CERAMIC FUEL ELEMENT MATERIAL FOR A NEUTRONIC REACTOR AND METHOD OF FABRICATING SAME

DOEpatents

Duckworth, W.H.

1957-12-01

This patent relates to ceramic composition, and to neutronic reactor fuel elements formed therefrom. These ceramic elements have high density and excellent strength characteristics and are formed by conventional ceramic casting and sintering at a temperature of about 2700 deg F in a nitrogen atmosphere. The composition consists of silicon carbide, silicon, uranium oxide and a very small percentage of molybdenum. Compositions containing molybdenum are markedly stronger than those lacking this ingredient.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polat, B. D.; Eryilmaz, O. L.; Keles, O

Compositionally graded and non-graded composite SiCu thin films were deposited by magnetron sputtering technique on Cu disks for investigation of their potentials in lithium ion battery applications. The compositionally graded thin film electrodes with 30 at.% Cu delivered a 1400 mAh g-1 capacity with 80% Coulombic efficiency in the first cycle and still retained its capacity at around 600 mAh g-1 (with 99.9% Coulombic efficiency) even after 100 cycles. On the other hand, the non-graded thin film electrodes with 30 at.% Cu exhibited 1100 mAh g-1 as the first discharge capacity with 78% Coulombic efficiency but the cycle life ofmore » this film degraded very quickly, delivering only 250 mAh g-1 capacity after 100th cycles. Not only the Cu content but also the graded film thickness were believed to be the main contributors to the much superior performance of the compositionally graded SiCu films. We also believe that the Cu-rich region of the graded film helped reduce internal stress build-up and thus prevented film delamination during cycling. In particular, the decrease of Cu content from interface region to the top of the coating reduced the possibility of stress build-up across the film during cycling, thus leading to a high electrochemical performance.« less

Biodiversity of mineral nutrient and trace element accumulation in Arabidopsis thaliana

USDA-ARS?s Scientific Manuscript database

In order to grow on soils that vary widely in chemical composition, plants have evolved mechanisms for regulating the elemental composition of their tissues to balance the mineral nutrient and trace element bioavailability in the soil with the requirements of the plant for growth and development. T...

Ca-,Al-rich inclusions in the unique chondrite ALH85085 - Petrology, chemistry, and isotopic compositions

NASA Technical Reports Server (NTRS)

Kimura, Makoto; El-Goresy, Ahmed; Palme, Herbert; Zinner, Ernst

1993-01-01

A comprehensive study is performed for the Ca-,Al-rich inclusions (CAIs) in the unique chondrite ALH85085. The ALH85085 inclusions are smaller (5-80 microns) and more refractory than their counterparts in carbonaceous chondrites. The study includes 42 inclusions for petrography and mineralogy, 15 for bulk major and minor element chemical composition, six for Mg-Al isotopic systematics, 10 for Ca isotopes, nine for Ti isotopes, and six for trace element abundances. In addition, oxygen-isotopic compositions were determined in minerals from a single inclusion. No correlation is found between mineralogy, major element chemistry, and trace element abundances. It is further shown that the high-temperature geochemical behavior of ultrarefractory trace elements is decoupled from that of the major elements Ca and Ti (Ti is correlated with the relatively volatile elements Nb and Yb) implying that perovskite is of only minor importance as carrier of ultrarefractories.

Use of Guided Acoustic Waves to Assess the Effects of Thermal-Mechanical Cycling on Composite Stiffness

NASA Technical Reports Server (NTRS)

Seale, Michael D.; Madaras, Eric I.

2000-01-01

The introduction of new, advanced composite materials into aviation systems requires it thorough understanding of the long-term effects of combined thermal and mechanical loading. As part of a study to evaluate the effects of thermal-mechanical cycling, it guided acoustic (Lamb) wave measurement system was used to measure the bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the velocity dispersion curve. A series of 16 and 32-ply composite laminates were subjected to it thermal-mechanical loading profile in load frames equipped with special environmental chambers. The composite systems studied were it graphite fiber reinforced amorphous thermoplastic polyimide and it graphite fiber reinforced bismaleimide thermoset. The samples were exposed to both high and low temperature extremes its well as high and low strain profiles. The bending and out-of-plane stiffnesses for composite sample that have undergone over 6,000 cycles of thermal-mechanical loading are reported. The Lamb wave generated elastic stiffness results have shown decreases of up to 20% at 4,936 loading cycles for the graphite/thermoplastic samples and up to 64% at 4,706 loading cycles for the graphite/thermoset samples.

Facile Co-Electrodeposition Method for High-Performance Supercapacitor Based on Reduced Graphene Oxide/Polypyrrole Composite Film.

PubMed

Chen, Junchen; Wang, Yaming; Cao, Jianyun; Liu, Yan; Zhou, Yu; Ouyang, Jia-Hu; Jia, Dechang

2017-06-14

A facile co-electrodeposition method has been developed to fabricate reduced graphene oxide/polypyrrole (rGO/PPy) composite films, with sodium dodecyl benzene sulfonate as both a surfactant and supporting electrolyte in the precursor solution. The introduction of rGO into the PPy films forms porous structure and enhances the conductivity across the film, leading to superior electrochemical performance. By controlling the deposition time and rGO concentration, the highest area capacitance can reach 411 mF/cm 2 (0.2 mA/cm 2 ) for rGO/PPy films, whereas optimized specific capacitance is as high as 361 F/g (0.2 mA/cm 2 ). All of the composite films exhibit excellent rate capability (at least 175 F/g at the current density of 12 mA/cm 2 ) compared with pure PPy film (only 12 F/g at the current density of 12 mA/cm 2 ). The rGO/PPy composite exhibits excellent cycling stability that maintains 104% of its initial capacitance after cycling for 2000 cycles and 80% for 5000 cycles. The two-electrode solid-state supercapacitor (SC) based on rGO/PPy composite electrodes demonstrates good rate performance, excellent cycling stability, as well as a high area capacitance of 222 mF/cm 2 . The solid-state planar SC based on the rGO/PPy composite exhibits an area capacitance of 9.4 mF/cm 2 , demonstrating great potential for fabrication of microsupercapacitors.

SURFACE DEGRADATION OF COMPOSITE RESINS BY ACIDIC MEDICINES AND pH-CYCLING

PubMed Central

Valinoti, Ana Carolina; Neves, Beatriz Gonçalves; da Silva, Eduardo Moreira; Maia, Lucianne Cople

2008-01-01

This study evaluated the effects of acidic medicines (Dimetapp® and Claritin®), under pH-cycling conditions, on the surface degradation of four composite resins (microhybrid: TPH, Concept, Opallis and Nanofilled: Supreme). Thirty disc-shaped specimens (Ø = 5.0 mm / thickness = 2.0 mm) of each composite were randomly assigned to 3 groups (n = 10): a control and two experimental groups, according to the acidic medicines evaluated. The specimens were finished and polished with aluminum oxide discs, and the surface roughness was measured by using a profilometer. After the specimens were submitted to a pH-cycling regimen and immersion in acidic medicines for 12 days, the surface roughness was measured again. Two specimens for each material and group were analyzed by scanning electron microscopy (SEM) before and after pH-cycling. Data were analyzed by the Student's-t test, ANOVA, Duncan's multiple range test and paired t-test (α=0.05). Significant increase in roughness was found only for TPH in the control group and TPH and Supreme immersed in Claritin® (p<0.05). SEM analyses showed that the 4 composite resins underwent erosion and surface degradation after being subjected to the experimental conditions. In conclusion, although the roughness was slightly affected, the pH-cycling and acidic medicines caused surface degradation of the composite resins evaluated. Titratable acidity seemed to play a more crucial role on surface degradation of composite resins than pH. PMID:19089257

Environmental Biochemistry--A New Approach for Teaching the Cycles of the Elements.

ERIC Educational Resources Information Center

Ricci, Juan C. Diaz; And Others

1988-01-01

Presents three dimensional models of biological pathways for the following cycles: carbon, nitrogen, sulfur, and a combination of the three. Discusses steps involved in each cycle and breaks each cycle into trophic and environmental regions. (MVL)

Determination of elemental tissue composition following proton treatment using positron emission tomography

NASA Astrophysics Data System (ADS)

Cho, Jongmin; Ibbott, Geoffrey; Gillin, Michael; Gonzalez-Lepera, Carlos; Min, Chul Hee; Zhu, Xuping; El Fakhri, Georges; Paganetti, Harald; Mawlawi, Osama

2013-06-01

Positron emission tomography (PET) has been suggested as an imaging technique for in vivo proton dose and range verification after proton induced-tissue activation. During proton treatment, irradiated tissue is activated and decays while emitting positrons. In this paper, we assessed the feasibility of using PET imaging after proton treatment to determine tissue elemental composition by evaluating the resultant composite decay curve of activated tissue. A phantom consisting of sections composed of different combinations of 1H, 12C, 14N, and 16O was irradiated using a pristine Bragg peak and a 6 cm spread-out Bragg-peak (SOBP) proton beam. The beam ranges defined at 90% distal dose were 10 cm the delivered dose was 1.6 Gy for the near monoenergetic beam and 2 Gy for the SOBP beam. After irradiation, activated phantom decay was measured using an in-room PET scanner for 30 min in list mode. Decay curves from the activated 12C and 16O sections were first decomposed into multiple simple exponential decay curves, each curve corresponding to a constituent radioisotope, using a least-squares method. The relative radioisotope fractions from each section were determined. These fractions were used to guide the decay curve decomposition from the section consisting mainly of 12C + 16O and calculate the relative elemental composition of 12C and 16O. A Monte Carlo simulation was also used to determine the elemental composition of the 12C + 16O section. The calculated compositions of the 12C + 16O section using both approaches (PET and Monte Carlo) were compared with the true known phantom composition. Finally, two patients were imaged using an in-room PET scanner after proton therapy of the head. Their PET data and the technique described above were used to construct elemental composition (12C and 16O) maps that corresponded to the proton-activated regions. We compared the 12C and 16O compositions of seven ROIs that corresponded to the vitreous humor, adipose/face mask, adipose tissue, and brain tissue with ICRU 46 elemental composition data. The 12C and 16O compositions of the 12C + 16O phantom section were estimated to within a maximum difference of 3.6% for the near monoenergetic and SOBP beams over an 8 cm depth range. On the other hand, the Monte Carlo simulation estimated the corresponding 12C and 16O compositions in the 12C + 16O section to within a maximum difference of 3.4%. For the patients, the 12C and 16O compositions in the seven ROIs agreed with the ICRU elemental composition data, with a mean (maximum) difference of 9.4% (15.2%). The 12C and 16O compositions of the phantom and patients were estimated with relatively small differences. PET imaging may be useful for determining the tissue elemental composition and thereby improving proton treatment planning and verification.

Elemental Markers in Elasmobranchs: Effects of Environmental History and Growth on Vertebral Chemistry

PubMed Central

Smith, Wade D.; Miller, Jessica A.; Heppell, Selina S.

2013-01-01

Differences in the chemical composition of calcified skeletal structures (e.g. shells, otoliths) have proven useful for reconstructing the environmental history of many marine species. However, the extent to which ambient environmental conditions can be inferred from the elemental signatures within the vertebrae of elasmobranchs (sharks, skates, rays) has not been evaluated. To assess the relationship between water and vertebral elemental composition, we conducted two laboratory studies using round stingrays, Urobatis halleri, as a model species. First, we examined the effects of temperature (16°, 18°, 24°C) on vertebral elemental incorporation (Li/Ca, Mg/Ca, Mn/Ca, Zn/Ca, Sr/Ca, Ba/Ca). Second, we tested the relationship between water and subsequent vertebral elemental composition by manipulating dissolved barium concentrations (1x, 3x, 6x). We also evaluated the influence of natural variation in growth rate on elemental incorporation for both experiments. Finally, we examined the accuracy of classifying individuals to known environmental histories (temperature and barium treatments) using vertebral elemental composition. Temperature had strong, negative effects on the uptake of magnesium (DMg) and barium (DBa) and positively influenced manganese (DMn) incorporation. Temperature-dependent responses were not observed for lithium and strontium. Vertebral Ba/Ca was positively correlated with ambient Ba/Ca. Partition coefficients (DBa) revealed increased discrimination of barium in response to increased dissolved barium concentrations. There were no significant relationships between elemental incorporation and somatic growth or vertebral precipitation rates for any elements except Zn. Relationships between somatic growth rate and DZn were, however, inconsistent and inconclusive. Variation in the vertebral elemental signatures of U. halleri reliably distinguished individual rays from each treatment based on temperature (85%) and Ba exposure (96%) history. These results support the assumption that vertebral elemental composition reflects the environmental conditions during deposition and validates the use of vertebral elemental signatures as natural markers in an elasmobranch. Vertebral elemental analysis is a promising tool for the study of elasmobranch population structure, movement, and habitat use. PMID:24098320

Elemental markers in elasmobranchs: effects of environmental history and growth on vertebral chemistry.

PubMed

Smith, Wade D; Miller, Jessica A; Heppell, Selina S

2013-01-01

Differences in the chemical composition of calcified skeletal structures (e.g. shells, otoliths) have proven useful for reconstructing the environmental history of many marine species. However, the extent to which ambient environmental conditions can be inferred from the elemental signatures within the vertebrae of elasmobranchs (sharks, skates, rays) has not been evaluated. To assess the relationship between water and vertebral elemental composition, we conducted two laboratory studies using round stingrays, Urobatis halleri, as a model species. First, we examined the effects of temperature (16°, 18°, 24°C) on vertebral elemental incorporation (Li/Ca, Mg/Ca, Mn/Ca, Zn/Ca, Sr/Ca, Ba/Ca). Second, we tested the relationship between water and subsequent vertebral elemental composition by manipulating dissolved barium concentrations (1x, 3x, 6x). We also evaluated the influence of natural variation in growth rate on elemental incorporation for both experiments. Finally, we examined the accuracy of classifying individuals to known environmental histories (temperature and barium treatments) using vertebral elemental composition. Temperature had strong, negative effects on the uptake of magnesium (DMg) and barium (DBa) and positively influenced manganese (DMn) incorporation. Temperature-dependent responses were not observed for lithium and strontium. Vertebral Ba/Ca was positively correlated with ambient Ba/Ca. Partition coefficients (DBa) revealed increased discrimination of barium in response to increased dissolved barium concentrations. There were no significant relationships between elemental incorporation and somatic growth or vertebral precipitation rates for any elements except Zn. Relationships between somatic growth rate and DZn were, however, inconsistent and inconclusive. Variation in the vertebral elemental signatures of U. halleri reliably distinguished individual rays from each treatment based on temperature (85%) and Ba exposure (96%) history. These results support the assumption that vertebral elemental composition reflects the environmental conditions during deposition and validates the use of vertebral elemental signatures as natural markers in an elasmobranch. Vertebral elemental analysis is a promising tool for the study of elasmobranch population structure, movement, and habitat use.

Tracking Radionuclide Fractionation in the First Atomic Explosion Using Stable Elements

DOE PAGES

Bonamici, Chloë E.; Hervig, Richard L.; Kinman, William S.

2017-08-25

Compositional analysis of postdetonation fallout is a tool for forensic identification of nuclear devices. However, the relationship between device composition and fallout composition is difficult to interpret because of the complex combination of physical mixing, nuclear reactions, and chemical fractionations that occur in the chaotic nuclear fireball. By using a combination of in situ microanalytical techniques (electron microprobe analysis and secondary ion mass spectrometry), we show that some heavy stable elements (Rb, Sr, Zr, Ba, Cs, Ba, La, Ce, Nd, Sm, Dy, Lu, U, Th) in glassy fallout from the first nuclear test, Trinity, are reliable chemical proxies for radionuclidesmore » generated during the explosion. Stable-element proxies show that radionuclides from the Trinity device were chemically, but not isotopically, fractionated by condensation. Moreover, stable-element proxies delineate chemical fractionation trends that can be used to connect present-day fallout composition to past fireball composition. Stable-element proxies therefore offer a novel approach for elucidating the phenomenology of the nuclear fireball as it relates to the formation of debris and the fixation of device materials within debris.« less

Tracking Radionuclide Fractionation in the First Atomic Explosion Using Stable Elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonamici, Chloë E.; Hervig, Richard L.; Kinman, William S.

Compositional analysis of postdetonation fallout is a tool for forensic identification of nuclear devices. However, the relationship between device composition and fallout composition is difficult to interpret because of the complex combination of physical mixing, nuclear reactions, and chemical fractionations that occur in the chaotic nuclear fireball. By using a combination of in situ microanalytical techniques (electron microprobe analysis and secondary ion mass spectrometry), we show that some heavy stable elements (Rb, Sr, Zr, Ba, Cs, Ba, La, Ce, Nd, Sm, Dy, Lu, U, Th) in glassy fallout from the first nuclear test, Trinity, are reliable chemical proxies for radionuclidesmore » generated during the explosion. Stable-element proxies show that radionuclides from the Trinity device were chemically, but not isotopically, fractionated by condensation. Moreover, stable-element proxies delineate chemical fractionation trends that can be used to connect present-day fallout composition to past fireball composition. Stable-element proxies therefore offer a novel approach for elucidating the phenomenology of the nuclear fireball as it relates to the formation of debris and the fixation of device materials within debris.« less

Tracking Radionuclide Fractionation in the First Atomic Explosion Using Stable Elements.

PubMed

Bonamici, Chloë E; Hervig, Richard L; Kinman, William S

2017-09-19

Compositional analysis of postdetonation fallout is a tool for forensic identification of nuclear devices. However, the relationship between device composition and fallout composition is difficult to interpret because of the complex combination of physical mixing, nuclear reactions, and chemical fractionations that occur in the chaotic nuclear fireball. Using a combination of in situ microanalytical techniques (electron microprobe analysis and secondary ion mass spectrometry), we show that some heavy stable elements (Rb, Sr, Zr, Ba, Cs, Ba, La, Ce, Nd, Sm, Dy, Lu, U, Th) in glassy fallout from the first nuclear test, Trinity, are reliable chemical proxies for radionuclides generated during the explosion. Stable-element proxies show that radionuclides from the Trinity device were chemically, but not isotopically, fractionated by condensation. Furthermore, stable-element proxies delineate chemical fractionation trends that can be used to connect present-day fallout composition to past fireball composition. Stable-element proxies therefore offer a novel approach for elucidating the phenomenology of the nuclear fireball as it relates to the formation of debris and the fixation of device materials within debris.

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.

Thermal expansion of selected graphite reinforced polyimide-, epoxy-, and glass-matrix composite

NASA Technical Reports Server (NTRS)

Tompkins, S. S.

1985-01-01

The thermal expansion of three epoxy-matrix composites, a polyimide-matrix composite and a borosilicate glass-matrix composite, each reinforced with continuous carbon fibers, has been measured and compared. The expansion of a composite with a rubber toughened epoxy-matrix and P75S carbon fibers was very different from the expansion of two different single phase epoxy-matrix composites with P75S fibers although all three had the same stacking sequence. Reasonable agreement was obtained between measured thermal-expansion data and results from classical laminate theory. The thermal expansion of a material may change markedly as a result of thermal cycling. Microdamage, induced by 250 cycles between -156 C and 121 C in the graphite/polyimide laminate, caused a 53 percent decrease in the coefficient of thermal expansion. The thermal expansion of the graphite/glass laminate was not changed by 100 thermal cycles from -129 C to 38 C; however, a residual strain of about 10 x 10 to the minus 6 power was measured for the laminate tested.

Applied Integrated Design in Composite UAV Development

NASA Astrophysics Data System (ADS)

Vasić, Zoran; Maksimović, Stevan; Georgijević, Dragutin

2018-04-01

This paper presents a modern approach to integrated development of Unmanned Aerial Vehicle made of laminated composite materials from conceptual design, through detail design, strength and stiffness analyses, definition and management of design and production data, detailed tests results and other activities related to development of laminated composite structures with main of its particularities in comparison to metal structures. Special attention in this work is focused to management processes of product data during life cycle of an UAV and experimental tests of its composite wing. Experience shows that the automation management processes of product data during life cycle, as well as processes of manufacturing, are inevitable if a company wants to get cheaper and quality composite aircraft structures. One of the most effective ways of successful management of product data today is Product Life cycle Management (PLM). In terms of the PLM, a spectrum of special measures and provisions has to be implemented when defining fiber-reinforced composite material structures in comparison to designing with metals which is elaborated in the paper.

Thermal Cycling of Thermal Control Paints on Carbon-Carbon and Carbon-Polyimide Composites

NASA Technical Reports Server (NTRS)

Jaworske, Donald A.

2006-01-01

Carbon-carbon composites and carbon-polyimide composites are being considered for space radiator applications owing to their light weight and high thermal conductivity. For those radiator applications where sunlight will impinge on the surface, it will be necessary to apply a white thermal control paint to minimize solar absorptance and enhance infrared emittance. Several currently available white thermal control paints were applied to candidate carbon-carbon and carbon-polyimide composites and were subjected to vacuum thermal cycling in the range of -100 C to +277 C. The optical properties of solar absorptance and infrared emittance were evaluated before and after thermal cycling. In addition, adhesion of the paints was evaluated utilizing a tape test. The test matrix included three composites: resin-derived carbon-carbon and vapor infiltrated carbon-carbon, both reinforced with pitch-based P-120 graphite fibers, and a polyimide composite reinforced with T-650 carbon fibers, and three commercially available white thermal control paints: AZ-93, Z-93-C55, and YB-71P.

Thermal Cycling of Thin and Thick Ply Composites

NASA Technical Reports Server (NTRS)

Tompkins, Stephen S.; Shen, James Y.; Lavoie, Andre J.

1994-01-01

An experimental study was conducted to determine the effects of ply thickness in composite laminates on thermally induced cracking and changes in the coefficient of thermal expansion (CTE). After a few thermal cycles, laminates with thick-plies cracked, resulting in large changes in CTE. CTE's of the thin-ply laminates were unaffected by microcracking during the first 500 thermal cycles, whereas, the CTE's of the thick-ply laminates changed significantly. After about 1500 cycles, microdamage had also reduced the CTE of the thin-ply laminates to a value of about half of their initial value.

Crosslinked Carbon Nanotubes/Polyaniline Composites as a Pseudocapacitive Material with High Cycling Stability

PubMed Central

Liu, Dong; Wang, Xue; Deng, Jinxing; Zhou, Chenglong; Guo, Jinshan; Liu, Peng

2015-01-01

The poor cycling stability of polyaniline (PANI) limits its practical application as a pseudocapacitive material due to the volume change during the charge-discharge procedure. Herein, crosslinked carbon nanotubes/polyaniline (C-CNTs/PANI) composites had been designed by the in situ chemical oxidative polymerization of aniline in the presence of crosslinked carbon nanotubes (C-CNTs), which were obtained by coupling of the functionalized carbon nanotubes with 1,4-benzoquinone. The composite showed a specific capacitance of 294 F/g at the scan rate of 10 mV/s, and could retain 95% of its initial specific capacitance after 1000 CV cycles. Such high electrochemical cycling stability resulting from the crosslinked skeleton of the C-CNTs makes them potential electrode materials for a supercapacitor. PMID:28347050

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohammed, Abdul Aziz, E-mail: azizM@uniten.edu.my; Rahman, Shaik Mohmmed Haikhal Abdul; Pauzi, Anas Muhamad, E-mail: anas@uniten.edu.my

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 maintainingmore » 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.« less

Settling properties of aerobic granular sludge (AGS) and aerobic granular sludge molasses (AGSM)

NASA Astrophysics Data System (ADS)

Mat Saad, Azlina; Aini Dahalan, Farrah; Ibrahim, Naimah; Yasina Yusuf, Sara; Aqlima Ahmad, Siti; Khalil, Khalilah Abdul

2018-03-01

Aerobic granulation technology is applied to treat domestic and industrial wastewater. The Aerobic granular sludge (AGS) cultivated has strong properties that appears to be denser and compact in physiological structure compared to the conventional activated sludge. It offers rapid settling for solid:liquid separation in wastewater treatment. Aerobic granules were developed using sequencing batch reactor (SBR) with intermittent aerobic - anaerobic mode with 8 cycles in 24 hr. This study examined the settling velocity performance of cultivated aerobic granular sludge (AGS) and aerobic granular sludge molasses (AGSM). The elemental composition in both AGS and AGSM were determined using X-ray fluorescence (XRF). The results showed that AGSM has higher settling velocity 30.5 m/h compared to AGS.

Elemental Compositions of Extrasolar Planetesimals

NASA Astrophysics Data System (ADS)

Xu, Siyi; Jura, M.

2014-01-01

The composition of extrasolar rocky planets is essential for understanding the formation and evolution of these alien worlds. Studying externally-polluted white dwarfs provides the only method to directly measure the elemental compositions of extrasolar planetesimals, the building blocks of planets. The standard model is that some planetesimals can survive to the white dwarf phase, get perturbed, enter into the tidal radius of the white dwarf and get accreted, polluting its pure hydrogen or helium atmosphere. We have been performing high-resolution spectroscopic observations on a number of polluted white dwarfs to measure the bulk compositions of the accreted objects. To have a full picture of the abundance pattern, we gathered data from both Keck/HIRES and HST/COS. I will present the analysis for one of the most interesting objects -- G29-38. It is the first white dwarf identified with an infrared excess from debris of pulverized planetesimals and among the very first identified polluted hydrogen atmosphere white dwarfs. Our analysis indicates that the accreted extrasolar planetesimal is enhanced in refractory elements and depleted in volatile elements. A detailed comparison with solar system objects show that the observed composition can be best interpreted as a blend of chondritic object with some refractory-rich material, a result from post-nebular processing. When all polluted white dwarfs are viewed as an ensemble, we find that the elemental compositions of accreted extrasolar planetesimals resemble to those of solar system objects to zeroth order. (i) The big four elements, O, Fe, Mg and Si are also dominant. Objects with exotic compositions, e.g. diamond planets and refractory-dominated planets, are yet to be found. (ii) Volatiles, such as carbon and water, are only trace constituents. In terms of bulk composition, solar system objects are essentially normal.

Microbiome succession during ammonification in eelgrass bed sediments

PubMed Central

Ettinger, Cassandra L.; Williams, Susan L.; Abbott, Jessica M.; Stachowicz, John J.

2017-01-01

Background Eelgrass (Zostera marina) is a marine angiosperm and foundation species that plays an important ecological role in primary production, food web support, and elemental cycling in coastal ecosystems. As with other plants, the microbial communities living in, on, and near eelgrass are thought to be intimately connected to the ecology and biology of eelgrass. Here we characterized the microbial communities in eelgrass sediments throughout an experiment to quantify the rate of ammonification, the first step in early remineralization of organic matter, also known as diagenesis, from plots at a field site in Bodega Bay, CA. Methods Sediment was collected from 72 plots from a 15 month long field experiment in which eelgrass genotypic richness and relatedness were manipulated. In the laboratory, we placed sediment samples (n = 4 per plot) under a N2 atmosphere, incubated them at in situ temperatures (15 °C) and sampled them initially and after 4, 7, 13, and 19 days to determine the ammonification rate. Comparative microbiome analysis using high throughput sequencing of 16S rRNA genes was performed on sediment samples taken initially and at seven, 13 and 19 days to characterize changes in the relative abundances of microbial taxa throughout ammonification. Results Within-sample diversity of the sediment microbial communities across all plots decreased after the initial timepoint using both richness based (observed number of OTUs, Chao1) and richness and evenness based diversity metrics (Shannon, Inverse Simpson). Additionally, microbial community composition changed across the different timepoints. Many of the observed changes in relative abundance of taxonomic groups between timepoints appeared driven by sulfur cycling with observed decreases in predicted sulfur reducers (Desulfobacterales) and corresponding increases in predicted sulfide oxidizers (Thiotrichales). None of these changes in composition or richness were associated with variation in ammonification rates. Discussion Our results showed that the microbiome of sediment from different plots followed similar successional patterns, which we infer to be due to changes related to sulfur metabolism. These large changes likely overwhelmed any potential changes in sediment microbiome related to ammonification rate. We found no relationship between eelgrass presence or genetic composition and the microbiome. This was likely due to our sampling of bulk sediments to measure ammonification rates rather than sampling microbes in sediment directly in contact with the plants and suggests that eelgrass influence on the sediment microbiome may be limited in spatial extent. More in-depth functional studies associated with eelgrass microbiome will be required in order to fully understand the implications of these microbial communities in broader host-plant and ecosystem functions (e.g., elemental cycling and eelgrass-microbe interactions). PMID:28828269

Review of footnotes and annotations to the 1949–2013 tables of standard atomic weights and tables of isotopic compositions of the elements (IUPAC Technical Report)

DOE PAGES

Coplen, Tyler B.; Holden, Norman E.

2016-01-01

Abstract The Commission on Isotopic Abundances and Atomic Weights uses annotations given in footnotes that are an integral part of the Tables of Standard Atomic Weights to alert users to the possibilities of quite extraordinary occurrences, as well as sources with abnormal atomic-weight values outside an otherwise acceptable range. The basic need for footnotes to the Standard Atomic Weights Table and equivalent annotations to the Table of Isotopic Compositions of the Elements arises from the necessity to provide users with information that is relevant to one or more elements, but that cannot be provided using numerical data in columns. Anymore » desire to increase additional information conveyed by annotations to these Tables is tempered by the need to preserve a compact format and a style that can alert users, who would not be inclined to consult either the last full element-by-element review or the full text of a current Standard Atomic Weights of the Elements report. Since 1989, the footnotes of the Tables of Standard Atomic Weights and the annotations in column 5 of the Table of Isotopic Compositions of the Elements have been harmonized by use of three lowercase footnotes, “g”, “m”, and “r”, that signify geologically exceptionally specimens (“g”), modified isotopic compositions in material subjected to undisclosed or inadvertent isotopic fractionation (“m”), and the range in isotopic composition of normal terrestrial material prevents more precise atomic-weight value being given (“r”). As some elements are assigned intervals for their standard atomic-weight values (applies to 12 elements since 2009), footnotes “g” and “r” are no longer needed for these elements.« less

Review of footnotes and annotations to the 1949–2013 tables of standard atomic weights and tables of isotopic compositions of the elements (IUPAC Technical Report)

USGS Publications Warehouse

Coplen, Tyler B.; Holden, Norman E.

2016-01-01

The Commission on Isotopic Abundances and Atomic Weights uses annotations given in footnotes that are an integral part of the Tables of Standard Atomic Weights to alert users to the possibilities of quite extraordinary occurrences, as well as sources with abnormal atomic-weight values outside an otherwise acceptable range. The basic need for footnotes to the Standard Atomic Weights Table and equivalent annotations to the Table of Isotopic Compositions of the Elements arises from the necessity to provide users with information that is relevant to one or more elements, but that cannot be provided using numerical data in columns. Any desire to increase additional information conveyed by annotations to these Tables is tempered by the need to preserve a compact format and a style that can alert users, who would not be inclined to consult either the last full element-by-element review or the full text of a current Standard Atomic Weights of the Elements report. Since 1989, the footnotes of the Tables of Standard Atomic Weights and the annotations in column 5 of the Table of Isotopic Compositions of the Elements have been harmonized by use of three lowercase footnotes, “g”, “m”, and “r”, that signify geologically exceptionally specimens (“g”), modified isotopic compositions in material subjected to undisclosed or inadvertent isotopic fractionation (“m”), and the range in isotopic composition of normal terrestrial material prevents more precise atomic-weight value being given (“r”). As some elements are assigned intervals for their standard atomic-weight values (applies to 12 elements since 2009), footnotes “g” and “r” are no longer needed for these elements.

In Situ Geochemical Analysis and Age Dating of Rocks Using Laser Ablation-Miniature Mass Spectrometer

NASA Technical Reports Server (NTRS)

Sinha, Mahadeva P.; Hecht, Michael H.; Hurowitz, Joel A.

2012-01-01

A miniaturized instrument for performing chemical and isotopic analysis of rocks has been developed. The rock sample is ablated by a laser and the neutral species produced are analyzed using the JPL-invented miniature mass spectrometer. The direct sampling of neutral ablated material and the simultaneous measurement of all the elemental and isotopic species are the novelties of this method. In this laser ablation-miniature mass spectrometer (LA-MMS) method, the ablated neutral atoms are led into the electron impact ionization source of the MMS, where they are ionized by a 70-eV electron beam. This results in a secondary ion pulse typically 10-100 microsecond wide, compared to the original 5-10-nanosecond laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer and measured in parallel by a modified CCD (charge-coupled device) array detector capable of detecting ions directly. Compared to conventional scanning techniques, simultaneous measurement of the ion pulse along the focal plane effectively offers a 100% duty cycle over a wide mass range. LAMMS offers a more quantitative assessment of elemental composition than techniques that detect laser-ionized species produced directly in the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the laser beam, and the ionization energies of the elements. The measurement of high-precision isotopic ratios and elemental composition of different rock minerals by LAMMS method has been demonstrated. The LA-MMS can be applied for the absolute age determination of rocks. There is no such instrument available presently in a miniaturized version that can be used for NASA space missions. Work is in progress in the laboratory for geochronology of rocks using LA-MMS that is based on K-Ar radiogenic dating technique.

Micron-scale Analysis of Carbonate-Associated Sulfate by Secondary Ionization Mass Spectrometry: Insights into Spatial Variability in δ34SCAS

NASA Astrophysics Data System (ADS)

Fike, D. A.; Jones, D. S.

2012-12-01

The proliferation of carbonate-associated sulfate (CAS) isotope analyses in recent years has revolutionized our understanding of marine sulfur cycling over much of Earth history. In marine carbonate rocks, δ34SCAS is thought to be a faithful recorder of the isotopic composition of marine sulfate (δ34SSO4). However, as the chemostratigraphic record becomes better resolved in time and space, reports of coeval but discordant δ34SCAS values are becoming increasingly common. These differences could arise in part from a) water column stratification or physiographic separations between separate ocean basins (i.e., paleoceanographic variability in δ34SSO4); b) syndepositional processes that decouple the relationship between δ34SSO4 and δ34SCAS during deposition or prior to lithification; or c) diagenetic alteration of the δ34SCAS signal following deposition. To help disentangle these processes, we have developed a microanalytical approach to determine the abundance and isotopic composition of CAS using secondary ionization mass spectrometry (SIMS). While our current precision (~1‰) cannot compete with that obtained from traditional bulk analysis on gas source isotope ratio mass spectrometers, we believe that the unparalleled spatial resolution can provide substantial insights into many of the fundamental questions that remain regarding the mechanisms by which CAS concentration and isotopic composition can be altered during carbonate precipitation and/or recrystallization. With a spatial resolution as low as ~ 5 μm, it is possible to analyze suites of primary and diagenetic phases, including individual carbonate allochems, muds, and cements. Preliminary results indicate that δ34SCAS can vary by as much as 10‰ between phases in a single sample. This scale of analysis allows for a rigorous evaluation of the susceptibility of δ34SCAS to syndepositional and diagenetic alteration, especially when coupled with parallel analysis of δ13Ccarb/δ18Ocarb and diagnostic trace element abundances. Such detailed measurements illuminate the complex relationships between the isotopic composition of individual constituents of carbonate rocks and the bulk δ34SCAS values on which much of our understanding of sulfur cycling in deep time is based. The resulting insights can be used to re-examine existing δ34SCAS records and our understanding of the evolution of sulfur cycling over Earth history.

Galactic cosmic ray composition

NASA Technical Reports Server (NTRS)

Meyer, J. P.

1986-01-01

An assessment is given of the galactic cosmic ray source (GCRS) elemental composition and its correlation with first ionization potential. The isotopic composition of heavy nuclei; spallation cross sections; energy spectra of primary nuclei; electrons; positrons; local galactic reference abundances; comparison of solar energetic particles and solar coronal compositions; the hydrogen; lead; nitrogen; helium; and germanium deficiency problems; and the excess of elements are among the topics covered.

Trace element levels and cognitive function in rural elderly Chinese.

PubMed

Gao, Sujuan; Jin, Yinlong; Unverzagt, Frederick W; Ma, Feng; Hall, Kathleen S; Murrell, Jill R; Cheng, Yibin; Shen, Jianzhao; Ying, Bo; Ji, Rongdi; Matesan, Janetta; Liang, Chaoke; Hendrie, Hugh C

2008-06-01

Trace elements are involved in metabolic processes and oxidation-reduction reactions in the central nervous system and could have a possible effect on cognitive function. The relationship between trace elements measured in individual biological samples and cognitive function in an elderly population had not been investigated extensively. The participant population is part of a large cohort study of 2000 rural elderly Chinese persons. Six cognitive assessment tests were used to evaluate cognitive function in this population, and a composite score was created to represent global cognitive function. Trace element levels of aluminum, calcium, cadmium, copper, iron, lead, and zinc were analyzed in plasma samples of 188 individuals who were randomly selected and consented to donating fasting blood. Analysis of covariance models were used to assess the association between each trace element and the composite cognitive score adjusting for demographics, medical history of chronic diseases, and the apolipoprotein E (APOE) genotype. Three trace elements-calcium, cadmium, and copper-were found to be significantly related to the composite cognitive score. Increasing plasma calcium level was associated with higher cognitive score (p <.0001). Increasing cadmium and copper, in contrast, were significantly associated with lower composite score (p =.0044 and p =.0121, respectively). Other trace elements did not show significant association with the composite cognitive score. Our results suggest that calcium, cadmium, and copper may be associated with cognitive function in the elderly population.

Minor Elements in Nakhlite Pyroxenes: Does Cr Record Changes in REDOX Conditions during Crystallization?

NASA Technical Reports Server (NTRS)

McKay, G.; Schwandt, C.; Le, L.; Mikouchi, T.

2007-01-01

Nakhlites are olivine-bearing clinopyroxene cumulates. Based on petrographic characteristics, they may be divided into groups that cooled at different rates and may have been formed at different depths in a single flow. The order of cooling rate from slowest to fastest is NWA998

Effect of weathering cycle and manufacturing method on performance of wood flour and high-density polyethylene composites

Treesearch

Nicole M. Stark

2006-01-01

Wood–plastic lumber is promoted as a low-maintenance high-durability product. When exposed to accelerated weathering, however, wood–plastic composites may experience a color change and loss in mechanical properties. Differences in weathering cycle and composite surface characteristics can affect the rate and amount of change caused by weathering. In this study, 50%...

Newer polyanionic bio-composite anode for sodium ion batteries

NASA Astrophysics Data System (ADS)

Karuppiah, Saravanan; Vellingiri, Suganya; Nallathamby, Kalaiselvi

2017-02-01

NASICON frame work Na3V2(PO4)3 (NVP), wrapped by nitrogen and sulfur doped bio-carbon matrix derived from human hair (HHC) has been investigated for its anode behavior in SIBs. Basically, NVP is bestowed with a crystal structure of 3D open framework and a moderate theoretical capacity of 118 mAh g-1, which are the twin advantages and motivation behind the selection of this material. Prepared through a simple, scalable and facile method, the key problems associated with pristine NVP electrode material, such as inferior conductivity and severe volume change have been mitigated to a great extent through the formation of a composite containing HHC. Herein, HHC is a cheap and eco-friendly composite additive, obtained from a universal bio-waste, viz., human hair and hence NVP/HHC qualifies itself as a green composite. Interestingly, NVP/HHC-10 (in-situ) and NVP/HHC-20 (ex-situ) anodes show excellent electrochemical performance in terms of cycling stability up to 500 cycles and rate capability @ 2 A g-1, which are superior than similar category NVP anodes reported in the literature. Further, post cycling structure and morphology of NVP/HHC composite anodes evidence the appreciable stability bestowed with the select composition, which is found to get maintained upon extended cycles and even after rate capability test.

Coatings for directional eutectics. [cyclic furnace oxidation tests

NASA Technical Reports Server (NTRS)

Jackson, M. R.; Rairden, J. R.; Hampton, L. V.

1974-01-01

Coating compositions were evaluated for oxidation protection of directionally solidified composite alloy NiTaC-13. These coatings included three NiCrAlY compositions (30-5-1, 25-10-1 and 20-15-1), two FeCrAlY compositions (30-5-1 and 25-10-1), a CoCrAlY composition (25-10-1), and one duplex coating, Ni-35Cr + Al. Duplicate pin samples of each composition were evaluated using two cyclic furnace oxidation tests of 100 hours at 871 C and 500 hours at 1093 C. The two best coatings were Ni-20Cr-15Al-lY and Ni-35Cr + Al. The two preferred coatings were deposited on pins and were evaluated in detail in .05 Mach cyclic burner rig oxidation to 1093 C. The NiCrAlY coating was protective after 830 hours of cycling, while the duplex coating withstood 630 hours. Test bars were coated and cycled for up to 500 hours. Tensile tests indicated no effect of coatings on strength. In 871 C air stress rupture, a degradation was observed for coated relative to bare material. The cycled NiCrAlY coating offered excellent protection with properties superior to the bare cycled NiTaC-13 in 1093 C air stress rupture.

An Evaluation on the Smart Composite Damaged by Thermal Shock

NASA Astrophysics Data System (ADS)

Lee, Jin Kyung; Lee, Sang Pill; Park, Young Chul; Lee, Joon Hyun

A shape memory alloy (SMA) as part of some products and system has been used to keep their shape at any specified temperature. By using this characteristic of the shape memory alloy it can be solved the problem of the residual stress by difference of coefficients of thermal expansion between reinforcement and matrix within composite. In this study, TiNi/Al6061 shape memory alloy composite was fabricated through hot press method, and the optimal fabrication condition was created. The bonding effect of the matrix and the reinforcement within the SMA composite was strengthened by cold rolling. The SMA composite can be applied as the part of airplane and vessel, and used under tough condition of repetitive thermal shock cycles of high and low temperatures. Therefore, the thermal shock test was performed for the SMA composite, and mechanical properties were evaluated. The tensile strength of the SMA composite showed a slight decline with the thermal shock cycles. In addition, acoustic emission (AE) technique was used to quantify the microscopic damage behavior of cold rolled TiNi/Al6061 shape memory alloy composite that underwent thermal shock cycles. The damage degree on the specimen that underwent thermal shock cycles was discussed. Actually AE parameters such as AE event, count and energy was analyzed, and these parameters was useful to evaluate the damage behavior and degree of the SMA composite. The waveform of the signal caused by debonding was pulse type, and showed the frequency range of 160 kHz, however, the signal by the fiber fracture showed the pulse type of high magnitude and frequency range of 220 kH.

Origin and evolution of SINEs in eukaryotic genomes

PubMed Central

Kramerov, D A; Vassetzky, N S

2011-01-01

Short interspersed elements (SINEs) are one of the two most prolific mobile genomic elements in most of the higher eukaryotes. Although their biology is still not thoroughly understood, unusual life cycle of these simple elements amplified as genomic parasites makes their evolution unique in many ways. In contrast to most genetic elements including other transposons, SINEs emerged de novo many times in evolution from available molecules (for example, tRNA). The involvement of reverse transcription in their amplification cycle, huge number of genomic copies and modular structure allow variation mechanisms in SINEs uncommon or rare in other genetic elements (module exchange between SINE families, dimerization, and so on.). Overall, SINE evolution includes their emergence, progressive optimization and counteraction to the cell's defense against mobile genetic elements. PMID:21673742

Exposure assessment of a cyclist to particles and chemical elements.

PubMed

Ramos, C A; Silva, J R; Faria, T; Wolterbeek, T H; Almeida, S M

2017-05-01

Cycle paths can be used as a route for active transportation or simply to cycle for physical activity and leisure. However, exposure to air pollutants can be boosted while cycling, in urban environments, due to the proximity to vehicular emissions and elevated breathing rates. The objective of this work was to assess the exposure of a cyclist to particles and to chemical elements by combining real-time aerosol mass concentration reading equipment and biomonitoring techniques. PM 10 and PM 2.5 were measured on three cycle paths located in Lisbon, during weekdays and weekends and during rush hours and off-peak hours resulting in a total of 60 campaigns. Lichens were exposed along cycle paths for 3 months, and their element contents were measured by instrumental neutron activation analysis using the k 0 methodology (k 0 -INAA). Using a bicycle commute route of lower traffic intensity and avoiding rush hours or other times with elevated vehicular congestion facilitate a reduction in exposure to pollutants. The implementation of cycle paths in cities is important to stimulate physical activity and active transportation; however, it is essential to consider ambient air and pollutant sources to create safer infrastructures.

Chemical systematics of the Shergotty meteorite and the composition of its parent body (Mars)

NASA Technical Reports Server (NTRS)

Laul, J. C.; Smith, M. R.; Waenke, H.; Jagoutz, E.; Dreibus, G.

1986-01-01

Sixty elements in two bulk samples of Shergotty meteorite and 30 elements in various mineral separates of Shergotty were identified, using mainly INAA and RNAA techniques. In addition, elements leached out from powdered samples of Shergotty and EETA 79001 meteorites by 0.1 N HCl, as well as the elements of their residues, were analyzed. The results have indicated that Shergotty meteorite is homogeneous in its major element composition, but heterogeneous with respect to large-ion lithophile elements, such as K, Ba, Sr, Zr, Hf, Ta, Th, and rare-earth elements (REEs). It is even more heterogeneous with respect to volatile elements, such as Cd, Te, Tl, and Bi, and the siderophiles Au and Ag. The REE patterns of the Shergotty and EETA 79001 residues are identical, indicating that the parent magmas of both meteorites are compositionally similar. However, their leachate (phosphate) patterns are different, suggesting two components for the Shergotty, one of which is similar to the EETA 79001 leachate.

In-situ thermal cycling in SEM of a graphite-aluminum composite

NASA Technical Reports Server (NTRS)

Cheong, Y. M.; Marcus, H. L.

1987-01-01

In situ SEM observations of a graphite-aluminum composite (unidirectional P100 graphite-fiber-reinforced 6061 aluminum MMC plates) were used to measure displacements within the graphite fiber relative to the interface between the graphite fiber and the aluminum matrix during thermal cycling. Specimens were thermally cycled from room temperature to 300 C or 500 C in a SEM chamber and then cooled to room temperature. The obtained shear strains within the fiber were then related to anomalous values of measured residual stresses and to the impact on the composite coefficient of expansion and potential damage under thermal fatigue loading. The shear mechanism was proposed as a source of temperature limits on the low coefficient of expansion of these composites, as well as a potential source of thermal fatigue degradation.

Emergy evaluation of water utilization benefits in water-ecological-economic system based on water cycle process

NASA Astrophysics Data System (ADS)

Guo, X.; Wu, Z.; Lv, C.

2017-12-01

The water utilization benefits are formed by the material flow, energy flow, information flow and value stream in the whole water cycle process, and reflected along with the material circulation of inner system. But most of traditional water utilization benefits evaluation are based on the macro level, only consider the whole material input and output and energy conversion relation, and lack the characterization of water utilization benefits accompanying with water cycle process from the formation mechanism. In addition, most studies are from the perspective of economics, only pay attention to the whole economic output and sewage treatment economic investment, but neglect the ecological function benefits of water cycle, Therefore, from the perspective of internal material circulation in the whole system, taking water cycle process as the process of material circulation and energy flow, the circulation and flow process of water and other ecological environment, social economic elements were described, and the composition of water utilization positive and negative benefits in water-ecological-economic system was explored, and the performance of each benefit was analyzed. On this basis, the emergy calculation method of each benefit was proposed by emergy quantitative analysis technique, which can realize the unified measurement and evaluation of water utilization benefits in water-ecological-economic system. Then, taking Zhengzhou city as an example, the corresponding benefits of different water cycle links were calculated quantitatively by emergy method, and the results showed that the emergy evaluation method of water utilization benefits can unify the ecosystem and the economic system, achieve uniform quantitative analysis, and measure the true value of natural resources and human economic activities comprehensively.

Influence of Thermal Cycling on Flexural Properties and Simulated Wear of Computer-aided Design/Computer-aided Manufacturing Resin Composites.

PubMed

Tsujimoto, A; Barkmeier, W W; Takamizawa, T; Latta, M A; Miyazaki, M

The purpose of this study was to evaluate the influence of thermal cycling on the flexural properties and simulated wear of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites. The six CAD/CAM resin composites used in this study were 1) Lava Ultimate CAD/CAM Restorative (LU); 2) Paradigm MZ100 (PM); 3) CERASMART (CS); 4) Shofu Block HC (SB); 5) KATANA AVENCIA Block (KA); and 6) VITA ENAMIC (VE). Specimens were divided randomly into two groups, one of which was stored in distilled water for 24 hours, and the other of which was subjected to 10,000 thermal cycles. For each material, 15 specimens from each group were used to determine the flexural strength and modulus according to ISO 6872, and 20 specimens from each group were used to examine wear using a localized wear simulation model. The test materials were subjected to a wear challenge of 400,000 cycles in a Leinfelder-Suzuki device (Alabama machine). The materials were placed in custom-cylinder stainless steel fixtures, and simulated localized wear was generated using a stainless steel ball bearing (r=2.387 mm) antagonist in a water slurry of polymethyl methacrylate beads. Simulated wear was determined using a noncontact profilometer (Proscan 2100) with Proscan and AnSur 3D software. The two-way analysis of variance of flexural properties and simulated wear of CAD/CAM resin composites revealed that material type and thermal cycling had a significant influence (p<0.05), but there was no significant interaction (p>0.05) between the two factors. The flexural properties and maximum depth of wear facets of CAD/CAM resin composite were different (p<0.05) depending on the material, and their values were influenced (p>0.05) by thermal cycling, except in the case of VE. The volume losses in wear facets on LU, PM, and SB after 10,000 thermal cycles were significantly higher (p<0.05) than those after 24 hours of water storage, unlike CS, KA, and VE. The results of this study indicate that the flexural properties and simulated wear of CAD/CAM resin composites are different depending on the material. In addition, the flexural properties and simulated wear of CAD/CAM resin composites are influenced by thermal cycling.

Mesoporous carbon spheres with controlled porosity for high-performance lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Wang, Dexian; Fu, Aiping; Li, Hongliang; Wang, Yiqian; Guo, Peizhi; Liu, Jingquan; Zhao, Xiu Song

2015-07-01

Mesoporous carbon (MC) spheres with hierarchical pores, controlled pore volume and high specific surface areas have been prepared by a mass-producible spray drying assisted template method using sodium alginate as carbon precursor and commercial colloidal silica particles as hard template. The resulting MC spheres, possessing hierarchical pores in the range of 3-30 nm, are employed as conductive matrices for the preparation of cathode materials for lithium-sulfur batteries. A high pressure induced one-step impregnation of elemental sulfur into the pore of the MC spheres has been exploited. The electrochemical performances of sulfur-impregnated MC spheres (S-MC) derived from MC spheres with different pore volume and specific surface area but with the same sulfur loading ratio of 60 wt% (S-MC-X-60) have been investigated in details. The S-MC-4-60 composite cathode material displayed a high initial discharge capacity of 1388 mAhg-1 and a good cycling stability of 857 mAhg-1 after 100 cycles at 0.2C, and shows also excellent rate capability of 864 mAhg-1 at 2C. More importantly, the sulfur loading content in MC-4 spheres can reach as high as 80%, and it still can deliver a capacity of 569 mAhg-1 after 100 cycles at 0.2C.

A life cycle assessment of environmental performances of two combustion- and gasification-based waste-to-energy technologies.

PubMed

Arena, Umberto; Ardolino, Filomena; Di Gregorio, Fabrizio

2015-07-01

An attributional life cycle analysis (LCA) was developed to compare the environmental performances of two waste-to-energy (WtE) units, which utilize the predominant technologies among those available for combustion and gasification processes: a moving grate combustor and a vertical shaft gasifier coupled with direct melting. The two units were assumed to be fed with the same unsorted residual municipal waste, having a composition estimated as a European average. Data from several plants in operation were processed by means of mass and energy balances, and on the basis of the flows and stocks of materials and elements inside and throughout the two units, as provided by a specific substance flow analysis. The potential life cycle environmental impacts related to the operations of the two WtE units were estimated by means of the Impact 2002+ methodology. They indicate that both the technologies have sustainable environmental performances, but those of the moving grate combustion unit are better for most of the selected impact categories. The analysis of the contributions from all the stages of each specific technology suggests where improvements in technological solutions and management criteria should be focused to obtain further and remarkable environmental improvements. Copyright © 2015 Elsevier Ltd. All rights reserved.

Regulated Breathing Effect of Silicon Negative Electrode for Dramatically Enhanced Performance of Li-Ion Battery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Xingcheng; Zhou, Weidong; Kim, Youngnam

Si is an attractive negative electrode material for lithium ion batteries due to its high specifi c capacity (≈3600 mAh g –1 ). However, the huge volume swelling and shrinking during cycling, which mimics a breathing effect at the material/electrode/cell level, leads to several coupled issues including fracture of Si particles, unstable solid electrolyte interphase, and low Coulombic effi ciency. In this work, the regulation of the breathing effect is reported by using Si–C yolk–shell nanocomposite which has been well-developed by other researchers. The focus is on understanding how the nanoscaled materials design impacts the mechanical and electrochemical response atmore » electrode level. For the fi rst time, it is possible to observe one order of magnitude of reduction on breathing effect at the electrode level during cycling: the electrode thickness variation reduced down to 10%, comparing with 100% in the electrode with Si nanoparticles as active materials. The Si–C yolk–shell nanocomposite electrode exhibits excellent capacity retention and high cycle effi ciency. In situ transmission electron microscopy and fi nite element simulations consistently reveals that the dramatically enhanced performance is associated with the regulated breathing of the Si in the new composite, therefore the suppression of the overall electrode expansion.« less

Mineral cycling in southeastern ecosystems. Proceedings of a symposium held at Augusta, Georgia May 1--3, 1974

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howell, F.G.; Gentry, J.B.; Smith, M.H.

1975-01-01

Sixty-six papers were presented on cycling of natural and man-made elements, including terrestrial, freshwater and marine environments, as well as current ideas on modeling. Principles governing elemental flow included radiocesium in natural environments, especially in the southeastern United States. Individual entries were made for 47 items.

Approximating the stress field within the unit cell of a fabric reinforced composite using replacement elements

NASA Technical Reports Server (NTRS)

Foye, R. L.

1993-01-01

This report concerns the prediction of the elastic moduli and the internal stresses within the unit cell of a fabric reinforced composite. In the proposed analysis no restrictions or assumptions are necessary concerning yarn or tow cross-sectional shapes or paths through the unit cell but the unit cell itself must be a right hexagonal parallelepiped. All the unit cell dimensions are assumed to be small with respect to the thickness of the composite structure that it models. The finite element analysis of a unit cell is usually complicated by the mesh generation problems and the non-standard, adjacent-cell boundary conditions. This analysis avoids these problems through the use of preprogrammed boundary conditions and replacement materials (or elements). With replacement elements it is not necessary to match all the constitutional material interfaces with finite element boundaries. Simple brick-shaped elements can be used to model the unit cell structure. The analysis predicts the elastic constants and the average stresses within each constituent material of each brick element. The application and results of this analysis are demonstrated through several example problems which include a number of composite microstructures.

Speleothem chronology with sub-annual resolution in a near-entrance cave setting using oxygen isotope and trace element records

NASA Astrophysics Data System (ADS)

Carlson, P. E.; Miller, N. R.; Banner, J.; Breecker, D.

2016-12-01

Speleothems that grow in well-ventilated zones of caves are typically avoided when selecting specimens for paleoclimate reconstruction, due to concerns about evaporation and kinetic isotope effects. Near-entrance cave environments are characterized by near-ambient CO2 concentrations year-round and are influenced by surface temperature fluctuations. At Westcave Preserve (Westcave), a shallow, well-ventilated cave in central Texas, we have found seasonal temperature differences recorded in both the oxygen isotope and trace element compositions of speleothem calcite. The seasonal nature of these records has been confirmed by monitoring the chemical composition of drip water and substrate calcite since 2009 (Feng et al., 2014; Casteel and Banner, 2015). We present an ultrahigh-resolution (weekly to monthly) record of δ18O, Mg, Sr, and Ba in Westcave stalagmite WC-3, as well as monthly measurements of drip water geochemistry. We find drip water δ18O and [Mg] are essentially invariant, while seasonal variations in stalagmite calcite δ18O and Mg compositions are in good agreement with predicted temperature-dependent fractionation between water and calcite. Both drip water and speleothem calcite Sr and Ba vary seasonally, which we hypothesize is due to seasonal changes in moisture conditions in the epikarst. We use each of these annual geochemical cycles as independent chronological controls in order to develop a single age model for the stalagmite. These independent chronological counts are consistent with each other, and with 14C bomb-peak and U-series evidence. We argue that the potential for this kind of multi-proxy, seasonally-resolved dating in near-entrance stalagmites makes them especially valuable paleoclimate archives that should not be ignored in speleothem studies.

Metagenomic analysis of size-fractionated picoplankton in a marine oxygen minimum zone

PubMed Central

Ganesh, Sangita; Parris, Darren J; DeLong, Edward F; Stewart, Frank J

2014-01-01

Marine oxygen minimum zones (OMZs) support diverse microbial communities with roles in major elemental cycles. It is unclear how the taxonomic composition and metabolism of OMZ microorganisms vary between particle-associated and free-living size fractions. We used amplicon (16S rRNA gene) and shotgun metagenome sequencing to compare microbial communities from large (>1.6 μm) and small (0.2–1.6 μm) filter size fractions along a depth gradient in the OMZ off Chile. Despite steep vertical redox gradients, size fraction was a significantly stronger predictor of community composition compared to depth. Phylogenetic diversity showed contrasting patterns, decreasing towards the anoxic OMZ core in the small size fraction, but exhibiting maximal values at these depths within the larger size fraction. Fraction-specific distributions were evident for key OMZ taxa, including anammox planctomycetes, whose coding sequences were enriched up to threefold in the 0.2–1.6 μm community. Functional gene composition also differed between fractions, with the >1.6 μm community significantly enriched in genes mediating social interactions, including motility, adhesion, cell-to-cell transfer, antibiotic resistance and mobile element activity. Prokaryotic transposase genes were three to six fold more abundant in this fraction, comprising up to 2% of protein-coding sequences, suggesting that particle surfaces may act as hotbeds for transposition-based genome changes in marine microbes. Genes for nitric and nitrous oxide reduction were also more abundant (three to seven fold) in the larger size fraction, suggesting microniche partitioning of key denitrification steps. These results highlight an important role for surface attachment in shaping community metabolic potential and genome content in OMZ microorganisms. PMID:24030599

Metagenomic analysis of size-fractionated picoplankton in a marine oxygen minimum zone.

PubMed

Ganesh, Sangita; Parris, Darren J; DeLong, Edward F; Stewart, Frank J

2014-01-01

Marine oxygen minimum zones (OMZs) support diverse microbial communities with roles in major elemental cycles. It is unclear how the taxonomic composition and metabolism of OMZ microorganisms vary between particle-associated and free-living size fractions. We used amplicon (16S rRNA gene) and shotgun metagenome sequencing to compare microbial communities from large (>1.6 μm) and small (0.2-1.6 μm) filter size fractions along a depth gradient in the OMZ off Chile. Despite steep vertical redox gradients, size fraction was a significantly stronger predictor of community composition compared to depth. Phylogenetic diversity showed contrasting patterns, decreasing towards the anoxic OMZ core in the small size fraction, but exhibiting maximal values at these depths within the larger size fraction. Fraction-specific distributions were evident for key OMZ taxa, including anammox planctomycetes, whose coding sequences were enriched up to threefold in the 0.2-1.6 μm community. Functional gene composition also differed between fractions, with the >1.6 μm community significantly enriched in genes mediating social interactions, including motility, adhesion, cell-to-cell transfer, antibiotic resistance and mobile element activity. Prokaryotic transposase genes were three to six fold more abundant in this fraction, comprising up to 2% of protein-coding sequences, suggesting that particle surfaces may act as hotbeds for transposition-based genome changes in marine microbes. Genes for nitric and nitrous oxide reduction were also more abundant (three to seven fold) in the larger size fraction, suggesting microniche partitioning of key denitrification steps. These results highlight an important role for surface attachment in shaping community metabolic potential and genome content in OMZ microorganisms.

Organic aerosol composition and sources in Pasadena, California, during the 2010 CalNex campaign

NASA Astrophysics Data System (ADS)

Hayes, P. L.; Ortega, A. M.; Cubison, M. J.; Froyd, K. D.; Zhao, Y.; Cliff, S. S.; Hu, W. W.; Toohey, D. W.; Flynn, J. H.; Lefer, B. L.; Grossberg, N.; Alvarez, S.; Rappenglück, B.; Taylor, J. W.; Allan, J. D.; Holloway, J. S.; Gilman, J. B.; Kuster, W. C.; de Gouw, J. A.; Massoli, P.; Zhang, X.; Liu, J.; Weber, R. J.; Corrigan, A. L.; Russell, L. M.; Isaacman, G.; Worton, D. R.; Kreisberg, N. M.; Goldstein, A. H.; Thalman, R.; Waxman, E. M.; Volkamer, R.; Lin, Y. H.; Surratt, J. D.; Kleindienst, T. E.; Offenberg, J. H.; Dusanter, S.; Griffith, S.; Stevens, P. S.; Brioude, J.; Angevine, W. M.; Jimenez, J. L.

2013-08-01

Organic aerosols (OA) in Pasadena are characterized using multiple measurements from the California Research at the Nexus of Air Quality and Climate Change (CalNex) campaign. Five OA components are identified using positive matrix factorization including hydrocarbon-like OA (HOA) and two types of oxygenated OA (OOA). The Pasadena OA elemental composition when plotted as H : C versus O : C follows a line less steep than that observed for Riverside, CA. The OOA components from both locations follow a common line, however, indicating similar secondary organic aerosol (SOA) oxidation chemistry at the two sites such as fragmentation reactions leading to acid formation. In addition to the similar evolution of elemental composition, the dependence of SOA concentration on photochemical age displays quantitatively the same trends across several North American urban sites. First, the OA/ΔCO values for Pasadena increase with photochemical age exhibiting a slope identical to or slightly higher than those for Mexico City and the northeastern United States. Second, the ratios of OOA to odd-oxygen (a photochemical oxidation marker) for Pasadena, Mexico City, and Riverside are similar, suggesting a proportional relationship between SOA and odd-oxygen formation rates. Weekly cycles of the OA components are examined as well. HOA exhibits lower concentrations on Sundays versus weekdays, and the decrease in HOA matches that predicted for primary vehicle emissions using fuel sales data, traffic counts, and vehicle emission ratios. OOA does not display a weekly cycle—after accounting for differences in photochemical aging —which suggests the dominance of gasoline emissions in SOA formation under the assumption that most urban SOA precursors are from motor vehicles.

SRXFA in the studies of the correlation between the element composition of human blood and environment objects

NASA Astrophysics Data System (ADS)

Koutzenogii, K. P.; Savchenko, T. I.; Chankina, O. V.; Popova, S. A.

2009-05-01

High correlation has been revealed both between the content of chemical elements in human blood and atmospheric aerosols and between blood elements and food components. The element compositions of blood and hair have been established to be strongly related to each other. These biosubstrates can be used to estimate the health of the population of the northern hemisphere. Variability of the multielement composition of the blood and hair of the inhabitants of Novosibirsk, the Tundra Nenetz, Yakuts, Chukchi and the Eskimos, food components and aerosols in the regions where they live was determined by the SRXFA method.

Nonlinear vibrations of thin arbitrarily laminated composite plates subjected to harmonic excitations using DKT elements

NASA Astrophysics Data System (ADS)

Chiang, C. K.; Xue, David Y.; Mei, Chuh

1993-04-01

A finite element formulation is presented for determining the large-amplitude free and steady-state forced vibration response of arbitrarily laminated anisotropic composite thin plates using the Discrete Kirchhoff Theory (DKT) triangular elements. The nonlinear stiffness and harmonic force matrices of an arbitrarily laminated composite triangular plate element are developed for nonlinear free and forced vibration analyses. The linearized updated-mode method with nonlinear time function approximation is employed for the solution of the system nonlinear eigenvalue equations. The amplitude-frequency relations for convergence with gridwork refinement, triangular plates, different boundary conditions, lamination angles, number of plies, and uniform versus concentrated loads are presented.

Nonlinear vibrations of thin arbitrarily laminated composite plates subjected to harmonic excitations using DKT elements

NASA Technical Reports Server (NTRS)

Chiang, C. K.; Xue, David Y.; Mei, Chuh

1993-01-01

A finite element formulation is presented for determining the large-amplitude free and steady-state forced vibration response of arbitrarily laminated anisotropic composite thin plates using the Discrete Kirchhoff Theory (DKT) triangular elements. The nonlinear stiffness and harmonic force matrices of an arbitrarily laminated composite triangular plate element are developed for nonlinear free and forced vibration analyses. The linearized updated-mode method with nonlinear time function approximation is employed for the solution of the system nonlinear eigenvalue equations. The amplitude-frequency relations for convergence with gridwork refinement, triangular plates, different boundary conditions, lamination angles, number of plies, and uniform versus concentrated loads are presented.

What Are the 50 Cent Euro Coins Made of?

ERIC Educational Resources Information Center

Peralta, Luis; Farinha, Ana Catarina; Rego, Florbela

2008-01-01

X-ray fluorescence is a non-destructive technique that allows elemental composition analysis. In this paper we describe a prescription to obtain the elemental composition of homogeneous coins, like 50 cent Euro coins, and how to get the quantitative proportions of each element with the help of Monte Carlo simulation. Undergraduate students can…

Strength and deformability of compressed concrete elements with various types of non-metallic fiber and rods reinforcement under static loading

NASA Astrophysics Data System (ADS)

Nevskii, A. V.; Baldin, I. V.; Kudyakov, K. L.

2015-01-01

Adoption of modern building materials based on non-metallic fibers and their application in concrete structures represent one of the important issues in construction industry. This paper presents results of investigation of several types of raw materials selected: basalt fiber, carbon fiber and composite fiber rods based on glass and carbon. Preliminary testing has shown the possibility of raw materials to be effectively used in compressed concrete elements. Experimental program to define strength and deformability of compressed concrete elements with non-metallic fiber reinforcement and rod composite reinforcement included design, manufacture and testing of several types of concrete samples with different types of fiber and longitudinal rod reinforcement. The samples were tested under compressive static load. The results demonstrated that fiber reinforcement of concrete allows increasing carrying capacity of compressed concrete elements and reducing their deformability. Using composite longitudinal reinforcement instead of steel longitudinal reinforcement in compressed concrete elements insignificantly influences bearing capacity. Combined use of composite rod reinforcement and fiber reinforcement in compressed concrete elements enables to achieve maximum strength and minimum deformability.

Chloride-reinforced carbon nanofiber host as effective polysulfide traps in lithium-sulfur batteries

DOE PAGES

Fan, Lei; Zhuang, Houlong; Zhang, Kaihang; ...

2016-01-01

Lithium-sulfur (Li-S) battery is one of the most promising alternatives for the current state-of-art lithium-ion batteries (LIBs) due to its high theoretical energy density and lower production cost from the use of earth abundant element - sulfur. However, the commercialization of Li-S batteries has been so far limited to the cyclability and the retention of active sulfur materials. Using co-electrospinning and physical vapor deposition procedures, we created a class of chloride-carbon nanofiber composites, and studied their effectiveness on polysulfides sequestration. By trapping sulfur reduction products in the modified-cathode through both chemical and physical confinements in a conductive host, these chloride-coatedmore » cathodes are shown to remarkably suppress the polysulfide dissolution and shuttling between lithium and sulfur electrodes. We show that not only the binding energy but also the electronic conductivity of the host plays an important role on the reversibility of sulfur-based cathode upon repeated cycles. Electrochemical analysis of the chloride-modified cathodes over hundreds of cycles indicates that too strong binding of the sulfur species may lead to the decay of Coulombic efficiency. Cells containing indium chloride-modified carbon nanofiber outperform cells with other halogenated salt modifications, delivering an average specific capacity of above 1200mAh g-1 at 0.2C over 200 cycles. Once loaded with high S content, it shows stable capacity retention with only 0.019% decay per cycle from 5th to 650th cycle. It also shows stabilized cyclability and enhanced Coulombic efficiency in the absence of traditional anode stabilizer lithium nitrite.« less

Investigation on LiBH4-CaH2 composite and its potential for thermal energy storage.

PubMed

Li, Yang; Li, Ping; Qu, Xuanhui

2017-01-31

The LiBH 4 /CaH 2 composite are firstly studied as Concentrating Solar Power Thermal Storage Material. The LiBH 4 /CaH 2 composite according to the stoichiometric ratio are synthesized by high-energy ball milling method. The kinetics, thermodynamics and cycling stability of LiBH 4 /CaH 2 composite are investigated by XRD (X-ray diffraction), DSC (Differential scanning calorimeter) and TEM (Transmission electron microscope). The reaction enthalpy of LiBH 4 /CaH 2 composite is almost 60 kJ/mol H 2 and equilibrium pressure is 0.482 MPa at 450 °C. The thermal storage density of LiBH 4 /CaH 2 composite is 3504.6 kJ/kg. XRD results show that the main phase after dehydrogenation is LiH and CaB 6 . The existence of TiCl 3 and NbF 5 can effectively enhance the cycling perfomance of LiBH 4 /CaH 2 composite, with 6-7 wt% hydrogen capacity after 10 cycles. The high thermal storage density, high working temperature and low equilibrium pressure make LiBH 4 /CaH 2 composite a potential thermal storage material.

Elemental stoichiometry and compositions of weevil larvae and two acorn hosts under natural phosphorus variation

NASA Astrophysics Data System (ADS)

Ji, Huawei; Du, Baoming; Liu, Chunjiang

2017-04-01

To understand how different trophic organisms in a parasite food chain adapt to the differences in soil nutrient conditions, we investigated stoichiometric variation and homeostasis of multiple elements in two acorn trees, Quercus variabilis and Quercus acutissima, and their parasite weevil larvae (Curculio davidi Fairmaire) at phosphorus (P)-deficient and P-rich sites in subtropical China where P-rich ores are scattered among dominant P-deficient soils. Results showed that elemental stoichiometry and compositions of both acorns and weevil larvae differed significantly between P-deficient and P-rich sites (p < 0.05), with the largest contribution of acorn and weevil larva P in distinguishing the stoichiometric compositions between the two site types. The two acorn species were statistically separated by their acorn elemental stoichiometry and compositions (p < 0.05), but no difference was observed on weevil larvae between the two acorn species. P was one of the few elements that were non strict homeostasis in both acorns and weevil larvae. These findings highlight the importance of both environmental influence in elemental stoichiometry and composition and physiological regulations of nutritional needs in organisms and provide possible stoichiometric responses of both plants and animals to P loading, a worldwide issue from excess release of P into the environment.